title: Thimerosal-induced apoptosis in mouse C2C12 myoblast cells occurs through suppression of the PI3K/Akt/survivin pathway.
abstract: BACKGROUND
  Thimerosal, a mercury-containing preservative, is one of the most widely used preservatives and found in a variety of biological products. Concerns over its possible toxicity have reemerged recently due to its use in vaccines. Thimerosal has also been reported to be markedly cytotoxic to neural tissue. However, little is known regarding thimerosal-induced toxicity in muscle tissue. Therefore, we investigated the cytotoxic effect of thimerosal and its possible mechanisms on mouse C2C12 myoblast cells.
  
  
  RESULTS
  The study showed that C2C12 myoblast cells underwent inhibition of proliferation and apoptosis after exposure to thimerosal (125-500 nM) for 24, 48 and 72 h. Thimerosal caused S phase arrest and induced apoptosis as assessed by flow cytometric analysis, Hoechst staining and immunoblotting. The data revealed that thimerosal could trigger the leakage of cytochrome c from mitochondria, followed by cleavage of caspase-9 and caspase-3, and that an inhibitor of caspase could suppress thimerosal-induced apoptosis. Thimerosal inhibited the phosphorylation of Akt(ser473) and survivin expression. Wortmannin, a PI3K inhibitor, inhibited Akt activity and decreased survivin expression, resulting in increased thimerosal-induced apoptosis in C2C12 cells, while the activation of PI3K/Akt pathway by mIGF-I (50 ng/ml) increased the expression of survivin and attenuated apoptosis. Furthermore, the inhibition of survivin expression by siRNA enhanced thimerosal-induced cell apoptosis, while overexpression of survivin prevented thimerosal-induced apoptosis. Taken together, the data show that the PI3K/Akt/survivin pathway plays an important role in the thimerosal-induced apoptosis in C2C12 cells.
  
  
  CONCLUSIONS
  Our results suggest that in C2C12 myoblast cells, thimerosal induces S phase arrest and finally causes apoptosis via inhibition of PI3K/Akt/survivin signaling followed by activation of the mitochondrial apoptotic pathway.
authors.affiliation: Department of Toxicology, Guangzhou Center for Disease Control and Prevention, Guangzhou, China.
authors.forename: Wen-Xue
authors.initials: WX
authors.lastname: Li
authors.forename: Si-Fan
authors.initials: SF
authors.lastname: Chen
authors.forename: Li-Ping
authors.initials: LP
authors.lastname: Chen
authors.forename: Guang-Yu
authors.initials: GY
authors.lastname: Yang
authors.forename: Jun-Tao
authors.initials: JT
authors.lastname: Li
authors.forename: Hua-Zhang
authors.initials: HZ
authors.lastname: Liu
authors.forename: Wei
authors.initials: W
authors.lastname: Zhu
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D053453:Caspase 9 / Q000235:genetics / Q000378:metabolism; D059447:Cell Cycle Checkpoints / Q000187:drug effects / Q000235:genetics; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D045304:Cytochromes c / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D051034:Inhibitor of Apoptosis Proteins / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D032446:Myoblasts / Q000187:drug effects* / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics* / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects / Q000235:genetics; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics* / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D016196:S Phase / Q000187:drug effects / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects* / Q000235:genetics; D000077022:Survivin; D013849:Thimerosal / Q000494:pharmacology*
chemical_list: D051017:Apoptosis Regulatory Proteins; C117749:Birc5 protein, mouse; D051034:Inhibitor of Apoptosis Proteins; D012097:Repressor Proteins; D000077022:Survivin; D013849:Thimerosal; D045304:Cytochromes c; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D053148:Caspase 3; D053453:Caspase 9