Neuroprotective role of vitamin D in primary neuronal cortical culture

A role of Vitamin D in brain development and function has been gaining support over the last decade. There are compelling pieces of evidence that suggest vitamin D may have a neuroprotective role. The administration of vitamin D or its metabolites has been shown to reduce neurological injury and/or neurotoxicity in a variety of animal systems. The detail biochemical mechanism mediating neurons, to its ability to withstand greater oxidative stress in the presence of Vitamin D is unclear. This study was undertaken to study the biochemical effect of treatments of primary cortical neuronal cultures, with the active form of vitamin D(1,25(OH)₂D3), against the induced oxidative stress.

Primary neuronal cultures from cerebral cortex were set up from neonatal (from 6 to 7 days old) Wister Rat's brain. Different doses of [1,25(OH)₂D₃], ranges from 0 to 1 μg/ml, was added to the culture medium and the cells were cultured in its presence for 24 h to 120 h. The effect of induced extracellular oxidative stress was measured by subjecting these cultured cells with 0.5 mM H₂O₂ for 2 h, prior to collection of condition medium and the cell pellet for biochemical assay. The control and H₂O₂ treated cultures were maintained in similar culture conditions, for similar periods of time without any [1,25(OH)₂D₃] treatments.

The optimum concentration of [1,25(OH)₂D₃] for treatment of primary cortical neuronal cultures was found to be 0.25 μg/ml by Trypan exclusion assay and MTT assay. Pre-treatments of cultured neuronal cells with 0.25 μg/ml of [1,25(OH)₂D₃] caused significantly increased levels of reduced glutathione, accompanied by a similar increase in the enzyme levels of GST, to neutralize the induced oxidative stress by H₂O₂. The level of Lipid peroxidation was significantly higher in the cells treated with H₂O₂ alone, but it was completely reversed in the neuronal cultures pre-treated with [1,25(OH)₂D₃]. The levels of Catalase enzyme also significantly reduced (≥0.05) in the [1,25(OH)₂D₃] pre-treated neuronal cultures.

We concluded that the systemic treatment of primary neuronal cultures with [1,25(OH)₂D₃] gave better protection to neurons against the induced oxidative stress, as shown by quantitative measurements of various biomarkers of oxidative stress. This study also suggested that Vitamin D is vital for the growth, survival, and proliferation of the neurons and hence it has a potential therapeutic role against various neurodegenerative diseases.