The Relationship between Apoptosis and High-Mobility Group Protein 1 Release from Murine Macrophages Stimulated with Lipopolysaccharide or Polyinosinic-Polycytidylic Acid

Abstract

High-mobility group protein 1 (HMGB1) is a nonhistone nuclear protein whose function depends on cellular location. Inside the cell, HMGB1 modulates a variety of important cellular processes, including transcription, whereas outside the cell, HMGB1 acts as a cytokine that can promote inflammation and mediate sepsis and arthritis in animal models. In in vitro studies, proinflammatory molecules such as LPS, lipoteichoic acid, polyinosinic-polycytidylic acid (poly(I:C)), TNF-α, and type I and II IFNs can induce HMGB1 release from macrophages. Although these agents can activate cells, they can also induce apoptosis under certain circumstances. Therefore, because of evidence that apoptotic as well as necrotic cells can contribute to HMGB1-mediated events in sepsis, we have investigated the relationship between apoptosis and HMGB1 release in macrophages and other cells. In these experiments, using RAW 264.7 cells as a model, LPS and poly(I:C) caused HMGB1 release into the medium whereas CpG ODN failed to induce this response. With both LPS and poly(I:C), the extent of HMGB1 release correlated with the occurrence of apoptosis as measured by caspase 3 activation, lactate dehydrogenase release, and TUNEL staining. Similar results were obtained with primary murine macrophages as well as human Jurkat T cells. For Jurkat cells, poly(I:C) and NO donors induced apoptosis as well as HMGB1 release. Together, these results indicate that HMGB1 release from macrophages is correlated with the occurrence of apoptosis and suggest that these processes reflect common mechanisms and can occur concomitantly.

Glycyrrhizin attenuates rat ischemic spinal cord injury by suppressing inflammatory cytokines and HMGB1

“…Together, these results indicate that inhibiting the release of HMGB1 with Gly results in less tissue damage and better functional recovery of neurons. In accordance with our experimental results, the relationship between apoptosis and HMGB1 release in macrophages and other cells was investigated in an in vitro study, and those results indicated that the release of HMGB1 from macrophages correlated with the occurrence of apoptosis, and suggested that these processes reflected common mechanisms and could occur concomitantly [31] . However, other studies have shown that HMGB1 production occurred downstream of apoptosis in the final common pathway to organ damage in severe sepsis [32] .…”

Antimicrobial cathelicidin peptide CAP11 suppresses HMGB1 release from lipopolysaccharide-stimulated mononuclear phagocytes via the prevention of necrotic cell death

“…The present findings that CAP11 suppressed the LPSinduced HMGB1 release and necrotic cell death but not apoptotic cell death, apparently suggest that HMGB1 is mostly released from LPS-stimulated necrotic RAW264.7 cells. In contrast, Jiang et al argued that HMGB1 is released from apoptotic RAW264.7 cells (assessed by caspase 3 activation), when stimulated with LPS or polyinosinicpolycytidylic acid (18). However, in their experiments LDH (a necrotic marker) was also extracellularly released under the stimulation conditions, and the release was correlated with HMGB1 release.…”

“…Previously, we revealed that CAP11 (cationic antibacterial polypeptide of 11-kDa), a member of cathelicidins isolated from guinea pig neutrophils, has potentials to not only kill bacteria but also neutralize LPS; CAP11 can inhibit the binding of LPS to CD14-positive target cells and protect mice from endotoxin shock (15,16). Moreover, we have found that administration of CAP11 suppresses the increase of serum HMGB1 level in mouse endotoxin shock model (17), and HMGB1 is reported to be released from macrophages by LPS-stimulation, accompanied with cell death (18). Thus, we hypothesized that CAP11 may suppress the release of HMGB1 from mononuclear phagocytes by regulating cell death of target cells in endotoxin shock model.…”

“…It has been previously reported that HMGB1 is extracellularly released from various types of cells accompanied with cell death (18,(21)(22)(23). Thus, we determined whether LPSstimulation also induces apoptotic and/or necrotic cell death in RAW264.7 cells.…”

“…Of interest, CAP11 can suppress the elevation of serum HMGB1 level in mouse endotoxin shock model and protect mice from endotoxin lethality (16,17). Moreover, HMGB1 is reported to be extracellularly released, accompanied with cell death (18,(21)(22)(23). Thus, to clarify the inhibitory mechanism of CAP11 on HMGB1 release, we evaluated the effect of CAP11 on the LPS-induced HMGB1 release and apoptotic/necrotic cell death using a murine macrophage cell line RAW264.7 as a target cell.…”