The Cellular Senescence Factor Extracellular HMGB1 Directly Inhibits Oligodendrocyte Progenitor Cell Differentiation and Impairs CNS Remyelination

Abstract

HMGB1 is a highly conserved, ubiquitous protein in eukaryotic cells. HMGB1 is normally localized to the nucleus, where it acts as a chromatin associated non-histone binding protein. In contrast, extracellular HMGB1 is an alarmin released by stressed cells to act as a danger associated molecular pattern (DAMP). We have recently determined that progenitor cells from multiple sclerosis patients exhibit a cellular senescent phenotype and release extracellular HMGB1 which directly impaired the maturation of oligodendrocyte progenitor cells (OPCs) to myelinating oligodendrocytes (OLs). Herein, we report that administration of recombinant HMGB1 into the spinal cord at the time of lysolecithin administration resulted in arrest of OPC differentiation in vivo, and a profound impairment of remyelination. To define the receptor by which extracellular HMGB1 mediates its inhibitory influence on OPCs to impair OL differentiation, we tested selective inhibitors against the four primary receptors known to mediate the effects of HMGB1, the toll-like receptors (TLRs)-2, -4, -9 or the receptor for advanced glycation end-products (RAGE). We found that inhibition of neither TLR9 nor RAGE increased OL differentiation in the presence of HMGB1, while inhibition of TLR4 resulted in partial restoration of OL differentiation and inhibiting TLR2 fully restored differentiation of OLs in the presence of HMGB1. Analysis of transcriptomic data (RNAseq) from OPCs identified an overrepresentation of NFκB regulated genes in OPCs when in the presence of HMGB1. We found that application of HMGB1 to OPCs in culture resulted in a rapid and concentration dependent shift in NFκB nuclear translocation which was also attenuated with coincident TLR2 inhibition. These data provide new information on how extracellular HMGB1 directly affects the differentiation potential of OPCs. Recent and past evidence for elevated HMGB1 released from senescent progenitor cells within demyelinated lesions in the MS brain suggests that a greater understanding of how this molecule acts on OPCs may unfetter the endogenous remyelination potential in MS.

HMGB1 in nervous system diseases: A common biomarker and potential therapeutic target

“…Furthermore, iNOS-mediated cytokine-induced nitric oxide excess can cause tissue damage in the central nervous system of EAE ( 124 ). Cellular senescence is a cellular feature of MS progenitor cells, and senescent neural progenitor cells can secrete HMGB1 oligodendrocyte progenitors (OPCs) to mature into myelinating oligodendrocytes (OLs), promoting chronic demyelination ( 125 , 126 ).…”

Chemically induced senescence prompts functional changes in human microglia-like cells

“…Extracellular HMGB1 acts as a damage-associated molecular pattern (DAMP) molecule which induces inflammation to the site of tissue damage (40, 41). However, under normal conditions, HMGB1 is localized in the nucleus as a chromatin associated non-histone binding protein (42). In senescent cells, HMGB1 translocates from the nucleus to the cytoplasm to be secreted (43) and it modulates senescence by binding to the surface of immune cells to initiate the signaling pathway responsible for the expression of pro-inflammatory cytokines (40).…”

“…2b ), but secretion of IL-1β and TNFα was not detected in any of the conditions. According to literature, HMC3 cells are unable to secrete TNFα (31) whereas the expression of IL-1β has been verified at both mRNA and protein level by western blot, but its secretion in the media remains elusive, possibly due to high turnover rate of the mature protein (42, 43). Importantly, secretion of both IL-6 and IL-8 was increased at baseline in SLO-treated cells, in line with the senescent-like profile exhibited by these cells ( Fig.…”

High Mobility Group Box 1 as an Autocrine Chemoattractant for Oligodendrocyte Lineage Cells in White Matter Stroke

“…A recent study by Rouillard et al 38 showed that extracellular HMGB1 impaired OPC differentiation and remyelination process in the spinal cord of a multiple sclerosis animal model. However, the study had many differences in design compared to our present study, including disease models and HMGB1 concentrations administered in vitro (1 ng/mL versus 500 ng/mL) and in vivo (0.25 μL, 100 ng/mL versus 1 μL, 1 mg/mL).…”