Effects of nerve growth factor-beta pretreatment on endoplasmic reticulum stress-induced cell apoptosis during ischemia-reperfusion in isolated rat hearts

Abstract

Objective To evaluate the effects of nerve growth factor-beta (NGF-β) pretreatment on cell apoptosis induced by endoplasmic reticulum stress during ischemia-reperfusion in isolated rat hearts.Methods Male Sprague-Dawley rats,weighing 180-220 g,were anesthetized with intraperitoneal 10％ chloral hydrate 300 mg/kg.The hearts were excised and perfused in a Langendorff apparatus with K-H solution aerated with 95％ O2 and 5％ CO2 at 37 ℃.Thirty-two isolated rat hearts were randomly divided into 4 groups (n =8 each) using a random number table:control group (group C),I/R group,NGF-β pretreatment group (group N) and NGF-β combined with K252a (trkA receptor antagonist) pretreatment group (group N + K).In group C,the hearts were continuously perfused with K-H solution for 195 min.The hearts were perfused with K-H solution for 45 min in group I/R.In N and N + K groups,the hearts were perfused with K-H solution for 15 min,and then with K-H solution containing 0.1 μg/ml NGF-β and 0.1 μg/ml NGF-β mixed with 100 nmol/L K252a,respectively,for 30 min.The perfusion was suspended for 30 min followed by 120 min of reperfusion with K-H solution in I/R,N and N + K groups.HR,left ventricular end-diastolic pressure (LVEDP),left ventricular developed pressure (LVDP) and + dp/dtmax were measured at the end of 15 min equilibration (baseline) and at 5,30,60 and 120 min of reperfusion.Myocardial specimens were obtained at 120 min of reperfusion for detection of myocardial apoptosis (by TUNEL) and expression of glucose-related protein 78 (GRP78),CCAAT/enhancer-binding protein homologous protein (CHOP),and caspase-12 (by Western blot analysis).Apoptosis index was calculated.Results Compared with group C,HR,LVDP and + dp/dtmax were significantly decreased,and LVEDP,apoptosis index and expression of GRP78 and CHOP were increased in I/R and N groups,and the expression of caspase-12 was upregulated in I/R group.Compared with group I/R,HR,LVDP,and + dp/dtmax were significantly increased,and LVEDP,apoptosis index and expression of GRP78,CHOP and caspase-12 were decreased in group N,and the expression of GRP78 was down-regulated in group N + K.There was no significant difference in cardiac function indexes between group I/R and N + K.Compared with group N,HR,LVDP and + dp/dtmax were significantly decreased,and LVEDP,apoptosis index,and expression of GRP78,CHOP and caspase-12 were increased in group N + K.Conclusion NGF-β pretreatment can protect the isolated rat hearts against ischemia-reperfusion injury,and inhibition of the endoplasmic reticulum stress-triggered cell apoptosis after activating trkA receptors is involved in the mechanism. Key words: Nerve growth factor; Endoplasmic reticulum; Stress; Apoptosis; Myocardial reperfusion injury