Name: NATHALIE TRISTÃO BANHOS DELGADO DE LIMA
Publication date: 02/08/2021
Advisor:
Name |
Role |
|---|---|
| NAZARE SOUZA BISSOLI | Co-advisor * |
| ROGER LYRIO DOS SANTOS | Advisor * |
Examining board:
| Name |
Role |
|---|---|
| CARMEM LUIZA SARTORIO | Internal Examiner * |
| JONES BERNARDES GRACELI | Internal Examiner * |
| ROGER LYRIO DOS SANTOS | Advisor * |
Summary: Introduction: The protective effect of oestrogen on the vasculature cannot be explained only by its action through the receptors ERα and ERβ. G protein-coupled oestrogen receptors (GPER) which are widely distributed throughout the cardiovascular system may also be involved in this response. However, little is known about the actions of GPER on this system, especially in pathological situations such as hypertension. Therefore, in this study we evaluated the vascular response mediated by GPER using a specific agonist, G-1, in spontaneously hypertensive rats (SHR). We hypothesized that G-1 would induce a relaxing response in resistance mesenteric arteries from SHR of both sexes.
Methods: This study was approved by the Ethics Committee of the Federal University of Espirito Santo (nº 048/2016). Concentration-response curves with G-1 (1 nM-10 μM) were performed in SHR (10 -12 weeks old) mesenteric arteries of both sexes before and after endothelial removal or incubation with nitric oxide synthase (NOS) inhibitors (Nω-nitro-L -arginine methyl ester - L-NAME 300 μM), cyclooxygenase (COX) (Indomethacin, INDO - 10 μM) alone or conjugated with a nonspecific cytochrome P450 (CYP) inhibitor (Clotrimazole, CLOT - 0.75 μM) or a degrader of hydrogen peroxide (H2O2) (Catalase, CAT - 1000 units / mL). We also evaluated the effect of nonspecific blockade of K+ channels (Tetraethylammonium, TEA - 5 mM). GPER immunolocalization was also investigated, and vascular hydrogen peroxide (H2O2) and EROs were evaluated using dichlorofluorescein (DCF, 10 μM) and dihydroethidium (DHE, 5 μM) staining, respectively. We also analyzed the concentration curve for acetylcholine (ACh, 0.1 nM - 10 μM) and phenylephrine (PE, 1 nM - 100 μM) after incubations with 0.1 and 10 μM of G-1. Finally, we evaluated weight and hemodynamic parameters, as well as reactivity to bradykinin (BK, 0.1 nM - 10 μM) and PE (1 nM - 100 μM) after treatment for 15 days with G36 (160 μg/Kg/day) in SHR females.
Results: GPER activation promoted a similar relaxation response between SHR males and females, but with the participation of different endothelial mediators. In males relaxation seems to be more dependent on the NO pathway, followed by the H2O2 pathway, while in females the endothelium and H2O2 pathway. Although relaxation was similar between sexes, the fluorescence intensity for GPER was
higher in females. G-1 was able to stimulate the production of only H2O2 in both sexes. The presence of 0.1 μM G-1 improved the ACh-induced relaxation response and reduced the PE-induced vasoconstrictor response only in females. Treatment with G36 did not change weight, hemodynamic and vascular reactivity parameters.
Conclusion: These findings show that the GPER agonist, G-1, can induce a relaxing response in mesenteric arteries from hypertensive rats of both sexes in a similar way, albeit with differential participation of endothelial mediators. Furthermore, GPER activation modulates vasodilator and vasoconstrictor agonist responses. Subchronic treatment with G36 did not change hemodynamic parameters and vascular reactivity in SHR females. These results contribute to the understanding of GPER activation on resistance mesenteric arteries in essential hypertension.
