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Stress, specifically chronic unpredictable stress and chronic restrained stress, induce depigmentation in C57BL/6 mice. Fluoxetine promoted melanin production and the migration of melanocytes via 5-HT1A receptor and 5-HT2A receptor, respectively.<br><br>Display Omitted<br>• Fluoxetine ameliorates CUMS and CRS induced depigmentation in C57BL/6 mouse. • Fluoxetine induces melanogenesis via activating the phosphorylation of p38 MAPK signaling pathways. • 5-HT1A and 2A receptors regulated fluoxetine increased melanocyte melanogenesis and migration.<br>Background: 5-HT1A receptor was participated in fluoxetine induced melanogenesis in melanocytes and in normal C57BL/6 mice, but we know little about whether other 5-HT receptors are involved in regulation of fluoxetine promotes pigmentation.<br>Objective: To investigate the role of 5-HT receptors in regulation of fluoxetine ameliorates chronic unpredictable mild stress (CUMS) and chronic restraint stress (CRS) induce hypopigmentation in C57BL/6 mice.<br>Methods: CUMS and CRS were used to induce depigmentation in mice and evaluate the effect of fluoxetine. Western blot, immunohistochemistry and Q-PCR assay were used to determine the levels of protein and mRNA. Masson Fontana staining was used for melanin staining and FITC-Phalloidin staining was used to detect the expression of F-actin. Zebrafish and B16F10 cells were used for the mechanism research.<br>Results: Fluoxetine (2.6 mg/kg, ig) ameliorated hypopigmentation induced by CUMS and CRS in mice, significantly increased the mRNA and protein levels of 5-HT1 A and 5-HT2 A receptors in mice and B16F10 cells. The effect of fluoxetine on melanogenesis in B16F10 cells and zebrafish were inhibited by WAY100635 (a selective 5-HT1 A receptor antagonist) and ketanserin (a 5-HT2 A receptor antagonist), respectively. Activation of p38 MAPK signaling pathways was contributed to fluoxetine induced melanogenesis and inhibited by WAY100635, but not ketanserin. However, ketanserin selectively weakened the action of fluoxetine promoted migration and up-regulated Rab27a protein expression in B16F10 cells.<br>Conclusions: 5-HT1 A and 2 A receptors contribute to melanogenesis and migration property of fluoxetine. The newly revealed mechanism indicates that fluoxetine and its analogues may be a potential drug for treatment of depigmentation disorders.

Abstract Ethnopharmacological relevance Tibetan medicine has been practiced for 3800 years. Anzhijinhua San (AZJHS), which is a traditional Tibetan medicine, has been effective in the treatment of indigestion, anorexia and cold diarrhea. However, the effects of AZJHS on allergic diarrhea have not been reported. Aim of the study The aim of the present study was to elucidate the effect of AZJHS on experimental ovalbumin-induced diarrhea and elucidate its possible mechanism. Materials and methods Female BALB/c mice were sensitized by intraperitoneal injection with 50 μg ovalbumin (OVA) and 1 mg alum in saline twice during a 2-week period. From day 28, mice were orally challenged with OVA (50 mg) every other day for a total of ten times. AZJHS (46.8 and 468.0 mg/kg) was orally administered every other day from day 0–46. Food allergy symptoms were evaluated. OVA- specific IgE, 5-HT and its metabolites in serum were determined. Immunohistochemical and histopathology were performed in gastrointestinal tract tissues. 5-HT-related gene expression was assayed in the colon. Results Severe symptoms of allergic diarrhea were observed in the model group (diarrhea, anaphylactic response, and rectal temperature). AZJHS (46.8 and 468.0 mg/kg) significantly reduced mouse diarrhea and significantly prevented the increases in OVA-specific IgE levels (P < 0.05), which challenge with OVA. AZJHS (46.8 and 468.0 mg/kg) significantly prevented the increases in 5-HT-positive cells. The nuclei of EC cells in the AZJHS (46.8 and 468.0 mg/kg) group increased in size and the secretory granules were fewer in number compared with those in the model group. AZJHS (46.8 and 468.0 mg/kg) significantly increased the relative fold changes of 5-HTP and 5-HT compared with the model group. The mRNA expression of the serotonin transporter (Sert) and serotonin receptor 3A (Htr3a) was significantly decreased after the 10th challenge with OVA, and AZJHS (46.8 and 468.0 mg/kg) significantly increased these levels. Conclusions We demonstrated that the administration of AZJHS attenuated OVA-induced diarrhea by regulating the serotonin pathway. These results indicated that AZJHS may be a potential candidate as an anti-allergic diarrhea agent. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]