NO regulates LPS-stimulated cyclooxygenase gene expression and activity in pulmonary artery endothelium

Relationship between gastrointestinal disturbances, blood lipid levels, inflammatory markers, and preterm birth

BACKGROUND

The challenging incidence of preterm birth, the underlying causes of preterm birth remain unclear. This study determined the relationship between disturbed gastrointestinal symptoms, inflammatory markers, blood lipid levels, and preterm birth.

METHOD

One hundred and twenty pregnant women with preterm labour were compared to 120 pregnant women with full-term deliveries. All subjects underwent lactose breath and serologic testing. The correlation between small intestinal bacterial overgrowth (SIBO)-positivity, gastrointestinal symptoms, inflammatory factors, and blood lipid metabolism and preterm birth was analysed using the Spearman method.

RESULTS

SIBO, hydrogen, and methane levels were significantly higher in the preterm birth (PTB) group than the full-term birth (FTB) group at different time points (P < 0.05); Levels of high-sensitivity C-reactive protein (hs-CRP) (3.95[2.70-5.77] vs. 2.47[1.45-3.83]), Interleukin (IL)-10 (3.05[2.27-4.33] vs. 2.09[1.04-3.47]), IL-6 (5.23[3.95-8.50] vs. 2.98[2.22-4.44]), tumour necrosis factor -alpha (TNF-α) (3.23[1.55-4.90] vs. 1.76[0.98-3.10]), total cholesterol (TC) (5.52[4.97-5.95] vs. 5.24[4.73-5.85]), and triglycerides (TG) (2.58[2.04-3.53] vs. 2.24[1.59-3.05]) were significantly higher in the PTB group than the FTB group (P < 0.05). Abdominal distension (2.67[1.67-3.00] vs. 2.33[1.67-2.67]) and constipation (2.00[1.33-2.00] vs. 1.67[1.33-2.00]) scores were also markedly higher in the PTB group than the FTB group (P < 0.05). Preterm birth was positively correlated with SIBO, TC, and TG levels. Additionally, SIBO was positively correlated with hs-CRP, IL-10, IL-6, and TNF-α levels, abdominal distension, and constipation (P < 0.05). Logistic regression analysis found the close association between positive SIBO, biochemistry indicators and preterm birth.

CONCLUSION

Gastrointestinal disturbances, hyperlipidaemia and SIBO-positivity are more likely to occur among pregnant women with preterm labour. Further research with a large sample size in multi-centers is needed to validate the results.

A curcumin derivative, 2,6-bis(2,5-dimethoxybenzylidene)-cyclohexanone (BDMC33) attenuates prostaglandin E2 synthesis via selective suppression of cyclooxygenase-2 in IFN-γ/LPS-stimulated macrophages

Our preliminary screening had shown that the curcumin derivative [2,6-bis(2,5-dimethoxybenzylidene)cyclohexanone] or BDMC33 exhibited improved anti-inflammatory activity by inhibiting nitric oxide synthesis in activated macrophage cells. In this study, we further investigated the anti-inflammatory properties of BDMC33 on PGE₂ synthesis and cyclooxygenase (COX) expression in IFN-γ/LPS-stimulated macrophages. We found that BDMC33 significantly inhibited PGE₂ synthesis in a concentration-dependent manner albeit at a low inhibition level with an IC₅₀ value of 47.33 ± 1.00 µM. Interestingly, the PGE₂ inhibitory activity of BDMC33 is not attributed to inhibition of the COX enzyme activities, but rather BDMC33 selectively down-regulated the expression of COX-2. In addition, BDMC33 modulates the COX expression by sustaining the constitutively COX-1 expression in IFN-γ/LPS-treated macrophage cells. Collectively, the experimental data suggest an immunodulatory action of BDMC33 on PGE₂ synthesis and COX expression, making it a possible treatment for inflammatory disorders with minimal gastrointestinal-related side effects.

Urocortin induced expression of COX-2 and ICAM-1 via corticotrophin-releasing factor type 2 receptor in rat aortic endothelial cells

BACKGROUND AND PURPOSE

Our previous study showed that urocortin (Ucn1) exacerbates the hypercoagulable state and vasculitis in a rat model of sodium laurate-induced thromboangiitis obliterans. Furthermore, the inflammatory molecules COX-2 and ICAM-1 may participate in this effect. In the present study, the effects of Ucn1 on COX-2 and ICAM-1 expression in lipopolysaccharide (LPS)-induced rat aortic endothelial cells (RAECs) were investigated and the mechanisms involved explored.

EXPERIMENTAL APPROACH

RAECs were isolated from adult male Wistar rats, and identified at the first passage. Experiments were performed on cells, from primary culture, at passages 5-8. The expression of COX-2 and ICAM-1 at both mRNA and protein levels was determined by semi-quantitative RT-PCR and Western blot analysis. Levels of PGE(2) and soluble ICAM-1 (sICAM-1) in culture medium were measured by enzyme-linked immunosorbent assay. Furthermore, the phosphorylation status of p38MAPK, ERK1/2, JNK, Akt and NF-kappaB was analysed by Western blot; nuclear translocation of NF-kappaB was observed by immunofluorescence.

KEY RESULTS

Ucn1 augmented LPS-induced expression of COX-2 and ICAM-1 in RAECs in a time- and concentration-dependent manner. Ucn1 increased PGE(2) and sICAM-1 levels. These effects were abolished by the CRF(2) receptor antagonist, antisauvagine-30, but not by the CRF(1) receptor antagonist, NBI-27914. Moreover, Ucn2 activated p38MAPK and augmented NF-kappaB nuclear translocation and phosphorylation, whereas ERK1/2, JNK and Akt pathways were not involved in this process.

CONCLUSIONS AND IMPLICATIONS

These findings suggest that Ucn1 exerts pro-inflammatory effects by augmenting LPS-induced expression of COX-2 and ICAM-1 in RAECs via CRF(2) receptors and the activation of p38MAPK and NF-kappaB.

Pulmonary and systemic hemodynamic responses to intravenous prostacyclin in broilers

The eicosanoid vasodilator prostacyclin (PGI2) reduces resistance to pulmonary blood flow and attenuates pulmonary hypertension in mammals. However, sparse information is available regarding the responsiveness of the avian pulmonary vasculature to PGI2. Accordingly, in 3 experiments we evaluated the pulmonary vascular responses to PGI2 in male broilers. In experiment 1, infusing PGI2 (10 microg/min) into clinically healthy broilers did not reduce their pulmonary vascular resistance (PVR) but did reduce their pulmonary arterial pressure (PAP) by lowering their cardiac output. Within 4 min after stopping the PGI2 infusion, the cardiac output and PAP returned to preinfusion levels. In experiment 2, the responses to PGI2 were evaluated after arachidonic acid (AA) had been infused to preconstrict the pulmonary vasculature. The AA infusion (400 microg/min) consistently triggered dramatic, sustained pulmonary vasoconstriction (increased PVR) and pulmonary hypertension (increased PAP). Concurrent PGI2 infusions did not reduce PVR but did reduce PAP by lowering cardiac output. Within 4 min after stopping the PGI2 infusion, PAP and cardiac output returned to their previous (hypertensive) levels attributable to the ongoing AA infusion. In experiment 3, PGI2 was infused (10 microg/min) into clinically healthy (PAP < or = 24 mmHg) or subclinically hypertensive (PAP > or = 27 mmHg) broilers. Throughout this experiment broilers in the hypertensive group had higher PAP values than broilers in the healthy group. The PGI2 infusion reduced PAP in both groups but did not reduce PVR. Instead, the pulmonary hypotensive response to PGI2 infusion was associated with a reduction in cardiac output in both groups. In all 3 experiments PGI2 reduced PAP by reducing cardiac output rather than by reducing PVR. There was no evidence that PGI2 acts as an effective pulmonary vasodilator in broilers regardless of whether their pulmonary vasculature was apparently normal (clinically healthy), had been pharmacologically preconstricted (AA infusion), or initially exhibited the vasoconstriction that is typical of the pathogenesis of pulmonary hypertension syndrome in broilers (PAP > or = 27 mmHg). The consistent failure of PGI2 to elicit pulmonary vasodilation in this study suggests fundamental differences in AA metabolism or the etiology of pulmonary hypertension may exist when broilers are compared with mammals.

Effect of lipopolysaccharide on diarrhea and gastrointestinal transit in mice: Roles of nitric oxide and prostaglandin E2

AIM: To investigate the effect of lipopolysaccharide (LPS) on the diarrheogenic activity, gastrointestinal transit (GIT), and intestinal fluid content and the possible role of nitric oxide (NO) and prostaglandin E₂ (PGE₂) in gastrointestinal functions of endotoxin-treated mice.

METHODS: Diarrheogic activity, GIT, and intestinal fluid content as well as nitric oxide and PGE₂ products were measured after intraperitoneal administration of LPS in mice.

RESULTS: LPS dose-dependently accumulated abundant fluid into the small intestine, induced diarrhea, but decreased the GIT. Both nitric oxide and PGE₂ were found to increase in LPS-treated mice. Western blot analysis indicated that LPS significantly induced the protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 in mice intestines. Pretreatment with N^G-nitro-L-arginine-methyl ester (L-NAME, a non-selective NOS inhibitor) or indomethacin (an inhibitor of prostaglandin synthesis) significantly attenuated the effects of LPS on the diarrheogenic activity and intestine content, but reversed the GIT.

CONCLUSION: The present study suggests that the pathogenesis of LPS treatment may mediate the stimulatory effect of LPS on nitric oxide and PGE2 production and NO/prostaglandin pathway may play an important role on gastrointestinal function.

Effect of prostaglandins against alloxan-induced cytotoxicity to insulin secreting insulinoma RIN cells in vitro

In the present study, we studied the effect of various prostaglandins (PGs) on alloxan-induced cytotoxicity to rat insulinoma (RIN) cells. Of all the PGs tested, PGE(1), PGE(2), PGI(2), PGF(1 alpha), and PGF(3 alpha) protected RIN cells from alloxan-induced cytotoxicity (P<0.05 compared to alloxan), whereas thromboxane B(2) and 6-keto-PGF(1 alpha) were not effective. PGE(1) induces a statistically significant increase in the activities of superoxide dismutase and glutathione peroxidase and decrease in lipid peroxides in alloxan-treated RIN cells (P<0.001). PGE(1) restored nitric oxide/lipid peroxide ratio to normalcy, suggesting that PGE(1) suppresses oxidant stress induced by alloxan in RIN cells in vitro. Furthermore, PGE(1) prevented DNA damage and apoptosis induced by alloxan. These results indicate that PGE(1) prevents alloxan-induced cytotoxicity to RIN cells in vitro.

Effect of Inducible Cyclooxygenase Expression on Local Microvessel Blood Flow in Acute Interstitial Pancreatitis

OBJECTIVE

To investigate the role of inducible cyclooxygenase (COX-2) mRNA expression in local microvessels in rats with acute interstitial pancreatitis (AIP) induced by caerulein injection.

METHODS

The reverse transcription polymerase chain reaction (RT-PCR) was used to detect COX-2 gene expression in pancreatic tissue. Parameters of acute pancreatitis, such as serum amylase (AMS) and plasma myeloperoxidase (MPO) activities, were assayed using spectrophotometry. Intravital fluorescence microscopy with fluorescein isothiocyanate-labelled erythrocytes was used to study the pancreatic microvessels of rats with AIP and normal control rats.

RESULTS

Highly significant increases in COX-2 expression and AMS and MPO activity were seen in rats with AIP compared with controls. After caerulein injection, pancreatic capillary blood flow was decreased (4 hours, p > 0.05; 8 hours, p < 0.001), functional capillary density was reduced (4 hours, p > 0.05; 8 hours, p < 0.001), and there was irregular and intermittent capillary perfusion at 8 hours. There was also a positive correlation between the level of COX-2 expression and MPO activity (plasma, r = 0.5449, p < 0.05; tissue, r = 0.5698, p < 0.05).

CONCLUSIONS

The correlations between increased COX-2 expression and decreased capillary perfusion and blood flow and increased oedema following AIP may show that COX-2 expression can induce neutrophil sequestration to the pancreas, which may be one of the cascading inflammatory factors in the development of AIP.

Nω-Nitro-L-Arginine Methyl Ester (L-NAME) Amplifies the Pulmonary Hypertensive Response to Endotoxin in Broilers

The pulmonary hypertensive response to bacterial lipopolysaccharide (LPS, endotoxin) varies widely among individual broilers, leading to the suggestion that innate variability may exist in the proportions or profiles of chemical mediators released during the ensuing inflammatory cascade. LPS induces the expression of nitric oxide synthase (iNOS), which produces the vasodilator nitric oxide (NO) to modulate the responses to concurrently produced vasoconstrictors. In experiment 1, broilers were given the NOS inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME), followed by a supra-maximal dose of LPS while the pulmonary arterial pressure was recorded. In experiment 2 the cardiac output also was recorded before and following the i.v. injection of L-NAME. In both experiments, injection with L-NAME modestly increased the pulmonary arterial pressure when compared with control values, confirming previous reports that tonic/basal NO synthesis is required to promote flow-dependent pulmonary vasodilation in chickens. This response to L-NAME occurred in spite of a tendency for cardiac output and stroke volume to decline and, therefore, can be attributed to pulmonary vasoconstriction (an increase in the pulmonary vascular resistance) rather than an increase in pulmonary blood flow. When L-NAME was used to block NO synthesis induced by LPS, an early peak of pulmonary hypertension was revealed that rarely develops in broilers in the absence of L-NAME, and that has been correlated with the release of platelet activating factor and thromboxane A2 in mammals. The control group responded to LPS with a delayed-onset pulmonary hypertension that was typical in timing, amplitude, and duration of the responses previously observed in broilers and that has been attributed to endothelin-mediated thromboxane A2 synthesis in mammals. This delayed-onset pulmonary hypertensive response to LPS was longer in duration and higher in amplitude in the L-NAME group when compared with the control group. These observations are consistent with the hypothesis that NO modulates the responses to vasoconstrictors released concurrently during the LPS-mediated inflammatory cascade. Inhibition of NOS by L-NAME apparently reduced the modulatory influence of NO and exposed a more dramatic pulmonary hypertensive response to LPS.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) sequentially upregulates nitric oxide and prostanoid production in primary human endothelial cells

Endothelial cells express tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptors, but the function of TRAIL in endothelial cells is not completely understood. We explored the role of TRAIL in regulation of key intracellular signal pathways in endothelial cells. The addition of TRAIL to primary human endothelial cells increased phosphorylation of endothelial nitric oxide synthase (eNOS), NOS activity, and NO synthesis. Moreover, TRAIL induced cell migration and cytoskeleton reorganization in an NO-dependent manner. TRAIL did not activate the NF-kappaB or COX-2 pathways in endothelial cells. Instead, TRAIL increased prostanoid production (PGE2=PGI2>TXA2), which was preferentially inhibited by the COX-1 inhibitor SC-560. Because NO and prostanoids play a crucial role in the state of blood vessel vasodilatation and angiogenesis, our data suggest that TRAIL might play an important role in endothelial cell function.

Free radicals and lipid signaling in endothelial cells

Lipid mediators generated by oxidative pathways play essential roles in vascular homeostasis and disease through activating signal transduction pathways that control a variety of cellular functions, including vascular tone, gene expression, and leukocyte and platelet activation. Several enzyme families generate oxidized lipids, and a number of these are either constitutively expressed or inducible in the endothelium, including prostaglandin H synthases, lipoxygenases, and cytochrome P450 isoforms. Mediators generated by these enzymes are predominantly arachidonate-derived and include lipid hydroxides, epoxides, hydroperoxides, and prostanoids. These enzymes may also generate low levels of lipid-derived radicals in the vasculature following escape of substrate radicals from the active site. Lipid oxidation enzymes are often up-regulated in atherosclerosis and hypertension, with several lines of evidence suggesting that they play a central role in the pathogenesis of the disease process itself. This review will describe the isoforms of lipid oxidation enzymes present in endothelial cells focusing on their physiological functions and proposed roles in initiation and progression of vascular disease.

Cyclooxygenase is regulated by ET-1 and MAPKs in peripheral lung microvascular smooth muscle cells

We examined the hypothesis that the potent vasoconstrictor endothelin (ET)-1 regulates both its own production and production of the vasodilator prostaglandins PGE(2) and prostacyclin in sheep peripheral lung vascular smooth muscle cells (PLVSMC). Confluent layers of PLVSMC were exposed to 10 nM ET-1; expression of the prepro (pp)-ET-1, cyclooxygenase (COX)-1, and COX-2 genes was examined by RT-PCR and Western analysis. Intracellular levels of ET-1 were measured by ELISA with and without addition of the protein synthesis inhibitor brefeldin A (50 microg/ml). Prostaglandin levels were measured by gas chromatography-mass spectrometry. Through use of ET(A) and ET(B) antagonists (BQ-610 and BQ-788, respectively), the contribution of the ET receptors to COX-1 and -2 expression and ppET-1 gene expression was examined. The contribution of phosphorylated p38 and p44/42 MAPK on COX-1 and COX-2 expression was also examined with MAPK inhibitors (p38, SB-203580 and p44/42, PD-98056). ET-1 resulted in transient increases in ppET-1, COX-1, and COX-2 gene and protein expression and release of 6-keto-PGF(1alpha) and PGE(2) (P < 0.05). Both internalization of ET-1 and synthesis of new peptide contributed to an increase in intracellular ET-1 (P < 0.05). Although increased ppET-1 was regulated by both ET(A) and ET(B), COX-2 expression was upregulated only by ET(A); COX-1 expression was unaffected by either antagonist. ET-1 treatment resulted in transient phosphorylation of p38 and p44/42 MAPK; inhibitors of these MAPKs suppressed expression of COX-2 but not COX-1. Our data indicate that local production of ET-1 regulates COX-2 by activation of the ET(A) receptor and phosphorylation of p38 and p44/42 MAPK in PLVSMC.

Cyclooxygenase inhibitor blocks rebound response after NO inhalation in an endotoxin model

This study addressed the possible role of cyclooxygenase (COX) and its products in the rebound response to inhaled nitric oxide (INO). Anesthetized, mechanically ventilated piglets were exposed to endotoxin alone, endotoxin combined with INO, or endotoxin with INO plus the COX inhibitor diclofenac (3 mg/kg iv) (n = 8 piglets/group). A control group of healthy pigs (n = 6) was also studied. Measurements were made of blood gases, hemodynamic parameters, lung tissue COX expression, and plasma concentrations of thromboxane B(2) (TxB(2)), PGF(2alpha), and 6-keto-PGF(1alpha). Endotoxin increased lung inducible COX (COX-2) expression and circulating prostanoids concentrations. Inhalation of NO during endotoxemia increased the constitutive COX (COX-1) expression, and the circulating TxB(2) and PGF(2alpha) increased further after INO withdrawal. The combination of COX inhibitor with INO blocked all these changes and eliminated the rebound reaction to INO withdrawal, which otherwise was seen in endotoxemic piglets given INO only. We conclude that the rebound response to INO discontinuation is related to COX products.