|
|
||||||||
Departments of 4Cellular and Integrative Physiology, 1Surgery, and 3Urology, and the 2Indiana Center for Vascular Biology and Medicine, Indiana University School of Medicine, Indianapolis, Indiana
Submitted 23 June 2004 ; accepted in final form 10 September 2004
| ABSTRACT |
|---|
|
|
|---|
, IL-1
, and IL-6 (RT-PCR, ELISA); IL-1
and IL-10 mRNA (RT-PCR); and activation of p38 MAPK (Western blot). All indexes of postischemic myocardial function [left ventricular developed pressure, left ventricular end-diastolic pressure, and maximal positive (+dP/dt) and negative (dP/dt) values of the first derivative of pressure] were significantly improved in females compared with males. Compared with males, females had decreased myocardial TNF-
, IL-1
, and IL-6 (mRNA, protein) and decreased activation of p38 MAPK pathway. These data demonstrate that hearts from age-matched adult females are relatively protected against I/R injury, possibly due to a diminished inflammatory response. myocardial infarction; tumor necrosis factor; signal transduction
, IL-1
, and IL-6, in response to I/R injury (12, 2126, 33). These inflammatory mediators contribute to myocardial functional depression and cardiomyocyte apoptosis. Observations of decreased mortality from sepsis in females have been correlated with decreased inflammatory cytokines (2, 17, 28). Furthermore, Horton et al. (14) have demonstrated improved myocardial function in females after burn injury. A critical component of the signal transduction pathway leading to myocardial inflammation is the activation of p38 mitogen-activated protein kinase (MAPK) (4, 30, 32, 35). Increased activation of myocardial p38 MAPK occurs after I/R injury (9, 19). In this regard, inhibition of p38 MAPK attenuates I/R-induced myocardial injury (29). In other systems, it appears that sex differences exist in the p38 MAPK signaling pathway. Angele et al. (1) demonstrated increased activated p38 MAPK in splenic and peritoneal macrophages in males after trauma-hemorrhage injury, whereas activated p38 MAPK was decreased in injured females compared with uninjured control groups.
We hypothesized that sex may have an important role in the acute injury response of otherwise normal hearts. Therefore, the purposes of this study were to investigate potential sex differences in 1) functional recovery of otherwise normal myocardium, 2) proinflammatory cytokine (IL-1, IL-6, TNF-
) production, and 3) p38 MAPK activation after I/R.
| METHODS |
|---|
|
|
|---|
Experimental groups. Rats were divided into four experimental groups: male stability control (n = 6), female stability control (n = 5), male I/R (n = 14), and female I/R (n = 13). Each I/R experiment lasted a total of 82 min, beginning with a mandatory equilibration period (15 min), followed by a standard I/R insult (27 min of global ischemia at 37°C and 40 min of reperfusion). Stability control hearts underwent 82 min of oxygenated perfusion without any periods of ischemia to ensure preparation stability.
I/R protocols.
Rats were anesthetized and heparinized with an intraperitoneal injection of pentobarbital sodium (Nembutal, 60 mg/kg) and heparin sodium (500 U; SoloPak Laboratories, Elk Grove Village, IL). After sternotomy, hearts were rapidly excised into 4°C Krebs-Henseleit solution. The aorta was cannulated, and the heart was perfused (37°C) with oxygenated buffer within 45 s. Hearts were perfused in the isolated, isovolumetric Langendorff mode (70 mmHg) with modified Krebs-Henseleit solution (in mM: 5.5 glucose, 119 NaCl, 1.2 CaCl2, 4.7 KCl, 25 NaHCO3, 1.18 KHPO4, 1.17 MgSO4) and saturated with 95% O2-5% CO2 to achieve a PO2 of 440460 mmHg, a PCO2 of 3941 mmHg, and a pH of 7.397.41 (ABL-4 blood gas analyzer; Radiometer, Copenhagen, Denmark). The perfusion buffer was continuously filtered through a 0.45-µm microfilter to remove particular contaminants. A pulmonary arteriotomy and left atrial resection were performed before insertion of a water-filled latex balloon through the left atrium into the left ventricle. The preload volume (balloon volume) was held constant during the entire experiment to allow continuous recording of the left ventricular developed pressure (LVDP). The balloon was adjusted to a mean left ventricular end-diastolic pressure (LVEDP) of 8 mmHg (range 610 mmHg = both the peak and the plateau of the LVEDP-LVDP curve) during the initial equilibration. Pacing wires were fixed to the right atrium, and pulmonary outflow tract and hearts were paced at
6 Hz, 3 V, and 2 ms (350 beats/min) throughout perfusion. Data were continuously recorded using a computerized MacLab 8 preamplifier/digitizer (AD Instruments, Milford, MA) and an Apple Quadra 800 computer (Apple Computers, Cupertino, CA). A three-way stopcock above the aortic root was used to create global ischemia, during which the heart was placed in a 37°C degassed organ bath. Coronary flow was measured by collecting pulmonary artery effluent. The maximal positive and negative values of the first derivative of pressure (+dP/dt and dP/dt, respectively) were calculated using PowerLab software.
RT-PCR.
Total RNA was extracted from each heart by use of RNA STAT-60 (Tel-Test, Friendswood, TX). A quantity of 0.5 µg of total RNA was subjected to cDNA synthesis using a cloned AMV first-strand cDNA synthesis kit (Invitrogen Life Technologies, Carlsbad, CA). cDNA from each sample was used for multiple PCR for TNF-
, IL-1
, IL-1
, and IL-6, using message screen rat inflammatory cytokine multiplex PCR kits (Biosource, Camarillo, CA), and for IL-10 using rat dual-PCR kit (Maxim Biotech, South San Francisco, CA), respectively. One negative control used deionized distilled water (ddH2O) instead of the RNA sample, and a second negative control used ddH2O instead of reverse transcriptase to exclude the presence of genomic contaminants. Positive controls were included in the kit to verify appropriate expression of respective markers. PCR products were separated by electrophoresis on 2% agarose gel stained with ethidium bromide. Representative gel photographs are shown, and densitometry was performed to assess relative quantity and represented as a ratio to GAPDH.
Myocardial TNF-
, IL-1, and IL-6 in the coronary effluent.
Coronary effluent was collected every 10 min during reperfusion. Myocardial TNF-
, IL-1
, and IL-6 in the coronary effluent were determined by ELISA (R&D Systems, Minneapolis, MN). ELISA was performed by adding 50 µl of each sample (tested in duplicate) to wells in a 96-well plate of a commercially available ELISA kit according to the manufacturer's instructions.
Western blotting.
Western blot analysis was performed on rat hearts, followed by I/R to measure the p38 MAP kinase pathway. Heart tissue was homogenized in cold buffer containing 20 mM Tris (pH 7.5), 150 mM NaCl, 1 mM EDTA, 1 mM EGTA, 1% Triton X-100, 2.5 mM sodium pyrophosphate, 1 mM
-glycerophosphate, 1 mM sodium orthovanadate, 1 µg/ml leupeptin, and 1 mM PMSF and centrifuged at 12,000 rpm for 5 min. The protein extracts (30 µg/lane) were eletrophoresed on a 12% Tris·HCl gel (Bio-Rad, Hercules, CA) and transferred to a nitrocellulose membrane, which was stained by Naphthol Blue-Black to confirm equal protein loading. The membranes were incubated in 5% dry milk for 1 h and then incubated with the following primary antibodies: p38 MAP kinase antibody and phospho-p38 MAP kinase (Thr180/Tyr182) antibody (Cell Signaling Technology, Beverly, MA), followed by incubation with horseradish peroxidase-conjugated goat anti-rabbit IgG secondary antibody and detection using SuperSignal West Pico Stable Peroxide Solution (Pierce, Rockford, IL).
Presentation of data and statistical analysis. All reported values are means ± SE. Data were compared at the corresponding time points between groups with the use of two-way ANOVA with post hoc Bonferroni test or Student's t-test. A two-tailed probability value of <0.05 was considered statistically significant.
| RESULTS |
|---|
|
|
|---|
|
, IL-1
, IL-1
, IL-6, and IL-10 to investigate whether sex differences exist in the response of inflammation to I/R injury. I/R resulted in TNF-
, IL-1
, IL-1
, and IL-6 mRNA expression (baseline: TNF-
, under detection; IL-1
, 0.183 ± 0.084; IL-1
, 0.063 ± 0.024; IL-6, 0.178 ± 0.093) (Fig. 2) and induced TNF-
, IL-1
, and IL-6 protein production (Fig. 3). However, females had significantly less myocardial TNF-
, IL-1
, IL-1
, and IL-6 (Figs. 2B and 3). I/R upregulated myocardial IL-10, which acts as a negative regulator of inflammatory cytokine synthesis. IL-10 mRNA expression (Fig. 4) was increased in both males and females after I/R injury. However, there were no differences between males and females in I/R-induced myocardial IL-10 mRNA levels.
|
|
|
|
| DISCUSSION |
|---|
|
|
|---|
Acute injury in the form of ischemia, endotoxemia, or burn trauma results in myocardial functional suppression, in part via the local production of inflammatory mediators such as TNF-
, IL-1
, and IL-6. I/R injury induces the local production of TNF-
, IL-1
, and IL-6 (13, 21, 23, 33). Finkel et al. (10) reported that TNF-
or IL-1 induces depression of myocardial function in an ex vivo crystalloid-superfused papillary muscle preparation. Indeed, a locally produced inflammatory mediator such as TNF-
, IL-1, or IL-6 may be an important contributor to postischemic myocardial dysfunction, apoptosis, and/or hypertrophy. Others have reported the existence of significant sex differences in immunological response after trauma-hemorrhage or other acute injury (1, 2, 15, 16). In our study, female hearts, which had better functional recovery after acute ischemia, expressed less myocardial TNF-
, IL-1
, IL-1
, and IL-6 (mRNA and protein) than male hearts subjected to the same I/R insult.
I/R induced an increase in myocardial IL-10 mRNA in both males and females, but there were no sex differences in myocardial IL-10 mRNA. IL-10 is a cytokine synthesis inhibitory factor that inhibits synthesis of TNF-
, IL-1, and IL-6 (7, 8, 11, 27). Myocardial TNF-
and IL-6 may induce the expression of IL-10, which may have a counterregulatory role in proinflammatory cytokine production after I/R. However, it does not appear that IL-10 is responsible for the decreased synthesis of proinflammatory cytokines observed in females.
Activation of myocardial p38 MAPK after I/R injury in the heart has been observed in animal and human studies (9, 19, 32). Inhibition of p38 MAPK activation results in improved myocardial function after I/R injury (18, 29). p38 MAPK may mediate myocardial dysfunction through the activation of immune cells and apoptosis. Indeed, activation of p38 MAPK is involved in mediating proinflammatory cytokine production (32, 35). Activation of p38 MAPK is required for TNF-
and IL-1 production in cardiomyocytes (30, 32). Furthermore, p38 MAPK inhibition reduces IL-6 production in cultured myocytes and vascular smooth muscle cells (4). Our observation of decreased p38 MAPK activation in females after I/R correlates with their decreased myocardial cytokine production.
Population-based studies on sex differences in mortality after acute myocardial infarction have yielded conflicting results. Some studies reported increased mortality in younger women compared with men (5, 31, 34), whereas other studies demonstrated increased mortality in older women compared with age-matched men (6). These effects are likely multifactorial, with involvement of comorbidities such as diabetes mellitus affecting overall mortality. Whereas these clinical studies examined patients with coronary artery disease, the current study examines acute myocardial injury in healthy cardiac tissue. This allows us to investigate the effect of estrogen on myocardial injury without confounding factors such as preexisting coronary artery disease, age, and associated comorbidities.
| GRANTS |
|---|
|
|
|---|
| FOOTNOTES |
|---|
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.
| REFERENCES |
|---|
|
|
|---|
. J Immunol 157: 1220, 1996.[Abstract]
, initiating the cytokine cascade in experimental canine myocardial ischemia/reperfusion. Circulation 98: 699710, 1998.
production: anti-inflammatory implications for preconditioning and transplantation. Immunology 92: 472477, 1997.[CrossRef][ISI][Medline]
production. Potential ultimate effector mechanism of preconditioning. Circulation 98, Suppl 19: II214II219, 1998.
expression following acute global ischemia in vivo. J Mol Cell Cardiol 30: 16831689, 1998.[CrossRef][ISI][Medline]
and IL-1
production. Shock 9: 256260, 1998.[ISI][Medline]
B activation, tumor necrosis factor-
production, and subsequent ischemia-induced apoptosis. Circ Res 92: 293299, 2003.
expression and improves myocardial function and survival in endotoxemia. Cardiovasc Res 59: 893900, 2003.This article has been cited by other articles:
![]() |
M. P. Hutchens, J. Dunlap, P. D. Hurn, and P. O. Jarnberg Renal Ischemia: Does Sex Matter? Anesth. Analg., July 1, 2008; 107(1): 239 - 249. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. R. Bell, E. R. Porrello, C. E. Huggins, S. B. Harrap, and L. M. D. Delbridge The intrinsic resistance of female hearts to an ischemic insult is abrogated in primary cardiac hypertrophy Am J Physiol Heart Circ Physiol, April 1, 2008; 294(4): H1514 - H1522. [Abstract] [Full Text] [PDF] |
||||
![]() |
P. D. Metcalfe, J. A. Leslie, M. T. Campbell, D. R. Meldrum, K. L. Hile, and K. K. Meldrum Testosterone exacerbates obstructive renal injury by stimulating TNF-{alpha} production and increasing proapoptotic and profibrotic signaling Am J Physiol Endocrinol Metab, February 1, 2008; 294(2): E435 - E443. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. A. Markel, P. R. Crisostomo, M. Wang, C. M. Herring, and D. R. Meldrum Activation of individual tumor necrosis factor receptors differentially affects stem cell growth factor and cytokine production Am J Physiol Gastrointest Liver Physiol, October 1, 2007; 293(4): G657 - G662. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Wang, W. Zhang, P. Crisostomo, T. Markel, K. K. Meldrum, X. Y. Fu, and D. R. Meldrum Endothelial STAT3 plays a critical role in generalized myocardial proinflammatory and proapoptotic signaling Am J Physiol Heart Circ Physiol, October 1, 2007; 293(4): H2101 - H2108. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Wang, W. Zhang, P. Crisostomo, T. Markel, K. K. Meldrum, X. Y. Fu, and D. R. Meldrum Sex differences in endothelial STAT3 mediate sex differences in myocardial inflammation Am J Physiol Endocrinol Metab, September 1, 2007; 293(3): E872 - E877. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. A. Markel, P. R. Crisostomo, M. Wang, C. M. Herring, T. Lahm, K. K. Meldrum, K. D. Lillemoe, F. J. Rescorla, and D. R. Meldrum Iron chelation acutely stimulates fetal human intestinal cell production of IL-6 and VEGF while decreasing HGF: the roles of p38, ERK, and JNK MAPK signaling Am J Physiol Gastrointest Liver Physiol, April 1, 2007; 292(4): G958 - G963. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Wang, T. Markel, P. Crisostomo, C. Herring, K. K. Meldrum, K. D. Lillemoe, and D. R. Meldrum Deficiency of TNFR1 protects myocardium through SOCS3 and IL-6 but not p38 MAPK or IL-1beta Am J Physiol Heart Circ Physiol, April 1, 2007; 292(4): H1694 - H1699. [Abstract] [Full Text] [PDF] |
||||
![]() |
P. K. Battiprolu, K. J. Harmon, and K. J. Rodnick Sex differences in energy metabolism and performance of teleost cardiac tissue Am J Physiol Regulatory Integrative Comp Physiol, February 1, 2007; 292(2): R827 - R836. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Wang, P. Crisostomo, G. M. Wairiuko, and D. R. Meldrum Estrogen receptor-{alpha} mediates acute myocardial protection in females Am J Physiol Heart Circ Physiol, June 1, 2006; 290(6): H2204 - H2209. [Abstract] [Full Text] [PDF] |
||||
![]() |
P. R. Crisostomo, M. Wang, G. M. Wairiuko, E. D. Morrell, and D. R. Meldrum Brief exposure to exogenous testosterone increases death signaling and adversely affects myocardial function after ischemia Am J Physiol Regulatory Integrative Comp Physiol, May 1, 2006; 290(5): R1168 - R1174. [Abstract] [Full Text] [PDF] |
||||
![]() |
D. R. Meldrum Estrogen increases protective proteins following trauma and hemorrhage Am J Physiol Regulatory Integrative Comp Physiol, March 1, 2006; 290(3): R809 - R811. [Full Text] [PDF] |
||||
![]() |
J. A. Moolman Unravelling the cardioprotective mechanism of action of estrogens Cardiovasc Res, March 1, 2006; 69(4): 777 - 780. [Full Text] [PDF] |
||||
![]() |
J. M. Pitcher, M. Wang, B. M. Tsai, A. Kher, N. T. Nelson, and D. R. Meldrum Endogenous estrogen mediates a higher threshold for endotoxin-induced myocardial protection in females Am J Physiol Regulatory Integrative Comp Physiol, January 1, 2006; 290(1): R27 - R33. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Wang, B. M. Tsai, M. W. Turrentine, Y. Mahomed, J. W. Brown, and D. R. Meldrum p38 Mitogen Activated Protein Kinase Mediates Both Death Signaling and Functional Depression in the Heart Ann. Thorac. Surg., December 1, 2005; 80(6): 2235 - 2241. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. Kher, K. K. Meldrum, M. Wang, B. M. Tsai, J. M. Pitcher, and D. R. Meldrum Cellular and molecular mechanisms of sex differences in renal ischemia-reperfusion injury Cardiovasc Res, September 1, 2005; 67(4): 594 - 603. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. Maric Sex Differences in Cardiovascular Disease and Hypertension: Involvement of the Renin-Angiotensin System Hypertension, September 1, 2005; 46(3): 475 - 476. [Full Text] [PDF] |
||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |