Immunomodulation by eicosanoids and anti-inflammatory drugs

Singapore Grouper Iridovirus Disturbed Glycerophospholipids Homeostasis: Cytosolic Phospholipase A2 Was Essential for Virus Replication

Singapore grouper iridovirus (SGIV), belonging to genus Ranavirus, family Iridoviridae, causes great economic losses in the aquaculture industry. Previous studies demonstrated the lipid composition of intracellular unenveloped viruses, but the changes in host-cell glyceophospholipids components and the roles of key enzymes during SGIV infection still remain largely unknown. Here, the whole cell lipidomic profiling during SGIV infection was analyzed using UPLC-Q-TOF-MS/MS. The lipidomic data showed that glycerophospholipids (GPs), including phosphatidylcholine (PC), phosphatidylserine (PS), glycerophosphoinositols (PI) and fatty acids (FAs) were significantly elevated in SGIV-infected cells, indicating that SGIV infection disturbed GPs homeostasis, and then affected the metabolism of FAs, especially arachidonic acid (AA). The roles of key enzymes, such as cytosolic phospholipase A2 (cPLA2), 5-Lipoxygenase (5-LOX), and cyclooxygenase (COX) in SGIV infection were further investigated using the corresponding specific inhibitors. The inhibition of cPLA2 by AACOCF3 decreased SGIV replication, suggesting that cPLA2 might play important roles in the process of SGIV infection. Consistent with this result, the ectopic expression of EccPLA2α or knockdown significantly enhanced or suppressed viral replication in vitro, respectively. In addition, the inhibition of both 5-LOX and COX significantly suppressed SGIV replication, indicating that AA metabolism was essential for SGIV infection. Taken together, our results demonstrated for the first time that SGIV infection in vitro disturbed GPs homeostasis and cPLA2 exerted crucial roles in SGIV replication.

Hypoxia, Serum Starvation, and TNF-α Can Modify the Immunomodulation Potency of Human Adipose-Derived Stem Cells

INTRODUCTION

Adipose-derived stem cells (ADSCs) are mesenchymal stem cells (MSCs) that are found in adipose tissues, which are easily obtained from liposuction procedures using an enzyme mixture. The adhering cells are then selectively cultivated. ADSCs have great potential in regenerative medicine because they are plentiful, easily accessible, and less invasive. They also have an impressive proliferation ability and can be differentiated into mesenchymal lineages and trans-differentiating into many other cell types. In particular, they have extraordinary abilities in immunomodulation. This study aimed to investigate the effects of culture conditions (hypoxia, starvation, and TNF-α treatment) on the immunomodulation of human ADSCs.

METHODS

Human ADSCs were expanded in vitro in the standard condition before they were cultured in different stress conditions. ADSCs from passages fifth were confirmed as MSCs by some standard assays suggested by the International Society for Cell and Gene Therapy. These MSCs were used to culture in four different stress conditions: hypoxia, serum starvation, and TNF-α treatment in 48 h. After treatments, MSCs were used to evaluate their immunomodulation capacity using MSCs mixed lymphocyte reaction assay, and the concentrations of IDO, PGE2, IL-6, and IL-10 were secreted in the culture medium.

RESULTS

In different stress conditions, ADSCs exhibited different responses related to their immunomodulation. In serum starvation, ADSCs exerted a strong secretion of IDO and PGE2, whereas they showed strong IL-6 secretion in the TNF-α-supplemented medium. When exposed to lymphocytes, ADSCs caused an increase in the ratio of regulatory T cells (Tregs), and co-culture lymphocytes with ADSCs induced in hypoxic malnutrition conditions increased the IL-10 level the most. In addition, when exposed to dendritic cells (DCs), ADSCs inhibited the mature marker expressions of the DCs.

CONCLUSION

The current research showed that ADSCs change their immunomodulation properties to survive in in vitro culture environments. Treatment of ADSCs in the starvation medium for 48 h can increase the immunomodulation of ADSCs.

Using dendritic cell maturation and IL-12 producing capacity as markers of function: a cautionary tale

Effective dendritic cell (DC) function depends on sufficient expression of antigen and costimulatory molecules, and secretion of interleukin (IL)-12. We sought to augment DC stimulatory capacity by optimizing DC phenotype and IL-12 production. DCs, obtained by CD14-selection, were matured using 8 different cytokine cocktails, and expression of costimulatory/major histocompatibility complex molecules and IL-12 production at the end of maturation was assessed. DC stimulatory capacity was determined after pulsing with immunogenic adenoviral CD8 peptide epitopes or after transduction with an Ad5f35-null vector. Resultant T-cell cultures were analyzed using pentamer and interferon-gamma enzyme-linked immunosorbent spot assays. On the basis of DC expression of maturation markers and IL-12 production, we defined prototype "minimal" [tumor necrosis factor-alpha (TNF-alpha), prostaglandin E2], "standard" (IL-1, IL-6, TNF-alpha, prostaglandin E2), and "optimal" (IL-1, IL-6, TNF-alpha, interferon-alpha, CD40 ligand) DC cocktails. Optimal DCs were functionally superior when pulsed with CD8 peptides, but when transduced with Ad5f35, functioned poorly as antigen-presenting cells. We investigated the mechanisms underlying this discrepancy and suggest that prolonged stimulation with potent cytokines (optimal cocktail) in combination with adenoviral transduction alters the kinetics of DC maturation such that the DCs are functionally exhausted by the traditional 48-hour maturation time point. Shortening the DC maturation period posttransduction restored optimal DC stimulatory capacity. Thus, maturation stimuli and viral transduction affects DC phenotype, IL-12 producing capacity, and kinetics of maturation, and all must be considered before designing protocols to generate the optimal DC for cytotoxic T lymphocyte generation.

Clinical correlations of recent developments in the pathogenesis of atopic dermatitis

Atopic dermatitis is a chronic inflammatory skin disease with a steadily increasing prevalence affecting 10-20 of infants and 1-3 of adults globally. It is often the first clinical manifestation of atopic disease preceding asthma and allergic rhinitis. Probably half of the children with atopic dermatitis develop some other form of atopic disease later in life. The pathogenesis involves a complex interplay of factors including genetic predisposition due to altered immune or skin barrier function, interactions with the environment such as food and allergen exposures, and infectious triggers of inflammation. In this review, we summarize the recent advances in understanding the contribution of different factors in the pathophysiology of atopic dermatitis and how insights provide new therapeutic potential for its treatment.

Cyclooxygenase-1 inhibition delays recovery of the cutaneous barrier disruption caused by mechanical scratching in mice

BACKGROUND

Atopic dermatitis is a chronic inflammatory disease characterized by severe pruritus, and cutaneous barrier disruption by scratching contributes to further aggravation of the condition. We have previously shown that indomethacin delayed recovery from the effects of cutaneous barrier disruption caused by mechanical scratching in mice.

OBJECTIVES

This study was designed to assess the role of cyclooxygenase (COX)-1 and COX-2 inhibitors on recovery from the effects of cutaneous barrier disruption induced by mechanical scratching in mice.

METHODS

We examined the effects of SC-560 (a COX-1-selective inhibitor) or NS-398 (a COX-2-selective inhibitor) on recovery from the effects of cutaneous barrier disruption in mice induced by a wire brush, in terms of the skin prostaglandin (PG) levels.

RESULTS

While SC-560 significantly delayed recovery from the effects of cutaneous barrier disruption, NS-398 had no such effect. SC-560 was significantly more effective than NS-398 in reducing skin PG levels at 6 and 24 h after cutaneous barrier disruption. SC-560 strongly inhibited biosynthesis of cutaneous PGD(2) to a greater extent than that of other PGs.

CONCLUSIONS

COX-1-coupled PGD(2) biosynthesis may be an important factor in the recovery of cutaneous barrier disruption.

Role of scratch-induced cutaneous prostaglandin D2production on atopic-like scratching behaviour in mice

NC/Nga mice are known to develop scratching dermatitis akin to atopic dermatitis, under conventional (Conv), but not under the specific-pathogen-free (SPF) condition. In this study, we examined the effects of mechanical-scratching on the spontaneous scratching counts (sign of itching), in relation to the cutaneous prostaglandin D2 (PGD2) levels in NC/Nga or BALB/c mice. Mechanical-scratching increased the cutaneous barrier damage and PGD2 levels in both strain mice under the SPF condition. By 4 weeks of cohabitation with the skin-lesioned NC/Nga mice, both the increase in the spontaneous scratching and development of dermatitis score were higher in the Conv-NC/Nga than in the Conv-BALB/c mice. At this time-point, the cutaneous PGD2 level induced by mechanical-scratching was significantly lower in the Conv-NC/Nga when compared with that in the SPF-NC/Nga mice, and that in the Conv-BALB/c was almost equal to that in the SPF-BALB/c mice. With mechanical scratches, the cohabitation-induced scratching was suppressed in the Conv-BALB/c, but not in the Conv-NC/Nga mice. These results suggest that the scratch-induced cutaneous PGD2 inhibits scratching and the subsequent development of dermatitis in BALB/c, while the impaired scratch-induced cutaneous PGD2 production in the NC/Nga mice resulted in no suppression of scratching, and aggravated the dermatitis.

The anti-pruritic efficacy of TS-022, a prostanoid DP1 receptor agonist, is dependent on the endogenous prostaglandin D2 level in the skin of NC/Nga mice

TS-022 is a prostanoid DP(1) receptor agonist, originally developed as a novel anti-pruritic drug for atopic dermatitis. The drug has been shown to suppress scratching and improve the skin inflammation in the NC/Nga (NC) mouse, a model of atopic dermatitis. Corticosteroids are commonly used as effective agents for the treatment of atopic dermatitis. We examined the anti-pruritic efficacy of TS-022 in NC mice cohabited with skin-lesioned NC mice, which showed spontaneous scratching without skin lesions in the early phase and chronic itching with severe dermatitis in the late phase, in comparison with that of dexamethasone. We have previously reported that prostaglandin D(2) might have a physiological role in the inhibition of pruritus. While after 2 weeks of cohabitation with skin-lesioned NC mice (early phase of dermatitis, characterized by the appearance of spontaneous scratching), topically applied TS-022 exhibited a weak anti-pruritic effect in the NC mice, after 6 weeks of cohabitation (late phase, characterized by both chronic scratching and dermatitis), the drug exerted potent anti-pruritic activity. In contrast, dexamethasone exerted potent anti-pruritic effect in both the early and late phases. Indomethacin aggravated the scratching in the early phase, but had no effect in the late phase. The skin prostaglandin D(2) level was significantly increased in the early phase, to subsequently declined and return to the basal level in the late phase. The cutaneous ability for prostaglandin D(2) production following topical application of arachidonic acid or mechanical scratching was decreased in the late phase. Moreover, the expression level of the prostanoid DP(1) receptor in the skin was increased in the late phase. These findings suggest that the potent anti-pruritic activity of TS-022 in the late phase might be attributable to the decrease of endogenous prostaglandin D(2) production and increase of prostanoid DP(1) receptor expression.

Putative mechanism of the itch-scratch circle: repeated scratching decreases the cutaneous level of prostaglandin D2, a mediator that inhibits itching

In atopic dermatitis, scratching of the skin as a reaction to itching causes injury to the skin, which, in turn, further increases the itching resulting in the establishment of the so-called itch-scratch circle. We have shown that prostaglandin (PG) D2 plays an inhibitory role against pruritus in mice with atopic-like dermatitis; therefore, we examined the relationship between scratching and the cutaneous PGD2 level using an artificial scratching model with a wire brush. Mechanical scratching induced a temporary increase of the skin PGs levels (PGE2, PGD2, 6-ketoPGF1alpha, PGF2alpha). The skin PGD2 level and the ability of PGD2 production decreased at 48 h after repeated scratch, compared to that of normal skin, not so after single scratch. Immunohistochemical analysis and Western blotting revealed a decrease in the levels of cyclooxygenase-1 (COX-1) and hematopoietic PGD synthase in mechanically scratched skin. The reduced ability of the skin for PGD2 production following mechanical scratching could be caused by this decrease in the expression levels of COX-1 and PGD2 synthase. The results suggest that repeated scratching in mice decreases the ability of the skin to produce PGD2, which is an endogenous mediator that inhibits pruritus, resulting in the establishment of the itch-scratch circle.

Time course changes of scratching counts, dermatitis symptoms, and levels of cutaneous prostaglandins in NC/Nga mice

NC/Nga (NC) mice are known to develop dermatitis resembling atopic dermatitis (AD) in conventional (Conv) conditions, but not in specific pathogen-free (SPF) conditions. We reported that the ability of skin prostaglandin D(2) (PGD(2)) production, which might be the endogenous inhibitor of itching, was attenuated in skin-lesioned Conv-NC mice. We examined the age-related change in scratching, dermatitis symptoms, and skin PGs of SPF- and Conv-NC mice. In Conv-NC, PGD(2) increased at 7 weeks, at which scratching counts increased, but dermatitis did not develop. PGE(2), PGI(2) and PGF(2alpha) increased at 10 and 13 weeks, at which dermatitis developed. The ability to produce skin PGs was examined by measuring PGs after application of arachidonic acid or after mechanical scratching using a wire brush. In Conv-NC, PGD(2) production at 13 weeks was lower than at 7 weeks. In Conv-NC, hematopoietic PGD synthase (hPGDS) expression in the skin at 13 weeks was lower than at 7 weeks by Western blotting and immunohistochemical analysis. The increase of skin PGD(2) level in the early phase of the development of dermatitis is due to the stress of extensive scratching, but did not increase in spite of the stress of extensive scratching in the late phase, due to decreasing capacity of PGD(2) production attributable to decreasing hPGDS expression in Conv-NC mice. These results suggest that a decreased ability to produce skin PGD(2) production could enhance scratching and aggravate dermatitis in Conv-NC mice.

COX-1 inhibition enhances scratching behaviour in NC/Nga mice with atopic dermatitis

NC/Nga (NC) mice, spontaneously develop an eczematous atopic dermatitis (AD)-like skin lesion when kept under conventional condition (Conv), but not under specific pathogen-free (SPF) conditions, have been thought to be an animal model of AD. We have previously shown that PGD(2) and arachidonic acid inhibited the scratching behaviour of NC mice, while indomethacin enhanced it. This study was designed to assess the role of cyclooxygenase (COX)-1 and COX-2 in the itch-related scratching behaviour of NC mice. We examined the expression of COX in the skin using real-time PCR and Western blotting and the effects of SC-560 (a COX-1 selective inhibitor) or NS-398 (a COX-2 selective inhibitor) on scratching behaviour in relation to skin prostaglandin (PG) levels in NC mice. COX-1 mRNA expression was unchanged and protein expression decreased in Conv NC mice compared with that of SPF mice. By contrast, COX-2 mRNA and protein expression increased in Conv NC mice. SC-560 increased scratching behaviour and significantly reduced skin PGD(2), PGE(2) and PGF(2alpha) levels, but NS-398 did not have effects on scratching and skin PG level. Moreover, the topical application of PGD(2), which might be the endogenous inhibitor of itching, suppressed the SC-560-induced enhancement of scratching behaviour by NC mice. These results suggest COX-1-coupled skin PGD(2) biosynthesis plays a physiological role in inhibiting regulation of pruritus in NC mice with AD.

Role of COX-1 and COX-2 on skin PGs biosynthesis by mechanical scratching in mice

We examined the involvement of cyclooxygenase (COX)-1 and COX-2 on mechanical scratching-induced prostaglandins (PGs) production in the skin of mice. The dorsal regions of mice were scratched using a stainless brush. COXs expressions in the skin were analyzed using real-time PCR and Western blotting. The effect of acetylsalicylic acid (ASA) on the ability of PGs production were determined based on skin PGs level induced by arachidonic acid (AA) application. Mechanical scratching increased PGD2, PGE2, PGI2 and PGF(2 alpha). COX-1 was constitutively expressed and COX-2 expression was enhanced by scratching. Intravenous administration of ASA inhibited PGs biosynthesis in the normal skin. PGs levels of the skin 6h after ASA administration (ASA 6 h) were almost equal to those of the skin 10 min after ASA administration (ASA 10 min). In the scratched skin, AA-induced PGE2 and PGI2 of ASA 6 h were significantly higher than those of ASA 10 min. The skin PGD2 and PGF(2 alpha) of ASA 10 min were almost same to those of ASA 6 h. In the normal skin of COX-1-deficient mice, skin PGD2 level was lower than that of wild-type mice, although PGE2, PGI2 and PGF(2 alpha) levels were almost equal to those of wild type. In the scratched skin of COX-1-deficient mice, PGD2, PGE2, PGI2 and PGF(2 alpha) levels were lower than those of wild-type mice. These results suggested that cutaneous PGD2 could be mainly produced by COX-1, and PGE2 and PGI2 could be produced by COX-1 and COX-2, respectively, in mice.

Increased scratching counts depend on a decrease in ability of cutaneous prostaglandin D2 biosynthesis in NC/Nga mice with atopic dermatitis

Spontaneous and 2,4,6-trinitrochlorobenzene (TNCB)-induced dermatitis models using NC/Nga mice have been recognized as animal models of atopic dermatitis. We reported that scratching behavior leads to dermatitis in a spontaneous dermatitis but not in a TNCB-induced dermatitis. Prostaglandin D2 (PGD2) suppressed the scratching behavior of NC/Nga mice, suggesting that PGD2 plays a physiological role on inhibiting pruritus. We studied whether there was a difference in skin PG contents between spontaneous and TNCB-induced dermatitis. Spontaneous dermatitis was induced by cohabitation with NC/Nga mice having severe skin lesions. TNCB-induced dermatitis was caused by applications of TNCB. PGD2, PGE2, 6keto-PGF1alpha, and PGF2alpha contents in the skin were examined using enzyme-immunoassay kits. For studying ability to produce skin PGs, PG contents were evaluated after topical treatment of arachidonic acid (AA) or mechanical scratching. In spontaneous dermatitis, PGE2, 6keto-PGF1alpha, and PGF2alpha contents increased with dermatitis, but only PGD2 did not do so. In TNCB-induced dermatitis, PGD2, PGE2, 6keto-PGF1alpha, and PGF2alpha increased. Determination of skin PG contents after AA treatment or mechanical scratching revealed that skin PGD2 production of conventional group of spontaneous dermatitis was lower than the specific pathogen-free group. It seemed that ability of skin PGD2 production was attenuated in spontaneous dermatitis. These results suggest that enhancement of scratching behavior in spontaneous dermatitis was caused by the defect of ability to produce PGD2, which plays a physiological role in inhibiting pruritus, resulting in development of dermatitis.

Prostaglandin D2 and prostaglandin E2 accelerate the recovery of cutaneous barrier disruption induced by mechanical scratching in mice

The role of prostaglandins in mechanical scratching-induced cutaneous barrier disruption in mice was investigated. Skin prostaglandins contents were measured after cutaneous barrier function was disrupted by scratching using a stainless-steal wire brush (mechanical scratching), then effects of prostanoids on recovery of cutaneous barrier functions were examined. This mechanical scratching increased transepidermal water loss and skin prostaglandins (prostaglandin D2, prostaglandin E2, 6-keto-prostaglandin F1alpha and prostaglandin F2alpha) contents, count-dependently. Topical application of indomethacin immediately after cutaneous barrier disruption delayed the recovery period of cutaneous barrier disruption. We examined effects of several prostanoids (prostaglandin D2, prostaglandin E2, prostaglandin F2alpha, prostaglandin I2 and U46619) on delay of the recovery process of mechanical scratching-induced cutaneous barrier disruption with treatment of indomethacin. Topically applied prostaglandin D2 and prostaglandin E2 accelerated the recovery of cutaneous barrier disruption and topical application of prostaglandin J2, limaprost, sulprostone and ONO-4819, but not 13,14-dihydro-15-keto-prostaglandin D2, 15-deoxy-Delta(12,14)-prostaglandin J2, 17-phenyl-trinor-prostaglandin E2 or butaprost had effects on recovery of the cutaneous barrier. These results suggest that prostaglandin D2 and prostaglandin E2 accelerate the recovery process of cutaneous barrier disruption caused by mechanical scratching, via specific prostanoid DP1, EP3 and EP4 receptors.

Elevated cyclooxygenase-2 expression in patients with early gastric cancer in the gastric pylorus

BACKGROUND

Duodenogastric reflux after surgery increases the risk of gastric carcinoma. To determine whether bile reflux influences the development of gastric cancer in patients who have not had surgery, we compared cyclooxygenase-2 (COX-2) immunoreactivity in early gastric cancer originating from the gastric pylorus and that originating from other locations. We also examined the effects of bile acids on the expression and activity of COX-2 in gastric cells in vitro.

METHODS

Tumor sections from 79 patients who underwent endoscopic mucosal resection for early intestinal-type gastric carcinoma were stained using a COX-2-specific monoclonal antibody. Immunoblotting of COX-2 was used to assess the effects of bile acids on COX-2 expression and activity in human gastric cell lines.

RESULTS

Among the 79 early gastric cancer lesions studied, 13 (16%) arose in the gastric pylorus. In this group, COX-2 immunoreactivity was negative to weak in 38% (5 of 13 lesions) and moderate to strong in 62% (8 of 13 lesions). In the control group, COX-2 immunoreactivity was negative to weak in 70% (46 of 66 lesions) and moderate to strong in 30% (20 of 66 lesions). COX-2 expression was significantly elevated in early gastric cancer located in the gastric pylorus, compared with that in the other locations. In human gastric cell lines, bile acids induced COX-2 expression, mediated by the ERK 1/2 mitogen-activated protein kinase pathway.

CONCLUSIONS

COX-2 expression is elevated in early gastric cancer of the gastric pylorus, a common site of gastric cancer. Bile acids induced COX-2 expression in human gastric cell lines, suggesting a role of bile reflux in gastric carcinogenesis.

A two-step induction of indoleamine 2,3 dioxygenase (IDO) activity during dendritic-cell maturation

Prostaglandins, a family of lipidic molecules released during inflammation, display immunomodulatory properties in several models. One use includes exposure of monocyte-derived dendritic cells (DCs) to a cocktail of cytokines that contains prostaglandin E2 (PGE2) for purposes of maturation; such cells are currently being used for cancer immunotherapy trials. Our analysis of the transcription profile of DCs matured in the presence of tumor necrosis factor alpha (TNFalpha) and PGE2 revealed a strong up-regulation of indoleamine 2-3 dioxygenase (IDO), an enzyme involved in tryptophan catabolism and implicated in both maternal and T-cell tolerance. Using quantitative assays to monitor levels of IDO mRNA, protein expression, and enzyme activity, we report that PGE2 induces mRNA expression of IDO; however, a second signal through TNF receptor (TNF-R) or a Toll-like receptor (TLR) is necessary to activate the enzyme. Interestingly, use of TNFalpha, lipopolysaccharide, or Staphylococcus aureus Cowan I strain (SAC) alone does not induce IDO. The effect of PGE2 is mediated by activation of adenylate cyclase via the Gs-protein-coupled receptor E prostanoid-2 (EP2). A better understanding of these regulatory mechanisms and the crosstalk between TNF-R/TLR and EP2 signaling pathways will provide insight into the regulation of T-cell activation by DCs and may help to improve existing immunotherapy protocols.

Isosteric ramatroban analogs: selective and potent CRTH-2 antagonists

The chemoattractant receptor-homologous molecule expressed on T(H)2 cells (CRTH-2), also found on eosinophils and basophils, is a prostaglandin D2 receptor involved in the recruitment of these cell types during an inflammatory response. In this report, we describe the synthesis and optimization of a ramatroban isostere that is a selective and potent antagonist of CRTH-2 which may be useful in the treatment of certain diseases.

Cyclooxygenase-2-issued prostaglandin e(2) enhances the production of endogenous IL-10, which down-regulates dendritic cell functions

PGE(2) is a well-known immunomodulator produced in the immune response by APCs, such as dendritic cells (DCs), the most potent APC of the immune system. We investigated the PGE(2) biosynthetic capacity of bone marrow-derived DC (BM-DC) and the effects of PG on the APC. We observed that BM-DC produce PGE(2) and other proinflammatory mediators, such as leukotriene B(4) and NO, after LPS exposure. Constitutively present in BM-DC, cyclooxygenase (COX)-1 did not contribute significantly to the total pool of PGE(2) compared with the LPS-induced COX-2-produced PGE(2). Treatment of BM-DC with exogenous PGE(2) induced the production of large amounts of IL-10 and less IL-12p70. In addition, selective inhibition of COX-2, but not COX-1, was followed by significant decrements in PGE(2) and IL-10, a concomitant restoration of IL-12 production, and an enhancement of DC stimulatory potential. In contrast, we found no demonstrable role for leukotriene B(4) or NO. In view of the potential of PGE(2) to stimulate IL-10, we examined the possibility that the suppressive effect of PGE(2) is mediated via IL-10. We found that exogenous IL-10 inhibits IL-12p70 production in the presence of NS-398, a COX-2 selective inhibitor, while the inhibitory effects of PGE(2) were totally reversed by anti-IL-10. We conclude that COX-2-mediated PGE(2) up-regulates IL-10, which down-regulates IL-12 production and the APC function of BM-DC.

Cutting edge: agonistic effect of indomethacin on a prostaglandin D2 receptor, CRTH2

Indomethacin is a widely used nonsteroidal anti-inflammatory drug and is generally known to exhibit its multiple biological functions by inhibiting cyclooxygenases or activating peroxisome proliferator-activated receptors. In this study, we present evidence demonstrating that the novel PGD(2) receptor chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2) is another functional target for indomethacin. Indomethacin induced Ca(2+) mobilization in CRTH2-transfected K562 cells at submicromolar concentrations (approximate EC(50), 50 nM) in a G(alphai)-dependent manner as PGD(2) did. Other nonsteroidal anti-inflammatory drugs (aspirin, sulindac, diclofenac, and acemetacin) had no such effect even at micromolar concentrations. In chemotaxis assay, three CRTH2-expressing cell types, Th2 cells, eosinophils, and basophils, were all significantly attracted by indomethacin (EC(50), 50-500 nM) as well as by PGD(2) (EC(50), 2-20 nM), and the effects of indomethacin were blocked by anti-CRTH2 mAb. These results suggest the involvement of CRTH2 in mediating some of therapeutic and/or unwanted side effects of indomethacin, independently of cyclooxygenases and peroxisome proliferator-activated receptors.

Effects of exercise and training on natural killer cell counts and cytolytic activity: a meta-analysis

Meta-analysis techniques have been used to accumulate data from 94 studies describing the natural killer (NK) cell response of some 900 volunteers to acute and chronic exercise. NK cell numbers have been indicated in terms of CD3-CD16+CD56+, CD16+ or CD56+ phenotypes, and cytolytic activity has been expressed per 10,000 peripheral blood mononuclear cells or in terms of lytic units. Acute exercise has been categorised as sustained moderate (50 to 65% of aerobic power), sustained vigorous (>75% of aerobic power), brief maximal or 'supramaximal', prolonged, eccentric or resistance, and repeated exercise. In general, there was a marked increase in NK cell count at the end of exercise, probably attributable to a catecholamine-mediated demargination of cells. Following exercise, cell counts dropped to less than half of normal levels for a couple of hours but, except in unusual circumstances (e.g. prolonged, intense and stressful exercise), normal resting values are restored within 24 hours. If activity is both prolonged and vigorous, the decrease in NK cell counts and cytolytic activity may begin during the exercise session. Although the usual depression of NK cell count seems too brief to have major practical importance for health, there could be a cumulative adverse effect on immunosurveillance and health experience in athletes who induce such changes several times per week. There is a weak suggestion of an offsetting increase in resting NK cell counts and cytolytic action in trained individuals, and this merits further exploration in studies where effects of recent training sessions are carefully controlled.

Differential effects of cyclo-oxygenase pathway metabolites on cytokine production by T lymphocytes

Cyclo-oxygenase pathway metabolites released in the microenvironment by activated platelets and endothelial cells are potential local modulators of the immune response. In the present study, we have investigated the modulatory role of PGE2, iloprost (prostacyclin analogue), U-46619 (thromboxane analogue) on the release of IL-2, IFN-gamma, TNF-alpha and IL-6 by T lymphocytes. Our results show that PGE2 and prostacyclin differ in the regulation of cytokine production. PGE2 inhibited the release of IL-2 and IFN-gamma, while iloprost did not affect their production. The addition of PGE2 or iloprost greatly decreased the amount of TNF-alpha measured in the supernatants, although the rates of inhibition differed according to the kind of stimulation. Unlike that of PGE2, inhibition by iloprost was stronger in alloactivated cultures than in PHA-stimulated ones. In vitro IL-6 production was stimulated by PGE2 in alloactivated cultures and by iloprost, whatever the stimulus. These results are probably due to other cellular subsets contaminating the T-lymphocyte preparations. After complete removal of monocytes from cell cultures, there were inhibitory effects of lloprost and PGE2 on IL-6 released in the supernatants. We did not observe any significant effect of thromboxane analogue on the production of either cytokine.

Endothelins-induce cyclicAMP formation in the guinea-pig trachea through an ETA receptor- and cyclooxygenase-dependent mechanism

1. The non-selective endothelin agonist, endothelin-1 (ET-1), and the selective ETB receptor agonist, sarafotoxin-S6c (SRTX-c), contracted guinea-pig isolated trachea in a concentration-dependent manner. The EC50 value for ET-1 (11 +/- 2.1 nM) was significantly higher than that of SRTX-c (3.2 +/- 0.21 nM) and the maximal developed tension due to SRTX-c was 42.8 +/- 2.3% higher than that produced by ET-1 (P < 0.05). 2. Pretreatment with the ETA antagonist, BQ-610, appreciably enhanced the developed tension due to ET-1 but not SRTX-c. Likewise, the cyclo-oxygenase inhibitor, indomethacin, markedly potentiated the contractile responses to ET-1, but not to SRTX-c. Combining BQ-610 with indomethacin was not more effective than either of them in augmenting ET-1-evoked tension. 3. ET-1 significantly increased cyclic AMP formation in the trachea in concentration- and time-dependent manners. A t1/2 value of 4.3 min, an EC50 value of 20 +/- 3 nM and a maximal cyclic AMP increment of 124% above the basal level, were obtained for ET-1. Similarly but less effectively, ET-3 (0.1 microM) increased cyclic AMP level (35 +/- 3.7% compared to 94 +/- 7.8% for the same concentration of ET-1). By contrast, SRTX-c did not alter the cyclicAMP level when applied in concentrations up to 1 microM. 4. Pre-incubation of the trachea with BQ-610 (1 microM) or indomethacin (1 microM) prevented cyclicAMP formation by either ET-1 or ET-3. 5. The results of the present study indicate a negative regulatory role mediated by the ETA receptor on the ETB-triggered mechanical response. This effect is likely to be mediated by activation of adenylate cyclase through a cyclo-oxygenase-dependent mechanism.

Prostaglandin E2 regulates inducible nitric oxide synthase in the murine macrophage cell line J774

We have evaluated the role of prostaglandin E2 (PGE2) in the synthesis of nitric oxide (NO) by the activation of the inducible form of nitric oxide synthase (NOS) in the murine macrophage cell line, J774, stimulated with different doses of lipopolysaccharide (LPS). The stimulation of the J774 line with suboptimal doses of LPS (0.1 microgram/mL) caused a production of endogenous PGE2 that was capable of stimulating NOS activity inducing an increase in the NO synthesis, as attested by the fact that cyclooxygenase enzyme inhibitor, indomethacin, significantly reduced NO secretion. On the contrary, a higher dose of LPS (1 microgram/mL) produced high levels of PGE2 that reduced the levels of NOS and, subsequently, NO production. Experiments carried out with exogenous PGE2 indicated that concentrations between 1 and 10 ng/mL are able to stimulate the expression of NOS and the release of NO, while higher concentrations (> 50 ng/mL) are inhibitory. Furthermore, our data indicate that there is a network of interaction which involves NO, PGE2, and tumor necrosis factor. High levels of PGE2 inhibited TNF alpha secretion, which in turn could exert inhibitory effects on NO synthesis.

Roles of tumor necrosis factor alpha, granulocyte-macrophage colony-stimulating factor, platelet-activating factor, and arachidonic acid metabolites in interleukin-1-induced resistance to infection in neutropenic mice

Treatment with a single low dose (80 to 800 ng) of interleukin-1 (IL-1) 24 h before a lethal bacterial challenge in granulocytopenic and in normal mice enhances nonspecific resistance. The mechanism behind this protection has only partially been elucidated. Since IL-1 induces production of tumor necrosis factor alpha (TNF-alpha), granulocyte-macrophage colony-stimulating factor (GM-CSF), platelet-activating factor (PAF), and arachidonic acid metabolites, we investigated the potential role of these substances in IL-1-induced protection. Low doses of murine TNF-alpha but not of human TNF-alpha enhanced survival, suggesting an effect via the type II TNF receptor rather than the type I TNF receptor, which has little species specificity. In line with this TNF-alpha-induced protection from infection, pretreatment with a low dose of a rat anti-murine TNF-alpha monoclonal antibody tended to inhibit IL-1-induced protection, suggesting a role of TNF-alpha as a mediator of IL-1-induced enhanced resistance to infection. Pretreatment with higher doses of anti-TNF-alpha, however, showed a dose-related protective effect per se, which could be further enhanced by a suboptimal dose of IL-1. A combination of optimal doses of anti-TNF-alpha and IL-1 produced an increase in survival similar to that produced by separate pretreatments. This lack of further enhancement of survival by combined optimal pretreatments suggests a similar mechanism of protection, most likely attenuation of deleterious effects of overproduced proinflammatory cytokines like TNF-alpha during lethal infection. Pretreatment with different doses of GM-CSF before a lethal Pseudomonas aeruginosa challenge in neutropenic mice did not enhance survival. Different doses of WEB 2170, a selective PAF receptor antagonist, of MK-886, a selective inhibitor of leukotriene biosynthesis, or of several cyclooxygenase inhibitors did not reduce the protective effect of IL-1 pretreatment. We conclude that IL-1-induced nonspecific resistance is partially mediated by induction of TNF-alpha and not by GM-CSF, PAF, and arachidonic acid metabolites. The mechanism of action of IL-1 seems to be similar to that of anti-TNF-alpha.

Characterization of ETB receptors mediating contractions induced by endothelin-1 or IRL 1620 in guinea-pig isolated airways: effects of BQ-123, FR139317 or PD 145065

1. We have characterized the receptors mediating contractions to endothelin-1 (ET-1) or IRL 1620, an ETB receptor selective agonist, in isolated strips of tissue prepared from different parts of the guinea-pig airways. We used as antagonists BQ-123 and FR139317 (ETA receptor-selective) and PD 145065 (ETA/ETB receptor non-selective). 2. ET-1 and IRL 1620 (10(-10) M to 10(-6) M) caused similar concentration-dependent contractions of strips of guinea-pig trachea and upper bronchus. In the guinea-pig trachea without epithelium or lung parenchyma, IRL 1620 was less potent than ET-1. 3. In the trachea, contraction to ET-1 (< 10(-8) M) was preceded by a transient relaxation which was inhibited by BQ-123 (10(-5) M) or FR 139317 (10(-5) M) or by the removal of the epithelium. The concentration-response curve to ET-1 in the trachea was shifted to the right by PD 145065 (10(-5) M to 10(-4) M). PD 145065 (10(-4) M) also inhibited the response to ET-1 (3 x 10(-7) M) by 55%. Contractions induced by IRL 1620 were not affected by BQ-123 (10(-6) M) or FR139317 (10(-6) M) but were significantly attenuated by 10(-5) M of either antagonist. PD 145065 at 10(-6) M strongly attenuated and at 10(-5) M abolished contractions induced by IRL 1620. 4. In the trachea, removal of the epithelium potentiated the effects of both agonists. BQ-123 (10-5 M)had no effect on contractions of the trachea without epithelium induced by ET-1, but FR139317 (10-5 M)caused a significant inhibition. PD 145065 (10-5 M to 10-4 M) caused a shift to the right of the ET-1 concentration-response curve without affecting the contractile effect at 3 x 10-7 M. All three antagonists inhibited contractions induced by IRL 1620.5. In the upper bronchus, BQ-123 (10-5 M) did not affect contractions induced by ET-1, whileFR139317 (10-5 M) attenuated (20-26%) only contractions induced by 1-3 x 10-7 M ET-1. PD 145065(10-5 M to 10-4 M) caused a shift to the right of the ET-1 concentration-response curve. The contractions induced by IRL 1620 were inhibited by BQ-123 or FR139317 (10-5M to 10-4 M). PD 145065(10-6 M) strongly inhibited contractions induced by IRL 1620 and PD 145065 (10-5 M) totally abolished them.6. The contractile action of ET-1 in the lung parenchyma was significantly and similarly attenuated by BQ-123 (10-5 M) or indomethacin (10-5 M), while FRI39317 (10-5 M) was less effective. PD 145065(10-6 to 10-5 M) inhibited contractions to ET-1. IRL 1620, which is less potent than ET-1 in this preparation, was antagonized by PD 145065 (10-5 to 10-6 M) but unaffected by BQ-123 (10-6 M to10-5M) or FR139317 (10-6 M).7. Thus, ETB receptors mediate contractions to ET-1 in all four guinea-pig airway preparations. In addition, contractions to ET-1 in the trachea and lung parenchyma are mediated in part by ETA receptors. In the latter tissue, these ETA receptors mediate contraction through the release of cyclooxygenase metabolites. Similarly, ETA receptors located on the epithelial cells also mediate the release of prostanoids in the trachea with epithelium but they are responsible for transient relaxations. Interestingly,contractions induced by IRL 1620 were more susceptible to inhibition by the different antagonists,most probably because it binds to the endothelin receptors in a reversible manner. High concentrations(10-5 M) of ETA-selective antagonists also inhibit responses to IRL 1620, most probably by an effect at ETB receptors in both the trachea and the upper bronchus.

Production of prostaglandins D2 and E2 by mouse fibroblasts and astrocytes in culture caused by Trypanosoma brucei brucei products and endotoxin

A study was made to characterize the effects of living Trypanosoma brucei brucei and its products on prostaglandin D2 (PGD2) and PGE2 production by fibroblasts and astrocytes. Cultured fibroblasts were prepared from Microtus agrestis embryos and astrocyte cultures were prepared from neonatal rats. The cultures were maintained in low-endotoxin or defined media (i.e. endotoxin-free). The PG production was compared with and studied in combination with a defined lipopolysaccharide (LPS) from Escherichia coli. Living T. b. brucei were without effect on PG production. Preparations of T. b. brucei prepared by freeze-thawing and sonication produced dose- and time-dependent increases in PGD2 and PGE2 synthesis by both cell types. LPS caused a similar pattern of increases. The combination of parasite products with LPS caused synergistic production to levels higher than the maximal production by each mitogen alone. The findings have important implications for several pathological features that accompany trypanosomiasis.

Interferon (IFN)-alpha, IFN-gamma, interleukin (IL)-2, and arachidonic acid metabolites modulate IL-4-induced IgE synthesis similarly in healthy persons and in atopic dermatitis patients

The role of cytokines and arachidonic acid metabolites in the regulation of IgE production in healthy persons and in atopic dermatitis patients with elevated IgE levels was studied. Interleukin-4 (IL-4) induced IgE production in peripheral blood mononuclear cells (PBMCs) of all donors, and no significant difference was found between the amounts of IgE produced by healthy persons and atopic dermatitis patients. Similarly, recombinant interferon (IFN)-alpha and IFN-gamma, as well as IL-2, inhibited IL-4-induced IgE production to a similar extent in both study groups. To evaluate the role of arachidonic acid (AA) metabolites in the regulation of IgE production, we added indomethacin, an inhibitor of the cyclooxygenase pathway, or nordihydroguaiaretic acid (NDGA), an inhibitor of the lipoxygenase pathway, to IL-4-treated cultures. Both indomethacin and NDGA strongly inhibited IL-4-induced IgE production. They also inhibited IL-4-induced IgG4 synthesis. No significant difference in the amount of inhibition was found between the two study groups. We were unable to restore the NDGA-induced inhibition of IgE-production by adding leukotrienes B4, C4, D4, or 5-HETE to the NDGA-treated cultures. PGE2 also failed to restore the indomethacin-mediated inhibitory effect. Consequently, NDGA- and indomethacin-mediated inhibitory effects do not appear to be mediated by any single factor studied. Collectively, our results show IFNs and IL-2 to be similar in effect in the modulation of IL-4-induced IgE synthesis in healthy and atopic persons.(ABSTRACT TRUNCATED AT 250 WORDS)

Phosphatidic acid stimulates the rolipram-sensitive cyclic nucleotide phosphodiesterase from rat thymocytes

The role of phospholipid metabolites in the modulation of cyclic AMP degradation during the early response of rat thymic lymphocytes to mitogenic stimulation was investigated by measuring their in vitro effect on the activity of five different cyclic nucleotide phosphodiesterase forms separated from thymocyte cytosol by means of an HPLC technique. Arachidonic acid was found to markedly inhibit four of the enzyme forms, with IC50 ranging from 14 to 60 microM, while its hydroperoxy and hydroxy derivatives proved inefficient. Dioctanoylglycerol, a biologically active diacylglycerol, was weakly inhibitory while phosphatidic acid, the diacylglycerol phosphorylated derivative, markedly stimulated the two cyclic-AMP-specific type-IV forms identified in thymocyte cytosol, by 50 and 70%. In intact cells labelled with tritiated arachidonate, the mitogenic lectin concanavalin A induced a rapid 4-5-fold increase in radiolabelled phosphatidic acid which peaked at 1 min, and remained elevated for at least 30 min. These observations suggest that phosphatidic acid formed during the mitogenic stimulation of T-cells might be responsible for an early activation of cyclic AMP degradation with, as a consequence, a lowering of cyclic AMP level, which is reported to be necessary for the occurrence of the first steps of mitogenesis.

Production of eicosanoids in response to endothelin-1 and identification of specific endothelin-1 binding sites in airway epithelial cells

The effect of endothelin-1 (ET-1) on arachidonate metabolism in the respiratory epithelium was investigated in primary cultures of feline tracheal epithelial cells. Subconfluent epithelial cell cultures were stimulated by ET-1, and eicosanoid generation was determined by high performance liquid chromatography (HLPC) of 3H-labeled arachidonic acid (AA) metabolites and by radioimmunoassay (RIA) of corresponding nonradiolabeled HPLC elution. The HPLC chromatograms of [3H]AA-prelabeled samples revealed that ET-1 (10(-5) M) augmented the release of prostaglandin (PG) E2, 12-hydroxyeicosatetraenoic acid (HETE), PGF2 alpha, and AA. RIA of corresponding nonradiolabeled HPLC elution demonstrated a significantly increased release of PGE2, PGF2 alpha, and 12-HETE as well as 5-HETE in response to ET-1 stimulation. 5-HETE release from ET-1-stimulated cells was further identified by gas chromatography/mass spectrometry (GC/MS). The stimulating effect of ET-1 on AA metabolism was dose dependent (10(-5) to 10(-7) M) and peaked within 1 h with a progressive decline over the subsequent hours. Using 125I-labeled ET-1 as radioligand, the presence of specific binding sites for ET-1 was demonstrated in cultured feline tracheal epithelial cells. ET-1 binding reached equilibrium within 1 h at 37 degrees C. Scatchard analysis suggested the existence of two saturable binding sites, with the estimated equilibrium dissociation constant (Kd) of 35.3 pM and maximal binding capacity (Bmax) of 15.0 fmol/10(7) cells for the higher affinity binding site and Kd of 205.9 pM and Bmax of 35.0 fmol/10(7) cells for the lower affinity binding site.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhanced metabolism of arachidonic acid by macrophages from nonobese diabetic (NOD) mice

The inbred nonobese diabetic (NOD) mouse spontaneously develops an autoimmune diabetes, which is now recognized as an experimental model for human type I insulin-dependent diabetes mellitus (IDDM). The autoimmune reaction, specifically directed against pancreatic beta cells (insulitis), involves both macrophages and T lymphocytes. The study of the production of cyclooxygenase and lipoxygenase derivatives of arachidonic acid metabolism shows that in some conditions, and in particular in the presence of zymosan A, macrophages from NOD mice produced significantly more 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) and leukotriene C4 (LTC4) than macrophages from age- and sex-matched C57BL/6 mice. Moreover, zymosan A-stimulated macrophages from NOD females produced significantly more LTC4 than did macrophages from NOD males. These results may be of interest, given the bidirectional relationship between the various cytokines involved in the destruction of beta cells of the islets of Langerhans and different eicosanoids.

Effect of indomethacin on the modulation of Mycobacterium avium growth in human macrophages by interferon gamma, retinoic acid and 1,25(OH)2-vitamin D3

A virulent strain of Mycobacterium avium was grown actively inside human adherent peripheral blood monocyte-derived macrophages with enhanced synthesis of prostaglandin E2 (PGE2). We therefore decided to investigate if the inability of human macrophages to control M. avium infection could be reversed using various immunomodulators, i.e. retinoic acid (RA), 1,25 dihydroxyvitamin D3 (D3) and interferon gamma (IFN gamma) alone or in combination, and whether this reversal was further potentiated by the addition of indomethacin (IND), a potent inhibitor of PGE2 biosynthesis. Among the various immunomodulators employed, only RA alone or in association with D3 or both D3 and IFN gamma were able to induce a clear mycobacteriostatic effect, which was further potentiated by IND. Our data suggest that immunosuppressive pathways induced in macrophages infected by M. avium result partly from an increased synthesis of PGE2 occurring soon after infection.

Endothelin-1 stimulates eicosanoid production in cultured human nasal mucosa

Endothelin (ET) has been shown to contract both vascular and nonvascular smooth muscle and to stimulate human nasal glandular secretion of serous and mucous cell products. Some effects of ET are thought to be mediated by eicosanoid production. To explore the direct effect of ET on arachidonate metabolism in cultured human nasal mucosal explants, eicosanoids were measured after ET-1 stimulation. After labeling the explants with [3H]arachidonic acid (AA), supernatant from control and ET-1-treated explants were fractionated by reverse-phase high-performance liquid chromatography (HPLC). The resulting elution pattern suggested the release of prostaglandin (PG) E2 and AA in response to ET-1 stimulation. Radioimmunoassay after HPLC resolution confirmed that ET-1 induced a significantly increased release of PGE2 as well as PGD2, PGF2 alpha, thromboxane B2, and 15-hydroxyeicosatetraenoic acid (15-HETE). Although significant amounts of 15-HETE were generated, cyclooxygenase product generation was most remarkable. Eicosanoid release after ET-1 exposure (10 to 0.1 microM) is concentration dependent and occurs within 1 h. Whereas 15-HETE release was maximal at 4 h, prostanoid production was maximal 1 h after exposure to ET-1. Other assayed AA metabolites, including the peptidoleukotrienes, did not significantly change after ET-1 stimulation. We conclude that ET-1 induces the release of predominantly cyclooxygenase products from cultured human nasal mucosal explants.