Nitric oxide synthase/COX cross-talk: nitric oxide activates COX-1 but inhibits COX-2-derived prostaglandin production

Modulation of the nitric oxide/cGMP pathway in cardiac contraction and relaxation: Potential role in heart failure treatment

Evidence exists that heart failure (HF) has an overall impact of 1-2 % in the global population being often associated with comorbidities that contribute to increased disease prevalence, hospitalization, and mortality. Recent advances in pharmacological approaches have significantly improved clinical outcomes for patients with vascular injury and HF. Nevertheless, there remains an unmet need to clarify the crucial role of nitric oxide/cyclic guanosine 3',5'-monophosphate (NO/cGMP) signalling in cardiac contraction and relaxation, to better identify the key mechanisms involved in the pathophysiology of myocardial dysfunction both with reduced (HFrEF) as well as preserved ejection fraction (HFpEF). Indeed, NO signalling plays a crucial role in cardiovascular homeostasis and its dysregulation induces a significant increase in oxidative and nitrosative stress, producing anatomical and physiological cardiac alterations that can lead to heart failure. The present review aims to examine the molecular mechanisms involved in the bioavailability of NO and its modulation of downstream pathways. In particular, we focus on the main therapeutic targets and emphasize the recent evidence of preclinical and clinical studies, describing the different emerging therapeutic strategies developed to counteract NO impaired signalling and cardiovascular disease (CVD) development.

Potential Therapeutic Applications of Plant-Derived Alkaloids against Inflammatory and Neurodegenerative Diseases

Alkaloids are a type of natural compound possessing different pharmacological activities. Natural products, including alkaloids, which originate from plants, have emerged as potential protective agents against neurodegenerative disorders (NDDs) and chronic inflammations. A wide array of prescription drugs are used against these conditions, however, not free of limitations of potency, side effects, and intolerability. In the context of personalized medicine, further research on alkaloids to unravel novel therapeutic approaches in reducing complications is critical. In this review, a systematic survey was executed to collect the literature on alkaloids and their health complications, from which we found that majority of alkaloids exhibit anti-inflammatory action via nuclear factor-κB and cyclooxygenase-2 (COX-2), and neuroprotective interaction through acetylcholinesterase (AChE), COX, and β-site amyloid precursor protein activity. In silico ADMET and ProTox-II-related descriptors were calculated to predict the pharmacological properties of 280 alkaloids isolated from traditional medicinal plants towards drug development. Out of which, eight alkaloids such as tetrahydropalmatine, berberine, tetrandrine, aloperine, sinomenine, oxymatrine, harmine, and galantamine are found to be optimal within the categorical range when compared to nicotine. These alkaloids could be exploited as starting materials for novel drug synthesis or, to a lesser extent, manage inflammation and neurodegenerative-related complications.

Hybrids as NO Donors

Cinnamic acid and its derivatives have been studied for a variety of biological properties, including anti-inflammatory, antioxidant, anticancer, antihypertensive, and antibacterial. Many hybrids of cinnamic derivatives with other bioactive molecules have been synthesized and evaluated as nitric oxide (NO) donors. Since NO plays a significant role in various biological processes, including vasodilation, inflammation, and neurotransmission, NO donor groups are incorporated into the structures of already-known bioactive molecules to enhance their biological properties. In this review, we present cinnamic hybrids with NO-donating ability useful in the treatment of several diseases.

Assessment of the Vanillin Anti-Inflammatory and Regenerative Potentials in Inflamed Primary Human Gingival Fibroblast

Background

Inflammatory responses have been associated with delayed oral mucosal wound healing and the pathogenesis of the periodontal disease. The invasion of microbes into the tissues and the establishment of a chronic infection may be due to impaired healing. The protracted inflammatory phase may delay wound healing and probably support tissue fibrosis and reduce tissue regeneration. Vanillin is a well-known natural compound with potential anti-inflammatory capacity. Hence, we hypothesized that Vanillin could accelerate wound healing reducing inflammation and especially cytokine production making the oral tissue repair process easier.

Methods

Our hypothesis was tested using primary human gingival fibroblast (HGF) cell pretreated with Vanillin and primed with IL-1β, as inductor of proinflammatory environment. After 24 hours of treatments, the gene expression and production of IL-6, TNF-α, IL-8, COX-2, iNOS, and nitric oxide (NO) generation and the wound healing rate were determined.

Results

In IL-1β-primed cells, preincubation with Vanillin reduced IL-6, IL-8, COX-2, and iNOS expression and NO release, compared to IL-1β-primed cells. Moreover, Vanillin determines the increased gene expression of nAChRα7, leading us to hypothesize a role of Vanillin in the activation of the cholinergic anti-inflammatory pathway. Furthermore, in presence of mechanical injury, the Vanillin preincubation, wound closure may be reducing the expression and release of IL-6 and TNF-α and upregulation of COX-2 and IL-8.

Conclusion

Together, the results of this study highlight the anti-inflammatory and tissue repair ability of Vanillin in IL-1β-primed HGF. Therefore, Vanillin shows a potential therapeutic interest as an inflammatory modulator molecule with novel application in periodontal regeneration and oral health.

El papel de las especies reactivas de oxígeno y nitrógeno en algunas enfermedades neurodegenerativas

Se analiza el importante papel de las especies reactivas de las moléculas de oxígeno y nitrógeno generadas a partir del metabolismo celular fisiológico en los procesos neurodegenerativos con el fin de tener indicios sólidos sobre los posibles tratamientos y prevenir el daño progresivo de enfermedades neurodegenerativas.

New Quinolylnitrones for Stroke Therapy: Antioxidant and Neuroprotective ( Z)- N- tert-Butyl-1-(2-chloro-6-methoxyquinolin-3-yl)methanimine Oxide as a New Lead-Compound for Ischemic Stroke Treatment

We describe herein the synthesis and neuroprotective capacity of an array of 31 compounds comprising quinolyloximes, quinolylhydrazones, quinolylimines, QNs, and related heterocyclic azolylnitrones. Neuronal cultures subjected to oxygen-glucose deprivation (OGD), as experimental model for ischemic conditions, were treated with our molecules at the onset of recovery period after OGD and showed that most of these QNs, but not the azo molecules, improved neuronal viability 24 h after recovery. Especially, QN ( Z)- N-tert-butyl-1-(2-chloro-6-methoxyquinolin-3-yl)methanimine oxide (23) was shown as a very potent neuroprotective agent. Antioxidant analysis based on the ability of QN 23 to trap different types of toxic radical oxygenated species supported and confirmed its strong neuroprotective capacity. Finally, QN 23 showed also neuroprotection induction in two in vivo models of cerebral ischemia, decreasing neuronal death and reducing infarct size, allowing us to conclude that QN 23 can be considered as new lead-compound for ischemic stroke treatment.

Effects of Watermelon Powder and l-arginine Supplementation on Azoxymethane-Induced Colon Carcinogenesis in Rats

Diets high in fruits and vegetables may help prevent colorectal cancer (CRC). Watermelon consumption may reduce CRC risk due to its concentration of l-citrulline and its role in endothelial nitric oxide (NO) production. Research suggests that increased NO levels have tumoricidal effects. The purpose of this study was to determine the effects of watermelon powder supplementation on aberrant crypt foci (ACF) formation, precancerous lesions, and expression of genes associated with colon carcinogenesis. Thirty-two male Sprague-Dawley rats were assigned into three groups: control, 0.36% l-arginine, or 0.5% watermelon powder and injected with azoxymethane (15 mg/kg body weight). Both l-arginine and watermelon powder groups exhibited lower total numbers of ACF and high multiplicity ACF (P < 0.01). The watermelon powder group exhibited higher NO levels and lower 8-hydroxyguanosine DNA damage (P < 0.05). Watermelon powder and l-arginine downregulated 8-oxoguanine DNA glycosylase gene expression and upregulated O⁶-methylguanine DNA methyltransferase gene expression (P < 0.05). Cyclooxgenase-2 gene expression was lower for rats fed with watermelon powder (P < 0.05). These results suggest that watermelon powder or l-arginine supplementation may reduce the risk of colon cancer by suppressing ACF formation through lowering oxidative DNA damage and inflammation, modulating DNA repair enzyme expression, and/or enhancing NO production.

Proteomic Analysis Shows Constitutive Secretion of MIF and p53-associated Activity of COX-2-/- Lung Fibroblasts

The differential expression of two closelyassociated cyclooxygenase isozymes, COX-1 and COX-2, exhibited functions beyond eicosanoid metabolism. We hypothesized that COX-1 or COX-2 knockout lung fibroblasts may display altered protein profiles which may allow us to further differentiate the functional roles of these isozymes at the molecular level. Proteomic analysis shows constitutive production of macrophage migration inhibitory factor (MIF) in lung fibroblasts derived from COX-2^−/− but not wild-type (WT) or COX-1^−/− mice. MIF was spontaneously released in high levels into the extracellular milieu of COX2^−/− fibroblasts seemingly from the preformed intracellular stores, with no change in the basal gene expression of MIF. The secretion and regulation of MIF in COX-2^−/− was “prostaglandin-independent.” GO analysis showed that concurrent with upregulation of MIF, there is a significant surge in expression of genes related to fibroblast growth, FK506 binding proteins, and isomerase activity in COX-2^−/− cells. Furthermore, COX-2^−/− fibroblasts also exhibit a significant increase in transcriptional activity of various regulators, antagonists, and co-modulators of p53, as well as in the expression of oncogenes and related transcripts. Integrative Oncogenomics Cancer Browser (IntroGen) analysis shows downregulation of COX-2 and amplification of MIF and/or p53 activity during development of glioblastomas, ependymoma, and colon adenomas. These data indicate the functional role of the MIF-COX-p53 axis in inflammation and cancer at the genomic and proteomic levels in COX-2-ablated cells. This systematic analysis not only shows the proinflammatory state but also unveils a molecular signature of a pro-oncogenic state of COX-1 in COX-2 ablated cells.

Extracellular histones disarrange vasoactive mediators release through a COX-NOS interaction in human endothelial cells

Extracellular histones are mediators of inflammation, tissue injury and organ dysfunction. Interactions between circulating histones and vascular endothelial cells are key events in histone-mediated pathologies. Our aim was to investigate the implication of extracellular histones in the production of the major vasoactive compounds released by human endothelial cells (HUVECs), prostanoids and nitric oxide (NO). HUVEC exposed to increasing concentrations of histones (0.001 to 100 μg/ml) for 4 hrs induced prostacyclin (PGI2) production in a dose-dependent manner and decreased thromboxane A2 (TXA2) release at 100 μg/ml. Extracellular histones raised cyclooxygenase-2 (COX-2) and prostacyclin synthase (PGIS) mRNA and protein expression, decreased COX-1 mRNA levels and did not change thromboxane A2 synthase (TXAS) expression. Moreover, extracellular histones decreased both, eNOS expression and NO production in HUVEC. The impaired NO production was related to COX-2 activity and superoxide production since was reversed after celecoxib (10 μmol/l) and tempol (100 μmol/l) treatments, respectively. In conclusion, our findings suggest that extracellular histones stimulate the release of endothelial-dependent mediators through an up-regulation in COX-2-PGIS-PGI2 pathway which involves a COX-2-dependent superoxide production that decreases the activity of eNOS and the NO production. These effects may contribute to the endothelial cell dysfunction observed in histone-mediated pathologies.

RAGE-TLR Crosstalk Sustains Chronic Inflammation in Neurodegeneration

Chronic inflammatory reactions are consistenly present in neurodegeneration of Alzheimer type and are considered important factors that accelerate progression of the disease. Receptors of innate immunity participate in triggering and driving inflammatory reactions. For example, Toll-like receptors (TLRs) and receptor for advanced glycation end product (RAGE), major receptors of innate immunity, play a central role in perpetuation of inflammation. RAGE activation should be perceived as a primary mechanism which determines self-perpetuated chronic inflammation, and RAGE cooperation with TLRs amplifies inflammatory signaling. In this review, we highlight and discuss that RAGE-TLR crosstalk emerges as an important driving force of chronic inflammation in Alzheimer's disease.

Anticonvulsive Effects of Licofelone on Status Epilepticus Induced by Lithium-pilocarpine in Wistar Rats: a Role for Inducible Nitric Oxide Synthase

Background and Purpose

Status epilepticus (SE) is a neurological disorder with high prevalence and mortality rates, requiring immediate intervention. Licofelone is a cyclooxygenase (COX) and 5-lipoxygenase (5-LOX) inhibitor, which its effectiveness to treat osteoarthritis has been approved. Increasing evidence suggests an involvement of COX and LOX enzymes in epileptic disorders. Thus, in the present study we investigate possible effects of licofelone on prevention and termination of SE. We also evaluated whether the nitrergic system could participate in this effect of licofelone.

Methods

We have utilized lithium-pilocarpine model of SE in adult Wistar rats to assess the potential effect of licofelone on seizure susceptibility. Licofelone was administered 1 h before pilocarpine. To evaluate probable role of nitric oxide (NO) system, L-arginine (60 mg/kg, i.p.), as a NO precursor; L-NAME (15 mg/kg, i.p.), as a non-selective nitric oxide synthase (NOS) inhibitor; aminoguanidine (100 mg/kg, i.p.), as an inducible NOS (iNOS) inhibitor and 7-nitroindazole (60 mg/kg, i.p.), as a neuronal NOS inhibitor were injected 15 min before licofelone. Also, licofelone and diazepam 10 mg/kg were administered 30 minutes after onset of SE.

Results

Pre-treatment with licofelone at the dosage of 10 mg/kg, significantly prevented the onset of SE in all subjects (p < 0.001). L-arginine significantly inverted this anticonvulsant effect (p < 0.05). However, L-NAME and aminoguanidine, potentiated the anticonvulsant effect of licofelone (p < 0.05, p < 0.01). Licofelone could not terminate seizures after onset which was terminated by diazepam.

Conclusions

Our findings showed that anticonvulsive effects of licofelone on SE could be mediated by iNOS. Also, we suggest that COX/5-LOX activation is possibly required in the initial stage of onset but SE recruits extra excitatory pathways with prolongation.

Anticancer and anti-inflammatory activities of girinimbine isolated from Murraya koenigii

Therapy that directly targets apoptosis and/or inflammation could be highly effective for the treatment of cancer. Murraya koenigii is an edible herb that has been traditionally used for cancer treatment as well as inflammation. Here, we describe that girinimbine, a carbazole alkaloid isolated from M. koenigii, induced apoptosis and inhibited inflammation in vitro as well as in vivo. Induction of apoptosis in human colon cancer cells (HT-29) by girinimbine revealed decreased cell viability in HT-29, whereas there was no cytotoxic effect on normal colon cells. Changes in mitochondrial membrane potential, nuclear condensation, cell permeability, and cytochrome c translocation in girinimbine-treated HT-29 cells demonstrated involvement of mitochondria in apoptosis. Early-phase apoptosis was shown in both acridine orange/propidium iodide and annexin V results. Girinimbine treatment also resulted in an induction of G0/G1 phase arrest which was further corroborated with the upregulation of two cyclin-dependent kinase proteins, p21 and p27. Girinimbine treatment activated apoptosis through the intrinsic pathway by activation of caspases 3 and 9 as well as cleaved caspases 3 and 9 which ended by triggering the execution pathway. Moreover, apoptosis was confirmed by downregulation of Bcl-2 and upregulation of Bax in girinimbine-treated cells. In addition, the key tumor suppressor protein, p53, was seen to be considerably upregulated upon girinimbine treatment. Induction of apoptosis by girinimbine was also evidenced in vivo in zebrafish embryos, with results demonstrating significant distribution of apoptotic cells in embryos after a 24-hour treatment period. Meanwhile, anti-inflammatory action was evidenced by the significant dose-dependent girinimbine inhibition of nitric oxide production in lipopolysaccharide/interferon-gamma-induced cells along with significant inhibition of nuclear factor-kappa B translocation from the cytoplasm to nucleus in stimulated RAW 264.7 cells. Girinimbine was also shown to have considerable antioxidant activity whereby 20 μg/mL of girinimbine was equivalent to 82.17±1.88 μM of Trolox. In mice with carrageenan-induced peritonitis, oral pretreatment with girinimbine helped limit total leukocyte migration (mainly of neutrophils), and reduced pro-inflammatory cytokine levels (interleukin-1beta and tumor necrosis factor-alpha) in the peritoneal fluid. These findings strongly suggest that girinimbine could act as a chemopreventive and/or chemotherapeutic agent by inducing apoptosis while suppressing inflammation. There is a potential for girinimbine to be further investigated for its applicability in treating early stages of cancer.

Copper oxide nanoparticles recruit macrophages and modulate nitric oxide, proinflammatory cytokines and PGE2 production through arginase activation

AIM

In the present study, we examine the effects of copper oxide nanoparticles (CuNP) on macrophage immune response and the signaling pathways involved.

MATERIALS & METHODS

A peritonitis model was used to determine in vivo immune cells recruitment, while primary macrophages were used as an in vitro model for the cellular and molecular analysis.

RESULTS

In vivo, CuNP induce significant macrophages recruitment to the site of injection. In vitro, in LPS-stimulated primary macrophages, the co-treatment with CuNP inhibited the production of NO in a dose-dependent manner. The mechanism underlying NO and proinflammatory cytokines inhibition was associated with an increased arginase activity. Macrophage stimulation with CuNP did not provoke any cytokine secretion; however, arginase inhibition promoted TNFα and MIP-1β production. In addition, CuNP induced the expression of COX-2 and the production of PGE2 through arginase activation.

CONCLUSION

Our results demonstrate that CuNP activate arginase and suppress macrophage innate immune response.

Genomic, Lipidomic and Metabolomic Analysis of Cyclooxygenase-null Cells: Eicosanoid Storm, Cross Talk, and Compensation by COX-1

The constitutively-expressed cyclooxygenase 1 (COX-1) and the inducible COX-2 are both involved in the conversion of arachidonic acid (AA) to prostaglandins (PGs). However, the functional roles of COX-1 at the cellular level remain unclear. We hypothesized that by comparing differential gene expression and eicosanoid metabolism in lung fibroblasts from wild-type (WT) mice and COX-2^-/- or COX-1^-/- mice may help address the functional roles of COX-1 in inflammation and other cellular functions. Compared to WT, the number of specifically-induced transcripts were altered descendingly as follows: COX-2^-/- > COX-1^-/- > WT + IL-1β. COX-1^-/- or COX-2^-/- cells shared about 50% of the induced transcripts with WT cells treated with IL-1β, respectively. An interactive “anti-inflammatory, proinflammatory, and redox-activated” signature in the protein–protein interactome map was observed in COX-2^-/- cells. The augmented COX-1 mRNA (in COX-2^-/- cells) was associated with the upregulation of mRNAs for glutathione S-transferase (GST), superoxide dismutase (SOD), NAD(P)H dehydrogenase quinone 1 (NQO1), aryl hydrocarbon receptor (AhR), peroxiredoxin, phospholipase, prostacyclin synthase, and prostaglandin E synthase, resulting in a significant increase in the levels of PGE₂, PGD₂, leukotriene B₄ (LTB₄), PGF_1α, thromboxane B₂ (TXB₂), and PGF_2α. The COX-1 plays a dominant role in shifting AA toward the LTB₄ pathway and anti-inflammatory activities. Compared to WT, the upregulated COX-1 mRNA in COX-2^-/- cells generated an “eicosanoid storm”. The genomic characteristics of COX-2^-/- is similar to that of proinflammatory cells as observed in IL-1β induced WT cells. COX-1^-/- and COX-2^-/- cells exhibited compensation of various eicosanoids at the genomic and metabolic levels.

Endothelial Dysfunction in Rheumatoid Arthritis: Mechanistic Insights and Correlation with Circulating Markers of Systemic Inflammation

Objectives

To determine mechanisms involved in endothelial dysfunction (ED) during the course of arthritis and to investigate the link between cytokines, chemokines and osteoprotegerin.

Approach and Results

Experiments were conducted on aortic rings at day 4 (preclinical), day 11 (onset of disease), day 33 (acute disease) and day 90 (chronic disease) after adjuvant-induced arthritis (AIA) in Lewis rats. At day 4, the unique vascular abnormality was a reduced norepinephrine-induced constriction. At day 11, endothelial function assessed by the relaxation to acetylcholine was normal despite increased cyclo-oxygenase-2 activity (COX-2) and overproduction of superoxide anions that was compensated by increased nitric oxide synthase (NOS) activity. At day 33, ED apparition coincides with the normalization of NOS activity. At day 90, ED was only observed in rats with a persisting imbalance between endothelial NOS and COX-2 pathways and higher plasma levels of IL-1β and TNFα. Plasma levels of IL-1β, TNFα and MIP-1α negatively correlated with Ach-induced relaxation throughout the course of AIA.

Conclusions

Our data identified increased endothelial NOS activity as an important compensatory response that opposes the ED in the early arthritis. Thereafter, a cross-talk between endothelial COX-2/NOS pathways appears as an important element for the occurrence of ED. Our results encourage determining the clinical value of IL-1β, TNFα and MIP-1α as biomarkers of ED in RA.

Modulation of oxidative and inflammatory cardiac response by nonselective 1- and 2-cyclooxygenase inhibitor and benznidazole in mice

OBJECTIVES

This study investigated the combined effects of benznidazole (BZ) and ibuprofen (IB) on the oxidative and inflammatory status of the cardiac tissue in vivo.

METHODS

Swiss mice were randomized in groups receiving BZ (100 mg/kg) and IB (400 mg/kg) alone or combined (BZ + IB 200 or 400 mg/kg). Control animals were concurrently treated with 1% carboxymethyl cellulose. All treatments were administered orally for 7 days.

KEY FINDINGS

BZ treatment increased cardiac production of nitrogen/oxygen-reactive species, malondialdeyde, carbonyl proteins, prostaglandins as well as the activities of catalase, superoxide dismutase and glutathione peroxidase. These parameters were attenuated by IB, with the best results at higher dose. Individually, BZ and IB significantly reduced the tissue levels of chemokine ligand 2, tumour necrosis factor-α and IL-10, but no reduction was observed when the treatments were combined.

CONCLUSIONS

BZ triggers an oxidative and nitrosative route, which is associated with increased prostaglandin synthesis and marked damages to the lipids and proteins of the cardiac tissue. IB treatment attenuated reactive stresses triggered by BZ, which was an independent effects of this drug on the endogenous antioxidant enzymes. Individually, but not together, BZ and IB reduced the cardiac inflammatory status, indicating a beneficial and complex drug interaction.

Anti-inflammatory properties of convolutamydine A and two structural analogues

AIMS

Convolutamydine A is an oxindole alkaloid that can be isolated from a marine bryozoan. Due to the variety of biological effects, two analogues were synthesized and their anti-inflammatory properties were evaluated.

MAIN METHODS

The anti-inflammatory effects of convolutamydine A and its analogues (ISA003 and ISA147) were investigated in a formalin-induced licking behaviour model, where mice received an intraplantar injection of formalin and their licking behaviour was evaluated for 30min. Additionally, inflammatory parameters were evaluated in a subcutaneous air pouch (SAP) model of carrageenan-induced inflammation. Exudates were collected for leukocyte counts; measurement of protein, prostaglandin E2 (PGE2) and cytokines by ELISA; and analysis of nitric oxide (NO) using a nitrate conversion protocol. Cyclooxygenase-2 (COX2) and inducible nitric oxide synthase (iNOS) from RAW 264.7 cells were quantified by immunoblotting.

KEY FINDINGS

Convolutamydine A and its two analogues inhibited the formalin-induced licking response at doses as low as 0.01mg/kg. An inhibitory effect was also observed on leukocyte migration and the production of NO, PGE2 and cytokines (IL-6 and TNF-α). The reduction in inflammatory parameters did not appear to be correlated with a direct reduction in the number of cells in the SAP, because a reduction in NO and PGE2 production by cultured macrophages was observed in addition to the inhibition of iNOS and COX2 enzyme expression.

SIGNIFICANCE

These results indicate that convolutamydine A and its two analogues have significant anti-inflammatory effects. These substances can be improved to generate lead compounds for the synthesis of new anti-inflammatory drugs.

Characterization of the inflammatory response during Ehrlich ascitic tumor development

INTRODUCTION

Ehrlich tumor is a mammary adenocarcinoma with aggressive behavior. Inoculated in mice peritoneal cavity, the Ehrlich tumor grows in ascitic form (EAT). Since inflammation modulates tumor progression we further investigated the inflammatory response during EAT growth.

METHODS

Balb/C mice were intraperitoneal inoculated with 5×10(5) Ehrlich cells and after every 2days, blood samples were collected for hemoglobin, hematocrit, platelets and leukocytes counts. The ascitic fluid was collected for protein concentration and cell count. Phenotype analysis of the peritoneal cells was made by FACS, prostaglandin E2 (PGE2) and cytokines by ELISA, nitric oxide (NO) by nitrate conversion protocol, and cyclooxygenase-1 (COX1), COX2 and inducible nitric oxide synthase (iNOS) by immunoblotting.

RESULTS

Following EAT inoculation into the peritoneal cavity there was a rapid increase in ascitis volume and protein concentration. The cell number in ascitis remained stable until day 8 (lag phase) followed by a sharp increase. As tumor progressed, blood leukocytes increased and erythrocyte decreased. Phenotypic analysis showed that during the lag phase the percentage of F4/80(+) cells remained similar to control levels and around 7% of this population was also positive for the GR1 marker. These double-positive cells (probably inflammatory monocytes) markedly increased at day 6. The percentage of F4/80-GR1(+)cells (probably neutrophils) was low and did not significantly vary during tumor progression. CD4(+) and CD8(+) cells were not detected in the time points analyzed. iNOS and COX1 expression increased after day 2 reaching peak levels on day 10. COX2 enzyme expression did not change significantly over time. Sustained increase in PGE2 and NO levels was observed. IL-10 and MCP-1 peaked at day 14 and IL-1β increased progressively till day 10. IFN-γ levels were low till day 10, increasing progressively after that.

DISCUSSION

These data extended the characterization of the inflammatory response during Ehrlich ascitis tumor growth, further validating it as a useful model for antitumor drugs screening.

Diethylcarbamazine inhibits NF-κB activation in acute lung injury induced by carrageenan in mice

Diethylcarbamazine citrate (DEC) is widely used to treat lymphatic filariasis and Tropical Pulmonary Eosinophilia. A number of studies have reported a possible role in the host immune system, but exactly how DEC exerts this effect is still unknown. The present study reports the effects of DEC pretreatment on NF-κB regulation using the pleurisy model induced by carrageenan. Swiss male mice (Mus musculus) were divided into four experimental groups: control (SAL); carrageenan (CAR); diethylcarbamazine (DEC) and curcumin (CUR). The animals were pretreated with DEC (50mg/kg, v.o), CUR (50mg/kg, i.p) or distilled water for three consecutive days before pleurisy. One way analysis of variance (ANOVA) was performed by Tukey post-hoc test, and values were considered statistically significant when p<0.05. DEC pretreatment reduced tissue damage and the production of inflammatory markers, such as NO, iNOS, PGE2, COX-2, and PARP induced by carrageenan. Similarly, a known inhibitor of NF-κB pathway (curcumin) was also able to reduce these parameters. Like curcumin, DEC prevents NF-κB activation by reducing NF-κB p65 phosphorylation and IκBα degradation. DEC prevented NF-κB activation via p38 MAPK, but did not interfere in the ERK pathway in this experimental model. However, further studies should be developed to confirm this hypothesis. These findings suggest that DEC could be a promising drug for inflammatory disorders, especially in pulmonary diseases such as Acute Lung Inflammation, due its high anti-inflammatory potential which prevents NF-κB activation.

Aortic valve sclerosis in mice deficient in endothelial nitric oxide synthase

Risk factors for fibrocalcific aortic valve disease (FCAVD) are associated with systemic decreases in bioavailability of endothelium-derived nitric oxide (EDNO). In patients with bicuspid aortic valve (BAV), vascular expression of endothelial nitric oxide synthase (eNOS) is decreased, and eNOS(-/-) mice have increased prevalence of BAV. The goal of this study was to test the hypotheses that EDNO attenuates profibrotic actions of valve interstitial cells (VICs) in vitro and that EDNO deficiency accelerates development of FCAVD in vivo. As a result of the study, coculture of VICs with aortic valve endothelial cells (vlvECs) significantly decreased VIC activation, a critical early phase of FCAVD. Inhibition of VIC activation by vlvECs was attenuated by N(G)-nitro-l-arginine methyl ester or indomethacin. Coculture with vlvECs attenuated VIC expression of matrix metalloproteinase-9, which depended on stiffness of the culture matrix. Coculture with vlvECs preferentially inhibited collagen-3, compared with collagen-1, gene expression. BAV occurred in 30% of eNOS(-/-) mice. At age 6 mo, collagen was increased in both bicuspid and trileaflet eNOS(-/-) aortic valves, compared with wild-type valves. At 18 mo, total collagen was similar in eNOS(-/-) and wild-type mice, but collagen-3 was preferentially increased in eNOS(-/-) mice. Calcification and apoptosis were significantly increased in BAV of eNOS(-/-) mice at ages 6 and 18 mo. Remarkably, these histological changes were not accompanied by physiologically significant valve stenosis or regurgitation. In conclusion, coculture with vlvECs inhibits specific profibrotic VIC processes. In vivo, eNOS deficiency produces fibrosis in both trileaflet and BAVs but produces calcification only in BAVs.

Interaction between NO and COX pathways modulating hepatic endothelial cells from control and cirrhotic rats

Reduced intrahepatic nitric oxide (NO) bioavailability and increased cyclooxygenase-1 (COX-1)-derived vasoconstrictor prostanoids modulate the hepatic vascular tone in cirrhosis. We aimed at investigating the reciprocal interactions between NO and COX in the hepatic endothelium of control and cirrhotic rats. NO bioavailability (DAF-FM-DA staining), superoxide (O₂⁻) content (DHE staining), prostanoid production (PGI₂ and TXA₂ by enzyme immunoassays) as well as COX expression (Western Blot), were determined in hepatic endothelial cells (HEC) from control and cirrhotic rats submitted to different experimental conditions: COX activation, COX inhibition, NO activation and NO inhibition. In control and cirrhotic HEC, COX activation with arachidonic acid reduced NO bioavailability and increased O₂⁻ levels. These effects were abolished by pre-treating HEC with the COX inhibitor indomethacin. In control, but not in cirrhotic HEC, scavenging of O₂⁻ by superoxide dismutase (SOD) incubation partially restored the decrease in NO bioavailability promoted by COX activation. NO supplementation produced a significant and parallel reduction in PGI₂ and TXA₂ production in control HEC, whereas it only reduced TXA₂ production in cirrhotic HEC. By contrast, in control and cirrhotic HEC, NO inhibition did not modify COX expression or activity. Our results demonstrate that NO and COX systems are closely interrelated in HEC. This is especially relevant in cirrhotic HEC where COX inhibition increases NO bioavailability and NO supplementation induces a reduction in TXA₂. These strategies may have beneficial effects ameliorating the vasoconstrictor/vasodilator imbalance of the intrahepatic circulation of cirrhotic livers.

Integrated analysis of COX-2 and iNOS derived inflammatory mediators in LPS-stimulated RAW macrophages pre-exposed to Echium plantagineum L. bee pollen extract

Oxidative stress and inflammation play important roles in disease development. This study intended to evaluate the anti-inflammatory and antioxidant potential of Echium plantagineum L. bee pollen to support its claimed health beneficial effects. The hydromethanol extract efficiently scavenged nitric oxide (^•NO) although against superoxide (O₂^•−) it behaved as antioxidant at lower concentrations and as pro-oxidant at higher concentrations. The anti-inflammatory potential was evaluated in LPS-stimulated macrophages. The levels of ^•NO and L-citrulline decreased for all extract concentrations tested, while the levels of prostaglandins, their metabolites and isoprostanes, evaluated by UPLC-MS, decreased with low extract concentrations. So, E. plantagineum bee pollen extract can exert anti-inflammatory activity by reducing ^•NO and prostaglandins. The extract is able to scavenge the reactive species ^•NO and O₂^•− and reduce markers of oxidative stress in cells at low concentrations.

Autocatalytic nitration of prostaglandin endoperoxide synthase-2 by nitrite inhibits prostanoid formation in rat alveolar macrophages

AIMS

Prostaglandin endoperoxide H(2) synthase (PGHS) is a well-known target for peroxynitrite-mediated nitration. In several experimental macrophage models, however, the relatively late onset of nitration failed to coincide with the early peak of endogenous peroxynitrite formation. In the present work, we aimed to identify an alternative, peroxynitrite-independent mechanism, responsible for the observed nitration and inactivation of PGHS-2 in an inflammatory cell model.

RESULTS

In primary rat alveolar macrophages stimulated with lipopolysaccharide (LPS), PGHS-2 activity was suppressed after 12 h, although the prostaglandin endoperoxide H(2) synthase (PGHS-2) protein was still present. This coincided with a nitration of the enzyme. Coincubation with a nitric oxide synthase-2 (NOS-2) inhibitor preserved PGHS-2 nitration and at the same time restored thromboxane A(2) (TxA(2)) synthesis in the cells. Formation of reactive oxygen species (ROS) was maximal at 4 h and then returned to baseline levels. Nitrite (NO(2)(-)) production occurred later than ROS generation. This rendered generation of peroxynitrite and the nitration of PGHS-2 unlikely. We found that the nitrating agent was formed from NO(2)(-), independent from superoxide ((•)O(2)(-)). Purified PGHS-2 treated with NO(2)(-) was selectively nitrated on the active site Tyr(371), as identified by mass spectrometry (MS). Exposure to peroxynitrite resulted in the nitration not only of Tyr(371), but also of other tyrosines (Tyr).

INNOVATION AND CONCLUSION

The data presented here point to an autocatalytic nitration of PGHS-2 by NO(2)(-), catalyzed by the enzyme's endogenous peroxidase activity and indicate a potential involvement of this mechanism in the termination of prostanoid formation under inflammatory conditions.

Exposure to nerve agents: from status epilepticus to neuroinflammation, brain damage, neurogenesis and epilepsy

Epilepsy is a common neurological disorder characterized by an initial injury due to stroke, traumatic brain injury, brain infection, or febrile seizures causing status epilepticus (SE). This phenomenon precedes recurrent (secondary) seizures, the latent period (period without seizures) and downstream appearance of spontaneous recurrent seizures (SRS). Epilepsy inducers include the organophosphorous (OP) compounds modified as chemical warfare nerve agents, such as soman. SE induced by soman is a result of cholinergic system hyperactivity caused by the irreversible inhibition of acetylcholinesterase, and the subsequent increase in the amount of the neurotransmitter acetylcholine at central and peripheral sites. SE leads to profound, permanent, complex and widespread brain damage and associated cognitive and behavioral deficits, accompanied by impaired neurogenesis. Several anticonvulsant and neuroprotective strategies have been studied in order to avoid the epileptogenesis which occurs after SE caused by soman exposure. In recent studies, we showed that SRS occur post-soman exposure and neuropathology can be reduced with diazepam (DZP) and valproic acid (VPA) when administered in combination treatment. These effects are accompanied by neurogenesis seen 15 days post-exposure in the hippocampal dentate gyrus (DG). This review discusses several findings about epilepsy induced by soman exposure such as behavioral changes, EEG anomalies, neuropathology, neuroinflammation, neurogenesis, possible circuitry changes and current strategies for treatment. The soman seizure model is an important model of temporal lobe epilepsy (TLE) and comparable in certain respects with well studied models in the literature such as pilocarpine and kainic acid. All these models together allow for a greater understanding of the different mechanisms of seizure induction, propagation and options for treatment. These studies are very necessary for current military and civilian treatment regimens, against OP nerve agent exposure, which fail to prevent SE resulting in severe neuropathology and epilepsy.

GM-CSF priming drives bone marrow-derived macrophages to a pro-inflammatory pattern and downmodulates PGE2 in response to TLR2 ligands

In response to pathogen recognition by Toll-like receptors (TLRs) on their cell surface, macrophages release lipid mediators and cytokines that are widely distributed throughout the body and play essential roles in host responses. Granulocyte macrophage colony-stimulating factor (GM-CSF) is important for the immune response during infections to improve the clearance of microorganisms. In this study, we examined the release of mediators in response to TLR2 ligands by bone marrow-derived macrophages (BMDMs) primed with GM-CSF. We demonstrated that when stimulated with TLR2 ligands, non-primed BMDMs preferentially produced PGE₂ in greater amounts than LTB₄. However, GM-CSF priming shifted the release of lipid mediators by BMDMs, resulting in a significant decrease of PGE₂ production in response to the same stimuli. The decrease of PGE₂ production from primed BMDMs was accompanied by a decrease in PGE-synthase mRNA expression and an increase in TNF-α and nitric oxide (NO) production. Moreover, some GM-CSF effects were potentiated by the addition of IFN-γ. Using a variety of TLR2 ligands, we established that PGE₂ release by GM-CSF-primed BMDMs was dependent on TLR2 co-receptors (TLR1, TLR6), CD14, MyD88 and the nuclear translocation of NFκB but was not dependent on peroxisome proliferator-activated receptor-γ (PPAR-γ) activation. Indeed, GM-CSF priming enhanced TLR2, TLR4 and MyD88 mRNA expression and phospho-IκBα formation. These findings demonstrate that GM-CSF drives BMDMs to present a profile relevant to the host during infections.

Α-aryl-N-alkyl nitrones, as potential agents for stroke treatment: synthesis, theoretical calculations, antioxidant, anti-inflammatory, neuroprotective, and brain-blood barrier permeability properties

We report the synthesis, theoretical calculations, the antioxidant, anti-inflammatory, and neuroprotective properties, and the ability to cross the blood-brain barrier (BBB) of (Z)-α-aryl and heteroaryl-N-alkyl nitrones as potential agents for stroke treatment. The majority of nitrones compete with DMSO for hydroxyl radicals, and most of them are potent lipoxygenase inhibitors. Cell viability-related (MTT assay) studies clearly showed that nitrones 1-3 and 10 give rise to significant neuroprotection. When compounds 1-11 were tested for necrotic cell death (LDH release test) nitrones 1-3, 6, 7, and 9 proved to be neuroprotective agents. In vitro evaluation of the BBB penetration of selected nitrones 1, 2, 10, and 11 using the PAMPA-BBB assay showed that all of them cross the BBB. Permeable quinoline nitrones 2 and 3 show potent combined antioxidant and neuroprotective properties and, therefore, can be considered as new lead compounds for further development in specific tests for potential stroke treatment.

Heterogenous vasodilator pathways underlie flow-mediated dilation in men and women

This study investigated the sex differences in the contribution of nitric oxide (NO) and prostaglandins (PGs) to flow-mediated dilation (FMD). Radial artery (RA) FMD, assessed as the dilatory response to 5-min distal cuff occlusion, was repeated after three separate brachial artery infusions of saline (SAL), N(G)-monomethyl-L-arginine (L-NMMA), and ketorolac (KETO) + L-NMMA in healthy younger men (M; n = 8) and women (W; n = 8). In eight subjects (4 M, 4W) RA FMD was reassessed on a separate day with drug order reversed (SAL, KETO, and L-NMMA + KETO). RA FMD was calculated as the peak dilatory response observed relative to baseline (%FMD) and expressed relative to the corresponding area under the curve shear stress (%FMD/AUC SS). L-NMMA reduced %FMD similarly and modestly (P = 0.68 for sex * trial interaction) in M and W (all subjects: 10.0 ± 3.8 to 7.6 ± 4.7%; P = 0.03) with no further effect of KETO (P = 0.68). However, all sex * trial and trial effects on %FMD/AUC SS for l-NMMA and KETO + l-NMMA were insignificant (all P > 0.20). There was also substantial heterogeneity of the magnitude and direction of dilator responses to blockade. After l-NMMA infusion, subjects exhibited both reduced (n = 14; range: 11 to 78% decrease) and augmented (n = 2; range: 1 to 96% increase) %FMD. Following KETO + l-NMMA, seven subjects exhibited reduced dilation (range: 10 to 115% decrease) and nine subjects exhibited augmented dilation (range: 1 to 212% increase). Reversing drug order did not change the nature of the findings. These findings suggest that RA FMD is not fully or uniformly NO dependent in either men or women, and that there is heterogeneity in the pathways underlying the conduit dilatory response to ischemia.

Nitric Oxide (NO) and Cyclooxygenase-2 (COX-2) Cross-Talk in Co-Cultures of Tumor Spheroids with Normal Cells

Cyclooxygenases (COX), prostaglandin E₂ (PGE₂) and nitric oxide (NO) are believed to be some of the most important factors related to colon cancer growth and metastasis. In this study, we aimed to investigate the associations between COX-2, PGE₂ and NO in co-cultures of human colon cancer spheroids obtained from different tumor grades with normal human colonic epithelium and myofibroblast monolayers. L-arginine (2 mM), a substrate for nitric oxide synthases (NOS), decreased COX-2 and PGE₂ levels, while N^G-nitro-L-arginine methyl ester (L-NAME) (2 mM), a NOS inhibitor, had no influence on COX-2 and PGE₂ levels but limited tumor cell motility. NS398 (75 μM), a selective COX-2 inhibitor, had no significant influence on NO level but decreased motility of tumor cells. COX-2, PGE₂ and NO levels depended on the tumor grade of the cells, being the highest in Duke’s stage III colon carcinoma. Summing up, we showed that addition of L-arginine at doses which did not stimulate NO level caused a significant decrease in COX-2 and PGE₂ amounts in co-cultures of colon tumor spheroids with normal epithelial cells and myofibroblasts. Any imbalances in NO level caused by exogenous factors influence COX-2 and PGE₂ amounts depending on the kind of cells, their reciprocal interactions and the local microenvironmental conditions. The knowledge of these effects may be useful in limiting colon carcinoma progression and invasion.

Convenient synthesis and biological profile of 5-amino-substituted 1,2,4-oxadiazole derivatives

We describe herein a convenient straightforward synthesis of 5-amino-substituted 1,2,4-oxadiazoles, upon the reactions of amidoximes with carbodiimides, as well as their further derivatization to acetamides, in good yields. Most of the compounds exhibited in general low interaction with the stable radical 1,1-diphenyl-2-picryl-hydrazyl. Compounds 32 and 39 inhibited significantly soybean lipoxygenase. Selected compounds were screened for their in vivo anti-inflammatory activity using the carrageenin paw edema model and showed significant anti-inflammatory activity (26, 51%). The ability of the compounds to release NO in the presence of a thiol factor has been also investigated.

Combining nitric oxide release with anti-inflammatory activity preserves nigrostriatal dopaminergic innervation and prevents motor impairment in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine model of Parkinson's disease

Background

Current evidence suggests a role of neuroinflammation in the pathogenesis of Parkinson's disease (PD) and in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of basal ganglia injury. Reportedly, nonsteroidal anti-inflammatory drugs (NSAIDs) mitigate DAergic neurotoxicity in rodent models of PD. Consistent with these findings, epidemiological analysis indicated that certain NSAIDs may prevent or delay the progression of PD. However, a serious impediment of chronic NSAID therapy, particularly in the elderly, is gastric, renal and cardiac toxicity. Nitric oxide (NO)-donating NSAIDs, have a safer profile while maintaining anti-inflammatory activity of parent compounds. We have investigated the oral activity of the NO-donating derivative of flurbiprofen, [2-fluoro-α-methyl (1,1'-biphenyl)-4-acetic-4-(nitrooxy)butyl ester], HCT1026 (30 mg kg^-1 daily in rodent chow) in mice exposed to the parkinsonian neurotoxin MPTP.

Methods

Ageing mice were fed with a control, flurbiprofen, or HCT1026 diet starting ten days before MPTP administration and continuing for all the experimental period. Striatal high affinity synaptosomial dopamine up-take, motor coordination assessed with the rotarod, tyrosine hydroxylase (TH)- and dopamine transporter (DAT) fiber staining, stereological cell counts, immunoblotting and gene expression analyses were used to assess MPTP-induced nigrostriatal DAergic toxicity and glial activation 1-40 days post-MPTP.

Results

HCT1026 was well tolerated and did not cause any measurable toxic effect, whereas flurbiprofen fed mice showed severe gastrointestinal side-effects. HCT1026 efficiently counteracted motor impairment and reversed MPTP-induced decreased synaptosomal [³H]dopamine uptake, TH- and DAT-stained fibers in striatum and TH⁺ neuron loss in subtantia nigra pars compacta (SNpc), as opposed to age-matched mice fed with a control diet. These effects were associated to a significant decrease in reactive macrophage antigen-1 (Mac-1)-positive microglial cells within the striatum and ventral midbrain, decreased expression of iNOS, Mac-1 and NADPH oxidase (PHOX), and downregulation of 3-Nitrotyrosine, a peroxynitrite finger print, in SNpc DAergic neurons.

Conclusions

Oral treatment with HCT1026 has a safe profile and a significant efficacy in counteracting MPTP-induced dopaminergic (DAergic) neurotoxicity, motor impairment and microglia activation in ageing mice. HCT1026 provides a novel promising approach towards the development of effective pharmacological neuroprotective strategies against PD.

Cochlospermum vitifolium induces vasorelaxant and antihypertensive effects mainly by activation of NO/cGMP signaling pathway

AIM OF THE STUDY

Cochlospermum vitifolium is a medicinal plant used for the treatment of diabetes, hepatobilary and cardiovascular illnesses. The aim of current study was to determine the in vivo antihypertensive and in vitro functional vasorelaxant mechanism of methanol extract of Cochlospermum vitifolium (MECv) and naringenin (NG).

MATERIALS AND METHODS

Test material was assayed on rat isolated aorta rings test with- and without-endothelium to determine their vasorelaxant mechanism. Also, the in vivo antihypertensive effect was evaluated on spontaneously hypertensive rat (SHR) model. In addition, presence of NG into the extract was confirmed by reverse phase high performance liquid chromatography (RP-HPLC) analysis.

RESULTS

MECv (120 mg/kg) and NG (50 and 160 mg/kg) showed acute antihypertensive effects on SHR when systolic and diastolic pressure were decreased at 1 h and 24 h after administration, respectively. Vasorelaxant effect of MECv and NG was shifted to the right when endothelium-intact aortic rings were pre-incubated with L-NAME (10 microM) and ODQ (1 microM). Also, NG relaxant curves were displaced to the right in the presence of tetraethylammonium (TEA, 1 mM) and 2-aminopyridine (2-AP, 100 microM) on endothelium-denuded aortic rings.

CONCLUSION

Experiments described above showed that MECv play an important role in hypertension regulation through NO synthesis and may be PGI(2) production and potassium channel activation on excessive endothelial dysfunction conditions. Unfortunately, presence of NG into the extract is not significant on bioactivity of the extract; however, this compound could be tested and evaluated as structural scaffold for future drug design for development of antihypertensive agents.

Echinacea and its alkylamides: effects on the influenza A-induced secretion of cytokines, chemokines, and PGE₂ from RAW 264.7 macrophage-like cells

The goal of this study was to determine whether extracts and isolated alkylamides from Echinacea purpurea would be useful for prevention of the inflammatory response that accompanies infections with H1N1 influenza A. Seventeen extracts and 4 alkylamides were tested for the ability to inhibit production of cytokines, chemokines, and PGE₂ from RAW 264.7 macrophage-like cells infected with the H1N1 influenza A strain PR/8/34. The alkylamides undeca-2Z,4E-diene-8,10-diynic acid isobutylamide, dodeca-2E,4E,8Z,10E/Z-tetraenoic acid isobutylamide, dodeca-2E,4E-dienoic acid isobutylamide, and undeca-2E-ene-8,10-diynoic acid isobutylamide suppressed production of TNF-α and PGE₂ from infected cells. Dodeca-2E,4E-dienoic acid isobutylamide was especially effective at inhibiting production of these mediators and also strongly inhibited production of G-CSF, CCL2/MCP-1, CCL3/MIP-1α and CCL5/RANTES. In contrast, the ethanol extracts (75%), which were prepared from dormant roots of E. purpurea grown in different locations throughout North Carolina, displayed a range of effects from suppression to stimulation of mediator production. Precipitation of the extracts with ethanol removed the stimulatory activity, however, even after precipitation; many of the extracts did not display any suppressive activity. Analysis of the extracts revealed slight variations in concentration of alkylamides, caftaric acid, and cichoric acid, but the activity of the extracts did not strongly correlate with concentrations of these compounds. Our in vitro experiments suggest that E. purpurea extracts have the potential for use in alleviating the symptoms and pathology associated with infections with influenza A; however, further study will be necessary to define procedures necessary to unmask the alkylamide activity in crude extracts.

Release of prostaglandin E(2) and nitric oxide from spinal microglia is dependent on activation of p38 mitogen-activated protein kinase

BACKGROUND

The spinal release of prostaglandins (PGs), nitric oxide (NO), and cytokines has been implicated in spinal nociceptive processing. Microglia represent a possible cell of origin for these proexcitatory mediators. Spinal microglia possess Toll-like receptor 4 (TLR4) and neurokinin 1 (NK1) receptors, and both receptors play a significant role in peripheral nerve injury- and inflammation-induced spinal sensitization. Accordingly, we examined the properties of the cascades activated by the respective targets, which led to the release of PGE(2) and an increase in nitrite (NO(2)(-)) (a marker of NO) from cultured rat spinal microglia.

METHODS

Spinal microglia isolated from Sprague-Dawley neonatal rats were cultured with lipopolysaccharide (LPS) or substance P (SP) alone, with LPS in combination with SP, and with LPS in the presence of each inhibitor of cyclooxygenase (COX), NO synthase 2 (NOS2) or p38 mitogen-activated protein kinase (p38), or minocycline for 24 hours and 48 hours. Concentrations of PGE(2) and NO(2)(-) in culture supernatants were measured using an enzyme immunoassay and a colorimetric assay, respectively.

RESULTS

Application of LPS (a TLR4 ligand, 0.1 to 10 ng/mL) to cultured microglia produced a dose- and time-dependent increase in PGE(2) and NO(2)(-) production, whereas no effects were observed after incubation with SP (an NK1 agonist, up to 10(-5) M) alone or in combination with LPS. Antagonist studies with SC-560 (COX-1 inhibitor) and SC-236 (COX-2 inhibitor) showed that LPS-induced PGE(2) release was generated from both COX-1 and COX-2. LPS-induced NO release was suppressed by 1400W, an inhibitor of NOS2. Minocycline, an agent blocking microglial activation, and SB203580, an inhibitor of p38, both attenuated the LPS-induced PGE(2) and NO release. The 1400W, at the doses that suppressed NO release, also blocked increased PGE(2) release.

CONCLUSIONS

Our findings suggest that (a) activation of spinal microglia via TLR4 but not NK1 receptors produces PGE(2) and NO release from these cells; (b) the evoked PGE(2) release is generated by both COX-1 and COX-2, and (c) the COX-PGE(2) pathway is regulated by p38 and NOS2. Taken together with our previous in vivo work, the current findings emphasize that p38 in spinal microglia is a key player in regulating production of pronociceptive molecules, such as PGE(2) and NO.

Mechanism of Cytosolic Phospholipase A(2) Activation in Ghrelin Protection of Salivary Gland Acinar Cells against Ethanol Cytotoxicity

Ghrelin, a peptide hormone, newly identified in oral mucosal tissues, has emerged recently as an important mediator of the processes of mucosal defense. Here, we report on the mechanism of ghrelin protection against ethanol cytotoxicity in rat sublingual salivary gland cells. The protective effect of ghrelin was associated with the increase in NO and PGE2, and upregulation in cytosolic phospholipase A₂ (cPLA₂) activity and arachidonic acid (AA) release. The loss in countering effect of ghrelin occurred with cNOS inhibitor, L-NAME, as well as indomethacin and COX-1 inhibitor, SC-560, while COX-2 inhibitor, NS-398, and iNOS inhibitor, 1400W, had no effect. The effect of L-NAME was reflected in the inhibition of ghrelin-induced cell capacity for NO production, cPLA₂ activation and PGE2 generation, whereas indomethacin caused only the inhibition in PGE2. Moreover, the ghrelin-induced up-regulation in AA release was reflected in the cPLA₂ phosphorylation and S-nitrosylation. Inhibition in ghrelin-induced S-nitrosylation was attained with L-NAME, whereas the ERK inhibitor, PD98059, caused the blockage in cPLA₂ protein phosphorylation as well as S-nitrosylation. Thus, ghrelin protection of salivary gland cells against ethanol involves cNOS-derived NO induction of cPLA₂ activation through S-nitrosylation for the increase in AA release at the site of COX-1 action for PGE2 synthesis.

Cardiovascular consequences when nitric oxide and lipid signaling converge

The identification of nitric oxide ((*)NO) as an endogenously produced free radical mediator of endothelial-dependent relaxation and host defense has fundamentally changed concepts of cell signal transduction. Ligand-receptor oriented paradigms of cell signaling were originally centered on the concept of a high affinity and specific interaction between a ligand and its receptor, resulting in the activation of secondary signaling events such as gene expression or modulation of catalytic protein function. While (*)NO ligation of the heme iron of soluble guanylate cyclase is consistent with this perspective, the readily diffusible and broadly reactive (*)NO is increasingly appreciated to react with a vast array of target molecules that mediate paracrine vasodilator actions, inhibition of thrombosis and neointimal proliferation, and both pro- and antiinflammatory signaling reactions that are not affected by inhibitors of soluble guanylate cyclase. There is an expanding array of functionally significant "off target" collateral reactions mediated by (*)NO that are guanylate cyclase-independent and rather are dictated by anatomic distribution and the formation of secondary (*)NO-derived species. These reactions are a critical element of redox-regulated signaling and are addressed herein in the context of the oxidation of unsaturated fatty acids to vascular and inflammatory signaling mediators. Because of their abundance and the intrinsic reactivity of unsaturated lipid intermediates and eicosanoid metabolism enzymes with (*)NO and other oxides of nitrogen, lipid signaling mechanisms are a significant target for regulation by (*)NO in the vascular compartment. This convergence of (*)NO and lipid signaling pathways thus adds another level of regulation to physiological responses such as vasodilation, thrombosis, and inflammation. Herein, interactions between (*)NO and lipid signaling events are placed in the context of cardiovascular regulation.

Involvement of constitutive nitric oxide synthase in ghrelin-induced cytosolic phospholipase A(2) activation in gastric mucosal cell protection against ethanol cytotoxicity

Ghrelin, an endogenous ligand for the growth hormone secretagogue receptor, is an important regulator of nitric oxide synthase (NOS) and cyclooxygenase (COX) enzyme systems, the products of which are of major significance to the processes of gastric mucosal defense and repair. Here, using primary culture of rat gastric mucosal cells, we report on the mechanism of ghrelin protection against ethanol cytotoxicity. We show that the protective effect of ghrelin was associated with the increase in NO and PGE2 production, and characterized by a marked up-regulation in cytosolic phospholipase A(2) (cPLA(2)) activity and arachidonic acid (AA) release. The loss in countering effect of ghrelin on the ethanol cytotoxicity was attained with constitutive NOS (cNOS) inhibitor, L-NAME, as well as indomethacin and a specific COX-1 inhibitor, SC-560, while specific COX-2 inhibitor, NS-398, and a selective inducible NOS (iNOS) inhibitor, 1400W, had no effect. The effect of L-NAME was reflected in the inhibition of ghrelin-induced mucosal cell capacity for NO production, cPLA(2) activation, and PGE2 generation, whereas indomethacin caused only the inhibition in PGE2 generation. Moreover, the ghrelin-induced up-regulation in AA release was reflected in the cPLA(2) enzyme protein phosphorylation and S-nitrosylation. Preincubation with L-NAME resulted in the inhibition of the ghrelin-induced S-nitrosylation, whereas the ERK inhibitor, PD98059, caused the blockage in cPLA(2) protein phosphorylation as well as S-nitrosylation. The findings demonstrate that ghrelin protection of gastric mucosa against ethanol cytotoxicity involves cNOS-derived NO induction of cPLA(2) activation for the increase in PGE2 synthesis. This activation process apparently includes the cPLA(2) phosphorylation followed by S-nitrosylation.

Prognostic significance of tumor iNOS and COX-2 in stage III malignant cutaneous melanoma

PURPOSE

New prognostic markers are needed for malignant melanoma. Inducible nitric oxide synthase (iNOS) and cyclooxygenase type 2 (COX-2) have been described to correlate with progression of melanoma. Moreover, activating mutations in BRAF/NRAS oncogenes are often detected in melanoma. The BRAF/NRAS mutation status and expression of COX-2 and iNOS were examined to compare their prognostic value for overall survival (OS) in stage III malignant cutaneous melanoma.

EXPERIMENTAL DESIGN

The expression of iNOS and COX-2 in metastatic lymph nodes from 21 rapidly progressing (OS from date of diagnosis of stage III disease < or =14 months) and 17 slowly progressing (OS > or =60 months) stage III cutaneous melanoma patients was examined by immunohistochemistry. The presence of BRAF/NRAS mutations was analyzed using direct DNA sequencing. Chi2 exact trend test and logistic regression analysis were used for statistical analysis.

RESULTS

Both iNOS (P = 0.002) and COX-2 (P = 0.048) alone significantly predicted OS. The BRAF/NRAS mutation status did not significantly differ between patient groups, although iNOS significantly (P = 0.013) correlated with BRAF mutation frequency. Furthermore, the odds ratio (OR) with respect to OS of iNOS (OR = 10.4) was higher than that of COX-2 (OR = 5.6) and was stable in the multivariate analysis of OS together with disease stage IIIB/C, ulceration, number of metastatic lymph nodes, and Breslow tumor thickness.

CONCLUSION

Our data show that iNOS is an independent and stronger prognostic factor for OS in stage III malignant cutaneous melanoma than COX-2.

Convergence of nitric oxide and lipid signaling: anti-inflammatory nitro-fatty acids

The signaling mediators nitric oxide ( NO) and oxidized lipids, once viewed to transduce metabolic and inflammatory information via discrete and independent pathways, are now appreciated as interdependent regulators of immune response and metabolic homeostasis. The interactions between these two classes of mediators result in reciprocal control of mediator synthesis that is strongly influenced by the local chemical environment. The relationship between the two pathways extends beyond coregulation of NO and eicosanoid formation to converge via the nitration of unsaturated fatty acids to yield nitro derivatives (NO(2)-FA). These pluripotent signaling molecules are generated in vivo as an adaptive response to oxidative inflammatory conditions and manifest predominantly anti-inflammatory signaling reactions. These actions of NO(2)-FA are diverse, with these species serving as a potential chemical reserve of NO, reacting with cellular nucleophiles to posttranslationally modify protein structure, function, and localization. In this regard these species act as potent endogenous ligands for peroxisome proliferator-activated receptor gamma. Functional consequences of these signaling mechanisms have been shown in multiple model systems, including the inhibition of platelet and neutrophil functions, induction of heme oxygenase-1, inhibition of LPS-induced cytokine release in monocytes, increased insulin sensitivity and glucose uptake in adipocytes, and relaxation of preconstricted rat aortic segments. These observations have propelled further in vitro and in vivo studies of mechanisms of NO(2)-FA signaling and metabolism, highlighting the therapeutic potential of this class of molecules as anti-inflammatory drug candidates.

Reactive nitrogen species: molecular mechanisms and potential significance in health and disease

Reactive nitrogen species (RNS) are various nitric oxide-derived compounds, including nitroxyl anion, nitrosonium cation, higher oxides of nitrogen, S-nitrosothiols, and dinitrosyl iron complexes. RNS have been recognized as playing a crucial role in the physiologic regulation of many, if not all, living cells, such as smooth muscle cells, cardiomyocytes, platelets, and nervous and juxtaglomerular cells. They possess pleiotropic properties on cellular targets after both posttranslational modifications and interactions with reactive oxygen species. Elevated levels of RNS have been implicated in cell injury and death by inducing nitrosative stress. The aim of this comprehensive review is to address the mechanisms of formation and removal of RNS, highlighting their potential cellular targets: lipids, DNA, and proteins. The specific importance of RNS and their paradoxic effects, depending on their local concentration under physiologic conditions, is underscored. An increasing number of compounds that modulate RNS processing or targets are being identified. Such compounds are now undergoing preclinical and clinical evaluations in the treatment of pathologies associated with RNS-induced cellular damage. Future research should help to elucidate the involvement of RNS in the therapeutic effect of drugs used to treat neurodegenerative, cardiovascular, metabolic, and inflammatory diseases and cancer.

Induced nitric oxide synthase as a major player in the oncogenic transformation of inflamed tissue

Nitric oxide (NO) is a free radical that is involved in the inflammatory process and carcinogenesis. There are four nitric oxide synthase enzymes involved in NO production: induced nitric oxide synthase (iNOS), endothelial NO synthase (eNOS), neural NO synthase (nNOS), and mitochondrial NOS. iNOS is an inducible and key enzyme in the inflamed tissue. Recent literatures indicate that NO as well as iNOS and eNOS can modulate cancer-related events including nitro-oxidative stress, apoptosis, cell cycle, angio-genesis, invasion, and metastasis. This chapter focuses on linking NO/iNOS/eNOS to inflammation and carcinogenesis from experimental evidence to potential targets on cancer prevention and treatment.

Peroxynitrite-mediated lipid oxidation and nitration: mechanisms and consequences

Lipid oxidation and nitration represents a novel area of research of relevance in the understanding of inflammatory processes. Peroxynitrite, the product of the diffusion-limited reaction between nitric oxide and superoxide anion, mediates oxidative modifications in lipid systems including cell membranes and lipoproteins. In this review, we discuss the mechanisms of lipid oxidation and nitration by peroxynitrite as well as the influence of physiological molecules and cell targets to redirect peroxynitrite reactivity. We also provide evidence to support that oxidation/nitration of lipids results in the formation of novel signaling modulators of key lipid-metabolizing enzymes.

Protein nitration in placenta - functional significance

Crucial roles of the placenta are disrupted in early and mid-trimester pregnancy loss, preeclampsia, eclampsia and intrauterine growth restriction. The pathophysiology of these disorders includes a relative hypoxia of the placenta, ischemia/reperfusion injury, an inflammatory response and oxidative stress. Reactive oxygen species including nitric oxide (NO), carbon monoxide and superoxide have been shown to participate in trophoblast invasion, regulation of placental vascular reactivity and other events. Superoxide, which regulates expression of redox sensitive genes, has been implicated in up-regulation of transcription factors, antioxidant production, angiogenesis, proliferation and matrix remodeling. When superoxide and nitric oxide are present in abundance, their interaction yields peroxynitrite a potent pro-oxidant, but also alters levels of nitric oxide, which in turn affect physiological functions. The peroxynitrite anion is extremely unstable thus evidence of its formation in vivo has been indirect via the occurrence of nitrated moieties including nitrated lipids and nitrotyrosine residues in proteins. Formation of 3-nitrotyrosine (protein nitration) is a "molecular fingerprint" of peroxynitrite formation. Protein nitration has been widely reported in a number of pathological states associated with inflammation but is reported to occur in normal physiology and is thought of as a prevalent, functionally relevant post-translational modification of proteins. Nitration of proteins can give either no effect, a gain or a loss of function. Nitration of a range of placental proteins is found in normal pregnancy but increased in pathologic pregnancies. Evidence is presented for nitration of placental signal transduction enzymes and transporters. The targets and extent of nitration of enzymes, receptors, transporters and structural proteins may markedly influence placental cellular function in both physiologic and pathologic settings.