PGRN knockdown alleviates pulmonary fibrosis regulating the Akt/GSK3β signaling pathway

Pulmonary fibrosis (PF) is a serious, chronic, and progressive disease with increased collagen deposition and the collapse of lung structures. Currently, the antifibrotic drugs for PF treatment, nintedanib and pirfenidone, have been proven to reduce the decline of pulmonary function in PF, but both have side effects, and to date, there is no significantly effective treatment to halt the progression of PF. The aim of this study was to investigate the molecular mechanism of pregranuloprotein (PGRN) in pulmonary fibrosis through in vitro and in vivo experiments.

PF models was induced in animals using bleomycin (BLM) and treated MRC-5 cells with TGF-β1. The mRNA expression of PGRN in fasting peripheral blood samples was measured via RT-qPCR and ELSA. PGRN siRNAs were synthesized and transfected into MRC-5 cells. MAZ51, an activator of the Akt/GSK3β pathway, was applied in recovery experiment. The proliferation and apoptosis of MRC-5 cells were determined using the CCK8 kit, MTT kit, and Muse® Cell Analyzer. H&E and Masson staining were applied to evaluate the inflammatory and fibrosis in mouse lung tissue. Levels of PGRN, inflammatory factors (IL-6 and IL-1β), fibrosis markers (α-SMA, COL-I and COL-III), and Akt/GSK3β pathway-related proteins (AKT, GSK-3β and β-catenin) were determined in tissues or cells by ELISA, RT-qPCR, western blot, or Immunofluorescence.

PGRN mRNA expression was elevated in the plasma of PF patients. In TGF-β1 induced MRC-5 cells, PGRN knockdown reduced the levels of IL-6, IL-1β, α-SMA, COL-I and COL-III, and suppressed the phosphorylation of AKT and GSK-β. Treatment with MAZ51 partially reversed the effect of PGRN knockdown on TGF-β1-induced PF. Moreover, PGRN knockdown mitigated BLM-induced alveolar destruction and wall thickening, inflammatory cell infiltration, and collagen deposition in mice. It also reduced the expression of α-SMA, TGF-β1, COL-I, COL-III, β-catenin, and the phosphorylation of AKT and GSK-3β in BLM-treated mice.

PGRN knockdown alleviates PF in vitro and in vivo by modulating the Akt/GSK3β signaling pathway, proposing that PGRN could serve as a potential therapy or adjuvant therapy for lung fibrosis.