Dynamic of neurochemical alterations in striatum, hippocampus and cortex after the 6-OHDA mesostriatal lesion.

Immediate neurochemical alterations produced by 6-OHDA could explain the general toxic pattern in the central nervous system. However, no evidences describe the effects of 6-OHDA on early changes of neurotransmitters in rats' striatum, cortex and hippocampus. In our study, unilateral 6-OHDA injection into medial forebrain bundle (MFB) was used in rats, then five neurotransmitters were analyzed at 3, 6, 12, 24, 48 and 72 h, respectively. Results showed that 6-OHDA injection caused a sharp decline of striatal dopamine (DA) levels in the first 12h followed by a further reduction between 12 and 48 h. However, striatal levels of homovanillic acid (HVA) were stable in the first 12h and showed a marked reduction between 12 and 24h. Striatal levels of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) decreased linearly for 72 h, whereas levels of norepinephrine (NE) showed a slight reduction in the first 48 h, and returned back to normal afterwards. Striatal HVA/DA ratio increased significantly in the first 12h, but 5-HIAA/5-HT ratio showed a sharp increase between 12 and 72 h. Besides, neurochemical alterations were also found in hippocampus and cortex, and the correlations of neurotransmitters were analyzed. Our study indicated that NE system had little influence in the early phase of 6-OHDA injection, moreover, early neurochemical alterations were involved with striatum, hippocampus and cortex.

Dynamic expressions of Beclin 1 and tyrosine hydroxylase in different areas of 6-hydroxydopamine-induced Parkinsonian rats.

Beclin 1, a regulator of the autophagy pathway, plays an important role in Parkinson's disease (PD). However, the crucial mechanism of Beclin 1 in PD remains unclear. Therefore, we investigated dynamic expressions of Beclin 1 and tyrosine hydroxylase (TH) in different brain areas of 6-OHDA-induced rats. Beclin 1 and TH expressions were analyzed by flow cytometry and immunohistochemistry, respectively. The results showed that Beclin 1 expressions were low in the sham group, but rose significantly after 6-OHDA injection. In the striatum and cortex, Beclin 1 increased at 3 h, peaking at 12 h, while in the hippocampus, it increased at 3 h and peaked at 24 h, then it declined slowly and remained steady at 72 h. Beclin 1 expression in the striatum and cortex areas was higher than that of the hippocampus area at 12 h. In addition, the time-course of TH expression in the striatum was similar to that in the mesencephalon. TH expression declined dramatically between 0 and 12 h. Pearson analysis showed significant negative correlations between TH and Beclin 1 expression in the areas we analyzed. While TH expression declined gradually between 12 and 72 h, significant positive correlations between TH and Beclin 1 were detected during that interval. This indicated that activation of Beclin 1-dependent autophagy may inhibit the loss of TH-positive neurons.

Beta-asarone attenuates ischemia-reperfusion-induced autophagy in rat brains via modulating JNK, p-JNK, Bcl-2 and Beclin 1.

Beta-asarone has significant pharmacological effects on the central nervous system. It can attenuate neuronal apoptosis, but its effects on the brain ischemia-reperfusion-induced autophagy have not been reported yet. Our study was a two-stage procedure: evaluation of ß-asarone effects on the autophagy at first, and then analysis of the possible mechanism. The middle cerebral artery occlusion (MCAO) model was adopted to make the brain injure and Beclin 1 was used to evaluate the autophagy. We hypothesized that the mechanism might be related to c-Jun N-terminal kinases (JNK), phospho-JNK (p-JNK), Bcl-2 and Beclin 1. To test this hypothesis, we evaluated JNK, p-JNK, Bcl-2 and Beclin 1 levels with flow cytometry. Additionally, we divided the brain into three regions: ischemic region, ischemic penumbra, and normal region, and analyzed them respectively. We found, compared to both groups II (model control) and III (low dose), Beclin 1 levels in groups IV (medium dose) and V (high dose) were significantly decreased. Beclin 1, JNK and p-JNK levels in groups VII (ß-asarone) and VIII (JNK inhibitor) were significantly decreased, but Bcl-2 levels were significantly increased. Additionally, Beclin 1, JNK, p-JNK and Bcl-2 levels among the three regions had no significant differences. We conclude that ß-asarone can attenuate the autophagy in a dose-dependent manner. The mechanism is likely that ß-asarone can decrease JNK and p-JNK levels at first, and then increase Bcl-2 level, finally interfere with the functions of Beclin 1 during the execution of autophagy. Additionally, ß-asarone can attenuate autophagy in a widespread manner.