High-mobility group box-B1 (HMGB1) mediates the hypoxia-induced mesenchymal transition of osteoblast cells via activating ERK/JNK signaling

HMGB1 enhances the migratory and invasive abilities of A2780/DDP cells by facilitating epithelial to mesenchymal transition via GSK‑3β

The aim of the present study was to investigate the impact and mechanism of high mobility group box 1 (HMGB1) on the regulation of cell migration and invasion in A2780/DDP cisplatin-resistant ovarian cancer cells. After transfecting small interfering (si)RNA-HMGB1 into A2780/DDP cells, Transwell migration and invasion assays were conducted to assess alterations in the cell migratory and invasive abilities. Additionally, western blotting analyses were performed to examine changes in HMGB1, phosphorylated (p)-GSK-3β, GSK-3β, E-cadherin and vimentin expression levels. The results of the present study demonstrated that the migratory and invasive abilities of A2780/DDP cells were significantly higher compared with those of A2780 cells. Additionally, the expression levels of HMGB1, p-GSK-3β and the mesenchymal phenotype marker, vimentin, in A2780/DDP cells were significantly elevated relative to the levels in A2780 cells. Conversely, the expression level of the epithelial phenotype marker, E-cadherin, was markedly decreased compared with that in A2780 cells. Following transfection of A2780/DDP cells with siRNA-HMGB1, there was a significant reduction in the rate of cell migration and invasion. Simultaneously, the expression levels of HMGB1, p-GSK-3β and vimentin were downregulated while the level of E-cadherin was upregulated. It was therefore concluded that the high expression of HMGB1 in A2780/DDP cells enhanced the cell migration and invasion abilities by facilitating epithelial to mesenchymal transition via GSK-3β.

The RAGE signaling in osteoporosis

Osteoporosis (OP), characterized by an imbalance of bone remodeling between formation and resorption, has become a health issue worldwide. The receptor for advanced glycation end product (RAGE), a transmembrane protein in the immunoglobin family, has multiple ligands and has been involved in many chronic diseases, such as diabetes and OP. Increasing evidence shows that activation of the RAGE signaling negatively affects bone remodeling. Ligands, such as advanced glycation end products (AGEs), S100, β-amyloid (Aβ), and high mobility group box 1 (HMGB1), have been well documented that they may negatively regulate the proliferation and differentiation of osteoblasts and positively stimulate osteoclastogenesis by activating the expression of RAGE. In this review, we comprehensively discuss the structure of RAGE and its biological functions in the pathogenesis of OP. The research findings suggest that RAGE signaling has become a potential target for the therapeutic management of OP.

HMGB1 in depression: An overview of microglial HMBG1 in the pathogenesis of depression

Depression is a prevalent psychiatric disorder with elusive pathogenesis. Studies have proposed that enhancement and persistence of aseptic inflammation in the central nervous system (CNS) may be closely associated with the development of depressive disorder. High mobility group box 1 (HMGB1) has obtained significant attention as an evoking and regulating factor in various inflammation-related diseases. It is a non-histone DNA-binding protein that can be released as a pro-inflammatory cytokine by glial cells and neurons in the CNS. Microglia, as the immune cell of the brain, interacts with HMGB1 and induces neuroinflammation and neurodegeneration in the CNS. Therefore, in the current review, we aim to investigate the role of microglial HMGB1 in the pathogenetic process of depression.

Immune and inflammatory mechanism of remote ischemic conditioning: A narrative review

The benefits of remote ischemic conditioning (RIC) on multiple organs have been extensively investigated. According to existing research, suppressing the immune inflammatory response is an essential mechanism of RIC. Based on the extensive effects of RIC on cardiovascular and cerebrovascular diseases, this article reviews the immune and inflammatory mechanisms of RIC and summarizes the effects of RIC on immunity and inflammation from three perspectives: (1) the mechanisms of the impact of RIC on inflammation and immunity; (2) evidence of the effects of RIC on immune and inflammatory processes in ischaemic stroke; and (3) possible future applications of this effect, especially in systemic infectious diseases such as sepsis and sepsis-associated encephalopathy. This review explores the possibility of using RIC as a treatment in more inflammation-related diseases, which will provide new ideas for the treatment of this kind of disease.

Histone methyltransferase Setdb1 mediates osteogenic differentiation by suppressing the expression of miR-212-3p under mechanical unloading

Emerging evidence indicates that multiple mechanisms are involved in bone loss induced by mechanical unloading. Thus far, few study has established the pathophysiological role of histone modification for osteogenic differentiation under mechanical unloading. Here we demonstrated that the histone H3 lysine 9 (H3K9) methyltransferase Setdb1, which was sensitive to mechanical unloading, was increased during osteogenic differentiation of MC3T3-E1 cells for the first time. Knockdown of Setdb1 significantly blocked osteoblast function in vivo and in vitro. Through bioinformatics analysis of candidate miRNAs regulated by H3K9me3, we further identified that Setdb1 inhibited the expression of miR-212-3p by regulating the formation of H3K9me3 in the promoter region. Mechanically, we revealed that miR-212-3p was upregulated under mechanical unloading and suppressed osteogenic differentiation by directly downregulating High mobility group box 1 protein (Hmgb1) expression. Furthermore, we verified the molecular mechanism of the SETDB1/miR-212-3p/HMGB1 pathway in hFOB cells under mechanical unloading. In summary, these data demonstrate the essential function of the Setdb1/miR-212-3p/Hmgb1 pathway in osteogenic differentiation under mechanical unloading, and present a potential protective strategies against bone loss induced by mechanical unloading.

Remote ischemic post‑conditioning alleviates ischemia/reperfusion‑induced intestinal injury via the ERK signaling pathway‑mediated RAGE/HMGB axis

Intestinal ischemia reperfusion (I/R) injury is a tissue and organ injury that frequently occurs during surgery and significantly contributes to the pathological processes of severe infection, injury, shock, cardiopulmonary insufficiency and other diseases. However, the mechanism of intestinal I/R injury remains to be elucidated. A mouse model of intestinal I/R injury was successfully established and the model mice were treated with remote ischemic post‑conditioning (RIPOC) and/or an ERK inhibitor (CC‑90003), respectively. Histopathological changes of the intestinal mucosa were determined by hematoxylin and eosin staining. In addition, the levels of high‑mobility group box 1 (HMGB1) and receptor for advanced glycation end products (RAGE) expression were confirmed by reverse transcription‑quantitative polymerase chain reaction, western blotting and immunohistochemistry assays. The levels of antioxidants, oxidative stress markers (8‑OHdG) and interleukin 1 family members were evaluated by ELISA assays and the levels of NF‑κB pathway proteins were analyzed by western blotting. The data demonstrated that RIPOC could attenuate the histopathological features of intestinal mucosa in the intestinal I/R‑injury mouse models via the ERK pathway. It was also revealed that HMGB1 and RAGE expression in the mouse models could be markedly reduced by RIPOC (P<0.05) and that these reductions were associated with inhibition of the ERK pathway. Furthermore, it was demonstrated that RIPOC produced significant antioxidant and anti‑inflammatory effects following an intestinal I/R injury and that these effects were mediated via the ERK pathway (P<0.05). In addition, RIPOC was demonstrated to suppress the NF‑κB (p65)/NLR family pyrin domain containing 3 (NLRP3) inflammatory pathways in the intestinal I/R injury mouse models via the ERK pathway. The findings of the present study demonstrated that RIPOC helped to protect mice with an intestinal I/R injury by downregulating the ERK pathway.

Local administration of HMGB-1 promotes bone regeneration on the critical-sized mandibular defects in rabbits

Reconstruction of a critical-sized osseous defect is challenging in maxillofacial surgery. Despite novel treatments and advances in supportive therapies, severe complications including infection, nonunion, and malunion can still occur. Here, we aimed to assess the use of a beta-tricalcium phosphate (β-TCP) scaffold loaded with high mobility group box-1 protein (HMGB-1) as a novel critical-sized bone defect treatment in rabbits. The study was performed on 15 specific pathogen-free New Zealand rabbits divided into three groups: Group A had an osseous defect filled with a β-TCP scaffold loaded with phosphate-buffered saline (PBS) (100 µL/scaffold), the defect in group B was filled with recombinant human bone morphogenetic protein 2 (rhBMP-2) (10 µg/100 µL), and the defect in group C was loaded with HMGB-1 (10 µg/100 µL). Micro-computed tomography (CT) examination demonstrated that group C (HMGB-1) showed the highest new bone volume ratio, with a mean value of 66.5%, followed by the group B (rhBMP-2) (31.0%), and group A (Control) (7.1%). Histological examination of the HMGB-1 treated group showed a vast area covered by lamellar and woven bone surrounding the β-TCP granule remnants. These results suggest that HMGB-1 could be an effective alternative molecule for bone regeneration in critical-sized mandibular bone defects.

Exosomal HMGB1 derived from hypoxia-conditioned bone marrow mesenchymal stem cells increases angiogenesis via the JNK/HIF-1α pathway

Mesenchymal stem cells (MSCs) have been described to induce angiogenesis in various tissues and have been used for the development of novel cell‐based therapies. Increasing evidence suggests that MSCs execute their paracrine function via the secretion of exosomes, especially under hypoxic conditions. However, the mechanisms by which MSC‐derived exosomes secreted under hypoxia enhance angiogenesis still remain unclear. To study exosome physiology under hypoxic or normoxic conditions, we isolated exosomes from bone marrow mesenchymal stem cells (BMSCs). Furthermore, we detected the uptake of exosomes by human umbilical vein endothelial cells (HUVECs) by immunofluorescence staining. In addition, we determined the effects of exosomes on cell viability, migration and tube formation in HUVECs by Cell Counting Kit‐8, migration and tube formation assays, respectively. We examined the expression of key proteins related to exosome‐induced angiogenesis by BMSCs cultured under hypoxic conditions by western blot. Exosomes released by BMSCs cultured under hypoxic conditions enhanced cell proliferation, migration and angiogenesis of HUVECs. Hypoxia induced the expression of high mobility group box 1 protein (HMGB1) in BMSC‐derived exosomes, and silencing of HMGB1 abolished the angiogenic effect in HUVECs. Furthermore, exosomal HMGB1 activated the JNK signaling pathway and induced hypoxia‐inducible factor‐1α/vascular endothelial growth factor expression, consequently enhancing angiogenesis in HUVECs. Our data reveal that exosomal HMGB1 promotes angiogenesis via JNK/hypoxia‐inducible factor‐1α signaling. Therefore, BMSC exosomes derived under hypoxia may have potential for development of novel treatment strategies for angiogenesis‐related diseases.

Hypoxia-induced epithelial-mesenchymal transition and fibrosis for the development of breast capsular contracture

Fibrosis has been considered as a major cause of capsular contracture. Hypoxia has widely emerged as one of the driving factors for fibrotic diseases. The aim of this study was to examine the association between hypoxia-induced fibrosis and breast capsular contracture formation. Fibrosis, epithelial-mesenchymal transition (EMT), expression levels of hypoxia-inducible factor-1α (HIF-1α), vimentin, fibronectin, and matrix metalloproteinase-9 (MMP-9) in tissues from patients with capsular contracture were determined according to the Baker classification system. Normal breast skin cells in patients with capsular contracture after implant-based breast surgery and NIH3T3 mouse fibroblasts were cultured with cobalt chloride (CoCl₂) to mimic hypoxic conditions. Treatment responses were determined by detecting the expression of HIF-1α, vimentin, fibronectin, N-cadherin, snail, twist, occludin, MMP-9, tissue inhibitor of metalloproteinase-1 (TIMP-1) and -2, as well as phosphorylated ERK. The expression levels of HIF-1α, vimentin, fibronectin, and fibrosis as well as EMT were positively correlated with the severity of capsular contracture. MMP-9 expression was negatively correlated the Baker score. Hypoxia up-regulated the expression of HIF-1α, vimentin, fibronectin, N-cadherin, snail, twist, TIMP-1 and -2, as well as phosphorylated ERK in normal breast skin cells and NIH3T3. Nonetheless, the expression levels of MMP-9 and occludin were down-regulated in response to CoCl₂ treatment. This study is the first to demonstrate the association of hypoxia-induced fibrosis and capsular contracture.

HMGB1 promotes bone fracture healing through activation of ERK signaling pathway in a rat tibial fracture model

This work was to investigate potential roles of HMGB1-mediated ERK pathway in the healing process of bone fracture. Rat tibial fracture models were established and divided into control (rats with normal saline), HMGB1 (rats with HMGB1), and HMGB1+ PD98059 groups (rats with HMGB1 and 1 mg/kg of ERK1/2 inhibitor PD98059) with 30 rats per each. The healing of rats' fracture was observed by X-ray films, the morphological changes of bone fractures by HE staining, the callus formation by micro-CT and biomechanical test, and the expression of osteogenesis-related genes, HMGB1 and ERK-related proteins by qRT-PCR and Western blot. Rats in the HMGB1 group was increased in X-ray scores, peak torque, torsional stiffness, and the bone volume fraction (bone volume/total volume, BV/TV); meanwhile, those rats presented elevations in osteogenesis-related genes and HMGB1 expressions, as well as p-ERK/ERK ratio. However, rats in the HMGB1+ PD98059 group was significantly reduced in X-ray score, peak torque, torsional stiffness, and BV/TV, as well as the expression of osteogenesis-related genes and the ratio of p-ERK/ERK, as compared to those from HMGB1 group. HMGB1 could promote the expressions of osteogenesis-related genes and accelerate the healing process of fracture via activation of the ERK signaling pathway.

Pro-inflammatory AGE-RAGE signaling is activated during arousal from hibernation in ground squirrel adipose

Background

Inflammation is generally suppressed during hibernation, but select tissues (e.g. lung) have been shown to activate both antioxidant and pro-inflammatory pathways, particularly during arousal from torpor when breathing rates increase and oxidative metabolism fueling the rewarming process produces more reactive oxygen species. Brown and white adipose tissues are now understood to be major hubs for the regulation of immune and inflammatory responses, yet how these potentially damaging processes are regulated by fat tissues during hibernation has hardly been studied. The advanced glycation end-product receptor (RAGE) can induce pro-inflammatory responses when bound by AGEs (which are glycated and oxidized proteins, lipids, or nucleic acids) or damage associated molecular pattern molecules (DAMPs, which are released from dying cells).

Methods

Since gene expression and protein synthesis are largely suppressed during torpor, increases in AGE-RAGE pathway proteins relative to a euthermic control could suggest some role for these pro-inflammatory mediators during hibernation. This study determined how the pro-inflammatory AGE-RAGE signaling pathway is regulated at six major time points of the torpor-arousal cycle in brown and white adipose from a model hibernator, Ictidomys tridecemlineatus. Immunoblotting, RT-qPCR, and a competitive ELISA were used to assess the relative gene expression and protein levels of key regulators of the AGE-RAGE pathway during a hibernation bout.

Results

The results of this study revealed that RAGE is upregulated as animals arouse from torpor in both types of fat, but AGE and DAMP levels either remain unchanged or decrease. Downstream of the AGE-RAGE cascade, nfat5 was more highly expressed during arousal in brown adipose.

Discussion

An increase in RAGE protein levels and elevated mRNA levels of the downstream transcription factor nfat5 during arousal suggest the pro-inflammatory response is upregulated in adipose tissue of the hibernating ground squirrel. It is unlikely that this cascade is activated by AGEs or DAMPs. This research sheds light on how a fat-but-fit organism with highly regulated metabolism may control the pro-inflammatory AGE-RAGE pathway, a signaling cascade that is often dysregulated in other obese organisms.

Role of Toll-Like Receptor 4 on Osteoblast Metabolism and Function

Inflammation is a process whose main function is to fight against invading pathogens or foreign agents. Nonetheless, it is widely accepted that inflammation takes part in multiple processes in a physiological or pathophysiological context. Among these processes the inflammation has been closely related to bone metabolism. It is well-known that in systemic inflammatory diseases such as rheumatoid arthritis the inflammatory environment contributes to the reduction of the bone mineral density. This has been further evidenced in different animals models of osteoporosis where the deletion of key inflammatory molecules dramatically reduced the bone loss. On the contrary, it is also well-known that certain degree of inflammation is required to allow bone fractures healing. In fact, excessive use of anti-inflammatory drugs inhibits bone fracture consolidation. The innate immune responses (IIRs) contribute to the development and maintenance of the inflammation. These responses have been observed in cells of the musculoskeletal system. Chondrocytes and osteoblasts are equipped with the molecular repertoire necessary to setting up these IIR, including the expression of several toll-like receptors. Specifically, toll-like receptor 4 (TLR4) activation in mesenchymal stem cells, osteoblasts, and osteocytes has been involved in catabolic and anabolic process. Accordingly, in this review we have summarized the current knowledge about the physiology of TLR4, including its signaling, and its endogenous agonists. In addition we have focused on its role on osteoblast metabolism and function.

Omega-3 polyunsaturated fatty acid attenuates the inflammatory response by modulating microglia polarization through SIRT1-mediated deacetylation of the HMGB1/NF-κB pathway following experimental traumatic brain injury

Background

Microglial polarization and the subsequent neuroinflammatory response are contributing factors for traumatic brain injury (TBI)-induced secondary injury. High mobile group box 1 (HMGB1) mediates the activation of the NF-κB pathway, and it is considered to be pivotal in the late neuroinflammatory response. Activation of the HMGB1/NF-κB pathway is closely related to HMGB1 acetylation, which is regulated by the sirtuin (SIRT) family of proteins. Omega-3 polyunsaturated fatty acids (ω-3 PUFA) are known to have antioxidative and anti-inflammatory effects. We previously demonstrated that ω-3 PUFA inhibited TBI-induced microglial activation and the subsequent neuroinflammatory response by regulating the HMGB1/NF-κB signaling pathway. However, no studies have elucidated if ω-3 PUFA affects the HMGB1/NF-κB pathway in a HMGB1 deacetylation of dependent SIRT1 manner, thus regulating microglial polarization and the subsequent neuroinflammatory response.

Methods

The Feeney DM TBI model was adopted to induce brain injury in rats. Modified neurological severity scores, rotarod test, brain water content, and Nissl staining were employed to determine the neuroprotective effects of ω-3 PUFA supplementation. Assessment of microglia polarization and pro-inflammatory markers, such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, and HMGB1, were used to evaluate the neuroinflammatory responses and the anti-inflammatory effects of ω-3 PUFA supplementation. Immunofluorescent staining and western blot analysis were used to detect HMGB1 nuclear translocation, secretion, and HMGB1/NF-κB signaling pathway activation to evaluate the effects of ω-3 PUFA supplementation. The impact of SIRT1 deacetylase activity on HMGB1 acetylation and the interaction between HMGB1 and SIRT1 were assessed to evaluate anti-inflammation effects of ω-3 PUFAs, and also, whether these effects were dependent on a SIRT1-HMGB1/NF-κB axis to gain further insight into the mechanisms underlying the development of the neuroinflammatory response after TBI.

Results

The results of our study showed that ω-3 PUFA supplementation promoted a shift from the M1 microglial phenotype to the M2 microglial phenotype and inhibited microglial activation, thus reducing TBI-induced inflammatory factors. In addition, ω-3 PUFA-mediated downregulation of HMGB1 acetylation and its extracellular secretion was found to be likely due to increased SIRT1 activity. We also found that treatment with ω-3 PUFA inhibited HMGB1 acetylation and induced direct interactions between SIRT1 and HMGB1 by elevating SIRT1 activity following TBI. These events lead to inhibition of HMGB1 nucleocytoplasmic translocation/extracellular secretion and alleviated HMGB1-mediated activation of the NF-κB pathway following TBI-induced microglial activation, thus inhibiting the subsequent inflammatory response.

Conclusions

The results of this study suggest that ω-3 PUFA supplementation attenuates the inflammatory response by modulating microglial polarization through SIRT1-mediated deacetylation of the HMGB1/NF-κB pathway, leading to neuroprotective effects following experimental traumatic brain injury.

Notch signaling molecule is involved in the invasion of MiaPaCa2 cells induced by CoCl2 via regulating epithelial‑mesenchymal transition

Pancreatic cancer exhibits a high mortality rate resulting from metastasis and there is currently no effective treatment strategy. Hypoxia serves an important role in cancer cells, where cellular metabolic rate is high. The underlying mechanisms that trigger hypoxia and the invasion of pancreatic cancer cells remain unknown. Investigation of the importance of hypoxia in the invasion of pancreatic cancer cells for potential, novel treatment strategies is of primary concern. Cell Counting Kit-8 assay, invasion assay, western blotting and reverse transcription-quantitative polymerase chain reaction were used to investigate invasion and epithelial mesenchymal transition (EMT) and the expression of Notch1 in MiaPaCa2 cells treated with cobalt II chloride (CoCl₂). Hypoxia-inducible factor 1α (HIF-1α) small interfering (si)RNA and Notch1 inhibitor N-[N-(3,5-Difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT) were also selected to investigate these mechanisms. Data indicated that CoCl₂ increased the invasion ability and altered EMT in MiaPaCa2 cells. CoCl₂ regulated the expression of HIF-1α and Notch1 in MiaPaCa2 cells. In addition, HIF-1α siRNA inhibited the effects of CoCl₂ on the expression of Notch1 and decreased Snail, EMT and invasion in MiaPaCa2 cells. DAPT increased the expression of epithelial-cadherin and decreased the content of neural-cadherin, Snail and invasion in MiaPaCa2 cells in the presence or absence of CoCl₂. CoCl₂ promoted invasion by stimulating the expression of HIF-1α and regulating the expression of Notch1 and EMT in MiaPaCa2 cells. Targeting the Notch1 signaling molecule may be a novel treatment strategy for the prevention and treatment of pancreatic cancer.

Saquinavir Ameliorates Liver Warm Ischemia-Reperfusion-Induced Lung Injury via HMGB-1- and P38/JNK-Mediated TLR-4-Dependent Signaling Pathways

Liver ischemia and reperfusion (I/R) induce local and distant tissue injuries, contributing to morbidity and mortality in a wider range of pathologies. This is especially seen under uncontrolled aseptic inflammatory conditions, leading to injury of remote organs, such as lung injury, and even failure. Saquinavir (SQV) is a kind of HIV protease inhibitor that possesses an anti-inflammatory property. In this study, we investigated whether SQV suppresses Toll-like receptor 4- (TLR4-) dependent signaling pathways of high-mobility group box 1 (HMGB1) and P38/JNK, conferring protection against murine liver I/R-induced lung injury. To investigate our hypothesis, C57BL/6 mice and TLR4 knockout mice (TLR4^−/−) were used to perform the study. SQV administration markedly attenuated remote lung tissue injury after 1-hour ischemia and 6-hour reperfusion of the liver. To our expectation, SQV attenuated I/R-induced lung edema, hyperpermeability, and pathological injury. The beneficial effects of SQV were associated with decreased levels of circulating and lung tissue inflammatory cytokines, such as IL-6, IL-1β, TNF-α, and iNOS. The protective effect of SQV was also associated with decreased lung tissue expression of HMGB1, TLR-4, and p-P38/JNK, but not p-ERK in wild-type liver I/R mice. Overall, this study demonstrated a new role of SQV, facilitating negative regulation of HMGB1- and P38/JNK-mediated TLR-4-dependent signaling pathways, conferring protection against liver I/R-induced lung injury.

200mM hypertonic saline resuscitation attenuates intestinal injury and inhibits p38 signaling in rats after severe burn trauma

BACKGROUND

An overabundant discharge of inflammatory mediators plays a significant role in intestinal injury throughout the early stages of critical burns. The present study aims to explore the outcome of 200mM hypertonic saline (HS) resuscitation on the intestinal injury of critically burned rats.

MATERIALS AND METHODS

Fifty-six Sprague-Dawley rats were randomized into three groups: sham group (group A), burn plus lactated Ringer's group (group B), and burn plus 200mM HS group (group C). Samples from the intestine were isolated and assayed for wet-weight-to-dry-weight (W/D) ratio, histopathology analyses, and p38 mitogen-activated protein kinase (MAPK) activity. Serum interleukin 1β (IL-1β) and high mobility group protein box 1 (HMGB1) concentrations were also examined.

RESULTS

Initial resuscitation with 200mM Na⁺ HS significantly decreased the intestinal W/D ratio and improved intestinal histopathology caused by severe burn. HS resuscitation also inhibited the increase of serum IL-1β and HMGB1 concentrations, and p38 MAPK activity in the intestine of critically burned rats.

CONCLUSIONS

The overall findings of this study suggest that preliminary resuscitation with 200mM HS after severe thermal injury reduces intestinal edema, inhibits systemic inflammatory response, and attenuates intestinal p38 MAPK activation, thus reduces burns-induced intestinal injury.