1,25-Dihydroxyvitamin D3 Inhibits Nuclear Factor Kappa B Activation by Stabilizing Inhibitor IκBα via mRNA Stability and Reduced Phosphorylation in Passively Sensitized Human Airway Smooth Muscle Cells

Excessive activation of nuclear transcription factor-kappa B (NF-kappa B) is involved in human airway smooth muscle cells (HASMCs) activities in asthma. We investigated the effects of 1,25 - dihydroxyvitamin D3 [1,25 - (OH) 2D3] on the NF-kappa B signaling pathway in passively sensitized HASMCs and the molecular mechanisms involved. HASMCs were treated with either healthy controls' serum, asthma patients' serum or pretreated with 1,25 - (OH) 2D3 prior to treatment with asthmatics' serum. At 1 h after serum treatment: electrophoretic mobility shift assay (EMSA) was used to detect NF-kappa B DNA binding activity; immunocytochemical staining was used to observe the nuclear translocation of NF-kappa B p65; Western blots were used for NF-kappa B p65, I kappa B alpha, and phospho-I kappa B alpha protein levels and the nuclear translocation of NF-kappa B p65; real-time quantitative PCR was used for NF-kappa B p65 and I kappa B alpha mRNA expressions; and actinomycin D treatment was used to determine I kappa B alpha mRNA stability. Our major findings were: (1) 1,25 - (OH) 2D3 significantly reduced asthma serum passively sensitized HASMCs NF-kappa B DNA binding activity and inhibited the nuclear translocation of NF-kappa B p65; (2) 1,25 - (OH) 2D3 increased the stability of I kappa B alpha mRNA with reduced I kappa B alpha phosphorylation in asthma serum passively sensitized HASMCs and significantly increased I kappa B alpha expression in these HASMCs. Inhibiting NF-kappa B signalling with 1,25 - dihydroxyvitamin D3 may be a therapeutic approach for controlling HASMC-related remodelling in asthma.