2,5-hexanedione (HD) induces apoptosis of nerve cells. However,the mechanism of HD-induced apoptosis remains unknown. Mesenchymal stem cells (MSCs) are multipotential stem cells with the ability to differentiate into various cell types. This study is designed to investigate the apoptosis induced by HD in rat bone marrow MSCs (BMSCs) and the related underlying mechanisms. The fifth generation of MSCs was treated with 0, 10, 20 and 40 mM HD respectively. The viability of BMSCs was observed by MTT. Apoptosis were estimated by Hoechst 33342 staining and TUNEL assay. The disruption of mitochondrial transmembrane potential (MMP) was examined by JC-1 staining. Moreover, the expression of Bax and Bcl-2, cytochrome c release, and caspase-3 activity were determined by real-time RT-PCR, Western blot and Spectrophotometry. Our results showed that HD induced apoptosis in MSCs in a dose dependent manner. Moreover, HD downregulated the Bcl-2 expression,upregulated the Bax expression and the Bax/Bcl-2 ratio, promoted the disruption of MMP, induced the release of cytochrome c from mitochondria to cytosol, and increased the activity of caspase-3 in MSCs. These results indicate that HD induces apoptosis in MSCs and the activated mitochondria-dependent caspase-3 pathway may be involved in the HD-induced apoptosis.

were found in the hippocampus of As-exposed mice. The expressions of the Bcl-2 gene and its protein in the hippocampus of As-exposed mice were significantly lower than those in the control group (p<0.05). However, the expressions of the Bax gene and its protein, and the expression ratio of Bax/Bcl-2 in the hippocampus were significantly higher in the groups exposed to As than in the control group (p<0.05). Moreover, the activity of caspase-3 in the hippocampus of mice exposed to As was higher than that in the control (p<0.05). Conclusions:These results indicate that subchronic exposure to As induces apoptosis in the hippocampus of mice by disturbing normal Bax/Bcl-2 regulatory pathways. Meanwhile, it is suggested that the induced apoptosis in the hippocampus may be at least partly responsible for As-induced neurotoxicity. (J Occup Health 2015; 57: 212-221) Key words: Apoptosis, Arsenic trioxide, Bax, Bcl-2, Hippocampus, Neurotoxicity Arsenic (As), a naturally occurring toxic metalloid found in both inorganic and organic forms, is ubiquitous in the environment and contaminates water as a result of geological and industrial pollution 1) . Moreover, some kinds of arsenide, such as arsenic trioxide (As 2 O 3 ), are also widely used for the treatment of malignant tumors 2) . In As-contaminated areas, the As concentration in drinking water or groundwater ranges from 0.25 to 2.1 ppm and even reaches >3.0 ppm in some severely contaminated areas 3−5) . Exposure to As has been associated with increasing incidences of various chronic diseases, including peripheral vascular disease, cardiovascular disease, diabetes mellitus, and various cancers 6) . As is also a potent neurotoxicant, and subchronic or chronic As exposure causes severe nervous system Abstract: Subchronic exposure to arsenic induces apoptosis in the hippocampus of the mouse brains through the Bcl-2/Bax pathway: Yachen WANG, et al. Department of Occupational and EnvironmentalHealth, Dalian Medical University, P.R. ChinaObjectives: The aim of this study was to identify whether arsenic (As) exposure could induce hippocampal neural apoptosis in vivo. Methods: Sixty-four mice were randomly divided into 4 groups of 16 each. Group 1 orally received drinking water alone as a control. Groups 2−4 were given arsenic trioxide (As 2 O 3 ) orally at the doses of 1 ppm, 2 ppm and 4 ppm, respectively. All the treatments continued for 60 days. Morphological changes in the hippocampus were observed by HE staining. Apoptosis in the hippocampus was examined by TUNEL assay and transmission electron microscopy. The expression levels of Bcl-2 and Bax genes and their proteins in the hippocampus were determined by realtime PCR and Western blotting. The activity of caspase-3 was determined by spectrophotometry. Results: Abnormal histopathological changes and apoptosis

We demonstrate that under optimized experimental conditions phonon-assisted anti-Stokes photoluminescence becomes the dominant light emission process in a freestanding GaN sample excited well below the bandgap. Potentially this up-conversion process can be used for efficient removal of phonons generated in the wide range of GaN-based electronic and optoelectronic devices and perhaps laser cooling based on nitride structures.

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Studies suggested that the conditioned medium of mesenchymal stem cells (MSC-CM) inhibited the increased apoptosis in various cells. However, there are no reports underlying the protection of MSC-CM against 2,5-hexanedione (HD)-induced apoptosis in neural cells. In the present study, the viability was observed in PC12 cells that received HD alone or with MSC-CM by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Apoptosis was estimated by Hoechst 33342 staining and flow cytometry. Mitochondrial transmembrane potential was examined by rhodamine 123. Moreover, we investigated the expression of Bax and Bcl-2, cytochrome c translocation, and caspase 3 activity by real-time polymerase chain reaction, Western blot, and immunochemistry. Nerve growth factor (NGF) was examined in MSCs and MSC-CM. Our results showed that MSC-CM promoted cell survival and reduced apoptosis in HD-exposed PC12 cells. Moreover, MSC-CM significantly reversed disturbance of Bax and Bcl-2, ameliorated disruption of mitochondrial transmembrane potential, and reduced release of cytochrome c and activity of caspase 3 in HD-exposed PC12 cells. In the meantime, NGF was detected in MSCs and MSC-CM. These findings demonstrate that MSC-CM protects against HD-induced apoptosis in PC12 cells via inhibiting mitochondrial pathway. Our results indicate that NGF in MSC-CM may be involved in the protection of MSC-CM against HD-induced apoptosis. Our study clarifies the protection of MSC-CM on HD neurotoxicity and its underlying mechanism.