HMGB1 derived from macrophages and enteric glial cells contributes to the butyrate-induced colonic hypersensitivity in mice

High mobility group box1 (HMGB1), a nuclear protein, once acetylated by histone acetyltransferase, is released into the extracellular space, and causes pain signals, thereby contributing to pathological pain. Repeated intracolonic administration of butyrate, known to inhibit histone deacetylase (HDAC), produces colonic hypersensitivity in rodents, being widely used as models for irritable bowel syndrome (IBS). Thus, we asked whether HMGB1 would participate in the butyrate-induced colonic hypersensitivity in mice, and analyzed the underlying mechanisms. Repeated butyrate treatment caused colonic hypersensitivity to distension and intraluminal sulfide, a functional enhancer of Ca_v3.2 channels, in mice, which was prevented by repeated treatment with an anti-HMGB1-neutralizing antibody, thrombomodulin alfa (TMα) capable of causing thrombin-dependent degradation of HMGB1, antagonists for RAGE, TLR4 and CXCR4, membrane receptors of HMGB1, liposomal clodronate, a macrophage depletor, and ethyl pyruvate capable of inhibiting HMGB1 release from macrophages. Butyrate treatment increased the number of Iba1-positive macrophages, but not S100B-positive enteric glial cells (EGCs), and the rate of cytosolic/whole cell HMGB1 levels in both types of cells in the colonic mucosa. In macrophage-like RAW264.7 cells and EGC-like CRL-2690 cells, butyrate as well as trichostatin A, a well-known HDAC inhibitor, at the same concentrations that increased histone acetylation, evoked cytoplasmic translocation and extracellular release of nuclear HMGB1. Together, butyrate is considered to cause HMGB1 release from macrophages and EGCs most probably by inhibiting HDAC, resulting in colonic hypersensitivity in mice. HMGB1 and its membrane receptors might serve as drug targets for colonic hypersensitivity in IBS patients.