Regulation of S100A4 expression via the JAK2–STAT3 pathway in rhomboid-phenotype pulmonary arterial smooth muscle cells exposure to hypoxia

► The expression of S100A4 is induced in the rhomboid VSMCs by hypoxia. ► IL-6/JAK2/STAT3 pathway can regulate the phenotype of hypoxic VSMCs. ► HIF-1 can regulate the phenotype of VSMCs exposure to hypoxia. ► Hypoxic VSMCs proliferation is controlled by S100A4 via HIF-1/JAK2/STAT3 pathway. To investigate the effect of JAKs–STATs signal pathway on expression of S100A4 in pulmonary arterial smooth muscle cells (PASMCs), the action of S100A4 and hypoxia induced factor 1 (HIF-1) on the proliferation of hypoxic PASMCs. The results showed that S100A4 immunostaining was localized in the cytoplasm and nuclei of PASMCs exposure to hypoxia and it was predominantly expressed in rhomboid cells (R-SMCs). The mRNA and protein levels of S100A4 expression increased in PASMCs after hypoxic stimulus for 4, 8, 16h. The immunofluorescence intensity and protein levels of S100A4 were suppressed, and the number of R-SMCs was reduced, when pretreatment with HIF-1α siRNA, STAT3 siRNA, S100A4 siRNA, and S100A4 inhibitor NSC 95397. Pretreatment with HIF-1α siRNA and anti-IL-6 antibodies, the levels of phospho-JAK2, -STAT3, and S100A4 were decreased, while HIF-1α kept stable in hypoxic cells. Importantly, pretreatment with HIF-1α siRNA, anti-IL-6 antibodies, STAT3 siRNA, and S100A4 siRNA, significantly attenuated the proliferation of PASMCs exposure to hypoxia. These data demonstrate that S100A4 is predominantly expressed in hypoxic R-SMCs, and regulated by the activation of JAK2–STAT3 signal pathway, which is dependent on hypoxia-induced HIF-1α expression. These results suggest that JAK2–STAT3 and HIF-1α could serve as targets for the regulation of phenotype modulation of PASMCs during the process of pulmonary vessel lesions.