Flare Elevation In Pigmented Rabbits Research Articles

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 µg/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 µmol/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 µmol/kg) and FR188582 (15 µmol/kg) 30 min before PGE₂ application inhibited 61 ± 8% of flare elevation. Dexamethasone phosphate disodium (15 µmol/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.

Effects of Topical Instillation of Traditional Herbal Medicines, Herbal Extracts, and Their Components on Prostaglandin E 2-induced Aqueous Flare Elevation in Pigmented Rabbits

Purpose: To evaluate the effect of topical instillation of traditional herbal medicines, herbal extracts, and their components on the elevation of aqueous flare induced by prostaglandin E 2 (PGE 2) in pigmented rabbits. Methods: Transcorneal diffusion of 25 μg/mL of PGE 2 was carried out through a glass cylinder placed on the cornea to induce aqueous flare elevation in pigmented rabbits. Traditional herbal medicines, herbal extracts, and their components were topically instilled before the PGE 2 application. Aqueous flare was measured with a laser flare-cell meter. Results: Two instillations, 60 and 30 minutes before PGE 2, of Kakkon-to, Sairei-to, Orengedoku-to, Senkanmeimoku-to, Scutellariae radix extract, Coptidis rhizoma extract, Gardeniae fructus extract, Phellodendri cortex extract, baicalein, baicalin, wogonin, crocetin, berberine, or glycyrrhizine did not inhibit the elevation induced by PGE 2. Two instillations, 60 and 30 minutes before PGE 2, of a Ligusticum wallichii extract (100 mg/mL) inhibited the elevation by 20%. Two instillations (5 and 3 hours before PGE 2) of baicalein (1 mg/mL) or baicalin (5 mg/mL) inhibited the elevation by 16% and 24%, respectively. Two instillations, 5 and 3 hours before PGE 2, of wogonin, crocetin, berberine, or glycyrrhizine did not inhibit the elevation. Conclusion: Two instillations of Ligusticum wallichii extract 60 and 30 minutes before the PGE 2, and two instillations of baicalein or baicalin, 5 and 3 hours before the PGE 2, inhibited the PGE 2-induced aqueous flare elevation in pigmented rabbits.

Effects of Topical Mydriatics and Vasoconstrictors on Prostaglandin-E2-Induced Aqueous Flare Elevation in Pigmented Rabbits

We evaluated the effects of topical instillation of mydriatics and vasoconstrictors on prostaglandin E₂ (PGE₂) induced aqueous flare elevation in pigmented rabbits. Transcorneal diffusion of PGE₂ (25 µg/ml) by means of a glass cylinder produced aqueous flare elevation. Mydriatics (atropine sulfate, tropicamide, tropicamide plus phenylephrine hydrochloride, phenylephrine hydrochloride, and cyclopentolate hydrochloride) or vasoconstrictors (naphazoline nitrate and tramazoline hydrochloride) were topically administered before PGE₂ application. Aqueous flare was measured with a laser flare-cell meter. One or two instillations of atropine sulfate 1.0%, tropicamide 0.4%, tropicamide 0.5% plus phenylephrine hydrochloride 0.5%, phenylephrine hydrochloride 5.0%, cyclopentrate hydrochloride 1.0%, and naphazoline nitrate 0.05% did not inhibit PGE₂-induced aqueous flare elevation. Tramazoline hydrochloride 0.118% inhibited significantly (p < 0.05) PGE₂-induced aqueous flare elevation. It is possible that vasoconstriction may be involved partly in inhibition of PGE₂-induced aqueous flare elevation by some drugs in pigmented rabbits.

Effects of Topical Corticosteroids and Nonsteroidal Anti-Inflammatory Drugs on Prostaglandin E2-Induced Aqueous Flare Elevation in Pigmented Rabbits

We evaluated the effects of anti-inflammatory potency of corticosteroids and nonsteroidal anti-inflammatory drugs on prostaglandin E₂ (PGE₂)-induced aqueous flare elevation in pigmented rabbits. Transcorneal diffusion of PGE₂, 25 µg/ml (7.09 × 10^–2 mmol/l), with the use of a glass cylinder was achieved to produce aqueous flare elevation. Anti-inflammatory drugs were topically administered once before PGE₂ application. Aqueous flare was measured with a laser flare-cell meter. Topical single instillation of dexamethasone sodium metasulfobenzoate 0.1%, dexamethasone sodium phosphate 0.1%, and fluorometholone 0.1% 6 h before PGE₂ application inhibited 56, 59, and 43% of flare elevation, respectively. Topical single instillation of bromfenac sodium 0.1% and pranoprofen 0.1% 1 h before PGE₂ application inhibited 33 and 15% of flare elevation, respectively. Indomethacin 0.5% did not inhibit flare elevation. Corticosteroid eyedrops needed several hours from topical instillation to exhibit inhibition of flare elevation. Most nonsteroidal anti-inflammatory drug eyedrops inhibited aqueous flare elevation when instilled 1 h before PGE₂ application.

Effect of Topical Betaxolol on the Acute Rise of Aqueous Flare Induced by Highly Selective Agonists for Prostaglandin E2 Receptor Subtypes in Pigmented Rabbits

Purpose: To evaluate the role of topical betaxolol on experimental ocular inflammation in rabbits. Method: Transcorneal diffusion of highly selective agonists for prostaglandin E₂ receptor subtypes (EP), 25 µg/ml, with the use of a glass cylinder, was performed to produce aqueous flare elevation in pigmented rabbits. Betaxolol was topically administered before EP agonist application. Aqueous flare was measured with a laser flare cell meter. Results: Performing topical instillation of 0.5% betaxolol 4 times inhibited 52 ± 9% of EP2-agonist (ONO-AE1-259-01)-induced aqueous flare elevation. The inhibition of flare elevation was dependent on the number of betaxolol instillations. Betaxolol did not suppress the elevation induced by an EP4 agonist (ONO-AE1-392). Conclusion: Betaxolol inhibited EP2-agonist-induced aqueous flare elevation in pigmented rabbits.

Effect of Topical Iganidipine on Experimental Elevation of Aqueous Flare Induced by Prostaglandin E2 and EP Agonists in Pigmented Rabbits

We evaluated the role of topical iganidipine on experimental aqueous flare elevation in rabbits. Transcorneal diffusion of prostaglandin E₂ (PGE₂), 25 µg/ml or 7.09 × 10^–2 mmol/l, or highly selective agonists for prostaglandin E₂ receptor subtypes (EP), 25 µg/ml, was achieved with the use of a glass cylinder to produce aqueous flare elevation in pigmented rabbits. Iganidipine was topically administered before application of PGE₂ or EP agonists. Aqueous flare was measured with a laser flare cell meter. Topical instillation of 0.1% iganidipine once or twice inhibited 64 ± 8% (p < 0.01) and 84 ± 9% (p < 0.01) of PGE₂-induced aqueous flare elevation, respectively. Two instillations of 0.1% iganidipine inhibited 95 ± 5% (p < 0.01) of EP2-agonist(ONO-AE1-259-01)-induced flare elevation and 98 ± 3% (p < 0.01) of EP4-agonist(ONO-AE1-392)-induced flare rise. Topical iganidipine may have anti-inflammatory activity in the eye.

Effects of Orengedoku-to and Scutellariae radix extract on aqueous flare elevation induced by intravitreal IL-1alpha in pigmented rabbits.

We investigated the effects of Orengedoku-to (huanglian-jie-du-tang in Chinese) and Scutellariae radix extract on experimental aqueous flare elevation in pigmented rabbits. To produce the elevation of aqueous flare in rabbits, interleukin-1 alpha (IL-1alpha) was injected intravitreally. Animals were pretreated with oral administration of 150 g/day of food containing 0.07%, 0.2% or 0.7% (w/w) Orengedoku-to; or 0.02%, 0.07% or 0.2% Scutellariae radix extract for 5 days. The animals were further treated with the same food for 7 days after intravitreal injection of IL-1alpha. Aqueous flare was measured with a laser flare-cell meter. Treatment with 0.2% or 0.7% Orengedoku-to and 0.07% or 0.2% Scutellariae radix extract significantly (p < 0.05) suppressed elevation of aqueous flare induced by IL-1alpha. Thus, orengedoku-to and Scutellariae radix extract have an inhibitory effect on experimental elevation of aqueous flare induced by IL-1alpha in rabbits.

Effect of Topical Betaxolol on Acute Rise of Aqueous Flare Induced by Prostaglandin E 2 in Pigmented Rabbits

Purpose: To evaluate the effects of topical betaxolol on experimental ocular inflammation. Methods: Transcorneal diffusion of 25 μg/mL (7.09 × 10 −2 mmol/L) of prostaglandin E 2 (PGE 2), placed in a glass cylinder, was employed to induce aqueous flare elevation in pigmented rabbits. Betaxolol was administered topically before PGE 2 application. Aqueous flare was measured with a laser flare cell meter. Results: Four-, two-, and one-time topical instillations of betaxolol inhibited the PGE 2-induced aqueous flare elevation by 44% ± 8%, 32 ± 7%, and 8 ± 6%(mean ± SD), respectively. The inhibition of flare elevation was dependent on the number of betaxolol instillations. Conclusion: Topical betaxolol has an inhibitory effect on PGE 2-induced aqueous flare elevation in rabbit eyes.

Aqueous flare elevation induced by transcorneal application of highly selective agonists for prostaglandin E2 receptor subtypes in pigmented rabbits: Effect of tetramethylpyrazine

We examined the disruptive effect of highly selective agonists for prostaglandin E 2 receptor subtypes (EP 1, EP 2, EP 3 and EP 4) on the blood-aqueous barrier, and evaluated the inhibitory effect of tetramethylpyrazine, an active component of Ligusticum wallichii, on the elevation of aqueous flare induced by the EP agonists in pigmented rabbits. Highly selective EP agonists (ONO-DI-004, EP 1 agonist; ONO-AE1-259-01, EP 2 agonist; ONO-AE-248, EP 3 agonist; ONO-AE1-329, EP 4 agonist) at 12.5 to 250 μg/ml were transcorneally administered to the eyes of pigmented rabbits using a glass cylinder. Animals were pretreated intravenously with tetramethylpyrazine (10 or 30 mg/kg) 30 minutes before application of the EP 2 or the EP 4 agonist. Aqueous flare was measured using a laser flare-cell meter. Aqueous flare intensity was expressed as the area under the curve (AUC) in arbitrary units. After administration of ONO-AE1-259-01 or ONO-AE1-329, aqueous flare increased and then gradually decreased. ONO-DI-004 and ONO-AE-248 had almost no effect on aqueous flare elevation. The AUC of eyes in rabbits pretreated with tetramethylpyrazine, 10 or 30 mg/kg i.v., was significantly smaller than that of eyes in rabbits treated with ONO-AE1-259-01 alone. The AUC of eyes in rabbits pretreated with tetramethylpyrazine, 10 or 30 mg/kg i.v., was not significantly smaller than that of eyes in rabbits treated with ONO-AE1-329 only. The results indicated that EP 2 and EP 4 agonists induced aqueous flare elevation in pigmented rabbits, and that tetramethylpyrazine inhibited the aqueous flare elevation induced by the EP 2 agonist but did not suppress the elevation induced by the EP 4 agonist.

Effects of α2-Adrenergic Agonists on Lipopolysaccharide-induced Aqueous Flare Elevation in Pigmented Rabbits

Purpose: To evaluate the effects of the α 2-adrenergic agonists (clonidine, apraclonidine, and guanfacine) on lipopolysaccharide (LPS)-induced aqueous flare elevation in pigmented rabbits. Methods: Anterior uveitis was induced with an intravenous injection of LPS (0.5 μg/kg) in an ear vein. The reproducibility of experimental uveitis induced by LPS (0.5 μg/kg) was also determined. Clonidine (0.01, 0.05, 0.25, or 1%), apraclonidine (1%), or guanfacine (1%) was topically instilled in the right eye 30 and 5 minutes before and 30 minutes after LPS application (N = 6 animals, respectively). Clonidine (0.25%) was topically administered three times at 30-minute intervals from 240 or 120 minutes before, or 120 or 240 minutes after LPS application (N = 6 animals, respectively). Then 1 mg/kg of yohimbine was injected into an ear vein 30 minutes before each topical three-time instillation of clonidine 1%, apraclonidine 1% or guanfacine 1% (N = 6 animals, respectively). Aqueous flare was measured with a laser flare-cell meter. Aqueous flare elevation was expressed as the area under the curve (AUC) in arbitrary units. Rabbits received the first LPS intravenous injection, and the control values of the AUC were obtained. Three months later, the α 2-agonist and the second LPS administration were given to the same animals. Results: The AUCs (5,184 ± 1,255 units) after the first application of LPS were similar to those (5,033 ± 1,290) after the second application 3 months after the first administration. Topical instillation of clonidine inhibited LPS-induced aqueous flare elevation in a dose-dependent manner (0.01–0.25%). Topical instillation of clonidine 1%, apraclonidine 1% or guanfacine 1% inhibited LPS-induced aqueous flare elevation by 98 ± 2.0% (mean ± SD), 86 ± 14% and 94 ± 5.7%, respectively. Pretreatment with intravenous yohimbine prevented the inhibitory effect on flare elevation induced by each agent. Conclusion: The present findings suggested that topical instillation of some α 2-agonists may have an inhibitory effect on ocular inflammation, which is mediated in part by α 2-receptors.

Effects of Topical Clonidine on Prostaglandin-E2-Induced Aqueous Flare Elevation in Pigmented Rabbits

We evaluated the role of topical clonidine on experimental ocular inflammation. Transcorneal diffusion of prostaglandin (PG) E₂, 7.09 × 10^–2 mmol/l, with the use of a glass cylinder was employed to produce aqueous flare elevation in pigmented rabbits. Clonidine was topically administered and yohimbine was injected intravenously. Aqueous flare was measured with a laser flare cell meter. Topical instillation of 0.25% clonidine inhibited 89% of PGE₂-induced aqueous flare elevation. Instillation of clonidine at 60 or 30 min before and 10 min after PGE₂ inhibited flare significantly. Pretreatment with intravenous yohimbine decreased the clonidine-induced inhibition of the flare elevation in a dose-dependent manner. It is possible that the anti-inflammatory action of topical clonidine may be mediated partly by α₂-receptors.

Effects of Kakkon-to and Sairei-to on Experimental Elevation of Aqueous Flare in Pigmented Rabbits

Purpose: To evaluate the possible inhibitory effects of Kakkon-to and Sairei-to, traditional Sino-Japanese herbal medicines, on experimental aqueous flare elevation in pigmented rabbits. Methods: Anterior uveitis was induced either by an application of prostaglandin E 2 (PGE 2), 10 μg/mL, to the cornea, or an intravenous injection of lipopolysaccharides (LPS), 0.5 μg/kg, in an ear vein. Dose dependency of experimental uveitis induced by LPS (0.1, 0.25, 0.5, or 1.0 μg/kg) was also determined. For pretreatment, about 150 g/day of food containing Kakkon-to (1% w/w) or Sairei-to (0.6% or 2% w/w) was given to two groups of animals for 5 days before experimental uveitis was induced. A third group of animals underwent pretreatment with betamethasone, 130 μg/kg, injection into an ear vein 4 hours before experimental uveitis was induced. A fourth group of rabbits with no herbal medicine or betamethasone pretreatment served as controls. Aqueous flare was measured using a laser flare-cell meter. Aqueous flare intensity was expressed as the area under the curve (AUC) in arbitrary units. Results: The increase in aqueous flare induced by LPS was dose-dependent. The AUC of PGE 2 (10 μg/mL) and LPS (0.5 μg/mL) induced aqueous flare elevations were 1,119 and 4,950 arbitrary units, respectively. Kakkon-to (AUC, 1,055) and Sairei-to (AUC, 965) did not inhibit the aqueous flare elevation induced by PGE 2. β-Methasone did inhibit the elevation (AUC, 271). Kakkon-to (AUC, 4,495) did not suppress the aqueous flare elevation induced by LPS. Both 0.6% and 2% Sairei-to (AUC, 2,478, and 978) and β-methasone (AUC, 443) did suppress the aqueous flare elevation induced by LPS significantly ( P < .05). Conclusion: Sairei-to could have an inhibitory effect on experimental anterior uveitis induced by LPS.

Effects of a nitric oxide synthase inhibitor on prostaglandin-induced aqueous flare elevation in pigmented rabbits.

To evaluate the possible role of nitric oxide in the pathogenesis of exogenous prostaglandin (PG) induced aqueous flare elevation, we examined the effect of NG-nitro-L-arginine methyl ester (L-NAME), an L-arginine analogue acting as a specific inhibitor of nitric oxide synthase, on the elevation of aqueous flare in pigmented rabbits. L-NAME was injected into the ear vein of the animals. PGE1, PGE2, and PGF2 alpha were administered topically to the cornea using a glass cylinder. Aqueous flare was measured using a laser flare cell meter. PGE1, PGE2, and PGF2 alpha increased the aqueous flare dose dependently (5-100 micrograms/ml). L-NAME inhibited PGE1-, PGE2-, or PGF2 alpha-induced aqueous flare elevation. L-NAME, injected 30-90 min before PG application, inhibited the aqueous flare elevation maximally. We believe that nitric oxide may be involved in the pathogenesis of PG-induced aqueous flare elevation in rabbits.