Sphingosine-1-phosphate induces pulmonary artery smooth muscle cell proliferation, migration and pulmonary arterial remodeling by modulating sonic hedgehog signaling effector FoxM1

Background: Sphingosine-1-phosphate (S1P), a metabolite of sphingosine, is associated with the proliferation of pulmonary artery smooth muscle cells (PASMCs). This study aims to address the mechanisms by which S1P induces PASMC proliferation, contributing to pulmonary arterial remodeling.

Methods: Primary cultured rat PASMCs were incubated with S1P. Cyclopamine was used to inhibit Smoothened (Smo) function, while siRNA transfection selectively knocked down the expression of signal transducer and activator of transcription 3 ( STAT3 ), glioma-associated oncogene homolog 1 ( GLI1 ), and forkhead box M1 ( FOXM1 ). Cell proliferation was measured by 5-bromo-2'-deoxyuridine (BrdU) and 5-ethynyl-2'-deoxyuridine (EdU) incorporation assay. Subcellular localization of Gli1 was determined using immunofluorescence staining. In a monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH) rat model, PF543 (the inhibitor of S1P synthetase), NSC74859 (the inhibitor of STAT3), and cyclopamine (the inhibitor of sonic Hedgehog [Shh] receptor) were administered to evaluate their effects on disease progression. Hemodynamic changes and histological examination were performed to evaluate the development of PAH. The protein levels of sphingosine kinase 1 (SphK1), phosphorylated/total STAT3 (p-/t-STAT3), Shh, Gli1 and FoxM1 were determined using immunoblotting.

Results: S1P increased Shh expression by STAT3 activation, which further caused Gli1 upregulation and nuclear translocation in PASMCs. Activation of Gli1 raised FoxM1 expression and then triggered PASMCs proliferation and migration. In MCT-induced PAH rat models, S1P levels were elevated in lung tissues and serum, triggering STAT3 activation and subsequent upregulation of Shh, Gli1, and FoxM1 in lung. Targeting these molecules alleviated pulmonary arterial remodeling and prevented the development of PAH.

Conclusions: S1P/STAT3/Shh/Gli1/FoxM1 pathway plays an important role in PASMCs proliferation and pulmonary arterial remodeling. Targeting this cascade may have potential value for the management of PAH.

FOXM1; Forkhead box M1; GLI1; Glioma-associated oncogene homolog 1; Pulmonary hypertension; S1P; Sonic hedgehog signaling; Sphingosine-1-phosphate.