[Ferroptosis inducer IKE ameliorate pulmonary fibrosis in collagen-induced arthritis (CIA) mice via decreasing the expression of IL-6, CCL5 and CXCL9].

Objective To investigate the impact of imidazole ketone erastin (IKE), a ferroptosis inducer, on pulmonary fibrosis progression in mice with collagen-induced arthritis (CIA), and to understand its potential mechanism. Methods Chick type II collagen emulsified in complete Freund's adjuvant (CFA) was injected into DBA/1 mice, aged 8 to 10 weeks, to induce CIA. Fourteen days later, type II collagen emulsified in incomplete Freund's adjuvant (IFA) was administered to the mice. The mice were randomly divided into a control group, a CIA group and a CIA combined IKE group. The development of arthritis was monitored by evaluating the arthritis scores every two days until day 39 and then the mice were sacrificed for organ collection. The histopathological changes of joints were evaluated by HE staining, Safranin O-fast green staining and toluidine blue staining. The histopathological changes of organs including heart, liver, spleen, lung, and kidney were evaluated by HE staining, and Masson's trichrome staining was used to assess pulmonary fibrosis. The expression levels of smooth muscle actin α (α-SMA), fibroblast activating protein α (FAPα), transforming growth factor β (TGF-β), type I collagen (Col1), interleukin 1(IL-1), IL-6, IL-17 and tumor necrosis factor α (TNF-α) were detected by immunohistochemical staining. The expression levels of serum cytokines including IL-17α, IL-17F, TGF-β1, ITG-β6, TNF receptor superfamily menber 11B(TNFRSF11B), TNFRSF12A, IL-6, IL-1α, IL-1β, IL-10, TNF-α, CCL5, CCL2, CXCL9, CXCL1, NADK, EPO, CSF2, TGF-α, CCL20 and CCL3 in serum were detected by Olink mouse exploratory panel. Results Histological staining in the CIA mice administered with IKE model demonstrated that IKE treatment reduced bone absorption and the degree of synovial inflammation when active inflammation was present. CIA mice administered with IKE showed lower expression levels of α-SMA, FAPα, TGF-β, Col1, IL-1, IL-6, IL-17 and TNF-α, according to the immunohistochemical staining of the lung. In addition, the expression levels of CCL5, CXCL9 and IL-6 were also decreased in serum of CIA mice treated with IKE. Conclusion IKE not only ameliorates joint inflammation and bone damage, but also alleviates the inflammation and the progression of pulmonary fibrosis in CIA mice.