BS36 Investigating the G-protein coupled receptor mediated vasoconstriction and the effect of an MEK 1/2 inhibitor U0126 on coronary vessels treated with doxorubicin

Introduction Doxorubicin (Dox) is one of the most efficient chemotherapeutic drugs used for various cancers, however, therapy with doxorubicin is associated with severe cardiotoxicity. The effect of doxorubicin on the vasculature remains an uncharted research area. Vascular stress can lead to increased G-protein coupled receptor (GPCR) mediated vasoconstriction through binding of specific GPCR ligands, such as 5-hydroxytryptamine 1B (5-HT1B) receptor and thromboxane A2 (TXA2) receptor. The activation of those two receptors leads to the signalling through mitogen-activated extracellular signal-regulated kinase (MEK) / extracellular signal-regulated kinase (ERK) 1/2 pathway. This study used an arterial organ culture model to investigate the GPCR mediated vascular tone in Dox-treated coronary vessels with and without the MEK1/2 inhibitor U0126. Methods Coronary artery from rats were dissected into four groups: Vehicle, 0.5 µM Dox, 0.5µM Dox with 5µM U0126, and 5µM U0126. Dose-response curves of 5-HT1B receptor agonist 5-carboxamidotryptamine (5-CT) (10–12M to 10–5.5M) and TXA2 agonist U46619 (10–12M to 10–6.5M) were obtained by wire-myography after 24h of organ culture in DMEM ± 0.5 µM Dox ± 5 µM U0126. Furthermore, the 5-HT1B and TXA2 mRNA levels and their expression and localisation in coronary arteries were investigated by Real-Time PCR and Immunohistochemistry. Results Application of Dox altered the coronary arteries vasoconstriction through GPCRs 5-HT1B and TXA2, with a significant increase at specific doses of 5-HT1B (10–8M to 10–5.5M, p<0.05) and TXA2 (10–8M to 10–6.5M, p<0.05) compared to vehicle-treated arteries. Meanwhile, the molecular assessment revealed that both transcriptional and translational mechanisms were unaltered by incubation with Dox, suggesting the potential involvement of a post-translational mechanism or the alteration of a GPCR-activated protein. The co-administration of U0126 with Dox allowed the vascular tension to revert to the baseline level observed in vehicle-treated arteries (figures 1 and 2), without altering receptors mRNA levels or protein expression in arteries, which highlights that the MEK/ERK 1/2 pathway plays a key role during the doxorubicin-altered GPCRs-mediated vasoconstriction. Conclusion Overall, this study has improved the understanding of Dox-mediated cardiovascular adverse effects and the vascular- and intracellular-mechanisms involved. We show that Dox incubation of coronary vessels increases the 5-HT1B- and TXA2-mediated vasocontraction through involvement of the MEK/ERK 1/2 pathway. Increased vasoconstriction is associated with increased risk of developing cardiovascular diseases, thus highlighting the vasotoxic effect of Dox. Further studies unravelling the involvement of GPCRs pathways and mediators will broaden our understanding of the effect of Dox on the vascular tone, and the potential of the MEK1/2 inhibitor U0126 as potential adjuvant therapy. Conflict of Interest No conflict of interest