Studies On Mechanisms Of Rapamycin Aganist Neuronal Apoptosis By Inhibiting Oxidative Stress And Activation Of MTOR Pathway In Cadmium-induced Mouse Brain

The present study, using hematoxylin and eosin (HE) staining, transmission electron microscopy (TEM), immunohistochemistry, Western blotting, etc., via in vitro experimental model of subacute Cd-exposed mice, investigated the protective effects of rapamycin (Rapa) on oxidative stress and apoptosis in neuronal cells of Cd-induced mouse brain, and discussed the mechanisms of rapamyicin against apoptosis by inhibiting activation of mTOR pathway in Cd-induced mouse brain tissues. This study is aimed at providing theoretical foundation and scientific guidance for Rapa prevention of Cd-induced neurodegenerative diseases. The results were summarized as follows:1Rapamycin exerts protection against apoptosis by inhibiting neuronal oxidative stress in Cd-induced mouse brainThirty-six healthy adult ICR male mice were chosen and randomly divided into a control group (treatment with0.9%physiological saline), a Rapa treatment group (7.5mg/kg body weight), two CdCl2treatment groups (0.5or1mg/kg body weight, respectively), and two Rapa/CdCl2treatment groups(7.5/0.5or7.5/1mg/kg body weight, respectively). The experimental drugs were administered by intraperitoneal injection for11d. Changes of brain histology and ultrastructure were observed by HE staining and TEM, respectively. ROS, GSH and CAT levels were assayed by biochemistry analysis in brain tissues. Neuronal apoptosis in brain were evaluated using TUNEL staining. The results showed that there existed an apparent confusion in Cerebral temporal lobe cortex of Cd-exposed mice, and loose arrangement was seen in hippocampus cells. In the neurons from Cd-treated brain, there were some mitochondria with distinct swelling and cristae disruption. However, Rapa significantly attenuated and protected from the events. Cd elicited increase of ROS level as well as decreases of GSH content and CAT activity, which was obviously ameliorated by Rapa. The increased number of TUNEL-positive cells was also significantly inhibited by Rapa in cerebral cortex and hippocampus of Cd-exposed mice. The findings suggest that Rapa may exert protection against apoptosis by inhibiting neuronal oxidative stress in Cd-induced mouse brain. 2Rapamyicin exerts protection against apoptosis by inhibiting activation of mTOR pathway in Cd-induced mouse brain tissuesThirty-six healthy adult ICR male mice were chosen and randomly divided into a control group (treatment with0.9%physiological saline), a Rapa treatment group (7.5mg/kg body weight), two CdCl2treatment groups (0.5or1mg/kg body weight, respectively), and two Rapa/CdCl2treatment groups(7.5/0.5or7.5/1mg/kg body weight, respectively). The experimental drugs were administered by intraperitoneal injection for11d. Expression of4E-BP1phosphorylaiton was assayed using immunohistochemistry, and expressions of Akt, S6K1,4E-BP1and caspase-3proteins were detected using Western blotting. The results for immunohistochemistry showed that the number of phospho-4E-BP1(Thr70)-positive cells significantly increased in the cerebral cortex and hippocampus CA1region of Cd-exposed mice, and Western blot analysis exhibited that Cd significantly induced increased phosphorylations of Akt, mTOR-mediated S6K1,4E-BP1, as well as elevated expression of cleaved-caspase-3in the brain, which was profoundly inhibited by Rapa. These data suggest that Rapa may exert protection against apoptosis by inhibiting activation of mTOR pathway in Cd-induced mouse brain tissues.