Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0030193 (pain)
 261,466 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The molecular identification of a second isoform of cyclooxygenase-2 (COX-2) led to a major investment by several pharmaceutical companies in the development of selective inhibitors. The central tenets of the rationale for developing selective COX-2 inhibitors are that prostaglandins that contribute to inflammation are derived from COX-2, whereas prostaglandins that are involved in normal physiological processes are derived from the constitutively expressed isoform COX-1. There is now considerable evidence that COX-2 is actually expressed constitutively in many tissues and performs important physiological functions. Thus, suppression of COX-2 with selective inhibitors should not be expected to be without some adverse consequences. Moreover, there is strong evidence that COX-1 contributes to inflammation and pain, so selective inhibition of COX-2 will not necessarily produce the same degree of efficacy that is seen with mixed inhibitors of COX-1 and COX-2.
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PMID:Distribution and expression of cyclooxygenase (COX) isoenzymes, their physiological roles, and the categorization of nonsteroidal anti-inflammatory drugs (NSAIDs). 1062 89

Nearly 30 years ago, cyclooxygenase (COX) was identified as an enzyme that initiates the biotransformation of arachidonic acid to prostanoids. It is now known that COX exists as two distinct but similar isozymes, COX-1 and COX-2. Prostaglandins (PGs) formed by the enzymatic activity of COX-1 are primarily involved in the regulation of homeostatic functions throughout the body, whereas PGs formed by COX-2 primarily mediate pain and inflammation. Based on structural differences in the active sites of COX-1 and COX-2, a new class of drugs has been developed that specifically inhibits COX-2 but not COX-1 activity. By preserving the synthesis of homeostatic PGs, these specific inhibitors of COX-2 provide the clinical benefits of nonsteroidal anti-inflammatory drugs and minimize the consequences of nonspecific inhibition of PG synthesis.
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PMID:COX-1 and COX-2 in health and disease. 1064 75

Both nitric oxide (NO) and prostaglandins (PG) and their associated enzymes nitric oxide synthases (NOS) and cyclooxygenases (COX) (specifically COX-2) have been implicated in the development of hyperalgesia. This study examined the effects of naturally occurring chronic inflammation, chronic mastitis, on spinal nociceptive processing in sheep and focused on potential alterations in spinal PG and NO signaling pathways. Mechanical withdrawal thresholds were significantly lower in animals suffering from chronic inflammation (n=6) compared to control animals (n=6). Hyperalgesia was restricted to the side contralateral to the inflammation (decrease from ipsilateral side: hindlimb 33.2+/-5%, forelimb 19.4+/-5%). Neuronal NOS-immunoreactivity was significantly reduced bilaterally in lumbar and cervical spinal cord throughout laminae I-III (decrease 18.4+/-5% and 16.9+/-4%, respectively) and in lamina X (decrease 29.1+/-6% and 17.1+/-4%, respectively) in mastitic animals relative to control animals. No difference was detected in eNOS or iNOS-immunoreactivity or in NADPH-diaphorase staining, a marker of dynamically active NOS. RT-PCR failed to detect any change in levels of nNOS, eNOS, iNOS, COX-1 or COX-2 mRNAs. However, a marked increase in the PGE receptor, EP(3) (but not EP(2)) mRNA was detected in ipsilateral spinal cord tissue from animals with chronic inflammation. This increase in EP(3) receptor expression indicates that spinal PGs are important in the spinal response to chronic peripheral inflammation. Contralateral mechanical hyperalgesia may not be directly linked to changes in spinal EP(3) receptor mRNA expression, however, the bilateral changes in nNOS suggest that this pathway may contribute to the adaptive behavioural response observed.
Pain 2000 Jun
PMID:The role of nitric oxide and prostaglandin signaling pathways in spinal nociceptive processing in chronic inflammation. 1081 61

Nepafenac, the amide analog of 2-amino-3-benzoylbenzeneacetic acid (amfenac), was examined in preclinical models for its potential utility as a topical ocular anti-inflammatory agent. Diclofenac was selected as the reference compound. In contrast to diclofenac (IC50 = 0.12 microM), nepafenac exhibited only weak COX-1 inhibitory activity (IC50 = 64.3 microM). However, amfenac was a potent inhibitor of both COX-1 (IC50 = 0.25 microM) and COX-2 activity (IC50 = 0.15 microM). Ex vivo, a single topical ocular dose of nepafenac (0.1%) inhibited prostaglandin synthesis in the iris/ciliary body (85-95%) and the retina/choroid (55%). These levels of inhibition were sustained for 6 h in the iris/ciliary body and 4 h in the retina/choroid. Diclofenac (0.1%) suppressed iris/ciliary body prostaglandin synthesis (100%) for only 20 min, with 75% recovery observed within 6 h following topical dosing. Diclofenac's inhibition of prostaglandin synthesis in the retina/choroid was minimal. Nepafenac's inhibitory efficacy and longer duration of action was confirmed in a trauma-induced rabbit model of acute ocular inflammation monitoring protein or PGE2 accumulation in aqueous humor. Results warrant further assessment of nepafenac's topical ocular efficacy in the treatment of postoperative ocular pain, inflammation, and posterior segment edema.
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PMID:Nepafenac, a unique nonsteroidal prodrug with potential utility in the treatment of trauma-induced ocular inflammation: I. Assessment of anti-inflammatory efficacy. 1085 Aug 57

Nonsteroidal anti-inflammatory drugs (NSAIDs) are responsible for substantial morbidity and mortality as a result of the complications associated with gastroduodenal ulcers, such as perforation and bleeding. The central mechanism leading to the gastroduodenal toxicity of NSAIDs is their ability to inhibit mucosal prostaglandin synthesis. Recent recognition that there are 2 isoforms of the enzyme cyclooxygenase (COX) responsible for prostaglandin synthesis has enabled the development of drugs capable of sparing the gastric mucosa. The inducible COX-2 enzyme is responsible for some aspects of pain and inflammation in arthritis while the constitutive COX-1 enzyme appears responsible for most of the gastro-protective prostaglandin synthesis in the stomach and duodenum. Drugs selective for COX-2 probably act by binding to a pocket in the enzyme that is present in COX-2 but not in COX-1. As a result, drugs that have little or no COX-1 activity across their therapeutic dosage range have been developed. Two drugs that are claimed to be highly selective or specific in their ability to inhibit COX-2, rofecoxib and celecoxib, are now available on prescription in the US and rofecoxib is available in Europe. Short term volunteer studies of 7 days' duration and patient studies of 6 months' duration have shown these drugs to have a level of gastroduodenal injury that is similar or equivalent to that seen with placebo, whereas high rates of damage and ulceration are seen with nonselective NSAIDs. In addition, there appear to have been fewer perforations, clinical ulcers and bleeds in the phase III clinical trials of these agents, compared with nonselective NSAIDS. However, more experience will be needed before this promise can be confirmed. In addition, COX-2 inhibitors share the adverse effects of NSAIDs outside the gastrointestinal tract that are dependent on COX-2 inhibition.
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PMID:COX-2 selective nonsteroidal anti-Inflammatory drugs: do they really offer any advantages? 1088 57

The prostaglandin endoperoxide H synthases-1 and 2 (PGHS-1 and PGHS-2; also cyclooxygenases-1 and 2, COX-1 and COX-2) catalyze the committed step in prostaglandin synthesis. PGHS-1 and 2 are of particular interest because they are the major targets of nonsteroidal anti-inflammatory drugs (NSAIDs) including aspirin, ibuprofen, and the new COX-2 inhibitors. Inhibition of the PGHSs with NSAIDs acutely reduces inflammation, pain, and fever, and long-term use of these drugs reduces fatal thrombotic events, as well as the development of colon cancer and Alzheimer's disease. In this review, we examine how the structures of these enzymes relate mechanistically to cyclooxygenase and peroxidase catalysis, and how differences in the structure of PGHS-2 confer on this isozyme differential sensitivity to COX-2 inhibitors. We further examine the evidence for independent signaling by PGHS-1 and PGHS-2, and the complex mechanisms for regulation of PGHS-2 gene expression.
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PMID:Cyclooxygenases: structural, cellular, and molecular biology. 1096 56

Research strongly indicates that increased expression of the isoenzyme cyclooxygenase-2 (COX-2) is responsible for elevated production of prostaglandins in inflamed joint tissues and is involved in the mediation of pain. In contrast, COX-1 is a constitutively produced isoenzyme that is involved in the synthesis of eicosanoids that have important homeostatic functions, for example, in the gastric mucosa and platelets. This new knowledge led to the development of drugs that are highly specific inhibitors of COX-2 while not inhibiting COX-1 at maximally efficacious dosages. The first COX-2 specific agent approved for clinical use in the United States was celecoxib. Large multicenter trials have shown that celecoxib at dosages of 100 mg BID and 200 mg BID is as effective as naproxen 500 mg BID in patients with osteoarthritis of the knee or hip. Another large multicenter trial also demonstrated that celecoxib 200 mg BTD and 400 mg BID is as effective as naproxen 500 mg BID in patients with rheumatoid arthritis (RA). A comparative trial showed that celecoxib 200 mg BID is as effective as diclofenac SR 75 mg BID in patients with RA. The potential of COX-2 specific inhibitors to provide antiinflammatory and analgesic efficacy equivalent to that of conventional nonsteroidal antiinflammatory drugs without the adverse gastrointestinal mucosal and platelet effects associated with nonspecific COX inhibitors promises to revolutionize the clinical care of arthritis patients.
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PMID:Antiinflammatory and analgesic efficacy of COX-2 specific inhibition: from investigational trials to clinical experience. 1103 98

Despite their substantial clinical benefits in the management of rheumatoid arthritis, osteoarthritis, pain, and other musculoskeletal complaints, conventional nonsteroidal antiinflammatory drugs (NSAID) are associated with significant toxicities that can frequently limit their use. The most common and noteworthy adverse effects of NSAID are gastrointestinal (GI), and range from dyspeptic symptoms to ulcers and serious ulcer complications. The upper GI toxicities associated with the use of conventional NSAID led to the search for medications that were as clinically effective as these agents, but with a significantly improved GI safety profile. It is now known that the constitutively expressed isoenzyme cyclooxygenase (COX)-1 catalyzes the synthesis of prostanoids that help to regulate normal physiologic processes, including GI mucosa protection, whereas the inducible isoenzyme COX-2 leads to the generation of prostaglandins that mediate inflammation, pain, and fever. This knowledge has led to the development of new compounds that, at therapeutic concentrations, inhibit COX-2 without affecting COX-1. The first COX-2 targeted agent approved by the US Food and Drug Administration (FDA) was celecoxib. This article reviews the risks of GI complications associated with conventional NSAID use and compares these risks with that of the new COX-2 specific inhibitor celecoxib.
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PMID:Significant upper gastrointestinal events associated with conventional NSAID versus celecoxib. 1103 99

Inhibition of prostaglandin biosynthesis via inhibition of the fatty acid cyclooxygenase (COX) is the mechanism of action of non-steroidal anti-inflammatory drugs (NSAIDs). This results in an inhibition of the inflammatory and pain-producing activities of prostaglandins at a site of tissue injury but also in inhibition of prostaglandin production in the gastrointestinal tract (GI) and platelets, i.e. sites where endogenous prostaglandins are possibly involved in control of physiological functions. The discovery of two COX isoenzymes, COX-1 and COX-2, and the detection of their separate function and regulation, has initiated the search for new and putatively more selective inhibitors of prostaglandin biosynthesis. Specifically, selective inhibitors of COX-2 were developed in order to improve the anti-inflammatory and analgetic specificity and potency of the compounds and to reduce side-effects in the GI tract. Available experimental and clinical data of selective COX-2 inhibitors, including flosulide, celecoxib or rofecoxib, suggest improved gastric tolerance as compared to conventional, non-selective NSAIDs. However, experimental evidence suggests that both, the analgetic and anti-inflammatory action of COX-inhibitors, might also require inhibition of COX-1. COX-2-selective compounds at anti-inflammatory doses might have other side-effects, and for example reduce vascular prostacyclin production. Evidence is accumulating that COX-2 might not only be considered as a putatively detrimental enzyme but rather a highly regulated enzyme that also contributes to tissue protection and is even constitutively expressed in healthy human stomach mucosa. This paper reviews some of these newer aspects of COX-2-selective inhibitors in clinical use and discusses their possible benefits and risks.
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PMID:Cyclooxygenase-2 inhibition and side-effects of non-steroidal anti-inflammatory drugs in the gastrointestinal tract. 1103 62

Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit prostaglandin synthesis via the cyclooxygenase (COX) enzyme, the key to both therapeutic benefits and toxicity. COX enzyme exists in 2 isoforms, COX-1 and COX-2. COX-1 enzyme is thought to mediate "housekeeping" or homeostatic functions, and COX-2 is considered an inducible enzyme in response to injury or inflammation. COX-2 inhibitors are the "next-generation" NSAIDs that may selectively block the COX-2 isoenzyme without affecting COX-1 function. This may result in control of pain and inflammation with a lower rate of adverse effects compared with older nonselective NSAIDs. Rapidly evolving evidence suggests that COX-2 enzyme has a diverse physiologic and pathologic role. This article addresses the role of COX-2 enzyme in health and disease as well as the potential therapeutic value and safety issues related to COX-2 inhibition.
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PMID:The "aspirin" of the new millennium: cyclooxygenase-2 inhibitors. 1104 Aug 51


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