Thaliporphine protects ischemic and ischemic‐reperfused rat hearts via an NO‐dependent mechanism

In ischemia or ischemia‐reperfusion (I/R), nitric oxide (NO) can potentially exert several beneficial effects. Thaliporphine, a natural alkaloid with Ca²⁺ channel‐activating and Na⁺/K⁺ channel‐blocking activities, increased NO levels and exerted cardioprotective action in ischemic or I/R rats. The role of NO in the cardioprotective actions of thaliporphine was assessed. The severity of rhythm disturbances and mortality in anesthetized rats with either coronary artery occlusion for 30 min, or 5 min followed by 30‐min reperfusion, were monitored and compared in thaliporphine‐ vs. placebo‐treated groups. Thaliporphine treatment significantly increased NO and decreased lactate dehydrogenase (LDH) levels in the blood during the end period of ischemia or I/R. These changes in NO and LDH levels by thaliporphine were associated with a reduction in the incidence and duration of ventricular tachycardia (VT) and ventricular fibrillation (VF) during ischemic or I/R period. The mortality of animals was also completely prevented by 1 × 10^–8 moles/kg of thaliporphine. In animals subjected to 4 h of left coronary artery occlusion, 1 × 10^–7 moles/kg of thaliporphine dramatic reduced cardiac infarct zone from 46 ± 6% to 7.1 ± 1.9%. Inhibition of NO synthesis with 3.7 × 10^–6 moles/kg of N^ω ‐nitro‐L‐arginine methyl ester (L‐NAME) abolished the beneficial effects of thaliporphine during 30 min or 4 h myocardial ischemia. However, the antiarrhythmic activity and mortality reduction efficacy of thaliporphine during reperfusion after 5 min of ischemia was only partially antagonized by L‐NAME. These results showed that thaliporphine efficiently exerted the cardioprotections either in acute or prolonged coronary artery occlusion or occlusion‐reperfusion situations. The fact that thaliporphine induced cardioprotective effects were abrogated by L‐NAME indicates that NO is an important mediator for the cardioprotective effects of thaliporphine in acute or prolonged ischemia, whereas antioxidant activities may contribute to the protection of I/R injury. Drug Dev. Res. 52:446–453, 2001. © 2001 Wiley‐Liss, Inc.     

Differential action of KR‐31378, a novel potassium channel activator,on cardioprotective and hemodynamic effects

The cardioprotective and hemodynamic effects of KR‐31378, a highly cardioselective ATP‐sensitive potassium channel activator with minimal hypotensive effect, were evaluated in rats and dogs, and compared with those of BMS‐191095 and lemakalim. KR‐31378 did not show any significant effect on methoxamine‐induced aortic constriction up to doses of 300 μM, whereas BMS 191095 produced a moderately potent relaxant effect (IC₅₀: 9.0 μM). In conscious rats, KR‐31378 slightly increased blood pressure only at high dose (100 mg/kg, iv), unlike BMS‐191095 that dose‐dependently decreased blood pressure (ED₂₀: 2.03 mg/kg). In anesthetized beagle dogs, KR‐31378 was approximately 100‐fold less potent than BMS‐191095 for most hemodynamic parameters (iv ED₂₀ for blood pressure lowering: 33.7 and 0.37 mg/kg, respectively). In anesthetized rats subjected to 45‐min coronary occlusion and 90‐min reperfusion, KR‐31378 (iv) dose‐dependently reduced the infarct zone from 58.6% to 42.1%, 36.6%, and 34.3% for 0.1, 0.3, and 1.0 mg/kg, respectively (P < 0.05), the effects being comparable to those of BMS 191095. In anesthetized beagle dogs that underwent 2‐h occlusion followed by 4.5‐h reperfusion, KR‐31378 (2 mg/kg, iv infusion) markedly reduced the infarct zone from 48.7% in controls to 19.1% at a dose of 2 mg/kg (P < 0.05). The reduction in infarct zone afforded by KR‐31378 in rats was inhibited by pretreatment with selective ATP‐sensitive potassium channel blockers, sodium 5‐hydroxydecanoate and glibenclamide. These results indicate that KR‐31378 is a potent cardioprotective agent with potentially minimal hypotensive effects. Thus, it could be potentially useful in the prevention and treatment of acute myocardial infarction. Drug Dev. Res. 54:182–190, 2001. © 2002 Wiley‐Liss, Inc.     

Attenuation of the LPS‐induced,ERK‐mediated upregulation of fibrosis‐related factors FGF‐2, uPA,MMP‐2, and MMP‐9 by Carthamus tinctorius L in cardiomyoblasts

Severe and potentially fatal hypotension and cardiac contractile dysfunction are common symptoms in patients with sepsis. LPS was previously found to dramatically upregulate expression of fibrosis‐related factors FGF‐2, uPA, MMP‐2, and MMP‐9 in primary cardiac fibroblasts. MMPs are capable of denaturing and degrading fibrillar collagens and other components of the extracellular matrix (ECM). Studies have shown that dysregulation of expression of MMPs is associated with development of myocardial extracellular matrix remodeling and cardiac fibrosis, which contribute to progression of heart failure. In this study, H9c2 cells and cardiac fibroblasts were divided into five treatment groups: control, LPS (1 μg/mL) and three concentrations of FC_EtOH (Carthami Flos ethanolic extract) (31.25, 62.5, and 125 μg/mL). Phosphorylation of ERK‐1/2 was observed to be rapidly induced upon treatment with LPS. In contrast, it was significantly suppressed by the administration of FC_EtOH (125 μg/mL). Effects of FC_EtOH on LPS‐induced MMP‐2 and MMP‐9 expression in H9c2 cells occurred directly through ERK1/2 were determined. H9c2 cells were therefore pretreated with EGF‐R to activate ERK pathway. Both protein levels of MMP‐2 and MMP‐9 and immunefluorescent signals of MMP‐9 were significantly enhanced by EGFR. In contrast, MMP‐2 and MMP‐9 were significantly reduced after FC_EtOH administration. Based on these findings, the authors concluded that FC_EtOH elicits a protective effect against LPS‐induced cardio‐fibrosis through the ERK1/2 pathway. Carthamus tinctorius L may potentially serve as a cardio‐protective agent against LPS‐ induced cardiac fibrosis. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 754–763, 2017.     

丙泊酚后处理对体外循环冠脉旁路移植术患者心肌缺血再灌注损伤的影响

目的:探讨主动脉开放即刻靶控输注丙泊酚1mg/L对体外循环下行冠状动脉旁路移植术患者心肌缺血再灌注损伤的影响。方法:择期体外循环下行冠状动脉旁路移植术患者40例,ASAⅡ级或Ⅲ级,随机分为七氟烷组(S组)和丙泊酚后处理组(P组)各20例。S组全程吸入0.5%～2%七氟烷;P组在主动脉开放前持续吸入0.5%～2%七氟烷,主动脉开放即刻靶控输注丙泊酚,血浆靶浓度为1mg/L,同时下调七氟烷吸入浓度,维持脑电双频谱指数(BIS)值在40～60范围直至手术结束。于麻醉诱导前即刻(T0)、主动脉开放后10min(T1)、回重症监护病房(ICU)后即刻(T2)、6h(T3)、12h(T4)、24h(T5)取桡动脉血测定心肌肌钙蛋白(IcTnI)、肌酸激酶同工酶(CK-MB)、可溶性细胞间黏附分子-1(sICAM-1)和CD11b水平。结果:2组不同时点cTnI、CK-MB、sICAM-1和CD11b浓度差异具有统计学意义(P<0.05);与S组比较,P组cTnI和CK-MB浓度在T3～5时降低、sICAM-1浓度在T2～5时降低、CD11b表达在T1～5时降低;2组术后心肌梗死、房颤和心肌缺血的发生率差异无统计学意义(P...     

地奥心血康对心肌缺血再灌注犬心功能及去甲肾上腺素含量的影响

２８只杂种犬分地奥心血康组（ＤＡＸＸＫ）和生理盐水组（ＮＳ）。结扎冠状动脉左前降支使心肌缺血。分别于结扎即刻静脉滴注ＤＡＸＸＫ（５．０ｍｇ／ｋｇ）和１００ｍｌＮＳ。ＮＳ组随缺血再灌注时间延长，ＣＩ，ＬＶＳＰ，±ｄＰ／ｄｔｍａｘ，等明显下降，而ＴＰＶＲ与血清Ｌｅｖ含量进行性升高。ＤＡＸＸＫ与ＮＳ比较，有显著改善心功能的效应。     

Sodium hydrosulfide improves the protective potential of the cardioplegic histidine buffer solution

Since H₂S has an emerging role as a cardioprotector, we hypothesized that NaHS addition to the new cardioplegic histidine buffer solution (HBS) could improve its cardioprotective potential. Male Wistar–Han rat hearts were divided in 4 groups: i) control, ii) perfusion control (perfusion only), iii) 6 h ischemia in HBS or in a modified-HBS with 100 μM of NaHS, a H₂S donor, (HBSM) and iv) as iii followed by 30 min reperfusion. During ischemia, aliquots of the cardioplegic solution were collected for NMR analysis. Heart mitochondria respiration and transmembrane potential were measured after ischemia or after ischemia followed by reperfusion. Proteins involved in the apoptotic signaling pathway were also quantified in both mitochondrial and tissue samples. Cardiac mechanic performance was evaluated by measuring the heart rate and the left ventricular pressure. In HBSM-preserved hearts, a) glucose consumption increased as well as lactate and alanine production during ischemia, b) heart mitochondria presented an improved phosphorylative efficiency, including decreased phosphorylative lag phase for complex I and complex II substrates, c) mitochondrial and tissue p53, Bax and caspase-9 were lower and d) there was a more positive atrial chronotropic response than in HBS-preserved hearts. We concluded that the addition of NaHS to HBS enhances glycolysis during ischemia, decreases mitochondrial dysfunction, especially by preserving the phosphorylative system, prevents apoptosis and during ischemia/reperfusion.     

Nandrolone potentiates arrhythmogenic effects of cardiac ischemia in the rat.

Anabolic steroid abuse has been associated with thrombosis and arteriosclerosis, both of which predispose to myocardial ischemia and infarction. However, there are reports of sudden cardiac death in the absence of thrombus and atheroma following anabolic steroid use. Although treatment with the commonly abused steroid, nandrolone, has been shown to decrease recovery of systolic function following ischemia in isolated rat hearts, it is unknown whether anabolic steroids can increase the incidence of fatal arrhythmia associated with cardiac ischemia. Anesthetized male Sprague-Dawley rats were administered vehicle or nandrolone (10-160 microg/kg/min iv) 10 min prior to 15-min occlusion of the left anterior descending coronary artery followed by 10-min reperfusion. Nandrolone, in this dose range, did not significantly change heart rate, blood pressure, or cardiac rhythm in the absence of ischemia. However, the fraction of rats surviving ischemia was significantly (p < 0.05) decreased by nandrolone at both 40 and 160 microg/kg/min, while survival time during ischemia was decreased significantly (p < 0.001) by nandrolone 160 microg/kg/min. An increase (p < 0.05) in the duration of ventricular fibrillation was noted at the highest compared to the lowest dose of nandrolone, corresponding to a significant increase in the fraction of rats experiencing ventricular fibrillation (p < 0.01). Nandrolone had no effect on the frequency or duration of ventricular fibrillation or survival time during reperfusion. Although the mechanisms underlying these effects are currently unclear, they indicate that exposure to anabolic steroids in combination with transient reductions in coronary blood flow may explain some reports of sudden cardiac death in anabolic steroid users.     

SSR69071, an elastase inhibitor,reduces myocardial infarct size following ischemia-reperfusion injury

Neutrophil elastase contributes to the severity of cardiac damage following coronary ischemia and reperfusion. We evaluated the effects of 2-(9-(2-piperidinoethoxy)-4-oxo-4H-pyridol[1,2-a]pyrimidin-2-yloxymethyl)-4-(1-methyethyl)-6-methoxy-1,2-benzisothiazol-3(2H)-one-1,1-dioxide hemihydrate (SSR69071), a novel, potent and selective inhibitor of neutrophil elastase, on infarct size in anaesthetized rabbits subjected to coronary artery occlusion for 30 min followed by reperfusion for 120 min. SSR69071 (3 mg/kg i.v.) reduced cardiac infarct size when administered before ischemia (-39%, P<0.05) or just prior to reperfusion (-37%, P<0.05). Subsequent experiments using the latter administration protocol confirmed the ability of SSR69071 (1 and 3 mg/kg i.v.) to reduce infarct size. This cardioprotective activity was associated with inhibition of cardiac elastase.     

芸香甙对脑缺血再灌损伤的保护作用

目的研究芸香甙（Ｒｕ）对脑缺血再灌损伤的保护作用。方法小鼠脑缺血再灌模型通过结扎双侧颈总动脉并尾部放血０．３ｍｌ，再灌后，记录异常神经症状和断头后张口喘气时间，测定脑组织中乳酸脱氢酶（ＬＤＨ）含量；利用４血管模型，大鼠前脑缺血３０ｍｉｎ后再灌注４０ｍｉｎ。取脑组织测定ＬＤＨ、过氧化物歧化酶（ＳＯＤ）、丙二醛（ＭＤＡ）、一氧化氮（ＮＯ）及脑水肿。结果Ｒｕ（５０，１００ｍｇ·ｋｇ－１，ｉｖ），显著改善小鼠脑缺血再灌损伤后的异常神经症状和抑制断头后张口喘气时间的缩短及脑组织中ＬＤＨ的减少。Ｒｕ显著抑制大鼠脑缺血再灌损伤所致的脑水肿形成和脑组织中ＬＤＨ、ＳＯＤ、ＭＤＡ及ＮＯ的变化。结论Ｒｕ对脑缺血再灌损伤有显著的保护作用，其机制与抗自由基和ＮＯ有关。     

Effects of KB-R9032, a new Na+/H+ exchange inhibitor, on canine coronary occlusion/reperfusion-induced ventricular arrhythmias

We investigated the effects of KB-R9032 (N-(4-isopropyl-2,2-dimethyl-3-oxo-3,4-dihydro-2H-benzo[1,4]oxazine-6-carbonyl) guanidine methanesulfonate), a new Na(+)/H(+) exchange inhibitor, on a coronary artery occlusion/reperfusion-induced arrhythmia model in pentobarbital anesthetized dogs. KB-R9032 reduced the number of ventricular premature contractions seen during the coronary occlusion, while it did not alter the heart rate, mean blood pressure, or electrocardiographic parameters (PR, QRS, or QTc interval). KB-R9032 also decreased the incidence of fatal ventricular fibrillation during coronary artery occlusion and/or after reperfusion. These antiarrhythmic effects were observed not only in the pre-ischemic administration group, but also in the group given KB-R9032 at the 15th min of the 30-min occlusion. These findings support the view that Na(+)/H(+) exchanger may play an important role in inducing coronary ischemia/reperfusion arrhythmias. This suggests that the use of Na(+)/H(+) exchange inhibitors, such as KB-R9032, may be an effective clinical approach to suppress sudden cardiac death due to acute myocardial ischemia/reperfusion such as during coronary bypass surgery, cardiac valve surgery, or percutaneous transluminal coronary angioplasty.     

腺苷A_1受体参与兔脊髓缺血预适应的保护作用

目的　探讨腺苷A1 受体是否参与兔脊髓缺血预适应 (IPC)的保护作用。方法　采用腹主动脉肾下段夹闭法建立兔脊髓缺血模型。动物分为 7组 ,即缺血损伤组 :使脊髓缺血 2 0min ;IPC组 :脊髓预缺血 6min ,再灌注 30min后再次使脊髓缺血 2 0min;8 环戊基 1 ,3 二丙黄嘌呤 (DPCPX ,腺苷A1 受体阻断剂 ) +IPC组及DMSO溶剂 +IPC组 :在IPC前分别ipDPCPX及DMSO ,其余步骤同IPC组 ;DPCPX +缺血损伤组 :在脊髓 2 0min缺血前ipDPCPX ,其余步骤同缺血损伤组 ;预缺血组 :使脊髓缺血 6min;DPCPX +预缺血组 :在脊髓 6min缺血前ipDPCPX ,其余步骤同预缺血组。所有组再灌注48h后 ,进行后肢神经功能评分 ,然后取脊髓进行组织病理学观察。结果　与缺血损伤组相比 ,IPC明显改善脊髓缺血后兔后肢神经功能和减轻脊髓病理学损伤 ;DPCPX完全取消IPC对脊髓缺血的保护作用 ,而DMSO不能取消IPC的保护作用 ;单给DPCPX并不能进一步加重缺血损伤。缺血 6min及DPCPX +缺血 6min均不能引起脊髓缺血损伤。结论　腺苷A1 受体参与兔脊髓IPC的保护作用     

异甜菊醇抗豚鼠离体心脏缺氧复灌损伤作用

目的　拟证实双萜类化合物异甜菊醇抗豚鼠离体心脏缺氧复灌损伤作用及与线粒体ATP敏感性钾通道 (mito KATP)的关系。方法　Langendorff装置逆向心脏灌注。预先灌注异甜菊醇 1,5和 10μmol·L- 1,5min ,流速约为 9.5mL·min- 1,全心停灌 30min ,复灌 2 0min ,观察心脏舒缩功能、冠脉流出液酶学和心肌组织学改变。结果异甜菊醇预处理有效减轻缺氧复灌引起的左室舒缩功能下降 ,降低冠脉流出液中乳酸脱氢酶和肌酸激酶浓度 ;延迟停灌后心脏出现挛缩的时间。mito KATP关闭剂 5 羟基癸酸 10 0 μmol·L- 1可部分逆转异甜菊醇 10 μmol·L- 1的心肌保护作用。光学和电子显微镜观察结果表明 ,异甜菊醇预处理可减轻缺氧复灌引起的心肌纤维和线粒体损伤。结论　异甜菊醇 1～ 10 μmol·L- 1预灌注可有效减轻豚鼠离体心肌缺氧复灌引起的损伤 ,该作用可能与mito KATP的开放有关。     

KR-31762, a novel KATP channel opener, exerts cardioprotective effects by opening SarcKATP channels in rat models of ischemia/reperfusion-induced heart injury

The cardioprotective effects of KR-31762, a newly synthesized K⁺ _ATP opener, were evaluated in rat models of ischemia/reperfusion (I/R) heart injury. In isolated rat hearts subjected to 30-min global ischemia followed by 30-min reperfusion, KR-31762 (3 and 10 μM) significantly increased the left ventricular developed pressure (LVDP) and double product (heart rate × LVDP) after 30-min referfusion in a concentration-dependent manner, while decreasing the left ventricular end-diastolic pressure (LVEDP). KR-31762 also significantly increased the time to contracture (TTC) during ischemic period (20.0, 22.4 and 26.4 min for control, 3 and 10 μM, respectively), while decreasing the release of lactate dehydrogenase (LDH) from the heart during 30 min reperfusion (30.4, 14.3 and 19.7 U/g heart weight, respectively). All these parameters except LDH release were reversed by glyburide (1 μM), a nonselective blocker of K⁺ _ATP channel, but not by 5-hydroxydecanoate, a selective blocker of mitoK⁺ _ATP channel. In anesthetized rats subjected to 45-min occlusion of left anterior descending coronary artery followed by 90-min reperfusion, KR-31762 significantly decreased the infarct size (60.8, 40.5 and 37.8% for control, 0.3 and 1.0 mg/kg, iv, respectively). KR-31762 slightly relaxed the isolated rat aorta precontracted with methoxamine (IC₅₀: 23.5 μM). These results suggest that KR-31762 exerts potent cardioprotective effects through the opening of sarcolemmal K_ATP channel in rat hearts with the minimal vasorelaxant effects.     

Nitric oxide and endothelium‐dependent hyperpolarization mediated by hydrogen peroxide in health and disease

The endothelium plays crucial roles in modulating vascular tone by synthesizing and releasing endothelium‐derived relaxing factors (EDRFs), including vasodilator prostaglandins, nitric oxide (NO) and endothelium‐dependent hyperpolarization (EDH) factors. Thus, endothelial dysfunction is the hallmark of atherosclerotic cardiovascular diseases. Importantly, the contribution of EDRFs to endothelium‐dependent vasodilatation varies in a distinct vessel size‐dependent manner; NO mainly mediates vasodilatation of relatively large, conduit vessels (eg epicardial coronary arteries), while EDH factors in small resistance vessels (eg coronary microvessels). Endothelium‐derived hydrogen peroxide (H₂O₂) is a physiological signalling molecule serving as one of the major EDH factors especially in microcirculations and has gained increasing attention in view of its emerging relevance for cardiovascular diseases. In the clinical settings, therapeutic approaches targeting NO (eg NO donors) or non‐specific elimination of reactive oxygen species (eg antioxidant supplements) are disappointingly ineffective for the treatment of various cardiovascular diseases, in which endothelial dysfunction and coronary microvascular dysfunction are substantially involved. These lines of evidence indicate the potential importance of the physiological balance between NO and H₂O₂/EDH factor. Further characterization and better understanding of endothelium‐dependent vasodilatations are important to develop novel therapeutic strategies in cardiovascular medicine. In this MiniReview, we will briefly summarize the current knowledge on the emerging regulatory roles of endothelium‐dependent vasodilatations in the cardiovascular system, with a special reference to the two major EDRFs, NO and H₂O₂/EDH factor, in health and disease.     

白介素8和兔心肌缺血/再灌注损伤研究

目的 探讨白介素8(rhIL-8)参与兔心肌缺血/再灌注损伤的机制,为减轻再灌注损伤探索新的治疗途径。方法 结扎兔冠状动脉左前降支(left anterior descending coronary artery,LAD)造成缺血1小时,再灌注3.5小时。实验分两组:缺血/再灌注组(MI/R,n=8)和假结扎组(Sham MI/R,n=8)。结果 MI/R组发生严重的心肌损伤,包括受累心肌髓过氧化物酶(myeloperoxidase,MPO)活性增大和血清肌酸磷酸激酶-MB同工酶(CPK-MB)、异构前列腺素(eoi-PGF_(2α))水平增高(均P<0.01)。血清IL-8浓度逐渐升高,免疫组化示受损心肌区血管内皮基底膜呈IL-8阳性染色。结论 血管内皮细胞释放的IL-8是吸引中性粒细胞浸润于缺血区心肌,造成缺血/再灌注损伤的因素之一。     

二苯乙烯苷对大鼠主动脉舒张作用及其一氧化氮含量的影响

目的　研究中药何首乌中有效成分二苯乙烯苷 (2 ,3,5 ,4′ 四羟基二苯乙烯 2 O β D 葡萄糖苷 ,THSG)与结构相似的白黎芦醇 (resveratrol)是否有类似的血管舒张作用。方法　采用血管张力记录法及NO比色法 ,观察THSG对大鼠主动脉环张力及NO含量的影响。结果　①在去氧肾上腺素预收缩的内皮完整及去内皮主动脉环上 ,THSG 0 .1～ 30 .0 μmol·L- 1浓度依赖性舒张主动脉环 ,其Emax分别为 75 %和5 2 % ,EC50 分别为 0 .86和 2 .70 μmol·L- 1。②在内皮完整的血管上 ,THSG 0 .1μmol·L- 1能增强乙酰胆碱1μmol·L- 1依血管内皮的舒张作用。③NO前体物L 精氨酸 1μmol·L- 1可增强THSG 1μmol·L- 1的血管舒张作用 ;而NOS抑制药Nω 硝基L 精氨酸甲酯0 .5 μmol·L- 1可部分削弱之。④鸟苷酸环化酶抑制药亚甲兰 1μmol·L- 1可部分削弱THSG 1μmol·L- 1的血管舒张作用。⑤THSG 30mg·kg- 1,iv ,可短暂降低麻醉大鼠动脉血压 ,但对心率无明显影响。⑥THSG 1μmol·L- 1显著提高大鼠胸主动脉血管组织NO含量。结论　THSG对大鼠主动脉具有舒张作用 ,此作用主要是依血管内皮的 ,并主要由NO介导     

Ferulic acid inhibits nitric oxide-induced apoptosis by enhancing GABA81 receptor expression in transient focal cerebral ischemia in rats

Aim:

Ferulic acid (4-hydroxy-3-methoxycinnamic acid, FA) provides neuroprotection against apoptosis in a transient middle cerebral artery occlusion (MCAo) model. This study was to further investigate the anti-apoptotic effect of FA during reperfusion after cerebral ischemia.

Methods:

Rats were subjected to 90 min of cerebral ischemia followed by 3 or 24 h of reperfusion after which they were sacrificed.

Results:

Intravenous FA (100 mg/kg) administered immediately after middle cerebral artery occlusion (MCAo) or 2 h after reperfusion effectively abrogated the elevation of postsynaptic density-95 (PSD-95), neuronal nitric oxide synthase (nNOS), inducible nitric oxide synthase (iNOS), nitrotyrosine, and cleaved caspase-3 levels as well as apoptosis in the ischemic cortex at 24 h of reperfusion. FA further inhibited Bax translocation, cytochrome c release, and p38 mitogen-activated protein (MAP) kinase phosphorylation. Moreover, FA enhanced the expression of gamma-aminobutyric acid type B receptor subunit 1 (GABA_B1) in the ischemic cortex at 3 and 24 h of reperfusion. In addition, nitrotyrosine-positive cells colocalized with cleaved caspase-3-positive cells, and phospho-p38 MAP kinase-positive cells colocalized with nitrotyrosine- and Bax-positive cells, indicating a positive relationship among the expression of nitrotyrosine, phospho-p38 MAP kinase, Bax, and cleaved caspase-3. The mutually exclusive expression of GABA_B1 and nitrotyrosine revealed that there is a negative correlation between GABA_B1 and nitrotyrosine expression profiles. Additionally, pretreatment with saclofen, a GABA_B receptor antagonist, abolished the neuroprotection of FA against nitric oxide (NO)-induced apoptosis.

Conclusion:

FA significantly enhances GABA_B1 receptor expression at early reperfusion and thereby provides neuroprotection against p38 MAP kinase-mediated NO-induced apoptosis at 24 h of reperfusion.     

Pharmacological characterization of AMP 579, a novel adenosine A1/A2 receptor agonist and cardioprotective

AMP 579 1S-[1α,2β,3β,4α(S*)]-4-[7-[[1-[(3-chloro-2-thienyl)methyl]propylamino]-3H-imidazo[4,5-b]pyridin-3-yl]-N-ethyl-2,3-dihydroxy cyclopentanecarboxamide) is a novel cardioprotective adenosine agonist with the following order of affinity at adenosine receptors: A₁ > A_2A > A₃. Agonism at A₁ receptors was demonstrated in vitro in three different systems: 1) inhibition of lipolysis in rat and human isolated adipocytes, 2) restoration of insulin-dependent glucose transport in rat adipocytes, and 3) reduction of heart rate in spontaneously beating rat right atria. Agonism at A_2A receptors was reflected in vasorelaxation of porcine coronary arterial rings (IC₅₀ = 0.3 μM); in comparison, agonism at A_2B receptors was ∼100-fold weaker, as reflected in relaxation of guinea pig aorta (IC₅₀ = 28 μM). When given iv to conscious Sprague-Dawley (SD) rats, AMP 579 dose-dependently lowered free fatty acids (FFA), heart rate (HR), and mean arterial pressure (MAP), but was 25-fold more potent at reducing FFA than at decreasing HR and MAP. In anesthetized rats undergoing myocardial ischemia-reperfusion injury, AMP 579 (3 μg/kg + 0.3 μg/kg/min iv and 10 μg/kg + 1 μg/kg/min iv) was able to reduce infarct size by 55% and 63%, respectively, compared to control animals, when given 10 min prior to and throughout the first hour of reperfusion. These cardioprotective doses of AMP 579 caused no significant change in blood pressure or coronary blood flow. In summary, AMP 579 is a novel adenosine A₁/A_2A receptor agonist which causes long-lasting reductions in FFA in vivo and has cardioprotective effects in a rat model of myocardial ischemia-reperfusion injury at doses which have minimal hemodynamic effects. Thus, AMP 579 has significant potential for the therapy of acute myocardial infarction. Drug Dev. Res. 45:30–43, 1998.© 1998 Wiley-Liss, Inc.     

The role of nitric oxide, superoxide and peroxynitrite in the anti-arrhythmic effects of preconditioning and peroxynitrite infusion in anaesthetized dogs

Background and purpose:

Both ischaemia preconditioning (PC) and the intracoronary infusion of peroxynitrite (PN) suppress ischaemia and reperfusion (I/R)-induced arrhythmias and the generation of nitrotyrosine (NT, a marker of PN). However, it is still unclear whether this latter effect is due to a reduction in nitric oxide (NO) or superoxide (O₂⁻) production.

Experimental approach:

Dogs anaesthetized with chloralose and urethane were infused, twice for 5 min, with either saline (control) or 100 nM PN, or subjected to similar periods of occlusion (PC), 5 min prior to a 25 min occlusion and reperfusion of the left anterior descending coronary artery. Severities of ischaemia and ventricular arrhythmias, as well as changes in the coronary sinus nitrate/nitrite (NOx) levels were assessed throughout the experiment. The production of myocardial NOx, O₂⁻ and NT was determined following reperfusion.

Key results:

Both PC and PN markedly suppressed the I/R-induced ventricular arrhythmias, compared to the controls, and increased NOx levels during coronary artery occlusion. Reperfusion induced almost the same increases in NOx levels in all groups, but superoxide production and, consequently, the generation of NT were significantly less in PC- and PN-treated dogs than in controls.

Conclusions and implications:

Since both PC and the administration of PN enhanced NOx levels during I/R, the attenuation of endogenous PN formation in these dogs is primarily due to a reduction in the amount of O₂ produced. Thus, the anti-arrhythmic effect of PC and PN can almost certainly be attributed to the preservation of NO availability during myocardial ischaemia.