Systemic administration of lipopolysaccharide upregulates angiotensin II expression in rat renal tubules: immunohistochemical and ELISA studies

Angiotensin-converting enzyme 2 overexpression protects against doxorubicin-induced cardiomyopathy by multiple mechanisms in rats

Angiotensin-converting enzyme 2 (ACE2) is considered a potential therapeutic target of the renin-angiotensin system (RAS) for the treatment of cardiovascular diseases. We aimed to explore the effects of ACE2 overexpression on doxorubicin-induced cardiomyopathy in rats. Rats were randomly divided into treatment and control groups. The rats of treatment group were injected intraperitoneally with 6 doses of doxorubicin (2.5 mg/kg) within a period of two weeks. Two weeks after the initial injection of doxorubicin, these rats were randomly divided into Mock, Ad-EGFP, Ad-ACE2, and Cilazapril groups. The rats of Ad-EGFP and Ad-ACE2 groups received intramyocardial injection of Ad-EGFP and Ad-ACE2, respectively. The rats of Cilazapril group received cilazapril (10 mg/kg/day) via intragastric intubation. Apoptosis, inflammation, oxidative stress, cardiac function, the extent of myocardial fibrosis, and levels of ACE2, ACE, angiotensin II (AngII), and angiotensin (1–7) were evaluated. Four weeks after ACE2 gene transfer, the Ad-ACE2 group showed not only reduced apoptosis, inflammatory response, oxidative stress, left ventricular (LV) volume, extent of myocardial fibrosis and mortality of rats, but also increased LV ejection fraction and ACE2 expression level compared with the Mock and Ad-EGFP groups. ACE2 overexpression was superior to cilazapril in improving doxorubicin-induced cardiomyopathy. The putative mechanisms may involve activation of the AMPK and PI3K-AKT pathways, inhibition of the ERK pathway, decrease of TGF-β1 expression, and interactions of shifting RAS components, such as decreased myocardium AngII levels, increased myocardium Ang (1–7) levels, and reduced ACE expression. Thus, ACE2 may be a novel therapeutic approach to prevent and treat doxorubicin-induced cardiomyopathy.

Peroxisome proliferator-activated receptor-alpha activator fenofibrate prevents high-fat diet-induced renal lipotoxicity in spontaneously hypertensive rats

We investigated the effects of a high-fat (HF) diet and peroxisome proliferator-activated receptor (PPAR)-alpha activation on the intrarenal lipotoxicity associated with the renin-angiotensin system (RAS) and oxidative stress using spontaneously hypertensive (SHR) rats. Male SHR and Wistar-Kyoto (WKY) rats at 8 weeks of age were fed either a normal-fat diet or an HF diet without or with fenofibrate treatment for 12 weeks. Severe intrarenal lipid accumulation was noted in the SHR rats fed an HF diet than in WYK rats fed an HF diet (P<0.05). This lipid accumulation was associated with a 70% decrease in renal PPARalpha expression in SHR rats, whereas an HF diet increased the expression of PPARalpha in WKY rats by threefold. An HF diet also activated intrarenal, not systemic, RAS and induced oxidative stress associated with reduced nitric oxide (NO) bioavailability. By contrast, fenofibrate attenuated weight gain, fat mass and insulin resistance. Fenofibrate recovered HF diet-induced decreases in intrarenal PPARalpha expression and fat accumulation, and abolished intrarenal RAS activation and oxidative stress in SHR-HF animals (P<0.01). These activities conferred protection against increased blood pressure (BP), glomerulosclerosis and renal inflammation. Intrarenal free fatty acid and triglyceride concentrations were positively correlated with angiotensin II (gamma=0.63, 0.36) and 24-h urinary 8-hydroxy-deoxyguanosine (gamma=0.36, 0.39), and negatively correlated with PPARalpha contents (gamma=-0.47, -0.44; P<0.05). An HF diet-induced lipotoxicity by depletion of intrarenal PPARalpha aggravated BP and renal inflammation as a result of intrarenal RAS activation and oxidative stress. Therefore, intervention with PPARalpha activators can effectively prevent diet-induced renal lipotoxicity in hypertensive rats.

Effects of maternal undernutrition on renal angiotensin II and chymase in hypertensive offspring

Intrauterine growth restriction (IUGR) can program the future development of hypertension in adulthood. The renin-angiotensin system has been reported to play a role in IUGR-induced hypertension. The aims of this study were to investigate the effects of IUGR on renal angiotensin-converting enzyme (ACE), angiotensin II (Ang II) and chymase in IUGR-induced hypertension. Timed pregnant Sprague-Dawley rats received 50% rations of control food intakes from days 15 to 21 of gestation. Control rats received regular food throughout the pregnancies. Arterial blood pressure and glomerular number were measured and immunohistochemical studies were performed on kidney tissues in adult male offspring at 16 weeks of age. IUGR rats exhibited significantly lower body and kidney weights and reduced number of glomeruli when compared with control rats. IUGR rats had significantly higher systolic blood pressure than control rats. Immunoreactivity of ACE was comparable between control and IUGR rats whereas immunoreactivities of chymase and Ang II were significantly higher in IUGR rats than in control rats. In conclusion, immunohistochemical studies document up-regulation of ACE-independent Ang II and chymase in IUGR kidney and indicate that overactivity of chymase may result in increased intrarenal Ang II production, which could contribute to the development of hypertension in intrauterine undernourished rats.

Overexpression of ACE2 Enhances Plaque Stability in a Rabbit Model of Atherosclerosis

Objective— The purpose of this study was to test the hypothesis that ACE2 overexpression may enhance atherosclerotic plaque stability by antagonizing ACE activity and converting angiotensin II to angiotensin 1–7.

Methods and Results— Atherosclerotic plaques were induced in the abdominal aorta of 114 rabbits by endothelial injury and atherogenic diet. Gene therapy was performed in group A at week 4 and in group B at week 12, respectively. Each group of rabbits were randomly divided into 3 subgroups which received, respectively, a recombinant ACE2 expressing vector (AdACE2), a control vector AdEGFP and AdACE2+A779, an antagonist of angiotensin 1–7 receptor. Local ACE2 overexpression attenuated the progression of lesions from week 4 to week 8, but not progression of plaque size from week 12 to week 16. In group B rabbits, local ACE2 overexpression resulted in stable plaque compositions, ie, fewer macrophages, less lipid deposition and more collagen contents, higher plaque stability scores, decreased angiotensin II levels, and increased angiotensin 1–7 levels in plaque tissues in the AdACE2 subgroup compared with those in the AdEGFP subgroup.

Conclusions— Overexpression of ACE2 results in stabilized atherosclerotic plaques and the mechanism is probably the conversion of vasoconstrictive angiotensin II to vessel protective angiotensin 1–7.