Thallium acetate induces C6 glioma cell apoptosis
Chee-Fah Chia1, Soul-Chin Chen, Chin-Shyang Chen
1Department of Surgery, School of Medicine, Taipei Medical University and Hospital, 252 Wu-Hsing St., Taipei, Taiwan.
Abstract:
Thallium acetate is a known neurotoxic agent. In this study, we investigated the mechanisms by which thallium acetate induces cell cycle arrest and cell apoptosis in cultured LC6 glioma cells. Exposure of C6 glioma cells to thallium acetate decreased cell viability as demonstrated by the MTT assay. Incubation of thallium acetate arrested cell cycle progression at the G2/M phase and caused cellular apoptosis at 300 microM as determined by trypan blue exclusion and flow cytometric analysis. The G2/M arrest was associated with a decrease in expression of CDK2 protein and an upregulation of p53 and the CDK inhibitor p21(Cip1), but not p27(Kip1). Thallium acetate did not alter the protein levels of cyclin A and B; cyclin D1, D2, and D3; and CDK4 expression in C6 glioma cells. Incubation of C6 glioma cells with thallium acetate upregulated the expression of proapoptotic proteins Bad and Apaf and downregulated the expression of anti-apoptotic proteins Bcl-xL and Bcl-2. In conclusion, these data suggest that thallium acetate inhibits cell cycle progression at G2/M phase by suppressing CDK activity through the p53-mediated induction of the CDK inhibitor p21(Cip1). Impairment of cell cycle progression may trigger the activation of a mitochondrial pathway and shifts the balance in the Bcl-2 family toward the proapoptotic members, promoting the formation of the apoptosome and, consequently, apoptosis.
Insights
Thallium acetate causes cell death in glioma cells by halting cell cycle progression at G2/M phase. This neurotoxic agent promotes apoptosis through p53-mediated pathways and altered Bcl-2 family protein expression.
Area of Science:
- Neuroscience
- Molecular Biology
- Cell Biology
Background:
- Thallium acetate is recognized as a neurotoxic agent.
- Glioma cells are susceptible to toxic insults, necessitating research into their response mechanisms.
Purpose of the Study:
- To elucidate the molecular mechanisms underlying thallium acetate-induced cell cycle arrest and apoptosis in C6 glioma cells.
- To investigate the role of specific cell cycle regulators and apoptosis-related proteins in thallium acetate toxicity.
Main Methods:
- Cell viability was assessed using the MTT assay.
- Cell cycle progression and apoptosis were analyzed by trypan blue exclusion and flow cytometry.
- Protein expression levels of key cell cycle proteins (CDK2, p53, p21(Cip1), p27(Kip1), cyclins A, B, D1-D3, CDK4) and apoptosis-related proteins (Bad, Apaf, Bcl-xL, Bcl-2) were evaluated.
Main Results:
- Thallium acetate exposure reduced C6 glioma cell viability.
- A significant G2/M phase cell cycle arrest was observed at 300 microM thallium acetate.
- This arrest correlated with decreased CDK2 and increased p53 and p21(Cip1) expression, but not p27(Kip1).
- Thallium acetate modulated the Bcl-2 family proteins, upregulating pro-apoptotic (Bad, Apaf) and downregulating anti-apoptotic (Bcl-xL, Bcl-2) members.
- Protein levels of cyclins A, B, D1-D3, and CDK4 remained unaltered.
Conclusions:
- Thallium acetate induces G2/M cell cycle arrest in C6 glioma cells by suppressing CDK activity via p53-mediated p21(Cip1) induction.
- The observed cell cycle impairment may activate a mitochondrial apoptotic pathway.
- Thallium acetate promotes apoptosis by shifting the Bcl-2 family balance towards pro-apoptotic proteins, facilitating apoptosome formation.