Effects of Gax gene transfection on proto-oncogene expression and proliferation of pulmonary arterial smooth muscle cells in hypoxic rat

Objective To explore the effects of growth arrest-specific homeobox(Gax) transfection on the expressions of c-fos and c-jun mRNA and proliferation of rat pulmonary arterial smooth muscle cells (PASMCs) under hypoxia.Methods PASMCs were transfected with Gax gene by adenoviral transduction of the gax homeobox gene (Ad-Gax).At 12 h after transfection under normoxia (21% O_2) or hypoxia(2.5% O_2),expressions of Gax mRNA and protein in PASMCs were detected by RT-PCR and immunocytochemis- try,and at the same time,expressions of c-fos and c-jun mRNA were evaluated by RT-PCR.~3H-TdR incor- poration was used to measure the PASMCs proliferation.Results The Gax overexpression in PASMCs transfected with Gax gene was confirmed by RT-PCR and immunocytochemistry.Compared with that in the non-transfection group,Gax expression increased significantly in PASMCs transfected with Gax gene under normoxia and hypoxia.The c-fos and c-jun mRNA levels in non-transfected PASMCs under hypoxia were higher than those under normoxia(P0.01).Compared with those of the non-transfected group under nor- moxia or hypoxia,the c-fos and c-jun mRNA levels in Gax-transfected PASMCs under normoxia decreased significantly(P0.05,0.01).Under hypoxic condition,the c-fos and c-jun mRNA levers in Gax-transfect- ed PASMCs were lower than those in the non-transfected group (P0.05).~3H-TdR incorporation in non- transfected PASMCs under hypoxia was significantly higher than that under normoxia (P0.01).Under normoxic and hypoxic conditions,~3H-TdR incorporation in Gax-transfected PASMCs was lower than that in non-transfected group(P0.05,0.01).Conclusion Hypoxia can down-regulate Gax expression,up-reg- ulate the expressions of c-fos and c-jun genes,and induce PASMCs proliferation.Gax overexpression might inhibit the PASMCs proliferation induced by hypoxia through the downregulation of c-fos and c-jun expres- sions.