The Mfn1-βIIPKC Interaction Regulates Mitochondrial Dysfunction via Sirt3 Following Experimental Subarachnoid Hemorrhage

Neuronal injury following subarachnoid hemorrhage (SAH) has been shown to be associated with mitochondrial dysfunction and oxidative stress. beta IIPKC, a subtype of protein kinase C (PKC), accumulates on the mitochondrial outer membrane and phosphorylates mitofusin 1 (Mfn1) at serine 86. Here, we investigated the role of Mfn1-beta IIPKC interaction in brain damage and neurological function in both in vivo and in vitro experimental SAH models. The expression of beta IIPKC protein and the interaction of Mfn1-beta IIPKC were found to be increased after OxyHb treatment in primary cultured cortical neurons and were also observed in the brain following SAH in rats. Treatment with the beta IIPKC inhibitor beta IIV5-3 or SAM beta A, a peptide that selectively antagonizes Mfn1-beta IIPKC association, significantly attenuated the OxyHb-induced neuronal injury and apoptosis. These protective effects were accompanied by inhibited mitochondrial dysfunction and preserved mitochondrial biogenesis. The results of western blot showed that beta IIV5-3 or SAM beta A markedly increased the expression of Sirt3 and enhanced the activities of its downstream mitochondrial antioxidant enzymes in OxyHb-treated neurons. Knockdown of Sirt3 via specific targeted small interfering RNA (siRNA) partially prevented the beta IIV5-3- or SAM beta A-induced protection and antioxidative effects. In addition, treatment with beta IIV5-3 or SAM beta A in vivo was found to obviously reduce brain edema, alleviate neuroinflammation, and preserve neurological function after experimental SAH in rats. In congruent with in vitro data, the protection induced by beta IIV5-3 or SAM beta A was reduced by Sirt3 knockdown in vivo. In summary, our present results showed that blocking Mfn1-beta IIPKC interaction protects against brain damage and mitochondrial dysfunction via Sirt3 following experimental SAH.