Constitutive expression and localization of COX-1 and COX-2 in rabbit iris and ciliary body

HGF mediates the anti-inflammatory effects of PRP on injured tendons

Platelet-rich plasma (PRP) containing hepatocyte growth factor (HGF) and other growth factors are widely used in orthopaedic/sports medicine to repair injured tendons. While PRP treatment is reported to decrease pain in patients with tendon injury, the mechanism of this effect is not clear. Tendon pain is often associated with tendon inflammation, and HGF is known to protect tissues from inflammatory damages. Therefore, we hypothesized that HGF in PRP causes the anti-inflammatory effects. To test this hypothesis, we performed in vitro experiments on rabbit tendon cells and in vivo experiments on a mouse Achilles tendon injury model. We found that addition of PRP or HGF decreased gene expression of COX-1, COX-2, and mPGES-1, induced by the treatment of tendon cells in vitro with IL-1β. Further, the treatment of tendon cell cultures with HGF antibodies reduced the suppressive effects of PRP or HGF on IL-1β-induced COX-1, COX-2, and mPGES-1 gene expressions. Treatment with PRP or HGF almost completely blocked the cellular production of PGE2 and the expression of COX proteins. Finally, injection of PRP or HGF into wounded mouse Achilles tendons in vivo decreased PGE2 production in the tendinous tissues. Injection of platelet-poor plasma (PPP) however, did not reduce PGE2 levels in the wounded tendons, but the injection of HGF antibody inhibited the effects of PRP and HGF. Further, injection of PRP or HGF also decreased COX-1 and COX-2 proteins. These results indicate that PRP exerts anti-inflammatory effects on injured tendons through HGF. This study provides basic scientific evidence to support the use of PRP to treat injured tendons because PRP can reduce inflammation and thereby reduce the associated pain caused by high levels of PGE2.

Cyclooxygenase-2 expression in the normal human eye and its expression pattern in selected eye tumours

PURPOSE

Cyclooxygenase-2 (COX-2) is an enzyme involved in neoplastic processes. The purpose of the present study is to investigate COX-2 expression in the normal human eye and the expression pattern in selected eye tumours involving COX-2 expressing cells.

METHODS

Immunohistochemical staining using antibodies against COX-2 was performed on paraffin sections of normal human eyes and selected eye tumours arising from cells expressing COX-2.

RESULTS

Cyclooxygenase-2 expression was found in various structures of the normal eye. Abundant expression was seen in the cornea, iris, ciliary body and retina. The COX-2 expression was less in tumours deriving from the ciliary epithelium and also in retinoblastoma.

CONCLUSION

Cyclooxygenase-2 is constitutively expressed in normal human eyes. The expression of COX-2 is much lower in selected eye tumours involving COX-2 expressing cells.

Cyclo-oxygenase enzyme in the perilymph of human inner ear

CONCLUSIONS

Cyclo-oxygenase-2 (COX-2) enzyme would not appear to be constitutively expressed in human perilymph while it is always induced in the perilymph of patients affected by sensorineural hearing loss (SNHL). The COX-2 isoform may be involved in hearing loss and, therefore, pathological states of the inner ear should possibly be further analyzed to clarify the clinical relevance of prostaglandin and selective COX-2 antagonist therapy.

OBJECTIVES

Perilymph samples from a group of patients with bilateral SNHL and another with conductive hearing loss were collected to evaluate the presence of the COX-2 enzyme. The possible correlation between different causes of deafness and the expression of COX-2 in the human ear was studied.

METHODS

A prospective clinical study of 14 patients with severe or profound hearing loss who underwent cochlear implant surgery and 4 patients with conductive hearing loss who underwent stapes surgery was carried out. Western blot analysis of perilymph samples was performed with monoclonal anti-human COX-2 antibody.

RESULTS

COX-2 enzyme was detected in all patients affected by SNHL and was absent in all those with conductive hearing loss due to otosclerosis.

Ocular penetration and anti-inflammatory activity of ketorolac 0.45% and bromfenac 0.09% against lipopolysaccharide-induced inflammation

PURPOSE

Anti-inflammatory activity of topical nonsteroidal anti-inflammatory drugs is mediated by suppression of cyclooxygenase (COX) isoenzymes. This study compared ocular penetration and inflammation suppression of topical ketorolac 0.45% and bromfenac 0.09% ophthalmic solutions in a rabbit model.

METHODS

At hour 0, 36 rabbits received ketorolac 0.45%, bromfenac 0.09%, or an artificial tear 3 times once every 20 min. Half of the rabbits in each group then received intravenous injections of lipopolysaccharide (LPS) and fluorescein isothiocyanate (FITC)-dextran at hour 1, and the other half at hour 10. Aqueous and iris-ciliary body (ICB) samples were collected in the former group at hour 2 (peak) and in the latter group at hour 11 (trough) An additional group of 6 animals received only FITC-dextran, and samples were collected 1 h later. Peak and trough nonsteroidal anti-inflammatory drug concentrations were compared with previously determined half-maximal inhibitory concentrations (IC(50)) for COX isoenzymes.

RESULTS

Peak and trough aqueous and ICB concentrations of ketorolac were at least 7-fold or greater than those of bromfenac. At peak levels, both ketorolac 0.45% and bromfenac 0.09% significantly inhibited LPS-induced aqueous prostaglandin E(2) and FITC-dextran elevation (P < 0.01). At trough, both study drugs significantly inhibited LPS-induced aqueous prostaglandin E(2) elevation (P < 0.05), but only ketorolac 0.45% significantly reduced LPS-induced aqueous FITC-dextran elevation (P < 0.01). Aqueous and ICB ketorolac concentrations exceeded its IC(50) for COX-1 and COX-2 at peak and trough. Aqueous and ICB bromfenac levels exceeded its IC(50) for COX-2 at peak and trough, but not for COX-1 at trough aqueous levels and peak and trough ICB levels.

CONCLUSIONS

Both ketorolac 0.45% and bromfenac 0.09% effectively suppressed inflammation at peak. At trough, only ketorolac 0.45% effectively suppressed inflammation as measured by FITC-dextran leakage. The difference in inflammation suppression may be due to differences in tissue concentrations and/or greater COX-1 suppression by ketorolac 0.45%.

Genetic deletion of COX-2 diminishes VEGF production in mouse retinal Müller cells

Non-steroidal anti-inflammatory drugs (NSAIDs), which inhibit COX activity, reduce the production of retinal VEGF and neovascularization in relevant models of ocular disease. We hypothesized that COX-2 mediates VEGF production in retinal Müller cells, one of its primary sources in retinal neovascular disease. The purpose of this study was to determine the role of COX-2 and its products in VEGF expression and secretion. These studies have more clearly defined the role of COX-2 and COX-2-derived prostanoids in retinal angiogenesis. Müller cells derived from wild-type and COX-2 null mice were exposed to hypoxia for 0-24 h. COX-2 protein and activity were assessed by western blot analysis and GC-MS, respectively. VEGF production was assessed by ELISA. Wild-type mouse Müller cells were treated with vehicle (0.1% DMSO), 10 microM PGE(2), or PGE(2) + 5 microM H-89 (a PKA inhibitor), for 12 h. VEGF production was assessed by ELISA. Hypoxia significantly increased COX-2 protein (p < 0.05) and activity (p < 0.05), and VEGF production (p < 0.0003). COX-2 null Müller cells produced significantly less VEGF in response to hypoxia (p < 0.05). Of the prostanoids, PGE(2) was significantly increased by hypoxia (p < 0.02). Exogenous PGE(2) significantly increased VEGF production by Müller cells (p < 0.0039), and this effect was inhibited by H-89 (p < 0.055). These data demonstrate that hypoxia induces COX-2, prostanoid production, and VEGF synthesis in Müller cells, and that VEGF production is at least partially COX-2-dependent. Our study suggests that PGE(2), signaling through the EP(2) and/or EP(4) receptor and PKA, mediates the VEGF response of Müller cells.

Ocular prostaglandin production and morphology in mice lacking a single isoform of cyclooxygenase

Prostaglandins have many important roles in ocular physiology and are used clinically for the treatment of glaucoma. The aim of this study was to analyse the contribution of each cyclooxygenase isoform to ocular prostaglandin production using isoform-specific knockout mice. Ex vivo PGE(2), 6-keto-PGF(1alpha), and TXB(2) production was measured from whole eyes, corneal tissue, uveoscleral tissue, lens, retina and optic nerve using enzyme-linked immunosorbant assays. Ocular immunohistochemical and histological analysis was also conducted for each genotype. Levels of each of the prostaglandins measured were significantly decreased in the corneal tissue, uveoscleral tissue, lens, retina and optic nerve of COX-1(-/-) mice in comparison with wild-type mice. In contrast, COX-2(-/-) mice had similar levels of ocular prostaglandin production to wild-type mice. These results suggest that COX-1 is the principal isoform responsible for prostaglandin production in the mouse eye. The absence of COX-1 or COX-2 did not appear to effect ocular development in these mice.

Comparison of tepoxalin, carprofen, and meloxicam for reducing intraocular inflammation in dogs

OBJECTIVE

To compare effects of orally administered tepoxalin, carprofen, and meloxicam for controlling aqueocentesis-induced anterior uveitis in dogs, as determined by measurement of aqueous prostaglandin E(2) (PGE(2)) concentrations.

ANIMALS

38 mixed-breed dogs.

PROCEDURES

Dogs were allotted to a control group and 3 treatment groups. Dogs in the control group received no medication. Dogs in each of the treatment groups received an NSAID (tepoxalin, 10 mg/kg, PO, q 24 h; carprofen, 2.2 mg/kg, PO, q 12 h; or meloxicam, 0.2 mg/kg, PO, q 24 h) on days 0 and 1. On day 1, dogs were anesthetized and an initial aqueocentesis was performed on both eyes; 1 hour later, a second aqueocentesis was performed. Aqueous samples were frozen at -80 degrees C until assayed for PGE(2) concentrations via an enzyme immunoassay kit.

RESULTS

Significant differences between aqueous PGE(2) concentrations in the first and second samples from the control group indicated that aqueocentesis induced uveitis. Median change in PGE(2) concentrations for the tepoxalin group (10 dogs [16 eyes]) was significantly lower than the median change for the control group (8 dogs [16 eyes]), carprofen group (9 dogs [16 eyes]), or meloxicam group (9 dogs [16 eyes]). Median changes in PGE(2) concentrations for dogs treated with meloxicam or carprofen were lower but not significantly different from changes for control dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

Tepoxalin was more effective than carprofen or meloxicam for controlling the production of PGE(2) in dogs with experimentally induced uveitis. Tepoxalin may be an appropriate choice when treating dogs with anterior uveitis.

Association of COX2 functional polymorphisms and the risk of vitiligo in Chinese populations

BACKGROUND

Cyclooxygenase-2 (COX2) plays an important role in the production of prostaglandin E2 (PGE2), which is made by epidermal keratinocytes in response to ultraviolet radiation (UVR). PGE2 is important for the proliferation and melanogenesis of epidermal melanocytes, the loss of which leads to vitiligo. COX2-1195A>G, -765G>C, and -8473T>C polymorphisms may influence the mRNA levels of COX2 and affect the production of PGE2 subsequently. Therefore, we supposed that these polymorphisms may be associated with vitiligo.

OBJECTIVE

The aim of the study was to elucidate the association between three functional COX2 polymorphisms and the risk of vitiligo.

METHODS

This was a hospital-based, case-control study of 755 vitiligo patients and 774 vitiligo-free controls who were frequency matched by age and sex. We genotyped COX2-1195A>G, -765G>C, and -8473T>C polymorphisms by using PCR-restriction fragment length polymorphism (RFLP) method and assessed their respective associations with the risk of vitiligo in Han Chinese populations.

RESULTS

We found a statistically significant increased risk of vitiligo to be associated with the COX2-1195 G variant allele (p=0.004). Significantly higher vitiligo risks were found among subgroups with these characteristics: age >20 years, male, active, nonsegmental vitiligo, and onset age >20 years. In addition, the interaction between COX2-1195 and COX2-8473 was statistically significant (p=0.004).

CONCLUSION

For the first time, we provide evidence that functional polymorphisms in the COX2 gene may influence the risk of vitiligo in Han Chinese populations, suggesting new clues that help to clarify the pathogenesis of vitiligo. Larger studies are needed to verify these findings.

Short-term/low-dose aspirin-induced duodenal erosions are not dependent on Helicobacter pylori infection, cyclooxygenase expression and prostaglandin E2 levels

OBJECTIVE

The mechanisms of interaction between Helicobacter pylori infection and low-dose aspirin in the induction of duodenal erosions are not fully understood. The aim of this study was to investigate the effects of low-dose aspirin on the induction of duodenal erosions, the expression of cyclooxygenases and prostaglandin (PG)-E(2) levels in healthy subjects according to their H. pylori status.

MATERIAL AND METHODS

Twenty healthy volunteers (H. pylori-negative n=10, H. pylori-positive n=10) received 100 mg aspirin/day for 1 week. During esophagogastroduodenoscopy, duodenal biopsies were taken before and at days 1, 3, and 7 of medication. COX-1 and -2 expressions were analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR), and immunohistochemistry; mucosal PGE(2) levels were determined by ELISA. Three months after successful eradication of infection, nine H. pylori-positive subjects repeated the protocol.

RESULTS

Aspirin-induced duodenal erosions occurred independently of whether H. pylori infection was present or not. There was no difference in duodenal COX-1 and COX-2 expression among the groups and expression was not affected by aspirin. Basal duodenal PGE(2) levels were similar among the different groups (H. pylori-negative 4.3+/-4.2, H. pylori-positive 5.2+/-1.3, following H. pylori eradication 5.2+/-1.4 ng/microg protein) and were not affected by low-dose aspirin.

CONCLUSIONS

In healthy subjects, low-dose aspirin-induced duodenal erosions are not influenced by H. pylori status. Low-dose aspirin medication for one week does not affect either cyclooxygenase expression or duodenal PGE(2) levels and therefore is likely to induce duodenal damage mainly through topical toxicity.

Comparison between two cyclooxygenase inhibitors in an experimental dry eye model in albino rabbits

The purpose of this study was to compare the topical anti-inflammatory effects of the nonselective cyclooxygenase (COX) inhibitor, ketorolac, with the selective COX-2 inhibitor, nimesulide, in an animal model of dry eye in albino rabbits. All animals were examined by the Schirmer test, tear break-up time (TBUT) and fluorescein corneal staining test. Dry eye model showed significant reduction in tear volume, TBUT, corneal staining and histopathological signs of dryness and inflammation. On treating dry eye model with nimesulide 0.1% eye drops and ketorolac 0.5% eye drops, there were improvements in Schirmer test values, TBUT and fluorescein corneal staining and histopathologically reduced inflammatory reaction, with signs of healing and regeneration. Both nimesulide and ketorolac ameliorate atropine sulphate induced dry eye in albino rabbits. The use of selective COX-2 inhibitor, nimesulide, is preferred to avoid local and systemic side effects which may occur with the use of the nonselective COX inhibitor, ketorolac.

Immunohistochemical evaluation of cyclooxygenase expression in corneal squamous cell carcinoma in horses

OBJECTIVE

To evaluate expression of cyclooxygenase (COX)-1 and COX-2 in the cornea, eyelid, and third eyelid of healthy horses and those affected with squamous cell carcinoma (SCC) by use of immunohistochemical techniques.

ANIMALS

15 horses with SCC involving ocular tissues and 5 unaffected control horses.

PROCEDURES

SCC-affected tissues were obtained from the cornea (n = 5 horses), eyelid (5), and third eyelid (5). Site-matched control tissues were obtained from 5 horses unaffected with SCC. Tissue sections of affected and control cornea, eyelid, and third eyelid were stained immunohistochemically for COX-1 and COX-2 via standard techniques. Stain uptake was quantified by use of computer-assisted image analysis of digital photomicrographs.

RESULTS

Immunoreactivity for both COX-1 and COX-2 was significantly greater in equine corneas with SCC than in control corneas. No significant differences in COX-1 or COX-2 immunoreactivity were detected in eyelid and third-eyelid SCC, compared with site-matched control tissues.

CONCLUSIONS AND CLINICAL RELEVANCE

Immunoreactivity for COX-1 and COX-2 is high in equine corneal SCC, possibly indicating that COX plays a role in oncogenesis or progression of this tumor type at this site. Pharmacologic inhibition of COX may represent a useful adjunctive treatment for corneal SCC in horses.

Ophthalmic drug delivery considerations at the cellular level: drug-metabolising enzymes and transporters

Ophthalmic drugs typically achieve < 10% ocular bioavailability. A drug applied to the surface of the eye may cross ocular-blood barriers where it may encounter metabolising enzymes and cellular transporters before it distributes to the site of action. Characterisation of ocular enzyme systems and cellular transporters and their respective substrate selectivity have provided new insight into the roles these proteins may play in ocular drug delivery and distribution. Altered metabolism and transport have been proposed to contribute to a number of ocular disease processes including inflammation, glaucoma, cataract, dry eye and neurodegeneration. As ocular enzyme and transport systems are better characterised, their properties become an integral consideration in drug design and development.

ORAL ADMINISTRATION OF LUMIRACOXIB REDUCES CHOROIDAL NEOVASCULAR MEMBRANE DEVELOPMENT IN THE RAT LASER-TRAUMA MODEL

PURPOSE

To determine whether lumiracoxib, a highly selective cyclooxygenase-2 (COX-2) inhibitor that exhibits anti-inflammatory and antiangiogenic properties, can inhibit experimental choroidal neovascular membrane (CNVM) development induced by focal laser trauma in a well-characterized Brown Norway rat CNVM model.

METHODS

Over a 35-day period, 24 rats received daily oral gavage dosages of 20 mg/kg lumiracoxib in a 0.5% (w/v) suspension of sodium carboxymethylcellulose (CMC), while a control group received the 0.5% CMC suspension only. After 7 days, eight laser photocoagulation sites were placed concentrically around the optic disk to induce CNVMs. Thirty-five days later, fundus photography and fluorescein angiography (FA) were performed and eyes were processed for histopathologic analysis.

RESULTS

Masked FA grading of lesion sites revealed a small, but statistically significant difference (P<0.0001) in late stage staining intensity and leakage between the mean group scores of treated (1.4) and control (1.7) eyes. Histopathologic analysis demonstrated that the mean CNVM thickness +/- SD of 38 +/-19 microm (n=24 eyes, 175 photocoagulation sites) in the lumiracoxib-treated animals was reduced by 30% (P<0.001) compared to the CNVM mean thickness+/- SD of 54+/- 20 microm (n=24 eyes, 171 photocoagulation sites) in the control animals.

CONCLUSION

Systemic administration of the selective COX-2 inhibitor lumiracoxib results in a partial but significant reduction in CNVM development in the rat laser-trauma model and thus may be clinically beneficial as a potential inhibitor of CNVM formation in exudative age-related macular degeneration.

COX-2 expression in the guinea pig cochlea is partly altered by moderate sound exposure

The cyclooxygenase-2 isoform (COX-2) was found recently to be constitutively expressed in the guinea pig inner ear. To gain knowledge about its role in sound perception, alterations in the COX-2 level of moderate noise-stimulated cochleae were determined. Staining intensities were quantified in different regions using an immunohistochemical staining procedure and computer-assisted system. After 70 dB and 90 dB noise exposure for 1 h at 8000 Hz, COX-2 downregulation was observed in the organ of Corti, which was most prominent in Deiters' cells near Hensen cells and outer hair cells. In pillar cells, COX-2 levels were only slightly reduced after 70 dB but strongly diminished after 90 dB exposure. In Hensen cells, COX-2 was downregulated after 70 dB stimulation, revealing a decreasing COX-2 content from the third to the first turn of the cochlea and a homogeneously reduced enzyme expression in all three turns after 90 dB. The COX-2 content in inner hair cells was nearly identical to unexposed cochleae after 70 dB exposure but significantly reduced after 90 dB stimulation. In spiral ganglion cells, stria vascularis, spiral ligament and limbus, COX-2 expression was unchanged after 70 dB and 90 dB. We suggest that alterations in COX-2 expression might contribute to diminished sensitivity at the cochlea after noise exposure to reduce subsequent noise distress, termed sound conditioning.

Selective COX-2 inhibitors and risk of myocardial infarction

Selective inhibitors of cyclooxygenase-2 (COX-2, 'coxibs') are highly effective anti-inflammatory and analgesic drugs that exert their action by preventing the formation of prostanoids. Recently some coxibs, which were designed to exploit the advantageous effects of non-steroidal anti-inflammatory drugs while evading their side effects, have been reported to increase the risk of myo cardial infarction and atherothrombotic events. This has led to the withdrawal of rofecoxib from global markets, and warnings have been issued by drug authorities about similar events during the use of celecoxib or valdecoxib/parecoxib, bringing about questions of an inherent atherothrombotic risk of all coxibs and consequences that should be drawn by health care professionals. These questions need to be addressed in light of the known effects of selective inhibition of COX-2 on the cardiovascular system. Although COX-2, in contrast to the cyclooxygenase-1 (COX-1) isoform, is regarded as an inducible enzyme that only has a role in pathophysiological processes like pain and inflammation, experimental and clinical studies have shown that COX-2 is constitutively expressed in tissues like the kidney or vascular endothelium, where it executes important physiological functions. COX-2-dependent formation of prostanoids not only results in the mediation of pain or inflammatory signals but also in the maintenance of vascular integrity. Especially prostacyclin (PGI(2)), which exerts vasodilatory and antiplatelet properties, is formed to a significant extent by COX-2, and its levels are reduced to less than half of normal when COX-2 is inhibited. This review outlines the rationale for the development of selective COX-2 inhibitors and the pathophysiological consequences of selective inhibition of COX-2 with special regard to vasoactive prostaglandins. It describes coxibs that are current ly available, evaluates the current knowledge on the risk of atherothrombotic events associated with their intake and critically discusses the consequences that should be drawn from these insights.

Effects of intravenous administration of FR122047 (a selective cyclooxygenase 1 inhibitor) and FR188582 (a selective cyclooxygenase 2 inhibitor) on prostaglandin-E2-induced aqueous flare elevation in pigmented rabbits

PURPOSE

Two isoforms of cyclooxygenase (COX-1 and COX-2) exist. To determine in vivo effects of the intravenous administration of FR122047 (a selective COX-1 inhibitor), FR188582 (a selective COX-2 inhibitor), diclofenac sodium or dexamethasone phosphate disodium on prostaglandin-E2 (PGE2)-induced aqueous flare elevation and mRNA levels for COX-1 and COX-2 in pigmented rabbits.

METHODS

To produce aqueous flare elevation in rabbits, PGE2, 25 microg/ml, was applied to the cornea with the use of a glass cylinder. FR122047, FR188582, diclofenac sodium or dexamethasone phosphate disodium was intravenously injected before PGE2 application. Aqueous flare was measured with a laser flare-cell meter. The mRNA levels for COX-1 and COX-2 in the iris-ciliary body were determined by real-time polymerase chain reaction.

RESULTS

FR122047, FR188582 and diclofenac sodium (15 micromol/kg each) injected intravenously 30 min before PGE2 application inhibited 29 +/- 5, 40 +/- 12 and 50 +/- 9% of aqueous flare elevation, respectively. Simultaneous injection of FR122047 (15 micromol/kg) and FR188582 (15 micromol/kg) 30 min before PGE2 application inhibited 61 +/- 8% of flare elevation. Dexamethasone phosphate disodium (15 micromol/kg) injected intravenously 300 min before PGE2 application inhibited 68 +/- 8% of aqueous flare elevation. Less than 3-fold changes in mRNA levels for COX-1 and COX-2 in the iris-ciliary body were noted after PGE2, FR122047, FR188582, diclofenac sodium or dexamethasone phosphate disodium treatment.

CONCLUSION

It is possible that enzyme activities of both COX-1 and COX-2 may be involved in the mechanism of PGE2-induced aqueous flare elevation in pigmented rabbits.

Localization of prostanoid receptors and cyclo-oxygenase enzymes in Guinea pig and human cochlea

Endogenous production of prostaglandins has been demonstrated in the cochlea, but no information is available on the distribution of the cyclo-oxygenase (COX) enzymes, or prostanoid receptors in the cochlea. The purpose of the present study was to investigate the localization of the FP, EP(1) and EP(3) prostanoid receptors as well as the COX-1 and COX-2 enzymes in the cochlea of guinea pig and man. Cochleas were processed for immunohistochemistry using routine techniques. Appropriate controls comprised incubation with specific blocking peptides, or incubation without primary antibodies. Both in guinea pig and man the FP prostanoid receptor was abundantly distributed in the cochlea, e.g., in stria vascularis, the spiral ligament, spiral ganglion, and organ of Corti. The immunohistochemical staining of the EP(1) and EP(3) receptors in the same structures was significantly weaker and sometimes lacking altogether (e.g., EP(3) receptor in human cochlea). Weak, but mostly consistent immunostaining of the COX-1 enzyme was found in the cochlear structures. The COX-2 enzyme appeared to be lacking. The abundant distribution of the FP receptor in several important cochlear structures both in guinea pig and man suggests a physiological function for PGF(2alpha) in the cochlea. The COX-1 enzyme seems to be constitutively expressed in the cochlea in contrast to COX-2.

Cyclooxygenase-2 expression in the cornea of dogs with keratitis

Cyclooxygenase-2 (COX-2) can be overexpressed at inflammatory sites, leading to the generation of proinflammatory prostanoids. Selective inhibitors of COX-2 have potential use in treating inflammatory conditions including ophthalmic diseases in veterinary medicine. Keratitis is considered the most common inflammatory eye disease in dogs. In this study we evaluated the expression of COX-2 in normal dog eyes and in dog eyes with keratitis by immunohistochemistry using isoform-specific antibodies. In the normal eye (n = 4), no COX-2 immunoreactivity was observed in the cornea. In keratitis, COX-2 (n = 12) expression was observed in all corneal layers (epithelium, stromal cells, and endothelium). COX-2 immunoreactivity was also noted in the stromal and epithelial cells of the iris and the stromal cells of the trabecular meshwork. These data indicate that COX-2 may play a pathophysiologic role in keratitis and suggest potential therapeutic implications of prostaglandin modulation in inflammatory eye diseases.

Enhanced expression of Cyclooxygenase-2 in glaucomatous dog eyes

OBJECTIVE

Cyclooxygenase-2 (COX-2)-derived prostaglandins (PGs) are shown to play important pathophysiologic roles in various disease states. Recently, the effectiveness of topical PGs in reducing intraocular pressure (IOP) has stimulated further interest in the physiologic function of COX-2 and PGs in normal and glaucomatous eyes. Therefore, we investigated the cell-type distribution and expression of COX-2 in normal and glaucomatous dog eyes.

PROCEDURES

Using isoform-specific antibodies, we immunohistochemically evaluated COX-2 expression in formalin-fixed and paraffin-embedded normal (n = 5) and glaucomatous (n = 17) dog eyes.

RESULTS

In the normal eyes, only minimal COX-2 immunoreactivity was observed in the ciliary epithelium. In the glaucomatous eyes, COX-2 expression was further observed in the cornea and corneoscleral limbus. In the cornea, moderate to strong COX-2 expression was observed in all corneal layers (epithelium, stromal cells and endothelium), with the greatest expression present in the epithelial layer. In the corneoscleral limbus area, COX-2 immunoreactivity was noted in the stromal cells of sclera, trabecular meshwork and endothelial cells of the angular aqueous plexus.

CONCLUSIONS

Increased expression of COX-2 in dog glaucomatous eyes suggests that COX-2-derived PGs may have a potential role in the pathogenesis of canine glaucoma.

Expression and localization of cyclooxygenase-1 and -2 in human sporadic amyotrophic lateral sclerosis

Prostaglandins (PGs) are critical mediators of physiologic processes and inflammation. They are produced by two different isoforms of the cyclooxygenase (COX) enzyme, namely COX-1 and COX-2. In particular COX-2 was demonstrated to be crucial for PG-synthesis in inflammation. Recently, inhibition of COX-2 was shown to prevent the loss of motor neurons in a model of amyotrophic lateral sclerosis (ALS). Furthermore, spinal COX-2 expression was shown to be increased in transgenic mice that produce an ALS-like syndrome. Therefore, we investigated the expression of COX-1 and COX-2 in the spinal cord of seven human sporadic ALS patients by means of immunohistochemistry. Specimens from seven patients without any neurological disease served as controls. COX-2 expression was dramatically increased in the spinal cord of patients with ALS. Its protein was found in motor neurons, interneurons and glial cells. Statistical analysis showed a significantly higher expression of COX-2 in ALS for both neurons and glia. In contrast, COX-1 expression was predominantly confined to microglia and no apparent difference was detected between controls and ALS. In addition, we studied the concentration of prostaglandin E2 (PG E2) as a marker for COX activity in the cerebrospinal fluid of nine patients diagnosed for ALS and compared the results with those from nine patients without motor neuron disease. PG E2 levels were markedly increased in ALS cases (45.8 +/- 35.1 pg/mL) compared to the non-ALS specimens (15.8 +/- 3.7 pg/mL). The results of our study corroborate a potential role for COX-2 in the pathogenesis of motor neuron death in ALS. Selective COX-2 inhibition might therefore offer a new possibility in the treatment of human ALS. However, to determine the exact role of COX-2 in human ALS will require further research.

Transcription of prostanoid receptor genes and cyclooxygenase enzyme genes in cultivated human iridial melanocytes from eyes of different colours

Several prostaglandin analogues used for glaucoma treatment have been shown to cause increased iridial pigmentation as side-effect. In the present study we identified the types of prostanoid receptors and cyclooxygenase (COX) enzymes that are expressed in human iridial melanocytes isolated from eyes of different colours. Iris specimens were obtained during trabeculectomy surgery, or from enucleated eyes, and the iridial melanocytes were isolated and cultivated. The transcription of the DP, EP1, EP2, EP3, EP4, FP, IP and TP prostanoid receptor genes as well as the COX-1 and COX-2 enzyme genes was investigated using reverse transcriptase-polymerase chain reaction (RT-PCR). Of the prostanoid receptors the FP receptor gene was found to be most consistently transcribed in the melanocytes isolated from both blue- and hazel-coloured eyes. No RNA of the DP, EP2 and TP receptor genes could be detected, whereas the EP1, EP3, EP4 and IP receptor genes were found to be transcribed in melanocytes from some eyes. The COX-2 gene was found to be transcribed, but the COX-1 gene less consistently. There was no difference in gene transcription pattern between melanocytes originating from eyes treated with latanoprost, and eyes not previously treated with the prostaglandin. These results indicate that the FP prostanoid receptor gene is transcribed in cultivated human iridial melanocytes of both blue and hazel eyes, whereas the other prostanoid receptor genes seem to be transcribed much less frequently, or not at all. Surprisingly, the COX-2 rather than the COX-1 gene, was found to be transcribed in the melanocytes.

Cellular localization of cyclooxygenase-1 and cyclooxygenase-2 in the normal mouse, rat, and human retina

Prostaglandins, synthesized by cyclooxygenase (COX), regulate diverse neurophysiological actions such as regulation of autonomic responses, transmission of pain, generation of fever, control of sleep-wake cycle, synaptic signaling, and cross-talk between neurons and glia in the central nervous system. Although prostaglandins have been widely studied in the anterior segment tissues of the eye, relatively little is known about prostaglandins in the neural retina. By using immunohistochemistry, we have compared the cellular expression and localization of COX-1 and COX-2 in the normal mouse, rat, and human retina. In the normal mouse retina, COX-1 immunoreactivity is present in the outer segments of photoreceptor cells, horizontal cells, microglia, retinal ganglion cells, and displaced amacrine cells. In the normal rat retina, COX-1 immunoreactivity is present in microglia, retinal ganglion cells, and displaced amacrine cells. In the normal human retina, COX-1 immunoreactivity is present in microglia, astrocytes, retinal ganglion cells, and displaced amacrine cells. In the normal mouse and rat retina, COX-2 immunoreactivity is present in processes of the outer plexiform layer and in certain amacrine cells and retinal ganglion cells. In the normal human retina, COX-2 immunoreactivity is only present in processes of the outer plexiform layer. These results suggest that prostaglandins, synthesized by COX-1 or COX-2, may contribute to normal physiological and homeostatic functions in the retina.

Production of prostaglandin e(2) by iridial melanocytes exposed to latanoprost acid, a prostaglandin F(2 alpha) analogue

Several prostaglandin analogues used for glaucoma treatment cause increased pigmentation of the iris. The purpose of the present study was investigate whether latanoprost, a PGF(2 alpha) analogue, has any effect on the production of endogenous prostaglandins in iridial melanocytes, which could be important in the mechanism leading to increased pigmentation. Bovine and human iridial melanocytes in culture were used for the experiments. Production of endogenous prostaglandins was measured by enzyme immunoassay, and the melanin content was measured spectrophotometrically. In bovine iridial melanocytes, latanoprost acid caused a significant increase of the PGE(2) production, which could be blocked by indomethacin and NS398, indicating an involvement of cyclo-oxygenase 2. In order to study the selectivity of the phenomenon other endogenous substances/drugs were tested, e.g., acetylcholine, carbachol, noradrenaline, neuropeptide Y, substance P and alpha-MSH, but none was found to have any significant effect. Human iridial melanocytes also responded to latanoprost acid with increased production of PGE(2) and in 1 out of 5 individuals increased melanogenesis coincided with increased PGE(2) production. In bovine iridial melanocytes, latanoprost acid did not stimulate melanogenesis. These results indicate that latanoprost acid cause enhanced formation of endogenous prostaglandins that may have auto- and/or paracrine effects in the melanocytes, possibly associated with melanogenesis.

Cyclooxygenase-2--10 years later

The enzyme cyclooxygenase (COX) catalyzes the first step of the synthesis of prostanoids. In the early 1990s, COX was demonstrated to exist as two distinct isoforms. COX-1 is constitutively expressed as a "housekeeping" enzyme in most tissues. By contrast, COX-2 can be up-regulated by various pro-inflammatory agents, including lipopolysaccharide, cytokines, and growth factors. Whereas many of the side effects of nonsteroidal anti-inflammatory drugs (NSAIDs) (e.g., gastrointestinal ulceration and bleeding, platelet dysfunctions) are caused by a suppression of COX-1 activity, inhibition of COX-2-derived prostanoids facilitates the anti-inflammatory, analgesic, and antipyretic effects of NSAIDs. During the past few years specific inhibitors of the COX-2 enzyme have emerged as important pharmacological tools for treatment of pain and arthritis. However, although COX-2 was initially regarded as a source of pathological prostanoids only, recent studies have indicated that this isoenzyme mediates a variety of physiological responses within the organism. The present review assesses recent advances in COX-2 research, with particular emphasis on new insights into pathophysiological and physiological functions of this isoenzyme.