Calcitonin gene-related peptide-mediated cardioprotection of postconditioning in isolated rat hearts

Previous studies have demonstrated that endogenous calcitonin gene-related peptide (CGRP) plays an important role in mediation of ischemic preconditioning. In the present study, we tested whether CGRP is also involved in mediation of the protective effects of postconditioning in isolated rat hearts. Sixty minutes of left coronary artery occlusion and followed by 60 min of reperfusion caused a significant decrease in cardiac function and a significant increase in creatine kinase (CK) release and infarct size. Postconditioning with three cycles of 1-min ischemia and 1-min reperfusion produced a marked improvement of cardiac function and decreased CK release and infarct size, concomitantly with an increase in the release of CGRP release in coronary effluent. However, the cardioprotection afforded by postconditioning was abolished by CGRP 8-37 (10^− 7 M), a selective CGRP receptor antagonist, or pretreatment with capsaicin (50 mg/kg, s.c.), which depletes transmitters in sensory nerves. Exogenous CGRP (5 × 10^− 9 M) administration of CGRP reappeared postconditioning-like cardioprotection in the rats pretreated with capsaicin. These results suggest that the protective effects of ischemic postconditioning are related to stimulation of endogenous CGRP release in rat hearts.     

Chronic type-I diabetes could not impede the anti-inflammatory and anti-apoptotic effects of combined postconditioning with ischemia and cyclosporine A in myocardial reperfusion injury

It has been shown that diabetes modifies the myocardial responses to ischemia/reperfusion (I/R) and to cardioprotective agents. In this study, we aimed to investigate the effects of combined treatment with ischemic postconditioning (IPostC) and cyclosporine A (CsA) on inflammation and apoptosis of the diabetic myocardium injured by I/R. Eight weeks after induction of diabetes in Wistar rats, hearts were mounted on a Langendorff apparatus and were subsequently subjected to a 30-min regional ischemia followed by 45-min reperfusion. IPostC was induced at the onset of reperfusion, by 3 cycles of 30-s reperfusion/ischemia (R/I). The concentration of creatine kinase (CK), tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 were determined; the levels of total and phosphorylated glycogen synthase kinase 3 beta (p-GSK3β) and B-cell lymphoma 2 (Bcl-2) were quantified by western blotting, and the rate of apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) staining. Administration of either IPostC or CsA alone in nondiabetic animals significantly reduced CK, TNF-α, IL-1β, and IL-6 concentrations, increased the p-GSK3β and Bcl-2, and decreased the level of apoptosis (P < 0.05) but had no effect on diabetic hearts. However, in diabetic animals, after administration of CsA, the cardioprotective effects of IPostC in increasing the p-GSK3β and Bcl-2 and decreasing apoptosis and inflammation were restored in comparison with nonpostconditioned diabetic hearts. IPostC or CsA failed to affect apoptosis and inflammation and failed to protect the diabetic myocardium against I/R injury. However, combined administration of IPostC and CsA at reperfusion can protect the diabetic myocardium by decreasing the inflammatory response and apoptosis.     

N-oleoyldopamine, a novel endogenous capsaicin-like lipid, protects the heart against ischemia-reperfusion injury via activation of TRPV1

N-oleoyldopamine (OLDA), a bioactive lipid originally found in the mammalian brain, is an endovanilloid that selectively activates the transient receptor potential vanilloid type 1 (TRPV1) channel. This study tests the hypothesis that OLDA protects the heart against ischemia and reperfusion (I/R) injury via activation of the TRPV1 in wild-type (WT) but not in gene-targeted TRPV1-null mutant (TRPV1(-/-)) mice. Hearts of WT or TRPV1(-/-) mice were Langendorffly perfused with OLDA (2 x 10(-9) M) in the presence or absence of CGRP8-37 (1 x 10(-6) M), a selective calcitonin gene-related peptide (CGRP) receptor antagonist; RP-67580 (1 x 10(-6) M), a selective neurokinin-1 receptor antagonist; chelerythrine (5 x 10(-6) M), a selective protein kinase C (PKC) antagonist; or tetrabutylammonium (TBA, 5 x 10(-4) M), a nonselective K(+) channel antagonist, followed by 35 min of global ischemia and 40 min of reperfusion (I/R). Left ventricular end-diastolic pressure (LVEDP), left ventricular developed pressure (LVDP), coronary flow (CF), and left ventricular peak positive dP/dt (+dP/dt) were evaluated after I/R. OLDA improved recovery of cardiac function after I/R in WT but not TRPV1(-/-) hearts by increasing LVDP, CF, and +dP/dt and by decreasing LVEDP. CGRP8-37, RP-67580, chelerythrine, or TBA abolished the protective effect of OLDA in WT hearts. Radioimmunoassay showed that the release of substance P (SP) and CGRP after OLDA treatment was higher in WT than in TRPV1(-/-) hearts, which was blocked by chelerythrine or TBA. Thus OLDA exerts a cardiac protective effect during I/R injury in WT hearts via CGRP and SP release, which is abolished by PKC or K(+) channel antagonists. The protective effect of OLDA is void in TRPV1(-/-) hearts, supporting the notion that TRPV1 mediates OLDA-induced protection against cardiac I/R injury.     

TRPV1 gene knockout impairs preconditioning protection against myocardial injury in isolated perfused hearts in mice

Although the transient receptor potential vanilloid type 1 (TRPV1)-containing afferent nerve fibers are widely distributed in the heart, the relationship between TRPV1 function and cardiac ischemic preconditioning (PC) has not been well defined. Using TRPV1 knockout mice (TRPV1(-/-)), we studied the role of TRPV1 in PC-induced myocardial protection. Hearts of gene-targeted TRPV1-null mutant (TRPV1(-/-)) or wild-type (WT) mice were Langendorffly perfused in the presence or absence of CGRP(8-37), a selective calcitonin gene-related peptide (CGRP) receptor antagonist; or RP-67580, a selective neurokinin-1 receptor antagonist when hearts were subjected to three 5-min periods of ischemia PC followed by 30 min of global ischemia and 40 min of reperfusion (I/R). PC before I/R decreased left ventricular (LV) end-diastolic pressure and increased LV developed pressure, coronary flow (CF), peak-positive maximum rate of rise of LV pressure in WT mice (PC-WT) compared with PC-TRPV1(-/-), TRPV1(-/-), or WT hearts (P < 0.05), and PC also decreased LV end-diastolic pressure in PC-TRPV1(-/-) compared with TRPV1(-/-). CGRP(8-37) or RP-67580 abolished PC-induced protection in WT but not TRPV1(-/-) hearts (P < 0.05). Moreover, PC decreased lactate dehydrogenase release and infarct size in PC-WT compared with PC-TRPV1(-/-), TRPV1(-/-), or WT hearts, and it also lowered these parameters in PC-TRPV1(-/-) compared with TRPV1(-/-) hearts (P < 0.05). Radioimmunoassay showed that the release of substance P and CGRP after PC was higher in WT hearts than in TRPV1(-/-) hearts (P < 0.05), which was attenuated by capsazepine in WT but not TRPV1(-/-) hearts. Thus PC-induced protection of the heart was impaired in TRPV1(-/-) hearts, indicating that TRPV1 contributes to the beneficial effects of preconditioning against I/R injury through release substance P and CGRP.     

Endogenous hydrogen sulphide mediates the cardioprotection induced by ischemic postconditioning

The present study aimed to investigate the role of hydrogen sulphide (H2S) in the cardioprotection induced by ischemic postconditioning and to examine the underlying mechanisms. Cardiodynamics and myocardial infarction were measured in isolated rat hearts. Postconditioning with six episodes of 10-s ischemia (IPostC) significantly improved cardiodynamic function, which was attenuated by the blockade of endogenous H2S production with d-l-propargylglycine. Moreover, IPostC significantly stimulated H2S synthesis enzyme activity during the early period of reperfusion. However, d-l-propargylglycine only attenuated the IPostC-induced activation of PKC-alpha and PKC-epsilon but not that of PKC-delta, Akt, and endothelial nitric oxide synthase (eNOS). These data suggest that endogenous H2S contributes partially to the cardioprotection of IPostC via stimulating PKC-alpha and PKC-epsilon. Postconditioning with six episodes of a 10-s infusion of NaHS (SPostC) or 2 min continuous NaHS infusion (SPostC2) stimulated activities of Akt and PKC, improved the cardiodynamic performances, and reduced myocardial infarct size. The blockade of Akt with LY-294002 (15 microM) or PKC with chelerythrine (10 microM) abolished the cardioprotection induced by H2S postconditioning. SPostC2, but not SPostC, also additionally stimulated eNOS. We conclude that endogenous H2S contributes to IPostC-induced cardioprotection. H2S postconditioning confers the protective effects against ischemia-reperfusion injury through the activation of Akt, PKC, and eNOS pathways.     

Reduction of SIRT1 blunts the protective effects of ischemic post-conditioning in diabetic mice by impairing the Akt signaling pathway

Ischemic post-conditioning (IPO) activates Akt signaling to confer cardioprotection. The responsiveness of diabetic hearts to IPO is impaired. We hypothesized that decreased cardiac SIRT1, a positive regulator of Akt, may be responsible for the impaired responsiveness of diabetic hearts to IPO-mediated cardioprotection. High-fat diet and streptozotocin-induced diabetic mice were subjected to myocardial ischemia/reperfusion (MI/R, 30 min ischemia and 180 min reperfusion) or IPO (three cycles of 10 s of reperfusion and ischemia at the onset of reperfusion). Adenoviral vectors encoding GFP or SIRT1 (Ad-SIRT1) were administered by direct injection into the left ventricular. Our results showed that IPO activated the Akt signaling pathway and reduced MI/R injury in non-diabetic hearts but not in diabetic hearts, in which reduced expression of SIRT1 and increased Akt acetylation were observed. Delivery of Ad-SIRT1 into the diabetic hearts reduced Akt acetylation and restored the cardioprotective effects of IPO by modulating Akt signaling pathway. In contrast, cardiac-specific SIRT1 knockout increased Akt acetylation and blunted the cardioprotective effects of IPO. In in vitro study, transfection with wild-type SIRT1 but not inactive mutant SIRT1 reduced the expression of Akt acetylation and restored the protective effects of hypoxic post-conditioning in high glucose-incubated cardiomyocytes. Moreover, the cardiomyocytes transfected with constitutive Akt acetylation showed repressed Akt phosphorylation and blunted protective effects against hypoxia/reoxygenation injury. These findings demonstrate that the reduction of SIRT1 blunts the protective effects of IPO by impairing Akt signaling pathway and that SIRT1 up-regulation restores IPO-mediated cardioprotection in diabetic mice via deacetylation-dependent activation of Akt signaling pathway.     

Evidence for calcitonin gene-related peptide-mediated ischemic preconditioning in the rat heart.

Previous studies have suggested that calcitonin gene-related peptide (CGRP) may play an important role in the mediation of ischemic preconditioning. In the present study, we examined the release of CGRP during ischemic preconditioning and the effect of preconditioning frequency on this effect in the isolated rat heart. Thirty minutes of global ischemia and 40 min of reperfusion caused a significant cardiac dysfunction and an increase in the release of creatine kinase (CK) during reperfusion. Preconditioning with one, two or three cycles of 5-min ischemia and 5-min reperfusion caused a marked improvement of cardiac function and a decrease in the release of CK, and there was no difference in the degree of improvement among groups. The protective effects of ischemic preconditioning were abolished by the CGRP receptor antagonist CGRP(8-37). A single preconditioning cycle induced a significant increase in the release of CGRP in the coronary effluent. In the hearts treated with two or three preconditioning cycles, the level of CGRP was highest in the first cycle, and was gradually decreased with increasing number of cycles of preconditioning. These results suggest that the protective effects of ischemic preconditioning are mediated by endogenous CGRP in the isolated rat heart.     

一氧化氮在乙醇后处理心肌保护中的作用

目的:探讨乙醇后处理心肌保护作用是否与一氧化氮生成有关。方法:局部结扎冠状动脉左前降支30min,复灌120 min复制离体大鼠心肌缺血/复灌模型。心肌缺血末5 min,复灌初期10min给予乙醇50mmol/L,共灌流15 min进行乙醇后处理干预。实验随机分为五组,正常组,缺血/复灌组,乙醇后处理组,乙醇后处理+L-NAME组和乙醇后处理+苍术苷组。测定心室动力学指标和复灌期间冠脉流出液中乳酸脱氢酶(LDH)含量,TTC染色法测定心肌梗死面积,硝酸还原法测定心肌组织一氧化氮(NO)含量。RT-PCR检测左心室前壁心尖组织Bc-l2和BaxmRNA的表达。结果:与单纯缺血/复灌相比,乙醇后处理明显促进了左室发展压、左室做功的恢复,降低复灌期冠脉流出液中LDH的释放和心肌梗死面积,心肌组织NO释放减少,Bc-l 2/Bax mRNA比值增高。一氧化氮合酶抑制剂L-NAME和线粒体渗透性转换孔道开放剂苍术苷均抑制了乙醇后处理心室功能的恢复、LDH释放的减少和梗死面积的降低,心肌组织NO释放进一步减少,Bc-l 2/Bax mRNA比值降低。结论:乙醇后处理的心肌保护作用可能与减少NO的释放、抑制线粒体渗透性转换孔道的开放和抑制细胞凋亡的发生有关。     

Sevoflurane postconditioning attenuates reperfusion-induced ventricular arrhythmias in isolated rat hearts exposed to ischemia/reperfusion injury

Sevoflurane postconditioning has been proven to protect the hearts against ischemia/reperfusion injury, manifested mainly by improved cardiac function, reduced myocardial specific biomarker release, and decreased infarct size. This study is to observe the effects of sevoflurane postconditioning on reperfusion-induced ventricular arrhythmias and reactive oxygen species generation in Langendorff perfused rat hearts. Compared with the unprotected hearts subjected to 25 min of global ischemia followed by 30 min of reperfusion, exposure of 3% sevoflurane during the first 15 min of reperfusion significantly improved cardiac function, reduced cardiac troponin I release, decreased infarct size and attenuated reperfusion-induced ventricular arrhythmia. Further analysis on arrhythmia during the 30 min of reperfusion showed that, sevoflurane postconditioning decreased both the duration and incidence of ventricular tachycardia and ventricular fibrillation. In the meantime, intracellular malondialdehyde and reactive oxygen species levels were also reduced. These above results demonstrate that sevoflurane postconditioning protects the hearts against ischemia/reperfusion injury and attenuates reperfusion-induced arrhythmia, which may be associated with the regulation of lipid peroxidation and reactive oxygen species generation.     

Hypercholesterolemic Myocardium Is Vulnerable to Ischemia-Reperfusion Injury and Refractory to Sevoflurane-Induced Protection

Recent studies have demonstrated that volatile anesthetic postconditioning confers myocardial protection against ischemia-reperfusion (IR) injury through activation of the reperfusion injury salvage kinase (RISK) pathway. As RISK has been shown to be impaired in hypercholesterolemia. Therefore, we investigate whether anesthetic-induced cardiac protection was maintained in hypercholesterolemic rats. In the present study, normocholesteolemic or hypercholesterolemic rat hearts were subjected to 30 min of ischemia and 2 h of reperfusion. Animals received 2.4% sevoflurane for 5 min or 3 cycles of 10-s ischemia/10-s reperfusion. The hemodynamic parameters, including left ventricular developed pressure, left ventricular end-diastolic pressure and heart rate, were continuously monitored. The infarct size, apoptosis, p-Akt, p-ERK1/2, p-GSK3β were determined. We found that both sevoflurane and ischemic postconditioning significantly improved heart pump function, reduced infarct size and increased the phosphorylation of Akt, ERK1/2 and their downstream target of GSK3β in the healthy rats. In the hypercholesterolemic rats, neither sevoflurane nor ischemic postconditioning improved left ventricular hemodynamics, reduced infarct size and increased the phosphorylated Akt, ERK1/2 and GSK3β. In contrast, GSK inhibitor SB216763 conferred cardioprotection against IR injury in healthy and hypercholesterolemic hearts. In conclusions, hyperchoesterolemia abrogated sevoflurane-induced cardioprotection against IR injury by alteration of upstream signaling of GSK3β and acute GSK inhibition may provide a novel therapeutic strategy to protect hypercholesterolemic hearts against IR injury.     

Cardioprotection mediated by sphingosine-1-phosphate and ganglioside GM-1 in wild-type and PKC epsilon knockout mouse hearts

Sphingosine-1-phosphate (S1P) protects neonatal rat cardiac myocytes from hypoxic damage through unknown signaling pathways. We tested the hypothesis that S1P-induced cardioprotection requires activation by the epsilon-isoform of protein kinase C (PKC epsilon) by subjecting hearts isolated from PKC epsilon knockout mice and wild-type mice to 20 min of global ischemia and 30 min of reperfusion. Pretreatment with a 2-min infusion of 10 nM S1P improved recovery of left ventricular developed pressure (LVDP) in both wild-type and PKC epsilon knockout hearts and reduced the rise in LV end-diastolic pressure (LVEDP) and creatine kinase (CK) release. Pretreatment for 2 min with 10 nM of the ganglioside GM-1 also improved recovery of LVDP and suppressed CK release in wild-type hearts but not in PKC epsilon knockout hearts. Importantly, GM-1 but not S1P, increased the proportion of PKC epsilon localized to particulate fractions. Our results suggest that GM-1, which enhances endogenous S1P production, reduces cardiac injury through PKC epsilon-dependent intracellular pathways. In contrast, extracellular S1P induces equivalent cardioprotection through PKC epsilon-independent signaling pathways.     

Targeted deletion of A2A adenosine receptors attenuates the protective effects of myocardial postconditioning

Endogenous adenosine is an important ligand trigger for the cardioprotective effects of postconditioning (POC), yet it is unclear which adenosine receptor subtype is primarily responsible. To evaluate the role of A(2A) adenosine receptors in POC-induced protection, global ischemia-reperfusion was performed with and without POC in isolated wild-type (WT) and A(2A) adenosine receptor knockout (A(2A)KO) mouse hearts. Injury was measured in terms of postischemic functional recovery and release of cardiac troponin I (cTnI). Activation of protective signaling with POC was assessed by Akt and extracellular signal-regulated kinase (ERK) 1/2 phosphorylation. In WT hearts, POC improved recovery of postischemic developed pressure in early (81.6 +/- 6.4% of preischemic baseline vs. 37.5 +/- 5.6% for non-POC WT at 1 min) and late (62.2 +/- 4.2% of baseline vs. 45.5 +/- 5.3% for non-POC WT at 30 min) reperfusion, reduced cTnI release by 37%, and doubled the phosphorylation of both Akt and ERK1/2. These beneficial effects of POC were blocked by treatment with the selective A(2A) adenosine receptor antagonist ZM-241385 during reperfusion. Postischemic functional recovery, cTnI release, and phosphorylation of Akt and ERK1/2 were not different between non-POC WT and A(2A)KO hearts. In A(2A)KO hearts, POC did not improve functional recovery, reduce cTnI release, nor increase phosphorylation of Akt or ERK1/2. Thus the protective effects of POC are attenuated by both selective A(2A) receptor antagonism and targeted deletion of the gene encoding A(2A) adenosine receptors. These observations support the conclusion that endogenous activation of A(2A) adenosine receptors is an essential trigger leading to the protective effects of POC in isolated murine hearts.     

不同强度及时间窗骨骼肌缺血后处理对兔心肌的保护作用

目的:通过比较不同强度及时间窗骨骼肌缺血后处理对兔缺血/再灌注心肌的保护效能,试图寻找最佳强度和时间窗的骨骼肌缺血后处理方案。方法:健康新西兰大白兔42只(雄性)随机分为7组(n=6):①假手术组(Sham)、②缺血对照组(CON)、③标准骨骼肌后处理组(SP)、④延迟6min骨骼肌后处理组(6M-DSP)、⑤延迟1 min骨骼肌后处理组(1M-DSP)、⑥骨骼肌后处理加强组(SSP)、⑦骨骼肌后处理减弱组(WSP)。以开胸结扎冠状动脉左室支固定部位方法制作缺血/再灌注模型,以游离并夹闭双侧腹股沟髂外动脉固定位置方法造成骨骼肌缺血,再灌注末以TTC法确定心肌梗死范围,并分别于心肌缺血前、后及再灌注1 h、2 h,以生化法测定血清肌酸激酶(CK)及乳酸脱氢酶(LDH)水平。结果:和CON组相比,1M-DSP组心肌梗死重量比及面积比分别下降了42.32%及42.68%、SP组分别下降了49.97%及43.78%、SSP组分别下降了48.36%及48.86%,(P均<0.05),但三组之间相比,心梗范围未见明显差异;而6M-DSP、WSP组与CON组相比未见心肌保护作用;肌酸激酶(CK)的水平和梗死范围变化趋势一致。结论:兔在心肌缺血/再灌注之前完成骨骼肌5 min缺血/1 min再灌注1次循环的缺血后处理,可以起到明显的心肌保护作用。     

Attenuation of ischemia–reperfusion injury by sevoflurane postconditioning involves protein kinase B and glycogen synthase kinase 3 beta activation in isolated rat hearts

Volatile anesthetic ischemic postconditioning reduces infarct size following ischemia/reperfusion. Whether phosphorylation of protein kinase B (PKB/Akt) and glycogen synthase kinase 3 beta (GSK3β) is causal for cardioprotection by postconditioning is controversial. We therefore investigated the impact of PKB/Akt and GSK3β in isolated perfused rat hearts subjected to 40 min of ischemia followed by 1 h of reperfusion. 2.0% sevoflurane (1.0 minimum alveolar concentration) was administered at the onset of reperfusion in 15 min as postconditioning. Western blot analysis was used to determine phosphorylation of PKB/Akt and its downstream target GSK3β after 1 h of reperfusion. Mitochondrial and cytosolic content of cytochrome C checked by western blot served as a marker for mitochondrial permeability transition pore opening. Sevoflurane postconditioning significantly improved functional cardiac recovery and decreased infarct size in isolated rat hearts. Compared with unprotected hearts, sevoflurane postconditioning-induced phosphorylation of PKB/Akt and GSK3β were significantly increased. Increase of cytochrome C in mitochondria and decrease of it in cytosol is significant when compared with unprotected ones which have reversal effects on cytochrome C. The current study presents evidence that sevoflurane-induced cardioprotection at the onset of reperfusion are partly through activation of PKB/Akt and GSK3β.     

Dexmedetomidine preconditioning activates pro-survival kinases and attenuates regional ischemia/reperfusion injury in rat heart

Pharmacological preconditioning limits myocardial infarct size after ischemia/reperfusion. Dexmedetomidine is an α(2)-adrenergic receptor agonist used in anesthesia that may have cardioprotective properties against ischemia/reperfusion injury. We investigate whether dexmedetomidine administration activates cardiac survival kinases and induces cardioprotection against regional ischemia/reperfusion injury. In in vivo and ex vivo models, rat hearts were subjected to 30 min of regional ischemia followed by 120 min of reperfusion with dexmedetomidine before ischemia. The α(2)-adrenergic receptor antagonist yohimbine was also given before ischemia, alone or with dexmedetomidine. Erk1/2, Akt and eNOS phosphorylations were determined before ischemia/reperfusion. Cardioprotection after regional ischemia/reperfusion was assessed from infarct size measurement and ventricular function recovery. Localization of α(2)-adrenergic receptors in cardiac tissue was also assessed. Dexmedetomidine preconditioning increased levels of phosphorylated Erk1/2, Akt and eNOS forms before ischemia/reperfusion; being significantly reversed by yohimbine in both models. Dexmedetomidine preconditioning (in vivo model) and peri-insult protection (ex vivo model) significantly reduced myocardial infarction size, improved functional recovery and yohimbine abolished dexmedetomidine-induced cardioprotection in both models. The phosphatidylinositol 3-kinase inhibitor LY-294002 reversed myocardial infarction size reduction induced by dexmedetomidine preconditioning. The three isotypes of α(2)-adrenergic receptors were detected in the whole cardiac tissue whereas only the subtypes 2A and 2C were observed in isolated rat adult cardiomyocytes. These results show that dexmedetomidine preconditioning and dexmedetomidine peri-insult administration produce cardioprotection against regional ischemia/reperfusion injury, which is mediated by the activation of pro-survival kinases after cardiac α(2)-adrenergic receptor stimulation.     

Calcitonin gene-related peptide-mediated ischemic preconditioning in the rat heart: influence of age

In the present study, we examined whether age-related reduction of ischemic preconditioning is related to calcitonin gene-related peptide (CGRP) release in the rat heart. Thirty minutes of global ischemia and 40 min of reperfusion caused a significant decrease of cardiac function and a marked increase of creatine kinase (CK) release at 2, 6 and 20 months of age. Ischemic preconditioning and pretreatment with CGRP for 5 min significantly improved cardiac function and reduced CK release during reperfusion at 2 and 6 months of age but not at 20 months of age. The content of CGRP in the coronary effluent during ischemic preconditioning was significantly increased in the first cycle at 2, 6 months of age but not at 20 months of age. These results suggest that the protection afforded by ischemic preconditioning is decreased in aging hearts, and the age-related change may be related to reduction of the release and effect of CGRP in the rat heart.     

Cardioprotection from ischemia-reperfusion injury due to Ras-GTPase inhibition is attenuated by glibenclamide in the globally ischemic heart

The present study was designed to see if acute local inhibition of Ras-GTPase before or after ischemia (during perfusion) would produce protection against ischemia and reperfusion (I/R)-induced cardiac dysfunction. The effect of glibenclamide, an inhibitor of cardiac mitochondrial ATP-sensitive potassium (mitoK(ATP)) channels, on Ras-GTPase-mediated cardioprotection was also studied. A 40 min episode of global ischemia followed by a 30 min reperfusion in perfused rat hearts produced significantly impaired cardiac function, measured as left ventricular developed pressure (P(max)) and left ventricular end-diastolic pressure (LVEDP). Perfusion with Ras-GTPase inhibitor FPT III before I/R [FPT(pre)], significantly enhanced cardiac recovery in terms of left ventricular contractility. P(max) was significantly higher at the end of 30 min reperfusion in FPT(pre)-treated hearts compared to pre-conditioned hearts. However, the degree of improvement in left ventricular contractility was significantly less when FPT III was given only after ischemia during reperfusion [FPT(post)]. Combination treatment with FPT III and glibenclamide before I/R resulted in significant reduction of FPT III-mediated cardioprotection. These data suggest that activation of Ras-GTPase signaling pathways during ischemia are critical in the development of left ventricular dysfunction and that opening of mitoK(ATP) channels, at least in part, contributes to cardioprotection produced by Ras-GTPase inhibition.     

Transient receptor potential vanilloid 1, calcitonin gene-related peptide, and substance P mediate nociception in acute pancreatitis

The mechanism of pancreatitis-induced pain is unknown. In other tissues, inflammation activates transient receptor potential vanilloid 1 (TRPV1) on sensory nerves to liberate CGRP and substance P (SP) in peripheral tissues and the dorsal horn to cause neurogenic inflammation and pain, respectively. We evaluated the contribution of TRPV1, CGRP, and SP to pancreatic pain in rats. TRPV1, CGRP, and SP were coexpressed in nerve fibers of the pancreas. Injection of the TRPV1 agonist capsaicin into the pancreatic duct induced endocytosis of the neurokinin 1 receptor in spinal neurons in the dorsal horn (T10), indicative of SP release upon stimulation of pancreatic sensory nerves. Induction of necrotizing pancreatitis by treatment with L-arginine caused a 12-fold increase in the number of spinal neurons expressing the proto-oncogene c-fos in laminae I and II of L1, suggesting activation of nociceptive pathways. L-arginine also caused a threefold increase in spontaneous abdominal contractions detected by electromyography, suggestive of referred pain. Systemic administration of the TRPV1 antagonist capsazepine inhibited c-fos expression by 2.5-fold and abdominal contractions by 4-fold. Intrathecal, but not systemic, administration of antagonists of CGRP (CGRP(8-37)) and SP (SR140333) receptors attenuated c-fos expression in spinal neurons by twofold. Thus necrotizing pancreatitis activates TRPV1 on pancreatic sensory nerves to release SP and CGRP in the dorsal horn, resulting in nociception. Antagonism of TRPV1, SP, and CGRP receptors may suppress pancreatitis pain.     

Sevoflurane postconditioning protects isolated rat hearts against ischemia-reperfusion injury: the role of radical oxygen species,extracellular signal-related kinases 1/2 and mitochondrial permeability transition pore

The roles of reactive oxygen species (ROS), extracellular signal-regulated kinase 1/2 (ERK 1/2) and mitochondrial permeability transition pore (mPTP) in sevoflurane postconditioning induced cardioprotection against ischemia-reperfusion injury in Langendorff rat hearts were investigated. When compared with the unprotected hearts subjected to 30 min of ischemia followed by 1 h of reperfusion, exposure of 3% sevoflurane during the first 15 min of reperfusion significantly improved functional recovery, decreased infarct size, reduced lactate dehydrogenase and creatine kinase-MB release, and reduced myocardial malondialdehyde production. However, these protective effects were abolished in the presence of either ROS scavenger N-acetylcysteine or ERK 1/2 inhibitor PD98059, and accompanied by prevention of ERK 1/2 phosphorylation and elimination of inhibitory effect on mPTP opening. These findings suggested that sevoflurane postconditioning protected isolated rat hearts against ischemia-reperfusion injury via the recruitment of the ROS-ERK 1/2-mPTP signaling cascade.