Iptakalim,an ATP-sensitive potassium channel opener,confers neuroprotection against cerebral ischemia/reperfusion injury in rats by protecting neurovascular unit cells

Objective:To investigate the role of iptakalim,an ATP-sensitive potassium channel opener,in transient cerebral ischemia/reperfusion (I/R) injury and its involved mechanisms.Methods:Intraluminal occlusion of middle cerebral artery (MCAO) in a rat model was used to investigate the effect of iptakalim at different time points.Infarct volume was measured by staining with 2,3,5-triphenyltetrazolium chloride,and immunohistochemistry was used to evaluate the expressions of Bcl-2 and Bax.In vitro,neurovascular unit (NVU) cells,including rat primary cortical neurons,astrocytes,and cerebral microvascular endothelial cells,were cultured and underwent oxygen-glucose deprivation (OGD).The protective effect of iptakalim on NVU cells was investigated by cell viability and injury assessments,which were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and release of lactate dehydrogenase.Caspase-3,Bcl-2 and Bax mRNA expressions were evaluated by real-time polymerase chain reaction (PCR).Results:Administration of iptakalim 0 or 1 h after reperfusion significantly reduced infarct volumes,improved neurological scores,and attenuated brain edema after cerebral I/R injury.Iptakalim treatment (0 h after reperfusion) also reduced caspase-3 expression and increased the ratio of Bcl-2 to Bax by immunohistochemistry.Iptakalim inhibited OGD-induced cell death in cultured neurons and astrocytes,and lactate dehydrogenase release from cerebral microvascular endothelial cells.Iptakalim reduced mRNA expression of caspase-3 and increased the ratio of Bcl-2 to Bax in NVU cells.Conclusions:Iptakalim confers neuroprotection against cerebral I/R injury by protecting NVU cells via inhibiting of apoptosis.

Cromakalin pretreatment affects mitochondrial structure and function in a rat model of ischemia/reperfusion injury

BACKGROUND：Mitochondrial structural changes and energy dysmetabolism frequently occur subsequent to cerebral ischemia.Adenosine triphosphate（ATP）-sensitive potassium channel openers exhibit protective effects on cerebral ischemia/reperfusion injury.OBJECTIVE：To validate the effects of cromakalin on mitochondrial structure and function in ischemic penumbra brain tissue in a rat model of middle cerebral artery occlusion（MCAO）.DESIGN,TIME AND SETTING：The present single-factor analysis of variance,randomized,controlled,animal experiment was performed at the Institute of Brain Science,Affiliated Hospital of Qingdao University Medical College between October 2007 and March 2008.MATERIALS：Forty male,Wistar rats were randomly divided into four groups,with 10 rats per group：sham-operated,MCAO,MCAO＋ATP-sensitive potassium channel opener（cromakalin）,and MCAO＋cromakalin＋ATP-sensitive potassium channel blocking agent（glibenclamide）.METHODS：Focal cerebral ischemia/reperfusion injury was induced by MCAO in all groups except the sham-operated group.The MCAO cromakalin group was administered 10 mg/kg cromakalin（i.p.） prior to MCAO induction.The MCAO＋cromakalin＋glibenclamide group received an injection of 10 mg/kg cromakalin（i.v.）,and subsequently an injection of 10 mg/kg cromakalin（i.p.） prior to MCAO induction.MAIN OUTCOME MEASURES：At 24 hours after cerebral ischemia/reperfusion injury,cellular apoptosis was detected by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate（dUTP） nick-end labeling technique.Cytochrome C expression was measured by immunohistochemistry.In addition,mitochondrial swelling,membrane fluidity,membrane phospholipid and malonaldehyde（MDA） contents,as well as Na^＋-K^＋-ATPase,Ca^2 ＋-ATPase,and superoxide dismutase（SOD） activities were determined.RESULTS：Compared with the sham-operated group,the three ischemia groups exhibited significantly elevated mitochondrial MDA content,reduced membrane phospholipid and ATP contents,down-regulated membrane fluidity,and reduced Na^＋-K^＋-ATPase,Ca^2＋-ATPase,and SOD activities（P 〈 0.05-0.01）.In the MCAO＋cromakalin group,the number of apoptotic cells decreased,and cytochrome C expression,as well as MDA content,were reduced.However,ATP content and Na^＋-K^＋-ATPase,Ca^2＋-ATPase,and SOD activities significantly increased compared with the MCAO group（P 〈 0.05-0.01）.Glibenclamide noticeably antagonized cromakalin protection of mitochondria.CONCLUSION：Pretreatment with the ATP-sensitive potassium channel opener cromakalin increased mitochondrial Na^＋-K^＋-ATPase,Ca2＋-ATPase,and SOD activities,decreased neuronal apoptosis,and inhibited cytochrome C expression following MCAO.