Distribution Of High Mobility Group Box 1 Research Articles

SIRT7 affects autophagy and activation of hepatic stellate cells by regulating the acetylation level of high mobility group protein 1

ObjectivePreventing the progression of hepatic fibrosis is an important strategy to improve the prognosis of liver disease. The purpose of this study was to investigate the role of sirtuin7 (SIRT7) and high mobility group box 1 (HMGB1) acetylation in the occurrence and development of hepatic fibrosis. Materials and methodsHepatic fibrosis mice model was induced by CCl4. TGF-β1 was used to activated quiescent hepatic stellate cell (qHSC) into activated HSC (aHSC). Hematoxylin-eosin evaluated hepatic fibrosis in vivo, and the distribution of α-smooth muscle actin (α-SMA) or HMGB1 was detected by immunohistochemistry or immunofluorescence. The expressions of SIRT7, autophagy related proteins, and HSC activation-related proteins were detected by Western blot. Immunoprecipitation detected the acetylation level of HMGB1. Lysine mutants of HMGB1 were constructed in vitro to explore the acetylation sites of HMGB1. ResultsHepatocyte autophagy and activation levels were enhanced in CCl4 group or aHSC group, and the acetylation level of HMGB1 was increased. Nuclear transfer of HMGB1 occurred in aHSC, and HMGB1was mainly distributed in cytoplasm. The expression of SIRT7 in CCl4 group or aHSC group was most significantly decreased, and knockdown of SIRT7 leads to increased levels of HSCs autophagy and activation. Overexpression of SIRT7 or interference of HMGB1 alone in aHSC can reduce the level of autophagy and activation of aHSC. However, continued overexpression of SIRT7 in shHMGB1-aHSC could not reduce the autophagy and activation levels of aHSC. Among the 11 Flag-HMGB1 mutants, the acetylation level of K86R-Flag-HMGB1 was the lowest. The acetylation level of K86R-Flag-HMGB1 did not change due to SIRT7 downregulation. ConclusionThis study proved that SIRT7 can directly target the K86R site of HMGB1 and participate in regulating the expression and distribution of HMGB1, thus affecting the autophagy and activation level of HSCs.

High-mobility group box protein 1 expression in inflammatory diseases of the middle ear.

High-mobility group box 1 (HMGB1) is a nuclear non-histone protein, playing a critical role as a mediator between innate and acquired immunity; when released extracellularly, it coordinates the cellular stress response (under necrosis, bacterial lipopolysaccharide stimulation) and acts as an inflammatory marker and cytokine. The aim of the study was to demonstrate whether HMGB1 is over-expressed in chronic middle-ear pathologies and whether the entity of expression and the localization are correlated with the degree of the inflammatory reaction, thus suggesting that HMGB1 may play a crucial role in chronic inflammatory disorders of the middle ear, as already demonstrated in other airway diseases.We analyzed 30 samples of middle-ear mucosa in patients affected by chronic suppurative otitis media with ear drum perforation with/without cholesteatoma and otosclerosis as control. The distribution of HMGB1 was evaluated as nuclear, cytoplasmic, and/or extracellular staining.The inflammatory cells observed in the biopsies were mostly lymphocytes and plasmacells. A statistically significant difference in inflammation score between otosclerosis and chronic otitis samples (P < 0.01; Anova test) and between otosclerosis and cholesteatoma samples (P < 0.05; Anova test) was observed; the HMGB1 positivity was in accordance with the density of the inflammatory infiltrate.HMGB1 is over-expressed in chronic middle-ear pathologies and may play a role in the progression of the inflammatory process from recurrent acute otitis media to chronic suppurative otitis media.

Relationship of dendritic cell density, HMGB1 expression, and tumor-infiltrating lymphocytes in non-small cell lung carcinomas.

Lung cancer is the leading cause of cancer death worldwide and non-small cell lung carcinoma (NSCLC) is the most common type of lung carcinomas. In adenocarcinomas, the most frequent histologic type of NSCLC, dendritic cells (DCs) are localized in close contact with tumor cells, and tumor-infiltrating lymphocytes (TILs) are observed in the peritumoral zones. In NSCLC, no studies investigating the density of intratumoral DCs and their impact on the density of TILs have been performed. In addition, the role of the alarmin high-mobility group box1 (HMGB1) in intratumoral DCs recruitment has not been analyzed. In the present study, a total of 82 cases of advanced stages of NSCLC were included. Tissue samples were obtained from biopsies and autopsies. DCs in biopsies or combinations of DCs and NK cells, CD3 T lymphocytes, or CD8 T lymphocytes from autopsy specimens were quantified in high power fields. Also, distribution of HMGB1 in tumor cells was detected. In lung adenocarcinomas, irrespective of subclassification, high densities of infiltrating DCs directly associated to high densities of peritumoral TILs. A 2.5-fold increase in TILs was found in specimens with high densities of infiltrating DCs compared with TILs from adenocarcinomas with low densities of infiltrating DCs. High densities of infiltrating DCs were associated with lung adenocarcinomas expressing cytoplasmic or nuclear-cytoplasmic HMGB1. Our results suggest that in adenocarcinoma patients, HMGB1 produced by tumor cells recruits DCs, which associate to an increase of TILs. Encouraging tumor-DCs-T lymphocytes interactions should improve the quality of life and survival of NSCLC patients.

Protective effect of curcumin against Aβ25-35-induced neurotoxicity in differentiated PC12 cells

To explore the effects of curcumin on the expression of high mobility group box1 (HMGB1) , cell viability and morphology in a cellular model of Alzheimer's disease (AD). Cultured PC12 cells in logarithmic growth phase were divided into 5 groups: normal cell group (A, non-treatment), model control group (B, 20 µmol/L Aβ25-35), curcumin treatment group (C, 20 µmol/L Aβ25-35+1 µmol/L Cur), Aβ25-35+rHMG1 (D, 20 µmol/L Aβ25-35+500 ng/ml HMGB1) and solvent control group (E, 20 µmol/L Aβ25-35+1 µl/ml DMSO). Cell viability was examined by methyl thiazolyl tetrazolium (MTT). And the cellular expression and distribution of HMGB1 were detected by immunofluorescence and Western blot 24 hours later. Compared with group A, the levels of cell viability in groups B, D and E significantly declined (0.76 ± 0.06, 0.63 ± 0.02, 0.75 ± 0.03 vs 1.22 ± 0.06, P < 0.05) while the expression of HMGB1 increased (1.19 ± 0.14, 1.12 ± 0.16, 1.16 ± 0.09 vs 0.85 ± 0.04, P < 0.05). Compared with group B, cell viability in group C significantly increased by 33% (1.01 ± 0.05, P < 0.05) while the expression of HMGB1 declined by 31% (0.78 ± 0.03, P < 0.05). A larger amount of extracellular HMGB1 was released in group B compared with group A. And the extracellular release of HMGB1 declined less in group C versus group B. Curcumin may reduce Aβ25-35-induced cytotoxicity through a down-regulated expression of HMGB1 and an inhibition of extracellular release of HMGB1 in PC12 cell.

High mobility group box 1 potentiates the pro-inflammatory effects of interleukin-1β in osteoarthritic synoviocytes

IntroductionHigh mobility group box 1 (HMGB1) is released by necrotic cells or secreted in response to inflammatory stimuli. Extracellular HMGB1 may act as a pro-inflammatory cytokine in rheumatoid arthritis. We have recently reported that HMGB1 is released by osteoarthritic synoviocytes after activation with interleukin-1beta (IL-1β) The present study investigated the role of HMGB1 in synovial inflammation in osteoarthritis (OA).MethodsHMGB1 was determined in human synovium using immunohistochemistry, comparing normal to OA. OA synoviocytes were incubated with HMGB1 at 15 or 25 ng/ml in the absence or presence of IL-1β (10 ng/ml). Gene expression was analyzed by quantitative PCR and protein expression by Western Blot and ELISA. Matrix metalloproteinase (MMP) activity was studied by fluorometric procedures and nuclear factor (NF)-κB activation by transient transfection with a NF-κB-luciferase plasmid.ResultsIn the normal synovium, HMGB1 was found in the synovial lining cells, sublining cells, and in the vascular wall cells. The distribution of HMGB1 in OA synovium was similar but the number of HMGB1 positive cells was higher and HMGB1 was also present in infiltrated cells. In normal synovial membrane cells, HMGB1 was found mostly in the nuclei, whereas in OA, HMGB1 was generally found mostly in the cytoplasm. In OA synoviocytes, HMGB1 alone at concentrations of 15 or 25 ng/ml did not affect the production of IL-6, IL-8, CCL2, CCL20, MMP-1 or MMP-3, but in the presence of IL-1β, a significant potentiation of protein and mRNA expression, as well as MMP activity was observed. HMGB1 also enhanced the phosphorylated ERK1/2 and p38 levels, with a lower effect on phosphorylated Akt. In contrast, JNK1/2 phosphorylation was not affected. In addition, HMGB1 at 25 ng/ml significantly potentiated NF-κB activation in the presence of IL-1β.ConclusionsOur results indicate that HMGB1 is overexpressed in OA synovium and mostly present in extracellular form. In OA synoviocytes, HMGB1 cooperates with IL-1β to amplify the inflammatory response leading to the production of a number of cytokines, chemokines and MMPs. Our data support a pro-inflammatory role for this protein contributing to synovitis and articular destruction in OA.