On the induction of cyclooxygenase-2, inducible nitric oxide synthase and soluble phospholipase A2 in rat mesangial cells by a nonsteroidal anti-inflammatory drug: the role of cyclic AMP

Non-steroidal anti-inflammatory drugs attenuate the vascular responses in aging metabolic syndrome rats

AIM

Metabolic syndrome (MS) and aging are low-grade systemic inflammatory conditions, and inflammation is a key component of endothelial dysfunction. The aim of this study was to investigate the effects of non-steroidal anti-inflammatory drugs (NSAIDs) upon the vascular reactivity in aging MS rats.

METHODS

MS was induced in young male rats by adding 30% sucrose in drinking water over 6, 12, and 18 months. When the treatment was finished, the blood samples were collected, and aortas were dissected out. The expression of COX isoenzymes and PLA2 in the aortas was analyzed using Western blot analysis. The contractile responses of aortic rings to norepinephrine (1 μmol/L) were measured in the presence or absence of different NSAIDs (10 μmol/L for each).

RESULTS

Serum levels of pro-inflammatory cytokines (IL-6, TNF-α, and IL-1β) in control rats were remained stable during the aging process, whereas serum IL-6 in MS rats were significantly increased at 12 and 18 months. The levels of COX isoenzyme and PLA2 in aortas from control rats increased with the aging, whereas those in aortas from MS rats were irregularly increased with the highest levels at 6 months. Pretreatment with acetylsalicylic acid (a COX-1 preferential inhibitor), indomethacin (a non-selective COX inhibitor) or meloxicam (a COX-2 preferential inhibitor) decreased NE-induced contractions of aortic rings from MS rats at all the ages, with meloxicam being the most potent. Acetylsalicylic acid also significantly reduced the maximum responses of ACh-induced vasorelaxation of aortic rings from MS rats, but indomethacin and meloxicam had no effect.

CONCLUSION

NSAIDs can directly affect vascular responses in aging MS rats. Understanding the effects of NSAIDs on blood vessels may improve the treatment of cardiovascular diseases and MS in the elders.

Downregulation of pro-inflammatory mediators by a water extract of Schisandra chinensis (Turcz.) Baill fruit in lipopolysaccharide-stimulated RAW 264.7 macrophage cells

Schisandra chinensis has a long-standing history of medicinal use as a tonic, a sedative, an anti-tussive, and an anti-aging drug. Nevertheless, the antagonistic effects of S. chinensis against lipopolysaccharide (LPS)-stimulated responses have not yet been studied. In this study, we investigated whether water extract of S. chinensis fruit (WESC) has the ability to attenuate the expression of pro-inflammatory mediators such as nitric oxide (NO), prostaglandin E2 (PGE2), and tumor necrosis factor-α (TNF-α) in LPS-stimulated RAW 264.7 macrophage cells. WESC inhibited the expression of LPS-induced pro-inflammatory mediators, namely, NO, PGE2, and TNF-α. Furthermore, gene expression of inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), and TNF-α was inhibited both at mRNA and protein synthesis levels, without any cytotoxic effect. Moreover, WESC significantly suppressed LPS-induced DNA-binding activity of NF-κB by inhibiting degradation of IκBα. It was found that pyrrolidine dithiocarbamate (PDTC), a specific NF-κB inhibitor, downregulates the expression of these pro-inflammatory genes to be closely regulated by NF-κB activity. Furthermore, we found that WESC retains dephosphorylation of Akt in response to LPS, and consequently suppressed the DNA-binding activity of NF-κB in RAW 264.7 macrophage cells. LY294002, a specific Akt inhibitor, attenuated LPS-induced pro-inflammatory gene expression via suppression of NF-κB activity. Taken together, our results indicate that WESC downregulates the expression of pro-inflammatory genes involved in the synthesis of NO, PGE2, and TNF-α in LPS-stimulated RAW 264.7 macrophage cells by suppressing Akt-dependent NF-κB activity.

Disruption of cyclooxygenase-2 prevents downregulation of cortical AQP2 and AQP3 in response to bilateral ureteral obstruction in the mouse

Bilateral ureteral obstruction (BUO) in rats is associated with increased cyclooxygenase type 2 (COX-2) expression, and selective COX-2 inhibition prevents downregulation of aquaporins (AQPs) in response to BUO. It was hypothesized that a murine model would display similar changes in renal COX-2 and AQPs upon BUO and that targeted disruption of COX-2 protects against BUO-induced suppression of collecting duct AQPs. COX-2(-/-) and wild-type littermates (C57BL/6) were employed to determine COX-1, -2, AQP2, and AQP3 protein abundances and localization after BUO. In a separate series, sham and BUO wild-type mice were treated with a selective COX-2 inhibitor, parecoxib. The COX-2 protein level increased in wild-type mice in response to BUO and was not detectable in COX-2(-/-). COX-1 protein abundance was increased in sham-operated and BUO mice. Total AQP2 and -3 mRNA and protein levels decreased significantly after BUO in the cortex+outer medulla (C+OM) and inner medulla (IM). The decrease in C+OM AQP2 and -3 levels was attenuated/prevented in COX-2(-/-) mice, whereas there was no change in the IM. In parallel, inhibition of COX-2 by parecoxib rescued C+OM AQP3 and IM AQP2 protein level in wild-type mice subjected to BUO. In summary, 1) In C57BL/6 mice, ureteral obstruction increases renal COX-2 expression in interstitial cells and lowers AQP2/-3 abundance and 2) inhibition of COX-2 activity by targeted disruption or pharmacological blockade attenuates obstruction-induced AQP downregulation. In conclusion, COX-2-derived prostaglandins contribute to downregulation of transcellular water transporters in the collecting duct and likely to postobstruction diureses in the mouse.

Prostaglandins in the kidney: developments since Y2K

There are five major PGs (prostaglandins/prostanoids) produced from arachidonic acid via the COX (cyclo-oxygenase) pathway: PGE(2), PGI(2) (prostacyclin), PGD(2), PGF(2alpha) and TXA(2) (thromboxane A(2)). They exert many biological effects through specific G-protein-coupled membrane receptors, namely EP (PGE(2) receptor), IP (PGI(2) receptor), DP (PGD(2) receptor), FP (PGF(2alpha) receptor) and TP (TXA(2) receptor) respectively. PGs are implicated in physiological and pathological processes in all major organ systems, including cardiovascular function, gastrointestinal responses, reproductive processes, renal effects etc. This review highlights recent insights into the role of each prostanoid in regulating various aspects of renal function, including haemodynamics, renin secretion, growth responses, tubular transport processes and cell fate. A thorough review of the literature since Y2K (year 2000) is provided, with a general overview of PGs and their synthesis enzymes, and then specific considerations of each PG/prostanoid receptor system in the kidney.

Acetylcholine-induced aortic relaxation studied in salbutamol treated rats

It has been proposed that the acetylcholine (ACh)-induced relaxation of the rat aorta is entirely mediated by endothelium derived-nitric oxide (NO). However, some authors have reported that indomethacin pretreatment attenuates ACh-induced relaxation of rat aortic ring preparations. Moreover, it has also been suggested that cAMP accumulation may regulate either nitric oxide synthase (NOS) or cyclooxygenase (COX) expression in different tissues. Thus, in this in vitro study we have investigated the endothelial mechanisms involved in the ACh-induced relaxation of ring preparations of the rat thoracic aorta, as well as the influence chronic treatment with the selective beta(2)-agonist salbutamol had upon such mechanisms. Results of functional experiments show that N(G)-monomethyl-L-arginine (L-NMMA, 3 x 10(-4) M) considerably inhibited the ACh-induced relaxation of rat aortic ring preparations. However, indomethacin (10(-5) M) was also found to partially attenuate this ACh response, suggesting that although NO is the most important mediator of the ACh-induced relaxation of the rat aortic ring preparations, vasorelaxation may also involve prostanoids. Moreover, the results suggest that treatment with salbutamol failed to produce any change in the ACh-induced relaxation of rat aortic ring preparations.

Prostacyclin signaling in the kidney: implications for health and disease

The balance between vasodilator and vasoconstrictor pathways is key to the maintenance of homeostasis and the outcome of disease. In the kidney, prostaglandins (PGs) uphold this balance and regulate renal function: hemodynamics, renin secretion, growth responses, tubular transport processes, and cell fate. With the advent of cyclooxygenase (COX)-2-selective inhibitors, targeted deletions in mice (COX knockouts, PG receptor knockouts), and the discovery of intracrine signaling options for PGs (peroxisome proliferator-activated receptors and perinuclear PGE2receptors: EP1,3,4), many advances have been made in the study of arachidonic acid metabolites. Although prostacyclin (PGI2) is a major product of the COX pathway, there is very little emphasis on its importance to the kidney. This review will discuss PGI2biology and its relevance to different aspects of renal disease (growth, fibrosis, apoptosis), highlighting the most significant research from the past decade of PGI2literature, what we have learned from other organ systems, while stressing the significance of cross talk between various PGI2signaling pathways and its implications for renal health and disease.

Interaction of Clonixin with EPC Liposomes Used as Membrane Models

In this work, an overall analysis of clonixin interaction with liposomes was achieved using different techniques, which allowed the evaluation of the change in different membrane's characteristics as well as the possible location of the drug in the membrane. Clonixin acidity constants were obtained and the values are 5.5 +/- 0.08 and 2.2 +/- 0.04. Clonixin partition coefficient (K(p)) between liposomes and water was also determined using derivative spectrophotometry, fluorescence quenching, and zeta-potential (zeta-potential). These three techniques yielded similar results. zeta-potential measurements were performed and an increase of the membrane negative charge with an increase of drug concentration was observed. Drug location within the bilayer was performed by fluorescence quenching using a set of n-(9-anthroyloxy) fatty acid probes (n = 2, 6, 9, and 12). The fluorescence intensity of all probes was quenched by the drug. This effect is more noticeable for the outer located probe, indicating that the drug is positioning in the external part of the membrane. These same probes were used for steady-state anisotropy measurements to determine the perturbation in membrane structure induced by clonixin. Clonixin increased membrane fluidity in a concentration dependent manner, with the highest perturbation occurring nearby the 2-AS probe, closely located to the bilayer surface.

Endothelial cell activation by endotoxin involves superoxide/NO-mediated nitration of prostacyclin synthase and thromboxane receptor stimulation

In bovine coronary artery segments, peroxynitrite inhibits prostacyclin (PGI2) synthase by tyrosine nitration. Using this pharmacological model, we show that a 1 h exposure of bovine coronary artery segments to endotoxin (lipopolysaccharide [LPS]) inhibits the relaxation phase following angiotensin II (Ang II) stimulation and causes a vasospasm that can be suppressed by a thromboxane A2 (TxA2) receptor blocker. In parallel, PGI2 synthesis decreases in favor of prostaglandin E2 formation. Immunoprecipitation and costaining with an anti-nitrotyrosine antibody identified PGI2 synthase as the main nitrated protein in the endothelium. All effects of LPS could be prevented in the presence of the nitric oxide (NO) synthase inhibitor Nomega-mono-methyl-L-arginine and polyethylene-glycolated Cu/Zn- superoxide dismutase. Thus, the early phase of endothelial cell activation in bovine coronary arteries by inflammatory agents proceeds by a protein synthesis-independent priming process for a source of superoxide that we tentatively attribute to xanthine oxidase. Upon receptor activation, Ang II stimulates NO and superoxide production, resulting in a peroxynitrite-mediated nitration and inhibition of PGI2 synthase. The remaining 15-hydroxy-prostaglandin 9,11-endoperoxide (PGH2) first activates the TxA2/PGH2 receptor and then is converted to prostaglandin E2 (PGE2) by smooth muscle cells. PGE2 together with a lack of NO and PGI2 is known to promote the adhesion of white blood cells and their immigration to the inflammatory locus.

Cyclooxygenase-2 in human non-small cell lung cancer

AIM

Recent studies report that the expression of cyclooxygenase (COX) in non-small cell lung cancer (NSCLC) is increased, especially in adenocarcinoma. Platelet activating factor (PAF), n-sodium butyrate (n-BT), and phorbol myristate acetate (PMA) are important mediators of the inflammatory process.

METHOD

Expression of COX-2 in 67 stage 1 NSCLC paraffin-embedded tumor samples was determined by immunohistochemistry (IHC). Four NSCL cell lines were incubated and stimulated by PAF, n-BT and PMA for 48 h. Expression of COX-2 was determined by IHC, immunoblotting, and reverse transcription-polymerase chain reaction (RT-PCR).

RESULT

IHC showed increasing immunoreactivity in 35 of 67 (52%) in stage I NSCLC, 31 of 53 (59%) in adenocarcinoma and 13 of 15 (87%) in bronchoalveolar cell carcinoma, but only 2 of 12 (17%) in epidermoid carcinoma. The COX-2 expression in NSCLC cells was 75% (3/4) and the COX-1 expression in NSCLC cells was 100% (4/4). After stimulation with PMA, n-BT, PAF and n-BT + PAF, the COX-2 expression in NSCLC cells was significantly increased in all cell lines.

CONCLUSIONS

The expression of COX-2 in NSCLC cells is high and was up-regulated by PMA, n-BT and PAF. We consider that COX-2 inhibitors will play an important role in the therapy of NSCLC.

Effect of misoprostol and indomethacin on cyclooxygenase induction and eicosanoid production in carrageenan-induced air pouch inflammation in rats

Effects of misoprostol, a synthetic prostaglandin E1 (PGE1) analogue, on cyclooxygenase-2 (COX-2) protein level and exudate prostaglandin E2 (PGE2) and thromboxane B2 (TXB2) level were investigated in acute carrageenan-induced air pouch inflammation in rats. Treatment with misoprostol (12.5, 25, and 50 microg/kg) has been started in separated groups, 30 min and 2 days before carrageenan injection and it was given twice a day (total of five doses) by orogastric route. Indomethacin, in doses of 0.5 and 5 mg/kg, and specific COX-2 inhibitor SC-58236, in doses of 5, 10, and 20 mg/kg were given 1 h before carrageenan injection by the orogastric route. Misoprostol increased the levels of PGE2 and COX-2 protein at all doses applied. Despite indomethacin and SC-58236 increased the level of COX-2 protein when they used alone, these drugs partially inhibited misoprostol-induced increase in the level of COX-2 protein. Partial inhibition of misoprostol-induced increase in the level of COX-2 protein by indomethacin or SC-58236 may indicate the modulatory roles of endogenous prostaglandins (PGs, especially, PGE2) on the COX-2 expression.

Identification of the phospholipase A(2) isoforms that contribute to arachidonic acid release in hypoxic endothelial cells: limits of phospholipase A(2) inhibitors

Changes in endothelium functions during ischemia are thought to be of importance in numerous pathological conditions, with, for instance, an increase in the release of inflammatory mediators like prostaglandins. Here, we showed that hypoxia increases phospholipase A(2) (PLA(2)) activity in human umbilical vein endothelial cells. Both basal PLA(2) activity and PG synthesis are sensitive to BEL and AACOCF3, respectively, inhibitors of calcium-independent PLA(2) (iPLA(2)) and cytosolic PLA(2) (cPLA(2)), while OPC, an inhibitor of soluble PLA(2) (sPLA(2)) only inhibited the hypoxia-induced AA release and PGF(2alpha) synthesis. Hypoxia does not alter expression of iPLA(2), sPLA(2) and cPLA(2) and cycloheximide did not inhibit PLA(2) activation, indicating that hypoxia-induced increase in PLA(2) activity is due to activation rather than induction. However, mRNA levels for sPLA(2) displayed a 2-fold increase after 2 hr incubation under hypoxia. BAPTA, an intracellular calcium chelator, partially inhibited the AA release in normoxia and in hypoxia. Direct assays of specific PLA(2) activity showed an increase in sPLA(2) activity but not in cPLA(2) activity after 2hr hypoxia. Taken together, these results indicate that the hypoxia-induced increase in PLA(2) activity is mostly due to the activation of sPLA(2).

Generation of 8-epi-prostaglandin F(2alpha) in isolated rat kidney glomeruli by a radical-independent mechanism

Isoprostanes comprise a group of free radical-catalyzed products of arachidonic acid. However, there is recent evidence pointing towards an enzyme-dependent formation of isoprostanes. With the use of isolated rat glomeruli we addressed the mechanisms of isoprostane generation. Synthesis of prostanoids and isoprostanes, including 8-epi-PGF(2alpha), was studied under conditions favouring radical formation. Cultured glomeruli formed different prostanoids including 8-epi-PGF(2alpha). Upon LPS challenge cyclo-oxygenase (COX)-2 expression was enhanced, and this was paralleled by a 2 - 9-fold increase in prostanoid formation, including isoprostanes. Addition of COX-isoform unselective inhibitors (diclofenac, indomethacin) or a selective inhibitor (NS-398) suppressed the synthesis of prostanoids, 8-epi-PGF(2alpha) and total isoprostane fraction; however, inhibition of the latter was less pronounced. Antioxidants such as butylated hydroxytoluene (BHT), nordihydroguaiaretic acid (NDGA), or dimethylurea exhibited an only minimal inhibitory effect on 8-epi-PGF(2alpha) synthesis. Moreover, ROS-generating drugs (menadione, methylviologen) or NADPH-driven radical formation were unable to cause the generation of significant amounts of 8-epi-PGF(2alpha) by rat glomeruli. In contrast, the total isoprostane fraction could be increased by menadione addition. These data provide further evidence for a radical-independent, but COX-dependent formation of 8-epi-PGF(2alpha) in renal tissue. Regarding the other isoprostanes, both radicals and COX enzymes contribute to their formation. Based on our data we assume that elevated release of vasoactive 8-epi-PGF(2alpha) has to be expected under conditions when the prostanoid system in the kidney is stimulated, e.g. under inflammatory conditions. Regarding renal oxidative injuries, the usefulness of 8-epi-PGF(2alpha) as a representative marker molecule of oxidative stress has to be questioned.

Acute effects of the anti-inflammatory cyclooxygenase-2 selective inhibitor, flosulide, on renal plasma flow and glomerular filtration rate in rats

Nephrotoxicity of nonsteroidal anti-inflammatory drugs is associated with other risk factors (volume-depletion) and may be secondary to functional changes mediated by the inhibition of renal cyclooxygenases. Acute anti-inflammatory doses of flosulide and indomethacin were determined on carrageenan paw edema and its effects on renal plasma flow (RPF) and glomerular filtration rate (GFR) were studied in normovolemic and hypovolemic rats. In normovolemic rats, flosulide increased RPF and GFR (25 mg/kg) and indomethacin (5-10 mg/kg) was without effect. Volume-depleted rats were obtained by oral furosemide (32 mg/kg), urinary eicosanoids were determined. After furosemide, plasma volume, RPF and GFR and PGE2 decreased. Treatment of hypovolemic rats with flosulide (5-25 mg/kg) or indomethacin 10 mg/kg reduced RPF and GFR. Flosulide at 5 mg/kg reduced 6-keto-PGF1alpha whereas at 25 mg/kg and after indomethacin at 10 mg/kg a fall in 6-keto-PGF1alpha and TXB2 appeared. Our data suggest that acute COX-2 selective inhibition may alter renal function.

Dysidotronic acid, a new sesquiterpenoid, inhibits cytokine production and the expression of nitric oxide synthase

In a previous study, we reported a new bioactive sesquiterpenoid, named dysidotronic acid, to be a potent, selective human synovial phospholipase A(2) inhibitor. Dysidotronic acid is a novel, non-complex manoalide analogue lacking the pyranofuranone ring. We now investigate the effect of this compound on cytokine, nitric oxide and prostanoid generation on the mouse macrophage cell line RAW 264.7, where it showed a dose-dependent inhibition with inhibitory concentration 50% values in the micromolar range. This effect was also confirmed in the mouse air pouch injected with zymosan. Dysidotronic acid inhibited the production of tumor necrosis factor alpha and interleukin-1 beta as well as the production of nitric oxide, prostaglandin E(2) and leukotriene B(4). Decreased nitric oxide generation was the consequence of inhibition of the expression of nitric oxide synthase, whereas PGE(2) and LTB(4) reduction was due to inhibition of arachidonic acid bioavailability through a direct inhibitory effect of dysodotronic acid on secretory phospholipase A(2).

Potentiation of cytokine induction of group IIA phospholipase A(2) in rat mesangial cells by ATP and adenosine via the A2A adenosine receptor

1. In rat mesangial cells extracellular nucleotides were found to increase arachidonic acid release by a cytosolic phospholipase A(2) through the P2Y(2) purinergic receptor. 2. In this study we investigated the effects of ATP and UTP on interleukin-1ss (IL-1ss)-induced mRNA expression and activity of group IIA phospholipase A(2) (sPLA(2)-IIA) in rat mesangial cells. 3. Treatment of cells for 24 h with extracellular ATP potentiated IL-1ss-stimulated sPLA(2)-IIA induction, whereas UTP had no effect. 4. We obtained the following evidence that the P2Y(2) receptor is not involved in the potentiation of sPLA(2)-IIA induction: (i) ATP-gamma-S had no enhancing effect; (ii) suramin, a P(2) receptor antagonist, did not inhibit ATP-mediated potentiation; (iii) inhibition of degradation of extracellular nucleotides by the 5'-ectonucleotidase inhibitor AOPCP did not enhance sPLA(2)-IIA induction and (iv) adenosine deaminase treatment completely abolished the ATP-mediated potentiation of sPLA(2)-IIA induction. 5. In contrast, treatment of mesangial cells with adenosine or the A2A receptor agonist CGS 21680 mimicked the effects of ATP in enhancing IL-1ss-stimulated sPLA(2)-IIA induction, whereas the specific A2A receptor antagonist ZM 241385 completely abolished the potentiating effect of ATP or adenosine. 6. The protein kinase A inhibitor Rp-8-Br-cyclic AMPS dose-dependently inhibited the enhancing effect of ATP or adenosine indicating the participation of an adenosine receptor-mediated cyclic AMP-dependent signalling pathway. 7. These data indicate that ATP mediates proinflammatory long-term effects in rat mesangial cells via its degradation product adenosine through the A2A receptor resulting in potentiation of sPLA(2)-IIA induction.

Distribution and cellular localization of prostacyclin synthase in human brain

Prostacyclin (PGI(2)) is a labile, lipid-derived metabolite of arachidonic acid synthesized through the sequential action of cyclo-oxygenase (COX) and prostacyclin synthase (PGIS). In addition to its well-characterized vasodilatory and thrombolytic effects, an increasing number of studies report an important role of PGI(2) in nociception in various animal species. In this study we investigated the regional distribution of PGIS in human brain by immunohistochemistry and in situ hybridization. PGIS-immunoreactive (ir) protein was localized to blood vessels throughout the brain. Neuronal cells and glial cells, such as microglia and oligodendrocytes, also showed intense labeling. The strongest expression of PGIS was seen in large principal neurons, such as pyramidal cells of the cortex, pyramidal cells of the hippocampus, and Purkinje cells of the cerebellum. Abundance of PGIS mRNA was observed in blood vessels and large neurons and correlated well with the immunohistochemical findings. The expression of PGIS in human brain was further demonstrated by immunoblotting and detection of 6-keto-PGF (1alpha), the stable degradation product of prostacyclin in human brain homogenate. These results demonstrate a widespread expression of PGIS in the central nervous system and suggest a potentially important role of prostacylin in modulating neuronal activity in human brain.

Role of the cyclic AMP-protein kinase A pathway in lipopolysaccharide-induced nitric oxide synthase expression in RAW 264.7 macrophages. Involvement of cyclooxygenase-2

The signaling pathway for lipopolysaccharide (LPS)-induced nitric oxide (NO) release in RAW 264.7 macrophages involves the protein kinase C and p38 activation pathways (Chen, C. C., Wang, J. K., and Lin, S. B. (1998) J. Immunol. 161, 6206-6214; Chen, C. C., and Wang, J. K. (1999) Mol. Pharmacol. 55, 481-488). In this study, the role of the cAMP-dependent protein kinase A (PKA) pathway was investigated. The PKA inhibitors, KT-5720 and H8, reduced LPS-induced NO release and inducible nitric oxide synthase (iNOS) expression. The direct PKA activator, Bt(2)cAMP, caused concentration-dependent NO release and iNOS expression, as confirmed by immunofluorescence studies. The intracellular cAMP concentration did not increase until after 6 h of LPS treatment. Two cAMP-elevating agents, forskolin and cholera toxin, potentiated the LPS-induced NO release and iNOS expression. Stimulation of cells with LPS or Bt(2)cAMP for periods of 10 min to 24 h caused nuclear factor-kappaB (NF-kappaB) activation in the nuclei, as shown by detection of NF-kappaB-specific DNA-protein binding. The PKA inhibitor, H8, inhibited the NF-kappaB activation induced by 6- or 12-h treatment with LPS but not that induced after 1, 3, or 24 h. The cyclooxygenase-2 (COX-2) inhibitors, NS-398 and indomethacin, attenuated LPS-induced NO release, iNOS expression, and NF-kappaB DNA-protein complex formation. LPS induced COX-2 expression in a time-dependent manner, and prostaglandin E(2) production was induced in parallel. These results suggest that 6 h of treatment with LPS increases intracellular cAMP levels via COX-2 induction and prostaglandin E(2) production, resulting in PKA activation, NF-kappaB activation, iNOS expression, and NO production.