Heparin Nebulization Attenuates Bleomycin-Induced Pulmonary Fibrosis through the Coagulation Activation Pathway: A Metabolomics Study

Objective: Pulmonary fibrosis represents a severe interstitial lung disease pathologically characterized by excessive collagen deposition. This study aimed to investigate the effects of heparin nebulization on bleomycin-induced pulmonary fibrosis in rats and elucidate the underlying metabolic mechanisms. Methods: Thirty-six Sprague-Dawley rats were randomly assigned to three groups via simple randomization:the sham group, the saline group and the heparin group. The pulmonary fibrosis rats was induced through intratracheal bleomycin instillation, and confirmed by computed tomography (CT). Commencing on day 7 post-induction, the heparin group received 7-day heparin nebulization therapy, while the saline group received saline nebulization therapy. The sham group underwent neither bleomycin instillation nor nebulization therapy.The study evaluated pulmonary imaging examinations, pathological analyses,blood biomarkers (D-dimer,Hydroxyproline (Hyp),Interleukin-6(IL-6), α2-plasmin inhibitor-plasmin complex(PAP),thrombin-antithrombin complex(TAT),Tumor Tecrosis Factor(TNF-α)) and metabolomic characteristics.Results: Upon the seventh day, both the saline and heparin groups exhibited notably heightened blood biomarkers in contrast to the sham group. By the fourteenth day, the heparin group had significantly lower levels of D-dimer,Hyp, IL-6, TAT and TNF-α than the saline group. Additionally, the lung imaging and pathology scores in the heparin group were significantly improved relative to those in the saline group. Metabolomic analysis demonstrated distinct metabolic profiles among the groups, In the heparin group, there were 21 up-regulated and 50 down-regulated in the positive ion mode, and 77 up-regulated and 87 down-regulated in the negative ion mode. The key metabolic pathways involved included linoleic acid metabolism,taurine and hypotaurine metabolism,purine metabolism,arachidonic acid metabolism. Conclusion: Nebulized heparin significantly attenuated pulmonary fibrosis in this rat model. Metabolomic analysis highlighted the involvement of coagulation-associated metabolic pathways, proposing novel therapeutic targets for pulmonary fibrosis.