The cytoprotection of milk-derived MFG-E8 on mitochondria-injured L6 cell via mediation of Akt/bcl-2/bax-caspase-3 signaling pathway

Abstract

Mitochondria-dependent myoblast apoptosis induced by oxidative stress and decrease in successful protein synthesis play a crucial role in loss of muscle mass and functionality further to result in sarcopenia. Here, we investigated the relationship between milk fat globule-EGF factor Ⅷ (MFG-E8) and mitochondrial-dependent apoptosis pathway. MFG-E8 exert cytoprotection through increasing L6 cells survival/apoptotic ratio, increasing mitochondrial membrane potential and regulating S and G2/M phases. By observing cell ultrastructure, MFG-E8 improved mitochondrial homeostasis mainly through decreasing cytochrome-c release, expression of caspase-9 and caspase-3, mitochondrial vacuolation and mitophagy thereby inhibiting cell apoptosis. From molecular perspective, MFG-E8 repaired mitochondria fragmentation by increasing mitochondrial DNA replication and regulated expression of key mitochondrial-apoptotic factors (upregulation: B-cell lymphoma-2 like 1 (bcl2l1), bcl2l2, cyclooxygenase-1 and mitochondrial uncoupling protein-2; Downregulation: p21 and p53) further to improve mitochondrial function and inhibit apoptosis. Moreover, MFG-E8 inhibited mitochondrial-dependent apoptosis via Akt/bcl-2/bax/caspase-3 signaling cascades. Taken together, our research provided a promising approach for deep exploration of MFG-E8 on cytoprotection against mitochondrial injury and mitochondrial-mediated apoptosis and application of anti-apoptosis in alleviating sarcopenia.