Role of the renin-angiotensin system as a risk factor for control of morbidity and mortality in coronary artery disease

Protective effects of enalapril, an angiotensin-converting enzyme inhibitor, on multiple organ damage following scald injury in rats

The aim of this study is to investigate the effects of enalapril, an angiotensin-converting enzyme inhibitor, on multiple organ damage after scald injury. Healthy adult rats (half male and half female; 8-12 weeks old) were randomly assigned to the following treatments: sham operation, scald injury, and intraperitoneal enalapril (1, 2, and 4 mg/kg body weight) treatment after scalding. At 1, 12, and 24 H postscald, left ventricular and aortic hemodynamics were measured using a multichannel physiological recorder. Functional and pathological changes of the heart, liver, and kidney were examined by biochemical and histological methods. Compared with sham controls, untreated scalded animals showed decreased hemodynamic parameters and increased myocardial angiotensin II, serum creatine kinase heart isoenzyme, and serum cardiac troponin I and histopathological inflammation in the myocardium 12 H postscald. These hemodynamic, functional, and pathological changes were attenuated by 1 mg/kg enalapril. Enalapril reversed scald-induced elevations in aspartate aminotransferase, alanine aminotransferase, blood urea nitrogen, and blood creatinine 12 H postscald, and ameliorated focal necrosis in the liver and erythrocyte cast formation in renal tubules. However, higher doses of enalapril yielded less or no improvement in organ dysfunction. Enalapril at 1 mg/kg attenuates scald-induced multiple organ damage in rats.

Increased Insulin-Stimulated Expression of Arterial Angiotensinogen and Angiotensin Type 1 Receptor in Patients With Type 2 Diabetes Mellitus and Atheroma

OBJECTIVE

Because inhibition of the renin-angiotensin system (RAS) reduces the onset of type 2 diabetes (T2D) and prevents atherosclerosis, we investigated the expression of RAS in the arterial wall of T2D and nondiabetic (CTR) patients.

METHODS AND RESULTS

mRNA and protein levels of angiotensinogen (AGT), angiotensin-converting enzyme (ACE) and AT1 receptor (AT1R) were determined in carotid atheroma plaque, nearby macroscopically intact tissue (MIT), and in vascular smooth muscle cells (VSMCs) before and after insulin stimulation from 21 T2D and 22 CTR patients. AGT and ACE mRNA and their protein levels were 2- to 3-fold higher in atheroma and in MIT of T2D patients. VSMCs from T2D patients had respectively 2.5- and 5-fold higher AGT and AT1R mRNA and protein contents. Insulin induced an increase in AGT and AT1R mRNA with similar ED50. These responses were blocked by PD98059, an inhibitor of MAP-kinase in the two groups whereas wortmannin, an inhibitor of PI3-kinase, partially prevented the response in CTR patients. Phosphorylated ERK1-2 was 4-fold higher in MIT from T2D than from CTR patients.

CONCLUSIONS

The arterial RAS is upregulated in T2D patients, which can be partly explained by an hyperactivation of the ERK1-2 pathway by insulin.

Cathepsin G is associated with atheroma formation in human carotid artery

OBJECTIVE

To elucidate the organization of the tissue angiotensin system, we investigated the expression and cellular localization of angiotensin system components and cathepsins D and G, potentially involved in intraparietal angiotensin II formation and atheroma.

METHODS

Total RNA was extracted from atheroma plaque, fatty streaks and macroscopically intact tissue obtained during carotid endarterectomy in 21 hypertensive patients. mRNA levels were compared between these tissues using a semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). In situ hybridization and immunohistochemistry were used to define the cellular localization of the transcripts and their respective proteins.

RESULTS

Apart from renin and angiotensin type 2 (AT2) receptors, which were never detected, the studied mRNAs could be measured in all patients. Angiotensin-converting enzyme (ACE) mRNA was increased five-fold in atheroma, and angiotensin type 1 receptor (AT1) mRNA decreased 2.5-fold in atheroma and 1.4-fold in fatty streaks compared to intact tissue. A two-fold increase in cathepsin G mRNA was observed in atheroma plaque. In atheroma and intact tissue, significant positive correlations were found between cathepsin G and angiotensinogen, AT1 receptor and ACE mRNAs. Angiotensinogen and cathepsin mRNAs and proteins were detected in both arterial layers. AT1 immunoreactivity was mainly associated with alpha-actin-positive cells.

CONCLUSION

All components required for angiotensin II formation are expressed locally in the arterial wall, where, in the absence of renin, cathepsin G could be a major angiotensin-generating enzyme. Overexpression of ACE and cathepsin G may lead to angiotensin II overproduction and contribute, with decreased number of differentiated smooth muscle cells, to the lower amount of AT1 receptor in atheroma.

Recipient RAS gene variants and renal allograft function

BACKGROUND

Genetic variants of the renin-angiotensin system (RAS) have been implicated in the progression of native kidney diseases. A decreased long-term renal allograft function has also been associated with increased activity of RAS, which may be genetically determined.

METHODS

The effect of the angiotensinogen (AGT), angiotensin-converting enzyme (ACE), angiotensin type 1 receptor (AGT1R), and aldosterone synthase (CYP11B2) genotypes on renal function was investigated in 223 first-allograft recipients. Graft function was estimated by yearly determinations of serum creatinine. Genotyping was performed for the M235T-AGT, the I/D-ACE, the A1166C-AGT1R, and the -344T/C-CYP11B2 gene polymorphisms using polymerase chain reaction.

RESULTS

The percentage of patients with preserved stable graft function up to 15 years after transplantation was higher when mean blood pressure was <97 mmHg, than when it was >117 mmHg (60 vs. 25% of patients). The CYP11B2 genotype predicted long-term stable graft function with more patients suffering from worsening renal function with the CYP11B2 TT than the CC genotype (P=0.002). There was a weak association between the AGT1R genotype (P=0.037), but not the AGT or ACE genotypes, and a preserved long-term graft function. Cox proportional hazards estimation showed no interactions between the observed effect of CYP11B2 genotype on renal function over time and the number of HLA class I and II matches, other RAS genotypes, graft function, or mean blood pressure at 1 year after transplantation.

CONCLUSIONS

The rate of decline in renal allograft function is strongly associated with the CYP11B2 but not AGT, ACE, or AGT1R genotypes. This finding suggests that certain genetic factors related to the RAS are important determinants of long-term renal allograft function.

Genetic polymorphisms of the renin-angiotensin-aldosterone system in end-stage renal disease

BACKGROUND

Hypertension contributes to the progression to renal failure. A genetic susceptibility to hypertension may predispose to the development of end-stage renal disease (ESRD) and promote a more rapid progression to ESRD in patients with renal diseases. Genes encoding for angiotensinogen (AGT), angiotensin-converting enzyme (ACE), and aldosterone synthase (CYP11B2) are candidates for abnormal blood pressure regulation.

METHODS

Genotyping was performed in 327 control subjects and 260 ESRD patients for the M235T-AGT, the insertion/deletion (I/D)-ACE, and the -344T/C-CYP11B2 gene polymorphisms using polymerase chain reaction, gel analysis, and appropriate restriction digest when required.

RESULTS

Genotype frequencies did not differ significantly between ESRD patients and controls. When ESRD diabetic subjects were compared with diabetic patients without nephropathy, the prevalence of the AGT-MM genotype was lower (28.1 vs. 52.8%, P < 0.01), while the AGT-TT genotype was higher (15.6 vs. 2.7%, P < 0.05). The AGT-TT genotype was associated with a faster progression to ESRD in patients with glomerulonephritis (P < 0.05). In the total ESRD population, progression of renal disease was faster with the ACE-DD than with the DI and II alleles (P < 0.05). This association was particularly strong when the interaction with the AGT genotype was analyzed, with a rapid progression in ACE-DD as compared with ACE-DI and II in patients with the AGT-MM genotype (P < 0.01).

CONCLUSIONS

Susceptibility for ESRD and faster progression to ESRD are linked with the AGT genotype in diabetic patients. Faster progression to ESRD is associated with the ACE genotype when the total population with ESRD and with the AGT genotype when patients with glomerulonephritis are considered. Thus, genes of the renin-angiotensin-aldosterone system are candidate genes for further understanding of the interindividual differences in the development and course of ESRD.

Influence of isoprostanes on vasoconstrictor effects of noradrenaline and angiotensin II

The isoprostanes, 8-iso-prostaglandin F2alpha and 8-iso-prostaglandin E2, which are released in vivo by free radical-catalyzed peroxidation of arachidonic acid, are potent vasoconstrictors. Increased formation of 8-iso-prostaglandin F2alpha has been detected in human cardiovascular diseases, in which enhanced plasma levels of noradrenaline and angiotensin II have harmful vasoconstrictor effects. Therefore, we investigated the influence of perfusions with the thromboxane A2 mimetic, U 46619, and with the isoprostanes, 8-iso-prostaglandin F2alpha, 8-iso-prostaglandin E2, 8-iso-prostaglandin E1 and 8-iso-prostaglandin F3alpha, on the vasoconstrictor effects of noradrenaline and angiotensin II in the isolated perfused rabbit ear. Our results demonstrate that perfusions with U 46619, 8-iso-prostaglandin E2 and 8-iso-prostaglandin F2alpha, at a subthreshold concentration (30 nM), amplified the vasoconstrictions induced by noradrenaline or angiotensin II significantly. In addition, the results show that U 46619, 8-iso-prostaglandin F2alpha, 8-iso-prostaglandin E2 and 8-iso-prostaglandin E1, which were applied as a bolus, induced much more pronounced vasoconstrictions than prostaglandin F2alpha, prostaglandin E2 and prostaglandin F3alpha. Prostaglandin E1 and 8-iso-prostaglandin F3alpha, showed no effects. In conclusion, it can be assumed that the powerful vasoconstrictions induced by 8-iso-prostaglandin E2 and 8-iso-prostaglandin F2alpha and their potentiating effects on vasoconstrictions induced by noradrenaline or angiotensin II might be of pathophysiological relevance in cardiovascular diseases.

Estrogen replacement therapy and cardiovascular protection: lipid mechanisms are the tip of an iceberg

Cardiovascular disease remains a major cause of mortality among postmenopausal women. After menopause, atherogenesis is promoted by a number of metabolic and vascular changes. A multitude of observational clinical studies have come to the conclusion that estrogen replacement therapy (ERT) reduces cardiovascular risk by approximately 50% and that estrogen's favorable effects on the lipid profile can explain only 25-50% of the overall observed reduction. Estrogens are now known to have potent anti-atherogenic properties through lipid and non-lipid mechanisms; both will be highlighted in view of the recent literature. Estrogens induce favorable changes on lipids and lipoproteins, partly by increasing HDL-cholesterol and decreasing both LDL-cholesterol and lipoprotein (a). Non-lipid mechanisms of estrogen action include decreasing insulin resistance, serum fibrinogen, factor VII and plasminogen activator inhibitor-1 (PAI-1). Moreover, estrogens maintain endothelial cell integrity, decrease expression of adhesion molecules, lower systemic blood pressure, promote vasodilatation, decrease platelet aggregability, inhibit vascular smooth muscle cell proliferation, possess potent antioxidant and calcium antagonist activities, inhibit adrenergic responses and downregulate platelet and monocyte reactivity. Also mentioned are recent reports linking estrogen to the renin-angiotensin system, relaxin, serotonin and homocysteine. What was once thought of as a simple action is now being increasingly appreciated as a complex, multifaceted mechanism, which serves to prove that estrogen is a powerful cardiovascular agent.