Activated AMPK by metformin protects against fibroblast proliferation during pulmonary fibrosis by suppressing FOXM1

Pulmonary fibrosis (PF) is a progressive and devastating lung disease of unknown etiology, excessive fibroblast proliferation serves as a key event to promote PF. Transcription factor forkhead box M1 (FOXM1) is not only a well-known proto-oncogene, but also an essential driver of cell proliferation. Recently, 5’-AMP-activated protein kinase (AMPK) is reported to reduce the incidence of PF. However, it remains elusive whether have an underlying relationship between AMPK and FOXM1 in fibroblast proliferation-mediated PF. Here, the progression of lung fibroblast proliferation and the expression levels of AMPK and FOXM1 were observed by intratracheally instilled of bleomycin (BLM) and intraperitoneal injection of metformin in C57BL/6 J mice. Meanwhile, human fetal lung fibroblast1 (HFL1) cells were respectively treated with AMPK activator metformin or AMPK inhibitor Compound C, or FOXM1 depletion by transfected small interfering RNA (siRNA) to unveil roles of AMPK, FOXM1 and the link between them on platelet-derived growth factor (PDGF)‐induced fibroblast proliferation. Our results demonstrated that AMPK activated by metformin could down-regulate FOXM1 and alleviate BLM-induced mouse PF model. In vitro, activation of AMPK attenuated PDGF‐induced fibroblast proliferation accompanied by the down-regulation of FOXM1. In contrast, inhibition of AMPK enhanced PDGF‐induced fibroblast proliferation along with activating FOXM1. These findings suggest that AMPK can ameliorate the progression of fibroblast proliferation during PF via suppressing the expression of FOXM1 and provide new insight into seek PF treatment approaches.