Lipopolysaccharide signaling in endothelial cells

Differential expression of Toll-like receptor 4 signaling pathway genes in Escherichia coli F18-resistant and - sensitive Meishan piglets

The Toll-like receptor 4 (TLR4) signaling pathway is an important inflammatory pathways associated with the progression of numerous diseases. The aim of the present study was to investigate the relationship between TLR4 signaling and resistance to Escherichia coli F18 in locally weaned Meishan piglets. Using a real-time PCR approach, expression profiles were determined for key TLR4 signaling pathway genes TLR4, MyD88, CD14, IFN-α, IL-1β and TNF-α in the spleen, thymus, lymph nodes, duodenum and jejunum of E. coli F18-resistant and -sensitive animals. TLR4 signaling pathway genes were expressed in all the immune organs and intestinal tissues, and the expression was generally higher in the spleen and lymph nodes. TLR4 transcription was higher in the spleen of sensitive piglets (p<0.05), but there was no significant difference in TLR4 mRNA levels in other tissues. Similarly, CD14 transcription was higher in lymph nodes of sensitive animals (p<0.05) but not in other tissues. IL-1β expression was higher in the spleen and in the duodenum of resistant piglets (p<0.05, p<0.01, respectively), and there were no significant differences in other tissues. There were also no significant differences in the expression of MyD88, TNF-α and IFN-α between sensitive and resistant piglets (p>0.05). These results further confirm the involvement of the TLR4 signaling pathway in resistance to E. coli F18 in Meishan weaned piglets. The resistance appeared to be mediated via downregulation of TLR4 and CD14, and upregulation of MyD88 that may promote the release of cytokines TNF-α, IL-1β, IFN-α and other inflammatory mediators which help to fight against E. coli F18 infection.

Molecular cloning and characterization of LrTLR4, analysis of its inductive expression and associated down-stream signaling molecules following lipopolysaccharide stimulation and Gram-negative bacterial infection

Toll-like receptors (TLRs) play key roles in innate immunity from lower to higher vertebrates. Among various TLR types, TLR4 was reported to recognize LPS in higher vertebrates resulting in the activation of down-stream signaling pathway. Except in some teleosts, function of TLR4 in most fish species including rohu (Labeo rohita) a commercially important fish species in the South-East Asian countries remained unknown. To investigate it, full-length cDNA of Labeo rohita TLR4 (LrTLR4) was cloned, and it consisted of 2729 bp, with a single ORF of 2469 bp encoding a polypeptide of 822 aa with a predicted molecular mass of 94.753 kDa. Structurally, LrTLR4 consisted of 25 LRRs (leucine rich repeat regions), one TM (trans-membrane) domain and one TIR (Toll/interleukin-1 receptor) domain, and was similar to higher vertebrate's TLR4. Phylogenetically, LrTLR4 exhibited highest (85%) identity with the common carp TLR4b amino acids sequence, and formed a separate subgroup in the phylogenetic tree. LrTLR4 was widely expressed in all tested organs/tissues, and amidst the tissues highest expression was detected in blood and the lowest in eye. In response to LPS-stimulation, LrTLR4 was induced with the activation of MyD88-dependent and TRIF-dependent signaling pathway resulting in pro-inflammatory cytokines (interleukin 6 and 8) and type I IFN gene expression. Infection of rohu with a Gram-negative fish pathogen (Aeromonas hydrophila), also activated LrTLR4. Together, these findings suggest the important role of TLR4 in LPS sensing and augmentation of innate immunity against Gram-negative bacterial infection in fish.

Lipopolysaccharide enhances interferon-γ-induced nitric oxide (NO) production in murine vascular endothelial cells via augmentation of interferon regulatory factor-1 activation

Lipopolysaccharide (LPS) enhances the production of nitric oxide (NO) in interferon (IFN)-γstimulated vascular endothelial cells. We studied the mechanism by which LPS enhances IFN-γ-induced NO production by using the murine vascular endothelial cell line, END-D. LPS enhanced IFN-γinduced NO production via augmented expression of inducible type NO synthase (iNOS) mRNA. LPS significantly augmented the activation of interferon regulatory factor (IRF)-1 in IFN-γ-stimulated END-D cells, although it did not affect the activation of either MyD88-dependent nuclear factor (NF)-κB or MyD88-independent IRF-3. SB203580, an inhibitor of p38 mitogen-activated protein kinase (MAPK), prevented the nuclear translocation of IRF-1 in LPS and IFN-γ-stimulated END-D cells, and inhibited the iNOS expression and NO production in those cells. Therefore, it is proposed that LPS enhanced NO production in IFN-γ-stimulated END-D cells via augmenting p38 MAPKmediated IRF-1 activation.

TRIF is a regulator of TLR2-induced foam cell formation

The activation of toll-like receptor 2 (TLR2) stimulates foam cell formation, which is a key early event in the process of atherosclerosis. In the present study, the role of toll/interleukin-1 receptor-domain-containing adaptor-inducing interferon-β (TRIF) in TLR2-mediated foam cell formation was investigated, and the importance of monocyte chemoattractant protein‑1 (MCP‑1), tissue factor (TF) and lectin‑like oxidized low‑density lipoprotein receptor‑1 (Lox‑1) were examined. Treatment of Raw 264.7 cells with the TLR2 agonist. Pam3CSK4, increased the gene expression of TRIF in a time‑dependent manner (RT‑PCR). The induced gene expression of TRIF stimulated by TLR2 was not observed in TLR2‑knockout mice‑derived bone marrow‑derived macrophages (BMDMs). Pam3CSK4 increased the mRNA expression of TRIF in the wild‑type BMDMs, but not in the TLR2‑knockout BMDMs. Knockdown of the expression of TRIF using small interfering RNA decreased Pam3CSK4‑induced foam cell formation (combination of oil‑red O and hematoxylin staining), suggesting a role of TRIF. Stimulation of TLR2 increased the expression levels of various genes, which are known to control atherosclerosis, including MCP‑1, TF and Lox‑1. The knockdown of TRIF also attenuated the Pam3CSK4‑induced expression of these genes. In addition, a reduction in TRIF affected the Pam3CSK4‑induced protein expression of MCP‑1 (EIA). Taken together, the results of the present study suggested that TRIF regulated foam cell formation via regulation of the expression levels of MCP‑1, TF and Lox‑1.

Heparin and LPS-induced COX-2 expression in airway cells: a link between its anti-inflammatory effects and GAG sulfation

PURPOSE/AIM

Previous studies have indicated that the sulfated polysaccharide heparin has anti-inflammatory effects. However, the mechanistic basis for these effects has not been fully elucidated.

MATERIALS AND METHODS

NCI-H292 (mucoepidermoid) and HBE-1 (normal) human bronchial epithelial cells were treated with LPS alone or in the presence of high-molecular-weight (HMW) fully sulfated heparin or desulfated HMW heparin. Cells were harvested to examine the phosphorylation levels of ERK1/2, p38, and NF-kB p65 and COX-2 protein expression by Western blot and gene expression of both COX-2 and CXCL-8 by TaqMan qRT-PCR.

RESULTS

Heparin is known to exert an influence on receptor-mediated signaling through its ability to both potentiate and inhibit the receptor-ligand interaction, depending upon its concentration. In H292 cells, fully-sulfated HMW heparin significantly reduced LPS-induced gene expression of both COX-2 and CXCL-8 for up to 48 hours, while desulfated heparin had little to no significant suppressive effect on signaling or on COX-2 gene or protein expression. Desulfated heparin, initially ineffective at preventing LPS-induced CXCL8 up-regulation, reduced CXCL8 transcription at 24 hours. In contrast, in normal HBE-1 cells, fully sulfated heparin significantly suppressed only ERK signaling, COX-2 gene expression at 12 hours, and CXCL-8 gene expression at 6 and 12 hours, while desulfated heparin had no significant effects on LPS-stimulated signaling or on gene or protein expression. Sulfation determines heparin's influence and may reflect the moderating role of GAG sulfation in lung injury and health.

CONCLUSIONS

Heparin's anti-inflammatory effects result from its nonspecific suppression of signaling and gene expression and are determined by its sulfation.

Anti-endotoxin and anti-inflammatory effects of Chinese herbal medicinal alkaloid ingredients in vivo

The aim of the research was to investigate the anti-endotoxin and anti-inflammatory effects of sinomenine, fangchinoline, stachydrine, chuanxionggzine, oxymartrine, and evodiamine alkaloids commonly found in Chinese herbal medicines. In an endotoxin (LPS) control group, each mouse was challenged with 1 mg LPS/kg by intraperitoneal (IP) injection. In high-, middle- and low-dose alkaloid groups, mice were initially challenged with 1 mg LPS/kg by IP injection and, 3 h later, dosed intramuscularly (IM) with one of the six alkaloids at one of three levels (1, 5, or 10 mg/kg body weight). In the drug control group, mice were dosed IM with 10 mg/kg body weight of a given alkaloid; mice in a naïve control group were administered the same volume of normal saline. The results revealed the six alkaloids could reduce the incidence/severity of LPS- induced toxicities, e.g., body temperature elevation, weight loss, systemic inflammation, multiple organ dysfunction. Taken together, the data suggested to us that these alkaloids might effectively regulate inflammatory responses and have a potential to be used in anti-endotoxin therapies.

Poncirin and its metabolite ponciretin attenuate colitis in mice by inhibiting LPS binding on TLR4 of macrophages and correcting Th17/Treg imbalance

ETHNOPHARMACOLOGICAL RELEVANCE

The fruit of Poncirus trifoliate, which contains poncirin as a main constituent, is frequently used in the traditional Chinese medicine for inflammation, asthma, and infection diseases.

AIM OF THE STUDY

To examine anti-colitic effects of poncirin and ponciretin, a metabolite of poncirin by gut microbiota.

MATERIALS AND METHODS

Colitis was induced in mice by the intrarectal injection of 2,4,6-trinitrobenzenesulfonic acid (TNBS). Inflammatory markers were analyzed by enzyme-linked immunosorbent assay, immunoblotting, quantitative polymerase chain reaction, confocal microscopy, and flow cytometry. Peritoneal macrophages were isolated from mice stimulated with 4% thioglycolate.

RESULTS

Poncirin was metabolized to ponciretin in vitro and in vivo by gut microbiota of mice. Orally administered poncirin and ponciretin suppressed TNBS-induced colitis in mice: these inhibited colon shortening, myeloperoxidase activity, NF-κB activation, and Th17 cell differentiation, but increased occludin, claudin-1, and ZO-1 expressions and Treg cell differentiation. Poncirin and ponciretin suppressed the differentiation of splenocytes into Th17 cells and expression of IL-17 and Foxp3 in vitro, as well as the activation of macrophages stimulated with lipopolysaccharide (LPS) by inhibiting the binding of LPS on TLR4 of macrophages. These increased the differentiation of splenocytes into Treg cells. The ant-inflammatory effect of ponciretin was superior to that of poncirin.

CONCLUSION

Orally administered poncirin is metabolized to ponciretin by gut microbiota and poncirin and ponciretin attenuates colitis by suppressing NF-κB activation through the inhibition of LPS binding on macrophages and correcting Th17/Treg cell imbalance.

Cardiac dysfunction, mitochondrial architecture, energy production, and inflammatory pathways: Interrelated aspects in endotoxemia and sepsis

Septic patients with myocardial dysfunction have a 3-fold increase in mortality compared with patients without cardiovascular impairment, and usually show myocarditis, disruption of the contractile apparatus, increased amounts of interstitial collagen, and damaged mitochondria. The presence of nitric oxide and cytokines in cardiac tissue constitute the molecular markers and the intracellular messengers of inflammatory conditions in the heart due to the onset of sepsis and endotoxemia, derived from the nuclear factor-κB pathway activation and proinflammatory gene transcription. Sepsis occurs with an exacerbated inflammatory response that damages tissue mitochondria and impaired bioenergetic processes. The heart consumes 20-30 times its own weight in adenosine triphosphate every day, and 90% of this molecule is derived from mitochondrial oxidative phosphorylation. Cardiac energy management is comprised in sepsis and endotoxemia; both a deficit in energy production and alterations in the source of energy substrates are believed to be involved in impaired cardiac function. Although several hypotheses try to explain the molecular mechanisms underlying the complex condition of sepsis and endotoxemia, the current view is that these syndromes are the result of an intricate balance between prevailing levels of mitochondrial stress, biogenesis/autophagy signaling and mitochondria quality control processes, rather on a single factor. The aim of this review is to discuss current hypothesis of cardiac dysfunction related to energy metabolism and mitochondrial function in experimental models of sepsis and endotoxemia, and to introduce the importance of lipids (mainly cardiolipin) in the mechanism of cardiac energy mismanagement in these inflammatory conditions.

Effect of Toll-Like Receptor 4 on Synovial Injury of Temporomandibular Joint in Rats Caused by Occlusal Interference

Synovitis is an important disease that causes intractable pain in TMJ. Some investigations suggested that the increasing expression of IL-1β secreted by synovial lining cells plays an important role in synovial inflammation and cartilage destruction in TMJ. In our previous research, the results demonstrated that TLR4 is involved in the expression of IL-1β in SFs from TMJ with lipopolysaccharide stimulation. However, the inflammatory response that occurred in synovial membrane is not caused by bacterial infection. In the current study, we investigated whether or not TLR4 participates in the inflammatory responses and the expression of IL-1β in synovial membrane of rats induced by occlusal interference. The results showed that obvious inflammation changes were observed in the synovial membranes and the expression of TLR4 and IL-1β was increased at both mRNA and protein levels in the occlusal interference rats. In addition, the inflammation reactions and the increased expression of IL-1β could be restrained by treatment with TAK-242, a blocker of TLR4 signaling. The results prompted us that the activation of TLR4 may be involved in the inflammatory reactions and increased expression of IL-1β in patients with synovitis and participate in the mechanisms of the initiation and development of synovial injury by regulating the expression of inflammatory mediators like IL-1β in synovial membranes.

Hepatic sinusoids in liver injury, inflammation, and fibrosis: new pathophysiological insights

Changes of hepatic sinusoids are crucial in the pathogenesis of liver cirrhosis and portal hypertension. Liver injury leads to distinct morphological abnormalities such as loss of sinusoidal fenestration, vasoconstriction, and angiogenesis as well as molecular changes. Communication between the two key cells in this hepatic microenvironment-hepatic stellate cells (HSC) and sinusoidal endothelial cells (SEC)-has been studied for many years and several canonical pathways have been elucidated, such as decreased eNOS activity or increased PDGF and TGF-β production leading to activation and migration of HSC. In recent studies, alternative pathways of intercellular communication in liver diseases have been described such as cell-derived extracellular vesicles called exosomes, which deliver cell compounds to their target cells. Moreover, such extracellular vesicles may link injury to inflammation in alcoholic hepatitis. While inflammation leading to liver fibrosis has been studied in detail, in some circumstances pathways other than the known canonical inflammatory pathways may contribute to hepatic fibrogenesis. For example, in congestive hepatopathy, sinusoidal dilatation and fibrosis have been shown to be mediated by non-inflammatory mechanisms and associated with sinusoidal thrombi. A recently developed murine model further enables experimental studies of this disease entity. Increasing knowledge about these alternative disease pathways in liver injury, inflammation, and fibrosis may reveal possible target molecules for future therapies. This article builds upon a seminar given at the recent 3rd JSGE International Topic Conference in Sendai, Japan, and reviews the areas outlined above.

Soluble CD14 in cerebrospinal fluid is associated with markers of inflammation and axonal damage in untreated HIV-infected patients: a retrospective cross-sectional study

Background

HIV-associated cognitive impairment has declined since the introduction of combination antiretroviral treatment (cART). However, milder forms of cognitive impairment persist. Inflammation in the cerebrospinal fluid (CSF) has been associated with cognitive impairment, and CSF neurofilament light chain protein (NFL) and CSF neopterin concentrations are increased in those patients. Microbial translocation in HIV infection has been suggested to contribute to chronic inflammation, and lipopolysaccharide (LPS) and soluble CD14 (sCD14) are markers of microbial translocation and the resulting monocyte activation, respectively. We hypothesised that microbial translocation contributes to inflammation and axonal damage in the central nervous system (CNS) in untreated HIV infection.

Methods

We analyzed paired samples of plasma and CSF from 62 HIV-infected, untreated patients without cognitive symptoms from Sahlgrenska University Hospital, Gothenburg, Sweden. Measurements of neopterin and NFL in CSF were available from previous studies. Plasma and CSF sCD14 was measured using ELISA (R&D, Minneapolis, MN), and plasma and CSF LPS was measured using LAL colorimetric assay (Lonza, Walkersville, MD, USA). Univariate and multivariate regression analyses were performed.

Results

LPS in plasma was associated with plasma sCD14 (r = 0.31, P = 0.015), and plasma sCD14 was associated with CSF sCD14 (r = 0.32, P = 0.012). Furthermore, CSF sCD14 was associated with NFL (r = 0.32, P = 0.031) and neopterin (r = 0.32, P = 0.012) in CSF. LPS was not detectable in CSF. In a multivariate regression model CSF sCD14 remained associated with NFL and neopterin after adjusting for age, CD4+ cell count, and HIV RNA in CSF.

Conclusions

In a group of untreated, HIV-infected patients LPS was associated with sCD14 in plasma, and plasma sCD14 was associated CSF sCD14. CSF sCD14 were associated with markers of CNS inflammation and axonal damage. This suggest that microbial translocation might be a driver of systemic and CNS inflammation. However, LPS was not detectable in the CSF, and since sCD14 is a marker of monocyte activation sCD14 may be increased due to other causes than microbial translocation. Further studies regarding cognitive impairment and biomarkers are warranted to fully understand causality.

Suppression of transient receptor potential melastatin 4 expression promotes conversion of endothelial cells into fibroblasts via transforming growth factor/activin receptor-like kinase 5 pathway

OBJECTIVE

To study whether transient receptor potential melastatin 4 (TRPM4) participates in endothelial fibrosis and to investigate the underlying mechanism.

METHODS

Primary human endothelial cells were used and pharmacological and short interfering RNA-based approaches were used to test the transforming growth factor beta (TGF-β)/activin receptor-like kinase 5 (ALK5) pathway participation and contribution of TRPM7 ion channel.

RESULTS

Suppression of TRPM4 expression leads to decreased endothelial protein expression and increased expression of fibrotic and extracellular matrix markers. Furthermore, TRPM4 downregulation increases intracellular Ca levels as a potential condition for fibrosis. The underlying mechanism of endothelial fibrosis shows that inhibition of TRPM4 expression induces TGF-β1 and TGF-β2 expression, which act through their receptor, ALK5, and the nuclear translocation of the profibrotic transcription factor smad4.

CONCLUSION

TRPM4 acts to maintain endothelial features and its loss promotes fibrotic conversion via TGF-β production. The regulation of TRPM4 levels could be a target for preserving endothelial function during inflammatory diseases.

Hsp90 inhibition suppresses NF-κB transcriptional activation via Sirt-2 in human lung microvascular endothelial cells

The ability of anti-heat shock protein 90 (Hsp90) drugs to attenuate NF-κB-mediated transcription is the major basis for their anti-inflammatory properties. While the molecular mechanisms underlying this effect are not clear, they appear to be distinct in human endothelial cells. We now show for the first time that type 2 sirtuin (Sirt-2) histone deacetylase binds human NF-κB target gene promoter and prevents the recruitment of NF-κB proteins and subsequent assembly of RNA polymerase II complex in human lung microvascular endothelial cells. Hsp90 inhibitors stabilize the Sirt-2/promoter interaction and impose a "transcriptional block," which is reversed by either inhibition or downregulation of Sirt-2 protein expression. Furthermore, this process is independent of NF-κB (p65) Lysine 310 deacetylation, suggesting that it is distinct from known Sirt-2-dependent mechanisms. We demonstrate that Sirt-2 is recruited to NF-κB target gene promoter via interaction with core histones. Upon inflammatory challenge, chromatin remodeling and core histone H3 displacement from the promoter region removes Sirt-2 and allows NF-κB/coactivator recruitment essential for RNA Pol II-dependent mRNA induction. This novel mechanism may have important implications in pulmonary inflammation.

Three diketopiperazines from marine-derived bacteria inhibit LPS-induced endothelial inflammatory responses

Diketopiperazine is a natural products found from bacteria, fungi, marine sponges, gorgonian and red algae. They are cyclic dipeptides possessing relatively simple and rigid structures with chiral nature and various side chains. Endothelial dysfunction is a key pathological feature of many inflammatory diseases, including sepsis. In the present study, three (1-3) of diketopiperazines were isolated from two strains of marine-derived bacteria. The compounds were investigated for their effects against lipopolysaccharide (LPS)-mediated endothelial inflammatory responses in vitro and in vivo. From 1 μM, 1-3 inhibited LPS-induced hyperpermeability, adhesion, and migration of leukocytes across a human endothelial cell monolayer and in mice in a dose-dependent manner suggesting that 1-3 may serve as potential scaffolds for the development of therapeutic agents to treat vascular inflammatory disorders.

Paricalcitol attenuates lipopolysaccharide-induced myocardial inflammation by regulating the NF-κB signaling pathway

Vitamin D deficiency is associated with an increased risk of cardiovascular disease, diabetes, colon and breast cancer, infectious diseases and allergies. Vascular alterations are an important pathophysiological mechanism of sepsis. Experimental data suggest that paricalcitol, a vitamin D2 analogue, exerts beneficial effects on renal inflammation and fibrosis. In the present study, we aimed to investigate the effects of paricalcitol on lipopolysaccharide (LPS)-induced myocardial inflammation and to elucidate the underlying mechanisms. We used primary cultured human umbilical vein endothelial cells for in vitro experiments, in which stimulation with tumor necrosis factor (TNF)-α was used to induce endothelial cell inflammation. For in vivo experiments, myocardial inflammation was induced by an intraperitoneal injection of 15 mg/kg LPS into C57BL6 mice pre-treated with or without 0.2 µg/kg paricalcitol. Treatment with paricalcitol suppressed the TNF-α-induced increase in the protein expression of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and fractalkine in endothelial cells. Treatment with paricalcitol also decreased the TNF-α-induced nuclear factor (NF)-κB binding activity. In a mouse model of LPS-induced myocardial inflammation, pre-treatment with paricalcitol prevented the LPS-induced increase in the expression of myocardial ICAM-1, phosphorylated p65 and myocardial TNF-α. Pre-treatment with paricalcitol also alleviated endotoxemia‑induced microvascular leakage in the myocardium. The findings of our study suggest that paricalcitol exerts a protective effect against LPS-induced myocardial inflammation by regulating the expression of cell adhesion molecules and TNF-α, and by improving myocardial permeability.

Phosphocreatine protects against LPS-induced human umbilical vein endothelial cell apoptosis by regulating mitochondrial oxidative phosphorylation

Phosphocreatine (PCr) is an exogenous energy substance, which provides phosphate groups for adenosine triphosphate (ATP) cycle and promotes energy metabolism in cells. However, it is still unclear whether PCr has influenced on mitochondrial energy metabolism as well as oxidative phosphorylation (OXPHO) in previous studies. Therefore, the aim of the present study was to investigate the regulation of PCr on lipopolsaccharide (LPS)-induced human umbilical vein endothelial cells (HUVECs) and mitochondrial OXPHO pathway. PCr protected HUVECs against LPS-induced apoptosis by suppressing the mitochondrial permeability transition, cytosolic release of cytochrome c (Cyt C), Ca(2+), reactive oxygen species and subsequent activation of caspases, and increasing Bcl2 expression, while suppressing Bax expression. More importantly, PCr significantly improved mitochondrial swelling and membrane potential, enhanced the activities of ATP synthase and mitochondrial creatine kinase (CKmt) in creatine shuttle, influenced on respiratory chain enzymes, respiratory control ratio, phosphorus/oxygen ratio and ATP production of OXPHO. Above PCr-mediated mitochondrial events were effectively more favorable to reduced form of flavin adenine dinucleotide (FADH2) pathway than reduced form of nicotinamide-adenine dinucleotid pathway in the mitochondrial respiratory chain. Our results revealed that PCr protects against LPS-induced HUVECs apoptosis, which probably related to stabilization of intracellular energy metabolism, especially for FADH2 pathway in mitochondrial respiratory chain, ATP synthase and CKmt. Our findings suggest that PCr may play a certain role in the treatment of atherosclerosis via protecting endothelial cell function.

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.

TLR4‑dependent signaling pathway modulation: A novel mechanism by which pioglitazone protects against nutritional fibrotic steatohepatitis in mice

Activation of the innate immune system is involved in the development of chronic liver diseases, including nonalcoholic steatohepatitis. Toll‑like receptor 4 (TLR4) is one of the sensors of the innate immune system. The aim of the present study was to elucidate the role of the TLR4‑dependent signaling pathway, and examine the effect of pioglitazone on hepatic fibrosis, through modulation of the TLR4 pathway in a mouse model of nutritional fibrotic steatohepatitis. Male C57BL/6J mice were fed a methionine‑choline deficient (MCD) diet for 8 weeks to induce nonalcoholic fibrotic steatohepatitis. The PPARγ agonist, pioglitazone, and PPARγ inhibitor, GW9662, were administered to the mice, respectively. The effects of the induction of PPARγ on liver biochemistry and histology, the modulation of TLR4 and its downstream pathway, and the expression levels of inflammatory and fibrogenic genes were assessed using reverse transcription‑quantitative polymerase chain reaction and Western blot analyses. The MCD‑fed mice exhibited progressive hepatic steatosis, necrotic inflammation and fibrosis, along with increase levels of serum alanine aminotransferase and aspartate aminotransferase, accompanied by the upregulation of TLR4, the TLR4‑myeloid differentiation primary response gene 88‑dependent pathway and downstream genes, and proinflammatory and profibrotic genes; and downregulation of basic membrane protein and activin membrane‑bound inhibitor. The administration of pioglitazone was found to reverse hepatic nutritional fibrosis via restoration of the expression levels of proinflammatory and profibrotic genes in the MCD‑fed mice. The results of the present study provide novel evidence supporting the protective role of pioglitazone in ameliorating nutritional fibrotic steatohepatitis, through modulation of the TLR4‑mediated signaling pathway.

Effect of intranasal rosiglitazone on airway inflammation and remodeling in a murine model of chronic asthma

BACKGROUND/AIMS

Asthma is characterized by airway hyperresponsiveness, inflammation, and remodeling. Peroxisome proliferator-activated receptors have been reported to regulate inflammatory responses in many cells. In this study, we examined the effects of intranasal rosiglitazone on airway remodeling in a chronic asthma model.

METHODS

We developed a mouse model of airway remodeling, including smooth muscle thickening, in which ovalbumin (OVA)-sensitized mice were repeatedly exposed to intranasal OVA administration twice per week for 3 months. Mice were treated intranasally with rosiglitazone with or without an antagonist during OVA challenge. We determined airway inflammation and the degree of airway remodeling by smooth muscle actin area and collagen deposition.

RESULTS

Mice chronically exposed to OVA developed sustained eosinophilic airway inflammation, compared with control mice. Additionally, the mice developed features of airway remodeling, including thickening of the peribronchial smooth muscle layer. Administration of rosiglitazone intranasally inhibited the eosinophilic inflammation significantly, and, importantly, airway smooth muscle remodeling in mice chronically exposed to OVA. Expression of Toll-like receptor (TLR)-4 and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) was increased in the OVA group and decreased in the rosiglitazone group. Co-treatment with GW9660 (a rosiglitazone antagonist) and rosiglitazone increased the expression of TLR-4 and NF-κB.

CONCLUSIONS

These results suggest that intranasal administration of rosiglitazone can prevent not only air way inf lammation but also air way remodeling associated with chronic allergen challenge. This beneficial effect is mediated by inhibition of TLR-4 and NF-κB pathways.

Endotoxin-Induced Tryptophan Degradation along the Kynurenine Pathway: The Role of Indolamine 2,3-Dioxygenase and Aryl Hydrocarbon Receptor-Mediated Immunosuppressive Effects in Endotoxin Tolerance and Cancer and Its Implications for Immunoparalysis

The degradation of tryptophan (TRP) along the kynurenine pathway plays a crucial role as a neuro- and immunomodulatory mechanism in response to inflammatory stimuli, such as lipopolysaccharides (LPS). In endotoxemia or sepsis, an enhanced activation of the rate-limiting enzyme indoleamine 2,3-dioxygenase (IDO) is associated with a higher mortality risk. It is assumed that IDO induced immunosuppressive effects provoke the development of a protracted compensatory hypoinflammatory phase up to a complete paralysis of the immune system, which is characterized by an endotoxin tolerance. However, the role of IDO activation in the development of life-threatening immunoparalysis is still poorly understood. Recent reports described the impact of inflammatory IDO activation and aryl hydrocarbon receptor- (AhR-) mediated pathways on the development of LPS tolerance and immune escape of cancer cells. These immunosuppressive mechanisms offer new insights for a better understanding of the development of cellular dysfunctions in immunoparalysis. This review provides a comprehensive update of significant biological functions of TRP metabolites along the kynurenine pathway and the complex regulation of LPS-induced IDO activation. In addition, the review focuses on the role of IDO-AhR-mediated immunosuppressive pathways in endotoxin tolerance and carcinogenesis revealing the significance of enhanced IDO activity for the establishment of life-threatening immunoparalysis in sepsis.

Pharmacologic immunosuppression of mononuclear phagocyte phagocytosis by caffeine

Caffeine is the most widely used neurostimulant in the world. There is considerable debate on its effect on immune cells as it has been shown to antagonize adenosine receptors (ARs), which mediate an anti-inflammatory switch in activated immune cells. A second target is phosphodiesterase, where it acts as an inhibitor. If the primary effect of caffeine on mononuclear phagocytes were to antagonize ARs we would expect cells exposed to caffeine to have a prolonged proinflammatory response. The aim of this study was to investigate the effects and mechanism of action of caffeine in mononuclear phagocytes. Human mononuclear phagocytes were separated from whole blood and pretreated with protein kinase A inhibitor (PKA) and then exposed to micromolar physiological concentrations of caffeine. Phagocytosis and phagocytosis exhaustion were quantified using flow cytometry. Treatments were analyzed and compared to controls, using a beta regression controlling for factors of age, gender, caffeine intake, and exercise. We found that caffeine suppresses phagocytosis at micromolar physiological concentrations. This suppression was prevented when mononuclear phagocytes were pretreated with PKA inhibitor, suggesting that caffeine's phagocytic suppression may be due to its function as a phosphodiesterase inhibitor, pushing cells towards an anti-inflammatory response. Additionally, these effects are altered by regular caffeine intake and fitness level, emphasizing that tolerance and immune robustness are important factors in mononuclear phagocyte activation. These results demonstrate that caffeine may be acting as a phosphodiesterase inhibitor and suppressing phagocytosis in mononuclear phagocytes by promoting an anti-inflammatory response.

Histone deacetylase inhibitors prevent pulmonary endothelial hyperpermeability and acute lung injury by regulating heat shock protein 90 function

Transendothelial hyperpermeability caused by numerous agonists is dependent on heat shock protein 90 (Hsp90) and leads to endothelial barrier dysfunction (EBD). Inhibition of Hsp90 protects and restores transendothelial permeability. Hyperacetylation of Hsp90, as by inhibitors of histone deacetylase (HDAC), suppresses its chaperone function and mimics the effects of Hsp90 inhibitors. In this study we assessed the role of HDAC in mediating lipopolysaccharide (LPS)-induced transendothelial hyperpermeability and acute lung injury (ALI). We demonstrate that HDAC inhibition protects against LPS-mediated EBD. Inhibition of multiple HDAC by the general inhibitors panobinostat or trichostatin provided protection against LPS-induced transendothelial hyperpermeability, acetylated and suppressed Hsp90 chaperone function, and attenuated RhoA activity and signaling crucial to endothelial barrier function. Treatment with the HDAC3-selective inhibitor RGFP-966 or the HDAC6-selective inhibitor tubastatin A provided partial protection against LPS-mediated transendothelial hyperpermeability. Similarly, knock down of HDAC3 and HDAC6 by specific small-interfering RNAs provided significant protection against LPS-induced EBD. Furthermore, combined pharmacological inhibition of both HDAC3 and -6 attenuated the inflammation, capillary permeability, and structural abnormalities associated with LPS-induced ALI in mice. Together these data indicate that HDAC mediate increased transendothelial hyperpermeability caused by LPS and that inhibition of HDAC protects against LPS-mediated EBD and ALI by suppressing Hsp90-dependent RhoA activity and signaling.

RelB activation in anti-inflammatory decidual endothelial cells: a master plan to avoid pregnancy failure?

It is known that excessive inflammation at fetal-maternal interface is a key contributor in a compromised pregnancy. Female genital tract is constantly in contact with microorganisms and several strategies must be adopted to avoid pregnancy failure. Decidual endothelial cells (DECs) lining decidual microvascular vessels are the first cells that interact with pro-inflammatory stimuli released into the environment by microorganisms derived from gestational tissues or systemic circulation. Here, we show that DECs are hypo-responsive to LPS stimulation in terms of IL-6, CXCL8 and CCL2 production. Our results demonstrate that DECs express low levels of TLR4 and are characterized by a strong constitutive activation of the non-canonical NF-κB pathway and a low responsiveness of the canonical pathway to LPS. In conclusion, DECs show a unique hypo-responsive phenotype to the pro-inflammatory stimulus LPS in order to control the inflammatory response at feto-maternal interface.

Pretreatment of human cerebrovascular endothelial cells with CO-releasing molecule-3 interferes with JNK/AP-1 signaling and suppresses LPS-induced proadhesive phenotype

OBJECTIVE

Exogenously administered CO interferes with PMN recruitment to the inflamed organs. The mechanisms of CO-dependent modulation of vascular proadhesive phenotype, a key step in PMN recruitment, are unclear.

METHODS

We assessed the effects/mechanisms of CO liberated from a water-soluble CORM-3 on modulation of the proadhesive phenotype in hCMEC/D3 in an in vitro model of endotoxemia. To this end, hCMEC/D3 were stimulated with LPS (1 μg/mL) for six hours. In some experiments hCMEC/D3 were pretreated with CORM-3 (200 μmol/L) before LPS-stimulation. PMN rolling/adhesion to hCMEC/D3 were assessed under conditions of laminar shear stress (0.7 dyn/cm(2) ). In parallel, expression of adhesion molecules E-selectin, ICAM-1, and VCAM-1 (qPCR), activation of transcription factors, NF-κB and AP-1 (ELISA), and MAPK-signaling (expression/phosphorylation of p38, ERK1/2, and JNK1/2; western blot) were assessed.

RESULTS

The obtained results indicate that CORM-3 pretreatment reduces PMN rolling/adhesion to LPS-stimulated hCMEC/D3 (p < 0.05). Decreased PMN rolling/adhesion to hCMEC/D3 was associated with CORM-3-dependent inhibition of MAPK JNK1/2 activation (Tyr-phosphorylation), inhibition of transcription factor, AP-1 (c-Jun phosphorylation), and subsequent suppression of VCAM-1 expression (p < 0.05).

CONCLUSIONS

These findings indicate that CORM-3 pretreatment interferes with JNK/AP-1 signaling and suppresses LPS-induced upregulation of the proadhesive phenotype in hCMEC/D3.

Differentially expressed genes of LPS febrile symptom in rabbits and that treated with Bai-Hu-tang, a classical anti-febrile Chinese herb formula

ETHNOPHARMACOLOGICAL RELEVANCE

Bai-Hu-Tang (BHT) has been traditionally used to clear heat and engender fluids.

AIM OF THE STUDY

To reveal the alteration of differentially expressed genes (DEGs) between lipopolysaccharide (LPS) febrile syndrome in rabbits and treatment with BHT which is a classical anti-febrile formula in traditional Chinese medicine.

MATERIALS AND METHODS

Febrile model was induced by LPS injection (i.v.) in rabbits, and BHT was gavaged to another group of febrile rabbits. After sacrifice of animals, total RNA of liver tissue was isolated, processed, and hybridized to rabbit cDNA microarrays obtained from Agilent Co. The data of DEGs were obtained by lazer scanning and analyzed with Cluster program 3.0. Then bioinformatic analysis of DEGs was conducted through gene ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. In addition, expression levels of four relative genes were detected by quantitative real time ployenzyme chain reaction (qRT-PCR) to validate the accuracy of microarrays.

RESULT

The results demonstrated that genes expression pattern could be clustered into three groups significantly, and there were 606 up-regulated genes and 859 down-regulated genes in the model group, and 106 up-regulated genes and 429 down-regulated genes in BHT treated group. There were 286 DEGs existed as the common in two experimental groups. Enrichment analysis of GO annotations indicated that DEGs in model and BHT treated animals mainly referred catalytic activity and oxidoreductase activity for metabolic processes located in the membrane system at intracellular part, and binding activities increased significantly in treatment with BHT. Enrichment of KEGG analysis showed that the pathways of phagosome and protein processing in endoplasmic reticulum contained the most altered genes in the LPS group, but the percentage of phagosome pathway almost doubled in BHT group. Most DEGs involved in the LPS signal recognition system was up-regulated in LPS group, but partly decreased in BHT group. RT-PCR results of eight relative genes were consistent with the results of microarrays.

CONCLUSION

DEGs of LPS febrile syndrome mainly involved oxidoreductase and catalytic activity of the metabolic processes, and pathways of processing protein for pyrotoxin recognition; BHT mostly regulated the DEGs in the phagosome pathway to clear LPS in the liver, and partly interfered with gene expression in LPS recognition system. The study provided an important pioneering result on gene expression profiling research, and will facilitate the clinical care or further studies of the formula.

Bilirubin inhibits the up-regulation of inducible nitric oxide synthase by scavenging reactive oxygen species generated by the toll-like receptor 4-dependent activation of NADPH oxidase

It has been previously shown that bilirubin prevents the up-regulation of inducible nitric oxide synthase (iNOS) in response to LPS. The present study examines whether this effect is exerted through modulation of Toll-Like Receptor-4 (TLR4) signaling. LPS-stimulated iNOS and NADPH oxidase (Nox) activity in RAW 264.7 murine macrophages was assessed by measuring cellular nitrate and superoxide ( [Formula: see text] ) production, respectively. The generation of both nitrate and [Formula: see text] in response to LPS was suppressed by TLR4 inhibitors, indicating that activation of iNOS and Nox is TLR4-dependent. While treatment with superoxide dismutase (SOD) and bilirubin effectively abolished LPS-mediated [Formula: see text] production, hydrogen peroxide and nitrate release were inhibited by bilirubin and PEG-catalase, but not SOD, supporting that iNOS activation is primarily dependent upon intracellular H2O2. LPS treatment increased nuclear translocation of the redox-sensitive transcription factor Hypoxia Inducible Factor-1α (HIF-1α), an effect that was abolished by bilirubin. Cells transfected with murine iNOS reporter constructs in which the HIF-1α-specific hypoxia response element was disrupted exhibited a blunted response to LPS, supporting that HIF-1α mediates Nox-dependent iNOS expression. Bilirubin, but not SOD, blocked the cellular production of interferon-β, while interleukin-6 production remained unaffected. These data support that bilirubin inhibits the TLR4-mediated up-regulation of iNOS by preventing activation of HIF-1α through scavenging of Nox-derived reactive oxygen species. Bilirubin also suppresses interferon-β release via a ROS-independent mechanism. These findings characterize potential mechanisms for the anti-inflammatory effects of bilirubin.

Hypoxia augments lipopolysaccharide-induced cytokine expression in periodontal ligament cells

Periodontitis is a chronic inflammatory disease characterized by the destruction of tooth supporting tissues. Hypoxia, the mainly changes of the plateau environment, can induce severe periodontitis by animal experiments. There is, however, very little information on hypoxia and lipopolysaccharide (LPS) induced cytokine expression in periodontal ligament (PDL) cells. In this article, we characterized hypoxia or P. gingivalis lipopolysaccharide (Pg LPS) induced tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, and IL-6 expression by human periodontal ligament (hPDL) cells. We found that hypoxia augmented Pg LPS induced TNF-α, IL-1β, and IL-6 expression in hPDL cells. We also demonstrated that nuclear factor kappa B pathway was involved in hypoxia augmenting Pg LPS induced cytokine expression in hPDL cells. Thus, our results suggest that the hypoxic environment may enhance the immune function of hPDL cells that is induced by Pg LPS.

Chinese herbal medicinal ingredients affect secretion of NO, IL-10, ICAM-1 and IL-2 by endothelial cells

The aim of this study was to investigate the anti-endotoxin effects of sinomenine, fangchinoline, stachydrine, chuanxionggzine, oxymartrine and evodiamine alkaloids commonly found in Chinese herbal medicines. Porcine endothelial cells were challenged with 1 μg LPS/ml for 3 h and then treated with one of the six alkaloids at three concentrations (1, 5 or 10 μg/ml) for a further 21 h. The supernatants of the cultures were then collected and analyzed for levels of nitric oxide (NO), interleukin (IL)-10, intercellular cell adhesion molecule-1 (ICAM-1) and IL-2 using ELISA kits. The results revealed that sinomenine, stachydrine and chuanxionggzine inhibited production of NO; stachydrine and evodiamine inhibited secretion of IL-10; sinomenine and chuanxionggzine down-regulated ICAM-1 expression; oxymartrine and evodiamine decreased production of IL-2 by the LPS-stimulated endothelial cells. Overall, the data from these studies suggested to us that these six alkaloids might effectively reduce inflammatory responses in situ via changes in the formation of these key regulatory molecules/proteins.

MicroRNA-19a regulates lipopolysaccharide-induced endothelial cell apoptosis through modulation of apoptosis signal-regulating kinase 1 expression

Background

MicroRNAs, small non-encoding RNAs that post-transcriptionally modulate expression of their target genes, have been implicated as critical regulatory molecules in endothelial cells.

Results

In the present study, we found that overexpression of miR-19a protects endothelial cells from lipopolysaccharide (LPS)-induced apoptosis through the apoptosis signal-regulating kinase 1 (ASK1)/p38 pathway. Quantitative real-time PCR demonstrated that the expression of miR-19a in endothelial cell was markedly down-regulated by LPS stimulation. Furthermore, LPS-induced apoptosis was significantly inhibited by over-expression of miR-19a. Finally, both a luciferase reporter assay and western blot analysis showed that ASK1 is a direct target of miR-19a.

Conclusions

MiR-19a regulates ASK1 expression by targeting specific binding sites in the 3’ untranslated region of ASK1 mRNA. Overexpression of miR-19a is an effective method to protect against LPS-induced apoptosis of endothelial cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12867-015-0034-8) contains supplementary material, which is available to authorized users.

Bacterial PAMPs and Allergens Trigger Increase in [Ca(2+)]i-induced Cytokine Expression in Human PDL Fibroblasts

An oral environment is constantly exposed to environmental factors and microorganisms. The periodontal ligament (PDL) fibroblasts within this environment are subject to bacterial infection and allergic reaction. However, how these condition affect PDL fibroblasts has yet to be elucidated. PDL fibroblasts were isolated from healthy donors. We examined using reverse transcription-polymerase chain reaction and measuring the intracellular Ca²⁺ concentration ([Ca²⁺]_i). This study investigated the receptors activated by exogenous bacterial pathogens (Lipopolysaccharide and peptidoglycan) and allergens (German cockroach extract and house dust mite) as well as these pathogenic mediators-induced effects on the intracellular Ca²⁺ signaling in human PDL fibroblasts. Moreover, we evaluated the expression of pro-inflammatory cytokines (interleukin (IL)-1β, IL-6, and IL-8) and bone remodeling mediators (receptor activator of NF-κB ligand and osteoprotegerin) and intracellular Ca²⁺-involved effect. Bacterial pathogens and allergic mediators induced increased expression of pro-inflammatory cytokines, and these results are dependent on intracellular Ca²⁺. However, bacterial pathogens and allergic mediators did not lead to increased expression of bone remodeling mediators, except lipopolysaccharide-induced effect on receptor activator of NF-κB ligand expression. These experiments provide evidence that a pathogens and allergens-induced increase in [Ca²⁺]_i affects the inflammatory response in human PDL fibroblasts.

Increased β2-adrenergic vasorelaxation at the early phase of endotoxemic shock in rats

BACKGROUND AND PURPOSE

The early management of the cardiovascular dysfunction of septic shock is critical as it is associated with a poor outcome. Although the use of catecholamines is a common therapy in this syndrome, no data are available on the involvement of β-adrenoceptor (β-AR) subtypes and only few studies report an alteration of β-adrenergic-induced vasodilation in septic shock. The purpose of the study was to evaluate vascular β1, β2 and β3-AR expression and function in an endotoxemic rat model.

EXPERIMENTAL APPROACH

Endotoxemia was induced in rats by intravenous injection of lipopolysaccharide (LPS). β1, β2 and β3-AR mRNA expression was evaluated by RT-PCR in aorta and vascular β1, β2 and β3-AR responses were determined on conducting (aorta) and/or resistance (mesenteric and renal) arteries by constructing relaxation curves in response to different β-AR agonists.

RESULTS

The maximal effect of isoproterenol decreased by 31 to 61% in the three vascular beds of LPS-treated rats compared to controls. In aortas from LPS-treated rats, β1 and β3-AR mRNA expression was decreased and associated to a reduced β1 and β3-induced vasodilation. Conversely, albeit β2-AR mRNA was unchanged, the maximal β2-AR-induced vasodilation increased by 49% in aortas from LPS-treated rats compared to controls. This increase was not affected by endothelium removal but was abolished in the presence of a β2-AR antagonist or an adenylate cyclase inhibitor.

CONCLUSIONS

In endotoxemia, β2-AR vasodilation was increased by a potential recruitment of β2-AR located on smooth muscle cells. This study suggests that vascular β2-AR should be a putative new therapeutic target in septic shock.

Angiopoietin-1 inhibits toll-like receptor 4 signalling in cultured endothelial cells: role of miR-146b-5p

AIMS

Bacterial lipopolysaccharides (LPS) induce innate immune inflammatory responses in endothelial cells by activating toll-like receptor 4 (TLR4) signalling. Here, we investigate the effects of angiopoietin-1 (Ang-1) on LPS-induced TLR4 signalling and the role of the miR-146 family of micro RNAs in the effects of Ang-1 on TRL4 signalling.

METHODS AND RESULTS

Leucocyte adhesion to human umbilical vein endothelial cells (HUVECs) was detected using fluorescence microscopy. Adhesion molecule, pro-inflammatory cytokine, miR-146a, and miR-146b-5p expressions in HUVECs were quantified using real-time PCR. TLR4 signalling protein levels were measured using immunoblotting. Exposure of HUVECs to LPS for 4-6 h induces robust inflammatory responses, including enhanced leucocyte adhesion, up-regulation of adhesion molecule expression (VCAM1, ICAM1, E-SELECTIN), enhanced cytokine production (TNFα, IL1β, IL6, and IL8), and increased NFκB luciferase reporter activity. Addition of Ang-1 to the culture medium for 24 h prior to LPS exposure significantly attenuates these responses. Prolonged Ang-1 exposure significantly decreases IRAK1 and TRAF6 protein levels but has no effect on TLR4, MYD88, IRAK4, or TAK1 expressions. Ang-1 triggers significant up-regulation of miR-146b-5p levels but has no effect on miR-146a or miR-146b-3p expressions. Transfection of HUVECs with a miR-146b-5p mimic significantly attenuates LPS-induced inflammatory responses and IRAK1 and TRAF6 expressions. In HUVECs transfected with a miR-146b-5p inhibitor, Ang-1 has no effect on LPS-induced inflammatory responses or IRAK1 and TRAF6 expressions.

CONCLUSION

Ang-1 disrupts TLR4 signalling, resulting in inhibition of LPS-induced inflammatory responses in endothelial cells. This inhibition occurs through selective targeting of IRAK1 and TRAF6 proteins by miR-146b-5p.

Docosahexaenoic acid and eicosapentaenoic acid suppress adhesion molecule expression in human aortic endothelial cells via differential mechanisms

SCOPE

Dietary PUFAs modulate the progression of cardiovascular disease, but the underlying mechanisms within vascular cells remain unclear. The aim of this study was to investigate the biological function and regulatory mechanisms of PUFAs in LPS-activated human aortic endothelial cells (HAECs).

METHODS AND RESULTS

To simulate the in vivo conditions of atherosclerosis, we have established an in vitro model in which THP-1 monocytes adhere to HAECs. Our results showed that n-3 PUFAs docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) remarkably attenuated the adhesion of THP-1 cells to HAECs, probably through inhibiting the expression of VCAM-1 and ICAM-1. Using lipid raft isolation and confocal microscopy, we found that DHA and EPA suppressed the translocation of TLR4 into lipid rafts. Furthermore, DHA and EPA inhibited the ubiquitination and translocation of TRAF6, and the phosphorylation of TAK1, p38, and IκBα. We demonstrated that DHA reduced the phosphorylation of PKR, but EPA increased the expression of A20. Additionally, silencing of A20 reversed the inhibitory effect of EPA on the expression of adhesion molecules.

CONCLUSION

Our study revealed differential signaling pathways modulated by n-3 PUFAs in LPS-stimulated HAECs. These signaling pathways are potential targets for the prevention of atherosclerotic progression.

Effect of TLR4/MyD88 signaling pathway on expression of IL-1β and TNF-α in synovial fibroblasts from temporomandibular joint exposed to lipopolysaccharide

Accumulating evidence from previous studies suggested that interleukin-1 (IL-1β) and tumor necrosis factor-α (TNF-α) play an important role in pathogenesis of temporomandibular disorders (TMD). However, the cell surface receptors and the intracellular signal pathways leading to these cytokines expression are not fully understood. In the current study, we investigated the roles of Toll-like receptor 4 (TLR4) and its adaptor myeloid differentiation factor 88 (MyD88) in the expression of IL-1β and TNF-α in synovial fibroblasts (SFs) separated from rat temporomandibular joint (TMJ) with lipopolysaccharide (LPS) stimulation. The results showed that treatment with LPS could increase TLR4, MyD88, IL-1β, and TNF-α expression at both mRNA and protein levels. In addition, increased expression of IL-1β and TNF-α could be blocked by treatment with TAK-242, a blocker of TLR4 signaling, and also by MyD88 inhibitory peptide (MIP). These findings suggested that maybe TLR4/MyD88 signal transduction pathway participates in enhanced expression of IL-1 and TNF-α in patients with TMD. The activation of TLR4/MyD88 signal transduction pathway which results in production of proinflammatory factors may play a role in the pathogenesis of TMD.

Isobavachalcone attenuates lipopolysaccharide-induced ICAM-1 expression in brain endothelial cells through blockade of toll-like receptor 4 signaling pathways

Inflammation has been implicated in the pathogenesis of various cerebral diseases. Thus, control of brain inflammation is regarded as one of the important therapeutic strategies for the treatment of neurodegenerative diseases such as Alzheimer׳s disease and stroke. Isobavachalcone, a flavonoid from Psoralea corylifolia, is known to possess a wide spectrum of biological activities and is expected to be useful in preventing or treating neurodegenerative diseases. However, very little is known regarding its effects on cerebral inflammation. In this study, we examined the effect of isobavachalcone on leukocyte adhesion and intercellular adhesion molecule-1 (ICAM-1) expression in brain endothelial cells activated with lipopolysaccharide (LPS) and explored the possible mechanisms involved. Isobavachalcone significantly down-regulated LPS-induced ICAM-1 expression and leukocyte-endothelial cell adhesion and suppressed NF-κB activity which is implicated in the expression of ICAM-1. It attenuated ICAM-1 expression as well as NF-κB transcriptional activity induced by macrophage-activating lipopeptide 2-kDa (MALP-2) or polyriboinosinic polyribocytidylic acid (poly[I:C]). Isobavachalcone also down-regulated LPS or poly[I:C]-induced expression of IFN-β, which can indirectly activate NF-κB. These data imply that isobavachalcone can modulate both MyD88-dependent and TRIF-dependent signaling of toll-like receptor 4 (TLR4). Taken together, our data suggest that isobavachalcone inhibits LPS-induced ICAM-1 expression and leukocyte adhesion to brain endothelial cell by blocking TLR4 signaling and thus, has the potential to ameliorate neuronal injury in brain diseases associated with inflammation.

The CD14 C-260T single nucleotide polymorphism (SNP) modulates monocyte/macrophage activation in treated HIV-infected individuals

Background

HIV-infected individuals have an increased risk of cardiovascular disease (CVD). T-allele carriers of the CD14 C-260T single-nucleotide polymorphism (SNP) have reported increased expression of the LPS-binding receptor, CD14 and inflammation in the general population. Our aim was to explore the relationship of this SNP with monocyte/macrophage activation and inflammation and its association with sub-clinical atherosclerosis in HIV-infected individuals.

Methods

Patients with no pre-existing CVD risk factors on suppressive antiretroviral therapy were recruited from University Malaya Medical Centre, Malaysia (n = 84). The CD14 C-260T and TLR4 SNPs, Asp299Gly and Thr399Ile were genotyped and soluble(s) CD14 and sCD163 and high-sensitivity C-reactive protein, hsCRP were measured in plasma. Subclinical atherosclerosis was assessed by measuring carotid intima media thickness (cIMT). The association between CD14 C-260T SNP carriage and cIMT was assessed in a multivariable quantile regression model where a p-value of <0.05 was considered significant.

Results

We found the CD14 C-260T T-allele in 56% of the cohort and evidence of subclinical atherosclerosis in 27%. TT genotype was associated with higher sCD163 (p = 0.009) but only marginally higher sCD14 (p = 0.209) and no difference in hsCRP (p = 0.296) compared to CC/CT. In multivariable analysis, only Framingham risk score was independently associated with higher cIMT while lower sCD163 was trending towards significance. No association was found in TT-genotype carriers and cIMT measurements.

Conclusion

The CD14 C-260T SNP was associated with increased monocyte activation but not systemic inflammation or cIMT in this HIV-infected cohort with low CVD risk profile.

Oxidized phospholipids protect against lung injury and endothelial barrier dysfunction caused by heat-inactivated Staphylococcus aureus

Increased endothelial cell (EC) permeability and vascular inflammation along with alveolar epithelial damage are key features of acute lung injury (ALI). Products of 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine oxidation (OxPAPC) showed protective effects against inflammatory signaling and vascular EC barrier dysfunction induced by gram-negative bacterial wall lipopolysaccharide (LPS). We explored the more general protective effects of OxPAPC and investigated whether delayed posttreatment with OxPAPC boosts the recovery of lung inflammatory injury and EC barrier dysfunction triggered by intratracheal injection of heat-killed gram-positive Staphylococcus aureus (HKSA) bacteria. HKSA-induced pulmonary EC permeability, activation of p38 MAP kinase and NF-κB inflammatory cascades, secretion of IL-8 and soluble ICAM1, fibronectin deposition, and expression of adhesion molecules ICAM1 and VCAM1 by activated EC were significantly attenuated by cotreatment as well as posttreatment with OxPAPC up to 16 h after HKSA addition. Remarkably, posttreatment with OxPAPC up to 24 h post-HKSA challenge dramatically accelerated lung recovery by restoring lung barrier properties monitored by Evans blue extravasation and protein content in bronchoalveolar lavage (BAL) fluid and reducing inflammation reflected by decreased MIP-1, KC, TNF-α, IL-13 levels and neutrophil count in BAL samples. These studies demonstrate potent in vivo and in vitro protective effects of posttreatment with anti-inflammatory oxidized phospholipids in the model of ALI caused by HKSA. These results warrant further investigations into the potential use of OxPAPC compounds combined with antibiotic therapies as a treatment of sepsis and ALI induced by gram-positive bacterial pathogens.

Novel insights in preventing Gram-negative bacterial infection in cirrhotic patients: review on the effects of GM-CSF in maintaining homeostasis of the immune system

Cirrhotic patients with dysfunctional and/or low numbers of leukocytes are often infected with bacteria, especially Gram-negative bacteria, which is characterized by producing lipopolysaccharide (LPS). Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a pleiotropic cytokine that influences the production, maturation, function, and survival of various immune cells. In this paper, we reviewed not only Toll-like receptors 4 (TLR4) signaling pathway and its immunological effect, but also the specific stimulating function and autocrine performance of GM-CSF on hematopoietic cells, as well as the recent discovery of innate response activator-B cells in protection against microbial sepsis and the direct LPS-TLR4 signaling on hematopoiesis. Thus we concluded that GM-CSF might play important roles in preventing Gram-negative bacterial infections in cirrhotic patients through maintaining immune system functions and homeostasis.

1α,25-dihydroxyvitamin D3 promotes osteogenic activity and downregulates proinflammatory cytokine expression in human periodontal ligament cells

BACKGROUND AND OBJECTIVE

The aim of this study was to assess the impact of 1α,25-dihydroxyvitamin D3 (vitamin D3) on osteogenic and inflammatory properties of human periodontal ligament (PDL) cells and investigate underlying mechanisms.

MATERIAL AND METHODS

Human PDL cells, obtained from four subjects, were stimulated with vitamin D3 for 4-48 h. The bone markers osteopontin and osteocalcin and proinflammatory cytokine/chemokine expression was determined by quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assay. Cytokine and chemokine expression was determined after stimulation with the inflammation promoter lipopolysaccharide (LPS) in the presence or absence of vitamin D3. Alkaline phosphatase activity was assessed using p-nitrophenylphosphate substrate.

RESULTS

Treatment with 30 ng/mL of vitamin D3, corresponding to an optimal plasma concentration of vitamin D, for 24 h had no effect on PDL cell number and morphology but increased PDL cell osteopontin and osteocalcin mRNA expression by about 70 and 40%, respectively, and, moreover, treatment with vitamin D3 for 48 h enhanced PDL cell alkaline phosphatase activity by about two times showing that vitamin D3 exerts pro-osteogenic effects in human PDL cells. Stimulation with LPS (1 μg/mL) for 4 h increased PDL cell interleukin (IL)-6 cytokine and chemokine ligand 1 (CXCL1) chemokine mRNA expression several fold. The LPS-induced increase in IL-6 and CXCL1 transcripts was attenuated by vitamin D3 (30 ng/mL). Treatment with vitamin D3 (3-300 ng/mL) for 24 h reduced the LPS-evoked increase in PDL cell IL-6 protein by about 50%. Vitamin D3 (30 ng/mL) had no effect on LPS-induced IL-1β and MCP-1 mRNA expression.

CONCLUSIONS

Vitamin D3 promotes osteogenic differentiation but also downregulates inflammation promoter-induced IL-6 cytokine and CXCL1 chemokine expression in human PDL cells, suggesting that vitamin D3 both stimulates bone regeneration and antagonizes inflammation in human periodontal tissue.