Dietary approach to attenuate oxidative stress, hypertension, and inflammation in the cardiovascular system

Abstract

Imbalance between production and scavenging of superoxide anion results in hypertension by the inactivation of nitric oxide, and the increased oxidative stress from the resultant peroxynitrite that is produced promotes inflammatory processes such as atherosclerosis. Induction of phase 2 proteins promotes oxidant scavenging. We hypothesized that intake of dietary phase 2 protein inducers would ameliorate both hypertension and atherosclerotic changes in the spontaneously hypertensive stroke-prone rat. For 5 days/week for 14 weeks, we fed rats 200 mg/day of dried broccoli sprouts that contained glucoraphanin, which is metabolized into the phase 2 protein-inducer sulforaphane (Group A), sprouts in which most of the glucoraphanin was destroyed (Group B), or no sprouts (Group C). After 14 weeks of treatment, no significant differences were seen between rats in Groups B and C. Rats in Group A had significantly decreased oxidative stress in cardiovascular and kidney tissues, as shown by increased glutathione (GSH) content and decreased oxidized GSH, decreased protein nitrosylation, as well as increased GSH reductase and GSH peroxidase activities. Decreased oxidative stress correlated with better endothelial-dependent relaxation of the aorta and significantly lower (20 mm Hg) blood pressure. Tissues from Groups B and C had considerable numbers of infiltrating activated macrophages, indicative of inflammation, whereas animals in Group A had few detectable infiltrating macrophages. There is interest in dietary phase 2 protein inducers as means of reducing cancer incidence. We conclude that a diet containing phase 2 protein inducers also reduces the risk of developing cardiovascular problems of hypertension and atherosclerosis.

Figures

Fig. 1.

Effect of Grn+ and Grn- diets compared with CT on GSH and GSSG in cardiovascular and kidney tissues of 19-week-old SHRsp and SD rats, n = 3–4 rats per group. Grn+ diet had no effect compared with CT in SD rats (A and B). SHRsp-CT and SHRsp-Grn- had significantly lower levels of GSH (A and B). SHRsp-CT had significantly higher levels of GSSG (C) in tissues examined compared with SD rats. When placed on the Grn+ diet, SHRsp rats demonstrated significant increases in GSH levels in all tissues examined (A and B). A Grn+ diet also decreased GSSG levels significantly in cardiovascular and kidney tissues in SHRsp (C). *, P < 0.05, for SHPsp controls or SHRsp-Grn- versus SD-CT and SD-Grn+; †, P < 0.05, for SHRsp-Grn+ versus SHRsp-Grn-.

Fig. 2.

GPx and GRed activities in cardiovascular and kidney tissues of 19-week-old SHRsp and SD rats; n = 3–4 per group. GPx (A) and GRed (B) activities are significantly lower in all tissues examined in SHRsp on CT compared with SD rats on CT. SHRsp fed Grn+ diet had significantly increased GPx and GRed activities. *, P < 0.05, for SHRsp-CT versus SD-CT; †, P < 0.05, for SHPsp-Grn+ versus SHRsp-CT.

Fig. 3.

Representative micrographs demonstrating localization of activated macrophages (arrows indicate bright fluorescent cells) in the inner tissue linings of the aorta (A), carotid artery (B), and ventricle of the heart (C), as well as in the medulla of the kidney (D) in 19 week-old SHRsp on CT or Grn+ diet. Few such activated macrophages are present in tissues of animals on Grn+ diet.

Fig. 4.

Micrographs (A and B) and Western blot (C) showing the localization of activated NF-κB in SHRsp fed CT or Grn+ diet in heart ventricle (A) and kidney medulla (B and C) of 19-week-old animals. Positive nuclear NF-κB p65 signal was observed in ventricular endothelium and in the tubules of the kidney of SHRsp-CT with few positive cells seen in the SHRsp-Grn+ group. (C) Left shows a representative Western blot of nuclearly localized NF-κB p65 is shown on the left, whereas Right quantification of NF-κB p65 relative to β-actin (y axis depicts relative units). Data taken from kidney tissues of three animals per group. *, P < 0.05, for SHRsp-Grn+ versus SHRsp-CT.

Fig. 5.

Aortic-relaxation function in SD rats on CT; SD on Grn+ diet; and SHRsp on CT, Grn+ diet, and Grn- diet (n = 9 per group). Aortic rings were precontracted with phenylephrine, followed by administration of acetylcholine (ACh), and decrease in tension was measured. Diet had no effect on relaxation properties in SD rats. SHRsp-CT had significantly poorer relaxation responses to ACh than either of the SD groups. SHRsp-Grn+ had significantly better relaxation response to ACh than SHRsp-CT, whereas SHRsp-Grn- had an intermediate response. *, P < 0.001, for SHRsp-Grn- versus SD-CT and SD-Grn+. †, P < 0.001, for SHRsp-Grn+ versus SHRsp-CT.

Fig. 6.

Systolic blood pressures over time in SD on CT; SD on Grn+ diet; and SHRsp on CT, Grn+ diet, and Grn- diet (n = 9 per group). No change in blood pressure is seen in SD over the 14-week period after weaning. Blood pressures progressively rise in all SHRsp groups for the first 8 weeks on the postweaning diet and are significantly higher than in SD rats. From 8 to 10 weeks, blood pressures rise further in SHRsp-CT and SHR-Grn- and then plateau. From 10 weeks of the dietary intervention onwards, blood pressure is significantly lower in SHRsp-Grn+ than in the two other SHRsp dietary groups. *, P < 0.05, for SD diet groups versus SHRsp diet groups; †, P < 0.05, for SHRsp-Grn+ vs. SHRsp-CT and SHRsp-Grn-.