Effects of Xiaoyaosan on imiquimod induced psoriatic lesions and depression neurotransmitters in mouse model

AIM: To observe the effect of Xiaoyaosan decoction on the psoriatic lesions and depression neurotransmitters induced by imiquimod in mice. METHODS: BALB/c male mice were randomly divided into control group, model group, methotrexate group and Xiaoyaosan high, medium and low dose groups, 6 mice in each group. Imiquimod (IMQ, 5%) was used on the back of the animals to induce psoriasis-like lesions in the mice. The psoriasis area and seve-rity index (PASI) were evaluated for daily scoring. The sugar water preference experiment was conducted to explore the behavioral differences in the mice. The morphological changes and epidermal thickness of the lesions were observed under light microscopy. Immunohistochemical method was used to detect the expression of CD3 on T lymphocyte surface. The expression of Ki67 in the skin lesions was detected by immunofluorescence. The contents of monoamine neurotransmitters such as adrenaline (AD), gamma-aminobutylic acid (GABA), glutamate (Glu), dopamine (DA) and their metabolites in the hippocampus and hypothalamus of mice were detected by high performance liquid chromatography-mass spectrometry (HPLC-MS). RESULTS: Compared with model group, the back skin lesions of Xiaoyaosan each dose group and methotrexate group were significantly improved, and the PASI score and epidermal thickness were both lower than those in model group (P<0.05). The expression levels of Ki67 and CD3⁺ T cells in Xiaoyaosan group and methotrexate group were lower than those in model group (P<0.05). Compared with model group, the body mass change range of Xiaoyaosan high-dose group and blank control group was significantly smaller than that in model group (P<0.05). The sugar water preference rate in blank control group was significantly higher than that in model group (P<0.01). Compared with model group, the sugar water preference rate in methotrexate and Xiaoyaosan groups showed a certain increase trend, but no statistical diffe-rence was observed. Compared model group, the levels of 3, 4-Dihydroxypheny-lacetic acid (DOPAC), AD, GLU and GABA levels in the mouse hippocampus in blank control group were decreased significantly (P<0.01), while the levels of DA and homovanillic acid (HVA) had no significant difference (P>0.05). No significant difference of DA, DOPAC, HVA and GLU levels in the mouse hypothalamus was observed between blank control group and model group (P>0.05), while the content of AD and GABA in the mouse hypothalamus in blank control group was lower than that in model group. The AD content of the hypothalamus in high-dose Xiaoyaosan group was significantly higher than that in model group (P<0.01), and the HVA content of the hypothalamus in low-dose Xiaoyaosan group was significantly higher than that in model group (P<0.01). PASI score was negatively correlated with the content of DOPAC, AD, GLU and GABA in the hippocampus and the content of AD, GLU and GABA in the hypothalamus, those were, the more severe the back skin lesion was, the lower the expression of depression-related neurotransmitters were, indicating the aggravation of depression in the mice. CONCLUSION: Xiaoyaosan improves the skin lesions induced by imiquimod in the mice with psoriasis, improves the behavior of depression in the mice with psoriasis, and up-regulates the expression of depression-related monoamine neurotransmitters. The expression of depression-related neurotransmitters is negatively correlated with the skin lesions induced by imiqumod in the mice with psoriasis. The degree of depression is increased with the aggravation of psoriatic lesions.