Therapeutic potential of a dietary phase 2 protein inducer in stroke-prone spontaneously hypertensive (SHRsp) rats.

摘要

Persistent hypertension is associated with a greater incidence of organ damage and conditions such as stroke, heart failure and end--stage kidney disease, which results in increased cardiovascular (CV) morbidity and mortality. Among the patients receiving antihypertensive treatment, the level of adequate blood pressure (BP) control (<140/90 mm Hg) is only 30%-50%. These antihypertensive drugs reduce the risk of CV events only by 20% and stroke by 40%, besides causing adverse effects.;We have previously shown that consumption of broccoli sprouts (BSp) decreased oxidative stress, inflammation and blood pressure in both male and female SHRsp. BSp contain sulforaphane glucosinolate (SGS), the precursor of the phase 2 protein inducer sulforaphane. BSp low in SGS did not have these effects. Furthermore, BSp did not have any measurable effects on the normal physiology of Sprague Dawley (SD) rats.;The objectives of this study were to determine: (1) the importance of a food matrix in causing these beneficial effects, i.e., can one get the same effects by administration of sulforaphane alone?, (2) whether dietary sulforaphane decreases the level of nitrosylated proteins in the kidneys of SHRsp, (3) whether dietary sulforaphane increases the phase 2 enzyme gamma-glutamyl-L-cysteine ligase expression (gamma-GCS ), (4) whether dietary sulforaphane increases the phase 2 enzyme glutathione reductase (GRed) expression, (5) whether dietary sulforaphane increases the phase 2 enzyme thioredoxin reductase (TrxR1) expression and (6) whether dietary sulforaphane protects renal artery structure.;After 1 week of adaptation, the 4 week old female SHRsp and SD rats were divided into four groups and administered daily by gavage: (i) Corn oil (vehicle) alone (Control); (ii) sulforaphane (5 mumol/kg body weight) in corn oil; (iii) sulforaphane (10 mumol/kg body weight) in corn oil; and (iv) sulforaphane (20 mumol/kg body weight) in corn oil. Systolic BP was determined weekly using a standard tail cuff noninvasive BP measurement system (model 29- SSP; Harvard Apparatus, St. Laurent, QC, Canada). The treatment lasted for 15 weeks. At the end of the treatment period, the animals were anesthetized with isoflurane (3%) and the BP was measured by the intra-arterial catheter method using a BP monitor (MK-2000 instrument; Muromachi Kikai Co., Ltd, Tokyo, Japan). Later, the animals were euthanized and perfused with normal saline, and tissues collected for histology, western blot, gene expression study or measurement of reduced glutathione (GSH).;The spontaneously hypertensive stroke-prone rat (SHRsp) is a good model of essential hypertension. It starts developing hypertension at 5-6 weeks of age which becomes established hypertension at 12-16 weeks. The SHRsp also develops oxidative stress (characterized by low glutathione levels) and inflammation.;The results of the study showed that chronic administration of sulforaphane in SHRsp significantly increased phase 2 proteins (i.e., significantly increased kidney gamma-GCS [0.93. +/- 0.07 arbitrary unit (AU)] when compared with SHRsp control [0.36 +/- 0.05(AU)] , decreased kidney nitrotyrosine (significantly lowered the levels of nitrotyrosine [0.917+/- 0.16 AU ] when compared with SHRsp control [1.37+/- 0.2 AU], protected the arterial structure of small resistance vessels in kidneys, and significantly attenuated the increase in blood pressure by 22-43 mm Hg by the end of the study. In conclusion, the results of this thesis demonstrate that: (i) A minimal change in our diet may have a major impact on our health, (ii) The beneficial health effects previously seen with consumption of BSp are due to the conversion of SGS to sulforaphane and (iii) Long term administration of sulforaphane in SHRsp attenuates the increase in BP and vascular alterations.