Prostaglandin E(2) inhibits IL-18-induced ICAM-1 and B7.2 expression through EP2/EP4 receptors in human peripheral blood mononuclear cells

Anti-Inflammatory Activity of a Cyclic Tetrapeptide in Mouse and Human Experimental Models

A cyclic tetrapeptide Pro-Pro-Pheβ³ho-Phe (4B8M) was tested for immunosuppressive activity and potential therapeutic utility in several in vitro and in vivo mouse and human models. The tetrapeptide was less toxic for mouse splenocytes in comparison to cyclosporine A (CsA) and a parent cyclolinopeptide (CLA). The tetrapeptide demonstrated potent anti-inflammatory properties in antigen-specific skin inflammatory reactions to oxazolone and toluene diisocyanate as well to nonspecific irritants such as salicylic acid. It also inhibited inflammatory processes in an air pouch induced by carrageenan. In addition, 4B8M proved effective in amelioration of animal models corresponding to human diseases, such as nonspecific colon inflammation induced by dextran sulfate and allergic pleurisy induced by ovalbumin (OVA) in sensitized mice. The tetrapeptide lowered expression of EP1 and EP3 but not EP2 and EP4 prostaglandin E2 (PGE2) receptors on lipopolysaccharide-stimulated Jurkat T cells and ICAM-1 expression on human peripheral blood mononuclear cells (PBMC). Its anti-inflammatory property in the carrageenan reaction was blocked by EP3 and EP4 antagonists. In addition, 4B8M induced an intracellular level of PGE2 in a human KERTr keratinocyte cell line. In conclusion, 4B8M is a low toxic and effective inhibitor of inflammatory disorders with potential therapeutic use, affecting the metabolism of prostanoid family molecules.

Differential Expression of Prostaglandin E2 Receptors in Porcine Kidney Transplants

BACKGROUND

Acute rejection of a kidney allograft results from adaptive immune responses and marked inflammation. The eicosanoid prostaglandin E2 (PGE2) modulates the inflammatory response, is generated by cyclooxygenase 2 (COX-2), and binds to 1 of the 4 G protein-coupled E prostanoid cell surface receptors (EP1-4). Receptor activation results in in proinflammatory (EP1 and EP3) or anti-inflammatory (EP2 and EP4) responses. We theorized that expression of the components of the COX-PGE2-EP signaling pathway correlates with acute rejection in a porcine model of allogeneic renal transplantation.

METHOD

COX-2 enzyme and EP receptor protein expression were quantitated with western blotting and immunohistochemistry from allotransplants (n = 18) and autotransplants (n = 5). Linear regression analysis was used to correlate EP receptor expression with the Banff category of rejection.

RESULTS

Pigs with advanced rejection demonstrated significant increases in serum PGE2 metabolites, while pigs with less rejection demonstrated higher tissue concentrations of PGE2 metabolites. A significant negative correlation between COX-2 expression and Banff category of rejection (R = -0.877) was shown. Rejection decreased expression of EP2 and EP4. For both receptors, there was a significant negative correlation with the extent of rejection (R = -0.760 and R = -0.891 for EP2 and EP4, respectively). Rejection had no effect on the proinflammatory receptors EP1 and EP3.

CONCLUSION

Downregulation of COX-2 and the anti-inflammatory EP2 and EP4 receptors is associated with acute rejection in unmatched pig kidney transplants, suggesting that the COX-2-PGE2-EP pathway may modulate inflammation in this model. Enhancing EP2 and/or EP4 activity may offer novel therapeutic approaches to controlling the inflammation of acute allograft rejection.

Specific inhibition of ICAM-1 effectively reduces bladder inflammation in a rat model of severe non-bacterial cystitis

The development and progression of bladder pain syndrome/interstitial cystitis (BPS/IC) is closely related to bladder inflammation. Intercellular adhesion molecule 1 (ICAM-1) is associated with bladder inflammation in BPS/IC. We investigated the effect of specific inhibition of ICAM-1 using an anti-ICAM-1 antibody (AIA) on bladder inflammation in a rat model of severe non-bacterial cystitis (NBC) resembling BPS/IC by evaluating the bladder inflammation grade, mast cell infiltration and related cytokines and receptors. We also compared the effects of AIA with the COX-2 inhibitor celecoxib and the neurokinin-1 receptor (NK1R) inhibitor aprepitant. Our NBC model was established by intraperitoneal injection of cyclophosphamide combined with intravesical protamine/lipopolysaccharide, which resulted in severe bladder inflammation and increased mast cell infiltration, similar to the pathological changes of BPS/IC. Inhibition of ICAM-1 by AIA significantly decreased the bladder inflammation grade and mast cell counts, which was accompanied by a reduction of purinergic receptors (P2X2/P2X3), prostaglandin E2, EP1/EP2 receptors, TNF-α, NK1R, and ICAM-1. Moreover, AIA showed superior effects to those of celecoxib and aprepitant treatment in improving the bladder inflammatory response. Our results suggest that ICAM-1 may play a critical role in bladder inflammation in severe NBC and may be used as a novel therapeutic target in non-bacterial bladder inflammation such as BPS/IC.

Molecular Characterization of E-Type Prostanoid Receptor 4 (EP4) from Ayu (Plecoglossus altivelis) and Its Functional Analysis in the Monocytes/Macrophages

Prostaglandin E2 (PGE2) plays an important role in a broad spectrum of physiological and pathological processes by interacting with E-type prostanoid receptors (EPs). EP4 is one of four EP subtypes known to mediate the immune response in mammalian monocytes/macrophages. However, the precise function and characteristics of EP4 in fish remain unclear. In this study, we characterized a novel EP4-like (PaEP4L) gene from ayu, Plecoglossus altivelis. The cDNA sequence of PaEP4L is 2781 nucleotides (nts) in length, encoding a polypeptide of 459 amino acid residues with a calculated molecular weight of 51.17 kDa. Sequence comparison and phylogenetic tree analysis showed that PaEP4L shared 76% amino acid identity with that of the Atlantic salmon (Salmo salar). PaEP4L mRNA was detected by real-time quantitative PCR (QPCR) in all tested tissues and head kidney-derived monocytes/macrophages (MO/MФ). It varied greatly in liver, spleen and MO/MФ upon Vibrio anguillarum infection. Western blot analysis revealed a significant increase of PaEP4L in cell homogenates from ayu MO/MФ upon V. anguillarum infection. Moreover, anti-PaEP4L IgG reversed the down-regulation of interleukin 1β (IL-1β) and tumor necrosis factor α (TNF-α) mRNA expression as well as phagocytosis in ayu MO/MФ caused by PGE2. There were no significant differences in the respiratory burst response between PGE2 treated and untreated cells. We further found that cAMP mediated PGE2/PaEP4L signal in ayu MO/MФ. In conclusion, our results indicate that PaEP4L mediates PGE2 effects on ayu MO/MФ function, revealing that EP4 also plays a role in the modulation of cells of the fish’s innate immune system.

Des-Aspartate-Angiotensin I Attenuates Mortality of Mice Exposed to Gamma Radiation via a Novel Mechanism of Action

ACE inhibitors and ARBs (angiotensin receptor blockers) have been shown to attenuate radiation injuries in animal models of lethal gamma irradiation. These two classes of drug act by curtailing the actions of angiotensin II-linked inflammatory pathways that are up-regulated during gamma radiation in organ systems such as the brain, lung, kidney, and bone marrow. ACE inhibitors inhibit ACE and attenuate the formation of angiotensin II from angiotensin I; ARBs block the angiotensin AT1 receptor and attenuate the actions of angiotensin II that are elicited through the receptor. DAA-I (des-aspartate-angiotensin I), an orally active angiotensin peptide, also attenuates the deleterious actions of angiotensin II. It acts as an agonist on the angiotensin AT1 receptor and elicits responses that oppose those of angiotensn II. Thus, DAA-I was investigated for its anticipated radioprotection in gamma irradiated mice. DAA-I administered orally at 800 nmole/kg/day for 30 days post exposure (6.4 Gy) attenuated the death of mice during the 30-day period. The attenuation was blocked by losartan (50 nmole/kg/day, i.p.) that was administered sequential to DAA-I administration. This shows that the radioprotection was mediated via the angiotensin AT1 receptor. Furthermore, the radioprotection correlated to an increase in circulating PGE2 of surviving animals, and this suggests that PGE2 is involved in the radioprotection in DAA-I-treated mice. At the hematopoietic level, DAA-I significantly improved two syndromes of myelosuppression (leucopenia and lymphocytopenia), and mice pre-treated with DAA-I prior to gamma irradiation showed significant improvement in the four myelodysplastic syndromes that were investigated, namely leucopenia, lymphocytopenia, monocytopenia and thrombocytopenia. Based on the known ability of PGE2 to attenuate the loss of functional hematopoietic stem and progenitor cells in radiation injury, we hypothesize that PGE2 mediated the action of DAA-I. DAA-I completely attenuated the increase in circulating level of two inflammatory cytokines, TNFα and IL-6, in irradiated mice; and this shows that DAA-I exerted additional anti-inflammatory actions, which could also have contributed to its radioprotection. These findings show that DAA-I acts via a novel mechanism of action on the angiotensin AT1 receptor to specifically release PGE2, which mediates radioprotection in the gamma irradiated mice.

Des-aspartate-angiotensin I, a novel angiotensin AT(1) receptor drug

The review describes DAA-I (des-aspartate-angiotensin-I) as a prototype of a novel class of drugs that acts as agonists on the angiotensin AT1 receptor or ARAs (angiotensin receptor agonists). DAA-I is a component of the renin angiotensin system. Earlier studies showed that it was rapidly metabolized to angiotensin III. However, when administered at doses below the Km of enzymes, DAA-I produces specific actions that antagonize the deleterious actions of angiotensin II. DAA-I exerts protective actions in animal models of eight human pathologies in which angiotensin II is implicated. The pathologies include cardiac hypertrophy, neointima growth and cardiovascular hypertrophy, myocardial-ischemia reperfusion injury, hyperglycemia and insulin resistance, chemical induced inflammation, and exercise-induced skeletal muscle inflammation. Binding of DAA-I to the angiotensin AT1 receptors releases prostaglandins, which could either function as autocrines/paracrines or second messengers and attenuate the deleterious actions of angiotensin II. It is possible that in in vivo DAA-I functions as a physiological antagonist to angiotensin II, and exogenous DAA-I is a novel class of angiotensin receptor drug that could rival the angiotensin receptor blockers.

Short-Term Adjuvant Therapy with Terminalia arjuna Attenuates Ongoing Inflammation and Immune Imbalance in Patients with Stable Coronary Artery Disease: In Vitro and In Vivo Evidence

The present study evaluated the cardioprotective effects of Terminalia arjuna on classical and immuno-inflammatory markers in coronary artery disease (CAD) as an adjuvant therapy. One hundred sixteen patients with stable CAD were administered placebo/T. arjuna (500 mg twice a day) along with medications in a randomized, double-blind clinical trial. To understand the specificity and efficacy of T. arjuna, we evaluated its effect through microarray and in silico analysis in few representative samples. Data was further validated via real-time PCR (n = 50) each at baseline, 3 months, and 6 months, respectively. rIL-18 cytokine was used to induce inflammation in vitro to compare its effects with atorvastatin. T. arjuna significantly down-regulated TG, VLDL-C, and immuno-inflammatory markers in stable CAD versus placebo-treated subjects. Microarray and pathway analysis of a few samples from T. arjuna/placebo-treated groups and real-time PCR validation further confirmed our observations. Our data demonstrate the anti-inflammatory and immunomodulatory effects of T. arjuna that may attenuate ongoing inflammation and immune imbalance in medicated CAD subjects.

Interleukin-18 increases TLR4 and mannose receptor expression and modulates cytokine production in human monocytes

Interleukin-18 is a proinflammatory cytokine belonging to the interleukin-1 family of cytokines. This cytokine exerts many unique biological and immunological effects. To explore the role of IL-18 in inflammatory innate immune responses, we investigated its impact on expression of two toll-like receptors (TLR2 and TLR4) and mannose receptor (MR) by human peripheral blood monocytes and its effect on TNF-α, IL-12, IL-15, and IL-10 production. Monocytes from healthy donors were stimulated or not with IL-18 for 18 h, and then the TLR2, TLR4, and MR expression and intracellular TNF-α, IL-12, and IL-10 production were assessed by flow cytometry and the levels of TNF-α, IL-12, IL-15, and IL-10 in culture supernatants were measured by ELISA. IL-18 treatment was able to increase TLR4 and MR expression by monocytes. The production of TNF-α and IL-10 was also increased by cytokine treatment. However, IL-18 was unable to induce neither IL-12 nor IL-15 production by these cells. Taken together, these results show an important role of IL-18 on the early phase of inflammatory response by promoting the expression of some pattern recognition receptors (PRRs) that are important during the microbe recognition phase and by inducing some important cytokines such as TNF-α and IL-10.

Inhibition of P2Y6 receptor-mediated phospholipase C activation and Ca(2+) signalling by prostaglandin E2 in J774 murine macrophages

Extracellular nucleotides act as inflammatory mediators through activation of multiple purinoceptors. Under inflammatory conditions, the purinergic signalling is affected by various inflammatory mediators. We previously showed that prostaglandin (PG) E2 suppressed the elevation of intracellular Ca(2+) concentration ([Ca(2+)]i) stimulated by P2X4, P2Y2, and P2Y6 receptors in J774 murine macrophages. In this study, we examined the mechanism of PGE2 inhibitory effects on P2Y6 receptor-mediated function in J774 cells. The P2Y6 receptor agonist UDP induced a sustained elevation of [Ca(2+)]i by stimulating the phospholipase C (PLC) signalling pathway. PGE2 inhibited [Ca(2+)]i elevation and phosphatidylinositol (PI) hydrolysis in a concentration-dependent manner. J774 cells highly expressed the E-type prostanoid 2 (EP2) receptor subtype, a Gs-coupled receptor. PGE2 and a selective EP2 receptor agonist caused cyclic AMP (cAMP) accumulation in J774 cells. The inhibitory effects of PGE2 on P2Y6 receptor-mediated responses were mimicked by the selective EP2 receptor agonist. Although EP2 receptor is linked to adenylyl cyclase activation, PGE2-induced inhibition of Ca(2+) response and PI hydrolysis could not be mimicked by a lipophilic cAMP derivative, dibutyryl cAMP, or an adenylyl cyclase activator, forskolin. The inhibition of UDP-induced PLC activation by PGE2 was not affected by down-regulation of protein kinase C by phorbol-12-myristate-13-acetate treatment. PGE2 inhibited PLC activation induced by aluminium fluoride, but not by the Ca(2+)-ionophore, ionomycin. Finally, the inhibition of UDP-induced PLC activation by PGE2 was impaired by Gs knockdown using siRNA. These results suggest that EP2 receptor activation in macrophages negatively controls the Gq/11-PLC signalling through a Gs-mediated, but cAMP-independent signalling mechanism.

Histamine inhibits high mobility group box 1-induced adhesion molecule expression on human monocytes

Cell-cell interaction through binding of adhesion molecules on monocytes to their ligands on T-cells plays roles in cytokine production and lymphocyte proliferation. High mobility group box 1 (HMGB1), an abundant and conserved nuclear protein, acts in the extracellular environment as a primary pro-inflammatory signal. HMGB1 induces expression of intercellular adhesion molecule (ICAM), B7.1, B7.2 and CD40 on monocytes, resulting in production of interferon (IFN)-γ and tumor necrosis factor (TNF)-α production and lymphocyte proliferation in human peripheral blood mononuclear cells (PBMCs). Histamine inhibits pro-inflammatory cytokine production via histamine H2-receptors; however, it is not known whether histamine inhibits HMGB1 activity. This study was designed to study the inhibitory effect of histamine on HMGB1 activity. We examined the effect of histamine on HMGB1-induced expression of ICAM-1, B7.1, B7.2 and CD40 on monocytes, production of IFN-γ and TNF-α and lymphocyte proliferation in PBMCs. Histamine inhibited HMGB1 activity in a concentration-dependent manner. The effects of histamine were partially ablated by the H2-receptor antagonist, famotidine, and mimicked by the H2/H4-receptor agonists, dimaprit and 4-methylhistamine. Histamine induced cyclic adenosine monophosphate (cAMP) production in the presence and absence of HMGB1. The effects of histamine were reversed by the protein kinase A (PKA) inhibitor, H89, and mimicked by the membrane-permeable cAMP analog, dibutyryl cAMP (dbcAMP), and the adenylate cyclase activator, forskolin. These results together indicated that histamine inhibited HMGB1 activity.

Prostaglandin receptor EP2 in the crosshairs of anti-inflammation, anti-cancer, and neuroprotection

Modulation of a specific prostanoid synthase or receptor provides therapeutic alternatives to nonsteroidal anti-inflammatory drugs (NSAIDs) for treating pathological conditions governed by cyclooxygenase-2 (COX-2 or PTGS2). Among the COX-2 downstream signaling pathways, the prostaglandin E2 (PGE2) receptor EP2 subtype (PTGER2) is emerging as a crucial mediator of many physiological and pathological events. Genetic ablation strategies and recent advances in chemical biology provide tools for a better understanding of EP2 signaling. In the brain, the EP2 receptor modulates some beneficial effects, including neuroprotection, in acute models of excitotoxicity, neuroplasticity, and spatial learning via cAMP-PKA signaling. Conversely, EP2 activation accentuates chronic inflammation mainly through the cAMP-Epac pathway, likely contributing to delayed neurotoxicity. EP2 receptor activation also engages β-arrestin in a G-protein-independent pathway that promotes tumor cell growth and migration. Understanding the conditions under which multiple EP2 signaling pathways are engaged might suggest novel therapeutic strategies to target this key inflammatory prostaglandin receptor.

Role of cell-cell interactions in high mobility group box 1 cytokine activity in human peripheral blood mononuclear cells and mouse splenocytes

Cell-cell interaction through binding of intercellular adhesion molecule (ICAM), B7.1, B7.2 and CD40 on monocytes to their ligands on T-cells plays a number of roles in cytokine . High mobility group box 1 (HMGB1), an abundant and conserved nuclproduction and lymphocyte proliferationear protein, acts in the extracellular environment as a primary pro-inflammatory signal. The receptor for advanced glycation end products (RAGE), toll-like receptor (TLR)-2 and TLR-4 are receptors for HMGB1. HMGB1 induces pro-inflammatory cytokine production in monocytes and T-cells. This study was designed to study the cellular mechanism of cytokine production. HMGB1 concentration-dependently induced ICAM-1, B7.1, B7.2 and CD40 expression on monocytes, and interferon (IFN)-γ and tumor necrosis factor (TNF)-α production and lymphocyte proliferation in human peripheral blood mononuclear cells (PBMCs). These HMGB1 activities depended on the stimulation of RAGE on monocytes. HMGB1 also up-regulated RAGE, but not TLR-2 or TLR-4, expression on monocytes, which was inhibited by antibodies (Abs) against ICAM-1, B7.1, B7.2 and CD40. These results together indicated that HMGB1 could induce an intimate cellular interplay between monocytes and T-cells in PBMCs through the stimulation and up-regulation of RAGE and other adhesive molecules on monocytes.

Relationship between inflammatory mediators, Aβ levels and ApoE genotype in Alzheimer disease

Activation of inflammatory processes is observed within the brain as well as periphery of subjects with Alzheimer's disease (AD). Whether or not inflammation represents a possible cause of AD or occurs as a consequence of the disease process, or, alternatively, whether the inflammatory response might be beneficial to slow the disease progression remains to be elucidated. The cytokine IL-18 shares with IL-1 the same pro-inflammatory features. Consequent to these similarities, IL-18 and its endogenous inhibitor, IL-18BP, were investigated in the plasma of AD patients versus healthy controls (HC). An imbalance of IL-18 and IL-18BP was observed in AD, with an elevated IL-18/IL-18BP ratio that might be involved in disease pathogenesis. As part of the inflammatory response, altered levels of RANTES, MCP-1 and ICAM- 1, molecules involved in cell recruitment to inflammatory sites, were observed in AD. Hence, correlations between IL-18 and other inflammatory plasma markers were analyzed. A negative correlation was observed between IL-18 and IL-18BP in both AD and HC groups. A positive correlation was observed between IL-18 and ICAM-1 in AD patients, whereas a negative correlation was evident in the HC group. IL-18 positively correlated with Aβ in both groups, and no significant correlations were observed between IL-18, RANTES and MCP-1. An important piece of evidence supporting a pathophysiologic role for inflammation in AD is the number of inflammatory mediators that have been found to be differentially regulated in AD patients, and specific ones may provide utility as part of a biomarker panel to not only aid early AD diagnosis, but follow its progression.

Regulation of the arachidonic acid mobilization in macrophages by combustion-derived particles

BACKGROUND

Acute exposure to elevated levels of environmental particulate matter (PM) is associated with increasing morbidity and mortality rates. These adverse health effects, e.g. culminating in respiratory and cardiovascular diseases, have been demonstrated by a multitude of epidemiological studies. However, the underlying mechanisms relevant for toxicity are not completely understood. Especially the role of particle-induced reactive oxygen species (ROS), oxidative stress and inflammatory responses is of particular interest.In this in vitro study we examined the influence of particle-generated ROS on signalling pathways leading to activation of the arachidonic acid (AA) cascade. Incinerator fly ash particles (MAF02) were used as a model for real-life combustion-derived particulate matter. As macrophages, besides epithelial cells, are the major targets of particle actions in the lung murine RAW264.7 macrophages and primary human macrophages were investigated.

RESULTS

The interaction of fly ash particles with macrophages induced both the generation of ROS and as part of the cellular inflammatory responses a dose- and time-dependent increase of free AA, prostaglandin E2/thromboxane B2 (PGE2/TXB2), and 8-isoprostane, a non-enzymatically formed oxidation product of AA. Additionally, increased phosphorylation of the mitogen-activated protein kinases (MAPK) JNK1/2, p38 and ERK1/2 was observed, the latter of which was shown to be involved in MAF02-generated AA mobilization and phosphorylation of the cytosolic phospolipase A2. Using specific inhibitors for the different phospolipase A2 isoforms the MAF02-induced AA liberation was shown to be dependent on the cytosolic phospholipase A2, but not on the secretory and calcium-independent phospholipase A2. The initiation of the AA pathway due to MAF02 particle exposure was demonstrated to depend on the formation of ROS since the presence of the antioxidant N-acetyl-cysteine (NAC) prevented the MAF02-mediated enhancement of free AA, the subsequent conversion to PGE2/TXB2 via the induction of COX-2 and the ERK1/2 and JNK1/2 phosphorylation. Finally we showed that the particle-induced formation of ROS, liberation of AA and PGE2/TXB2 together with the phosphorylation of ERK1/2 and JNK1/2 proteins was decreased after pre-treatment of macrophages with the metal chelator deferoxamine mesylate (DFO).

CONCLUSIONS

These results indicate that one of the primary mechanism initiating inflammatory processes by incinerator fly ash particles seems to be the metal-mediated generation of ROS, which triggers via the MAPK cascade the activation of AA signalling pathway.

Protective actions of des-aspartate-angiotensin I in mice model of CEES-induced lung intoxication

The present study investigated the protective actions of des-aspartate-angiotensin I (DAA-I) in mice that were intranasally administered 2-chloroethyl ethyl sulfide (CEES), a half sulfur mustard. The protection was dose-dependent, and an oral dose of 75 mg kg⁻¹ per day administered 18 h post exposure and for the following 13 days, offered maximum protection that increased survival by a third. DAA-I attenuated the early processes of inflammation seen in the CEES-inoculated mice. DAA-I attenuated (i) elevated pulmonary ROS, and gp91-phox protein of NADPH oxidase, a non phagocytic enzyme that generates superoxide and subsequent ROS; (ii) intercellular adhesion molecule-1 (ICAM⁻¹) that is involved in the extravasation of circulating leucocytes; and (iii) myeloperoxidase activity, which is a surrogate enzymatic measurement of neutrophil infiltration. These actions led to improved histological lung structures, and survival of type-1 pneumocytes. The action of DAA-I on animal survival was blocked by losartan, a selective angiotensin AT1 receptor blocker, indicting that the AT1 receptor mediates the protection. The presence of elevated PGE2 and PGI2 in lung supernatants of DAA-I treated CEES-inoculated mice indicates that the two prostaglandins are involved in signaling the protective actions of DAA-I. This finding complements earlier studies showing that DAA-I acts on an indomethacin-sensitive angiotensin AT1 receptor. The findings of the present study are the first demonstration of an angiotensin peptide as an effective antidote for CEES intoxication. DAA-I is also an effective therapeutic intervention against CEES that was instituted at 18 h post exposure, and challenges conventional assumptions of limited efficacy with delayed action against alkylating agents.

The PGE2 EP2 receptor and its selective activation are beneficial against ischemic stroke

BACKGROUND

The prostaglandin E2 EP2 receptor has been shown to be important in dictating outcomes in various neuroinflammatory disorders. Here, we investigated the importance of the EP2 receptor in short- and long-term ischemic outcomes by subjecting wildtype (WT) and EP2 knockout (EP2-/-) mice to two distinct and complementary stroke models [transient and permanent middle cerebral artery occlusion (tMCAO and pMCAO)] and by using the EP2 receptor agonist ONO-AE1-259-01.

METHODS

First, WT and EP2-/- mice were subjected to 90-min tMCAO with a monofilament followed by 4-day reperfusion. Second, WT mice were infused intracerebroventricularly with vehicle or ONO-AE1-259-01 45-50 min before being subjected to tMCAO. Finally, WT and EP2-/- mice were subjected to pMCAO and allowed to survive for an extended period of 7 days.

RESULTS

Infarct volumes in EP2-/- mice were 55.0 +/- 9.1% larger after tMCAO and 33.3 +/- 8.6% larger after pMCAO than those in WT mice. Neurobehavioral deficits also were significantly greater in the EP2-/- mice. These results suggest that EP2 is beneficial and that activation is sustained for days after the stroke. We also found that pharmacologic activation of EP2 with 1.0- and 2.0-nmol doses of ONO-AE1-259-01 was sufficient to significantly reduce the infarct volume in WT mice compared with that in vehicle-treated controls (20.1 +/- 3.9% vs. 37.1 +/- 4.6%). This reduction correlated with improved neurologic scores. No significant effect on physiologic parameters was observed.

CONCLUSION

Together, our results reveal that pharmacologic stimulation of the EP2 receptor has an important beneficial role in cerebral ischemia and might be considered as an adjunct therapy for ischemic stroke.

Phosphatidylserine-containing liposomes inhibit the differentiation of osteoclasts and trabecular bone loss

Liposomes containing phosphatidylserine (PS) are engulfed by phagocytes including macrophages, microglia, and dendritic cells. PS liposomes (PSLs) mimic the effects of apoptotic cells on these phagocytes to induce the secretion of anti-inflammatory molecules and to inhibit the maturation of dendritic cells. However, the effects of PSLs on osteoclasts, which are also differentiated from the common myeloid precursors, remain to be determined. This study investigated the effects of PSLs on the osteoclastogenesis. In the rat bone marrow culture system, osteoclast precursors phagocytosed PSLs to secrete TGF-beta1 and PGE(2), which in turn inhibited osteoclastogenesis through the downregulation of receptor activator for NF-kappaB ligand, receptor activator of NF-kappaB, ICAM-1, and CD44. Consistent with these in vitro observations, i.m. injection of PSLs significantly increased the plasma level of TGF-beta1 and PGE(2) and decreased the expression of receptor activator for NF-kappaB ligand, receptor activator of NF-kappaB, and ICAM-1 in the skeletal tissues of ankle joints of rats with adjuvant arthritis (AA). A quantitative analysis using microcomputed tomography revealed that PSLs as well as TGF-beta1 together with PGE(2) significantly inhibited AA-induced trabecular bone loss. These observations strongly suggest that PSLs generate TGF-beta1 and PGE(2) release, leading to inhibit osteoclastogenesis and AA-induced trabecular bone loss. Because PS is a component of the cell membrane, PSLs therefore can be a potentially effective pharmacological intervention against abnormal bone loss, such as osteoporosis without deleterious side effects.

Influence of cyclooxygenase-2 (COX-2) gene promoter polymorphism -765 on graft loss after renal transplantation

A G-->C polymorphism has been identified in the human cyclooxygenase-2 (COX-2) gene promoter at position -765 with C allele leading to a decreased promoter activity with low prostaglandin E2 (PGE2) production. PGE2 has strong immunomodulatory properties that could influence graft survival. We studied the association between this polymorphism and allograft failure in two independent cohorts of renal transplant recipients (RTRs) including a total of 603 patients. The functional effect of COX-2 gene promoter polymorphism was analyzed by measuring serum levels of PGE2. Median follow-up was 8.7 and 7.9 years for the first and second cohort, respectively. Analysis of 603 patients identified 20 CC (3.3%), 179 GC (29.7%) and 404 GG (67%) carriers. Patients with the GG genotype had significantly higher serum PGE2 concentrations than patients with the C allele. Carriers with a C allele have an independent increased risk of graft loss (hazard ratio (HR) 2.43 [95% CI 1.19-4.97], p = 0.015 for cohort 1; HR 1.72 [95% CI 0.99-3.77], p = 0.051 for cohort 2) compared to GG patients. COX-2 gene promoter polymorphism at position -765 (G-->C) is associated with a higher rate of graft loss in RTRs. Such findings may be used to influence immunosuppressive strategies and optimize patient management.

Advanced glycation end products enhance monocyte activation during human mixed lymphocyte reaction

Posttransplant diabetes mellitus (PTDM) is a frequent complication among transplant recipients. Ligation of advanced glycation end products (AGEs) with their receptor (RAGE) on monocytes/macrophages plays roles in the diabetes complications. The enhancement of adhesion molecule expression on monocytes/macrophages activates T-cells, leading to reduced allograft survival. We investigated the effect of four distinct AGE subtypes (AGE-2/AGE-3/AGE-4/AGE-5) on the expressions of intracellular adhesion molecule (ICAM)-1, B7.1, B7.2 and CD40 on monocytes, the production of interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha and the proliferation of T-cells during human mixed lymphocyte reaction (MLR). AGE-2 and AGE-3 selectively induced the adhesion molecule expression, cytokine production and T-cell proliferation. The AGE-induced up-regulation of adhesion molecule expression was involved in the cytokine production and T-cell proliferation. AGE-2 and AGE-3 up-regulated the expression of RAGE on monocytes; therefore, the AGEs may activate monocytes, leading to the up-regulation of adhesion molecule expression, cytokine production and T-cell proliferation.

Prostaglandin E2 inhibits advanced glycation end product-induced adhesion molecule expression, cytokine production, and lymphocyte proliferation in human peripheral blood mononuclear cells

Advanced glycation end product (AGE) subtypes, proteins or lipids that become glycated after exposure to sugars, induce complications in diabetes. Among the various AGE subtypes, glyceraldehyde-derived AGE (AGE-2) and glycolaldehyde-derived AGE (AGE-3) have been indicated to play roles in inflammation in diabetic patients. The engagement of AGEs and receptor for AGEs activates monocytes. Because the engagement of intercellular adhesion molecule-1 (ICAM-1), B7.1, B7.2, and CD40 on monocytes with their ligands on T cells plays roles in cytokine production, we investigated the effects of AGE-2 and AGE-3 on the expressions of ICAM-1, B7.1, B7.2, and CD40 on monocytes, the production of interferon gamma and tumor necrosis factor alpha, and the lymphocyte proliferation in human peripheral blood mononuclear cells and their modulation by prostaglandin E(2) (PGE(2)). AGE-2 and AGE-3 induced the expressions of adhesion molecule, the cytokine production, and the lymphocyte proliferation. PGE(2) concentration-dependently inhibited the actions of AGE-2 and AGE-3. The effects of PGE(2) were mimicked by an E-prostanoid (EP)(2)-receptor agonist, 11,15-O-dimethyl prostaglandin E(2) (ONO-AE1-259-01), and an EP(4) receptor agonist, 16-(3-methoxymethyl)phenyl-omega-tetranor-3,7-dithia prostaglandin E(1) (ONO-AE1-329). An EP(2)-receptor antagonist, 6-isopropoxy-9-oxaxanthene-2-carboxylic acid (AH6809), and an EP(4)-receptor antagonist, (4Z)-7-[(rel-1S,2S,5R)-5-(1,1'-biphenyl-4-yl)methoxy)-2-(4-morpholinyl)-3-oxocyclopentyl]-4-heptenoic acid (AH23848), inhibited the actions of PGE(2). The stimulation of EP(2) and EP(4) receptors is reported to increase cAMP levels. The effects of PGE(2) were reversed by a protein kinase A (PKA) inhibitor, H89, and mimicked by a dibutyryl cAMP and an adenylate cyclase activator, forskolin. These results as a whole indicated that PGE(2) inhibited the actions of AGE-2 and AGE-3 via EP(2)/EP(4) receptors and the cAMP/PKA pathway.

Multipotent adult progenitor cells can suppress graft-versus-host disease via prostaglandin E2 synthesis and only if localized to sites of allopriming

Multipotent adult progenitor cells (MAPCs) are nonhematopoietic stem cells capable of giving rise to a broad range of tissue cells. As such, MAPCs hold promise for tissue injury repair after transplant. In vitro, MAPCs potently suppressed allogeneic T-cell activation and proliferation in a dose-dependent, cell contact-independent, and T-regulatory cell-independent manner. Suppression occurred primarily through prostaglandin E(2) synthesis in MAPCs, which resulted in decreased proinflammatory cytokine production. When given systemically, MAPCs did not home to sites of allopriming and did not suppress graft-versus-host disease (GVHD). To ensure that MAPCs would colocalize with donor T cells, MAPCs were injected directly into the spleen at bone marrow transplantation. MAPCs limited donor T-cell proliferation and GVHD-induced injury via prostaglandin E(2) synthesis in vivo. Moreover, MAPCs altered the balance away from positive and toward inhibitory costimulatory pathway expression in splenic T cells and antigen-presenting cells. These findings are the first to describe the immunosuppressive capacity and mechanism of MAPC-induced suppression of T-cell alloresponses and illustrate the requirement for MAPC colocalization to sites of initial donor T-cell activation for GVHD inhibition. Such data have implications for the use of allogeneic MAPCs and possibly other immunomodulatory nonhematopoietic stem cells for preventing GVHD in the clinic.

Emerging roles of PGE2 receptors in models of neurological disease

This review presents an overview of the emerging field of prostaglandin signaling in neurological diseases, focusing on PGE(2) signaling through its four E-prostanoid (EP) receptors. A large number of studies have demonstrated a neurotoxic function of the inducible cyclooxygenase COX-2 in a broad spectrum of neurological disease models in the central nervous system (CNS), from models of cerebral ischemia to models of neurodegeneration and inflammation. Since COX-1 and COX-2 catalyze the first committed step in prostaglandin synthesis, an effort is underway to identify the downstream prostaglandin signaling pathways that mediate the toxic effect of COX-2. Recent epidemiologic studies demonstrate that chronic COX-2 inhibition can produce adverse cerebrovascular and cardiovascular effects, indicating that some prostaglandin signaling pathways are beneficial. Consistent with this concept, recent studies demonstrate that in the CNS, specific prostaglandin receptor signaling pathways mediate toxic effects in brain but a larger number appear to mediate paradoxically protective effects. Further complexity is emerging, as exemplified by the PGE(2) EP2 receptor, where cerebroprotective or toxic effects of a particular prostaglandin signaling pathway can differ depending on the context of cerebral injury, for example, in excitotoxicity/hypoxia paradigms versus inflammatory-mediated secondary neurotoxicity. The divergent effects of prostaglandin receptor signaling will likely depend on distinct patterns and dynamics of receptor expression in neurons, endothelial cells, and glia and the specific ways in which these cell types participate in particular models of neurological injury.

Prostaglandin E(2) suppresses staphylococcal enterotoxin-induced eosinophilia-associated cellular responses dominantly through an E-prostanoid 2-mediated pathway in nasal polyps

BACKGROUND

Recent investigations have revealed that staphylococcal enterotoxins (SEs), COX metabolism, or both might participate in the pathogenesis of eosinophilic airway diseases, such as chronic rhinosinusitis with nasal polyposis.

OBJECTIVE

We sought to determine whether COX metabolism, especially prostaglandin (PG) E(2), plays a significant role in SE-induced cellular responses in nasal polyps.

METHODS

Dispersed nasal polyp cells (DNPCs) were prepared from nasal polyps by means of enzymatic digestion. DNPCs were cultured with SEB in the presence or absence of COX inhibitors (diclofenac and indomethacin) for 72 hours; then the levels of IL-5, IL-13, RANTES, and eotaxin in the supernatants were measured. The effect of PGE(2) on SEB-induced responses by diclofenac-treated DNPCs was examined, especially in terms of receptor specificity.

RESULTS

DNPCs produced significant amounts of IL-5, IL-13, and RANTES in response to SEB. COX inhibitors significantly increased the production of these cytokines. The degree of local eosinophilia was significantly and positively correlated with the changes in IL-5 production induced by diclofenac treatment. PGE(2) significantly and dose-dependently inhibited SEB-induced IL-5, IL-13, and RANTES production by diclofenac-treated DNPCs. E-prostanoid (EP) 2 receptor-selective agonist strongly inhibited the production of all 3 cytokines. EP3 and EP4 receptor-selective agonists partially suppressed these responses, whereas EP1 receptor-selective agonist did not. Interestingly, all of the combined treatments with 2 of the 4 EP receptor-selective agonists significantly inhibited the SEB-induced responses by diclofenac-treated DNPCs.

CONCLUSIONS

These results suggest that PGE(2) inhibits the pathogenesis of SEB-induced eosinophilic inflammation primarily through the EP2-mediated pathway in patients with chronic rhinosinusitis with nasal polyposis.

Butyrate and trichostatin A attenuate nuclear factor kappaB activation and tumor necrosis factor alpha secretion and increase prostaglandin E2 secretion in human peripheral blood mononuclear cells

The effects of short-chain fatty acids (butyrate, propionate, and acetate) and trichostatin A (TSA), a typical histone deacetylase inhibitor, on tumor necrosis factor (TNF)-alpha secretion and nuclear factor kappaB (NF-kappaB) activation in peripheral blood mononuclear cells induced with lipopolysaccharide were evaluated in relation to prostaglandin E(2) (PGE(2)) secretion. Treatment of cells with butyrate; tributyrin, a prodrug of butyrate; propionate; acetate; and TSA down-regulated TNF-alpha secretion but all up-regulated PGE(2) secretion. Butyrate, propionate, and TSA inhibited NF-kappaB activation. The effects of the cyclooxygenase-nonspecific inhibitor, indomethacin; the cyclooxygenase-2 selective inhibitor, N-[2-(cyclohexyloxy)-4-nitro-phenyl] methanesulfonamide; and the general lipoxygenase inhibitor, nordihydroguaiaretic acid, varied in cells treated with each short-chain fatty acids. N-[2-(cyclohexyloxy)-4-nitro-phenyl] methanesulfonamide inhibited the effect of propionate on TNF-alpha secretion, and nordihydroguaiaretic acid inhibited that of acetate. The results showed that butyrate, propionate, and TSA inhibited TNF-alpha production via PGE(2) secretion and down-regulated NF-kappaB activation by lipopolysaccharide. These data suggest that the mechanism of butyrate and propionate action is through histone deacetylation and acetate through lipoxygenase activation in the regulation of proinflammatory responses in cells.

G protein-coupled receptor connectivity to NF-kappaB in inflammation and cancer

Complex intracellular network interactions regulate gene expression and cellular behavior. Whether at the site of inflammation or within a tumor, individual cells are exposed to a plethora of signals. The transcription factor nuclear factor-kappaB (NF-kappaB) regulates genes that control key cellular activities involved in inflammatory diseases and cancer. NF-kappaB is regulated by several distinct signaling pathways that may be activated individually or simultaneously. Multiple ligands and heterologous cell-cell interactions have an impact on NF-kappaB activity. The G protein-coupled receptor (GPCR) superfamily makes up the largest class of transmembrane receptors in the human genome and has multiple molecularly distinct natural ligands. GPCRs regulate proliferation, differentiation, and chemotaxis and play a major role in inflammatory diseases and cancer. Both GPCRs and NF-kappaB have been, and continue to be, major targets for drug discovery. A clear understanding of network interactions between GPCR signaling pathways and those that control NF-kB may be valuable for the development of better drugs and drug combinations.

Contribution of dectin-1 and granulocyte macrophage-colony stimulating factor (GM-CSF) to immunomodulating actions of beta-glucan

beta-Glucans are major cell wall structural components in fungi. As they are not found in animals, these carbohydrates are considered to be classic pathogen-associated molecular patterns (PAMPs), and are recognized by the innate immune system. Although their immunomodulating activities have been shown to be associated with the recognition of some fungi, and with their medicinal properties in the field of cancer immunotherapy, it is still unclear how beta-glucans mediate their effects. Recent studies have started to shed some light on their cellular receptors, such as dectin-1, and their molecular mechanisms of action. We have extensively investigated the response of leukocytes to beta-glucan, focusing on cytokine induction by SCG, which is a major 6-branched 1,3-beta-d-glucan in Sparassis crispa Fr. There is a strain difference in the reactivity of mice to SCG, and DBA/1 and DBA/2 mice are highly sensitive strains. In the process of research on cytokine induction by SCG in DBA/2 mice, we found that GM-CSF plays a key biological role in this activity. Cytokine induction by SCG was completely abolished in dendritic cells from dectin-1 knockout mice. On the other hand, controlling the level of endogenous GM-CSF production and/or dectin-1 expression could regulate the reactivity to beta-glucan. These results indicate that the key factors in the responsiveness to beta-glucan are GM-CSF production and dectin-1 expression. In this review, we describe how the key molecules related to the expression of the immunomodulating activities of beta-glucan were identified, and how the response to beta-glucan is controlled.

Effects of adenosine on adhesion molecule expression and cytokine production in human PBMC depend on the receptor subtype activated

BACKGROUND AND PURPOSE

Adenosine suppresses immune responses through adenosine(2A) (A(2A)) receptors, by raising intracellular cAMP. Interleukin (IL)-18 up-regulates the expression of intercellular adhesion molecule (ICAM)-1 on monocytes, leading to production of pro-inflammatory cytokines such as IL-12, interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha by human peripheral blood mononuclear cells (PBMC). We have previously demonstrated that elevation of cAMP inhibits this IL-18-induced expression of adhesion molecules. In the present study, we examined the effect of adenosine on the IL-18-induced up-regulation of ICAM-1 on human monocytes and production of IL-12, IFN-gamma and TNF-alpha by PBMC.

EXPERIMENTAL APPROACH

The expression of ICAM-1 was examined by flow cytometry. IL-12, IFN-gamma and TNF-alpha were determined by ELISA assay.

KEY RESULTS

Adenosine inhibited the IL-18-induced up-regulation of ICAM-1 on human monocytes and it abolished the IL-18-enhanced production of IL-12, IFN-gamma and TNF-alpha. While an A(2A) receptor antagonist reversed the action of adenosine, an A(1) or A(3) receptor antagonist enhanced them. An A(2A) receptor agonist, CGS21680, mimicked the effects of adenosine and its effects were abolished not only by the A(2A) receptor antagonist but also by A(1) or A(3) receptor agonists. Activation via A(2A) receptors resulted in elevation of cAMP in monocytes, whereas the stimulation of A(1) or A(3) receptors inhibited it, suggesting that intracellular signal transduction following ligation of A(2A) receptors might be blocked by activation of A(1) or A(3) receptors.

CONCLUSIONS AND IMPLICATIONS

Adenosine differentially regulates IL-18-induced adhesion molecule expression and cytokine production through several subtypes of its receptors.

Interleukin-18 as a potential therapeutic target in chronic autoimmune/inflammatory conditions

Interleukin-18 (IL-18), a recently identified immunoregulatory and inflammatory cytokine, has attracted a profound interest as a potential therapeutic target in autoimmune/inflammatory disorders. In this review the authors focus on: IL-18 biology as an important link between innate and adaptive immunity; evidence of its pro-inflammatory role in several human autoimmune and chronic inflammatory disorders; and data indicating that IL-18 blockade in animal models results in prevention/amelioration of the disease process and preservation of the target tissue integrity and function. Finally, the authors analyse strategies presently under development to block IL-18 function and potential pitfalls resulting from IL-18 blockade that should be considered in ongoing/future clinical trials.

Modulation of ocular inflammatory responses by EP1 receptors in mice

The purpose of the study was to investigate the role of EP1 receptors in intraocular inflammation and to determine possible interplay between EP1, EP2 and EP4 receptors. The eyes of separate groups of EP1 receptor knockout and wild type mice were: 1) treated topically with prostaglandin E2 (PGE2) or the EP2 receptor selective agonist, butaprost; 2) given intravitreal injection of LPS; or 3) paracentesis performed. Another group of knockout mice were pretreated topically with an EP4 receptor selective antagonist prior to paracentesis or LPS treatment. Results demonstrated a significant increase (50% or more) in the protein levels of aqueous humor of the EP1 knockout mice in response to PGE2, paracentesis or LPS. The leukocyte infiltration in the aqueous humor of the knockout mice was 47% higher when compared with that in the wild type controls in response to LPS injection. No significant change was observed in the protein levels in response to butaprost. Pretreating the knockout mice with an EP4 receptor antagonist prior to paracentesis and LPS treatment substantially reduced the aqueous humor protein levels. Also, the leukocyte count in the aqueous humor of the knockout mice in response to LPS was reduced 4 fold after pretreatment with EP4 receptor antagonist when compared with the findings in knockout mice receiving LPS only. We concluded that EP1 receptor has no modulatory effect on EP2 receptors but there is definitely cross-talk between EP1 and EP4 receptors.

Effect of nicotine on IL-18-initiated immune response in human monocytes

Nicotine is thought to inhibit the production of proinflammatory cytokines from macrophages through an anti-inflammatory pathway that is dependent on nicotinic acetylcholine receptor alpha7 subunit (alpha7-nAChR). IL-18, an important proinflammatory cytokine, is reported to induce the expression of adhesion molecules on monocytes, thus enhancing cell-to-cell interactions with T-cells and contributing to IL-18-initiated cytokine production. Accordingly, inhibition of IL-18 suppresses systemic inflammatory responses. In the present study, we found that nicotine inhibited the IL-18-enhanced expression of ICAM-1, B7.2, and CD40 on monocytes, and the production of IL-12, IFN-gamma, and TNF-alpha by PBMC. A nonselective and a selective alpha7-nAChR antagonist, mecamylamine, and alpha-bungarotoxin abolished the effects of nicotine, suggesting that this depends on alpha7-nAChR stimulation. It is reported that nicotine induces prostaglandinE2 (PGE(2)) production in PBMC through the up-regulation of cyclooxygenase (COX)-2 expression. PGE(2) is known to activate the EP2/EP4-receptor, leading to an increase in cyclic adenosine monophosphate (cAMP) levels and protein kinase A (PKA) activity. Consistent with this, we found that COX-2 and PKA inhibitors prevented the effects of nicotine on adhesion molecule expression and cytokine production, indicating that the mechanism of action of nicotine may be via endogenous PGE(2) production.

E prostanoid 2 (EP2)/EP4-mediated suppression of antigen-specific human T-cell responses by prostaglandin E2

Prostaglandin E2 (PGE2) is a lipid mediator that displays important immunomodulatory properties, such as polarization of cytokine production by T cells. Recent investigations have revealed that the effect of PGE2 on cytokine production is greatly influenced by external stimuli; however, it is unclear whether PGE2 plays a significant role in major histocompatibility complex-mediated antigen-specific T-cell responses via binding to one of four subtypes of E prostanoid (EP) receptor alone or in combination. In the present study, we sought to determine the effect of PGE2 on antigen-specific CD4+ T-cell responses in humans, especially in terms of receptor specificity. We used purified protein derivative (PPD) and Cry j 1 as T helper type 1 (Th1) and Th2-inducing antigens, respectively. We generated several different Cry j 1- and PPD-specific T-cell lines (TCLs). PGE2 significantly and dose-dependently inhibited the proliferation and subsequent production of interleukin-4 by Cry j 1-specific TCLs and of interferon-gamma by PPD-specific TCLs upon antigen stimulation. Administration of EP2 receptor agonist and EP4 receptor agonist suppressed these responses in an adenylate cyclase-dependent manner, while EP1 and EP3 receptor agonists did not. Messenger RNA for EP2, EP3 and EP4, but not EP1, receptors were detected in Cry j 1- and PPD-specific TCLs, and no differences in EP receptor expression were observed between them. Furthermore, PGE2 and EP2 receptor agonist significantly inhibited interleukin-5 and interferon-gamma production by peripheral blood mononuclear cells in response to Cry j 1 and PPD stimulation, respectively. These results suggest that PGE2 suppresses both Th1- and Th2-polarized antigen-specific human T-cell responses via a cAMP-dependent EP2/EP4-mediated pathway.

The immunosuppressive effects of ciprofloxacin during human mixed lymphocyte reaction

Interleukin (IL)-18, which is elevated in the plasma during acute rejection after organ transplantation, is known to induce the expression of intercellular adhesion molecule (ICAM)-1, B7.1, B7.2, CD40 and CD40 ligand (CD40L) on monocytes, the production of interferon (IFN)-gamma and IL-12 and the proliferation of lymphocytes during the human mixed lymphocyte reaction (MLR). Ciprofloxacin (CIP), which is useful for the clinical treatment of infections due to its antibacterial properties after transplantation, was shown to suppress the IFN-gamma and IL-12 production, the lymphocyte proliferation and the ICAM-1, B7.1, B7.2 and CD40 expression on monocytes during MLR in the presence of IL-18. CIP also induced the production of prostaglandin (PG) E2. In order to determine whether the effects of CIP on the expression of the activation markers were due to CIP-dependent production of PGE2, we examined the effect of cyclooxygenase (COX)-2 and protein kinase A (PKA) inhibitors on the actions of CIP. Thereby, the inhibitors were found to abolish the actions of CIP. These results therefore suggest that CIP might exert its immune modulatory effects via the production of PGE2.

Cell to Cell Contact Through ICAM-1-LFA-1 and TNF-α Synergistically Contributes to GM-CSF and Subsequent Cytokine Synthesis in DBA/2 Mice Induced by 1,3-β-D-Glucan SCG

SCG is a major 6-branched 1,3-beta-D-glucan in Sparassis crispa Fr. showing antitumor activity. We recently found that the splenocytes from naive DBA/1 and DBA/2 mice are potently induced by SCG to produce interferon- gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), granulocyte-macrophage colony-stimulating factor (GM-CSF), and interleukin-12p70 (IL-12p70), and that GM-CSF plays a key biologic role among these cytokines. In this study, we investigated the contribution of cell-cell contact and soluble factors to cytokine induction by SCG in DBA/2 mice. Cell-cell contact involving intercellular adhesion molecule-1 (ICAM-1) and lymphocyte function-associated antigen-1 (LFA-1) was an essential step for the induction of GM-CSF and IFN-gamma by SCG but not for the induction of TNF-alpha or IL-12p70 by SCG. SCG directly induced adherent splenocytes to produce TNF-alpha and IL-12p70. GM-CSF was required for the induction of TNF-alpha by SCG, and in turn, TNF-alpha enhanced the release of GM-CSF and thereby augmented the induction of IL-12p70 and IFN-gamma by SCG. Neutralization of IL-12 significantly inhibited the induction of IFN-gamma by SCG. We concluded that induction of GM-CSF production by SCG was mediated through ICAM-1 and LFA-1 interaction, GM-CSF subsequently contributed to further cytokine induction by SCG, and reciprocal actions of the cytokines were essential for enhancement of the overall response to SCG in DBA/2 mice.

Differential modulation in the functions of intestinal dendritic cells by long- and medium-chain fatty acids

BACKGROUND

Although dendritic cells (DCs) play significant roles in intestinal immune responses, little is known regarding the direct effects of luminal foods on DC functions in the intestinal mucosa. In this study, we examined the effects of fatty acids (FAs) with various chain length on the phagocytic function, antigen presentation, and chemotaxis of intestinal DCs.

METHODS

DCs obtained from the thoracic duct lymph of mesenteric lymphadenectomized rats were cultured with long [arachidonic acid (AA) or oleic acid] or medium (octanoic acid) chain FAs with interleukin-4 and granulocyte macrophage-colony stimulating factor. Tumor necrosis factor-alpha was added in the maturation group. Phagocytic function was examined by the intake of fluorescent microbeads. The expression of cell surface molecules was determined by immunocytochemistry or fluorescence-activated cell sorting (FACS). Antigen presentation ability was evaluated by coincubating keyhole limpet hemocyanin (KLH)-sensitized spleen lymphocytes and KLH-pulsed DCs. Migratory ability of DCs toward the chemokines CC chemokine ligand (CCL) 20 and CCL21 was also assessed.

RESULTS

There was a maturation-induced decrease in phagocytic function, and an increased expression of major histocompatibility complex (MHC) class II molecules. Exposure of DCs to both long- and medium-chain FAs maintained phagocytic ability. The expression of MHC class II molecules was significantly suppressed only by long-chain FAs. The expression of costimulatory factors was suppressed only by AA. Long- but not medium-chain FAs suppressed the antigen presentation ability of DCs induced by maturation. Chemotactic ability of mature DCs toward CCL21 was abrogated only by long-chain FAs.

CONCLUSIONS

The data suggest that intraluminal exposure to long- and medium-chain FAs may differentially modulate the immune functions of intestinal DCs.

Effect of ciprofloxacin-induced prostaglandin E2 on interleukin-18-treated monocytes

Ciprofloxacin, a fluorinated 4-quinolone, is useful for the clinical treatment of infections due to its antibacterial properties and also modulates the immune response of monocytes isolated from human peripheral blood mononuclear cells. In the present study, we found that ciprofloxacin induced the production of prostaglandin E(2) in monocytes in a concentration-dependent manner regardless of the presence of interleukin-18 by enhancing the expression of cyclooxygenase-2 protein and that this in turn led to the elevation of intercellular cyclic AMP in monocytes via the stimulation of prostaglandin receptors. The prostaglandin E(2) and cyclic AMP production increased by ciprofloxacin was inhibited by indomethacin, a nonselective cyclooxygenase-2 inhibitor, and NS398, a selective cyclooxygenase-2 inhibitor. In addition, ciprofloxacin suppressed the interleukin-18-induced production of tumor necrosis factor alpha, gamma interferon, and interleukin-12 in peripheral blood mononuclear cells by inhibiting the expression of intercellular adhesion molecule 1, B7.1, B7.2, and CD40 on monocytes, and this effect could be reversed by the addition of indomethacin or NS398. These results indicate that ciprofloxacin exerts immunomodulatory activity via the production of prostaglandin E(2) and imply therapeutic potential of ciprofloxacin for the treatment of systemic inflammatory responses initiated by interleukin-18.

Prostaglandins E1 and E2 inhibit lipopolysaccharide-induced interleukin-18 production in monocytes

The purpose of this present study was to explore the therapeutic potential of prostaglandins E1 and E2 on the systemic inflammatory response evoked by endotoxin. Since interleukin-18, a monocyte-derived cytokine, is increased during sepsis, decreasing the production of interleukin-18 is important in treating this condition. Prostaglandin E1 and E2 inhibited interleukin-18 production in human monocytes treated with lipopolysaccharide and prostanoid IP-, EP2- and EP4-receptor agonists mimicked the effects of prostaglandins E1 and E2. Therefore, prostanoid IP, EP2- and EP4-receptors might be involved in the decrease in interleukin-18 production during sepsis.

Recombinant HBsAg inhibits LPS-induced COX-2 expression and IL-18 production by interfering with the NFkappaB pathway in a human monocytic cell line, THP-1

BACKGROUND/AIMS

Hepatitis B virus suppresses the human immune-system and HBsAg inhibits the induction of cytokines by LPS in human macrophages, but the mechanisms involved remain unclear. COX-2 and its product, PGE2, play a role in hepatitis B and IL-18 has also been shown to inhibit HBV infection in vivo. We investigated whether rHBsAg affects induction of COX-2 and IL-18 by LPS and, if so, which signal pathways are involved in a human monocytic cell line, THP-1.

METHODS

Cell culture, Western blotting for COX-2, ERK and IKB-alpha, immunofluorescence for HBsAg and NFkappaB protein and ELISA for PGE2, IL-18 and IL-12 were performed.

RESULTS

rHBsAg inhibits LPS-induced COX-2 expression in a time- and dose-dependent manner by blocking the ERK and NFkappaB pathways. LPS-induced IL-18 production was also down-regulated by rHBsAg by interfering mainly with the NFkappaB pathway. PGE2 reversed the inhibition of LPS-induced IL-18 production by rHBsAg. rHBsAg was also found to inhibit the induction of IL-12 by LPS in THP-1 cells.

CONCLUSIONS

These results showed a novel anti-inflammatory property of rHBsAg which involves inhibition of COX-2 and suggested that hepatitis B virus may regulate IFN-gamma production by inhibiting IL-18 and IL-12 production.

Involvement of prostaglandin receptors (EPR2–4) in in vivo immunosuppression of PGE2 in rat skin transplant model

BACKGROUND

Prostaglandin E2 (PGE2) is known to modulate immune responses and is widely viewed as a general immunosuppressant. There have been recognized four receptors for PGE2 (EP1-EP4 receptor) so far, and EP2 and EP4 receptors are mainly involved in the immunosuppressive effect of PGE2 in vitro. In the present study we examined the in vivo immunosuppressive effects of selective EP receptor agonists using a high-responder rat skin transplantation model.

MATERIALS AND METHODS

Skin allografts from ACI donors were transplanted onto LEW recipients. Agents were injected everyday between day 0 and day 5 after skin transplantation at the dose of 300 microg/kg subcutaneously. Survival of the skin allograft, histological changes and changes of the intragraft cytokine expressions were analyzed using the reverse transcription polymerase chain reaction (RT-PCR). We also assessed the mixed lymphocyte reaction (MLR) assay using splenocytes.

RESULTS

PGE2 significantly prolonged allograft survival (18.8+/-1.5 days) compared with untreated control (14.8+/-0.8 days). EP2R+EP3R+EP4R agonists also prolonged allograft survival (18.0+/-1.0 days) although EP3R agonist or EP2R+EP4R agonists alone failed (15.5+/-0.7, 15.4+/-1.3 days, respectively). RT-PCR analysis in the skin grafts demonstrated IL-10 up-regulation and IFN-gamma down-regulation in all groups except untreated control and EP2R agonist-treated groups. MLR was significantly reduced in groups of EP2R+EP4R agonists, EP2R+EP3R+EP4R agonists and PGE2, compared with untreated control.

CONCLUSIONS

The effect of PGE2 to prolong the survival of skin transplant requires the action of a combination of three receptors, i.e., EP2+EP3+EP4.

Differential effect of prostaglandins E1 and E2 on lipopolysaccharide-induced adhesion molecule expression on human monocytes

The effect of prostaglandins E1 and E2 on the 1 ng/ml lipopolysaccharide-induced expression of intercellular adhesion molecule (ICAM)-1, B7.1, B7.2, CD40 and CD40 ligand (CD40L) on monocytes was examined. Prostaglandin E1 suppressed B7.1 and CD40 expression, but prostaglandin E2 did not effect on any type of adhesion molecule expression. Both prostaglandins inhibited tumor necrosis factor (TNF)-alpha production and T-cell proliferation of lipopolysaccharide-treated human peripheral blood mononuclear cells (PBMC). Among prostaglandin E1 receptors (IP/EP1/EP2/EP3/EP4) agonists, ONO-1301, a prostanoid IP-receptor agonist, prevented B7.1 and CD40 expression. ONO-AE1-259-01 a prostanoid EP2-receptor agonist, ONO-AE1-329, a prostanoid EP4-receptor agonist, and ONO-1301 inhibited TNF-alpha production and T-cell proliferation. Moreover, anti-B7.1 and anti-CD40 Abs prevented lipopolysaccharide-induced TNF-alpha production and T-cell proliferation. Therefore, the effect of prostaglandin E1 on TNF-alpha production and T-cell proliferation might depend on the inhibition of B7.1 and CD40 expression, but that of prostaglandin E2 might be independent of adhesion molecules expression. In conclusion, the mechanism responsible for the effect of prostaglandin E1 on lipopolysaccharide-induced responses is distinct from that of prostaglandin E2.

Effect of Antibodies Against Intercellular Adhesion Molecule-1, B7, and CD40 on Interleukin-18-Treated Human Mixed Lymphocyte Reaction

The interleukin (IL)-18 level in plasma is elevated during the acute rejection after organ transplantation. IL-18 elicits adhesion molecule expression as well as interferon-gamma/IL-12 production and T-cell proliferation in the human mixed lymphocyte reaction, an in vitro model of acute rejection. We examined whether antibodies (Abs) against intercellular adhesion molecule (ICAM)-1, B7, CD40, and CD40, ligand (CD40L) affect the cytokine production and T-cell proliferation. Anti-ICAM-1 and B7 Abs suppressed the cytokine production, while all Abs inhibited T-cell proliferation. ICAM-1 and B7 as well as CD40 may play different roles in the acute rejection.

Differential effect of LFA703, pravastatin, and fluvastatin on production of IL-18 and expression of ICAM-1 and CD40 in human monocytes

A novel, proinflammatory cytokine, interleukin (IL)-18 production was detected in the medium of human monocytes treated with 3-hydroxy-3-methylglutaryl coenzyme-A (HMG-CoA) reductase inhibitors, pravastatin, and fluvastatin (0.1 and 1 muM) but not with the statin-derived lymphocyte function-associated antigen-1 (LFA-1) inhibitor LFA703, which did not inhibit HMG-CoA reductase. Pravastatin and fluvastatin also induced the production of IL-18, tumor necrosis factor alpha (TNF-alpha) and interferon-gamma (IFN-gamma) in human peripheral blood mononuclear cells (PBMC) in contrast to LFA703. IL-18 production by PBMC is located upstream of the cytokine cascade activated by these statins. The IL-18-induced cytokine production was demonstrated to be dependent on adhesion molecule expression on monocytes. In the absence and presence of lower concentrations (0.1 and 1 ng/ml) of IL-18, pravastatin and fluvastatin inhibited the expression of intercellular adhesion molecule (ICAM)-1 and induced the expression of CD40, whereas LFA703 had no effect. In the presence of higher concentrations (5, 10, and 100 ng/ml) of IL-18, pravastatin, fluvastatin, and LFA703 similarly inhibited the expression of ICAM-1 and CD40 as well as the production of IL-12, TNF-alpha, and IFN-gamma in PBMC. The effects of pravastatin and fluvastatin but not LFA703 were abolished by the addition of mevalonate, indicating the involvement of HMG-CoA reductase in the action of pravastatin and fluvastatin. Thus, the effects of LFA703 were distinct from those of pravastatin and fluvastatin in the presence of lower concentrations of IL-18. It was concluded that LFA703 has the inhibitory effect on an IL-18-initiated immune response without any activation on monocytes.

Mechanism of prostaglandin (PG)E2-induced prolactin expression in human T cells: cooperation of two PGE2 receptor subtypes, E-prostanoid (EP) 3 and EP4, via calcium- and cyclic adenosine 5'-monophosphate-mediated signaling pathways

We previously reported that prolactin gene expression in the T-leukemic cell line Jurkat is stimulated by PGE(2) and that cAMP acts synergistically with Ca(2+) or protein kinase C on the activation of the upstream prolactin promoter. Using the transcription inhibitor actinomycin D, we now show that PGE(2)-induced prolactin expression requires de novo prolactin mRNA synthesis and that PGE(2) does not influence prolactin mRNA stability. Furthermore, PGE(2)-induced prolactin expression was inhibited by protein kinase inhibitor fragment 14-22 and BAPTA-AM, which respectively, inhibit protein kinase A- and Ca(2+)-mediated signaling cascades. Using specific PGE(2) receptor agonists and antagonists, we show that PGE(2) induces prolactin expression through engagement of E-prostanoid (EP) 3 and EP4 receptors. We also found that PGE(2) induces an increase in intracellular cAMP concentration as well as intracellular calcium concentration via EP4 and EP3 receptors, respectively. In transient transfections, 3000 bp flanking the leukocyte prolactin promoter conferred a weak induction of the luciferase reporter gene by PGE(2) and cAMP, whereas cAMP in synergy with ionomycin strongly activated the promoter. Mutation of a C/EBP responsive element at -214 partially abolished the response of the leukocyte prolactin promoter to PGE(2), cAMP, and ionomycin plus cAMP.

EP2/EP4 signalling inhibits monocyte chemoattractant protein-1 production induced by interleukin 1beta in synovial fibroblasts

BACKGROUND

Besides its proinflammatory properties, prostaglandin E(2) (PGE(2)) acts as a regulator of the expression of inducible genes. Inhibition of PGE(2) synthesis might thus result in a paradoxical deleterious effect on inflammation.

OBJECTIVE

To examine the effect of PGE(2) on monocyte chemoattractant protein-1 (MCP-1) expression in cultured synovial fibroblasts (SF) stimulated with interleukin (IL)1beta.

METHODS

MCP-1 expression was assessed in SF stimulated with IL1beta in the presence of PGE(2) or different NSAIDs by RT-PCR or northern blot and immunocytochemistry. Expression of cyclo-oxygenase (COX) isoforms was studied by western blot techniques. The role of PGE(2) receptors (EP) in PGE(2) action was assessed employing EP receptor subtype-specific agonists.

RESULTS

PGE(2) significantly inhibited IL1beta induced MCP-1 expression in SF in a dose dependent manner. IL1beta increased COX-2 and did not alter COX-1 synthesis in SF. 11-Deoxy-PGE(1), an EP(2)/EP(4) agonist, reproduced PGE(2) action on MCP-1 expression. Butaprost, a selective EP(2) agonist, was less potent than PGE(2). Sulprostone, an EP(1)/EP(3) agonist, had no effect on IL1beta induced MCP-1 expression. Inhibition of endogenous PGE(2) synthesis by NSAIDs further enhanced MCP-1 mRNA expression in IL1beta stimulated SF, an effect prevented by addition of exogenous PGE(2).

CONCLUSION

Activation of EP(2)/EP(4) receptors down regulates the expression of MCP-1 in IL1beta stimulated SF, while PGE(2) pharmacological inhibition cuts off this signalling pathway and results in a superinduction of MCP-1 expression. The data suggest that NSAIDs may intercept a natural regulatory circuit controlling the magnitude of inflammation, which questions their continuous administration in inflammatory joint diseases.

Increased circulating levels and salivary gland expression of interleukin-18 in patients with Sjögren's syndrome: relationship with autoantibody production and lymphoid organization of the periductal inflammatory infiltrate

IL-18, an immunoregulatory and proinflammatory cytokine, has been shown to play an important pathogenic role in Th1-driven autoimmune disorders. In this study, we evaluated the circulating levels and salivary-gland expression of IL-18 in patients with Sjögren's syndrome (SS), a mainly Th1-mediated disease. IL-18 serum levels were measured by ELISA in 37 patients with primary SS, 42 with rheumatoid arthritis, and 21 normal controls. We demonstrated high IL-18 serum levels in SS, similar to those in rheumatoid arthritis patients and significantly higher than in controls (P < 0.01). In addition, IL-18 serum concentrations were significantly higher in anti-SSA/Ro+ and anti-SSB/La+ than in anti-SSA/Ro- and anti-SSB/La- SS patients (respectively, P = 0.01, P < 0.01). Serum IL-18 correlated strongly with anti-SSA/Ro (P = 0.004) and anti-SSB/La (P = 0.01) titers. Salivary gland IL-18 expression was investigated by single/double immunohistochemistry in 13 patients with primary SS and in 10 with chronic sialoadenitis, used as controls. The expression of IL-18 was also examined in periductal inflammatory foci in relation to the acquisition of features of secondary lymphoid organs such as T-B compartmentalization, formation of follicular dendritic cell networks, and presence of germinal-center-like structures. IL-18 expression in SS salivary glands was detected in 28 of 32 periductal foci of mononuclear cells (87.5%), while no IL-18 production by infiltrating cells was detected in patients with chronic sialoadenitis. Within the inflammatory foci, IL-18 immunoreactivity co-localized almost exclusively with CD68+ macrophages. In addition, IL-18 was found in 15 of 19 foci (78.9%) with no evidence of T-B cell compartmentalization (nonsegregated) but in 100% of the segregated aggregates, both in T- and B-cell-rich areas. Strikingly, IL-18 was strongly expressed by CD68+ tingible body macrophages in germinal-centre-like structures both in SS salivary glands and in normal lymph nodes. IL-18 expression was observed in the ducts of all SS biopsies but in only 4 of 10 patients with nonspecific chronic sialoadenitis (P < 0.01). This study provides the first evidence of increased circulating levels and salivary gland expression of IL-18 in SS, suggesting an important contribution of this cytokine to the modulation of immune inflammatory pathways in this condition.

Prostaglandin E2Inhibits Alveolar Macrophage Phagocytosis through an E-Prostanoid 2 Receptor-Mediated Increase in Intracellular Cyclic AMP

Prostaglandin E(2) is a potent lipid mediator of inflammation that effects changes in cell functions through ligation of four distinct G protein-coupled receptors (E-prostanoid (EP)1, EP2, EP3, and EP4). During pneumonia, PGE(2) production is enhanced. In the present study, we sought to assess the effect of endogenously produced and exogenously added PGE(2) on FcRgamma-mediated phagocytosis of bacterial pathogens by alveolar macrophages (AMs), which are critical participants in lung innate immunity. We also sought to characterize the EP receptor signaling pathways responsible for these effects. PGE(2) (1-1000 nM) dose-dependently suppressed the phagocytosis by rat AMs of IgG-opsonized erythrocytes, immune serum-opsonized Klebsiella pneumoniae, and IgG-opsonized Escherichia coli. Conversely, phagocytosis was stimulated by pretreatment with the cyclooxygenase inhibitor indomethacin. PGE(2) suppression of phagocytosis was associated with enhanced intracellular cAMP production. Experiments using both forskolin (adenylate cyclase activator) and rolipram (phosphodiesterase IV inhibitor) confirmed the inhibitory effect of cAMP stimulation. Immunoblot analysis of rat AMs identified expression of only EP2 and EP3 receptors. The selective EP2 agonist butaprost, but neither the EP1/EP3 agonist sulprostone nor the EP4-selective agonist ONO-AE1-329, mimicked the effects of PGE(2) on phagocytosis and cAMP stimulation. Additionally, the EP2 antagonist AH-6809 abrogated the inhibitory effects of both PGE(2) and butaprost. We confirmed the specificity of our results by showing that AMs from EP2-deficient mice were resistant to the inhibitory effects of PGE(2). Our data support a negative regulatory role for PGE(2) on the antimicrobial activity of AMs, which has important implications for future efforts to prevent and treat bacterial pneumonia.

E-prostanoid (EP)2/EP4 receptor-dependent maturation of human monocyte-derived dendritic cells and induction of helper T2 polarization

Prostaglandin (PG) E(2) induces dendritic cell maturation in cooperation with proinflammatory cytokines [such as tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta]. To clarify the involvement of E-prostanoid (EP) receptors in the effect of prostaglandin E(2) on human monocyte-derived dendritic cell (MoDC) maturation, we examined the effect of four types of EP receptor-selective agonists on MoDC maturation. PGE(2) as well as 11,15-O-dimethyl prostaglandin (E(2)ONO-AE1-259-01) (EP2 receptor agonist) and ONO-AE1-329 (EP4 receptor agonist) concentration dependently enhanced the expression of CD80, CD86, CD83, and HLA-DR on MoDCs during maturation, especially in the presence of TNF-alpha, whereas 17S-2,5-ethano-6-oxo-17,20-dimethyl prostaglandin E(1) (EP1 receptor agonist) and 16S-9-deoxy-9beta-chloro-15-deoxy-16-hyfroxy-17,17-trimethylene-19,20-didehydro prostaglandin F(2) (EP3 receptor agonist) showed no effect. The maximal effect of ONO-AE1-259-01 was higher than that of ONO-AE1-329; however, the stimulation with ONO-AE1-259-01 was less effective than that with PGE(2). Simultaneous stimulation with both EP receptor agonists produced additive effects and 11-deoxy-PGE(1) (EP2/EP4 receptor mixed agonist) mimicked the effects of PGE(2). Dibutyryl cAMP mimicked the effects of PGE(2), indicating the mediation of PGE(2) action by cAMP. Matured MoDCs induced by PGE(2) or EP2 and/or EP4 receptor agonists showed a decrease in lipopolysaccharide (LPS)-stimulated IL-12p70, IL-6, and IL-10 production. The coculture of naive T cells with matured MoDCs induced under different conditions showed that EP2/EP4-stimulated MoDCs preferentially induced alloresponsive helper T (Th)2 cells. Together, it was concluded that the cooperative stimulation of EP2 and EP4 receptor subtypes by PGE(2) promoted MoDC maturation and inhibited LPS-induced cytokine production in MoDCs. The matured MoDCs under such conditions preferably induced Th2 polarization, indicating the importance of EP2 and EP4 receptors in the determination of Th1/Th2 development of naive T cells.

β2-Adrenergic receptor agonist induces IL-18 production without IL-12 production

Endogenous catecholamine, epinephrine and norepinephrine, and isoproterenol concentration-dependently induced the production of interleukin (IL)-18, tumor necrosis factor (TNF)-alpha and interferon (IFN)-gamma, and inhibited that of IL-10 in human peripheral blood mononuclear cells (PBMC). All responses by these stimulations were antagonized by the selective beta 2-adrenergic receptor (AR) antagonist, butoxamine, but not by alpha 1-, alpha 2- and beta 1-AR antagonists. The selective beta 2-AR agonists, salbutamol and terbutaline, induced a similar pattern of cytokine production, indicating that the effect of these AR agonists on cytokine production was through beta 2-AR stimulation. Anti-IL-18 Ab or caspase-1 inhibitor prevented all increase/decrease effects, suggesting that IL-18 might affect the production of all other cytokines. While endogenous IL-18 produced by salbutamol and terbutaline reached a sufficient concentration to induce IL-12 production, these beta 2-AR agonists did not induce the production of IL-12 at all. Epinephrine/norepinephrine/isoproterenol/beta 2-AR agonists increased the production of IL-18 in monocytes, but had no effect on IL-12, TNF-alpha, IFN-gamma and IL-10 production. The lack of beta 2-AR-induced effect on IL-12 production was due to a beta 2-AR-induced inhibition of an IL-18-elicited upregulation of both CD40 and CD40 ligand (CD40L/CD154) expressions on monocytes. The sympathetic innervating lymphoid organs may be under the control of beta2-AR stimulation, maintaining the basal cytokine environment in the tissues.

Identification in human airways smooth muscle cells of the prostanoid receptor and signalling pathway through which PGE2 inhibits the release of GM-CSF

1. The prostanoid receptor(s) on human airways smooth muscle (HASM) cells that mediates the inhibitory effect of PGE(2) on interleukin (IL)-1 beta-induced granulocyte/macrophage colony-stimulating factor (GM-CSF) release has been classified. 2. IL-1 beta evoked the release of GM-CSF from HASM cells, which was suppressed by PGE(2), 16,16-dimethyl PGE(2) (nonselective), misoprostol (EP(2)/EP(3)-selective), ONO-AE1-259 and butaprost (both EP(2)-selective) with pIC(50) values of 8.61, 7.13, 5.64, 8.79 and 5.43, respectively. EP-receptor agonists that have selectivity for the EP(1)-(17-phenyl-omega-trinor PGE(2)) and EP(3)-receptor (sulprostone) subtypes as well as cicaprost (IP-selective), PGD(2), PGF(2 alpha) and U-46619 (TP-selective) were poorly active or inactive at concentrations up to 10 microM. 3. AH 6809, a drug that can be used to selectively block EP(2)-receptors in HASM cells, antagonised the inhibitory effect of PGE(2), 16,16-dimethyl PGE(2) and ONO-AE1-259 with apparent pA(2) values of 5.85, 6.09 and 6.1 respectively. In contrast, the EP(4)-receptor antagonists, AH 23848B and L-161,982, failed to displace to the right the concentration-response curves that described the inhibition of GM-CSF release evoked by PGE(2) and ONO-AE1-259. 4. Inhibition of GM-CSF release by PGE(2) and 8-Br-cAMP was abolished in cells infected with an adenovirus vector encoding an inhibitor protein of cAMP-dependent protein kinase (PKA) but not by H-89, a purported small molecule inhibitor of PKA. 5. We conclude that prostanoid receptors of the EP(2)-subtype mediate the inhibitory effect of PGE(2) on GM-CSF release from HASM cells by recruiting a PKA-dependent pathway. In addition, the data illustrate that caution should be exercised when using H-89 in studies designed to assess the role of PKA in biological processes.