High-mobility group box-1 induces proinflammatory cytokines production of Kupffer cells through TLRs-dependent signaling pathway after burn injury

Stress hyperglycaemia following trauma - a survival benefit or an outcome detriment?

PURPOSE OF REVIEW

Stress hyperglycaemia occur often in critically injured patients. To gain new consideration about it, this review compile current as well as known immunological and biochemical findings about causes and emergence.

RECENT FINDINGS

Glucose is the preferred energy substrate for fending immune cells, reparative tissue and the cardiovascular system following trauma. To fulfil these energy needs, the liver is metabolically reprogrammed to rebuild glucose from lactate and glucogenic amino acids (hepatic insulin resistance) at the expenses of muscles mass and - to a less extent - fat tissue (proteolysis, lipolysis, peripheral insulin resistance). This inevitably leads to stress hyperglycaemia, which is evolutionary preserved and seems to be an essential and beneficial survival response. It is initiated by damage-associated molecular patterns (DAMPs) and pathogen-associated molecular patterns (PAMPs), intensified by immune cells itself and mainly ruled by tumour necrosis factor (TNF)α and catecholamines with lactate and hypoxia inducible factor (HIF)-1α as intracellular signals and lactate as an energy shuttle. Important biochemical mechanisms involved in this response are the Warburg effect as an efficient metabolic shortcut and the extended Cori cycle.

SUMMARY

Stress hyperglycaemia is beneficial in an acute life-threatening situation, but further research is necessary, to prevent trauma patients from the detrimental effects of persisting hyperglycaemia.

EXTRACELLULAR VESICLES AS REGULATORS OF IMMUNE FUNCTION IN TRAUMATIC INJURIES AND SEPSIS

ABSTRACT

Despite advancements in critical care and resuscitation, traumatic injuries are one of the leading causes of death around the world and can bring about long-term disabilities in survivors. One of the primary causes of death for trauma patients are secondary phase complications that can develop weeks or months after the initial insult. These secondary complications typically occur because of systemic immune dysfunction that develops in response to injury, which can lead to immunosuppression, coagulopathy, multiple organ failure, unregulated inflammation, and potentially sepsis in patients. Recently, extracellular vesicles (EVs) have been identified as mediators of these processes because their levels are increased in circulation after traumatic injury and they encapsulate cargo that can aggravate these secondary complications. In this review, we will discuss the role of EVs in the posttrauma pathologies that arise after burn injuries, trauma to the central nervous system, and infection. In addition, we will examine the use of EVs as biomarkers for predicting late-stage trauma outcomes and as therapeutics for reversing the pathological processes that develop after trauma. Overall, EVs have emerged as critical mediators of trauma-associated pathology and their use as a therapeutic agent represents an exciting new field of biomedicine.

Regulation of Key Immune-Related Genes in the Heart Following Burn Injury

Immune cascade is one of major factors leading to cardiac dysfunction after burn injury. TLRs are a class of pattern-recognition receptors (PRRs) that initiate the innate immune response by sensing conserved molecular patterns for early immune recognition of a pathogen. The Rat Toll-Like Receptor (TLR) Signaling Pathway RT² Profiler PCR Array profiles the expression of 84 genes central to TLR-mediated signal transduction and innate immunity, and is a validated tool for identifying differentially expressed genes (DEGs). We employed the PCR array to identify burn-induced cardiac TLR-signaling-related DEGs. A total of 38 up-regulated DEGs and 19 down-regulated DEGs were identified. Network analysis determined that all DEGS had 10 clusters, while up-regulated DEGs had 6 clusters and down-regulated DEGs had 5 clusters. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that DEGs were involved in TLR signaling, the RIG-I-Like receptor signaling pathway, the IL-17 signaling pathway, and the NFkB signaling pathway. Function analysis indicated that DEGs were associated with Toll-like receptor 2 binding, Lipopeptide binding, Toll-like receptor binding, and NAD(P)+ nucleosidase activity. The validation of 18 up-regulated DEGs (≥10-fold change) and 6 down-regulated DEGs (≤5-fold change) demonstrated that the PCR array is a trusted method for identifying DEGs. The analysis of validated DEG-derived protein–protein interaction networks will guide our future investigations. In summary, this study not only identified the TLR-signaling-pathway-related DEGs after burn injury, but also confirmed that the burn-induced cardiac cytokine cascade plays an important role in burn-induced heart dysfunction. The results will provide the novel therapeutic targets to protect the heart after burn injury.

Burn Injury Induces Proinflammatory Plasma Extracellular Vesicles That Associate with Length of Hospital Stay in Women: CRP and SAA1 as Potential Prognostic Indicators

Severe burn injury is a devastating form of trauma that results in persistent immune dysfunction with associated morbidity and mortality. The underlying drivers of this immune dysfunction remain elusive, and there are no prognostic markers to identify at-risk patients. Extracellular vesicles (EVs) are emerging as drivers of immune dysfunction as well as biomarkers. We investigated if EVs after burn injury promote macrophage activation and assessed if EV contents can predict length of hospital stay. EVs isolated early from mice that received a 20% total body surface area (TBSA) burn promoted proinflammatory responses in cultured splenic macrophages. Unbiased LC-MS/MS proteomic analysis of early EVs (<72 h post-injury) from mice and humans showed some similarities including enrichment of acute phase response proteins such as CRP and SAA1. Semi-unbiased assessment of early human burn patient EVs found alterations consistent with increased proinflammatory signaling and loss of inhibition of CRP expression. In a sample of 50 patients with large burn injury, EV SAA1 and CRP were correlated with TBSA injury in both sexes and were correlated with length of hospital stay in women. These findings suggest that EVs are drivers of immune responses after burn injury and their content may predict hospital course.

Absence of Stress Hyperglycemia Indicates the Most Severe Form of Blunt Liver Trauma

Background: Stress hyperglycemia is common in trauma patients. Increasing injury severity and hemorrhage trigger hepatic gluconeogenesis, glycogenolysis, peripheral and hepatic insulin resistance. Consequently, we expect glucose levels to rise with injury severity in liver, kidney and spleen injuries. In contrast, we hypothesized that in the most severe form of blunt liver injury, stress hyperglycemia may be absent despite critical injury and hemorrhage. Methods: All patients with documented liver, kidney or spleen injuries, treated at a university hospital between 2000 and 2020 were charted. Demographic, laboratory, radiological, surgical and other data were analyzed. Results: A total of 772 patients were included. In liver (n = 456), spleen (n = 375) and kidney (n = 152) trauma, an increase in injury severity past moderate to severe (according to the American Association for the Surgery of Trauma, AAST III-IV) was associated with a concomitant rise in blood glucose levels independent of the affected organ. While stress-induced hyperglycemia was even more pronounced in the most severe forms (AAST V) of spleen (median 10.7 mmol/L, p < 0.0001) and kidney injuries (median 10.6 mmol/L, p = 0.004), it was absent in AAST V liver injuries, where median blood glucose level even fell (5.6 mmol/L, p < 0.0001). Conclusions: Absence of stress hyperglycemia on hospital admission could be a sign of most severe liver injury (AAST V). Blood glucose should be considered an additional diagnostic criterion for grading liver injury.

High mobility group box-1 serves a pathogenic role in spinal cord injury via the promotion of pro-inflammatory cytokines

Traumatic spinal cord injury (SCI) is a devastating condition marked by permanent motor, sensory, and autonomic dysfunction, in which the inflammatory response serves an important and preventable role. High mobility group box-1 (HMGB1) is a potent regulator of inflammation in numerous acute and chronic inflammatory conditions.; however, the role of HMGB1 in SCI remains unclear. The present study aimed to characterize the temporal dynamics of HMGB1 release after SCI, to investigate the role of spinal microglia activation in mediating the effects of HMGB1 on SCI, and to explore the therapeutic potential of intrathecal anti-HMGB1 polyclonal antibody on alleviating SCI. The present study demonstrated that HMGB1 expression was increased immediately after traumatic injury of a primary spinal neuron culture. It was found that neutralizing HMGB1 significantly ameliorated SCI pathogenesis and hind limb paralysis. Moreover, the levels of a number of pro-inflammatory cytokines in the SCI lesion were reduced when local HMGB1 was blocked by anti-HMGB1 antibody. In addition, the injured neuron-derived conditioned medium increased TNF-α secretion and the NF-κB pathway in the BV2 microglia cell line via HMGB1. Collectively, these results indicated that HMGB1 served an important role in SCI inflammation and suggested the therapeutic potential of an anti-HMGB1 antibody for SCI.

Plasma extracellular vesicles released after severe burn injury modulate macrophage phenotype and function

Extracellular vesicles (EVs) have emerged as key regulators of immune function across multiple diseases. Severe burn injury is a devastating trauma with significant immune dysfunction that results in an ∼12% mortality rate due to sepsis-induced organ failure, pneumonia, and other infections. Severe burn causes a biphasic immune response: an early (0-72 h) hyper-inflammatory state, with release of damage-associated molecular pattern molecules, such as high-mobility group protein 1 (HMGB1), and proinflammatory cytokines (e.g., IL-1β), followed by an immunosuppressive state (1-2+ wk post injury), associated with increased susceptibility to life-threatening infections. We have reported that early after severe burn injury HMGB1 and IL-1β are enriched in plasma EVs. Here we tested the impact of EVs isolated after burn injury on phenotypic and functional consequences in vivo and in vitro using adoptive transfers of EV. EVs isolated early from mice that underwent a 20% total body surface area burn injury (burn EVs) caused similar hallmark cytokine responses in naïve mice to those seen in burned mice. Burn EVs transferred to RAW264.7 macrophages caused similar functional (i.e., cytokine secretion) and immune gene expression changes seen with their associated phase of post-burn immune dysfunction. Burn EVs isolated early (24 h) induced MCP-1, IL-12p70, and IFNγ, whereas EVs isolated later blunted RAW proinflammatory responses to bacterial endotoxin (LPS). We also describe significantly increased HMGB1 cargo in burn EVs purified days 1 to 7 after injury. Thus, burn EVs cause immune outcomes in naïve mice and macrophages similar to findings after severe burn injury, suggesting EVs promote post-burn immune dysfunction.

Protective Effect of Calcium Dobesilate on Induced AKI in Severely Burned Mice

BACKGROUND

Early acute kidney injury (AKI) predicts a high mortality rate in severely burned patients. However, the pathophysiology of early AKI induced by severe burn has not been well-defined. This study was designed to examine the protective effects of calcium dobesilate (CaD) against severe burn-induced early AKI in mice and explore the mechanism.

METHODS

The shaved backs of mice were immersed in 100°C water for 10 s to make severe burn (40% of the total body surface area). CD-57 male mice were randomly divided into sham, burn, burn + vehicle, and burn + CaD groups. Renal function, reactive oxygen species generation, tubular necrosis, and phosphorylation of mitogen-activated protein kinase, protein kinase B (Akt), and nuclear factor (NF)-κB were measured at 24 and 48 h after the burn. Renal histology, ELISA, qRT-PCR, and Western blotting were performed on the renal tissue of mice to examine the effects and mechanisms at 24 and 48 h after the burn.

RESULTS

Tubular damage, cast formation, and elevations of serum creatinine, BUN, and renal tissue kidney injury molecule 1 levels were all observed in the burned mice, and these were all alleviated in the mice with CaD treatment. In addition, the levels of oxidation-reduction potential and malondialdehyde were decreased, while the activities of the endogenous antioxidative enzymes were increased in the kidney tissues from the mice after CaD treatment. Furthermore, the activities of Akt, p38, extracellular sign-regulated kinase, Jun N-terminal kinase, and NF-κB signaling were increased in the kidney of burned mice and normalized after CaD treatment.

CONCLUSION

This study has established, for the first time, the protective effect of CaD against early AKI in severely burned mice. CaD may exert its protective effect through alleviating oxidative stress, apoptosis, and inflammation, as well as modulating some signaling pathways in the kidney.

Damage-Associated Molecular Patterns and the Systemic Immune Consequences of Severe Thermal Injury

Thermal injury is often associated with a proinflammatory state resulting in serious complications. After a burn, the innate immune system is activated with subsequent immune cell infiltration and cytokine production. Although the innate immune response is typically beneficial, an excessive activation leads to cytokine storms, multiple organ failure, and even death. This overwhelming immune response is regulated by damage-associated molecular patterns (DAMPs). DAMPs are endogenous molecules that are actively secreted by immune cells or passively released by dead or dying cells that can bind to pathogen recognition receptors in immune and nonimmune cells. Recent studies involving animal models along with human studies have drawn great attention to the possible pathological role of DAMPs as an immune consequence of thermal injury. In this review, we outline DAMPs and their function in thermal injury, shedding light on the mechanism of sterile inflammation during tissue injury and identifying new immune targets for treating thermal injury.

Anti-nociceptive effects of Sedum Lineare Thunb. on spared nerve injury-induced neuropathic pain by inhibiting TLR4/NF-κB signaling in the spinal cord in rats

Neuropathic pain is still a critical public health problem worldwide. Thereby, the search for novel and more effective strategies against neuropathic pain is urgently considered. It is known that neuroinflammation plays a crucial role in the pathogenesis of neuropathic pain. SedumLineare Thunb. (SLT), a kind of Chinese herb originated from the whole grass of Crassulaceae plant, was reported to possess anti-inflammatory activity. However, whether SLT has anti-nociceptive effect on neuropathic pain and its possible underlying mechanisms remains poorly elucidated. In this study, a rat model of neuropathic pain induced by spared nerve injury (SNI)was applied. SLT (p.o.) was administered to SNI rats once every day lasting for 14 days. Pain-related behaviors were assessed by using paw withdrawal threshold (PWT) and CatWalk gait parameters. Expression levels of inflammatory mediators and pain-related signaling molecules in the spinal cord were detected using western blotting assay. The results revealed that SLT (30, 100, and 300 mg/kg, p.o.) treatment for SNI rats ameliorated mechanical hypersensitivity in a dose-dependent manner. Application of SLT at the most effective dose of 100 mg/kg to SNI rats not only significantly blocked microglial activation, but also markedly reduced the protein levels of spinal HMGB1, TLR4, MyD88, TRAF6, IL-1β, IL-6, and TNF-α, along with an enhancement in gait parameters. Furthermore, SLT treatment dramatically inhibited the phosphorylation levels of both IKK and NF-κB p65 but obviously improved both IκB and IL-10 protein expression in the spinal cord of SNI rats. Altogether, these data suggested that SLT could suppress spinal TLR4/NF-κB signaling pathway in SNI rats, which might at least partly contribute to its anti-nociceptive action, indicating that SLT may serveas a potential therapeutic agent for neuropathic pain.

Disulfide High-Mobility Group Box 1 Drives Ischemia-Reperfusion Injury in Human Liver Transplantation

BACKGROUND AND AIMS

Sterile inflammation is a major clinical concern during ischemia-reperfusion injury (IRI) triggered by traumatic events, including stroke, myocardial infarction, and solid organ transplantation. Despite high-mobility group box 1 (HMGB1) clearly being involved in sterile inflammation, its role is controversial because of a paucity of patient-focused research.

APPROACH AND RESULTS

Here, we examined the role of HMGB1 oxidation states in human IRI following liver transplantation. Portal blood immediately following allograft reperfusion (liver flush; LF) had increased total HMGB1, but only LF from patients with histopathological IRI had increased disulfide-HMGB1 and induced Toll-like receptor 4-dependent tumor necrosis factor alpha production by macrophages. Disulfide HMGB1 levels increased concomitantly with IRI severity. IRI+ prereperfusion biopsies contained macrophages with hyperacetylated, lysosomal disulfide-HMGB1 that increased postreperfusion at sites of injury, paralleling increased histone acetyltransferase general transcription factor IIIC subunit 4 and decreased histone deacetylase 5 expression. Purified disulfide-HMGB1 or IRI+ blood stimulated further production of disulfide-HMGB1 and increased proinflammatory molecule and cytokine expression in macrophages through a positive feedback loop.

CONCLUSIONS

These data identify disulfide-HMGB1 as a mechanistic biomarker of, and therapeutic target for, minimizing sterile inflammation during human liver IRI.

Hepatic inflammation after burn injury is associated with necroptotic cell death signaling

BACKGROUND

Burn injury still has a high attributable mortality. The elevated mortality rate of severe burns is still concerning. Hepatic inflammation and injury are common after burns and are associated with poor outcomes. Necroptosis is a programmed cell death linked with inflammation. Thus, assessing necroptotic pathways in the liver can lead to new therapeutic modalities to improve mortality after severe burns.

METHODS

Mice underwent 15% total body surface area burn or sham injury. Three hours after burn, the mice were euthanized to collect blood and livers. Histology, injury markers, genes expression, and tissue protein levels were compared between groups.

RESULTS

Compared with sham, burned mice had heightened liver inflammatory cell infiltration and edema. Serum aspartate aminotransferase and alanine aminotransferase were increased by 4.9- and 3.4-fold, respectively, in burned mice relative to sham (p < 0.05). Expression of tumor necrosis factor α, interleukin-6, interleukin-1β, and CXCL1 (KC) genes were elevated in livers of burned mice by 10-, 86-, 10-, and 828-fold, respectively, compared with sham (p < 0.05). Expression of necroptotic genes, namely, receptor-interacting protein kinases 1 and 3, and mixed lineage kinase domain-like in livers of burned mice were increased by 10-, 13-, and 4.5-fold, respectively, relative to sham (p < 0.05). Receptor-interacting protein kinase 1 and phosphorylated mixed lineage kinase domain-like protein levels measured by Western-blot in livers after burn injury were elevated by 22- and 17-fold, respectively, compared with sham (p < 0.05).

CONCLUSION

Liver damage occurs early after burns in mice and is associated with elevation of proinflammatory cytokines, chemokine, and proteins involved in the necroptotic pathway. This study suggests that necroptosis plays a role in the pathogenesis of liver failure secondary to burn injury.

Negative Regulation of Tec Kinase Alleviates LPS-Induced Acute Kidney Injury in Mice via theTLR4/NF-κB Signaling Pathway

Tec kinase is an important mediator in inflammatory immune response that enhances the activity of neutrophils and macrophages. However, information on its function in lipopolysaccharide- (LPS-) induced acute kidney injury (AKI) is limited. This study is aimed at determining whether Tec kinase was a regulator in AKI. An AKI model in mice was successfully established using intraperitoneal LPS. Results showed that the serum levels of creatinine (Cr), blood urea nitrogen (BUN), and cystatin-C (Cys-C) increased after intraperitoneal LPS injection. Renal tissue sustained significantly severe injury as measured by pathological scores. Pretreatment with LFM-A13 improved the function of the kidney in mice and decreased the renal injury score. Enzyme-linked immunosorbent assay showed that LFM-A13 significantly reduced the release of IL-1β and TNF-α in mice exposed to LPS. LFM-A13 can evidently abrogate the expression of Tec protein, MyD88, TLR4, NF-κB p65, and Tec's phosphorylated protein as determined by Western blot. Immunohistochemistry analysis revealed that LFM-A13 markedly downregulated the expression of Tec kinase in renal tubular epithelial cells. In vitro, Tec kinase protein was expressed highly in NRK-52E cells after LPS exposure. Tec-siRNA also decreased IL-1β and TNF-α production and obviously abolished phospho-p65 and phospho-IκBα expression in NRK-52E cell stimulated by LPS; however, Tec-siRNA increased the IκBα level. Altogether, these data suggested that Tec kinase can be a modulating protein in AKI through TLR4/NF-κB activation.

Suppression of Cisplatin-Induced Hepatic Injury in Rats Through Alarmin High-Mobility Group Box-1 Pathway by Ganoderma lucidum: Theoretical and Experimental Study

Purpose

Drug-induced liver injury (DILI) is the most common cause of acute liver failure. The aim of this study was to investigate the molecular mechanisms by which Ganoderma lucidum mushroom (GLM) may ameliorate cisplatin (CP)-induced hepatotoxicity theoretically and experimentally.

Materials and Methods

Thirty-six male Sprague-Dawley (SD) rats were divided into six groups, two of them are normal and Ganoderma lucidum control groups. Liver injury was induced by a single dose of CP (12 mg/kg i.p) in four groups, one of them is CP control group. Besides cisplatin injection in day 1, rats in groups (4–6) were subjected to GLM (500 mg/kg/day) either every other day or daily oral dose or via i.p injection for 10 consecutive days.

Results

In this study, GLM supplementation caused significant reduction of elevated high-mobility group box-1 (HMGB-1) with a concurrent decline in TNF-α and upregulation of IL-10 compared to the CP group (P<0.05). The histopathological and fibrosis evaluation significantly confirmed the improvement upon simultaneous treatment with GLM. Moreover, immunohistochemical examination also confirmed the recovery following GLM treatment indicated by downregulation of NF-κB, p53 and caspase-3 along with upsurge of B-cell lymphoma 2 (Bcl-2) expression (P<0.05). GLM treatment significantly decreased serum levels of hepatic injury markers; ALT, AST, T. bilirubin as well as oxidative stress markers; MDA and H₂O₂ with a concomitant increase in hepatic GSH and SOD. Also, the performed docking simulation of ganoderic acid exhibited good fitting and binding with HMGB-1 through hydrogen bond formation with conservative amino acids which gives a strong evidence for its hepatoprotective effect and may interpret the effect of Ganoderma lucidum.

Conclusion

GLM attenuated hepatic injury through downregulation of HMGB-1/NF-kB and caspase-3 resulted in modulation of the induced oxidative stress and the subsequent cross-talk between the inflammatory and apoptotic cascade indicating its promising role in DILI.

Notoginsenoside R1 protects human keratinocytes HaCaT from LPS-induced inflammatory injury by downregulation of Myd88

Burn injury is a gigantic challenge in public health which brings multiple negative effects to patients both in physical and spiritual aspects. Inflammation plays vital roles in the progression of burn injury, and our study investigated whether notoginsenoside R1 (NGR1) alleviated lipopolysaccharide (LPS)-induced human keratinocyte HaCaT cell inflammatory injury. Inflammatory injury was induced by LPS in HaCaT cells. Stimulated cells were then treated by NGR1 in different concentrations. Cell viability and cell apoptosis were detected by Cell Counting Kit-8 and flow cytometry, respectively. The concentration of tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6) was measured by enzyme-linked immunosorbent assay (ELISA). The accumulated levels of apoptosis-related proteins (caspase-3 and caspase-9), nuclear factor κB (NF-κB), p38 mitogen-activated protein kinase (p38MAPK) signal pathways–related proteins (p65, IκBα, and p38MAPK), and myeloid differentiation primary response 88 (MyD88) were examined by western blot. Transfection was used to alter the expression of MyD88. We found that LPS stimulated HaCaT cells and induced cell inflammation, evidenced by decreasing cell viability, increasing cell apoptosis, and elevating TNF-α and IL-6 expressions. Then, we found that NGR1 reversed the results by enhancing cell viability, inhibiting cell apoptosis, and reducing TNF-α and IL-6 expressions. In addition, NGR1 decreased the phosphorylation of p65, IκBα, and p38MAPK, which increased by LPS. Moreover, NGR1 negatively regulated the expression of MyD88, and transfection with pMyD88 led to the opposite results with what showed by NGR1 in LPS-stimulated HaCaT cells. To sum up, NGR1 alleviates LPS-induced HaCaT cell inflammatory injury by downregulation of MyD88, as well as inactivation of NF-κB and p38MAPK signal pathways.

Electroacupuncture Alleviates Spared Nerve Injury-Induced Neuropathic Pain And Modulates HMGB1/NF-κB Signaling Pathway In The Spinal Cord

Background

Neuropathic pain with complications greatly affects patients worldwide. High mobility group box 1 (HMGB1) has been shown to contribute to the pathogenesis of neuropathic pain; thus, suppression of HMGB1 may provide a novel therapeutic option for neuropathic pain. Electroacupuncture (EA) has been indicated to be effective in attenuating neuropathic pain, but the underlying mechanism remains to be fully clarified. We aim to explore whether 2Hz EA stimulation regulates the spinal HMGB1/NF-κB signaling in neuropathic pain induced by spared nerve injury (SNI).

Materials and methods

Paw withdrawal threshold and CatWalk gait analysis were used to assess the effect of 2Hz EA on pain-related behaviors in SNI rats. Administration of 2Hz EA to SNI rats once every other day lasting for 21 days. Expression of spinal protein molecules were detected using Western blot and immunofluorescence staining.

Results

It was found that SNI significantly induced mechanical hypersensitivity and decrease of gait parameters, and subsequently increased the levels of HMGB1, TLR4, MyD88, and NF-κB p65 protein expression. 2Hz EA stimulation led to remarkable attenuation of mechanical hypersensitivity, upregulation of spinal HMGB1, TLR4, MyD88, and NF-κB p65 protein expressions induced by SNI, and significant improvement in gait parameters. Furthermore, immunofluorescence staining also confirmed that 2Hz EA obviously suppressed the co-expression of microglia activation marker CD11b and TLR4 or MyD88, as well as the activation of NF-κB p65 in SNI rats.

Conclusion

This study suggested that blockade of HMGB1/NF-κB signaling in the spinal cord may be a promising therapeutic approach for 2Hz EA management of SNI-induced neuropathic pain.

High mobility group box 1 protein released in the course of aseptic necrosis of tissues sensitizes rats to pyrogenic effects of lipopolysaccharide

It is still an open question as to whether or not aseptic injuries affect the generation of fever due to exogenous pyrogens including bacterial products. Therefore, in the present paper we have investigated the course of endotoxin fever in rats induced with lipopolysaccharide (LPS; given intraperitoneally in a dose of 50 μg/kg) 48 h after subcutaneous administration of turpentine oil (TRP; 0.1 mL per rat) that causes aseptic necrosis of tissues. We found that febrile response was significantly augmented in the animals pre-treated with turpentine compared to control rats (pre-treated with saline), and that observed excessive elevation of body temperature (Tb) was accompanied by enhanced release of fever mediators: interleukin-6 (IL-6) and prostaglandin E₂ (PGE₂) into plasma. Moreover, we found that sensitization to pyrogenic effects of lipopolysaccharide was associated with the increase in plasma level of high mobility group box 1 protein (HMGB1), one of the best-known damage-associated molecular patterns (DAMP), which was recently discovered as inflammatory mediator. Since the injection of anti-HMGB1 antibodies weakened observed hyperpyrexia in the animals pre-treated with turpentine, we conclude that HMGB1 is a plasma-derived factor released in the course of aseptic injury that enhances pyrogenic effects of LPS.

HMGB1 from Lampetra japonica promotes inflammatory activation in supraneural body cells

High mobility group box protein 1 (HMGB1) acts as a potent proinflammatory cytokine that involves in the pathogenesis of diverse inflammatory and infectious disorders. In previous study, we identified a homolog of HMGB1 in the Lampetra japonica(L-HMGB1), and further revealed that L-HMGB1 was able to induce the production of tumor necrosis factor-α (TNF-α) in activated human acute monocytic leukemia cells. However, the role of L-HMGB1 played in lamprey was unknown. Here, we found that L-HMGB1 was located in the cytoplasm of lamprey leukocytes and supraneural body (SB) cells. Importantly, we demonstrated that L-HMGB1 participated in activation of various key molecules in inflammation signaling pathway. LPS also promoted the release of L-HMGB1 from SB cells similar to Hu-HMGB1, and then extracellular L-HMGB1 in turn induced the release of cytokines. This study revealed that the synergistic action of LPS and L-HMGB1 played a crucial role in inflammation in lamprey. Our results suggested that lampreys used L-HMGB1 to activate their innate immunity for the purpose of pathogen defense.

p38MAPK plays a pivotal role in the development of acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a life-threatening illness characterized by a complex pathophysiology, involving not only the respiratory system but also nonpulmonary distal organs. Although advances in the management of ARDS have led to a distinct improvement in ARDS-related mortality, ARDS is still a life-threatening respiratory condition with long-term consequences. A better understanding of the pathophysiology of this condition will allow us to create a personalized treatment strategy for improving clinical outcomes. In this article, we present a general overview p38 mitogen-activated protein kinase (p38MAPK) and recent advances in understanding its functions. We consider the potential of the pharmacological targeting of p38MAPK pathways to treat ARDS.

Sodium butyrate inhibits the production of HMGB1 and attenuates severe burn plus delayed resuscitation-induced intestine injury via the p38 signaling pathway

BACKGROUND

Inflammatory response triggered by high mobility group box-1 (HMGB1) protein and oxidative stress play critical roles in the intestinal injury after severe burn. Sodium butyrate, a histone deacetylase inhibitor, has potential anti-inflammatory properties, inhibiting the expression of inflammatory mediators such as HMGB1 in diverse diseases. This study was designed to investigate the effects of sodium butyrate on severe burn plus delayed resuscitation-induced intestine injury, intestinal expressions of HMGB1 and intracellular adhesion molecule-1 (ICAM-1), oxidative stress, and signal transduction pathway changes in rats.

MATERIALS AND METHODS

Fifty-six Sprague-Dawley rats were divided into 3 groups randomly: (1) sham group, animals underwent sham burn; (2) burn group, rats subjected to full-thickness burns of 30% total body surface area (TBSA) and received 2ml/kg/TBSA lactated Ringer solution for resuscitation at 6, 12, and 36h after burn injury; (3) burn plus sodium butyrate (burn+SB) group, animals received burn injury and lactated Ringer solution with sodium butyrate inside for resuscitation in the same manner. Diamine oxidase (DAO) concentration in plasma was measured by enzyme-linked immunosorbent assay. Intestinal fatty acid binding protein (I-FABP) and ICAM-1 expressions in the intestine were analyzed by immunohistochemical method. HMGB1 and p38 mitogen-activated protein kinase (MAPK) expressions in the intestine tissues were examined by Western blot. The intestinal concentration of malondialdehyde (MDA) was also determined.

RESULTS

Intestinal HMGB1 expression was significantly increased in burn group compared with sham group. Sodium butyrate administration significantly inhibited the HMGB1 expression in the intestine, decreased the DAO concentration in plasma, reduced the intestinal I-FABP expression, and improved the intestinal histologic changes induced by burn injury plus delayed resuscitation. Sodium butyrate treatment also markedly reduced the increase of intestinal ICAM-1 expression and MDA content, and inhibited p38 MAPK activity in the intestine of severely burned rats with delayed resuscitation.

CONCLUSIONS

Sodium butyrate inhibits HMGB1 expression which could be attributed to p38 MAPK signal transduction pathway and decreases intestinal inflammatory responses and oxidative stress, thus attenuates burn plus delayed resuscitation-induced intestine injury.

Hypertonic saline resuscitation protects against kidney injury induced by severe burns in rats

BACKGROUND

Proper fluid resuscitation can relieve visceral damage and improve survival in severely burned patients. This study compared the effectiveness of resuscitation with 400mEq/L hypertonic saline (HS) and sodium lactate Ringer's solution (LR) in rats with kidney injury caused by burn trauma.

METHODS

Rats (Sprague-Dawley) underwent burn injury and were randomized into sham, LR, and HS groups. Samples from the kidney were assayed for water content ratio, histopathology, and oxidative stress (superoxide dismutase (SOD) and malondialdehyde (MDA)). Serum sodium, renal function (creatinine and cystatin (Cys)-C), and inflammatory response (tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and high mobility group protein box (HMGB)-1) were also examined as serum markers.

RESULTS

Hypertonic saline resuscitation reduced the renal water content ratio and improved renal histopathology caused by severe burns. This effect was accompanied by reductions in serum creatinine and Cys-C as well as TNF-α, IL-1β, and HMGB1. Serum sodium concentration and SOD activity were increased, whereas MDA content was decreased in the kidney tissue of the HS group.

CONCLUSIONS

The data indicate that 400mEq/L HS solution reduces hyponatremia and renal edema, inhibits the release of inflammatory mediators, and alleviates oxidative stress injury, thus protecting against kidney injury induced by severe burns.

High-Mobility Group Box-1 and Liver Disease

High‐mobility group box‐1 (HMGB1) is a ubiquitous protein. While initially thought to be simply an architectural protein due to its DNA‐binding ability, evidence from the last decade suggests that HMGB1 is a key protein participating in the pathogenesis of acute liver injury and chronic liver disease. When it is passively released or actively secreted after injury, HMGB1 acts as a damage‐associated molecular pattern that communicates injury and inflammation to neighboring cells by the receptor for advanced glycation end products or toll‐like receptor 4, among others. In the setting of acute liver injury, HMGB1 participates in ischemia/reperfusion, sepsis, and drug‐induced liver injury. In the context of chronic liver disease, it has been implicated in alcoholic liver disease, liver fibrosis, nonalcoholic steatohepatitis, and hepatocellular carcinoma. Recently, specific posttranslational modifications have been identified that could condition the effects of the protein in the liver. Here, we provide a detailed review of how HMGB1 signaling participates in acute liver injury and chronic liver disease.

Inhibitory effects of miR-25 targeting HMGB1 on macrophage secretion of inflammatory cytokines in sepsis

High mobility group box 1 (HMGB1) can promote the migration of macrophages and the release of inflammatory cytokines, functions associated with the occurrence of sepsis. The role of microRNA (miR)-25 in the targeted regulation of HMGB1 expression and the release of macrophage inflammatory cytokines remains uncharacterized. The present study investigated the association between miR-25, HMGB1 and sepsis by analyzing the expression of miR-25 and HMGB1 in patients with sepsis. The present study also investigated whether miR-25 serves a role in targeting the regulation of HMGB1 expression and macrophage inflammatory factor release. Patients with sepsis were selected from the Intensive Care Unit, and serum levels of HMGB1. The expression of miR-25 and HMGB1 in serum and peripheral blood mononuclear cells (PBMCs) was compared. Macrophages were cultured in vitro and divided into 5 groups following treatment with lipopolysaccharide (LPS). The expression levels of miR-25, HMGB1, phosphorylated (p-)p65, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and HMGB-1 were compared, and the migration ability of cells was investigated by Transwell assays. Compared with the healthy controls, patients with sepsis exhibited elevated expression of HMGB1 and decreased expression of miR-25 in serum and PBMCs. Following treatment with LPS, the expression of HMGB1 and p-p65 was elevated, and the expression of miR-25 was decreased in macrophages compared with untreated cells. Following transfection with miR-25 mimics and/or short interfering RNA-HMGB1, the expression of HMGB1 in macrophages decreased significantly, the expression of p-p65, HMGB-1, TNF-α and IL-6 in the culture solution were also decreased, and the migration ability of macrophages was attenuated. The present study suggests that miR-25 attenuated the induction of HMGB1 by LPS, decreased the activity of nuclear factor-κB and the transcriptional activation of TNF-α and IL-6, and suppressed the migration of macrophages. Inhibiting expression of miR-25 may serve a role in upregulating HMGB1 expression, promoting the secretion of inflammatory cytokines and resulting in sepsis.

Follicular B Cells Promote Atherosclerosis via T Cell–Mediated Differentiation Into Plasma Cells and Secreting Pathogenic Immunoglobulin G

Objective—

B cells promote or protect development of atherosclerosis. In this study, we examined the role of MHCII (major histocompatibility II), CD40 (cluster of differentiation 40), and Blimp-1 (B-lymphocyte–induced maturation protein) expression by follicular B (FO B) cells in development of atherosclerosis together with the effects of IgG purified from atherosclerotic mice.

Approach and Results—

Using mixed chimeric Ldlr −/− mice whose B cells are deficient in MHCII or CD40, we demonstrate that these molecules are critical for the proatherogenic actions of FO B cells. During development of atherosclerosis, these deficiencies affected T–B cell interactions, germinal center B cells, plasma cells, and IgG. As FO B cells differentiating into plasma cells require Blimp-1, we also assessed its role in the development of atherosclerosis. Blimp-1-deficient B cells greatly attenuated atherosclerosis and immunoglobulin—including IgG production, preventing IgG accumulation in atherosclerotic lesions; Blimp-1 deletion also attenuated lesion proinflammatory cytokines, apoptotic cell numbers, and necrotic core. To determine the importance of IgG for atherosclerosis, we purified IgG from atherosclerotic mice. Their transfer but not IgG from nonatherosclerotic mice into Ldlr −/− mice whose B cells are Blimp-1-deficient increased atherosclerosis; transfer was associated with IgG accumulating in atherosclerotic lesions, increased lesion inflammatory cytokines, apoptotic cell numbers, and necrotic core size.

Conclusions—

The mechanism by which FO B cells promote atherosclerosis is highly dependent on their expression of MHCII, CD40, and Blimp-1. FO B cell differentiation into IgG-producing plasma cells also is critical for their proatherogenic actions. Targeting B–T cell interactions and pathogenic IgG may provide novel therapeutic strategies to prevent atherosclerosis and its adverse cardiovascular complications.

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.

Inhibitor of Tec kinase, LFM-A13, decreases pro-inflammatory mediators production in LPS-stimulated RAW264.7 macrophages via NF-κB pathway

Tec kinase, a prototypical member of the Tec tyrosine kinases family, was shown to mainly govern lymphocyte proliferation. In the present study, we investigated the role of Tec kinase in acute inflammatory response in lipopolysaccharide (LPS) challenge. First, we demonstrate that Tec kinase activity was observed in RAW264.7 macrophages exposed to LPS. Tec and phosphorylated Tec expression were upregulated in a dose- and time-dependent manner after LPS stimulation. LPS increased monocyte chemotactic protein (MCP)-1 secretion and intercellular adhesion molecule (ICAM)-1 expression, and increasing mRNA expression was consistently observed. LPS also induced IκBα phoshporylaytion and its degradation, increased NF-κB p65 phoshporylaytion and translocation to nuclei in RAW264.7 cells. Pretreatment with LFM-A13 decreased LPS-induced cytokines and chemokines production and mRNA levels, blocked NF-κB transactivation. These effects of LPS were also prevented by Tec-siRNA. Additionally, LFM-A13 or Tec-siRNA obviously inhibited LPS-induced TGFβ-activated kinase 1(TAK1) phosphorylation. Taken together, our results suggest that Tec kinase involves in acute inflammation process in LPS-stimulated RAW264.7 cells, at least mediated by activating TAK1/ NF-κB signal pathway.

Toll-Like Receptor Signaling in Burn Wound Healing and Scarring

Significance: Damage-associated molecular patterns (DAMPs) and pathogen-associated molecular patterns (PAMPs) emanate from burn-injured tissue and enter systemic circulation. Locally and systemically, they activate pattern-recognition receptors, including toll-like receptors (TLRs), to stimulate cytokine secretion, which in the severest burns typically results in extreme systemic cytokine levels, a dysfunctioning immune system, infection, impaired healing, and excessive scarring. This system-wide disruption of homeostasis can advance to life-threatening, multiorgan dysfunction syndrome. Knowledge of DAMP- and PAMP-TLR signaling may lead to treatments that ameliorate local and systemic inflammation and reduce scarring and other burn injury sequela. Recent Advances: Many PAMPs and DAMPs, the TLRs they activate, and their downstream signaling molecules have been shown to contribute to local and systemic inflammation and tissue damage following burn injury. Critical Issues: Whether TLR-pathway-targeting treatments applied at different times postburn injury might improve scarring remains an open question. The evaluation of this question requires the use of appropriate preclinical and clinical burn models carried out until after mature scar has formed. Future Directions: After TLR-pathway-targeting treatments are evaluated in porcine burn wound models and their safety is demonstrated, they can be tested in proof-of-concept clinical burn wound models.

The liver is a metabolic and immunologic organ: A reconsideration of metabolic decompensation due to infection in inborn errors of metabolism (IEM)

Metabolic decompensation in inborn errors of metabolism (IEM) is characterized by a rapid deterioration in metabolic status leading to life-threatening biochemical perturbations (e.g. hypoglycemia, hyperammonemia, acidosis, organ failure). Infection is the major cause of metabolic decompensation in patients with IEM. We hypothesized that activation of the immune system during infection leads to further perturbations in end-organ metabolism resulting in increased morbidity. To address this, we established model systems of metabolic decompensation due to infection. Using these systems, we have described the pathologic mechanisms of metabolic decompensation as well as changes in hepatic metabolic reserve associated with infection. First and foremost, our studies have demonstrated that the liver experiences a significant local innate immune response during influenza infection that modulates hepatic metabolism. Based on these findings, we are the first to suggest that the role of the liver as a metabolic and immunologic organ is central in the pathophysiology of metabolic decompensation due to infection in IEM. The dual function of the liver as a major metabolic regulator and a lymphoid organ responsible for immunosurveillance places this organ at risk for hepatotoxicity. Mobilization of hepatic reserve and the regenerative capacity of a healthy liver compensates for this calculated risk. However, activation of the hepatic innate immune system may be deleterious in IEM. Based on this assertion, strategies aimed at modulating the innate immune response may be a viable target for intervention in the treatment of hepatic metabolic decompensation.

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.

High-mobility Group Box 1 Is Associated with the Inflammatory Infiltration and Alveolar Bone Destruction in Rats Experimental Periapical Lesions

INTRODUCTION

This study was conducted to observe the immunohistochemical localization of high-mobility group box 1 (HMGB1) and its receptor, Toll-like receptor 4 (TRL4), in the development of periapical lesions induced in rats. The possible role of these molecules in the pathogenesis of periapical lesions was also explored.

METHODS

Periapical lesions developed within 35 days after mandibular first molar pulp exposure in Wistar rats. The animals were randomly killed at 0, 7, 14, 21, 28, and 35 days after pulp exposure. The jaws that contained the first molar were obtained and prepared for histologic analysis, enzyme histochemistry, immunohistochemistry, and double immunofluorescence staining.

RESULTS

From day 0 to 35, the areas of periapical bone loss increased and appeared to be stabilized on day 35. A few HMGB1-positive, TLR4-positive cells and osteoclasts could be observed on day 7. From day 7 to 28, the HMGB1 and TLR4 protein expression increased and subsequently remained stable. The number of osteoclasts multiplied from day 0 to 14 and then gradually decreased from day 14 to 35. Double immunofluorescence staining results showed HMGB1-positive, TLR4-positive cells around periapical lesions surrounding the apical foramen.

CONCLUSIONS

Thus, HMGB1 and TLR4 may be associated with the pathogenesis of the periapical lesions.

Effect of disrupted mitochondria as a source of damage-associated molecular patterns on the production of tumor necrosis factor α by splenocytes from dogs

OBJECTIVE To evaluate the effects of damage-associated molecular patterns (DAMPs) derived from disrupted mitochondria on canine splenocytes and other immune cells. SAMPLES Liver, spleen, and bone marrow samples obtained from 8 cadavers of healthy research Beagles that had been euthanized for other purposes. PROCEDURES Mitochondria were obtained from canine hepatocytes, and mitochondrial DAMPs (containing approx 75% mitochondrial proteins) were prepared. Mitochondrial DAMPs and the nuclear cytokine high-mobility group box protein 1 were applied to splenocytes, bone marrow-differentiated dendritic cells, and a canine myelomonocytic cell (DH82) line for 6 or 24 hours. Cell culture supernatants from splenocytes, dendritic cells, and DH82 cells were assayed for tumor necrosis factor α with an ELISA. Expression of tumor necrosis factor α mRNA in splenocytes was evaluated with a quantitative real-time PCR assay. RESULTS In all cell populations evaluated, production of tumor necrosis factor α was consistently increased by mitochondrial DAMPs at 6 hours (as measured by an ELISA). In contrast, high-mobility group box protein 1 did not have any independent proinflammatory effects in this experimental system. CONCLUSIONS AND CLINICAL RELEVANCE The study revealed an in vitro inflammatory effect of mitochondrial DAMPs (containing approx 75% mitochondrial proteins) in canine cells and validated the use of an in vitro splenocyte model to assess DAMP-induced inflammation in dogs. This experimental system may aid in understanding the contribution of DAMPs to sepsis and the systemic inflammatory response syndrome in humans. Further studies in dogs are needed to validate the biological importance of these findings and to evaluate the in vivo role of mitochondrial DAMPs in triggering and perpetuating systemic inflammatory states.

Toll-like receptor responses are suppressed in trauma ICU patients

BACKGROUND

Inflammation and activation of the innate immune system are often associated with traumatic injury and may involve alterations in toll-like receptor (TLR)-mediated responses.

METHODS

A prospective observational study was designed and conducted. Twenty-one severely injured (ISS = 16-41) trauma intensive care unit (ICU) patients and six healthy volunteers that served as controls were enrolled. Anticoagulated whole blood was collected at 2-12 d after ICU admission and incubated in the presence of media alone (baseline), zymosan (TLR2 agonist) or lipopolysaccharide (LPS; TLR4 agonist) for 3 h. Supernatant levels of inflammatory cytokines (IL-1β, IL-6, IL-10, and TNFα) were determined.

RESULTS

TLR2-mediated and TLR4-mediated activation of whole blood cell cultures from both healthy volunteers and subjects-induced elevated cytokine levels over that observed in unstimulated cultures. Baseline values of IL-6 were significantly elevated in subject cultures as compared to healthy volunteers. Healthy volunteer cultures had 2-3-fold greater levels of IL-6 and TNFα than subject cultures when stimulated with zymosan (TLR2 agonist) or LPS (TLR4 agonist). IL-1β and IL-10 levels did not differ significantly between healthy volunteers and subjects.

CONCLUSIONS

The ability of circulating leukocytes from trauma ICU patients to be activated by TLR agonists is markedly suppressed and may play a role in the development of subsequent infectious complications.

Hypoxia/reoxygenation-induced HMGB1 translocation and release promotes islet proinflammatory cytokine production and early islet graft failure through TLRs signaling

High-mobility group box 1 (HMGB1) translocation and release, which is involved in several tissue types of ischemia-reperfusion injuries, activate innate immunity by inducing proinflammatory cytokine production through its interaction with toll-like receptors (TLRs). Our objective was to determine the role of HMGB1 and the degree of activation of TLR-related signal transduction pathways in hypoxia/reoxygenation (H/R)-induced proinflammatory cytokine production and intra-islet graft inflammation. After islets are exposed to hypoxia-reoxygenation for 24h, TLR2/4 expression and TLR-mediated signaling was up-regulated in islets, and HMGB1 was translocated from the nucleus to the cytoplasm and released to the extracellular space. With H/R exposure, proinflammatory cytokine production (IL-1β and TNF-α) and islet injury were significantly increased, and these effects depend on TLR2/4 signaling pathways. Exogenous HMGB1 also induces islet inflammation and increases the phosphorylation of STAT3, p38 and IκBα in wild-type islets. TLR2 deficiency in TLR2-KO islets resulted in the inhibition of IL-1β production and STAT3/p38 phosphorylation after HMGB1 exposure. TLR4 deficiency in TLR4-KO islets resulted in the inhibition of TNF-α production and IκBα phosphorylation after HMGB1 exposure. Pre-incubation of the STAT3, p38, or NF-κB inhibitors significantly inhibited HMGB1-induced IL-1β or TNF-α production in islets, but the effect of HMGB1 or H/R-induced islet injury was not counteracted by a separate treatment of the STAT3 inhibitor, p38 inhibitor, or NF-κB inhibitors. HMGB1 inhibition by ethyl pyruvate or blockade by neutralizing antibodies significantly decreased the phosphorylation of STAT3, p38 and IκBα, the production of IL-1β and TNF-α, and the islet injury in wild-type islets after exposure to H/R and significantly improved early islet graft failure. Thus, our results suggest that HMGB1 released from H/R induced islets works in an autocrine manner to up-regulate STAT or p38 and augment IL-1β production via TLR2, and up-regulate NF-κB and augment TNF-α production via TLR4 in intra-islet, which are associated with H/R-induced islet injury and early graft failure.

HMGB1 translocation and release mediate cigarette smoke-induced pulmonary inflammation in mice through a TLR4/MyD88-dependent signaling pathway

Cigarette smoke (CS) increases up-regulation of TLR4-mediated signaling and induces TLR4-dependent inflammation in lungs. CS exposure–induced HMGB1 translocation and release of HMGB1 controls CS-induced inflammatory response. MGB1 induces TLR4-mediated proinflammatory cytokine production and activates NF-κB and JNK/p38 pathways.

We performed studies to determine the role of high-mobility group box 1 (HMGB1) in cigarette smoke (CS)–induced pulmonary inflammation. After mice were exposed to five cigarettes four times a day for 3 d, toll-like receptor 4 (TLR4) expression and TLR4-mediated signaling were significantly up-regulated, and HMGB1 had translocated from the nucleus to the cytoplasm in lung epithelial cells and then been released into the extracellular lung space. On CS exposure, inflammatory cell recruitment and proinflammatory cytokine production were significantly increased in lung tissue and bronchoalveolar lavage, and these effects depended on the TLR4 signaling pathway. HMGB1 inhibition decreased the CS-induced inflammatory response, whereas treatment with exogenous HMGB1 aggravated the damage and increased the phosphorylation of JNK, p38, and IκBα in the lungs of wild-type mice but not in TLR4-knockout mice. Blockade of TLR4 action or TLR4 knockout significantly inhibited HMGB1-induced proinflammatory cytokine production in mouse tracheal epithelial (MTE) cells and lung tissues. In addition, a MyD88 deficiency inhibited JNK, p38, and IκBα phosphorylation, and this effect was associated with the suppressed production of TNF-α and IL-1β in MTE cells and lung tissues in response to CS stimulation. Thus HMGB1 activates the NF-κB and JNK/p38 pathways through TLR4/MyD88-dependent signaling and induces an inflammatory response in lungs exposed to CS.

Damage-associated molecular patterns (DAMPs) released after burn are associated with inflammation and monocyte activation

Burns are associated with activation of the innate immunity that can contribute to complications. Damage-associated molecular patterns (DAMPs) released after tissue injury play a critical role in the activation of the innate immunity, which appears to be mediated via toll-like receptors (TLRs). Previous findings have shown that TLRs and TLR-mediated responses are up-regulated after burn. Nonetheless, it is unclear what impact burn has on circulating levels of DAMPs. To study this, male C57BL/6 mice were subjected to a major burn or sham procedure. Three hours to 7days thereafter, plasma was collected and assayed for the representative DAMPs (i.e., HMGB1, cytochrome C, DNA and S100A) and extracellular cleavage products (fibronectin and hyaluronan). HMGB1, cytochrome C, fibronectin and hyaluronan levels were elevated in a time-dependent manner after burn as compared to sham levels. A significant elevation in TNF-α, IL-6 and IL-10 cytokine plasma levels was also found after burn. All cytokine levels were increased as early as 3h and remained elevated up to 24h. Circulating CD11b⁺ monocytes were increased at 24h after burn and showed increased expression of TLR-2. In conclusion, these findings support the concept that burn-induced elevations in circulating DAMPs are in part responsible for monocyte activation and the development of inflammatory complications under such conditions and warrants further investigation.

High-Mobility Group Box 1 (HMGB1) Is Elevated Systemically in Persons with Acute or Chronic Traumatic Spinal Cord Injury

Inflammation in traumatic spinal cord injury (SCI) has been proposed to promote damage acutely and oppose functional recovery chronically. However, we do not yet understand the signals that initiate or prolong inflammation in persons with SCI. High-Mobility Group Box 1 (HMGB1) is a potent systemic inflammatory cytokine-or damage-associated molecular pattern molecule (DAMP)-studied in a variety of clinical settings. It is elevated in pre-clinical models of traumatic spinal cord injury (SCI), where it promotes secondary injury, and strategies that block HMGB1 improve functional recovery. To investigate the potential translational relevance of these observations, we measured HMGB1 in plasma from adults with acute (≤ 1 week post-SCI, n = 16) or chronic (≥ 1 year post-SCI, n = 47) SCI. Plasma from uninjured persons (n = 51) served as controls for comparison. In persons with acute SCI, average HMGB1 levels were significantly elevated within 0-3 days post-injury (6.00 ± 1.8 ng/mL, mean ± standard error of the mean [SEM]) or 4-7 (6.26 ± 1.3 ng/mL, mean ± SEM), compared with controls (1.26 ± 0.24 ng/mL, mean ± SEM; p ≤ 0.001 and p ≤ 0.01, respectively). In persons with chronic SCI who were injured for 15 ± 1.5 years (mean ± SEM), HMGB1 also was significantly elevated, compared with uninjured persons (3.7 ± 0.69 vs. 1.26 ± 0.24 ng/mL, mean ± SEM; p ≤ 0.0001). Together, these data suggest that HMGB1 may be a common, early, and persistent danger signal promoting inflammation in individuals with SCI.

Age-dependent alterations to paraventricular nucleus insulin-like growth factor 1 receptor as a possible link between sympathoexcitation and inflammation

Modifications to neural circuits of the paraventricular hypothalamic nucleus (PVN) have been implicated in sympathoexcitation and systemic cardiovascular dysfunction. However, to date, the role of insulin-like growth factor 1 receptor (IGF-1R) expression on PVN pathophysiology is unknown. Using confocal immunofluorescence quantification and electrophysiological recordings from acute PVN slices, we investigated the mechanism through which age-dependent IGF-1R depletion contributes to the progression of inflammation and sympathoexcitation in the PVN of spontaneously hypertensive rats (SHR). Four and twenty weeks old SHR and Wistar Kyoto (WKY) rats were used for this study. Our data showed that angiotensin I/II and pro-inflammatory high mobility box group protein 1 (HMGB1) exhibited increased expression in the PVN of SHR versus WKY at 4 weeks (p < 0.01), and were even more highly expressed with age in SHR (p < 0.001). This correlated with a significant decrease in IGF-1R expression, with age, in the PVN of SHR when compared with WKY (p < 0.001) and were accompanied by related changes in astrocytes and microglia. In subsequent analyses, we found an age-dependent change in the expression of proteins associated with IGF-1R signaling pathways involved in inflammatory responses and synaptic function in the PVN. MAPK/ErK was more highly expressed in the PVN of SHR by the fourth week (p < 0.001; vs. WKY), while expression of neuronal nitric oxide synthase (p < 0.001) and calcium-calmodulin-dependent kinase II alpha (CamKIIα; p < 0.001) were significantly decreased by the 4th and 20th week, respectively. Age-dependent changes in MAPK/ErK expression in the PVN correlated with an increase in the expression of vesicular glutamate transporter (p < 0.001 vs. WKY), while decreased levels of CamKIIα was associated with a decreased expression of tyrosine hydroxylase (p < 0.001) by the 20th week. In addition, reduced labeling for ϒ-aminobutyric acid in the PVN of SHR (p < 0.001) correlated with a decrease in neuronal nitric oxide synthase labeling (p < 0.001) when compared with the WKY by the 20th week. Electrophysiological recordings from neurons in acute slice preparations of the PVN of 4 weeks old SHR revealed spontaneous post-synaptic currents of higher frequency when compared with neurons from WKY PNV slices of the same age (p < 0.001; n = 14 cells). This also correlated with an increase in PSD-95 in the PVN of SHR when compared with the WKY (p < 0.001). Overall, we found an age-dependent reduction of IGF-1R, and related altered expression of associated downstream signaling molecules that may represent a link between the concurrent progression of synaptic dysfunction and inflammation in the PVN of SHR.

TSG-6 secreted by human umbilical cord-MSCs attenuates severe burn-induced excessive inflammation via inhibiting activations of P38 and JNK signaling

The hMSCs have become a promising approach for inflammation treatment in acute phase. Our previous study has demonstrated that human umbilical cord-MSCs could alleviate the inflammatory reaction of severely burned wound. In this study, we further investigated the potential role and mechanism of the MSCs on severe burn-induced excessive inflammation. Wistar rats were randomly divided into following groups: Sham, Burn, Burn+MSCs, Burn+MAPKs inhibitors, and Burn, Burn+MSCs, Burn+Vehicle, Burn+siTSG-6, Burn+rhTSG-6 in the both experiments. It was found that MSCs could only down-regulate P38 and JNK signaling, but had no effect on ERK in peritoneal macrophages of severe burn rats. Furthermore, suppression of P38 and JNK activations significantly reduced the excessive inflammation induced by severe burn. TSG-6 was secreted by MSCs using different inflammatory mediators. TSG-6 from MSCs and recombinant human (rh)TSG-6 all significantly reduced activations of P38 and JNK signaling induced by severe burn and then attenuated excessive inflammations. On the contrary, knockdown TSG-6 in the cells significantly increased phosphorylation of P38 and JNK signaling and reduced therapeutic effect of the MSCs on excessive inflammation. Taken together, this study suggested TSG-6 from MSCs attenuated severe burn-induced excessive inflammation via inhibiting activation of P38 and JNK signaling.

Modulation of Human Macrophage Responses to Mycobacterium tuberculosis by Silver Nanoparticles of Different Size and Surface Modification

Exposure to silver nanoparticles (AgNP) used in consumer products carries potential health risks including increased susceptibility to infectious pathogens. Systematic assessments of antimicrobial macrophage immune responses in the context of AgNP exposure are important because uptake of AgNP by macrophages may lead to alterations of innate immune cell functions. In this study we examined the effects of exposure to AgNP with different particle sizes (20 and 110 nm diameters) and surface chemistry (citrate or polyvinlypyrrolidone capping) on cellular toxicity and innate immune responses against Mycobacterium tuberculosis (M.tb) by human monocyte-derived macrophages (MDM). Exposures of MDM to AgNP significantly reduced cellular viability, increased IL8 and decreased IL10 mRNA expression. Exposure of M.tb-infected MDM to AgNP suppressed M.tb-induced expression of IL1B, IL10, and TNFA mRNA. Furthermore, M.tb-induced IL-1β, a cytokine critical for host resistance to M.tb, was inhibited by AgNP but not by carbon black particles indicating that the observed immunosuppressive effects of AgNP are particle specific. Suppressive effects of AgNP on the M.tb-induced host immune responses were in part due to AgNP-mediated interferences with the TLR signaling pathways that culminate in the activation of the transcription factor NF-κB. AgNP exposure suppressed M.tb-induced expression of a subset of NF-κB mediated genes (CSF2, CSF3, IFNG, IL1A, IL1B, IL6, IL10, TNFA, NFKB1A). In addition, AgNP exposure increased the expression of HSPA1A mRNA and the corresponding stress-induced Hsp72 protein. Up-regulation of Hsp72 by AgNP can suppress M.tb-induced NF-κB activation and host immune responses. The observed ability of AgNP to modulate infectious pathogen-induced immune responses has important public health implications.

High-mobility group box 1 promotes extracellular matrix synthesis and wound repair in human bronchial epithelial cells

High mobility group box 1 (HMGB1) is a damage-associated molecular pattern (DAMP) protein that binds Toll-like receptors (e.g., TLR4) and the receptor for advanced glycated end products (RAGE). The direct effects of HMGB1 on airway structural cells are not fully known. As epithelial cell responses are fundamental drivers of asthma, including abnormal repair-restitution linked to changes in extracellular matrix (ECM) synthesis, we tested the hypothesis that HMGB1 promotes bronchial epithelial cell wound repair via TLR4 and/or RAGE signaling that regulates ECM (fibronectin and the γ2-chain of laminin-5) and integrin protein abundance. To assess impact of HMGB1 we used molecular and pharmacological inhibitors of RAGE or TLR4 signaling in scratch wound, immunofluorescence, and immunoblotting assays to assess wound repair, ECM synthesis, and phosphorylation of intracellular signaling. HMGB1 increased wound closure, and this effect was attenuated by blocking RAGE and TLR4 signaling. HMGB1-induced fibronectin and laminin-5 (γ2 chain) was diminished by blocking RAGE and/or blunting TLR4 signaling. Similarly, induction of α3-integrin receptor for fibronectin and laminin-5 was also diminished by blocking TLR4 signaling and RAGE. Lastly, rapid and/or sustained phosphorylation of SMAD2, ERK1/2, and JNK signaling modulated HMGB1-induced wound closure. Our findings suggest a role for HMGB1 in human airway epithelial cell repair and restitution via multiple pathways mediated by TLR4 and RAGE that underpin increased ECM synthesis and modulation of cell-matrix adhesion.

Effects of hydrogen-rich saline on early acute kidney injury in severely burned rats by suppressing oxidative stress induced apoptosis and inflammation

Background

Early acute kidney injury (AKI) in severely burned patients predicts a high mortality that is multi-factorial. Hydrogen has been reported to alleviate organ injury via selective quenching of reactive oxygen species. This study investigated the potential protective effects of hydrogen against severe burn-induced early AKI in rats.

Methods

Severe burn were induced via immersing the shaved back of rats into a 100°C bath for 15 s. Fifty-six Sprague–Dawley rats were randomly divided into Sham, Burn + saline, and Burn + hydrogen-rich saline (HS) groups, and renal function and the apoptotic index were measured. Kidney histopathology and immunofluorescence staining, quantitative real-time PCR, ELISA and western blotting were performed on the sera or renal tissues of burned rats to explore the underlying effects and mechanisms at varying time points post burn.

Results

Renal function and tubular apoptosis were improved by HS treatment. In addition, the oxidation–reduction potential and malondialdehyde levels were markedly reduced with HS treatment, whereas endogenous antioxidant enzyme activities were significantly increased. HS also decreased the myeloperoxidase levels and influenced the release of inflammatory mediators in the sera and renal tissues of the burned rats. The regulatory effects of HS included the inhibition of p38, JNK, ERK and NF-κB activation, and an increase in Akt phosphorylation.

Conclusion

Hydrogen can attenuate severe burn-induced early AKI; the mechanisms of protection include the inhibition of oxidative stress induced apoptosis and inflammation, which may be mediated by regulation of the MAPKs, Akt and NF-κB signalling pathways.

The sterile inflammation in the exacerbation of HBV-associated liver injury. Mediators Inflamm. 2015;2015:508681. [PMID: 25892853 DOI: 10.1155/2015/508681]

Exacerbation of hepatitis B virus-associated liver injury is characterized by abnormal immune response which not only mobilizes specific antiviral effects but also poses a potentially lethal nonspecific sterile inflammation to the host. How nonspecific sterile inflammation is triggered after the preexisting injury caused by specific immune injury remains elusive. In the setting of sterile inflammation, endogenous damage-associated molecular patterns are released by stressed and dying hepatocytes, which alarm the immune system through their potential pattern recognition receptors and related signaling pathways, orchestrate the influx of diverse cytokines, and ultimately amplify liver destruction. This review highlights current knowledge about the sterile hepatic inflammation in the exacerbation of chronic hepatitis B.

Immunity in arterial hypertension: associations or causalities?

Numerous studies describe associations between markers of inflammation and arterial hypertension (aHT), but does that imply causality? Interventional studies that reduce blood pressure reduced also markers of inflammation, but does immunosuppression improve hypertension? Here, we review the available mechanistic data. Aberrant immunity can trigger endothelial dysfunction but is hardly ever the primary cause of aHT. Innate and adaptive immunity get involved once hypertension has caused vascular wall injury as immunity is a modifier of endothelial dysfunction and vascular wall remodelling. As vascular remodelling progresses, immunity-related mechanisms can become significant cofactors for cardiovascular (CV) disease progression; vice versa, suppressing immunity can improve hypertension and CV outcomes. Innate and adaptive immunity both contribute to vascular wall remodelling. Innate immunity is driven by danger signals that activate Toll-like receptors and other pattern-recognition receptors. Adaptive immunity is based on loss of tolerance against vascular autoantigens and includes autoreactive T-cell immunity as well as non-HLA angiotensin II type 1 receptor-activating autoantibodies. Such processes involve numerous other modulators such as regulatory T cells. Together, immunity is not causal for hypertension but rather an important secondary pathomechanism and a potential therapeutic target in hypertension.

High-mobility group box-1 gene, a potent proinflammatory mediators, is upregulated in more degenerated human discs in vivo and its receptor upregulated by TNF-α exposure in vitro

Mechanisms which control and enhance proinflammatory cytokine expression during human disc degeneration are still poorly understood. The high-mobility group box-1 gene (HMGB1) produces a protein which can itself act as a cytokine, or can function as a potent proinflammatory mediator. Little is known about expression of HMGB1 in the human disc. Since proinflammatory cytokines increase significantly during human disc degeneration, in this work we hypothesized that HMGB1 may show upregulation with advancing stages of degeneration, and upregulation in cells exposed to TNF-α. Immunohistochemistry was performed to confirm the presence of HMGB1 in the human disc, and human annulus cells were cultured and challenged with 10(3)pM TNF-α for 14days in 3D culture. Cells with positive HMGB1 immunolocalization were abundant in the outer annulus. Molecular analysis of cultured cells showed an 8-fold significant increase in HMGB1 expression in more degenerated Thompson grade V discs compared to healthier grade I/II discs (p=0.033). Human disc tissue was assessed in molecular studies. Herniated specimens showed a 6.3-fold significantly greater expression level than that seen in control specimens (p=0.001). In culture experiments, expression of the receptor to HMGB1, toll-like receptor 2, showed a 24-fold upregulation in vitro in cells exposed to TNF-α vs. controls (p=0.0003).

HMGB1 promotes a p38MAPK associated non-infectious inflammatory response pathway in human fetal membranes

Objective

Spontaneous preterm birth (PTB) and preterm prelabor rupture of membranes (pPROM) are major pregnancy complications often associated with a fetal inflammatory response. Biomolecular markers of this fetal inflammatory response to both infectious and non-infectious risk factors and their contribution to PTB and pPROM mechanism are still unclear. This study examined fetal membrane production, activation and mechanistic properties of high mobility group box 1 (HMGB1) as a contributor of the non-infectious fetal inflammatory response.

Materials and Methods

HMGB1 transcripts and active HMGB1 were profiled in fetal membranes and amniotic fluids collected from PTB and normal term birth. In vitro, normal term not in labor fetal membranes were exposed to lipopolysaccharide (LPS) and water soluble cigarette smoke extract (CSE). HMGB1-transcripts and its protein concentrations were documented by RT-PCR and ELISA. Recombinant HMGB1 treated membranes and media were subjected to RT-PCR for HMGB1 receptors, mitogen activated protein kinase pathway analysis, cytokine levels, and Western blot for p38MAPK.

Results

HMGB1 expression and its active forms were higher in PTB and pPROM than normal term membranes and amniotic fluid samples. Both LPS and CSE enhanced HMGB1 expression and release in vitro. Fetal membrane exposure to HMGB1 resulted in increased expression of TLR2 and 4 and dose-dependent activation of p38MAPK-mediated inflammation.

Conclusions

HMGB1 increase by fetal membrane cells in response to either oxidative stress or infection can provide a positive feedback loop generating non-infectious inflammatory activation. Activation of p38MAPK by HMGB1 promotes development of the senescence phenotype and senescence associated sterile inflammation. HMGB1 activity is an important regulator of the fetal inflammatory response regardless of infection.

The adaptation model of immunity

Although 'self-nonself' and 'danger' theories have improved our understanding of the immune system, successful immunotherapy of cancer and many autoimmune diseases still remain far from reach. This indicates that our knowledge of how the immune system decides to respond effectively or ineffectively is limited. Emerging evidence suggest that decision-making during the immune response is not solely determined by 'nonself' entity of the antigen or damage-associated 'danger' signals. This article provides an overview of the 'self-nonself' and 'danger' models, and suggests that 'adaptation' signals are needed to guarantee immunological tolerance that has been observed during the immune response toward 'self', 'nonself' or even 'danger'. This should be facilitated by dynamic expression of adapting receptors (ARs) and adapting ligands on cells of the immune system and other somatic cells. Any alterations in the expression of ARs on certain tissues would result in tissue-specific autoimmune diseases or spontaneous regression of cancer. Identification of such ARs and their nominal adapting ligands could lead to the discovery of currently unknown receptors and their implications in the treatment of cancer, solid organ transplantation and autoimmune diseases.

Current understanding of tyrosine kinase BMX in inflammation and its inhibitors

Tec family kinases, which include tyrosine kinase expressed in hepatocellular carcinoma (TEC), Bruton’s tyrosine kinase (BTK), interleukin (IL)-2-inducible T-cell kinase (ITK), tyrosine-protein kinase (TXK), and bone marrow tyrosine kinase on chromosome X (BMX), are the second largest group of non-receptor tyrosine kinases and have a highly conserved carboxyl-terminal kinase domain. BMX was identified in human bone marrow cells, and was demonstrated to have been expressed in myeloid hematopoietic lineages cells, endothelial cells, and several types of cancers. Significant progress in this area during the last decade revealed an important role for BMX in inflammation and oncologic disorders. This review focuses on BMX biology, its role in inflammation and possible signaling pathways, and the potential of selective BMX inhibitors.

Toll like receptor 2 knock-out attenuates carbon tetrachloride (CCl4)-induced liver fibrosis by downregulating MAPK and NF-κB signaling pathways

Innate immune signaling associated with Toll-like receptors (TLRs) is a key pathway involved in the progression of liver fibrosis. In this study, we reported that TLR2 is required for hepatic fibrogenesis induced by carbon tetrachloride (CCl4). After CCl4 treatment, TLR2(-/-) mice had reduced liver enzyme levels, diminished collagen deposition, decreased inflammatory infiltration and impaired activation of hepatic stellate cells (HSCs) than wild type (WT) mice. Furthermore, after CCl4 treatment, TLR2(-/-) mice demonstrated downregulated expression of profibrotic and proinflammatory genes and impaired mitogen-activated protein kinases (MAPK) and nuclear factor kappa B (NF-κB) activation than WT mice. Collectively, our data indicate that TLR2 deficiency protects against CCl4-induced liver fibrosis.