High mobility group protein 1: A collaborator in nucleosome dynamics and estrogen-responsive gene expression

circKCNQ5 promotes the proliferation of DNA-methyltransferase 3A R882 mutated acute myeloid leukemia cells by elevating high-mobility group box 1 expression

BACKGROUND

Patients with acute myeloid leukemia (AML) harboring the DNA-methyltransferase 3 A (DNMT3A) R882 mutation (DR882MUT) usually have a high recurrence rate and poor prognosis. circKCNQ5 levels were aberrantly elevated in patients with AML according to the microarray platform. Therefore, the purpose of this study is to investigate the effect and mechanism of circKCNQ5 on DR882MUT AML cell proliferation.

METHODS

A DR882MUT cell line model was established. circKCNQ5 expression in AML cells expressing wild-type DNMT3A (DNMT3A-WT) or DR882MUT was analyzed using RT-qPCR. The proliferation of DNMT3A-WT and DR882MUT AML cells after transfection was measured using a CCK-8 assay. High-mobility group box 1 (HMGB1) protein expression was assessed by western blotting. The regulatory mechanism of circKCNQ5 on HMGB1 expression was studied using RNA pull-down and co-immunoprecipitation assays.

RESULTS

circKCNQ5 expression increased gradually in HS-5, DNMT3A-WT, and DR882MUT AML cells. circKCNQ5 overexpression facilitated the proliferation of DNMT3A-WT KG-1a and HL-60 cells, whereas circKCNQ5 silencing blocked DR882MUT KG-1a and HL-60 cell proliferation. CircKCNQ5 interacts with HMGB1 and enhanced HMGB1 protein levels by inhibiting HMGB1 ubiquitination. HMGB1 protein levels increased gradually in HS-5, DNMT3A-WT, and DR882MUT AML cells. Furthermore, circKCNQ5 overexpression elevated HMGB1 protein levels in DNMT3A-WT KG-1a and HL-60 cells, whereas circKCNQ5 silencing reduced HMGB1 protein levels in DR882MUT KG-1a and HL-60 cells. HMGB1 overexpression remarkably increased the proliferative ability of DR882MUT KG-1a and HL-60 cells and circKCNQ5 silencing.

CONCLUSIONS

These findings verified that circKCNQ5 promotes the proliferation of DR882MUT AML cells by increasing HMGB1 expression.

The Role of PARP1 and PAR in ATP-Independent Nucleosome Reorganisation during the DNA Damage Response

The functioning of the eukaryotic cell genome is mediated by sophisticated protein-nucleic-acid complexes, whose minimal structural unit is the nucleosome. After the damage to genomic DNA, repair proteins need to gain access directly to the lesion; therefore, the initiation of the DNA damage response inevitably leads to local chromatin reorganisation. This review focuses on the possible involvement of PARP1, as well as proteins acting nucleosome compaction, linker histone H1 and non-histone chromatin protein HMGB1. The polymer of ADP-ribose is considered the main regulator during the development of the DNA damage response and in the course of assembly of the correct repair complex.

High-Mobility Group Box-1 and Its Potential Role in Perioperative Neurocognitive Disorders

Aseptic surgical trauma provokes the release of HMGB1, which engages the innate immune response after binding to pattern-recognition receptors on circulating bone marrow-derived monocytes (BM-DM). The initial systemic inflammation, together with HMGB1, disrupts the blood-brain barrier allowing penetration of CCR2-expressing BM-DMs into the hippocampus, attracted by the chemokine MCP-1 that is upregulated by HMGB1. Within the brain parenchyma quiescent microglia are activated and, together with the translocated BM-DMs, release proinflammatory cytokines that disrupt synaptic plasticity and hence memory formation and retention, resulting in postoperative cognitive decline (PCD). Neutralizing antibodies to HMGB1 prevents the inflammatory response to trauma and PCD.

HMGB1: an important regulator of myeloid differentiation and acute myeloid leukemia as well as a promising therapeutic target

Abstract

High mobility group box 1 (HMGB1) is a non-histone nuclear protein which has been intensively studied in various physiological and pathological processes including leukemia. Here in this study, we further demonstrated that HMGB1 presents higher expression in the bone marrow mononuclear cells of acute myeloid leukemia (AML) patients compared with the normal controls and contributes to the AML pathogenesis and progression by inhibiting apoptosis, facilitating proliferation, and inducing myeloid differentiation blockade of AML cells. Mechanistic investigation revealed that transforming growth factor beta-induced (TGFBI) acts as a potential downstream target of HMGB1 and lentivirus-mediated knockdown of TGFBI expression impaired phorbol-12-myristate-13-acetate (PMA) and all-trans retinoic acid (ATRA)–induced myeloid differentiation of AML cell lines. On the other hand, chidamide, an orally histone deacetylase inhibitor, decreases HMGB1 expression significantly in AML cells with concomitant upregulation of TGFBI expression, and confers therapeutic effect on AML by inducing cell differentiation, apoptosis and inhibiting cell proliferation. In conclusion, our findings provide additional insights that HMGB1 is a promising therapeutic target of AML, and also present experimental evidence for the clinical application of chidamide as a novel agent in AML therapy by downregulating HMGB1 expression.

Key messages

HMGB1 induces cell proliferation and myeloid differentiation blockade and inhibits apoptosis of AML cells.

TGFBI acts as a potential target of HMGB1.

Chidamide, a selective HDAC inhibitor, confers promising therapeutic effect for AML via downregulating HMGB1 expression.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00109-020-01998-5.

Nucleosome Crowding in Chromatin Slows the Diffusion but Can Promote Target Search of Proteins

Dynamics of nuclear proteins in crowded chromatin has only been poorly understood. Here, we address the diffusion, target search, and structural dynamics of three proteins in a model chromatin using coarse-grained molecular simulations run on the K computer. We prepared two structures of chromatin made of 20 nucleosomes with different nucleosome densities and investigated dynamics of two transcription factors, HMGB1 and p53, and one signaling protein, ERK, embedded in the chromatin. We found fast and normal diffusion of the nuclear proteins in the low-density chromatins and slow and subdiffusional movements in the high-density chromatin. The diffusion of the largest transcription factor, p53, is slowed by high-density chromatin most markedly. The on rates and off rates for DNA binding are increased and decreased, respectively, in the high-density chromatin. To our surprise, the DNA sequence search was faster in chromatin with high nucleosome density, though the diffusion is slower. We also found that the three nuclear proteins preferred to bind on the linker DNA and the entry and exit regions of nucleosomal DNA. In addition to these regions, HMGB1 and p53 also bound to the dyad.

Repeated abortion in adulthood induces cognition impairment in aged mice

Age-related cognitive decline is one of the major aspects that impede successful aging in humans. Repeated abortion in adulthood can accelerate or aggravate cognitive deficiency during aging. Here we used repeated abortion in female mice adulthood and investigated the consequences of this treatment on cognitive performance during aging. We observed a substantial impairment of learning memory in 15 months old. This cognitive dysfunction was supported by Aβ elevation in CA region. Repeated abortion mice have uniform estrous cycles and decreased ERα expression in hypothalamus and hippocampus. Furthermore, repeated abortion not only significantly increased the HMGB1 expression in hippocampus but also increased the plasma and hippocampal protein levels of IL-1β, IL-6, and TNF-α. Finally, we identified that MPP-induced cell apoptosis and increased HMGB1 expression as well as IL-1β, IL-6, and TNF-α expression as following Aβ elevation. Taken together, our results identify possible molecular mechanisms underlying cognitive impairment during aging, and demonstrated the repeated abortion in adulthood on cognitive function in aged mice.

MicroRNA-381 reduces inflammation and infiltration of macrophages in polymyositis via downregulating HMGB1

The downregulation of microRNA (miR)-381 has been detected in various diseases. The present study aimed to investigate the effects, and underlying mechanisms of miR-381 on inflammation and macrophage infiltration in polymyositis (PM). A mouse model of experimental autoimmune myositis (EAM) was generated in this study. Hematoxylin and eosin staining was conducted to detect the inflammation of muscle tissues. In addition, ELISA and immunohistochemistry were performed to determine the expression levels of associated factors, and reverse transcription-quantitative polymerase chain reaction and western blotting were used to detect the expression levels of related mRNAs and proteins. A luciferase activity assay was used to confirm the binding of miR-381 and high mobility group box 1 (HMGB1) 3' untranslated region. Transwell assays were also performed to assess the migratory ability of macrophages. The results demonstrated that serum creatine kinase (s-CK), HMGB1 and cluster of differentiation (CD)163 expression in patients with PM were increased compared within healthy controls. Conversely, the expression levels of miR-381 were downregulated in patients with PM. Furthermore, high HMGB1 expression was associated with poor survival rate in patients with PM. In the mouse studies, muscle inflammation and CD163 expression were decreased in the anti-IL-17 and anti-HMGB1 groups, compared with in the EAM model group. The expression levels of s-CK, HMGB1, IL-17 and intercellular adhesion molecule (ICAM)-1 were also downregulated in response to anti-IL-17 and anti-HMGB1. These findings indicated that HMGB1 was closely associated with inflammatory responses. In addition, the present study indicated that transfection of macrophages with miR-381 mimics reduced the migration of inflammatory macrophages, and the expression levels of HMGB1, IL-17 and ICAM-1. Conversely, miR-381 inhibition exerted the opposite effects. The effects of miR-381 inhibitors were reversed by HMGB1 small interfering RNA. In conclusion, miR-381 may reduce inflammation and the infiltration of macrophages; these effects were closely associated with the downregulation of HMGB1.

Protective effect of high mobility group box-1 silence on diabetic retinopathy: an in vivo study

PURPOSE

To explore the effects of HMGB1 silence on cell apoptosis, inflammatory response and endothelial permeability barrier.

METHODS

Retinal tissues were isolated from 8 week-old SD rats and cells were cultured and identified. Effects of HMGB1 silence were detected by qRT-PCR and Western blot. Proliferation capability of cells was detected by MTT assay and LDH activity assays. Cell apoptosis was analyzed by flow cytometry, Hoechst staining and Caspase-3 activity assay. Furthermore, concentrations of VEGF, ICAM-1, VCAM-1, TNF-α and MCP-1 in the cell media were measured.

RESULTS

Results of our study showed that high concentration of glucose caused increased cell apoptosis and inflammatory response, and also influenced the endothelial permeability barrier. Whereas, these damaging effects of high concentration of glucose could be relieved by HMGB1 silence.

CONCLUSION

The present study indicates that HMGB silence is a promising therapeutic option for diabetic retinopathy, and also provides theoretical basis for further exploration of diabetic retinopathy treatment.

Proinflammatory effect of high-mobility group protein B1 on keratinocytes: an autocrine mechanism underlying psoriasis development

Psoriasis is an autoimmune skin disease, in which keratinocytes play a crucial pathogenic role. High-mobility group protein B1 (HMGB1) is an inflammatory factor that can be released from keratinocyte nuclei in psoriatic lesions. We aimed to investigate the proinflammatory effect of HMGB1 on keratinocytes and the contribution of HMGB1 to psoriasis development. Normal human keratinocytes were treated with recombinant human HMGB1, and the production of inflammatory factors and the intermediary signalling pathways were examined. Furthermore, the imiquimod-induced psoriasis-like mouse model was used to investigate the role of HMGB1 in psoriasis development in vivo. A total of 11 inflammatory factors were shown to be upregulated by HMGB1 in keratinocytes, among which interleukin (IL)-18 showed the greatest change. We then found that activation of the nuclear factor-κB signalling pathway and inflammasomes accounted for HMGB1-induced IL-18 expression and secretion. Moreover, HMGB1 and downstream IL-18 contributed to the development of psoriasiform dermatitis in the imiquimod-treated mice. In addition, T-helper 17 immune response in the psoriasis-like mouse model could be inhibited by both HMGB1 and IL-18 blockade. Our findings indicate that HMGB1 secreted from keratinocytes can facilitate the production and secretion of inflammatory factors such as IL-18 in keratinocytes in an autocrine way, thus promoting the development of psoriasis. Blocking the proinflammatory function of the HMGB1-IL-18 axis may be useful for psoriasis treatment in the future. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.