Role of autophagy in methylmercury-induced neurotoxicity in rat primary astrocytes.

Autophagy is an evolutionarily conserved process in which cytoplasmic proteins and organelles are degraded and recycled for reuse. There are numerous reports on the role of autophagy in cell growth and death; however, the role of autophagy in methylmercury (MeHg)-induced neurotoxicity has yet to be identified. We studied the role of autophagy in MeHg-induced neurotoxicity in astrocytes. MeHg reduced astrocytic viability in a concentration- and time-dependent manner, and induced apoptosis. Pharmacological inhibition of autophagy with 3-methyladenine or chloroquine, as well as the silencing of the autophagy-related protein 5, increased MeHg-induced cytotoxicity and the ratio of apoptotic astrocytes. Conversely, rapamycin, an autophagy inducer, along with as N-acetyl-L-cysteine, a precursor of reduced glutathione, decreased MeHg-induced toxicity and the ratio of apoptotic astrocytes. These results indicated that MeHg-induced neurotoxicity was reduced, at least in part, through the activation of autophagy. Accordingly, modulation of autophagy may offer a new avenue for attenuating MeHg-induced neurotoxicity.

Urban-Rural Differences in Subjective Well-Being of Older Adult Learners in China.

Population aging has brought great challenges to many regions throughout the world. Enhancing the sense of participation, access, and well-being of older adults is the goal of China's aging development. This study, taking urban-rural difference as the entry point, examined the difference in subjective well-being between urban and rural older learners. A total of 2,007 older adults learners (n = 2007) aged over 50 years were recruited in Zhejiang, Anhui, and Shandong Provinces in China, including 773 rural older adults and 1,234 urban older adults. This study found that there was a significant positive correlation between senior learning and the subjective well-being of urban and rural older adult learners. Furthermore, there was a significant difference between the subjective well-being of urban and rural older adult learners' and there was also an urban-rural difference between the effects of older adult learning on the subjective well-being. Based on the above findings, this study reveals the mechanism of the impact of older adult learning on subjective well-being of urban and rural older adults and gives relevant suggestions for improving the subjective well-being of urban and rural older learners.

Real time TaqMan RT-PCR assay for the detection of Cucumber green mottle mosaic virus.

A real time reverse-transcription polymerase chain reaction (RT-PCR) was developed for efficient detection of Cucumber green mottle mosaic virus (CGMMV). The method was designed to use a duo-primer system with a TaqMan probe targeting the conserved sequence in 3' noncoding region (NCR) of CGMMV to detect isolates of this virus collected in China. The sensitivity of the real time RT-PCR assay was 0.13 pg of total RNA or 50 molecules of RNA transcripts. This level of sensitivity indicated that the one step real time RT-PCR developed in the present study could be used for routine testing assays. The real time RT-PCR method could assist in the implementation of quarantine measures for prevention and control of the disease caused by CGMMV.

Preconditioning of endoplasmic reticulum stress protects against acrylonitrile-induced cytotoxicity in primary rat astrocytes: The role of autophagy.

This study explored the protective effects of endoplasmic reticulum (ER) stress preconditioning induced by 2-deoxy-d-glucose (2-DG) or oxidized dithiothreitol (DTTox) on acrylonitrile (AN)-induced cytotocity in primary rat astrocytes. Cells were pretreated with 2-DG or DTTox for different times at various concentration. Next, astrocytes were treated with 2.5mM AN for an additional 12h. Cell viability and cytotoxicity were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction and lactate dehydrogenase (LDH) leakage, respectively. Reactive oxygen species (ROS) and mitochondrial membrane potential (ΔΨm) were determined. Expression of glucose-regulated protein 78 (GRP78), phosphorylated-eukaryotic translation initiation factor 2α (p-eIF2α), microtubule-associated protein light chain 3 (LC3), P62, and Beclin1 were used to assess autophagy. In addition, 3-methyadenine (3-MA), an autophagy-specific inhibitor, was used to assess the role of autophagy in ER stress preconditioning-induced protection against AN cytotoxicity. The results showed that AN alone significantly decreased astrocytic viability and enhanced cytotoxicity. Compared to the AN-alone group, preconditioning with 2-DG or DTTox significantly increased cell viability and reduced cytotoxicity to indistinguishable levels. Decreased ROS generation and increased ΔΨm were also inherent to ER stress preconditioning with these compounds. Furthermore, autophagy was activated by both 2-DG and DTTox. Blockage of autophagy attenuated the protection afforded by 2-DG or DTTox preconditioning in AN-treated astrocytes. These results establish that ER stress preconditioning affords cellular protection against AN, and that activation of autophagy mediates the cytoprotection. Modulation of ER stress and resultant activation of autophagy may be a novel target for to ameliorate AN toxicity.

Differential protection of pre- versus post-treatment with curcumin, Trolox, and N-acetylcysteine against acrylonitrile-induced cytotoxicity in primary rat astrocytes.

OBJECTIVE: This study was designed to examine the differential protection of pre- versus post-treatment with three different antioxidants, curcumin (CUR), Trolox, and N-acetylcysteine (NAC), on acrylonitrile (AN)-induced cytotoxicity in primary rat astrocytes. METHODS: Primary astrocyte cultures were treated with CUR, Trolox and NAC for 4h prior to, or following 24h treatment with AN (2.5mM). 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), lactate dehydrogenase (LDH) release, lipid peroxidation, glutathione, reactive oxygen species (ROS) and mitochondrial membrane potential were measured to evaluate protection associated with the three antioxidants. Knockdown of Nrf2 expression by liposome transfection with siRNA was used to confirm the role of Nrf2 activation in the protection associated with the three antioxidants. RESULTS: Compared with AN treatment alone, pre-treatment with CUR at either concentration significantly increased cell viability and mitochondrial membrane potential, and reduced glutathione levels; lipid peroxidation and ROS production were significantly decreased as well. NAC also showed significant efficacy in attenuating AN-induced toxicity at higher concentration. However, pre-treatment with Trolox failed to ameliorate the AN-induced toxicity. When post-treatment with Trolox, this antioxidant led to significant protective effects at both concentrations, while CUR and NAC were efficacious only at the higher concentrations. Knockdown of Nrf2 only abolished the protective effects of CUR pre-treatment on AN-induced cytotoxicity, while the protective effects of NAC and Trolox pre-treatment groups showed no differences between the Nrf2-knockdown and non-knockdown treatments. CONCLUSIONS: The selected antioxidants exert differential cellular protection when administered prior or subsequent to AN-induced cytotoxic events in decreasing cellular viability, antioxidative capacity and mitochondrial function, enhanced cytotoxicity and ROS production. These results suggest that antioxidants should be carefully chosen for their efficacy in preventing or diminishing oxidative damage caused by AN. The differential effect of pre- and post-treatment may be attributed to activation of the Nrf2 signaling pathway.