Résumé
OBJECTIVE Cranial radiotherapy is clinically used in the treatment of brain tumors;however, the conse?quent cognitive and emotional dysfunctions seriously impair the life quality of patients. LW-AFC, an active fraction combi?nation extracted from classical traditional Chinese medicine prescription Liuwei Dihuang decoction, can improve cogni?tive and emotional dysfunctions in many animal models;however, the protective effect of LW-AFC on cranial irradiation-induced cognitive and emotional dysfunctions has not been reported. Recent studies indicate that impairment of adult hippocampal neurogenesis (AHN) and alterations of the neurogenic microenvironment in the hippocampus constitute crit?ical factors in cognitive and emotional dysfunctions following cranial irradiation. Here, our research further investigated the potential protective effects and mechanisms of LW-AFC on cranial irradiation-induced cognitive and emotional dys?functions in mice. METHODS LW-AFC (1.6 g·kg-1) was intragastrically administered to mice for 14 d before cranial irra?diation (7 Gyγ-ray). AHN was examined by quantifying the number of proliferative neural stem cells and immature neu?rons in the dorsal and ventral hippocampus. The contextual fear conditioning test, open field test, and tail suspension test were used to assess cognitive and emotional functions in mice. To detect the change of the neurogenic microenvi?ronment, colorimetry and multiplex bead analysis were performed to measure the level of oxidative stress, neurotrophic and growth factors, and inflammation in the hippocampus. RESULTS LW-AFC exerted beneficial effects on the contex?tual fear memory, anxiety behavior, and depression behavior in irradiated mice. Moreover, LW-AFC increased the num?ber of proliferative neural stem cells and immature neurons in the dorsal hippocampus, displaying a regional specificity of neurogenic response. For the neurogenic microenvironment, LW-AFC significantly increased the contents of superox?ide dismutase, glutathione peroxidase, glutathione, and catalase and decreased the content of malondialdehyde in the hippocampus of irradiated mice, accompanied by the increase in brain-derived neurotrophic factor, insulin-like growth factor-1, and interleukin-4 content. Together, LW-AFC improved cognitive and emotional dysfunctions, promoted AHN preferentially in the dorsal hippocampus, and ameliorated disturbance in the neurogenic microenvironment in irradiated mice. CONCLUSION LW-AFC ameliorates cranial irradiation-induced cognitive and emotional dysfunctions, and the underlying mechanisms are mediated by promoting AHN in the dorsal hippocampus and improving the neurogenic micro?environment. LW-AFC might be a promising therapeutic agent to treat cognitive and emotional dysfunctions in patients receiving cranial radiotherapy.
Résumé
SRG3 (SWI3-related gene) is a core subunit of mouse SWI/SNF complex and is known to play a critical role in stabilizing the SWI/SNF complex by attenuating its proteasomal degradation. SWI/SNF chromatin remodeling complex is reported to act as an important endogenous regulator in the proliferation and differentiation of mammalian neural stem cells. Because limited expression of SRG3 occurs in the brain and thymus during mouse embryogenesis, it was hypothesized that the altered SRG3 expression level might affect the process of adult hippocampal neurogenesis. Due to the embryonic lethality of homozygous knockout mice, this study focuses on dissecting the effect of overexpressed SRG3 on adult hippocampal neurogenesis. The BrdU incorporation assay, immunostaing with neuronal markers for each differentiation stage, and imunoblotting analysis with intracellular molecules involved in survival in adult hippocampal neurogenesis found no alteration, suggesting that the overexpression of SRG3 protein in mature neurons had no effect on the entire process of adult hippocampal neurogenesis including proliferation, differentiation, and survival.