title: Hypoxia/reoxygenation-induced HMGB1 translocation and release promotes islet proinflammatory cytokine production and early islet graft failure through TLRs signaling.
abstract: High-mobility group box 1 (HMGB1) translocation and release, which is involved in several tissue types of ischemia-reperfusion injuries, activate innate immunity by inducing proinflammatory cytokine production through its interaction with toll-like receptors (TLRs). Our objective was to determine the role of HMGB1 and the degree of activation of TLR-related signal transduction pathways in hypoxia/reoxygenation (H/R)-induced proinflammatory cytokine production and intra-islet graft inflammation. After islets are exposed to hypoxia-reoxygenation for 24h, TLR2/4 expression and TLR-mediated signaling was up-regulated in islets, and HMGB1 was translocated from the nucleus to the cytoplasm and released to the extracellular space. With H/R exposure, proinflammatory cytokine production (IL-1β and TNF-α) and islet injury were significantly increased, and these effects depend on TLR2/4 signaling pathways. Exogenous HMGB1 also induces islet inflammation and increases the phosphorylation of STAT3, p38 and IκBα in wild-type islets. TLR2 deficiency in TLR2-KO islets resulted in the inhibition of IL-1β production and STAT3/p38 phosphorylation after HMGB1 exposure. TLR4 deficiency in TLR4-KO islets resulted in the inhibition of TNF-α production and IκBα phosphorylation after HMGB1 exposure. Pre-incubation of the STAT3, p38, or NF-κB inhibitors significantly inhibited HMGB1-induced IL-1β or TNF-α production in islets, but the effect of HMGB1 or H/R-induced islet injury was not counteracted by a separate treatment of the STAT3 inhibitor, p38 inhibitor, or NF-κB inhibitors. HMGB1 inhibition by ethyl pyruvate or blockade by neutralizing antibodies significantly decreased the phosphorylation of STAT3, p38 and IκBα, the production of IL-1β and TNF-α, and the islet injury in wild-type islets after exposure to H/R and significantly improved early islet graft failure. Thus, our results suggest that HMGB1 released from H/R induced islets works in an autocrine manner to up-regulate STAT or p38 and augment IL-1β production via TLR2, and up-regulate NF-κB and augment TNF-α production via TLR4 in intra-islet, which are associated with H/R-induced islet injury and early graft failure.
authors.affiliation: Department of Immunology, College of Basic Medicine, Chongqing Medical University, Chongqing 400016, P.R. China; Department of Hepatobiliary Surgery, The Second Affiliated Hospital, Chongqing Medical University, Chongqing 400016, P.R. China.
authors.forename: Yao
authors.initials: Y
authors.lastname: Cheng
authors.affiliation: Department of Pancreatic Surgery, West China Hospital, Sichuan University, Chengdu 610041, P.R. China.
authors.forename: Junjie
authors.initials: J
authors.lastname: Xiong
authors.affiliation: Department of Immunology, College of Basic Medicine, Chongqing Medical University, Chongqing 400016, P.R. China.
authors.forename: Quan
authors.initials: Q
authors.lastname: Chen
authors.affiliation: Key Laboratory of Molecular Biology for Infectious Diseases, Ministry of Education, Chongqing Medical University, Chongqing 400016, P.R. China.
authors.forename: Jie
authors.initials: J
authors.lastname: Xia
authors.affiliation: Department of Pancreatic Surgery, West China Hospital, Sichuan University, Chengdu 610041, P.R. China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Immunology, College of Basic Medicine, Chongqing Medical University, Chongqing 400016, P.R. China.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Yang
authors.affiliation: Department of Immunology, College of Basic Medicine, Chongqing Medical University, Chongqing 400016, P.R. China.
authors.forename: Kun
authors.initials: K
authors.lastname: Tao
authors.affiliation: Department of Immunology, College of Basic Medicine, Chongqing Medical University, Chongqing 400016, P.R. China.
authors.forename: Shuang
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Department of Immunology, College of Basic Medicine, Chongqing Medical University, Chongqing 400016, P.R. China. Electronic address: hesirong@cqmu.edu.cn.
authors.forename: Sirong
authors.initials: S
authors.lastname: He
mesh_terms: D000818:Animals; D015687:Cell Hypoxia; D016207:Cytokines / Q000276:immunology*; D006085:Graft Survival; D024243:HMGB1 Protein / Q000276:immunology*; D007249:Inflammation / Q000209:etiology* / Q000276:immunology / Q000473:pathology; D007515:Islets of Langerhans / Q000276:immunology* / Q000473:pathology; D016381:Islets of Langerhans Transplantation / Q000276:immunology* / Q000473:pathology; D008810:Mice, Inbred C57BL; D021381:Protein Transport; D015427:Reperfusion Injury / Q000150:complications* / Q000276:immunology / Q000473:pathology; D015398:Signal Transduction; D051193:Toll-Like Receptors / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology
chemical_list: D016207:Cytokines; D024243:HMGB1 Protein; C582808:HMGB1 protein, mouse; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha
keywords: High mobility group box 1; Hypoxia/reoxygenation; Intra-islet graft inflammation; Toll-like receptors