Title: CaMKII inhibition prevent Doxorubicin-induced mitochondrial dysfunction, independent from Drp1 and MCU.
Background: Doxorubicin (Dox), an anticancer drug, causes mitochondrial dysfunction by reducing mitochondrial membrane potential, which leads to cardiotoxicity. Although Dox activates calmodulin kinase II (CaMKII), it is unclear whether and how CaMKII is involved in impaired MMP by Dox. In addition, Dox activates Drp1 and MCU by phosphorylation. However, their roles in mitochondrial dysfunction by Dox is remained to be determined.
Method: To clarify the roles of CaMKII in mitochondrial dysfunction by Dox in H9C2 cells, we tested inhibitory effects of CaMKII, Drp1, and MCU on impaired MMP by Dox with fluorescence dye, JC-1. Furthermore, we examined inhibitory effects of CaMKII and Drp1 on activated mitophagy by Dox with fluorescence dye, Mtphagy, and those of CaMKII and MCU on increased levels of mitochondrial Ca2+ content by Dox with fluorescence dye, Rhod2-AM.
Result: Dox exposure significantly reduced MMP, increased the levels of mitochondrial calcium content and number of the cells with mitophagy compared with control (p<0.05 in all). Whereas CaMKII inhibition significantly reversed these events caused by Dox (p<0.05), the inhibition of MCU and Drp1 showed no reversal effects on impaired MMP by Dox.
Conclusion: This study suggests that CaMKII is involved in mitochondrial dysfunction via impairment of MMP in Dox-induced cardiotoxicity, independent from Drp1 and MCU, suggesting that excessive mitophagy and increased mitochondrial calcium content are not the mechanisms. Further study is warranted to clarify a direct target of CaMKII to impair MMP.