L-茶氨酸局部给药抑制皮肤神经末梢的异常生长缓解小鼠银屑病瘙痒

Topical Application of L-theanine Relieves Mouse Psoriasis Pruritus by Inhibiting Abnormal Growth of Skin Nerve Endings

【目的】观察L-茶氨酸是否在咪喹莫特(IMQ)诱导的银屑病小鼠中具有止痒作用并初步探讨机制。【方法】将IMQ软膏局部应用于小鼠背部皮肤建立银屑病模型;L-茶氨酸经口服(10 mg/kg·d)或病损皮肤局部涂抹(50、125、250 mmol/L,2次/d)进行防治处理。采用抓挠等自发性行为学测试检测治疗效果;并运用免疫荧光染色(IF)、Western Blot(WB)及原代背根神经节(DRG)神经元培养技术探讨相关机制。【结果】口服L-茶氨酸对IMQ诱导的瘙痒无明显作用,但病损皮肤局部应用明显改善银屑病模型小鼠皮肤不舒适感诱发的舔或咬及畏缩等自发性行为,并呈浓度依赖性。IF和WB结果显示,L-茶氨酸不仅能抑制模型小鼠皮肤TNF-α过表达,还能阻止β3-tubulin神经纤维的异常生长和瘙痒相关分子瞬态受体电位香草酸1(TRPV1)的上调。体外实验进一步证实L-茶氨酸能浓度依赖性地直接抑制IMQ引起的CGRP+、β3-tubulin+神经突起异常生长。【结论】局部应用L-茶氨酸通过抑制皮肤神经纤维的异常生长缓解小鼠银屑病模型的皮肤瘙痒不适感。因此,L-茶氨酸局部给药可成为治疗银屑病慢性瘙痒的一种潜在方法。

【Objective】To investigate whether L-theanine exerts anti-pruritic effect on mice with imiquimod(IMQ)-induced psoriasis and its related mechanisms.【Methods】We established the psoriasis model by applying the IMQ ointment topically on mice back skin and oral(10 mg/kg·d)or topical pretreatment(50,125,250 mmol/L,twice one day)of L-theanine was used as the treatment. Spontaneous behavior,such as scratching,was used to detect the therapeutic effect.Immunofluorescence(IF),Western Blot(WB)and primary dorsal root ganglion(DRG)neuronal culture were used to investigate the mechanisms.【Results】Oral administration of L-theanine had no apparent effect on IMQ-induced pruritus,but topical delivery in the lesional skin significantly improved the spontaneous behavior such as licking or biting and flinching in a dose-dependent manner. IF and WB results showed that L-theanine not only inhibited the overexpression of TNF-α in model mouse skin,but also prevented the abnormal growth of β3-tubulin+nerve fibers and the upregulation of transient receptor potential vanilloid 1(TRPV1),an itch-related molecule. Moreover,the results from the experiments with primary cultured DRG neurons further confirmed that L-theanine directly reduced IMQ-induced abnormal outgrowth of CGRP+,β3-tubulin+ neurites in a concentration dependent manner.【Conclusions】Topical application of L-theanine can relieve pruritus or discomfort in IMQ-induced psoriasis mouse model by inhibiting abnormal growth of skin nerve fiber endings. Therefore,L-theanine could be a potential treatment for chronic itch in psoriasis.