LPS Primes Brain Responsiveness to High Mobility Group Box-1 Protein.

Verena Peek,Lois M Harden,Joachim Roth,Marita Meurer,Jelena Damm,Sabine Schulz,Bernhard Spengler,Christoph Rummel,Ferial Aslani,Maren Von Köckritz-Blickwede,Stephan Leisengang,Rüdiger Gerstberger

doi:10.3390/ph14060558

Abstract

High mobility group box (HMGB)1 action contributes to late phases of sepsis, but the effects of increased endogenous plasma HMGB1 levels on brain cells during inflammation are unclear. Here, we aimed to further investigate the role of HMGB1 in the brain during septic-like lipopolysaccharide-induced inflammation in rats (LPS, 10 mg/kg, i.p.). HMGB-1 mRNA expression and release were measured in the periphery/brain by RT-PCR, immunohistochemistry and ELISA. In vitro experiments with disulfide-HMGB1 in primary neuro-glial cell cultures of the area postrema (AP), a circumventricular organ with a leaky blood–brain barrier and direct access to circulating mediators like HMGB1 and LPS, were performed to determine the direct influence of HMGB1 on this pivotal brain structure for immune-to-brain communication. Indeed, HMGB1 plasma levels stayed elevated after LPS injection. Immunohistochemistry of brains and AP cultures confirmed LPS-stimulated cytoplasmatic translocation of HMGB1 indicative of local HMGB1 release. Moreover, disulfide-HMGB1 stimulation induced nuclear factor (NF)-κB activation and a significant release of interleukin-6, but not tumor necrosis factor α, into AP culture supernatants. However, only a few AP cells directly responded to HMGB1 with increased intracellular calcium concentration. Interestingly, priming with LPS induced a seven-fold higher percentage of responsive cells to HMGB1. We conclude that, as a humoral and local mediator, HMGB1 enhances brain inflammatory responses, after LPS priming, linked to sustained sepsis symptoms.

Highlights

Introduction conditions of the Creative CommonsHigh mobility group box (HMGB)1 is a ubiquitous nuclear DNA-binding protein, which is involved in modulating chromatin structure [1], DNA replication, repair, and transcription [2,3]
We show that LPS-induced septic inflammation in rats is accompanied by late (24 h) and prolonged plasma HMGB1 levels, increased cytoplasmatic
HMGB1 staining in the median preoptic nucleus (MnPO) and area postrema (AP) and reduced nuclear HMGB-IR (AP) in primary neuro-glial AP-cell cultures

Summary

Introduction

Introduction conditions of the Creative CommonsHigh mobility group box (HMGB) is a ubiquitous nuclear DNA-binding protein, which is involved in modulating chromatin structure [1], DNA replication, repair, and transcription [2,3]. Its release by immune cells, neurons, astrocytes and microglia or other cell types in the periphery is accompanied by translocation from the nucleus to the cytoplasm [5,6,7]. These cells release HMGB1, they can be stimulated by it to release immune mediators including the pro-inflammatory cytokines interleukin (IL-) and/or tumor necrosis factor (TNF)α [6,8,9,10]. HMGB1 signals via toll-like receptor (TLR) or the receptor for advanced glycation end products (RAGE) and is known to induce nuclear factor (NF)κB activation [4]

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