Effect of a nitric oxide-releasing naproxen derivative on hypertension and gastric damage induced by chronic nitric oxide inhibition in the rat

The anti-inflammatory and vasoprotective properties of mPGES-1 inhibition offer promising therapeutic potential

INTRODUCTION

Prostaglandin E2 (PGE2) is produced by cyclooxygenases (COX-1/2) and the microsomal prostaglandin E synthase 1 (mPGES-1). PGE2 is pro-inflammatory in diseases such as rheumatoid arthritis, cardiovascular disorders, and cancer. While Nonsteroidal anti-inflammatory drugs (NSAIDs) targeting COX can effectively reduce inflammation, their use is limited by gastrointestinal and cardiovascular side effects resulting from the blockade of all prostanoids. To overcome this limitation, selective inhibition of mPGES-1 is being explored as an alternative therapeutic strategy to inhibit PGE2 production while sparing or even upregulating other prostaglandins. However, the exact timing and location of PGH2 conversion to PGD2, PGI2, TXB2 or PGF2α, and whether it hinders or supports the therapeutic effect of mPGES-1 inhibition, is not fully understood.

AREAS COVERED

The article briefly describes prostanoid history and metabolism with a strong focus on the vascular effects of prostanoids. Recent advances in mPGES-1 inhibitor development and results from pre-clinical and clinical studies are presented. Prostanoid shunting after mPGES-1 inhibition is highlighted and particularly discussed in the context of cardiovascular diseases.

EXPERT OPINION

The newest research demonstrates that inhibition of mPGES-1 is a potent anti-inflammatory treatment strategy and beneficial and safer regarding cardiovascular side effects compared to NSAIDs. Inhibitors of mPGES-1 hold great potential to advance to the clinic and there are ongoing phase-II trials in endometriosis.

Vascular Inflammation in Hypertension: Targeting Lipid Mediators Unbalance and Nitrosative Stress

Arterial hypertension is a worldwide public health threat. High Blood Pressure (BP) is commonly associated with endothelial dysfunction, nitric oxide synthases (NOS) unbalance and high peripheral vascular resistance. In addition to those, inflammation has also been designated as one of the major components of BP increase and organ damage in hypertension. This minireview discusses vascular inflammatory triggers of high BP and aims to fill the existing gaps of antiinflammatory therapy of hypertension. Among the reasons discussed, enhanced prostaglandins rather than resolvins lipid mediators, immune cell infiltration and oxidative/nitrosative stress are pivotal players of BP increase within the inflammatory hypothesis. To address these inflammatory targets, this review also proposes new concepts in hypertension treatment with non-steroidal antiinflammatory drugs (NSAIDs), nitric oxide-releasing NSAIDs (NO-NSAIDs) and specialized proresolving mediators (SPM). In this context, the failure of NSAIDs in hypertension treatment seems to be associated with the reduction of endogenous NO bioavailability, which is not necessarily an effect of all drug members of this pharmacological class. For this reason, NO-releasing NSAIDs seem to be safer and more specific therapy to treat vascular inflammation in hypertension than regular NSAIDs.

Nonsteroidal Anti-Inflammatory Therapy: A Journey Toward Safety

The efficacy of nonsteroidal anti-inflammatory drugs (NSAIDs) against inflammation, pain, and fever has been supporting their worldwide use in the treatment of painful conditions and chronic inflammatory diseases until today. However, the long-term therapy with NSAIDs was soon associated with high incidences of adverse events in the gastrointestinal tract. Therefore, the search for novel drugs with improved safety has begun with COX-2 selective inhibitors (coxibs) being straightaway developed and commercialized. Nevertheless, the excitement has fast turned to disappointment when diverse coxibs were withdrawn from the market due to cardiovascular toxicity. Such events have once again triggered the emergence of different strategies to overcome NSAIDs toxicity. Here, an integrative review is provided to address the breakthroughs of two main approaches: (i) the association of NSAIDs with protective mediators and (ii) the design of novel compounds to target downstream and/or multiple enzymes of the arachidonic acid cascade. To date, just one phosphatidylcholine-associated NSAID has already been approved for commercialization. Nevertheless, the preclinical and clinical data obtained so far indicate that both strategies may improve the safety of nonsteroidal anti-inflammatory therapy.

Endothelial dysfunction in rats with ligature-induced periodontitis: Participation of nitric oxide and cycloxygenase-2-derived products

OBJECTIVES

Considering the evident relationship between periodontitis and cardiovascular diseases in humans, we aimed to study the in vitro vascular reactivity of aorta rings prepared from rats with ligature-induced periodontitis.

METHODS

Seven days after the induction of unilateral periodontitis, the animals were euthanised; rings were prepared from the descending abdominal aortas and mounted in tissue baths for the in vitro measurement of the isometric force responses to norepinephrine (NE) and acetylcholine (ACh), as well as in the presence of inhibitors of nitric oxide synthase (NOS) and cycloxygenase (COX) isoenzymes. Aortic COX and NOS gene expressions were analysed by RT-PCR, as well as protein COX-2 expression by Western blot.

RESULTS

Periodontitis resulted in significant alveolar bone loss and did not affect arterial pressure. However, both NE-induced contraction and ACh-induced relaxation were significantly decreased and related to the presence of endothelium. Diminished eNOS and augmented COX-2 and iNOS expressions were found in the aortas from rats with periodontitis, and the pharmacological inhibition of COX-2 or iNOS improved the observed vasomotor deficiencies.

CONCLUSIONS

We can thus conclude that periodontitis induces significant endothelial dysfunction in rat aorta which is characterized by decreased eNOS expression and mediated by upregulated iNOS and COX-2 products.

Characterization of the anti-inflammatory properties of NCX 429, a dual-acting compound releasing nitric oxide and naproxen

AIMS

Cyclooxygenase (COX)-inhibiting nitric oxide donors (CINODs) are a new class of drugs that structurally combine a COX inhibitor with a nitric oxide (NO) donating moiety. This combination reduces potential toxicity of the non-steroidal anti-inflammatory drugs (NSAIDs) whilst maintaining the analgesic and anti-inflammatory effects. The present study was undertaken to investigate the anti-inflammatory effects of NCX 429, a naproxen-based CINOD, and to assess the additional properties of NO donation beyond those related to naproxen.

MAIN METHODS

We evaluated the in vitro effects of NCX 429 on oxy-radical production, phagocytosis, cytokine release, MMP-9, PPARγ expression and NF-κB activation in human monocytes/MDM and compared to naproxen. Moreover, we compared the in vivo efficacy of NCX 429 and naproxen in a murine model of peritonitis.

KEY FINDINGS

In all the experiments performed in vitro, NCX 429 reduced the inflammatory responses with equal or higher efficacy compared to naproxen. Moreover, in in vivo experiments, NCX 429, at the lowest dose tested, was able to significantly inhibit cell influx in response to IL-1β administration although naproxen was found to be more potent than NCX 429 at reducing PGE2 in inflammatory exudates.

SIGNIFICANCE

These results demonstrate that both in vitro and in vivo--in a murine model of peritonitis--NCX 429 elicits significant anti-inflammatory activity, beyond the simple COX inhibition or pure NO release. Therefore, NO donation along with COX inhibition may represent a strategy for investigating inflammatory diseases in which pain and function are not fully resolved by analgesics/anti-inflammatory drugs.

A comparative study on the anti-inflammatory effects of single oral doses of naproxen and its hydrogen sulfide (H2S)-releasing derivative ATB-346 in rats with carrageenan-induced synovitis

BACKGROUND

Non-steroidal antiinflammatory drugs (NSAIDs) are the most commonly prescribed agents for arthritic patients, although gastric effects limit their long-term use. Considering the reported gastric safety of hydrogen sulfide (H2S)-releasing NSAIDs, in addition to the anti-inflammatory effects of H2S administration to rats with synovitis, we decided to evaluate the effects of the H2S-releasing naproxen derivative ATB-346 in this animal model.

METHODS

Male Wistar rats were anesthetized with inhalatory halothane and pre-treated with equimolar oral doses of either naproxen (0.3, 1, 3 or 10 mg/kg) or ATB-346 (0.48, 1.6, 4.8, or 16 mg/kg) 30 min before the i.art. injection of 7.5 mg of carrageenan (CGN) into the right knee joint cavity. Joint swelling and pain score were assessed after 1, 3 and 5 h, and tactile allodynia after 2 and 4 h. After the last measurement, the joint cavity lavages were performed for counting of the recruited leukocytes. The drugs (at the highest doses) were also tested for their gastric effects by evaluating macroscopical damage score and neutrophil recruitment (measured as myeloperoxidase - MPO activity) in the stomachs 5 h after administration of the drugs. In addition, the serum naproxen pharmacokinetic profiles of both compounds, administered at the highest equimolar doses, were obtained during the first 6 h after dosing.

RESULTS

At the two highest tested doses, both naproxen and ATB-346 reduced edema and pain score (measured 3 and 5 h after CGN; P < 0.001). Tactile allodynia was similarly inhibited by ~45% 4 h after CGN by both naproxen (at 1, 3 and 10 mg/kg) and ATB-346 (at 1.6 and 4.8 mg/kg; P < 0.001), as well as leukocyte infiltration. Naproxen (but not ATB-346) induced significant gastric damage and, despite the increased gastric MPO activity by ~130% in the naproxen-, but not in the ATB-346-treated rats, this effect was of no statistical significance.

CONCLUSION

The presence of a H2S-releasing moiety in the ATB-346 structure does not impair the antiinflammatory activity of the parent compound in rats with CGN-induced synovitis. In addition, released H2S may account for the absence of deleterious gastric effects, thus making of ATB-346 a potentially useful therapeutic alternative to traditional naproxen for treatment of patients with arthritis.

Effects of naproxcinod on blood pressure in patients with osteoarthritis

Nonsteroidal anti-inflammatory drugs are associated with increases in blood pressure (BP), particularly in patients treated with antihypertensive therapy. Naproxcinod is a nitric oxide-donating cyclooxygenase inhibitor in development for osteoarthritis (OA). Thus, we characterized the effects of naproxcinod on BP in an integrated safety analysis of 3 pivotal trials of patients with OA of the hip or knee involving 2,734 patients. The changes from baseline in the systolic BP after 13 weeks of therapy with naproxcinod (375 and 750 mg), naproxen 500 mg (equipotent to naproxcinod 750 mg), or placebo twice daily were evaluated in all patients and in the subgroup taking renin-angiotensin system inhibitors. Heterogeneity testing showed no treatment-by-study interaction. The effects of naproxcinod 750 mg on the systolic BP was not different from placebo (mean change from baseline vs placebo -0.4 mm Hg, 95% confidence interval -1.6 to 0.8). Naproxen increased the systolic BP relative to placebo (mean change from baseline vs placebo +1.4 mm Hg, 95% confidence interval 0.1 to 2.7). In the renin-angiotensin system inhibitor-treated patients, the effect of naproxcinod 750 mg compared to naproxen 500 mg in the changes from baseline in the systolic BP was -4.3 mm Hg (95% confidence interval -8.5 to -0.0). In conclusion, naproxcinod had effects on BP similar to that of placebo in patients with OA. These results imply that naproxcinod would be less likely to alter systolic BP control in patients with OA than a conventional nonsteroidal anti-inflammatory drug, particularly in those treated with renin-angiotensin system inhibitor agents.

Blood pressure effects of naproxcinod in hypertensive patients

The blood pressure (BP) effects of naproxcinod and naproxen were assessed in an 8-week, double-blind, crossover study in 131 hypertensive patients aged 50 to 74 years. Patients received naproxcinod 750 mg twice daily or naproxen 500 mg twice daily, then the alternate treatment, each for 14 days, with placebo run-in/washout before each active treatment period and 24-hour ambulatory BP monitoring conducted before and after each active treatment period. Mean change from baseline in average 24-hour systolic BP (SBP) after 2 weeks of treatment numerically favored naproxcinod 750 mg twice daily (least-squares [LS] mean for naproxcinod minus naproxen: -1.6 mm Hg; P=.12). Post hoc analyses showed statistically significant SBP differences favoring naproxcinod for the 8 elapsed hours (LS mean: -4.4 mm Hg; P<.0001) and the 24 hours following morning dosing (LS mean: -2.4 mm Hg; P=.006). Naproxcinod may be a beneficial alternative for patients with osteoarthritis requiring nonsteroidal anti-inflammatory drugs.

Treatment strategies for osteoarthritis patients with pain and hypertension

Out of 100 patients with osteoarthritis (OA), almost 40 have a concomitant diagnosis of hypertension. Nonsteroidal anti-inflammatory drugs (NSAIDs) and cyclooxygenase-2 (COX-2) inhibitors may trigger a rise in blood pressure (BP), which is more marked in patients with established hypertension. NSAIDs and COX-2 inhibitors attenuate the antihypertensive effect of several antihypertensive agents. Frequent BP controls are needed in treated hypertensive patients who are concomitantly receiving NSAIDs or COX-2 inhibitors because even a small increase in BP may be associated with an important rise in the risk of major cardiovascular complications. In meta-analyses, an increase in systolic BP of 5mmHg was associated with a 25% higher risk of cardiovascular events. These data have been confirmed in randomized studies with rofecoxib and celecoxib, where a modest increase in BP was associated with a significantly higher risk of cardiovascular disease. There is emerging evidence that the COX-inhibiting nitric oxide donator (CINOD) class is promising in the treatment of patients with OA. Naproxcinod, the first CINOD investigated in clinical trials, is composed of the traditional NSAID naproxen covalently bound to the nitric oxide (NO)-donating moiety butanediol mono-nitrate (BDMN). The molecule has the potential to provide a sustained release of NO. In clinical studies, naproxcinod prevented the BP rise in normotensive and hypertensive patients observed with naproxen. The BP benefit of naproxcinod over naproxen was greater in patients concomitantly receiving angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers. These investigational data suggest that naproxcinod is a valuable alternative to NSAIDs and COX-2 inhibitors for treatment of OA patients.

Nonsteroidal Anti-Inflammatory Drugs (NSAIDs): Progress in Small Molecule Drug Development

Ever since the discovery of aspirin, small molecule therapeutics have been widely prescribed to treat inflammation and pain. Aspirin and several small molecule NSAIDs are known to inhibit the enzymes cyclooxygenase-1 (COX-1) and -2 (COX-2). Despite the success of NSAIDs to treat inflammatory disorders, the development of a clinically useful small molecule NSAIDs with decreased side effect profiles is an ongoing effort. The recent discovery and development of selective COX-2 inhibitors was a step toward this direction. Emerging trends are represented by the progress in the development of hybrid agents such as nitric oxide donor-NSAIDs (NO-NSAIDs) and dual COX/lipoxygenase (LOX) inhibitors. This review focuses on the recent advances in the rational design of small molecule NSAIDs in therapy.

Treatment of osteoarthritis in hypertensive patients

IMPORTANCE OF THE FIELD

Osteoarthritis and hypertension commonly co-exist. Treatment of osteoarthritis in hypertensive patients is a therapeutic challenge due to the adverse effects of some analgesics, especially non-steroidal anti-inflammatory drugs (NSAIDs), on blood pressure. Even small drug-induced rises in blood pressure due to therapy may significantly increase cardiovascular risk in these patients if sustained over the long term. Patients treated with certain classes of antihypertensive agent may be at particular risk of deterioration in blood pressure control with NSAID therapy. NSAIDs may also increase cardiovascular risk due to mechanisms other than by raising blood pressure.

AREAS COVERED IN THIS REVIEW

We discuss the management of osteoarthritis in the hypertensive patient, review the evidence for the effects of paracetamol and NSAIDs on blood pressure and discuss novel therapeutic strategies for osteoarthritis that might diminish this problem. A literature search was undertaken in PubMed including the years 1980 - 2009.

WHAT THE READER WILL GAIN

Insight will be gained into the complexity of treating patients with co-existent osteoarthritis and hypertension and into possible new approaches to treating osteoarthritis symptoms effectively in these patients while minimising any adverse impact on blood pressure control.

TAKE HOME MESSAGE

There are ways to minimise the adverse impact of treatment of osteoarthritis on blood pressure control in hypertensive patients.

Markedly reduced toxicity of a hydrogen sulphide-releasing derivative of naproxen (ATB-346)

BACKGROUND AND PURPOSE

Hydrogen sulphide is an important mediator of gastric mucosal defence. The use of non-steroidal anti-inflammatory drugs continues to be limited by their toxicity, particularly in the upper gastrointestinal tract. We evaluated the gastrointestinal safety and anti-inflammatory efficacy of a novel hydrogen sulphide-releasing derivative of naproxen, ATB-346 [2-(6-methoxy-napthalen-2-yl)-propionic acid 4-thiocarbamoyl-phenyl ester].

EXPERIMENTAL APPROACH

The ability of ATB-346 versus naproxen to cause gastric damage was evaluated in healthy rats and in rats with compromised gastric mucosal defence. Effects on the small intestine and on the healing of ulcers were also assessed. The ability of ATB-346 to inhibit cyclooxygenase-1 and 2 and to reduce inflammation in vivo was also evaluated.

KEY RESULTS

ATB-346 suppressed gastric prostaglandin E(2) synthesis as effectively as naproxen, but produced negligible damage in the stomach and intestine. In situations in which the gastric mucosa was rendered significantly more susceptible to naproxen-induced damage (e.g. ablation of sensory afferent nerves, inhibition of endogenous nitric oxide or hydrogen sulphide synthesis, co-administration with aspirin, antagonism of K(IR)6.x channels), ATB-346 did not cause significant damage. Unlike naproxen and celecoxib, ATB-346 accelerated healing of pre-existing gastric ulcers. In a mouse airpouch model, ATB-346 suppressed cyclooxygenase-2 activity and inhibited leukocyte infiltration more effectively than naproxen. ATB-346 was as effective as naproxen in adjuvant-induced arthritis in rats, with a more rapid onset of activity. Unlike naproxen, ATB-346 did not elevate blood pressure in hypertensive rats.

CONCLUSIONS AND IMPLICATIONS

ATB-346 exhibits anti-inflammatory properties similar to naproxen, but with substantially reduced gastrointestinal toxicity.

Naproxcinod, a new cyclooxygenase-inhibiting nitric oxide donator (CINOD)

BACKGROUND

COX-inhibiting nitric oxide donators (CINODs) are a new class of drugs that combine the actions of the parent COX inhibitor with nitric oxide (NO), with the aim of reducing potential toxicity of the parent drug, while maintaining its analgesic and anti-inflammatory effects. AZD3582 (Naproxcinod) is the first in the class of CINODs.

OBJECTIVE/METHODS

To review the effects of NO donation, CINODS in general and naproxen in osteoarthritis (OA), based on literature in PubMed.

RESULTS

In preclinical and human studies, this drug produced similar analgesic and anti-inflammatory effects to its parent naproxen, with improved gastrointestinal safety in OA patients. The results of recent clinical trials, which were designed to study effects on blood pressure, are expected shortly, after peer-review.

CONCLUSIONS

As naproxen is considered the safest COX inhibitor choice from a cardiovascular perspective, AZD3582 has the potential to become a new drug treatment in patients with OA, in whom pain and function are not controlled by the use of analgesics.

Effects of the cyclooxygenase inhibiting nitric oxide donator naproxcinod versus naproxen on systemic blood pressure in patients with osteoarthritis

Traditional nonsteroidal anti-inflammatory drugs are associated with the destabilization of blood pressure (BP) control, particularly in hypertensive patients treated with blockers of the renin-angiotensin system. To assess the potential impact of nitric oxide donation, the effects of naproxcinod with naproxen and placebo on changes in BP were compared in a randomized clinical trial of 916 patients with osteoarthritis after 13 weeks of therapy. In addition, the effects of naproxcinod versus naproxen and placebo on systolic BP in patients with hypertension treated with renin-angiotensin system blockers were evaluated. Naproxcinod 750 mg twice daily reduced systolic BP compared to naproxen 500 mg twice daily (p <0.02). The 2 doses of naproxcinod showed reductions from baseline in diastolic BP relative to naproxen (p <0.04) and similar changes compared to placebo. In 207 patients with hypertension treated with renin-angiotensin-blocking agents alone or with diuretics, the difference in mean change from baseline in systolic BP between naproxen 500 mg and naproxcinod 750 mg was 6.5 mm Hg in favor of naproxcinod (p <0.02). The proportion of patients in the overall population with systolic BP increases > or =10 mm Hg was greater with naproxen 500 mg (22%) compared to naproxcinod 750 mg (14%, p = 0.04), naproxcinod 375 mg (14%, p = 0.055), and placebo (15.6%, p = 0.155). In conclusion, naproxcinod did not induce elevations of BP seen with naproxen, and it had similar effects on BP to that of placebo in patients with osteoarthritis.

Modulation of carcinogen metabolism by nitric oxide-aspirin 2 is associated with suppression of DNA damage and DNA adduct formation

Nitric oxide (NO)-donating non-steroidal anti-inflammatory drugs (NSAIDs) represent a promising new class of drugs developed to provide a safer alternative than their conventional NSAID counterparts in chemoprevention. We tested the effects of NO-aspirin 2 on Phase I and Phase II carcinogen-metabolizing enzymes. In HepG2 human hepatoma cells and in LS180 colonic adenocarcinoma cells, NO-aspirin 2 inhibited 2,3,7,8-tetrachlordibenzo-p-dioxin (TCDD)-induced cytochrome P450 (CYP) enzyme activity and CYP1A1 and CYP1A2 mRNA expression. These effects were further characterized as being mediated through transcriptional regulation: NO-aspirin 2 inhibited binding of ligand (TCDD)-activated aryl hydrocarbon receptor to the CYP1A1 enhancer sequence; additionally, NO-aspirin 2 suppressed carcinogen-induced expression of CYP1A heterogeneous nuclear RNA. The fate of carcinogen metabolites depends not only on activation by CYP enzymes but also detoxification by Phase II enzymes. Both HepG2 and LS180 cells treated with NO-aspirin 2 showed an increase in glutathione S-transferase-P1 (GST-P1), glutamate-cysteine ligase (GCL), and NAD(P)H:quinone oxidoreductase-1 (NQO1) expression. Compared with two other NO-releasing compounds, diethylenetriamine-NO and the organic nitrate, isosorbide dinitrate, the inhibitory effects of NO-aspirin 2 on TCDD-induced CYP activity and mRNA expression were considerably more potent. Furthermore, aspirin alone had no inhibitory effect on TCDD-induced CYP activity, nor did aspirin up-regulate GCL, GST-P1, or NQO1 expression. Consequent to the effects on carcinogen-metabolizing enzymes, NO-aspirin 2 inhibited [3H]benzo[a]pyrene-DNA adduct formation and DNA damage elicited by TCDD or benzo[a]pyrene. Our results demonstrate that NO-aspirin 2 may be an effective chemopreventive agent by favorably affecting the inhibitory and enhancing effects of Phase I and Phase II carcinogen metabolism, thereby protecting DNA from carcinogenic insult.

Efficacy, safety, and tolerability of the cyclooxygenase-inhibiting nitric oxide donator naproxcinod in treating osteoarthritis of the hip or knee

OBJECTIVE

Naproxcinod, a cyclooxygenase-inhibiting nitric oxide donator antiinflammatory drug, was evaluated in this phase 2, double-blind, randomized, parallel group study to determine its optimal dose in patients with osteoarthritis (OA).

METHODS

In total 543 patients with OA of the hip or knee were randomized to receive naproxcinod 750 mg once daily (qd), 750 mg twice daily (bid), 1125 mg bid, rofecoxib 25 mg qd, or placebo for 6 weeks. The primary efficacy variable was the within-patient change from baseline to the average of Weeks 4 and 6 in WOMAC pain subscale score. Treatment-group differences were compared using ANCOVA with factors for treatment and country, and baseline pain subscale score as a covariate. Safety endpoints included vital signs and adverse events. Treatment-group differences in mean change from baseline to Week 6 in systolic blood pressure (SBP) were compared using an ANCOVA with treatment and country as fixed factors and baseline SBP as covariate.

RESULTS

All active treatments showed statistically significant reductions in WOMAC pain score compared to placebo (p<or=0.02). Naproxcinod was well tolerated. The 750 mg bid dose appeared to have the best balance of benefit versus safety. All 3 naproxcinod doses showed a reduction in SBP, while an increase was shown for rofecoxib. The changes for the naproxcinod groups were statistically significantly better compared to rofecoxib (p<or=0.02).

CONCLUSION

This dose-finding study identified naproxcinod 750 mg bid as the upper dose for further therapeutic confirmatory clinical trials. Naproxcinod at all doses decreased mean SBP compared to an increase with rofecoxib.

Treatment of patients with hypertension and arthritis pain: new concepts

Arthritis pain often occurs concurrently with hypertension and other cardiovascular risk factors. Treating patients with hypertension who have arthritis and other painful conditions can be a challenge because of potential risks associated with the agents commonly used to treat pain and inflammation. Hypertension is associated with endothelial dysfunction and decreased bioavailability of nitric oxide (NO). Naproxcinod, an investigational drug, is the first in a new class of agents called cyclooxygenase-inhibiting NO donators. They differ from traditional nonsteroidal anti-inflammatory drugs in their ability to donate NO, a signaling molecule known to have potentially beneficial effects on the vasculature and the gastrointestinal tract. Naproxcinod, by donating NO, offers a therapeutic option that might mitigate the negative blood pressure effects and adverse gastrointestinal effects associated with traditional arthritis therapies. This article reviews some preliminary preclinical and clinical studies of key safety data of an investigational new NO-donating anti-inflammatory agent.

Nitric oxide and cardiovascular effects: new insights in the role of nitric oxide for the management of osteoarthritis

Nitric oxide (NO) is an important mediator in both health and disease. In addition to its effects on vascular tone and platelet function, it plays roles in inflammation and pain perception that may be of relevance in osteoarthritis. Many patients with osteoarthritis take nonsteroidal anti-inflammatory drugs (NSAIDs) long term for pain control. Over recent years concern has been raised about the possible cardiovascular side effects of NSAIDs. The reasons for this possible increased cardiovascular risk with NSAIDs are not yet entirely clear, although changes in blood pressure, renal salt handling and platelet function may contribute. Recently, drugs that chemically link a NSAID with a NO donating moiety (cyclo-oxygenase-inhibiting NO-donating drugs [CINODs]) were developed. NO is an important mediator of endothelial function, acting as a vasodilator and an inhibitor of platelet aggregation, and having anti-inflammatory properties. The potential benefits of CINODs include the combination of effective analgesic and anti-inflammatory actions with NO release, which might counterbalance any adverse cardiovascular effects of NSAIDs. Effects of CINODs in animal studies include inhibition of vasopressor responses, blood pressure reduction in hypertensive rats and inhibition of platelet aggregation. CINODs may also reduce ischemic damage to compromised myocardial tissue. In addition, endothelial dysfunction is a recognized feature of inflammatory arthritides, and therefore a drug that might provide slow release of NO to the vasculature while treating pain is an attractive prospect in these conditions. Further studies of the effects of CINODs in humans are required, but these agents represent a potential exciting advance in the management of osteoarthritis.

Nitric oxide: new evidence for novel therapeutic indications

BACKGROUND

Nitric oxide (NO) deficiency is implicated in many pathophysiological processes in mammals. NO is a ubiquitous molecule involved in multiple cellular functions. Uncontrolled or inappropriate production of NO may lead to several disease states including septic shock, rheumatoid and inflammatory arthropathies, and expansion of cerebral damage after stroke. However, to date, there are no therapeutic agents available that can overcome these conditions. Similarly, underproduction of NO by NO synthase or enhanced breakdown of NO also leads to diseases such as hypertension, ischemic conditions, pre-eclampsia, premature delivery, among others. NO donor therapies are indicated in these conditions.

RESULTS

Nitroglycerin and nitrates (NO donors) have been used as therapeutic agents for the past century, particularly to treat vascular disease, and the only significant adverse effects are headaches. NO donors are highly cost-effective and have beneficial effects in multiple body systems. When the body cannot generate NO via NO synthase or due to rapid turnover leading to inadequate amounts of NO available for biological homeostasis, administration of exogenous NO, or prolongation of the actions of endogenous NO, are practical ways to supplement NO.

CONCLUSION

Recipients of such therapy include patients with angina pectoris, coronary artery disease, hypertension, osteoporosis, gastrointestinal motility disorders, pregnancy-related disorders including premature delivery, pre-eclampsia, vulvodynia, and erectile dysfunction in men. Postmenopausal NO deficiency is rectified with hormone replacement therapy, which enhances local production of NO. Declining local NO production secondary to estrogen deficiency in postmenopausal women and perhaps in older men could be one of the reasons for age-related increased incidences of cardiovascular events and sexual dysfunction. Thus, in addition to supplementation of NO compounds in acute situations like alleviating angina and erectile dysfunction, chronic NO therapy is cost-effective in decreasing cardiovascular events, and improving the urogenital system and skeletal health.

Frontiers in nephrology: targeting inflammation using novel nitric oxide donors

Chimeric molecules are single-chemical entities that possess at least two separate functions. In the design of new chimeric medicines, the two biologic actions are often designed to be synergistic and, thereby, complement each other in activating a specific target, such as a gene, a receptor, or an enzyme. In most chimeric molecules, one functionality is designed to provide a high affinity to a designated site, thereby permitting the targeting of the second functionality, which is usually nonspecific. This review focuses on the development of two classes of chimeric medicines, anti-inflammatory and diuretic chimeric agents, both of which incorporate a nitric oxide moiety into the parent pharmacophore.

Building a better aspirin: gaseous solutions to a century-old problem

The gastrointestinal adverse effects of nonsteroidal anti-inflammatory drugs (NSAIDs) have been recognized since shortly after the introduction of aspirin to the marketplace over a century ago. However, the underlying pathogenesis of NSAID-induced gastropathy remains incompletely understood. Advances in understanding some of the factors that contribute to the mucosal injury have provided clues for the development of safer NSAIDs. The inhibitory effects of nitric oxide (NO) on NSAID-induced leukocyte adherence were exploited in the development of NO-releasing NSAIDs. As well as eliciting less gastrointestinal damage than conventional NSAIDs, these drugs do not elevate blood pressure and show anti-inflammatory effects, additional to those of the parent drugs. Modification of other drugs in a similar manner (i.e., NO-releasing derivatives) has similarly resulted in more effective drugs. More recently, hydrogen sulphide-releasing derivatives of NSAIDs and of other drugs, have been developed, based on the observed ability of H(2)S to reduce inflammation and pain in experimental models. H(2)S-releasing NSAIDs produce negligible gastric damage and exhibit enhanced anti-inflammatory potency as compared to the parent drugs. The NO-NSAIDs and H(2)S-releasing NSAIDs represent examples of new anti-inflammatory drugs with greatly reduced toxicity and improved therapeutic activity, both created through the concept of exploiting the beneficial effects of endogenous gaseous mediators.

NMI-1182, a gastro-protective cyclo-oxygenase-inhibiting nitric oxide donor

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used to treat inflammation and to provide pain relief but suffer from a major liability concerning their propensity to cause gastric damage. As nitric oxide (NO) is known to be gastro-protective we have synthesized a NO-donating prodrug of naproxen named NMI-1182. We evaluated two cyclo-oxygenase (COX)-inhibiting nitric oxide donors (CINODs), NMI-1182 and AZD3582, for their ability to be gastro-protective compared to naproxen and for their anti-inflammatory activity. NMI-1182 and AZD3582 were found to produce similar inhibition of COX activity to that produced by naproxen. Both NMI-1182 and AZD3582 produced significantly less gastric lesions after oral administration than naproxen. All three compounds effectively inhibited paw swelling in the rat carrageenan paw edema model. In the carrageenan air pouch model all three compounds significantly reduced PGE2 levels in the pouch exudate but only NMI-1182 and naproxen inhibited leukocyte influx. These data demonstrate that NMI-1182 has comparable anti-inflammatory activity to naproxen but with a much reduced likelihood to cause gastric damage.

Pharmacologic Profile and Therapeutic Potential of NCX 4016, a Nitric Oxide-releasing Aspirin, for Cardiovascular Disorders

NCX 4016, 2-(acetyloxy)benzoic acid 3-[(nitrooxy)methyl]phenyl ester, is a new molecule in which a nitric oxide (NO)-releasing moiety is covalently linked to aspirin. After enzymatic metabolism, NCX 4016 releases both components. In vitro and in some animal models, these components exert their pharmacologic effects simultaneously. Nitric oxide (NO) is a small gaseous molecule that exerts several activities which may prevent atherothrombotic disorders. Moreover, it displays a protective activity on the gastric mucosa. NCX 4016 has been shown to inhibit platelet activation in vitro more effectively than aspirin, to inhibit smooth muscle cell proliferation, to exert an endothelial cell protective activity and to suppress the function of several inflammatory cells potentially involved in atherothrombosis. In animal models, NCX 4016 protected from platelet thromboembolism, prevented restenosis in atherosclerosis-prone animals, protected the heart from ischemia/reperfusion injury, and induced neoangiogenesis in critically ischemic limbs. Moreover, it displayed little or no gastric toxicity and appeared to protect stomach from noxious stimuli, including aspirin. NCX 4016 has been evaluated in healthy volunteers and found to inhibit platelet cyclo-oxygenase-1 (COX-1) similarly to or slightly less than aspirin, to raise the circulating levels of NO-degradation products, and to have little or no gastric toxicity in short term studies. In particular, in phase II studies, NCX 4016 had favorable effects on effort-induced endothelial dysfunction in intermittent claudication and on platelet-activation parameters elicited by short-term hyperglycemia in type II diabetics. In patients with type II diabetes the effects of NCX 4016 on microalbuminuria and on some hemodynamic parameters were promising. The pharmacokinetics of in vivo aspirin- and NO- released by NCX 4016, as well as the bioavailability of the two molecules, were not yet adequately studied. Also, the long-term tolerability of NCX 4016, as well as its possible effectiveness in preventing ischemic cardiovascular events and progression of atherosclerosis, should be explored.

A randomised, placebo controlled, comparative trial of the gastrointestinal safety and efficacy of AZD3582 versus naproxen in osteoarthritis

OBJECTIVE

To evaluate the gastrointestinal safety and efficacy of the COX inhibiting nitric oxide donator AZD3582 in patients with hip or knee osteoarthritis.

METHODS

970 patients were randomised (7:7:2) to AZD3582 750 mg twice daily, naproxen 500 mg twice daily, or placebo twice daily in a double blind study. The primary end point was the six week incidence of endoscopic gastroduodenal ulcers (diameter > or =3 mm). Overall damage measured on the Lanza scale was a secondary end point. Safety and tolerability assessments included endoscopic upper gastrointestinal erosions and the gastrointestinal symptom rating scale (GSRS). Efficacy was primarily assessed by WOMAC.

RESULTS

The incidence of ulcers with AZD3582 was 9.7% and with naproxen 13.7% (p = 0.07, NS), v 0% on placebo. The incidence of Lanza scores >2 was higher with naproxen (43.7%) than with AZD3582 (32.2%) (p<0.001). Compared with baseline, significantly fewer ulcers and erosions developed in stomach and stomach/duodenum combined, and fewer erosions developed in stomach, duodenum, and both combined on AZD3582 than on naproxen. GSRS reflux and abdominal pain subscale scores were lower for AZD3582 than for naproxen but there was no difference for indigestion, constipation, and diarrhoea. AZD3582 was as effective as naproxen at improving WOMAC scores. Both agents were well tolerated, with no significant effects on blood pressure.

CONCLUSIONS

At doses with similar efficacy in relieving osteoarthritis symptoms, the primary end point of six week endoscopic gastroduodenal ulcer incidence was not significantly different between AZD3582 and naproxen. Most secondary endoscopic gastrointestinal end points favoured AZD3582.

Nitric Oxide (NO)-Releasing Naproxen (HCT-3012 [(S)-6-Methoxy-α-methyl-2-naphthaleneacetic Acid 4-(Nitrooxy)butyl Ester]) Interactions with Aspirin in Gastric Mucosa of Arthritic Rats Reveal a Role for Aspirin-Triggered Lipoxin, Prostaglandins, and NO in Gastric Protection

Administration of selective and nonselective cyclooxygenase (COX)-2 inhibitors to rheumatoid arthritis patients taking low doses of acetylsalicylic acid (ASA) for cardiovascular prevention associates with increased risk of gastrointestinal bleeding. The present study was undertaken to investigate whether administration of HCT-3012 [(S)-6-methoxy-alpha-methyl-2-naphthaleneacetic acid 4-(nitrooxy)butyl ester], a nitric oxide (NO)-releasing derivative of naproxen, exacerbates gastric mucosal injury in arthritic rats administered low doses of ASA. Our results demonstrated that while treating arthritic rats with a dose of 30 mg/kg/day ASA causes detectable mucosal injury, but had no effect on arthritis score and interleukin-6 plasma levels, coadministration of naproxen (10 mg/kg/day) and celecoxib (30 mg/kg/day), in combination with ASA from day 7 to day 21, attenuates arthritis development (P <0.01 versus arthritis alone), but markedly enhanced gastric mucosal damage caused by ASA (P <0.01 versus ASA alone). In contrast, coadministration of HCT-3012 (15 mg/kg/day) significantly attenuated arthritis development, because HCT-3012 was equally or more effective than naproxen and celecoxib in attenuating local and systemic inflammation (P >0.001 versus arthritis) without exacerbating gastric mucosal injury caused by ASA. Arthritis development associates with gastric COX-2 induction, mRNA and protein, and enhanced gastric prostaglandin E2 (PGE2) synthesis (P <0.01 versus control rats). Although all treatments, including celecoxib, were effective in reducing gastric PGE2 synthesis, administering arthritic rats with ASA resulted in a significant increase in gastric content of aspirin-triggered lipoxin (ATL), a COX-2-derived lipid mediator that regulates proinflammatory responses at the neutrophils/endothelial interface. Administering arthritic rats with naproxen and celecoxib abrogates ATL formation induced by ASA although enhanced neutrophils accumulate into the gastric mucosa (P <0.01 versus ASA alone). In contrast, whereas HCT-3012 inhibited ATL formation, it did not increase neutrophil recruitment into the gastric microcirculation. Collectively, these data indicate that HCT-3012 derived from NO has the potential to compensate for inhibition of PGE2 and ATL and to protect the gastric mucosa by limiting the recruitment of neutrophils. These data suggest that HCT-3012 might be a safer alternative to nonsteroidal anti-inflammatory drugs and coxibs in rheumatic patients that take low doses of ASA.

Antiproliferative effect of nitrosulindac (NCX 1102), a new nitric oxide-donating non-steroidal anti-inflammatory drug, on human bladder carcinoma cell lines

Non-steroidal anti-inflammatory drugs (NSAIDs) are potent antitumoral agents but their side effects limit their clinical use. A novel class of drugs, nitric oxide-donating NSAIDs (NO-NSAIDs), was found to be safer and more active than classical NSAIDs. This study explored the effect of the NO-donating sulindac derivative, NCX 1102, on three human urothelial epithelial carcinoma cell lines (T24, 647V, and 1207) and primary cultures of normal urothelial cells. Cytotoxicity, antiproliferative effect, cell cycle alterations, morphological changes, and apoptosis were investigated after treatment with NCX 1102 in comparison with the native molecule. After treatment, there was a cytotoxic effect (with IC50 at 48 h of 23.1 μm on 647V, 19.4 μm on T24, and 14.5 μm on 1207) and an antiproliferative effect on all three cell lines with NCX 1102 but not with sulindac. No effect was detected on normal urothelial cells. Flow cytometric analysis showed a differential NCX 1102-induced accumulation of cells in various phases of the cell cycle, depending on cell line and concentration. NCX 1102 induced an occurrence of multinucleated cells in all cell lines and mitotic arrest in 647V and 1207. NCX 1102-treated T24 and 647V cell lines showed a significant difference of apoptotic cell amount when compared to controls. Our results demonstrated a greater antiproliferative potency of NCX 1102 compared to its parent molecule sulindac, and suggested that this new NO-NSAID may have therapeutic impact in the management of bladder cancer.

NO-aspirin: mechanism of action and gastrointestinal safety

Nitric oxide-releasing aspirins are new chemical entities obtained by adding a nitric oxide-releasing moiety to aspirin. NCX-4016 is the prototype of this family of molecules. NCX-4016 consists of the parent molecule (aspirin) linked to a 'spacer' via an ester linkage, which is in turn connected to a nitric oxide-releasing moiety. Both aspirin and nitric oxide moieties of NCX-4016 contribute to its effectiveness, the latter occurring via both cyclic guanosyl monophosphate-dependent and -independent mechanisms. In vitro studies have shown that NCX-4016 inhibits platelet aggregation induced by aspirin-sensitive (arachidonic acid) and aspirin-insensitive (thrombin) agonist. In contrast to aspirin, NCX-4016 exerts a multilevel regulation of inflammatory target, including caspase-1 and NF-kappaB. This broad spectrum of activities translates to an increased potency of this drug in modulating cardiovascular inflammation. Human studies have shown, that while nitric oxide-aspirin maintains its anti-thrombotic activity, it spares the gastrointestinal tract. Indeed, a 7-day course of NCX-4016 results in 90% reduction of gastric damage caused by equimolar doses of aspirin. Further studies are ongoing to define whether this superior anti-inflammatory and anti-thrombotic profile translates in clinical benefits in patients with cardiovascular diseases.

Pharmacology and potential therapeutic applications of nitric oxide-releasing non-steroidal anti-inflammatory and related nitric oxide-donating drugs

This review examines the biological significance, therapeutic potential and mechanism(s) of action of a range of nitric oxide-releasing non-steroidal anti-inflammatory drugs (NO-NSAID) and related nitric oxide-releasing donating drugs (NODD). The slow release of nitric oxide (NO) from these compounds leads to subtle changes in the profile of pharmacological activity of the parent, non-steroidal anti-inflammatory drugs (NSAID). For example, compared with NSAID, NO-NSAID cause markedly diminished gastrointestinal toxicity and improved anti-inflammatory and anti-nociceptive efficacy. In addition, nitroparacetamol exhibits hepatoprotection as opposed to the hepatotoxic activity of paracetamol. The possibility that NO-NSAID or NODD may be of therapeutic benefit in a wide variety of disease states including pain and inflammation, thrombosis and restenosis, neurodegenerative diseases of the central nervous system, colitis, cancer, urinary incontinence, liver disease, impotence, bronchial asthma and osteoporosis is discussed.

Cyclo-oxygenase-2 inhibition increases blood pressure in rats

1 It is known that nonselective cyclo-oxygenase (COX) inhibitors have small but significant effects on blood pressure (BP), most notably in hypertensive patients on antihypertensive medication. Whether selective COX-2 inhibitors also interfere with BP regulation is not well understood. Therefore, we aimed to examine the effect of chronic treatment with a selective COX-2 inhibitor (rofecoxib) on systolic blood pressure (sBP) in normotensive Wistar-Kyoto rats (WKY) and on the developmental changes of sBP in young spontaneously hypertensive rats (SHR). In addition, we investigated a possible influence of salt intake on the effects of COX-2 inhibition on BP in these two rat strains. 2 Rofecoxib dose dependently increased sBP and decreased plasma levels of 6-keto prostaglandin (PG)F(1alpha) in WKY rats fed a normal salt diet (0.6% NaCl, wt wt(-1)), without affecting serum thromboxane (TX)B(2) levels. 3 Rofecoxib significantly elevated sBP in both rat strains fed normal salt or high salt diet (8% NaCl, wt wt(-1)), but not in rats on low salt intake (0.02% NaCl, wt wt(-1)). 4 Rofecoxib significantly decreased plasma levels of 6-keto PGF(1alpha) in both rat strains fed normal or high salt diet, but not in rats during low salt intake. 5 Rofecoxib exerted no influence on the changes of body weight nor on water intake. Plasma renin activity (PRA) and renocortical renin mRNA abundance were not changed by rofecoxib, but plasma aldosterone concentration (PAC) was significantly reduced. 6 These results suggest that chronic inhibition of COX-2 causes an increase of blood pressure that depends on prostacyclin synthesis. Furthermore, this increase is independent on genetic predisposition and can be prevented by salt deprivation. Since water intake and body weight gain were not changed by rofecoxib, fluid retention appears not to be a major reason for the development of hypertension. Similarly, an activation of the renin-angiotensin-aldosterone axis appears to be an unlikely candidate mechanism.

Potential cardioprotective actions of no-releasing aspirin

The use of low doses of aspirin on a daily basis has increased greatly in the past 20 years, based on observations that it can significantly reduce the risk of heart attacks and strokes. However, aspirin can also cause severe damage to the stomach. A modified version of aspirin that releases nitric oxide has been developed that seems to offer important advantages over its 103-year-old parent--namely, improved protection for the heart without the unwanted effects on the stomach.

Nitric oxide-releasing NSAIDs: a review of their current status

Nonsteroidal anti-inflammatory drugs (NSAIDs) are among the most widely prescribed drugs worldwide owing to their anti-inflammatory, antipyretic and analgesic properties. However, their use is hampered by gastrointestinal (GI) toxicity, the most common drug-related serious adverse event in industrialised nations. Nitric oxide (NO)-releasing NSAIDs, a recently described class of drugs, are generated by adding a nitroxybutyl or a nitrosothiol moiety to the parent NSAID via a short-chain ester linkage. While efficacy of nitrosothiol-NO-NSAIDs still awaits investigation, nitroxybutyl-NO-NSAIDs have been extensively studied in animals, thus the abbreviation NO-NSAIDs used here refers to the latter group of NSAID derivatives. NO-NSAIDs retain the anti-inflammatory and antipyretic activity of original NSAIDs, although they exhibit markedly reduced gastrointestinal toxicity. NO-NSAIDs are nonselective cyclo-oxygenase (COX) inhibitors, and they also exert COX-independent activities that are NO-dependent. Indeed, NO-NSAIDs suppress production of the cytokines interleukin (IL)-1beta, IL-18 and interferon-gamma by causing the S-nitrosilation/inhibition of caspase-1. In acute and chronic animal models of inflammation, it has been demonstrated that NO-NSAIDs abrogated prostaglandin E2 as well as thromboxane B2 generation. In a murine model, NO-naproxen was approximately 10-fold more potent than naproxen in reducing animal writhing after intraperitoneal injection of acetic acid. Similar data have been obtained in chronic models of pain such as rat adjuvant arthritis. In vivo and in vitro studies suggest that NO-aspirin (acetylsalicylic acid) exerts more potent antithrombotic action than aspirin, probably by coupling the ability to inhibit COX-1 with the anti-adhesive effect of NO. Moreover, in a model of renal injury NO-flurbiprofen not only has been demonstrated to be devoid of nephrotoxicity but also to ameliorate renal function. Finally, in an animal model of chronic neurodegenerative disease, NO-flurbiprofen and NO-aspirin attenuated the brain inflammatory response. The GI toxicity of NO-flurbiprofen and NO-naproxen is currently being investigated in healthy individuals.

Colon cancer prevention with NO-releasing NSAIDs

A seminal advance in the prevention of colon cancer has been the observation that nonsteroidal antiinflammatory drugs (NSAIDs) reduce the incidence of and mortality from colon cancer by about half. Among current efforts to overcome the side effects of NSAIDs, an important limitation for their application as chemopreventive agents, is the synthesis of nitric oxide-releasing NSAIDs. These novel compounds may display greater safety and greater efficacy compared to their parent traditional NSAIDs and thus hold significant promise as chemopreventive agents against human colon cancer. In this review we discuss salient features of their pharmacology, in vitro and animal data pertaining to colon cancer, their mechanisms of action, and assess their potential in the chemoprevention of colon cancer.

Vasorelaxant effect of nitric oxide releasing steroidal and nonsteroidal anti-inflammatory drugs

The effect of several nitric oxide releasing-non-steroidal anti-inflammatory drugs (NO-NSAID) and nitroprednisolone on blood vessel relaxation in vitro and in vivo was studied. Nitroflurbiprofen (NOF; EC(50), 688.8+/-93.8 microM), nitroaspirin (NOA; EC(50), 57.9+/-6.5 microM), nitroparacetamol (NOPARA; EC(50), 71.5+/-14.6 microM) and nitroprednisolone (EC(50), 15.1+/-1.4 microM) caused concentration-related relaxation of noradrenaline (NA)-contracted rat aortic rings. All NO releasing compounds tested were approximately three orders of magnitude less potent than sodium nitroprusside (SNP, EC(50), 35.7+/-3.5 nM). The vasorelaxant effect of NOF and NOPARA in the rat aorta was potentiated by zaprinast (5 microM) and reduced by ODQ (5 microM). Flurbiprofen and paracetamol (100 microM) caused minimal (<10%) relaxation of the rat aorta and did not affect the response to SNP. The effect of NOF was unchanged in the presence of L-NAME (100 microM; EC(30), 181.8+/-35.1 microM cf. EC(30), 125.1+/-17.0 microM, P>0.05) but increased by removal of the endothelium (EC(30), 164.3+/-26.3 microM cf. EC(50), 688.8+/-93.8 microM, P<0.05). NOF (0.1 - 50 microM) produced a small but not concentration-related vasodilation of the NA-preconstricted (i.e. "high tone") perfused rat mesentery preparation (cf. SNP, EC(30), 4.4+/-0.7 microM). In contrast, NOF (1 - 100 microM) produced concentration-related vasodilation of the "high tone" perfused rat kidney with an EC(50) of 33.1+/-4.4 microM. Neither NOF (74 mg kg(-1), i.p.) nor NOA (91.9 mg kg(-1), i.p.) nor equimolar doses of flurbiprofen (50 mg kg(-1), i.p.) or aspirin (50 mg kg(-1), i.p.) affected mean arterial blood pressure (MAP) or heart rate (HR) of pentobarbitone-anaesthetized rats over a 1 h period. NO-NSAID relax blood vessels in vitro by an NO-dependent mechanism. The absolute vasorelaxant effect of NO releasing drug varies greatly with the choice of compound and between blood vessel preparations.

Vasorelaxant effects of a nitric oxide-releasing aspirin derivative in normotensive and hypertensive rats

1. Nonsteroidal anti-inflammatory drugs have been reported to exacerbate hypertension and to interfere with the effectiveness of some anti-hypertensive therapies. In this study, we tested the effects of a gastric-sparing, nitric oxide-releasing derivative of aspirin (NCX-4016) on hypertension in rats. 2. Hypertension was induced by administering L-NAME in the drinking water (400 mg l(-1)). Groups of rats were treated daily with aspirin, NCX-4016 or vehicle. 3. NCX-4016 significantly reduced blood pressure relative to the aspirin-treated group over the 2-week period of treatment. Aspirin and, to a lesser extent, NCX-4016 suppressed whole blood thromboxane synthesis. 4. In anaesthetized rats, acute intravenous administration of NCX-4016 caused a significant fall in mean arterial pressure in hypertensive rats, but was devoid of such effects in normotensive controls. 5. In vitro, NCX-4016 relaxed phenylephrine-pre-contracted aortic rings obtained from both normotensive and hypertensive rats, and significantly reduced their responsiveness to the contractile effects of phenylephrine. 6. These results suggest that NCX-4016 reduces blood pressure in hypertensive rats, not simply through the direct vasodilatory actions of the nitric oxide released by this compound, but also through possible interference with the effects of endogenous pressor agents. These properties, added to its anti-thrombotic effects, suggest that NCX-4016 may be a safer alternative to aspirin for use by hypertensive patients.

Antihypertensive properties of a nitric oxide-releasing naproxen derivative in two-kidney, one-clip rats

Nonsteroidal anti-inflammatory drugs have been reported to exacerbate hypertension. In this study, we tested the hypothesis that a nitric oxide-releasing derivative of naproxen would ameliorate hypertension in the rat. Hypertension was induced by partially occluding one renal artery (the "2K,1C" model), and 2 wk later the rats started receiving naproxen, the nitric oxide-releasing derivative HCT-3012, or vehicle each day for 2 wk. Naproxen significantly exacerbated the hypertension. HCT-3012 significantly reduced blood pressure relative to both the naproxen- and vehicle-treated groups. Both naproxen and HCT-3012 markedly suppressed whole blood thromboxane B(2) synthesis. In studies of anesthetized rats, naproxen significantly enhanced the late hypertensive response to endothelin-1 and significantly blunted the early hypotensive response. In contrast, HCT-3102 did not affect either response to endothelin-1. In vitro, HCT-3012 significantly reduced the responsiveness of aortic rings to the contractile effects of phenylephrine. These studies suggest that HCT-3012 reduces blood pressure in hypertensive rats, not simply through the vasodilatory actions of the nitric oxide it releases, but through alterations in the responsiveness of the vasculature to endogenous pressor agents.

Selective cyclo-oxygenase-2 inhibition with celecoxib elevates blood pressure and promotes leukocyte adherence

1. Selective inhibitors of cyclo-oxygenase-2 have been shown to be effective anti-inflammatory drugs with reduced gastrointestinal toxicity relative to conventional nonsteroidal anti-inflammatory drugs (NSAIDs). In the present study, we examined the possibility that selective COX-2 inhibition, by blocking prostacyclin synthesis, would increase blood pressure and cause leukocyte adherence and platelet aggregation. 2. Normal rats and rats with hypertension induced by chronic administration of Nomega-nitro-L-arginine methylester were given celecoxib (10 mg kg(-1)) daily for 3 weeks. Celecoxib significantly elevated of blood pressure in both the normal and hypertensive rats (mean increase of >33 mm Hg after 3 weeks). 3. In normal rats, celecoxib had no effect on serum 6-keto prostaglandin (PG)F(1alpha) levels. Hypertensive rats exhibited a significant increase (82%) in serum 6-keto PGF(1alpha) levels, and this was reduced to the levels of normal rats by treatment with celecoxib. 4. Rats treated with celecoxib exhibited significant increases in weight gain (20%), plasma arginine-vasopressin levels (148%) and plasma urea (69%) relative to vehicle-treated controls. Plasma creatinine levels were unaffected by treatment with celecoxib, while plasma renin levels were significantly decreased (30%) relative to controls. 5. Superfusion of mesenteric venules with celecoxib (3 microM) in vivo resulted in significant increases in leukocyte adherence to the endothelium in both normal and hypertensive rats. 6. These studies suggest that suppression of COX-2 significantly influences vascular and/or renal function, leading to elevated blood pressure and leukocyte adherence.

Wound collagen deposition in rats: effects of an NO-NSAID and a selective COX-2 inhibitor

Selective cyclo-oxygenase (COX)-2 inhibitors and nitric oxide-releasing nonsteroidal anti-inflammatory drugs (NSAIDs) exhibit reduced toxicity in the gastrointestinal tract, but may affect wound healing in other tissues. In this study, we have compared the effects of a selective COX-2 inhibitor (celecoxib), a nitric-oxide releasing derivative of naproxen (HCT-3012) and naproxen in a model of wound collagen deposition in the rat. Polyvinyl alcohol sponges were implanted subcutaneously in rats. The rats were treated daily for 5 days with the test drugs at equieffective anti-inflammatory doses. Naproxen (10 mg kg(-1)) significantly decreased (45%) collagen deposition at the wound site relative to the vehicle-treated control group. In contrast, HCT-3012 (14.5 mg kg(-1)) significantly increased (62%) collagen deposition, while celecoxib (10 mg kg(-1)) had no effect. Naproxen and HCT-3012 suppressed prostaglandin (PG) E(2) levels at the wound site and whole blood thromboxane synthesis to similar degrees. Celecoxib had no significant effect on wound fluid PGE(2) levels, but slightly reduced whole blood thromboxane synthesis (by 17%). COX-1 mRNA and protein were expressed in the wound exudate, the skin surrounding the wound and in normal skin. In contrast, COX-2 mRNA, but not protein, was expressed in wound and normal skin. These results demonstrate that HCT-3012 can significantly enhance collagen deposition at a wound site, despite inhibiting prostaglandin synthesis to the same extent as the parent drug. Nitric oxide-releasing NSAIDs may represent a safer alternative to standard NSAIDs for use as anti-inflammatory and analgesic agents by post-surgery patients.