The Role of High Mobility Group Box 1 (HMGB1) in Neurodegeneration: A Systematic Review

Background: High mobility group box 1 (HMGB1) protein is a damage-associated molecular pattern (DAMP) molecule that plays an important role in the repair and regeneration of tissue injury. It also acts as a pro-inflammatory cytokine through the activation of toll-like receptor 4 (TLR4) and receptor for advanced glycation end products (RAGE), to elicit the neuroinflammatory response. HMGB1 may aggravate several cellular responses which may lead to pathological inflammation and cellular death. Thus, there have been a considerable amount of research into the pathological role of HMGB1 in diseases. However, whether the mechanism of action of HMGB1 is similar in all neurodegenerative disease pathology remains to be determined. Objective: Therefore, this systematic review aimed to critically evaluate and elucidate the role of HMGB1 in the pathology of neurodegeneration based on the available literature. Methods: A comprehensive literature search was performed on four databases; EMBASE, PubMed, Scopus, and CINAHL Plus. Results: A total of 85 articles were selected for critical appraisal, after subjecting to the inclusion and exclusion criteria in this study. The selected articles revealed that HMGB1 levels were found elevated in most neurodegeneration except in Huntington’s disease and Spinocerebellar ataxia, where the levels were found decreased. This review also showcased that HMGB1 may act on distinctive pathways to elicit its pathological response leading to the various neurodegeneration processes/diseases. Conclusion: While there have been promising findings in HMGB1 intervention research, further studies may still be required before any HMGB1 intervention may be recommended as a therapeutic target for neurodegenerative diseases.

High Mobility Group Box-1 Protein and Interleukin 33 Expression in Allergic Rhinitis

<b><i>Background:</i></b> Allergic rhinitis (AR) is characterized by an inflammatory reaction. High mobility group box 1 (HMGB1) protein and interleukin (IL)-33 are damage-associated molecular pattern molecules and have many characteristics similar to pro-inflammatory cytokines. However, the role of IL-33 and HMGB1 in AR remains unclear. The aim of this study is to explore the role of HMGB1 and IL-33 in AR. <b><i>Methods:</i></b> Twenty patients with AR (AR group) and 10 normal controls (normal group) were enrolled in this study. HMGB1 and IL-33 expression were analyzed by immunohistochemistry in epithelial cells of the inferior turbinate mucosa samples. Then, the human nasal mucosa epithelial cells (HNECs) were cultured in vitro, and the house dust mite allergen (Derp1) was used to stimulate the cells. Quantitative real-time PCR and ELISA assay were performed to detect HMGB1 and IL-33 expression in HNECs. <b><i>Results:</i></b> The expression of HMGB1 and IL-33 in the nasal mucosa was higher in the AR group than in the normal group, with a statistically significant difference (<i>p</i> &#x3c; 0.05). In HNECs of AR, the expression of both HMGB1 and IL-33 in stimulated groups was higher than that in non-stimulated groups. The differences were statistically significant (<i>p</i> &#x3c; 0.05). In addition, they increased gradually with the prolonging time and the concentration of the added Derp1. <b><i>Conclusions:</i></b> The expression of HMGB1 and IL-33 were both increased in AR. HMGB1 and IL-33 may have a close relationship in AR.

HMGB1 signaling phosphorylates Ku70 and impairs DNA damage repair in Alzheimer’s disease pathology

DNA damage is increased in Alzheimer’s disease (AD), while the underlying mechanisms are unknown. Here, we employ comprehensive phosphoproteome analysis, and identify abnormal phosphorylation of 70 kDa subunit of Ku antigen (Ku70) at Ser77/78, which prevents Ku70-DNA interaction, in human AD postmortem brains. The abnormal phosphorylation inhibits accumulation of Ku70 to the foci of DNA double strand break (DSB), impairs DNA damage repair and eventually causes transcriptional repression-induced atypical cell death (TRIAD). Cells under TRIAD necrosis reveal senescence phenotypes. Extracellular high mobility group box 1 (HMGB1) protein, which is released from necrotic or hyper-activated neurons in AD, binds to toll-like receptor 4 (TLR4) of neighboring neurons, and activates protein kinase C alpha (PKCα) that executes Ku70 phosphorylation at Ser77/78. Administration of human monoclonal anti-HMGB1 antibody to post-symptomatic AD model mice decreases neuronal DSBs, suppresses secondary TRIAD necrosis of neurons, prevents escalation of neurodegeneration, and ameliorates cognitive symptoms. TRIAD shares multiple features with senescence. These results discover the HMGB1-Ku70 axis that accounts for the increase of neuronal DNA damage and secondary enhancement of TRIAD, the cell death phenotype of senescence, in AD.

HMGB1 Protein Interactions in Prostate and Ovary Cancer Models Reveal Links to RNA Processing and Ribosome Biogenesis through NuRD, THOC and Septin Complexes

This study reports the HMGB1 interactomes in prostate and ovary cancer cells lines. Affinity purification coupled to mass spectrometry confirmed that the HMGB1 nuclear interactome is involved in HMGB1 known functions such as maintenance of chromatin stability and regulation of transcription, and also in not as yet reported processes such as mRNA and rRNA processing. We have identified an interaction between HMGB1 and the NuRD complex and validated this by yeast-two-hybrid, confirming that the RBBP7 subunit directly interacts with HMGB1. In addition, we describe for the first time an interaction between two HMGB1 interacting complexes, the septin and THOC complexes, as well as an interaction of these two complexes with Rab11. Analysis of Pan-Cancer Atlas public data indicated that several genes encoding HMGB1-interacting proteins identified in this study are dysregulated in tumours from patients diagnosed with ovary and prostate carcinomas. In PC-3 cells, silencing of HMGB1 leads to downregulation of the expression of key regulators of ribosome biogenesis and RNA processing, namely BOP1, RSS1, UBF1, KRR1 and LYAR. Upregulation of these genes in prostate adenocarcinomas is correlated with worse prognosis, reinforcing their functional significance in cancer progression.

Galantamine prevents and reverses neuroimmune induction and loss of adult hippocampal neurogenesis following adolescent alcohol exposure

Background Binge ethanol exposure during adolescence reduces hippocampal neurogenesis, a reduction which persists throughout adulthood despite abstinence. This loss of neurogenesis, indicated by reduced doublecortin+ immunoreactivity (DCX+IR), is paralleled by an increase in hippocampal proinflammatory signaling cascades. As galantamine, a cholinesterase inhibitor, has anti-inflammatory actions, we tested the hypothesis that galantamine would prevent (study 1) or restore (study 2) AIE induction of proinflammatory signals within the hippocampus as well as AIE-induced loss of hippocampal neurogenesis. Methods Galantamine (4 mg/kg) or vehicle (saline) was administered to Wistar rats during adolescent intermittent ethanol (AIE; 5.0 g/kg ethanol, 2 days on/2 days off, postnatal day [P] 25-54) (study 1, prevention) or after AIE during abstinent maturation to adulthood (study 2, restoration). Results Results indicate AIE reduced DCX+IR and induced cleaved caspase3 (Casp3) in DCX-expressing immature neurons. Excitingly, AIE induction of activated Casp3 in DCX-expressing neurons is both prevented and reversed by galantamine treatment, which also resulted in prevention and restoration of neurogenesis (DCX+IR). Similarly, galantamine prevented and/or reversed AIE induction of proinflammatory markers, including the chemokine (C-C motif) ligand 2 (CCL2), cyclooxygenase-2 (COX-2), and high mobility group box 1 (HMGB1) protein, suggesting that AIE induction of proinflammatory signaling mediates both cell death cascades and hippocampal neurogenesis. Interestingly, galantamine treatment increased Ki67+IR generally as well as increased pan-Trk expression specifically in AIE-treated rats but failed to reverse AIE induction of NADPH-oxidase (gp91phox). Conclusions Collectively, our studies suggest that (1) loss of neurogenesis after AIE is mediated by persistent induction of proinflammatory cascades which drive activation of cell death machinery in immature neurons, and (2) galantamine can prevent and restore AIE disruptions in the hippocampal environmental milieu to then prevent and restore AIE-mediated loss of neurogenesis.

Zinc L-Carnosine Inhibits The Secretion of Pro-Inflammatory HMGB1 Protein From Lipopolysaccharide-Induced RAW 264.7 Murine Macrophage

Dysregulation in the secretion of high mobility group box 1(HMGB1) protein has been shown to modulate the progression of sepsis. Hence, the primary objective of this study is to explore the potential of zinc L-carnosine (ZnC) in inhibiting the secretion of HMGB1 from RAW 264.7 murine macrophages after induced with lipopolysaccharide (LPS). Generally, RAW 264.7 cells were pretreated with ZnC (0–100 µM) for 2 hours before challenged with LPS (1 µg/mL). After 22 hours of LPS induction, RAW 264.7 cells pretreated with ZnC showed significantly higher intracellular HMGB1 protein levels in a dose-dependent manner, indicating that ZnC was capable to suppress the secretion of HMGB1 protein into the extracellular compartments. Besides, significant increment in intracellular free thiol level was also detected in ZnC pretreated cells. In addition, ZnC was demonstrated to inhibit the late phase NF-κB activation, but not the early phase NF-κB activation. Moreover, after induced with LPS for 30 minutes, pretreatment with ZnC was also demonstrated to increase the phosphorylated-Akt/Akt ratio in RAW 264.7 cells, indicating that the immunomodulatory effects of ZnC may associated with the Akt signaling pathway. In summary, ZnC can prevent the secretion of HMGB1 from RAW 264.7 cells and suppress the NF-κB activation after induction with LPS. Results from this present study propose that ZnC possesses good potential to be used in the management and treatment of sepsis by inhibiting the secretion of HMGB1 from immune cells.

HIGH-MOBILITY GROUP BOX 1 (HMGB1) PROTEIN EVALUATION IN MPTP-INDUCED ZEBRAFISH MODEL OF PARKINSON’S DISEASE

Molecular studies have proven beneficial in understanding the pathophysiology of PD. Besides, the advancing application of zebrafish as a PD model has enabled researchers to conduct molecular studies with more promising outcomes and significance. Current evidence reported on the association of HMGB1 protein with neuroinflammation-induced PD pathogenesis. However, to the extent ofour knowledge, the molecular mechanism pertaining to HMGB1 involvement in PD are still elusive. Hence, we propose to conduct a study on HMGB1 protein, to elucidate its role in the pathogenesis of the MPTP-induced zebrafish model of PD. This study will answer the question pertaining to the involvement of HMGB1 in PD development and whether the knockdown of this protein can improve PD symptoms in zebrafish, particularly MPTP-induced motilitydisorders.

High Mobility Group Box 1 in Pig Amniotic Membrane Experimentally Infected with E. coli O55

Intra-amniotic infections (IAI) are one of the reasons for preterm birth. High mobility group box 1 (HMGB1) is a nuclear protein with various physiological functions, including tissue healing. Its excessive extracellular release potentiates inflammatory reaction and can revert its action from beneficial to detrimental. We infected the amniotic fluid of a pig on the 80th day of gestation with 1 × 104 colony forming units (CFUs) of E. coli O55 for 10 h, and evaluated the appearance of HMGB1, receptor for glycation endproducts (RAGE), and Toll-like receptor (TLR) 4 in the amniotic membrane and fluid. Sham-infected amniotic fluid served as a control. The expression and release of HMGB1 were evaluated by Real-Time PCR, immunofluorescence, immunohistochemistry, and ELISA. The infection downregulated HMGB1 mRNA expression in the amniotic membrane, changed the distribution of HMGB1 protein in the amniotic membrane, and increased its level in amniotic fluid. All RAGE mRNA, protein expression in the amniotic membrane, and soluble RAGE level in the amniotic fluid were downregulated. TLR4 mRNA and protein expression and soluble TLR4 were all upregulated. HMGB1 is a potential target for therapy to suppress the exaggerated inflammatory response. This controlled expression and release can, in some cases, prevent the preterm birth of vulnerable infants. Studies on suitable animal models can contribute to the development of appropriate therapy.

Computational Analysis of the Messenger RNA Variants Encoding Two Isoforms of the High-mobility Group box 1 Protein

High-mobility group box 1 protein (HMGB1) is a multifunctional nonhistone chromosomal protein. This widespread nuclear protein has a dual function-in the nucleus - it binds DNA and participates in practically all DNA-dependent processes. On the other hand, the protein plays an important role in the extracellular matrix as an “alarmin”, which interacts with certain receptors and stimulates biochemical pathways, associated with carcinogenesis and metastasis. HMGB1 is a critical damage-associated molecular pattern molecule, has been implicated in several inflammatory diseases and cancer types. This universality makes it an attractive target for innovative therapeutic strategies in the treatment of various diseases. The updated database for the HMGB1 gene, encoding the high-mobility group box 1 protein, was used for computational analysis of the annotated mRNA splice variants. Results showed that five of the splice variants encode an HMGB1 protein, containing 215 amino acid residues. However, two of the splice variants encode a shorter HMGB1 protein with 158 residues. Presently, the existence of a shorter HMGB1 protein is not registered in the protein databanks. This inconsistency is not yet resolved.