Effects of the Janus kinase inhibitor CP-690550 (tofacitinib) in a rat model of oxazolone-induced chronic dermatitis.

The effect of CP-690550 (tofacitinib), a new Janus kinase (JAK) inhibitor, was evaluated in chronic allergic dermatitis. Allergic contact dermatitis was induced in rat ears by repeated application of oxazolone. This dermatitis was accompanied by sustained ear swelling and marked epidermal hyperplasia. In the induced ear, a lot of inflammatory cells infiltrated into the dermis site and the amounts of interferon (IFN)-γ, tumor necrosis factor (TNF)-α, and interleukin (IL)-22 were elevated. Orally administered CP-690550 significantly suppressed ear swelling as well as epidermal thickening, and the effect at 10 mg/kg was comparable to that of cyclosporin A and etanercept. These results suggest a great potential of CP-690550, a JAK inhibitor, as a treatment for chronic dermatitis featuring epidermal hyperplasia (in the pathogenesis of which IFN-γ, TNF-α and IL-22 play a role) such as psoriasis and chronic atopic dermatitis.

Inhibitory effect of ramosetron on corticotropin releasing factor- and soybean oil-induced delays in gastric emptying in rats.

BACKGROUND AND AIM: Symptoms of functional dyspepsia (FD) are highly prevalent in patients with irritable bowel syndrome (IBS). However, the effects of therapeutic agents for IBS on the pathophysiology of FD are unclear. In this study, therefore, we examined the effects of ramosetron, a serotonin 5-HT(3) receptor antagonist, on corticotropin releasing factor (CRF)- and soybean oil-induced delays in gastric emptying of rats, in comparison with anti-diarrheal agent and spasmolytics. The involvement of 5-HT and the 5-HT(3) receptor in delayed gastric emptying was also evaluated. METHODS: Corticotropin releasing factor was administered intravenously to rats 10min before oral administration of 0.05% phenol red solution, and the amount remaining in the stomach was measured after 30min. Soybean oil was administered orally with glass beads, and the number of residual beads in the stomach was counted 1h later. RESULTS: Both CRF and soybean oil inhibited gastric emptying dose-dependently. Ramosetron and itopride, a gastro-prokinetic agent, significantly reduced both CRF- and soybean oil-induced delays in gastric emptying, while an anti-diarrheal agent and spasmolytics aggravated them. Pretreatment with p-chlorophenylalanine for 2days to reduced the synthesis of endogenous 5-HT diminished the effects of both CRF and soybean oil on gastric emptying. A 5-HT(3) receptor agonist m-chlorophenylbiguanide suppressed gastric emptying of both phenol red and glass beads, and those effects were reversed by ramosetron. CONCLUSIONS: These results suggest that CRF and soybean oil suppress gastric emptying in rats by activating 5-HT(3) receptors, and that by antagonizing these receptors, ramosetron may ameliorate symptoms of FD in clinical settings.

Repeated topical application of glucocorticoids augments irritant chemical-triggered scratching in mice.

Topical glucocorticoids, widely used for the treatment of a variety of dermatitises, are known to exacerbate atopic dermatitis after long-term or inappropriate use. In some animal models, topical glucocorticoids augment the allergic cutaneous inflammation after repeated application, suggesting a relationship between these and clinical observations. We investigated whether topical glucocorticoids augment itching, rather than inflammation, resulting in the exacerbation of atopic dermatitis. Mice receiving repeated topical application of glucocorticoids, betamethasone valerate or dexamethasone, to the ear for 1 week showed significantly higher scratching frequency after application of an irritant chemical, 2,4-dinitrofluorobenzene (DNFB) or 12-O-tetradecanoilphorbol 13-acetate (TPA) than those receiving either a glucocorticoid or irritant chemical alone. In contrast, the increase in ear thickness induced by application of TPA was significantly suppressed by dexamethasone. Substance P (SP) and nerve growth factor (NGF) levels were higher in the ear receiving betamethasone valerate followed by DNFB application than in that receiving DNFB alone. In addition, histopathological studies revealed an increased density of nerve fibers in the ear receiving betamethasone valerate or dexamethasone followed by DNFB application. Oral administration of betamethasone valerate was not associated with an increase in either scratching frequency or SP or NGF level in the ear. These results suggest that repeated topical application of glucocorticoids may augment irritant chemical-triggered scratching through an increase in SP and NGF levels and nerve fiber density at the application site. These findings might explain the etiology of the exacerbation of atopic dermatitis and other dermatitises, occurring after long-term or inappropriate use of topical glucocorticoids.