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Selective antimitochondrial agents inhibit calmodulin
Abstract:
Certain cationic-lipophilic compounds are known to selectively accumulate in tumor mitochondria and inhibit energy production. Since these substances bear a structural resemblance to known inhibitors of calmodulin, we studied whether rhodamine-123 or a bis-4-aminoquinaldinium could antagonize the action of calmodulin. Rhodamine-123 (IC50 = 58 microM) and dequalinium (IC50 = 1 microM) inhibited the activity of a calmodulin-stimulated cyclic nucleotide phosphodiesterase. Propylinium, a compound similar to dequalinium except for having a 3 rather than 10 carbon alkyl bridge connecting two non-substituted quinoline rings, had no inhibitory effect. Kinetic analysis showed that dequalinium competitively inhibited calmodulin's activation of phosphodiesterase. We also studied the antiproliferative effects of the compounds on the C6 astrocytoma cell line. Rhodamine-123 and dequalinium inhibited the proliferation of this cell line while propylinium had no effect. These studies demonstrate that rhodamine-123 and dequalinium are calmodulin-antagonists and inhibit cellular proliferation.
Insights
Rhodamine-123 and dequalinium, compounds that accumulate in tumor mitochondria, act as calmodulin antagonists. They inhibit energy production and cell proliferation, offering potential therapeutic strategies.
Area of Science:
- Biochemistry
- Cell Biology
- Pharmacology
Background:
- Cationic-lipophilic compounds accumulate in tumor mitochondria, inhibiting energy production.
- Structural similarities exist between these compounds and known calmodulin inhibitors.
Purpose of the Study:
- To investigate if rhodamine-123 and dequalinium antagonize calmodulin activity.
- To evaluate the antiproliferative effects of these compounds on C6 astrocytoma cells.
Main Methods:
- Assessed inhibition of calmodulin-stimulated cyclic nucleotide phosphodiesterase.
- Performed kinetic analysis to determine the mechanism of inhibition.
- Studied antiproliferative effects on the C6 astrocytoma cell line.
Main Results:
- Rhodamine-123 (IC50 = 58 microM) and dequalinium (IC50 = 1 microM) inhibited phosphodiesterase activity.
- Dequalinium competitively inhibited calmodulin's activation of phosphodiesterase.
- Both rhodamine-123 and dequalinium inhibited C6 astrocytoma cell proliferation, while propylinium did not.
Conclusions:
- Rhodamine-123 and dequalinium function as calmodulin antagonists.
- These compounds inhibit cellular proliferation, suggesting potential anticancer applications.