Dissecting Cellular Mechanisms of Long-Chain Acylcarnitines-Driven Cardiotoxicity: Disturbance of Calcium Homeostasis, Activation of Ca2+-Dependent Phospholipases, and Mitochondrial Energetics Collapse.

Alexey V Berezhnov,Vitaly A Kasymov,Evgeniya I Fedotova,Oleg Yu Pimenov,Miroslav N Nenov,Vladimir V Dynnik

doi:10.3390/ijms21207461

Abstract

Long-chain acylcarnitines (LCAC) are implicated in ischemia-reperfusion (I/R)-induced myocardial injury and mitochondrial dysfunction. Yet, molecular mechanisms underlying involvement of LCAC in cardiac injury are not sufficiently studied. It is known that in cardiomyocytes, palmitoylcarnitine (PC) can induce cytosolic Ca2+ accumulation, implicating L-type calcium channels, Na+/Ca2+ exchanger, and Ca2+-release from sarcoplasmic reticulum (SR). Alternatively, PC can evoke dissipation of mitochondrial potential (ΔΨm) and mitochondrial permeability transition pore (mPTP). Here, to dissect the complex nature of PC action on Ca2+ homeostasis and oxidative phosphorylation (OXPHOS) in cardiomyocytes and mitochondria, the methods of fluorescent microscopy, perforated path-clamp, and mitochondrial assays were used. We found that LCAC in dose-dependent manner can evoke Ca2+-sparks and oscillations, long-living Ca2+ enriched microdomains, and, finally, Ca2+ overload leading to hypercontracture and cardiomyocyte death. Collectively, PC-driven cardiotoxicity involves: (I) redistribution of Ca2+ from SR to mitochondria with minimal contribution of external calcium influx; (II) irreversible inhibition of Krebs cycle and OXPHOS underlying limited mitochondrial Ca2+ buffering; (III) induction of mPTP reinforced by PC-calcium interplay; (IV) activation of Ca2+-dependent phospholipases cPLA2 and PLC. Based on the inhibitory analysis we may suggest that simultaneous inhibition of both phospholipases could be an effective strategy for protection against PC-mediated toxicity in cardiomyocytes.

Highlights

The distinct mechanisms of cardiac dysfunction after acute ischemia-reperfusion (I/R) are not sufficiently studied yet
We found that enlargement of mitochondrial calcium retention capacity (CRC) with Pi increased the value of the lag period approximately up to three times (Figure 4B), while the inhibition of oxidative phosphorylation (OXPHOS) (CRC = 0) abrogated stabilization of [Ca2+]i within this lag period and resulted in immediate smooth rise of [Ca2+]i (Figure 4D)
We demonstrate that long-chain acylcarnitines PC and MC in dose-dependent manner evoke Ca2+-sparks and oscillations, long-living Ca2+ enriched microdomains, and, Ca2+ overload leading to hypercontracture and cardiomyocyte death

Summary

Introduction

The distinct mechanisms of cardiac dysfunction after acute ischemia-reperfusion (I/R) are not sufficiently studied yet. It was suggested that the flux of Na+ from one cell to another may result in reverse mode operation of Na+/Ca2+ exchanger (NCX), intracellular Ca2+ ([Ca2+]i) accumulation, cell-to-cell propagation of hypercontracture, and CM death [1]. It was shown in [2] that palmitoylcarnitine (PC), known ischemic metabolite, induced Ca2+ overload, implicating L-type calcium channels (LCC) and Ca2+ release from the sarcoplasmic/endoplasmic reticulum (SR/ER) stores. Recent studies have suggested that PC and Ca2+ can be used as mPTP inducers in liver mitochondria, and could act synergistically by reinforcing the effects of each other [16]

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Conclusion