Dissecting Cellular Mechanisms of Long-Chain Acylcarnitines-Driven Cardiotoxicity: Disturbance of Calcium Homeostasis, Activation of Ca(2+)-Dependent Phospholipases, and Mitochondrial Energetics Collapse

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 Ca(2+) accumulation, implicating L-type calcium channels, Na(+)/Ca(2+) exchanger, and Ca(2+)-release from sarcoplasmic reticulum (SR). Alternatively, PC can evoke dissipation of mitochondrial potential (ΔΨ(m)) and mitochondrial permeability transition pore (mPTP). Here, to dissect the complex nature of PC action on Ca(2+) 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 Ca(2+)-sparks and oscillations, long-living Ca(2+) enriched microdomains, and, finally, Ca(2+) overload leading to hypercontracture and cardiomyocyte death. Collectively, PC-driven cardiotoxicity involves: (I) redistribution of Ca(2+) from SR to mitochondria with minimal contribution of external calcium influx; (II) irreversible inhibition of Krebs cycle and OXPHOS underlying limited mitochondrial Ca(2+) buffering; (III) induction of mPTP reinforced by PC-calcium interplay; (IV) activation of Ca(2+)-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.