One of the most common and significant symptoms for skin disorders is pruritus. Additionally, it serves as a significant catalyst for the exacerbation or reoccurrence of skin diseases. Pruritus seriously affects patients' physical and mental health, and even the quality of life. It brings a heavy burden to the patients, the families, even the whole society. The pathogenesis and regulation mechanisms for pruritus are complicated and have not yet been elucidated. Previous clinical studies have shown that itch worsens at night in scabies, chronic pruritus, atopic dermatitis, and psoriasis, suggesting that skin pruritus may change with circadian rhythm. Cortisol, melatonin, core temperature, cytokines, and prostaglandins are the main regulatory factors of the circadian rhythm of pruritus. Recent studies have shown that some CLOCK genes, such as BMAL1, CLOCK, PER, and CRY, play an important role in the regulation of the circadian rhythm of pruritus by regulating the Janus tyrosine kinase (JAK)-signal transducer and activator of transcription (STAT) and nuclear factor kappa-B (NF-κB) signaling pathways. However, the mechanisms for circadian clock genes in regulation of circadian rhythm of pruritus have not been fully elucidated. Further studies on the mechanism of circadian clock genes in the regulation of circadian rhythm of pruritus will lay a foundation for elucidating the regulatory mechanisms for pruritus, and also provide new ideas for the control of pruritus and the alleviation of skin diseases.
瘙痒是皮肤病最典型和最重要的临床症状之一，也是皮肤病加重或复发的重要诱因之一。瘙痒严重影响患者的身心健康和生活质量，给患者、家庭和社会带来沉重的负担。瘙痒的发生和调控机制复杂，目前尚未阐明。临床研究显示在疥疮、慢性瘙痒、特应性皮炎和银屑病中均存在瘙痒夜间加重的情况，提示皮肤瘙痒可呈昼夜节律性改变。皮质醇、褪黑素、人体核心温度、细胞因子及前列腺素等因素是瘙痒昼夜节律的主要调控因素。一些生物钟基因如BMAL1、CLOCK、PER和CRY等，通过调节Janus激酶(Janus tyrosine kinase，JAK)-信号转导和转录激活因子(signal transducer and activator of transcription，STAT)通路与转录因子蛋白家族核因子κB(nuclear factor kappa-B，NF-κB)等信号通路，在瘙痒的昼夜节律的调节中扮演重要角色。然而生物钟基因对瘙痒昼夜节律调控的具体作用机制尚未完全阐明，进一步研究生物钟基因在瘙痒昼夜节律调控中的作用机制，将为阐明瘙痒的调控机制奠定基础，亦可为控制瘙痒和缓解皮肤病提供新的思路。.
Keywords: atopic dermatitis; biological clock; circadian rhythm; pruritus.