Mechanism of over-activation in direct pathway mediated by dopamine D₁ receptor in rats with levodopa-induced dyskinesia / 神经科学通报·英文版

<p><b>OBJECTIVE</b>To study the changes of prodynorphin (PDyn) gene expression and dopamine and cAMP-regulated phosphoprotein of 32 kDa (DARPP-32) phosphorylation in rats with levodopa-induced dyskinesia (LID), and to explore the mechanism of over-activation in direct pathway mediated by dopamine D₁ receptor.</p><p><b>METHODS</b>Parkinson's disease (PD) rats were received levodopa (10 mg/kg, i.p.) for 28 d to get the LID rats. According to the behavior scale, LID rats were divided into mild (n = 8) and severe (n = 16) groups. On day 29, 8 rats in severe LID group were given an acute intraperitoneal injection of MK-801 (0.1 mg/kg) 15 min before levodopa treatment (MK-801 group, n = 8). The normal rats received same course and dosage of levodopa as the control group (n = 8). Hybridization in situ was used to measure the expression of PDyn mRNA in striatum. Protein and mRNA levels of total DARPP-32 and phospho-Thr-34 DARPP-32 level were measured by immunoblotting and RT-PCR, respectively.</p><p><b>RESULTS</b>The levels of PDyn mRNA and phospho-Thr-34 DARPP-32 increased significantly in LID rats compared with control rats (P < 0.01), and they also increased markedly in severe LID group compared with mild group (P < 0.01).</p><p><b>CONCLUSION</b>Phospho-Thr-34 DARPP-32 level was increased in LID rats, which contributed to the over-activation of direct pathway mediated by dopamine D₁ receptor.</p>

Effect of thrombin on blood brain barrier permeability and its mechanism / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Previous studies have indicated that thrombin (TM) may play a major role in brain edema after intracerebral hemorrhages (ICHs). However, the mechanism of TM-induced brain edema is poorly understood. In this study, we explored the effect of TM on the permeability of the blood brain barrier (BBB) and investigated its possible mechanism, aiming at providing a potential target for brain edema therapy after ICHs.</p><p><b>METHODS</b>TM or TM + cathepsin G (CATG) was stereotaxically injected into the right caudate nucleus of Sprague-Dawley rats in vivo. BBB permeability was measured by Evans-Blue extravasation. Brain water content was determined by the dry-wet weight method. Brain microvascular endothelial cells were then cultured in vitro. After TM or TM + CATG was added to the endothelial cell medium, changes in the morphology of cells were dynamically observed by phase-contrast light microscopy, and the expression of matrix metalloproteinase-2 (MMP-2) protein was measured by immunohistochemical method.</p><p><b>RESULTS</b>BBB permeability increased at 6 hours after a TM injection into the ipsilateral caudate nucleus (P < 0.05), peaked between 24 hours (P < 0.01) and 48 hours (P < 0.05) after the injection, and then declined. Brain water content changed in parallel with the changes in BBB permeability. However, at all time points, BBB permeability and brain water content after a TM + CATG injection were not significantly different from the respective parameters in the control group (P > 0.05). TM induced endothelial cell contraction in vitro in a time-dependent manner and enhanced the expression of MMP-2 protein. After incubation with TM + CATG, cell morphology and MMP-2 expression did not change significantly as compared to the control group (P > 0.05).</p><p><b>CONCLUSIONS</b>Increased BBB permeability may be one of the mechanisms behind TM-induced cerebral edema. TM induces endothelial cell contraction and promotes MMP-2 expression by activating protease activated receptor-1 (PAR-1), possibly leading to the opening of the BBB.</p>

Effects of endoplasmic reticulum stress and its related apoptosis on selective death of dopaminergic neurons / 中华老年医学杂志

Objective To explore the effects of endoplasmic reticulum stress response(ERS) and its related apoptosis on dopaminergic neurons death.Methods NGF treated-PC12 cells were treated with 6-OHDA,MPP+ and rotenone.MTT assay and flow cytometry were used to measure the cell viability and the rate of cells apoptosis induced by those neurotoxins at different concentrations and times.The expressions of ERS-related gene XBP1,Grp78,CHOP,caspase-12 in drug-treated group and reserpine preincubation group were determined by RT-polymerase chain reaction(RT-PCR) and immunohistochemistry.Results After exposing to different concentration toxins,the vitality of PC12 cells was decreased by 52% at 100?mol/L 6-OHDA,by 44% at 75?mol/L MPP~+,and by 40% at 20 nmol/L rotenone for 24 hours respectively and ws decreased in a dose dependent manner. FCM assay confirmed time-dependent cell apoptosis.The apoptotic cells ratio of 24 h groups were (31.22?3.21)%,(27.46?2.35)%,(29.26?2.53)%,respectively(P＜0.01).In 6-OHDA groups,the gene expressions of XBP1,Grp78 were approximately 2-fold increased after 8 h exposure, CHOP reached peak level at 16 h(149.5?3.3% vs 35.9?1.8%,P＜0.01).The transcription level of caspase-12 was significantly higher than normal control at 16h[(95.4?2.8% vs(23.8?3.0)%, P＜0.01],but was alleviated by reserpine prcincubation(62.15?4.3%,P＜0.05).The increased expressions of Grp78 and CHOP after drug exposure were confirmed by immunochemistry stain.The similar results were observed in MPP~+ and rotenone groups.Conclusions The excessive ERS and ERS-activated cell apoptosis pathway may be involved in selective death of dopaminergic neurons.