AUTHOR=Xie Chaoqin , Kauffman Justin , Akar Fadi G. TITLE=Functional crosstalk between the mitochondrial PTP and KATP channels determine arrhythmic vulnerability to oxidative stress JOURNAL=Frontiers in Physiology VOLUME=5 YEAR=2014 URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2014.00264 DOI=10.3389/fphys.2014.00264 ISSN=1664-042X ABSTRACT=

Background: Mitochondrial permeability transition pore (mPTP) opening is a terminal event leading to mitochondrial dysfunction and cell death under conditions of oxidative stress (OS). However, mPTP blockade with cyclosporine A (CsA) has shown variable efficacy in limiting post-ischemic dysfunction and arrhythmias. We hypothesized that strong feedback between energy dissipating (mPTP) and cardioprotective (mK_ATP) channels determine vulnerability to OS.

Methods and Results: Guinea pig hearts (N = 61) were challenged with H₂O₂ (200 μM) to elicit mitochondrial membrane potential (ΔΨ_m) depolarization. High-resolution optical mapping was used to measure ΔΨ_m or action potentials (AP) across the intact heart. Hearts were treated with CsA (0.1 μM) under conditions that altered the activity of mK_ATP channels either directly or indirectly via its regulation by protein kinase C. mPTP blockade with CsA markedly blunted (P < 0.01) OS-induced ΔΨ_m depolarization and delayed loss of LV pressure (LVP), but did not affect arrhythmia propensity. Surprisingly, prevention of mK_ATP activation with the chemical phosphatase BDM reversed the protective effect of CsA, paradoxically exacerbating OS-induced ΔΨ_m depolarization and accelerating arrhythmia onset in CsA treated compared to untreated hearts (P < 0.05). To elucidate the putative molecular mechanisms, mPTP inhibition by CsA was tested during conditions of selective PKC inhibition or direct mK_ATP channel activation or blockade. Similar to BDM, the specific PKC inhibitor, CHE (10 μM) did not alter OS-induced ΔΨ_m depolarization directly. However, it completely abrogated CsA-mediated protection against OS. Direct pharmacological blockade of mK_ATP, a mitochondrial target of PKC signaling, equally abolished the protective effect of CsA on ΔΨ_m depolarization, whereas channel activation with 30 μM Diazoxide protected against ΔΨ_m depolarization (P < 0.0001). Conditions that prevented mK_ATP activation either directly or indirectly via PKC inhibition led to accelerated ΔΨ_m depolarization and early onset of VF in response to OS. Investigation of the electrophysiological substrate revealed accelerated APD shortening in response to OS in arrhythmia-prone hearts.

Conclusions: Cardioprotection by CsA requires mK_ATP channel activation through a PKC-dependent pathway. Increasing mK_ATP activity during CsA administration is required for limiting OS-induced electrical dysfunction.