The mode of action of aspirin-like drugs: effect on inducible nitric oxide synthase

Eugenosedin-A amelioration of lipopolysaccharide-induced up-regulation of p38 MAPK, inducible nitric oxide synthase and cyclooxygenase-2

In this study, we investigate the protective effects of eugenosedin-A on p38 mitogen-activated protein kinase (MAPK), inflammatory nitric oxide (NO) and cyclooxygenase-2 (COX-2) pathways in a rat model of endotoxin shock. Rats were pretreated with eugenosedin-A, trazodone, yohimbine (1 mg kg(-1), i.v.), aminoguanidine or ascorbic acid (15 mg kg(-1), i.v.) 30 min before endotoxin challenge. Endotoxaemia was induced by a single i.v. injection of lipopolysaccharide (LPS, 10 mg kg(-1)). In rats not treated with eugenosedin-A, LPS increased plasma concentrations of NO and prostaglandin E(2) (PGE(2)), and levels of p38 MAPK, inducible NO synthase (iNOS) and COX-2 proteins in the liver, lung, aorta and lymphocytes. In the pre-treated rats, eugenosedin-A not only inhibited the LPS-induced NO and PGE(2) levels but also attenuated the LPS-induced increase in p38 MAPK and iNOS levels in the liver, aorta and lymphocytes. Eugenosedin-A also reduced LPS-induced COX-2 proteins in the aorta and lymphocytes. Likewise, aminoguanidine, ascorbic acid, yohimbine and trazodone were also found to decrease NO and PGE(2) concentrations after endotoxin challenge. While aminoguanidine and ascorbic acid also attenuated the LPS-induced increase in p38 MAPK, iNOS and COX-2 proteins in the aorta and lymphocytes, trazodone and yohimbine inhibited only the increase in p38 MAPK, iNOS and COX-2 proteins in lymphocytes. Finally, eugenosedin-A (10(-10)-10(-8) M) significantly inhibited the biphasic response induced by hydrogen peroxide (10(-6)-3 x 10(-5) M) in rat denudated aorta. Taken together, the results of this study indicate that eugenosedin-A, as well as ascorbic acid, can attenuate free-radical-mediated aortic contraction and relaxation. It may therefore be able to reduce the damage caused by septic shock by inhibiting formation of p38 MAPK, iNOS, COX-2 and free radicals.

Nitric oxide synthase and cyclooxygenase interactions in cartilage and meniscus: relationships to joint physiology, arthritis, and tissue repair

Rheumatoid arthritis and osteoarthritis are painful and debilitating diseases with complex pathophysiology. There is growing evidence that pro-inflammatory cytokines (e.g., interleukin-1 and tumor necrosis factor alpha) and mediators (e.g., prostaglandins, leukotrienes, and nitric oxide) play critical roles in the development and perpetuation of tissue inflammation and damage in joint tissues such as articular cartilage and meniscus. While earlier studies have generally focused on cells of the synovium (especially macrophages), there is increasing evidence that chondrocytes and meniscal cells actively contribute to inflammatory processes. In particular, it is now apparent that mechanical forces engendered by joint loading are transduced to biological signals at the cellular level and that these signals modulate gene expression and biochemical processes. Here we give an overview of the interplay of cytokines and mechanical stress in the production of cyclooxygenases and prostaglandins; lipoxygenases and leukotrienes; and nitric oxide synthases and nitric oxide in arthritis, with particular focus on the interactions of these pathways in articular cartilage and meniscus.

Inhibition of nitric oxide synthase enhances cocaine's developmental toxicity: vascular and CNS effects

Ischemia and/or reperfusion injury from free radicals may cause cocaine's toxicity, including its effect upon neurobehavioral development. We previously used salicylate to measure hydroxyl free radicals in chick embryos exposed to cocaine. The combination was more toxic than cocaine alone. We postulated that salicylate enhanced the vasoconstriction and toxicity via inhibition of compensatory processes (eg by inhibition of the synthesis of vasodilatory prostanoids and/or nitric oxide). A nontoxic dose of N(G)-nitro-L-arginine methyl ester (L-NAME) was used to inhibit nitric oxide synthase to test this hypothesis. In one experiment, cocaine was injected every 1.5 h (total dose =67.5 mg/kg egg) on day 15 of development, 1 h after injection of L-NAME (200 mg/kg egg) to determine viability and hatchability, which are measures of toxicity. Another experiment measured diameters of blood vessels after L-NAME injection, followed by NaCl or cocaine infusion (0.23 mg/egg/min; total dose=67.5 mg/kg egg) at 15 and 5 min afterwards. Lastly, brains of embryos pretreated with L-NAME before cocaine injections were analyzed for nitric oxide synthase activity. Cocaine decreased viability and hatchability. L-NAME enhanced cocaine's effect upon both parameters. Blood vessel diameters were decreased by cocaine after 15 min of infusion. L-NAME+cocaine caused a decrease in vessel diameter as soon as 5 min into the infusion and was greater with time, compared with other groups. Enzyme activity in brains was decreased only in the L-NAME+cocaine group. Thus, inhibition of nitric oxide synthesis interferes with the embryos' capacity to mount a compensatory vasodilatory response.

Effects of ß-glucan fromAureobasidium pullulans on acute inflammation in mice

The effects of beta-glucan isolated from Aureobasidium pullulans were observed on acute xylene-induced inflammation. beta-glucan at a dose of 62.5, 125 or 250 mg/kg were administered once orally to xylene-treated mice (0.03 mL of xylene was applied on the anterior surface of the right ear to induce inflammation), and the body weight change, ear weight, histological profiles and histomorphometrical analyses of ear were conducted upon sacrifice. The xylene was topically applied 30 min after dosing with beta-glucan. The results were compared to those of diclofenac, indomethacin and dexamethasone (15 mg/kg injected once intraperitoneally). All animals were sacrificed 2 h after xylene application. Xylene application resulted in marked increases in induced ear weights compared to that of intact control ear; hence, the differences between intact and induced ear were also significantly increased. The histological characteristics of acute inflammation, such as severe vasodilation, edematous changes of skin and infiltration of inflammatory cells, were detected in xylene-treated control ears with marked increase in the thickness of the ear tissues. However, these xylene-induced acute inflammatory changes were significantly and dose-dependently decreased by beta-glucan treatment. We conclude that beta-glucan from A. pullulans has a somewhat favorable effect in the reduction of the acute inflammatory responses induced by xylene application in mice.

Nonsteroidal anti-inflammatory drugs in Parkinson's disease: possible involvement of quinone formation

It has been revealed that nonsteroidal anti-inflammatory drugs (NSAIDs) have neuroprotective properties based not only on their cyclooxygenase-inhibitory action, but also on other properties including their inhibitory effects on the synthesis of nitric oxide radicals and agonistic action for peroxisome proliferator-activated receptor gamma, in addition to some as yet unknown properties. Recently, a number of experimental and clinical studies have examined the neuroprotective effects of NSAIDs on the pathogenesis of several neurodegenerative diseases, including Parkinson's disease. In this article, various pharmacological effects of NSAIDs (except for their cyclooxygenase-inhibitory action) are reviewed, and possible neuroprotective effects of NSAIDs on Parkinson's disease are discussed. The neurotoxicity of dopamine quinones, or DOPA quinones, has recently received attention as a dopaminergic neuron-specific oxidative stress that is known to play a role in the pathogenesis of Parkinson's disease and neurotoxin-induced parkinsonism. NSAIDs inhibit prostaglandin H synthase, thus suppressing dopamine oxidation and subsequent dopamine quinone formation. Therefore, this article also reviews possible suppressive effects of some NSAIDs against dopamine quinone generation.

Cyclooxygenase-independent effects of aspirin on HT-29 human colon cancer cells, revealed by oligonucleotide microarrays

Aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) inhibit proliferation of human colon cancer cells in vitro. Transmission electron microscope detected morphological features of apoptosis in the aspirin-treated (5 mM, 72 h) HT-29 cells in which cyclooxygenoase-2 is catalytically inactive. We investigated aspirin-induced genome-wide expression changes in HT-29 cells and further studied the time- and concentration-dependent expression changes in 374 apoptosis-related genes, which is the first to show stimulation of genome-wide expression of HT-29 cells by aspirin. The most marked effects of aspirin are on ribosome assembly and rRNA metabolism, which could explain why the quasi-apoptotic morphological changes are not accompanied by a classical DNA ladder. These findings demonstrate that aspirin induces apoptosis in HT-29 cells, bolstering the hypothesis that apoptosis may be a mechanism by which NSAIDs inhibit colon carcinogenesis.

Effects of Platycodon grandiflorum on Lipopolysaccharide-Stimulated Production of Prostaglandin E2, Nitric Oxide, and Interleukin-8 in Mouse Microglial BV2 Cells

The roots of Platycodon grandiflorum, which belongs to the Campanulaceae family, have been used as a food material and as a traditional Oriental medicine. The effect of P. grandiflorum against lipopolysaccharide (LPS)-stimulated inflammation was investigated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, reverse transcription-polymerase chain reaction, prostaglandin E(2 )(PGE(2)) immunoassay, nitric oxide (NO) detection assay, and interleurkin-8 (IL- 8) immunoassay on BV2 microglial cells. The aqueous extract of P. grandiflorum was shown to suppress PGE(2 )synthesis and NO production by inhibiting LPS-stimulated cyclooxygenase (COX)-2 activity and expression of inducible NO synthase (iNOS) mRNAs. In addition, the treatment with P. grandiflorum reduced the LPS-induced IL-8 release. These results suggest that P. grandiflorum inhibits PGE(2) and NO production through its suppression of LPS-induced COX-2 and iNOS expression, and also reduces IL-8 secretion by microglial cells.

Cortisol promotes survival and regeneration of axotomised retinal ganglion cells and enhances effects of aurintricarboxylic acid

BACKGROUND

Neuroprotection is essential for repair processes after a traumatic insult in the central nervous system. We have demonstrated previously significant neuroprotective properties of the anti-apoptotic drug aurintricarboxylic acid in the model of axotomised retinal ganglion cells. Glucocorticoids are widely used to treat injuries of the nervous system. Due to the anti-inflammatory and microglia-inhibiting properties of glucocorticoids, we studied the neuroprotective effects of intravitreally administered cortisol after an optic nerve cut.

METHODS

Ninety-eight adult Sprague-Dawley rats were used in this study. The optic nerve was cut intra-orbitally. Either vehicle or compound solution was injected intravitreally. Fluorescent dye was put onto the optic nerve stump to label retinal ganglion cells retrogradely. Retinal whole mounts were prepared 2 weeks after axotomy, and surviving retinal ganglion cells were counted.

RESULTS

Two weeks after axotomy, up to 50+/-7% of all retinal ganglion cells survived if cortisol was injected into the eye compared with 17+/-5% survival if only vehicle solution was injected. The neuroprotective effects of aurintricarboxylic acid (43+/-5% survival) could be further enhanced if combined with cortisol (up to 61+/-5% survival). Regeneration of cut retinal ganglion cell axons into a peripheral nerve graft could also be enhanced by an intravitreal injection of cortisol (169+/-42 regenerating retinal ganglion cells per mm2 vs. 73+/-12 cells per mm2 after vehicle injection). The increase was not as high as with aurintricarboxylic acid (192+/-40 cells per mm2), although more retinal ganglion cells survived with cortisol. This indicates that neuronal survival alone is not sufficient for subsequent axonal regeneration. Nevertheless, regeneration could be markedly increased if aurintricarboxylic acid and cortisol were combined (308+/-72 cells per mm2).

CONCLUSIONS

Whereas aurintricarboxylic acid seems to act directly on lesioned retinal ganglion cells, cortisol seems to act on the glial environment, as indicated by microglial cell morphology and enhanced glial fibrillary acidic protein expression. The results show that both neuroprotection and regeneration can be enhanced by the combination of two simple compounds acting on different sites.

Neuroprotective effects of indomethacin and aminoguanidine in the newborn rats with hypoxic-ischemic cerebral injury

Nitric oxide (NO) and prostaglandins (PG) play important roles in delayed mechanisms of brain injury. While NO disrupts oxidative metabolism, prostaglandins are responsible for free radical attack in reperfusion interval. Relatively little is known about neuroprotection exerted at this level in perinatal models. The aim of this study was to investigate the effect of indomethacin and aminoguanidine on endogenous inducible nitric oxide synthase (iNOS) biosynthesis and neuroprotection in the newborn rats with hypoxic ischemic cerebral injury.Seven-day old rat pups with model of hypoxic-ischemic cerebral injury were randomly divided into four study groups. Group C (n=18; served as a control) pups were given physiologic saline (SF). Group I (n=18) pups were treated with indomethacin at a dose of 0,2 mg/kg per 12 h. Group A (n=20) pups were treated with aminoguanidine at a dose of 300 mg/kg per 8 h. Administration of drugs and SF were begun half an hour after hypoxic-ischemic insult in these groups. Group I+A (n=18) pups were treated with indomethacin at a single dose of 0.2 mg/kg 1 h before hypoxia-ischemia followed by aminoguanidine as in group A. Drugs and SF were administered for three consecutive days. On the tenth day, rat pups were decapitated and coronal sections at the level of dorsal hippocampal region of brains were evaluated. In the histopathologic examination; the mean infarcted area in group I+A was significantly lower than the control group (P<0.05). Although there was no statistically significant difference between treatment groups in terms of iNOS expression, the risk of iNOS expression was 7 times less for group I (CI: 1.6-30.8, P=0.01), 19.8 times less for group A (CI: 3.8-104, P=0.001) and 12.3 times less for group I+A (CI: 2.5-59, P=0.002) compared to group C. In conclusion, only indomethacin administration before hypoxic ischemia and followed by aminoguanidine was more effective to reduce infarct area, but we did not find any difference between treatment groups and control group for iNOS expression. So we suggest that this neuroprotection may not be related to depression of iNOS expression.

Immunomodulatory and Anti-inflammatory Effects of Semecarpus anacardium LINN. Nut Milk Extract in Experimental Inflammatory Conditions

Immunomodulatory effects of Semecarpus anacardium LINN. nut milk extract (SA) were investigated in adjuvant induced arthritis by studying the alterations in humoral and cell mediated immune responses and also the anti-inflammatory effects by evaluating the changes in paw edema, tumour necrosis factor (TNF-alpha), nitric oxide and myeloperoxidase activities. Pharmacological studies were also conducted with SA and indomethacin on experimental animals for evaluating the anti-inflammatory, analgesic, antipyretic and ulcerogenic activities. The alterations in the humoral and cell mediated immunity were significantly reverted back to near normal levels on treatment with SA. The drug significantly reduced the elevation in the paw edema, TNF-alpha, nitric oxide and myeloperoxidase levels when compared with adjuvant induced arthritic animals, which shows the anti-inflammatory activity of the drug. SA showed strong anti-inflammatory effects in xylene-induced ear edema and formalin-induced inflammation. In analgesic test, the extract elicited a potential activity on both acetic acid-induced writhing response as well as hot plate test showing its central and peripheral mediated action. The drug also elicited antipyretic action in yeast-induced hyperemia in rats. In addition, the extract did not produce any ulceration on gastric mucosa during ulcerogenic test and did not produce any serious adverse effects. All these effects are nearly similar to the activities of indomethacin except the ulceration where indomethacin produced significant ulceration. From this study, the protective immunological and pharmacological role of SA is demonstrated.

NO-donating aspirin inhibits both the expression and catalytic activity of inducible nitric oxide synthase in HT-29 human colon cancer cells

Nitric oxide-releasing aspirin (NO-ASA) is emerging as a potentially important chemopreventive agent against colon cancer. We examined in HT-29 human colon adenocarcinoma cells the effect of NO-ASA on the inducible form of nitric oxide synthase (NOS2), an enzyme implicated in colon carcinogenesis. NO-ASA inhibited in a time- and concentration-dependent manner the expression of NOS2 up to 70% compared to control (IC50 for this effect = 46 microM). NO-ASA also decreased the corresponding steady-state mRNA levels and this reduction preceded the reduction of protein levels by at least 6 h. NO-ASA also reduced the enzymatic activity of NOS2, as determined by a direct enzyme assay (maximal reduction = 80%) and by determining the accumulation of NO in the culture medium (IC50 for this effect = 36 microM). These effects of NO-ASA on NOS2 were paralleled by inhibition in cell growth (IC50 = 8.5 microM). These findings indicate that NO-ASA profoundly inhibits both the expression and enzymatic activity of NOS2 and suggest that these effects may represent an important mechanism for the colon cancer chemopreventive effect of NO-ASA.

Mononuclear metal complexes with Piroxicam: Synthesis, structure and biological activity

Piroxicam (=Hpir) is a non-steroidal anti-inflammatory and an anti-arthritic drug. VO(2+), Mn(2+), Fe(3+), MoO(2)(2+) and UO(2)(2+) complexes with deprotonated piroxicam have been prepared and characterized with the use of infrared, UV-Vis, nuclear magnetic resonance and electron paramagnetic resonance spectroscopies. The experimental data suggest that piroxicam acts as a deprotonated bidentate ligand in all complexes and is coordinated to the metal ion through the pyridine nitrogen and the amide oxygen. Molecular mechanics calculations in the gas state have been performed in order to propose a model for the Fe(3+), VO(2+) and MoO(2)(2+) complexes. Potential anticancer cytostatic and cytotoxic effects of piroxicam complexes with VO(2+), Mn(2+) and MoO(2)(2+) on human promyelocytic leukemia HL-60 cells have been investigated. Among all complexes, only VO(pir)(2)(H(2)O) clearly induces apoptosis after 24-h incubation, whereas piroxicam induces apoptosis after 57-h incubation.

NF-kappa B-mediated MyoD decay during muscle wasting requires nitric oxide synthase mRNA stabilization, HuR protein, and nitric oxide release

Muscle wasting (cachexia) is a consequence of chronic diseases, such as cancer, and is associated with degradation of muscle proteins such as MyoD. The cytokines tumor necrosis factor alpha and gamma interferon induce muscle degeneration by activating the transcription factor NF-kappaB and its target genes. Here, we show that a downstream target of NF-kappaB is the nitric oxide (NO) synthase gene (iNos) and suggest that NO production stimulates MyoD mRNA loss. In fact, although cytokine treatment of iNos(-/-) mice activated NF-kappaB, it did not trigger MyoD mRNA degeneration, demonstrating that NF-kappaB-mediated muscle wasting requires an active iNOS-NO pathway. The induced expression of iNOS by cytokines relies on both transcriptional activation via NF-kappaB and increased mRNA stability via the RNA-binding protein HuR. Moreover, we show that HuR regulates iNOS expression in an AMP-activated protein kinase (AMPK)-dependent manner. Furthermore, AMPK activation results in HuR nuclear sequestration, inhibition of iNOS synthesis, and reduction in cytokine-induced MyoD loss. These results define iNOS and HuR as critical players in cytokine-induced cachexia, establishing them as potential therapeutic targets.

A direct nitric oxide gas delivery system for bacterial and mammalian cell cultures

Nitric oxide (NO) is the smallest known gaseous signaling molecule released by mammalian and plant cells. To investigate the pathophysiologic role of exogenous NO gas (gNO) in bacterial and mammalian cell cultures, a validated in vitro delivery method is required. The system should be able to deliver gNO directly to bacterial and/or cell cultures in a continuous, predictable, and reproducible manner over a long period of time (days). To accomplish this, a gas delivery system was designed to provide optimal growth conditions for bacteria and/or mammalian cells. Parameters for cell exposure, such as concentration of gNO, nitrogen dioxide (NO(2)), oxygen (O(2)), temperature, and relative humidity (RH) were continuously monitored and evaluated. Uptake of gNO into various media was monitored by measuring the nitrite concentration using the Griess reagent technique. A selection of standard growth media [saline, tryptic soy broth (TSB), Middlebrook 7H9 (MB 7H9), and Dulbecco's modified Eagle's medium (DMEM)] exposed to various concentrations of gNO revealed a steady and consistent transfer of gNO into the aqueous phase over a 48-h period. Validation of optimal growth conditions within the device, as compared to a conventional incubator, were accomplished by growing and observing viability of Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and human fibroblast cultures in the absence of gNO. These results indicate that an optimal growth environment for the above tested cells was accomplished inside the proposed delivery system. Dose-dependent toxicological data revealed a significant bacteriostatic effect on P. aeruginosa and S. aureus with continuous exposure to 80 ppm gNO. No toxic effects were observed on dermal fibroblast proliferation at concentrations up to 400 ppm gNO for 48 h. In conclusion, the designed gNO exposure system is capable of supporting cellular viability for a representative range of prokaryote and eukaryotic cells. The exposure system is also capable of obtaining toxicological data. Therefore, the proposed device can be utilized to continuously expose cells to various levels of gNO for up to 72 h to study the in vitro effects of gNO therapy.

Therapeutic potential of macrolide immunosuppressants in dermatology

Dermatologists are frequently presented with inflammatory dermatoses that are responsive to treatment with immunomodulating drugs. Corticosteroids, particularly when applied topically, have been the mainstay of treatment in the past. Their undoubted efficacy, however, has been undermined by problems with repeated use including tachyphylaxis and side effects such as skin atrophy and hypertension. Macrolide immunosuppressive drugs, originally used for prophylaxis of organ transplant rejection, have been shown to be effective in the treatment of inflammatory dermatoses. The original drugs used in dermatology in this class have their own limitations including poor absorption when used topically and their distinct side-effect profiles. A search for other immunosuppressive macrolide antibiotics has led to the development of new agents, which have enhanced profiles for the treatment of skin disease. This review discusses the main dermatoses that may be targeted by this class of drugs and summarises the topical and systemic macrolides either currently in use, in clinical trials or preclinical development.

Armeniacae semen Extract Suppresses Lipopolysaccharide-Induced Expressions of Cycloosygenase-2 and Inducible Nitric Oxide Synthase in Mouse BV2 Microglial Cells

Armeniacae semen is the seed of Prunus armeniaca L. var. ansu MAXIM which is classified into Rosaceae. In traditional oriental medicine, Armeniacae semen has been used for the treatment of pain and inflammatory diseases. In this study, the effect of Armeniacae semen extract on lipopolysaccharide-induced inflammation was investigated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, reverse transcription-polymerase chain reaction (RT-PCR), Western blot, prostaglandin E2 immunoassay, and nitric oxide detection on mouse BV2 microglial cells. In the present results, Armeniacae semen extract suppressed prostaglandin E2 synthesis and nitric oxide production by inhibiting the lipopolysaccharide-stimulated enhancement of cyclooxygenase-2 and inducible nitric oxide synthase mRNA expression in BV2 cells. These results show that Armeniacae semen exerts anti-inflammatory and analgesic effects probably by suppression of cyclooxygenase-2 and inducible nitric oxide synthase expressions.

Effect of inhalation aspirin challenge on exhaled nitric oxide in patients with aspirin-inducible asthma

BACKGROUND

A complex relationship between arachidonic acid metabolites and nitric oxide (NO) synthesis has been reported in asthma. The effects of inhaled aspirin on fractional exhaled NO (FENO) in patients with aspirin-tolerant (ATA) and aspirin-inducible (AIA) asthma compared with normal controls have been investigated.

METHODS

The FENO was measured baseline, after saline and lysine-aspirin (L-ASA) bronchial challenge in 10 patients with ATA and in 10 patients with AIA [mean (PD(20)FEV(1) L-ASA): 14.7 +/- 12.7 mg], who had comparable age and baseline FEV(1). Ten healthy subjects served as controls. Sputum eosinophils were counted after saline and after L-ASA challenge in the two groups of asthmatics.

RESULTS

Asthmatic patients had baseline FENO significantly higher than controls (29.7 +/- 6.8 vs 9.8 +/- 2.05 p.p.b. respectively, P < 0.0001). No difference was observed in methacholine PD(20)FEV(1) and baseline FENO between ATA and AIA patients. After L-ASA inhalation, FENO increased significantly only in patients with AIA, reaching the peak value 4 h after bronchoconstriction (from 31.1 +/- 6 to 43 +/- 4.8 p.p.b., P < 0.001), while no change was observed in patients with ATA and in controls. Sputum eosinophils increased significantly after L-ASA inhalation only in patients with AIA (from 8.1 +/- 2.7 to 11.1 +/- 2.8%, P < 0.005) and there was a significant relationship between the increase in sputum eosinophils and the increase in FENO after ASA challenge.

CONCLUSION

Exhaled NO may indicate eosinophilic airway inflammation during ASA exposure in patients with ASA inducible asthma.

Harpagophytum procumbens suppresses lipopolysaccharide-stimulated expressions of cyclooxygenase-2 and inducible nitric oxide synthase in fibroblast cell line L929

Harpagophytum procumbens (Pedaliaceae) has been used for the treatment of pain and arthritis. The effect of Harpagophytum procumbens against lipopolysaccharide-induced inflammation was investigated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, reverse transcription-polymerase chain reaction, prostaglandin E(2) (PGE(2)) immunoassay, and nitric oxide detection on mouse fibroblast cell line L929. The aqueous extract of Harpagophytum procumbens was shown to suppress PGE(2) synthesis and nitric oxide production by inhibiting lipopolysaccharide-stimulated enhancement of the cyclooxygenase-2 and inducible nitric oxide synthase (iNOS) mRNAs expressions in L929 cells. These results suggest that Harpagophytum procumbens exerts anti-inflammatory and analgesic effects probably by suppressing cyclooxygenase-2 and iNOS expressions.

Effect of aspirin on constitutive nitric oxide synthase and the biovailability of NO

INTRODUCTION

Aspirin decreases the activity of iNOS and the formation of prostanoids. Constitutive nitric oxide synthase (cNOS) is present in endothelial cells, platelets, leukocytes and neurons, yet no data are available on the effect of aspirin on cNOS and the bioavailability of NO produced by this enzyme.

MATERIALS AND METHODS

Human umbilical vein endothelial cells (HUVECs), rat adrenal gland pheochromocytoma cells (PC-12) and human platelets were incubated with different aspirin concentrations. The kinetics of NO, O2- and ONOO- release were measured simultaneously in single cells or platelet suspensions using tandem electrochemical nanosensors. The NO, O2- and ONOO- release from cells and platelets was stimulated with calcium ionophore and collagen, respectively. cNOS expression was estimated by Western blot analysis.

RESULTS

Incubation of HUVECs and PC-12 with 10(-5) mol/l of aspirin increased cNOS expression by 70 +/- 7% and 50 +/- 5, respectively. However, the NO concentration increased only by 33% in HUVECs incubated with the same aspirin concentration. Incubation of HUVECs with aspirin also increased the O2- and ONOO- production. Therefore the bioavailability of NO increased only slightly in endothelium and did not reflect the increase in eNOS. This was in contrast to platelets, where maximal NO bioavailability almost doubled after incubation with aspirin.

CONCLUSIONS

Aspirin did not have a significant effect on the NO bioavailability in endothelial cells. However, aspirin highly improved the NO production in platelets. The high NO production in platelets may counteract the effect of thromboxane, inhibit platelet aggregation, and compensate for the reduction of prostacycline concentration by aspirin.

Vasoconstriction caused by cocaine is enhanced by sodium salicylate: is inducible nitric oxide synthase mRNA related?

We have previously found that sodium salicylate (NaSal), injected into chicken eggs at nontoxic doses used for quantifying hydroxyl free radicals in hearts and brains of embryos, caused or exacerbated hemorrhages and dramatically reduced hatchability when combined with cocaine (Coc). It has also been reported that inducible nitric oxide synthase (iNOS) gene expression is altered in brain in response to vascular damage and inflammation. In this study we measured diameters of membrane-bound blood vessels (BV) before and after pretreatment with saline (NaCl) or NaSal (100 mg/kg egg), followed by infusion of either NaCl or Coc HCl (total of 67.5 mg/kg egg) during 15 min. Brains and hearts of the embryos were then analyzed for iNOS messenger RNA (mRNA) concentrations. Coc caused vasoconstriction that was significant 5 min postinfusion (5 min PI) of the entire dose (ie after 67.5 mg/kg egg). Significant vasoconstriction was evident within 5 min in the group injected with NaSal followed by infusion with Coc (ie after 22.5 mg Coc/kg egg). Expression of iNOS mRNA was significantly increased only in the brains of the group exposed to NaSal plus Coc, and the increase was inversely related to BV diameter. These data are discussed in relation to effects of salicylate upon prostanoid synthesis and/or nitric oxide synthesis via iNOS inhibition and their possible relationship to Coc-associated cerebral vascular and/or cardiovascular events in abusing humans.

The role of biomechanics and inflammation in cartilage injury and repair

Osteoarthritis is a painful and debilitating disease characterized by progressive degenerative changes in the articular cartilage and other joint tissues. Biomechanical factors play a critical role in the initiation and progression of this disease, as evidenced by clinical and animal studies of alterations in the mechanical environment of the joint caused by trauma, joint instability, disuse, or obesity. The onset of these changes after joint injury generally has been termed posttraumatic arthritis and can be accelerated by factors such as a displaced articular fracture. Within this context, there is considerable evidence that interactions between biomechanical factors and proinflammatory mediators are involved in the progression of cartilage degeneration in posttraumatic arthritis. In vivo studies have shown increased concentrations of inflammatory cytokines and mediators in the joint in mechanically induced models of osteoarthritis. In vitro explant studies confirm that mechanical load is a potent regulator of matrix metabolism, cell viability, and the production of proinflammatory mediators such as nitric oxide and prostaglandin E2. Knowledge of the interaction of inflammatory and biomechanical factors in regulating cartilage metabolism would be beneficial to an understanding of the etiopathogenesis of posttraumatic osteoarthritis and in the improvement of therapies for joint injury.

Cyclooxygenase-2-derived E prostaglandins down-regulate matrix metalloproteinase-1 expression in fibroblast-like synoviocytes via inhibition of extracellular signal-regulated kinase activation

We examined the regulation of matrix metalloproteinase (MMP) production by mitogen-activated protein kinases and cyclooxygenases (COXs) in fibroblast-like synoviocytes (FLSCs). IL-1beta and TNF-alpha stimulated FLSC extracellular signal-regulated kinase (ERK) activation as well as MMP-1 and -13 release. Pharmacologic inhibitors of ERK inhibited MMP-1, but not MMP-13 expression. Whereas millimolar salicylates inhibited both ERK and MMP-1, nonsalicylate COX and selective COX-2 inhibitors enhanced stimulated MMP-1 release. Addition of exogenous PGE(1) or PGE(2) inhibited MMP-1, reversed the effects of COX inhibitors, and inhibited ERK activation, suggesting that COX-2 activity tonically inhibits MMP-1 production via ERK inhibition by E PGs. Exposure of FLSCs to nonselective COX and selective COX-2 inhibitors in the absence of stimulation resulted in up-regulation of MMP-1 expression in an ERK-dependent manner. Moreover, COX inhibition sufficient to reduce PGE levels increased ERK activity. Our data indicate that: 1) ERK activation mediates MMP-1 but not MMP-13 release from FLSCs, 2) COX-2-derived E PGs inhibit MMP-1 release from FLSCs via inhibition of ERK, and 3) COX inhibitors, by attenuating PGE inhibition of ERK, enhance the release of MMP-1 by FLSC.

Effect of Non-Steroidal Anti-Inflammatory Drugs on Amyloid-β Formation and Macrophage Activation after Platelet Phagocytosis

Recently, we showed that platelet phagocytosis occurs in human atherosclerotic plaques and leads to foam cell formation. Platelet phagocytosis, resulting in macrophage activation and iNOS induction, was associated with the formation of amyloid-beta peptide (Abeta) via proteolytic cleavage of platelet-derived amyloid precursor protein (APP), possibly by secretases. To test the involvement of gamma-secretase in this process, we used indomethacin, ibuprofen, and sulindac sulfide, non-steroidal anti-inflammatory drugs (NSAIDs) known to alter the gamma-secretase cleaving site of APP, on their ability to inhibit macrophage activation evoked by platelet phagocytosis. J774 macrophages were incubated with human platelets or lipopolysaccharide (LPS) with or without NSAIDs. Nitrite was quantified as a measure for inducible nitric oxide synthase (iNOS) activity. Indomethacin, ibuprofen, sulindac sulfide, and meloxicam concentration-dependently reduced nitrite production by macrophages incubated with platelets, but did not alter LPS-induced iNOS activity or platelet uptake. However, acetylsalicylic acid and naproxen, two NSAIDs without effect on the gamma-secretase cleaving site of APP, did not affect nitrite production in either platelet- or LPS-stimulated macrophages. Surface-enhanced laser desorption/ionization time-of-flight mass-spectrometry demonstrated time-dependent formation of Abeta-containing peptides after platelet phagocytosis, which could be inhibited by indomethacin. In conclusion, these results point to the involvement of gamma-secretase in macrophage activation following platelet phagocytosis.

In vivo study on cross talk between inducible nitric-oxide synthase and cyclooxygenase in rat gastric mucosa: effect of cyclooxygenase activity on nitric oxide production

The integrity of gastric mucosa during endotoxemia is maintained by the balance of inflammatory mediators, such as prostanoids originated from cyclooxygenase-2 (COX-2) and nitric oxide (NO) from inducible nitric-oxide synthase (iNOS). Thus, we elucidated in vivo cross talk between prostanoids and NO in gastric mucosa during endotoxemia, using an iNOS-specific inhibitor, N-(3-(aminomethyl)benzyl)acetamidine (1400W); a nonspecific COX inhibitor, indomethacin; and a COX-2-specific inhibitor, N-(2-[cyclohexyloxy]-4-nitrophenyl)methanesulfonamide (NS-398). Gastric mucosal NO and prostaglandin E2 (PGE2), a predominant product of COX, expressed as mean +/- S.D. of five rats per group, were assayed by electron paramagnetic resonance spectrometry and enzyme immunoassay technique, respectively. The levels of NO and PGE2 increased gradually up to 6 h after administration of bacterial lipopolysaccharide (LPS) (NO: control, 0.35 +/- 0.16; 6 h, 13.3 +/- 3.3 nmol/g tissue/30 min; and PGE2: control, 288 +/- 16; 6 h, 806 +/- 15 pg/g tissue). Pretreatment with 1400W decreased the increase in NO level without any effect on the PGE2 level (NO, 4.0 +/- 0.4 nmol/g tissue/30 min; PGE2, 788 +/- 26 pg/g tissue). In contrast, treatment with indomethacin and NS-398 inhibited not only PGE2 level but also NO level in a dose-dependent manner without any significant effect on both iNOS and COX protein and mRNA expression. These results demonstrate that in the LPS-treated rat gastric mucosa, PGE2 enhances the release of NO after activation of iNOS, although NO produced by iNOS does not stimulate the release of PGE2 by COXs. The effect of COX activity on iNOS-NO pathway can be important in the regulation of gastric mucosal integrity in inflammatory states.

Sodium salicylate-induced amelioration of experimental autoimmune encephalomyelitis in Lewis rats is associated with the suppression of inducible nitric oxide synthase and cyclooxygenases

We studied the effects of oral administration of sodium salicylate on the expression of the pro-inflammatory mediators, nitric oxide synthase (iNOS) and cyclooxygenase- (COX-) 1 and 2, in rats with experimental autoimmune encephalomyelitis (EAE). Sodium salicylate (200 mg/kg) was administered orally for 13 days after the induction of EAE by immunization with guinea pig myelin basic protein and complete Freund's adjuvant. The onset (P<0.0001) and severity (P<0.05) of EAE paralysis in salicylate-treated animals were delayed and suppressed significantly compared with vehicle-treated controls. Western blot analysis showed that expression of COX-2 and iNOS, but not COX-1, decreased significantly in the spinal cords of salicylate-treated rats compared with vehicle-treated controls (P<0.05) and this finding was paralleled by immunohistochemical observations. These results suggest that the amelioration by salicylate of paralysis in rats with EAE is mediated in part by the suppression of COX and iNOS.

Atractylodes japonica Suppresses Lipopolysaccharide-Stimulated Expressions of Inducible Nitric Oxide Synthase and Cyclooxygenase-2 in RAW 264.7 Macrophages

Atractylodes japonica has traditionally been used for the treatment of pain and arthritis. The effect of Atractylodes japonica against lipopolysaccharide-induced inflammation was investigated using reverse transcription-polymerase chain reaction (RT-PCR), nitric oxide detection, and prostaglandin E2 (PGE2) immunoassay in mouse RAW 264.7 macrophages. The aqueous extract of Atractylodes japonica suppressed nitric oxide production and PGE2 synthesis by inhibition of the lipopolysaccharide-stimulated enhancement of inducible nitric oxide synthase and cyclooxygenase-2 mRNAs expressions in RAW 264.7 macrophages. These results suggest that Atractylodes japonica exerts anti-inflammatory and analgesic effects probably by suppression of the inducible nitric oxide synthase and cyclooxygenase-2 expressions.

Neuroprotective strategies in Parkinson's disease : an update on progress

In spite of the extensive studies performed on postmortem substantia nigra from Parkinson's disease patients, the aetiology of the disease has not yet been established. Nevertheless, these studies have demonstrated that, at the time of death, a cascade of events had been initiated that may contribute to the demise of the melanin-containing nigro-striatal dopamine neurons. These events include increased levels of iron and monoamine oxidase (MAO)-B activity, oxidative stress, inflammatory processes, glutamatergic excitotoxicity, nitric oxide synthesis, abnormal protein folding and aggregation, reduced expression of trophic factors, depletion of endogenous antioxidants such as reduced glutathione, and altered calcium homeostasis. To a large extent, the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 6-hydroxydopamine (6-OHDA) animal models of Parkinson's disease confirm these findings. Furthermore, neuroprotection can be afforded in these models with iron chelators, radical scavenger antioxidants, MAO-B inhibitors, glutamate antagonists, nitric oxide synthase inhibitors, calcium channel antagonists and trophic factors. Despite the success obtained with animal models, clinical neuroprotection is much more difficult to accomplish. Although the negative studies obtained with the MAO-B inhibitor selegiline (deprenyl) and the antioxidant tocopherol (vitamin E) may have resulted from an inappropriate choice of drug (selegiline) or an inadequate dose (tocopherol), the niggling problem that still remains is why these drugs, and others, do work in animals while they fail in the clinic. One reason for this may be related to the fact that in normal human brains the number of dopaminergic neurons falls by around 3-5% every decade, while in Parkinson's disease this decline is greater. Brain autopsy studies have shown that by the time the disease is identified, some 70-75% of the dopamine-containing neurons have been lost. More sensitive reliable methods and clinical correlative markers are required to discern between confoundable symptomatic effects versus a possible neuroprotective action of drugs, namely, the ability to delay or forestall disease progression by protecting or rescuing the remaining dopamine neurons or even restoring those that have been lost.A number of other possibilities for the clinical failure of potential neuroprotectants also exist. First, the animal models of Parkinson's disease may not be totally reflective of the disease and, therefore, the chemical pathologies established in the animal models may not cause, or contribute to, the progression of the disease clinically. Second, because of the series of events occurring in neurodegeneration and our ignorance about which of these factors constitutes the primary event in the pathogenic process, a single drug may not be adequate to induce neuroprotection and, as a consequence, use of a cocktail of drugs may be more appropriate. The latter concept receives support from recent complementary DNA (cDNA) microarray gene expression studies, which show the existence of a gene cascade of events occurring in the nigrostriatal pathway of MPTP, 6-OHDA and methamphetamine animal models of Parkinson's disease. Even with the advent of powerful new tools such as genomics, proteomics, brain imaging, gene replacement therapy and knockout animal models, the desired end result of neuroprotection is still beyond our current capability.

Dexamethasone suppresses iNOS yet induces GTPCH and CAT-2 mRNA expression in rat lungs

The in vivo mechanisms by which glucocorticoids inhibit nitric oxide expression await detailed investigation. In cell culture experiments, glucocorticoids have been shown to inhibit inducible nitric oxide synthase (iNOS) formation and activity. Glucocorticoids can inhibit iNOS activity in cultured cells by blocking arginine transport and inhibiting tetrahydrobiopterin biosynthesis. We recently reported that changes in intrapulmonary formation of nitric oxide in endotoxemic rats correspond with changes in transcription of the predominant arginine transporter cationic amino acid transporter (CAT)-2. Realizing that hemorrhagic shock induces nitric oxide overproduction in intact animals, we sought to explore whether glucocorticoids attenuate hemorrhagic shock-induced increases in intrapulmonary nitric oxide formation and whether they might do so by inhibiting the formation of tetrahydrobiopterin, iNOS protein, and CAT-2. We randomly assigned 10 male Sprague-Dawley rats to receive dexamethasone or normal saline. Bleeding the animals to a mean systemic blood pressure of between 40 and 45 mmHg created the hemorrhagic shock. Dexamethasone abrogated the increase in exhaled nitric oxide concentrations caused by hemorrhagic shock. At the end of the experiment, plasma nitrate/nitrite values were lower in the dexamethasone group than in the control group. The iNOS protein concentrations were also lower in the dexamethasone group than in the control group. Dexamethasone decreased the intrapulmonary iNOS mRNA concentrations yet increased both guanosine triphosphate cyclohydrolase I mRNA and CAT-2 mRNA. Our results support the idea that dexamethasone inhibits nitric oxide formation in a manner that is independent of tetrahydrobiopterin and arginine transport yet dependent on downregulation of iNOS mRNA expression.

An inducible nitric oxide synthase-luciferase reporter system for in vivo testing of anti-inflammatory compounds in transgenic mice

The inducible NO synthase gene (iNOS) plays a role in a number of chronic and acute conditions, including septic shock and contact hypersensitivity autoimmune diseases, such as rheumatoid arthritis, gastrointestinal disorders, and myocardial ischemia. The iNOS gene is primarily under transcriptional control and is induced in a variety of conditions. The ability to monitor and quantify iNOS expression in vivo may facilitate a better understanding of the role of iNOS in different diseases. In this study, we describe a transgenic mouse (iNos-luc) in which the luciferase reporter is under control of the murine iNOS promoter. In an acute sepsis model produced by injection of IFN-gamma and LPS, we observed an induction of iNOS-driven luciferase activity in the mouse liver. This transgene induction is dose and time dependent and correlated with an increase of liver iNOS protein and iNOS mRNA levels. With this model, we tested 11 compounds previously shown to inhibit iNOS induction in vitro or in vivo. Administration of dexamethasone, epigallocatechin gallate, alpha-phenyl-N-tert-butyl nitrone, and ebselen significantly suppressed iNOS transgene induction by IFN-gamma and LPS. We further evaluated the use of the iNos-luc transgenic mice in a zymosan-induced arthritis model. Intra-articular injection of zymosan induced iNos-luc expression in the knee joint. The establishment of the iNos-luc transgenic model provides a valuable tool for studying processes in which the iNOS gene is induced and for screening anti-inflammatory compounds in vivo.

Paracetamol effectively reduces prostaglandin E2 synthesis in brain macrophages by inhibiting enzymatic activity of cyclooxygenase but not phospholipase and prostaglandin E synthase

Epidemiological studies indicate that nonsteroidal anti-inflammatory drugs (NSAIDs) are neuroprotective, although the mechanisms underlying their beneficial effect remain largely unknown. Given their well-known adverse effects, which of the NSAIDs is the best for neurodegenerative disease management remains a matter of debate. Paracetamol is a widely used analgesic/antipyretic drug with low peripheral adverse effects, possibly related to its weak activity as inhibitor of peripheral cyclooxygenase (COX), the main target of NSAIDs. As microglia play an important role in CNS inflammation and pathogenesis of neurodegenerative diseases, we investigate the effect of paracetamol on rat microglial cultures. Although less potent than other NSAIDs, (indomethacin approximately NS-398 > flurbiprofen approximately piroxicam > paracetamol approximately acetylsalicylic acid), paracetamol completely inhibited the synthesis of prostaglandin E(2) (PGE(2)) in lipopolysaccharide-stimulated microglia, when used at concentrations comparable to therapeutic doses. The drug did not affect the expression of the enzymes involved in PGE(2) synthesis, i.e., COX-1, COX-2, and microsomal PGE synthase, or the release of the precursor arachidonic acid (AA). Paracetamol inhibited the conversion of exogenous AA, but not PGH(2), into PGE(2) indicating that the target of the drug is COX activity. Consistently, paracetamol inhibited with similar IC(50) the synthesis of PGF(2alpha) and thromboxane B(2), two other COX metabolites. Finally, none of the NSAIDs affected the productions of nitric oxide and tumor necrosis factor(alpha), two inflammatory mediators released by activated microglia. As paracetamol was reported to inhibit PG synthesis in peripheral macrophages with an IC(50) at least three orders of magnitude higher than in microglia, we suggest that this drug represents a good tool for treating brain inflammation without compromising peripheral PG synthesis.

Capsaicin exhibits anti-inflammatory property by inhibiting IkB-a degradation in LPS-stimulated peritoneal macrophages

Capsaicin, a major ingredient of hot pepper, was considered to exhibit an anti-inflammatory property. In order to clarify the signalling mechanism underlying the anti-inflammatory action of capsaicin, we investigated the effect of capsaicin on the production of inflammatory molecules in lipopolysaccharide (LPS)-stimulated murine peritoneal macrophages. The level of PGE2 was measured by EIA. The expression levels of COX-2, iNOS, IkB-a, and vanilloid receptor-1 (VR-1) were determined at the protein and mRNA levels. Significant inhibition of the production of LPS-induced PGE2 by capsaicin was observed in a dose-dependent manner. Capsaicin did not affect the COX-2 expression at either the protein or mRNA level, but inhibited the enzyme activity of COX-2 and the expression of the iNOS protein. Capsaicin completely blocked LPS-induced disappearance of IkB-a and therefore inactivated NF-kB. The inhibitory action of capsaicin on PGE2 production was not abolished by capsazepine, a specific antagonist to VR-1. A high expression level of the VR-1 like protein (VRL-1) was observed in peritoneal macrophages, while the expression of VR-1 was not detected. These findings suggest that the anti-inflammatory action of capsaicin may occur through a novel mechanism, not by a VR-1 receptor-mediated one. Both capsaicin and capsazepine may be a promising drug candidates for ameliorating inflammatory diseases and cancer.

Aspirin inhibits p44/42 mitogen-activated protein kinase and is protective against hypoxia/reoxygenation neuronal damage

BACKGROUND AND PURPOSE

Acetylsalicylic acid (ASA) is preventive against stroke and protects against focal brain ischemia in rats. We studied the mechanisms of the manner in which ASA provides neuroprotection against hypoxia/reoxygenation (H/R) injury.

METHODS

Spinal cord cultures exposed to 20 hours of hypoxia followed by reoxygenation were treated with a vehicle, ASA or inhibitors of inducible nitric oxide synthase (iNOS), mitogen-activated protein kinases p38 MAPK and ERK1/2, or an N-methyl-d-aspartic acid (NMDA) receptor antagonist. Cell viability was assessed by LDH release measurement and cell counts. Prostaglandin production was measured by enzyme immunoassay, MAPK signaling by immunoblotting, and DNA binding of nuclear factor-kappaB (NF-kappaB) and activating protein-1 (AP-1) by electrophoretic mobility shift assay.

RESULTS

One to 3 mmol/L ASA inhibited H/R-induced neuronal death when present during H/R but not when administered only for the reoxygenation period. Prostaglandin E2 production was very low and was not altered by ASA. The AP-1 and NF-kappaB DNA binding activities increased after H/R. ASA increased the H/R-induced AP-1 binding but had no effect on NF-kappaB binding. H/R induced a sustained ERK1/2 activation followed by neuronal death, whereas no changes in p38 or c-Jun N-terminal kinase were detected. ASA strongly inhibited this ERK1/2 activation. PD98059, an ERK1/2 inhibitor, was also neuroprotective, prevented H/R-induced ERK1/2 activation, and had no effect on NF-kappaB binding activity. Inhibition of NMDA receptors, iNOS, or p38 MAPK did not provide neuroprotection.

CONCLUSIONS

Inhibition of the sustained activation of ERK1/2 may partially contribute to neuroprotection achieved by ASA against H/R injury.

Treating inflammation: some (needless) difficulties for gaining acceptance of effective natural products and traditional medicines

The quality of so-called 'natural medicines' is extraordinarily variable. Lack of resolute pharmacological assays contributes to this hiatus. More stringent evaluation of anti-inflammatory and anti-pyretic activities in rats can help resolve some of the uncertainties surrounding (a) preparations of some herbal products including so-called 'nature's aspirin' (e.g. willowbark, ginger), cat's claw, celery seed, etc., and (b) some animal lipids (e.g. Lyprinol(R) (NZ Mussel), emu and fish oils). These animal products can be a remarkable resource for supplementing conventional/allopathic therapy for inflammatory disease, e.g. providing lipoxygenase inhibitors. Beyond the verifiable science, the healing professions and the general public still need to examine more carefully criteria for QUALITY(S) in any alternative medicine-to ensure the good (= both reputations and products) are not destroyed by the bad-in essence counteracting Gresham's Law which states: the bad tends to displace the good.

Salicylate suppresses macrophage nitric-oxide synthase-2 and cyclo-oxygenase-2 expression by inhibiting CCAAT/enhancer-binding protein-beta binding via a common signaling pathway

We determined whether salicylate at pharmacological concentrations inhibits nitric-oxide synthase-2 (NOS-2) and cyclo-oxygenase-2 (COX-2) expressions in RAW 264.7 stimulated with lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma). Cells were treated with sodium salicylate (10(-7)-10(-4) m) or vehicle for 30 min followed by LPS+IFN-gamma for up to 24 h. Salicylate suppressed NOS-2 and COX-2 protein levels and promoter activities stimulated by LPS+IFN-gamma for 4 h in a concentration-dependent manner but had no effect on NOS-2 expression stimulated by the combined agonists for 24 h. Results from promoter analysis indicate that the binding of CCAAT/enhancer-binding protein beta (C/EBPbeta) to its cognate site at -150/-142 on the NOS-2 promoter region was essential for NOS-2 expression at 4 h but not at 24 h. Salicylate reduced C/EBPbeta binding at 4 h and did not alter its binding at 24 h. NOS-2 and COX-2 protein levels and C/EBPbeta binding stimulated by LPS+IFN-gamma for 4 h were inhibited by a similar battery of signaling inhibitors, suggesting a common pathway for NOS-2 and COX-2 expression. Kinetic analysis indicates that NOS-2, similar to COX-2 expression, at 4 h was largely due to the action of LPS, which induced C/EBPbeta binding, whereas its expression at a longer time point was contributed by IFN-gamma. Our findings implicate two distinct pathways for NOS-2 expression induced by LPS+IFN-gamma. Salicylate at pharmacological concentrations is capable of suppressing the early phase of NOS-2 and COX-2 expression by blocking C/EBPbeta binding.

Prostaglandins are involved in acetylcholine- and 5-hydroxytryptamine-induced, nitric oxide-mediated vasodilatation in human forearm

Both acetylcholine (ACh) and 5-hydroxytryptamine (5HT) are used to examine nitric oxide (NO)-mediated vasodilatation in humans. Animal data suggest that both substances can also induce the release of prostacyclin (PGI ). This study was designed to investigate the role of the prostaglandin pathway in Ach- and 5HT-induced vasodilation in humans. The experiments were done in three groups of healthy male volunteers. In group 1 (n = 6), ACh (100-1,000 ng/kg/min) and sodium-nitroprusside (10-100 ng/kg/min) were infused into the brachial artery alone, together with a continuous infusion of indomethacin (1.3 micro g/kg/min) and during a combined infusion of indomethacin and the competitive NO synthase inhibitor N -monomethyl-l-arginine (l-NMMA; 30 micro g/kg/min). In group 2 (n = 5), 5HT (0.3-1.0 ng/kg/min) was infused alone and together with a continuous infusion of indomethacin and l-NMMA. In group 3 (n = 6), the synthetic prostaglandin analog iloprost (0.5-4.5 ng/kg/min) was infused together with a continuous infusion of saline, l-NMMA, and l-NMMA with indomethacin, respectively. The infusions of indomethacin and l-NMMA started 10 min before the infusion of ACh, 5HT, iloprost, and sodium nitroprusside. Forearm blood flow was measured using computerized venous occlusion plethysmography. Both the Ach- and 5HT-induced vasodilator responses were significantly attenuated by indomethacin (p < 0.05 for both), but not further influenced by a concomitant infusion of l-NMMA. The vasodilatation induced by iloprost was significantly inhibited by l-NMMA (p < 0.05) and not affected by indomethacin. The sodium nitroprusside-induced vasodilation was influenced by neither l-NMMA nor indomethacin. It is concluded that in the human forearm, the prostaglandin pathway is involved in both the Ach- and 5HT-induced NO-mediated vasodilatation.

Structure-function relationship and role of tumor necrosis factor-alpha-converting enzyme in the down-regulation of L-selectin by non-steroidal anti-inflammatory drugs

It has been recently described that some non-steroidal anti-inflammatory drugs (NSAIDs) are able to induce the shedding of L-selectin in neutrophils, an adhesion molecule that plays an essential role in the inflammatory response. We have found that, according to this capability, NSAIDs could be grouped into three categories. A high releaser group (flufenamic, meclofenamic, and mefenamic acids, diclofenac and aceclofenac), a group of moderate releasers (aspirin, indomethacin, nimesulide, flurbiprofen, and ketoprofen), and a non-releaser group (phenylbutazone and the oxicams, piroxicam and meloxicam). Only NSAIDs from the high releaser group shared diphenylamine in their chemical structure. The amine group of this chemical agent proved to be essential for the anti-L-selectin activity of diphenylamine-based NSAIDs. The presence of a carboxylic acid group in the diphenylamine (N-phenylanthranilic acid) highly increased its ability to reduce the L-selectin surface expression in neutrophils. Diphenylamine and N-phenylanthranilic acid neither affected COX activity in platelets nor modified the activation state of neutrophils. Diphenylamine-related compounds, which include the diphenylamine-based NSAIDs caused a variable reduction in the neutrophil intracellular ATP concentration, which correlated with the differential ability of such compounds to trigger L-selectin shedding (r = 0.97, p < 0.01). Diphenylamine-related compounds failed to down-regulate L-selectin in a tumor necrosis factor-alpha-converting enzyme (TACE)-deficient murine monocytic cell line. Our data indicate that diphenylamine seems to be the structural core of NSAIDs accounting for their down-regulatory activity of L-selectin leukocyte expression. Diphenylamine and its related compounds exert this action on L-selectin through a prostaglandin-independent, TACE-dependent mechanism that seems to be linked to the capability of these agents to uncouple the mitochondrial oxidative phosphorylation.

Aspirin provides cyclin-dependent kinase 5-dependent protection against subsequent hypoxia/reoxygenation damage in culture

Aspirin [acetylsalicylic acid (ASA)] is an anti-inflammatory drug that protects against cellular injury by inhibiting cyclooxygenases (COX), inducible nitric oxide synthase (iNOS) and p44/42 mitogen-activated protein kinase (p44/42 MAPK), or by preventing translocation of nuclear factor kappaB (NF-kappaB). We studied the effect of ASA pre-treatment on neuronal survival after hypoxia/reoxygenation damage in rat spinal cord (SC) cultures. In this injury model, COX, iNOS and NF-kappaB played no role in the early neuronal death. A 20-h treatment with 3 mm ASA prior to hypoxia/reoxygenation blocked the hypoxia/reoxygenation-induced lactate dehydrogenase (LDH) release from neurons. This neuroprotection was associated with increased phosphorylation of neurofilaments, which are substrates of p44/42 MAPK and cyclin-dependent kinase 5 (Cdk5). PD90859, a p44/42 MAPK inhibitor, had no effect on ASA-induced tolerance, but olomoucine and roscovitine, Cdk5 inhibitors, reduced ASA neuroprotection. Hypoxia/reoxygenation alone reduced both the protein amount and activity of Cdk5, and this reduction was inhibited by pre-treatment with ASA. Moreover, the protein amount of a neuronal Cdk5 activator, p35, recovered after reoxygenation only in ASA-treated samples. The prevention of the loss in Cdk5 activity during reoxygenation was crucial for ASA-induced protection, because co-administration of Cdk5 inhibitors at the onset ofreoxygenation abolished the protection. In conclusion, pre-treatment with ASA induces tolerance against hypoxia/reoxygenation damage in spinal cord cultures by restoring Cdk5 and p35 protein expression.

Inhibition of interleukin-1beta-induced COX-2 and EP3 gene expression by sodium salicylate enhances pancreatic islet beta-cell function

Previous work has suggested that functional interrelationships may exist between inhibition of insulin secretion by interleukin (IL)-1beta and the endogenous synthesis of prostaglandin E(2) (PGE(2)) in the pancreatic islet. These studies were performed to ascertain the relative abundance of E prostaglandin (EP) receptor mRNAs in tissues that are major targets, or major degradative sites, of insulin; to identify which EP receptor type mediates PGE(2) inhibition of insulin secretion in pancreatic islets; and to examine possible sites of action through which sodium salicylate might affect IL-1beta/PGE(2) interactions. Real-time fluorescence-based RT-PCR indicated that EP3 is the most abundant EP receptor type in islets, liver, kidney, and epididymal fat. EP3 mRNA is the least, whereas EP2 mRNA is the most, abundant type in skeletal muscle. Misoprostol, an EP3 agonist, inhibited glucose-induced insulin secretion from islets, an event that was prevented by preincubation with pertussis toxin, by decreasing cAMP. Electromobility shift assays demonstrated that sodium salicylate inhibits IL-1beta-induced nuclear factor-kappaB (NF-kappaB) activation. Sodium salicylate also prevented IL-1beta from inducing EP3 and cyclooxygenase (COX)-2 gene expression in islets and thereby prevented IL-1beta from inhibiting glucose-induced insulin secretion. These findings indicate that the sites of action through which sodium salicylate inhibits these negative effects of IL-1beta on beta-cell function include activation of NF-kappaB as well as generation of PGE(2) by COX-2.

Ethanol extract of propolis inhibits nitric oxide synthase gene expression and enzyme activity

Propolis obtained from honeybee hives has been used in Oriental folk medicine as an anti-inflammatory, anti-carcinogenic, or immunomodulatory agent. However, the molecular basis for anti-inflammatory properties of propolis has not yet been established. Since nitric oxide (NO) synthesized by inducible nitric oxide synthase (iNOS) has been known to be involved in inflammatory and autoimmune-mediated tissue destruction, modulation of NO synthesis or action represents a new approach to the treatment of inflammatory and autoimmune diseases. The present study, therefore, examined effects of ethanol extract of propolis (EEP) on iNOS expression and activity of iNOS enzyme itself. Treatment of RAW 264.7 cells with EEP significantly inhibited NO production and iNOS protein expression induced by lipopolysaccharide (LPS) plus interferon-gamma (IFN-gamma). EEP also inhibited iNOS mRNA expression and nuclear factor-kappa B (NF-kappaB) binding activity in a concentration-dependent manner. Furthermore, transfection of RAW 264.7 cells with iNOS promoter linked to a chloramphenicol acetyltransferase (CAT) reporter gene, revealed that EEP inhibited the iNOS promoter activity induced by LPS plus IFN-gamma through the NF-kappaB sites of the iNOS promoter. In addition, EEP directly interfered with the catalytic activity of murine recombinant iNOS enzyme. These results suggest that EEP may exert its anti-inflammatory effect by inhibiting the iNOS gene expression via action on the NF-kappaB sites in the iNOS promoter and by directly inhibiting the catalytic activity of iNOS.

Beta-amyloid precursor protein transgenic mice that harbor diffuse A beta deposits but do not form plaques show increased ischemic vulnerability: role of inflammation

beta-amyloid (A beta), derived form the beta-amyloid precursor protein (APP), is important for the pathogenesis of Alzheimer's disease (AD), which is characterized by progressive decline of cognitive functions, formation of A beta plaques and neurofibrillary tangles, and loss of neurons. However, introducing a human wild-type or mutant APP gene to rodent models of AD does not result in clear neurodegeneration, suggesting that contributory factors lowering the threshold of neuronal death may be present in AD. Because brain ischemia has recently been recognized to contribute to the pathogenesis of AD, we studied the effect of focal brain ischemia in 8- and 20-month-old mice overexpressing the 751-amino acid isoform of human APP. We found that APP751 mice have higher activity of p38 mitogen-activated protein kinase (p38 MAPK) in microglia, the main immune effector cells within the brain, and increased vulnerability to brain ischemia when compared with age-matched wild-type mice. These characteristics are associated with enhanced microglial activation and inflammation but not with altered regulation of cerebral blood flow, as assessed by MRI and laser Doppler flowmetry. Suppression of inflammation with aspirin or inhibition of p38 MAPK with a selective inhibitor, SD-282, abolishes the increased neuronal vulnerability in APP751 transgenic mice. SD-282 also suppresses the expression of inducible nitric-oxide synthase and the binding activity of activator protein 1. These findings elucidate molecular mechanisms of neuronal injury in AD and suggest that antiinflammatory compounds preventing activation of p38 MAPK in microglia may reduce neuronal vulnerability in AD.

Therapeutic effects of acetylsalicylic acid in giant cell arteritis

OBJECTIVE

In giant cell arteritis (GCA), inflammatory lesions typically produce interferon-gamma(IFNgamma)-- and nuclear factor kappaB (NF-kappaB)-dependent monokines. Corticosteroids influence disease activity by repressing NF-kappaB-dependent genes but have only marginal effects on IFNgamma. The current study explored whether acetylsalicylic acid (ASA) had cytokine-repressing activity in GCA and could function as a steroid-sparing agent.

METHODS

Temporal artery-severe combined immunodeficiency (SCID) mouse chimeras were created by engrafting inflamed temporal arteries into SCID mice. Chimeras were treated with ASA, indomethacin, or dexamethasone for 3 weeks. Temporal artery grafts were harvested and cytokine message was semiquantified by polymerase chain reaction-enzyme-linked immunosorbent assay. The ability of dexamethasone and ASA to suppress IFNgamma and interleukin-1beta (IL-1beta) messenger RNA and protein production was also tested in vitro using T cell clones and monocytes derived from patients with GCA. Drug-induced effects on the transcription factors NF-kappaB and activator protein 1 (AP-1) were assessed by electrophoretic mobility shift assays (EMSAs).

RESULTS

At clinically relevant doses, 20-100 mg/kg, ASA was a highly effective inhibitor of cytokine transcription in temporal arteries. While dexamethasone preferentially targeted NF-kappaB-regulated monokines, ASA acted predominantly by suppressing IFNgamma. Indomethacin failed to reduce tissue IFNgamma transcription, which therefore excluded the inhibition of cyclooxygenases as a critical mechanism. IFNgamma production by T cell clones was highly sensitive to ASA-mediated suppression, whereas IL-1beta production by lipopolysaccharide-stimulated monocytes responded primarily to dexamethasone. The combination of ASA and dexamethasone had synergistic effects. EMSAs demonstrated that ASA interfered with the formation of AP-1, whereas dexamethasone suppressed the nuclear translocation of NF-kappaB.

CONCLUSION

The results of this study provide evidence of the complementary action of ASA and corticosteroids in suppressing proinflammatory cytokines in the vascular lesions of GCA.

Caffeic acid phenethyl ester inhibits nitric oxide synthase gene expression and enzyme activity

Since nitric oxide (NO) synthesized by inducible nitric oxide synthase (iNOS) has been known to be involved in inflammatory and autoimmune-mediated tissue destruction, modulation of NO synthesis or action represents a new approach to the treatment of inflammatory and autoimmune diseases. Caffeic acid phenethyl ester (CAPE), an active component of honeybee propolis, has been identified to show anti-inflammatory, anti-viral and anti-cancer activities. The present study, therefore, examined effects of CAPE on iNOS expression and activity of iNOS enzyme itself. Treatment of RAW 264.7 cells with CAPE significantly inhibited NO production and iNOS protein expression induced by lipopolysaccharide (LPS) plus interferon-gamma (IFN-gamma). CAPE also inhibited iNOS mRNA expression and nuclear factor-kappa B (NF-kappaB) binding activity in a concentration-dependent manner. Furthermore, transfection of RAW 264.7 cells with iNOS promoter linked to a chloramphenicol acetyltransferase reporter gene, revealed that CAPE inhibited the iNOS promoter activity induced by LPS plus IFN-gamma through the NF-kappaB sites of the iNOS promoter. In addition, CAPE directly interfered with the catalytic activity of murine recombinant iNOS enzyme. These results suggest that CAPE may exert its anti-inflammatory effect by inhibiting the iNOS gene expression at the transcriptional level through the suppression of NF-kappaB activation, and by directly inhibiting the catalytic activity of iNOS.

Cyclooxygenase selectivity of nonsteroidal anti-inflammatory drugs in canine blood

OBJECTIVE

To evaluate cyclooxygenase (COX) selectivity of several nonsteroidal anti-inflammatory drugs (NSAID) in canine blood in vitro.

ANIMALS

11 healthy adult male hound crosses.

PROCEDURE

9 NSAID were studied at 5 concentrations. Thromboxane B2 (TxB2) was assayed as a measure of COX-1 activity in clotted blood. Prostaglandin E2 (PGE2) was assayed as a measure of COX-2 activity in heparinized, lipopolysaccharide (LPS)-stimulated blood. All assays were competitive ELISA tests. Cyclooxygenase selectivity was expressed as a ratio of the concentration of an NSAID that inhibited 50% of the activity (IC50) of COX-1 to the IC50 of COX-2. A separate ratio of the concentration that inhibited 80% of COX activity (IC80) was also determined. A ratio of < 1.0 indicated selectivity for COX-1, whereas a ratio of > 1.0 indicated COX-2 selectivity.

RESULTS

Ketoprofen, aspirin, and etodolac were COX-1 selective. Piroxicam, meloxicam, and carprofen had COX-2 selectivity. The IC50 and IC80 values were similar for most NSAID.

CONCLUSIONS

This methodology provides repeatable data from individual dogs and is comparable to results of previous in vitro and ex vivo models. Findings are also consistent with those of canine studies performed in vivo, suggesting that this is a viable in vitro assessment of the COX selectivity of NSAID in dogs.

Sodium salicylate enhances the expression of cyclooxygenase-2 in endotoxin-stimulated human mononuclear cells

The effects of salicylate on the expression of cyclooxygenases, and on prostaglandin E(2) biosynthesis were examined in human peripheral blood mononuclear cells. Peripheral blood mononuclear cells were incubated in the presence of endotoxin, which induced expression of cyclooxygenase-2 protein, and caused a time-dependent increase of immunoreactive prostaglandin E(2) in the supernatant. The cycooxygenase-2 selective inhibitor N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide (NS-398, 1 microM) suppressed the endotoxin-induced increase of prostaglandin E(2), without significantly affecting the expression of cyclooxygenase-1 or cyclooxygenase-2. In peripheral blood mononuclear cells exposed to endotoxin (18 h), 1.0 and 3.0 mM sodium salicylate reduced the prostaglandin E(2) concentration of the supernatant, and, at the same time, stimulated cyclooxygenase-2 expression. After a subsequent 2 h incubation of peripheral blood mononuclear cells in drug-free medium, prostaglandin E(2) concentrations in samples that had been exposed to endotoxin together with 1.0 or 3.0 mM salicylate were significantly higher than in samples exposed to endotoxin alone. These results show that salicylate can enhance the expression of cyclooxygenase-2 in endotoxin-exposed peripheral blood mononuclear cells and at the same time reduce prostaglandin E(2) formation. After washout and removal of salicylate-induced cyclooxygenase inhibition, increased cyclooxygenase-2 expression resulted in enhanced prostaglandin E(2) formation. It seems possible that under certain conditions salicylate-induced stimulation of cyclooxygenase-2 expression may contribute to its clinical pharmacological profile.

Acetylsalicylic acid inhibits the pituitary response to exercise-related stress in humans

PURPOSE

Prostaglandins (PGs) modulate the activity of the hypothalamus-pituitary axis, and pituitary hormones are largely involved in the physiological responses to exercise. The purpose of this study was to analyze the effects of acetylsalicylic acid (ASA), an inhibitor of PGs synthesis, in the pituitary responses to physical stress in humans.

METHODS

Adrenocorticotropin (ACTH), beta-endorphin, cortisol, growth hormone (GH), and prolactin (PRL) responses to exercise were evaluated after administration of either placebo or ASA. Blood samples for hormone evaluations before (-30, -15, and 0 pre) and after (0 post, +15, +30, +45, +60, and +90 min) a 30-min treadmill exercise (75% of .VO(2max)) were taken from 12 male athletes during two exercise trials. One tablet of ASA (800 mg), or placebo, was administered two times daily for 3 d before and on the morning of each exercise-test.

RESULTS

The results clearly show that, compared with placebo, ASA ingestion significantly blunted the increased serum ACTH, beta-endorphin, cortisol, and GH levels before exercise (anticipatory response) and was associated with reduced cortisol concentrations after exercise. Furthermore, although no differences in the GH response to exercise were shown, a significantly reduced total PRL response to stress condition was observed after ASA.

CONCLUSION

ASA influences ACTH, beta-endorphin, cortisol, GH, and PRL responses to exercise-related stress in humans (preexercise activation/exercise-linked response). Even though it is not possible to exclude direct action for ASA, our data indirectly confirm a role of PGs in these responses. We have to further evaluate the nature of the preexercise endocrine activation and, because of the large use of anti-inflammatory drugs in athletes, whether the interaction between ASA and hormones might positively or negatively influence health status, performance, and/or recovery.