Saroglitazar Ameliorates Pulmonary Fibrosis Progression in Mice by Suppressing NF-κB Activation and Attenuating Macrophage M1 Polarization

Background and Objectives: Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal interstitial lung disease with limited therapeutic options. Current therapies (pirfenidone, nintedanib) exhibit modest efficacy and significant side effects, underscoring the need for novel strategies targeting early pathogenic drivers. Saroglitazar (SGZ), a dual PPARα/γ agonist with anti-inflammatory properties approved for diabetic dyslipidemia, has not been explored for IPF. We aimed to investigate SGZ's therapeutic potential in pulmonary fibrosis and elucidate its mechanisms of action. Materials and Methods: Using a bleomycin (BLM)-induced murine pulmonary fibrosis model, we administered SGZ therapeutically. A histopathological assessment (H&E, Masson's trichrome, Collagen I immunofluorescence), Western blotting, and qRT-PCR analyzed the fibrosis progression and inflammatory markers. Flow cytometry evaluated the macrophage polarization. In vitro studies used RAW264.7 macrophages stimulated with BLM/LPS and MRC-5 fibroblast co-cultures. The NF-κB/NLRP3 pathway activation was assessed through protein and gene expression. Results: SGZ significantly attenuated BLM-induced histopathological hallmarks, including alveolar wall thickening, Collagen deposition, and inflammatory infiltration. Fibrotic markers (OPN, α-SMA) and pro-inflammatory cytokines (IL-1β, TNF-α, IL-6) were downregulated in the SGZ-treated mice. Mechanistically, SGZ suppressed the M1 macrophage polarization (reduced CD86⁺ populations) and inhibited the NF-κB/NLRP3 pathway activation in the alveolar macrophages. In the RAW264.7 cells, SGZ decreased the NLRP3 inflammasome components (ASC, cleaved IL-1β) and cytokine secretion. Co-cultures demonstrated that the SGZ-treated macrophage supernatants suppressed the fibroblast activation (α-SMA, Collagen I) in MRC-5 cells. Conclusions: SGZ attenuates pulmonary fibrosis by suppressing macrophage-driven inflammation via NF-κB/NLRP3 inhibition and disrupting the macrophage-fibroblast crosstalk. These findings nominate SGZ as a promising candidate for preclinical optimization and future clinical evaluation in IPF.

M1 macrophage polarization; NF-κB pathway; inflammation; pulmonary fibrosis; saroglitazar.