Expression and Activation of BKCa Channels in Mice Protects Against Ischemia-Reperfusion Injury of Isolated Hearts by Modulating Mitochondrial Function

Sumanta Kumar Goswami; Devasena Ponnalagu; Ahmed T Hussain; Kajol Shah; Priyanka Karekar; Shubha Gururaja Rao; Andrea L Meredith; Mahmood Khan; Harpreet Singh

doi:10.3389/fcvm.2018.00194

Expression and Activation of BK_Ca Channels in Mice Protects Against Ischemia-Reperfusion Injury of Isolated Hearts by Modulating Mitochondrial Function

Front Cardiovasc Med. 2019 Jan 28:5:194. doi: 10.3389/fcvm.2018.00194. eCollection 2018.

Authors

Sumanta Kumar Goswami^{1

2}, Devasena Ponnalagu^{1

2}, Ahmed T Hussain¹, Kajol Shah¹, Priyanka Karekar^{1

2}, Shubha Gururaja Rao^{1

2}, Andrea L Meredith³, Mahmood Khan^{2

4}, Harpreet Singh^{1

2}

Affiliations

¹ Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA, United States.
² Department of Physiology and Cell Biology, Wexner Medical Center, Ohio State University, Columbus, OH, United States.
³ Department of Physiology, University of Maryland, Baltimore, MD, United States.
⁴ Department of Emergency Medicine, Wexner Medical Center, Ohio State University, Columbus, OH, United States.

Abstract

Aims: Activation and expression of large conductance calcium and voltage-activated potassium channel (BK_Ca) by pharmacological agents have been implicated in cardioprotection from ischemia-reperfusion (IR) injury possibly by regulating mitochondrial function. Given the non-specific effects of pharmacological agents, it is not clear whether activation of BK_Ca is critical to cardioprotection. In this study, we aimed to decipher the mechanistic role of BK_Ca in cardioprotection from IR injury by genetically activating BK_Ca channels. Methods and Results: Hearts from adult (3 months old) wild-type mice (C57/BL6) and mice expressing genetically activated BK_Ca (Tg-BK_Ca ^R207Q, referred as Tg-BK_Ca) along with wild-type BK_Ca were subjected to 20 min of ischemia and 30 min of reperfusion with or without ischemic preconditioning (IPC, 2 times for 2.5 min interval each). Left ventricular developed pressure (LVDP) was recorded using Millar's Mikrotip® catheter connected to ADInstrument data acquisition system. Myocardial infarction was quantified by 2,3,5-triphenyl tetrazolium chloride (TTC) staining. Our results demonstrated that Tg-BK_Ca mice are protected from IR injury, and BK_Ca also contributes to IPC-mediated cardioprotection. Cardiac function parameters were also measured by echocardiography and no differences were observed in left ventricular ejection fraction, fractional shortening and aortic velocities. Amplex Red® was used to assess reactive oxygen species (ROS) production in isolated mitochondria by spectrofluorometry. We found that genetic activation of BK_Ca reduces ROS after IR stress. Adult cardiomyocytes and mitochondria from Tg-BK_Ca mice were isolated and labeled with Anti-BK_Ca antibodies. Images acquired via confocal microscopy revealed localization of cardiac BK_Ca in the mitochondria. Conclusions: Activation of BK_Ca is essential for recovery of cardiac function after IR injury and is likely a factor in IPC mediated cardioprotection. Genetic activation of BK_Ca reduces ROS produced by complex I and complex II/III in Tg-BK_Ca mice after IR, and IPC further decreases it. These results implicate BK_Ca-mediated cardioprotection, in part, by reducing mitochondrial ROS production. Localization of Tg-BK_Ca in adult cardiomyocytes of transgenic mice was similar to BK_Ca in wild-type mice.

Keywords: BKCa channels; cardiac mitochondria; ischemia-reperfusion injury; ischemic preconditioning; myocardial infarction; reactive oxygen species.

Abstract

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