TLR4 as receptor for HMGB1-mediated acute lung injury after liver ischemia/reperfusion injury

Down-regulating lncRNA KCNQ1OT1 relieves type II alveolar epithelial cell apoptosis during one-lung ventilation via modulating miR-129-5p/HMGB1 axis induced pulmonary endothelial glycocalyx

OBJECTIVE

Endothelial glycocalyx (EG) maintains vascular homeostasis and is destroyed after one-lung ventilation (OLV)-induced lung injury. Long noncoding RNAs (lncRNAs) are critically involved in various lung injuries. This study aimed to investigate the role and regulatory mechanism of KCNQ1 overlapping transcript 1 (KCNQ1OT1) in OLV-induced lung injury and LPS-induced type II alveolar epithelial cell (AECII) apoptosis.

METHODS

The rat OLV model was established, and the effects of KCNQ1OT1 on OLV-induced ALI in vivo were explored. Bax and Caspase-3 expression in rat lung tissues was measured by immunochemistry (IHC). AECIIs were isolated from rat lungs and treated with LPS or normal saline (control) for in vitro analysis. The expression of KCNQ1OT1, miR-129-5p, and HMGB1 was measured by quantitative real-time PCR (qRT-PCR) or Western blot (WB). Cell proliferation and apoptosis were examined by 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di- phenytetrazoliumromide (MTT) and flow cytometry. The downstream targets of KCNQ1OT1 were predicted by bioinformatics, and the binding relationship between KCNQ1OT1 and miR-129-3p was verified by dual-luciferase reporter assays. The potential target of miR-129-5p was further explored on the Targetscan website and revealed to target HMGB1. Enzyme-linked immunosorbent assay (ELISA) or WB was adopted to determine the levels of IL-1β, TNF-α, MDA, SOD, heparanase (HPA), matrix metalloproteinase 9 (MMP9), heparan sulfate (HS) and syndecan-1 (SDC-1).

RESULTS

KCNQ1OT1 and HMGB1 were up-regulated during OLV-induced lung injury, and their expression was positively correlated. KCNQ1OT1 knockdown reduced OLV-induced pulmonary edema and lung epithelial cell apoptosis, increased vascular permeability, reduced IL-1β, TNF-α, MDA, and SOD levels and glycocalyx markers by targeting miR-129-5p or upregulating HMGB1. Overexpressing KCNQ1OT1 promoted cell apoptosis, reduced cell proliferation, aggravated inflammation and oxidative stress, and up-regulated HMGB1, HPA and MMP9 in LPS-treated AECIIs, while the HMGB1 silencing showed the opposite effects. MiR-129-5p mimics partially eliminated the KCNQ1OT1-induced effects, while recombinant HMGB1 restored the effects of miR-129-5p overexpression on AECIIs. Additionally, KCNQ1OT1 was demonstrated to promote the activation of the p38 MAPK/Akt/ERK signaling pathways in AECIIs via HMGB1.

CONCLUSION

KCNQ1OT1 knockdown alleviated AECII apoptosis and EG damage during OLV by targeting miR-129-5p/HMGB1 to inactivate the p38 MAPK/Akt/ERK signaling. The findings of our study might deepen our understanding of the molecular basis in OLV-induced lung injury and provide clues for the targeted disease management.

LPS-induced monocarboxylate transporter-1 inhibition facilitates lactate accumulation triggering epithelial-mesenchymal transformation and pulmonary fibrosis

The epithelial-mesenchymal transformation (EMT) process of alveolar epithelial cells is recognized as involved in the development of pulmonary fibrosis. Recent evidence has shown that lipopolysaccharide (LPS)-induced aerobic glycolysis of lung tissue and elevated lactate concentration are associated with the pathogenesis of sepsis-associated pulmonary fibrosis. However, it is uncertain whether LPS promotes the development of sepsis-associated pulmonary fibrosis by promoting lactate accumulation in lung tissue, thereby initiating EMT process. We hypothesized that monocarboxylate transporter-1 (MCT1), as the main protein for lactate transport, may be crucial in the pathogenic process of sepsis-associated pulmonary fibrosis. We found that high concentrations of lactate induced EMT while moderate concentrations did not. Besides, we demonstrated that MCT1 inhibition enhanced EMT process in MLE-12 cells, while MCT1 upregulation could reverse lactate-induced EMT. LPS could promote EMT in MLE-12 cells through MCT1 inhibition and lactate accumulation, while this could be alleviated by upregulating the expression of MCT1. In addition, the overexpression of MCT1 prevented LPS-induced EMT and pulmonary fibrosis in vivo. Altogether, this study revealed that LPS could inhibit the expression of MCT1 in mouse alveolar epithelial cells and cause lactate transport disorder, which leads to lactate accumulation, and ultimately promotes the process of EMT and lung fibrosis.

Parecoxib sodium attenuates acute lung injury following burns by regulating M1/M2 macrophage polarization through the TLR4/NF-κB pathway

High temperature-induced burn injury often leads to an excessive inflammatory cascade resulting in multiple organ dysfunction syndrome, such as acute lung injury (ALI), in addition to skin tissue damage. As a specific COX2 inhibitor, parecoxib sodium suppresses the inflammatory response during burn injury. The effect of parecoxib sodium on ALI induced by burn injury and the associated molecular mechanism still need to be investigated. The role of parecoxib sodium in burn injury-induced ALI through the TLR4/NF-κB pathway was explored in the present study. A burn-induced ALI mouse model was constructed, and M1/M2 macrophages in lung tissue and markers involved in the TLR4/NF-κB signalling pathway were evaluated in bronchoalveolar lavage fluid (BALF) and MH-S mouse alveolar macrophages in vitro. The results indicated that parecoxib sodium attenuated lung injury after burn injury, decreased iNOS and TNF-α expression, increased IL-10 expression in BALF, and regulated the CD86-and CD206-mediated polarization of M1/M2 macrophages in lung tissue along with MH-S mouse alveolar macrophages. The effect of parecoxib sodium might be reversed by a TLR4 agonist. Overall, the results suggested that parecoxib sodium can regulate the polarization of M1/M2 macrophages through the TLR4/NF-κB pathway to attenuate ALI induced by skin burns.

Bhlhe40 deficiency attenuates LPS-induced acute lung injury through preventing macrophage pyroptosis

BACKGROUND

Acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome (ARDS) as common life-threatening lung diseases with high mortality rates are mostly associated with acute and severe inflammation in lungs. Recently, increasing evidence supports activated inflammation and gasdermin D (GSDMD)-mediated pyroptosis in macrophage are closely associated with ALI. Basic helix-loop-helix family member e40 (Bhlhe40) is a transcription factor that is comprehensively involved in inflammation. However, there is little experimental evidence connecting Bhlhe40 and GSDMD-driven pyroptosis. The study sought to verify the hypothesis that Bhlhe40 is required for GSDMD-mediated pyroptosis in lipopolysaccharide (LPS)-induced inflammatory injury.

METHOD

We performed studies using Bhlhe40-knockout (Bhlhe40 -/-) mice, small interfering RNA (siRNA) targeting Bhlhe40 and pyroptosis inhibitor disulfiram to investigate the potential roles of Bhlhe40 on LPS-induced ALI and the underlying mechanisms.

RESULTS

Bhlhe40 was highly expressed in total lung tissues and macrophages of LPS-induced mice. Bhlhe40-/- mice showed alleviative lung pathological injury and inflammatory response upon LPS stimulation. Meanwhile, we found that Bhlhe40 deficiency significantly suppressed GSDMD-mediated pyroptosis in macrophage in vivo and in vitro. By further mechanistic analysis, we demonstrated that Bhlhe40 deficiency inhibited GSDMD-mediated pyroptosis and subsequent ALI by repressing canonical (caspase-1-mediated) and non-canonical (caspase-11-mediated) signaling pathways in vivo and in vitro.

CONCLUSION

These results indicate Bhlhe40 is required for LPS-induced ALI. Bhlhe40 deficiency can inhibit GSDMD-mediated pyroptosis and therefore alleviate ALI. Targeting Bhlhe40 may be a potential therapeutic strategy for LPS-induced ALI.

Targeting Cx43 to Reduce the Severity of Pressure Ulcer Progression

In the skin, repeated incidents of ischemia followed by reperfusion can result in the breakdown of the skin and the formation of a pressure ulcer. Here we gently applied paired magnets to the backs of mice to cause ischemia for 1.5 h and then removed them to allow reperfusion. The sterile inflammatory response generated within 4 h causes a stage 1 pressure ulcer with an elevation of the gap junction protein Cx43 in the epidermis. If this process is repeated the insult will result in a more severe stage 2 pressure ulcer with a breakdown of the epidermis 2-3 days later. After a single pinch, the elevation of Cx43 in the epidermis is associated with the inflammatory response with an increased number of neutrophils, HMGB1 (marker of necrosis) and RIP3 (responsible for necroptosis). Delivering Cx43 specific antisense oligonucleotides sub-dermally after a single insult, was able to significantly reduce the elevation of epidermal Cx43 protein expression and reduce the number of neutrophils and prevent the elevation of HMGB1 and RIP3. In a double pinch model, the Cx43 antisense treatment was able to reduce the level of inflammation, necroptosis, and the extent of tissue damage and progression to an open wound. This approach may be useful in reducing the progression of stage 1 pressure ulcers to stage 2.

High mobility group box 1 and a network of other biomolecules influence fatigue in patients with Crohn's disease

BACKGROUND

Fatigue is common in patients with chronic inflammatory and autoimmune diseases, often with a severe impact on the patient's daily life. From a biological point of view, fatigue can be regarded as an element of the sickness behavior response, a coordinated set of responses induced by pathogens to enhance survival during an infection and immunological danger. The mechanisms are not fully understood but involve activation of the innate immune system, with pro-inflammatory cytokines, in particular interleukin (IL)-1β, acting on cerebral neurons. These mechanisms are also active during chronic inflammatory conditions. High mobility group box 1 (HMGB1) protein has interleukin-1 like properties and is a strong inducer of innate immune responses. Its role in generation of fatigue is not clarified. Emerging evidence indicates that also other biomolecules may influence sickness behavior. We aimed to elucidate how HMGB1 influences fatigue in patients with Crohn's disease, and how the protein interacts with other candidate biomarkers of fatigue.

METHODS

In 56 patients with newly diagnosed Crohn's disease, fatigue was evaluated using three different fatigue instruments: the fatigue visual analog scale (fVAS), Fatigue Severity Scale (FSS), and the vitality subscale of Medical Outcomes Study Short-Form Health Survey (SF-36vs). The biochemical markers IL-1 receptor antagonist (RA), soluble IL-1 receptor type 2 (sIL-RII), heat shock protein 90 alpha (HSP90α), HMGB1, anti-fully reduced (fr)HMGB1 antibodies (abs), hemopexin (HPX), and pigment epithelium-derived factor (PEDF) were measured in plasma. Multivariable regression and principal component analyses (PCA) were applied.

RESULTS

Multivariable regression analyses revealed significant contributions to fatigue severity for HMGB1 in the FSS model, HSP90α in the fVAS model and IL-1RA in the SF-36vs model. Depression and pain scores contributed to all three models. In PCA, two components described 53.3% of the variation. The "inflammation and cellular stress dimension" was dominated by IL-1RA, sIL-1RII, HSP90α, HPX, and PEDF scores, where the "HMGB1 dimension" was dominated by HMGB1, anti-frHMGB1 abs, and fVAS scores.

CONCLUSION

This study supports the hypothesis that HMGB1 and a network of other biomolecules influence fatigue severity in chronic inflammatory conditions. The well-known association with depression and pain is also acknowledged.

ALCAM Deficiency Alleviates LPS-Induced Acute Lung Injury by Inhibiting Inflammatory Response

We investigated the effects and underlying mechanisms of activated leukocyte adhesion molecule (ALCAM) on acute lung injury (ALI) by using lipopolysaccharide (LPS)-induced ALI animal model and LPS-induced inflammation in vitro. In LPS-stimulated mice, ALCAM deficiency relieved lung injury, which manifested as reduced pathological changes in the lung tissue, reduced pulmonary edema, and reduced vascular permeability. Furthermore, we demonstrated that ALCAM deficiency reduced the infiltration of inflammatory cells, including neutrophil, eosinophil, and macrophages; the release of inflammatory cytokines, including IL-1β, IL-6, TNF-α, and COX2; and reduced the protein level of TLR4/NF-κB pathway (TLR4, MyD88, p-IkBɑ, and p-NF-κB p65). We also demonstrated that ALCAM deficiency reduced the expression of oxidative stress-related proteins (Nrf-2, HO-1, and NQO-1) and endoplasmic reticulum stress-related proteins (CHOP, GRP78, ATF-6, and p-eIF2ɑ). In addition, in LPS-induced inflammation in vitro, ALCAM overexpression promoted inflammatory response, oxidative stress, and ER stress. We established that ALCAM deficiency can suppress the ALI process by reducing inflammatory response, oxidative stress, and endoplasmic reticulum stress.

BMSC-Derived Exosomes Alleviate Sepsis-Associated Acute Respiratory Distress Syndrome by Activating the Nrf2 Pathway to Reverse Mitochondrial Dysfunction

Type II alveolar epithelial cell (AECII) apoptosis is one of the most vital causes of sepsis-induced acute respiratory distress syndrome (ARDS). Recent evidence has proved that bone mesenchymal stem cell-derived exosomes (BMSC-exos) can effectively reduce sepsis-induced ARDS. However, the function and molecular mechanism of BMSC-exos in sepsis-induced AECII apoptosis remain to be elucidated. In the present study, a more significant number of AECII apoptosis, high mitochondrial fission p-Drp1 protein levels, and low levels of mitochondrial biogenesis-related PGC1α, Tfam, and Nrf1 proteins accompanied with ATP content depression were confirmed in AECIIs in response to sepsis. Surprisingly, BMSC-exos successfully recovered mitochondrial biogenesis, including the upregulated expression of PGC1α, Tfam, Nrf1 proteins, and ATP contents, and prohibited p-Drp1-mediated mitochondrial fission by promoting Nrf2 expression. However, the aforementioned BMSC-exo reversal of mitochondrial dysfunction in AECIIs can be blocked by Nrf2 inhibitor ML385. Finally, BMSC-exos ameliorated the mortality rate, AECII apoptosis, inflammatory cytokine storm including HMGB1 and IL-6, and pathological lung damage in sepsis mice, which also could be prevented by ML385. These findings reveal a new mechanism of BMSC-exos in reversing mitochondrial dysfunction to alleviate AECII apoptosis, which may provide novel strategies for preventing and treating sepsis-induced ARDS.

Research progress of lncRNA and miRNA in hepatic ischemia-reperfusion injury

BACKGROUND

Hepatic ischemia-reperfusion injury (HIRI) is a common complication of liver surgeries, such as hepatectomy and liver transplantation. In recent years, several non-coding RNAs (ncRNAs) including long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) have been identified as factors involved in the pathological progression of HIRI. In this review, we summarized the latest research on lncRNAs, miRNAs and the lncRNA-miRNA regulatory networks in HIRI.

DATA SOURCES

The PubMed and Web of Science databases were searched for articles published up to December 2021 using the following keywords: "hepatic ischemia-reperfusion injury", "lncRNA", "long non-coding RNA", "miRNA" and "microRNA". The bibliography of the selected articles was manually screened to identify additional studies.

RESULTS

The mechanism of HIRI is complex, and involves multiple lncRNAs and miRNAs. The roles of lncRNAs such as AK139328, CCAT1, MALAT1, TUG1 and NEAT1 have been established in HIRI. In addition, numerous miRNAs are associated with apoptosis, autophagy, oxidative stress and cellular inflammation that accompany HIRI pathogenesis. Based on the literature, we conclude that four lncRNA-miRNA regulatory networks mediate the pathological progression of HIRI. Furthermore, the expression levels of some lncRNAs and miRNAs undergo significant changes during the progression of HIRI, and thus are potential prognostic markers and therapeutic targets.

CONCLUSIONS

Complex lncRNA-miRNA-mRNA networks regulate HIRI progression through mutual activation and antagonism. It is necessary to screen for more HIRI-associated lncRNAs and miRNAs in order to identify novel therapeutic targets.

Hypoxia modeling techniques: A review

Hypoxia is the main cause and effect of a large number of diseases, including the most recent one facing the world, the coronavirus disease (COVID-19). Hypoxia is divided into short-term, long-term, and periodic, it can be the result of diseases, climate change, or living and traveling in the high mountain regions of the world. Since each type of hypoxia can be a cause and a consequence of various physiological changes, the methods for modeling these hypoxias are also different. There are many techniques for modeling hypoxia under experimental conditions. The most common animal for modeling hypoxia is a rat. Hypoxia models (hypoxia simulations) in rats are a tool to study the effect of various conditions on the oxygen supply of the body. These models can provide a necessary information to understand hypoxia and also provide effective treatment, highlighting the importance of various reactions of the body to hypoxia. The main parameters when choosing a model should be reproducibility and the goal that the scientist wants to achieve. Hypoxia in rats can be reproduced both ways exogenously and endogenously. The reason for writing this review was the aim to systematize the models of rats available in the literature in order to facilitate their selection by scientists. The relative strengths and limitations of each model need to be identified and understood in order to evaluate the information obtained from these models and extrapolate these results to humans to develop the necessary generalizations. Despite these problems, animal models have been and remain vital to understanding the mechanisms involved in the development and progression of hypoxia. The eligibility criteria for the selected studies was a comprehensive review of the methods and results obtained from the studies. This made it possible to make generalizations and give recommendations on the application of these methods. The review will assist scientists in choosing an appropriate hypoxia simulation method, as well as assist in interpreting the results obtained with these methods.

Astrocytic CD24 Protects Neuron from Recombinant High-Mobility Group Box 1 Protein(rHMGB1)-Elicited Neuronal Injury

Endogenous host-derived molecules named damage-associated molecular patterns (DAMPs) can induce excessive non-sterile inflammatory responses on recognition of specific membrane-tethered receptors. Here in this study, we aimed to explore the role of DAMP molecule HMGB1 in astrocyte-mediated sterile neuroinflammation and the resultant influences on neurons. In vitro cultured astrocytes were challenged with rHMGB1 and then harvested at 6 h, 12 h, 24 h, 36 h, and 48 h, respectively. The astrocytic CD24 expression was determined by quantitative real-time polymerase chain reaction (qPCR), Western blot analysis and immunofluorescence, nuclear factor kappa B (NF-κB) binding activity was detected by electrophoretic mobility shift assay (EMSA), and the proinflammatory factors, tumor necrosis factor-α (TNF-α), and interleukin 1β (IL-1β), were measured by qPCR. The neuronal morphology was assessed with phase-contrast microscopy. The results showed that astrocytic mRNA and protein CD24 expression began to rise at 24 h, peaked at 36 h, and remained elevated at 48 h after rHMGB1 stimulation, accompanied with enhanced NF-κB binding activity and augmented expression of TNF-α and IL-1β. Furthermore, rHMGB1 caused cocultured neuron damage and was aggregated upon CD24 knockdown. Taken together, these novel findings suggested that rHMGB1 could promote astrocytic CD24 expression, the inhibition of which could aggregate neuronal damage.

Trained Immunity as a Trigger for Atherosclerotic Cardiovascular Disease-A Literature Review

Atherosclerosis remains the leading cause of cardiovascular diseases and represents a primary public health challenge. This chronic state may lead to a number of life-threatening conditions, such as myocardial infarction and stroke. Lipid metabolism alterations and inflammation remain at the forefront of the pathogenesis of atherosclerotic cardiovascular disease, but the overall mechanism is not yet fully understood. Recently, significant effects of trained immunity on atherosclerotic plaque formation and development have been reported. An increased reaction to restimulation with the same stimulator is a hallmark of the trained innate immune response. The impact of trained immunity is a prominent factor in both acute and chronic coronary syndrome, which we outline in this review.

High Mobility Group Box 1: Biological Functions and Relevance in Oxidative Stress Related Chronic Diseases

In the early 1970s, a group of non-histone nuclear proteins with high electrophoretic mobility was discovered and named high-mobility group (HMG) proteins. High-mobility group box 1 (HMGB1) is the most studied HMG protein that detects and coordinates cellular stress response. The biological function of HMGB1 depends on its subcellular localization and expression. It plays a critical role in the nucleus and cytoplasm as DNA chaperone, chromosome gatekeeper, autophagy maintainer, and protector from apoptotic cell death. HMGB1 also functions as an extracellular alarmin acting as a damage-associated molecular pattern molecule (DAMP). Recent findings describe HMGB1 as a sophisticated signal of danger, with a pleiotropic function, which is useful as a clinical biomarker for several disorders. HMGB1 has emerged as a mediator in acute and chronic inflammation. Furthermore, HMGB1 targeting can induce beneficial effects on oxidative stress related diseases. This review focus on HMGB1 redox status, localization, mechanisms of release, binding with receptors, and its activities in different oxidative stress-related chronic diseases. Since a growing number of reports show the key role of HMGB1 in socially relevant pathological conditions, to our knowledge, for the first time, here we analyze the scientific literature, evaluating the number of publications focusing on HMGB1 in humans and animal models, per year, from 2006 to 2021 and the number of records published, yearly, per disease and category (studies on humans and animal models).

Moxibustion may delay the aging process of Wistar rats by regulating intestinal microbiota

As one of the important treatments of health care and anti-aging in traditional Chinese medicine (TCM), moxibustion has been proved to have the effects of scavenging free radicals, anti-oxidation, reducing inflammatory reaction, regulating immunity and so on. Recent studies have shown that intestinal microbiota affect the process of aging. The relationship between aging, moxibustion and intestinal microbiota is still unclear. In this study, we explored the effects of moxibustion at Guanyuan (RN4) acupoint on intestinal microbiota, short-chain fatty acids and immunological characteristics of young and elder female Wistar rats to explore the relationship between aging, moxibustion and intestinal microbiota. Six 12-week-old female Wistar rats were young group (Y), and twelve 36-week-old female Wistar rats were randomly divided into elder group (C) and moxibustion group (M). The rats in M group were received mild moxibustion at Guanyuan (RN4) acupoint, 20 min/d for 40 days. The rats in Y group and C group were not given any therapeutic intervention. The results showed that moxibustion increased the abundance of intestinal probiotics (mainly Lactobacillus) and the level of short chain fatty acids, the microcirculation blood flow around Guanyuan (RN4) acupoint was also significantly improved in elder rats. In addition, the expression of MyD88, MAPK, TRAF6, NF-κB in intestinal tissue was down-regulated, and the levels of inflammatory cytokines in intestinal were decreased.

Silencing of CREB Inhibits HDAC2/TLR4/NF-κB Cascade to Relieve Severe Acute Pancreatitis-Induced Myocardial Injury

The purpose of the present study is to investigate the role of CREB in cardiomyocytes proliferation in regulation of HDAC2-dependent TLR4/NF-κB pathway in severe acute pancreatitis (SAP)-induced myocardial injury. The SAP rat model was developed by injecting sodium touracholate into SD rats and then infected with lentivirus vectors expressing sh-CREB in the presence/absence of LPS. The pathological alterations of rat pancreatic and cardiac tissues were observed by HE staining. TUNEL assay was used to study apoptosis of cardiomyocytes. Next, the loss- and gain-function assay was conducted in LPS-induced myocardial injury cardiomyocytes to define the roles of CREB, HDAC2, and TLR4 in cardiomyocyte proliferation, apoptosis, inflammation, and myocardial injury in vitro. ChIP assay was used to study the enrichment of CREB bound to HDAC2 promoter. RT-qPCR and Western blot analysis were used to detect the expressions of related mRNA and proteins in the NF-κB pathway, respectively. CREB was found to be overexpressed in both SAP tissues and cells. CREB directly bound to the promoter of HDAC2 and activated its expression. Overexpressed CREB or HDAC2 inhibited proliferation and promoted apoptosis of cardiomyocytes. Suppression of CREB inhibited the HDAC2/TLR4/NF-κB cascade to promote proliferation and inhibit apoptosis of cardiomyocytes. The in vitro results were validated in vivo experiments. Coherently, suppression of CREB can inhibit HDAC2/TLR4/NF-κB cascade to promote cardiomyocyte proliferation, thus ameliorating SAP-induced myocardial injury.

Targeting HMGB1/TLR4/NF-κB signaling pathway by protocatechuic acid protects against l-arginine induced acute pancreatitis and multiple organs injury in rats

Acute pancreatitis (AP) is a common pancreatic inflammation associated with substantial morbidity and mortality. AP may be mild or severe which can spread systemically causing multiple organs failure (MOF) and even death. In the current study, protocatechuic acid (PCA), a natural phenolic acid, was investigated for its possible protective potential against L-arginine induced AP and multiple organs injury (MOI) in rats. AP was induced by L-arginine (500 mg/100 g, ip). Two dose levels of PCA were tested (50 and 100 mg/kg, oral, 10 days before L-arginine injection). PCA successfully protected against L-arginine induced AP and MOI that was manifested by normalizing pancreatic, hepatic, pulmonary, and renal tissue architecture and restoring the normal values of pancreatic enzymes (amylase and lipase), serum total protein, liver enzymes (alanine transaminase (ALT) and aspartate transaminase (AST)) and kidney function biomarkers (blood urea nitrogen (BUN) and serum creatinine (Cr)) that were significantly elevated upon L-arginine administration. Additionally, PCA restored balanced oxidant/antioxidants status that was disrupted by L-arginine and normalized pancreatic levels of inducible nitric oxide synthase (iNOS) and nitric oxide (NO) content. Moreover, PCA significantly decreased L-arginine induced elevation in pancreatic high motility group box protein 1 (HMGB1), toll like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88), nuclear factor kappa B (NF-κB), tumor necrosis factor- α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) expression. PCA significantly ameliorated L-arginine-induced AP and MOI through its anti-inflammatory and antioxidant effects. HMGB1/TLR4/NF-κB was the major pathway involved in the observed protective potential.

Pretreatment with Propofol Reduces Pulmonary Injury in a Pig Model of Intestinal Ischemia-Reperfusion via Suppressing the High-Mobility Group Box 1 Protein (HMGB1)/Toll-Like Receptor 4 (TLR4)/Protein Kinase R (PKR) Signaling Pathway

BACKGROUND Propofol improves rodent pulmonary injury after intestinal ischemia-reperfusion (IIR). However, its effect and underlying mechanisms in large animals remain unclear. Here, we examined whether pretreatment with propofol could relieve lung injury during IIR in pigs, then investigated the underlying mechanism. MATERIAL AND METHODS A porcine model of IIR-induced lung injury was built by clamping the super mesenteric artery for 2 h and loosening the clamp for 4 h. Randomized grouping was used, and pigs were assigned to a sham-operated group, an IIR with saline pretreatment group, and an IIR with propofol pretreatment group. Pulmonary histopathologic changes, permeability, and oxygenation were assessed to evaluate the effect of propofol. We assessed levels of methane dicarboxylic aldehyde (MDA), superoxide dismutase (SOD), myeloperoxidase (MPO), high-mobility group box 1 protein (HMGB1), Toll-like receptor 4 (TLR4), and double-stranded RNA activated protein kinase R (PKR) to investigate the underlying mechanism. RESULTS IIR caused severe lung damage, including morphological changes, high permeability, airway resistance, low static compliance, hypoxemia, and acidemia. Pulmonary and plasma MDA content and MPO activity increased, whereas SOD activity decreased. The HMGB1/TLR4/PKR signaling pathway was activated following IIR. Pretreatment with propofol markedly attenuated lung injury (such as reducing the lung edema and permeability), increased MDA content and MPO activity, and restored SOD activity induced by IIR, accompanied by inhibiting the effect of the HMGB1/TLR4/PKR signaling pathway. CONCLUSIONS IIR caused acute lung injury in pigs. Pretreatment with propofol alleviated the lung injury, which was related to its suppression of the HMGB1/TLR4/PKR signaling pathway.

HMGB1/TLR4 Signaling Affects Regulatory T Cells in Acute Lung Injury

Background

High-mobility group box-1 protein (HMGB1) serves as the prototypic damage-associated molecular pattern molecule, and TLR4 is considered a receptor for HMGB1. Regulatory T cells (Tregs) play a crucial role in infectious diseases. The role of HMGB1 in the modulation of Tregs is of great interest.

Methods

Serum HMGB1 and Treg proportions were detected in 58 patients with acute lung injury (ALI) and 36 healthy volunteers. The correlations of these parameters with disease severity were analyzed. The WT and TLR4^-/- mice were administered HMGB1 by intratracheal injection. After 48 h, the mice were sacrificed. The morphological changes and wet/dry ratio of the lung were measured. Spleen CD4⁺CD25⁺ Tregs were sorted from spleen cells, the expression of FOXP3 and CTLA-4, and releasing of cytokines was detected. CD4⁺CD25⁺ Tregs were cocultured with effector T cells, the inhibitory effect, and release of cytokines was detected.

Results

Significantly increased plasma levels of HMGB1 and reduced CD4⁺CD25⁺CD127^low Tregs were detected in ALI patients. In the mouse model, lung injury was significantly increased after HMGB1 instillation in the WT and TLR4^-/- groups compared with control group. The lung wet/dry ratio and the TNF-α and IL-1β contents in BALF were significantly increased, and the severity of WT mice was higher than that of TLR4^-/- mice. The expression of FOXP3 and CTLA-4 in TLR4^-/- mice was significantly increased compared with that in WT mice and was associated with a similar trend of IL-10 and TGF-β levels (p<0.05). In coculture with effector T cells, Tregs isolated from TLR4^-/- mice exhibited decreased IL-2 and IFN-γ and increased IL-4 levels compared with Tregs from WT mice. Increased polarization of TLR4^-/- CD4⁺CD25⁺ Treg cells to Th2 cells was observed.

Conclusion

In HMGB1-induced lung injury, HMGB1 affects the expression of FOXP3 and CTLA-4 through TLR4, thus reducing the immunosuppressive function of Treg cells.

MitoQ alleviates LPS-mediated acute lung injury through regulating Nrf2/Drp1 pathway

Lipopolysaccharide (LPS) has been known to cause alveolar epithelial cell (AEC) apoptosis and barrier breakdown that characterize acute lung injury (ALI) and acute respiratory distress syndrome. We aimed to investigate whether mitoquinone (MitoQ), a mitochondria-targeted antioxidant, could alleviate LPS-induced AEC damage in ALI and its underlying mechanisms. In vitro studies in AEC A549 cell line, we noted that LPS could induce dynamin-related protein 1 (Drp1)-mediated mitochondrial fission, AEC apoptosis and barrier breakdown, which could be reversed with MitoQ and mitochondrial division inhibitor 1 treatment. Moreover, the protective role of MitoQ was attenuated with Drp1 overexpression. Nuclear factor E2-related factor 2 (Nrf2) downregulation could block the effect of MitoQ by decreasing the expression of Nrf2 target genes in LPS-treated AEC, such as heme oxygenase-1 (HO-1) and NAD(P)H:quinone oxidoreductase 1 (NQO1). Nrf2 gene knockdown in LPS-treated A549 cells prevented the protective effect of MitoQ from decreasing Drp1-mediated mitochondrial fission, AEC apoptosis and barrier breakdown. The lung protective effect of MitoQ by regulating the Drp1-mediated mitochondrial fission, AEC apoptosis and barrier breakdown was further confirmed in vivo with LPS-induced ALI mouse model. Additionally, the protective effect of MitoQ was inhibited by Nrf2 inhibitor ML385. We therefore conclude that MitoQ exerts ALI-protective effects by preventing Nrf2/Drp1-mediated mitochondrial fission, AEC apoptosis as well as barrier breakdown.

Alleviation of remote lung injury following liver ischemia/reperfusion: Possible protective role of vildagliptin

Lung injury is a serious condition encountered following hepatic ischemia/reperfusion (IR). This study aimed to explore whether a dipeptidyl peptidase-4 inhibitor agent vildagliptin (V) could alleviate the lung injury caused by hepatic IR in a rat model and if so elucidate its molecular protective mechanism. Three groups of rats were used. Sham group: received normal saline and exposed to a sham operation, IR group: received normal saline and subjected to the operation of hepatic I (45 min)/ R (180 min), V+IR group: received for 10 days intraperitoneal injection of V (10 mg/kg/day). After reperfusion, liver and lung were collected for biochemical and histological evaluation. Hepatic IR exhibited significant elevation in serum alanine aminotransferase (ALT), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH) enzyme levels, serum and lung malondialdehyde (MDA) and tumor necrosis factor-alpha (TNF-α) in addition to lung nitric oxide (NO) levels, hypoxia-inducible factor 1-alpha (HIF-1α) mRNA and protein levels, hepatocyte growth factor (HGF) mRNA expression, and inducible nitric oxide synthase (iNOS) mRNA and protein expressions in lung tissue along with a marked reduction in the serum and lung content of catalase in comparison to the sham group. Moreover, liver and lung injury in the IR group was detected by histopathological examination. Vildagliptin ameliorated markedly the biochemical changes as well as liver and lung architecture in comparison to the IR group. Vildagliptin mitigated the induced lung injury by hepatic IR via suppression of oxidative stress markers, pro-inflammatory cytokine TNF-α as well as the HIF1-α/iNOS/HGF expressions in lung tissue.

Cardiopulmonary Bypass Induces Acute Lung Injury via the High-Mobility Group Box 1/Toll-Like Receptor 4 Pathway

During cardiopulmonary bypass (CPB), pulmonary ischemia/reperfusion (I/R) injury can cause acute lung injury (ALI). Our previous research confirmed that abnormal high-mobility group box 1 (HMGB1) release after CPB was closely related to ALI. However, the mechanism underlying the HMGB1-mediated induction of ALI after CPB is unclear. Our previous study found that HMGB1 binds Toll-like receptor 4 (TLR4), leading to lung injury, but direct evidence of a role for these proteins in the mechanism of CPB-induced lung injury has not been shown. We examined the effects of inhibiting HMGB1 or reducing TLR4 expression on CPB-induced lung injury in rats administered anti-HMBG1 antibody or TLR4 short-hairpin RNA (shTLR4), respectively. In these rat lungs, we studied the histologic changes and levels of interleukin- (IL-) 1β, tumour necrosis factor- (TNF-) α, HMGB1, and TLR4 after CPB. After CPB, the lung tissues from untreated rats showed histologic features of injury and significantly elevated levels of IL-1β, TNF-α, HMGB1, and TLR4. Treatment with anti-HMGB1 attenuated the CPB-induced morphological inflammatory response and protein levels of IL-1β, TNF-α, HMGB1, and TLR4 in the lung tissues and eventually alleviated the ALI after CPB. Treatment with shTLR4 attenuated the CPB-induced morphological inflammatory response and protein levels of IL-1β, TNF-α, and TLR4 in the lung tissues and eventually alleviated the ALI after CPB, but could not alleviate the HMGB1 protein levels induced by CPB. In summary, the present study demonstrated that the HMGB1/TLR4 pathway mediated the development of ALI induced by CPB.

Compound amino acid combined with high-dose vitamin B6 attenuate traumatic coagulopathy via inhibiting inflammation by HMGB1/TLR4/NF-κB pathway

BACKGROUND

Traumatic coagulopathy (TC) arises primarily from coagulation system failure to maintain adequate hemostasis after serious blood loss or trauma. Circulatory homeostasis restoration is the mainstay of the therapeutic approach to TC, but the effects are significantly inhibited by coagulopathy.

OBJECTIVE

To identify the therapeutic effects and underlying mechanism of compound amino acid (CAA) combined with high-dosage of vitamin B6 (VB6) on TC.

METHODS

Rabbit traumatic model and cellular model were used to evaluate the effect of CAA combined with high-dosage of VB6 in TC. Blood concentrations of AST and ALT were measured using the Vitros 250 device while blood APTT, PT and TT concentrations were measured using commercial diagnostics kits. Furthermore, qRT-PCR, ELISA and Western blotting were used to determine the expression of clotting factor (II, VII, IX, X and XI), inflammatory factors (TNF-α, IL-6 and IL-1β) and HMGB1/TLR4/NF-κB signaling-related proteins, respectively.

RESULTS

In the rabbit traumatic model, CAA combined with high-dosage of VB6 therapy inhibited the high expression of AST and ALT, but increased the expression of coagulation factors. Additionally, in both the rabbit trauma model and cellular injury model, CAA combined with high-dosage of VB6 inhibited the expression of inflammatory factors (IL-6, TNF-α and IL-1β) and proteins (HMGB1, TLR4 and p-p65) in HMGB1/TLR4/NF-κB pathway. Most importantly, over-expression of HMGB1 reversed the effect of CAA and VB6 in HUVECs and EA.hy926 cells injury model.

CONCLUSION

CAA combined with high-dosage of VB6 alleviated TC and inhibited the expression and secretion of inflammatory factors by inhibiting HMGB1-mediated TLR4/NF-κB pathway.

microRNA-802 accelerates hepatocellular carcinoma growth by targeting RUNX3

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide. Prognosis is often unfavorable. In this study, the effects of microRNA-802 (miR-802) on HCC progression were assessed in vivo and in vitro. miR-802 was found to be significantly upregulated in HCC tumor tissue compared to paired adjacent nontumor tissue. In vitro, transfection with a miR-802 mimic accelerated SMMC-7721 cellular proliferation, increased accumulation of the cell-cycle S-phase cell populations, as well as cell migration. In vivo injection of a miR-802 agomir promoted HCC proliferation in nude mice. Targets of miR-802 were predicted by miRWalk, miRanda, RNA22, and Targetscan. By luciferase reporter assay RUNX3 was identified as a direct target of miR-802. As judged by western blot analysis, RUNX3 was upregulated when miR-802 was inhibited. These data demonstrate increased miR-802 expression in patients with HCC and that miR-802 overexpression promotes tumor cell growth, in a RUNX3-dependent manner.

Macrophages in xenotransplantation

Xenotransplantation refers to organ transplantation across species. Immune rejection of xenografts is stronger and faster than that of allografts because of significant molecular differences between species. Recent studies have revealed the involvement of macrophages in xenograft and allograft rejections. Macrophages have been shown to play a critical role in inflammation, coagulation, and phagocytosis in xenograft rejection. This review presents a recent understanding of the role of macrophages in xenograft rejection and possible strategies to control macrophage-mediated xenograft rejection.

Electroacupuncture Pretreatment Attenuates Acute Lung Injury Through α7 Nicotinic Acetylcholine Receptor-Mediated Inhibition of HMGB1 Release in Rats After Cardiopulmonary Bypass

Supplemental Digital Content is available in the text

Acute lung injury is a common complication after cardiopulmonary bypass (CPB). α7 Nicotinic acetylcholine receptors (α7nAChR) and α7nAChR-dependent cholinergic signaling are implicated in suppressing the release of high-mobility group box 1 (HMGB1) and reducing the inflammatory response. A previous study has shown the electroacupuncture (EA) pretreatment induces tolerance against lung injury. However, the role of EA in CPB is poorly understood. This study used EA and a rat model of CPB to determine whether EA was associated with CPB-induced lung injury. Rats were treated with EA at “Zusanli (ST36)” and “Feishu (BL13)” acupoints for 5 days before being subjected to CPB. Two hours post-CPB, samples of blood, bronchoalveolar lavage fluid (BALF), and lung tissues were processed for investigations. Our results showed that the expression of α7nAChR in lung tissue was significantly decreased after CPB. EA pretreatment prevented the reduction in the expression of α7nAChR, EA pretreatment reduced lung edema, inhibited inflammatory cytokines release in serum and lung as well as protein concentrations in BALF and HMGB1 release after CPB, and the beneficial effects were attenuated by α-BGT. Our study demonstrates that EA pretreatment plays a protective role in CPB-induced ALI, and inhibits HMGB1 release through α7nAChR activation in rats.

High Mobility Group Box 1 Mediates TMAO-Induced Endothelial Dysfunction

The intestinal microbe-derived metabolite trimethylamine N-oxide (TMAO) is implicated in the pathogenesis of cardiovascular diseases (CVDs). The molecular mechanisms of how TMAO induces atherosclerosis and CVDs’ progression are still unclear. In this regard, high-mobility group box protein 1 (HMGB1), an inflammatory mediator, has been reported to disrupt cell–cell junctions, resulting in vascular endothelial hyper permeability leading to endothelial dysfunction. The present study tested whether TMAO associated endothelial dysfunction results via HMGB1 activation. Biochemical and RT-PCR analysis showed that TMAO increased the HMGB1 expression in a dose-dependent manner in endothelial cells. However, prior treatment with glycyrrhizin, an HMGB1 binder, abolished the TMAO-induced HMGB1 production in endothelial cells. Furthermore, Western blot and immunofluorescent analysis showed significant decrease in the expression of cell–cell junction proteins ZO-2, Occludin, and VE-cadherin in TMAO treated endothelial cells compared with control cells. However, prior treatment with glycyrrhizin attenuated the TMAO-induced cell–cell junction proteins’ disruption. TMAO increased toll-like receptor 4 (TLR4) expression in endothelial cells. Inhibition of TLR4 expression by TLR4 siRNA protected the endothelial cells from TMAO associated tight junction protein disruption via HMGB1. In conclusion, our results demonstrate that HMGB1 is one of the important mediators of TMAO-induced endothelial dysfunction.

HMGB1 enhances AGE-mediated VSMC proliferation via an increase in 5-LO-linked RAGE expression

Receptors for advanced glycation end-product (RAGE) play a pivotal role in the progression of proliferative vascular diseases. However, the precise mechanisms regulating RAGE expression in vascular smooth muscle cells (VSMCs) of the injured vasculatures is unclear. Given the potential importance of 5-lipoxygenase (5-LO) derived mediators in cellular responses mediated by RAGE, this study aimed to evaluate in VSMCs treated with high mobility group box 1 (HMGB1): 1) the RAGE expression; 2) the AGE-induced VSMC proliferation; 3) the role of 5-LO signaling in HMGB1-induced RAGE expression. In cultured human VSMCs stimulated with HMGB1 (100 ng/ml), RAGE mRNA and protein expression were markedly increased along with an increase in AGE-mediated VSMC proliferation. Both of these effects were markedly attenuated in cells pretreated with zileuton (1-10 μM), a 5-LO inhibitor, as well as in cells transfected with 5-LO siRNA, suggesting a potential involvement of 5-LO signaling in HMGB1-mediated RAGE expression in VSMCs. Moreover, 5-LO expression, accompanied by production of leukotrienes was markedly increased in HMGB1-stimulated VSMCs, which was attenuated in cells deficient of TLR2 or RAGE. Taken together, our results suggest that HMGB1-induced increase in 5-LO expression enhances RAGE expression in VSMCs, which stimulates AGE-mediated VSMC proliferation. Thus, the 5-LO-RAGE signaling axis in VSMCs might serve as a potential therapeutic target for vascular remodeling in the injured vasculature.

Postoperative remote lung injury and its impact on surgical outcome

Postoperative remote lung injury is a complication following various surgeries and is associated with short and long-term mortality and morbidity. The release of proinflammatory cytokines, damage-associated molecular patterns such as high-mobility group box-1, nucleotide-biding oligomerization domain (NOD)-like receptor protein 3 and heat shock protein, and cell death signalling activation, trigger a systemic inflammatory response, which ultimately results in organ injury including lung injury. Except high financial burden, the outcome of patients developing postoperative remote lung injury is often not optimistic. Several risk factors had been classified to predict the occurrence of postoperative remote lung injury, while lung protective ventilation and other strategies may confer protective effect against it. Understanding the pathophysiology of this process will facilitate the design of novel therapeutic strategies and promote better outcomes of surgical patients. This review discusses the cause and pathology underlying postoperative remote lung injury. Risk factors, surgical outcomes and potential preventative/treatment strategies against postoperative remote lung injury are also addressed.

The Janus face of HMGB1 in heart disease: a necessary update

High mobility group box 1 (HMGB1) is a ubiquitous nuclear protein involved in transcription regulation, DNA replication and repair and nucleosome assembly. HMGB1 is passively released by necrotic tissues or actively secreted by stressed cells. Extracellular HMGB1 acts as a damage-associated molecular pattern (DAMPs) molecule and gives rise to several redox forms that by binding to different receptors and interactors promote a variety of cellular responses, including tissue inflammation or regeneration. Inhibition of extracellular HMGB1 in experimental models of myocardial ischemia/reperfusion injury, myocarditis, cardiomyopathies induced by mechanical stress, diabetes, bacterial infection or chemotherapeutic drugs reduces inflammation and is protective. In contrast, administration of HMGB1 after myocardial infarction induced by permanent coronary artery ligation ameliorates cardiac performance by promoting tissue regeneration. HMGB1 decreases contractility and induces hypertrophy and apoptosis in cardiomyocytes, stimulates cardiac fibroblast activities, and promotes cardiac stem cell proliferation and differentiation. Interestingly, maintenance of appropriate nuclear HMGB1 levels protects cardiomyocytes from apoptosis by preventing DNA oxidative stress, and mice with HMGB1cardiomyocyte-specific overexpression are partially protected from cardiac damage. Finally, higher levels of circulating HMGB1 are associated to human heart diseases. Hence, during cardiac injury, HMGB1 elicits both harmful and beneficial responses that may in part depend on the generation and stability of the diverse redox forms, whose specific functions in this context remain mostly unexplored. This review summarizes recent findings on HMGB1 biology and heart dysfunctions and discusses the therapeutic potential of modulating its expression, localization, and oxidative-dependent activities.

Short-term use of MyD88 inhibitor TJ-M2010-5 prevents d-galactosamine/lipopolysaccharide-induced acute liver injury in mice

Excessive activation of the TLR/MyD88 signaling pathway contributes to several inflammation-related diseases. Previously, our laboratory synthesized a novel thiazaol-aminoramification MyD88 inhibitor named TJ-M2010-5. In this study, we interrogated the role of MyD88, as well as the protective effect of TJ-M2010-5, in a d-gal/LPS-induced acute liver injury mouse model. In order to induce acute liver injury, BALB/c mice received intraperitoneal injection of d-gal and LPS at a dose of 800 mg/kg and 80 μg/kg body weight, respectively. All mice died within 48 h of injection without intervention. However, pre-treatment with TJ-M2010-5 as well as knock-out (KO) of the MyD88 gene significantly improved mouse survival rate to 73.3% and 80% at 48 h, respectively, and both treatments protected liver function. These pathological results demonstrated that TJ-M2010-5 and MyD88 KO reduced the infiltration of inflammatory cells and protected hepatocytes against apoptosis. Furthermore, TJ-M2010-5 remarkably inhibited NF-κB and MAPK signaling in vivo. LPS-induced activation of macrophages as well as pro-inflammatory factors were also shown to be decreased after TJ-M2010-5 treatment in vivo and in vitro. Taken together, these results suggested that blockage of the TLR/MyD88 signaling pathway by TJ-M2010-5 has an important role in the prevention of inflammation-related acute liver injury.

WISP1 mediates lung injury following hepatic ischemia reperfusion dependent on TLR4 in mice

BACKGROUND

Hepatic ischemia-reperfusion injury (IRI) is a common pathological phenomenon, which causes hepatic injury as well as remote organ injuries such as the lung. Several mediators, such as oxidative stress, Ca²⁺ overload and neutrophil infiltration, have been implied in the pathogenesis of liver and remote organ injuries following reperfusion. WNT1 inducible signaling pathway protein 1 (WISP1) is an extracellular matrix protein that has been associated with the onset of several malignant diseases. Previous work in our group has demonstrated WISP1 is upregulated and contributes to proinflammatory cascades in hepatic IRI. However, the role of WISP1 in the pathogenesis of lung injury after hepatic IRI still remains unknown.

METHODS

Male C57BL/6 mice were used to examine the expression and role of WISP1 in the pathogenesis of lung injuries after hepatic IRI and explore its potential mechanisms in mediating lung injuries.

RESULTS

We found WISP1 was upregulated in lung tissues following hepatic IRI. Treatment with anti-WISP1 antibody ameliorated lung injuries with alteration of cytokine profiles. Administration with rWISP1 aggravated lung injuries following hepatic IRI through excessive production of proinflammatory cytokines and inhibition of anti-inflammatory cytokines.

CONCLUSIONS

In this study, we concluded that WISP1 contributed to lung injuries following hepatic IRI through TLR4 pathway.

SRT1720 ameliorates sodium taurocholate-induced severe acute pancreatitis in rats by suppressing NF-κB signalling

Severe acute pancreatitis (SAP) is a medical emergency that is often associated with multiple organ failure and high mortality. Although an SAP diagnosis requires prompt treatment, therapeutic options remain limited. SRT1720 is a newly formulatedSIRT1 activator that exerts multiple pharmacological activities with beneficial health effects. However, its potential as an SAP treatment has not been explored. The current study assessed the effect of SRT1720 on a rat model of sodium taurocholate-induced SAP and explored the underlying mechanism. SAP was induced in rats by retrograde injection of a 3.5% sodium taurocholate solution (1 ml/kg) in the biliopancreatic duct. SRT1720 (5 mg/kg) was administered intraperitoneally after sodium taurocholate exposure. Serum samples were analysed for inflammatory cytokine levels and select enzymatic activities using the enzyme-linked immunosorbent assay and commercial enzyme activity assay kits, respectively; protein expression levels were evaluated by western blotting; mRNA levels of biomarkers were determined by quantitative real-time PCR; histopathological changes were analysed by haematoxylin and eosin staining and immunohistochemistry.SRT1720 treatment significantly reduced serum amylase, lipase, pancreatic histological scores, proinflammatory cytokine (TNF-α and IL-6) levels, and expression of NF-κB and p65 in sodium taurocholate-induced SAP rats. Importantly, the treatment stimulated SIRT1 and IκBα levels in pancreatic tissue. Our data suggest that SRT1720 protects rats from sodium taurocholate-induced SAP by suppressing the NF-κB signalling pathway.

NLRP3/ASC-mediated alveolar macrophage pyroptosis enhances HMGB1 secretion in acute lung injury induced by cardiopulmonary bypass

Our previous study showed that high levels of HMGB1 existed in rats following cardiopulmonary bypass (CPB)-induced acute lung injury (ALI) and neutralization of high-mobility group box 1(HMGB1) reduced CPB-induced ALI. However, the mechanism by which CPB increases HMGB1 secretion is unclear. Recent studies have shown that inflammasome-mediated cell pyroptosis promotes HMGB1 secretion. This study aimed to investigate the relationship between inflammasome-mediated pyroptosis and HMGB1 in CPB-related ALI. We employed oxygen-glucose deprivation (OGD)-induced alveolar macrophage (AM) NR8383 pyroptosis to measure HMGB1 secretion. We found that OGD significantly increased the levels of caspase-1 cleaved p10, IL-1β and ASC expression, caspase-1 activity and the frequency of pyroptotic AM, and promoted the cytoplasm transportation and secretion of HMGB1, which were significantly mitigated by ASC silencing or pre-treatment with glyburide (a Nlrp3 inhibitor) in AM. CPB also increased the expression levels of Nlrp3, ASC, caspase-1 P10, and IL-1β, and the percentages of AM pyroptosis in the lungs of experimental rats accompanied by increased levels of serum and bronchoalveolar lavage fluid (BALF) HMGB1. Treatment with glyburide significantly mitigated the CPB-increased ASC, caspase-1 p10 and IL-1β expression, and the percentages of AM pyroptosis in the lungs, as well as the levels of HMGB1 in serum and BALF in rats. Therefore, our data indicated that the Nlrp3/ASC-mediated AM pyroptosis increased HMGB1 secretion in ALI induced by CPB. These findings may provide a therapeutic strategy to reduce lung injury and inflammatory responses during CPB.

Exploring the biological functional mechanism of the HMGB1/TLR4/MD-2 complex by surface plasmon resonance

BACKGROUND

High Mobility Group Box 1 (HMGB1) was first identified as a nonhistone chromatin-binding protein that functions as a pro-inflammatory cytokine and a Damage-Associated Molecular Pattern molecule when released from necrotic cells or activated leukocytes. HMGB1 consists of two structurally similar HMG boxes that comprise the pro-inflammatory (B-box) and the anti-inflammatory (A-box) domains. Paradoxically, the A-box also contains the epitope for the well-characterized anti-HMGB1 monoclonal antibody "2G7", which also potently inhibits HMGB1-mediated inflammation in a wide variety of in vivo models. The molecular mechanisms through which the A-box domain inhibits the inflammatory activity of HMGB1 and 2G7 exerts anti-inflammatory activity after binding the A-box domain have been a mystery. Recently, we demonstrated that: 1) the TLR4/MD-2 receptor is required for HMGB1-mediated cytokine production and 2) the HMGB1-TLR4/MD-2 interaction is controlled by the redox state of HMGB1 isoforms.

METHODS

We investigated the interactions of HMGB1 isoforms (redox state) or HMGB1 fragments (A- and B-box) with TLR4/MD-2 complex using Surface Plasmon Resonance (SPR) studies.

RESULTS

Our results demonstrate that: 1) intact HMGB1 binds to TLR4 via the A-box domain with high affinity but an appreciable dissociation rate; 2) intact HMGB1 binds to MD-2 via the B-box domain with low affinity but a very slow dissociation rate; and 3) HMGB1 A-box domain alone binds to TLR4 more stably than the intact protein and thereby antagonizes HMGB1 by blocking HMGB1 from interacting with the TLR4/MD-2 complex.

CONCLUSIONS

These findings not only suggest a model whereby HMGB1 interacts with TLR4/MD-2 in a two-stage process but also explain how the A-box domain and 2G7 inhibit HMGB1.

Ischemic preconditioning attenuates acute lung injury after partial liver transplantation

Pulmonary complications frequently occur after liver transplantation and are often life-threatening. Thus, we investigated whether hepatic ischemic preconditioning (IP) attenuates acute lung injury (ALI) after small-for-size liver transplantation. Rat livers were explanted after 9-min ischemia plus 5-min reperfusion, reduced to 50% of original size ex vivo, and implanted into recipients with approximately twice the donor body weight, resulting in quarter-size liver grafts (QSG). After QSG transplantation, hepatic Toll-like receptor 4 (TLR4) and tumor necrosis factor-α (TNFα ) expression increased markedly and high mobility group box-1 (HMGB1), an endogenous damage-associated molecular pattern molecule (DAMP), was released from QSG into the blood. IP blunted TLR4 and TNFα expression and HMGB1 release from QSG. In the lungs of QSG recipients without IP treatment, nuclear factor-κB (NF-κB) activation and intercellular adhesion molecule (ICAM)-1 expression increased; alveolar septal walls thickened with increased cellularity as neutrophils, monocytes/macrophage and T lymphocytes infiltrated into alveolar septa and alveolar spaces; and pulmonary cleaved caspase-8 and -3 and TUNEL-positive cells increased. In contrast, in the lungs of recipients of ischemic-preconditioned QSG, NF-κB activation and ICAM-1 expression were blunted; leukocyte infiltration was decreased; and alveolar septal wall thickening, caspase activation, and cell apoptosis were attenuated. IP did not increase heat-shock proteins in the lungs of QSG recipients. In conclusion, toxic cytokine and HMGB1 released from failing small-for-size grafts leads to pulmonary adhesion molecule expression, leukocyte infiltration and injury. IP prevents DAMP release and toxic cytokine formation in small-for-size grafts, thereby attenuating ALI.

HMGB1 Increases IL-1β Production in Vascular Smooth Muscle Cells via NLRP3 Inflammasome

Vascular smooth muscle cells (VSMCs) are the major cell type in the blood vessel walls, and their phenotypic modulation is a key cellular event driving vascular remodeling. Although high mobility group box-1 (HMGB1) plays a pivotal role in inflammatory processes after vascular injuries, the importance of the links between VSMCs, HMGB1 and vascular inflammation has not been clarified. To prove the hypothesis that VSMCs might be active players in vascular inflammation by secreting inflammatory cytokines, we investigated the proinflammatory effects of HMGB1 and its intermediary signaling pathways in VSMCs. When cultured human VSMCs were stimulated with HMGB1 (10–500 ng/ml), IL-1β production was markedly increased. HMGB1 also increased the expression of NLRP3 inflammasome components including NLRP3, ASC and caspase-1. Among these components, HMGB1-induced expressions of NLRP3 and caspase-1 were markedly attenuated in TLR2 siRNA-transfected cells, whereas ASC and caspase-1 expressions were reduced in RAGE-deficient cells. In TLR4-deficient cells, HMGB1-induced caspase-1 expression was significantly attenuated. Moreover, IL-1β production in HMGB1-stimulated cells was significantly reduced in cells transfected with caspase-1 siRNA as well as in cells treated with monoclonal antibodies or siRNAs for TLR2, TLR4 and RAGE. Overall, this study identified a pivotal role for NLRP3 inflammasome and its receptor signaling involved in the production of IL-1β in VSMCs stimulated with HMGB1. Thus, targeting HMGB1 signaling in VSMCs offers a promising therapeutic strategy for treating vascular remodeling diseases.

Augmenter of liver regeneration (ALR) regulates acute pancreatitis via inhibiting HMGB1/TLR4/NF-κB signaling pathway

This research aimed to explore the effect of augmenter of liver regeneration (ALR) in acute pancreatitis (AP) of mice and the underlying mechanism. Caerulein were given to mice to get AP models. AP mice were given saline, ALR plasmids or negative control plasmids. Then, pancreas tissues were fixed and stained for histological examination. The levels of serum amylase, serum lipase, MPO, HMGB1, TNF-α, IL-1β as well as MCP-1 were detected by ELISA assay. The mRNA levels of TLR4, p65, IκBα, iNOS, COX-2 and GAPDH were examined by RT-qPCR. The protein levels of HMGB1, TLR4, MD2, MyD88, IκBα and GAPDH were detected by western blotting. ALR decreased serum amylase as well as lipase levels and alleviated the histopathological alterations of the pancreas in AP mice. ALR decreased the MPO activity of pancreas in AP Mice. ALR decreased the HMGB1/TLR4 signaling pathway in AP Mice. ALR decreased pancreas IL-1β and MCP-1 in AP mice, and also decreased plasma TNF-α and IL-1β in AP mice. ALR attenuated the cerulein-caused increase in p65 mRNA and protein levels, but had no effects on mRNA and protein levels of IκBα. The AP mice significantly promoted the mRNA levels of iNOS and COX-2 that was inhibited by ALR. HNE formation was also increased in AP mice, but it was decreased by ALR. ALR alleviates acute pancreatitis by inhibiting HMGB1/TLR4/NF-κB signaling pathway. It is promising to alleviate the syndromes of patients with acute via targeting ALR.

Penehyclidine hydrochloride inhibits TLR4 signaling and inflammation, and attenuates blunt chest trauma and hemorrhagic shock-induced acute lung injury in rats

Blunt chest trauma with hemorrhagic shock (THS) frequently induces pulmonary inflammation that leads to acute lung injury (ALI). Penehyclidine hydrochloride (PHC) possesses anti‑inflammatory properties that may attenuate the systemic inflammatory response. The present study aimed to evaluate the molecular mechanism of PHC in modifying THS‑induced ALI in rats. Rats underwent either THS or a sham procedure. At 6 h subsequent to blunt chest trauma, arterial blood was drawn for blood gas and pro‑inflammatory factors analyses, and lung tissue samples were collected to examine pulmonary histopathological alterations, the wet/dry weight ratio, myeloperoxidase activity, and the protein expression levels of Toll-like receptor 4 (TLR4), phosphorylated (p‑)p38 mitogen‑activated protein kinase (MAPK), nuclear factor (NF)‑κB and activator protein‑1 (AP‑1). THS caused significant reductions in heart rate and mean arterial blood pressure, and was associated with significant increases in tumor necrosis factor‑α, interleukin (IL)‑6, IL‑1β, p‑p38MAPK, NF‑κB and AP‑1 activation, in addition to TLR4 expression, in the lung. PHC effectively attenuated THS‑induced ALI, and inhibited TLR4 expression, reduced the activation of p‑p38MAPK, NF‑κB and AP‑1, and downregulated the expression of pro‑inflammatory mediators. In conclusion, the results of the present study demonstrated that PHC may exert an anti‑inflammatory effect and attenuate THS‑induced ALI by inhibiting the TLR4 signaling pathway. These preclinical findings may offer a novel therapeutic strategy to restrict TLR4 overactivation in ALI.

Activation of the HMGB1‑TLR4‑NF‑κB pathway may occur in patients with atopic eczema

High mobility group protein B1 (HMGB1) has been reported to serve important roles in various pathological conditions. Toll‑like receptor 4 (TLR4), as one of the HMGB1 receptors, has been reported to be involved in the development of certain inflammatory diseases by activating nuclear factor NF‑κ‑B (NF‑κB). However, there are few studies investigating the effects of HMGB1, TLR4 and NF‑κB on human inflammatory dermatoses. In the present study, the distribution and characteristics of HMGB1, TLR4 and NF‑κB p65 expression in psoriasis and atopic eczema (AE) were investigated. In addition, immunohistochemical analysis was performed to evaluate their expression and distribution in normal skin, and in patients with AE or psoria-sis. Spearman's correlation analysis was used to predicate their relevancy. The present study identified that the p65 level in epithelial nuclei in AE skin was increased compared with normal and psoriasis skin (P<0.01). The level of extracellular HMGB1 in AE skin was also increased compared with normal and psoriasis skin (P<0.01). Meanwhile, TLR4 expression on the epithelial membranes of AE skin was increased compared with psoriasis skin (P<0.01). Furthermore, the level of extracellular HMGB1 was positively correlated with epithelial membrane TLR4 (r=0.3856; P<0.05) and epithelial nuclear p65 (r=0.5894; P<0.01) in AE skin. These results indicated that the HMGB1‑TLR4‑NF‑κB signaling pathway is activated in AE and may account for its pathogenesis, but not in psoriasis. Therefore, HMGB1, TLR4 and NF‑κB p65 have the potential to be targets for the treatment of human inflammatory dermatoses, including AE.

Danger signals in regulating the immune response to solid organ transplantation

Endogenous danger signals, or damage-associated molecular patterns (DAMPs), are generated in response to cell stress and activate innate immunity to provide a pivotal mechanism by which an organism can respond to damaged self. Accumulating experimental and clinical data have established the importance of DAMPs, which signal through innate pattern recognition receptors (PRRs) or DAMP-specific receptors, in regulating the alloresponse to solid organ transplantation (SOT). Moreover, DAMPs may incite distinct downstream cellular responses that could specifically contribute to the development of allograft fibrosis and chronic graft dysfunction. A growing understanding of the role of DAMPs in directing the immune response to transplantation has suggested novel avenues for the treatment or prevention of allograft rejection that complement contemporary immunosuppression and could lead to improved outcomes for solid organ recipients.

Autophagy induced by DAMPs facilitates the inflammation response in lungs undergoing ischemia-reperfusion injury through promoting TRAF6 ubiquitination

Lung ischemia-reperfusion (I/R) injury remains one of the most common complications after various cardiopulmonary surgeries. The inflammation response triggered by the released damage-associated molecular patterns (DAMPs) aggravates lung tissue damage. However, little is known about the role of autophagy in the pathogenesis of lung I/R injury. Here, we report that a variety of inflammation-related and autophagy-associated genes are rapidly upregulated, which facilitate the inflammation response in a minipig lung I/R injury model. Left lung I/R injury triggered inflammatory cytokine production and activated the autophagy flux as evidenced in crude lung tissues and alveolar macrophages. This was associated with the release of DAMPs, such as high mobility group protein B1 (HMGB1) and heat shock protein 60 (HSP60). Indeed, treatment with recombinant HMGB1 or HSP60 induced autophagy in alveolar macrophages, whereas autophagy inhibition by knockdown of ATG7 or BECN1 markedly reduced DAMP-triggered production of inflammatory cytokines including IL-1β, TNF and IL12 in alveolar macrophages. This appeared to be because of decreased activation of MAPK and NF-κB signaling. Furthermore, knockdown of ATG7 or BECN1 inhibited Lys63 (K63)-linked ubiquitination of TNF receptor-associated factor 6 (TRAF6) in DAMP-treated alveolar macrophages. Consistently, treatment with 3-MA inhibited K63-linked ubiquitination of TRAF6 in I/R-injured lung tissues in vivo. Collectively, these results indicate that autophagy triggered by DAMPs during lung I/R injury amplifies the inflammatory response through enhancing K63-linked ubiquitination of TRAF6 and activation of the downstream MAPK and NF-κB signaling.

HMGB1 Protein: A Therapeutic Target Inside and Outside the Cell

High-mobility group box 1 protein (HMGB1) is a nonhistone chromosomal protein discovered more than 30 years ago. It is an abundant nuclear protein that has a dual function-in the nucleus, it binds DNA and participates in practically all DNA-dependent processes serving as an architectural factor. Outside the cell, HMGB1 plays a different role-it acts as an alarmine that activates a large number of HMGB1-"competent" cells and mediates a broad range of physiological and pathological responses. This universality makes it an attractive target for innovative therapeutic strategies in the treatment of various diseases. Here we present an overview of the major nuclear and extracellular properties of HMGB1 and describe its interaction with different molecular partners as specific receptors or inhibitors, which are important for its role as a target in multiple diseases. We highlight its pivotal role as a target for cancer treatment at two aspects: first in terms of its substantial impact on the repair capacity of cancer cells, thus affecting the effectiveness of chemotherapy with the antitumor drug cis-platinum and, second, the possibility to be targeted by microRNAs influencing different pathways of human diseases, thus making it a promising candidate for a new strategy for therapeutic interventions against various pathological conditions but mainly cancer.

Necroptosis is a key mediator of enterocytes loss in intestinal ischaemia/reperfusion injury

Cell death is an important biological process that is believed to have a central role in intestinal ischaemia/reperfusion (I/R) injury. While the apoptosis inhibition is pivotal in preventing intestinal I/R, how necrotic cell death is regulated remains unknown. Necroptosis represents a newly discovered form of programmed cell death that combines the features of both apoptosis and necrosis, and it has been implicated in the development of a range of inflammatory diseases. Here, we show that receptor‐interacting protein 1/3 (RIP1/3) kinase and mixed lineage kinase domain‐like protein recruitment mediates necroptosis in a rat model of ischaemic intestinal injury in vivo. Furthermore, necroptosis was specifically blocked by the RIP1 kinase inhibitor necrostatin‐1. In addition, the combined treatment of necrostatin‐1 and the pan‐caspase inhibitor Z‐VAD acted synergistically to protect against intestinal I/R injury, and these two pathways can be converted to one another when one is inhibited. In vitro, necrostatin‐1 pre‐treatment reduced the necroptotic death of oxygen‐glucose deprivation challenged intestinal epithelial cell‐6 cells, which in turn dampened the production of pro‐inflammatory cytokines (tumour necrosis factor‐α and interleukin‐1β), and suppressed high‐mobility group box‐1 (HMGB1) translocation from the nucleus to the cytoplasm and the subsequent release of HMGB1 into the supernatant, thus decreasing the activation of Toll‐like receptor 4 and the receptor for advanced glycation end products. Collectively, our study reveals a robust RIP1/RIP3‐dependent necroptosis pathway in intestinal I/R‐induced intestinal injury in vivo and in vitro and suggests that the HMGB1 signalling is highly involved in this process, making it a novel therapeutic target for acute ischaemic intestinal injury.

HMGB1 blockade differentially impacts pulmonary inflammation and defense responses in poly(I:C)/LPS-exposed heart transplant mice

A large number of recipients are in a compromised immune defense condition because of the routine application of immunosuppressive regimens after heart transplantation. Our previous work demonstrated that blockade of high-mobility group box 1 (HMGB1) prolongs the graft survival. Whether and how HMGB1 blockade impacts respiratory responses against pathogen-like challenge in organ transplant recipients when it improves cardiac graft are not elucidated. At the present study, after abdominal heterotopic heart transplantation, the recipient mice were treated with HMGB1 mAb, and then challenged with poly(I:C) or LPS intratracheally on day 7 post transplantation. We found that the level of bronchoalveolar lavage (BAL) HMGB1 was elevated after heart transplantation, and aggravated responses to respiratory tract poly(I:C)/LPS challenge were observed. HMGB1 neutralizing mAb treatment in poly(I:C)-challenged recipient mice alleviated pulmonary histopathological changes, neutrophil infiltration and inflammatory cytokine release, but unaffected the level of IFN-β, the distribution of CD11b(+)CD27(+)/CD11b(+)CD27(-) NK cell subsets, and CD8(+) T cell responses. In LPS-exposed recipient mice, HMGB1 mAb treatment ameliorated pulmonary inflammatory damage and enhanced the phagocytosis of phagocytic cells. Thus, this study may establish a basis for the application of HMGB1 blockade to improve the outcomes of heart transplant recipients because HMGB1 inhibition ameliorates pulmonary inflammation, but maintains defense-associated responses.