Programmed death-ligand 1 triggers PASMCs pyroptosis and pulmonary vascular fibrosis in pulmonary hypertension.

Pyroptosis is a pro-inflammatory form of programmed cell death, whose genesis directly depended on caspase-1 activation. Pulmonary hypertension (PH) is a disease characterized, in part, by vascular fibrosis. Up to now, there is no report on the relationship between pyroptosis and vascular fibrosis in PH. Here, we confirmed that pyroptosis had occurred in the media of pulmonary arteries in two PH rat models and hypoxic human pulmonary arterial smooth muscle cells (hPASMCs). Caspase-1 inhibition attenuated the pathogenesis of PH, as assessed by vascular remodeling, right ventricular systolic pressure, right ventricle hypertrophy and hemodynamic parameters of pulmonary vasculature. Moreover, caspase-1 inhibition suppressed pulmonary vascular fibrosis as demonstrated by Masson staining, as well as immunohistochemistry and Western blot analysis of fibrillar collagen. In addition, Programmed death-ligand 1 (PD-L1) was markedly increased in PH, which was regulated by the transcription factor STAT1. Furthermore, PD-L1 knockdown in hPASMCs repressed the onset of hypoxia-induced pyroptosis and fibrosis. Overall, these data identify a critical STAT1-dependent posttranscriptional modification that promotes PD-L1 expression in the pyroptosis of PASMCs to modulate pulmonary vascular fibrosis and accelerate the progression of PH.