Oxidative stress generated by hemorrhagic shock recruits Toll-like receptor 4 to the plasma membrane in macrophages

Vitamin C and Microvascular Dysfunction in Systemic Inflammation

Sepsis, life-threatening organ dysfunction caused by a dysfunctional host response to infection, is associated with high mortality. A promising strategy to improve the outcome is to inject patients intravenously with ascorbate (vitamin C). In animal models of sepsis, this injection improves survival and, among others, the microvascular function. This review examines our recent work addressing ascorbate's ability to inhibit arteriolar dysfunction and capillary plugging in sepsis. Arteriolar dysfunction includes impaired vasoconstriction/dilation (previously reviewed) and impaired conduction of vasoconstriction/dilation along the arteriole. We showed that ascorbate injected into septic mice prevents impaired conducted vasoconstriction by inhibiting neuronal nitric oxide synthase-derived NO, leading to restored inter-endothelial electrical coupling through connexin 37-containing gap junctions. Hypoxia/reoxygenation (confounding factor in sepsis) also impairs electrical coupling by protein kinase A (PKA)-dependent connexin 40 dephosphorylation; ascorbate restores PKA activation required for this coupling. Both effects of ascorbate could explain its ability to protect against hypotension in sepsis. Capillary plugging in sepsis involves P-selectin mediated platelet-endothelial adhesion and microthrombi formation. Early injection of ascorbate prevents capillary plugging by inhibiting platelet-endothelial adhesion and endothelial surface P-selectin expression. Ascorbate also prevents thrombin-induced platelet aggregation and platelet surface P-selectin expression, thus preventing microthrombi formation. Delayed ascorbate injection reverses capillary plugging and platelet-endothelial adhesion; it also attenuates sepsis-induced drop in platelet count in systemic blood. Thrombin-induced release of plasminogen-activator-inhibitor-1 from platelets (anti-fibrinolytic event in sepsis) is inhibited by ascorbate pH-dependently. Thus, under acidotic conditions in sepsis, ascorbate promotes dissolving of microthrombi in capillaries. We propose that protected/restored arteriolar conduction and capillary bed perfusion by ascorbate contributes to reduced organ injury and improved survival in sepsis.

Oxidized Hemoglobin Is Antigenic and Immunogenic in Lupus

Hemolysis-associated anemia is characteristic of diseases such as atherosclerosis, lupus, malaria, and leishmaniasis; the toxic effects of free hemoglobin (Hb) have been extensively described. This study was based on the premise that release of this sequestered, inflammatory molecule can result in deleterious immunological consequences, particularly in the context of pre-existing lupus. IgG anti-Hb responses were detected in the sera of lupus patients. Lupus-prone mice exhibited heightened plasma Hb levels, and ferric (Fe³⁺) Hb triggered preferential release of lupus-associated cytokines from splenocytes derived from aging lupus-prone mice. Anti-Hb B cell precursor frequencies were heightened in such mice, which also expressed increased titers of anti-Hb antibodies in serum and in kidney eluates. Fe³⁺ Hb preferentially increased the functional maturation of bone marrow-derived dendritic cells (BMDCs) from lupus-prone mice, effects abrogated upon the inhibition of Stat3. Hb interacted with lupus-associated autoantigens extruded during apoptosis and coincubation of Hb and apoptotic blebs had additional maturation-inducing effects on lupus BMDCs. Immunization with Hb in lupus-prone mice induced antigen spreading to lupus-associated moieties; Hb-interacting autoantigens were preferentially targeted and increased complement deposition and glomerulosclerosis were observed. Hb therefore demonstrates both antigenicity and immunogenicity and triggers specific immuno-pathological effects in a lupus milieu.

Inhibition of Inflammatory Response by Crocin Attenuates Hemorrhagic Shock-Induced Organ Damages in Rats

Hemorrhagic shock (HS) is associated with an excessive activation of inflammation, contributing to multiple organ failure in numerous medical or surgical conditions. To explore the therapeutic potential of crocin, a natural compound with anti-inflammatory properties, we administered crocin to rats during resuscitation following HS induced by withdrawing blood. Compared with control animals which were sham-treated, HS-operated rats showed organ damages as manifested by enhanced markers of multiple organ dysfunctions. Crocin treatment substantially reduced these parameters in rats subjected to HS, suggesting an alleviation of tissue injuries such as in the kidney, liver, pancreas, and muscle. The activation of NF-κB (nuclear factor κB) pathway in lung tissue by HS, as shown by increased nuclear translocation of p65 and IκBα phosphorylation, was diminished by crocin treatment. The crocin administration also significantly decreased the serum levels of proinflammatory cytokine TNF-α (tumor necrosis factor-α) and interleukin (IL)-6, whereas increased the level of anti-inflammatory cytokine IL-10 in HS-operated rats. These studies indicate that crocin administration may reduce inflammation-driven tissue damage in patients with HS.

Protective Effects of Dioscin against Lipopolysaccharide-Induced Acute Lung Injury through Inhibition of Oxidative Stress and Inflammation

The protective effects of dioscin, a natural steroidal saponin from some medicinal plants including Dioscorea nipponica Makino, against lipopolysaccharide (LPS)- induced acute liver and renal damages have been reported in our previous works. However, the actions of dioscin against LPS-induced acute lung injury (ALI) is still unknown. In the present study, we investigated the effects and mechanisms of dioscin against LPS-induced ALI in vitro and in vivo. The results showed that dioscin obviously inhibited cell proliferation and markedly decreased reactive oxidative species level in 16HBE cells treated by LPS. In addition, dioscin significantly protected LPS-induced histological changes, inhibited the infiltration of inflammatory cells, as well as decreased the levels of MDA, SOD, NO and iNOS in mice and rats (p < 0.05). Mechanistically, dioscin significantly decreased the protein levels of TLR4, MyD88, TRAF6, TKB1, TRAF3, phosphorylation levels of PI3K, Akt, IκBα, NF-κB, and the mRNA levels of IL-1β, IL-6, and TNF-α against oxidative stress and inflammation (p < 0.05). Dioscin significantly reduced the overexpression of TLR4, and obviously down-regulated the levels of MyD88, TRAF6, TKB1, TRAF3, p-PI3K, p-Akt, p-IκBα, and p-NF-κB. These findings provide new perspectives for the study of ALI. Dioscin has protective effects on LPS-induced ALI via adjusting TLR4/MyD88- mediated oxidative stress and inflammation, which should be a potent drug in the treatment of ALI.

Benznidazole, the trypanocidal drug used for Chagas disease, induces hepatic NRF2 activation and attenuates the inflammatory response in a murine model of sepsis

Molecular mechanisms on sepsis progression are linked to the imbalance between reactive oxygen species (ROS) production and cellular antioxidant capacity. Previous studies demonstrated that benznidazole (BZL), known for its antiparasitic action on Trypanosoma cruzi, has immunomodulatory effects, increasing survival in C57BL/6 mice in a model of polymicrobial sepsis induced by cecal ligation and puncture (CLP). The mechanism by which BZL inhibits inflammatory response in sepsis is poorly understood. Also, our group recently reported that BZL is able to activate the nuclear factor erytroide-derived 2-Like 2 (NRF2) in vitro. The aim of the present work was to delineate the beneficial role of BZL during sepsis, analyzing its effects on the cellular redox status and the possible link to the innate immunity receptor TLR4. Specifically, we analyzed the effect of BZL on Nrf2 regulation and TLR4 expression in liver of mice 24hours post-CLP. BZL was able to induce NRF2 nuclear protein localization in CLP mice. Also, we found that protein kinase C (PKC) is involved in the NRF2 nuclear accumulation and induction of its target genes. In addition, BZL prompted a reduction in hepatic CLP-induced TLR4 protein membrane localization, evidencing its immunomodulatory effects. Together, our results demonstrate that BZL induces hepatic NRF2 activation with the concomitant increase in the antioxidant defenses, and the attenuation of inflammatory response, in part, by inhibiting TLR4 expression in a murine model of sepsis.

Oxidative Stress Increases Surface Toll-Like Receptor 4 Expression in Murine Macrophages Via Ceramide Generation

Multiorgan failure is a major cause of late mortality following trauma. Oxidative stress generated during shock/resuscitation contributes to tissue injury by priming the immune system for an exaggerated response to subsequent inflammatory stimuli, such as lipopolysaccharide (LPS). We recently reported that oxidative stress causes rapid recruitment of the LPS receptor Toll-like receptor 4 (TLR4) to membrane lipid rafts, thus increasing LPS responsiveness and cellular priming. We hypothesized that activation of Src family kinases by oxidants might contribute to these events. We utilized microscopy, flow cytometry, Western blotting, and thin-layer chromatography methods. Using hydrogen peroxide in vitro and hemorrhagic shock/resuscitation in vivo, oxidant-induced TLR4 translocation in macrophages occurred in an Src-dependent manner. Approaches supporting this conclusion included pharmacologic inhibition of the Src family kinases by PP2, Src inhibition by a molecular approach of cell transfection with Csk, and genetic inhibition of all Src kinases relevant to the monocyte/macrophage lineage in hckfgrlyn triple knockout mice. To evaluate the upstream molecules involved in Src activation, we evaluated the ability of oxidative stress to activate the bioactive lipid molecule ceramide. Oxidants induced ceramide generation in macrophages both in vitro and in vivo, an effect that appears to be due to activation of the acid sphingomyelinase. Using pharmacological approaches, ceramide was shown to be both necessary and sufficient to mediate TLR4 translocation to the plasma membrane in an Src-dependent manner. This study identifies a hierarchy of signaling molecules following oxidative stress that might represent novel targets for therapy in critical illness and organ injury.

Role of TLRs and DAMPs in allograft inflammation and transplant outcomes

Graft inflammation impairs the induction of solid organ transplant tolerance and enhances acute and chronic rejection. Elucidating the mechanisms by which inflammation is induced after organ transplantation could lead to novel therapeutics to improve transplant outcomes. In this Review we describe endogenous substances--damage-associated molecular patterns (DAMPs)--that are released after allograft reperfusion and induce inflammation. We also describe innate immune signalling pathways that are activated after solid organ transplantation, with a focus on Toll-like receptors (TLRs) and their signal adaptor, MYD88. Experimental and clinical studies have yielded a large body of evidence that TLRs and MYD88 are instrumental in initiating allograft inflammation and promoting the development of acute and chronic rejection. Ongoing clinical studies are testing TLR inhibition strategies in solid organ transplantation, although avoiding compromising host defence to pathogens is a key challenge. Further elucidation of the mechanisms by which sterile inflammation is induced, maintained and amplified within the allograft has the potential to lead to novel anti-inflammatory treatments that could improve outcomes for solid organ transplant recipients.

Caveolae and Caveolin-1 Integrate Reverse Cholesterol Transport and Inflammation in Atherosclerosis

Lipid disorder and inflammation play critical roles in the development of atherosclerosis. Reverse cholesterol transport is a key event in lipid metabolism. Caveolae and caveolin-1 are in the center stage of cholesterol transportation and inflammation in macrophages. Here, we propose that reverse cholesterol transport and inflammation in atherosclerosis can be integrated by caveolae and caveolin-1.

Src kinases central to T-cell receptor signaling regulate TLR-activated innate immune responses from human T cells

TLRs have a fundamental role in immunity. We have recently reported that stimulation of TLR2 and TLR5 in freshly isolated and activated human T cells with microbial ligands without concomitant activation through the TCR brings about secretion of neutrophil chemoattractant, CXCL8, and effector cytokine, IFN-γ, respectively. However, the mechanism of TLR signaling in T cells has not been worked out. Here, we show that the Src family kinases, p56(lck)(Lck) and p59(fyn)(Fyn), which are essential for activation of T cells through the TCR, are also critical for signal transduction through TLRs in human T cells. The secretion of CXCL8 following stimulation of the model human T cell line, Jurkat, with the TLR5 ligand, flagellin, was reduced in presence of the Src-kinase inhibitor, PP2 and specific inhibitors of Lck and Fyn. These inhibitors suppressed generation of activated JNK and p38, which were both required for TLR-induced CXCL8 production. The Lck-deficient derivative of Jurkat, JCam1.6, responded poorly to TLR2, TLR5 and TLR7 agonists, and did not generate active signaling intermediates. Lck and Fyn inhibitors also reduced TLR5-induced IFN-γ secretion from the activated T cell phenotype-representing T cell line, HuT78, without modulating JNK and p38 activation. These results reveal that TCR and TLRs share key proximal signaling regulators in T cells.

High-throughput imaging method for direct assessment of GM1 ganglioside levels in mammalian cells

GM1-gangliosidosis is an inherited autosomal recessive disorder caused by mutations in the gene GLB1, which encodes acid β-galactosidase (β-gal). The lack of activity in this lysosomal enzyme leads to accumulation of GM1 gangliosides (GM1) in cells. We have developed a high-content-imaging method to assess GM1 levels in fibroblasts that can be used to evaluate substrate reduction in treated GLB1^−/− cells [1]. This assay allows fluorescent quantification in a multi-well system which generates unbiased and statistically significant data. Fluorescently labeled Cholera Toxin B subunit (CTXB), which specifically binds to GM1 gangliosides, was used to detect in situ GM1 levels in a fixed monolayer of fibroblasts. This sensitive, rapid, and inexpensive method facilitates in vitro drug screening in a format that allows a high number of replicates using low working volumes.

Close teamwork between Nrf2 and peroxiredoxins 1 and 6 for the regulation of prostaglandin D2 and E2 production in macrophages in acute inflammation

Inflammation is a complex biological self-defense reaction triggered by tissue damage or infection by pathogens. Acute inflammation is regulated by the time- and cell type-dependent production of cytokines and small signaling molecules including reactive oxygen species and prostaglandins. Recent studies have unveiled the important role of the transcription factor Nrf2 in the regulation of prostaglandin production through transcriptional regulation of peroxiredoxins 1 and 6 (Prx1 and Prx6) and lipocalin-type prostaglandin D synthase (L-PGDS). Prx1 and Prx6 are multifunctional proteins important for cell protection against oxidative stress, but also work together to facilitate production of prostaglandins E2 and D2 (PGE2 and PGD2). Prx1 secreted from cells under mild oxidative stress binds Toll-like receptor 4 and induces NF-κB activation, important for the expression of cyclooxygenase-2 and microsomal PGE synthase-1 (mPGES-1) expression. The activated MAPKs p38 and ERK phosphorylate Prx6, leading to NADPH oxidase-2 activation, which contributes to production of PGD2 by hematopoietic prostaglandin D synthase (H-PGDS). PGD2 and its end product 15-deoxy-∆(12,14)-prostaglandin J2 (15d-PGJ2) activate Nrf2 thereby forming a positive feedback loop for further production of PGD2 by L-PGDS. Maintenance of cellular glutathione levels is an important role of Nrf2 not only for cell protection but also for the synthesis of prostaglandins, as mPGES-1 and H-PGDS require glutathione for their activities. This review is aimed at describing the functions of Prx1 and Prx6 in the regulation of PGD2 and PGE2 production in acute inflammation in macrophages and the importance of 15d-PGJ2 as an intrinsic Nrf2 activator.

Association of Nrf2 with airway pathogenesis: lessons learned from genetic mouse models

Nrf2 is a key transcription factor for antioxidant response element (ARE)-bearing genes involved in diverse host defense functions including redox balance, cell cycle, immunity, mitochondrial biogenesis, energy metabolism, and carcinogenesis. Nrf2 in the airways is particularly essential as the respiratory system continuously interfaces with environmental stress. Since Nrf2 was determined to be a susceptibility gene for a model of acute lung injury, its protective capacity in the airways has been demonstrated in experimental models of human disorders using Nrf2 mutant mice which were susceptible to supplemental respiratory therapy (e.g., hyperoxia, mechanical ventilation), cigarette smoke, allergens, virus, environmental pollutants, and fibrotic agents compared to wild-type littermates. Recent studies also determined that Nrf2 is indispensable in developmental lung injury. While association studies with genetic NRF2 polymorphisms supported a protective role for murine Nrf2 in oxidative airway diseases, somatic NRF2 mutations enhanced NRF2-ARE responses, and were favorable for lung carcinogenesis and chemoresistance. Bioinformatic tools have elucidated direct Nrf2 targets as well as Nrf2-interacting networks. Moreover, potent Nrf2-ARE agonists protected oxidant-induced lung phenotypes in model systems, suggesting a therapeutic or preventive intervention. Further investigations on Nrf2 should yield greater understanding of its contribution to normal and pathophysiological function in the airways.

A phosphoproteomic study reveals shp-1 cleavage reprograms LPS signaling via a PI-3K/NF-κB and mTORC1 related mechanism

The reprogrammed lipopolysaccharide (LPS) pathway has been reported to render patients more susceptible to the development of post-traumatic multiple organ dysfunction syndrome (MODS). To facilitate thorough understanding of this mechanism, a phosphoproteomic study was utilized to screen the potential signaling molecules. Interestingly, a truncated form of Src homology 2-domain-containing tyrosine phosphatase 1 (shp-1) emerged in human THP-1 macrophages sequentially treated with H2O2 and LPS and not with either of the treatments alone. Subsequent immunoblot analysis confirmed the cleavage of shp-1 and reduction of shp-1 activity in rat alveolar macrophages, mast cells, and neutrophils. Mechanistically, calpain is essential but not sufficient for shp-1 cleavage. In addition, shp-1 cleavage renders the activation of phosphatidylinositol 3-kinase (PI-3K)/nuclear factor-κB (NF-κB) and mechanistic target of rapamycin complex 1 (mTORC1) in macrophages, resulting in enhanced cytokine induced neutrophil chemoattractant (CINC) secretion, which is critical for neutrophil recruitment in MODS. On the other hand, shp-1 cleavage results in the activation of PI-3K/Akt, enhancing the survival of neutrophils. Collectively, these results highlight the cleavage of shp-1 as a critical event in reprogramming LPS pathway to promote both neutrophil recruitment and survival and provide a novel mechanistic framework for the investigation of the post-traumatic MODS.

The effect of ex vivo CDDO-Me activation on nuclear factor erythroid 2-related factor 2 pathway in white blood cells from patients with septic shock

Nuclear factor erythroid 2-related factor 2 (NRF2) has been shown to protect against experimental sepsis in mice and lipopolysaccharide (LPS)-induced inflammation in ex vivo white blood cells from healthy subjects by upregulating cellular antioxidant genes. The objective of this study was to test the hypothesis that ex vivo methyl 2-cyano-3,12-dioxoolean-1,9-dien-28-oate (CDDO-Me) activates NRF2-regulated antioxidant genes in white blood cells from patients with septic shock and protects against LPS-induced inflammation and reactive oxidative species production. Peripheral blood was collected from 18 patients with septic shock who were being treated in medical and surgical intensive care units. Real-time polymerase chain reaction was used to quantify the expression of NRF2 target genes (NQO1, HO-1, GCLM, and FTL) and IL-6 in peripheral blood mononuclear cells (PBMCs), monocytes, and neutrophils after CDDO-Me treatment alone or after subsequent LPS exposure. Superoxide anion (O2) was measured to assess the effect of CDDO-Me pretreatment on subsequent LPS exposure. Treatment with CDDO-Me increased the gene expression of NQO1 (P = 0.04) and decreased the expression of HO-1 (P = 0.03) in PBMCs from patients with septic shock. Purified monocytes exhibited significant increases in the expression of NQO1 (P = 0.01) and GCLM (P = 0.003) after CDDO-Me treatment. Levels of other NRF2 target genes (HO-1 and FTL) remained similar to those of vehicle-treated cells. Peripheral blood mononuclear cells showed a trend toward increased IL-6 gene expression after CDDO-Me treatment, whereas purified monocytes showed a trend toward decreased IL-6. There was no discernible trend in the IL-6 expression subsequent to LPS treatment in either vehicle-treated or CDDO-Me-treated PBMCs and monocytes. Treatment with CDDO-Me significantly increased O2 production in PBMCs (P = 0.04). Although CDDO-Me pretreatment significantly attenuated O2 production to subsequent LPS exposure (P = 0.03), the change was comparable to that observed in vehicle-treated PBMCs. Pretreatment with CDDO-Me followed by LPS exposure had no significant effect on O2 levels in purified monocytes. These data suggest that the NRF2 pathway is differentially responsive to CDDO-Me activation in peripheral blood cells from patients with septic shock and results in increased O2 production. The data may also suggest a suppressed NRF2 pathway in white blood cells from critically ill patients.

Dynasore enhances the formation of mitochondrial antiviral signalling aggregates and endocytosis-independent NF-κB activation

BACKGROUND AND PURPOSE

Dynasore has been used extensively as an inhibitor of clathrin-mediated endocytosis. While studying the role of endocytosis in LPS-induced signalling events, we discovered that dynasore itself induced activation of NF-κB, independently of its effects on endocytosis and without involving the Toll-like receptor 4 signalling pathways. The purpose of this study was to characterize this novel effect and to explore the underlying mechanism of action.

EXPERIMENTAL APPROACH

We utilized gel electrophoresis, microscopy, gene knockdown and luciferase-based promoter activity to evaluate the effect of dynasore on cell signalling pathways and to delineate the mechanisms involved in its effects,

KEY RESULTS

Dynasore activated the NF-κB and IFN-β pathways by activating mitochondrial antiviral signalling protein (MAVS). We showed that MAVS is activated by NOX/Rac and forms high molecular weight aggregates, similar to that observed in response to viral infection. We also demonstrated that dynasore-induced activation of JNK occurs downstream of MAVS and is required for activation of NF-κB and IFN-β.

CONCLUSION AND IMPLICATIONS

These findings demonstrate a novel effect of dynasore on cell signalling. We describe a novel Rac1-, ROS- and MAVS-mediated signalling cascade through which dynasore dramatically activates NF-κB, mimicking the viral induction of this key inflammatory signalling pathway. Our results call attention to the need for a broader interpretation of results when dynasore is used in its traditional fashion as an inhibitor of clathrin-mediated endocytosis. These results suggest the intriguing possibility that dynasore or one of its analogues might be of value as an antiviral therapeutic strategy or vaccine adjuvant.

Immunohistochemical expression of nuclear factor erythroid-2-related factor 2 and heme oxygenase 1 in normal bovine lung and bovine lung infected with Mannheimia haemolytica

Mannheimia haemolytica is an important cause of pneumonia in feedlot cattle. Nuclear factor erythroid-2-related factor 2 (Nrf2) is a redox-sensitive transcription factor responsible for the induction of antioxidant enzymes, such as heme oxygenase 1 (HO-1), within the lung. The expression of Nrf2 and HO-1 was immunohistochemically evaluated in 4 calves 24 h after experimental infection with M. haemolytica. Calves receiving normal saline served as controls. In the infected lungs, cytoplasmic Nrf2 expression was high in macrophages and bronchioles and low in alveolar epithelium, whereas nuclear expression was high in endothelial cells, macrophages, and bronchioles and lowest in alveolar epithelium. Normal lung samples displayed only faint Nrf2 cytoplasmic staining within bronchiolar epithelium. Expression of HO-1 was detected within the cytoplasm of macrophages and bronchiolar epithelial cells in all infected lung samples, whereas normal lungs displayed only weak cytoplasmic staining in bronchiolar epithelial cells. These findings suggest that bronchiolar epithelial cells and macrophages up-regulate Nrf2 expression early in the course of infection, which results in increased expression of HO-1 within these cells.

Role of alveolar macrophages in the inflammatory response after trauma

Acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome (ARDS), can result from both direct and indirect pulmonary damage caused by trauma and shock. In the course of ALI/ARDS, mediators released from resident cells, such as alveolar macrophages, may act as chemoattractants for invading cells and stimulate local cells to build up a proinflammatory micromilieu. Depending on the trauma setting, the role of alveolar macrophages is differentially defined. This review focuses on alveolar macrophage function after blunt chest trauma, ischemia/reperfusion, hemorrhagic shock, and thermal burns.

Coenzyme Q10 supplementation downregulates the increase of monocytes expressing toll-like receptor 4 in response to 6-day intensive training in kendo athletes

This study examined changes in toll-like receptor 4 (TLR-4)-expressing monocytes and lymphocyte subpopulations in response to continuous intensive exercise training in athletes, as well as the effect of coenzyme Q10 (CoQ10) supplementation on these changes. Eighteen male elite kendo athletes in Japan were randomly assigned to a CoQ10-supplementation group (n = 9) or a placebo-supplementation group (n = 9) using a double-blind method. Subjects in the CoQ10 group took 300 mg CoQ10 per day for 20 days. Subjects in the placebo group took the same dosage of placebo. All subjects practiced kendo 5.5 h per day for 6 consecutive days during the study period. Blood samples were collected 2 weeks before training, on the first day (day 1), third day (day 3), and fifth day of training (day 5), and 1 week after the training period (post-training) to ascertain TLR-4(+)/CD14(+) monocyte and lymphocyte subpopulations (CD3(+), CD4(+), CD8(+), CD28(+)/CD4(+), CD28(+)/CD8(+), and CD56(+)/CD3(-) cells) using flow cytometry analysis. The group × time interaction for TLR-4(+)/CD14(+) cells did not reach significance (p = 0.08). Within the CoQ10 group, the absolute number of TLR-4(+)/CD14(+) cells was significantly higher only at day 5. The placebo group showed a significant increase in the absolute number of TLR-4(+)/CD14(+) cells at day 3, day 5, and post-training (p < 0.05). There was no significant group × time interaction for any lymphocyte subpopulation. CD3(+), CD8(+), and CD56(+)/CD3(-) cells were significantly reduced at day 3 in both groups (p < 0.05). In conclusion, CoQ10 supplementation might downregulate the increase of TLR-4-expressing monocytes in response to continuous strenuous exercise training in kendo athletes.

Cross-talk between HPA-axis-increased glucocorticoids and mitochondrial stress determines immune responses and clinical manifestations of patients with sepsis

Various stressors activate the hypothalamo-pituitary-adrenal axis (HPA-axis) that stimulates adrenal secretion of glucocorticoids, thereby playing critical roles in the modulation of immune responses. Transcriptional regulation of nuclear genes has been well documented to underlie the mechanism of glucocorticoid-dependent modulation of cytokine production and immune reactions. Glucocorticoids also regulate inflammatory responses via non-genomic pathways in cytoplasm and mitochondria. Recent studies have revealed that glucocorticoids modulate mitochondrial calcium homeostasis and generation of reactive oxygen species (ROS). Although redox status and ROS generation in inflammatory cells have been well documented to play important roles in defense against pathogens, the roles of glucocorticoids and mitochondria in the modulation of immunological responses remain obscure. This review describes the role of stress-induced activation of the HPA-axis and glucocorticoid secretion by the adrenal gland in mitochondria-dependent signaling pathways that modulate endotoxin-induced inflammatory reactions and innate immunity.

Effects of simvastatin on cell viability and proinflammatory pathways in lung adenocarcinoma cells exposed to hydrogen peroxide

Lung cancer is characterized by a high mortality rate probably attributable to early metastasis. Oxidative stress is involved in development and progression of lung cancer, through cellular and molecular mechanisms which at least in part overlap with proinflammatory pathways. Simvastatin is a statin with pleiotropic effects that can also act as an anti-oxidant agent, and these pharmacologic properties may contribute to its potential anti-cancer activity. Therefore, the aim of this study was to evaluate, in the human lung adenocarcinoma cell line GLC-82, the effects of a 24-hour treatment with simvastatin on hydrogen peroxide (H2O2)-induced changes in cell viability, ERK phosphorylation, matrix metalloproteinase (MMP) expression, innate immunity signaling, NF-κB activation and IL-8 secretion. Cell counting was performed after trypan blue staining, cell proliferation was assessed using MTT assay, and apoptosis was evaluated through caspase-3 activation and Tunel assay. Western blotting was used to analyze protein extracts, and IL-8 release into cell culture supernatants was assessed by ELISA. Our results show that simvastatin (30 μM) significantly (P <0.01) inhibited the proliferative effect of H2O2 (0.5 mM) and its stimulatory actions on ERK1/2 phosphorylation, NF-κB activation and IL-8 production. Furthermore, simvastatin decreased H2O2-mediated induction of the cellular expression of MMP-2 and MMP-9, as well as of several components of the signaling complex activated by innate immune responses, including MyD88, TRAF2, TRAF6 and TRADD. In conclusion, these findings suggest that simvastatin could play a role in prevention and treatment of lung cancer via modulation of important proinflammatory and tumorigenic events promoted by oxidative stress.

Cardioprotection: a review of current practice in global ischemia and future translational perspective

The idea of protecting the heart from ischemic insult during heart surgery to allow elective cardiac arrest is as old as the idea of cardiac surgery itself. The current gold standard in clinical routine is a high potassium regimen added either to crystalloid or blood cardioplegic solutions inducing depolarized arrest. Ongoing patient demographic changes with increasingly older, comorbidly ill patients and increasing case complexity with increasingly structurally abnormal hearts as morphological correlate paired with evolutions in pediatric cardiac surgery allowing more complex procedures than ever before redefine requirements for cardioprotection. Many, in part adversarial, regimens to protect the myocardium from ischemic insults have entered clinical routine; however, functional recovery of the heart is still often impaired due to perfusion injury. Myocardial reperfusion damage is a key determinant of postoperative organ functional recovery, morbidity, and mortality in adult and pediatric patients. There is a discrepancy between what current protective strategies are capable of and what they are expected to do in a rapidly changing cardiac surgery community. An increased understanding of the molecular players of ischemia reperfusion injury offers potential seeds for new cardioprotective regimens and may further displace boundaries of what is technically feasible.

The role of oxidative stress during inflammatory processes

Abstract The production of various reactive oxidant species in excess of endogenous antioxidant defense mechanisms promotes the development of a state of oxidative stress, with significant biological consequences. In recent years, evidence has emerged that oxidative stress plays a crucial role in the development and perpetuation of inflammation, and thus contributes to the pathophysiology of a number of debilitating illnesses, such as cardiovascular diseases, diabetes, cancer, or neurodegenerative processes. Oxidants affect all stages of the inflammatory response, including the release by damaged tissues of molecules acting as endogenous danger signals, their sensing by innate immune receptors from the Toll-like (TLRs) and the NOD-like (NLRs) families, and the activation of signaling pathways initiating the adaptive cellular response to such signals. In this article, after summarizing the basic aspects of redox biology and inflammation, we review in detail the current knowledge on the fundamental connections between oxidative stress and inflammatory processes, with a special emphasis on the danger molecule high-mobility group box-1, the TLRs, the NLRP-3 receptor, and the inflammasome, as well as the transcription factor nuclear factor-κB.

Primary sensory neurons regulate Toll-like receptor-4-dependent activity of glial cells in dorsal root ganglia

Toll-like receptor-4 (TLR4) has been identified in primary sensory neurons, both in vivo and in vitro, but is reportedly absent from satellite glial cells (SGCs). Herein we reveal that, in rat dorsal root ganglia (DRG), SGCs do express TLR4 but this expression is inhibited by direct contact with neurons. Thus, TLR4 mRNA and protein is strongly up-regulated in isolated DRG glial cells in the absence of neurons. Lipopolysaccharide (LPS) increased cyclooxygenase-2 (COX-2) and tumor necrosis factor-α (TNFα) mRNA expression with greater efficacy in DRG glial cell cultures than in mixed DRG cell cultures containing TLR4-positive neurons. Using an insert co-culture system, we have shown that neuronal inhibition of glial cell TLR4 is likely to be dependent on cell-cell contact rather than diffusible factors from neurons. LPS stimulated prostaglandin E2 (PGE2) production from DRG glial cells in a TLR4- and COX-2-dependent manner. In addition, exogenous PGE2 potentiated LPS-stimulated COX-2 mRNA while inhibiting TNFα mRNA expression by DRG cells, suggestive of a complex regulatory system to control inflammation within the DRG. In addition to LPS, conditioned medium from heat-shocked DRG neurons also increased COX-2 mRNA expression in DRG glial cells in a partially TLR4-dependent manner. We therefore hypothesize that neuronal suppression of glial TLR4 activity is a protective mechanism to prevent uncontrolled inflammation within the DRG. Under conditions where DRG neuronal viability is compromised, DRG glial cells become responsive to PAMPs (pathogen-associated molecular patterns) and DAMPs (danger-associated molecular patterns) and generate a range of classical inflammatory responses.

Low-molecular weight fractions of Japanese soy sauce act as a RAGE antagonist via inhibition of RAGE trafficking to lipid rafts

Advanced glycation end-products (AGE) have been implicated in aging and the pathogenesis of diabetic complications, inflammation, Alzheimer's disease, and cancer. AGE engage the cell surface receptor for AGE (RAGE), which in turn elicits intracellular signaling, leading to activation of NF-κB to cause deterioration of tissue homeostasis. AGE are not only formed within our bodies but are also derived from foods, endowing them with flavor. In the present study, we assessed the agonistic/antagonistic effects of food-derived AGE on RAGE signaling in a reporter assay system and found that low-molecular weight AGE can antagonize the action of AGE-BSA. Foods tested were Japanese soy sauce, coffee, cola, and red wine, all of which showed fluorescence characteristics of AGE. Soy sauce and coffee contained N(ε)-carboxymethyl-lysine (CML). Soy sauce, coffee, and red wine inhibited the RAGE ligand-induced activation of NF-κB, whereas cola had no effect on the ligand induction of NF-κB. The liquids were then fractionated into high-molecular weight (HMW) fractions and low-molecular weight (LMW) fractions. Soy sauce-, coffee-, and red wine-derived LMW fractions consistently inhibited the RAGE ligand induction of NF-κB, whereas the HMW fractions of these foods activated RAGE signaling. Using the LMW fraction of soy sauce as a model food-derived RAGE antagonist, we performed a plate-binding assay and found that the soy sauce LMW fractions competitively inhibited AGE-RAGE association. Further, this fraction significantly reduced AGE-dependent monocyte chemoattractant protein-1 (MCP-1) secretion from murine peritoneal macrophages. The LMF from soy sauce suppressed the AGE-induced RAGE trafficking to lipid rafts. These results indicate that small components in some, if not all, foods antagonize RAGE signaling and could exhibit beneficial effects on RAGE-related diseases.

Ischemia/reperfusion Injury and its Consequences on Immunity and Inflammation

Ischemia/reperfusion injury (IRI), an inherent component of transplantation, affects organ quality and transplant outcomes. Although the complexity of the pathophysiology is recognized, detailed mechanisms remain unclear, and strategies preventing the consequences of IRI have been challenging. Of critical significance appears the link between IRI, the initiation of innate immune responses, and the (potential) augmentation of adaptive immunity. An improved understanding of those complex mechanisms and interactions may pave the way for more effective treatment strategies.

Lung cell-specific modulation of LPS-induced TLR4 receptor and adaptor localization

Lung infection by Gram-negative bacteria is a major cause of morbidity and mortality in humans. Lipopolysaccharide (LPS), located in the outer membrane of the Gram-negative bacterial cell wall, is a highly potent stimulus of immune and structural cells via the TLR4/MD2 complex whose function is sequentially regulated by defined subsets of adaptor proteins. Regulatory mechanisms of lung-specific defense pathways point at the crucial role of resident alveolar macrophages, alveolar epithelial cells, the TLR4 receptor pathway, and lung surfactant in shaping the innate immune response to Gram-negative bacteria and LPS. During the past decade intracellular spatiotemporal localization of TLR4 emerged as a key feature of TLR4 function. Here, we briefly review lung cell type- and compartment-specific mechanisms of LPS-induced TLR4 regulation with a focus on primary resident hematopoietic and structural cells as well as modifying microenvironmental factors involved.

Glycyrrhizin inhibits the inflammatory response in mouse mammary epithelial cells and a mouse mastitis model

Glycyrrhizin, a triterpene glycoside isolated from licorice root, is known to have anti-inflammatory activities. However, the effect of glycyrrhizin on mastitis has not been reported. The purpose of this study was to investigate the anti-inflammatory effect and mechanism of action of glycyrrhizin on lipopolysaccharide (LPS)-induced mastitis in mouse. An LPS-induced mouse mastitis model was used to confirm the anti-inflammatory activity of glycyrrhizin in vivo. Primary mouse mammary epithelial cells were used to investigate the molecular mechanism and targets of glycyrrhizin. In vivo, glycyrrhizin significantly attenuated the mammary gland histopathological changes, myeloperoxidase activity and infiltration of neutrophilic granulocytes and downregulated the expression of tumor necrosis factor-α, interleukin (IL)-1β and IL-6 caused by LPS. In vitro, glycyrrhizin dose-dependently inhibited the LPS-induced expression of tumor necrosis factor-α, IL-6, and RANTES. Western blot analysis showed that glycyrrhizin suppressed LPS-induced nuclear factor-κB and interferon regulatory factor 3 activation. However, glycyrrhizin did not inhibit nuclear factor-κB and interferon regulatory factor 3 activation induced by MyD88-dependent (MyD88, IKKβ) or TRIF-dependent (TRIF, TBK1) downstream signaling components. Moreover, glycyrrhizin did not act though affecting the function of CD14 or expression of Toll-like receptor 4. Finally, we showed that glycyrrhizin decreased the levels of cholesterol of lipid rafts and inhibited the translocation of Toll-like receptor 4 to lipid rafts. Moreover, glycyrrhizin activated ATP-binding cassette transporter A1, which could induce cholesterol efflux from lipid rafts. In conclusion, we find that the anti-inflammatory effects of glycyrrhizin may be attributable to its ability to activate ATP-binding cassette transporter A1. Glycyrrhizin might be a useful therapeutic reagent for the treatment of mastitis and other inflammatory diseases.

The alarmin concept applied to human renal transplantation: evidence for a differential implication of HMGB1 and IL-33

The endogenous molecules high mobility group box 1 (HMGB1) and interleukin-33 (IL-33) have been identified as alarmins, capable of mediating danger signals during tissue damage. Here, we address their possible role as innate-immune mediators in ischemia-reperfusion injury (IRI) following human kidney transplantation. We analysed serum and urinary HMGB1 and IL-33 levels, all determined by enzyme-linked immunosorbent assay, in a cohort of 26 deceased renal transplant recipients. Urinary HMGB1 and IL-33 levels were significantly increased as soon as 30 min after reperfusion, as compared to those before treatment. Moreover, both serum and urinary IL-33 (but not HMGB1) increase was positively correlated with cold ischemia time, from 30 min to 3 days post-transplantation. In vitro, human umbilical vein endothelial cells subjected to hypoxia conditions released both HMGB-1 and IL-33, while only the latter was further increased upon subsequent re-oxygenation. Finally, we postulate that leukocytes from renal recipient patients are targeted by both HMGB1 and IL-33, as suggested by increased transcription of their respective receptors (TLR2/4 and ST2L) shortly after transplantation. Consistent with this view, we found that iNKT cells, an innate-like T cell subset involved in IRI and targeted by IL-33 but not by HMGB1 was activated 1 hour post-transplantation. Altogether, these results are in keeping with a potential role of IL-33 as an innate-immune mediator during kidney IRI in humans.

Glycyrrhizin inhibits lipopolysaccharide-induced inflammatory response by reducing TLR4 recruitment into lipid rafts in RAW264.7 cells

BACKGROUND

The aim of this study was to investigate the effect of glycyrrhizin on LPS-induced endotoxemia in mice and clarify the possible mechanism.

METHODS

An LPS-induced endotoxemia mouse model was used to confirm the anti-inflammatory activity of glycyrrhizin in vivo. In vitro, RAW264.7 cells were stimulated with LPS in the presence or absence of glycyrrhizin. The expression of cytokines was determined by ELISA. Toll-like receptor 4 (TLR4) was determined by Western blot analysis. Nuclear factor-kB (NF-κB) and Interferon regulatory factor 3 (IRF3) activation were detected by Western blotting and luciferase assay. Lipid raft staining was detected by immunocytochemistry.

RESULTS

In vivo, the results showed that glycyrrhizin can improve survival during lethal endotoxemia. In vitro, glycyrrhizin dose-dependently inhibited the expression of TNF-α, IL-6, IL-1β and RANTES in LPS-stimulated RAW264.7 cells. Western blot analysis showed that glycyrrhizin suppressed LPS-induced NF-κB and IRF3 activation. However, glycyrrhizin did not inhibit NF-κB and IRF3 activation induced by MyD88-dependent (MyD88, IKKβ) or TRIF-dependent (TRIF, TBK1) downstream signaling components. Moreover, glycyrrhizin did not affect the expression of TLR4 and CD14 induced by LPS. Significantly, we found that glycyrrhizin decreased the levels of cholesterol of lipid rafts and inhibited translocation of TLR4 to lipid rafts. Moreover, glycyrrhizin activated ABCA1, which could induce cholesterol efflux from lipid rafts.

CONCLUSION

Glycyrrhizin exerts an anti-inflammatory property by disrupting lipid rafts and inhibiting translocation of TLR4 to lipid rafts, thereby attenuating LPS-mediated inflammatory response.

GENERAL SIGNIFICANCE

Learning the anti-inflammatory mechanism of glycyrrhizin is crucial for the anti-inflammatory drug development.

Lipid rafts and detergent-resistant membranes in epithelial keratinocytes

Our understanding of the plasma membrane has markedly increased since Singer and Nicolson proposed the fluid mosaic model in 1972. While their revolutionary theory of the lipid bilayer remains largely valid, it is now known that lipids and proteins are not randomly dispersed throughout the plasma membrane but instead may be organized within membrane microdomains, commonly referred to as lipid rafts. Lipid rafts are highly dynamic, detergent resistant, and enriched with both cholesterol and glycosphingolipids. The two main types are flotillin-rich planar lipid rafts and caveolin-rich caveolae. It is proposed that flotillin and caveolin proteins regulate cell communication by compartmentalizing and interacting with signal transduction proteins within their respective lipid microdomains. Consequently, membrane rafts play an important role in vital cellular functions including migration, invasion, and signaling; thus, alterations in their microenvironment can initiate signaling pathways that affect cellular function and behavior. Therefore, the identification of lipid rafts and their associated proteins is integral to the study of transmembrane signaling. Here, we review the current standard protocols and biochemical approaches used to isolate and define raft proteins from epithelial cells and tissues. Furthermore, in Section 3 of this chapter, detailed protocols are offered for isolating lipid rafts by subjection to detergent and sucrose density centrifugation, as well as an approach for selectively isolating caveolae. Methods to manipulate rafts with treatments such as methyl-β-cyclodextrin and flotillin III are also described.

Selenium attenuates high glucose-induced ROS/TLR-4 involved apoptosis of rat cardiomyocyte

The potential mechanism of high glucose-induced cardiomyocyte apoptosis and selenium's protective effects were investigated in this study. Myocytes isolated from neonate rats were cultured in high-glucose medium (25.5 mmol/L glucose) to mimic sustained hyperglycemia. Before high-glucose incubation, myocytes were pretreated by sodium selenite solution. Cell apoptosis was evaluated by annexin V/propidium iodide (PI) staining and caspase activation. Expression of Toll-like receptor 4 (TLR-4) and myeloid differentiation factor 88 (MyD-88) was examined at both mRNA and protein levels. The intracellular reactive oxygen species (ROS) production and glutathione peroxidase (GPx) activity in myocytes were also detected. We found high glucose-induced cell apoptosis and activation of TLR-4/MyD-88/caspase-8/caspase-3 signaling, accompanied by increased production of ROS. Selenium pretreatment attenuated apoptosis in high glucose-incubated myocytes, and mechanically, this protective effect was found to be associated with attenuating oxidative status by increasing activity of GPx, decreasing the generation of ROS, as well as inhibition of the activation of TLR-4/MyD-88/caspase-8/caspase-3 signaling in myocytes. These results suggest that activation of TLR-4/MyD-88 signaling pathway plays an important role in high glucose-induced cardiomyocyte apoptosis. Additionally, by modulating TLR-4/MyD-88 signaling pathway, which is linked to ROS formation, selenium exerts its antioxidative and antiapoptotic effects in high glucose-incubated myocytes.

Toll-like receptors: sensing and reacting to diabetic injury in the kidney

Accumulating evidence indicates that immunologic and inflammatory elements play an important role in initiating and orchestrating the development of diabetic nephropathy (DN), but until recently, the identity of specific innate immune pattern recognition receptors or sensors that recognize diverse diabetic 'danger signals' to trigger the proinflammatory cascade during DN remains unknown. Toll-like receptors (TLRs) are an emerging family of receptors that recognize pathogen-associated molecular patterns as well as damage-associated molecular patterns to promote the activation of leukocytes and intrinsic renal cells in non-immune kidney disease. Recent data from in vitro and in vivo studies have highlighted the critical role of TLRs, mainly TLR2 and TLR4, in the pathogenesis of DN. This review focuses on emerging findings elucidating how TLR signaling could sense and react to the metabolic stress and endogenous ligands activated by the diabetic state, thereby initiating and perpetuating renal inflammation and fibrogenesis in diabetic kidney disease. Novel strategies potentially targeting TLR signaling that could have therapeutic implications in DN are also discussed.

Uptake of oxLDL and IL-10 production by macrophages requires PAFR and CD36 recruitment into the same lipid rafts

Macrophage interaction with oxidized low-density lipoprotein (oxLDL) leads to its differentiation into foam cells and cytokine production, contributing to atherosclerosis development. In a previous study, we showed that CD36 and the receptor for platelet-activating factor (PAFR) are required for oxLDL to activate gene transcription for cytokines and CD36. Here, we investigated the localization and physical interaction of CD36 and PAFR in macrophages stimulated with oxLDL. We found that blocking CD36 or PAFR decreases oxLDL uptake and IL-10 production. OxLDL induces IL-10 mRNA expression only in HEK293T expressing both receptors (PAFR and CD36). OxLDL does not induce IL-12 production. The lipid rafts disruption by treatment with βCD reduces the oxLDL uptake and IL-10 production. OxLDL induces co-immunoprecipitation of PAFR and CD36 with the constitutive raft protein flotillin-1, and colocalization with the lipid raft-marker GM1-ganglioside. Finally, we found colocalization of PAFR and CD36 in macrophages from human atherosclerotic plaques. Our results show that oxLDL induces the recruitment of PAFR and CD36 into the same lipid rafts, which is important for oxLDL uptake and IL-10 production. This study provided new insights into how oxLDL interact with macrophages and contributing to atherosclerosis development.

Eritoran attenuates tissue damage and inflammation in hemorrhagic shock/trauma

BACKGROUND

Severe injury and associated hemorrhagic shock lead to an inflammatory response and subsequent increased tissue damage. Numerous reports have shown that injury-induced inflammation and the associated end-organ damage is driven by Toll-like receptor 4 (TLR4) activation via damage-associated molecular patterns. We examined the effectiveness of Eritoran tetrasodium (E5564), an inhibitor of TLR4 function, in reducing inflammation induced during hemorrhagic shock with resuscitation (HS/R) or after peripheral tissue injury (bilateral femur fracture, BFF).

MATERIAL AND METHODS

Mice underwent HS/R or BFF with or without injection of Eritoran (5 mg/kg body weight) or vehicle control given before, both before and after, or only after HS/R or BFF. Mice were sacrificed after 6 h and plasma and tissue cytokines, liver damage (histology; aspartate aminotransferase/alanine aminotransferase), and inflammation (NF-κB) and gut permeability were assessed.

RESULTS

In HS/R Eritoran significantly reduced liver damage (values ± SEM: alanine aminotransferase 9910 ± 3680 U/L versus 1239 ± 327 U/L and aspartate aminotransferase 5863 ± 2000 U/L versus 1246 ± 243 U/L, P < 0.01) at 6 h compared with control when given just before HS and again just prior to resuscitation. Eritoran administration also led to lower IL-6 levels in plasma and liver and less NF-κB activation in liver. Increases in gut barrier permeability induced by HS/R were also prevented with Eritoran. Eritoran similarly diminished BFF-mediated systemic inflammatory responses.

CONCLUSION

These data suggest Eritoran can inhibit tissue damage and inflammation induced via TLR4/myeloid differentiation factor 2 signaling from damage-associated molecular patterns released during HS/R or BFF. Eritoran may represent a promising therapeutic for trauma patients to prevent multiple organ failure.

Inhibition of reactive oxygen species generation attenuates TLR4-mediated proinflammatory and proliferative phenotype of vascular smooth muscle cells

Reactive oxygen species (ROS) are associated with inflammation and vasculature dysfunction. This study aimed to investigate the potential role of the ROS on vascular Toll-like receptor 4 (TLR4)-mediated proinflammatory and proliferative phenotype of vascular smooth muscle cells (VSMCs). A wire-induced carotid injury model was used in male TLR4-deficient (TLR4(-/-)) and wild-type C57BL/6J mice to induce neointima formation. In the presence or absence of the ROS scavenger apocynin for 14 days, increased TLR4 and proinflammatory cytokines were observed in wire injury-induced carotid neointima and in platelet-derived growth factor-BB (PDGF-BB)-stimulated VSMCs. The TLR4(-/-) protected the injured carotid from neointimal formation and impaired the cellular proliferation and migration in response to PDGF-BB. Apocynin attenuated intimal hyperplasia. Pre-treatment with apocynin significantly inhibited intracellular ROS generation, accompanied by a significant suppression of TLR4 and proinflammatory cytokines expression, and VSMC proliferation and migration. However, the results were not obvious in TLR4(-/-) condition. These findings highlight the importance of ROS inhibition in TLR4-mediated proinflammatory and proliferative phenotype of VSMCs, and suggest ROS as an essential therapeutic target for TLR4-associated vascular inflammation and vascular diseases.

MFG-E8 and HMGB1 are involved in the mechanism underlying alcohol-induced impairment of macrophage efferocytosis

Efferocytosis is a unique phagocytic process for macrophages to remove apoptotic cells in inflammatory loci. This event is maintained by milk fat globule-EGF factor 8 (MFG-E8), but attenuated by high mobility group box 1 (HMGB1). Alcohol abuse causes injury and inflammation in multiple tissues. It alters efferocytosis, but precise molecular mechanisms for this effect remain largely unknown. Here, we showed that acute exposure of macrophages to alcohol (25 mmol/L) inhibited MFG-E8 gene expression and impaired efferocytosis. The effect was mimicked by hydrogen peroxide. Moreover, N-acetylcysteine (NAC), a potent antioxidant, blocked acute alcohol effect on inhibition of macrophage MFG-E8 gene expression and efferocytosis. In addition, recombinant MFG-E8 rescued the activity of alcohol-treated macrophages in efferocytosis. Together, the data suggest that acute alcohol exposure impairs macrophage efferocytosis via inhibition of MFG-E8 gene expression through a reactive oxygen species dependent mechanism. Alcohol has been found to suppress or exacerbate immune cell activities depending on the length of alcohol exposure. Thus, we further examined the role of chronic alcohol exposure on macrophage efferocytosis. Interestingly, treatment of macrophages with alcohol for seven days in vitro enhanced MFG-E8 gene expression and efferocytosis. However, chronic feeding of mice with alcohol caused increase in HMGB1 levels in serum. Furthermore, HMGB1 diminished efferocytosis by macrophages that were treated chronically with alcohol, suggesting that HMGB1 might attenuate the direct effect of chronic alcohol on macrophage efferocytosis in vivo. Therefore, we speculated that the balance between MFG-E8 and HMGB1 levels determines pathophysiological effects of chronic alcohol exposure on macrophage efferocytosis in vivo.

Roles nrf2 plays in myeloid cells and related disorders

The Keap1-Nrf2 system protects animals from oxidative and electrophilic stresses. Nrf2 is a transcription factor that induces the expression of genes essential for detoxifying reactive oxygen species (ROS) and cytotoxic electrophiles. Keap1 is a stress sensor protein that binds to and ubiquitinates Nrf2 under unstressed conditions, leading to the rapid proteasomal degradation of Nrf2. Upon exposure to stress, Keap1 is modified and inactivated, which allows Nrf2 to accumulate and activate the transcription of a battery of cytoprotective genes. Antioxidative and detoxification activities are important for many types of cells to avoid DNA damage and cell death. Accumulating lines of recent evidence suggest that Nrf2 is also required for the primary functions of myeloid cells, which include phagocytosis, inflammation regulation, and ROS generation for bactericidal activities. In fact, results from several mouse models have shown that Nrf2 expression in myeloid cells is required for the proper regulation of inflammation, antitumor immunity, and atherosclerosis. Moreover, several molecules generated upon inflammation activate Nrf2. Although ROS detoxification mediated by Nrf2 is assumed to be required for anti-inflammation, the entire picture of the Nrf2-mediated regulation of myeloid cell primary functions has yet to be elucidated. In this review, we describe the Nrf2 inducers characteristic of myeloid cells and the contributions of Nrf2 to diseases.

Temporal dynamics of cardiac immune cell accumulation following acute myocardial infarction

Acute myocardial infarction (MI) causes sterile inflammation, which is characterized by recruitment and activation of innate and adaptive immune system cells. Here we delineate the temporal dynamics of immune cell accumulation following MI by flow cytometry. Neutrophils increased immediately to a peak at 3 days post-MI. Macrophages were numerically the predominant cells infiltrating the infarcted myocardium, increasing in number over the first week post-MI. Macrophages are functionally heterogeneous, whereby the first responders exhibit high expression levels of proinflammatory mediators, while the late responders express high levels of the anti-inflammatory cytokine IL-10; these macrophages can be classified into M1 and M2 macrophages, respectively, based on surface-marker expression. M1 macrophages dominated at 1-3 days post-MI, whereas M2 macrophages represented the predominant macrophage subset after 5 days. The M2 macrophages expressed high levels of reparative genes in addition to proinflammatory genes to the same levels as in M1 macrophages. The predominant subset of dendritic cells (DCs) was myeloid DC, which peaked in number on day 7. Th1 and regulatory T cells were the predominant subsets of CD4(+) T cells, whereas Th2 and Th17 cells were minor populations. CD8(+) T cells, γδT cells, B cells, natural killer (NK) cells and NKT cells peaked on day 7 post-MI. Timely reperfusion reduced the total number of leukocytes accumulated in the post-MI period, shifting the peak of innate immune response towards earlier and blunting the wave of adaptive immune response. In conclusion, these results provide important knowledge necessary for developing successful immunomodulatory therapies.

Potential role of Toll-like receptors in programming of vascular dysfunction

The developmental origins of the metabolic syndrome have been established through the consistent observation that small-for-gestational age and large-for-gestational age fetuses have an increased risk for hypertension and related metabolic disorders later in life. These phenotypes have been reproduced in various species subjected to a range of intrauterine insults and ongoing research is directed towards understanding the underlying molecular mechanisms. Current evidence suggests that the creation of a pro-inflammatory and pro-oxidant intrauterine milieu is a common thread among prenatal factors that have an impact upon fetal size. Furthermore, studies demonstrate that a shift in fetal redox status consequent to environmental cues persists after birth and drives the progression of vascular dysfunction and hypertension in postnatal life. TLR (Toll-like receptor) signalling has emerged as a key link between inflammation and oxidative stress and a pathogenic contributor to hypertension, insulin resistance and obesity, in both human patients and animal models of disease. Thus TLR activation and dysregulation of its signalling components represent potential molecular underpinnings of programmed hypertension and related disorders in those subjected to suboptimal intrauterine conditions, yet their contributions to developmental programming remain unexplored. We propose that danger signals mobilized by the placenta or fetal tissues during complicated pregnancy activate the fetal innate immune system through TLRs and thereby potentiate the generation of ROS (reactive oxygen species) and orchestrate fetal adaptive responses, including changes in gene expression, which later translate to vascular dysfunction. Furthermore, we suggest that, after birth, continual activation of TLR signalling propagates vascular oxidative stress and thereby accelerates the advancement of hypertension and heart failure.

A perspective on the role of extracellular hemoglobin on the innate immune system

Host cell-derived danger-associated molecular patterns (DAMPs), such as the hemoglobin (Hb) can interact with the innate immune system either directly or through binding to pathogen-associated molecular patterns (PAMPs). Hemolysis occurs under various pathological conditions, leading to hemoglobinemia. In the extracellular environment, the Hb becomes a redox-reactive DAMP molecule. In severe hemolysis, the massive level of extracellular pro-oxidative Hb generates reactive oxygen species (ROS), which perturbs the innate immune homeostasis. The Hb also binds to PAMPs and triggers Toll-like receptor-mediated signal transduction. In this perspective, we review the roles of cell-free Hb in the innate immune system, focusing on the plausible interactions among Hb, pathogens, host cell components, and innate immune cells, all of which remain to be explored with experiential detail.

Lycopene suppresses proinflammatory response in lipopolysaccharide-stimulated macrophages by inhibiting ROS-induced trafficking of TLR4 to lipid raft-like domains

We recently showed that lycopene inhibited lipopolysaccharide (LPS)-induced productions of nitric oxide (NO) and interleukin-6 (IL-6) in murine RAW264.7 macrophages by mechanisms related to inhibition of ERK and nuclear factor-κB. Since the assembly of Toll-like receptor 4 (TLR4) in lipid rafts is a key element in LPS induced signaling, we investigated whether this process would be influenced by lycopene. We found that pretreatment of RAW264.7 cells with lycopene inhibited LPS-induced recruitment of TLR4 into fractions - enriched with lipid raft marker. By the methods of immunoprecipitation and immunoblotting, we also found that lycopene inhibited the subsequent formation of the complex of TLR4 with its adaptors including myeloid differentiation primary-response protein 88 and TIR domain-containing adaptor-inducing IFN-β. We also found that the lycopene induced inhibition was associated with reduced formation of reactive oxygen species (ROS), which was an upstream mechanism for the effects of lycopene, because treating the cells with the antioxidant N-acetyl-l-cysteine and NADPH oxidase inhibitor diphenyleneiodonium chloride significantly inhibited LPS-induced recruitment of TLR4 into lipid raft-like domains as well as the production of proinflammatory molecule NO and IL-6. Thus, our findings suggest that lycopene may prevent LPS-induced TLR4 assembly into lipid rafts through reducing intracellular ROS level.

Genes of innate immunity and the biological response to inhaled ozone

Ambient ozone has a significant impact on human health. We have made considerable progress in understanding the fundamental mechanisms that regulate the biological response to ozone. It is increasingly clear that genes of innate immunity play a central role in both infectious and noninfectious lung disease. The biological response to ambient ozone provides a clinically relevant environmental exposure that allows us to better understand the role of innate immunity in noninfectious airways disease. In this brief review, we focus on (1) specific cell types in the lung modified by ozone, (2) ozone and oxidative stress, (3) the relationship between genes of innate immunity and ozone, (4) the role of extracellular matrix in reactive airways disease, and (5) the effect of ozone on the adaptive immune system. We summarize recent advances in understanding the mechanisms that ozone contributes to environmental airways disease.

Regulation of mitochondrial function and energetics by reactive nitrogen oxides

Endogenous nitric oxide (NO) generated from L-arginine by NO synthase regulates mitochondrial function by binding to cytochrome c oxidase in competition with oxygen. This interaction can elicit a variety of intracellular signaling events of both physiological and pathophysiological significance. Recent lines of research demonstrate that inorganic nitrate and nitrite, derived from oxidized NO or from the diet, are metabolized in vivo to form NO and other bioactive nitrogen oxides with intriguing effects on cellular energetics and cytoprotection. Here we discuss the latest advances in our understanding of the roles of nitrate, nitrite, and NO in the modulation of mitochondrial function, with a particular focus on dietary nitrate and exercise.