N-n-Butyl haloperidol iodide inhibits the augmented Na + /Ca 2+ exchanger currents and L-type Ca 2+ current induced by hypoxia/reoxygenation or H 2 O 2 in cardiomyocytes Yongpan Huang a , Fenfei Gao a , Yanmei Zhang a , Yicun Chen a , Bin Wang a , Yanshan Zheng a , Ganggang Shi a,b,⇑ a Department of Pharmacology, Shantou University Medical College, Shantou, China b Department of Cardiovascular Diseases, First Affiliated Hospital, Shantou University Medical College, Shantou, China article info Article history: Received 13 March 2012 Available online 2 April 2012 Keywords: N-n-butyl haloperidol iodide Na + /Ca 2+ exchanger currents L-type Ca 2+ current Ventricular myocytes Patch-clamp techniques abstract N-n-butyl haloperidol iodide (F 2 ), a novel quaternary ammonium salt derivative of haloperidol, was reported to antagonize myocardial ischemia/reperfusion injuries. To investigate its mechanisms, we char- acterized the effects of F 2 on Na + /Ca 2+ exchanger currents (I NCX ) and the L-type Ca 2+ channel current (I Ca,L ) of cardiomyocytes during either hypoxia/reoxygenation or exposure to H 2 O 2 . Using whole-cell patch- clamp techniques, the I NCX and I Ca,L were recorded from isolated rat ventricular myocytes. Exposure of cardiomyocytes to hypoxia/reoxygenation or H 2 O 2 enhanced the amplitude of the inward and outward of I NCX and I Ca,L .F 2 especially inhibited the outward current of Na + /Ca 2+ exchanger, as well as the I Ca,L , in a concentration-dependent manner. F 2 inhibits cardiomyocyte I NCX and I Ca,L after exposure to hypoxia/reoxygenation or H 2 O 2 to antagonize myocardial ischemia/reperfusion injury by inhibiting Ca 2+ overload. Ó 2012 Elsevier Inc. All rights reserved. 1. Introduction Ischemic heart disease is the leading cause of morbidity and mortality worldwide. Subsequent reperfusion of acutely ischemic myocardium is essential for myocardial rescue, but also leads to a unique type of injury known as myocardial ischemia/reperfusion (I/R) injury [1]. Such an injury is often related to endothelial and microvascular dysfunction, impaired blood flow, metabolic dysfunction, and cellular necrosis [2], and its mechanism is asso- ciated with cytosolic and mitochondrial calcium overload, release of reactive oxygen species (ROS), and an acute inflammatory re- sponse [3,4]. As one of the important mechanisms of I/R injury, much research has focused on the precise intracellular signaling pathways and elements responsible for calcium overload in ische- mia/reperfusion. Ca 2+ influx via both activation of L-type calcium channel and reversal of the Na + /Ca 2+ exchanger (NCX) have been reported to occur in cardiocytes following I/R [1,5,6]. Simulta- neously, ROS, including superoxide radicals, hydroxyl radicals, and oxidants such as H 2 O 2 are generated in significant amounts during reperfusion and could contribute to intracellular Ca 2+ overload in the heart through reversal or inhibition of the NCX [7,8]. Calcium overload may lead to deleterious consequences such as stunning, apoptosis, and necrosis, which contribute to in- farct formation [9–12]. Due to the pivotal role of calcium overload in I/R injury, attenuation of cellular calcium overload remains an important therapeutic goal. N-n-butyl haloperidol iodide, a novel quaternary ammonium salt derivative of haloperidol, was found to maintain the cardiac and vascular effects without adverse extrapyramidal reactions. Our previous studies showed that F 2 could block L-type calcium channels in ventricular myocytes under physiological conditions [13–15]. Subsequently, we demonstrated that F 2 could antago- nize myocardial I/R injury in different animal models [13,16]. So, we inferred that the mechanism by which F 2 antagonizes myocardial I/R injury might be related to the inhibition of Ca 2+ overload via suppression of cardiomyocyte Na + /Ca 2+ exchanger (I NCX ) currents and L-type Ca 2+ channel (I Ca,L ) during I/R. In this study, we established a model of cardiomyocyte hypoxia/reoxy- genation (H/R) and exposure to H 2 O 2 , to simulate heart I/R conditions, and characterized the changes of I NCX and I Ca,L during H/R and exposure to H 2 O 2 . We further characterized the effects of F 2 on I NCX and I Ca,L during H/R and exposure to H 2 O 2 to eluci- date the mechanisms and ability of F 2 to block myocardial I/R injury. 0006-291X/$ - see front matter Ó 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.bbrc.2012.03.119 ⇑ Corresponding author at: Department of Pharmacology, Shantou University Medical College, 22 Xinling Road, Shantou, Guangdong 515041, China. Fax: +86 754 88557562. E-mail addresses: yongpanhuangxy@yahoo.cn, ggshi@stu.edu.cn (G. Shi). Biochemical and Biophysical Research Communications 421 (2012) 86–90 Contents lists available at SciVerse ScienceDirect Biochemical and Biophysical Research Communications journal homepage: www.elsevier.com/locate/ybbrc