Roles of calcitonin gene-related peptide on growth of premature rat type Ⅱ alveolar epithelial cells exposed to hyperoxia
AIM: To explore the influence of 600 mL/L oxygen and the effects of calcitonin gene-related peptide ( CGRP) on the growth of type Ⅱ alveolar epithelial cells ( AEC Ⅱ ) isolated from premature rat lungs in vitro. METHODS: AEC Ⅱ were isolated from 19 d fetal rat lungs and cultured for 12 h to attach. AEC Ⅱ were then randomly divided into four groups: Air group, hyperoxia group, hyperoxia plus CGRP group, and hyperoxia plus CGRP and CGRP(8-37) group. AEC Ⅱ of air group and hyperoxia group were exposed to 210 mL/L or 600 mL/L oxygen respectively for 24 h while CGRP was added in hyperoxia plus CGRP group and CGRP and CGRP( 8-37 ) ( CGRP receptor antagonist) were added in hyperoxia plus CGRP and CGRP (8-37) group before they were placed into chamber of 600 mL/L oxygen. Cell proliferation ability was determined by MTT assay and cell cycles were examined by flow cytometry. The mRNA levels and protein contents of surfactant protein C ( SPC) in the four groups were measured by RT-PCR and immunofluorescence respectively. RESULTS: Exposure to 600 mL/L oxygen for 24 h inhibited AEC Ⅱ proliferation, increased cell proportion of G0/G1 phase with the decrease of cells in S and G2/M phases, and reduced the levels of mRNA and proteins of SPC. CGRP of 10 -8M promoted AEC Ⅱ proliferation, enhanced cell proportions of S and G2/M phases, and increased the expression of SPC mRNA and protein. CONCLUSION: Exposure to 600 mL/L oxygen for 24 h inhibits AEC Ⅱ growth, proliferation and differentiation whereas CGRP partially counteracts the inhibitory effects of hyperoxia on AEC Ⅱ and plays a protective role against hyperoxia-induced lung injury.
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