Novel actions of aspirin and sodium salicylate: discordant effects on nitric oxide synthesis and induction of nitric oxide synthase mRNA in a murine macrophage cell line

The Histological and Biochemical Assessment of Monoiodoacetate-Induced Knee Osteoarthritis in a Rat Model Treated with Salicylic Acid-Iron Oxide Nanoparticles

Iron oxide nanoparticles (IONPs) represent an important advance in the field of medicine with application in both diagnostic and drug delivery domains, offering a therapeutic approach that effectively overcomes physical and biological barriers. The current study aimed to assess whether oral administration of salicylic acid-functionalized iron oxide nanoparticles (SaIONPs) may exhibit beneficial effects in alleviating histological lesions in a murine monoiodoacetate (MIA) induced knee osteoarthritis model. In order to conduct our study, 15 Wistar male rats were randomly distributed into 3 work groups: Sham (S), MIA, and NP. At the end of the experiments, all animals were sacrificed for blood, knee, and liver sampling. Our results have shown that SaIONPs reached the targeted sites and also had a chondroprotective effect represented by less severe histological lesions regarding cellularity, altered structure morphology, and proteoglycan depletion across different layers of the knee joint cartilage tissue. Moreover, SaIONPs induced a decrease in malondialdehyde (MDA) and circulating Tumor Necrosis Factor-α (TNF-α) levels. The findings of this study suggest the therapeutic potential of SaIONPs knee osteoarthritis treatment; further studies are needed to establish a correlation between the administrated dose of SaIONPs and the improvement of the morphological and biochemical parameters.

Neutrophils influx and proinflammatory cytokines inhibition by sodium salicylate, unlike aspirin, in Candida albicans-induced peritonitis model

Sodium salicylate (NaS) and aspirin (ASA) are known to have a variety of effects on microorganisms, such as fungus (C. albicans and C. neoformans), moreover, it have effects in leukocyte adhesion and migration in vitro. In this report, we investigated the effect of ASA and NaS in neutrophil migration and cytokine production in C. albicans-induced peritonitis murine model. For this, mice were treated intraperitoneally (i.p) or orally (po) with NaS or ASA; after they were stimulated i.p. with C. albicans, the cellular migration was evaluated 24 h after stimulation. NaS, in mice treated i.p., unlike ASA, was able to inhibit the neutrophil migration and proinflammatory cytokine production induced by C. albicans, such as TNF-α, IL-1, IFN-γ, IL-12, and IL-10, but did not alter the IL-4 levels in these animals. However, the po treatment with same the dose of NaS or ASA did not affect the influx of this cell for inflammatory site. These results suggest that the NaS inhibits cellular migration and proinflammatory cytokine by different anti-inflammatory mechanism compared to ASA.

Treatment with acetylsalicylic acid prevents short to mid-term radiographic progression of nontraumatic osteonecrosis of the femoral head: a pilot study

BACKGROUND

Nontraumatic osteonecrosis of the femoral head (ONFH) is a progressive disease in young adults producing substantial morbidity and frequently resulting in total hip arthroplasty. Although hip-preserving surgical procedures represent the current mainstay of treatment for early disease, medical therapies targeting specific pathways in the ONFH pathogenesis could help prevent disease progression while producing less morbidity. Acetylsalicylic acid (ASA) is a promising alternative to other therapies for ONFH owing to its anti-inflammatory and antithrombotic mechanisms of action and its relatively benign side effect profile.

METHODS

We followed a prospective cohort of 10 patients (12 hips) with precollapse ONFH who were given ASA to prevent disease progression. Their outcomes were compared with those of a historic control group taken from the literature.

RESULTS

Progression occurred in 1 of 12 (8%) patients taking ASA compared with 30 of 45 (66.6%) controls (p = 0.002) at a mean follow-up of 3.7 years. Patients taking ASA also tended to exhibit decreased femoral head involvement at the end of therapy.

CONCLUSION

This hypothesis-generating study leads us to believe that ASA may be a simple and effective treatment option for delaying disease progression in patients with early-stage ONFH.

Investigation of localized delivery of diclofenac sodium from poly(D,L-lactic acid-co-glycolic acid)/poly(ethylene glycol) scaffolds using an in vitro osteoblast inflammation model

Nonunion fractures and large bone defects are significant targets for osteochondral tissue engineering strategies. A major hurdle in the use of these therapies is the foreign body response of the host. Herein, we report the development of a bone tissue engineering scaffold with the ability to release anti-inflammatory drugs, in the hope of evading this response. Porous, sintered scaffolds composed of poly(D,L-lactic acid-co-glycolic acid) (PLGA) and poly(ethylene glycol) (PEG) were prepared with and without the anti-inflammatory drug diclofenac sodium. Analysis of drug release over time demonstrated a profile suitable for the treatment of acute inflammation with ∼80% of drug released over the first 4 days and a subsequent release of around 0.2% per day. Effect of drug release was monitored using an in vitro osteoblast inflammation model, comprised of mouse primary calvarial osteoblasts stimulated with proinflammatory cytokines interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and interferon-γ (IFN-γ). Levels of inflammation were monitored by cell viability and cellular production of nitric oxide (NO) and prostaglandin E2 (PGE2). The osteoblast inflammation model revealed that proinflammatory cytokine addition to the medium reduced cell viability to 33%, but the release of diclofenac sodium from scaffolds inhibited this effect with a final cell viability of ∼70%. However, releasing diclofenac sodium at high concentrations had a toxic effect on the cells. Proinflammatory cytokine addition led to increased NO and PGE2 production; diclofenac-sodium-releasing scaffolds inhibited NO release by ∼64% and PGE2 production by ∼52%, when the scaffold was loaded with the optimal concentration of drug. These observations demonstrate the potential use of PLGA/PEG scaffolds for localized delivery of anti-inflammatory drugs in bone tissue engineering applications.

Growth promotion in broilers by both oxytetracycline and Macleaya cordata extract is based on their anti-inflammatory properties

The non-antibiotic anti-inflammatory theory of antimicrobial growth promoters (AGP) predicts that alternatives can be selected by simple in vitro tests. In vitro, the known AGP oxytetracycline (OTC) and a Macleaya cordata extract (MCE) had an anti-inflammatory effect with a half-maximal inhibitory concentration of 88 and 132 mg/l, respectively. In vivo, chickens received three different concentrations of MCE in drinking-water, OTC in feed and a control. Body weight (BW), feed intake (FI) and gain:feed (G:F) ratio were determined on days 14, 21 and 35. On day 35, body composition was determined. Plasma α1-acid glycoprotein (α1-AG) concentration was measured on days 21 and 35, and the expression of several jejunal inflammatory genes was determined on day 35. OTC-fed chickens showed a significantly higher BW, FI and G:F ratio compared with the control group at all time points. MCE had a significant linear effect on BW on days 21 and 35, and the G:F ratio was improved only over the whole period, whereas FI was not different. Only MCE but not OTC decreased the percentage of abdominal fat. Plasma α1-AG concentration increased from day 21 to 35, with the values being lower in the treatment groups. Both OTC and MCE significantly reduced the jejunal mucosal expression of inducible NO synthase. For most parameters measured, there was a clear linear dose-response to treatment with MCE. In conclusion, the results are consistent with the anti-inflammatory theory of growth promotion in production animals.

Attenuation of early liver fibrosis by pharmacological inhibition of smoothened receptor signaling

Hedgehog (Hh) signaling is involved in the pathogenesis of liver fibrosis. It has been previously shown that Hh-inhibitor cyclopamine (CYA) can reduce liver fibrosis in rats. However, CYA is not stable in vivo, which limits its clinical application. This study compares the antifibrotic potential of two known Hh antagonists, vismodegib (GDC-0449, abbreviated to GDC) and CYA. GDC is a synthetic molecule presently in clinical cancer trials and has been reported to be safe and efficacious. These drugs attenuated early liver fibrosis in common bile duct ligated rats, improved liver function, and prevented hepatic stellate cell (HSC) activation, thereby suppressing epithelial to mesenchymal transition (EMT). While both CYA and GDC increased the number of proliferating cell nuclear antigen positive liver cells in vivo, only CYA increased Caspase-3 expression in HSCs in rat livers, suggesting that while GDC and CYA effectively attenuate early liver fibrosis, their hepatoprotective effects may be mediated through different modes of action. Thus, GDC has the potential to serve as a new therapeutic agent for treating early liver fibrosis.

Aspirin and immune system

The time-tested gradual exploration of aspirin's diverse pharmacological properties has made it the most reliable therapeutic agent worldwide. In addition to its well-argued anti-inflammatory effects, many new and exciting data have emerged regarding the role of aspirin in cells of the immune system and certain immunopathological states. For instance, aspirin induces tolerogenic activity in dendritic cells and determines the fate of naive T cells to regulatory phenotypes, which suggests its immunoregulatory potential in relevance to immune tolerance. It also displays some intriguing traits to modulate the innate and adaptive immune responses. In this article, the immunomodulatory relation of aspirin to different immune cells, such as neutrophils, macrophages, dendritic cells (DCs), natural killer (NK) cells, and the T and B lymphocytes has been highlighted. Moreover, the clinical prospects of aspirin in terms of autoimmunity, allograft rejection and immune tolerance have also been outlined.

Cyclopamine attenuates acute warm ischemia reperfusion injury in cholestatic rat liver: hope for marginal livers

Cholestasis is a significant risk factor for immediate hepatic failure due to ischemia reperfusion (I/R) injury in patients undergoing liver surgery or transplantation. We recently demonstrated that inhibition of Hedgehog (Hh) signaling with cyclopamine (CYA) before I/R prevents liver injury. In this study we hypothesized that Hh signaling may modulate I/R injury in cholestatic rat liver. Cholestasis was induced by bile duct ligation (BDL). Seven days after BDL, rats were exposed to either CYA or vehicle for 7 days daily before being subjected to 30 min of ischemia and 4 h of reperfusion. Expression of Hh ligands (Sonic Hedgehog, Patched-1 and Glioblastoma-1), assessment of liver injury, neutrophil infiltration, cytokines, lipid peroxidation, cell proliferation and apoptosis were determined. Significant upregulation of Hh ligands was seen in vehicle treated BDL rats. I/R injury superimposed on these animals resulted in markedly elevated serum alanine transaminase (ALT), aspartate transaminase (AST), total bilirubin accompanied with increased neutrophil recruitment and lipid peroxidation. Preconditioning with CYA reduced the histological damage and serum liver injury markers. CYA also reduced neutrophil infiltration, proinflammatory cytokines such as TNF-α and IL-1β expression of α-smooth muscle actin and type 1 collagen resulting in reduced fibrosis. Furthermore CYA treated animals showed reduced cholangiocyte proliferation, and apoptosis. Hepatoprotection by CYA was conferred by reduced activation of protein kinase B (Akt) and extracellular signal regulated kinase (ERK). Endogenous Hh signaling in cholestasis exacerbates inflammatory injury during liver I/R. Blockade of Hh pathway represents a clinically relevant novel approach to limit I/R injury in cholestatic marginal liver.

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.

Aspirin modulates LPS-induced nitric oxide release in rat glial cells

Nitric oxide and prostaglandins are among the numerous substances released by activated glial cells. The aim of this study was to evaluate the effect of high-level aspirin on iNOS expression in cultured rat glial cells treated with lipopolysaccharide (LPS) as pathological stimulator. Using Western Blotting, we verified that aspirin enhanced LPS-induced iNOS expression and the presence of 15-deoxy-Delta(12,14)-prostaglandin (15d-PGJ2) suppressed this aspirin effect. However, the exposure of LPS-treated glial cells to aspirin resulted in a decrease of NO production. These results suggest that aspirin interferes with the cross-talk of prostaglandins and NO, blocking the endogenous negative control exerted by COX products on iNOS expression. On the other side, aspirin seems to act directly on iNOS reducing its activity, even if it does not completely block NO release by LPS-stimulated glial cells. Then aspirin could maintain homeostatic functions of NO, while it prevents toxic effects, corresponding to high NO concentrations.

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.

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.

Signalling events involved in interferon-gamma-inducible macrophage nitric oxide generation

Nitric oxide (NO) produced by macrophages (Mphi) in response to interferon-gamma (IFN-gamma) plays a pivotal role in the control of intracellular pathogens. Current knowledge of the specific biochemical cascades involved in this IFN-gamma-inducible Mphi function is still limited. In the present study, we evaluated the participation of various second messengers--Janus kinase 2 (JAK2), signal transducer and activator of transcription (STAT) 1alpha, MAP kinase kinase (MEK1/2), extracellular signal-regulated kinases 1 and 2 (Erk1/Erk2) and nuclear factor kappa B (NF-kappaB)--in the regulation of NO production by IFN-gamma-stimulated J774 murine Mphi. The use of specific signalling inhibitors permitted us to establish that JAK2/STAT1alpha- and Erk1/Erk2-dependent pathways are the main players in IFN-gamma-inducible Mphi NO generation. To determine whether the inhibitory effect was taking place at the pre- and/or post-transcriptional level, we evaluated the effect of each antagonist on inducible nitric oxide synthase (iNOS) gene and protein expression, and on the capacity of IFN-gamma to induce JAK2, Erk1/Erk2 and STAT1alpha phosphorylation. All downregulatory effects occurred at the pretranscriptional level, except for NF-kappaB, which seems to exert its role in NO production through an iNOS-independent event. In addition, electrophoretic mobility shift assay (EMSA) analysis revealed that STAT1alpha is essential for IFN-gamma-inducible iNOS expression and NO production, whereas the contribution of NF-kappaB to this cellular regulation seems to be minimal. Moreover, our data suggest that Erk1/Erk2 are responsible for STAT1alpha Ser727 residue phosphorylation in IFN-gamma-stimulated Mphi, thus contributing to the full activation of STAT1alpha. Taken together, our results indicate that JAK2, MEK1/2, Erk1/Erk2 and STAT1alpha are key players in the IFN-gamma-inducible generation of NO by Mphi.

The effect of vasodilators on aspirin-induced antagonism of t-PA thrombolysis

Although i.v. t-PA has proven successful in reducing neurologic deficits in acute ischemic stroke, the disadvantages of a narrow therapeutic time window and the failure of thrombolysis in more than 50% of patients treated have necessitated an examination of adjuvant therapies to improve the rate of thrombolysis. Experimentally, the combination of aspirin therapy with t-PA has resulted in a paradoxical antagonism of thrombolysis. Reversal of this antagonism with nitric oxide (NO) donors suggested that aspirin may inhibit/ antagonize NO-related mechanisms. Using this rabbit model of thromboembolic stroke, this hypothesis is now expanded to compare two clinically relevant anti-hypertensive agents, atenolol (NO-dependent) and hydralazine (NO-independent), for their ability to improve t-PA-mediated clot lysis following aspirin pre-treatment. Thirty rabbits (10 per group) were pre-treated with aspirin (20mg kg(-1), i.v.) and then randomized to receive either vehicle, atenolol (20 microg kg(-1) h(-1), i.v.) or hydralazine (10 microg kg(-1) min(-1), i.v.) beginning 30 min following autologous clot embolization. All rabbits then received t-PA (6.3 mg kg(-1), i.v.) beginning 1 h after embolization, with completion of the protocol 4 h after embolization. Aspirin therapy reduced regional cerebral blood flow (rCBF) from 82.8m +/- 4.7 to 62.5 +/- 6.6 (n = 30; p = 0.0005). In the aspirin control group only 30% (3 of 10) rabbits demonstrated complete clot lysis, whereas the combined atenolol (60%) and hydralazine (70%) groups experienced a clot lysis rate of 65% (13 of 20 rabbits), similar to clot lysis rates previously observed with t-PA alone. In a separate series of experiments, all agents able to reverse aspirin antagonism of thrombolysis demonstrated an improvement in rCBF, suggesting a common mechanism for this diverse group of agents in reversing aspirin's antagonism of thrombolysis.

Effect of Helicobacter pylori eradication on cyclooxygenase 2 (COX-2) and inducible nitric oxide synthase (iNOS) expression during gastric adaptation to aspirin (ASA) in humans

Gastric adaptation to aspirin is impaired in Helicobacter pylori infection, but the mechanisms underlying this phenomenon are unclear. In this study, we compared gastric mucosal expression of iNOS and COX-2 during 14 days of aspirin ingestion in the same subjects before and 3 months after eradication of H. pylori. Compared to non-infected controls, mucosal expression of COX-2 and iNOS was enhanced before and 3 months after eradication of H. pylori. During aspirin ingestion, mucosal expression of COX-2 remained unchanged before eradication of H. pylori, but increased gradually after successful antimicrobial treatment. Independent of H. pylori status, expression of iNOS increased at the beginning of aspirin intake, but then returned to initial values. We conclude that COX-2 but not iNOS might be involved in gastric adaptation to aspirin in humans and that this mechanism appears to be impaired in H. pylori infection.

Aspirin dose dependently inhibits the interleukin-1 beta-stimulated increase in inducible nitric oxide synthase, nitric oxide, and prostaglandin E(2) production in rat ovarian dispersates cultured in vitro

OBJECTIVE

Determine if aspirin inhibits the IL-1 beta-stimulated expression of inducible nitric oxide synthase (iNOS), nitric oxide (NO), and prostaglandin E(2) (PGE(2)) in rat ovarian dispersates cultured in vitro.

DESIGN

Prospective, controlled in vitro study.

SETTING

Academic research laboratory.

ANIMALS

Ovaries collected from immature rats.

INTERVENTION(S)

Ovaries were collected from immature rats and enzymatically dispersed. Ovarian dispersates were placed into plates containing media alone or media supplemented with IL-1 beta (100 U/mL) and varying concentrations of aspirin (0, 1, 3, 5 and 10 mM). Ovarian dispersates were cultured in a humidified environment of 5% CO(2) in air at 37 degrees C for 24 or 48 hours.

MAIN OUTCOME MEASURE(S)

Twenty-four- and 48-hour iNOS, nitrite (a stable metabolite of NO), and PGE(2) levels were determined from ovarian dispersates cultured in vitro.

RESULT(S)

Administration of IL-1 beta increased nitrite and PGE(2) levels over that observed in the control group after culture of ovarian dispersates for 24 and 48 hours. Aspirin dose dependently reduced the IL-1 beta-stimulated increase in nitrite production from ovarian dispersates after culture for 24 and 48 hours. Aspirin completely (24 hours) or dose dependently (48 hours) prevented the IL-beta-stimulated increase in PGE(2.) Coadministration of IL-1 beta and aspirin (10 mM) attenuates IL-1 beta-stimulated iNOS expression after culture for 24 and 48 hours.

CONCLUSION(S)

Aspirin significantly inhibits the IL-1 beta-stimulated expression of iNOS, NO, and PGE(2) in ovarian dispersates cultured in vitro.

Neuroprotective effects of non-steroidal anti-inflammatory drugs by direct scavenging of nitric oxide radicals

Recently, it has been reported that inflammatory processes are associated with the pathophysiology of Alzheimer's disease and that treatment of non-steroidal anti-inflammatory drugs reduce the risk for Alzheimer's disease. In the present study, we examined nitric oxide radical quenching activity of non-steroidal anti-inflammatory drugs and steroidal drugs using our established direct in vitro nitric oxide radical detecting system by electron spin resonance spectrometry. The non-steroidal anti-inflammatory drugs, aspirin, mefenamic acid, indomethacin and ketoprofen directly and dose-dependently scavenged generated nitric oxide radicals. In experiments of nitric oxide radical donor, NOC18-induced neuronal damage, these four non-steroidal drugs significantly prevented the NOC18-induced reduction of cell viability and apoptotic nuclear changes in neuronal cells without affecting the induction of inducible nitric oxide synthase-like immunoreactivity. However, ibuprofen, naproxen or steroidal drugs, which had less or no scavenging effects in vitro, showed almost no protective effects against NOC18-induced cell toxicity. These results suggest that the protective effects of the former four non-steroidal anti-inflammatory drugs against apoptosis might be mainly due to their direct nitric oxide radical scavenging activities in neuronal cells. These direct NO. quenching activities represent novel effects of non-steroidal anti-inflammatory drugs. Our findings identified novel pharmacological mechanisms of these drugs to exert not only their anti-inflammatory, analgesic, antipyretic activities but also neuroprotective activities against neurodegeneration.

Nitric oxide: a review for veterinary surgeons

Nitric oxide (NO) is an endogenous gas that serves as a biologic messenger in many physiologic processes including neurotransmission, blood-pressure control, the immune system's ability to kill tumor cells, and wound healing. NO is produced after oxidation of L-arginine by a family of nitric oxide synthase (NOS) enzymes. Two of the NOS enzymes are present continuously and are thereby termed constitutive NOS. One of the enzymes, inducible NOS, is not typically expressed in resting cells and is induced by various substances including endotoxin, some cytokines, and microbial products. Thus, NO often has paradoxical activities. When NO is over- or underproduced, it can result in potentiation of disease states with disastrous results. This review discusses the biochemistry of NO, its functions in normal and disease states, and therapy for modulating NO production in disease states.

Arginase I: a limiting factor for nitric oxide and polyamine synthesis by activated macrophages?

Because arginase hydrolyzes arginine to produce ornithine and urea, it has the potential to regulate nitric oxide (NO) and polyamine synthesis. We tested whether expression of the cytosolic isoform of arginase (arginase I) was limiting for NO or polyamine production by activated RAW 264.7 macrophage cells. RAW 264.7 cells, stably transfected to overexpress arginase I or beta-galactosidase, were treated with interferon-gamma to induce type 2 NO synthase or with lipopolysaccharide or 8-bromo-cAMP (8-BrcAMP) to induce ornithine decarboxylase. Overexpression of arginase I had no effect on NO synthesis. In contrast, cells overexpressing arginase I produced twice as much putrescine after activation than did cells expressing beta-galactosidase. Cells overexpressing arginase I also produced more spermidine after treatment with 8-BrcAMP than did cells expressing beta-galactosidase. Thus endogenous levels of arginase I are limiting for polyamine synthesis, but not for NO synthesis, by activated macrophage cells. This study also demonstrates that it is possible to alter arginase I levels sufficiently to affect polyamine synthesis without affecting induced NO synthesis.

Effects of aspirin-like drugs on nitric oxide synthesis in rat vascular smooth muscle cells

The purpose of this study was to investigate the effects of aspirin-like drugs on nitric oxide (NO) synthesis in rat vascular smooth muscle cells (VSMCs). We measured the accumulation of nitrite, a stable oxidation product of NO, and the expression of inducible NO synthase (iNOS) mRNA and protein in rat cultured VSMCs. Sodium salicylate, aspirin, and indomethacin dose-dependently enhanced nitrite production by interleukin (IL)-1beta-stimulated VSMCs at therapeutic plasma concentration ranges. Increased nitrite production by aspirin-like drugs was accompanied by increased iNOS mRNA and protein accumulation in VSMCs. Addition of IL-1beta activated nuclear factor kappaB (NF-kappaB) in VSMCs, but sodium salicylate did not affect IL-1beta-induced NF-kappaB activation. The nonselective lipoxygenase (LO) inhibitor nordihydroguaiaretic acid inhibited sodium salicylate-induced nitrite production, whereas the selective 5-LO inhibitor caffeic acid did not influence production of nitrite. The 12-LO product 12-HETE dose-dependently enhanced nitrite production by IL-1beta-stimulated VSMCs, whereas the 15-LO product 15-HETE did not. Our study demonstrates that aspirin and the aspirin-like drugs, sodium salicylate and indomethacin, increase NO synthesis in IL-1beta-stimulated VSMCs by upregulation of iNOS transcription via a 12-LO pathway. These effects were independent of NF-kappaB activation. In addition to the direct inhibition of platelet function, aspirin-like drugs may contribute to the reduction of atherothrombotic risk in myocardial ischemia via enhancing NO production by VSMCs.

Biochemistry of the infarcted heart

I am honored by the invitation to contribute to a volume in Neuroscience, dedicated to Professor Galoyan, whose accomplishments in the field of neuroscience and circulation have been unique. In his book, Dr. Galoyan has summarized the results of his discovery of cardioactive neurohormones. His discovery of biosynthesis of cytokines in the neurosecretory cells of the hypothalamus have opened a new page in immunology.

Sodium salicylate inhibits macrophage TNF-alpha production and alters MAPK activation

INTRODUCTION

Transcriptional activation of the TNF-alpha gene in LPS-stimulated macrophages is dependent upon nuclear factor kappa-B (NF-kappaB) activity. Salicylates may interfere with NF-kappaB activity through a MAPK (mitogen-activated protein kinase)-dependent process. These studies investigate the effects of sodium salicylate (NaSal) on TNF-alpha production and MAPK activation in macrophages.

METHODS

Rat peritoneal macrophages were pretreated or not with sodium salicylate or ibuprofen for 1 h and then stimulated with 100 ng/ml LPS. Six hours following stimulation, cell viability was assessed by MTT assay. At specified time intervals after LPS stimulation, supernatant TNF-alpha was measured by ELISA. Western blots of cell lysates were performed for analysis of total and activated (phosphorylated) MAPKs.

RESULTS

Salicylate and LPS, alone or combined, did not significantly alter macrophage viability. Salicylate, but not ibuprofen, significantly reduced TNF-alpha production in LPS-stimulated macrophages. LPS-stimulated activation of ERK and SAPK/JNK was inhibited by NaSal pretreatment. NaSal treatment of macrophages activated p38 MAPK independent of LPS stimulation. Pretreatment of samples with the specific p38 MAPK inhibitor, SB203580, did not significantly alter TNF-alpha production in either LPS or NaSal and LPS-treated samples.

CONCLUSIONS

Salicylates alter MAPK signaling and suppress TNF-alpha production in LPS-stimulated macrophages. Salicylate-induced control of inflammatory mediator production in macrophages may, in part, underlie the clinically significant anti-inflammatory effects of these compounds.

Production of prostanoids and nitric oxide by infarcted heart in situ and the effect of aspirin

The production of prostacyclin (PGI2) and thromboxane A2 (TXA2) in infarcted and noninfarcted portions of the rabbit heart was studied prior to and following administration of acetylsalicylic acid (aspirin). Aspirin was administered intravenously (iv) as water-soluble Aspisol, d-lysinmono (acetylsalicylate) (Bayer, Leverkusen, Germany) into an ear vein. A branch of the left circumflex coronary artery was ligated. The animals were divided into three groups. The first group received 150 mg/kg/day of aspirin (75 mg/kg of aspirin every 12 h, n = 10). The first administration of aspirin was 1 h after ligation of the coronary artery and the last injection was 1 h before euthanasia. The second group received 5 mg/kg/day of aspirin (every 24 h, n = 10). A separate group of rabbits not receiving aspirin served as controls (n = 12). Two days following onset of ischemia, inducible form of nitric oxide synthase (iNOS) was measured in heart muscle and the oxidation products of nitric oxide (nitrite, NO-2 plus nitrate, NO-3: their sum referred to as NOx) were determined in arterial and coronary venous blood. Concentrations of both PGI2 and TXA2 were elevated in the infarcted portions of the heart compared to the noninfarcted regions. Formation of prostanoids was accompanied by increased activation of iNOS. Both doses of aspirin diminished the concentrations of PGI2 and TXA2 in infarcted heart muscle; in contrast, small doses of aspirin failed to influence myocardial iNOS activity. Apparently small doses of aspirin changed the relationship of iNOS to cyclooxygenase (COX). Coronary arterial-venous difference of NOx and myocardial iNOS activity showed parallel increases. Diminution of prostacyclin by aspirin can damage gastric mucosa and interfere with vasodilatation. Since NO counters these deficiencies, a combination of aspirin with a nitric oxide donor may be advantageous.

Expression of endothelial cell-derived nitric oxide synthase (eNOS) is increased during gastric adaptation to chronic aspirin intake in humans

BACKGROUND

Gastric adaptation to aspirin is well-documented. However, the mechanisms underlying the reduction of aspirin-induced mucosal damage despite continued ingestion of the drug remain poorly understood.

METHODS

Eight healthy volunteers who received aspirin 1 g b.d. for 14 days were compared with eight placebo-dosed controls. Gastroscopy with mucosal biopsy was performed, and gastric mucosal blood flow was measured before and following 3, 7 and 14 days of aspirin treatment. At the same time points, tissue concentration and the content of prostaglandin E2 in the gastric juice were determined and expression of endothelial cell-derived nitric oxide synthase (eNOS) in mucosal biopsies was measured using Western blot analysis.

RESULTS

Aspirin-induced mucosal damage that reached a maximum on day 3, declining significantly by day 14. Concomitantly, mucosal blood flow significantly increased on day 3 and returned to initial values on day 14. Aspirin intake led to a significant decrease in prostaglandin E2 concentration in the gastric mucosa and in gastric juice during the whole period of aspirin consumption. eNOS expression started to increase on day 7 in oxyntic mucosa and on day 3 in antral mucosa, reaching its highest values at the end of the consumption of aspirin.

CONCLUSIONS

The human gastric mucosa adapts to prolonged aspirin intake, and this is accompanied by an increase in mucosal blood flow and reduced prostaglandin synthesis. Increase of mucosal eNOS expression might compensate for reduced prostaglandin synthesis and be responsible for gastric adaptation to chronic aspirin intake in humans.

4-trifluoromethyl derivatives of salicylate, triflusal and its main metabolite 2-hydroxy-4-trifluoromethylbenzoic acid, are potent inhibitors of nuclear factor kappaB activation

1. The effect of two derivatives of salicylate, 2-hydroxy-4-trifluoromethylbenzoic acid (HTB) and 2-acetoxy-4-trifluoromethylbenzoic acid (triflusal), on the activation of NF-kappaB elicited by tumour necrosis factor-alpha (TNF-alpha) on human umbilical vein endothelial cells (HUVEC) was tested. 2. The expression of the mRNA of vascular cell adhesion molecule-1 (VCAM-1) was studied as an example of a gene the expression of which is regulated by NF-kappaB. To extend these findings to other systems, the induction of nitric oxide synthase in rat adherent peritoneal macrophages was studied. 3. Both HTB and triflusal were more potent than aspirin or salicylate as inhibitors of the nuclear translocation of NF-kappaB. The calculation of the IC50 values showed approximately 2 mM for HTB, 4 mM for aspirin and >4 mM for salicylate. 4. Comparison of the potency of these compounds on VCAM-1 mRNA expression showed complete inhibition by both triflusal and HTB at a concentration of 4 mM whereas aspirin and salicylate produced only 36-43% inhibition at the same concentration. 5. Inhibition of NF-kappaB activation was also observed in rat peritoneal macrophages stimulated via their receptors for the Fc portion of the antibody molecule with IgG/ovalbumin immune complexes. This was accompanied by a dose-dependent inhibition of nitrite production by the L-arginine pathway via iNOS. IC50 values for this effect were 1.13+/-0.12 mM (triflusal), 1.84+/-0.34 (HTB), 6.08+/-1.53 mM (aspirin) and 9.16+/-1.9 mM (salicylate). 6. These data indicate that the incorporation of a 4-trifluoromethyl group to the salicylate molecule strongly enhances its inhibitory effect on NF-kappaB activation, VCAM-1 mRNA expression and iNOS induction, irrespective of the presence of the acetyl moiety involved in the inhibition of cyclo-oxygenase.

Modes of action of aspirin-like drugs: salicylates inhibit erk activation and integrin-dependent neutrophil adhesion

The anti-inflammatory effects of high-dose salicylates are well recognized, incompletely understood and unlikely due entirely to cyclooxygenase (COX) inhibition. We have previously reported a role for activation of the kinase Erk in CD11b/CD18 integrin-dependent adhesiveness of human neutrophils, a critical step in inflammation. We now report the effects of salicylates on neutrophil Erk and adhesion. Exposure of neutrophils to aspirin or sodium salicylate (poor COX inhibitor) inhibited Erk activity and adhesiveness of formylmethionyl-leucyl-phenylalanine- and arachidonic acid-stimulated neutrophils, consistent with anti-inflammation but not COX inhibition (IC50s = 1-8 mM). In contrast, indomethacin blocked neither Erk nor adhesion. Inhibition of Mek (proximal activator of Erk) also blocked stimulation of Erk and adhesion by formylmethionyl-leucyl-phenylalanineand arachidonic acid. Salicylate inhibition of Erk was independent of protein kinase A activation and generation of extracellular adenosine. These data are consistent with a role for Erk in stimulated neutrophil adhesion, and suggest that anti-inflammatory effects of salicylates may be mediated via inhibition of Erk signaling required for integrin-mediated responses.

Differential regulation of arginases and inducible nitric oxide synthase in murine macrophage cells

Activated macrophages avidly consume arginine via the action of inducible nitric oxide synthase (iNOS) and/or arginase. In contrast to our knowledge regarding macrophage iNOS expression, the stimuli and mechanisms that regulate expression of the cytosolic type I (arginase I) or mitochondrial type II (arginase II) isoforms of arginase in macrophages are poorly defined. We show that one or both arginase isoforms may be induced in the RAW 264.7 murine macrophage cell line and that arginase expression is regulated independently of iNOS expression. For example, 8-bromo-cAMP strongly induced both arginase I and II mRNAs but not iNOS. Whereas interferon-gamma induced iNOS but not arginase, 8-bromo-cAMP and interferon-gamma mutually antagonized induction of iNOS and arginase I mRNAs. Dexamethasone, which did not induce either arginase or iNOS, almost completely abolished induction of arginase I mRNA by 8-bromo-cAMP but enhanced induction of arginase II mRNA. Lipopolysaccharide (LPS) induced arginase II mRNA, but 8-bromo-cAMP plus LPS resulted in synergistic induction of both arginase I and II mRNAs. In all cases, increases in arginase mRNAs were sufficient to account for the increases in arginase activity. These complex patterns of expression suggest that the arginase isoforms may play distinct, although partially overlapping, functional roles in macrophage arginine metabolism.

Effect of acetylsalicylic acid on nitric oxide production in infarcted heart in situ

The effect of Acetylsalicylic Acid (ASA, Aspirin) on the myocardial production of the inducible form of nitric oxide synthase (iNOS) and the oxidation products of nitric oxide (nitrite, NO-2 and nitrate, NO-3: NOx) were studied in the rabbit heart two days after ligation of a branch of the left circumflex coronary artery. ASA was administered intravenously as AspisolR, DL-Lysinmono(acetylsalicylate) which is soluble in water. Animals received a total dose of 250, 375, or 500 mg/kg of ASA in five divided doses intravenously. Significant inhibition of iNOS was noted in the infarcted portion of the myocardium at 375 and 500 mg/kg of ASA. The reduction in myocardial nitric oxide (NO) production was paralleled by a diminution in coronary arterial-venous difference of NOx, demonstrating that ASA inhibition extended also to the oxidation products of NO. ASA is an inhibitor of cyclooxygenase (COX). The inhibition of iNOS by ASA demonstrates the close relationship between COX and iNOS activity in the heart in situ. Whether activity of the infarcted heart is influenced by the diminution in the production of NO by ASA is not known.

Aspirin and salicylate enhances the induction of inducible nitric oxide synthase in cultured rat smooth muscle cells

Aspirin and sodium salicylate enhance to a similar extent the production of nitric oxide (NO) in cultured smooth muscle cells following stimulation by interleukin-1beta (IL-1beta). The similar potencies of aspirin and sodium salicylate indicate that acetylation of cellular macromolecules is not essential for the enhancement of NO production. The failure of added prostaglandin E2 (PGE2) or Thromboxane A2 (TXA2) to overcome the effects of aspirin or sodium salicylate indicates that these effects are not simply the result of inhibition of prostaglandin synthesis. The enhancement of NO production occurs dependent of the effects of these agents on induction of inducible nitric oxide synthase (iNOS) expression by IL-1beta. Aspirin and sodium salicylate enhance the induction of iNOS expression by IL-1beta. We previously reported that pretreatment of vascular smooth muscle cells (VSMCs) with high glucose decreased the response of the cells by IL-1beta, that is, the induction of iNOS expression and NO production. We investigated the effect of aspirin and sodium salicylate on the response by IL-1beta of VSMCs pretreated with high glucose (25 mM). Aspirin and sodium salicylate ameliorate the down-regulation of iNOS expression and the decrease of NO production caused by pretreatment with high glucose (25 mM). These results suggest a possible therapeutic role in atherosclerotic disease and diabetes mellitus for aspirin and sodium salicylate by enhancing the level of iNOS expression and NO production.

The role of prostaglandin E2 and nitric oxide in cell death in J774 murine macrophages

We investigated the role of prostaglandin E2 (PGE2) and its interactions with nitric oxide (NO) on cell death and NO-mediated cytotoxicity in the murine macrophage cell line J774. Stimulation of the J774 cells with lipopolysaccharide together with interferon-gamma resulted in a dose-dependent cytotoxicity and production of PGE2 and NO, measured as nitrite. Our results showed a linear correlation between PGE2 release and cytotoxicity. The cyclooxygenase (COX) inhibitor indomethacin completely inhibited PGE2 biosynthesis, without affecting NO production or cell death. This supports previous reports suggesting that overproduction of endogenous PGE2 is mainly the consequence of cell death and does not cause it. In contrast, the NO synthase inhibitor N(omega)-monomethyl-L-arginine (L-NMMA) gave a significant, though incomplete suppression of NO release and cell death. This points to the presence of other cytotoxic factors besides NO. To evaluate the toxic effect solely due to NO, macrophages were exposed to the NO donor S-nitroso-N-acetyl-D,L-penicillamine (SNAP). Incubation with SNAP also resulted in a concentration-dependent cell injury and PGE2 production. When exogenously added, PGE2 protected against SNAP-mediated cytotoxicity and simultaneously increased PGE2 release into the medium, without inducing COX-2. The cytoprotection and the stimulation of PGE2 release were both reversed by indomethacin. In conclusion, PGE2 biosynthesis may represent a mechanism by which inflammatory macrophages protect themselves against the cytotoxic effects of NO.

Effects of aspirin on nitric oxide formation and de novo protein synthesis by RINm5F cells and rat islets

Aspirin and aspirin-like drugs are the most commonly indicated agents for the treatment of inflammation. Mechanisms of action for these drugs, however, are not clearly understood. In this study, we examined the effects of aspirin on production of nitric oxide (NO), a proinflammatory mediator, and show that aspirin inhibits NO production by transformed pancreatic beta cells (RINm5F) and rat islets in a concentration-dependent manner with an IC50 value of approximately 3 mM. Therapeutic concentrations of aspirin (1-5 mM) that block NO production affected neither nuclear factor-kappaB activation nor inducible NO synthase (iNOS) mRNA transcription but potently inhibited iNOS protein expression by both RINm5F cells and rat islets. The effects of aspirin on islet function were examined by measuring glucose-stimulated insulin secretion in the presence of various concentrations of aspirin. Aspirin (1-5 mM) did not affect insulin secretion at basal or glucose-stimulated conditions, whereas higher concentrations of aspirin (10-20 mM) significantly increased basal insulin secretion. Aspirin at high concentrations of 10 and 20 mM inhibited de novo protein synthesis as demonstrated by inhibition of [35S]methionine incorporation into total islet protein and by inhibition of rabbit reticulocyte expression by Brome mosaic virus mRNA, suggesting that inhibition of iNOS expression at these high concentrations of aspirin may be due to the impairment of the translational machinery. These findings indicate that inhibition of iNOS expression and NO production may explain, in part, the beneficial effects of aspirin as an anti-inflammatory agent at therapeutic concentrations, whereas inhibition of de novo protein synthesis may possibly explain clinical and side effects of aspirin in the inflamed tissues and organs such as stomach and kidney that may accumulate high concentrations of aspirin.

Nitric oxide reverses aspirin antagonism of t-PA thrombolysis in a rabbit model of thromboembolic stroke

Randomized trials of thrombolytic therapy in stroke have reported an improvement in neurologic outcome; however, the addition of aspirin has resulted in a significant increase in mortality and antagonism of clot lysis in clinical and animal studies, respectively. This finding is in contradistinction to the known synergy in mortality reduction for aspirin and thrombolytics in myocardial infarction. It is hypothesized that aspirin antagonism of clot lysis is related to inhibition of nitric oxide (NO) and may be reversed by providing a source of NO. Twenty rabbits were treated with aspirin (20 mg/kg, i.v.) prior to internal carotid clot embolization. One-half hour following embolization, rabbits were randomized to receive vehicle (n = 5), the NO precursor L-arginine (300 mg/kg, i.v. bolus at 0.5 and 2.5 h postembolus; n = 5), or a nitric oxide donor (nitroprusside, 1 mg/kg/h, i.a., or nitroglycerin, 10 microg/kg/min, i.v., n = 5 each agent). Tissue plasminogen activator (t-PA) (6.3 mg/kg) was administered from 1 to 3 h after embolization. Lysis of the tin-tagged clot was followed with serial X rays and gross examination. No rabbit in the control group experienced complete clot lysis. However, 2 of 5 rabbits in the L-arginine group and 6 of 10 rabbits in the nitric oxide donor (nitroprusside and nitroglycerin) groups noted complete clot lysis (P < 0.05, Fisher exact test). Thus, administration of an NO donor (nitroglycerin or nitroprusside) and, to a lesser extent L-arginine, reversed aspirin's antagonism of t-PA thrombolysis. This study may help explain the discrepant results seen with aspirin and thrombolytics.

Up-regulation of cyclooxygenase-2 expression in cultured microglia by prostaglandin E2, cyclic AMP and non-steroidal anti-inflammatory drugs

Cyclooxygenase-2, the inducible isoform of cyclooxygenase, is highly expressed in microglial cells activated by bacterial lipopolysaccharide and is a major regulatory factor in the synthesis of prostanoids, such as prostaglandins, prostacyclin and thromboxanes. Since prostanoids are potent modulators of inflammation, immune responses and neurotoxicity, the regulation of their synthesis may be crucial for balancing microglial neuroprotective and neurotoxic activities. The present study shows that expression of cyclooxygenase-2 and prostanoid production in cultured rat microglia activated by lipopolysaccharide is up-regulated by cyclic AMP (cAMP), as indicated by experiments performed in the presence of adenylyl cyclase activators, cAMP analogues and protein kinase A-specific inhibitors. Exogenous prostaglandin E2 (PGE2), which elevates the cAMP level in microglial cells, also increased the lipopolysaccharide-induced expression of cyclooxygenase-2 and production of thromboxane in a dose- and time-dependent manner. The observations that the lipopolysaccharide-induced prostanoid production was specifically increased by 11-deoxy-16,16-dm PGE2, a selective agonist at the PGE2 receptor EP2 coupled to the activation of adenylyl cyclase, and that the enhancing effect of PGE2 was partially prevented by specific inhibitors of adenylyl cyclase and protein kinase A, suggest that the up-regulation of cyclooxygenase-2 expression by PGE2 is mediated by cAMP, through a putative microglial EP2 receptor. Unexpectedly, non-steroidal anti-inflammatory drugs such as indomethacin and 6-methoxy naphthalene acetic acidic, which inhibit cyclooxygenase enzymatic activity and abrogate prostanoid synthesis, caused a moderate but consistent up-regulation of cyclooxygenase-2 expression. In conclusion, while the strong up-regulation of cyclooxygenase-2 expression by exogenous PGE2 appears to be mediated by EP2 receptors and cAMP, the limited down-regulation caused by anti-inflammatory drug treatments may be either due to arachidonic acid metabolites other than PGE2, or to PGE2 itself, acting through a distinct cAMP-independent signalling pathway.

Inhibition of nitric oxide synthase expression and activity in macrophages by 3-hydroxyanthranilic acid, a tryptophan metabolite

Indoleamine 2,3-dioxygenase (IDO) and nitric oxide synthase (NOS) type II are induced in macrophages by interferon (IFN)-gamma and lipopolysaccharide (LPS). Nitric oxide has been previously shown to inhibit IDO activity. We studied whether metabolites of tryptophan via the IDO pathway could alter NOS II activity. In RAW 264.7 cells, the phenolic antioxidant 3-hydroxyanthranilic acid (OH-AA), but not anthranilic acid, inhibited citrulline synthesis by NOS II at sub-millimolar concentrations, when added 1 h before IFN-gamma and LPS. OH-AA inhibited NOS II activity in cytosolic extracts, suggesting a direct action of OH-AA on NOS II protein. Moreover, expression of NOS II mRNA and activation of the nuclear factor kappa B (NF-kappa B) in RAW 264.7 cells were decreased by a pretreatment with OH-AA, but not anthranilic acid, before addition of IFN-gamma and LPS. This pretreatment also inhibited activation of NF-kappa B in response to TNF-alpha in lymphoblastoid J.Jhan5-1 cells. Finally, expression of a long terminal repeat of the human immunodeficiency virus (HIV-LTR)-driven luciferase reporter gene, controlled by NF-kappa B activation, was severely decreased by OH-AA or 3-hydroxykynurenine in J.Jhan5-1 cells. Other tryptophan derivatives were inactive. These data identify OH-AA as an aminophenolic tryptophan derivative inhibiting NF-kappa B activation and impairing both NOS II expression and activity in a millimolar concentration range.