In vitro metabolism of a nitroderivative of acetylsalicylic acid (NCX4016) by rat liver: LC and LC-MS studies

The evolving landscape for cellular nitric oxide and hydrogen sulfide delivery systems: A new era of customized medications

Nitric oxide (NO) and hydrogen sulfide (H2S) are industrial toxins or pollutants; however, both are produced endogenously and have important biological roles in most mammalian tissues. The recognition that these gasotransmitters have a role in physiological and pathophysiological processes has presented opportunities to harness their intracellular effects either through inhibition of their production; or more commonly, through inducing their levels and or delivering them by various modalities. In this review article, we have focused on an array of NO and H2S donors, their hybrids with other established classes of drugs, and the various engineered delivery platforms such a fibers, polymers, nanoparticles, hydrogels, and others. In each case, we have reviewed the rationale for their development.

Reconsidering the Role of Cyclooxygenase Inhibition in the Chemotherapeutic Value of NO-Releasing Aspirins for Lung Cancer

Nitric oxide-releasing aspirins (NO-aspirins) are aspirin derivatives that are safer than the parent drug in the gastrointestinal context and have shown superior cytotoxic effects in several cancer models. Despite the rationale for their design, the influence of nitric oxide (NO^•) on the effects of NO-aspirins has been queried. Moreover, different isomers exhibit varying antitumor activity, apparently related to their ability to release NO^•. Here, we investigated the effects and mode of action of NO-aspirins in non-small-cell lung cancer (NSCLC) cells, comparing two isomers, NCX4016 and NCX4040 (-meta and -para isomers, respectively). NCX4040 was more potent in decreasing NSCLC cell viability and migration and exhibited significant synergistic effects in combination with erlotinib (an epidermal growth factor receptor inhibitor) in erlotinib-resistant cells. We also studied the relationship among the effects of NO-aspirins, NO^• release, and PGE₂ levels. NCX4040 released more NO^• and significantly decreased PGE₂ synthesis relative to NCX4016; however, NO^• scavenger treatment reversed the antiproliferative effects of NCX4016, but not those of NCX4040. By contrast, misoprostol (a PGE₂ receptor agonist) significantly reversed the antiproliferative effect of NCX4040, but not those of NCX4016. Furthermore, misoprostol reversed the antimigratory effects of NCX4040. Overall, these results indicate that PGE₂ inhibition is important in the mode of action of NO-aspirins.

Degradation of NF-κB, p53 and other regulatory redox-sensitive proteins by thiol-conjugating and -nitrosylating drugs in human tumor cells

The ionized cysteines present on the surfaces of many redox-sensitive proteins play functionally essential roles and are readily targeted by the reactive oxygen and reactive nitrogen species. Using disulfiram (DSF) and nitroaspirin (NCX4016) as the model compounds that mediate thiol-conjugating and nitrosylating reactions, respectively, we investigated the fate of p53, nuclear factor-kappaB (NF-κB) and other redox-responsive proteins following the exposure of human cancer cell lines to the drugs. Both drugs induced glutathionylation of bulk proteins in tumor cells and cell-free extracts. A prominent finding of this study was a time- and dose-dependent degradation of the redox-regulated proteins after brief treatments of tumor cells with DSF or NCX4016. DSF and copper-chelated DSF at concentrations of 50-200 µM induced the disappearance of wild-type p53, mutant p53, NF-κB subunit p50 and the ubiquitin-activating enzyme E1 (UBE1) in tumor cell lines. DSF also induced the glutathionylation of p53. The recombinant p53 protein modified by DSF was preferentially degraded by rabbit reticulocyte lysates. The proteasome inhibitor PS341 curtailed the DSF-induced degradation of p53 in HCT116 cells. Further, the NCX4016 induced a dose-dependent disappearance of the UBE1 and NF-κB p50 proteins in cell lines, besides a time-dependent degradation of aldehyde dehydrogenase in mouse liver after a single injection of 150 mg/kg. The loss of p53 and NF-kB proteins correlated with decreases in their specific binding to DNA. Our results demonstrate the hitherto unrecognized ability of the non-toxic thiolating and nitrosylating agents to degrade regulatory proteins and highlight the exploitable therapeutic benefits.

Aspirin and low-dose nitric oxide-donating aspirin increase life span in a Lynch syndrome mouse model

Nonsteroidal anti-inflammatory drugs (NSAID) appear to be effective cancer chemopreventives. Previous cellular studies showed that aspirin (acetylsalicylic acid: ASA) and nitric oxide-donating ASA (NO-ASA) suppressed microsatellite instability (MSI) in mismatch repair (MMR)-deficient cells linked to the common cancer predisposition syndrome hereditary nonpolyposis colorectal cancer or Lynch syndrome (LS/HNPCC), at doses 300- to 3,000-fold less than ASA. Using a mouse model that develops MMR-deficient intestinal tumors that appear pathologically identical to LS/HNPCC, we show that ASA (400 mg/kg) and low-dose NO-ASA (72 mg/kg) increased life span by 18% to 21%. We also note a trend where ASA treatment resulted in intestinal tumors with reduced high MSI (H-MSI) and increased low MSI (L-MSI) as defined by the Bethesda Criteria. Low-dose NO-ASA had a minimal effect on MSI status. In contrast to previous studies, high-dose NO-ASA (720/1,500 mg/kg) treatments increased tumor burden, decreased life span, and exacerbated MSI uniquely in the LS/HNPCC mouse model. These results suggest that MMR-deficient tissues/mice may be specifically sensitive to intrinsic pharmacokinetic features of this drug. It is likely that long-term treatment with ASA may represent a chemopreventive option for LS/HNPCC patients. Moreover, as low-dose NO-ASA shows equivalent life span increase at 10-fold lower doses than ASA, it may have the potential to significantly reduce the gastropathy associated with long-term ASA treatment.

(Nitrooxyacyloxy)methyl esters of aspirin as novel nitric oxide releasing aspirins

A series of (nitrooxyacyloxy)methyl esters of aspirin were synthesized and evaluated as new NO-donor aspirins. Different amounts of aspirin were released in serum from these products according to the nature of nitrooxyacyloxy moiety present. In the aromatic series, there is a rather good linear correlation between the amount of aspirin released and the potencies of the products in inhibiting platelet aggregation induced by collagen. Both the native compounds and the related nitrooxy-substituted acid metabolites were able to relax rat aorta strips precontracted with phenylephrine, in keeping with a NO-induced activation of the sGC as a mechanism that underlies the vasodilator effect. The products here described are new improved examples of NO-donor aspirins containing nitrooxy groups. They could represent an alternative to the use of aspirin in a variety of clinical applications.

NCX 4040, a nitric oxide-donating aspirin, exerts anti-inflammatory effects through inhibition of I kappa B-alpha degradation in human monocytes

NO-donating aspirins consist of aspirin to which a NO-donating group is covalently linked via a spacer molecule. NCX 4040 and NCX 4016 are positional isomers with respect to the -CH(2)ONO(2) group (para and meta, respectively) on the benzene ring of the spacer. Because positional isomerism is critical for antitumor properties of NO-donating aspirins, we aimed to compare their anti-inflammatory effects with those of aspirin in vitro. Thus, we assessed their impacts on cyclooxygenase-2 activity (by measuring PGE(2) levels), protein expression, and cytokine generation(IL-1beta, IL-18, TNF-alpha, and IL-10) in human whole blood and isolated human monocytes stimulated with LPS. Interestingly, we found that micromolar concentrations of NCX 4040, but not NCX 4016 or aspirin, affected cyclooxygenase-2 expression and cytokine generation. We compared the effects of NCX 4040 with those of NCX 4016 or aspirin on IkappaB-alpha stabilization and proteasome activity in the LPS-stimulated human monocytic cell line THP1. Differently from aspirin and NCX 4016, NCX 4040, at a micromolar concentration range, inhibited IkappaB-alpha degradation. In fact, NCX 4040 caused concentration-dependent accumulation of IkappaB-alpha and its phosphorylated form. This effect was not reversed by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, an inhibitor of guanylyl cyclase, thus excluding the contribution of NO-dependent cGMP generation. In contrast, IkappaB-alpha accumulation by NCX 4040 may involve an inhibitory effect on proteasome functions. Indeed, NCX 4040 inhibited 20S proteasome activity when incubated with intact cells but not in the presence of cell lysate supernatants, thus suggesting an indirect inhibitory effect. In conclusion, NCX 4040 is an inhibitor of IkappaB-alpha degradation and proteasome function, and it should be taken into consideration for the development of novel anti-inflammatory and chemopreventive agents.

Anti-inflammatory agents as cancer therapeutics

Cancer prevention sometimes referred to as tertiary prevention or chemoprevention makes use of specific xenobiotics or drugs to prevent, delay, or retard the development of cancer. Over the last two decades or so cancer prevention has made significant strides. For example, prevention of lung cancer through smoking cessation; cervical cancer prevention through regular Pap smear tests; colon cancer prevention through screening colonoscopy; and prostate cancer reductions by prostate-specific antigen measurements in conjunction with regular prostate examinations. The seminal epidemiological observation that nonsteroidal anti-inflammatory drugs (NSAIDs) prevent colon and other cancers has provided the impetus to develop novel chemoprevention approaches against cancer. To that end, a number of "designer drugs" have been synthesized that are in different stages of development, evaluation, and deployment. Some include the cyclooxygenase-2-specific inhibitors (coxibs), nitric oxide-releasing NSAIDs (NO-NSAIDs and NONO-NSAIDs), hydrogen sulfide-releasing NSAIDs, modulators of the lipoxygenase pathway, prostanoid receptor blockers, and chemokine receptor antagonists. In addition to these novel agents, there are also a host of naturally occurring compounds/micronutrients that have chemopreventive properties. This chapter reviews these classes of compounds, their utility and mechanism(s) of action against the background of mediators that link inflammation and cancer.

(1S,4S,5S,8R)-8-Nitro-oxy-2,6-dioxa-bicyclo-[3.3.0]octan-4-yl 3,4,5-triacetoxy-benzoate

In the title compound, C₁₉H₁₉NO₁₃, one of the two fused furan­ose rings adopts an envelope conformation whereas the other displays a twisted conformation. The crystal structure is stabilized by inter­molecular C—H⋯π inter­actions between a methine H atom and the triacetoxy­phenyl ring of an adjacent mol­ecule, and by weak non-classical inter­molecular C—H⋯O hydrogen bonds.

Pharmacokinetic and pharmacodynamic study of NO-donating aspirin in F344 rats

Nitric oxide-donating aspirin (NO-ASA) represents class of promising chemopreventive NO-NSAIDs. NO-ASA combines the beneficial effects of ASA and the gut-sparing effect of the NO moiety. There is, however, limited information on its pharmacokinetic and pharmacodynamic effects in vivo. Herein, experiments were designed to identify the optimal dose, the effective route of administration, and targeted markers in plasma and colonic tissues of male F344 rats. Seven weeks old male F344 rats were randomized into 9 groups (16/group) and fed the control diet. At eight weeks of age, groups 2-5 were each administered one of four different doses of NO-ASA by gavage (33, 66, 132 and 264 mg/kg) and each of groups 6-9 were fed diets containing NO-ASA (35, 700, 1,400 and 2,800 ppm) for two weeks. Rats were sacrificed 2 and 10 h after completion of the two weeks of treatment with NO-ASA and plasma and colonic mucosa were collected and analyzed for NO-ASA, its metabolites, and PGE2 and TXB2 levels. Our results indicate that NO-ASA is rapidly metabolized, predominantly to salicylic acid; no intact NO-ASA was detected in plasma. Compared to diet-fed NO-ASA, gavaging generated much higher salicylic acid levels over a wide range of doses and a relatively broad time period (10 h). Regardless of its route of administration, NO-ASA lowered the levels of PGE2 in colonic tissues and plasma, as well as TxB2 in plasma in a dose- and time-dependent manner. These findings may have practical utility for the administration of NO-ASA to humans.

Nitrates and NO-NSAIDs in cancer chemoprevention and therapy: in vitro evidence querying the NO donor functionality

Properties of the NO-ASA family of NO-donating NSAIDs (NO-NSAIDs), notably NCX 4016 (mNO-ASA) and NCX 4040 (pNO-ASA), reported in more than one hundred publications, have included positive preclinical data in cancer chemoprevention and therapy. Evidence is presented that the antiproliferative, the chemopreventive (antioxidant/electrophile response element (ARE) activation), and the anti-inflammatory activity of NO-ASA in cell cultures is replicated by X-ASA derivatives that are incapable of acting as NO donors. pBr-ASA and mBr-ASA are conisogenic with NO-ASA, but are not NO donors. The biological activity of pNO-ASA is replicated by pBr-ASA; and both pNO-ASA and pBr-ASA are bioactivated to the same quinone methide electrophile. The biological activity of mNO-ASA is replicated by mBr-ASA; mNO-ASA and mBr-ASA are bioactivated to different benzyl electrophiles. The observed activity is likely initiated by trapping of thiol biomolecules by the quinone and benzyl electrophiles, leading to depletion of GSH and modification of Cys-containing sensor proteins. Whereas all NO-NSAIDs containing the same structural "linker" as NCX 4040 and NCX 4016 are anticipated to possess activity resulting from bioactivation to electrophilic metabolites, this expectation does not extend to other linker structures. Nitrates require metabolic bioactivation to liberate NO bioactivity, which is often poorly replicated in vitro, and NO bioactivity provided by NO-NSAIDs in vivo provides proven therapeutic benefits in mitigation of NSAID gastrotoxicity. The in vivo properties of X-ASA drugs await discovery.

Searching for new NO-donor aspirin-like molecules: a new class of nitrooxy-acyl derivatives of salicylic acid

A new class of products in which the phenol group of salicylic acid is linked to alkanoyl moieties bearing nitrooxy functions has been synthesized and studied for their polyvalent actions. The products were stable in acid and neutral media, while they were hydrolyzed in human serum. Their half-lives were dependent upon the structure of alkanoyl moieties. The products showed anti-inflammatory activities similar to aspirin when tested in the carrageenan-induced paw edema assay in the rat. Interestingly, unlike aspirin, they showed reduced or no gastrotoxicity in a lesion model in rats at equimolar doses. A number of them were able to inhibit platelet aggregation induced by collagen in human platelet-rich plasma. All of the products were capable of relaxing rat aortic strips precontracted with phenylephrine in a concentration-dependent manner. Selected members of this new class of nonsteroidal anti-inflammatory drugs might represent possible safer alternatives to aspirin in different clinical settings.

Nitroaspirin (NCX-4016), an NO donor, is antiangiogenic through induction of loss of redox-dependent viability and cytoskeletal reorganization in endothelial cells

We recently reported that NCX-4016, a derivative of aspirin containing a nitro moiety that releases nitric oxide (NO) in a sustained fashion in biologic systems, is a potent cytotoxic agent inhibiting the proliferation of cisplatin-resistant human ovarian cancer cells. Therefore, we hypothesize that NCX-4016 possesses antiangiogenic properties. Our study with the bovine lung microvascular endothelial cells (BLMVECs) revealed that NCX-4016 significantly induced the loss of redox-dependent cell viability in a dose- and time-dependent manner, as assayed by the redox-sensitive Alamar blue cell viability assay. Fluorescence microscopy of cells labeled with NO-specific fluorophore (DAF-FM) confirmed that NCX-4016 generated significant levels of intracellular NO. NO donors, including S-nitroso-N-acetylpenicillamine, spermine NONOate, and isosorbide dinitrite, were less effective in causing loss of cell viability. Thiol-protectant, N-acetylcysteine, significantly attenuated the NCX-4016-induced loss of cell viability, suggesting the role of alteration of thiol-redox status therein. NCX-4016 also suppressed oxygen consumption, decreased transendothelial electrical resistance (EC barrier dysfunction), and induced actin cytoskeletal reorganization in BLMVECs. The in vitro assay with human umbilical vein ECs and BLMVECs revealed that NCX-4016, in a dose-dependent manner, significantly inhibited angiogenesis with almost complete inhibition at a 100-microM concentration, suggesting that NCX-4016 can act as an antiangiogenic drug.

Role of oxygen in postischemic myocardial injury

Myocardial function is dependent on a constant supply of oxygen from the coronary circulation. A reduction of oxygen supply due to coronary obstruction results in myocardial ischemia, which leads to cardiac dysfunction. Reperfusion of the ischemic myocardium is required for tissue survival. Thrombolytic therapy, coronary artery bypass surgery and coronary angioplasty are some of the treatments available for the restoration of blood flow to the ischemic myocardium. However, the restoration of blood flow may also lead to reperfusion injury, resulting in myocyte death. Thus, any imbalance between oxygen supply and metabolic demand leads to functional, metabolic, morphologic, and electrophysiologic alterations, causing cell death. Myocardial ischemia reperfusion (IR) injury is a multifactorial process that is mediated by oxygen free radicals, neutrophil activation and infiltration, calcium overload, and apoptosis. Controlled reperfusion of the ischemic myocardium has been advocated to prevent the IR injury. Studies have shown that reperfusion injury and postischemic cardiac function are related to the quantity and delivery of oxygen during reperfusion. Substantial evidence suggests that controlled reoxygenation may ameliorate postischemic organ dysfunction. In this review, we discuss the role of oxygenation during reperfusion and subsequent biochemical and pathologic alterations in reperfused myocardium and recovery of heart function.

Evaluation of nitrate-substituted pseudocholine esters of aspirin as potential nitro-aspirins

Herein we explore some designs for nitro-aspirins, compounds potentially capable of releasing both aspirin and nitric oxide in vivo. A series of nitrate-bearing alkyl esters of aspirin were prepared based on the choline ester template preferred by human plasma butyrylcholinesterase. The degradation kinetics of the compounds were followed in human plasma solution. All compounds underwent hydrolysis rapidly (t(1/2) approximately 1min) but generating exclusively the corresponding nitro-salicylate. The one exception, an N-propyl, N-nitroxyethyl aminoethanol ester produced 9.2% aspirin in molar terms indicating that the nitro-aspirin objective is probably achievable if due cognisance can be paid to the demands of the activating enzyme. Even at this low level of aspirin release, this compound is the most successful nitro-aspirin reported to date in the key human plasma model.

The mechanism of action of nitric oxide-donating aspirin

NO-donating aspirin (NO-ASA) is a promising anticancer drug. We studied the contribution of NO-ASA's components (ASA, NO-releasing moiety, and spacer linking them) to its effect. The ASA and NO-releasing moieties play no biological role: ASA inhibits the growth of colon cancer cells >100-fold less potently that NO-ASA; and denitrated NO-ASA plus the NO-donor SNAP releasing the same amount of NO as NO-ASA, inhibit the growth of cancer cells >50-fold less potently than NO-ASA. The biologically active moiety of NO-ASA is the spacer: it is chemically reactive (studies with NO-ASA radiolabeled at the spacer demonstrated that it binds to proteins); and compounds in which the ASA or the NO-releasing groups are replaced inhibit cell growth similar to NO-ASA. We propose a mechanism of action of NO-ASA involving formation of quinone methide from its para and ortho isomers and of a carbocation from the meta, with the NO-releasing group functioning as a leaving group.

Prevention of Postischemic Myocardial Reperfusion Injury by the Combined Treatment of NCX-4016 and Tempol

Nitric oxide (NO) plays a protective role in myocardial ischemia-reperfusion (I/R) injury. However, the concomitant production of superoxide and other reactive oxygen species (ROS) during I/R may diminish the bioavailability of NO and hence compromise the beneficial effects. The objective of this study was to investigate the protective effect of the coadministration of NCX-4016 [2-(acetyloxy)benzoic acid 3-(nitrooxymethyl)phenyl ester] (an NO donor) with antioxidants Tempol, superoxide dismutase (SOD), or urate on I/R injury. Isolated rat hearts, perfused with Krebs-Henseleit buffer, were subjected to 30 minutes of global ischemia, followed by 45 minutes of reperfusion. Before the induction of ischemia, the hearts were infused for 1 minute with NCX-4016 (100 microM) either alone or in combination with Tempol (100 microM), SOD (200 U/mL), or urate (100 microM). Hearts pretreated with NCX-4016 showed a significantly enhanced recovery of function and decreased infarct size and LDH/CK release compared with the controls. However, treatment of hearts with NCX-4016 + Tempol, SOD, or urate showed a significantly enhanced recovery of heart function compared with NCX-4016 alone. The treatment of hearts with NCX-4016 + Tempol showed significantly enhanced NO generation and decreased ROS and dityrosine (a marker of peroxynitrite) formation. In conclusion, NCX-4016 in combination with Tempol demonstrated significant cardioprotection and, thus, may offer a novel therapeutic strategy to prevent I/R-mediated myocardial injury.

Nitric oxide–releasing aspirin and indomethacin are potent inhibitors against colon cancer in azoxymethane-treated rats: effects on molecular targets

Nitric oxide-releasing nonsteroidal anti-inflammatory drugs (NO-NSAID) are promising chemoprevention agents; unlike conventional NSAIDs, they seem free of appreciable adverse effects, while they retain beneficial activities of their parent compounds. Their effect on colon carcinogenesis using carcinoma formation as an end point is unknown. We assessed the chemopreventive properties of NO-indomethacin (NCX 530) and NO-aspirin (NCX 4016) against azoxymethane-induced colon cancer. Seven-week-old male F344 rats were fed control diet, and 1 week later, rats received two weekly s.c. injections of azoxymethane (15 mg/kg body weight). Two weeks after azoxymethane treatment, rats (48 per group) were fed experimental diets containing NO-indomethacin (0, 40, or 80 ppm), or NO-aspirin (1,500 or 3,000 ppm), representing 40% and 80% of the maximum tolerated dose. All rats were killed 48 weeks after azoxymethane treatment and assessed for colon tumor efficacy and molecular changes in colonic tumors and normally appearing colonic mucosa of different dietary groups. Our results suggest that NO-indomethacin at 40 and 80 ppm and NO-aspirin at 3,000 ppm significantly suppressed both tumor incidence (P < 0.01) and multiplicity (P < 0.001). The degree of inhibition was more pronounced with NO-indomethacin at both dose levels (72% and 76% inhibition) than with NO-aspirin (43% and 67%). NO-indomethacin at 40 and 80 ppm and NO-aspirin at 3,000 ppm significantly inhibited the colon tumors' (P < 0.01 to P < 0.001) total cyclooxygenase (COX), including COX-2 activity (52-75% inhibition) and formation of prostaglandin E2 (PGE2), PGF2alpha, and 6-keto-PGF1alpha, and TxB2 from arachidonic acid (53-77% inhibition). Nitric oxide synthase 2 (NOS-2) activity and beta-catenin expression were suppressed in animals given NO-NSAID. In colonic crypts and tumors of animals fed these two NO-NSAIDs, there was a significant decrease in proliferating cell nuclear antigen labeling when compared with animals fed the control diet. The results of this study provide strong evidence that NO-NSAIDs possess strong inhibitory effect against colon carcinogenesis; their effect is associated with suppression of COX and NOS-2 activities and beta-catenin levels in colon tumors. These results pave the way for the rational design of human clinical trials.

Reversal to cisplatin sensitivity in recurrent human ovarian cancer cells by NCX-4016, a nitro derivative of aspirin

Ovarian cancer is a gynecological malignancy that is commonly treated by cytoreductive surgery followed by cisplatin treatment. However, the cisplatin treatment, although successful initially, is not effective in the treatment of the recurrent disease that invariably surfaces within a few months of the initial treatment. The refractory behavior is attributed to the increased levels of cellular thiols apparently caused by the cisplatin treatment. This observation prompted us to choose a cytotoxic drug whose activity is potentiated by cellular thiols with enhanced specificity toward the thiol-rich cisplatin-resistant cells. We used NCX-4016 [2-(acetyloxy)benzoic acid 3-(nitrooxymethyl)phenyl ester], a derivative of aspirin containing a nitro group that releases nitric oxide in a sustained fashion for several hours in cells and in vivo, and we studied its cytotoxic efficacy against human ovarian cancer cells (HOCCs). Cisplatin-sensitive and cisplatin-resistant (CR) HOCCs were treated with 100 microM NCX-4016 for 6 h, and/or 0.5 microg/ml cisplatin for 1 h and assayed for clonogenecity. NCX-4016 significantly reduced the surviving fractions of cisplatin-sensitive (63 +/- 6%) and CR (70 +/- 10%) HOCCs. NCX-4016 also caused a 50% reduction in the levels of cellular glutathione in CR HOCCs. Treatment of cells with NCX-4016 followed by cisplatin showed a significantly greater extent of toxicity when compared with treatment of cells with NCX-4016 or cisplatin alone. In conclusion, this study showed that NCX-4016 is a potential inhibitor of the proliferation of CR HOCCs and thus might specifically kill cisplatin-refractory cancer cells in patients with recurrent ovarian cancer.

The effect of NCX4016 [2-acetoxy-benzoate 2-(2-nitroxymethyl)-phenyl ester] on the consequences of ischemia and reperfusion in the streptozotocin diabetic rat

The aim of this study was to assess the effect of chronic administration of NCX4016 [2 acetoxy-benzoate 2-(2-nitroxymethyl)-phenyl ester], a nitric oxide-releasing aspirin derivative on the consequences of coronary artery occlusion in streptozotocin-diabetic rats. Rats were made diabetic by injection of streptozotocin (60 mg kg(-1)) and received insulin (2.5 U kg(-1) s.c.) daily for 4 weeks. Animals received vehicle (1 ml kg(-1) polyethylene glycol), aspirin (65.2 mg kg(-1)), NCX4016 (60 mg kg(-1)), or (iv) NCX4016 (120 mg kg(-1)) orally, once daily for the last 5 days before coronary artery occlusion (CAO). One hour after the last dose, pentobarbital-anesthetized rats were subjected to CAO for 30 min followed by 120-min reperfusion. Neither drug significantly modified initial hemodynamics or plasma glucose levels compared with vehicle treatment in either nondiabetic or diabetic rats. Neither drug modified the total ventricular premature beat (VPB) count in normal animals, although NCX4016, but not aspirin, reduced the total VPB count and the incidence of ventricular tachycardia in diabetic rats. In nondiabetic animals, both aspirin and NCX4016 reduced infarct size. However, in diabetic rats, infarct size was reduced only by the larger dose of NCX4016 (120 mg kg(-1)) but not by aspirin or the lower dose of NCX4016. These results demonstrate that the cardioprotective effects of NCX4016 are reduced in the presence of diabetes compared with the effects seen in nondiabetic animals. In summary, the present study confirms the protective effect of NCX4016 against ischemia-reperfusion injury in the normal rat heart and demonstrates for the first time its protective effect in the heart of streptozotocin-diabetic rats.

Direct and irreversible inhibition of cyclooxygenase-1 by nitroaspirin (NCX 4016)

Benzoic acid, 2-(acetyl-oxy)-3-[(nitrooxy)methyl]phenyl ester (NCX 4016), a new drug made by an aspirin molecule linked, through a spacer, to a nitric oxide (NO)-donating moiety, is now under clinical testing for the treatment of atherothrombotic conditions. Aspirin exerts its antithrombotic activity by irreversibly inactivating platelet cyclooxygenase (COX)-1. NCX 4016 in vivo undergoes metabolism into deacetylated and/or denitrated metabolites, and it is not known whether NCX 4016 needs to liberate aspirin to inhibit COX-1, or whether it can block it as a whole molecule. The aim of our study was to evaluate the effects of NCX 4016 and its analog or metabolites on platelet COX-1 and whole blood COX-2 and on purified ovine COX (oCOX)-1 and oCOX-2. In particular, we have compared the mechanism by which NCX 4016 inhibits purified oCOX enzymes with that of aspirin using a spectrophotometric assay. All the NCX 4016 derivatives containing acetylsalicylic acid inhibited the activity of oCOX-1 and oCOX-2, whereas the deacetylated metabolites and the nitric oxide-donating moiety were inactive. Dialysis experiments showed that oCOX-1 inhibition by NCX 4016, similar to aspirin, is irreversible. Reversible COX inhibitors (indomethacin) or salicylic acid incubated with the enzyme before NCX 4016 prevent the irreversible inhibition of oCOX-1 by NCX 4016 as well as by aspirin. In conclusion, our data show that NCX 4016 acts as a direct and irreversible inhibitor of COX-1 and that the presence of a spacer and NO-donating moiety in the molecule slows the kinetics of COX-1 inhibition by NCX 4016, compared with aspirin.

Nitric-oxide-donating NSAIDs as agents for cancer prevention

Nitric-oxide-donating nonsteroidal anti-inflammatory drugs (NO-NSAIDs), which consist of an NSAID with an NO-donating moiety covalently attached to it, promise to contribute significantly towards the development of effective chemoprevention strategies against cancer. NO-NSAIDs inhibit the growth of cultured cancer cells 10-6000-fold more potently than their parent NSAIDs and prevent colon cancer in animal tumor models. Clinical data indicate that they are extremely safe. Mechanistically, NO-aspirin, the best-studied NO-NSAID, has pleiotropic effects on cell signaling (it inhibits Wnt signaling, induces nitric oxide synthase and NF-kappaB activation and induces cyclooxygenase-2 expression), and this mechanistic redundancy might be central to its mode of action against cancer. The apparent safety and superior efficacy of NO-NSAIDs makes them promising chemopreventive agents against cancer.

In Vitro Metabolism of Nitric Oxide-Donating Aspirin: The Effect of Positional Isomerism

NO-donating aspirin (NO-ASA) is a potentially important chemopreventive agent against cancer. Since positional isomerism affects strongly its potency in inhibiting colon cancer cell growth, we studied the metabolic transformations of its ortho-, meta-, and para-isomers in rat liver and colon cytosolic, microsomal, and mitochondrial fractions as well as in intact HT-29 human colon cancer cells. NO-ASA and metabolites were determined by high-performance liquid chromatography and products identified by mass spectroscopy, as required. For all three isomers, the acetyl group on the ASA moiety was hydrolyzed rapidly. This was followed by hydrolysis of the ester bond linking the salicylate anion to the spacer. The ortho- and para-isomers produced salicylic acid and a putative intermediate consisting of the remainder of the molecule, which via a rapid step generated nitrate, (hydroxymethyl)phenol, and a conjugate of spacer with glutathione. The meta-isomer, in contrast, generated salicylic acid and (nitroxymethyl)phenol, the latter leading to (hydroxymethyl)phenol and the glutathione-spacer conjugate. This metabolic pathway takes place in its entirety only in the cytosolic fraction of the tissues tested and in intact human colon cancer cells, perhaps reflecting exposure to the cytosolic glutathione S-transferase, which catalyzes the formation of the spacer-glutathione conjugate. Thus, the three positional isomers of NO-ASA differ in their metabolism and these differences correlate with their differential effects on cancer cell growth, underscoring the importance of positional isomerism in modulating drug effects.

Nitrates and NO release: contemporary aspects in biological and medicinal chemistry

Nitroglycerine has been used clinically in the treatment of angina for 130 years, yet important details on the mechanism of action, biotransformation, and the associated phenomenon of nitrate tolerance remain unanswered. The biological activity of organic nitrates can be said to be nitric oxide mimetic, leading to recent, exciting progress in realizing the therapeutic potential of nitrates. Unequivocally, nitroglycerine and most other organic nitrates, including NO-NSAIDs, do not behave as NO donors in the most fundamental action: in vitro activation of sGC to produce cGMP. The question as to whether the biological activity of nitrates results primarily or exclusively from NO donation will not be satisfactorily answered until the location, the apparatus, and the mechanism of reduction of nitrates to NO are defined. Similarly, the therapeutic potential of nitrates will not be unlocked until this knowledge is attained. Aspects of the therapeutic and biological activity of nitrates are reviewed in the context of the chemistry of nitrates and the elusive efficient 3e- reduction required to generate NO.

Nitric oxide release and distribution following oral and intraperitoneal administration of nitroaspirin (NCX 4016) in the rat

The metabolic fate of nitric oxide (NO) released from nitroaspirin, benzoic acid, 2-(acetyloxy)-3-[(nitrooxy)methyl]phenyl ester (NCX 4016), the lead compound of a new class of NO-releasing non steroidal anti-inflammatory drugs (NO-NSAIDs), has been studied in the rat following p.o. and i.p. administration of 100 mg/kg, by monitoring in plasma the bioactive storage forms of NO (S-nitrosothiols, RS-NO) and its oxidation products (nitrites/nitrates, NOx) by a chemiluminescent assay. In parallel, plasma was analyzed for unchanged drug and metabolites by reverse-phase HPLC. In orally treated rats, no unchanged drug is observed in the 0-24 h interval post-dosing, but only salicylic acid (SA), NOx and RS-NO. The time-course of SA formation parallels that of plasma NOx (plateau after 6 h). Nitrosothiols in plasma are detectable at 1 h, peak at 4 h post-administration, and decline thereafter. The results relative to i.p. administration show a more pronounced and rapid NO delivery (peak of both NOx and RS-NO at 1 h and plateau between 1 and 2 h), still coincident with the peak of SA, and the presence in plasma of NCX 4015 (a metabolite of NCX 4016 which still bears the nitrate function). In myocardial tissue from p.o. treated rats, no drug or metabolites were ever detected, and the NOx levels were always in the range of the controls. Conversely, following i.p. treatment, we observed a rapid compartmentalization within the heart of the unchanged drug, which rapidly disappears in favour of its breakdown products NCX 4015 and SA, with a concomitant rise in myocardial NOx levels up to 2 h. To check the stability of NCX 4016 in the acidic gastric milieu and to explain the different distribution of the drug following p.o. or i.p. administration, the gastric content of the orally-treated animals at different post-dosing times was analysed by HPLC. The unchanged drug was detected up to 8 h post-dosing (levels slowly decreased with time), and the only metabolite to be detected was the O-deacetylated derivative (NCX 4023), which was present in low concentrations up to 4 h post-dosing. This indicates that NCX 4016 does not undergo biotransformation in the upper part of gastrointestinal tract (no direct release of NO in this district) and that the stomach acts as a reservoir for the drug.

Chemiluminescence and LC–MS/MS analyses for the study of nitric oxide release and distribution following oral administration of nitroaspirin (NCX 4016) in healthy volunteers

The metabolic fate of nitric oxide (NO) released from nitroaspirin, benzoic acid, 2-(acetyloxy)-3-[(nitrooxy)methyl]phenyl ester (NCX 4016), the lead compound of a new class of NO-releasing non-steroidal anti-inflammatory drugs (NO-NSAIDs) has been studied in eight healthy male Caucasian subjects following p.o. administration of 1600 mg (single dose), by monitoring at different times in plasma the bioactive storage forms of NO, S-nitrosothiols (RSNO) and its oxidation products (NOx). Plasma levels of NOx and RSNO and urinary levels of NOx were determined by an ozone-based chemiluminescent assay using a sensitive Nitric Oxide Analyzer (LOQ: 10 pmol NO injected). In parallel plasma samples were analyzed by a newly developed LC-MS/MS method for analysis of NCX 4015, the metabolite bearing the nitrate ester function. Using MS/MS with multiple reaction monitoring (MRM) in negative ion mode for NCX 4015 and the internal standard (NCX 4015- 13C-D2) it was possible to detect with sufficient accuracy and precision the metabolite in plasma with a quantification limit of 78.1 ng ml(-1). Concentration versus time profile of plasma NCX 4015 gave a Cmax value of 161.94 +/- 47.4 ng ml(-1) and a tmax 4.5 +/- 1 h. The results indicate that both NOx and RSNO (these last for the first time determined in vivo in man following oral administration of a NO-donor drug) are effective plasma markers of NO release in vivo, the latter being an earlier indicator of NO distribution (tmax 2.0 +/- 0.6 h versus 5.4 +/- 1.2 h).

Effect of nitric oxide-donating agents on human monocyte cyclooxygenase-2

COX-2 is involved in inflammation and ischemic cardiovascular disease. As NO regulates COX activity in various cells, we investigated the effect of NO-donors and the novel NO-aspirin NC-4016 on human monocyte COX-2. Whole blood was incubated with LPS and PGE(2) was measured in plasma as an index of monocyte COX-2 activity. Serum TxB(2) was assessed as an index of platelet COX-1 activity. SNP, DetaNONOate, and NO-aspirin inhibited dose-dependently PGE(2) production while aspirin was ineffective. The guanylyl-cyclase inhibitor ODQ partially reversed the suppression of COX-2 activity by NO-aspirin, demonstrating a role of cGMP increase. NC-4016 and aspirin inhibited platelet COX-1 comparably while NO-donors were ineffective. COX-2 expression was not affected by NO-donors or NO-aspirin while aspirin or the selective COX-2-inhibitor DUP697 increased it. In conclusion, Nitroaspirin inhibits monocyte COX-2 activity by a cGMP-dependent mechanism. This might represent an advantage over aspirin, given the possible detrimental role of COX-2 in cardiovascular disease.