Vitamin D inhibits growth of human airway smooth muscle cells through growth factor-induced phosphorylation of retinoblastoma protein and checkpoint kinase 1

作者：Damera G; Fogle H W; Lim P; Goncharova E A; Zhao H; Banerjee A; Tliba O; Krymskaya V P; Panettieri R A Jr^*

来源：British Journal of Pharmacology, 2009, 158(6): 1429-1441.

DOI：10.1111/j.1476-5381.2009.00428.x

• asthma
• airway remodelling
• cell cycle
• hyperplasia
• chronic obstructive pulmonary disease

Background and purpose:
Airway remodelling in asthma is manifested, in part, as increased airway smooth muscle (ASM) mass, reflecting myocyte proliferation. We hypothesized that calcitriol, a secosteroidal vitamin D receptor (VDR) modulator, would inhibit growth factor-induced myocyte proliferation.
Experimental approach:
Human ASM cell cultures were derived from bronchial samples taken during surgery. ASM cells were treated with platelet-derived growth factor (PDGF) (10 ng center dot mL-1) for 24 h in the presence of calcitriol, dexamethasone or a checkpoint kinase 1 (Chk1) inhibitor (SB218078). The effects of calcitriol on PDGF-mediated cell proliferation were assessed by thymidine incorporation assay, propidium iodide-based cell cycle analysis, caspase-3 assay and immunoblotting for specific cell cycle modulators.
Key results:
Calcitriol, but not dexamethasone, inhibited PDGF-induced ASM DNA synthesis concentration dependently (IC(50) = 520 +/- 52 nM). These effects were associated with VDR-mediated expression of cytochrome CYP24A1 with no effects on ASM apoptosis. Calcitriol substantially inhibited (P < 0.01) PDGF-stimulated cell growth in ASM derived from both normal (59 +/- 8%) and asthmatic subjects (57 +/- 9%). Calcitriol inhibited PDGF-induced phosphorylation of retinoblastoma protein (Rb) and Chk1, with no effects on PDGF-mediated activation of extracellular signal-regulated kinases 1/2, PI3-kinase and S6 kinase, or expression of p21Waf/Cip-1, p27Kip1, cyclin D and E2F-1. Consistent with these observations, SB218078 also inhibited (IC(50) = 450 +/- 100 pM) PDGF-induced cell cycle progression.
Conclusions and implications:
Calcitriol decreased PDGF-induced ASM cell growth by inhibiting Rb and Chk1 phosphorylation.
This Research Paper is the subject of a Commentary in this issue by Clifford and Knox (pp. 1426-1428). To view this article visit http://www3.interscience.wiley.com/journal/121548564/issueyear?year=2009.

• 出版日期2009-11