NSAIDs do not require the presence of a carboxylic acid to exert their anti-inflammatory effect – why do we keep using it?

The carboxylic acid group (–COOH) present in classical NSAIDs is partly responsible for the gastric toxicity associated with the administration of these drugs. This concept has been extensively proven using NSAID prodrugs. However, the screening of NSAIDs with no carboxylic acid at all has been neglected. The goal of this work was to determine if new NSAID derivatives devoid of acidic moieties would retain the anti-inflammatory activity of the parent compound, without causing gastric toxicity. To test this concept, we replaced the carboxylic acid group in ibuprofen, flurbiprofen, and naproxen with three ammonium moieties. We tested the resulting water-soluble NSAID derivatives for anti-inflammatory and ulcerogenic activity in vitro and in vivo. In this regard, we observed that all non-acidic NSAIDs exerted a potent anti-inflammatory activity, suggesting that the acid group in commercial 2-phenylpropionic acid NSAIDs not be an essential requirement for anti-inflammatory activity. These data provide complementary evidence supporting the discontinuation of ulcerogenic acidic NSAIDs.     

Site specific chemical delivery of NSAIDs to inflamed joints: synthesis, biological activity and gamma-imaging studies of quaternary ammonium salts of tropinol esters of some NSAIDs or their active metabolites

Quaternized tropinol ester derivatives of some commonly used non-steroidal anti-inflammatory drugs (NSAIDs) or their active metabolites, were prepared and studied for their anti-inflammatory activity in a chronic inflammation model and for inflamed tissue tropism. The quaternized esters were radiolabeled with 99mTechnetium (99mTc) and their selective localization in the inflamed tissue was traced using scintigraphy. In the chronic arthritis rodent model, most of the quaternized esters exhibited anti-inflammatory effect comparable to their respective parent drugs. In the gamma-imaging studies only the quaternary derivatives exhibited selective accumulation into the inflamed tissue unlike the parent NSAIDs or the unquaternized tropinol esters. This work is a step ahead in the direction of use of quaternary ammonium ester derivatives for site specific chemical delivery of commonly used NSAIDs to the inflamed tissues to minimize their GIT side effect or other systemic toxicities.     

Synthesis of new chemical entities from paracetamol and NSAIDs with improved pharmacodynamic profile

It was envisaged to combine high antipyretic activity of paracetamol into commonly used NSAIDs. To achieve this goal new chemical entities were synthesized by chemically combining paracetamol and NSAIDs, and biologically evaluated for their antipyretic, analgesic, anti-inflammatory and ulcerogenic potential. The acid chloride of parent NSAIDs was reacted with excess of p-aminophenol to yield the desired p-amidophenol derivatives (1B–7B). Acetate derivatives (1C–7C) of these phenols (1B–7B) were also prepared by their treatment with acetic anhydride, in order to see the impact of blocking the free phenolic group on the biological activity of the derivatives. All the synthesized p-amidophenol derivatives showed improved antipyretic activity than paracetamol with retention of anti-inflammatory activity of their parent NSAIDs. These compounds elicited no ulcerogenicity unlike their parent drugs.     

Synthesis, anti-inflammatory activity and ulcerogenic liability of novel nitric oxide donating/chalcone hybrids

A group of novel nitric oxide (NO) donating chalcone derivatives was prepared by binding various amino chalcones with different NO donating moieties including; nitrate ester, oximes and furoxans. Most of the prepared compounds showed significant anti-inflammatory activity using carrageenan-induced rat paw edema method compared with indomethacin. The prepared compounds exhibited more protection than indomethacin in regard to gastric toxicity. Histopathological investigation confirmed the beneficial effects of the NO releasing compounds in reducing ulcer formation. The incorporation of the NO-donating group into the parent chalcone derivatives caused a moderate increase in the anti-inflammatory activity with a marked decrease in gastric ulcerations compared to their parent chalcone derivatives.     

Role of nitric oxide in the gastrointestinal tract

Worldwide osteoarthritis (OA) affects more than 9.6% of men and 18% of women older that 60 years. Treatment for OA often requires chronic use of selective or nonselective nonsteroidal anti-inflammatory drugs (NSAIDs), which have been associated with gastrointestinal and cardiovascular complications. An increased risk for upper gastrointestinal bleeding with NSAIDs alone and when combined with low-dose aspirin has been described in numerous studies. Although cyclo-oxygenase-2 inhibitors have been shown to carry a lower risk for gastrointestinal injury than nonselective NSAIDs, research continues to identify new treatments that not only are effective but also provide an improved benefit/risk profile, including better gastrointestinal tolerability. Nitric oxide (NO) is known to have a protective effect on the gastrointestinal tract. In preclinical studies NO was shown to help maintain gastric mucosal integrity, to inhibit leukocyte adherence to the endothelium, and to repair NSAID-induced damage. In addition, epidemiologic studies have shown that the use of NO-donating agents with NSAIDs or aspirin resulted in reduced risk for gastrointestinal bleeding. Recent studies have shown that cyclo-oxygenase inhibiting NO-donating drugs (CINODs), in which a NO molecule is chemically linked to an NSAID, are effective anti-inflammatory agents and may result in less gastrointestinal damage than is associated with NSAID use. Therefore, these agents provide a potential therapeutic option for patients with arthritis who require long-term NSAID therapy.     

Synthesis and biological evaluation of loxoprofen derivatives

Non-steroidal anti-inflammatory drugs (NSAIDs) achieve their anti-inflammatory actions through an inhibitory effect on cyclooxygenase (COX). Two COX subtypes, COX-1 and COX-2, are responsible for the majority of COX activity at the gastrointestinal mucosa and in tissues with inflammation, respectively. We previously suggested that both gastric mucosal cell death due to the membrane permeabilization activity of NSAIDs and COX-inhibition at the gastric mucosa are involved in NSAID-induced gastric lesions. We have also reported that loxoprofen has the lowest membrane permeabilization activity among the NSAIDs we tested. In this study, we synthesized a series of loxoprofen derivatives and examined their membrane permeabilization activities and inhibitory effects on COX-1 and COX-2. Among these derivatives, 2-{4'-hydroxy-5-[(2-oxocyclopentyl)methyl]biphenyl-2-yl}propanoate 31 has a specificity for COX-2 over COX-1. Compared to loxoprofen, oral administration of 31 to rats produced fewer gastric lesions but showed an equivalent anti-inflammatory effect. These results suggest that 31 is likely to be a therapeutically beneficial and safer NSAID.     

Evaluation of classical NSAIDs and COX-2 selective inhibitors on purified ovine enzymes and human whole blood.

Cyclooxygenase is the key enzyme in the biosynthesis of prostanoids, biologically active substances involved in several physiological processes and also in pathological conditions such as inflammation. It has been well known for 10 years that this enzyme exists under two forms: a constitutive (COX-1) and an inducible form (COX-2). Both enzymes are sensitive to inhibition by conventional non-steroidal anti-inflammatory drugs (NSAIDs). Observations were made that COX-1 was mainly involved in homeostatic processes, while the COX-2 expression was associated with pathological conditions leading to the development of COX-2 selective inhibitors. Several methods have been reported for the evaluation of the COX-1 and COX-2 inhibitory potency and selectivity of conventional or COX-2 selective NSAIDs. In this study, we evaluated the COXs inhibitory profile of both conventional NSAIDs and COX-2 selective inhibitors using two different in vitro methods: the first test was performed using purified enzymes while the second method consisted of a whole blood assay. The results obtained with reference drugs in these two assays will be discussed and compared in this article.     

Synthesis and pharmacological evaluation of amide conjugates of NSAIDs with L-cysteine ethyl ester, combining potent antiinflammatory and antioxidant properties with significantly reduced gastrointestinal toxicity

The synthesis and pharmacological evaluation of a series of amide derivatives of NSAIDs with L-cysteine ethyl ester is described. The novel derivatives are potent antiinflammatory, antioxidant and hypocholesterolemic-hypolipidemic agents, while they demonstrate considerably reduced gastrointestinal toxicity. This molecular modification may offer a general route to safer antiinflammatory agents, potentially suitable for chronic use in conditions such as neurodegenerative disorders.     

Cod liver oil inhibits indomethacin induced gastropathy without affecting its bioavailability and pharmacological activity

The upper gastrointestinal toxicity is one of the most common side effects associated with the use of nonsteroidal anti-inflammatory drugs (NSAIDs). Many attempts to prepare potent NSAIDs free from gastrotoxicity have failed. Hence, development of formulations to mask the gastropathy of NSAIDs are warranted. The present study was undertaken to investigate the effect of concomitant use of cod liver oil (CLO) on pharmacological activity and gastropathy of indomethacin in rats. The animals were treated with CLO (5 and 10 ml/kg body weight) along with indomethacin (30 mg/kg, body weight). Blood samples were collected for analysis of indomethacin at 0.25, 0.5, 1.0, 1.5, 2.0, 4.0, 6.0 and 24 hours. The anti-inflammatory activity of indomethacin alone and in combination with CLO was studied using carrageenan-induced paw oedema. Our studies related to the effect of these drugs on gastrointestinal tract showed that concurrent use of CLO protects gastric mucosa against indomethacin induced depletion of gastric wall mucus, non protein sulfhydryl (NP-SH) levels and gastric lesions. The result of this study also showed that the concurrent use of the CLO does not affect the bioavailability and anti-inflammatory activity of indomethacin while it inhibits the ulcerogenic effect of indomethacin in a dose dependent manner. These findings suggest that NSAIDs formulations containing CLO may reduce gastrotoxicity without affecting their therapeutic efficacy.     

In vitro scavenging activity for reactive oxygen and nitrogen species by nonsteroidal anti-inflammatory indole, pyrrole, and oxazole derivative drugs

This study was undertaken to evaluate the scavenging activity for reactive oxygen species (ROS) and reactive nitrogen species (RNS) by several nonsteroidal anti-inflammatory drugs (NSAIDs), namely indole derivatives (indomethacin, acemetacin, etodolac), pyrrole derivatives (tolmetin and ketorolac), and an oxazole derivative (oxaprozin). The inhibition of prostaglandin synthesis constitutes the primary mechanism of the anti-inflammatory action of these drugs. Nevertheless, it has been suggested that the anti-inflammatory activity of NSAIDs may be also partly due to their ability to scavenge ROS and RNS and to inhibit the respiratory burst of neutrophils triggered by various activator agents. Thus, the scavenging activity of these NSAIDs was evaluated against an array of ROS (O(2)(-), HO, HOCl, and ROO) and RNS (NO and ONOO(-)) using noncellular in vitro systems. The results obtained demonstrated that tolmetin, ketorolac, and oxaprozin were not active against O(2)(-), while acemetacin, indomethacin, and etodolac exhibited concentration-dependent effects. Oxaprozin was also the least active scavenger for HO, among all the tested NSAIDs shown to be active. The scavenging effect for HOCl was not observed for any of the tested NSAIDs. The ROO was effectively scavenged by etodolac, with the other tested NSAIDs being much less active. NO and ONOO(-) were scavenged by all the tested NSAIDs. These effects may strongly contribute to the anti-inflammatory therapy benefits that may be attained with some of the studied NSAIDs.     

Development and Characterization of Zein-Based Micro Carrier System for Sustained Delivery of Aceclofenac Sodium

Nonsteroidal anti-inflammatory drugs (NSAIDs) induce gastric injury on long-term usage. This study aims at reducing the side effect of NSAIDs by encapsulating in zein, an acid-resistant biopolymer. Aceclofenac-loaded zein microspheres were prepared by emulsification and solvent evaporation method. The stability of zein microspheres at gastric pH retarded the release of the entrapped drug and hence reduces the possibility of gastric injury. However, the in vitro release of aceclofenac was sustained up to 72 h at intestinal pH. Thus, zein microspheres pave the way for the development of safe and sustained delivery system for NSAIDs thereby achieving the desired therapeutic potential with reduced side effects for chronic inflammatory disorders.     

NSAIDs induce both necrosis and apoptosis in guinea pig gastric mucosal cells in primary culture

A major clinical problem encountered with the use of nonsteroidal anti-inflammatory drugs (NSAIDs) such as indomethacin is gastropathy. In this study, we examined, using guinea pig gastric mucosal cells in primary culture, how NSAIDs damage gastric mucosal cells. The short-term treatment of cells with high concentrations of indomethacin decreased cell viability in the absence of apoptotic DNA fragmentation, chromatin condensation, or caspase activation. Cells lost membrane integrity with this short-term indomethacin treatment, suggesting that indomethacin induced necrosis under these conditions. In contrast, the long-term treatment of cells with low concentrations of indomethacin decreased cell viability and was accompanied by apoptotic DNA fragmentation, chromatin condensation, and caspase activation. Pretreatment of cells with inhibitors of caspases or protein synthesis suppressed cell death caused by long-term indomethacin treatment, suggesting that apoptosis was induced when the inhibitors were not present. These results imply that NSAIDs cause gastric mucosal damage through both necrosis and apoptosis of gastric mucosal cells.     

Synthesis and biological evaluation of 2,5-disubstituted 1,3,4-oxadiazole derivatives with both COX and LOX inhibitory activity

Dual cyclooxygenase/lipoxygenase (COX/LOX) inhibitors constitute a valuable alternative to classical nonsteroidal anti-inflammatory drugs (NSAIDs) and selective COX-2 inhibitors for the treatment of inflammatory diseases. A series of 3-(5-phenyl/phenylamino-[1,3,4]oxadiazol-2-yl)-chromen-2-one and N-[5-(2-oxo-2H-chromen-3-yl)-[1,3,4]oxadiazol-2-yl]-benzamide derivatives were synthesized and screened for anti-inflammatory, analgesic activity. All the derivatives prepared are active in inhibiting oedema induced by carrageenan. Compound 4e was found more potent with 89% of inhibition followed by compound 4b (86%). Compounds with >70% of anti-inflammatory activity were tested for analgesic, ulcerogenic, and lipid peroxidation profile. Selected compounds were also evaluated for inhibition of COXs (COX-1 and COX-2) and LOXs (LOX-5, LOX-12, and LOX-15). Compound 4e was comparatively selective for COX-2, LOX-5, and LOX-15. Study revealed that these derivatives were more effective than ibuprofen with reduced side effects. It can be suggested that these derivatives could be used to develop more potent and safer NSAIDs.     

Synthesis and evaluation of carbaborane derivatives of indomethacin as cyclooxygenase inhibitors

Nonsteroidal anti-inflammatory drugs (NSAIDs) exert their pharmacological activities by inhibiting cyclooxygenase (COX)-1 and COX-2. Previous studies have shown that esters and amides of non-selective inhibitors such as indomethacin are selective against COX-2, which is the therapeutically relevant isoform. Structure-activity analysis indicates that substituted phenyl rings are tolerated as ester components. In the present study, the introduction of inorganic ortho- and meta-carbaborane moieties was explored with the aim to create COX-2 inhibitors and more importantly to investigate the validity of using these boron clusters as drug entities. Interestingly, only the ortho-carbaborane ester was active whereas the meta isomer was not. A similar lack of inhibitory potency was observed when an adamantyl substituent or alkylene spacers at the carbaborane were introduced in the ester functionality.     

Cyclooxygenase isoforms and atherosclerosis

Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used in the treatment of arthritis and pain. However, their long-term use is limited by gastrointestinal (GI) side effects such as gastric ulcers. NSAIDs act by inhibiting an enzyme called cyclooxygenase. Cyclooxygenase (COX) catalyses the generation of prostaglandins from arachidonic acid. Two isoforms of the enzyme exist--COX-1 and COX-2--both of which are targets for NSAIDs. Although they are associated with GI toxicity, NSAIDs have important antithrombotic and anti-inflammatory effects. The GI injury has been attributed to COX-1 inhibition and the anti-inflammatory effects to COX-2 inhibition. As COX-2 is traditionally viewed as an inducible enzyme, selective inhibition of COX-2 by 'coxibs' (selective COX-2 inhibitors) has been employed to achieve anti-inflammatory and analgesic effects without GI side effects. However, recently there have been suggestions that chronic administration of coxibs might increase the risk of cardiovascular events, such as atherosclerosis, compared with traditional NSAIDs. In vascular disease, there is increased expression of both COX-1 and COX-2, resulting in enhanced prostaglandin generation. The specific role of COX-1 and COX-2 in vascular regulation is still unknown but such knowledge is essential for the effective use of coxibs. Although more evidence is pointing to selective COX-1 inhibition as a therapeutic measure in inflammatory atherosclerosis, there are some studies that suggest that inhibition of COX-2 might have a potential benefit on atherosclerosis.     

NOSH-aspirin (NBS-1120), a novel nitric oxide- and hydrogen sulfide-releasing hybrid is a potent inhibitor of colon cancer cell growth in vitro and in a xenograft mouse model

Nonsteroidal anti-inflammatory drugs (NSAIDs) are prototypical anti-cancer agents. However, their long-term use is associated with adverse gastrointestinal effects. Recognition that endogenous gaseous mediators, nitric oxide (NO) and hydrogen sulfide (H(2)S) can increase mucosal defense mechanisms has led to the development of NO- and H(2)S-releasing NSAIDs with increased safety profiles. Here we report on a new hybrid, NOSH-aspirin, which is an NO- and H(2)S-releasing agent. NOSH-aspirin inhibited HT-29 colon cancer growth with IC(50)s of 45.5 ± 2.5, 19.7 ± 3.3, and 7.7 ± 2.2 nM at 24, 48, and 72 h, respectively. This is the first NSAID based agent with such high degree of potency. NOSH-aspirin inhibited cell proliferation, induced apoptosis, and caused G(0)/G(1) cell cycle block. Reconstitution and structure-activity studies representing a fairly close approximation to the intact molecule showed that NOSH-aspirin was 9000-fold more potent than the sum of its parts towards growth inhibition. NOSH-aspirin inhibited ovine COX-1 more than ovine COX-2. NOSH-ASA treatment of mice bearing a human colon cancer xenograft caused a reduction in volume of 85%. Taken together, these results demonstrate that NOSH-aspirin has strong anti-cancer potential and merits further evaluation.     

Idiosyncratic NSAID drug induced oxidative stress

Many idiosyncratic non-steroidal anti-inflammatory drugs (NSAIDs) cause GI, liver and bone marrow toxicity in some patients which results in GI bleeding/ulceration/fulminant hepatic failure/hepatitis or agranulocytosis/aplastic anemia. The toxic mechanisms proposed have been reviewed. Evidence is presented showing that idiosyncratic NSAID drugs form prooxidant radicals when metabolised by peroxidases known to be present in these tissues. Thus GSH, NADH and/or ascorbate were cooxidised by catalytic amounts of NSAIDs and hydrogen peroxide in the presence of peroxidase. During GSH and NADH cooxidation, oxygen uptake and activation occurred. Furthermore the formation of NSAID oxidation products was prevented during the cooxidation indicating that the cooxidation involved redox cycling of the first formed NSAID radical product. The order of prooxidant catalytic effectiveness of fenamate and arylacetic acid NSAIDs was mefenamic acid>tolfenamic acid>flufenamic acid, meclofenamic acid or diclofenac. Diphenylamine, a common moiety to all of these NSAIDs was a more active prooxidant for NADH and ascorbate cooxidation than these NSAIDs which suggests that oxidation of the NSAID diphenylamine moiety to a cation and/or nitroxide radical was responsible for the NSAID prooxidant activity. The order of catalytic effectiveness found for sulfonamide derivatives was sulfaphenazole>sulfisoxazolez.Gt;dapsone>sulfanilic acid>procainamide>sulfamethoxazole>sulfadiazine>sulfadimethoxine whereas sulfanilamide, sulfapyridine or nimesulide had no prooxidant activity. Although indomethacin had little prooxidant activity, its major in vivo metabolite, N-deschlorobenzoyl indomethacin had significant prooxidant activity. Aminoantipyrine the major in vivo metabolite of aminopyrine or dipyrone was also more prooxidant than the parent drugs. It is hypothesized that the NSAID radicals and/or the resulting oxidative stress initiates the cytotoxic processes leading to idiosyncratic toxicity.     

Aromatic amide derivatives of 5,6-dimethoxy-2,3-dihydro-1H-inden(-1-yl)acetic acid as anti-inflammatory agents free of ulcerogenic liability

Amide derivatives of 5,6-dimethoxy-2,3-dihydro-1H-inden(-1-yl)acetic acid were synthesized and evaluated for their anti-inflammatory and analgesic activity. Few selected compounds were also screened for their antipyretic, anti-arthritic, and ulcerogenic potential. Most of the compounds exhibited good activity profile and were free of gastrointestinal toxicity of common NSAIDs. However these compounds failed to decrease secondary lesions of adjuvant induced arthritis and also did not inhibit TNF- in lipopolysaccharide induced pyresis.     

Selective toxicity of the polyene antibiotics and their methyl ester derivatives.

The methyl ester hydrochlorides of amphotericin B and nystatin are less effective than the parent compounds in causing K⁺ release from human erythrocytes. The parent compounds and the derivatives are of comparable activity toward $\text{Candida albicans}$. The enhanced selective toxicity of polyene methyl ester salts for $\text{C. albicans}$ may mean that these antibiotics will be more effective therapeutic agents for systemic fungal infections.     

Selective inhibition of Abeta42 production by NSAID R-enantiomers

Non-steroidal anti-inflammatory drugs (NSAIDs) have been associated with reduced risk for Alzheimer's disease (AD) and selected NSAIDs racemates suppress beta-amyloid (Abeta) accumulation in vivo and Abeta42 production in vitro. Clinical use of NSAIDs for preventing or treating AD has been hampered by dose-limiting toxicity believed to be due to cyclooxygenase (COX)-inhibition that is reportedly not essential for selective Abeta42 reduction. Profens have racemates and R-enantiomers were supposed to be inactive forms. Here we demonstrate that R-ibuprofen and R-flurbiprofen, with poor COX-inhibiting activity, reduce Abeta42 production by human cells. Although these R-enantiomers inhibit nuclear factor-kappaB (NF-kappaB) activation and NF-kappaB can selectively regulate Abeta42, Abeta42 reduction is not mediated by inhibition of NF-kappaB activation. Because of its efficacy at lowering Abeta42 production and low toxicity profile, R-flurbiprofen is a strong candidate for clinical development.