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. 2022 Oct 21;12(1):17633.
doi: 10.1038/s41598-022-21107-5.

Epigallocatechin gallate (EGCG) alleviates vascular dysfunction in angiotensin II-infused hypertensive mice by modulating oxidative stress and eNOS

Nurul Aiza Mohd Sabri  1 , Siew-Keah Lee  1 , Dharmani Devi Murugan  2 , Wei Chih Ling  3
Affiliations

Epigallocatechin gallate (EGCG) alleviates vascular dysfunction in angiotensin II-infused hypertensive mice by modulating oxidative stress and eNOS

Nurul Aiza Mohd Sabri et al. Sci Rep. .

Abstract

Epigallocatechin gallate (EGCG) has been shown to have antihypertensive activity. However, the role of epigallocatechin gallate (EGCG) in improving vascular function via modulation of endothelial nitric oxide synthase (eNOS) in hypertensive subjects is not well researched. Angiotensin II-infused hypertensive mice (8-10 weeks old) received EGCG (50 mg/kg/day) for 14 days via oral gavage. The arterial systolic blood pressure (SBP) was measured using the tail-cuff method every three days. At the end of the treatment, the vascular reactivity of the isolated aortae was studied using wire myographs. The level of nitric oxide (NO), cyclic guanosine monophosphate (cGMP) and tetrahydrobiopterine (BH4) were determined using assay kits while the presence of proteins (NOS, p-eNOS and NOx-2) were determined using by Western blotting. In vivo treatment with EGCG for 14 days significantly attenuated the increase in SBP, alleviated the vascular dysfunction, increased the vascular cGMP and BH4 level as well as the expression of p-eNOS and decreased elevated ROS level and NOx-2 protein in angiotensin II-infused hypertensive mice. Collectively, treatment with EGCG in hypertensive mice exerts a blood pressure lowering effect which is partly attributed to the improvement in the vascular function due to its ability to reduce vascular oxidative stress in the aortic tissue leading to a decrease in eNOS uncoupling thus increasing NO bioavailability.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
The average systolic blood pressure (SBP) in control and angiotensin (Ang) II-infused hypertensive mice with and without in vivo treatment with epigallocatechin gallate (EGCG). Data are expressed as means ± SEM (n = 6–7). *p ≤ 0.05 Ang II—vehicle compared to control—vehicle; †p ≤ 0.05 Ang II—vehicle compared to Ang II—vehicle; #p ≤ 0.05 Ang II—vehicle compared to control—vehicle.
Figure 2
Figure 2
Relaxation to increasing concentration of acetylcholine (ACh) and sodium nitroprusside (SNP) in aortic rings of control and angiotensin (Ang) II-infused hypertensive C57BL/6J mice. (A) Representative traces of acetylcholine-induced relaxation in phenylephrine (PE)-contracted aortic rings of all experimental groups. (B) Relaxation curves and (C) area under the curve for percentage of relaxation in aortic rings of control and angiotensin II-infused hypertensive mice, with and without in vivo treatment with epigallocatechin gallate (EGCG) to ACh. (D) Relaxation curves and (E) area under the curve to SNP of all experimental groups. Data are expressed as means ± SEM (n = 5–6). *p ≤ 0.05 compared to control—vehicle; †p ≤ 0.05 compared to Ang II—vehicle.
Figure 3
Figure 3
Plasma nitrite level (A) and vascular NO level (B) of control and angiotensin (Ang) II-infused hypertensive C57BL/6J mice, with or without in vivo treatment with epigallocatechin gallate (EGCG) measured using commercially available kit and DAF-FM staining, respectively. The upper panel shows representative fluorescence images of the stained aortae and the bottom panel shows the quantified fluorescence intensity (B). Data are expressed as means Data are expressed as means ± SEM (n = 5–6). *p ≤ 0.05 compared to control—vehicle; †p ≤ 0.05 compared to Ang II—vehicle.
Figure 4
Figure 4
Vascular BH4 (A) and vascular cGMP (B) levels measured using commercially available ELISA kits and the presence of total phosphorylated eNOS (p-eNOS) at ser1177 (C) detected by Western blotting in the aortic tissues of control and angiotensin (Ang) II-infused hypertensive C57BL/6J mice, with and without in vivo treatment with epigallocatechin gallate (EGCG). The upper panel shows representative Western blots and the bottom panel shows the ratio of protein to eNOS (C). Data are expressed as means ± SEM (n = 5–6). *p ≤ 0.05 compared to control—vehicle; †p ≤ 0.05 compared to Ang II—vehicle.
Figure 5
Figure 5
Vascular ROS level (A) and the presence of Nox-2 protein (B) in aortic tissue of control and angiotensin (Ang) II-infused hypertensive C57BL/6J mice with and without in vivo treatment with epigallocatechin gallate (EGCG) measured by DHE fluorescence. The upper panel shows representative fluorescence images of the stained aortae and the bottom panel shows the quantified fluorescence intensity (A). The upper panel shows representative Western blots and the bottom panel shows the ratio of protein to β-actin (B). Data are expressed as means ± SEM (n = 5–6). *p ≤ 0.05 compared to control–vehicle; †p ≤ 0.05 compared to Ang II—vehicle.
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