Lipopolysaccharide signals an endothelial apoptosis pathway through TNF receptor-associated factor 6-mediated activation of c-Jun NH2-terminal kinase

Effects of Alkalinity Exposure on Antioxidant Status, Metabolic Function, and Immune Response in the Hepatopancreas of Macrobrachium nipponense

The oriental river prawn Macrobrachium nipponense is an important freshwater economic species in China, producing huge economic benefits. However, M. nipponense shows lower alkali tolerance than fish species, thus genetic selection is urgently needed in order to improve alkali tolerance in this species. In the present study, the effects of alkalinity exposure on the hepatopancreas of M. nipponense were measured under the alkali concentrations of 0 (control), 4, 8, and 12 mmol/L with the exposure time of 96 h through histological observations, measurement of antioxidant enzymes, metabolic profiling analysis, and transcriptome profiling analysis. The present study identified that the low concentration of alkali treatment (<4 mmol/L) did not result in morphological changes in the hepatopancreas and activity changes in antioxidant enzymes, while high-alkali treatment (>8 mmol/L) damaged the normal structures of the lumen and vacuoles and significantly stimulated the levels of superoxide dismutase, catalase, and total antioxidant capacity, indicating these antioxidant enzymes play essential roles in the protection of the body from the damage caused by the alkali treatment. Metabolic profiling analysis revealed that the main enriched metabolic pathways of differentially expressed metabolites in the present study were consistent with the metabolic pathways caused by environmental stress in plants and other aquatic animals. Transcriptome profiling analysis revealed that the alkali concentration of <8 mmol/L did not lead to significant changes in gene expression. The main enriched metabolic pathways were selected from the comparison between 0 mmol/L vs. 12 mmol/L, and some significantly up-regulated genes were selected from these metabolic pathways, predicting these selected metabolic pathways and genes are involved in the adaptation to alkali treatment in M. nipponense. The expressions of Ras-like GTP-binding protein, Doublesex and mab-3 related transcription factor 1a, and Hypothetical protein JAY84 are sensitive to changes in alkali concentrations, suggesting these three genes participated in the process of alkali adaptation in M. nipponense. The present study identified the effects of alkalinity exposure on the hepatopancreas of M. nipponense, including the changes in antioxidant status and the expressions of metabolites and genes, contributing to further studies of alkali tolerance in this species.

Forkhead box protein A2 alleviates toll-like receptor 4-mediated inflammation, endoplasmic reticulum stress, autophagy, and apoptosis induced by lipopolysaccharide in bovine hepatocytes

Lipopolysaccharide (LPS) is an important stimulus of inflammation via binding to toll-like receptor 4 (TLR4), but the role of TLR4 in LPS-induced cellular homeostasis disruption indicated by the increased level of endoplasmic reticulum (ER) stress, autophagy, and apoptosis is unknown in the liver of dairy cows. Previous studies show that forkhead box protein A2 (FOXA2) is an important transcriptional factor to maintain cellular metabolic homeostasis, but the mechanisms by which FOXA2 mediates cellular homeostasis disruption in response to LPS remains unclear. To achieve the aims, hepatocytes separated from dairy cows at ∼160 d in milk were pretreated with a specific TLR4 inhibitor TAK-242 for 12 h, followed by LPS treatment for another 12 h to investigate the role of TLR4 in LPS-induced disruption of cellular homeostasis. The results indicated that LPS-induced nuclear factor-κB (NF-κB)-mediated inflammatory cascades, ER stress, autophagy, and apoptosis via activating TLR4 and downregulating FOXA2 expression in bovine hepatocytes. The application of TLR4 inhibitor alleviated LPS-induced inflammation through inactivating NF-κB proinflammatory pathway, restored cell homeostasis by decreasing the level of ER stress, autophagy, and apoptosis, and upregulated FOXA2 expression. Furthermore, we also elevated FOXA2 expression with an overexpression plasmid to clarify its molecular role in response to LPS challenge. FOXA2 overexpression reduced LPS-caused inflammation by inhibiting NF-κB signaling pathway. Also, FOXA2 could alleviate ER stress to block unfolded protein response and suppress autophagic flux. In addition, FOXA2 enhanced mitochondrial membrane potential via reducing pro-apoptotic protein BAX, CASPASE3, and Cleaved CASPASE3 expression and elevating anti-apoptotic protein BCL-2 expression to mitigate LPS-induced apoptosis. Taken together, these findings suggested that FOXA2 is a mediator to alleviate TLR4-controlled inflammation, ER stress, autophagy, and apoptosis in LPS-treated bovine hepatocytes, it could serve as a potential target to intervene cell homeostasis disruption caused by LPS in the liver of dairy cows.

TIRAP drives myelosuppression through an Ifnγ-Hmgb1 axis that disrupts the endothelial niche in mice

Inflammation is associated with bone marrow failure syndromes, but how specific molecules impact the bone marrow microenvironment is not well elucidated. We report a novel role for the miR-145 target, Toll/interleukin-1 receptor domain containing adaptor protein (TIRAP), in driving bone marrow failure. We show that TIRAP is overexpressed in various types of myelodysplastic syndromes (MDS) and suppresses all three major hematopoietic lineages. TIRAP expression promotes up-regulation of Ifnγ, leading to myelosuppression through Ifnγ-Ifnγr–mediated release of the alarmin, Hmgb1, which disrupts the bone marrow endothelial niche. Deletion of Ifnγ blocks Hmgb1 release and is sufficient to reverse the endothelial defect and restore myelopoiesis. Contrary to current dogma, TIRAP-activated Ifnγ-driven bone marrow suppression is independent of T cell function or pyroptosis. In the absence of Ifnγ, TIRAP drives myeloproliferation, implicating Ifnγ in suppressing the transformation of MDS to acute leukemia. These findings reveal novel, noncanonical roles of TIRAP, Hmgb1, and Ifnγ in the bone marrow microenvironment and provide insight into the pathophysiology of preleukemic syndromes.

Curcumin analogue C66 attenuates obesity-induced myocardial injury by inhibiting JNK-mediated inflammation

Obesity has been recognized as a major risk factor for the development of chronic cardiomyopathy, which is associated with increased cardiac inflammation, fibrosis, and apoptosis. We previously developed an anti-inflammatory compound C66, which prevented inflammatory diabetic complications via targeting JNK. In the present study, we have tested the hypothesis that C66 could prevent obesity-induced cardiomyopathy by suppressing JNK-mediated inflammation. High-fat diet (HFD)-induced obesity mouse model and palmitic acid (PA)-challenged H9c2 cells were used to develop inflammatory cardiomyopathy and evaluate the protective effects of C66. Our data demonstrate a protective effect of C66 against obesity-induced cardiac inflammation, cardiac hypertrophy, fibrosis, and dysfunction, overall providing cardio-protection. C66 administration attenuates HFD-induced myocardial inflammation by inhibiting NF-κB and JNK activation in mouse hearts. In vitro, C66 prevents PA-induced myocardial injury and apoptosis in H9c2 cells, accompanied with inhibition against PA-induced JNK/NF-κB activation and inflammation. The protective effect of C66 is attributed to its potential to inhibit JNK activation, which led to reduced pro-inflammatory cytokine production and reduced apoptosis in cardiomyocytes both in vitro and in vivo. In summary, C66 provides significant protection against obesity-induced cardiac dysfunction, mainly by inhibiting JNK activation and JNK-mediated inflammation. Our data indicate that inhibition of JNK is able to provide significant protection against obesity-induced cardiac dysfunction.

Proteomic analysis using isobaric tags for relative and absolute quantification technology reveals mechanisms of toxic effects of tris (1,3-dichloro-2-propyl) phosphate on RAW264.7 macrophage cells

Tris (1,3-dichloro-2-propyl) phosphate (TDCIPP) is one of the most commonly used organophosphorus flame retardants. Immuno-toxicity induced by TDCIPP is becoming of increasing concern. However, effects of TDCIPP on immune cells and mechanisms resulting in those effects are poorly understood. In this study, it was determined, for the first time, by use of isobaric tags for relative and absolute quantification (iTRAQ) based proteomic techniques expression of global proteins in RAW264.7 cells exposed to 10 μM TDCIPP. A total of 180 significantly differentially expressed proteins (DEPs) were identified. Of these, 127 were up-regulated and 53 were down-regulated. The DEPs associated with toxic effects of TDCIPP were then screened by use of Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes for enrichment analysis. Results showed that these DEPs were involved in a number of pathways including apoptosis, DNA damage, cell cycle arrest, immune-toxicity, and signaling pathways, such as the Toll-like receptor, PPAR and p53 signaling pathways. The complex regulatory relationships between different DEPs, which might play an important role in cell death were also observed in the form of a protein-protein interaction network. Meanwhile, mitochondrial membrane potential (MMP) in RAW264.7 cells after TDCIPP treatment was also analyzed, the collapse of the MMP was speculated to play an important role in TDCIPP induced apoptosis. Moreover, some of the important regulator proteins discovered in this study, such as Chk1, Aurora A, would provide novel insight into the molecular mechanisms involved in toxic responses to TDCIPP.

β2M Signals Monocytes Through Non-Canonical TGFβ Receptor Signal Transduction

RATIONALE

Circulating monocytes can have proinflammatory or proreparative phenotypes. The endogenous signaling molecules and pathways that regulate monocyte polarization in vivo are poorly understood. We have shown that platelet-derived β2M (β-2 microglobulin) and TGF-β (transforming growth factor β) have opposing effects on monocytes by inducing inflammatory and reparative phenotypes, respectively, but each bind and signal through the same receptor. We now define the signaling pathways involved.

OBJECTIVE

To determine the molecular mechanisms and signal transduction pathways by which β2M and TGF-β regulate monocyte responses both in vitro and in vivo.

METHODS AND RESULTS

Wild-type- (WT) and platelet-specific β2M knockout mice were treated intravenously with either β2M or TGF-β to increase plasma concentrations to those in cardiovascular diseases. Elevated plasma β2M increased proinflammatory monocytes, while increased plasma TGFβ increased proreparative monocytes. TGF-βR (TGF-β receptor) inhibition blunted monocyte responses to both β2M and TGF-β in vivo. Using imaging flow cytometry, we found that β2M decreased monocyte SMAD2/3 nuclear localization, while TGF-β promoted SMAD nuclear translocation but decreased noncanonical/inflammatory (JNK [jun kinase] and NF-κB [nuclear factor-κB] nuclear localization). This was confirmed in vitro using both imaging flow cytometry and immunoblots. β2M, but not TGF-β, promoted ubiquitination of SMAD3 and SMAD4, that inhibited their nuclear trafficking. Inhibition of ubiquitin ligase activity blocked noncanonical SMAD-independent monocyte signaling and skewed monocytes towards a proreparative monocyte response.

CONCLUSIONS

Our findings indicate that elevated plasma β2M and TGF-β dichotomously polarize monocytes. Furthermore, these immune molecules share a common receptor but induce SMAD-dependent canonical signaling (TGF-β) versus noncanonical SMAD-independent signaling (β2M) in a ubiquitin ligase dependent manner. This work has broad implications as β2M is increased in several inflammatory conditions, while TGF-β is increased in fibrotic diseases. Graphic Abstract: A graphic abstract is available for this article.

Toll-like receptors: Triggers of regulated cell death and promising targets for cancer therapy

Toll-like receptors (TLRs) belong to a family of pattern recognition receptors (PRRs). It is well known that TLRs play an essential role in activating innate and adaptive immune responses. TLRs are involved in mediating inflammatory responses and maintaining epithelial barrier homeostasis, and they are highly likely to activate various signalling pathways during cancer chemotherapy. For a long time, much research focused on the immune modulating function of TLRs in cancer genesis, pathology and therapeutic strategies. However, recent reports have suggested that except for the innate and adaptive immune responses that they initiate, TLRs can signal to induce regulated cell death (RCD), which also plays an important role in the antitumor process. TLR agonists also have been investigated as cancer therapeutic agents under clinical evaluation. In this review, we focused on the mechanism of RCD induced by TLR signals and the important role that they play in anticancer therapy combined with recent experimental and clinical trial data to discuss the possibility of TLRs as promising targets for cancer therapy. TLRs represent triggers of regulated cell death and targets for cancer therapy. The molecular mechanisms of TLR-induced RCD and relationship between TLR-signalling pathways and cancer remain to be investigated by further studies.

Ruscogenin alleviates LPS-induced pulmonary endothelial cell apoptosis by suppressing TLR4 signaling

Acute lung injury (ALI) or its most advanced form, acute respiratory distress syndrome (ARDS) is a severe inflammatory pulmonary process triggered by varieties of pathophysiological factors, among which apoptosis of pulmonary endothelial cells plays a critical role in the progression of ALI/ARDS. Ruscogenin (RUS) has been found to exert significant protective effect on ALI induced by lipopolysaccharides (LPS), but there is little information about its role in LPS-induced pulmonary endothelial cell apoptosis. The aim of the present study was to investigate the underlying mechanism in which RUS attenuates LPS-induced pulmonary endothelial cell apoptosis. Mice were challenged with LPS (5 mg/kg) by intratracheal instillation for 24 h to induce apoptosis of pulmonary endothelial cells in model group. RUS (three doses: 0.1, 0.3, and 1 mg/kg) was administrated orally 1 h prior to LPS challenge. The results showed that RUS could attenuate LPS-induced lung injury and pulmonary endothelial apoptosis significantly. And we observed that RUS inhibited the activation of TLR4/MYD88/NF-κB pathway in pulmonary endothelium after LPS treatment. In murine lung vascular endothelial cells (MLECs) we further confirmed that RUS (1 μmol/L) markedly ameliorated MLECs apoptosis by suppressing TLR4 signaling. By using TLR4 knockout mice we found that TLR4 was essential for the RUS-mediated eff ;ect on LPS-stimulated pulmonary endothelial apoptosis. Collectively, our results indicate that RUS plays a protective role against LPS-induced endothelial cell apoptosis via regulating TLR4 signaling, and may be a promising agent in the management of ALI.

Expression of the Phosphatase Ppef2 Controls Survival and Function of CD8+ Dendritic Cells

Apoptotic cell death of Dendritic cells (DCs) is critical for immune homeostasis. Although intrinsic mechanisms controlling DC death have not been fully characterized up to now, experimentally enforced inhibition of DC-death causes various autoimmune diseases in model systems. We have generated mice deficient for Protein Phosphatase with EF-Hands 2 (Ppef2), which is selectively expressed in CD8⁺ DCs, but not in other related DC subtypes such as tissue CD103⁺ DCs. Ppef2 is down-regulated rapidly upon maturation of DCs by toll-like receptor stimuli, but not upon triggering of CD40. Ppef2-deficient CD8⁺ DCs accumulate the pro-apoptotic Bcl-2-like protein 11 (Bim) and show increased apoptosis and reduced competitve repopulation capacities. Furthermore, Ppef2^−/− CD8⁺ DCs have strongly diminished antigen presentation capacities in vivo, as CD8⁺ T cells primed by Ppef2^−/− CD8⁺ DCs undergo reduced expansion. In conclusion, our data suggests that Ppef2 is crucial to support survival of immature CD8⁺ DCs, while Ppef2 down-regulation during DC-maturation limits T cell responses.

Isoalantolactone suppresses LPS-induced inflammation by inhibiting TRAF6 ubiquitination and alleviates acute lung injury

Isoalantolactone (IAL) is a sesquiterpene lactone extracted from roots of Inula helenium L and has shown anti-inflammatory effects. In this study we investigated the therapeutic effects of IAL on acute lung injury (ALI) and elucidated the mechanisms underlying its anti-inflammation potential in vitro and in vivo. Treatment with lipopolysaccharide (LPS, 100 ng/mL) drastically stimulated production of inflammatory mediators such as NO, TNF-α, IL-1β, and IL-6 in mouse bone marrow-derived macrophages (BMDMs), which was dose-dependently suppressed by pretreatment with IAL (2.5, 5, 10, 20 μM). We further revealed that IAL suppressed LPS-induced NF-κB, ERK, and Akt activation. Moreover, the downregulation of non-degradable K63-linked polyubiquitination of TRAF6, an upstream transcription factor of NF-κB, contributed to the anti-inflammatory effects of IAL. ALI was induced in mice by intratracheal injection of LPS (5 mg/kg). Administration of IAL (20 mg/kg, i.p.) significantly suppressed pulmonary pathological changes, neutrophil infiltration, pulmonary permeability, and pro-inflammatory cytokine expression. Our results demonstrate that IAL is a potential therapeutic reagent against inflammation and ALI.

Rho Kinase Type 1 (ROCK1) Promotes Lipopolysaccharide-induced Inflammation in Corneal Epithelial Cells by Activating Toll-Like Receptor 4 (TLR4)-Mediated Signaling

Background

Rho kinases (ROCKs) are the typical downstream effectors of RhoA, which can regulate corneal epithelial wound healing. In this study, the role of ROCK1 in lipopolysaccharide (LPS)-induced cornea inflammation was investigated.

Material/Methods

The expression of ROCK1 in human corneal epithelial cells (HCECs) was bilaterally modulated with ROCK1 expression vector and ROCK1 inhibitor Y-27632. The effects of ROCK1 modulation on the inflammatory response, cell viability, cell apoptosis, and cell cycle distribution were detected by ELISA assay, MTT assay, and flow cytometry, respectively. The pathways involved in the effect of ROCK1 in HCECs was preliminarily explained by detecting changes of TLR4-mediated NF-κB and ERK signaling using western blotting and electrophoretic mobility shift assays.

Results

Overexpression of ROCK1 promoted LPS-induced production of IL-6, IL-8, IL-1β, and TNF-α, and the apoptotic process in HCECs. Augmented inflammation and apoptosis were associated with stronger activation of TLR4-mediated signal transduction; the phosphorylation of IκBα, JNK, ERK1/2, and p38, and nuclear translocation of NF-κB p65 induced by LPS were further increased by overexpression of ROCK1. Inhibition of ROCK1 function by Y-27632 blocked the effect of LPS on HCECs; both LPS-induced inflammation and apoptosis was alleviated by Y-27632, which was associated with suppression of TLR4-mediated NF-κB and ERK signaling.

Conclusions

LPS-induced inflammation and apoptosis in HCECs depended on the function of ROCK1, inhibition of which would attenuate impairments on cornea cells due to LPS.

Cereblon suppresses the lipopolysaccharide-induced inflammatory response by promoting the ubiquitination and degradation of c-Jun

Chronic inflammation is associated with multiple human disorders, such as rheumatoid arthritis, metabolic diseases, and neurodegenerative diseases. Therefore, alleviation of inflammation induced by environmental stimuli is important for disease prevention or treatment. Cereblon (CRBN) functions as a substrate receptor of the cullin-4 RING E3 ligase to mediate protein ubiquitination and degradation. Although it has been reported that CRBN reduces the inflammatory response through its nonenzymatic function, its role as a substrate receptor of the E3 ligase is not explored in mediating this process. Here we used a quantitative proteomics approach to find that the major component of the activator protein 1 (AP-1) complex, c-Jun, is significantly down-regulated upon CRBN expression. Biochemical approaches further discover that CRBN interacts and partially colocalizes with c-Jun and promotes the formation of Lys⁴⁸-linked polyubiquitin chains on c-Jun, enhancing c-Jun degradation. We further reveal that CRBN attenuates the transcriptional activity of the AP-1 complex and reduces the mRNA expression and protein level of several pro-inflammatory cytokines. Moreover, flow cytometry analyses show that CRBN attenuates lipopolysaccharide-induced apoptosis in differentiated THP-1 cells. Through genetic manipulation and pharmacological inhibition, we uncover a new molecular mechanism by which CRBN regulates the inflammatory response and apoptosis induced by lipopolysaccharide. Our work and previous studies demonstrate that CRBN suppresses the inflammatory response by promoting or inhibiting the ubiquitination of two key molecules at different levels of the inflammatory cascade through its enzymatic function as a substrate receptor and its nonenzymatic function as a protein binding partner.

Induction of antitumor cytotoxic lymphocytes using engineered human primary blood dendritic cells

Dendritic cell (DC)-based cancer immunotherapy has achieved modest clinical benefits, but several technical hurdles in DC preparation, activation, and cancer/testis antigen (CTA) delivery limit its broad applications. Here, we report the development of immortalized and constitutively activated human primary blood dendritic cell lines (ihv-DCs). The ihv-DCs are a subset of CD11c+/CD205+ DCs that constitutively display costimulatory molecules. The ihv-DCs can be genetically modified to express human telomerase reverse transcriptase (hTERT) or the testis antigen MAGEA3 in generating CTA-specific cytotoxic T lymphocytes (CTLs). In an autologous setting, the HLA-A2+ ihv-DCs that present hTERT antigen prime autologous T cells to generate hTERT-specific CTLs, inducing cytolysis of hTERT-expressing target cells in an HLA-A2-restricted manner. Remarkably, ihv-DCs that carry two allogeneic HLA-DRB1 alleles are able to prime autologous T cells to proliferate robustly in generating HLA-A2-restricted, hTERT-specific CTLs. The ihv-DCs, which are engineered to express MAGEA3 and high levels of 4-1BBL and MICA, induce simultaneous production of both HLA-A2-restricted, MAGEA3-specific CTLs and NK cells from HLA-A2+ donor peripheral blood mononuclear cells. These cytotoxic lymphocytes suppress lung metastasis of A549/A2.1 lung cancer cells in NSG mice. Both CTLs and NK cells are found to infiltrate lung as well as lymphoid tissues, mimicking the in vivo trafficking patterns of cytotoxic lymphocytes. This approach should facilitate the development of cell-based immunotherapy for human lung cancer.

Dual function of peroxiredoxin I in lipopolysaccharide-induced osteoblast apoptosis via reactive oxygen species and the apoptosis signal-regulating kinase 1 signaling pathway

Lipopolysaccharide (LPS)-induced osteoblast apoptosis is a prominent factor to the defect in periodontal tissue repair in periodontal disease. LPS challenge contributes to the production of reactive oxygen species (ROS) in periodontitis, and peroxiredoxin 1 (Prx1) is an antioxidant protein that protect cells against oxidative damage from ROS. Without LPS stimulation, apoptotic rates were higher in both Prx1 knockout (Prx1^KO) and Prx1 overexpression (Prx1^OE) cells compared with wild type. After LPS stimulation, intracellular ROS in Prx1^KO cells showed the highest level and Prx1^OE cells showed the least. Treatment with LPS significantly elevated the expression of Bax, Cyto-c, and caspase 3 in Prx1^KO cells compared with wild type, although this could be completely abolished by NAC. In Prx1^OE cells, the expression and activation of ASK1 were significantly increased, and this was slightly reduced by LPS stimulation. NQDI-1 completely abolished the increased phosphorylation of JNK and p38 and the expression of caspase 3 in LPS-stimulated cells. These results indicate that Prx1 eliminates intracellular ROS and exhibits a cytoprotective role in LPS-induced apoptosis. However, under physiological conditions, Prx1 overexpression acts as a H₂O₂ messenger, triggering the expression of ASK1 and its downstream cascades.

Hepatoprotective effect of quercetin via TRAF6/JNK pathway in acute hepatitis

Quercetin, as a member of the flavonoids family, has many beneficial properties. The aim of our study was to evaluate the protective effect of quercetin in ConA-induced hepatitis in mice, and to clarify its mechanism of action. Hepatitis was induced by using ConA (25 mg/kg), and quercetin was administered intragastrically at the dose of 100 mg/kg or 200 mg/kg for 5 days before ConA injection. The serum levels of liver enzymes, inflammatory cytokines and other marker proteins were determined at 2 h, 8 h and 24 h after ConA injection. Following ConA injection, serum levels of liver enzymes and inflammatory cytokines were significantly increased. Quercetin ameliorated liver damage and histopathological changes, and suppressed the release of inflammatory cytokines. The expression of Bax, Bcl-2, Beclin-1, LC3, P62 and caspase 9 were markedly affected by quercetin pretreatment. The expression of TRAF6 and p-JNK were decreased in the quercetin groups. Quercetin attenuated apoptosis and autophagy in ConA-induced autoimmune hepatitis by inhibiting TRAF6/JNK pathway.

Geraniol alleviates LPS-induced acute lung injury in mice via inhibiting inflammation and apoptosis

Geraniol (GOH), a special type of acyclic monoterpene alcohol, has been widely used to treat many diseases associated with inflammation and apoptosis. Acute lung injury (ALI) is a common clinical disease in humans characterized by pulmonary inflammation and apoptosis. In the present study, we investigated the protective effects of GOH in a mouse model of ALI induced by the intranasal administration of lipopolysaccharide (LPS) and elucidated the underlying molecular mechanisms in RAW 264.7 cells. In vivo, GOH treatment markedly ameliorated pathological injury and pulmonary cell apoptosis and reduced the wet/dry (W/D) weight ratio of lungs, myeloperoxidase (MPO) activity and the production of pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α). In vitro, the levels of pro-inflammatory cytokines, iNOS and COX-2 were significantly increased in LPS-stimulated RAW 264.7 cells, an effect that was decreased by GOH treatment. Moreover, GOH treatment dramatically reduced the expression of Toll-like receptor 4 (TLR4) and then prevented the nuclear factor-κB (NF-κB) activation. GOH treatment also promoted anti-apoptotic Bcl-2 expression and inhibited pro-apoptotic Bax and Caspase-3 expression. Furthermore, knockdown of TLR4 expression exerted a similar effect and inhibited the phosphorylation of p65, as well as the Bax and Caspase-3 expression. Taken together, these results suggest that GOH treatment alleviates LPS-induced ALI via inhibiting pulmonary inflammation and apoptosis, a finding that might be associated with the inhibition of TLR4-mediated NF-κB and Bcl-2/Bax signalling pathways.

Highly electronegative low-density lipoprotein L5 evokes microglial activation and creates a neuroinflammatory stress via Toll-like receptor 4 signaling

Atherogenic risk factors, such as hypercholesterolemia, are associated with increased risk of neurodegeneration, especially Alzheimer's dementia. Human plasma electronegative low-density lipoprotein [LDL(-)], especially L5, may serve as an important contributing factor. L5 promoting an inflammatory action in atherosclerosis has been extensively studied. However, the role of L5 in inducing neuroinflammation remains unknown. Here, we examined the impact of L5 on immune activation and cell viability in cultured BV-2 microglia. BV-2 cells treated with lipopolysaccharide or human LDLs (L1, L5, or oxLDL) were subjected to molecular/biochemical assays for measuring microglial activation, levels of inflammatory factors, and cell survival. A transwell BV-2/N2a co-culture was used to assess N2a cell viability following BV-2 cell exposure to L5. We found that L5 enables the activation of microglia and elicits an inflammatory response, as evidenced by increased oxygen/nitrogen free radicals (nitric oxide, reactive oxygen species, and peroxides), elevated tumor necrosis factor-α levels, decreased basal interleukin-10 levels, and augmented production of pro-inflammatory proteins (inducible nitric oxide synthase and cyclooxygenase-2). L5 also triggered BV-2 cell death primarily via apoptosis. These effects were markedly disrupted by the application of signaling pathway inhibitors, thus demonstrating that L5 interacts with Toll-like receptor 4 to modulate multiple pathways, including MAPKs, PI3K/Akt, and NF-κB. Decreased N2a cell viability in a transwell co-culture was mainly ascribed to L5-induced BV-2 cell activation. Together, our data suggest that L5 creates a neuroinflammatory stress via microglial Toll-like receptor 4, thereby leading to the death of BV-2 microglia and coexistent N2a cells. Atherogenic L5 possibly contributes to neuroinflammation-related neurodegeneration.

Human Host Defense Cathelicidin Peptide LL-37 Enhances the Lipopolysaccharide Uptake by Liver Sinusoidal Endothelial Cells without Cell Activation

The liver is a major organ that removes waste substances from the blood, and liver sinusoidal endothelial cells (LSECs) are professional scavenger cells, which incorporate and degrade various endogenous and exogenous molecules including pathogenic factor LPS. Mammalian cells express a number of peptide antibiotics that function as effectors in the innate host defense systems. LL-37, a human cathelicidin antimicrobial peptide, has a potent LPS-neutralizing activity and exhibits protective actions on various infection models. However, the effect of LL-37 on the LPS clearance has not been clarified. In this study, to further understand the host-protective mechanism of LL-37, we evaluated the effect of LL-37 on the LPS clearance in vitro. LL-37 enhanced the LPS uptake by human LSECs. Of interest, LL-37 was similarly incorporated into LSECs both in the presence and the absence of LPS, and the incorporated LPS and LL-37 were colocalized in LSECs. Importantly, the uptake of LPS and LL-37 was inhibited by endocytosis inhibitors, heparan sulfate proteoglycan analogs, and glycosaminoglycan lyase treatment of the cells. Moreover, the uptake of LL-37-LPS did not activate TLR4 signaling in both MyD88-dependent and -independent pathways. In addition, the incorporated LL-37-LPS was likely transported to the lysosomes in LSECs. Together these observations suggest that LL-37 enhances the LPS uptake by LSECs via endocytosis through the complex formation with LPS and the interaction with cell-surface heparan sulfate proteoglycans, thereby facilitating the intracellular incorporation and degradation of LPS without cell activation. In this article, we propose a novel function of LL-37 in enhancing LPS clearance.

Lacritin Salvages Human Corneal Epithelial Cells from Lipopolysaccharide Induced Cell Death

Innate immunity of the corneal epithelium is conferred by proteinaceous secretions from the epithelium and associated lacrimal and meibomian glands. Lacritin, an eye-specific protein with anti-microbial, cytoprotective and wound-healing properties, predominantly secreted by lacrimal glands, is absent in conditions such as Dry eye and Keratitis. In view of the biological significance of lacritin in human eye, we investigated its role in human corneal epithelial (HCE) cells during lipopolysaccharide (LPS)-induced infection. LPS-challenged HCE cells demonstrated apoptosis-mediated cell death and elevated lacritin levels. The LPS-induced cell death is alleviated with exogenous supplementation of recombinant lacritin. This cytoprotective effect of lacritin is mediated through Cyclooxygenase-2 (COX-2). This study is the first to highlight the protective role of lacritin and mechanism of its action during bacterial infection of cornea in vitro.

Modulation of inflammatory response of wounds by antimicrobial photodynamic therapy

BACKGROUND AND AIMS

Management of infections caused by Pseudomonas aeruginosa is becoming difficult due to the rapid emergence of multi-antibiotic resistant strains. Antimicrobial photodynamic therapy (APDT) has a lot of potential as an alternative approach for inactivation of antibiotic resistant bacteria. In this study we report results of our investigations on the effect of poly-L-lysine conjugate of chlorine p6 (pl-cp6) mediated APDT on the healing of P.aeruginosa infected wounds and the role of Nuclear Factor kappa B (NF-kB) induced inflammatory response in this process.

MATERIALS AND METHOD

Excisional wounds created in Swiss albino mice were infected with ∼10(7) colony forming units of P.aeruginosa. Mice with wounds were divided into three groups: 1) Uninfected, 2) Infected, untreated control (no light, no pl-cp6), 3) Infected, APDT. After 24 h of infection (day 1 post wounding), the wounds were subjected to APDT [pl-cp6 applied topically and exposed to red light (660 ± 25 nm) fluence of ∼ 60 J/cm(2)]. Subsequent to APDT, on day 2 and 5 post wounding (p.w), measurements were made on biochemical parameters of inflammation [toll like receptor-4 (TLR-4), NF-kB, Inteleukin (IL)-[1α, IL-β, and IL-2)] and cell proliferation [(fibroblast growth factor-2 (FGF-2), alkaline phosphatase (ALP)].

RESULTS

In comparison with untreated control, while expression of TLR-4, NF-kB (p105 and p50), and proinflammatory interleukins (IL-1α, IL-1β,IL-2) were reduced in the infected wounds subjected to APDT, the levels of FGF-2 and ALP increased, on day 5 p.w.

CONCLUSION

The measurements made on the inflammatory markers and cell proliferation markers suggest that APDT reduces inflammation caused by P.aeruginosa and promotes cell proliferation in wounds.

Lipopolysaccharide pretreatment inhibits LPS-induced human umbilical cord mesenchymal stem cell apoptosis via upregulating the expression of cellular FLICE-inhibitory protein

Mesenchymal stem cell (MSC)-based regenerative therapy is currently regarded as a novel approach with which to repair damaged tissues. However, the efficiency of MSC transplantation is limited due to the low survival rate of engrafted MSCs. Lipopolysaccharide (LPS) production is increased in numerous diseases and serves an essential function in the regulation of apoptosis in a variety of cell types. Previous studies have indicated that low-dose LPS pretreatment contributes to cytoprotection. In the current study, LPS was demonstrated to induce apoptosis in human umbilical cord mesenchymal stem cells (hUCMSCs) via the activation of caspase, in a dose-dependent manner. Low-dose LPS pretreatment may protect hUCMSCs against apoptosis induced by high-dose LPS, by upregulating the expression of cellular FADD-like IL-1β-converting enzyme-inhibitory protein (c-FLIP). The results of the present study indicate that pretreatment with an appropriate concentration of LPS may alleviate high-dose LPS-induced apoptosis.

The synthetic curcuminoid BHMC restores endotoxin-stimulated HUVEC dysfunction:Specific disruption on enzymatic activity of p38 MAPK

2,6-bis-(4-hydroxyl-3-methoxybenzylidine)cyclohexanone (BHMC) has been proven to selectively inhibit the synthesis of proinflammatory mediators in lipopolysaccharide-induced U937 monocytes through specific interruption of p38 Mitogen-Activated Protein Kinase enzymatic activity and improves the survival rate in a murine lethal sepsis model. The present study addressed the effects of BHMC upon lipopolysaccharide-induced endothelial dysfunction in human umbilical vein endothelial cells to determine the underlying mechanisms. The cytotoxicity effect of BHMC on HUVEC were determined by MTT assay. The effects of BHMC on endothelial dysfunction induced by lipopolysaccharide such as endothelial hyperpermeability, monocyte-endothelial adhesion, transendothelial migration, up-regulation of adhesion molecules and chemokines were evaluated. The effects of BHMC at transcriptional and post-translational levels were determined by Reverse Transcriptase-Polymerase Chain Reaction and Western Blots. The mode of action of BHMC was dissected by looking into the activation of Nuclear Factor-kappa B and Mitogen-Activated Protein Kinases. BHMC concentration-dependently reduced endothelial hyperpermeability, leukocyte-endothelial cell adhesion and monocyte transendothelial migration through inhibition of the protein expression of adhesion molecules (Intercellular Adhesion Molecule-1 and Vascular Cell Adhesion Molecule-1) and secretion of chemokines (Monocyte Chemotactic Protein-1) at the transcriptional level. BHMC restored endothelial dysfunction via selective inhibition of p38 Mitogen-Activated Protein Kinase enzymatic activity which indirectly prevents the activation of Nuclear Factor-kappaB and Activator Protein-1 transcription factors. These findings further support earlier observations on the inhibition of BHMC on inflammatory events through specific disruption of p38 Mitogen-Activated Protein Kinase enzymatic activity and provide new insights into the inhibitory effects of BHMC on lipopolysaccharide-induced endothelial dysfunction.

Noncoding RNAs regulate NF-κB signaling to modulate blood vessel inflammation

Cardiovascular diseases such as atherosclerosis are one of the leading causes of morbidity and mortality worldwide. The clinical manifestations of atherosclerosis, which include heart attack and stroke, occur several decades after initiation of the disease and become more severe with age. Inflammation of blood vessels plays a prominent role in atherogenesis. Activation of the endothelium by inflammatory mediators leads to the recruitment of circulating inflammatory cells, which drives atherosclerotic plaque formation and progression. Inflammatory signaling within the endothelium is driven predominantly by the pro-inflammatory transcription factor, NF-κB. Interestingly, activation of NF-κB is enhanced during the normal aging process and this may contribute to the development of cardiovascular disease. Importantly, studies utilizing mouse models of vascular inflammation and atherosclerosis are uncovering a network of noncoding RNAs, particularly microRNAs, which impinge on the NF-κB signaling pathway. Here we summarize the literature regarding the control of vascular inflammation by microRNAs, and provide insight into how these microRNA-based pathways might be harnessed for therapeutic treatment of disease. We also discuss emerging areas of endothelial cell biology, including the involvement of long noncoding RNAs and circulating microRNAs in the control of vascular inflammation.

TRAF6 upregulation in spinal astrocytes maintains neuropathic pain by integrating TNF-α and IL-1β signaling

The proinflammatory cytokines tumor necrosis factor (TNF) α and interleukin (IL) 1β have been strongly implicated in the pathogenesis of neuropathic pain, but the intracellular signaling of these cytokines in glial cells is not fully understood. TNF receptor-associated factor 6 (TRAF6) plays a key role in signal transduction in the TNF receptor superfamily and the IL-1 receptor superfamily. In this study, we investigated the role of TRAF6 in neuropathic pain in mice after spinal nerve ligation (SNL). SNL induced persistent TRAF6 upregulation in the spinal cord. Interestingly, TRAF6 was mainly colocalized with the astrocytic marker glial fibrillary acidic protein on SNL day 10 and partially expressed in microglia on SNL day 3. In cultured astrocytes, TRAF6 was upregulated after exposure to TNF-α or IL-1β. TNF-α or IL-1β also increased CCL2 expression, which was suppressed by both siRNA and shRNA targeting TRAF6. TRAF6 siRNA treatment also inhibited the phosphorylation of c-Jun N-terminal kinase (JNK) in astrocytes induced by TNF-α or IL-1β. JNK inhibitor D-NKI-1 dose-dependently decreased IL-1β-induced CCL2 expression. Moreover, spinal injection of TRAF6 siRNA decreased intrathecal TNF-α- or IL-1β-induced allodynia and hyperalgesia. Spinal TRAF6 inhibition via TRAF6 siRNA, shRNA lentivirus, or antisense oligodeoxynucleotides partially reversed SNL-induced neuropathic pain and spinal CCL2 expression. Finally, intrathecal injection of TNF-α-activated astrocytes induced mechanical allodynia, which was attenuated by pretreatment of astrocytes with TRAF6 siRNA. Taken together, the results suggest that TRAF6, upregulated in spinal cord astrocytes in the late phase after nerve injury, maintains neuropathic pain by integrating TNF-α and IL-1β signaling and activating the JNK/CCL2 pathway in astrocytes.

Geniposide inhibited lipopolysaccharide-induced apoptosis by modulating TLR4 and apoptosis-related factors in mouse mammary glands

AIMS

Geniposide, a major iridoid glycoside found in gardenia fruit, is widely used in Asian countries for its anti-inflammatory, anti-tumor and anti-apoptotic activities. Although the anti-inflammatory effect of geniposide has been widely reported, its anti-apoptotic role in mastitis remains unclear. In the present study, we investigated whether geniposide exerts anti-apoptotic activity in lipopolysaccharide (LPS)-induced mouse mammary glands.

MAIN METHODS

We established a LPS-induced mouse mastitis model and LPS-stimulated primary mouse mammary epithelial cells (mMECs) model to investigate the anti-apoptotic effect of geniposide and the underlying mechanism of action. In the in vivo studies, apoptosis in mammary glands was detected by TUNEL. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot were used to analyze the expression of Bax, Bcl-2, Caspase-3 and p53. In the in vitro study, the apoptosis in mammary epithelial cells was measured by Live-Dead staining. Western blot and qRT-PCR analysis were used to analyze the expression of Bax, Bcl-2, Caspase-3, p53 and TLR4.

KEY FINDINGS

Geniposide alleviated mammary gland apoptosis, down-regulated Bax expression, inhibited Caspase-3 cleavage and p53 phosphorylation and up-regulated Bcl-2 expression in vivo. In vitro, geniposide decreased the ratio of dead cells in a dose-dependent manner. Geniposide inhibited Bax expression and Caspase-3 cleavage, and up-regulated the expression of Bcl-2. Moreover, geniposide down-regulated the expression of TLR4 and repressed the phosphorylation of p53.

SIGNIFICANCE

These results demonstrate that the anti-apoptotic property of geniposide is due to its modulation of TLR4 and apoptosis-related factors (p53, Bax, Bcl-2 and Caspase-3) in LPS-induced mouse mastitis.

Inhibition of JNK phosphorylation by a novel curcumin analog prevents high glucose-induced inflammation and apoptosis in cardiomyocytes and the development of diabetic cardiomyopathy

Hyperglycemia-induced inflammation and apoptosis have important roles in the pathogenesis of diabetic cardiomyopathy. We recently found that a novel curcumin derivative, C66, is able to reduce the high glucose (HG)-induced inflammatory response. This study was designed to investigate the protective effects on diabetic cardiomyopathy and its underlying mechanisms. Pretreatment with C66 significantly reduced HG-induced overexpression of inflammatory cytokines via inactivation of nuclear factor-κB in both H9c2 cells and neonatal cardiomyocytes. Furthermore, we showed that the inhibition of Jun NH2-terminal kinase (JNK) phosphorylation contributed to the protection of C66 from inflammation and cell apoptosis, which was validated by the use of SP600125 and dominant-negative JNK. The molecular docking and kinase activity assay confirmed direct binding of C66 to and inhibition of JNK. In mice with type 1 diabetes, the administration of C66 or SP600125 at 5 mg/kg significantly decreased the levels of plasma and cardiac tumor necrosis factor-α, accompanied by decreasing cardiac apoptosis, and, finally, improved histological abnormalities, fibrosis, and cardiac dysfunction without affecting hyperglycemia. Thus, this work demonstrated the therapeutic potential of the JNK-targeting compound C66 for the treatment of diabetic cardiomyopathy. Importantly, we indicated a critical role of JNK in diabetic heart injury, and suggested that JNK inhibition may be a feasible strategy for treating diabetic cardiomyopathy.

Antiapoptotic and proapoptotic signaling of cyclophilin A in endothelial cells

Endothelial cell (EC) dysfunction is a key event in the onset and progression of atherosclerosis. Apoptosis may lead to endothelial dysfunction and contribute to vascular complications. Cyclophilin A (CyPA) is the main reactive oxygen species-induced factor that enhances the inflammatory activity of vascular cells in atherosclerotic plaques. However, the mechanism by which CyPA induces EC apoptosis is not entirely clear. Through Western blot, it demonstrated that extracellular CyPA activated the Akt and NF-κB pathway, followed by the upregulation of antiapoptotic protein Bcl-2 expression in ECs. When blocking intracellular CyPA by small interfering RNA in ECs, the effects of TNF-α-induced EC apoptosis and proapoptotic protein caspase-3 expression were significantly inhibited. This study shows that CyPA may initiate antiapoptotic and proapoptotic signaling in ECs, especially in response to reactive oxygen species stimulation. It serves as a potential target for atherosclerosis therapy.

Apigenin protects endothelial cells from lipopolysaccharide (LPS)-induced inflammation by decreasing caspase-3 activation and modulating mitochondrial function

Acute and chronic inflammation is characterized by increased reactive oxygen species (ROS) production, dysregulation of mitochondrial metabolism and abnormal immune function contributing to cardiovascular diseases and sepsis. Clinical and epidemiological studies suggest potential beneficial effects of dietary interventions in inflammatory diseases but understanding of how nutrients work remains insufficient. In the present study, we evaluated the effects of apigenin, an anti-inflammatory flavonoid abundantly found in our diet, in endothelial cells during inflammation. Here, we show that apigenin reduced lipopolysaccharide (LPS)-induced apoptosis by decreasing ROS production and the activity of caspase-3 in endothelial cells. Apigenin conferred protection against LPS-induced mitochondrial dysfunction and reestablished normal mitochondrial complex I activity, a major site of electron leakage and superoxide production, suggesting its ability to modulate endothelial cell metabolic function during inflammation. Collectively, these findings indicate that the dietary compound apigenin stabilizes mitochondrial function during inflammation preventing endothelial cell damage and thus provide new translational opportunities for the use of dietary components in the prevention and treatment of inflammatory diseases.

Heterotrimeric Gi/Go proteins modulate endothelial TLR signaling independent of the MyD88-dependent pathway

The innate immune recognition of bacterial lipopolysaccharide (LPS) is mediated by Toll-like receptor 4 (TLR4) and results in activation of proinflammatory signaling including NF-κB and MAPK pathways. Heterotrimeric G proteins have been previously implicated in LPS signaling in macrophages and monocytes. In the present study, we show that pertussis toxin sensitive heterotrimeric G proteins (Gα(i/o)) are involved in the activation of MAPK and Akt downstream of TLR2, TLR3, and TLR4 in endothelial cells. Gα(i/o) are also required for full activation of interferon signaling downstream of TLR3 and TLR4 but are not required for the activation of NF-κB. We find that Gα(i/o)-mediated activation of the MAPK is independent of the canonical MyD88, interleukin-1 receptor-associated kinase, and tumor necrosis factor receptor-associated factor 6 signaling cascade in LPS-stimulated cells. Taken together, the data presented here suggest that heterotrimeric G proteins are widely involved in TLR pathways along a signaling cascade that is distinct from MyD88-TRAF6.

Human anti-microbial cathelicidin peptide LL-37 suppresses the LPS-induced apoptosis of endothelial cells

Sepsis is a systemic disease resulting from harmful host response to bacterial infections. During the exacerbation of severe sepsis or septic shock, apoptosis of endothelial cells is induced in susceptible organs such as the lung and liver and triggers microcirculatory disorder and organ dysfunction. LPS, an outer membrane component of Gram-negative bacteria, is one of the major virulence factors for the pathogenesis. We previously reported that LL-37, a human anti-microbial cathelicidin peptide, potently neutralizes the biological activity of LPS and protects mice from lethal endotoxin shock. However, the effect of LL-37 on the LPS-induced endothelial cell apoptosis remains to be clarified. In this study, to further elucidate the action of LL-37 on severe sepsis/endotoxin shock, we investigated the effects of LL-37 on the LPS-induced endothelial cell apoptosis in vitro and in vivo using lung-derived normal human microvascular blood vessel endothelial cells (HMVEC-LBls) and D-galactosamine hydrochloride (D-GalN)-sensitized murine endotoxin shock model. LL-37 suppressed the LPS-induced apoptosis of HMVEC-LBls. In addition, LL-37 inhibited the binding of LPS possibly to the LPS receptors (CD14 and toll-like receptor 4) expressed on the cells. Thus, LL-37 can suppress the LPS-induced apoptosis of HMVEC-LBls via the inhibition of LPS binding to the cells. Furthermore, LL-37 drastically suppressed the apoptosis of hepatic endothelial cells as well as hepatocytes in the liver of murine endotoxin shock model. Together, these observations suggest that LL-37 could suppress the LPS-induced apoptosis of endothelial cells, thereby attenuating lethal sepsis/endotoxin shock.

Escherichia coli Shiga Toxin Mechanisms of Action in Renal Disease

Shiga toxin-producing Escherichia coli is a contaminant of food and water that in humans causes a diarrheal prodrome followed by more severe disease of the kidneys and an array of symptoms of the central nervous system. The systemic disease is a complex referred to as diarrhea-associated hemolytic uremic syndrome (D⁺HUS). D⁺HUS is characterized by thrombocytopenia, microangiopathic hemolytic anemia, and acute renal failure. This review focuses on the renal aspects of D⁺HUS. Current knowledge of this renal disease is derived from a combination of human samples, animal models of D⁺HUS, and interaction of Shiga toxin with isolated renal cell types. Shiga toxin is a multi-subunit protein complex that binds to a glycosphingolipid receptor, Gb3, on select eukaryotic cell types. Location of Gb3 in the kidney is predictive of the sites of action of Shiga toxin. However, the toxin is cytotoxic to some, but not all cell types that express Gb3. It also can cause apoptosis or generate an inflammatory response in some cells. Together, this myriad of results is responsible for D⁺HUS disease.

Lipopolysaccharide-induced dental pulp cell apoptosis and the expression of Bax and Bcl-2 in vitro

Lipopolysaccharide exerts many effects on many cell lines, including cytokine secretion, and cell apoptosis and necrosis. We investigated the in vitro effects of lipopolysaccharide on apoptosis of cultured human dental pulp cells and the expression of Bcl-2 and Bax. Dental pulp cells showed morphologies typical of apoptosis after exposure to lipopolysaccharide. Flow cytometry showed that the rate of apoptosis of human dental pulp cells increased with increasing lipopolysaccharide concentration. Compared with controls, lipopolysaccharide promoted pulp cell apoptosis (P < 0.05) from 0.1 to 100 μg/mL but not at 0.01 μg/mL. Cell apoptosis was statistically higher after exposure to lipopolysaccharide for 3 days compared with 1 day, but no difference was observed between 3 and 5 days. Immunohistochemistry showed that expression of Bax and Bcl-2 was enhanced by lipopolysaccharide at high concentrations, but no evident expression was observed at low concentrations (0.01 and 0.1 μg/mL) or in the control groups. In conclusion, lipopolysaccharide induced dental pulp cell apoptosis in a dose-dependent manner, but apoptosis did not increase with treatment duration. The expression of the apoptosis regulatory proteins Bax and Bcl-2 was also up-regulated in pulp cells after exposure to a high concentration of lipopolysaccharide.

Chronic exposure to nicotine and saquinavir decreases endothelial Notch-4 expression and disrupts blood-brain barrier integrity

Since the advent of HAART, there have been substantial improvements in HIV patient survival; however, the prevalence of HIV associated dementia has increased. Importantly, HIV positive individuals who smoke progress to HIV associated neurological conditions faster than those who do not. Recent in vitro data have shown that pharmacological levels of saquinavir causes endothelial oxidative stress and significantly decreases Notch-4 expression, a primary protein involved in maintaining stability of blood-brain barrier (BBB) endothelium. This is concerning as nicotine can also generate reactive oxygen species in endothelium. It is largely unknown if pharmacological doses of these drugs can cause a similar in vivo down-regulation of Notch-4 and if there is a concurrent destabilization of the integrity of the BBB. The data herein show: (i) nicotine and protease inhibitors cause an additive oxidative stress burden in endothelium; (ii) that the integrity of the BBB is disrupted after concurrent chronic nicotine and protease inhibitor administration; and (iii) that BBB endothelial dysfunction is correlated with a decrease in Notch-4 and ZO-1 expression. Considering the high prevalence of smoking in the HIV infected population (3- to 4-fold higher than in the general population) this data must be followed up to determine if all protease inhibitors cause a similar BBB disruption or if there is a safer alternative. In addition, this data may suggest that the induced BBB disruption may allow foreign molecules to gain access to brain and be a contributing factor to the slow progression of HIV associated dementia.

TRAF6 as the key adaptor of TLR4 signaling pathway is involved in acute pancreatitis

OBJECTIVES

To study the potential role of tumor necrosis factor receptor-associated factor 6 (TRAF6) as the key adaptor of the toll-like receptor 4 (TLR4) signaling pathway in acute pancreatitis (AP) in mice.

METHODS

Acute pancreatitis was induced by 7 intraperitoneal injections of cerulein in TLR4-deficient (TLR4-Def) and TLR4 wild-type (TLR4-WT) mice. Inflammatory severity was scored and evaluated based on pathological study. TRAF6 expression was determined by reverse transcriptase polymerase chain reaction, Western blot, and immunohistochemistry.

RESULTS

Acute pancreatitis was successfully induced in both mice strains, but the inflammatory progression was different. In TLR4-Def mice, pancreatic inflammation was blunt and mild first, then became increasingly intensive and peaked at the later stage, whereas in the TLR4-WT mice, the response was fast initiated and peaked at the early stage of AP, then alleviated gradually. TRAF6 expression in TLR4-Def mice was significantly higher than that in the TLR4-WT mice. Immunohistochemistry located TRAF6 expressed mainly in the pancreatic acinar cells.

CONCLUSIONS

The TLR4-TRAF6 signaling pathway is critically involved in AP. Other signaling pathways beyond TLR4 may participate in the pancreatic inflammatory process via TRAF6. As a convergence point of the TLR4-dependent and the TLR4-independent signaling pathways, TRAF6 plays an important role in AP.

c-Jun N-Terminal Kinase Primes Endothelial Cells at Atheroprone Sites for Apoptosis

Objective— Atherosclerosis is a focal disease that occurs predominantly at branches and bends of the arterial tree. Endothelial cells (EC) at atherosusceptible sites are prone to injury, which can contribute to lesion formation, whereas EC at atheroprotected sites are resistant. The c-Jun N-terminal kinase (JNK) is activated constitutively in EC at atherosusceptible sites but is inactivated at atheroprotected sites by mitogen-activated protein kinase phosphatase-1 (MKP-1). Here, we examined the effects of JNK activation on EC physiology at atherosusceptible sites.

Methods and Results— We identified transcriptional programs regulated by JNK by applying a specific pharmacological inhibitor to cultured EC and assessing the transcriptome using microarrays. This approach and subsequent validation by gene silencing revealed that JNK positively regulates the expression of numerous proapoptotic molecules. Analysis of aortae of wild-type, JNK1 −/− , and MKP-1 −/− mice revealed that EC at an atherosusceptible site express proapoptotic proteins and are primed for apoptosis and proliferation in response to lipopolysaccharide through a JNK1-dependent mechanism, whereas EC at a protected site expressed lower levels of proapoptotic molecules and were protected from injury by MKP-1.

Conclusion— Spatial variation of JNK1 activity delineates the spatial distribution of apoptosis and turnover of EC in arteries.

Caspase-3 is activated and rapidly released from human umbilical vein endothelial cells in response to lipopolysaccharide

Endothelial cell injury/dysfunction is considered to play a critical role in the pathogenesis of severe sepsis and septic shock. Although it is considered that endothelial cell apoptosis is involved in endothelial injury/dysfunction, physiological involvement remains ambiguous since the induction of apoptosis requires the inhibition of endogenous apoptosis inhibitors. Here we show that caspase-3 activation, a biological indicator of apoptosis, is observed in response to lipopolysaccharide (LPS) stimulation even under the influence of endogenous apoptosis inhibitors, and that activated caspase-3 is rapidly released from human umbilical vein endothelial cells (HUVEC). In the presence of cycloheximide (CHX), an increase in intracellular caspase-3/7 activity in response to LPS was not detected in HUVEC up to 24 h following stimulation even in the presence of LPS-binding protein (LBP), soluble CD14 and soluble MD-2, whereas the decrease in cell viability and increase in release of the cellular enzyme lactate dehydrogenase (LDH) were observed in a soluble CD14/LBP-dependent manner. On the other hand, even in the absence of CHX, a significant increase in caspase-3/7 activity and a cleaved caspase-3 fragment with a slight increase in LDH release was observed in culture supernatants in response to LPS. This increase in caspase-3/7 activity was observed even when LDH release was undetected. These results indicate that caspase-3 is activated by LPS under physiological conditions and suggest that HUVEC escape from cell death by rapidly releasing activated caspase-3 into extracellular space. Failure of this escape mechanism may result in endothelial injury/dysfunction.

Down-regulation of tumor necrosis factor-associated factor 6 is associated with progression of acute pancreatitis complicating lung injury in mice

Acute lung injury is one of the critical complications of acute pancreatitis (AP). Tumor necrosis factor-associated factor 6 (TRAF6) is a key adaptor that regulates various inflammatory signaling pathways, including those mediated by Toll-like receptors (TLRs). This study was performed to investigate the potential role of TRAF6 in the pathogenesis of AP and pancreatitis-associated acute lung injury using a mouse model of caerulein-induced AP (CAP). CAP was induced by intraperitoneal injection of caerulein hourly for 7 times (50 microg/kg), and control mice were treated with saline of the same volume. Typical pancreatic and lung inflammation was observed in the early stage (1 h) of CAP, as judged by morphological changes. Likewise, in CAP mice, the pancreatic myeloperoxidase activity and serum levels of interleukin-6 and interleukin-10 were significantly increased after 2 h, peaked at 4h, and then decreased by 24 h. The expression of TRAF6 was then studied by real time-PCR, immunohistochemistry, and Western blot analysis. Compared with control group, TRAF6 mRNA level was decreased in CAP group within the first 12 h, and then significantly increased after 24 h, which was in accordance with the protein level detected by Western blot analysis and immunohistochemistry. Moreover, TRAF6 protein was expressed in both pancreatic acinar cells and lung bronchial epithelial cells. In conclusion, the down-regulation of TRAF6 was associated with increased inflammatory severity in the pancreas and lung, suggesting that TRAF6 is involved in the anti-inflammatory process during AP. TRAF6 may be a potential molecular target for treating AP.

Lipopolysaccharide-induced apoptosis in transformed bovine brain endothelial cells and human dermal microvessel endothelial cells: the role of JNK

Stimulation of transformed bovine brain endothelial cells (TBBEC) with LPS leads to apoptosis while human microvessel endothelial cells (HMEC) need the presence of cycloheximide (CHX) with LPS to induce apoptosis. To investigate the molecular mechanism of LPS-induced apoptosis in HMEC or TBBEC, we analyzed the involvement of MAPK and PI3K in TBBEC and HMEC. LPS-induced apoptosis in TBBEC was hallmarked by the activation of caspase 3, caspase 6, and caspase 8 after the stimulation of LPS, followed by poly(ADP-ribose) polymerase cleavage and lactate dehydrogenase release. We also observed DNA cleavage determined by TUNEL staining in TBBEC treated with LPS. Herbimycin A, a tyrosine kinase inhibitor, and SP600125, a JNK inhibitor, suppressed the activation of caspases and lactate dehydrogenase release. Moreover, a PI3K inhibitor (LY294002) suppressed activation of caspases and combined treatment with both SP600125 and LY294002 completely inhibited the activation of caspases. These results suggest that the JNK signaling pathway through the tyrosine kinase and PI3K pathways is involved in the induction of apoptosis in LPS-treated TBBEC. On the other hand, we observed sustained JNK activation in HMEC treated with LPS and CHX, and neither ERK1/2 nor AKT were activated. The addition of SP600125 suppressed phosphorylation of JNK and the activation of caspase 3 in HMEC treated with LPS and CHX. These results suggest that JNK plays an important role in the induction of apoptosis in endothelial cells.

Activation by C5a of endothelial cell caspase 8 and cFLIP

OBJECTIVES AND DESIGN

In this study, we examine the relationship between C5a and activation of cysteine aspartic acid protease 8 (caspase 8) in human umbilical vein endothelial cells (HUVEC).

MATERIALS OR SUBJECTS

Primary cultures of HUVEC were used.

TREATMENTS

Recombinant human C5a (50 ng/ml) was used in the presence or absence of 10 microg/ml cycloheximide (CHX).

METHODS

HUVEC were treated with C5a alone and in the presence of CHX, then monitored for cell viability, poly- ADP-ribose 1 (PARP-1) and caspase 8 activities. Gene and protein expressions were assessed for caspase 8 and the caspase 8 homologue, FLICE -inhibitory protein (cFLIP).

RESULTS

We found a 43.1 +/- 6.9 percent reduction in viability of HUVEC stimulated for 18 h with 50 ng/ml C5a in the presence of 10 microg/ml CHX (p < 0.05). In contrast, the cell viability of cells stimulated for 18 h with 50 ng/ml C5a or 10 microg/ml CHX alone was not significantly different compared to the non-stimulated control. Treatment of HUVEC with C5a induced an increase in caspase 8 activity but did not significantly affect cFLIP levels.

CONCLUSIONS

These data suggest caspase 8 activation induced by C5a leads to cell death if protein synthesis of antiapoptotic protein(s) is blocked.

In vivo interstitial migration of primitive macrophages mediated by JNK-matrix metalloproteinase 13 signaling in response to acute injury

Interstitial cell migration through extracellular matrix is a hallmark of the inflammation response, tumor invasion, and metastasis. We have established a stable zebrafish transgenic line expressing enhanced GFP under the lysozyme C promoter for visualizing and measuring primitive macrophage migration in vivo. We show that tissue-resident primitive macrophages migrate rapidly through extracellular matrix to the site of acute injury induced by tail transection. Mechanistically, the specific inhibition of JNK, but not p38 and ERK, dramatically abolished the chemotactic migration in a dose-dependent manner, suppressing the trauma-induced recruitment of phosphorylated C-Jun transcription factor to proximal AP-1 sites in the promoter of matrix metalloproteinase 13 (mmp13), a gene specifically expressed in primitive macrophages during embryogenesis and required for the interstitial migration. Furthermore, dexamethasone suppressed the trauma-induced JNK phosphorylation and macrophage migration accompanied by simultaneous up-regulation of mkp-1, a well-known phosphatase capable of inactivating phosphorylated JNK. The results indicate that the JNK-Mmp13 signaling pathway plays an essential role in regulating the innate immune cell migration in response to severe injury in vivo.

TRAF6 is a critical signal transducer in IL-33 signaling pathway

IL-33 has been shown to induce Th2 responses by signaling through the IL-1 receptor-related protein, ST2L. However, the signal transduction pathways activated by the ST2L have not been characterized. Here, we found that IL-33-induced monocyte chemoattractant protein (MCP)-1, MCP-3 and IL-6 expression was significantly inhibited in TNF receptor-associated Factor 6 (TRAF6)-deficient MEFs. IL-33 rapidly induced the formation of ST2L complex containing IL-1 receptor-associated kinase (IRAK), however, lack of TRAF6 abolished the recruitment of IRAK to ST2L. Consequently, p38, JNK and Nuclear factor-kappaB (NF-kappaB) activation induced by IL-33 was completely inhibited in TRAF6-deficient MEFs. On the other hand, IL-33-induced ERK activation was observed regardless of the presence of TRAF6. The introduction of TRAF6 restored the efficient activation of p38, JNK and NF-kappaB in TRAF6 deficient MEFs, resulting in the induction of MCP-1, MCP-3 and IL-6 expression. Moreover, IL-33 augmented autoubiquitination of TRAF6 and the reconstitution of TRAF6 mutant (C70A) that is defective in its ubiquitin ligase activity failed to restore IL-33-induced p38, JNK and NF-kappaB activation. Thus, these data demonstrate that TRAF6 plays a pivotal role in IL-33 signaling pathway through its ubiquitin ligase activity.

Toll-like receptors' two-edged sword: when immunity meets apoptosis

Toll-like receptors (TLR) have emerged as key players in the detection of pathogens and the induction of anti-microbial immune response. TLR recognize pathogen-associated molecular patterns, and trigger anti-microbial innate immune responses ranging from the secretion of pro-inflammatory mediators to the increase of natural killer cell cytotoxicity. Besides activating the innate immune response, TLR engagement also shapes the adaptive immune response. Indeed, the broad diversity of signaling pathways initiated by TLR is progressively unraveled. Recent reports suggested that among the anti-microbial defenses they initiate, members of the TLR family can induce apoptosis. This review focuses on this newly described function of TLR, and emphasizes the similarities and differences between the different apoptosis-signaling pathways described downstream of TLR. The functional relevance of TLR-triggered apoptosis is also discussed, as therapeutic applications are likely to ensue in the near future.

FOXO3a Turns the Tumor Necrosis Factor Receptor Signaling Towards Apoptosis Through Reciprocal Regulation of c-Jun N-Terminal Kinase and NF-κB

Objective— We evaluated the full range effects of FOXO3a in endothelial cells (ECs) by microarray analysis and investigated the role of FOXO3a regulating TNF receptor signaling pathway.

Methods and Results— Human umbilical vein endothelial cells (HUVECs) were transfected with adenoviral vectors expressing constitutively active FOXO3a (Ad-TM-FOXO3a). Ad-TM-FOXO3a transfection caused remarkable apoptosis, which were accompanied with upregulation of genes related with TNF receptor signaling, such as TNF-α, TANK (TRAF-associated NF-κB activator), and TTRAP (TRAF and TNF receptor-associated protein). Furthermore, κB-Ras1 (IκB-interacting Ras-like protein-1) which is known to block IκB degradation was found increased, and intranuclear translocation of NF-κB was inhibited. GADD45β and XIAP, negative regulators of c-Jun N-terminal kinase (JNK), were suppressed and JNK activity was increased. Attenuation of TNF signaling pathway either by blocking antibody for TNF receptor or by blocking JNK with DMAP (6-dimethylaminopurine) or Ad-TAM67 (dominant negative c-Jun) cotransfection, significantly reduced FOXO3a-induced apoptosis. Finally, treatment of vasculature with heat shock, an activator of endogenous FOXO3a, resulted in EC apoptosis, which was completely rescued by Ad-TAM67.

Conclusion— FOXO3a promotes apoptosis of ECs, through activation of JNK and suppression of NF-κB. These data identify a novel role of FOXO3a to turn TNF receptor signaling to a proapoptotic JNK-dependent pathway.