Vitamin D deficiency downregulates TASK-1 channels and induces pulmonary vascular dysfunction

Abstract

Vitamin D (vitD) receptor (VDR) 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 five weeks. Then, rats were further divided into controls or PH, which was induced by a single dose of Su5416 (20 mg/kg) and exposure to hypoxia (10% O2) for 2 weeks. 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, reduced Bmp4, Bmp6, Ddit4 and 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 Su5416 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 the KCNK3 mRNA expression. Altogether, these data strongly suggest that the deficit in vitD induces pulmonary vascular dysfunction.

Restoration of Vitamin D Levels Improves Endothelial Function and Increases TASK-Like K+ Currents in Pulmonary Arterial Hypertension Associated with Vitamin D Deficiency

“…Male Wistar rats of 180 g body weight were obtained from Envigo (Barcelona, Spain) and maintained in the general animal facilities at the School of Medicine of Universidad Complutense. All animals (n = 17) were fed with a vitD-free diet (Teklad Custom Diet TD.120008, Envigo) for five weeks [24]. Then, all animals received a single subcutaneous injection of Su5416 (Tocris, Bristol, UK; 20 mg/kg) and they were exposed to chronic hypoxia (10% O 2 ) for 3 weeks to cause PAH [5].…”

“…with 80 mg/kg ketamine plus 8 mg/kg xylazine and ventilated with room air (tidal volume 9 mL/kg, 60 breaths/min, positive end-expiratory pressure of 2 cm H 2 O). Systolic, diastolic and mean pulmonary arterial pressures (sPAP, dPAP and mPAP) were measured in open-chest rats with a pressure transducer via a catheter advanced through the right ventricle into the PA [5,24].…”

“…Elastin was visualized by its green autofluorescence. PA (26-100 µm outer diameter) were analyzed in a blinded fashion and categorized as muscular, partially muscular or non-muscular as previously described [5,24]. The medial wall thickness was calculated as external elastic lamina diameter minus the internal lamina diameter using ImageJ software.…”

“…The ramp was applied again after 5 min perfusion with an external solution buffered at pH 6.3. Non-inactivating TASK currents were identified as the current sensitive to pH [24]. Currents were normalized to cell capacitance and expressed in pA/pF.…”

“…We have recently evaluated the impact of vitD deficiency on a rat model of PAH [24]. VitD-free diet decreased the expression and the activity of the two-pore domain K + channel TASK-1, which is known to be mutated in some patients with familial PAH and downregulated in idiopathic PAH.…”