Vitamin D3 Regulates Mitochondrial Function and Redox Homeostasis in the Brain

Mitochondria are essential for metabolic homeostasis and neuronal function, extending beyond ATP production to roles in cell signaling, inflammation, and stress responses. Mitochondrial dysfunction, marked by abnormal morphology, ATP deficiency, and oxidative stress, is a key feature of aging-related diseases and neurodegenerative disorders like Parkinsons. Given the importance of mitochondrial homeostasis to brain function, this study aimed to determine the possible vitamin D (VD3) effects on mitochondrial susceptibility to Ca2+-induced mitochondrial permeability transition pore (mPTP), bioenergetics in brain mitochondria, and redox balance. We demonstrated that VD3 protects isolated brain mitochondria. Male rats were divided into control and VD3-treated groups. Brain mitochondria were isolated for assessments of Ca2+-induced mitochondrial swelling secondary to MPTP opening, oxygen consumption (states 3 - ADP-stimulated and state 4 - in the presence of oligomycin), and the respiratory control ratio (RCR). Oxidative stress parameters (nitrite and lipid peroxidation), superoxide dismutase (SOD) activity, and reduced glutathione (GSH) levels were also evaluated. The results revealed that VD3 treatment blocked Ca2+-induced mitochondrial swelling secondary to MPTP opening. Additionally, VD3 improved mitochondrial RCR compared to controls, in the presence of complex I (malate/glutamate) and complex II (succinate) substrates, reduced mitochondrial succinate-driven H2O2 release, and enhanced SOD activity and GSH levels. These changes occurred in parallel with decreased nitrite and TBARS formation. These results suggest that vitamin D{square} confers mitochondrial neuroprotection, emphasizing its prospective role in maintaining neuronal homeostasis and mitigating neurodegenerative processes.