In vitro genotoxicity study of silver nanoparticles and titanium dioxide nanoparticles.

Nanoparticles are widely used in cosmetic, pharmaceutical, and food industries, but their safety and genetic toxicity are still unclear. In this study, the genotoxicity of silver nanoparticles (AgNPs) and titanium dioxide nanoparticles (titanium dioxide nanoparticles) were evaluated by in vitro comet assay and PIG-A assay in TK6 cells. We exposed TK6 cells to two types of nanoparticles at the highest concentration of 200 µmol/L for 4 h and conducted the in vitro comet assay. We examined the mutation results of PIG-A gene in vitro after 4 h, 24 ho and 10 days of exposure, respectively. We also examined the endocytosis of nanoparticles in TK6 cells exposed to nanoparticles for 24 h. In the endocytosis assay, with the increase of nano-material concentration, the side scatter (SSC) of TK6 cells in flow cytometry showed a concentration-dependent and time-dependent increase, indicating that TK6 cells could uptake both types of nanoparticles. In the comet assay, AgNPs could induce a concentration-dependent increase in DNA tail intensity. However, titanium dioxide NPs could not induce the concentration-dependent increase of DNA fluorescence intensity of comet tail. In the PIG-A assay, both AgNPs and TiO2NPs did not induce PIG-A gene mutation frequency in TK6 cells. The results showed that AgNPs could induce DNA damage in TK6 cells, but could not induce increase of PIG-A gene mutation frequency. TiO2NPs neither induce DNA damage in TK6 cells nor increase PIG-A mutation frequency. Further tests are needed to determine whether TiO2NPs are genotoxic.

Schisandrin B protects PC12 cells against oxidative stress of neurodegenerative diseases.

Increasing evidence places Schisandrin B (Sch B) at an important position in nerve protection, indicating that Sch B might play a positive role in the therapy of neurodegenerative diseases. However, there is little information on it. Our studies showed that pretreatment with Sch B could reduce lactate dehydrogenase, malondialdehyde, and reactive oxygen species release and significantly increase the cell viability and the superoxide dismutase level. Sch B (10 µM) markedly inhibited cell apoptosis, whereas LY294002 (20 µM), a phosphatidylinositol-3 kinase inhibitor, blocked the antiapoptotic effect. More importantly, Sch B (10 µM) increased the phosphoprotein kinase B/protein kinase B (Akt) and B-cell lymphoma-2/Bcl-2 associated X protein ratios on preincubation with cells for 2 h, which was then inhibited by LY294002 (20 µM). Results indicate that Sch B can protect PC12 cells from apoptosis by activating the phosphatidylinositol-3 kinase/Akt signaling pathway and may emerge as a potential drug for neurodegenerative diseases.

[Effect of Schisandra chinensis lignans on neuronal apoptosis and p-AKT expression of rats in cerebral ischemia injury model].

OBJECTIVE: To observe the effect of Schisandra chinensis lignans (SCL) on neuronal apoptosis and PI3K/AKT signaling pathway of rats in the cerebral ischemia injury model, and study its possible mechanism. METHOD: Rats were orally administered SCL high, middle and low dose groups (100, 50, 25 mg x kg(-1)) for 14 days. The cerebral ischemia injury model was established by using the suture-occluded method to rate the neurological functions. The cerebral infarction area was observed by TTC staining. The pathological changes in brain tissues were determined by HE staining. Bcl-2 and Bax expressions were detected by immunohistochemical assay. The protein expressions of p-AKT and AKT were assayed by Western blotting. RESULT: Compared with the model group, SCL high, middle and low dose groups showed reduction in the cerebral infarction area to varying degrees, improve the pathological changes in brain tissues, promote the expression of apoptin Bcl-2 and p-AKT, and inhibit the expression of apoptin Bax. CONCLUSION: SCL shows a protective effect on rats with cerebral ischemia injury. Its mechanism may be related to the increase in p-AKT ability and antiischemic brain injury capacity and the inhibition of nerve cells.

Induction of apoptosis by shikonin through a ROS/JNK-mediated process in Bcr/Abl-positive chronic myelogenous leukemia (CML) cells.

This study examined the signaling events induced by shikonin that lead to the induction of apoptosis in Bcr/Abl-positive chronic myelogenous leukemia (CML) cells (e.g., K562, LAMA84). Treatment of K562 cells with shikonin (e.g., 0.5 muM) resulted in profound induction of apoptosis accompanied by rapid generation of reactive oxygen species (ROS), striking activation of c-Jun-N-terminal kinase (JNK) and p38, marked release of the mitochondrial proteins cytochrome c and Smac/DIABLO, activation of caspase-9 and -3, and cleavage of PARP. Scavenging of ROS completely blocked all of the above-mentioned events (i.e., JNK and p38 phosphorylation, cytochrome c and Smac/DIABLO release, caspase and PARP cleavage, as well as the induction of apoptosis) following shikonin treatment. Inhibition of JNK and knock-down of JNK1 significantly attenuated cytochrome c release, caspase cleavage and apoptosis, but did not affect shikonin-mediated ROS production. Additionally, inhibition of caspase activation completely blocked shikonin-induced apoptosis, but did not appreciably modify shikonin-mediated cytochrome c release or ROS generation. Altogether, these findings demonstrate that shikonin-induced oxidative injury operates at a proximal point in apoptotic signaling cascades, and subsequently activates the stress-related JNK pathway, triggers mitochondrial dysfunction, cytochrome c release, and caspase activation, and leads to apoptosis. Our data also suggest that shikonin may be a promising agent for the treatment of CML, as a generator of ROS.