HMGB1-Binding Heptamer Confers Anti-Inflammatory Effects in Primary Microglia Culture

Abstract

High mobility group box 1 (HMGB1) is an endogenous danger signal molecule. In the postischemic brain, HMGB1 is massively released during NMDA-induced acute damage and triggers inflammatory processes. In a previous study, we demonstrated that intranasally delivered HMGB1 binding heptamer peptide (HBHP; HMSKPVQ) affords robust neuroprotective effects in the ischemic brain after middle cerebral artery occlusion (MCAO, 60 minutes). In the present study, we investigated HBHP-induced anti-inflammatory effects on microglia activation. In LPS-treated primary microglia culture, HMGB1 was rapidly released and accumulated in culture media. Furthermore, LPS-conditioned media collected from primary microglia cultures (LCM) activated naïve microglia and markedly induced NO and proinflammatory cytokines. However, the suppression of HMGB1 by siRNA-HMGB1, HMGB1 A box, or anti-HMGB1 antibody significantly attenuated LCM-induced microglial activation, suggesting that HMGB1 plays a critical role in this process. A pull-down assay using biotin-labeled HBHP showed that HBHP binds directly to HMGB1 (more specifically to HMGB1 A box) in LCM. In addition, HBHP consistently inhibited LCM-induced microglial activation and suppressed the inductions of iNOS and proinflammatory cytokines. Together these results suggest that HBHP confers anti-inflammatory effects in activated microglia cultures by forming a complex with HMGB1.

RNA-Seq transcriptomic profiling of primary murine microglia treated with LPS or LPS + IFNγ

“…Finally, Hmgb1 interacts with and represses Mecp2 69 . However, LPS + IFNγ downregulates Hmgb1 , thus increasing Mecp2 expression and blocking secretion of pro-inflammatory mediators 70 , 71 . Thus, these results suggest that LPS + IFNγ treatment reduces genes involved in neuropathic pain, as well as microglial migration and proliferation, whereas it also promotes some anti-inflammatory responses.…”

Persistent Increase in Microglial RAGE Contributes to Chronic Stress–Induced Priming of Depressive-like Behavior

“…Weber and colleagues (2015) reported that acute exposure to inescapable tail shock increases microglial HMGB1 release and sensitization to ex vivo LPS challenge 1 day after stress [19]. Pharmacological blockade of HMGB1 signaling using the selective antagonist BoxA, attenuated HMGB1-mediated potentiation of LPS responses in cultured primary microglia (22, 23). In addition, in vivo administration of glycyrrhizic acid (GZA), a non-selective antagonist of HMGB1, protects rodents against LPS-induced depressive-like behaviors (24) and cognitive deficits following fluid percussion injury (25).…”

Cell permeable HMGB1-binding heptamer peptide ameliorates neurovascular complications associated with thrombolytic therapy in rats with transient ischemic stroke

“…Currently, there are several approaches to block HMGB1-mediated inflammation and thereby protecting neurovascular unit, including neutralizing monoclonal antibody (mAb) [ 13 , 14 ], N-terminal domain of HMGB1 (competitively binds to receptors) [ 31 ], non-specific inhibitors like glycyrrhizin [ 32 ], and blocking peptide (HBHP) [ 15 , 19 , 33 ]. Among them, mAb requires intracerebroventricular injection, whereas HMGB1 N-terminal domain and glycyrrhizin lack target specificity.…”

“…Different doses of TAT-HBHP (YGRKKRRQRRR-HMSKPVQ, 1, 5, 10 mg/kg) were intravenously administered after tPA treatment within 30 min (Fig. 3a ) [ 15 , 19 ]. TAT-scramble peptide (YGRKKRRQRRR-PMQSKHV, 5 mg/kg) was employed as vehicle control.…”