Papers of the Week

High mobility group box 1 (HMGB1), a nuclear protein, once released to the extracellular space, facilitates pain signals as well as inflammation. Intraplantar or intraspinal application of HMGB1 elicits hyperalgesia/allodynia in rodents by activating the advanced glycosylation end-product specific receptor (receptor for advanced glycation end-products; RAGE) or Toll-like receptor 4 (TLR4). Endogenous HMGB1 derived from neurons, perineuronal cells or immune cells accumulating in the dorsal root ganglion or sensory nerves participates in somatic and visceral pain consisting of neuropathic and/or inflammatory components. Endothelial thrombomodulin (TM) and recombinant human soluble TM, TMα, dramatically promote thrombin-dependent degradation of HMGB1, and systemic administration of TMα prevents and reverses various HMGB1-dependent pathological pain. Small molecules that directly inactivate HMGB1 or antagonize HMGB1-targeted receptors would be useful to reduce various intractable pain. Thus, HMGB1 and its receptors are considered to serve as promising targets in developing novel agents to prevent or treat pathological pain.