Unique regulation profile of prostaglandin e1 on adhesion molecule expression and cytokine production in human peripheral blood mononuclear cells

Prostaglandin E1 protects cardiomyocytes against hypoxia-reperfusion induced injury via the miR-21-5p/FASLG axis

Background: Prostaglandin-E1 (PGE1) is a potent vasodilator with anti-inflammatory and antiplatelet effects. However, the mechanism by which PGE1 contributes to the amelioration of cardiac injury remains unclear.

Methods: The present study was designed to investigate how PGE1 protects against hypoxia/reoxygenation (H/R)-induced injuries by regulating microRNA-21-5p (miR-21-5p) and fas ligand (FASLG). Rat H9C2 cells and isolated primary cardiomyocytes were cultured under hypoxic conditions for 6 h (6H, hypoxia for 6 h), and reoxygenated for periods of 6 (6R, reoxygenation for 6 h), 12, and 24 h, respectively. Cells from the 6H/6R group were treated with various doses of PGE1; after which, their levels of viability and apoptosis were detected.

Results: The 6H/6R treatment regimen induced the maximum level of H9C2 cell apoptosis, which was accompanied by the highest levels of Bcl-2-associated X protein (Bax) and cleaved-caspase-3 expression and the lowest level of B-cell lymphoma 2 (Bcl-2) expression. Treatment with PGE1 significantly diminished the cell cytotoxicity and apoptosis induced by the 6H/6R regimen, and also decreased expression of IL-2, IL-6, P-p65, TNF-α, and cleaved-caspase-3. In addition, we proved that PGE1 up-regulated miR-21-5p expression in rat cardiomyocytes exposed to conditions that produce H/R injury. FASLG was a direct target of miR-21-5p, and PGE1 reduced the ability of H/R-injured rat cardiomyocytes to undergo apoptosis by affecting the miR-21-5p/FASLG axis. In addition, we proved that PGE1 could protect primary cardiomyocytes against H/R-induced injuries.

Conclusions: These results indicate that PGE1 exerts cardioprotective effects in H9C2 cells during H/R by regulating the miR-21-5p/FASLG axis.

Brief Story on Prostaglandins, Inhibitors of their Synthesis, Hematopoiesis, and Acute Radiation Syndrome

Prostaglandins and inhibitors of their synthesis (cyclooxygenase (COX) inhibitors, non-steroidal anti-inflammatory drugs) were shown to play a significant role in the regulation of hematopoiesis. Partly due to their hematopoiesis-modulating effects, both prostaglandins and COX inhibitors were reported to act positively in radiation-exposed mammalian organisms at various pre- and post-irradiation therapeutical settings. Experimental efforts were targeted at finding pharmacological procedures leading to optimization of therapeutical outcomes by minimizing undesirable side effects of the treatments. Progress in these efforts was obtained after discovery of selective inhibitors of inducible selective cyclooxygenase-2 (COX-2) inhibitors. Recent studies have been able to suggest the possibility to find combined therapeutical approaches utilizing joint administration of prostaglandins and inhibitors of their synthesis at optimized timing and dosing of the drugs which could be incorporated into the therapy of patients with acute radiation syndrome.

A sustained-release drug-delivery system of synthetic prostacyclin agonist, ONO-1301SR: a new reagent to enhance cardiac tissue salvage and/or regeneration in the damaged heart

Cardiac failure is a major cause of mortality and morbidity worldwide, since the standard treatment for cardiac failure in the clinical practice is chiefly to focus on removal of insults against the heart or minimisation of additional factors to exacerbate cardiac failure, but not on regeneration of the damaged cardiac tissue. A synthetic prostacyclin agonist, ONO-1301, has been developed as a long-acting drug for acute and chronic pathologies related to regional ischaemia, inflammation and/or interstitial fibrosis by pre-clinical studies. In addition, poly-lactic co-glycolic acid-polymerised form of ONO-1301, ONO-1301SR, was generated to achieve a further sustained release of this drug into the targeted region. This unique reagent has been shown to act on fibroblasts, vascular smooth muscle cells and endothelial cells in the tissue via the prostaglandin IP receptor to exert paracrinal release of multiple protective factors, such as hepatocyte growth factor, vascular endothelial growth factor or stromal cell-derived factor-1, into the adjacent damaged tissue, which is salvaged and/or regenerated as a result. Our laboratory developed a new surgical approach to treat acute and chronic cardiac failure using a variety of animal models, in which ONO-1301SR is directly placed over the cardiac surface to maximise the therapeutic effects and minimise the systemic complications. This review summarises basic and pre-clinical information of ONO-1301 and ONO-1301SR as a new reagent to enhance tissue salvage and/or regeneration, with a particular focus on the therapeutic effects on acute and chronic cardiac failure and underlying mechanisms, to explore a potential in launching the clinical study.

Cutaneous vascular and sweating responses to intradermal administration of prostaglandin E1 and E2 in young and older adults: a role for nitric oxide?

Cyclooxygenase (COX) contributes to cutaneous vasodilation and sweating responses; however, the mechanisms underpinning these responses remain unknown. We hypothesized that prostaglandin E1 (PGE1) and E2 (PGE2) (COX-derived vasodilator products) directly mediate cutaneous vasodilation and sweating through nitric oxide synthase (NOS)-dependent mechanisms in young adults. Furthermore, we hypothesized that this response is diminished in older adults, since aging attenuates COX-dependent cutaneous vasodilation and sweating. In 9 young (22 ± 5 yr) and 10 older (61 ± 6 yr) adults, cutaneous vascular conductance (CVC) and sweat rate were evaluated at four intradermal forearm skin sites receiving incremental doses (0.05, 0.5, 5, 50, 500 μM each for 25 min) of PGE1 or PGE2 with and without coadministration of 10 mM N(ω)-nitro-l-arginine, a nonspecific NOS inhibitor. N(ω)-nitro-l-arginine attenuated PGE1-mediated increases in CVC at all concentrations in young adults, whereas it reduced PGE2-mediated increases in CVC at lower concentrations (0.05-0.5 μM) in older adults (all P < 0.05). However, the magnitude of the PGE1- and PGE2-mediated increases in CVC did not differ between groups (all P > 0.05). Neither PGE1 nor PGE2 increased sweat rate at any of the administered concentrations for either the young or older adults (all P > 0.05). We show that although cutaneous vascular responsiveness to PGE1 and PGE2 is similar between young and older adults, the cutaneous vasodilator response is partially mediated through NOS albeit via low-to-high concentrations of PGE1 in young adults and low concentrations of PGE2 in older adults, respectively. We also show that in both young and older adults, PGE1 and PGE2 do not increase sweat rate under normothermic conditions.

Misoprostol modulates cytokine expression through a cAMP pathway: Potential therapeutic implication for liver disease

Dysregulated cytokine metabolism plays a critical role in the pathogenesis of many forms of liver disease, including alcoholic and non-alcoholic liver disease. In this study we examined the efficacy of Misoprostol in modulating LPS-inducible TNFα and IL-10 expression in healthy human subjects and evaluated molecular mechanisms for Misoprostol modulation of cytokines in vitro. Healthy subjects were given 14day courses of Misoprostol at doses of 100, 200, and 300μg four times a day, in random order. Baseline and LPS-inducible cytokine levels were examined ex vivo in whole blood at the beginning and the end of the study. Additionally, in vitro studies were performed using primary human PBMCs and the murine macrophage cell line, RAW 264.7, to investigate underlying mechanisms of misoprostol on cytokine production. Administration of Misoprostol reduced LPS inducible TNF production by 29%, while increasing IL-10 production by 79% in human subjects with no significant dose effect on ex vivo cytokine activity; In vitro, the effect of Misoprostol was largely mediated by increased cAMP levels and consequent changes in CRE and NFκB activity, which are critical for regulating IL-10 and TNF expression. Additionally, chromatin immunoprecipitation (ChIP) studies demonstrated that Misoprostol treatment led to changes in transcription factor and RNA Polymerase II binding, resulting in changes in mRNA levels. In summary, Misoprostol was effective at beneficially modulating TNF and IL-10 levels both in vivo and in vitro; these studies suggest a potential rationale for Misoprostol use in ALD, NASH and other liver diseases where inflammation plays an etiologic role.

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.

Prostaglandin E₂-induced intercellular adhesion molecule-1 expression is mediated by cAMP/Epac signalling modules in bEnd.3 brain endothelial cells

BACKGROUND AND PURPOSE

Prostaglandin E₂ (PGE₂) has been implicated in the regulation of adhesion molecules, leukocyte adhesion and infiltration into inflamed site. However, the underlying mechanism therein involved remains ill-defined. In this study, we explored its cellular mechanism of action in the regulation of the intercellular adhesion molecule-1 (ICAM-1) expression in the brain endothelial cells.

EXPERIMENTAL APPROACH

bEnd.3 cells, the murine cerebrovascular endothelial cell line and primary mouse brain endothelial cells were treated with PGE₂ with or without agonists/antagonists of PGE₂ receptors and associated signalling molecules. ICAM-1 expression, Akt phosphorylation and activity of NF-κB were determined by reverse transcription polymerase chain reaction (RT-PCR), immunoblot analysis, luciferase assay and immunocytochemistry.

KEY RESULTS

PGE₂ significantly up-regulated the expression of ICAM-1, which was blocked by EP4 antagonist (ONO-AE2-227) and knock-down of EP4. PGE₂ effects were mimicked by forskolin, dibutyryl cAMP (dbcAMP) and an exchange protein directly activated by cAMP (Epac) activator (8-Cpt-cAMP) but not a protein kinase A activator (N⁶-Bnz-cAMP). PGE₂-induced ICAM-1 expression was reduced by knock-down of Epac1. A PI3K specific inhibitor (LY294002), Akt inhibitor VIII (Akti) and NF-κB inhibitors (Bay-11-7082 and MG-132) attenuated the induction of ICAM-1 by PGE₂. PGE₂, dbcAMP and 8-Cpt-cAMP induced the phosphorylation of Akt, IκB kinase and IκBα and the translocation of p65 to the nucleus and increased NF-κB dependent reporter gene activity, which was diminished by Akti.

CONCLUSION AND IMPLICATIONS

Our findings suggest that PGE₂ induces ICAM-1 expression via EP4 receptor and Epac/Akt/NF-κB signalling pathway in bEnd.3 brain endothelial cells, supporting its pathophysiological role in brain inflammation.

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.

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.

Stimulatory action of cyclooxygenase inhibitors on hematopoiesis: a review

The presented review summarizes experimental data obtained with a mouse model when investigating the relationship between inhibition of prostaglandin production and hematopoiesis. While prostaglandin E2 acts in a negative feedback control of myelopoiesis, inhibition of cyclooxygenases, responsible for its production, shifts the feedback to positive control. Based on these relationships, agents inhibiting cyclo-oxygenases, known as non-steroidal anti-inflammatory drugs (NSAIDs), can activate hematopoiesis and be protective or curative under myelosuppressive states. The effectiveness of therapeutic use of NSAIDs in these situations is expressive especially under the selective inhibition of cyclooxygenase-2 (COX-2), when undesirable side effects of cyclooxygenase-1 inhibition, like gastrointestinal damage, are absent. The effects of the clinically approved selective COX-2 inhibitor, meloxicam, were investigated and demonstrated significant hematopoiesis-stimulating and survival-enhancing actions of this drug in sublethally or lethally γ-irradiated mice. These effects were connected with the ability of meloxicam to increase serum levels of the granulocyte colony-stimulating factor. It can be inferred from these findings that selective COX-2 inhibitors might find their use in the treatment of myelosuppressions of various etiologies.

Ciprofloxacin inhibits advanced glycation end products-induced adhesion molecule expression on human monocytes

BACKGROUND AND PURPOSE Advanced glycation end products (AGEs) subtypes, proteins or lipids that become glycated after exposure to sugars, can induce complications in diabetes. Among the various AGE subtypes, glyceraldehyde-derived AGE (AGE-2) and glycolaldehyde-derived AGE (AGE-3) are involved in inflammation in diabetic patients; monocytes are activated by these AGEs. Ciprofloxacin (CIP), a fluorinated 4-quinolone, is often used clinically to treat infections associated with diabetis due to its antibacterial properties. It also modulates immune responses in human peripheral blood mononuclear cells (PBMC) therefore we investigated the involvement of AGEs in these effects. EXPERIMENTAL APPROACH Expression of intercellular adhesion molecule (ICAM)-1, B7.1, B7.2 and CD40 was examined by flow cytometry. The production of tumour necrosis factor (TNF)-alpha, interferon (IFN)-gamma, prostaglandin E(2) (PGE(2)) and cAMP were determined by enzyme-linked immunosorbent assay. Cyclooxygenase (COX)-2 expression was determined by Western blot analysis. Lymphocyte proliferation was determined by [(3)H]-thymidine uptake. KEY RESULTS CIP induced PGE(2) production in monocytes, irrespective of the presence of AGE-2 and AGE-3, by enhancing COX-2 expression; this led to an elevation of intracellular cAMP in monocytes. Non-selective and selective COX-2 inhibitors, indomethacin and NS398, inhibited CIP-induced PGE(2) and cAMP production. In addition, CIP inhibited AGE-2- and AGE-3-induced expressions of ICAM-1, B7.1, B7.2 and CD40 in monocytes, the production of TNF-alpha and IFN-gamma and lymphocyte proliferation in PBMC. Indomethacin, NS398 and a protein kinase A inhibitor, H89, inhibited the actions of CIP. CONCLUSIONS AND IMPLICATIONS CIP exerts immunomodulatory activity via PGE(2), implying therapeutic potential of CIP for the treatment of AGE-2- and AGE-3-induced inflammatory responses.

Effect of nicotine on advanced glycation end product-induced immune response in human monocytes

The up-regulation of adhesion molecule expressions on monocytes enhances cell-to-cell interactions with T cells, leading to cytokine production. Advanced glycation end products (AGEs) are modifications of proteins/lipids that become nonenzymatically glycated after contact with aldose sugars. Among various subtypes of AGEs, glyceraldehyde-derived AGE (AGE-2) and glycolaldehyde-derived AGE (AGE-3) induce the expressions of intercellular adhesion molecule-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. Nicotine is reported to inhibit the activation of monocytes via nicotinic acetylcholine receptor alpha7 subunit (alpha7-nAChR). In the present study, we found that nicotine inhibited the actions of AGE-2 and AGE-3. A nonselective and selective alpha7-nAChR antagonist, mecamylamine and alpha-bungarotoxin, reversed the inhibitory effects of nicotine, suggesting the involvement of alpha7-nAChR stimulation. Nicotine induced the expression of cyclooxygenase-2, prostaglandin E(2) (PGE(2)), and cAMP in the presence and absence of AGE-2 and AGE-3. PGE(2) is known to activate the EP(2)/EP(4) receptor, increasing the cAMP level and protein kinase A (PKA) activity. The actions of nicotine were reversed in part by an EP(2)-receptor antagonist, AH6809, an EP(4)-receptor antagonist, AH23848, and a PKA inhibitor, N-[2-(p-bromocinnamyl-amino)ethyl]-5-isoquinolinesulfonamide dihydrochloride (H89). These results indicate that the mechanism of action of nicotine may be partially via endogenous PGE(2) production.

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.

Anti-atherosclerotic effects of dihomo-gamma-linolenic acid in ApoE-deficient mice

AIM

Dihomo-gamma-linolenic acid (DGLA) is an n-6 polyunsaturated fatty acid that is mainly metabolized to an anti-inflammatory eicosanoid, prostaglandin (PG) E1, via the cyclooxygenase (COX) pathway. We evaluated the effect of DGLA on atherosclerosis in apoE-deficient mice and studied the mechanism of the anti-atherosclerotic effect.

METHODS

ApoE-deficient mice were fed a normal diet supplemented with 0.5% DGLA or vehicle for 6 months. ApoE-deficient mice were also fed a high-cholesterol diet supplemented with 0.5% DGLA or vehicle for 1 month. To clarify the influence of a COX inhibitor, naproxen, on the anti-atherosclerotic effect of DGLA, age-matched apoE-deficient mice fed a high-cholesterol diet supplemented with 0.5% DGLA were given oral naproxen for 1 month.

RESULTS

In normal diet-fed mice, acetylcholine-induced vascular relaxation was significantly greater in the DGLA group than in the vehicle group. NADPH oxidase subunits, p22phox and gp91phox, intercellular adhesion molecule-1, and vascular cellular adhesion molecule-1 were significantly lower in the DGLA group than in the vehicle group, and DGLA significantly prevented atherosclerosis. In high-cholesterol diet-fed mice, DGLA also significantly prevented atherosclerosis, but the anti-atherosclerotic effect was attenuated by naproxen.

CONCLUSION

DGLA may have an anti-atherosclerotic effect in apoE-deficient mice via PGE1 formation.

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.

Enteral refeeding rapidly restores PN-induced reduction of hepatic mononuclear cell number through recovery of small intestine and portal vein blood flows

BACKGROUND

Absence of enteral nutrition (EN) reduces hepatic mononuclear cell (MNC) numbers and impairs their functions. However, enteral refeeding (ER) for as little as 12 hours following parenteral nutrition (PN) rapidly restores hepatic MNC numbers. We hypothesized that changes in small intestine and portal vein blood flows related to feeding route might be responsible for this phenomenon.

METHODS

In experiment 1, mice (n = 19) were randomized to Chow (n = 5), PN (n = 7) or ER (n = 7) groups. The Chow group was given chow ad libitum with intravenous (IV) saline for 5 days. The PN group was fed parenterally for 5 days, while the ER group was re-fed with chow for 12 hours following 5 days of PN. Then, small intestine and portal vein blood flows were monitored and hepatic MNCs were isolated and counted. In experiment 2, the effects of intravenous administration of prostaglandin E(1) (PGE(1)) on hepatic MNC numbers were examined in fasted mice for 12 hours. Mice (n = 28) were randomized to Control (n = 8), PG0 (n = 10), or PG1 (n = 10) groups. The Control group was fed chow ad libitum with IV saline, while the PG0 and PG1 groups were fasted for 12 hours with infusions, respectively, of saline and PGE(1) at 1 microg/kg/minute. Blood flows and hepatic MNC numbers were examined.

RESULTS

Experiment 1: ER restored PN-induced reductions in small intestine and portal vein blood flows and hepatic MNC number to the levels in the Chow group. Small intestine and portal vein blood flows correlated positively with hepatic MNC number. Experiment 2: Fasting decreased small intestine and portal vein blood flows and hepatic MNC number. However, PGE(1) restored portal vein blood flow to the level of the Control group, and moderately increased hepatic MNC number. There was a positive correlation between portal blood flow and hepatic MNC number.

CONCLUSIONS

Reduced small intestine and portal vein blood flows may contribute to impaired hepatic immunity in the absence of EN. ER quickly restores hepatic MNC number through recovery of blood flow in both the small intestine and the portal vein.

Histamine inhibits advanced glycation end products-induced adhesion molecule expression on human monocytes

Advanced glycation end products (AGEs) are modifications of proteins/lipids that become nonenzymatically glycated after contact with aldose sugars. Among various subtypes of AGEs, glyceraldehyde-derived AGE (AGE-2) and glycolaldehyde-derived AGE (AGE-3) are suggested to play roles in inflammation in diabetic patients. Because the engagement of intercellular adhesion molecule (ICAM)-1, B7.1, B7.2, and CD40 on monocytes with their ligands on T cells plays roles in cytokine production, we examined the effects of AGE-2 and AGE-3 on the expression of adhesion molecules and cytokine production in human peripheral blood mononuclear cells (PBMC) and their modulation by histamine in the present study. AGE-2 and AGE-3 induced the expressions of ICAM-1, B7.1, B7.2, and CD40 on monocytes and the production of interferon-gamma in PBMC. Histamine concentration-dependently inhibited the action of AGE-2 and AGE-3. The effects of histamine were antagonized by an H2 receptor antagonist, famotidine, and mimicked by H2/H4 receptor agonists dimaprit and 4-methylhistamine. Histamine induced cAMP production in the presence and absence of AGE-2 and AGE-3. The effects of histamine were reversed by a protein kinase A (PKA) inhibitor, N-[2-(4-bromocinnamylamino)ethyl]-5-isoquinoline (H89), and mimicked by a dibutyryl cAMP and an adenylate cyclase activator, forskolin. These results as a whole indicated that histamine inhibited the AGE-2- and AGE-3-induced adhesion molecule expression and cytokine production via H2 receptors and the cAMP/PKA pathway.

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.

Adenosine receptors and inflammation

Extracellular adenosine is produced in a coordinated manner from cells following cellular challenge or tissue injury. Once produced, it serves as an autocrine- and paracrine-signaling molecule through its interactions with seven-membrane-spanning G-protein-coupled adenosine receptors. These signaling pathways have widespread physiological and pathophysiological functions. Immune cells express adenosine receptors and respond to adenosine or adenosine agonists in diverse manners. Extensive in vitro and in vivo studies have identified potent anti-inflammatory functions for all of the adenosine receptors on many different inflammatory cells and in various inflammatory disease processes. In addition, specific proinflammatory functions have also been ascribed to adenosine receptor activation. The potent effects of adenosine signaling on the regulation of inflammation suggest that targeting specific adenosine receptor activation or inactivation using selective agonists and antagonists could have important therapeutic implications in numerous diseases. This review is designed to summarize the current status of adenosine receptor signaling in various inflammatory cells and in models of inflammation, with an emphasis on the advancement of adenosine-based therapeutics to treat inflammatory disorders.

Adenosine A2A-receptor stimulation inhibits lipopolysaccharide-induced interleukin-18 production in monocytes

Adenosine inhibited interleukin (IL)-18 production in lipopolysaccharide (LPS)-stimulated monocytes. The action of adenosine was antagonized by an adenosine A2A-receptor (A2AR) antagonist and was mimicked by an A2AR agonist, suggesting that the stimulation of A2AR may be involved in the actions of adenosine. On the other hand, the stimulation of A1R and A3R inhibited the actions of A2AR stimulation, whereas the stimulation of A2BR had no effect on them. Activation of A2AR is known to increase cyclic adenosine monophosphate (cAMP) levels and to activate protein kinase A (PKA). A PKA inhibitor prevented the actions of A2AR stimulation, indicating that the action mechanism of A2AR stimulation may be via the activation of the cAMP/PKA pathway.

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.

Stimulated recovery of perturbed haematopoiesis by inhibition of prostaglandin production — promising therapeutic strategy

Inhibitors of prostaglandin production, designated as classical non-steroidal anti-inflammatory drugs (NSAIDs) and acting on the base of non-selective inhibition of cyclooxygenases, have been found in numerous studies to potentiate recovery of perturbed haematopoiesis by removing the negative feedback control mediated by prostaglandins. However, classical NSAIDs show pronounced undesirable gastrointestinal side effects, which limits the possibility of their utilization for various pathophysiological states including myelosuppression. Specific cyclooxygenase-2 (COX-2) inhibitors, targeted at selective inhibition of this inducible cyclooxygenase isoform and having much better gastrointestinal side effect profile, have been found in recent studies to retain the haematopoiesis-stimulating effects of classical NSAIDs. These results suggest that the indication spectrum of selective COX-2 inhibitors may be extended to the indication of myelosuppression of various etiology. Combining the anti-tumour and haematopoiesis-stimulating activities in a single COX-2 inhibitor may have a positive clinical impact.

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.

Cimetidine Induces Interleukin-18 Production through H2-Agonist Activity in Monocytes

The present study demonstrates a possible mechanism for the improvement of gastrointestinal cancer patients' prognosis by the histamine receptor type 2 (H2R) antagonist cimetidine. This agent, but not the H2R antagonists ranitidine and famotidine, induced the production of an antitumor cytokine, interleukin (IL)-18, by human monocytes and dendritic cells (DC). In fact, ranitidine and famotidine antagonized cimetidine-induced IL-18 production. Cimetidine induced the activation of caspase-1, which is reported to modify immature IL-18 to mature/active IL-18, and the elevation of intracellular cAMP, leading to the activation of protein kinase A (PKA). The PKA inhibitor H89 abolished the IL-18 production induced by cimetidine. Moreover, the effects of cimetidine on IL-18 production were reproduced in peripheral blood mononuclear cells from wild-type mice, but not in those from H2R knockout mice. In conclusion, cimetidine, a partial agonist for H2R, has a pharmacological profile different from ranitidine and famotidine, possibly contributing to its antitumor activity on gastrointestinal cancers.

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.

THE EFFECT OF CIPROFLOXACIN ON CD14 AND TOLL-LIKE RECEPTOR-4 EXPRESSION ON HUMAN MONOCYTES

CD14/toll-like receptor (TLR)-4 complex on monocytes/macrophages can bind lipopolysaccharide (LPS) and transduce the signals intracellularly. An antibacterial drug, ciprofloxacin (CIP), has been reported to modulate the inflammatory and immune responses. In the present study, we examined the effects of CIP on the LPS-induced activation of monocytes isolated from human peripheral blood mononuclear cells (PBMC). CIP suppressed the expression of CD14, TLR-4, intercellular adhesion molecule (ICAM)-1, B7.1, B7.2, and CD40 and the production of tumor necrosis factor (TNF)-alpha induced by LPS in monocytes. CIP induced the production of prostaglandin (PG)E2 and increased intracellular cyclic adenosine monophosphate (cAMP) levels. Cyclooxygenase (COX)-2 inhibitors, NS398 and indomethacin, reversed the effects of CIP on TNF-alpha production and reduced the levels of different surface antigens, whereas a protein kinase A (PKA) inhibitor, H89, did not. Therefore, CIP might regulate the TNF-alpha production induced by LPS by inhibiting the expression of LPS receptor complex, which seems to be mediated by COX-2 but not the cAMP/PKA pathway.

β2-Adrenergic receptor stimulation inhibits LPS-induced IL-18 and IL-12 production in monocytes

We examined the effects of beta2-adrenergic receptor (beta2-AR) agonists on monocyte-derived cytokines, interleukin (IL)-18 and IL-12 production in lipopolysaccharide (LPS)-stimulated monocytes derived from human peripheral blood mononuclear cells (PBMCs), as in vitro model of sepsis. The study found that beta2-AR agonists inhibited IL-18 and IL-12 production in monocytes, and that AR agonist activity was antagonized by the selective beta2-AR antagonist, butoxamine. The selective beta2-AR agonists salbutamol and terbutaline induced a similar inhibitory pattern of IL-18 and IL-12 production. IL-12 production induced by LPS was inhibited by anti-IL-18 Ab, but IL-18 production by LPS was not inhibited by anti-IL-12 Ab, showing that LPS induced IL-18 production without IL-12 production. Therefore, the stimulation of beta2-AR might be beneficial in the treatment of sepsis through inhibiting LPS-elicited IL-18.

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.

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.

Nafamostat Mesilate Induces Production of Interleukin-12 and -18 in Human Peripheral Blood Mononuclear Cells

Little has been reported on the drugs inducing production of monocyte-derived cytokines like interleukin (IL)-18 and IL-12. We found that nafamostat mesilate elicits IL-12, IL-18, tumor necrosis factor-alpha and interferon-gamma production, and the expression of intercellular adhesion molecules-1, B7.1, B7.2, CD40, and CD40 ligand in human peripheral blood mononuclear cells. The cytokine production and adhesion molecule expression were abolished by anti-IL-12 and IL-18 antibodies. Therefore, IL-18 and IL-12 may play roles in the significant and immediate effects of nafamostat mesilate.

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.

Histamine inhibits lipopolysaccharide-induced interleukin (IL)-18 production in human monocytes

Lipopolysaccharide (LPS) is an inducer of interleukin (IL)-18, which in turn plays important roles in immune responses. Previously, we reported that tumor necrosis factor (TNF)-alpha production could be detected in human peripheral blood mononuclear cells (PBMCs) treated with relatively low concentration of LPS (1 ng/ml), but that same concentration of LPS could not induce IL-18 production. In the present study, we found that LPS at relatively high concentrations (10-1000 ng/ml) induced IL-18 production in a concentration-dependent manner both in monocytes isolated from PBMC, and that histamine (10(-7) to 10(-4) M) inhibited IL-18 production induced by LPS. The studies using receptor subtype-selective agonists and antagonists suggested that the effect of histamine was mediated by H2 receptor but not by H1, H3 and H4 receptors. Therefore, the stimulation of H2 receptor might be beneficial in the treatment of sepsis through inhibiting LPS-elicited IL-18.