Vitamin D (VitD) receptor regulates the expression of several genes involved in signaling pathways affected in
pulmonary hypertension (PH). VitD deficiency is highly prevalent in PH, and low levels are associated with poor prognosis. We investigated if VitD deficiency may predispose to or exacerbate PH. Male Wistar rats were fed with a standard or a VitD-free diet for 5 wk. Next, rats were further divided into controls or PH, which was induced by a single dose of
Su-5416 (20 mg/kg) and exposure to
hypoxia (10% O2) for 2 wk. VitD deficiency had no effect on pulmonary pressure in normoxic rats, indicating that, by itself, it does not trigger PH. However, it induced several moderate but significant changes characteristic of PH in the pulmonary arteries, such as increased muscularization, endothelial dysfunction, increased
survivin, and reduced
bone morphogenetic protein (Bmp) 4, Bmp6, DNA damage-inducible transcript 4, and K+ two-pore domain channel subfamily K member 3 (Kcnk3) expression. Myocytes isolated from pulmonary arteries from VitD-deficient rats had a reduced whole voltage-dependent
potassium current density and
acid-sensitive (TASK-like)
potassium currents. In rats with PH induced by
Su-5416 plus
hypoxia, VitD-free diet induced a modest increase in pulmonary pressure, worsened endothelial function, increased the hyperreactivity to
serotonin, arterial muscularization, decreased total and TASK-1
potassium currents, and further depolarized the pulmonary artery smooth muscle cell membrane. In human pulmonary artery smooth muscle cells from controls and patients with PH, the active form of VitD
calcitriol significantly increased KCNK3
mRNA expression. Altogether, these data strongly suggest that the deficit in VitD induces pulmonary vascular dysfunction.