[Effects of hypoxia on heme oxygenase/carbon monoxide and type I collagen in pulmonary artery smooth muscle cells of rats].

OBJECTIVE: To explore changes of expression of heme oxygenase (HO) and production of endogenous carbon monoxide in hypoxic pulmonary artery smooth muscle cells (PASMCs) of rats and study their effects on type I collagen under hypoxia. METHODS: PASMCs of rats were cultured in vitro and incubated under hypoxic condition for 24 hours. The relative content of CO released into medium by PASMCs was detected using spectrophotometry. Western blot was applied to assay the expressions of HO-1 and transforming growth factor-beta(3) (TGF-beta(3)). The expressions of HO-1, TGF-beta(3) and type I collagen were detected by immunohistochemical assay. The expressions of procollagen type I were detected by in situ hybridization. RESULTS: Hypoxia induced the expression of TGF-beta(3), type I collagen and mRNA in rat PASMCs, elevated the expression of HO-1 and CO content compared to controls by 67.45% (P<0.01) and 35.41% (P<0.05), respectively. In the hypoxic PASMCs treated with protoporphyrin-IX (ZnPP)(10 micromol x L(-1)), an inhibitor of HO, the expression of HO-1 and the CO content were 23.9%(P<0.05), 7.88% (P<0.01) lower than those of hypoxic PASMCs, respectively. ZnPP promoted the expression of TGF-beta(3) (393%,P<0.01), type I collagen protein and mRNA in hypoxic PASMCs. Hemin (20 micromol x L(-1)), an inducer of HO, caused an increase in the expression of HO-1 and CO content in hypoxic rat PASMCs by 105% (P<0.05), 8.83% (P<0.01) compared to hypoxic PASMCs, respectively. Hemin inhibited the expression of TGF-beta(3) by 68.12% (P<0.01), and type I collagen protein and mRNA in hypoxic PASMCs. CONCLUSION: HO/CO system is up-regulated by hypoxia and endogenous CO may play an important role in decreasing collagen synthesis and inhibiting the expression of TGF-beta(3) in hypoxic rat PASMCs.