Doxorubicin alters G-protein coupled receptor-mediated vasocontraction in rat coronary arteries.

Doxorubicin (Doxo)-associated cardio-and vasotoxicity has been recognised as a serious complication of cancer chemotherapy. The purpose of this novel paper was to determine the effect of Doxo on G-protein coupled receptor (GPCR)-mediated vasocontraction located on vascular smooth muscle cells. Rat left anterior descending artery segments were incubated for 24 h with 0.5 µM Doxo. The vasocontractile responses by activation of endothelin receptor type A (ET A ) and type B (ET B ), serotonin receptor 1B (5-HT 1B ) and thromboxane A2 prostanoid receptor (TP) were investigated by a sensitive myography using specific agonists, while the specificity of the GPCR agonists was verified by applying selective antagonists (i.e. ET A and ET B agonist = 10 - 14 -10 - 7.5 M endothelin-1 (ET-1); ET A antagonist = 10 µM BQ123; ET B agonists = 10 - 14 -10 - 7.5 M sarafotoxin 6c (S6c) and ET-1; ET B antagonist = 0.1 µM BQ788; 5-HT 1B agonist = 10 - 12 -10 - 5.5 M 5-carboxamidotryptamine (5-CT); 5-HT 1B antagonist = 1 µM GR55562; TP agonist = 10 - 12 -10 - 6.5 M U46619; TP antagonist = 1 µM Seratrodast). Our results show that 0.5 µM Doxo incubation of LAD segments leads to an increased VSMC vasocontraction through the ET B , 5-HT 1B and TP GPCRs, with a 2.2-fold increase in ET B -mediated vasocontraction at 10 - 10.5 M S6c, a 2.0-fold increase in 5-HT 1B -mediated vasocontraction at 10 - 5.5 M 5-CT, and a 1.3-fold increase in TP-mediated vasocontraction at 10 - 6.5 M U46619. Further studies unravelling the involvement of intracellular GPCR signalling pathways will broaden our understanding of the Doxo-induced vasotoxicity, and thus pave the way to mitigate the adverse effects by potential implementation of adjunct therapy options.