Crisaborole Inhibits Itch and Pain by Preventing Neutrophil Infiltration in a Mouse Model of Atopic Dermatitis.

Crisaborole, a phosphodiesterase 4 (PDE4) inhibitor, has been approved for the treatment of mild to moderate atopic dermatitis. Atopic dermatitis is often associated with increased pain. Using a mouse model, this study investigated whether crisaborole suppresses pain associated with atopic dermatitis and the potential mechanisms underlying it. The mouse model for atopic dermatitis was developed by repeatedly applying MC903. MC903-treated mice had increased spontaneous scratching (itch-related behaviour) and wiping behaviour (pain-related behaviour). Crisaborole was topically applied to the cheek skin of MC903-treated mice, and it reduced both itch- and pain-related behaviours in these mice. Immunofluorescence staining revealed that crisaborole reduced neutrophil infiltration and interaction of neutrophils with sensory neurones. Intradermal injection of S100A8/A9, proinflammatory neutrophil mediator, enhanced not only itch-related behaviours evoked by histamine or chloroquine, but also pain-related behaviours evoked by capsaicin. Calcium imaging of mouse dorsal root ganglion neurones revealed that pretreatment with S100A8/A9 significantly increased calcium responses to histamine and capsaicin, and the proportion of chloroquine-sensitive neurones. These findings suggest that the PDE4 inhibitor reduces itch and pain, in part by inhibiting infiltration of S100A8/A9-containing neutrophils in a mouse model of MC903-induced atopic dermatitis.

The Effects of Cannabinoid Agonist, Heat Shock Protein 90 and Nitric Oxide Synthase Inhibitors on Increasing IL-13 and IL-31 Levels in Chronic Pruritus.

BACKGROUND: Heat shock protein 90 (Hsp90) inhibitor and cannabinoid agonists ameliorate dry skin-induced chronic itch. We have recently reported that cannabinoids, hsp90 and nitric oxide (NO) are involved in dry skin-induced itch. Here, we investigated the contribution of the Th2 cell signaling pathway to the antipruritic effect of the hsp90 inhibitor 17-Alilamino-17-demethoxygeldanamycin (17-AAG), nitric oxide synthase (NOS) inhibitor Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME) and cannabinoid agonist WIN 55,212-2 on a dry skin-induced scratch. METHODS: Dry skin-induced chronic itching was created by topical application of AEW (acetone/diethyl ether/water). WIN 55,212-2 (1 mg/kg, i.p.), L-NAME (1 mg/kg, i.p.) and increasing doses of 17-AAG (1, 3 and 5 mg/kg,i.p.) were administered to Balb/c mice (for each group, n = 6). After these applications, skin tissues were taken from the nape region of all of the mice. Gene and protein expressions of IL-13 and IL-31 were evaluated in skin tissues by RT-PCR and immunohistochemistry, respectively. RESULTS: IL-13 and IL-31 mRNA expressions and immune positive cell counts were increased in the AEW applied groups. WIN 55,212-2 reduced both of the increased cytokines levels, while L-NAME decreased only the IL-13. 17-AAG dose-dependently reduced the increased cytokine levels. IL-13 and IL-31 levels significantly decreased following the co-administration of these agents. CONCLUSION: These results show that increased levels of IL-13 and IL-31 are associated with pruritus. Hsp90 inhibition and cannabinoid system activation may induce antipruritic effects through down-regulation of these cytokines.

Topical application of metformin accelerates cutaneous wound healing in streptozotocin-induced diabetic rats.

BACKGROUND: Diabetic chronic wound, which is one of the diabetic complications caused by hyperglycemia, characterized by prolonged inflammation has become one of the most serious challenges in the clinic. Hyperglycemia during diabetes not only causes prolonged inflammation and delayed wound healing but also modulates the activation of nuclear factor-kappa B (NF-κB) and the expression of matrix metalloproteinases (MMPs). Although metformin is the oldest oral antihyperglycemic drug commonly used for treating type 2 diabetes, few studies have explored the molecular mechanism of its topical effect on wound healing. Therefore, we aimed to investigate the molecular effects of topical metformin application on delayed wound healing, which's common in diabetes. METHODS AND RESULTS: In this context, we created a full-thickness excisional wound model in Wistar albino rats and, investigated NF-κB p65 DNA-binding activity and expression levels of RELA (p65), MMP2 and MMP9 in wound samples taken on days 0, 3, 7, and 14 from diabetic/non-diabetic rats treated with metformin and saline. As a result of our study, we showed that topically applied metformin accelerates wound healing by suppressing NF-κB p65 activity and diminishing the expression of MMP2 and MMP9. CONCLUSIONS: Diabetic wounds treated with metformin healed even faster than those in the control group that mimicked standard wound healing.

The Effects of the Heat Shock Protein 90 Inhibitor 17-Allylamino-17-Demethoxygeldanamycin, Cannabinoid Agonist WIN 55,212-2, and Nitric Oxide Synthase Inhibitor Nω-Nitro-L-Arginine Methyl Ester Hydrochloride on the Serotonin and Dry Skin-Induced Itch.

INTRODUCTION: In many types of itch, the interaction between immune system cells, keratinocytes, and sensory nerves involved in the transmission of itch is quite complex. Especially for patients with chronic itching, current treatments are insufficient, and their quality of life deteriorates significantly. OBJECTIVE: In this study, we aimed to investigate the role of the heat shock protein 90 (Hsp90) inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG), cannabinoid agonist WIN 55,212-2, and nitric oxide (NO) synthase inhibitor Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME) in pruritus. METHODS: We created a serotonin (5-HT)-induced (50 µg/µL/mouse, i.d.) acute and acetone-ether-water (AEW)-induced chronic itching models. 17-AAG (1, 3, and 5 mg/kg, intraperitoneally [i.p.]), WIN 55,212-2 (1 mg/kg, i.p.), and L-NAME (1 mg/kg, i.p.) were applied to Balb/c mice. RESULTS: We found that 17-AAG suppressed the scratches of mice, depending on the dose. The itch behavior was reduced by WIN 55,212-2, but L-NAME showed no antipruritic effect at the administered dose. The combined application of these agents in both pruritus models showed synergism in terms of the antipruritic effect. Our results showed that NO did not play a role in the antipruritic effect of WIN 55,212-2 and 17-AAG. Increased plasma IgE levels with AEW treatment decreased with the administration of 17-AAG (5 mg/kg, i.p.) and WIN 55,212-2. CONCLUSION: These results demonstrate that Hsp90 may play a role in the peripheral pathway of pruritus, and cannabinoid agonists and Hsp90 inhibitors can be used together in the treatment of pruritus.