Elevated interleukin 6 is induced by prostaglandin E2 in a murine model of inflammation: possible role of cyclooxygenase-2

Peripheral lipopolysaccharide administration induces cytokine mRNA expression in the viscera and brain of fever-refractory mice lacking microsomal prostaglandin E synthase-1

We examined the expression of interleukin (IL)-1beta, IL-6 and tumour necrosis factor (TNF) alpha in mice lacking microsomal prostaglandin E synthase-1 (mPGES-1), which neither produce prostaglandin E(2), nor mount a febrile response upon immune challenge. Intraperitoneal lipopolysaccharide (LPS) injection resulted in a strongly induced expression of all three cytokines in the brain and viscera, similar to wild-type animals. Several brain regions additionally showed modest induction of receptors for these cytokines in both genotypes. Telemetric recordings of body temperature showed that the mPGES-1 deficient mice remained afebrile upon LPS challenge, in contrast to the prominent fever displayed by the wild-type mice. These data demonstrate that LPS-induced cytokine expression occurs independently of prostaglandin E(2), and imply that endogenously expressed IL-1beta, IL-6, and TNFalpha are not pyrogenic per se, supporting the role of prostaglandin E(2) as the final and obligatory mediator of LPS-induced fever.

Cholera toxin: A paradigm for multi-functional engagement of cellular mechanisms (Review)

Cholera toxin (Ctx) from Vibrio cholerae and its closely related homologue, heat-labile enterotoxin (Etx) from Escherichia coli have become superb tools for illuminating pathways of cellular trafficking and immune cell function. These bacterial protein toxins should be viewed as conglomerates of highly evolved, multi-functional elements equipped to engage the trafficking and signalling machineries of cells. Ctx and Etx are members of a larger family of A-B toxins of bacterial (and plant) origin that are comprised of structurally and functionally distinct enzymatically active A and receptor-binding B sub-units or domains. Intoxication of mammalian cells by Ctx and Etx involves B pentamer-mediated receptor binding and entry into a vesicular pathway, followed by translocation of the enzymatic A1 domain of the A sub-unit into the target cell cytosol, where covalent modification of intracellular targets leads to activation of adenylate cyclase and a sequence of events culminating in life-threatening diarrhoeal disease. Importantly, Ctx and Etx also have the capacity to induce a wide spectrum of remarkable immunological processes. With respect to the latter, it has been found that these toxins activate signalling pathways that modulate the immune system. This review explores the complexities of the cellular interactions that are engaged by these bacterial protein toxins, and highlights some of the new insights to have recently emerged.

Macrophage secretory phospholipase A2 group X enhances anti-inflammatory responses, promotes lipid accumulation, and contributes to aberrant lung pathology

Secreted phospholipase A2 group X (sPLA(2)-X) is one of the most potent enzymes of the phospholipase A(2) lipolytic enzyme superfamily. Its high catalytic activity toward phosphatidylcholine (PC), the major phospholipid of cell membranes and low-density lipoproteins (LDL), has implicated sPLA(2)-X in chronic inflammatory conditions such as atherogenesis. We studied the role of sPLA(2)-X enzyme activity in vitro and in vivo, by generating sPLA(2)-X-overexpressing macrophages and transgenic macrophage-specific sPLA(2)-X mice. Our results show that sPLA(2)-X expression inhibits macrophage activation and inflammatory responses upon stimulation, characterized by reduced cell adhesion and nitric oxide production, a decrease in tumor necrosis factor (TNF), and an increase in interleukin (IL)-10. These effects were mediated by an increase in IL-6, and enhanced production of prostaglandin E(2) (PGE(2)) and 15-deoxy-Delta12,14-prostaglandin J(2) (PGJ(2)). Moreover, we found that overexpression of active sPLA(2)-X in macrophages strongly increases foam cell formation upon incubation with native LDL but also oxidized LDL (oxLDL), which is mediated by enhanced expression of scavenger receptor CD36. Transgenic sPLA(2)-X mice died neonatally because of severe lung pathology characterized by interstitial pneumonia with massive granulocyte and surfactant-laden macrophage infiltration. We conclude that overexpression of the active sPLA(2)-X enzyme results in enhanced foam cell formation but reduced activation and inflammatory responses in macrophages in vitro. Interestingly, enhanced sPLA(2)-X activity in macrophages in vivo leads to fatal pulmonary defects, suggesting a crucial role for sPLA(2)-X in inflammatory lung disease.

Prostaglandin E2-mediated dysregulation of proinflammatory cytokine production in pristane-induced lupus mice

Systemic lupus erythematosus (SLE) is characterized by inflammatory and dysregulatory immune responses including overactive B cells, overproduction of proinflammatory cytokines, and T cell hyperactivity. PGE(2) modulates a variety of immune processes at sites of inflammation, including production of inflammatory cytokines. However, the role of PGE(2) in dysregulatory inflammatory and immune responses in lupus remains unclear. We investigated whether PGE(2) mediates production of inflammatory cytokines in pristane-induced lupus BALB/c mice. Our results showed that levels of serum and BAL PGE(2) and LPS-stimulated production of PGE(2) by peritoneal macrophages were remarkably increased in pristane-induced lupus mice compared to healthy controls. Exogenous PGE(2) enhanced production of IL-6, IL-10, and NO but decreased TNF-alpha by macrophages and augmented IFN-gamma, IL-6, and IL-10 by splenocytes from pristane-induced lupus mice compared to healthy controls. Exogenous PGE(2) also enhanced production of IFN-gamma, IL-6, and IL-10 by thymocytes from pristane-induced lupus mice. Indomethacin (Indo), a PGE(2) synthesis inhibitor, greatly inhibited LPS-induced production of IL-6 and IL-10 by macrophages from pristane-induced lupus mice, while enhanced TNF-alpha. Indo remarkably inhibited Con A-increased production of IFN-gamma, IL-6, and IL-10 by splenocytes and thymocytes from pristane-induced lupus mice. Therefore, our findings suggest that endogenous PGE(2) may mediate dysregulation of production of proinflammatory cytokines, such as IL-6, IL-10, and IFN-gamma, and NO in pristane-induced lupus mice.

DPPC regulates COX-2 expression in monocytes via phosphorylation of CREB

The major phospholipid in pulmonary surfactant dipalmitoyl phosphatidylcholine (DPPC) has been shown to modulate inflammatory responses. Using human monocytes, this study demonstrates that DPPC significantly increased PGE(2) (P<0.05) production by 2.5-fold when compared to untreated monocyte controls. Mechanistically, this effect was concomitant with an increase in COX-2 expression which was abrogated in the presence of a COX-2 inhibitor. The regulation of COX-2 expression was independent of NF-kappaB activity. Further, DPPC increased the phosphorylation of the cyclic AMP response element binding protein (CREB; an important nuclear transcription factor important in regulating COX-2 expression). In addition, we also show that changing the fatty acid groups of PC (e.g. using l-alpha-phosphatidylcholine beta-arachidonoyl-gamma-palmitoyl (PAPC)) has a profound effect on the regulation of COX-2 expression and CREB activation. This study provides new evidence for the anti-inflammatory activity of DPPC and that this activity is at least in part mediated via CREB activation of COX-2.

Chronic inflammation and oxidative stress in human carcinogenesis

A wide array of chronic inflammatory conditions predispose susceptible cells to neoplastic transformation. In general, the longer the inflammation persists, the higher the risk of cancer. A mutated cell is a sine qua non for carcinogenesis. Inflammatory processes may induce DNA mutations in cells via oxidative/nitrosative stress. This condition occurs when the generation of free radicals and active intermediates in a system exceeds the system's ability to neutralize and eliminate them. Inflammatory cells and cancer cells themselves produce free radicals and soluble mediators such as metabolites of arachidonic acid, cytokines and chemokines, which act by further producing reactive species. These, in turn, strongly recruit inflammatory cells in a vicious circle. Reactive intermediates of oxygen and nitrogen may directly oxidize DNA, or may interfere with mechanisms of DNA repair. These reactive substances may also rapidly react with proteins, carbohydrates and lipids, and the derivative products may induce a high perturbation in the intracellular and intercellular homeostasis, until DNA mutation. The main substances that link inflammation to cancer via oxidative/nitrosative stress are prostaglandins and cytokines. The effectors are represented by an imbalance between pro-oxidant and antioxidant enzyme activities (lipoxygenase, cyclooxygenase and phospholipid hydroperoxide glutathione-peroxidase), hydroperoxides and lipoperoxides, aldehydes and peroxinitrite. This review focalizes some of these intricate events by discussing the relationships occurring among oxidative/nitrosative/metabolic stress, inflammation and cancer.

Expression of a cyclo-oxygenase-2 transgene in murine liver causes hepatitis

BACKGROUND

It has been proved that cyclo-oxygenase-2 (COX-2) is rapidly induced by inflammatory mediators. However, it is not known whether overexpression of COX-2 in the liver is sufficient to promote activation or secretion of inflammatory factors leading to hepatitis.

AIM

To investigate the role forced expression of COX-2 in liver by using inducible COX-2 transgenic (TG) mice.

METHODS

TG mice that overexpress the human COX-2 gene in the liver using the liver-specific transthyretin promoter and non-TG littermates were derived and fed the normal diet for up to 12 months. Hepatic prostaglandin E(2) (PGE(2)) content was determined using enzyme immunoassay, nuclear factor kappaB (NF-kappaB) activation by electrophoretic mobility shift assays, apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labelling and proliferation by Ki-67 immunohistochemistry.

RESULTS

COX-2 TG mice exhibited strongly increased COX-2 and PGE(2), elevated serum alanine aminotransferase level and histological hepatitis. Hepatic COX-2 expression in the TG mice resulted in activation of NF-kappaB and inflammatory cytokine cascade, with a marked expression of the proinflammatory cytokines tumour necrosis factor (TNF)-alpha (9.4-fold), interleukin (IL)-6 (4.4-fold), IL-1beta (3.6-fold), and of the anti-inflammatory cytokine IL-10 (4.4-fold) and chemokine macrophage inflammatory protein-2 (3.2-fold). The inflammatory response of the COX-2 TG mice was associated with infiltration macrophages and lymphocytes, increased cell proliferation and high rates of cell apoptosis. Administration of the COX-2 inhibitor celecoxib in TG mice restored liver histology to normal.

CONCLUSION

Enhanced COX-2 expression in hepatocytes is sufficient to induce hepatitis by activating NF-kappaB, stimulating the secretion of proinflammatory cytokines, recruiting macrophage and altering cell kinetics. Inhibition of COX-2 represents a mechanism-based chemopreventive approach to hepatitis.

Cyclooxygenase-2 expression and its association with increased angiogenesis in human abdominal aortic aneurysms

Although the mechanism whereby non-steroidal anti-inflammatory drugs may reduce abdominal aortic aneurysm (AAA) development is unknown, one potential route is via inhibition of the cyclooxygenase (COX) enzyme. Despite the fact that evidence from animal models suggests a role for the COX-2 isoform in promotion of AAA development, only very limited data exist on COX-2 expression in human AAAs. Semiquantitative immunohistochemistry for COX-2 was performed on a series of formalin-fixed, paraffin-embedded human AAAs (n = 49). Associated clinicopathological data, including the degree of inflammatory cell infiltration and neorevascularization, were obtained. COX-2 protein was detected in 46 of 49 (94%) human AAAs. Expression of COX-2 protein varied widely between AAAs. COX-2 protein localized to cells in the inflammatory infiltrate with a morphology characteristic of macrophages. COX-2 expression increased with the extent of inflammatory cell infiltration (P < 0.001) and with the degree of AAA neorevascularization (P < 0.001). Logistic regression analysis identified neorevascularization (P < 0.001) as the only significant independent predictor of COX-2 positivity in human AAAs. COX-2 protein is present at increased levels in the majority of human AAAs and is expressed by mononuclear cells in the inflammatory cell infiltrate. Promotion of angiogenesis by COX-2 may play a role in AAA development.

AID and Igh switch region-Myc chromosomal translocations

Chromosomal translocations involving Ig heavy chain switch regions and an oncogene, like Myc, represent early initiating events in the development of many B cell malignancies. These translocations are widely believed to result from aberrant class switch recombination (CSR). Recent reports have produced conflicting models for the role of activation-induced cytidine deaminase (AID) in this process. Here, we discuss possible roles of AID, CSR, and somatic hypermutation in generating chromosomal translocations and in tumor progression.

Peptidoglycan-induced IL-6 production in RAW 264.7 macrophages is mediated by cyclooxygenase-2, PGE2/PGE4 receptors, protein kinase A, I kappa B kinase, and NF-kappa B

In this study, we investigated the signaling pathway involved in IL-6 production caused by peptidoglycan (PGN), a cell wall component of the Gram-positive bacterium, Staphylococcus aureus, in RAW 264.7 macrophages. PGN caused concentration- and time-dependent increases in IL-6, PGE(2), and cAMP production. PGN-mediated IL-6 production was inhibited by a nonselective cyclooxygenase (COX) inhibitor (indomethacin), a selective COX-2 inhibitor (NS398), a PGE(2) (EP2) antagonist (AH6809), a PGE(4) (EP4) antagonist (AH23848), and a protein kinase A (PKA) inhibitor (KT5720), but not by a nonselective NO synthase inhibitor (N(G)-nitro-l-arginine methyl ester). Furthermore, PGE(2), an EP2 agonist (butaprost), an EP2/PGE(3) (EP3)/EP4 agonist (misoprostol), and misoprostol in the presence of AH6809 all induced IL-6 production, whereas an EP1/EP3 agonist (sulprostone) did not. PGN caused time-dependent activations of IkappaB kinase alphabeta (IKKdbeta) and p65 phosphorylation at Ser(276), and these effects were inhibited by NS398 and KT5720. Both PGE(2) and 8-bromo-cAMP also caused IKKdbeta kinase alphabeta phosphorylation. PGN resulted in two waves of the formation of NF-kappaB-specific DNA-protein complexes. The first wave of NF-kappaB activation occurred at 10-60 min of treatment, whereas the later wave occurred at 2-12 h of treatment. The PGN-induced increase in kappaB luciferase activity was inhibited by NS398, AH6809, AH23848, KT5720, a protein kinase C inhibitor (Ro31-8220), and a p38 MAPK inhibitor (SB203580). These results suggest that PGN-induced IL-6 production involves COX-2-generated PGE(2), activation of the EP2 and EP4 receptors, cAMP formation, and the activation of PKA, protein kinase C, p38 MAPK, IKKdbeta, kinase alphabeta, p65 phosphorylation, and NF-kappaB. However, PGN-induced NO release is not involved in the signaling pathway of PGN-induced IL-6 production.

Modulation of dendritic cell differentiation and cytokine secretion by the hydatid cyst fluid of Echinococcus granulosus

Chronic infection by Echinococcus granulosus results in establishment of fluid-filled cysts (hydatid cysts) in liver or lungs of infected hosts, which can escape destruction by the host immune system for long periods. This study explores the modulation by hydatid cyst fluid of the in vitro human monocyte to dendritic cell (DC) transition induced by granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4). Addition of the fluid to adherent peripheral blood monocytes cultured in GM-CSF/IL-4 stimulates release of prostaglandin E2 (PGE2) and IL-6. Exposure of differentiating DC to the fluid during the 7-day culture in GM-CSF/IL-4 impairs their subsequent ability to secrete IL-12, IL-6 or PGE2 in response to lipopolysaccharide (LPS) stimulation. This inhibition is not dependent on the initial release of PGE2. The presence of hydatid cyst fluid also modulates the phenotype of the cells generated during culture, resulting in increased CD14 expression and decreased expression of CD1a. Finally, hydatid fluid can stimulate predifferentiated DC to mature, as evidenced by release of IL-12 and IL-6, and by up-regulation of class II major histocompatibility complex and CD86. The possible role of dendritic cell modulation in regulating the host immune response to hydatid cysts is discussed.

Schizophrenia as an inflammation-mediated dysbalance of glutamatergic neurotransmission

This overview tries to bridge the gap between psychoneuroimmunological findings and recent results from pharmacological, neurochemical and genetic studies in schizophrenia. Schizophrenia is a disorder of dopaminergic neurotransmission, but modulation of the dopaminergic system by glutamatergic neurotransmission seems to play a key role. This view is supported by genetic findings of the neuregulin- and dysbindin genes, which have functional impact on the glutamatergic system. Glutamatergic hypofunction, however, is mediated by the N-methyl-D-aspartate (NMDA)-receptor antagonism. The only endogenous NMDA receptor antagonist identified up to now is kynurenic acid (KYNA). Despite the NMDA receptor antagonism, KYNA also blocks, in lower doses, the nicotinergic acetycholine receptor, i.e., increased KYNA levels can explain psychotic symptoms and cognitive deterioration. KYNA levels are described to be higher in the cerebrospinal fluid (CSF) and in critical central nervous system (CNS) regions of schizophrenics as compared to controls. Another line of evidence suggests that a (prenatal) infection is involved in the pathogenesis of schizophrenia. Due to an early sensitization process of the immune system or to a (chronic) infection, which is not cleared through the immune response, an immune imbalance between the type-1 and the type-2 immune responses takes place in schizophrenia. The type-1 response is partially inhibited, while the type-2 response is over-activated. This immune constellation is associated with inhibition of the enzyme indoleamine dioxygenase (IDO), because IDO - located in astrocytes and microglial cells - is inhibited by type-2 cytokines. IDO catalyzes the first step in tryptophan metabolism, the degradation from tryptophan to kynurenine, as does tryptophan 2,3-dioxygenase (TDO). Due to the inhibition of IDO, tryptophan-kynurenine is predominantly metabolized by TDO, which is located in astrocytes, not in microglial or other CNS cells. In schizophrenia, astrocytes in particular are activated, as increased levels of S100B appear. Additionally, they do not have the enzymatic equipment for the normal metabolism-route of tryptophan. Due to the lack of kynurenine hydroxylase (KYN-OHase) in astrocytes, KYNA accumulates in the CNS, while the metabolic pathway in microglial cells is blocked. Accordingly, an increase of TDO activity has been observed in critical CNS regions of schizophrenics. These mechanisms result in an accumulation of KYNA in critical CNS regions. Thus, the immune-mediated glutamatergic-dopaminergic dysregulation may lead to the clinical symptoms of schizophrenia. Therapeutic consequences, e.g., the use of anti-inflammatory cyclo-oxygenase-2 inhibitors, which can also decrease KYNA directly, are discussed.

Cholesterol-induced Apoptotic Macrophages Elicit an Inflammatory Response in Phagocytes, Which Is Partially Attenuated by the Mer Receptor

Macrophage apoptosis and the ability of phagocytes to clear these apoptotic cells are important processes in advanced atherosclerosis. Phagocytic clearance not only disposes of dead cells but usually elicits an anti-inflammatory response. To study this process in a model of advanced lesional macrophage death, macrophages rendered apoptotic by free cholesterol loading (FC-AMs) were incubated briefly with fresh macrophages ("phagocytes"). FC-AMs were promptly ingested by the phagocytes, which was dependent upon actin polymerization and the phagocyte Mer receptor. Surprisingly, this brief exposure to FC-AMs triggered a modest proinflammatory response in the phagocytes: tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-1beta were induced, whereas the levels of transforming growth factor-beta and IL-10 were not increased. This response required cell contact between the FC-AMs and phagocytes but not FC-AM ingestion. TNF-alpha and IL-1beta induction required one or more proteins on the FC-AM surface and was dependent on signaling through extracellular signal-regulated kinase-1/2 mitogen-activated protein kinase and nuclear factor-kappaB in the phagocytes. TNF-alpha production was markedly greater when Mer-defective phagocytes were used, indicating that Mer attenuated the inflammatory response. Interestingly, a more typical anti-inflammatory response was elicited when phagocytes were exposed to macrophages rendered apoptotic by oxidized low density lipoprotein or UV radiation. Thus, the proinflammatory milieu of advanced atherosclerotic lesions may be promoted, or at least not dampened, by contact between FC-induced apoptotic macrophages and neighboring phagocytes prior to apoptotic cell ingestion.

Atorvastatin Reduces the Expression of COX-2 mRNA in Peripheral Blood Monocytes from Patients with Acute Myocardial Infarction and Modulates the Early Inflammatory Response

Background: We examined the effect of atorvastatin on the expression of COX-2 in peripheral blood monocytes from patients with early stage of acute myocardial infarction (AMI), and the plasma C-reactive protein (CRP) concentrations were also examined.

Methods: Patients with AMI (n = 40) and with stable coronary heart disease (CHD; n = 18) were registered, and patients with AMI were randomly separated to a group that received routine therapy (group A, n = 20) or to a group that received routine therapy plus atorvastatin at 20 mg/day (group B, n = 20) for a week. Peripheral blood monocytes from patients with AMI both before and after treatment and from patients with stable CHD were isolated and cultured for 24 h. COX-2 mRNA expression was analyzed by reverse transcription-PCR. We measured concentrations of CRP in plasma by ELISA.

Results: COX-2 expression was activated in peripheral blood monocytes from patients with AMI [0.92 (0.13)] compared with patients with stable CHD [0.19 (0.08)]; after a week of treatment, COX-2 expression in group B (reduced by 66%) was obviously lower than in group A (reduced by 24%; P &lt;0.05). Plasma concentrations of CRP from patients with AMI [43.3 (14.9) mg/L] were increased compared with those from patients with stable CHD [1.65 (0.78) mg/L; P &lt;0.05]; after a week of treatment, CRP concentrations in group B (reduced by 62%) were lower than in group A (reduced by 35%; P &lt;0.05). COX-2 expression in peripheral blood monocytes from patients with AMI was positively correlated with plasma CRP concentration (r = 0.662; P &lt;0.05).

Conclusions: COX-2 may promote acute inflammatory process after AMI. Atorvastatin may improve the antiinflammatory effects through the COX-2 pathway.

A multicenter phase II trial of thalidomide and celecoxib for patients with relapsed and refractory multiple myeloma

Preclinical data indicates that cyclooxygenase-2 (COX-2) inhibition impairs plasma cell growth and potentially synergizes with thalidomide. We performed a trial in previously treated patients with myeloma using thalidomide up to a maximum dose of 800 mg/d with celecoxib (400 mg bid). Outcomes were compared with a prior trial of thalidomide. Sixty-six patients with median age of 67 (range, 43-85) received a median dose of thalidomide and celecoxib of 400 and 800 mg/d, respectively, with median durations of treatment of 27 and 13 weeks, respectively. The most common toxicities associated with premature discontinuation of celecoxib (n = 30 of 53, 57%) were fluid retention and deterioration of renal function. Overall response rate (RR) was 42% and with 20 months median follow-up; the actuarial median progression-free survival and overall survival were 6.8 and 21.4 months, respectively. Unlike our prior study, age >65 years was not predictive of inferior RR due to improvement in RR in older patients with the combination (37% versus 15%, P = 0.08). The RR was superior in patients who received a total dose of celecoxib exceeding 40 g in the first 8 weeks of therapy (62% versus 30%, P = 0.021). Progression-free survival and overall survival were also improved. Other predictors for inferior progression-free survival were age >65 years (P = 0.016) and elevated beta(2)-microglobulin (P = 0.017). This study provides evidence that the addition of high-dose celecoxib adds to the antimyeloma activity of thalidomide but this comes with unacceptable toxicity. Future studies should use newer COX-2 inhibitors with thalidomide, or their respective derivatives.

COX-2 inhibitors as adjunctive therapy in schizophrenia: rationale for use and evidence to date

A better understanding of the human immune system and its complex interactions has resulted in new insights into the pathoaetiological mechanisms of psychiatric disorders. As a result, new treatment options are being explored. Several findings suggest that an imbalanced immune response is involved in the pathophysiology of schizophrenia. COX-2 inhibitors are known to influence the immune system in a way that may redirect this imbalance. Based on these suggestions, the COX-2 inhibitor celecoxib has been tested as a possible adjunctive therapeutic approach in the treatment of schizophrenia. While the first trial using celecoxib as add-on therapy to an atypical antipsychotic showed a significant beneficial effect, recent studies demonstrated that this effect may be limited to patients with recent-onset schizophrenia.

Induction of apoptosis by the hydrocarbon oil pristane: implications for pristane-induced lupus

Intraperitoneal injection of the hydrocarbon oil pristane into normal mice leads to a lupus-like autoimmune syndrome. Although advances in defining the roles of cellular and humoral mediators involved in this syndrome have been made, the mechanisms that initiate a break in tolerance leading to autoimmunity remain unknown. We describe in this study that pristane induces apoptosis both in vivo and in vitro. Pristane arrests cell growth and induces cell death by apoptosis via the mitochondrial pathway of caspase activation in a dose-dependent manner. Nuclear autoantigens created by pristane-induced apoptosis of lymphoid cells within the peritoneal cavity in the setting of a profoundly altered cytokine milieu may be the initiating event in the development of autoimmunity in this syndrome. These findings suggest that apoptosis may be a critical initial event in the pathogenesis of pristane-induced lupus and are of potential relevance for human systemic lupus erythematosus.

Insertion of Myc into Igh accelerates peritoneal plasmacytomas in mice

Gene-targeted mice that contain a His6-tagged mouse c-Myc cDNA, Myc(His), inserted head to head into different sites of the mouse immunoglobulin heavy-chain locus, Igh, mimic the chromosomal T(12;15)(Igh-Myc) translocation that results in the activation of Myc in the great majority of mouse plasmacytomas. Mice carrying Myc(His) just 5' of the intronic heavy-chain enhancer Emu (strain iMyc(Emu)) provide a specific model of the type of T(12;15) found in a subset (approximately 20%) of plasmacytomas that develop "spontaneously" in the gut-associated lymphoid tissue (GALT) of interleukin-6 transgenic BALB/c (C) mice. Here we show that the transfer of the iMyc(Emu) transgene from a mixed genetic background of segregating C57BL/6 x 129/SvJ alleles to the background of C increased the incidence of GALT plasmacytomas by a factor of 2.5 in first-generation backcross mice (C.iMyc(Emu) N1). Third-generation backcross mice (C.iMyc(Emu) N3, approximately 94% C alleles) were hypersusceptible to inflammation-induced peritoneal plasmacytomas (tumor incidence, 100%; mean tumor onset, 86 +/- 28 days) compared with inbred C mice (tumor incidence, 5% on day 150 after tumor induction). Peritoneal plasmacytomas of C.iMyc(Emu) N3 mice overexpressed Myc(His), produced monoclonal immunoglobulin, and exhibited a unique plasma cell signature upon gene expression profiling on mouse Lymphochip cDNA microarrays. These findings indicated that the iMyc(Emu) transgene accelerates plasmacytoma development by collaborating with tumor susceptibility alleles of strain C and circumventing the requirement for tumor precursors to acquire deregulated Myc by chromosomal translocation.

Platelet-activating factor and prostaglandin E2 impair esophageal ACh release in experimental esophagitis

ACh is a neurotransmitter in cat esophageal circular muscle, as atropine nearly abolishes contraction of in vitro circular muscle strips in response to electric field stimulation (EFS) (5, 12). Experimental esophagitis reduced EFS- but not ACh-induced contraction of esophageal circular muscle, suggesting that esophagitis impairs neurotransmitter release. Because IL-1beta and IL-6 are produced in esophagitis and reproduce these changes in normal esophageal muscle (12), we examined the role of IL-1beta and IL-6 in this motor dysfunction. IL-1beta, IL-6 (12), H2O2, PGE2, and platelet-activating factor (PAF) were elevated in esophagitis specimens. Normal muscle incubated (2 h) in IL-1beta and IL-6 had increases in H2O2, PGE2, and PAF levels. H2O2 contributed to increased PGE2 and PAF, as the increase was partially (60-80%) reversed by the H2O2 scavenger catalase. EFS-induced [3H]ACh release from muscle strips significantly (42%) decreased in esophagitis and after 2 h incubation in PGE2 and in PAF C-16. Similarly, EFS-induced but not ACh-induced muscle contraction decreased in esophagitis and after incubation in PGE2 and PAF C-16. Finally, in normal muscle strips treated with IL-1beta electrical field stimulation (EFS)-induced contraction was partially restored by indomethacin or by the PAF antagonist CV3988 and was completely restored by the combination of CV3988 and indomethacin, whereas in strips treated with IL-6, EFS-induced contraction was partially restored by the PAF antagonist CV3988 and not affected by indomethacin. We conclude that IL-1beta-induced production of H2O2 causes formation of PGE2 and PAF that inhibit ACh release from esophageal cholinergic neurons without affecting ACh-induced contraction of esophageal circular muscle. IL-6 causes production of H2O2, PAF, and other unidentified inflammatory mediators.

Enhanced expression of cyclooxygenase-2 and prostaglandin E2 in response to endotoxin after trauma is dependent on MAPK and NF-kappaB mechanisms

Macrophage prostaglandin E2 (PGE2) production is important in cellular immune suppression and in affecting the potential development of sepsis after trauma. We hypothesized that macrophage PGE2 production after trauma is regulated by mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-kappaB). Mice were subjected to trauma and splenic macrophages isolated 7 days later. Macrophages from traumatized mice showed increased cyclooxygenase-2 (COX-2) mRNA, protein expression, and PGE2 production compared with controls. Increased phosphorylation of extracellular signal-regulated kinase (ERK), c-jun N-terminal kinase (JNK), and p38 kinase was observed in macrophages from traumatized mice. Pharmacologic inhibition of MAPK blocked trauma-induced COX-2 expression, and PGE2 production. Trauma macrophages showed increased IkappaBalpha phosphorylation and NF-kappaB binding to DNA. Inhibiting IkappaBalpha blocked trauma-induced NF-kappaB activity, COX-2 expression and PGE2 production. This suggests that trauma-induced PGE2 production is mediated through MAPK and NF-kappaB activation and offers potential for modifying the macrophages' responses following injury.

Resetting of peripheral circadian clock by prostaglandin E2

In mammals, the master circadian pacemaker is located in the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN is thought to drive peripheral oscillators by controlling neuronal and humoral signals that can entrain the peripheral clocks. Here, we show that prostaglandin E2 (PGE2), a proinflammatory compound known to have diverse biological effects, is able to act as an in vivo clock-resetting agent. We find that in cultured NIH3T3 fibroblasts, PGE2 is able to induce transient expression of Period 1 messenger RNA and the following circadian oscillation of clock gene expression. Furthermore, we demonstrate that intraperitoneal administration of PGE2 results in the phase shift of circadian gene expression in mouse peripheral tissues in a time-dependent manner. This phase shift is also induced by the EP1/EP3 agonist sulprostone but not by the EP2 agonist butaprost. The PGE2-induced phase shift is inhibited by the EP1 antagonist SC-51322. These results suggest that PGE2 acts as an in vivo clock-resetting factor by means of the EP1 subtype of PGE receptors.

Inhibition of inflammatory responses by FC-77, a perfluorochemical, in lipopolysaccharide-treated RAW 264.7 macrophages

OBJECTIVE

This study tested whether FC-77, a perfluorochemical, inhibits inflammatory responses in lipopolysaccharide (LPS) stimulated RAW 264.7 macrophages. The possible anti-inflammatory mechanisms involved were also investigated.

METHODS

RAW 264.7 macrophages were simultaneously incubated with pure FC-77 at final volume of 10% or 30% (v/v) and LPS (1 microg/ml) for 12 or 24 h on a mechanical shaker. In some tests FC-77 was added after cells stimulated by LPS for 12 h. Then the levels of prostaglandin E2(PGE2), tumor necrosis factor alpha (TNF-alpha), and interleukins (IL)-1beta, -6), and -10 were measured in medium. Alterations in cyclooxygenase (COX) 2 expression and nuclear transcription factor (NF) kappaB activation in cells were also evaluated.

RESULTS

Pre- or posttreatment with FC-77 dose-dependently reduced the LPS-induced TNF-alpha, IL-1beta, and IL-6 formation and enhanced IL-10 production compared to LPS-stimulated alone cells. FC-77 also attenuated the LPS-induced PGE2 formation accompanied by suppressing COX-2 expression, the degradation of cytosolic inhibitor of kappaB-alpha and NF-kappaB activation.

CONCLUSIONS

FC-77 inhibits inflammatory responses in LPS-stimulated macrophages by a mechanism that involves the attenuation of NF-kappaB dependent induction of COX-2/PGE2 pathway and the pro- /anti-inflammatory cytokine ratio.

Role of cyclooxygenase-2 in deoxynivalenol-induced immunoglobulin a nephropathy

Ingestion of the trichothecene mycotoxin deoxynivalenol (DON) induces serum IgA elevation and kidney mesangial IgA deposition in a manner that mimics the early stages of IgA nephropathy (IgAN), the most common human glomerulonephritis. Previous studies indicate that elevated interleukin-6 (IL-6) expression is crucial for this model and that DON induction of cyclooxygenase-2 (COX-2) might drive IL-6 upregulation. We hypothesized that COX-2 and its metabolites are essential for DON-induced IgAN and thus might be a suitable target for prophylaxis against aberrant IgA upregulation. DON feeding studies using COX-2 knockout mice or the COX-2 specific inhibitor, rofecoxib (Vioxx), were employed to test the hypothesis. Study 1 results demonstrated that DON consumption induced serum IgA and IgA-immune complex (IC) accumulation, IgA kidney deposition and splenic IgA secretion in wild-type mice. COX-2 deficiency did not affect upregulation of these parameters but rather, promoted DON-induced serum IgA elevation. Study 2 demonstrated that rofecoxib could not block DON-induced serum IgA, serum IgA-IC and mesangial IgA accumulation but instead increased enhanced serum IgA upregulation. These corroborating results suggest that COX-2 is not a requisite for DON-induced IgAN and furthermore, that COX-2 inhibitors such as rofecoxib would be contraindicated for the prevention of early stages of IgAN.

Up‐regulation of interleukin‐6 induced by prostaglandin E 2 from invading macrophages following nerve injury: an in vivo and in vitro study

The mechanisms underlying neuropathic pain caused by nerve injury are not well understood. Inflammatory responses in injured nerves are likely to be key contributing factors in the generation and maintenance of neuropathic pain. The pro-inflammatory cytokine interleukin-6 (IL-6) is up-regulated in invading macrophages and has been implicated in the development of neuropathic pain. We previously demonstrated that invading macrophages up-regulate cyclooxygenase 2 (COX2) and prostaglandin E2 (PGE2) receptors EP1 and EP4, suggesting that PGE2 may affect macrophage function via autocrine or paracrine mechanisms. This study was undertaken to determine whether PGE2 is involved in the up-regulation of IL-6 in invading macrophages. Two weeks following partial sciatic nerve ligation, numerous IL-6 immunoreactive (IR) cell profiles were present in injured nerves. Colocalization of IL-6 with the invading macrophage marker ED1 or with COX2 was frequently observed. IL-6-IR, COX2-IR and ED1-IR cells were present only in cultures derived from injured nerve segments. PGE2 and IL-6 release from cultured cells derived from injured nerves was increased significantly compared with uninjured nerves. Non-selective and selective COX2 inhibitors suppressed PGE2 and IL-6 release. Treatment with PGE2 further enhanced IL-6 release in a concentration- and time-dependent manner. A selective EP4 receptor antagonist L-161982 was able to suppress IL-6 release, whereas an EP1 receptor antagonist, SC19220, was ineffective. Moreover, a protein kinase C inhibitor, calphostin C, dramatically suppressed IL-6 release, whereas a protein kinase A inhibitor H-89 and a Ca2+ chelator EGTA failed. Taken together, our data suggest that PGE2 is involved in mediating the up-regulation of IL-6 occurring in invading macrophages. This action is mediated through an EP4 receptor and the protein kinase C signaling pathway.

COX-2 inhibitors as adjunctive therapy in schizophrenia

Cyclooxygenase-2 (COX-2) is constitutively expressed in the central nervous system, and is thought to have an important functional role therein. COX-2 interacts with neurotransmitters such as acetylcholine, 5-hydroxytryptamine and glutamate but is also involved in the regulation of the central nervous system immune system and in inflammation via the effects of prostaglandins, in particular prostaglandin E2. A general therapeutic effect of the COX-2 inhibitor celecoxib on symptoms of schizophrenia was observed during a prospective, randomised, double-blind study of celecoxib add-on treatment to the atypical antipsychotic risperidone. The results from this trial of adjunctive therapy with a COX-2 inhibitor in schizophrenia are encouraging, and the findings support the view that an immunological/inflammatory process is involved in the pathogenesis of the disease. The add-on to an antipsychotic design of the study was chosen due to ethical reasons; in less acute schizophrenic states a monotherapy with COX-2 inhibitors would be interesting. From a theoretical point of view, other psychiatric indications for selective COX-2 inhibitors are discussed. COX-2 inhibitors have failed to show therapeutic effects in Alzheimer's disease but studies from basic research and a clinical perspective suggest it has an effect on disturbed cognition. In depression, however, signs of inflammation have been described for many years. Although results of clinical studies with COX-2 inhibitors in depression are still lacking, clinical improvement of a depressive syndrome has been observed in patients who have been treated with the COX-2 inhibitor rofecoxib due to other indications. These preliminary clinical data are encouraging for clinical therapeutic effects of the selective COX-2 inhibitors in psychiatric disorders, although these effects have to be confirmed in larger clinical studies.

Cyclooxygenases, Thromboxane, and Atherosclerosis

Background— Antagonism or deletion of the receptor (the TP) for the cyclooxygenase (COX) product thromboxane (Tx)A 2 , retards atherogenesis in apolipoprotein E knockout (ApoE KO) mice. Although inhibition or deletion of COX-1 retards atherogenesis in ApoE and LDL receptor (LDLR) KOs, the role of COX-2 in atherogenesis remains controversial. Other products of COX-2, such as prostaglandin (PG) I 2 and PGE 2 , may both promote inflammation and restrain the effects of TxA 2 . Thus, combination with a TP antagonist might reveal an antiinflammatory effect of a COX-2 inhibitor in this disease. We addressed this issue and the role of TxA 2 in the promotion and regression of diffuse, established atherosclerosis in Apobec-1/LDLR double KOs (DKOs).

Methods and Results— TP antagonism with S18886, but not combined inhibition of COX-1 and COX-2 with indomethacin or selective inhibition of COX-2 with Merck Frosst (MF) tricyclic, retards significantly atherogenesis in DKOs. Although indomethacin depressed urinary excretion of major metabolites of both TxA 2 , 2,3-dinor TxB 2 (Tx-M), and PGI 2 , 2,3-dinor 6-keto PGF 1α (PGI-M), only PGI-M was depressed by the COX-2 inhibitor. None of the treatments modified significantly the increase in lipid peroxidation during atherogenesis, reflected by urinary 8,12-iso-iPF 2α -VI. Combination with the COX-2 inhibitor failed to augment the impact of TP antagonism alone on lesion area. Rather, analysis of plaque morphology reflected changes consistent with destabilization of the lesion coincident with augmented formation of TxA 2 . Despite a marked effect on disease progression, TP antagonism failed to induce regression of established atherosclerotic disease in this model.

Conclusions— TP antagonism is more effective than combined inhibition of COX-1 and COX-2 in retarding atherogenesis in Apobec-1/LDLR DKO mice, which perhaps reflects activation of the receptor by multiple ligands during disease initiation and early progression. Despite early intervention, selective inhibition of COX-2, alone or in combination with a TP antagonist, failed to modify disease progression but may undermine plaque stability when combined with the antagonist. TP antagonism failed to induce regression of established atherosclerotic disease. TP ligands, including COX-1 (but not COX-2)–derived TxA 2 , promote initiation and early progression of atherogenesis in Apobec-1/LDLR DKOs but appear unimportant in the maintenance of established disease.

γ-Herpesvirus neoplasia: A growing role for COX-2

Both human gamma-herpesviruses, Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV) induce neoplasia. Burkitt's and Hodgkin's lymphomas harbor EBV sequences, while KSHV has been associated with Kaposi's sarcoma (KS), primary effusion lymphoma (PEL), and multicentric castleman's disease (MCD). Each of these gamma-herpesvirus-associated malignancies displays typical characteristics of neoplasia, such as angiogenesis and cell survival. One enzyme commonly overexpressed in breast, prostate, and colon cancers is cyclooxygenase-2 (COX-2). Recently, COX-2 overexpression has been reported in herpesvirus infections in vitro. This review will outline potential mechanisms by which COX-2 may participate in herpesvirus-induced neoplasia.

ICAM G241A polymorphism and soluble ICAM-1 serum levels: evidence for an active immune process in schizophrenia

OBJECTIVES

We have previously reported reduced serum levels of soluble intercellular adhesion molecule-1 (sICAM-1) in schizophrenic patients. A single-nucleotide polymorphism (SNP) of the ICAM-1 gene was described at position 241. The G-->A SNP results in a nonsynonymous amino acid exchange of the ICAM-1 protein, and the A allele was shown to be also associated with several immunological disorders like rheumatoid arthritis.

METHODS

We investigated 70 schizophrenic patients and 128 unrelated healthy control persons regarding the relationship between the serum levels of sICAM-1 and the ICAM-1 G214A polymorphism.

RESULTS

We were able to replicate our previous finding of reduced sICAM-1 levels in schizophrenia. Healthy control persons carrying the polymorphic A allele showed markedly lower sICAM-1 serum levels than carriers of the homozygous GG wild type (p < 0.004). In contrast, no significant difference in the sICAM-1 serum levels were seen regarding the G241A genotype distribution in schizophrenic patients.

CONCLUSION

We hypothesize that the biochemical effect of the G241A SNP is masked in schizophrenic patients, indicating a disease-related mechanism leading to reduced levels of sICAM-1 in schizophrenia.

Monocyte cyclooxygenase-2 overactivity: a new marker of subclinical atherosclerosis in asymptomatic subjects with cardiovascular risk factors?

AIMS

Cyclooxygenase-2 (COX-2)-mediated prostaglandin production by activated macrophages is associated with inflammation and atherosclerosis. We investigated the relationship between COX-2-mediated prostaglandin-E2 (PGE2) release, cardiovascular risk factors, and carotid atherosclerosis in apparently healthy subjects.

METHODS AND RESULTS

PGE2 release by lipopolysaccharide-stimulated blood monocytes was measured by ELISA in 291 subjects (76.5% men, mean age 58) who underwent global vascular risk assessment and carotid ultrasonography. COX-2 expression (real-time RT-PCR) was analysed in a subgroup of 100 subjects (76% men, mean age 59). Inducible PGE2 production was associated with smoking and diabetes (P<0.05), but not with arterial hypertension, dyslipidaemia, or obesity. Subjects in the highest tertile of PGE2 (>8.1 ng/mL) had significantly higher mean carotid intima-media thickness (IMT) than those in the lowest tertile (P<0.01). No significant differences among tertiles were observed in the levels of inflammatory markers (C-reactive protein, fibrinogen, and von Willebrand factor). The association between PGE2 and carotid IMT remained statistically significant (P=0.012) after adjustment for a number of cardiovascular and inflammatory risk factors. A correlation between COX-2 expression and PGE2 production was observed (P<0.005).

CONCLUSIONS

COX-2-mediated PGE2 overproduction by stimulated monocytes might provide a new marker of subclinical atherosclerosis in asymptomatic subjects exposed to cardiovascular risk factors.

Prostanoids and prostanoid receptors in signal transduction

Prostanoids are arachidonic acid metabolites and are generally accepted to play pivotal functions in amongst others inflammation, platelet aggregation, and vasoconstriction/relaxation. Inhibition of their production with, for instance, aspirin has been used for over a century to combat a large variety of pathophysiological processes, with great clinical success. Hence, the cellular changes induced by prostanoids have been subject to an intensive research effort and especially prostanoid-dependent signal transduction has been extensively studied. In this review, we discuss the impact of the five basic prostanoids, TxA(2), PGF(2alpha), PGE(2), PGI(2), and PGD(2), via their receptors on cellular physiology. These inflammatory lipids may stimulate serpentine plasma membrane-localized receptors, which in turn affect major signaling pathways, such as the MAP kinase pathway and the protein kinase A pathway, finally resulting in altered cellular physiology. In addition, prostanoids may activate the PPARgamma members of the steroid/thyroid family of nuclear hormone receptors, which act as transcription factors and may thus directly influence gene transcription. Finally, evidence exists that prostanoids act as second messengers downstream of mitogen receptor activation, mediating events, such as cytoskeletal changes, maybe via direct interaction with GTPase activating proteins. The final cellular reaction to prostaglandin stimulation will most likely depend on combined effects of the above-mentioned levels of interaction between prostaglandins and their cellular receptors.

Interleukin (IL)-6, but not IL-1, induction in the brain downstream of cyclooxygenase-2 is essential for the induction of febrile response against peripheral IL-1alpha

IL-1 is an endogenous pyrogen produced upon inflammation or infection. Previously, we showed that, upon injection with turpentine, IL-1 is induced in the brain in association with the development of fever. The role of endogenous IL-1 in the brain and the signaling cascade to activate thermosensitive neurons, however, remain to be elucidated. In this report, febrile response was analyzed after peripheral injection of IL-1alpha. We found that a normal febrile response was induced even in IL-1alpha/beta-deficient mice, indicating that production of IL-1 in the brain is not necessarily required for the response. In contrast, IL-6-deficient mice did not exhibit a febrile response. Cyclooxygenase (Cox)-2 expression in the brain was strongly induced 1.5 h after injection of IL-1alpha, whereas IL-6 expression was observed 3 h after the injection. Cox-2 expression in the brain was not influenced by IL-6 deficiency, whereas indomethacin, an inhibitor of cyclooxygenases, completely inhibited induction of IL-6. These observations suggest a mechanism of IL-1-induced febrile response in which IL-1 in the blood activates Cox-2, with the resulting prostaglandin E(2) inducing IL-6 in the brain, leading to the development of fever.

Identification of an AID-independent pathway for chromosomal translocations between the Igh switch region and Myc

Chromosomal translocations involving immunoglobulin heavy chain (Igh) switch regions and an oncogene such as Myc represent initiating events in the development of many B cell malignancies. These translocations are widely thought to result from aberrant class-switch recombination. To test this model, we measured translocations in mice deficient in activation-induced cytidine deaminase (AID) that lack class-switch recombination. We found that AID made no measurable contribution to the generation of initial translocations, indicating that the intrinsic fragility of the switch regions or a pathway unrelated to AID is responsible for these translocations. In contrast, the outgrowth of translocation-positive cells was dependent on AID, raising the possibility that AID is important in tumor progression, perhaps by virtue of its mutagenic properties.

Characterization of pristane-induced arthritis, a murine model of chronic disease: Response to antirheumatic agents, expression of joint cytokines, and immunopathology

OBJECTIVE

To characterize chronic murine pristane-induced arthritis (PIA) with regard to the response to antirheumatic agents, expression levels of proinflammatory cytokines, and immunopathologic features.

METHODS

Male DBA/1 mice were injected intraperitoneally with pristane oil to induce a chronic polyarthritis, which was monitored by visual scoring. Serum antibody and splenocyte responses to a panel of putative joint-derived autoantigens were measured. Whole paws were evaluated postmortem for changes in the levels of proinflammatory cytokines tumor necrosis factor alpha (TNFalpha), interleukin-1beta (IL-1beta), and IL-6 by enzyme-linked immunosorbent assay, and standard histopathology techniques were used to determine joint structural changes. Therapeutic studies were performed for up to 8 weeks of dosing with prednisolone, methotrexate, 3 nonsteroidal antiinflammatory drugs (celecoxib, diclofenac, and indomethacin), a p38 MAPK inhibitor, SB242235, and human soluble TNF receptor (sTNFR; etanercept) and murine sTNFR fusion proteins.

RESULTS

Antibody and cellular responses to the putative joint autoantigens revealed a broad extent of autoimmunity in PIA. TNFalpha, IL-1beta, and IL-6 were all persistently up-regulated in PIA joints. Prednisolone, methotrexate, celecoxib, indomethacin, and SB242235 all significantly reduced the arthritis scores. Etanercept was ineffective in reducing the arthritis scores, whereas murine sTNFR produced a significant, but nonsustained, benefit. Only prednisolone significantly reduced the expression of TNFalpha, IL-1beta, and IL-6 in the joints. Prednisolone and methotrexate demonstrated the most effective joint protection.

CONCLUSION

We have markedly extended the characterization of PIA as a murine model of chronic inflammatory arthritis by demonstrating cellular and humoral autoantigenicity, elevation of clinically precedented joint cytokines, and variation in the response to several antirheumatic therapies. PIA offers significant potential for the long-term study of immunopathologic mechanisms and novel therapies in rheumatoid arthritis.

Deoxynivalenol-induced mitogen-activated protein kinase phosphorylation and IL-6 expression in mice suppressed by fish oil

The trichothecene mycotoxin deoxynivalenol (DON) induces IgA hyperelevation and mesangial IgA deposition in mice that mimics the early stages of human IgA nephropathy (IgAN). Among potential mediators of this disease, interleukin-6 (IL-6) is likely to play a particularly critical role in IgA elevation and disease exacerbation. Based on previous findings that dietary fish oil (FO) suppresses DON-induced IgAN, we hypothesized that FO inhibits the induction of IL-6 expression by this mycotoxin in vivo and in vitro. Mice were fed modified AIN 93G diet amended with 7% corn oil (CO) or with 1% corn oil plus 6% menhaden fish oil (FO) for up to 8 weeks and then exposed acutely to DON by oral gavage. DON-induced plasma IL-6 and splenic mRNA elevation in FO-fed mice were significantly suppressed after 8 weeks when compared to the CO-fed group. The effects of FO on phosphorylation of mitogen-activated protein kinases (MAPKs), critical upstream transducers of IL-6 up-regulation, were also assessed. DON-induced phosphorylation of extracellular signal regulated protein kinases 1 and 2 (ERK1/2) and c-Jun N-terminal kinases 1 and 2 (JNK1/2) was significantly suppressed in spleens of mice fed with FO, whereas p38 was not. Splenic COX-2 mRNA expression, which has been previously shown to enhance DON-induced IL-6, was also significantly decreased by FO, whereas plasma levels of the COX-2 metabolite, prostaglandin E2, were not affected. To confirm in vivo findings, the effects of pretreatment with the two primary n-3 PUFAs in FO, eicosapentaenoic acid (20:5[n-3]; EPA) and docosahexaenoic acid, (22:6[n-3]; DHA), on DON-induced IL-6 expression were assessed in LPS-treated RAW 264.7 macrophage cells. Consistent with the in vivo findings, both EPA and DHA significantly suppressed IL-6 superinduction by DON, as well as impaired DON-induced ERK1/2 and JNK1/2 phosphorylation. In contrast, the n-6 PUFA arachidonic acid (20:4[n-3]) had markedly less effects on these MAPKs. Taken together, the capacity of FO and its component n-3 PUFAs to suppress IL-6 expression as well as ERK 1/2 and JNK 1/2 activation might explain, in part, the reported suppressive effects of these lipids on DON-induced IgA nephropathy.

Direct and indirect effects of aldosterone on cyclooxygenase-2 and interleukin-6 expression in rat cardiac cells in culture and after myocardial infarction

Aldosterone contributes to cardiac failure, which is associated with induction of inflammatory mediators. Moreover, aldosterone was shown to induce a vascular inflammatory phenotype in the rat heart. Using Western blotting and/or real-time RT-PCR, we examined the effect of aldosterone on the expression of the proinflammatory molecules, cyclooxygenase-2 (COX-2), and IL-6 in neonatal rat ventricular cardiac myocytes and fibroblasts as well as in adult cardiomyocytes after myocardial infarction. In cardiomyocytes, aldosterone induced COX-2 but not IL-6 expression. After 4-18 h of stimulation with 1 microm aldosterone, a significant increase in COX-2 protein expression was observed, preceded by an increase of COX-2 mRNA levels. After 18 h treatment, 100 nm and 1 microm aldosterone increased COX-2 protein amount by 2- and 4-fold, respectively. Consistently, aldosterone increased by 2.5-fold prostaglandin E(2) secretion in cardiomyocytes. In cardiac fibroblasts, aldosterone increased neither COX-2 nor IL-6 mRNA expression. Interestingly, prostaglandin E(2) (100 nm) strongly induced both proinflammatory molecules in fibroblasts and cardiomyocytes. Our results indicate that aldosterone directly induces COX-2 expression in cardiomyocytes and suggest that the subsequent increase in prostaglandin secretion may act in an autocrine and/or paracrine manner inducing in turn COX-2 and IL-6 expression. In vivo, myocardial infarction strongly increased both COX-2 and IL-6 expression in ventricular cardiomyocytes. Administration of the aldosterone antagonist RU28318 completely prevented COX-2 induction by infarction and partially inhibited the increase in IL-6 mRNA. These data suggest that after myocardial infarction, mineralocorticoid receptor activity is responsible for COX-2 induction and indirectly participates in IL-6 expression in cardiomyocytes.

Comparative effects of AT1-antagonism and angiotensin-converting enzyme inhibition on markers of inflammation and platelet aggregation in patients with coronary artery disease

OBJECTIVES

We evaluated whether renin-angiotensin system (RAS) blockade attenuates cardiovascular events.

BACKGROUND

Because inflammation and enhanced thrombogenesis are hallmarks of atherosclerosis, we assessed whether RAS inhibition elicits anti-inflammatory and anti-aggregatory effects.

METHODS

Interleukin 6 (IL-6), high-sensitivity C-reactive protein (hsCRP), metalloprotease 9 (MMP-9), and interleukin 10 (IL-10) were determined in patients with coronary artery disease (CAD) and arterial hypertension six to eight weeks after coronary angioplasty (low-density lipoprotein serum levels <150 mg/dl). Patients were randomized double-blind to either 20 mg enalapril (ENAL, n = 27) or 300 mg irbesartan (IRB, n = 21) for 3 months. Blood samples were drawn at baseline and at three months. Thromboxane A2-induced platelet aggregation was determined turbidimetrically; urine bicyclo-prostaglandin E2 (PGE(2)) and inflammatory markers were measured by enzyme-linked immunosorbent assay technique.

RESULTS

Both treatment regimens enhanced serum IL-10 levels (IRB p < 0.001, ENAL p < 0.03) and reduced serum MMP-9 protein (IRB p < 0.001, ENAL p < 0.05) and MMP-9 activity (IRB p < 0.005, ENAL p < 0.05). Only IRB reduced serum IL-6 and hsCRP levels significantly compared with baseline (p < 0.01), whereas ENAL did not (hsCRP p < 0.02 IRB vs. ENAL, p < 0.01 IRB vs. ENAL). Platelet aggregation was only reduced by IRB (p < 0.001, ENAL p < 0.06, IRB vs. ENAL p < 0.001) while urine PGE(2) levels remained unchanged.

CONCLUSIONS

Angiotensin-converting enzyme (ACE) inhibition and angiotensin II type 1 receptor (AT1) blockade reduced serum MMP-9 protein/activity to a similar extent, and only AT1 blockade reduced hsCRP, IL-6, and platelet aggregation in patients with CAD. Thus, AT1-blockade appears to exert stronger systemic anti-inflammatory and anti-aggregatory effects compared with ACE inhibition.

Synergistic induction of the nicotinamide adenine dinucleotide-linked 15-hydroxyprostaglandin dehydrogenase by an androgen and interleukin-6 or forskolin in human prostate cancer cells

The nicotinamide adenine dinucleotide-dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH) catalyzes the oxidation of 15 (S)-hydroxyl group of prostaglandins and lipoxins and participates along with cyclooxygenases and lipoxygenases in controlling the cellular levels of prostaglandins and lipoxins. 15-PGDH could be induced by IL-6 and forskolin in addition to androgens in a time- and dose-dependent manner but not by other cytokines and growth factors in LNCaP cells. Concurrent addition of IL-6 and forskolin showed additive effect in the induction of 15-PGDH activity. However, combined addition of dihydrotestosterone (DHT) and IL-6 or DHT plus forskolin exhibited synergistic induction of 15-PGDH activity. The increase in enzyme activity was correlated with the expression of the enzyme protein as shown by Western blot analysis. The induction by DHT or IL-6 or forskolin or their combinations was inhibited by antiandrogen, casodex, in a dose-dependent manner, indicating that a functional androgen receptor was required for the action of any of these three agents. The induction by forskolin plus DHT or by either agent or by IL-6 alone was greatly inhibited by H-89, indicating the involvement of protein kinase A in the actions of forskolin, DHT, and IL-6. The induction of 15-PGDH by IL-6 was also blocked by some other protein kinase inhibitors, indicating the participation of MAPK, MAPK/ERK kinase, and STAT3 in the signaling pathway of IL-6. These results indicate that the induction of 15-PGDH by DHT, IL-6, and forskolin in LNCaP cells may involve a functional androgen receptor and phosphorylation-dependent multiple signaling pathways.

Selenium Deficiency Abrogates Inflammation-Dependent Plasma Cell Tumors in Mice

The role of the micronutrient, selenium, in human cancers associated with chronic inflammations and persistent infections is poorly understood. Peritoneal plasmacytomas (PCTs) in strain BALB/c (C), the premier experimental model of inflammation-dependent plasma cell transformation in mice, may afford an opportunity to gain additional insights into the significance of selenium in neoplastic development. Here, we report that selenium-depleted C mice (n = 32) maintained on a torula-based low-selenium diet (5-8 micro g of selenium/kg) were totally refractory to pristane induction of PCT. In contrast, 11 of 26 (42.3%) control mice maintained on a selenium adequate torula diet (300 micro g of selenium/kg) and 15 of 40 (37.5%) control mice fed standard Purina chow (440 micro g of selenium/kg) developed PCT by 275 days postpristane. Abrogation of PCT was caused in part by the striking inhibition of the formation of the inflammatory tissue in which PCT develop (pristane granuloma). This was associated with the reduced responsiveness of selenium-deficient inflammatory cells (monocytes and neutrophils) to chemoattractants, such as thioredoxin and chemokines. Selenium-deficient C mice exhibited little evidence of disturbed redox homeostasis and increased mutant frequency of a transgenic lacZ reporter gene in vivo. These findings implicate selenium, via the selenoproteins, in the promotion of inflammation-induced PCT and suggest that small drug inhibitors of selenoproteins might be useful for preventing human cancers linked with chronic inflammations and persistent infections.

Radiation-induced edema is dependent on cyclooxygenase 2 activity in mouse brain

Cerebrovascular dysfunction, characterized by compromise of the blood-brain barrier and formation of cerebral edema, is common during the acute period after brain irradiation and may contribute to delayed pathology (e.g. vascular collapse, white matter necrosis) that leads to functional deficits. Another response of normal brain tissue to radiation is the induction of inflammatory markers, such as cytokine expression and glial activation. In particular, radiation-induced neuroinflammation is associated with an elevation in cyclooxygenase 2 (COX2), one of two isoforms of the obligate enzyme in prostanoid synthesis and the principal target of non-steroid anti-inflammatory drugs. Since prostanoids serve as autocrine and paracrine mediators in numerous physiological and pathological processes, including vasoregulation, we investigated COX2 protein expression and COX2-mediated prostanoid production in radiation-induced cerebral edema in male C57/BL6 mice. We found that radiation induces COX2 protein that is accompanied by specific increases in prostaglandin E(2) and thromboxane A(2) within 4 and 24 h after brain irradiation. Furthermore, we showed that treatment with NS-398, a selective COX2 inhibitor, attenuated prostanoid induction and edema formation. These results suggest that radiation-induced changes in vascular permeability are dependent on COX2 activity, implicating this enzyme and its products as targets for potential therapeutic treatment/protection from the effects of radiation on normal brain tissue.

Histamine mediates the pro-inflammatory effect of latex of Calotropis procera in rats

INTRODUCTION

Calotropis procera is known to produce contact dermatitis and the latex of this plant produces intense inflammation when injected locally. However, the precise mode of its pro-inflammatory effect is not known. In present study we have pharmacologically characterized the inflammation induced by latex of C. procera in a rat paw edema model and determined the role of histamine in latex-induced inflammation.

METHODS

Inflammation was induced in the hind paw of rats by injecting different doses of dried latex (DL) of C. procera. The inhibitory effect of phenylbutazone, dexamethasone, celecoxib, cyproheptadine, chlorpheniramine and compound 48/80 on edema volume was evaluated and compared with that against carrageenan. The histamine content of DL was measured fluorometrically.

RESULTS

DL produced dose-dependent inflammation of the rat paw. Cyproheptadine and chlorpheniramine effectively inhibited DL-induced inflammation (90%; p < 0.01), while anti-inflammatory drugs phenylbutazone, dexamethasone and celecoxib were more effective against carrageenan-induced inflammation. Depletion of mast cell histamine by compound 48/80 produced a significant decrease in DL-induced inflammation as compared with carrageenan (500% versus 25%). DL was also found to contain about 6 microg/g of histamine.

CONCLUSIONS

Thus, our study shows that the biogenic amines play a significant role in C. procera latex-induced inflammation and antihistaminic drugs could be effectively used to inhibit inflammatory response elicited by exposure to latex.

Invasive and angiogenic phenotype of MCF-7 human breast tumor cells expressing human cyclooxygenase-2

To evaluate the direct effect of human cyclooxygenase-2 (hCox-2) on human breast tumor cell proliferation, invasion, and angiogenesis, hCox-2 cDNA was transfected into slow growing, non-metastatic MCF-7 human breast tumor cells that express low levels of Cox-2. Two stable transfectant clones, designated MCF-7/hCox-2 clones 8 and 10, had significantly decreased (P < 0.05) doubling time, with two-fold greater number of cells during exponential growth compared to the MCF-7/vector control. Proliferation of both of the MCF-7/hCox-2 clones was significantly inhibited in a time- and dose-dependent manner by celecoxib. The MCF-7/hCox-2 clones 8 and 10 formed larger and greater numbers of colonies in soft agar than the MCF-7/vector control, with a corresponding increased invasion across an artificial Matrigel basement membrane in response to recombinant human epidermal growth factor (hEGF). The MCF-7/hCox-2 clones 8 and 10 had higher mRNA levels of two splice variants of vascular endothelial growth factor (VEGF), V145 and V165. These results demonstrate that hCox-2 directly increases breast tumor cell proliferation, stimulates invasion across a basement membrane, and induces synthesis of specific heparin binding splice variants of VEGF.

CCL19/CCL21-triggered signal transduction and migration of dendritic cells requires prostaglandin E2

The control of dendritic cell (DC) migration is pivotal for the initiation of cellular immune responses. When activated with inflammatory stimuli, the chemokine receptor CCR7 is up-regulated on DCs. Activated DCs home to lymphoid organs, where the CCR7 ligands CCL19 and CCL21 are expressed. We previously found that human monocyte-derived DCs (MoDCs) exclusively migrated to CCL19 and CCL21 when matured in the presence of prostaglandin (PG) E2. Because PGE2 did not alter CCR7 cell surface expression, we examined whether PGE2 may exert its effect by coupling CCR7 to signal transduction modules. Indeed, stimulation with CCR7 ligands led to enhanced phosphatidylinositol-3-kinase–mediated phosphorylation of protein kinase B when MoDCs were matured in the presence of PGE2. Moreover, CCL19/CCL21-induced intracellular calcium mobilization in MoDCs occurred only when PGE2 was present during maturation. MoDC migration to CCL19 and CCL21 was dependent on phospholipase C and intracellular calcium flux but not on phosphatidylinositol-3 kinase. Hence, our data provide insight into CCL19/CCL21-triggered signal transduction pathways and identify a novel function for PGE2 in controlling the migration of mature MoDCs by facilitating CCR7 signal transduction.

Estrogen suppresses IL-1beta-mediated induction of COX-2 pathway in rat cerebral blood vessels

Interleukin (IL)-1beta is a potent inducer of inflammatory prostaglandins, which are important mediators of vascular response to cerebral injury, whereas estrogen reduces brain injury in models of ischemic stroke. Thus we examined the effects of in vivo IL-1beta exposure on cerebrovascular cyclooxygenase (COX)-2 expression and function in an animal model of chronic estrogen replacement. Estrogen-treated and nontreated ovariectomized female rats received IL-1beta injections (10 microg/kg i.p.), and then cerebral vessels were isolated for biochemical and contractile measurements. In estrogen-deficient rats, IL-1beta induced cerebrovascular COX-2 protein expression; a peak response occurred 3 h after injection. COX-2 was localized to arterial endothelium using confocal microscopy. IL-1beta increased PGE2 but not PGI2 production and decreased vascular tone as measured in isolated cerebral arteries; the latter effect was partially reversed by treatment with the selective COX-2 inhibitor NS-398 (10 micromol/l). In contrast, in animals treated with estrogen, IL-1beta had no significant effect on COX-2 protein levels, PGE2 production, or vascular tone. Combined treatment with 17beta-estradiol and medroxyprogesterone acetate also prevented increases in PGE2 production after IL-1beta treatment, but treatment with 17alpha-estradiol had no effect. IL-1beta induction of COX-2 protein was prevented by treatment with the nuclear factor-kappaB inhibitor caffeic acid phenethyl ester (20 mg/kg i.p.), and estrogen treatment reduced cerebrovascular nuclear factor-kappaB activity. Estrogen thus has potent anti-inflammatory effects with respect to cerebral vascular responses to IL-1beta. These effects may have important implications for the incidence and severity of cerebrovascular disease.

Role of cyclooxygenase enzymes in a murine model of experimental cholera

Nonsteroidal anti-inflammatory drugs (e.g., indomethacin) inhibit and reduce the fluid secretion responses elicited by cholera toxin (CT), but it has not been conclusively determined which cyclooxygenase (COX) isoform is involved in CT's action. This study evaluated the role of the COX enzymes and their arachidonic acid metabolites in experimental cholera. Swiss-Webster mice were dosed with celecoxib and rofecoxib and challenged with CT in ligated small intestinal loops, and intestinal segments from mice deficient in COX-1 and COX-2 were challenged with CT. The effects of CT on fluid accumulation, prostaglandin E(2) production, mucosal tissue injury, and markers of oxidative stress were measured. Celecoxib and rofecoxib given at 160 micro g per mouse inhibited CT-induced fluid accumulation by 48% and 31%, respectively, but there was no significant difference among cox-1(-/-) and cox-2(-/-) mice in response to CT compared to wild-type controls. CT elevated tissue levels of oxidized glutathione and lipid peroxides and elicited small intestinal tissue injury in two of five cox-1(-/-) and four of five cox-2(-/-) mice. A role for COX-2 in CT's mechanism of action has previously been suggested by the effectiveness of COX-2 inhibitors in reducing CT-induced fluid secretion, but CT challenge of COX-1 and COX-2 knockout mice did not corroborate the pharmacological data. The results of this study show that CT induced oxidative stress in COX-deficient mice and suggest a tissue-protective role for arachidonic acid metabolites in the small intestine against oxidative stress.

Eicosanoids in cirrhosis and portal hypertension

In the last decade, the knowledge of the pathogenesis of portal hypertension and cirrhosis has increased dramatically. In portal hypertension, almost all the known vasoactive systems/substances are activated or increased and the most recent studies have stressed the importance of the endothelial factors, in particular, prostaglandins. Prostaglandins are formed following the oxygenation of arachidonic acid by the cyclooxygenase (Cox) pathway. An important consideration in portal hypertension and cirrhosis in the periphery is the altered hemodynamic profile and its contributory role in controlling endothelial release of these vasoactive substances. Prostaglandins are released from the endothelium in response to both humoral and mechanical stimuli and can profoundly affect both intrahepatic and peripheral vascular resistance. Within the liver, intrahepatic resistance is altered due to a diminution in sinusoidal responsiveness to vasodilators and an increase in prostanoid vasoconstrictor responsiveness. This review will examine the contributory role of both hormonal and/or hemodynamic force-induced changes in prostaglandin production and signaling in cirrhosis and portal hypertension and the consequence of these changes on the structural and functional response of both the vasculature and the liver.