Abstract
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease involving progressive motor neuron loss. Given the high energy reliance of motor neurons, mitochondrial dysfunction especially excessive fission critically contributes to disease pathogenesis. Mitochondrial division inhibitor-1 (Mdivi-1), an inhibitor of the fission protein Drp1, has shown neuroprotective potential, but its mechanism of action on mitochondrial quality control in ALS remains unclear. Here, we examined the effects of Mdivi-1 on mitochondrial dysfunction and cell injury in NSC34 cells expressing mutant SOD1^G93A and in SOD1^G93A transgenic mice. ALS models exhibited increased reactive oxygen species accumulation, reduced mitochondrial content, loss of mitochondrial membrane potential, enhanced apoptotic signaling, and increased phosphorylation of CaMK2 and Drp1. Mdivi-1 treatment improved cell viability, reduced oxidative stress, restored mitochondrial integrity and membrane potential, and suppressed apoptosis. In addition, Mdivi-1 decreased Drp1 phosphorylation, whereas co-treatment with the CaMK2 activator DCP-LA partially reversed these effects. Furthermore, direct inhibition of CaMK2 with KN93 reduced CaMK2 and Drp1 phosphorylation, providing additional evidence that CaMK2 regulates Drp1 activation in SOD1^G93A cells. These findings indicate that pharmacological modulation of the CaMK2/Drp1 pathway can attenuate aberrant mitochondrial fission and associated cellular dysfunction in ALS models.