Degradation of histone deacetylase 4 via the TLR4/JAK/STAT1 signaling pathway promotes the acetylation of high mobility group box 1 (HMGB1) in lipopolysaccharide-activated macrophages

Roles of Histone Deacetylase 4 in the Inflammatory and Metabolic Processes

Histone deacetylase 4 (HDAC4), a class IIa HDAC, has gained attention as a potential therapeutic target in treating inflammatory and metabolic processes based on its essential role in various biological pathways by deacetylating non-histone proteins, including transcription factors. The activity of HDAC4 is regulated at the transcriptional, post-transcriptional, and post-translational levels. The functions of HDAC4 are tissue-dependent in response to endogenous and exogenous factors and their substrates. In particular, the association of HDAC4 with non-histone targets, including transcription factors, such as myocyte enhancer factor 2, hypoxia-inducible factor, signal transducer and activator of transcription 1, and forkhead box proteins, play a crucial role in regulating inflammatory and metabolic processes. This review summarizes the regulatory modes of HDAC4 activity and its functions in inflammation, insulin signaling and glucose metabolism, and cardiac muscle development.

3'-Sialyllactose protects against LPS-induced endothelial dysfunction by inhibiting superoxide-mediated ERK1/2/STAT1 activation and HMGB1/RAGE axis

AIM

Endothelial hyperpermeability is an early stage of endothelial dysfunction associated with the progression and development of atherosclerosis. 3'-Sialyllactose (3'-SL) is the most abundant compound in human milk oligosaccharides, and it has the potential to regulate endothelial dysfunction. This study investigated the beneficial effects of 3'-SL on lipopolysaccharide (LPS)-induced endothelial dysfunction in vitro and in vivo.

MAIN METHODS

We established LPS-induced endothelial dysfunction models in both cultured bovine aortic endothelial cells (BAECs) and mouse models to determine the effects of 3'-SL. Western blotting, qRT-PCR analysis, immunofluorescence staining, and en face staining were employed to clarify underlying mechanisms. Superoxide production was measured by 2',7'-dichlorofluorescin diacetate, and dihydroethidium staining.

KEY FINDINGS

LPS significantly decreased cell viability, whereas 3'-SL treatment mitigated these effects via inhibiting ERK1/2 activation. Mechanistically, 3'-SL ameliorated LPS-induced ROS accumulation leading to ERK1/2 activation-mediated STAT1 phosphorylation and subsequent inhibition of downstream transcriptional target genes, including VCAM-1, TNF-α, IL-1β, and MCP-1. Interestingly, LPS-induced ERK1/2/STAT1 activation leads to the HMGB1 release from the nucleus into the extracellular space, where it binds to RAGE, while 3'-SL suppressed EC hyperpermeability by suppressing the HMGB1/RAGE axis. This interaction also led to VE-cadherin endothelial junction disassembly and endothelial cell monolayer disruption through ERK1/2/STAT1 modulation. In mouse endothelium, en face staining revealed that 3'-SL abolished LPS-stimulated ROS production and VCAM-1 overexpression.

SIGNIFICANCE

Our findings suggest that 3'-SL inhibits LPS-induced endothelial hyperpermeability by suppressing superoxide-mediated ERK1/2/STAT1 activation and HMGB1/RAGE axis. Therefore, 3'-SL may be a potential therapeutic agent for preventing the progression of atherosclerosis.

High-mobility group box 1 emerges as a therapeutic target for asthma

High-mobility group box 1 (HMGB1) is a highly conserved nonhistone nuclear protein found in the calf thymus and participates in a variety of intracellular processes such as DNA transcription, replication and repair. In the cytoplasm, HMGB1 promotes mitochondrial autophagy and is involved in in cellular stress response. Once released into the extracellular, HMGB1 becomes an inflammatory factor that triggers inflammatory responses and a variety of immune responses. In addition, HMGB1 binding with the corresponding receptor can activate the downstream substrate to carry out several biological effects. Meanwhile, HMGB1 is involved in various signaling pathways, such as the HMGB1/RAGE pathway, HMGB1/NF-κB pathway, and HMGB1/JAK/STAT pathway, which ultimately promote inflammation. Moreover, HMGB1 may be involved in the pathogenesis of asthma by regulating downstream signaling pathways through corresponding receptors and mediates a number of signaling pathways in asthma, such as HMGB1/TLR4/NF-κB, HMGB1/RAGE, HMGB1/TGF-β, and so forth. Accordingly, HMGB1 emerges as a therapeutic target for asthma.

Review: The role of HMGB1 in spinal cord injury

High mobility group box 1 (HMGB1) has dual functions as a nonhistone nucleoprotein and an extracellular inflammatory cytokine. In the resting state, HMGB1 is mainly located in the nucleus and regulates key nuclear activities. After spinal cord injury, HMGB1 is rapidly expressed by neurons, microglia and ependymal cells, and it is either actively or passively released into the extracellular matrix and blood circulation; furthermore, it also participates in the pathophysiological process of spinal cord injury. HMGB1 can regulate the activation of M1 microglia, exacerbate the inflammatory response, and regulate the expression of inflammatory factors through Rage and TLR2/4, resulting in neuronal death. However, some studies have shown that HMGB1 is beneficial for the survival, regeneration and differentiation of neurons and that it promotes the recovery of motor function. This article reviews the specific timing of secretion and translocation, the release mechanism and the role of HMGB1 in spinal cord injury. Furthermore, the role and mechanism of HMGB1 in spinal cord injury and, the challenges that still need to be addressed are identified, and this work will provide a basis for future studies.

HAT- and HDAC-Targeted Protein Acetylation in the Occurrence and Treatment of Epilepsy

Epilepsy is a common and severe chronic neurological disorder. Recently, post-translational modification (PTM) mechanisms, especially protein acetylation modifications, have been widely studied in various epilepsy models or patients. Acetylation is regulated by two classes of enzymes, histone acetyltransferases (HATs) and histone deacetylases (HDACs). HATs catalyze the transfer of the acetyl group to a lysine residue, while HDACs catalyze acetyl group removal. The expression of many genes related to epilepsy is regulated by histone acetylation and deacetylation. Moreover, the acetylation modification of some non-histone substrates is also associated with epilepsy. Various molecules have been developed as HDAC inhibitors (HDACi), which have become potential antiepileptic drugs for epilepsy treatment. In this review, we summarize the changes in acetylation modification in epileptogenesis and the applications of HDACi in the treatment of epilepsy as well as the mechanisms involved. As most of the published research has focused on the differential expression of proteins that are known to be acetylated and the knowledge of whole acetylome changes in epilepsy is still minimal, a further understanding of acetylation regulation will help us explore the pathological mechanism of epilepsy and provide novel ideas for treating epilepsy.

MicroRNA‑23a‑3p targeting of HMGB1 inhibits LPS‑induced inflammation in murine macrophages in vitro

Inflammatory cytokines, including high mobility group box 1 (HMGB1), play a key role in sepsis via various mechanisms, some of which remain unknown. Sepsis is a common cause of death in patients admitted to the intensive care unit. MicroRNAs (miRs) serve an important role in the inflammatory response. The present study aimed to investigate the role of miR-23a-3p in macrophage inflammation and the targeted regulation of HMGB1 expression. The murine macrophage cell line RAW264.7 was subjected to lipopolysaccharide (LPS) treatment to mimic the inflammation involved in sepsis in vitro. Reverse transcription-quantitative PCR was performed to measure miR-23a-3p expression and mRNA expression. Protein levels were determined using ELISA and western blotting. The target binding relationship between miR-23a-3p and the HMGB1 3'untranslated region was predicted and validated with a dual luciferase reporter assay. HMGB1 expression was increased and miR-23a-3p expression significantly reduced in patients with sepsis and in LPS-treated RAW264.7 cells in comparison with controls. Overexpression of miR-23a-3p reduced interleukin (IL)-6 and tumor necrosis factor (TNF)-α expression in RAW264.7 cells under LPS stimulation, while silencing of miR-23a-3p elevated the expression of IL-6 and TNF-α in comparison with controls. The inhibitory effect of miR-23a-3p on LPS-induced inflammation could be abolished by HMGB1 upregulation in RAW264.7 cells. HMGB1 was targeted by miR-23a-3p. miR-23a-3p is expressed at reduced levels during inflammation in sepsis, and overexpression of miR-23a-3p inhibits LPS-induced inflammation in murine macrophages in vitro by directly downregulating HMGB1. The results of the present study provided a novel insight into the molecular mechanism underlying HMGB1 expression at the post-transcriptional level in sepsis.

The mechanism of HMGB1 secretion and release

High mobility group box 1 (HMGB1) is a nonhistone nuclear protein that has multiple functions according to its subcellular location. In the nucleus, HMGB1 is a DNA chaperone that maintains the structure and function of chromosomes. In the cytoplasm, HMGB1 can promote autophagy by binding to BECN1 protein. After its active secretion or passive release, extracellular HMGB1 usually acts as a damage-associated molecular pattern (DAMP) molecule, regulating inflammation and immune responses through different receptors or direct uptake. The secretion and release of HMGB1 is fine-tuned by a variety of factors, including its posttranslational modification (e.g., acetylation, ADP-ribosylation, phosphorylation, and methylation) and the molecular machinery of cell death (e.g., apoptosis, pyroptosis, necroptosis, alkaliptosis, and ferroptosis). In this minireview, we introduce the basic structure and function of HMGB1 and focus on the regulatory mechanism of HMGB1 secretion and release. Understanding these topics may help us develop new HMGB1-targeted drugs for various conditions, especially inflammatory diseases and tissue damage.

A nuclear protein that gets released after cell death or is actively secreted by immune cells offers a promising therapeutic target for treating diseases linked to excessive inflammation. Daolin Tang from the University of Texas Southwestern Medical Center in Dallas, USA, and colleagues review how cellular stresses can trigger the accumulation of HMGB1, a type of alarm signal protein that promotes the recruitment and activation of inflammation-promoting immune cells. The researchers discuss various mechanisms that drive both passive and active release of HMGB1 into the space around cells. These processes, which include enzymatic modifications of the HMGB1 protein, cell–cell interactions and molecular pathways of cell death, could be targeted by drugs to lessen tissue damage and inflammatory disease caused by HMGB1-induced immune responses

microRNA-124-3p attenuates myocardial injury in sepsis via modulating SP1/HDAC4/HIF-1α axis

Sepsis-induced cardiac dysfunction can lead to death in sepsis. In this case, we targeted to explore in detail the relative mechanism of microRNA (miR)-124-3p in sepsis-induced myocardial injury via the specific protein 1/histone deacetylase 4/hypoxia-inducing factor 1α (SP1/HDAC4/HIF-1α) axis. Septic rats were modeled by cecal ligation puncture while in vitro septic cardiomyocyte H9C2 were induced by lipopolysaccharide (LPS). miR-124-3p/SP1/HDAC4/HIF-1α expression levels in myocardial tissues of septic rats and LPS-treated H9C2 cells were measured. miR-124-3p overexpression and SP1 silencing assays were implemented on LPS-treated H9C2 cells to explore theirs actions in inflammation, oxidative stress and cell apoptosis. The interactions of miR-124-3p, SP1, and HDAC4 were testified. miR-124-3p was lowly expressed while SP1, HDAC4, and HIF-1α were highly expressed in sepsis. Upregulation of miR-124-3p ameliorated inflammation, oxidative stress, and apoptosis of LPS-treated H9C2 cells. Silencing SP1 improved LPS-induced damage to cardiomyocytes. miR-124-3p targeted SP1 and HDAC4 interacted with SP1. SP1 overexpression antagonized miR-124-3p upregulation-induced improvements in LPS-induced cardiomyocyte damage. This study illustrates that miR-124-3p improves myocardial injury in septic rats through targeted regulation of SP1 to mediate HDAC4/HIF-1α.

Epigenomic and transcriptomic analyses reveal differences between low-grade inflammation and severe exhaustion in LPS-challenged murine monocytes

Emerging studies suggest that monocytes can be trained by bacterial endotoxin to adopt distinct memory states ranging from low-grade inflammation to immune exhaustion. While low-grade inflammation may contribute to the pathogenesis of chronic diseases, exhausted monocytes with pathogenic and immune-suppressive characteristics may underlie the pathogenesis of polymicrobial sepsis including COVID-19. However, detailed processes by which the dynamic adaption of monocytes occur remain poorly understood. Here we exposed murine bone-marrow derived monocytes to chronic lipopolysaccharide (LPS) stimulation at low-dose or high-dose, as well as a PBS control. The cells were profiled for genome-wide H3K27ac modification and gene expression. The gene expression of TRAM-deficient and IRAK-M-deficient monocytes with LPS exposure was also analyzed. We discover that low-grade inflammation preferentially utilizes the TRAM-dependent pathway of TLR4 signaling, and induces the expression of interferon response genes. In contrast, high dose LPS uniquely upregulates exhaustion signatures with metabolic and proliferative pathways. The extensive differences in the epigenomic landscape between low-dose and high-dose conditions suggest the importance of epigenetic regulations in driving differential responses. Our data provide potential targets for future mechanistic or therapeutic studies.

Revealing potential diagnostic gene biomarkers of septic shock based on machine learning analysis

Background

Sepsis is an inflammatory response caused by infection with pathogenic microorganisms. The body shock caused by it is called septic shock. In view of this, we aimed to identify potential diagnostic gene biomarkers of the disease.

Material and methods

Firstly, mRNAs expression data sets of septic shock were retrieved and downloaded from the GEO (Gene Expression Omnibus) database for differential expression analysis. Functional enrichment analysis was then used to identify the biological function of DEmRNAs (differentially expressed mRNAs). Machine learning analysis was used to determine the diagnostic gene biomarkers for septic shock. Thirdly, RT-PCR (real-time polymerase chain reaction) verification was performed. Lastly, GSE65682 data set was utilized to further perform diagnostic and prognostic analysis of identified superlative diagnostic gene biomarkers.

Results

A total of 843 DEmRNAs, including 458 up-regulated and 385 down-regulated DEmRNAs were obtained in septic shock. 15 superlative diagnostic gene biomarkers (such as RAB13, KIF1B, CLEC5A, FCER1A, CACNA2D3, DUSP3, HMGN3, MGST1 and ARHGEF18) for septic shock were identified by machine learning analysis. RF (random forests), SVM (support vector machine) and DT (decision tree) models were used to construct classification models. The accuracy of the DT, SVM and RF models were very high. Interestingly, the RF model had the highest accuracy. It is worth mentioning that ARHGEF18 and FCER1A were related to survival. CACNA2D3 and DUSP3 participated in MAPK signaling pathway to regulate septic shock.

Conclusion

Identified diagnostic gene biomarkers may be helpful in the diagnosis and therapy of patients with septic shock.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07056-4.

Inhaled [D-Ala2]-Dynorphin 1-6 Prevents Hyperacetylation and Release of High Mobility Group Box 1 in a Mouse Model of Acute Lung Injury

COVID-19 is a respiratory infection caused by the SARS-CoV-2 virus that can rapidly escalate to life-threatening pneumonia and acute respiratory distress syndrome (ARDS). Recently, extracellular high mobility group box 1 (HMGB1) has been identified as an essential component of cytokine storms that occur with COVID-19; HMGB1 levels correlate significantly with disease severity. Thus, the modulation of HMGB1 release may be vital for treating COVID-19. HMGB1 is a ubiquitous nuclear DNA-binding protein whose biological function depends on posttranslational modifications, its redox state, and its cellular localization. The acetylation of HMGB1 is a prerequisite for its translocation from the nucleus to the cytoplasm and then to the extracellular milieu. When released, HMGB1 acts as a proinflammatory cytokine that binds primarily to toll-like receptor 4 (TLR4) and RAGE, thereby stimulating immune cells, endothelial cells, and airway epithelial cells to produce cytokines, chemokines, and other inflammatory mediators. In this study, we demonstrate that inhaled [D-Ala²]-dynorphin 1-6 (leytragin), a peptide agonist of δ-opioid receptors, significantly inhibits HMGB1 secretion in mice with lipopolysaccharide- (LPS-) induced acute lung injury. The mechanism of action involves preventing HMGB1's hyperacetylation at critical lysine residues within nuclear localization sites, as well as promoting the expression of sirtuin 1 (SIRT1), an enzyme known to deacetylate HMGB1. Leytragin's effects are mediated by opioid receptors, since naloxone, an antagonist of opioid receptors, abrogates the leytragin effect on SIRT1 expression. Overall, our results identify leytragin as a promising therapeutic agent for the treatment of pulmonary inflammation associated with HMGB1 release. In a broader context, we demonstrate that the opioidergic system in the lungs may represent a promising target for the treatment of inflammatory lung diseases.

Role of HMGB1 in Chemotherapy-Induced Peripheral Neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN), one of major dose-limiting side effects of first-line chemotherapeutic agents such as paclitaxel, oxaliplatin, vincristine, and bortezomib is resistant to most of existing medicines. The molecular mechanisms of CIPN have not been fully understood. High mobility group box 1 (HMGB1), a nuclear protein, is a damage-associated molecular pattern protein now considered to function as a pro-nociceptive mediator once released to the extracellular space. Most interestingly, HMGB1 plays a key role in the development of CIPN. Soluble thrombomodulin (TMα), known to degrade HMGB1 in a thrombin-dependent manner, prevents CIPN in rodents treated with paclitaxel, oxaliplatin, or vincristine and in patients with colorectal cancer undergoing oxaliplatin-based chemotherapy. In this review, we describe the role of HMGB1 and its upstream/downstream mechanisms in the development of CIPN and show drug candidates that inhibit the HMGB1 pathway, possibly useful for prevention of CIPN.

Melatonin Ameliorates Lipopolysaccharide-Induced Microglial Inflammation via Triggering SIRT1/HMGB1 Signaling Axis

Stroke is one of the highest incidence neurological disorder with great morbidity and mortality rate. The secondary neuroinflammation contributed by microglial activation is a consequential response observed in the pathogenesis of stroke. High-mobility group box 1, a non-histone nuclear protein, interacts with immune cells, such as microglia, and leads to a cascade amplification of the secondary neuroinflammatory responses, which are related to neuronal damage later. Melatonin is a neurohormone, well-known as its anti-oxidative and anti-inflammatory effects. However, until now, more findings are required for better understanding about anti-inflammatory effect of melatonin on HMGB1 and HMGB1-triggered pathway in LPS-induced microglial activation. Melatonin effect on the viability of BV2 microglial cells was measured by CCK-8 assay; mRNA levels of HMGB1 and other inflammatory cytokines were determined by quantitative real-time polymerase chain reaction assay or enzyme-linked immunosorbent assays; the protein expression levels of TLR4/MyD88/NF-κB and SIRT1 were detected by Western blot, and HMGB1 translocation and release from BV2 microglial cells were examined by immunofluorescence assay. The results of this study demonstrated that melatonin suppressed LPS-triggered BV2 microglial activation-mediated inflammation by inhibiting high expression and release of HMGB1 and moderating the activation of subsequent TLR4/MyD88/NF-κB signaling pathway, which was activated by SIRT1 elevation. Furthermore, LPS-induced expression of pro-inflammatory cytokines (i.e., TNF-α, IL-6, and IL-1β) was notably reversed by melatonin pre-treatment. In summary, our findings suggest that melatonin may act as a promising therapeutic agent for reducing post-stroke neuroinflammation by targeting HMGB1 and the subsequent signaling axis.

High-mobility Group Box 1 Facilitates CD4 T Cell Self-aggregation Via Integrin and STAT3 Activation Before Homing

BACKGROUND

High-mobility group box 1 (HMGB1) is one of the delayed pro-inflammatory cytokines produced in the later stages of pathogenesis and plays an important role in the progression of various inflammatory and autoimmune diseases. High-mobility group box 1 is able to stimulate interaction between integrins and cell adhesion molecules to facilitate cell-cell aggregation in "tissue-specific" endothelium; however, whether and how HMGB1 affects the adhesive capability of early acting immune cells in bloodstream remains largely unknown.

METHODS

Human peripheral blood samples were collected from healthy adult donors. The CD4 T cells were isolated from blood using CD4 T cell isolation kit and identified using flow cytometry and immunofluorescence staining. The effect of HMGB1 on adhesive ability of CD4 T cells was accessed by cell self-aggregation assay and endothelial adhesion assay. The migratory ability of CD4 T cells was evaluated by cell migration assay. Secretion of pro-inflammatory cytokines or chemokine C-X-C motif chemokine 12 (CXCL12) were detected by ELISA. Expression of integrins β1, β7, and α4β7 were determined by flow cytometric analysis. Inhibition of integrins was achieved with anti-integrin antibodies or cyclic peptide inhibitors. Activation of signal transducers and activators of transcription 3 (STAT3) was measured by flow cytometry and fluorescent staining.

RESULTS

High-mobility group box 1 facilitated CD4 T cell self-aggregation with simultaneous reduction of CD4 T single-cell counts in the bloodstream. The CD4 T cell self-aggregation induced by HMGB1 resulted in upregulation of integrins β1, β7, and α4β7; release of other pro-inflammatory cytokines or chemokine CXCL12; and activation of STAT3 signaling. Intriguingly, pro-inflammatory cytokines induced by HMGB1 could further amplify CD4 T cell self-aggregation. HMGB1 induced CD4 T cell apoptosis via activation of caspase-3/7. Furthermore, HMGB1 promoted migration and adhesion of CD4 T cells to endothelial cells.

CONCLUSIONS

These results provide proof of concept that HMGB1 promotes CD4 T cell self-aggregation before homing to inflammatory sites and highlight the potential of blocking immune cell self-aggregation in blood as a novel therapeutic approach against the development and progression of HMGB1-related inflammatory diseases.HMGB1 induces CD4 T cell self-aggregation in blood resulting in upregulation of integrins expression and release of pro-inflammatory cytokines/chemokines via activation of STAT3 signaling. This study highlights the potential of preventive and therapeutic intervention on immune cell self-aggregation in the bloodstream.

Comparison of Cardioprotective Effects of Propofol versus Sevoflurane in Pediatric Living Donor Liver Transplantation

Background

Our study compared the myocardiac protective effect of propofol vs. sevoflurane in pediatric patients receiving living donor liver transplantation (LDLT) surgery.

Material/Methods

We randomly and equally divided 120 children who underwent LDLT into a sevoflurane group and a propofol group. Preoperative, intraoperative, and postoperative data were collected and compared between the 2 groups. The concentrations of cTnI, CK-MB, IL-6, TNF-α, and HMGB1 at 5 min after induction (T0), 30 min in the anhepatic period (T1), and 3 h after reperfusion (T2), and at the end of surgery (T3) were measured.

Results

There was no statistically significant difference in the characteristics of children in the 2 groups. Compared with T0, the levels of IL-6 and TNF-α at T1, T2, and T3 were higher, while the HMGB1 at T2 and T3 were higher (P<0.05). A similar trend for IL-6, TNF-α, and HMGB1 at different time points in the 2 groups was observed. Compared with T0, the cTnI and CK-MB at T2 and T3 were significantly higher (P<0.05), but there was no significant difference at different time points in the 2 groups. For the adverse events, there was no significant difference between the 2 groups.

Conclusions

Our study shows that the cardioprotective effect in pediatric patients undergoing living donor liver transplantation is similar with propofol and sevoflurane anesthesia.

LPS Induces Active HMGB1 Release From Hepatocytes Into Exosomes Through the Coordinated Activities of TLR4 and Caspase-11/GSDMD Signaling

High-mobility group box-1 (HMGB1), a ubiquitous nuclear protein, acts as a late mediator of lethality when released extracellularly during sepsis. The major source of circulating HMGB1 in sepsis is hepatocytes. However, the mechanism of HMGB1 release of hepatocytes during sepsis is not very clear. We have previously shown that bacterial endotoxin [lipopolysaccharide (LPS)] sensing pathways, including Toll-like receptor (TLR)4 and caspase-11, regulate hepatocyte HMGB1 release in response to LPS. Here, we report the novel function of caspase-11 and gasdermin D (GsdmD) in LPS-induced active HMGB1 released from hepatocytes. HMGB1 release during endotoxemia was caspase-11/GsdmD dependent via an active way in vivo and in vitro. Caspase-11/GsdmD was responsible for HMGB1 translocation from nucleus to the cytoplasm via calcium changing-induced phosphorylation of calcium-calmodulin kinase kinase (camkk)β during endotoxemia. Cleaved GsdmD accumulated on the endoplasmic reticulum, suggesting this may lead to calcium leak and intracellular calcium increase. Furthermore, we investigated that exosome was an important pathway for HMGB1 release from hepatocytes; this process was dependent on TLR4, independent of caspase-11 and GsdmD in vivo and in vitro. These findings provide a novel mechanism that TLR4 signaling results in an increase in caspase-11 expression, as well as increased exosome release, while caspase-11/GsdmD activation/cleavage leads to accumulation of HMGB1 in the cytoplasm through a process associated with the release of calcium from the endoplasmic reticulum and camkkβ activation.

Epigenetic Modification in Macrophages: A Promising Target for Tumor and Inflammation-associated Disease Therapy

Macrophages are essential for supporting tissue homeostasis, regulating immune response, and promoting tumor progression. Due to its heterogeneity, macrophages have different phenotypes and functions in various tissues and diseases. It is becoming clear that epigenetic modification playing an essential role in determining the biological behavior of cells. In particular, changes of DNA methylation, histone methylation and acetylation regulated by the corresponding epigenetic enzymes, can directly control macrophages differentiation and change their functions under different conditions. In addition, epigenetic enzymes also have become anti-tumor targets, such as HDAC, LSD1, DNMT, and so on. In this review, we presented an overview of the latest progress in the study of macrophages phenotype and function regulated by epigenetic modifications, including DNA methylation and histone modifications, to better understand how epigenetic modification controls macrophages phenotype and function in inflammation-associated diseases, and the application prospect in anti-tumor.

Ethyl pyruvate attenuates ventilation-induced diaphragm dysfunction through high-mobility group box-1 in a murine endotoxaemia model

Mechanical ventilation (MV) can save the lives of patients with sepsis. However, MV in both animal and human studies has resulted in ventilator-induced diaphragm dysfunction (VIDD). Sepsis may promote skeletal muscle atrophy in critically ill patients. Elevated high-mobility group box-1 (HMGB1) levels are associated with patients requiring long-term MV. Ethyl pyruvate (EP) has been demonstrated to lengthen survival in patients with severe sepsis. We hypothesized that the administration of HMGB1 inhibitor EP or anti-HMGB1 antibody could attenuate sepsis-exacerbated VIDD by repressing HMGB1 signalling. Male C57BL/6 mice with or without endotoxaemia were exposed to MV (10 mL/kg) for 8 hours after administrating either 100 mg/kg of EP or 100 mg/kg of anti-HMGB1 antibody. Mice exposed to MV with endotoxaemia experienced augmented VIDD, as indicated by elevated proteolytic, apoptotic and autophagic parameters. Additionally, disarrayed myofibrils and disrupted mitochondrial ultrastructures, as well as increased HMGB1 mRNA and protein expression, and plasminogen activator inhibitor-1 protein, oxidative stress, autophagosomes and myonuclear apoptosis were also observed. However, MV suppressed mitochondrial cytochrome C and diaphragm contractility in mice with endotoxaemia (P < 0.05). These deleterious effects were alleviated by pharmacologic inhibition with EP or anti-HMGB1 antibody (P < 0.05). Our data suggest that EP attenuates endotoxin-enhanced VIDD by inhibiting HMGB1 signalling pathway.

Doxorubicin conjugated with nanodiamonds and in free form commit glioblastoma cells to heterodromous fates

Aim: To mechanistically compare the effects of doxorubicin (DOX) and DOX conjugated with nanodiamonds (Nano–DOX) on human glioblastoma cells (GC). Materials & methods: GC viablity, proliferation and activation of apoptosis and autophagy was assayed in response to DOX and Nano–DOX. Expression and release of HMGB1 were measured and its role in apoptosis and autophagy probed in response to DOX and Nano–DOX.  Results: DOX induced apoptosis in GC while Nano–DOX induced autophagy. Inhibition of autophagy in Nano–DOX-treated GC promoted apoptosis. DOX suppressed the emission of HMGB1 while Nano–DOX stimulated HMGB1 emission which was attenuated when autophagy was repressed. Blocking of HMGB1 emission mitigated autophagy and enhanced apoptosis in Nano–DOX-treated GC. Exogenously administered HMGB1 promoted autophagy and protected against apoptosis in both Nano–DOX-treated GC and DOX-treated GC. Conclusions: Nano–DOX is a potent autophagy activator as opposed to DOX as an apoptosis inducer. Nano–DOX initiates a mutual reinforcement loop between autophagy and HMGB1 in GC and thereby protects GC against apoptosis.