MD-2 is required for disulfide HMGB1-dependent TLR4 signaling

Innate immune receptors for pathogen- and damage-associated molecular patterns (PAMPs and DAMPs) orchestrate inflammatory responses to infection and injury. Secreted by activated immune cells or passively released by damaged cells, HMGB1 is subjected to redox modification that distinctly influences its extracellular functions. Previously, it was unknown how the TLR4 signalosome distinguished between HMGB1 isoforms. Here we demonstrate that the extracellular TLR4 adaptor, myeloid differentiation factor 2 (MD-2), binds specifically to the cytokine-inducing disulfide isoform of HMGB1, to the exclusion of other isoforms. Using MD-2–deficient mice, as well as MD-2 silencing in macrophages, we show a requirement for HMGB1-dependent TLR4 signaling. By screening HMGB1 peptide libraries, we identified a tetramer (FSSE, designated P5779) as a specific MD-2 antagonist preventing MD-2–HMGB1 interaction and TLR4 signaling. P5779 does not interfere with lipopolysaccharide-induced cytokine/chemokine production, thus preserving PAMP-mediated TLR4–MD-2 responses. Furthermore, P5779 can protect mice against hepatic ischemia/reperfusion injury, chemical toxicity, and sepsis. These findings reveal a novel mechanism by which innate systems selectively recognize specific HMGB1 isoforms. The results may direct toward strategies aimed at attenuating DAMP-mediated inflammation while preserving antimicrobial immune responsiveness

Gut mucosal DAMPs in IBD: From mechanisms to therapeutic implications

Endogenous damage-associated molecular patterns (DAMPs) are released during tissue damage and have increasingly recognized roles in the etiology of many human diseases. The inflammatory bowel diseases (IBD), ulcerative colitis (UC) and Crohn’s disease (CD), are immune-mediated conditions where high levels of DAMPs are observed. DAMPs such as calprotectin (S100A8/9) have an established clinical role as a biomarker in IBD. In this review, we use IBD as an archetypal common chronic inflammatory disease to focus on the conceptual and evidential importance of DAMPs in pathogenesis and why DAMPs represent an entirely new class of targets for clinical translation. </p

Thecal Sac Ligation in the Setting of Thoracic Spondyloptosis With Complete Cord Transection

BACKGROUND: Traumatic spondyloptosis (TS) with complete spinal cord transection and unrepairable durotomy is particularly rare and can lead to a difficult-to-manage cerebrospinal fluid (CSF) leak. METHODS: We performed a systematic review of the literature on TS and discuss the management strategies and outcomes of TS with cord transection and significant dural tear. We also report a novel case of a 26-year-old female who presented with thoracic TS with complete spinal cord transection and unrepairable durotomy with high-flow CSF leak. RESULTS: Of 93 articles that resulted in the search query, 13 described cases of TS with complete cord transection. The approach to dural repair was only described in 8 (n = 20) of the 13 articles. The dura was not repaired in two (20%) of the cases. Ligation of the proximal end of the dural defect was done in 15 (75%) of the cases, all at the same institution. One (5%) case report describes ligation of the distal end; one (5%) case describes the repair of the dura with duraplasty; and another (5%) case describes repair using muscle graft to partially reconstruct the defect. CONCLUSION: Suture ligation of the thecal sac in the setting of traumatic complete spinal cord transection with significant dural disruption has been described in the international literature and is a safe and successful technique to prevent complications associated with persisting high-flow CSF leakage. To the best of our knowledge, this is the first report of thecal sac ligation of the proximal end of the defect from the United States