1α,25-Dihydroxyvitamin D3 mechanism of action: Modulation of L-type calcium channels leading to calcium uptake and intermediate filament phosphorylation in cerebral cortex of young rats

Abstract

The involvement of calcium-mediated signaling pathways in the mechanism of action of 1α,25-dihydroxyvitamin D3 (1,25D) is currently demonstrated. In this study we found that 1,25D induces nongenomic effects mediated by membrane vitamin D receptor (VDRm) by modulating intermediate filament (IF) phosphorylation and calcium uptake through L-type voltage-dependent calcium channels (L-VDCC) in cerebral cortex of 10day-old rats. Results showed that the mechanism of action of 1,25D involves intra- and extracellular calcium levels, as well as the modulation of chloride and potassium channels. The effects of L-VDCCs on membrane voltage occur over a broad potential range and could involve depolarizing or hyperpolarizing coupling modes, supporting a cross-talk among Ca2+ uptake and potassium and chloride channels. Also, the Na+/K+-ATPase inactivation by ouabain mimicked the 1,25D action on 45Ca2+ uptake. The Na+/K+-ATPase inhibition observed herein might lead to intracellular Na+ accumulation with subsequent L-VDCC opening and consequently increased 45Ca2+ (calcium, isotope of mass 45) uptake. Moreover, the 1,25D effect is dependent on the activation of the following protein kinases: cAMP‐dependent protein kinase (PKA), Ca2+/calmodulin‐dependent protein kinase (PKCaMII), phosphatidylinositol 3‐kinase (PI3K) and mitogen‐activated protein kinase p38 (p38MAPK). The modulation of calcium entry into neural cells by the 1,25D we are highlighting, might take a role in the regulation of a plethora of intracellular processes. Considering that vitamin D deficiency can lead to brain illness, 1,25D may be a possible candidate to be used, at least as an adjuvant, in the pharmacological therapy of neuropathological conditions.