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Am J Physiol Endocrinol Metab 292: E1656-E1665, 2007. First published February 6, 2007; doi:10.1152/ajpendo.00502.2006
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Experimental arthritis inhibits the insulin-like growth factor-I axis and induces muscle wasting through cyclooxygenase-2 activation

Miriam Granado, Ana I Martín, Mª Ángeles Villanúa, and Asunción López-Calderón

Facultad de Medicina, Departamento Fisiología, Universidad Complutense, Madrid, Spain

Submitted 15 September 2006 ; accepted in final form 5 February 2007


   ABSTRACT
TOP
 ABSTRACT
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 
Chronic arthritis induces cachexia associated with an inhibition of the growth hormone (GH)-insulin-like growth factor-I (IGF-I) system and an activation of the E3 ubiquitin-ligating enzymes muscle atrophy F-box (MAFbx) and muscle Ring finger 1 (MuRF1) in the skeletal muscle. The aim of this work was to study the role of cyclooxygenase (COX)-2 in chronic arthritis-induced cachexia. Arthritis was induced in rats by Freund's adjuvant injection, and the effects of two COX inhibitors (indomethacin, a nonspecific inhibitor, and meloxicam, a selective COX-2 inhibitor on pituitary GH and on liver and serum IGF-I levels) were tested. Arthritis decreased body weight gain and GH and liver IGF-I gene expression. In the arthritic rats, both inhibitors, indomethacin and meloxicam, prevented the inhibitory effect of arthritis on body weight gain. Indomethacin and meloxicam administration to arthritic rats increased pituitary GH and liver IGF-I mRNA as well as serum levels of IGF-I. These data suggest that induction of COX-2 during chronic inflammation is involved in the inhibition of the GH-IGF-I axis and in the body weight loss. In the gastrocnemius muscle, arthritis increased the gene expression of tumor necrosis factor (TNF)-{alpha}, the E3 ubiquitin-ligating enzymes MAFbx and MuRF1, as well as of IGF-I and IGF-binding protein-5 (IGFBP-5). Inhibition of COX-2 by meloxicam administration increased gastrocnemius weight and decreased MAFbx, MuRF1, TNF-{alpha}, and IGFBP-5 gene expression. In summary, our data indicate that chronic arthritis-induced cachexia and muscle wasting are mediated by the COX-2 pathway resulting in a decreased GH-IGF-I secretion and increased expression of MAFbx and MuRF1 mRNA.

indomethacin; meloxicam; tumor necrosis factor-{alpha}; muscle Ring finger 1; muscle atrophy F-box

CHRONIC INFLAMMATION IS ASSOCIATED with a decrease in body weight and cachexia. One of the numerous factors that can be involved in inflammatory cachexia is the neuroendocrine system. The neuroendocrine response to inflammation is characterized by an increase in the secretion of catabolic hormones such as glucocorticoids and a decreased secretion of anabolic factors such as insulin-like growth factor-I (IGF-I) (24). These modifications, together with the increased release of cytokines, can result in hypermetabolism and a decrease in body weight.

Adjuvant-induced arthritis is an experimental model of rheumatoid arthritis that is induced in rats by an intradermal injection of Freund's adjuvant. Ten days after adjuvant injection, rats start to lose body weight even before the external signs of the illness are manifested (37). Cachexia and hypermetabolism have also been reported in rheumatoid arthritis patients (52). Rheumatoid cachexia has been postulated as an important contributor in increasing morbidity and premature mortality in rheumatoid arthritis patients (61). Cachexia in experimental arthritis is associated with a decreased secretion of the growth hormone (GH)-IGF-I axis, whereas GH administration to arthritic rats is able to increase body weight gain (28). The increased production of cytokines, mainly tumor necrosis factor-{alpha} (TNF-{alpha}), seems also to be involved in inflammatory cachexia, since the neutralization of TNF-{alpha} in arthritic rats increases body weight gain as well as pituitary GH and liver IGF-I gene expression (21).

Possible factors that can mediate the cachetic effect of TNF-{alpha} are prostaglandins. Proinflammatory cytokines induce the production of PGE2, which plays an important role in the inflammatory response. Cyclooxygenases (COXs) are the key enzymes in regulating the biosynthesis of prostaglandins. There are two COX isoforms, encoded by different genes: COX-1 which is constitutively expressed, and COX-2, which is inducible by proinflammatory cytokines and other stimuli. COX-2-induced synthesis of prostaglandins has been associated with chronic inflammation, including arthritis, since the anti-inflammatory effect of selective COX-2 inhibitors is as effective as nonselective inhibitors (17). However, the role of COX-1 in inflammation has also been proposed (13).

Body weight loss in cachexia is secondary to muscle wasting and to enhanced protein breakdown by the ubiquitin-proteasome proteolitic pathway (34). Muscle atrophy F-box (MAFbx) and muscle Ring finger 1 (MuRF1) are muscle-specific E3 ubiquitin-ligating enzymes that play an important role in muscle atrophy and serve as early markers of skeletal muscle atrophy, aiding in the diagnosis of muscle disease. MAFbx overexpression in C2C12 cells induces a decrease in myotube diameter, and mice deficient in MAFbx or MuRF1 are resistant to denervation-induced muscle atrophy (7). In addition, MAFbx and MuRF1 mRNA are increased in atrophying muscle in many inflammatory conditions, including sepsis (63) and chronic arthritis (20).

Proinflammatory cytokines such as interleukin-1 and TNF-{alpha} have been reported to increase muscle protein proteolysis by the ubiquitin-proteasome pathway (for review, see Ref. 1). In addition to cytokines, the increased activity of COX can be responsible for muscle wasting and cachexia. Activation of COX-2 pathways has been observed in several cachetic state conditions such as cancer and sepsis (15, 19). COX inhibitors are able to ameliorate cancer cachexia and to improve body composition both in experimental animals and humans (15, 27, 39). Inhibition of COX activity prevents muscular wasting in cancer and reduces the ubiquitin ligases (25). However, the anticachexic effect of the inhibitors of prostaglandin synthesis has been reported in several types of cancer, whereas they are unable to prevent cancer cachexia in others (23).

The use of nonsteroidal anti-inflammatory drugs (NSAIDS) or unspecific COX inhibitors has possible side effects on gastrointestinal function and hematological tissues, especially in chemotherapy treatments in cancer patients. However, NSAIDS are widely used in inflammatory conditions such as rheumatoid arthritis because of their effective anti-inflammatory activity. Accordingly, the aim of this work was to elucidate the effect of COX inhibition on experimental arthritis-induced cachexia. For that reason, we compared the response in arthritic rats to treatment with an unspecific COX inhibitor, indomethacin, and a COX-2 inhibitor, meloxicam, on body weight, on the GH-IGF-I system, and in the gene expression of the E3 ubiquitin-ligating enzymes MAFbx and MuRF1 in skeletal muscle. We have previously observed that arthritis increases TNF-{alpha} and IGF-binding protein-5 (IGFBP-5) gene expression in the gastrocnemius (20). Because they can be negative regulators of IGF-I signaling and of muscular growth, the expression of these two genes were also analyzed.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 
Arthritic and control male Wistar rats weighing 150–175 g (6 wk old) at the beginning of the experiment were purchased from Charles River (Barcelona, Spain). Arthritis was induced in the rats by an intradermal injection of 1 mg heat-inactivated Mycobacterium butyricum in incomplete Freund's adjuvant in the right paw. Control animals were injected with mineral oil. Rats were housed 3–4/cage under controlled conditions of light (lights on from 0730 to 1930) and temperature (22 ± 2°C). Food and water were available ad libitum. Assessment of arthritis was performed by measuring the arthritis index of each animal, which was scored by grading each paw from zero to four. Grading was determined as follows: 0, no erythema or swelling; 1, slight erythema or swelling of one or more digits; 2, swelling of entire paw; 3, erythema and swelling of the ankle; and 4, ankylosis, incapacity to bend the ankle. The severity score was the sum of the clinical scores of each limb, with the maximum value being 16. The procedures followed the guidelines recommended by the European Union for the care and use of laboratory animals, and were approved by the University animal care committee.

Indomethacin administration. On day 15 after adjuvant injection, control and arthritic rats were randomly divided into 2 groups; one was injected daily with the unspecific COX inhibitor indomethacin (4 mg/kg sc; Sigma, Madrid, Spain), and the second was injected with vehicle (250 µl of 0.5% NaHCO3). Indomethacin dose was selected after a study showing that this dose prevents muscle wasting in cancer and weight loss in arthritic rats (25, 58). Body weight, food intake, and the arthritis index scores were examined daily. Food intake per cage was calculated by measuring the difference between the initial and the remaining amount of pellets in the feeder and expressed as gram per rat per 100 g body weight per day. All rats were killed by decapitation 22 days after adjuvant or vehicle injection and, after 8 days of indomethacin treatment, 2.5 h after the last injection. Trunk blood was collected in cooled tubes, allowed to clot, and centrifuged, and the serum was stored at –20°C until IGF-I assay was performed and at –80°C until PGE2 analysis was performed. The left hindpaw was amputated at the ankle level, and the volume was measured by water displacement. Immediately after decapitation, the pituitary and the liver were removed, dissected, frozen in liquid nitrogen, and stored at –80°C until RNA extraction.

Meloxicam administration. The effect of meloxicam administration, a COX-2 inhibitor, was examined. On day 15, arthritic and control rats were divided into two groups; one was injected with meloxicam (1 mg/kg sc; Sigma), and the second received 250 µl of saline subcutaneously from day 16 to 22. This dosage was selected, since it was reported to be close to an optimal analgesic dose as previously described (54). Rats were injected and weighed, and the arthritis score index and the food intake were examined daily. None of the rats died during the experimental procedures. On day 22 after adjuvant injection, rats were killed, blood was allowed to clot and centrifuged, and the serum was stored until IGF-I and PGE2 assays were performed. The left hindpaw volume, gastrocnemius muscle, pituitary, kidney, and heart weights were measured. The pituitary, liver, and gastrocnemius muscle were dissected, frozen in liquid nitrogen, and stored at –80°C until RNA extraction.

Serum IGF-I and PGE2. Serum IGF-I concentrations were measured by a double-antibody RIA. Serum IGFBPs were removed by acid-ethanol extraction. The IGF-I antiserum (UB2-495) was a gift from Dr. L. Underwood and Dr. J. Van Wyk, and it is distributed by the Hormone Distribution Program of National Institute of Diabetes and Digestive and Kidney Diseases through the National Hormone and Pituitary Program. Levels of IGF-I were expressed in terms of IGF-I from Gropep (Adelaide, Australia). The intra-assay coefficient of variation was 8%. Samples from one experiment were run in the same assay.

Serum concentrations of PGE2 were measured by an enzymeimmunoassay system using a commercial kit (Amersham Biosciences, Buckinghamshire, UK) following the manufacturer's instructions (http://amersham.com).

Real-time PCR. RNA was extracted by the guanidine thiocyanate method using a commercial kit (Ultraspec RNA; Biotecx Laboratories, Houston, TX). The integrity of the RNA was confirmed using agarose gel electrophoresis. For RT-PCR analysis, 2 µg pituitary, liver, or skeletal muscle total RNA were reverse transcribed in a total volume of 30 µl at 37°C for 15 min with 125 units of Moloney murine leukemia virus RT (Maxim Biotch, San Francisco, CA).

Primers for PCR (Table 1), were obtained from Qiagen (Valencia, CA) from previously published sequences of IGF-I, TNF-{alpha} and MuRF1 (16), hypoxanthine-guanine phosphoribosyl transferase (Hprt; see Ref. 47), COX-2 (5), or by using the rat GenBank and the EXIQON ProbeLibrary GH, IGFBP-5, and MAFbx. Primers were designed to span a single sequence derived from two exons (i.e., separated by an intron in genomic DNA and primary RNA transcripts to minimize amplification).


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  		Table 1. Primers for real-time PCR

 
Each real-time PCR reaction contained 10 ng of synthesized cDNA, 1x Takara SYBR Green Premix Ex Taq (Takara BIO), and 300 nM forward and reverse primers for the candidate gene in a reaction volume of 25 µl. Reactions were carried out on a SmartCycler (Cepheid, Sunnyvale, CA).

Parameters included an initial activation of hotStarTaq DNA polymerase at 95°C for 15 min, followed by 40 cycles of denaturation at 94°C for 15 s, annealing at 60°C and extension at 72°C for 30 s. Specific amplification was confirmed by the presence of one single peak in the melting curve plots. In addition, the PCR products were analyzed by agarose gel electrophoresis. Results were calculated as percent of control rats, using the cycle threshold 2{Delta}{Delta}Ct method (36) with the Hprt as reference gene.

Statistical analysis. All data are presented as means ± SE. Statistics were computed using the statistics program STATGRAPHICS plus for Windows. Differences among experimental groups were analyzed by one-way (organ weights) or two-way ANOVA. Where there were differences among the groups, post hoc comparisons were made by using the unpaired Student's t-test. Significance was assumed when P < 0.05.


   RESULTS
TOP
 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 GRANTS
 REFERENCES
 
Arthritis induced a significant increase in COX-2 gene expression (P < 0.01) in all the tissues analyzed (pituitary, liver, and skeletal muscle; Fig. 1). As expected, when the serum concentration of PGE2 was measured in arthritic rats treated with the two COX inhibitors, both treatments were able to induce a significant (P < 0.01) decrease in the serum levels of PGE2 (Fig. 2).


Figure 1
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  		Fig. 1. Effect of adjuvant-induced arthritis on cyclooxygenase (COX)-2 gene expression in the pituitary, liver, and skeletal muscle (gastrocnemius). Tissues were obtained on day 23 after adjuvant injection. COX mRNA was measured by real-time PCR as described in MATERIALS AND METHODS. Results are expressed as %control (nonarthritic) rats for at least 7 rats/group. **P < 0.01 vs. control rats.

 

Figure 2
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  		Fig. 2. Serum concentration of PGE2 in arthritic rats treated with the COX inhibitors indomethacin and meloxicam (gray bars) or with vehicle (white bars). Both inhibitors decreased the serum concentrations of PGE2 in arthritic rats. Values shown are means ± SE for 8–10 rats/group. °°P < 0.01 vs. respective group injected with vehicle.

 
Three rats from the arthritic group injected with indomethacin died during the experiment, whereas none of the arthritic rats injected with vehicle or meloxicam died during the entire experimental procedure. In the control group injected with indomethacin, one rat died and two rats were excluded from the experiment because they started to lose weight and had ascites. Indomethacin administration to arthritic rats dramatically decreased arthritis index scores (Fig. 3), being significantly lower than in the arthritic rats injected with vehicle on the 3rd day of indomethacin treatment (and 17 days after adjuvant injection). Arthritis increased the paw volume (P < 0.01), and indomethacin treatment reduced paw volume in arthritic rats (P < 0.01, Fig. 3), whereas indomethacin administration had no effect on paw volume in control rats. The anti-inflammatory effect of treatment with meloxicam was similar to that of indomethacin (Fig. 4). Meloxicam administration decreased the external signs of the arthritis, measured as arthritis scores, from the 1st day of treatment. This difference was significant, starting from the 3rd day of treatment (Fig. 4). Meloxicam administration for 8 days also decreased the paw volume in the arthritic rats (P < 0.01) but not in controls.


Figure 3
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  		Fig. 3. Evolution of arthritis scores (left) and paw volume (right) in arthritic rats (AA) or control rats injected with indomethacin (4 mg/kg sc) or vehicle (250 µl) for 8 days (treatments started 15 days after adjuvant injection). Values shown are means ± SE (n = 8–10 rats). There was an interaction between the effect of arthritis and indomethacin on paw volume [F(1,31) = 11, P < 0.01], since indomethacin decreased paw volume in arthritic rats but not in control rats. **P < 0.01, vs. control rats injected with vehicle. ++P < 0.01 vs. control rats injected with indomethacin. °P < 0.05 and °°P < 0.01 vs. arthritic rats injected with vehicle.

 

Figure 4
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  		Fig. 4. Evolution of arthritis scores (left) and paw volume (right) in arthritic rats (AA) or control rats injected with meloxicam (1 mg/kg sc) or vehicle for 8 days (treatments started 15 days after adjuvant injection). Values shown are means ± SE (n = 10–12 rats). There was an interaction between the effect of arthritis and meloxicam on paw volume [F(1,36) = 15, P < 0.01], since meloxicam decreased paw volume in arthritic rats but not in control rats. P < 0.01 vs. control rats injected with vehicle (**), vs. control rats injected with meloxicam (++), and vs. arthritic rats injected with vehicle (°°).

 
The effect of arthritis and indomethacin administration on body weight and food intake is shown in Fig. 5. Arthritic rats had lower body weight than control rats when starting the indomethacin treatment 15 days after adjuvant injection. In the arthritic rats injected with vehicle, the body weight gain during the 8 days of treatment was lower than that of control rats injected with vehicle (P < 0.01). In both experiments, arthritis decreased (P < 0.01) the cumulative food intake during the 8 days of treatment (Figs. 5 and 6), but this effect was not significant during the last 2 days of treatment before the rats were killed (Figs. 5 and 6). Indomethacin induced a significant increase in body weight in arthritic rats starting 24 h after administration. Moreover, indomethacin prevented the inhibitory effect of arthritis on body weight gain, since the arthritic rats injected with indomethacin had a cumulative body weight similar to that of control rats injected with vehicle, although the absolute body weight remained lower than the control rats injected with vehicle (Fig. 5). In contrast, indomethacin administration to nonarthritic rats induced a decrease in food intake (P < 0.01, Fig. 5) and in body weight gain, where the cumulative body weight gain during the 8 days of treatment was lower than that of the arthritic rats injected with indomethacin (Fig. 5).


Figure 5
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  		Fig. 5. Effect of 8-day indomethacin administration (4 mg/kg sc) on cumulative body weight gain (A), absolute body weight evolution (B), and daily food intake during the 8 days (C) or during the last 2 days (D) of treatment in control or arthritic (AA) rats. There was an interaction between the effect of arthritis and indomethacin on body weight gain [F(1,33) = 37, P < 0.01] and on food intake during the 8 days [F(1,24) = 41, P < 0.01] or during the last 2 days [F(1,24) = 40, P < 0.01] of treatment, since indomethacin decreased the body weight gain and food intake in control rats, whereas it increased body weight gain and food intake in arthritic rats. Values represent means ± SE for n = 6–12. **P < 0.01 vs. control rats injected with vehicle. °P < 0.05 and °°P < 0.01 vs. arthritic rats injected with vehicle. ++P < 0.01 vs. control rats injected with indomethacin.

 

Figure 6
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  		Fig. 6. Effect of 8-day meloxicam administration (1 mg/kg sc) on cumulative body weight gain (A), absolute body weight evolution (B), and daily food intake during the 8 days (C) or during the last 2 days (D) of treatment in control or arthritic (AA) rats. There was an interaction between the effect of arthritis and meloxicam on body weight gain [F(1,36) = 25, P < 0.01] and on food intake during the 8 days [F(1,24) = 16, P < 0.01] or during the last 2 days [F(1,20) = 44, P < 0.01] of treatment, since meloxicam increased the body weight gain and food intake in arthritic rats but not in control rats. Values represent means ± SE for n = 4–12. *P < 0.05 and **P < 0.01 vs. control rats injected with vehice. °P < 0.5 and °°P < 0.01 vs. arthritic rats injected with vehicle. ++P < 0.01 vs. control rats injected with meloxicam.

 
The effect of meloxicam administration on body weight and food intake is shown in Fig. 6. Meloxicam administration to arthritic rats prevented the inhibitory effect of arthritis on body weight, since the evolution of body weight during the 8 days of treatment in the arthritic rats injected with meloxicam was similar to that of the control rats. Meloxicam administration had no appreciable effect on food intake in control rats but induced a marked increase in food intake in arthritic rats (P < 0.01), even at higher levels than the food intake observed in control rats (Fig. 6).

In the group treated with vehicle, arthritis induced a significant decrease in pituitary GH (P < 0.05) and liver IGF-I (P < 0.01) gene expression, as well as in serum concentrations of IGF-I (P < 0.01, Fig. 7). As observed with food intake and body weight, indomethacin administration decreased serum concentrations of IGF-I and IGF-I gene expression in the liver (P < 0.01) in control rats. There was a significant decrease in serum IGF-I levels in the control rats that received indomethacin. In contrast, in arthritic rats, indomethacin administration increased serum concentrations of IGF-I (P < 0.05) and liver IGF-I mRNA, although this increase was not statistically significant. Indomethacin treatment did not modify pituitary GH mRNA in control rats but blunted the inhibitory effect of arthritis on pituitary GH mRNA.


Figure 7
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  		Fig. 7. Effect of indomethacin administration over 8 days on pituitary growth hormone (GH) mRNA (A), liver insulin-like growth factor (IGF)-I mRNA (B), and on serum concentrations of IGF-I (C) in control or arthritic (AA) rats. mRNAs were quantified using real-time RT-PCR as described in MATERIALS AND METHODS and are presented as a percentage of the mean value in the control group injected with vehicle. There was an interaction between the effect of indomethacin and arthritis on liver IGF-I mRNA [F(1,24) = 11, P < 0.01] and on serum concentrations of IGF-I [F(1,32) = 17, P < 0.01], since arthritis decreased circulating IGF-I and its gene expression in the liver in vehicle-injected rats but not in the rats treated with indomethacin. Values represent means ± SE for n = 7–10. *P < 0.05 and **P < 0.01 vs. control rats injected with vehicle. °P < 0.05 vs. arthritic rats injected with vehicle.

 
In contrast to the data obtained with the indomethacin treatment, meloxicam administration to control rats did not modify liver IGF-I mRNA or serum concentrations of IGF-I (Fig. 8). In arthritic rats, meloxicam administration increased the serum concentration of IGF-I as well as its gene expression in the liver, reaching levels similar to those observed in the control rats (Fig. 8). Similarly, meloxicam administration also blunted the inhibitory effect of arthritis on GH mRNA (Fig. 8).


Figure 8
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  		Fig. 8. Effect of meloxicam treatment over 8 days on pituitary GH mRNA (A), liver IGF-I mRNA (B), and on serum concentrations of IGF-I (C) in control or arthritic (AA) rats. mRNAs were quantified using real-time RT-PCR as described in MATERIALS AND METHODS and are presented as percentage of the mean value in the control group injected with vehicle. There was an interaction between the effect of meloxicam and arthritis on serum concentrations of IGF-I [F(1,35) = 5, P < 0.05], since arthritis decreased the serum concentration of IGF-I in the rats treated with saline but not in the group treated with meloxicam. Values represent means ± SE for n = 7–10. *P < 0.05 and **P < 0.01 vs. control rats injected with vehicle. °P < 0.05 vs. arthritic rats injected with vehicle.

 
Because of the observed side effects of indomethacin, and taking into account that in the arthritic rats the effect of indomethacin and meloxicam on body weight and on the GH-IGF-I axis was similar, we studied the skeletal muscle response only in the rats treated with meloxicam. The effect of arthritis and meloxicam administration to arthritic rats on gastrocnemius, heart, kidney, and pituitary weights is shown in Fig. 9. Arthritis decreased the weight of all organs studied, but there were differences among them. Arthritis induced a dramatic decrease in skeletal muscle, where the gastrocnemius was 28% (P < 0.01) of gastrocnemius weight of the control rats injected with saline. The weight of organs such as the heart, kidney, and pituitary were also decreased by arthritis, but their decreases were lower (73–84% of control values) than that of the skeletal muscle decrease. In the control rats, meloxicam administration had no effect in all the organs analyzed (data not shown). These data indicate that the inhibitory effect of arthritis on body weight is mainly the result of skeletal muscle atrophy. Similarly, the stimulatory effect of meloxicam on body weight in arthritic rats is concomitant with an increase in the weight of the organs studied, where this effect is more marked in skeletal muscle weights than in kidney, heart, or pituitary weights (Fig. 9).


Figure 9
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  		Fig. 9. Weight of gastrocnemius, heart, kidney, and pituitary of arthritic rats injected with vehicle (AA-vehicle) or meloxicam (AA-meloxicam, 1 mg/kg sc). Data are expressed as %weight of the control rats injected with vehicle for 10 rats/group. P < 0.01 vs. control rats injected with vehicle (**) and vs. arthritic rats injected with vehicle (°°).

 
The effect of arthritis on IGF-I gene expression in the gastrocnemius is different from the liver, since IGF-I mRNA was higher (P < 0.05) in arthritic rats than in control rats injected with saline (Fig. 10). Meloxicam treatment, although it increased IGF-I mRNA in the gastrocnemius, had no statistical significance in control or in arthritic rats. Arthritis also induced an increase (P < 0.01) in IGFBP-5 mRNA in the gastrocnemius (Fig. 10). Meloxicam administration did not modify the IGFBP-5 mRNA in the gastrocnemius of control rats, whereas it decreased the IGFBP-5 mRNA in the arthritic rats, reaching levels similar to those of control rats.


Figure 10
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  		Fig. 10. Effect of meloxicam administration on IGF-I (top) or IGFBP-5 mRNA (bottom) in the gastrocnemius of control or arthritic (AA) rats. mRNAs were quantified using real-time RT-PCR as described in MATERIALS AND METHODS and are presented as %mean value in control group injected with vehicle. There was an interaction between the effect of arthritis and meloxicam on IGFBP-5 mRNA [F(1,33) = 7.2, P < 0.05], since arthritis increased the IGFBP-5 mRNA in the gastrocnemius of the rats injected with vehicle but not in those injected with meloxicam. Results are expressed as means ± SE for n = 8–10/group; *P < 0.05 and **P < 0.01 vs. control rats injected with vehicle. °°P < 0.01 vs. arthritic rats injected with vehicle.

 
The effect of meloxican administration on MAFbx and MuRF1 gene expression in the gastrocnemius of control or arthritic rats is shown in Fig. 11. In the control rats, meloxicam administration did not modify either MAFbx or MuRF1 mRNAs. Arthritis induced a significant increase in MAFbx (P < 0.01) and MuRF1 (P < 0.05) mRNAs in the gastrocnemius, and meloxicam treatment totally prevented the effect of arthritis on these mRNAs (Fig. 11).


Figure 11
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  		Fig. 11. Muscle atrophy F-box (MAFbx; top) and muscle Ring finger 1 (MuRF1; bottom) mRNAs in gastrocnemius of control and arthritic (AA) rats injected with vehicle or 1 mg/kg meloxicam for 8 days. MAFbx and MuRF1 mRNA were analyzed by real-time PCR, and the data were normalized to the expression of hypoxanthine-guanine phosphoribosyl transferase (Hprt) RNA. There was an interaction between the effects of arthritis and meloxicam administration on MAFbx [F(1,32) = 25, P < 0.01] and on MuRF1 [F(1,30) = 8, P < 0.01] gene expression in the gastrocnemius, since arthritis increased both mRNAs in vehicle but not in meloxicam-treated rats. Results represent means ± SE for 7–10 rats/group. **P < 0.01 and *P < 0.05 vs. control rats injected with vehicle. °°P < 0.01 and °P < 0.05 vs. arthritic rats injected with vehicle.

 
Arthritis also induced an increase on TNF-{alpha} gene expression in skeletal muscle (Fig. 12). Meloxicam administration did not modify the TNF-{alpha} mRNA in control rats, whereas in arthritic rats meloxicam induced a significant decrease in TNF-{alpha} mRNA, reaching control values.


Figure 12
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  		Fig. 12. Effect of meloxicam administration (1 mg/kg for 8 days) on TNF-{alpha} mRNA in control and arthritic (AA) rats. mRNAs were quantified using real-time PCR as described in MATERIALS AND METHODS and are presented as a percentage of the mean value in control group injected with vehicle. There was an interaction between the effect of arthritis and meloxicam on TNF-{alpha} mRNA [F(1,30) = 5, P < 0.05], since meloxicam decreased TNF-{alpha} in arthritic rats, whereas it had no effect in control rats. Results represent means ± SE for 8–9 rats/group. **P < 0.01 vs. control rats injected with vehicle. °°P < 0.01 vs. arthritic rats injected with vehicle.

 

   DISCUSSION
TOP
 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
GRANTS
 REFERENCES
 
Our data show that arthritis increases COX-2 gene expression, whereas inhibition of COX-2 activity prevents arthritis-induced muscle wasting and the increase in the E3 ubiquitin-ligating enzymes MAFbx and MuRF1. These effects are associated with an amelioration of the GH-IGF-I axis and a decrease in the gene expression of IGFBP-5 and TNF-{alpha} in the skeletal muscle, taking into account that the anti-inflammatory effect of both treatments (indomethacin, a nonselective inhibitor, and meloxicam, a preferential selective COX-2 inhibitor) was similar. The inhibitory effect of arthritis on the GH-IGF-I system and on body and skeletal muscle weights seems to be mediated through activation of the COX-2 pathway.

The antianorexigenic effect of COX inhibitors is well known, and it has been postulated that eicosanoids are more important in anorexia than host cytokines (51). In the present data, the two COX inhibitors increased food intake and body weight gain in the arthritic rats. The antianorexigenic effect of indomethacin in the arthritic rats contrasts with its effect in control rats in which indomethacin decreased food intake, body weight gain, IGF-I gene expression in the liver, and circulating IGF-I. Toxicity to indomethacin but not to meloxicam was observed, as indicated by mortality and a decrease in body weight gain in the control rats injected with indomethacin. A toxic effect of 5 mg/kg indomethacin has previously been reported, but without mortality (17). In arthritic rats undergoing treatment with a lower indomethacin dosage (3 mg/kg), one group did not report having adverse effects of indomethacin (49), whereas another one reported mortality (58). Indomethacin side effects have been attributed to gastrointestinal damage because of COX-1 inhibition. A detrimental effect of a COX-1 inhibitor on body weight has been reported, since COX-1 inhibition or genetic inactivation of COX-1 augmented and prolonged body weight loss during inflammation (29). In control rats injected with indomethacin, the gastrointestinal damage can be the cause of the decrease in food intake. The decrease in body weight gain and in IGF-I gene expression in the control rats injected with indomethacin can be related to the decrease in food intake. According to this, pituitary GH gene expression is not affected by indomethacin in the control rats, since GH is not as related to food intake as IGF-I is.

Although the rats in this study were not pair-fed, we have previously found that the inhibitory effect of arthritis on body weight and IGF-I is not the result of anorexia, since pair-fed rats gained similar body weight to control rats fed "ad libitum" (38). A possible explanation is that the anorexic effect of arthritis is small, the food intake is 90% that of the control rats, whereas the body weight gain is 11% of the control rats during the 8 days of the experiment. In addition, there is no difference in food intake from day 21 to 23 (the last 2 days before the animals died) between arthritic and control rats injected with vehicle. Furthermore, recombinant human GH administration to arthritic rats increased body weight gain without increasing food intake (28). On the contrary, anti-TNF-{alpha} administration to arthritic rats increases food intake to control levels, but the body weight gain was still lower than the control rats (21). In cancer, it has been reported that initially body wasting occurs independently of anorexia (6, 25, 62). In other cachectic conditions such as lipopolysaccharide (LPS) administration, the mechanism by which LPS reduces food intake is also dissociated from its effect on weight loss (42). All these data indicate that, in addition to the decrease in food intake, the decrease in body weight in adjuvant arthritis is related to other mechanisms.

The effect of both COX inhibitors on body weight in the arthritic rats can be secondary to its effect on GH and IGF-I, since the immunosuppresor cyclosporine A blocks the inhibitory effect of arthritis on circulating GH and IGF-I and also prevents the inhibitory effect of arthritis on body weight (59). Taking into account that exogenous GH is able to counteract the decline in skeletal muscle function in chronic cardiac failure (14), part of the effect of meloxicam in preventing cachexia can be secondary to the increased gene expression on GH and liver and serum IGF-I. The inhibitory effect of arthritis on GH does not seem to be mediated by the increased release of PGE2, since this prostanoid has been reported to be a GH secretagogue (12, 43). A stimulatory effect of lipoxygenase products on pituitary GH synthesis and secretion has also been reported (12, 53). Therefore, the inhibitory effect of arthritis on pituitary GH can be secondary to another inhibitory substance that is released after COX-2 activation. In the liver, COX-2 upregulation potentiates liver injury induced by allyl alcohol, where PGD2, but not PGE2, has a similar effect in isolated hepatocytes (19). A direct inhibitory effect of PGA and -J on IGF-I gene expression has been reported (9, 10), whereas PGE2 has a stimulatory effect on IGF-I gene expression in osteoblasts (8, 54). Therefore, it is also possible that another prostaglandin different from PGE2 inhibits the pituitary GH and liver IGF-I during inflammation.

IGF-I has a prominent role in muscle hypertrophy, but when chronically deactivated it also has an important role in muscle atrophy (31). Accordingly, the increased IGF-I mRNA in skeletal muscle of arthritic rats contrasts with the notable muscle wasting induced by arthritis. One possible explanation for this fact is that muscular IGFBP-5 might inhibit IGF-I activity in skeletal muscle by preventing its interaction with the IGF-I receptor. In addition to its IGF-I-dependent action, IGFBP-5 is also able to decrease cell proliferation by an IGF-I-independent effect in myoblast cultures (44). Similarly, transgenic mice overexpressing IGFBP-5 show growth retardation and decreased skeletal muscle mass relative to body weight (57). In the present data, COX-2 inhibition in arthritic rats decreased IGFBP-5 mRNA in the skeletal muscle. It is possible that meloxicam directly decreases IGFBP-5 gene expression by decreasing prostanoid biosynthesis in skeletal muscle. A stimulatory effect of PGE2 on IGFBP-5 in osteoblast cells has also been described (46). Moreover, PGE2-responsive elements have been reported in the IGFBP-5 promoter (4, 40). Changes in pituitary GH secretion can also modify muscular IGFBP-5 mRNA, since GH inhibits the expression of IGFBP-5 in mammary epithelial cells (56).

Local COX-2 pathways can play an important role in muscle wasting. Arthritis increases COX-2 and specific E3 ubiquitin-ligating enzyme, MAFbx and MuRF1, gene expression in the muscle. In septic patients, an increase in COX-2 and activation of the ubiquitin proteolitic pathway in muscle have been reported (50). In addition, COX-2 inhibition by celecoxib decreases muscle weakness in elderly patients with acute inflammation (35). The preservation of muscle mass in the arthritic rats injected with meloxicam was associated with a decrease in the muscular expression of both atrogenes. These results suggest that the COX-2 pathway is involved in the upregulation of MAFbx and MuRF1 during chronic arthritis. Taking into account that these genes are considered as markers of skeletal muscle atrophy, our data suggest that the COX-2 pathway is involved in muscular wasting.

It is possible that the improvement in mobility, rather than the decrease in prostaglandins per se, may lead to the observed changes in gene expression in the gastrocnemius. We cannot exclude this possibility, because we did not measure mobility. However, this does not seem to be the cause, since with systemic anti-TNF-{alpha} administration, inflammation was also decreased in a similar way (21), but no modifications in IGFBP-5, MAFbx or MuRF1 mRNA, or gastrocnemius weight were observed (22). Taking into account that TNF-{alpha} is also an important trigger of muscular atrophy and it upregulates MAFbx and MuRF1 gene expression (31, 35), the lack of effect of systemic anti-TNF-{alpha} in preventing muscular wasting was unexpected (22). A possible explanation can be that the "in vivo" anti-TNF-{alpha} therapy is not able to suppress COX activity in the muscle, as is the case of the synovial tissue from rheumatoid arthritis patients (33). These data emphasize the importance of the COX pathway in the inflammatory cachexia. Another explanation could be that muscle proteolysis by the ubiquitin-proteasome pathway is activated by local TNF-{alpha} rather than by circulating TNF-{alpha}, since systemic anti-TNF-{alpha} therapy is not able to prevent the increased gene expression of TNF-{alpha} in the gastrocnemius muscle (22). In the present data, normalization of MuRF1 and MAFbx is associated with a decrease in muscular TNF-{alpha}, which means that there is a relationship between prostaglandin inhibition and TNF-{alpha} gene expression. Supporting these data, normalization of TNF-{alpha} gene expression by NSAID administration has previously been reported in cancer (32), in endotoxemic rats (3), in diabetic retinopathy (30), and has been explained by the inhibitory effect of the NSAIDs on NF-kB signaling.

Nuclear factor (NF)-{kappa}B plays an important role in muscle atrophy as well. It is upregulated in muscle in several conditions of muscle wasting such as disuse, sepsis, cancer, and angiotensin administration (26, 48, 55, 60). Blockade of NF-{kappa}B prevents muscle atrophy, and transgenic mice with activated NF-{kappa}B have muscle wasting and increased MuRF1 gene expression (11). All of these data indicate that NF-{kappa}B is a central component of the muscular atrophy process involved in the activation of proteolytic pathways. Taking into account that meloxicam inhibits the activation of NF-{kappa}B (2, 30, 64), this can be one of the mechanisms by which meloxicam prevented the arthritis-induced increase of MAFbx and MuRF1 expression and muscle wasting.

In conclusion, our data suggest that overactivation of COX-2 is responsible for chronic inflammation-induced cachexia, through an inhibition of the GH-IGF-I axis and an activation of the ubiquitin-proteasome pathway and muscle wasting. At the muscular level, COX-2 seems to be also involved in the increase in local IGFBP-5 and TNF-{alpha} gene expression that contributes to the activation of the MAFbx and MuRF1 ubiquitin ligases. These findings have implications not only on the knowledge of the mechanism leading to cachexia in chronic inflammation but on therapeutic strategies in managing chronic arthritis.


   GRANTS
TOP
 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
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REFERENCES
 
This work was supported by Programa Nacional de Promoción General del Conocimiento, Plan Nacional de Investigación Científica, from Ministerio de Educación Ciencia (BFI-2003-02149), by Universidad Complutense/SantanderCentralHispano Grant PR27/05-14055, and a Fellowship from Ministerio de Educación y Ciencia to M. Granado (FPU, AP2003-2564).


   ACKNOWLEDGMENTS
 
We are indebted to Antonio Carmona for technical assistance and to Christina Bickart for the English correction of the manuscript.


   FOOTNOTES
 

Address for reprint requests and other correspondence: A. López-Calderón, Dept. Fisiología, Faculty Medicina, Univ Complutense, 28040, Madrid (e-mail: ALC{at}med.ucm.es)

The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.


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 ABSTRACT
 MATERIALS AND METHODS
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  1. Argiles JM, Busquets S, López-Soriano FJ. The pivotal role of cytokines in muscle wasting during cancer. Int J Biochem Cell Biol 37: 1609–1619, 2005.[CrossRef][ISI][Medline]
  2. Asano K, Sakai M, Matsuda T, Tanaka H, Fujii K, Hisamitsu T. Suppression of matrix metalloproteinase production from synovial fibroblasts by meloxicam in-vitro. J Pharm Pharmacol 58: 359–66, 2006.[CrossRef][ISI][Medline]
  3. Azab AN, Kobal S, Rubin M, Kaplanski J. Effects of nimesulide, a selective cyclooxygenase-2 inhibitor, on cardiovascular alterations in endotoxemia. Cardiology 103: 92–100, 2005.[CrossRef][ISI][Medline]
  4. Beattie J, Allan GJ, Lochrie JD, Flint DJ. Insulin-like growth factor-binding protein-5 (IGFBP-5): a critical member of the IGF axis. Biochem J 395: 1–19, 2006.[CrossRef][ISI][Medline]
  5. Bianchi A, Moulin D, Sebillaud S, Koufany M, Galteau MM, Netter P, Terlain B, Jouzeau JY. Contrasting effects of peroxisome-proliferator-activated receptor (PPAR)gamma agonists on membrane-associated prostaglandin E2 synthase-1 in IL-1beta-stimulated rat chondrocytes: evidence for PPARgamma-independent inhibition by 15-deoxy-Delta12,14prostaglandin J2. Arthritis Res Ther 7: R1325–R1337, 2005.[CrossRef][ISI][Medline]
  6. Bibby MC, Double JA, Ali SA, Fearon KC, Brennan RA, Tisdale MJ. Characterization of a transplantable adenocarcinoma of the mouse colon producing cachexia in recipient animals. J Natl Cancer Inst 78: 539–546, 1987.[ISI][Medline]
  7. Bichell DP, Rotwein P, McCarthy TL. Prostaglandin E2 rapidly stimulates insulin-like growth factor-I gene expression in primary rat osteoblast cultures: evidence for transcriptional control. Endocrinology 133: 1020–1028, 1993.[Abstract]
  8. Bodine SC, Latres E, Baumhueter S, Lai VK, Nunez L, Clarke BA, Poueymirou WT, Panaro FJ, Na E, Dharmarajan K, Pan ZQ, Valenzuela DM, DeChiara TM, Stitt TN, Yancopoulos GD, Glass DJ. Identification of ubiquitin ligases required for skeletal muscle atrophy. Science 294: 1704–1708, 2001.[Abstract/Free Full Text]
  9. Bui T, Kuo C, Rotwein P, Straus DS. Prostaglandin A2 specifically represses insulin-like growth factor-I gene expression in C6 rat glioma cells. Endocrinology 138: 985–993, 1997.[Abstract/Free Full Text]
  10. Bui T, Straus DS. Effects of cyclopentenone prostaglandins and related compounds on insulin-like growth factor-I and Waf1 gene expression. Biochim Biophys Acta 1397: 31–42, 1998.[Medline]
  11. Cai D, Frantz JD, Tawa NE Jr, Melendez PA, OHBC, Lidov HG, Hasselgren PO, Frontera WR, Lee J, Glass DJ, Shoelson SE. IKKbeta/NF-kappaB activation causes severe muscle wasting in mice. Cell 119: 285–298, 2004.[CrossRef][ISI][Medline]
  12. Canonico PL, Speciale C, Sortino MA, Cronin MJ, MacLeod RM, Scapagnini U. Growth hormone releasing factor (GRF) increases free arachidonate levels in the pituitary: a role for lipoxygenase products. Life Sci 38: 267–272, 1986.[CrossRef][ISI][Medline]
  13. Chillingworth NL, Morham SG, Donaldson LF. Sex differences in inflammation and inflammatory pain in cyclooxygenase-deficient mice. Am J Physiol Regul Integr Comp Physiol 291: R327–R334, 2006.[Abstract/Free Full Text]
  14. Dalla Libera L, Ravara B, Volterrani M, Gobbo V, Della Barbera M, Angelini A, Danieli Betto D, Germinario E, Vescovo G. Beneficial effects of GH/IGF-1 on skeletal muscle atrophy and function in experimental heart failure. Am J Physiol Cell Physiol 286: C138–C144, 2004.[Abstract/Free Full Text]
  15. Davis TW, Zweifel BS, O'Neal JM, Heuvelman DM, Abegg AL, Hendrich TO, Masferrer JL. Inhibition of cyclooxygenase-2 by celecoxib reverses tumor-induced wasting. J Pharmacol Exp Ther 308: 929–934, 2004.[Abstract/Free Full Text]
  16. Dehoux M, Van Beneden R, Pasko N, Lause P, Verniers J, Underwood L, Ketelslegers JM, Thissen JP. Role of the insulin-like growth factor I decline in the induction of atrogin-1/MAFbx during fasting and diabetes. Endocrinology 145: 4806–4812, 2004.[Abstract/Free Full Text]
  17. Egan CG, Lockhart JC, Ferrell WR. Pathophysiology of vascular dysfunction in a rat model of chronic joint inflammation. J Physiol 557: 635–643, 2004.[Abstract/Free Full Text]
  18. Fafeur V, Tiberghien C, Haour F, Dray F. Control of growth hormone release by growth hormone-releasing factor and prostaglandin E2 in a system of perfused rat anterior pituitary cells. Reprod Nutr Dev 28: 229–231, 1988.[ISI][Medline]
  19. Ganey PE, Barton YW, Kinser S, Sneed RA, Barton CC, Roth RA. Involvement of cyclooxygenase-2 in the potentiation of allyl alcohol-induced liver injury by bacterial lipopolysaccharide. Toxicol Appl Pharmacol 174: 113–121, 2001.[CrossRef][ISI][Medline]
  20. Granado M, Priego T, Martín AI, Villanúa MA, López-Calderón A. Ghrelin receptor agonist GHRP-2 prevents arthritis-induced increase in E3 ubiquitin-ligating enzymes MuRF1 and MAFbx gene expression in skeletal muscle. Am J Physiol Endocrinol Metab 289: E1007–E1014, 2005.[Abstract/Free Full Text]
  21. Granado M, Priego T, Martín AI, Vara E, López-Calderón A, Villanúa MA. Anti-tumor necrosis factor agent PEG-sTNFRI improves the growth hormone/insulin-like growth factor-I system in adjuvant-induced arthritic rats. Eur J Pharmacol 536: 204–210, 2006.[CrossRef][ISI][Medline]
  22. Granado M, Martín AI, Priego T, López-Calderón A, Villanúa MA. TNF blockade did not prevent the increase of muscular MuRF-1 and MAFbx in arthritic rats. J Endocrinol 191: 319–326, 2006.[Abstract/Free Full Text]
  23. Graves E, Ramsay E, McCarthy DO. Inhibitors of COX activity preserve muscle mass in mice bearing the Lewis lung carcinoma, but not the B16 melanoma. Res Nurs Health 29: 87–97, 2006.[CrossRef][ISI][Medline]
  24. Heemskerk VH, Daemen MA, Buurman WA. Insulin-like growth factor-1 (IGF-1) and growth hormone (GH) in immunity and inflammation. Cytokine Growth Factor Rev 10: 5–14, 1999.[CrossRef][ISI][Medline]
  25. Hitt A, Graves E, McCarthy DO. Indomethacin preserves muscle mass and reduces levels of E3 ligases and TNF receptor type 1 in the gastrocnemius muscle of tumor-bearing mice. Res Nurs Health 28: 56–66, 2006.[CrossRef][ISI]
  26. Hunter RB, Stevenson E, Koncarevic A, Mitchell-Felton H, Essig DA, Kandarian SC. Activation of an alternative NF-kappaB pathway in skeletal muscle during disuse atrophy. FASEB J 16: 529–38, 2002.[Abstract/Free Full Text]
  27. Hussey HJ, Tisdale MJ. Effect of the specific cyclooxygenase-2 inhibitor meloxicam on tumour growth and cachexia in a murine model. Int J Cancer 87: 95–100, 2000.[CrossRef][ISI][Medline]
  28. Ibáñez de Cáceres I, Villanúa MA, Soto L, Martín I, López-Calderón A. IGF-I and IGF-I-binding proteins in rats with adjuvant-induced arthritis given recombinant human growth hormone. J Endocrinol 165: 537–544, 2000.[Abstract]
  29. Johnson PM, Vogt SK, Burney MW, Muglia LJ. COX-2 inhibition attenuates anorexia during systemic inflammation without impairing cytokine production. Am J Physiol Endocrinol Metab 282: E650–E656, 2002.[Abstract/Free Full Text]
  30. Joussen AM, Poulaki V, Mitsiades N, Kirchhof B, Koizumi K, Dohmen S, Adamis AP. Nonsteroidal anti-inflammatory drugs prevent early diabetic retinopathy via TNF-alpha suppression. FASEB J 16: 438–440, 2002.[Free Full Text]
  31. Kandarian SC, Jackman RW. Intracellular signaling during skeletal muscle atrophy. Muscle Nerve 33: 155–165, 2006.[CrossRef][ISI][Medline]
  32. Konturek PC, Rembiasz K, Burnat G, Konturek SJ, Tusinela M, Bielanski W, Rehfeld J, Karcz D, Hahn E. Effects of cyclooxygenase-2 inhibition on serum and tumor gastrins and expression of apoptosis-related proteins in colorectal cancer. Dig Dis Sci 51: 779–787, 2006.[CrossRef][ISI][Medline]
  33. Korotkova M, Westman M, Gheorghe KR, af Klint E, Trollmo C, Ulfgren AK, Klareskog L, Jakobsson PJ. Effects of antirheumatic treatments on the prostaglandin E2 biosynthetic pathway. Arthritis Rheum 52: 3439–3447, 2005.[CrossRef][ISI][Medline]
  34. Lecker SH, Jagoe RT, Gilbert A, Gomes M, Baracos V, Bailey J, Price SR, Mitch WE, Goldberg AL. Multiple types of skeletal muscle atrophy involve a common program of changes in gene expression. FASEB J 18: 39–51, 2004.[Abstract/Free Full Text]
  35. Li YP, Chen Y, John J, Moylan J, Jin B, Mann DL, Reid MB. TNF-alpha acts via p38 MAPK to stimulate expression of the ubiquitin ligase atrogin1/MAFbx in skeletal muscle. FASEB J 19: 362–370, 2005.[Abstract/Free Full Text]
  36. Livak KJ, Schmittgen TD. Analysis of relative gene expression data using real-time quantitative PCR and the 2[-Delta Delta C(T)] method. Methods Enzymol 25: 402–408, 2001.[CrossRef]
  37. López-Calderón A, Soto L, Martín AI. Chronic inflammation inhibits GH secretion and alters the serum insulin-like growth factor system in rats. Life Sci 65: 2049–2060, 1999.[CrossRef][ISI][Medline]
  38. López-Calderón A, Ibañez de Cáceres I, Soto L, Priego T, Martín AI, Villanúa MA. The decrease in hepatic IGF-I gene expression in arthritic rats is not associated with modifications in hepatic GH receptor mRNA. Eur J Endocrinol 144: 529–534, 2001.[Abstract]
  39. Lundholm K, Daneryd P, Korner U, Hyltander A, Bosaeus I. Evidence that long-term COX-treatment improves energy homeostasis and body composition in cancer patients with progressive cachexia. Int J Oncol 24: 505–512, 2004.[ISI][Medline]
  40. McCarthy TL, Casinghino S, Mittanck DW, Ji CH, Centrella M, Rotwein P. Promoter-dependent and -independent activation of insulin-like gr owth factor binding protein-5 gene expression by prostaglandin E2 in primary rat osteoblasts. J Biol Chem 271: 6666–6671, 1996.[Abstract/Free Full Text]
  41. Mets T, Bautmans I, Njemini R, Lambert M, Demanet C. The influence of celecoxib on muscle fatigue resistance and mobility in elderly patients with inflammation. Am J Geriatr Pharmacother 2: 230–238, 2004.[CrossRef][Medline]
  42. Ogimoto K, Harris MK Jr, Wisse BE. MyD88 is a key mediator of anorexia, but not weight loss, induced by lipopolysaccharide (LPS) and interleukin-1beta (IL1beta). Endocrinology 147: 4445–4453, 2006.[Abstract/Free Full Text]
  43. Ojeda SR, Jameson HE, McCann SM. Prostaglandin E2 (PGE2)-induced growth hormone (GH) release: effect of intrahypothalamic and intrapituitary implants. Prostaglandins 13: 943–955, 1977.[CrossRef][ISI][Medline]
  44. Pampusch MS, Xi G, Kamanga-Sollo E, Loseth KJ, Hathaway MR, Dayton WR, White ME. Production of recombinant porcine IGF-binding protein-5 and its effect on proliferation of porcine embryonic myoblast cultures in the presence and absence of IGF-I and Long-R3-IGF-I. J Endocrinol 185: 197–206, 2005.[Abstract/Free Full Text]
  45. Pash JM, Delany AM, Adamo ML, Roberts CT Jr, LeRoith D, Canalis E. Regulation of insulin-like growth factor I transcription by prostaglandin E2 in osteoblast cells. Endocrinology 136: 33–38, 1995.[Abstract]
  46. Pash JM, Canalis E. Transcriptional regulation of insulin-like growth factor-binding protein-5 by prostaglandin E2 in osteoblast cells. Endocrinology 137: 2375–2382, 1996.[Abstract]
  47. Peinnequin A, Mouret C, Birot O, Alonso A, Mathieu J, Clarencon D, Agay D, Chancerelle E, Multon Y. Rat pro-inflammatory cytokine and cytokine related mRNA quantification by real-time polymerase chain reaction using SYBR green. BMC Immunology 5: 3–10, 2004.[CrossRef][Medline]
  48. Penner CG, Gang G, Wray C, Fischer JE, Hasselgren PO. The transcription factors NF-kappab and AP-1 are differentially regulated in skeletal muscle during sepsis. Biochem Biophys Res Commun 281: 1331–1336, 2001.[CrossRef][ISI][Medline]
  49. Philippe L, Gegout-Pottie P, Guingamp C, Bordji K, Terlain B, Netter P, Gillet P. Relations between functional, inflammatory, and degenerative parameters during adjuvant arthritis in rats. Am J Physiol Regul Integr Comp Physiol 273: R1550–R1556, 1997.[Abstract/Free Full Text]
  50. Rabuel C, Renaud E, Brealey D, Ratajczak P, Damy T, Alves A, Habib A, Singer M, Payen D, Mebazaa A. Human septic myopathy: induction of cyclooxygenase, heme oxygenase and activation of the ubiquitin proteolytic pathway. Anesthesiology 101: 583–590, 2004.[CrossRef][ISI][Medline]
  51. Ross JA, Fearon KC. Eicosanoid-dependent cancer cachexia and wasting. Curr Opin Clin Nutr Metab Care 5: 241–248, 2002.[CrossRef][ISI][Medline]
  52. Roubenoff R, Roubenoff RA, Cannon JG, Kehayias JJ, Zhuang H, Dawson-Hughes Dinarello CA B, Rosenberg IH. Rheumatoid cachexia: cytokine-driven hypermetabolism and loss of lean body mass in chronic inflammation. J Clin Invest 93: 2379–2386, 1994.[ISI][Medline]
  53. Roudbaraki MM, Drouhault R, Bacquart T, Vacher P. Arachidonic acid-induced hormone release in somatotropes: involvement of calcium. Neuroendocrinology 63: 244–256, 1996.[ISI][Medline]
  54. Roughan JV, Flecknell PA. Evaluation of a short duration behaviour-based post-operative pain scoring system in rats. Eur J Pain 7: 397–406, 2003.[CrossRef][ISI][Medline]
  55. Russell ST, Wyke SM, Tisdale MJ. Mechanism of induction of muscle protein degradation by angiotensin II. Cell Signal 18: 1087–1096, 2006.[CrossRef][ISI][Medline]
  56. Sakamoto K, Yano T, Kobayashi T, Hagino A, Aso H, Obara Y. Growth hormone suppresses the expression of IGFBP-5, and promotes the IGF-I-induced phosphorylation of Akt in bovine mammary epithelial cells. Domest Anim Endocrinol 32: 260–272, 2006.[ISI][Medline]
  57. Salih DA, Tripathi G, Holding C, Szestak TA, Gonzalez MI, Carter EJ, Cobb LJ, Eisemann JE, Pell JM. Insulin-like growth factor-binding protein 5 (Igfbp5) compromises survival, growth, muscle development, and fertility in mice. Proc Natl Acad Sci USA 101: 4314–4319, 2004.[Abstract/Free Full Text]
  58. Shelton DL, Zeller J, Ho WH, Pons J, Rosenthal A. Nerve growth factor mediates hyperalgesia and cachexia in auto-immune arthritis. Pain 116: 8–16, 2005.[CrossRef][ISI][Medline]
  59. Soto L, Martín AI, Vara E, López-Calderón A. Cyclosporin a treatment is able to revert the decrease in circulating GH and IGF-I and the increase in IGFBPs induced by adjuvant arthritis. Horm Metab Res 33: 590–595, 2001.[CrossRef][ISI][Medline]
  60. Tisdale MJ. Protein loss in cancer cachexia. Science 289: 2293–2294, 2000.[Free Full Text]
  61. Walsmith J, Abad L, Kehayias J, Roubenoff R. Tumor necrosis factor-alpha production is associated with less body cell mass in women with rheumatoid arthritis. J Rheumatol 31: 23–29, 2004.[ISI][Medline]
  62. Wang W, Lonnroth C, Svanberg E, Lundholm K. Cytokine and cyclooxygenase-2 protein in brain areas of tumor-bearing mice with prostanoid-related anorexia. Cancer Res 61: 4707–4715, 2001.[Abstract/Free Full Text]
  63. Wray CJ, Mammen JM, Hershko DD, Hasselgren PO. Sepsis upregulates the gene expression of multiple ubiquitin ligases in skeletal muscle. Int J Biochem Cell Biol 35: 698–705, 2003.[CrossRef][ISI][Medline]
  64. Yamamoto Y, Yin MJ, Lin KM, Gaynor RB. Sulindac inhibits activation of the NF-kappaB pathway. J Biol Chem 274: 27307–27314, 1999.[Abstract/Free Full Text]




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