TRPV1 antagonist can suppress the atopic dermatitis-like symptoms by accelerating skin barrier recovery

Background: Transient receptor potential vanilloid type 1 (TRPV1) is a cation channel activated by diverse obnoxious stimuli like capsaicin, low pH or heat. Recently, it was revealed that TRPV1 might be deeply associated with skin permeability barrier function, suggesting that modulation of TRPV1 might be beneficial for the skin disorders with barrier damages. Objective: We aimed to investigate whether the blockade of TRPV1 activation might accelerate skin barrier recovery and alleviate atopic dermatitis (AD)-like symptoms, employing a novel TRPV1 antagonist, PAC-14028. Methods: TRPV1 antagonistic effects of PAC-14028 in human keratinocytes and skin were confirmed through capsaicin-evoked calcium influx assay and capsaicin-induced blood perfusion increase. Effects of PAC-14028 on skin barrier recovery were examined in vivo tape-stripping-induced barrier disruption in hairless mice. To determine the effects of PAC-14028 on AD, Dermatophagoides farina (Df)- and oxazolone (OXZ)-induced AD models were employed. Results: PAC-14028 could inhibit capsaicin-evoked calcium influx in keratinocytes at sub-micromolar concentrations. This potent TRPV1 antagonistic activity in keratinocytes was manifested in vivo as the blockade of capsaicin-induced blood perfusion increase, and the accelerated barrier recovery from tape-stripping-induced barrier damages in hairless mice. PAC-14028 could also attenuate dermatitis-associated barrier damages in Df and OXZ models as determined by lower TEWL (trans-epidermal water loss), reformation of neutral lipid layer and reversion of changes in loricrin and filaggrin expression. Importantly, along with accelerated recovery of skin barrier function, PAC-14028 alleviated the general AD-like symptoms, including serum IgE increase, mast cell degranulation, scratching behavior and clinical severity of dermatitis. Conclusions: These results reflect that the blockade of TRPV1 activation can suppress the atopic dermatitis-like symptoms by accelerating skin barrier recovery. (C) 2010 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.