마우스에서 세로토닌 유발 가려움의 분자 기전에 관한 연구

Abstract

Itch, a very unpleasant sensation causing the desire to scratch or scratch behavior, is a common clinical symptom of skin disease and the leading cause of significant decrease of the quality of life of patients. Serotonin (5HT: 5-hydroxytryptamine) is pruritogen in humans and indicated to be entailed in some pruritic diseases. Although histamine-dependent itch among various endogenous pruritogens has been studied, mechanisms for 5HT-induced itch are not explored yet. Here, I showed that TRPC4 acts as the molecular target in 5HT-induced itch using in vitro, in vivo and ex-vivo experiment. 5HT-induced itch responses (144.5±9.74 bouts/30 min, n = 5) after intradermal injection of 5HT (10 g/50 l) to nape were reduced to 32±8.78 bouts/30 min (n = 5) by 5HT1,2 receptor antagonist (methysergide 20 g/50 l) and 5HT2B,C antagonist (SB 206553 10 g/50 l; 38.2±9.024 bout/30min, n=5) reduced to 5HT-induced itch but it was not altered by 5HT2A,C receptor antagonist (cyproheptadine 10 g/50 l; 175.75±4.59 bouts/30 min, n = 5). Injection of 5HT2 receptor agonist (α-methyl-5HT 10 g/50 l; 137.66±4.86 bouts/30 min, n = 5) evoked itch responses similar to 5HT-induced itch behavior. In addition, 5HT2B antagonist (RS127445 20 g/50 l; 41±4.35 bouts/30 min, n = 5) reduced 5HT-induced itch. Next, I investigated whether transient receptor potential (TRP) channel involved in 5HT2B receptor-mediated itching responses. After intradermal injection of 5HT2B receptor agonist, TRPC4 antagonist (ML204 40 g/50 l; 58.66±15.56 bouts/30 min, n = 5) reduced to 5HT2B receptor agonist-induced itch and also it reduced to 5HT-induced itch (ML204 40 g/50 l; 57±13.55, bouts/30 min, n=5), while itch responses were not altered in TRPV1-knock out mouse (131.25±25.59 bouts/30 min, n = 4). Also, 5HT-induced itch was reduced in TRPC4 knock down mouse (47.75±19.19 bouts/30min, n = 6). In vitro and ex-vivo experiment, the α-methyl-5HT-induced Ca2+ transient response, the inward current and the discharge rates of single C-fiber were reduced by TRPC4 blockers, niflumic acid and ML204. Finally, I confirmed co-loccalization using immunohistochemistry. TRPC4 was expressed in DRG with 5HT 2B receptor and GRP (11 cells/59cells, 18%). Taken together, these results revealed that the activation of TRPC4 via 5HT2B receptor involved in 5HT-induced itch response. It is suggested that TRPC4 can be served as new therapeutics of itching.