Keratin utilizes H2S to promote HMGB1 sulfhydration for inflammation resolution.

Despite the established importance of hydrogen sulfide (H2S) in redox biology, strategies to modulate its endogenous levels remain largely unexplored. Here, we show that a keratin fraction (KF) obtained from natural sources modulates H2S homeostasis and protein redox state through sulfhydration. Chemoproteomic analysis identified keratin 2 (K2; UniProtKB P25691, keratin, type II microfibrillar, component 5) as the most hyperreactive keratin toward sulfhydration. Oral administration of K2 to mice alleviated lipopolysaccharide (LPS)-induced inflammatory fever and led to the generation of K2-derived peptides (K2Ps) and their sulfhydrated form (K2P-SSH) in the intestine. Compared with K2Ps, K2P-SSH showed enhanced anti-inflammatory and antioxidant activities and promoted widespread protein sulfhydration. Mechanistically, K2P-SSH induced sulfhydration of high-mobility group box 1 (HMGB1) at Cys23 and Cys106, which was associated with reduced disulfide bond formation and dimerization, impaired interaction with toll-like receptor 4 (TLR4), and attenuation of downstream inflammatory signaling. Taken together, this study reveals a previously unrecognized role of K2 in converting H2S into protective sulfhydration signals and identifies K2P-SSH as a bioactive intermediate that alleviates oxidative-inflammatory stress via sulfhydration of HMGB1 at Cys23 and Cys106.