Redox Modification of Cysteine Residues Regulates the Cytokine Activity of High Mobility Group Box-1 (HMGB1)

Abstract

High mobility group box 1 (HMGB1) is a nuclear protein with extracellular inflammatory cytokine activity. It is released passively during cell injury and necrosis, and secreted actively by immune cells. HMGB1 contains three conserved redox-sensitive cysteine residues: C23 and C45 can form an intramolecular disulfide bond, whereas C106 is unpaired and is essential for the interaction with Toll-Like Receptor (TLR) 4. However, a comprehensive characterization of the dynamic redox states of each cysteine residue and of their impacts on innate immune responses is lacking. Using tandem mass spectrometric analysis, we now have established that the C106 thiol and the C23-C45 disulfide bond are required for HMGB1 to induce nuclear NF-κB translocation and tumor necrosis factor (TNF) production in macrophages. Both irreversible oxidation to sulphonates and complete reduction to thiols of these cysteines inhibited TNF production markedly. In a proof of concept murine model of hepatic necrosis induced by acetaminophen, during inflammation, the predominant form of serum HMGB1 is the active one, containing a C106 thiol group and a disulfide bond between C23 and C45, whereas the inactive form of HMGB1, containing terminally oxidized cysteines, accumulates during inflammation resolution and hepatic regeneration. These results reveal critical posttranslational redox mechanisms that control the proinflammatory activity of HMGB1 and its inactivation during pathogenesis.

TLR4-dependant pro-inflammatory effects of HMGB1 on human adipocyte

“…This point is crucial, since the redox isoform determines the function of HMGB1. 16 Fully reduced HMGB1 is a chemotactic factor, disulfide HMGB1 a cytokine-inducing factor while sulfonyl HMGB1 has no known biological function. Studies to elucidate these processes in adipose tissue may help to figure out novel therapeutic interventions based on controlling the redox states of HMGB1.…”

Consensus guidelines for the detection of immunogenic cell death

“…Of note, the biological activity of extracellular HMGB1 appears to be regulated by its redox state. [215][216][217][218][219][220][221] Moreover, HMGB1 binds not only to TLR2, TLR4 and RAGE, but also to hepatitis A virus cellular receptor 2 (HAVCR2, best known as TIM-3), hence mediating immunosuppressive (as opposed to immunostimulatory) effects. [222][223][224] Taken together, these observations suggest that the biological activity of HMGB1 exhibits a consistent degree of contextdependency.…”

p53-dependent release of Alarmin HMGB1 is a central mediator of senescent phenotypes

“…The redox status of reactive HMGB1 cysteines distinguishes its cytokine-inducing and chemokine activity Yang et al, 2012). To determine the redox status of HMGB1 secreted by SEN cells, we collected CM from PRE and SEN cells 24 h and 7 d after XRA, and analyzed CM before () or after (+) addition of dithiothreitol (DTT).…”