Masatomo Kato

Beneficial pharmacological effects of selective glucocorticoid receptor agonist in external eye diseases.

PURPOSE Glucocorticoids exert their actions via the glucocorticoid receptor through at least 2 intracellular mechanisms, known as transrepression and transactivation. It has been hypothesized that transrepression is the basis of their anti-inflammatory effects, whereas transactivation has been assumed to cause their side effects. ZK209614, a recently identified, novel selective glucocorticoid receptor agonist, exerts strong transrepression and weak transactivation. The objective of this study was to determine whether its pharmacological effects can be dissociated from its side effects. For this, we employed in vitro assays and topical in vivo models. METHODS ZK209614 and dexamethasone were used in in vitro transrepression and transactivation assays. To evaluate anti-inflammatory and antiallergic activities in vivo, ZK209614 and betamethasone phosphate were tested in the carrageenan-induced conjunctivitis model and allergic conjunctivitis model in rats. To evaluate side effects in vivo, treatments with ZK209614 and betamethasone phosphate were tested for the ocular hypertensive effects in a feline model, each drug being administered topically. RESULTS ZK209614 showed strong transrepression and weak transactivation in the in vitro assays. When given as eyedrops, ZK209614 and betamethasone phosphate each had an inhibitory effect on edema weight in the rat carrageenan-induced conjunctivitis model. In the rat allergic conjunctivitis model, ZK209614 reduced the elevated vascular permeability at a concentration of 0.1%. In the feline intraocular pressure (IOP)-elevation experiment, topically administered betamethasone phosphate elevated IOP, but ZK209614 had no effect on IOP. CONCLUSION The present investigations suggest that ZK209614 eyedrops have both anti-inflammatory and antiallergic effects, but no unwanted IOP-elevating effect. On that basis, ZK209614 might be a promising candidate as an ophthalmic drug with a better therapeutic index than classic glucocorticoids.

The role of platelet activating factor and the efficacy of apafant ophthalmic solution in experimental allergic conjunctivitis.

Platelet-activating factor (PAF) may be an important mediator in allergic conjunctivitis. In this study, apafant, a potent PAF antagonist, was evaluated for topical ocular anti-PAF activity in PAF and antigen stimulated conjunctivitis models. PAF, when injected into parpebral conjunctiva, provoked an acute increase, measured as dye leakage, in conjunctival vascular permeability. Apafant inhibited this response in a dose-related manner, and the inhibitory action of 0.1% apafant lasted for at least 6 hours duration. PAF, when instilled into the conjunctival sac, induced itch-scratching behavior and clinical symptoms, such as conjunctival redness and edema. These were inhibited by pretreatment with apafant ophthalmic solution. In a passive conjunctival anaphylaxis model in guinea pigs, significant inhibition of the allergic response was observed following topical ocular administration of apafant 5 and 15 minutes prior to the antigen challenge. We have demonstrated that PAF plays an important role in the development of allergic conjunctivitis. These results clearly indicate that apafant has potential as a topical ocular anti-PAF for treating allergic conjunctivitis.