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Specific vanilloid responses in C6 rat glioma cells
1Molecular Mechanisms of Tumor Promotion Section, Laboratory of Cellular Carcinogenesis and Tumor Promotion, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Brain Research. Molecular Brain Research
|May 29, 1998
Summary
Rat C6 glioma cells respond to capsaicin and resiniferatoxin (RTX) via C-type vanilloid receptors, influencing cell proliferation and differentiation. Capsazepine acts as an agonist in long-term effects, suggesting distinct mechanisms and impacting vanilloid pathways.
Area of Science:
- Neuroscience
- Cell Biology
- Pharmacology
Background:
- Capsaicin and resiniferatoxin (RTX) are known activators of vanilloid receptors on sensory neurons.
- The presence and function of vanilloid receptors in non-neuronal cells like glioma cells are less understood.
- Understanding vanilloid receptor subtypes (C-type vs. R-type) is crucial for their targeted therapeutic applications.
Purpose of the Study:
- To investigate the specific vanilloid receptor responses in rat C6 glioma cells.
- To characterize the effects of capsaicin and RTX on C6 cell calcium uptake, proliferation, and differentiation.
- To explore the distinct mechanisms of short-term and long-term vanilloid actions and the role of capsazepine.
Main Methods:
- Measurement of 45Ca uptake in C6 cells stimulated with capsaicin and RTX.
- Antagonist studies using capsazepine and ruthenium red to identify receptor types.
- Assessment of cell proliferation, differentiation, and apoptosis following vanilloid treatment.
- Investigation of [3H]RTX binding to C6 cells.
Main Results:
- C6 cells exhibited capsaicin- and RTX-induced 45Ca uptake, similar to dorsal root ganglion neurons (DRGs), and showed desensitization.
- The response profile suggests the presence of C-type vanilloid receptors but not R-type receptors in C6 cells, as [3H]RTX binding was undetectable.
- Long-term exposure to capsaicin inhibited proliferation, altered differentiation, and induced apoptosis, while RTX had no such effect.
- Capsazepine acted as an agonist in long-term experiments, with higher potency than capsaicin, indicating a distinct mechanism.
Conclusions:
- Rat C6 glioma cells possess functional C-type vanilloid receptors mediating calcium influx and desensitization.
- The differential long-term effects of capsaicin and RTX, and the agonist role of capsazepine, point to distinct signaling pathways.
- These findings necessitate a reevaluation of in vivo vanilloid response pathways and highlight the significance of the neuron-glial network.