SMAD2 and pulmonary arterial hypertension: However, QLJP inhibited the TGF-β1/Smad2 signaling pathway, down-regulated the expression levels of α-SMA, COL1A1, MMP2, and improved pulmonary fibrosis and pulmonary arteriole remodeling induced by low-temperature exposure to play a role in the prevention and treatment of PAH.