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.