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The mitogen-activated protein kinase pathway contributes to vanadate toxicity in vascular smooth muscle cells
G Daum1, B Levkau, N L Chamberlain
1Department of Surgery, University of Washington, Seattle 98195, USA.
Abstract:
Vanadate has been considered in the treatment of diabetes because of its insulin-like effects. However, it has severe toxic effects in both animal and man. In cultured cells, vanadate can either cause death or be growth stimulatory, depending on the cell type and growth conditions. Here, we report that in baboon aortic smooth muscle cells (SMCs), vanadate induced p42/p44 mitogen-activated protein kinase (MAPK) activity. This effect was abolished in the presence of the specific MAPK kinase (MAPKK) inhibitor PD098059. Although activation of p42/p44MAPK/MAPKK is generally thought to be necessary for proliferation, in SMCs, vanadate did not promote DNA synthesis and inhibited thymidine incorporation stimulated by platelet-derived growth factor (PDGF)-BB in a dose dependent fashion (IC50: 30 microM). Prolonged exposure to vanadate exerted cytotoxic effects. Cells retracted, rounded up and detached from the substratum. These vanadate-induced morphological changes were blocked in the presence of PD098059. The addition of PDGF-BB further activated p42/p44MAPK/MAPKK in the presence of vanadate and substantially increased vanadate toxicity. We conclude from these observations that activation of the p42/p44MAPK/MAPKK signalling module contributes to the cytotoxic effects induced by vanadate.
Insights
Vanadate, explored for diabetes treatment, activates a key cell signaling pathway (MAPK/MAPKK) in smooth muscle cells. This activation, however, leads to cell death rather than growth, highlighting vanadate
Area of Science:
- Cell Biology
- Biochemistry
- Pharmacology
Background:
- Vanadate exhibits insulin-like effects, making it a candidate for diabetes treatment.
- However, vanadate possesses significant toxic effects in various biological systems.
- Cellular responses to vanadate vary, ranging from growth promotion to cell death.
Purpose of the Study:
- To investigate the effects of vanadate on baboon aortic smooth muscle cells (SMCs).
- To elucidate the role of mitogen-activated protein kinase (MAPK) signaling in vanadate's cellular actions.
- To determine if vanadate's effects on SMCs are cytotoxic or proliferative.
Main Methods:
- Treatment of baboon aortic SMCs with vanadate.
- Assessment of p42/p44 MAPK activity using specific inhibitors (PD098059).
- Measurement of DNA synthesis and thymidine incorporation.
- Evaluation of cell morphology and viability under various conditions, including PDGF-BB stimulation.
Main Results:
- Vanadate induced p42/p44 MAPK/MAPKK activation in SMCs, which was blocked by PD098059.
- Vanadate inhibited DNA synthesis and thymidine incorporation stimulated by PDGF-BB.
- Prolonged vanadate exposure resulted in cytotoxic effects, including cell retraction, rounding, and detachment.
- PDGF-BB enhanced vanadate-induced MAPK activation and increased vanadate toxicity.
Conclusions:
- Activation of the p42/p44 MAPK/MAPKK signaling pathway contributes to vanadate-induced cytotoxicity in SMCs.
- Vanadate's effects on SMCs are primarily cytotoxic, not proliferative, despite MAPK activation.
- The findings suggest that vanadate's toxicity mechanism involves this specific signaling cascade.