Moderate activation of autophagy regulates the intracellular calcium ion concentration and mitochondrial membrane potential in beta-amyloid-treated PC12 cells.

Alzheimer's disease (AD) is an age-related and progressive neurodegenerative disease. Aggregated beta-amyloid (Aß) disturbs Ca(2+) homeostasis and causes mitochondrial dysfunction and finally underlies AD. Recent evidence suggests that autophagy initiation by Beclin-1 protein might be involved in the pathogenesis of AD. However, the effects of Beclin-1 dependent autophagy on intracellular calcium ion concentration ([Ca(2+)]i) and mitochondrial membrane potential (MMP) is unclear. The effects of Beclin-1 dependent autophagy that were activated by a gradient concentration of autophagy activator rapamycin or inhibited by autophagy inhibitor 3-methyladenine (3-MA) on cell viability and cell morphology were examined. Pretreatment with rapamycin significantly up-regulated the expression of Beclin-1 in response to Aß1-42 application, but after pretreatment with 3-MA it was significantly down-regulated. Moderate activation of Beclin-1 dependent autophagy had an up regulation effect on cell viability and could maintain the original morphology of cells. Furthermore, rapamycin or 3-MA on [Ca(2+)]i and MMP in Aß1-42 treatment of PC12 cells were evaluated. We also report that PC12 cells treated with Aß1-42 showed an increase in [Ca(2+)]i but a decrease in MMP when compared to the normal control. However the application of rapamycin prior to this prevented the increase in [Ca(2+)]i and the decrease in MMP in response to Aß1-42. When 3-MA was applied this exacerbated the effect of Aß1-42 on the [Ca(2+)]i and the MMP. This shows that moderate activation of Beclin-1 dependent autophagy by rapamycin can modulate Ca(2+) homeostasis and maintain MMP in response to Aß1-42 induced cytotoxicity and so may have a preventive function in AD.

Beta-asarone attenuates amyloid beta-induced autophagy via Akt/mTOR pathway in PC12 cells.

Alzheimer's disease (AD) is an age related and progressive neurodegenerative disease. Autophagy is a self-degradative process and plays a critical role in removing long-lived proteins and damaged organelles. Recent evidence suggests that autophagy might be involved in the pathogenesis of AD. ß-asarone have various neuroprotective effects. However, the effect of ß-asarone on autophagy in amyloid ß-peptide (Aß) induced cell injury is unclear, and little is known about the signaling pathway of ß-asarone in autophagy regulation. The aim of the present study was to determine whether ß-asarone protects cells from Aß1-42 induced cytotoxicity via regulation of Beclin-1 dependent autophagy and its regulating signaling pathway. We examined effects of ß-asarone on cell morphology, cell viability, neuron specific enolase (NSE) levels, autophagosomes and regulating Beclin-1, p-Akt and p-mTOR expressions in Aß1-42 treated PC12 cells. We found that ß-asarone could maintain the original morphology of cells and increase cell viability and decrease NSE levels significantly. Meanwhile, ß-asarone decreased Beclin-1 expression significantly. In addition, ß-asarone can increase levels of p-Akt and p-mTOR. These results showed that ß-asarone protected cells from Aß1-42 induced cytotoxicity and attenuated autophagy via activation of Akt-mTOR signaling pathway, which could be involved in neuroprotection of ß-asarone against Aß toxicity. Our findings suggest that ß-asarone might be a potential preventive drug for AD.

Protective effect of Sijunzi decoction on neuromuscular junction ultrastructure in autoimmune myasthenia gravis rats.

OBJECTIVE: To investigate the protective role of Sijunzi decoction in neuromuscular junction (NMJ) and muscle cell mitochondria ultrastructure; as well as its effects on the amount of adenosine triphosphate (ATP) and the activities of mitochondrial respiratory chain complexes I, II, III, and IV in autoimmune myasthenia gravis rats. METHODS: An experimental autoimmune myasthenia gravis (EAMG) rat model was established by inoculating rats with acetylcholine receptors extracted from Torpedo. Rats were divided into three groups: model, prednisone, and Sijunzi decoction, and were fed physiological saline, prednisone, or Sijunzi decoction, respectively. NMJ and muscle cell mitochondria ultrastructure were observed by transmission electron microscope. The amount of ATP was assessed by high performance liquid chromatography. The activities of mitochondrial respiratory chain complexes I, II, III, and IV was determined using the Clark oxygen electrode method. RESULTS: In the model group, there were sparse muscle fibers, with decreased mitochondria, and sparse, diffluent, or absent NMJ folds. After intervention with Sijunzi decoction, the above pathology changes were improved: muscle fiber structure was clear and complete; the mitochondria count was higher; and the NMJ structure was close to normal. Gastrocnemius muscle mitochondria in the model group produced significantly less ATP than those in the prednisone group (P < 0.01). Conversely, the ATP of Sijunzi decoction group was significantly higher than prednisone group (P < 0.01). The activities of gastrocnemius muscle mitochondrial respiratory chain complexes I, II, III, and IV in both the prednisone and Sijunzi decoction groups was dramatically higher compared with the model group (P < 0.05). The activities of complexes I and III in the Sijunzi decoction group were significantly higher than those in the prednisone group (P < 0.05), but there was no obvious difference in complex II or IV activities between the two groups (P > 0.05). CONCLUSION: Sijunzi decoction improved pathological changes in muscle mitochondria and NMJ, enhanced the amount of ATP in gastrocnemius muscle mitochondria, and improved the activities of respiratory chain complexes I, II, III, and IV (especially I and III) of the EAMG rats.