Coordinate depression of bradykinin receptor recycling and microtubule-dependent transport by taxol

Significant cardiovascular side effects have limited the use of taxol as an anticancer drug. A link between decreased plasma membrane dynamics and taxol has been implied because taxol can inhibit intracellular vesicle movements. Reduced membrane recycling caused by taxol could inhibit agonist-evoked Ca²⁺ signaling within endothelial cells, resulting in endothelium-dependent vasodilation. Bradykinin and ATP are two agonists that evoke Ca²⁺ transients in endothelial cells. Since the bradykinin receptor-agonist complex is internalized and recycled whereas the ATP agonist-receptor complex is not, we expected that a taxol inhibition of recycling would decrease bradykinin but not ATP receptor activity. We found that taxol depresses (i) the frequency (to 41% of control) and velocity (to 55% of control) of microtubule-dependent vesicle transport and (ii) bradykinin-evoked cytosolic Ca²⁺ transients (to 76% of control) in bovine aortic endothelial cells. In studying bradykinin receptor desensitization, which reflects receptor recycling, we demonstrate that taxol inhibits bradykinin-evoked Ca²⁺ transients by 50%. Taxol did not significantly alter ATP-evoked Ca²⁺ transients in either single-exposure or desensitization experiments. We suggest that taxol's reduction of bradykinin-evoked Ca₂₊ transients is due to altered microtubule-dependent membrane recycling. This report describes taxol's ability to alter plasma membrane composition through effects on vesicle transport and membrane trafficking pathways. This finding provides a possible mechanism by which taxol can substantially alter cardiovascular function.