Fucosylated haptoglobin promotes inflammation via Mincle in sepsis: an observational study

Haptoglobin (Hp) scavenges cell-free hemoglobin and correlates with the prognosis of human sepsis, a life-threatening systemic inflammatory condition. Despite extensive research on Hp glycosylation as a glyco-biomarker for cancers, understanding glycosylated modifications of Hp in sepsis patients (SPs) remains limited. Our study reveals elevated levels of terminal fucosylation at Asn207 and Asn211 of Hp in SP plasma, along with heightened inflammatory responses, compared to healthy controls (trial registration NCT05911711). Fucosylated (Fu)-Hp purified from SPs upregulates inflammatory cytokines and chemokines, along with NLRP3 inflammasome activation. Single-cell RNA sequencing identifies a distinct macrophage-like cell population with increased expressions of inflammatory mediators and FUT4 in response to Fu-Hp. Additionally, Mincle, a C-type lectin receptor, interacts with Fu-Hp to amplify the inflammatory responses and signaling. Moreover, the Hp fucosylation (AAL) level significantly correlates with the levels of inflammatory cytokines in sepsis patients, suggesting that Fu-Hp is clinically relevant. Finally, Fu-Hp treatment significantly enhances the levels of inflammatory cytokines in the plasma and various tissues of mice. Together, our findings reveal a role of Fu-Hp, derived from sepsis patients, in driving inflammation, and suggest that targeting Fu-Hp could serve as a promising intervention for combating sepsis. Trial registration NCT05911711 Overall design: Total RNA of Fu-Hp-treated human primary PBMCs (derived from 3 healthy donors)

结合珠蛋白（Haptoglobin, Hp）可清除游离血红蛋白，且与危及生命的全身性炎症性疾病——人类脓毒症（sepsis）的预后密切相关。尽管学界已针对作为癌症糖生物标志物的结合珠蛋白糖基化开展了大量研究，但目前对脓毒症患者（sepsis patients, SPs）体内结合珠蛋白的糖基化修饰的认知仍十分有限。本研究发现，与健康对照相比，脓毒症患者血浆中结合珠蛋白的Asn207与Asn211位点的末端岩藻糖基化水平显著升高，同时伴随炎症反应加剧（临床试验注册号：NCT05911711）。从脓毒症患者体内纯化的岩藻糖基化结合珠蛋白（Fu-Hp）可上调炎症细胞因子与趋化因子的表达，并激活NLRP3炎性小体（NLRP3 inflammasome）。单细胞RNA测序（Single-cell RNA sequencing）鉴定出一类独特的巨噬细胞样细胞群，该群体在响应Fu-Hp刺激时，炎症介质与FUT4的表达水平均显著升高。此外，C型凝集素受体Mincle可与Fu-Hp相互作用，进而放大炎症反应与下游信号通路。进一步研究显示，结合珠蛋白岩藻糖基化（AAL）水平与脓毒症患者体内的炎症细胞因子水平显著相关，这提示Fu-Hp具有重要的临床相关性。最后，Fu-Hp处理可显著提升小鼠血浆及多种组织中的炎症细胞因子水平。综上，本研究揭示了脓毒症患者来源的Fu-Hp在驱动炎症反应中的关键作用，并提示靶向Fu-Hp或可成为对抗脓毒症的潜在干预手段。临床试验注册号：NCT05911711 整体实验设计：对从3名健康供体中分离的人原代外周血单个核细胞（Peripheral Blood Mononuclear Cells, PBMCs）进行Fu-Hp处理后提取总RNA。