Prostaglandin-E2 regulation of tumor necrosis factor receptor release in human monocytic THP-1 cells

Immunomodulatory differences between mesenchymal stem cells from different oral tissues

Mesenchymal stem cells (MSCs) have recently been identified as having potentially therapeutic immunomodulatory properties. MSCs isolated from different oral tissues have similar morphology and immunophenotypes, however, direct comparisons of their gene expression and immunomodulatory properties have not been conducted. We isolated alveolar bone-derived MSCs (aBMSCs), dental pulp stem cells (DPSCs) and gingiva-derived MSCs (GMSCs) from the same patients and compared their immunophenotypes and transcriptomes. Additionally, we compared their production of soluble immunomodulatory cytokines as well as their immunoregulatory properties in coculture with THP-1 human monocytic cells. RNA sequencing revealed distinct gene expression in DPSCs while aBMSCs and GMSCs had less differentially expressed genes. DPSCs also had significantly less secretion of osteopontin compared to aBMSCs and GMSCs. Finally, DPSCs did not exhibit an immunosuppresive effect on THP-1 cells to the same degree as aBMSCs and GMSCs. These findings demonstrate that MSCs from different oral tissues have distinct transcriptomes and immunoregulatory properties.

Elevated levels of Metrnl in rheumatoid arthritis: Association with disease activity

BACKGROUND

Meteorin-like (Metrnl) is a novel adipokine that is highly expressed in white adipose tissues. Whether Metrnl plays a role in rheumatoid arthritis (RA) remains unclear. In this study, sera from 159 RA patients, 28 osteoarthritis (OA) patients, and 50 healthy individuals were included. The serum levels of Metrnl were measured using an enzyme-linked immunosorbent assay. Clinical parameters, including disease activity score 28 (DAS28), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), rheumatoid factor (RF), antibodies to cyclic citrulline peptide (anti-CCP), inflammatory cytokines, and blood biochemical indices were collected.

RESULTS

Metrnl levels were higher in RA patients compared to OA patients and controls. In the RA group, serum Metrnl levels were positively correlated with DAS28, RF, and CRP levels. However, in the RA group, serum Metrnl levels were not correlated with ESR, anti-CCP, immunoglobulins, and blood biochemical indices.

CONCLUSION

This study showed that Metrnl is involved in the pathogenesis of RA. Increase in serum Metrnl levels is closely related to RA activity.

METEORIN-LIKE is a cytokine associated with barrier tissues and alternatively activated macrophages

Cytokines are involved in many functions of the immune system including initiating, amplifying and resolving immune responses. Through bioinformatics analyses of a comprehensive database of gene expression (BIGE: Body Index of Gene Expression) we observed that a small secreted protein encoded by a poorly characterized gene called meteorin-like (METRNL), is highly expressed in mucosal tissues, skin and activated macrophages. Further studies indicate that Metrnl is produced by Alternatively Activated Macrophages (AAM) and M-CSF cultured bone marrow macrophages (M2-like macrophages). In the skin, METRNL is expressed by resting fibroblasts and IFNγ-treated keratinocytes. A screen of human skin-associated diseases showed significant over-expression of METRNL in psoriasis, prurigo nodularis, actinic keratosis and atopic dermatitis. METRNL is also up-regulated in synovial membranes of human rheumatoid arthritis. Taken together, these results indicate that Metrnl represents a novel cytokine, which is likely involved in both innate and acquired immune responses.

Hemocompatibility and biocompatibility of antibacterial biomimetic hybrid films

In previous work, we developed novel antibacterial hybrid coatings based on dextran containing dispersed Ag NPs (~5 nm, DEX-Ag) aimed to offer dual protection against two of the most common complications associated with implant surgery, infections and rejection of the implant. However, their blood-material interactions are unknown. In this study, we assess the hemocompatibility and biocompatibility of DEX-Ag using fresh blood and two cell lines of the immune system, monocytes (THP-1 cells) and macrophages (PMA-stimulated THP-1 cells). Glass, polyurethane (PU) and bare dextran (DEX) were used as reference surfaces. PU, DEX and DEX-Ag exhibited non-hemolytic properties. Relative to glass (100%), platelet attachment on PU, DEX and DEX-Ag was 15%, 10% and 34%, respectively. Further, we assessed cell morphology and viability, pro-inflammatory cytokines expression (TNF-α and IL-1β), pro-inflammatory eicosanoid expression (Prostaglandin E2, PGE2) and release of reactive oxygen species (ROS, superoxide and H2O2) following incubation of the cells with the surfaces. The morphology and cell viability of THP-1 cells were not affected by DEX-Ag whereas DEX-Ag minimized spreading of PMA-stimulated THP-1 cells and caused a reduction in cell viability (16% relative to other surfaces). Although DEX-Ag slightly enhanced release of ROS, the expression of pro-inflammatory cytokines remained minimal with similar levels of PGE2, as compared to the other surfaces studied. These results highlight low toxicity of DEX-Ag and hold promise for future applications in vivo.

Reduced peripheral PGE2 biosynthesis in Plasmodium falciparum malaria occurs through hemozoin-induced suppression of blood mononuclear cell cyclooxygenase-2 gene expression via an interleukin-10-independent mechanism

Molecular immunologic determinants of disease severity during Plasmodium falciparum malaria are largely undetermined. Our recent investigations showed that peripheral blood mononuclear cell (PBMC) cyclooxygenase-2 (COX-2) gene expression and plasma prostaglandin E(2) (PGE(2)) production are suppressed in children with falciparum malaria relative to healthy, malaria-exposed children with partial immunity. Furthermore, decreased COX-2/PGE(2) levels were significantly associated with increased plasma interleukin-10 (IL-10), an anti-inflammatory cytokine that inhibits the expression of COX-2 gene products. To determine the mechanism(s) responsible for COX-2-derived PGE(2) suppression, PBMCs were cultured from children with falciparum malaria. PGE(2) production was suppressed under baseline and COX-2-promoting conditions (stimulation with lipopolysaccharide [LPS] and interferon [IFN]-gamma) over prolonged periods, suggesting that an in vivo-derived product(s) was responsible for reduced PGE(2) biosynthesis. Ingestion of hemozoin (malarial pigment) by PBMC was investigated as a source of COX-2/PGE(2) suppression in PBMCs from healthy, malaria-naive adults. In addition, synthetically prepared hemozoin, beta-hematin, was used to investigate the effects of the core iron component of hemozoin, ferriprotoporphyrin-IX (FPIX). Physiologic concentrations of hemozoin or b-hematin suppressed LPS- and IFN-gamma-induced COX-2 mRNA in a time- and dose-dependent manner, resulting in decreased COX-2 protein and PGE(2) production. Suppression of COX-2/PGE(2) by hemozoin was not due to decreased cell viability as evidenced by examination of mitochondrial bioactivity. These data illustrate that ingestion of FPIX by blood mononuclear cells is responsible for suppression of COX-2/PGE(2). Although hemozoin induced overproduction of IL-10, neutralizing IL-10 antibodies failed to restore PGE(2) production. Thus, acquisition of hemozoin by blood mononuclear cells is responsible for suppression of PGE(2) in malaria through inhibition of de novo COX-2 transcripts via molecular mechanisms independent of increased IL-10 production.

The Potential Contributions of Chronic Inflammation to Lung Carcinogenesis

A number of lines of evidence suggests that chronic inflammation contributes to the process of carcinogenesis. In this article, this theme is explored with particular emphasis on the involvement of inflammation in the development of lung cancer. A number of molecular pathways activated in chronic inflammation may contribute to lung carcinogenesis. The challenge is to conceptualize a cohesive picture of this complex biology that allows for effective pharmaceutical intervention. Initial therapeutic efforts involve strategies to block single pathways, such as with cyclooxygenase (COX) activity. However, the more that is learned about the consequences of COX activity, the more evident are the relationships of this enzyme to other classes of regulatory molecules such as the potent nuclear factor-kB. In light of this emerging picture, more global intervention strategies, such as with drug combinations, may be essential for success. Further basic study is essential to sort out possible molecular relationships and to permit elucidation of the most critical regulatory circuits. Given the complexity of these molecular interactions, well-designed clinical trials that specifically evaluate the precise effects of particular antiinflammatory drugs on lung carcinogenesis will also be critical to sort out the complexity and to validate successful approaches to arresting lung carcinogenesis.

In vitro effects of eicosanoids derived from different 20-carbon Fatty acids on production of monocyte-derived cytokines in human whole blood cultures

INTRODUCTION

Prostaglandins (PG) and leukotrienes (LT) are usually formed from arachidonic acid (e.g. PGE(2), LTB(4), LTC(4)). The anti-inflammatory effects of fish oil may be mediated through the production of alternative PG and/or LT formed from eicosapentaenoic acid (e.g. PGE(3), LTC(5)). This study examines the effects of PG and LT derived from different fatty acid precursors on lipopolysaccharide-induced cytokine production by cultured human whole blood. Methods Human whole blood was diluted 1:5 and incubated for 48h with lipopolysaccharide. PGE and LT were added and the concentrations of inflammatory cytokines in the cell culture supernatants determined.

RESULTS

Tumour necrosis factor (TNF)-alpha concentrations were significantly decreased by the addition of PGE. At the maximum concentration used (10(-6)M) TNF-alpha concentration was reduced to 100%, 90% and 70% by PGE(1), PGE(2) and PGE(3) respectively. Likewise, interleukin (IL)-1beta concentration was decreased to 60%, 30% and 40% by 10(-6)M PGE(1), PGE(2) and PGE(3), respectively. IL-6 and IL-10 concentrations were not altered by PG. LTB(4), LTC(4) or LTC(5) did not significantly affect cytokine concentrations.

CONCLUSIONS

PGE inhibit lipopolysaccharide-stimulated TNF-alpha and IL-1beta production in human whole blood cultures. PGE(1), PGE(2) and PGE(3) show a similar pattern and magnitude of effect. This suggests that the anti-inflammatory effects of dietary fish oil may not be mediated through a simple substitution of one family of eicosanoids for another.

The ability of fish oil to suppress tumor necrosis factor alpha production by peripheral blood mononuclear cells in healthy men is associated with polymorphisms in genes that influence tumor necrosis factor alpha production

BACKGROUND

Tumor necrosis factor alpha (TNF-alpha) mediates inflammation. High TNF-alpha production has adverse effects during disease. Polymorphisms in the TNF-alpha and lymphotoxin alpha genes influence TNF-alpha production. Fish oil suppresses TNF-alpha production and has variable antiinflammatory effects on disease.

OBJECTIVE

We examined the relation between TNF-alpha and lymphotoxin alpha genotypes and the ability of dietary fish oil to suppress TNF-alpha production by peripheral blood mononuclear cells (PBMCs) in healthy men.

DESIGN

Polymorphisms in the TNF-alpha (TNF*1 and TNF*2) and lymphotoxin alpha (TNFB*1 and TNFB*2) genes were determined in 111 healthy young men. TNF-alpha production by endotoxin-stimulated PBMCs was measured before and 12 wk after dietary supplementation with fish oil (6 g/d).

RESULTS

Homozygosity for TNFB*2 was 2.5 times more frequent in the highest than in the lowest tertile of inherent TNF-alpha production. The percentage of subjects in whom fish oil suppressed TNF-alpha production was lowest (22%) in the lowest tertile and doubled with each ascending tertile. In the highest and lowest tertiles, mean TNF-alpha production decreased by 43% (P < 0.05) and increased by 160% (P < 0.05), respectively. In the lowest tertile of TNF-alpha production, only TNFB*1/TNFB*2 heterozygous subjects were responsive to the suppressive effect of fish oil. In the middle tertile, this genotype was 6 times more frequent than the other lymphotoxin alpha genotypes among responsive individuals. In the highest tertile, responsiveness to fish oil appeared unrelated to lymphotoxin alpha genotype.

CONCLUSION

The ability of fish oil to decrease TNF-alpha production is influenced by inherent TNF-alpha production and by polymorphisms in the TNF-alpha and lymphotoxin alpha genes.

Contribution of the two Gs-coupled PGE2-receptors EP2-receptor and EP4-receptor to the inhibition by PGE2 of the LPS-induced TNFalpha-formation in Kupffer cells from EP2-or EP4-receptor-deficient mice. Pivotal role for the EP4-receptor in wild type Kupffer cells

BACKGROUND/AIMS

Prostaglandin E2 (PGE2) is known to inhibit the lipopolysaccharide (LPS)-induced tumor necrosis factor alpha (TNFalpha) formation in Kupffer cells via an increase in cAMP. Four receptor-subtypes have been cloned for PGE2 so far. Two of them, the EP2-receptor and the EP4-receptor are linked to stimulatory Gs-proteins and could mediate the inhibition by PGE2 of TNFalpha-formation.

METHODS

The significance of both receptors for PGE2-dependent inhibition of LPS-induced TNFalpha-formation was studied using Kupffer cells of mice in which either one of the two receptors had been eliminated by homologous recombination.

RESULTS

The mRNAs of both receptors were expressed in wild type mouse Kupffer cells. Exogenous PGE2 inhibited TNFalpha-formation in Kupffer cells lacking either EP2-receptor or EP4-receptor to a similar extent as in control cells, however, 10-fold higher PGE2 concentrations were needed for half maximal inhibition in cells lacking the EP4-receptor than in control or EP2-receptor-deficient cells. The response to endogenous PGE2 was blunted in EP4-receptor-deficient mice only and especially after prolonged incubation.

CONCLUSIONS

The data indicate, that PGE2 can inhibit TNFalpha-formation via both the EP2- and the EP4-receptor and that, however, the EP4-receptor appears to be physiologically more relevant in Kupffer cells since it conferred a high affinity response to PGE2.

Nutritional modulation of immune function

The inflammatory response to injury and infection, although an essential part of immune function, carries the risk of severe tissue depletion and immunosuppression. These outcomes increase morbidity and delay recovery. Evidence is accumulating that single-nucleotide polymorphisms in the genes controlling pro-inflammatory cytokine production adversely influence the response. Immunonutrition provides a means of modulating the inflammatory response to injury and infection, and thereby improves clinical outcome. n-3 Polyunsaturated fatty acids (n-3 PUFA), glutamine, arginine, S amino acids and nucleotides are important components of immunonutrient mixes. While animal model studies suggest that all these components may exert a beneficial effect in patients, the number of large randomized placebo-controlled trials utilizing immunonutrition is fairly limited and the observed effects are relatively small. Meta-analyses suggest that while immunonutrition may not reduce mortality rates, a reduction in hospital length of stay, decreased requirements for ventilation and lower infection rates are achieved by this mode of nutrition. The present paper discusses some underlying reasons for the difficulty in demonstrating the clinical efficacy of immunonutrition. Paramount among these reasons is the antioxidant status and genetic background of the patient. A number of studies suggest that there is an inverse relationship between inflammation and T-cell function. Immuno-enhancive effects have been shown in a number of studies in which n-3 PUFA, glutamine and N-acetyl cysteine have been employed. All these nutrients may exert their effects by suppressing inflammation; n-3 PUFA by direct suppression of the process and glutamine and N-acetyl cysteine by acting indirectly on antioxidant status. Glutamine and nucleotides exert a direct effect on lymphocyte proliferation. Preliminary data suggests that not all genotypes are equally sensitive to the effects of immunonutrition. When further studies have been conducted to discern the precise interaction between each individual's genotype of relevance to the response to injury and infection, and immunonutrients, the level of precision in the application of immunonutrition will undoubtedly improve.

Modulatory effect of prostaglandins on human monocyte activation for killing of high- and low-virulence strains of Paracoccidioides brasiliensis

The effect of indomethacin (Indo), a cyclo-oxygenase inhibitor, on the monocyte-mediated killing of a low- (Pb265) and a high- (Pb18) virulence strain of Paracoccidioides brasiliensis was examined. The Pb18 strain was not killed by either non-activated or interferon-gamma (IFN-gamma) -activated human monocytes but these cells did show fungicidal activity if pretreated with Indo. In contrast with IFN-gamma, tumour necrosis factor-alpha (TNF-alpha) was very effective at stimulating the fungicidal activity of monocytes. While the low-virulence strain, Pb265, could not be killed by monocytes, cells preincubated with IFN-gamma demonstrated fungicidal activity. The killing of this strain was also induced by pretreatment of monocytes with Indo. The results suggest a negative role for prostaglandins, which are synthesized via the cyclo-oxygenase pathway, in the regulation of monocyte-mediated killing of virulent and avirulent strains of P. brasiliensis and that TNF-alpha generation during the fungus-monocyte interaction is more important in the killing of Pb265 than Pb18.

Prostaglandin E2 suppressed IL-15-mediated human NK cell function through down-regulation of common gamma-chain

NK cell function is regulated by cytokines and certain biochemical mediators in a positive or negative manner. This study was performed to investigate the suppressive effects of PGE(2) on IL-15-activated human NK cell function. Purified NK cells were cultured with 200 ng/ml IL-15 for 2 days in the presence or absence of 10-200 ng/ml PGE(2). PGE(2) significantly suppressed NK cell-mediated cytotoxicity and IFN-gamma production at the secretional and the transcriptional levels. We also evaluated the effect of PGE(2) on the IL-15R complex that consists of IL-2Rbeta, common gamma-chain (gamma(c)-chain), and a specific chain IL-15Ralpha. Percentage of positive cells and number of binding sites for gamma(c)-chain were significantly increased after IL-15 treatment; however, a substantial decrease was observed with PGE(2) cotreatment. In contrast, constitutive expression of IL-2Rbeta was significantly decreased after IL-15 treatment, with no change detected in the presence of PGE(2.) At the transcriptional level, neither IL-15 nor PGE(2) had significant effects on the expression of beta- or gamma(c)-chains. There was a 3-fold increase in the expression of IL-15Ralpha at the transcriptional level that peaked at 8 h after IL-15 treatment; however, PGE(2) had no significant effect. Suppression of NK function by PGE(2) was not due to the endogenous production of IL-4, IL-10, or TGF-beta(1) by NK cells. These results suggest that down-regulation of surface expression of gamma(c)-chain on NK cells may be one mechanism through which PGE(2) mediates suppression of IL-15-activated NK cell function.

A 63 kDa tumor necrosis factor inhibitor released from a human monocytic leukemia cell line, THP-1

A human monocytic cell line, THP-1-S, was cultured in a serum-free medium. The effect of the culture supernatant of THP-1-S on the cytotoxicity of rTNF-alpha to three kinds of cell lines and the binding of rTNF to its receptor were tested. The supernatant inhibited the cytotoxicity of rTNF-alpha when tested by the neutral red uptake method. In addition, the supernatant blocked the binding of 125I-rTNF-alpha to its receptor. Furthermore, following precipitation with PEG we detected complexes between rTNF-alpha and the inhibitory factor which formed during incubation with the culture supernatant from THP-1-S cells. However, the supernatant did not bind to or down-regulate the receptor for TNF-alpha on the cell surface of L-M-2d6 cells. This factor eluted with an apparent molecular mass of 63,000 Da by gel filtration and did not react with antibodies against p55 and p75 TNF receptors. These data suggest that human monocytic cells are capable of releasing an inhibitory factor against rTNF-alpha in serum-free culture conditions.

Hydrogen peroxide enhances shedding of type I soluble tumor necrosis factor receptor from pulmonary epithelial cells

Reactive oxygen intermediates (ROIs) are among the important mediators in the pathogenesis of lung diseases in which tumor necrosis factor (TNF) plays a pivotal role. However, the effects of ROIs on the TNF- TNF receptor system remain unclear. Effects of hydrogen peroxide on the shedding of soluble tumor necrosis factor receptor (sTNF-R) were investigated in a pulmonary epithelial cell line (A549) using enzyme-linked immunoassay. A549 cells spontaneously released type I sTNF-R (sTNF-RI) into the culture medium. Hydrogen peroxide accelerated the release of sTNF-RI from the A549 cells time- and dose- dependently. Stimulated release of sTNF-RI by hydrogen peroxide or phorbol myristate acetate (PMA) was inhibited by pretreatment with the intracellular hydroxyl radical scavengers dimethyl sulfoxide and dimethyl thiourea. A synthetic metalloproteinase inhibitor (KB-R8301) inhibited not only spontaneous release of sTNF-RI but also shedding enhanced by hydrogen peroxide and PMA. Preincubation with a protein kinase C inhibitor, calphostin C, downregulated the hydrogen peroxide- or PMA-induced shedding of sTNF-RI. Neither genistein, a tyrosine kinase inhibitor, nor H-89, a protein kinase A inhibitor, inhibited shedding of sTNF-RI by hydrogen peroxide and PMA. Although the surface expression of TNF-R assessed by 125I-TNF specific binding was decreased in the presence of hydrogen peroxide or PMA, TNF-RI mRNA transcript levels remained unchanged. These results show that hydrogen peroxide is involved in the activation of metalloproteinase and protein kinase C responsible for the shedding of sTNF-RI. Accordingly, ROIs may alter TNF action by enhanced shedding of sTNF-RI and reducing its surface receptor expression.

Regulation of serum amyloid A protein expression during the acute-phase response

The acute-phase (AP) serum amyloid A proteins (A-SAA) are multifunctional apolipoproteins which are involved in cholesterol transport and metabolism, and in modulating numerous immunological responses during inflammation and the AP response to infection, trauma or stress. During the AP response the hepatic biosynthesis of A-SAA is up-regulated by pro-inflammatory cytokines, and circulating concentrations can increase by up to 1000-fold. Chronically elevated A-SAA concentrations are a prerequisite for the pathogenesis of secondary amyloidosis, a progressive and fatal disease characterized by the deposition in major organs of insoluble plaques composed principally of proteolytically cleaved A-SAA, and may also contribute to physiological processes that lead to atherosclerosis. There is therefore a requirement for both positive and negative control mechanisms that permit the rapid induction of A-SAA expression until it has fulfilled its host-protective function(s) and subsequently ensure that its expression can be rapidly returned to baseline. These mechanisms include modulation of promoter activity involving, for example, the inducer nuclear factor kappaB (NF-kappaB) and its inhibitor IkappaB, up-regulatory transcription factors of the nuclear factor for interleukin-6 (NF-IL6) family and transcriptional repressors such as yin and yang 1 (YY1). Post-transcriptional modulation involving changes in mRNA stability and translation efficiency permit further up- and down-regulatory control of A-SAA protein synthesis to be achieved. In the later stages of the AP response, A-SAA expression is effectively down-regulated via the increased production of cytokine antagonists such as the interleukin-1 receptor antagonist (IL-1Ra) and of soluble cytokine receptors, resulting in less signal transduction driven by pro-inflammatory cytokines.