Effects of the BMP signaling pathway on DUSP1 expression in pulmonary smooth muscles

Abstract Background The activated endothelin pathway, inadequate prostacyclin IP receptor pathway and impaired bone morphogenetic protein (BMP) signaling pathway play an important role in the development of pulmonary arterial hypertension (PAH). The pulmonary artery smooth muscle cells (PASMCs) of pulmonary arteriole in patients with PAH indicate abnormally activated p38MAPK and abnormal outgrowth. We have reported that dual specificity protein phosphatase 1 (DUSP1), which inactivates p38MAPK, is downregulated in the lungs of PAH patients, and that IP receptor agonist upregulates DUSP1 expression and suppresses abnormal PASMC proliferation. The relationship between the BMP pathway, the IP receptor pathway, and the endothelin pathway is complicated and has not been clarified. Purpose The purpose of this study is to confirm the association of DUSP1 in the inhibition of cell proliferation by the BMP signaling pathway. Methods We stimulated purchased human PASMCs by endothelin 1 (ET-1), a non-prostanoid IP receptor agonist MRE-269, BMP2, or combination of them in vitro. Quantitative PCR was performed to quantify mRNA expression. Results ET-1 alone did not alter the expression of DUSP1. DUSP1 was induced independently by either BMP2 alone or MRE-269 alone. The combination of ET-1 with BMP2 and ET-1 with MRE-269 further accelerated the expression of DUSP1 induced by BMP2 alone and MRE-269 alone. ET-1 alone, BMP2 alone, and MRE-269 alone had no effect on cyclin D1 expression. The combination of ET-1 and BMP2 significantly enhanced cyclin D1 expression, while the combination of ET-1 and MRE-269 significantly suppressed it. BMP2 did not affect the expression of MSK1, whereas MRE-269 decreased that. Conclusions Here we report that BMP2 alone and in combination with ET-1 induces DUSP1, suggesting a novel mechanism of anti-proliferative effect of the BMP pathway. Since activated p38MAPK promotes cyclin D1 and cell proliferation and induce DUSP1 expression through MSK1 forming negative feedback system, the difference in expression of cyclin D1 and MSK1 by BMP2 and MRE-269 suggests that the expression of DUSP1 by MRE-269 is not through the negative feedback system, and that the accelerated expression of DUSP1 by the combination of ET-1 and BMP2 is through it. The importance of combined use of endothelin receptor antagonists in therapy targeting the BMP/TGF system was also suggested.