Profiling of fatty acids released during calcium-induced mitochondrial permeability transition in isolated rabbit kidney cortex mitochondria

Increases in intracellular Ca²⁺ during cellular stress often lead to the mitochondrial permeability transition (MPT). We examined changes in fatty acids (FAs) released from isolated renal cortical mitochondria subjected to Ca²⁺-induced MPT. Exposing mitochondria to Ca²⁺ stimulated mitochondrial swelling and release of FAs such as arachidonic (20:4) and docosahexenoic acids which increased 71% and 32%, respectively, and linoleic (18:2) which decreased 23% compared to controls. Stearic (18:0), oleic (18:1), and linoleic (18:3) acids were unchanged. To elucidate a mechanism for FA release, mitochondria were pre-treated with bromoenolactone (BEL) to inhibit Ca²⁺-independent phospholipase A₂ gamma activity (iPLA₂γ). BEL blocked Ca²⁺-induced release of arachidonic and behenic (22:0) acids. Finally, four FAs were released in the absence of Ca²⁺ in a BEL-sensitive manner, including arachidonic and docosatrienoic acids. Thus, extensive FA release occurs during Ca²⁺-induced MPT, and that mitochondrial iPLA₂γ maintains mitochondrial arachidonic acid homeostasis under both basal and Ca²⁺-induced stress conditions.