Natural Carvacrol Induces Itch By Activation Of TRPV3 Channels

Itch?pruritus?is defined as an unpleasant skin sensation that elicits the desire or reflex to scratch.It is a predominant symptom of many cutaneous disorders like atopic dermatitis,urticaria,contact dermatitis,prurigo nodularis,fungal disease,and various systemic diseases,such as liver failure and end-stage renal disease?ESRD?,as well as certain neuropsychiatric diseases.Itch elicited scratching aggravates lesions of the skin and induces the release of pruritogens,further intensifying itch and severely impacting the quality of life.Itch signaling pathways and molecular mechanisms are becoming to emerge,which includes the histamine-dependent and independent pruritic pathways.TRPV3 is a warm-sensitive Ca²⁺-permeable nonselective cation channel.Recent observations indicate that TRPV3 is involved in itch signaling.Both rodents and humans with gain-of-function TRPV3 point mutations have shown robust scratching,whereas TRPV3 knockout significantly reduces scratching in mice,indicating the role of TRPV3 in the pathogensis of pruritus.However,there is lack of specific TRPV3 antagonist that can be used to validate whether TRPV3 can serve as an antipruritic target,which also impedes understanding of the role of TRPV3 in pruritic pathway.In the present study,we utilized a novel TRPV3 channel specific antagonist and investigated the role of TRPV3 in pruritic pathway.However,how and whether TRPV3 plays an essential role in histamine-independent itch sensation in vivo remains unclear.Objective:To dissect the essential role of TRPV3 channel in cutaneous sensation of itch,we took advantage of a natural compound carvacrol from oregano that exhibits a similar potency in activating both TRPA1 and TRPV3,and tested its effect on the induction of scratching behavior in mice.Methods:Gene identification,Cell culture and transfection,Whole cell patch clamp experiment,Establishment of the itching model,Animal behavior test.Results:1.Carvacrol?250?M?activates and rapidly desensitize TRPA1 current in thecontinuous presence of agonist,whereas TRPV3 is strongly activated before a slow desensitization by carvacrol,further confirming that carvacrol actives both TRPV3 and TRPA1;2.Carvacrol can cause a robust pruritus in SD rats and also induces a severe inflammation in mice,preliminarily suggesting that carvacrol could induce pruritus;3.Intradermal injection of carvacrol induced obvious scratching behaviors in C57BL/6 mice with a concentration-dependent manner,further suggesting that carvacrol could induce pruritus;4.In contrast,the carvacrol-induced scratching was significantly suppressed about 65%from 275 scratching bouts down to 90 in TRPV3 deficit mice,compared with TRPV3^+/+mice,indicating that TRPV3 plays a major role in carvacrol-induced itch;5.Moreover,we used DAP-1,the TRPV3 specific antagonist,and evalutated the inhibitory effect of DAP-1 on the carvacrol-induced itch.The findings from this study showed that DAP-1 at 100?M or 300?M resulted in the inhibition of carvacrol-induced itch by 74%and 85%,respectively.These data are further evidences that TRPV3 plays an essential role in itch induced by skin sensitizer natural carvacrol.Conclusion:In summary,our findings demonstrate that carvacrol from plant oregano is a skin sensitizer or allergen that primarily activates TRPV3 channel,supporting the view that TRPV3 plays an essential role in itch.Thus,TRPV3 may be a critical target for itch and allergy therapy.