Idiopathic pulmonary fibrosis (IPF) is a severe and progressive interstitial lung disease characterized by extensive fibroblast proliferation and excessive extracellular matrix deposition, leading to irreversible scarring, impaired gas exchange, and ultimately respiratory failure. Its pathogenesis is complex, involving persistent micro-injury, dysregulated wound healing, and chronic inflammation, and currently, no curative therapy is available. Dehydroepiandrosterone (DHEA), an endogenous steroid hormone predominantly secreted by the adrenal cortex, exhibits notable anti-inflammatory and anti-fibrotic properties. This study aims to investigate the protective role of DHEA in pulmonary fibrosis (PF) and to elucidate its underlying molecular mechanisms, with a particular focus on the TLR4/NF-κB/NLRP3 signaling axis.

An in vitro PF model was established using phorbol 12-myristate 13-acetate (PMA)-differentiated THP-1 macrophages and MRC-5 fibroblasts. Cells were pretreated with DHEA or TAK242, a specific inhibitor of Toll-like receptor 4 (TLR4). The concentrations of inflammatory cytokines, including tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), interleukin-1 beta (IL-1β), and interleukin-18 (IL-18), were quantified via enzyme-linked immunosorbent assay (ELISA). Protein expression levels of components within the TLR4/NF-κB/NLRP3 inflammasome pathway, as well as extracellular matrix (ECM)-related proteins such as α-smooth muscle actin (α-SMA) and Collagen I, were assessed by Western blotting. Cell proliferation and cell cycle distribution were analyzed using CCK-8 assay and flow cytometry.

DHEA significantly reduced the secretion of TNF-α, IL-6, IL-1β, and IL-18 in PMA-differentiated THP-1 macrophages. Mechanistically, DHEA downregulated TLR4 expression, inhibited phosphorylation of nuclear factor-kappa B (NF-κB) p65, and subsequently suppressed the activation of the NLRP3 inflammasome in these cells. Furthermore, DHEA effectively arrested the cell cycle progression of MRC-5 fibroblasts at the G0/G1 phase, curbed their aberrant proliferation, and markedly downregulated the expression of α-SMA and Collagen I in PF model cells, indicating attenuation of fibroblast activation and extracellular matrix deposition.

DHEA alleviates inflammatory responses and pulmonary fibrosis by blocking the TLR4/NF-κB/NLRP3 signaling cascade in macrophages, thereby suppressing downstream fibroblast activation. These findings highlight DHEA as a promising therapeutic candidate for the treatment of PF.