5-Hydroxytryptamine (5-HT) Positively Regulates Pigmentation via Inducing Melanoblast Specification and Melanin Synthesis in Zebrafish Embryos

Abstract

It has been reported that 5-hydroxytryptamine (5-HT) is related to melanogenesis in mice and melanoma cells. However, the underlying mechanisms of 5-HT in regulating pigmentation remains unknown. In this study, we aim to clarify the regulatory mechanism of 5-HT in the pigmentation of zebrafish embryos and B16F10 cells. Our results show that 5-HT induces the pigmentation of zebrafish embryos in a dosage-dependent manner at concentrations of 0.01–1 mM. Whole mount in situ hybridizations and qRT-PCR in zebrafish embryos indicate that the expression of neural crest cells marker gene sox10 is not changed in embryos treated with 5-HT compared to control group. The expression of mitfa, the marker gene of melanoblasts, is increased in the presence of 5-HT. Furthermore, 5-HT increased the expression of regeneration associated genes, namely kita, mitfa, and dct, after ablation of the melanogenic cells in zebrafish embryos. The experiments in B16F10 cells show that 5-HT promotes melanin synthesis by up-regulating the expression of key proteins MITF, TYR, TRP-1, and TRP-2. Especially, the small molecule inhibitor of PKA signaling, but not AKT and MAPK signaling, attenuates the up-regulation of MITF and TYR resulted from 5-HT induction in B16F10 cells. These results will help us to further understand the regulatory network of vertebrate pigmentation.

Serotonin (5-HT) 2A Receptor Involvement in Melanin Synthesis and Transfer via Activating the PKA/CREB Signaling Pathway

“…Previous studies have shown that 5-HT could promote the development of melanocytes in zebrafish embryos and the function of melanin synthesis in cultured melanocytes [ 21 ]. In this study, we confirmed the regulation of melanocyte function by 5-HT through adding excess 5-HT into the B16F10 melanoma cell line (in vitro) and PTU-treated zebrafish embryos (in vivo); α-MSH was used as a positive control.…”

Zebrafish in dermatology: a comprehensive review of their role in investigating abnormal skin pigmentation mechanisms

“…Furthermore (Figure 5), while many chemical inducers of pigmentation in zebrafish appear non-toxic in the short term (Karunarathne et al, 2019;Lv et al, 2020a;Liu et al, 2020;Molagoda et al, 2020;Ding Q. et al, 2021;Hong et al, 2022), comprehensive evaluations of long-term and acute toxicities remain scarce. Such assessments are paramount for the zebrafish model's broader application in therapeutic evaluations.…”

“…Additionally, 5-HT was found to increase the expression of regeneration-associated genes, including kita, mitfa, and DCT34. These suggest that 5-HT may specifically activate the PKA/p-CREB signaling pathway, thereby up-regulating the expression of MITF and TYR to promote synthesis of melanin (Liu et al, 2020). Recent research has further elucidated the role of the 5-HT receptor in melanogenesis, showing that it enhances the pigmentation response to environmental stressors through the cAMP-PKA-MAPK, Rab27a/RhoA, and PI3K/AKT signaling pathways (Tang et al, 2023).…”

“…Tryptophan is decomposed by enzyme tryptophan hydroxylase to produce the precursor 5-hydroxytryptophan, which is then transformed into 5-HT by amino acid decarboxylase. Recent studies have demonstrated that 5-HT can stimulate melanin production in zebrafish embryos, leading to an increase in melanin content and a darkening of the skin stripes (Liu et al, 2020;Tang et al, 2023). Zebrafish embryos were…”

Peripheral benzodiazepine receptor TSPO needs to be reconsidered before using as a drug target for a pigmentary disorder

“…The primers used for RT‐PCR are listed in Table S1. The procedure of the whole‐mount in situ hybridization was followed as a previous report 31 . After hybridization, each embryo was photographed under a dissecting microscope using a digital camera.…”