The role of C-reactive protein in ischemia/reperfusion injury and preconditioning in a rat model of myocardial infarction

For the first time the involvement of C-Reactive protein (CRP) in early (acute) and delayed ischemic (IPC) and pharmacological (chemical) preconditioning (CPC) in an in vivo model of rat myocardial infarction was presented. Acute IPC was produced by three 5 minute occlusion (ischemia) periods interspersed with 5 minute reperfusion, followed by 30 minute occlusion of the left coronary artery and 2 hour reperfusion injury. Acute CPC was produced by a k-opioid receptor agonist U50488H (5 mg/kg) applied i.v. 15 minutes before 30 minute ischemia/ 2 hour reperfusion. Delayed preconditioning was produced by 30 minute ischemia/ 2 hour reperfusion, induced 24 hour after either ischemic or pharmacological preconditioning. The myocardial ischemia/reperfusion injury was evaluated on the basis of total and cardiac creatine kinase isoenzyme activity, functional recovery of the heart (ECG), infarct size (% IS/RA) and mortality at the end of the experiments. The results obtained showed that: k-opioid receptor agonist U50488H mimics both the acute and delayed IPC in the above experimental protocol; Both acute IPC and most probably CPC act by opening of K(ATP) channels (the effects were blocked by nonspecific ATP-sensitive K channel blocker glybenclamide), and via activation of protein kinase C (a selective protein kinase C inhibitor chelerythrine blocked the efects); C-reactive protein (CRP) was significantly elevated by 54% in non-preconditioned acute ischemia/reperfusion injury. The elevation was more pronounced (82% increase) 24 hour after non-preconditioned ischemia/reperfusion injury. It reflected very well the increase in cardiac isoenzymes, infarct size and mortality of the rats, and can be used as a marker of the severity of myocardial injury in this model; The increase of CRP was prevented by both IPC and CPC in early, and especially in late preconditioning. This confirms the involvement of CRP as a marker in cardiac ischemic/reperfusion injury. It was concluded that in addition to the established involvement of adenosine, bradykinin, opioid and other receptors, a suppression of myocardial CRP/complement production might be involved in the biological mechanism of preconditioning. This could be a promising perspective in clinical interventions against ischemia/reperfusion injuries of the heart.     

缺血后功能低下大鼠心肌钙与水含量的变化及高渗甘露醇的影响

缺血后心室功能减低(myocardial stunning)的发生机制迄今尚不明了。本实验以 Lang-cndorff 法在离体灌流的大鼠心脏,研究了全心缺血20min 及再灌注40min 后心肌 Ca~(2+)、Na~+K~+、Mg~(2+)及 H_2O 含量的变化,以及高渗甘露醇对缺血后功能低下心肌的影响。实验发现:(1)缺血/再灌注后心肌组织中 Ca~(2+),H_2O 的含量与非缺血组相比分别增加42%(P<0.01)及7.6%(P0.05)。(2)于再灌注同时给予12%高渗甘露醇可明显改善缺血后心室功能:再灌注40min 时,心率-左室压乘积恢复达缺血前的85%,而不给甘露醇仅恢复66.3%(p<0.01);高渗甘露醇同时消除了缺血后功能低下心肌中 Ca~(2+)超负荷与心肌水肿,此现象提示缺血/再灌注引起的肌膜非特异性通透性改变,很可能是钙进入细胞内的路径之一。本研究结果表明,心肌 Ca~(2+)超负荷及轻度心肌水肿参与了缺血后心室功能低下,高渗甘露醇在离体大鼠心脏可明显改善缺血后功能低下心肌的功能,此作用至少部分是由于其具有减低心肌钙与水含量的效应。     

Cardiac ischemia and reperfusion in spontaneously diabetic rats with and without application of EGb 761: I. cardiomyocytes

Diabetic cardiomyopathy is known to result in increased mortality after ischemic events. Permanently increased oxidative stress with formation of oxygen-free radicals plays a key role in the development of specific heart muscle disease. Associated lesions include structural alterations to cardiomyocytes. Antioxidative treatment in addition to the usual insulin substitution would seem sensible in preventing or delaying long-term diabetic complications and protecting the myocardium against acute ischemic events. We investigated the effects of radical scavenger Ginkgo biloba extract EGb 761 against diabetes-induced damage to cardiomyocytes and additional ischemia/reperfusion injury in spontaneously diabetic BioBreeding/Ottawa Karlsburg (BB/OK) rats, as a model of diabetic myocardium infarction. Morphological and morphometric parameters of heart muscles were analyzed by light and electron-microscopic techniques. We used immunohistochemistry to evaluate parameters of oxidative stress (superoxide dismutase [SOD]) and inducible nitric oxide synthase (iNOS) protein expression. Our results indicated that A) Diabetic myocardium appears more vulnerable to ischemia/reperfusion damage concerning ultrastructure of cardiomyocytes (sarcomeres, vacuoles, mitochondria), expression of antioxidative enzymes (CuZnSOD, MnSOD), and iNOS than normal myocardium; B) Pre-treatment of diabetic myocardium with EGb and additional ischemia/reperfusion leads to a relative improvement in myocardial ultrastructure compared to unprotected myocardium. In summary, EGb appears to be promising as an adjuvant therapeutic drug in diabetics with respect to ischemic myocardium injury. It may contribute to the prevention of late diabetic complications in diabetic cardiomyopathy.     

Reactive oxygen species may cause myocardial reperfusion injury

The pathogenic mechanisms responsible for heart damage following temporary coronary artery occlusion are unknown. Some damage may be mediated by a normal cellular enzyme, xanthine dehydrogenase, which converts to xanthine oxidase during myocardial ischemia. Reperfusion, with restoration of oxygen supply, may then lead to formation of superoxide by xanthine oxidase, possibly initiating a cascade of oxidative events. In support of this, reperfusion of transiently ischemic canine myocardium leads to a rapid loss of cellular glutathione and a decrease in catalase activity, both indicative of enhanced generation of activated oxygen. Allopurinol--an inhibitor of xanthine oxidase--ameliorates both biochemical damage and functional deficits ordinarily triggered by ischemia and reperfusion, suggesting one possible mode of pharmacologic intervention following acute myocardial infarction.     

Myocardial ischemia and reperfusion injury in rats: lysosomal hydrolases and matrix metalloproteinases mediated cellular damage

The aim of this study was to evaluate the time course events of cellular damage during myocardial ischemia and reperfusion injury in rats and to find out a correlation between the structural alterations with respect to the biochemical changes. Cardiac biomarkers and lysosomal enzymes viz. cathepsin D, acid phosphatase and β-glucuronidase and matrix metalloproteinases (MMPs) were evaluated at different time points, in response to ischemia-reperfusion induced oxidative stress in an isolated rat heart model perfused in Langendorff mode. Microscopically, changes in myocardial architecture, myofibrillar degradation, and collagen (COL) integrity were studied using hematoxylin-eosin, Masson’s trichrome and toluidine blue staining techniques. A three-fold increase in the level of myoglobin was observed after 30 min of ischemia followed by 120 min of reperfusion as compared to 15 min ischemia, 120 min reperfusion. Similarly, a significant increase (P < 0.05) in the levels of lipid peroxides and superoxide anion coupled with a decrease in enzymatic and nonenzymatic antioxidant levels were observed. A concomitant increase in the activity of cathepsin D (24.07 ± 0.95) and a higher expression of MMPs after 120 min of reperfusion following 30 min ischemia were shown to correlate with the myocardial damage as shown by histopathology, suggesting that free radical induced activation of cathepsin D and MMPs could mediate early damage during myocardial ischemia and reperfusion.     

Myocardial ischemia/reperfusion injury in the inducible nitric oxide synthase knockout mice.

Inducible nitric oxide synthase (iNOS) plays an important role in the inflammatory process of certain major cardiac disorders including myocardial infarction and allograft rejection. However, the role of iNOS in acute myocardial ischemia has not been well defined. We determined the effects of genetically disruption of the intact iNOS system on cardiac tolerance to ischemia/reperfusion injury. Adult male wild-type (WT) and iNOS knockout (KO) B6,129 mice were subjected to 20 min global ischemia and 30 min reperfusion in a Langendorff isolated perfused heart model (37 degrees C, n = 10/each group). Ventricular contractile function, heart rate, coronary flow, and leakage of intracellular enzymes (CK and LDH) were not significantly different between the groups during pre-ischemia as well as reperfusion period (P > 0.05). Myocardial infarct size was also not significantly different between WT (20.2+/-2.0% of risk area) and KO mice (23.5+/-3.8%; Mean+/-SEM, P > 0.05). However, the post-ischemic heart rate was significantly preserved in KO as compared to WT (P < 0.05). We conclude that disruption of iNOS gene does not exacerbate ischemia/ reperfusion injury in the heart.     

Effect of Pulmonary-Generated Reactive Oxygen Species on Left-Ventricular Dysfunction Associated with Cardio-Pulmonary Ischemia–Reperfusion Injury

The purpose of the present study was to demonstrate the contribution of pulmonary-generated reactive oxygen species (ROS) on cardiac dysfunction using a rat model of ischemia–reperfusion (IR) injury. Three groups of rats were subjected to regional IR injury in (i) lung, (ii) heart, (iii) lung + heart. A fourth (control) group of rats were instrumented using the same methods but without induction IR. Hemodynamic data were recorded in real time. Blood from the proximal aorta was sampled during baseline, ischemia, and reperfusion, mixed with α-phenyl-N-tert-butylnitrone (PBN) for measuring ROS by electron paramagnetic resonance spectrometry. Data were analyzed by a two-way analysis of variance. The results showed that the lung IR generated an increased burst of ROS that resulted in significant cardiac dysfunction, including hypotension and ECG changes. The results indicated that generation of ROS as a result of acute IR lung injury may be sufficiently large enough to cause direct cardiac dysfunction that is independent of injury caused to the myocardium as a result of regional myocardial IR injury alone.     

培养心肌细胞内的SDH图象分析——大豆磷脂脂质体对缺血再灌心肌膜损伤的影响

琥珀酸脱氢酶(SDH)的活性在判断心肌缺血,再灌性损伤中起重要作用。本文通过IBAS图象分析系统对缺血再灌的培养心肌细胞内的SDH定量评估,以求探讨大豆磷脂脂质体对心肌缺血再灌性损伤的保护作用。结果表明,在缺血及再灌组的心肌细胞内出现较强的SDH损伤性反应,大豆磷脂脂质体能明显减轻这种反应,提示大豆磷脂脂质体对缺血及缺血/再灌心肌具有明显的保护作用。     

Brief exposure to exogenous testosterone increases death signaling and adversely affects myocardial function after ischemia

Chronic endogenous testosterone exposure adversely affects proinflammatory and proapoptotic signaling after ischemia/reperfusion; however, it remains unknown whether a single acute testosterone exposure is equally detrimental. We hypothesized that acute exogenous testosterone infusion before ischemia would worsen myocardial functional recovery, increase the activation of MAPKs and caspase-3, and increase myocardial proinflammatory cytokine production. To study this, isolated-perfused rat hearts (Langendorff) from adult females and castrated males were subjected to 25-min ischemia and 40-min reperfusion with and without acute testosterone infusion (17beta-hydroxy-4-androstenone, 10 ng x ml(-1) x min(-1)) before ischemia. Myocardial contractile function was continuously recorded. After ischemia/reperfusion, hearts were assessed for levels of testosterone (ELISA), expression of proinflammatory cytokines (ELISA), and activation of MAPKs and caspase-3 (Western blot analysis). Data were analyzed with two-way ANOVA or Student's t-test; P < 0.05 was statistically significant. All indices of postischemic functional recovery were decreased with acute exogenous testosterone compared with the untreated groups. Acute testosterone infusion increased activation of MAPKs and caspase-3 following ischemia/reperfusion. However, there were no significant differences in the myocardial proinflammatory cytokine production after brief testosterone infusion. A single acute exposure to exogenous testosterone before ischemia worsens myocardial functional recovery and increases activation of MAPKs and caspase-3. These findings confirm the deleterious effects of testosterone on myocardium, elucidate the nongenomic mechanistic pathways of testosterone, and may have important clinical implications for patients who have acute exposure to exogenous testosterone.     

Role of nitric oxide in the reperfusion induced injury in hyperthyroid rat hearts

We recently reported that hyperthyroidism affects the heart response to ischemia/reperfusion. A significant tachycardia during reperfusion was associated with an increase in the oxidative stress of hearts from T3-treated animals. In the present study we checked the possible role of nitric oxide (NO) in this major stress induced by the hyperthyroid state. We compared the functional recovery from ischemia/reperfusion of Langendorff preparations from euthyroid (E) and hyperthyroid (H, ten daily intraperitoneal injections of T3, 10 microg/100 g body weight) rats, in the presence and in the absence of 0.2 mM Nomega-nitro-L-arginine (L-NNA). At the end of the ischemia/reperfusion protocol (10 min preischemic perfusion, 20 min global ischemia, 30 min reperfusion) lipid peroxidation, antioxidant capacity (CA) and susceptibility to in vitro oxidative stress were determined on heart homogenates. The main effect of hyperthyroidism on the reperfusion functional response was confirmed to be a strong tachycardic response (154% recovery at 25 min reperfusion) accompanied by a low recovery in both left ventricular diastolic pressure (LVDP) and left ventricular dP/dtmax. This functional response was associated with a reduction in CA and an increase in both lipid peroxidation and susceptibility to oxidative stress. Perfusion of hearts with L-NNA per se had small but significant negative chronotropic and positive inotropic effects on preischemic performance of euthyroid rat hearts only. More importantly, L-NNA perfusion completely blocked the reperfusion tachycardic response in the hyperthyroid rats. Concomitantly, myocardium oxidative state (lipid peroxidation, CA and in vitro susceptibility to oxidative stress) of L-NNA perfused hearts was similar to that of E animals. These results suggest that the higher reperfusion-induced injury occurring in hyperthyroid animals is associated with overproduction of nitric oxide.     

黑木耳多糖对抗离体心脏缺血/再灌注损伤的研究

目的:探讨黑木耳多糖(AAP)对离体大鼠心脏缺血/再灌注(I/R)损伤的防护作用及其机制。方法:健康雄性SD大鼠灌胃黑木耳多糖(50,100,200mg/(kg.d))4周后,采用离体心脏Langendorff灌流方法,全心停灌30min,复灌120min建立I/R模型。测定左心室动力学指标和再灌注各时间点冠脉流出液中乳酸脱氢酶(LDH)含量;实验结束测定心肌组织甲月赞(formazan)、丙二醛(MDA)含量及超氧化物歧化酶(SOD)活性的变化。结果:与单纯I/R组相比,AAP预处理明显提高心肌细胞的formazan含量,降低再灌注期间冠脉流出液中LDH含量,明显增强左室发展压、左心室内压最大上升速率和心率与发展压乘积的恢复,缓解冠脉流量的减少;高剂量AAP改善I/R心肌功能的作用要好于丹参预处理(4ml/(kg.d),gastricperfusion)组。中剂量AAP(100mg/(kg.d))预处理4周后明显抑制I/R心肌MDA的增加和SOD活性的减弱(P0.01),其效果要好于丹参阳性对照组。结论:在大鼠离体心脏灌流模型上,黑木耳多糖预处理具有抗心脏I/R损伤的作用,这种保护作用可能与其增加心肌SOD活性,减少脂质过氧化损伤有关。     

Urotensin II protects ischemic reperfusion injury of hearts through ROS and antioxidant pathway

Urotensin II (UII) is a vasoactive peptide which is bound to a G protein-coupled receptor. UII and its receptor are upregulated in ischemic and chronic hypoxic myocardium, but the effect of UII on ischemic reperfusion (I/R) injury is still controversial. The aim of the present study was to investigate whether UII protects heart function against I/R injury. Global ischemia was performed using isolated perfused Langendorff hearts of Sprague-Dawley rats. Hearts were perfused with Krebs-Henseleit buffer for 20min pre-ischemic period followed by a 20min global ischemia and 50min reperfusion. Pretreatment with UII (10nM) for 10min increased recovery percentage of the post-ischemic left ventricular developed pressure and ±dp/dt, and decreased post-ischemic left ventricular end-diastolic pressure as compared with I/R group. UII decreased infarct size and an increased lactate dehydrogenase level during reperfusion. Cardioprotective effects of UII were attenuated by pretreatment with UII receptor antagonist. The hydrogen peroxide activity was increased in UII-treated heart before ischemia. The Mn-SOD, catalase, heme oxygenase-1 and Bcl-2 levels were increased, and the Bax and caspase-9 levels were decreased in UII-treated hearts. These results suggest that UII has cardioprotective effects against I/R injury partly through activating antioxidant enzymes and reactive oxygen species.     

HDAC Inhibition Elicits Myocardial Protective Effect through Modulation of MKK3/Akt-1

We and others have demonstrated that HDAC inhibition protects the heart against myocardial injury. It is known that Akt-1 and MAP kinase play an essential role in modulation of myocardial protection and cardiac preconditioning. Our recent observations have shown that Akt-1 was activated in post-myocardial infarction following HDAC inhibition. However, it remains unknown whether MKK3 and Akt-1 are involved in HDAC inhibition-induced myocardial protection in acute myocardial ischemia and reperfusion injury. We sought to investigate whether the genetic disruption of Akt-1 and MKK3 eliminate cardioprotection elicited by HDAC inhibition and whether Akt-1 is associated with MKK3 to ultimately achieve protective effects. Adult wild type and MKK3^−/−, Akt-1^−/− mice received intraperitoneal injections of trichostatin A (0.1mg/kg), a potent inhibitor of HDACs. The hearts were subjected to 30 min myocardial ischemia/30 min reperfusion in the Langendorff perfused heart after twenty four hours to elicit pharmacologic preconditioning. Left ventricular function was measured, and infarct size was determined. Acetylation and phosphorylation of MKK3 were detected and disruption of Akt-1 abolished both acetylation and phosphorylation of MKK3. HDAC inhibition produces an improvement in left ventricular functional recovery, but these effects were abrogated by disruption of either Akt-1 or MKK3. Disruption of Akt-1 or MKK3 abolished the effects of HDAC inhibition-induced reduction of infarct size. Trichostatin A treatment resulted in an increase in MKK3 phosphorylation or acetylation in myocardium. Taken together, these results indicate that stimulation of the MKK3 and Akt-1 pathway is a novel approach to HDAC inhibition -induced cardioprotection.     

Permanent Ligation of the Left Anterior Descending Coronary Artery in Mice: A Model of Post-myocardial Infarction Remodelling and Heart Failure

Heart failure is a syndrome in which the heart fails to pump blood at a rate commensurate with cellular oxygen requirements at rest or during stress. It is characterized by fluid retention, shortness of breath, and fatigue, in particular on exertion. Heart failure is a growing public health problem, the leading cause of hospitalization, and a major cause of mortality. Ischemic heart disease is the main cause of heart failure.Ventricular remodelling refers to changes in structure, size, and shape of the left ventricle. This architectural remodelling of the left ventricle is induced by injury (e.g., myocardial infarction), by pressure overload (e.g., systemic arterial hypertension or aortic stenosis), or by volume overload. Since ventricular remodelling affects wall stress, it has a profound impact on cardiac function and on the development of heart failure. A model of permanent ligation of the left anterior descending coronary artery in mice is used to investigate ventricular remodelling and cardiac function post-myocardial infarction. This model is fundamentally different in terms of objectives and pathophysiological relevance compared to the model of transient ligation of the left anterior descending coronary artery. In this latter model of ischemia/reperfusion injury, the initial extent of the infarct may be modulated by factors that affect myocardial salvage following reperfusion. In contrast, the infarct area at 24 hr after permanent ligation of the left anterior descending coronary artery is fixed. Cardiac function in this model will be affected by 1) the process of infarct expansion, infarct healing, and scar formation; and 2) the concomitant development of left ventricular dilatation, cardiac hypertrophy, and ventricular remodelling.Besides the model of permanent ligation of the left anterior descending coronary artery, the technique of invasive hemodynamic measurements in mice is presented in detail.     

ATPase inhibitory factor 1 protects the heart from acute myocardial ischemia/reperfusion injury through activating AMPK signaling pathway

Rationale: Myocardial ischemia/reperfusion (I/R) injury is a common clinic scenario that occurs in the context of reperfusion therapy for acute myocardial infarction (AMI). The mitochondrial F1Fo-ATPase inhibitory factor 1 (IF1) blocks the reversal of the F1Fo-ATP synthase to prevent detrimental consumption of cellular ATP and associated demise. In the present study, we study the role and mechanism of IF1 in myocardial I/R injury.Methods: Mice were ligated the left anterior descending coronary artery to build the I/R model in vivo. Rat hearts were isolated and perfused with constant pressure according to Langendorff. Also, neonatal cardiomyocytes hypoxia-reoxygenation (H/R) model was also used. Myocardial infarction area, cardiac function, cellular function, and cell viability was conducted and compared.Results: Our data revealed that IF1 is upregulated in hearts after I/R and cardiomyocytes with hypoxia/re-oxygenation (H/R). IF1 delivered with adenovirus and adeno-associated virus serotype 9 (AAV9) ameliorated cardiac dysfunction and pathological development induced by I/R ex vivo and in vivo. Mechanistically, IF1 stimulates glucose uptake and glycolysis activity and stimulates AMPK activation during in vivo basal and I/R and in vitro OGD/R conditions, and activation of AMPK by IF1 is responsible for its cardioprotective effects against H/R-induced injury.Conclusions: These results suggest that increased IF1 in the I/R heart confer cardioprotective effects via activating AMPK signaling. Therefore, IF1 can be used as a potential therapeutic target for the treatment of pathological ischemic injury and heart failure.     

Targeted deletion of A(3) adenosine receptors improves tolerance to ischemia-reperfusion injury in mouse myocardium

A(3) adenosine receptors (A(3)ARs) have been implicated in regulating mast cell function and in cardioprotection during ischemia-reperfusion injury. The physiological role of A(3)ARs is unclear due to the lack of widely available selective antagonists. Therefore, we examined mice with targeted gene deletion of the A(3)AR together with pharmacological studies to determine the role of A(3)ARs in myocardial ischemia-reperfusion injury. We evaluated the functional response to 15-min global ischemia and 30-min reperfusion in isovolumic Langendorff hearts from A(3)AR(-/-) and wild-type (A(3)AR(+/+)) mice. Loss of contractile function during ischemia was unchanged, but recovery of developed pressure in hearts after reperfusion was improved in A(3)AR(-/-) compared with wild-type hearts (80 +/- 3 vs. 51 +/- 3% at 30 min). Tissue viability assessed by efflux of lactate dehydrogenase was also improved in A(3)AR(-/-) hearts (4.5 +/- 1 vs. 7.5 +/- 1 U/g). The adenosine receptor antagonist BW-A1433 (50 microM) decreased functional recovery following ischemia in A(3)AR(-/-) but not in wild-type hearts. We also examined myocardial infarct size using an intact model with 30-min left anterior descending coronary artery occlusion and 24-h reperfusion. Infarct size was reduced by over 60% in A(3)AR(-/-) hearts. In summary, targeted deletion of the A(3)AR improved functional recovery and tissue viability during reperfusion following ischemia. These data suggest that activation of A(3)ARs contributes to myocardial injury in this setting in the rodent. Since A(3)ARs are thought to be present on resident mast cells in the rodent myocardium, we speculate that A(3)ARs may have proinflammatory actions that mediate the deleterious effects of A(3)AR activation during ischemia-reperfusion injury.     

Role of nitric oxide in the reperfusion induced injury in hyperthyroid rat hearts

We recently reported that hyperthyroidism affects the heart response to ischemia/reperfusion. A significant tachycardia during reperfusion was associated with an increase in the oxidative stress of hearts from T₃-treated animals. In the present study we checked the possible role of nitric oxide (NO) in this major stress induced by the hyperthyroid state. We compared the functional recovery from ischemia/reperfusion of Langendorff preparations from euthyroid (E) and hyperthyroid (H, ten daily intraperitoneal injections of T₃, 10 μg/100 g body weight) rats, in the presence and in the absence of 0.2 mM N^ω-nitro-L-arginine (L-NNA). At the end of the ischemia/reperfusion protocol (10 min preischemic perfusion, 20 min global ischemia, 30 min reperfusion) lipid peroxidation, antioxidant capacity (C_A) and susceptibility to in vitro oxidative stress were determined on heart homogenates. The main effect of hyperthyroidism on the reperfusion functional response was confirmed to be a strong tachycardic response (154% recovery at 25 min reperfusion) accompanied by a low recovery in both left ventricular diastolic pressure (LVDP) and left ventricular dP/dt_max. This functional response was associated with a reduction in C_A and an increase in both lipid peroxidation and susceptibility to oxidative stress. Perfusion of hearts with L-NNA per se had small but significant negative chronotropic and positive inotropic effects on preischemic performance of euthyroid rat hearts only. More importantly, L-NNA perfusion completely blocked the reperfusion tachycardic response in the hyperthyroid rats. Concomitantly, myocardium oxidative state (lipid peroxidation, C_A and in vitro susceptibility to oxidative stress) of L-NNA perfused hearts was similar to that of E animals. These results suggest that the higher reperfusion-induced injury occurring in hyperthyroid animals is associated with overproduction of nitric oxide.     

SMT对大鼠在体心脏缺血-再灌注损伤超微结构的保护作用

目的：研究ＳＭＴ对心脏缺血－再灌注损伤（ＩＲＩ）心肌超微结构的影响。方法：ＳＤ大鼠１８只,体重３２０￣３８０ｇ,随机分为三组：①缺血－再灌注组（ＩＲ）：夹闭冠状动脉左前降支６０ｍｉｎ,松夹２０ｍｉｎ。②缺血－再灌注＋ＳＭＴ组（ＳＭＴ）：再灌注前５ｍｉｎ,股静脉注射ｉＮＯＳ抑制剂Ｓ－ｍｅｔｈｙｌｉｓｏｔｈｉｏｕｒｅａ ｓｕｌｆａｔｅ（ＳＭＴ ５ｍｇ／ｋｇ ｗ）,余同ＩＲ组;③对照组（Ｃ）：暴露心脏后     

Role of endogenous testosterone in myocardial proinflammatory and proapoptotic signaling after acute ischemia-reperfusion

Myocardial ischemia is the leading cause of death in both men and women; however, very little information exists regarding the effect of testosterone on the response of myocardium to acute ischemic injury. We hypothesized that testosterone may exert deleterious effects on myocardial inflammatory cytokine production, p38 MAPK activation, apoptotic signaling, and myocardial functional recovery after acute ischemia-reperfusion (I/R). To study this, isolated, perfused rat hearts (Langendorff) from adult males, castrated males, and males treated with a testosterone receptor blocker (flutamide) were subjected to 25 min of ischemia followed by 40 min of reperfusion. Myocardial contractile function (left ventricular developed pressure, left ventricular end-diastolic pressure, positive and negative first derivative of pressure) was continuously recorded. After reperfusion, hearts were analyzed for expression of tissue TNF-alpha, IL-1beta, and IL-6 (ELISA) and activation of p38 MAPK, caspase-1, caspase-3, caspase-11, and Bcl-2 (Western blot). All indices of postischemic myocardial functional recovery were significantly higher in castrated males or flutamide-treated males compared with untreated males. After I/R, castrated male and flutamide-treated male hearts had decreased TNF-alpha, IL-1beta, and IL-6; decreased activated p38 MAPK; decreased caspase-1, caspase-3, and caspase-11; and increased Bcl-2 expression compared with untreated males. These results show that blocking the testosterone receptor (flutamide) or depleting testosterone (castration) in normal males improves myocardial function after I/R. These effects may be attributed to the proinflammatory and/or the proapoptotic properties of endogenous testosterone. Further understanding may allow therapeutic manipulation of sex hormone signaling mechanisms in the treatment of acute I/R.