The extracellular release of HMGB1 during apoptotic cell death

Abstract

High mobility group box 1 protein (HMGB1) is a non-histone nuclear protein with dual function. Inside the cell, HMGB1 binds DNA and regulates transcription, whereas outside the cell, it serves as a cytokine and mediates the late effects of LPS. The movement of HMGB1 into the extracellular space has been demonstrated for macrophages stimulated with LPS as well as cells undergoing necrosis but not apoptosis. The differential release of HMGB1 during death processes could reflect the structure of chromatin in these settings as well as the mechanisms for HMGB1 translocation. Since apoptotic cells can release some nuclear molecules such as DNA to which HMGB1 can bind, we therefore investigated whether HMGB1 release can occur during apoptosis as well as necrosis. For this purpose, Jurkat cells were treated with chemical inducers of apoptosis (staurosporine, etoposide, or camptothecin), and HMGB1 release into the medium was assessed by Western blotting. Results of these experiments indicate that HMGB1 appears in the media of apoptotic Jurkat cells in a time-dependent manner and that this release can be reduced by Z-VAD-fmk. Panc-1 and U937 cells treated with these agents showed similar release. In addition, HeLa cells induced to undergo apoptosis showed HMGB1 release. Furthermore, we showed using confocal microscopy that HMGB1 and DNA change their nuclear location in Jurkat cells undergoing apoptosis. Together, these studies indicate that HMGB1 release can occur during the course of apoptosis as well as necrosis and suggest that the release process may vary with cell type.

Necrotic cell-derived high mobility group box 1 attracts antigen-presenting cells but inhibits hepatocyte growth factor-mediated tropism of mesenchymal stem cells for apoptotic cell death

“…However, HMGB1 release from apoptotic cells has also been reported, including from staurosporine-treated Jurkat, U937 and HeLa cells. 27 Although apoptotic cardiomyocytic and neuronal cells also released in vitro moderate doses of HMGB1 in this study, these failed to attract monocytes or iDC, whereas HMGB1 from necrotic cells or recombinant HMGB1 did. This may be due to a dose effect.…”

“…[23][24][25] Moreover, HMGB1 is a prototypic damageassociated molecular pattern passively released from necrotic cells. 26 Although it may be released from apoptotic cells as well, 27 it appears to be preferentially retained in apoptotic bodies because of enhanced chromatin binding 26 and to be inactive due to oxidization of the crucial cysteine residues 23, 45 and 106, 28,29 which is critical for the tolerogenic nature of apoptotic cell death. Either secreted or passively released from necrotic cells, HMGB1 exerts its effects via the receptor of advanced glycation end products (RAGE) 30 and the tolllike receptors TLR-2 and TLR-4, 31 and may form complexes with chemokines-such as chemokine C-X-C motif ligand 12 (CXCL12), enhancing their activity.…”

Clinical Significance of Serum HMGB-1 and sRAGE Levels in Systemic Sclerosis: Association with Disease Severity

“…Although HMGB-1 is regarded as a trigger of these immune/inflammatory disorders mediated via RAGE and TLR and also affects immunological abnormalities [5,6,9,12,23], correlation of serum…”

“…Although these abnormalities were associated with several organ involvement and systemic vascular damage, the mechanism and pathogenesis of SSc remain unknown [4]. Recent studies have shown that damaged, necrotic, and apoptotic cells release high mobility group box 1 protein (HMGB-1) [5,6]. HMGB-1 is a non-histone nuclear protein with dual function.…”

“…HMGB-1 released from damaged, necrotic, and apoptotic cells binds to receptor for advanced glycation end products (RAGE), toll-like receptor (TLR)2, TLR4, and also TLR9. HMGB-1 system induces the nuclear factor-κB (NFκB) phosphorylation and productions of several cytokines and chemokines, such as TNF-α, IL-1β, IL-6, macrophage inflammatory protein-1α, and 6 transforming growth factor-β by endothelial cells, fibroblasts, and various immune cells, such as macrophages, monocytes, T cells, and B cells [5,6,[9][10][11][12]. RAGE, the first receptor that was identified for HMGB-1, is encoded in the MHC class III region, together with the genes encoding the receptors for several complement components, as well as the genes encoding TNF, lymphotoxin, and heat-shock protein 70 [9].…”