Salt and Nitric Oxide Inhibition Induced Hypertension: The Role of Prostacycline and 8-Isoprostane

2,3,7,8-Tetrachlorodibenzo-p-dioxin-induced hypertension

Objective:

The purpose of the present study was to evaluate the effects of melatonin on biochemical and cardiovascular changes resulting from exposure to 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD), a polychlorinated dibenzo- para-dioxin.

Methods:

A total of 24 Sprague-Dawley rats were divided equally into the following four groups: (1) control group was administered with 0.5 mL corn oil by gavage and 0.5 cc vehicle of melatonin (proportionally nine parts physiological serum + one part ethyl alcohol) intraperitoneally for 4 weeks, (2) the melatonin group was given 5 mg/kg/day melatonin intraperitoneally for 4 weeks, (3) the TCDD group was given 500 ng/kg/day TCDD by gavage for 4 weeks and (4) the TCDD + melatonin group was given TCDD (500 ng/kg/day) by gavage and melatonin (5 mg/kg/day) intraperitoneally simultaneously for 4 weeks. Systolic blood pressure was evaluated by the tail-cuff method. Vascular responses to phenylephrine and acetylcholine were evaluated in the isolated thoracic aortas.

Results:

TCDD not only augmented the systolic blood pressure but also increased the contractile responses to phenylephrine in aorta. Melatonin reversed the blood pressure augmented by TCDD and decreased the contractile responses to phenylephrine in aorta. TCDD induced an increase in the malondialdehyde levels in kidney tissue and melatonin did not change it. Therefore, TCDD caused a decrease in glutathione levels in kidney tissues and melatonin reversed it.

Conclusion:

Present data demonstrated that TCDD may lead to an increase in blood pressure via increased renal oxidative stress and vascular reactivity. However, melatonin might ameliorate the blood pressure disturbed by TCDD in part by decreasing the oxidant activity induced by TCDD.

Novel concepts in the genesis of hypertension: role of LOX-1

Hypertension is a common disease and a potent risk factor for cardiovascular disease. Tremendous strides have been made in understanding its genesis in the last 2 decades. Hypertension is often clustered with other cardiovascular risk factors, such as dyslipidemia and diabetes. The state of hypertension is often associated with increased vascular oxidative stress. Oxidative stress promotes proliferation and hypertrophy of vascular smooth muscle cell and collagen deposition, leading to thickening of the vascular media and narrowing of the vascular lumen. Oxidative stress also injures endothelium, impairs endothelium-dependent vascular relaxation and increases vascular contractile activity. Further, oxidative stress also oxidizes LDL-cholesterol. It has been shown that oxidized low-density lipoprotein (ox-LDL) activates renin-angiotensin system (RAS) and angiotensin II via its type 1 receptor activates ox-LDL receptor LOX-1. This mutually facilitative cross-talk between ox-LDL and RAS may be an important component in the development of hypertension. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is a receptor for ox-LDL. This review summarizes the role of LOX-1 in the pathogenesis of hypertension.

Assessment of lifestyle effect on oxidative stress biomarkers in free-living elderly in rural Japan

BACKGROUND

Oxidative stress is believed to play a crucial role in aging and age-related diseases, and is widely thought to increase morbidity and mortality in the elderly. Assessment of biomarkers of oxidative stress, such as 8-isoprostane and 8-hydroxy-2-deoxyguanosine, are considered to be useful in predicting disease risks at the population level.

OBJECTIVE

The aim of the present study was to assess the health status of the elderly by comparing their lifestyles and levels of oxidative stress biomarkers.

METHODS

We carried out a cross-sectional study where urine samples from a total of 100 elderly men and women were assayed for 8-isoprostane, 8-hydroxy-2-deoxyguanosine, selenium, cadmium and creatinine. They were asked to answer a questionnaire that included questions about their lifestyle.

RESULTS

Most of the participants were prehypertensive, non-alcohol users and on a rich plant-based diet. There were no differences in any biomarkers of oxidative stress between men and women. 8-Isoprostane was found to correlate positively with systolic blood pressure in women, but not in men. There was a slight increase of 8-isoprostane in participants with a poor intake of vegetables, and a decrease of 8-hydroxy-2-deoxyguanosine in participants who consumed fish. Multiple regression analysis showed that oxidative stress biomarkers were positively associated with cadmium, and negatively associated with selenium and fish intake in all participants, 89% of which were non-smokers.

CONCLUSION

Results from the present study show that fish intake has the potential of decreasing oxidative stress among elderly persons.