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.