a1 Key Laboratory of Brain Function and Diseases, School of Life Science, University of Science and Technology of China, Chinese Academy of Sciences, Hefei 230027, Anhui, China
Corticotropin-releasing hormone (CRH) is considered the driving force of the hypothalamo-pituitary-adrenal (HPA) axis and plays an important role in mood regulation. The HPA axis is reported to be closely related to acute stress-induced tau phosphorylation in the rodent hippocampus. However, the relationship between the hyperactive HPA axis and tau phosphorylation in the hippocampus and hence the functional implications for chronic stress are not fully understood. In this study, we aimed to examine tau phosphorylation and the effect on axonal transport of mitochondria in the hippocampus of a chronic stress model. A mouse model was created by neonatal isolation before weaning, followed by chronic mild stress by social isolation after weaning. Behavioural tests showed that the model had a typical depression/anxiety-like behaviour accompanied by increased plasma corticosterone level and hypothalamic CRH mRNA expression. Phosphorylated tau increased significantly, accompanied by increased synaptosomal mitochondrial levels in hippocampus of the chronic stress model. CRH receptor 1 antagonist (CP154,526) treatment, not glucocorticoid receptor antagonist (RU486) treatment, decreased tau phosphorylation and synaptosomal mitochondrial levels in the hippocampus of the mouse model. Consistent with an in-vivo model, when hyperphosphorylated tau was inhibited by lithium in cultured primary hippocampal neurons, mitochondrial transport monitored by live imaging was also decreased. We show here for the first time that phosphorylated tau in the hippocampus of a chronic stress model, accompanied by increased mitochondrial transport, was mediated by CRH receptor 1, not by glucocorticoid receptors, which suggests that centrally derived CRH may be involved in the process of mitochondrial axon transport and hence play an important role in hippocampus of a chronic stress model.
(Received October 29 2010)
(Reviewed December 29 2010)
(Revised January 27 2011)
(Accepted February 11 2011)
(Online publication March 22 2011)
c1 Address for correspondence: J.-N. Zhou, M. D., Ph.D., Department of Neurobiology and Biophysics, School of Life Science, University of Science and Technology of China, 443 Huang-Shan Road, Hefei, Anhui 230027 China. Tel.: +86 551 3607658 Fax: +86 551 3607778 Email: firstname.lastname@example.org