Ethyl Rosmarinate Prevents the Impairment of Vascular Function and Morphological Changes in L-NAME-Induced Hypertensive Rats

Abstract

Background and Objectives: The potent, endothelium-independent, vasorelaxant effect of ethyl rosmarinate, an ester derivative of rosmarinic acid, makes it of interest as an alternative therapeutic agent for use in hypertension. This study was designed to investigate the effect of ethyl rosmarinate on N^ω-nitro-L-arginine methyl ester (L-NAME)-induced hypertensive rats. Materials and Methods: L-NAME was given orally to male Wistar rats for 6 weeks to induce hypertension concurrently with treatment of ethyl rosmarinate at 5, 15, or 30 mg/kgor enalapril at 10 mg/kg Systolic blood pressure (SBP), heart rate, and body weight of all experimental groups were recorded weekly, while the vascular sensitivity and histological changes of the aorta were evaluated at the end of the experiment. Results: For all treatment groups, the data indicated that ethyl rosmarinate significantly attenuated the SBP in hypertensive rats induced by L-NAME, with no significant differences in heart rate and body weight. In addition, the response of vascular sensitivity to acetylcholine (ACh) was improved but there was no significant difference in the response to sodium nitroprusside (SNP). Furthermore, the sensitivity of the aorta to phenylephrine (PE) was significantly decreased. The thickness of the aortic wall did not differ between groups but the expression of endothelial nitric oxide synthase (eNOS) was increased in ethyl rosmarinate- and enalapril-treated groups compared with the hypertensive group. Conclusions: Ethyl rosmarinate is an interesting candidate as an alternative treatment for hypertension due to its ability to improve vascular function and to increase the expression of eNOS similar to enalapril which is a drug commonly used in hypertension.

Keywords: endothelial dysfunction; ethyl rosmarinate; hypertension; vascular function.

Figure 1

The alteration in (a) systolic blood pressure, (b) heart rate, and (c) body weight recorded weekly from the control group (CTRL), the control group plus 30 mg/ kg ethyl rosmarinate (CTRL + ER 30 mg/kg), hypertension group (HT), hypertension group plus 5, 15, or 30 mg/kg ethyl rosmarinate (HT + ER 5, 15, 30 mg/kg), and the hypertension group plus enalapril 10 mg/kg (HT + Enal 10 mg/kg). Data are expressed as mean ± SEM. *p < 0.05 vs. control group and ^#p < 0.05 vs. hypertension group.

Figure 1

The alteration in (a) systolic blood pressure, (b) heart rate, and (c) body weight recorded weekly from the control group (CTRL), the control group plus 30 mg/ kg ethyl rosmarinate (CTRL + ER 30 mg/kg), hypertension group (HT), hypertension group plus 5, 15, or 30 mg/kg ethyl rosmarinate (HT + ER 5, 15, 30 mg/kg), and the hypertension group plus enalapril 10 mg/kg (HT + Enal 10 mg/kg). Data are expressed as mean ± SEM. *p < 0.05 vs. control group and ^#p < 0.05 vs. hypertension group.

Figure 2

The cumulative concentration-response curves of acetylcholine (ACh) (10^−12.5–10⁻⁵ M) on vascular tone of isolated aortic rings from the control group (CTRL), the control group plus ethyl rosmarinate at 30 mg/kg (CTRL + ER 30 mg/kg), the hypertension group (HT), the hypertension group plus ethyl rosmarinate at 5, 15, or 30 mg/kg (HT + ER 5, 15, 30 mg/kg), and the hypertension group plus enalapril at 10 mg/kg (HT + Enal 10 mg/kg). The relaxations were expressed as the percentage decrease in pre-contraction with phenylephrine (PE). Data are expressed as mean ± SEM. *p < 0.05 vs. control group and ^#p < 0.05 vs. hypertension group.

Figure 3

The cumulative concentration-response curves of sodium nitroprusside (SNP) (10^−12.5–10⁻⁶ M) on vascular tone of isolated aortic rings from the control group (CTRL), the control group plus ethyl rosmarinate at 30 mg/kg (CTRL + ER 30 mg/kg), the hypertension group (HT), the hypertension group plus ethyl rosmarinate at 5, 15, or 30 mg/kg (HT + ER 5, 15, 30 mg/kg), and the hypertension group plus enalapril 10 mg/kg (HT + Enal 10 mg/kg). The relaxations were expressed as the percentage decrease in pre-contraction with PE. Data are expressed as mean ± SEM.

Figure 4

The cumulative concentration-response curves of PE (10^−9.5–10⁻⁵ M) on vascular tone of isolated aortic rings from the control group (CTRL), the control group plus ethyl rosmarinate at 30 mg/kg (CTRL + ER 30 mg/kg), the hypertension group (HT), the hypertension group plus ethyl rosmarinate at 5, 15, or 30 mg/kg (HT + ER 5, 15, 30 mg/kg), and the hypertension group plus enalapril 10 mg/kg (HT + Enal 10 mg/kg). Data are expressed as mean ± SEM of the percentage contractions induced by PE. *p < 0.05 vs. Control group.

Figure 5

Effect of ethyl rosmarinate on vascular thickening and the expression of endothelial nitric oxide synthase (eNOS) in endothelial cell cytoplasm represented as aortic staining with H&E and eNOS. (a) Arrows indicate positive staining of eNOS in endothelial cells. (b) The existing eNOS expression measured by immunohistochemistry represented as mean ± SEM. *p < 0.05 vs. control group and ^#p < 0.05 vs. hypertension group.

Figure 6

The cumulative concentration-response curves of ACh (10⁻¹⁰-10⁻⁵ M) on vascular tone of endothelium-intact aortic rings of the control group (CTRL), the ethyl rosmarinate 100 µM group (ER 100 µM), the L-NAME 100 µM group (L-NAME 100 µM), and the ethyl rosmarinate 100 µM plus L-NAME 100 µM group (ER + L-NAME). The data are expressed as the percentage decrease in pre-contraction with PE. *p < 0.05 vs. control group and ^#p < 0.05 vs. hypertension group.