Calpain-1, a
calcium-activated neutral
cysteine proteases, has been reported to be involved in the formation of
pulmonary hypertension. HIF-1α, an
oxygen-sensitive
transcription factor, has been reported to activate genes involved in cell proliferation and extracellular matrix recombination. This study was designed to investigate the effect of calpain-1 in hypoxic
pulmonary hypertension (HPH) and to explore whether there is a relationship between calpain-1 and HIF-1α in this disease. In the
hypoxia-induced model of HPH, we found that
hypoxia resulted in increased right ventricular systolic pressure,
right ventricular hypertrophy, pulmonary vascular remodelling and
collagen deposition in lung tissues of mice. The levels of calpain-1 and HIF-1α were up-regulated in the lung tissues of
hypoxia-treated mice and pulmonary arterial smooth muscle cells (PASMCs). Knock-out of calpain-1 restrained haemodynamic and histological changes induced by chronic
hypoxia in mice, and inhibition of calpain-1 also repressed the abnormal proliferation and migration of PASMCs. Besides, knock-out or inhibition of calpain-1 suppressed
hypoxia-induced expression of HIF-1α,
VEGF,
PCNA, TGF-β1, MMP2 and
collagen I in vivo and in vitro. While inhibition of HIF-1α abolished the above effects of calpain-1. Furthermore, we found that calpain-1 mediates the expression of HIF-1α through NF-κB (P65) under
hypoxia conditions. In conclusion, our results suggest that calpain-1 plays a pivotal role in
hypoxia-induced pulmonary vascular remodelling and
fibrosis through HIF-1α, providing a better understanding of the pathogenesis of HPH.