Activation of cardiac renin-angiotensin system in unstable angina

T Cell-Based RAS Activity and Insulin Levels in Obese Subjects with Low Grade Inflammation

BACKGROUND

Obesity is a major contributor to inflammation and oxidative stress that are key underlying causes for insulin resistance (IR) and diabetes. Accumulated evidence suggest that RAS may serve as a strong link between IR and obesity. We investigated RAS activity in circulating T cells by obese subjects with and without angiotensin (Ang) II stimulation in presence or not of IR and of low-grade inflammation.

METHODS

We studied 29 obese and 10 healthy subjects. After T-lymphocytes isolation, mRNAs for angiotensin converting enzyme (ACE) and angiotensin 1-receptor (AT1-R) were quantified by reverse transcription polymerase chain reaction (RT-PCR). High-sensitivity C-reactive protein (hs-CRP), insulin and inflammatory cytokines serum levels, plasma renin activity (PRA) and ACE activity in cell pellet and supernatant, and angiotensin (Ang) II T cell content were also measured.

RESULTS

Under baseline conditions, RAS gene expressions, ACE activity and Ang II levels in T cells, but not PRA, of obese subjects with or without IR and with or without hs-CRP ≥3mg/dl were higher than in controls (p < 0.05). The increase in all parameters induced by Ang II was significantly higher in T cells from the obese subjects with hs-CRP≥3 mg/dl than in controls or in the obese subjects with hs-CRP<3 mg/dl. In the obese subjects with low grade inflammation and IR, the cytokine serum levels and T cells RAS gene expression was inversely correlated with insulin serum concentration.

CONCLUSIONS

Low grade inflammation amplifies the T cell RAS response to Ang II stimulation. T cell RAS gene expressions and serum levels of inflammatory cytokines were inversely related with insulin serum concentration. A protective role of insulin towards the development of inflammatory events can be hypothesized.

Differential role of specific cardiovascular neuropeptides in pain regulation: Relevance to cardiovascular diseases

In many instances, the perception of pain is disproportionate to the strength of the algesic stimulus. Excessive or inadequate pain sensation is frequently observed in cardiovascular diseases, especially in coronary ischemia. The mechanisms responsible for individual differences in the perception of cardiovascular pain are not well recognized. Cardiovascular disorders may provoke pain in multiple ways engaging molecules released locally in the heart due to tissue ischemia, inflammation or cellular stress, and through neurogenic and endocrine mechanisms brought into action by hemodynamic disturbances. Cardiovascular neuropeptides, namely angiotensin II (Ang II), angiotensin-(1-7) [Ang-(1-7)], vasopressin, oxytocin, and orexins belong to this group. Although participation of these peptides in the regulation of circulation and pain has been firmly established, their mutual interaction in the regulation of pain in cardiovascular diseases has not been profoundly analyzed. In the present review we discuss the regulation of the release, and mechanisms of the central and systemic actions of these peptides on the cardiovascular system in the context of their central and peripheral nociceptive (Ang II) and antinociceptive [Ang-(1-7), vasopressin, oxytocin, orexins] properties. We also consider the possibility that they may play a significant role in the modulation of pain in cardiovascular diseases. The rationale for focusing attention on these very compounds was based on the following premises (1) cardiovascular disturbances influence the release of these peptides (2) they regulate vascular tone and cardiac function and can influence the intensity of ischemia - the factor initiating pain signals in the cardiovascular system, (3) they differentially modulate nociception through peripheral and central mechanisms, and their effect strongly depends on specific receptors and site of action. Accordingly, an altered release of these peptides and/or pharmacological blockade of their receptors may have a significant but different impact on individual sensation of pain and comfort of an individual patient.

Persistent and selective upregulation of renin-angiotensin system in circulating T lymphocytes in unstable angina

Introduction:

Unstable angina is associated with an acute systemic inflammatory reaction and circulating T lymphocytes are activated. We investigated whether in unstable angina with marked immune system activation a selective upregulation of the circulating T-cell renin–angiotensin system, modulated by angiotensin II, could occur.

Methods:

We studied 13 unstable angina patients, 10 patients with stable angina and 10 healthy subjects. After T-lymphocyte isolation, mRNAs for angiotensin-converting enzyme (ACE) and angiotensin type 1 receptor (AT1-R) were quantified at baseline and after angiotensin II stimulation. ACE activity in cell pellet and supernatant and angiotensin II cell content were measured.

Results:

Plasma renin activity was similar in controls, stable and unstable angina patients. At baseline ACE and AT1-R mRNA levels were higher (P<0.05) in T cells from unstable angina patients than in T cells from stable angina patients and controls, and further increased after angiotensin II addition to cultured T cells. ACE activity of unstable angina T cells was significantly higher than that of T cells from controls and stable angina patients. Only in T cells from unstable angina patients did angiotensin II stimulation cause the almost complete release of ACE activity in the supernatant.

Conclusions:

The circulating T-cell-based renin–angiotensin system from unstable angina patients was selectively upregulated. In vivo unstable angina T cells could locally increase angiotensin II concentration in tissues where they migrate independently of the circulating renin–angiotensin system.

Serum sodium concentration is significantly associated with the angiographic characteristics of coronary atherosclerosis

AIM

To explore the relationship between serum sodium concentration and coronary atherosclerosis.

METHODS

The study population consisted of 896 consecutive patients (684 males and 212 females) who underwent coronary angiography for suspected or known coronary atherosclerosis. Smoking and drinking were investigated. The anthropometric measurements, including body mass index, systolic blood pressure and diastolic blood pressure, and the serum measurements, including sodium, potassium, chlorine, lipids, blood glucose, urea, creatinine, and uric acid for every patient were conducted. The severity of coronary atherosclerosis was defined by the Gensini score system. The statistical methods, including one-way ANOVA, Kruskal-Wallis test, Spearman correlation analysis, partial correlation analysis, multivariate stepwise linear regression analysis, and multinomial logistic regression analysis were employed to explore the relationship between serum sodium concentration and the Gensini score.

RESULTS

The analysis of the Kruskal-Wallis test indicated that the distribution of the Gensini score (P=0.000) differed among the groups according to serum sodium concentration, quartile values of which were used as cut-off points. The Spearman correlation and partial correlation analysis controlling for gender, smoking status, and drinking status indicated that the Gensini score significantly correlated with the sodium concentration (r=-0.241, P=0.000 for the Spearman correlation, r=-0.114, P=0.000 for the partial correlation). The results from the multivariate stepwise linear regression analysis showed that the left ventricular ejection fraction (beta=-0.228, P=0.000), age (beta=0.137, P=0.010), glucose level (beta=0.129, P=0.000), and sodium level (beta=-0.106, P=0.004) were significantly and independently associated with the Gensini score. The results of the multinomial logistic regression analysis suggested that the hyponatremia was the risk factor for the higher Gensini score.

CONCLUSION

The serum sodium concentration was significantly and negatively associated with the Gensini score; and the actual mechanism underlying the association needs further study.

How frequent is altered gene expression among susceptibility genes to human complex disorders?

It is regularly thought that human complex disorder susceptibility genes show differences in gene expression between normal and pathologic tissues. Thus, differences of transcript amounts could be indicative of complex disorder susceptibility loci and, therefore, be used for the discovery or the validation of human susceptibility genes to complex disorders/traits. Whether human complex disorder susceptibility genes effectively display differences in transcript amounts was tested by meta-analysis of the published literature comparing transcript amounts of well-validated human susceptibility genes to complex traits/disorders. A total of 94 gene-disease associations, which were studied in at least three independent studies and showed strong evidence of positive association, were analyzed. For 23 out of these 94 well-validated gene-disease associations, 120 gene expression studies comparing normal and pathologic human tissues were found. For 60 out of these 120 gene expression studies, the difference of level expression between normal and pathologic human tissues was statistically significant. This result was highly significant, as only 6 significant results were expected randomly under the null hypothesis (P < 10(-112)). A large excess of replication studies were also found, which were in agreement with the original report (P = 6 x 10(-4)). However, the overall level of expression change between normal and pathologic human tissues was relatively moderate, because only 36 (60%) and 19 (31.6%) out of the 62 statistically significant gene expression studies reached 2- or 3-fold changes in expression level, respectively. The present meta-analysis confirms statistical differences of expression levels between normal and pathologic human tissues for human susceptibility genes to complex traits/disorders. However, the levels of differences in transcript amounts appear to be relatively weak. These findings rationalize the use of gene expression for the discovery/validation of human susceptibility genes, but the weak differences of expression typically found should be taken into account for the design of such studies.

Angiotensin II and norepinephrine release: interaction and effects on the heart

BACKGROUND

Angiotensin (Ang) II may enhance the influence of the sympathetic nervous system at various levels by facilitating norepinephrine (NE) release. We investigated whether such an interaction is evident in the human heart and whether it has an impact on left ventricular (LV) structure.

METHODS AND RESULTS

Ang I and Ang II concentrations were determined in arterial and coronary sinus (CS) plasma samples in a group of normotensive (n = 10) and hypertensive (n = 18) subjects. Total systemic and cardiac NE spillover was measured using isotope dilution methodology and LV structure by echocardiography. Arterial and CS concentrations of Ang I and Ang II were similar in both groups (Ang II CS, 5.8 +/- 4.0 versus 3.7 +/- 3.1 fmol/ml; P = not significant), as was the Ang II/Ang I ratio (CS, 0.56 +/- 0.17 versus 0.54 +/- 0.22 fmol/fmol; P = not significant). Total systemic (223 +/- 145 versus 374 +/- 149 ng/min; P < 0.05) and cardiac NE spillover (11.7 +/- 6.3 versus 19.4 +/- 10.5 ng/min; P < 0.05) were increased in hypertensive patients, as was LV mass index (LVMI) (86.7 +/- 14.7 versus 117.2 +/- 19.4 g/m; P < 0.001). LVMI correlated with cardiac NE spillover (r = 0.47; P < 0.02). No correlation was evident between CS Ang II and cardiac NE spillover (r = 0.001; P = not significant) or LVMI (r = -0.20; P = not significant). Arterial Ang II tended to correlate with total systemic NE spillover (r = 0.34; P = 0.081). When hypertensive subjects were divided into two groups with either high or low CS Ang II concentration, cardiac NE spillover and LVMI did not differ between the two groups.

CONCLUSION

These findings suggest a growth-promoting effect of increased cardiac sympathetic tone on cardiomyocytes in hypertensive patients, but do not support the notion of a significant role of Ang II for norepinephrine release and LV hypertrophy in the hypertensive human heart.

Deletion of ribosomal S6 kinases does not attenuate pathological, physiological, or insulin-like growth factor 1 receptor-phosphoinositide 3-kinase-induced cardiac hypertrophy

Ribosomal S6 kinases (S6Ks) have been depicted as critical effectors downstream of growth factor pathways, which play an important role in the regulation of protein synthesis by phosphorylating the ribosomal protein, S6. The goal of this study was to determine whether S6Ks regulate heart size, are critical for the induction of cardiac hypertrophy in response to a pathological or physiological stimulus, and whether S6Ks are critical downstream effectors of the insulin-like growth factor 1 (IGF1)-phosphoinositide 3-kinase (PI3K) pathway. For this purpose, we generated and characterized cardiac-specific S6K1 and S6K2 transgenic mice and subjected S6K1(-/-), S6K2(-/-), and S6K1(-/-) S6K2(-/-) mice to a pathological stress (aortic banding) or a physiological stress (exercise training). To determine the genetic relationship between S6Ks and the IGF1-PI3K pathway, S6K transgenic and knockout mice were crossed with cardiac-specific transgenic mice overexpressing the IGF1 receptor (IGF1R) or PI3K mutants. Here we show that overexpression of S6K1 induced a modest degree of hypertrophy, whereas overexpression of S6K2 resulted in no obvious cardiac phenotype. Unexpectedly, deletion of S6K1 and S6K2 had no impact on the development of pathological, physiological, or IGF1R-PI3K-induced cardiac hypertrophy. These studies suggest that S6Ks alone are not essential for the development of cardiac hypertrophy.

Cardiac Angiotensin II Participates in Coronary Microvessel Inflammation of Unstable Angina and Strengthens the Immunomediated Component

Angiotensin (Ang) II is now recognized to be a mediator of a wide variety of inflammatory processes. This study investigated renin-angiotensin system (RAS) components and a number of inflammatory mediators in left ventricular biopsies from 2-vessel disease unstable angina (UA) (n=43) and stable angina (SA) (n=15) patients undergoing coronary bypass surgery. Biopsy samples from 6 patients undergoing valve replacement for mitral stenosis served as controls. UA patients were randomly assigned to angiotensin-converting enzyme (ACE)-inhibitor (ramipril), AT1 antagonist (valsartan), or placebo and treated during the 5 days preceding coronary bypass surgery, performed from 6 to 9 days after coronary angiography. During coronary angiography coronary blood flow was measured and samples were obtained from aorta and coronary sinus for determination of Ang I and Ang II gradients. The hearts of UA patients produced Ang II in a greater amount than in SA patients ( P <0.01). UA biopsy samples showed numerous DR + cells, identified as lymphocytes, macrophages, and endothelial cells. Reverse-transcriptase polymerase chain reaction showed overexpression of AGTN, ACE, and AT1-R genes, as well as upregulation of TNF-α, IL-6, IFN-γ, and iNOS genes ( P <0.01), with no differences between nonischemic and potentially ischemic areas. AGTN, ACE, and cytokine genes were mainly localized on endothelial cells. Ramipril and valsartan markedly decreased the expression levels of TNF-α, IL-6, and iNOS, and, to a lesser extent, of IFN-γ genes, but did not affect the number of DR + cells, with no significant difference between the 2 treatments. These results show that locally generated Ang II amplifies the immunomediated inflammatory process of coronary microvessels occurring in unstable angina.

The insulin-like growth factor 1 receptor induces physiological heart growth via the phosphoinositide 3-kinase(p110alpha) pathway

Insulin-like growth factor 1 (IGF1) was considered a potential candidate for the treatment of heart failure. However, some animal studies and clinical trials have questioned whether elevating IGF1 chronically is beneficial. Secondary effects of increased serum IGF1 levels on other tissues may explain these unfavorable results. The aim of the current study was to examine the role of IGF1 in cardiac myocytes in the absence of secondary effects, and to elucidate downstream signaling pathways and transcriptional regulatory effects of the IGF1 receptor (IGF1R). Transgenic mice overexpressing IGF1R in the heart displayed cardiac hypertrophy, which was the result of an increase in myocyte size, and there was no evidence of histopathology. IGF1R transgenics also displayed enhanced systolic function at 3 months of age, and this was maintained at 12-16 months of age. The phosphoinositide 3-kinase (PI3K)-Akt-p70S6K1 pathway was significantly activated in hearts from IGF1R transgenics. Cardiac hypertrophy induced by overexpression of IGF1R was completely blocked by a dominant negative PI3K(p110alpha) mutant, suggesting IGF1R promotes compensated cardiac hypertrophy in a PI3K(p110alpha)-dependent manner. This study suggests that targeting the cardiac IGF1R-PI3K(p110alpha) pathway could be a potential therapeutic strategy for the treatment of heart failure.

Immunomediated and ischemia-independent inflammation of coronary microvessels in unstable angina

This study investigated whether the myocardium is involved in the acute inflammatory reaction associated with bursts of unstable angina (UA). We looked for the presence of activated DR+ inflammatory cells and the expression patterns, localization, and immunostaining identification of genes for cytokines (IL-1beta, TNF-alpha, IL-6, and IFN-gamma), MCP-1, and iNOS in the left ventricle biopsies from 2-vessel disease anginal patients, 24 with UA and 12 with stable angina (SA), who underwent coronary bypass surgery. Biopsy specimens from 6 patients with mitral stenosis who underwent valve replacement were examined as control hearts (CHs). Plasma levels of IL-2 soluble receptor (sIL-2R) were measured as a marker of systemic immune reaction. In CHs, DR+ cells were undetectable, and cytokine and iNOS mRNA expression were negligible. UA patients had higher sIL-2R levels than SA patients (P<0.01), and their biopsy specimens showed both numerous DR+ cells identified as lymphocytes, macrophages, endothelial cells, and elevated expression levels of cytokine and iNOS genes (from 2.4- to 6.1-fold vs SA; P<0.01). Cytokine and iNOS genes and proteins were localized in endothelial cells without involvement of myocytes. IL-1beta and MCP-1 mRNAs were nearly undetectable. No significant differences were found in the number of DR+ cells, levels of cytokine, and iNOS genes between potentially ischemic and nonischemic left ventricle areas. In SA specimens, DR+ cells were very rare and only mRNAs for TNF-alpha and iNOS genes were overexpressed versus CHs. These results indicated that an acute immunomediated inflammatory reaction, essentially involving coronary microvessels, is demonstrable in UA patients.

Local renin-angiotensin systems: the unanswered questions

The concept of local renin-angiotensin systems has been introduced almost 20 years ago to explain the beneficial blood pressure-independent effects of ACE inhibitors and AT(1) receptor antagonists in cardiovascular diseases. In the past decade, research has focussed on the local effects of angiotensin II rather than on the mechanism(s) of its local generation. This review addresses several of the unanswered questions with regard to tissue angiotensin II generation, focussing in particular on the heart and vascular wall: (1) what is the origin of the renin that is required to generate angiotensin II locally, (2) where does tissue angiotensin generation occur (intra- versus extracellular), (3) what is the importance of alternative (non-renin, non-ACE) angiotensin-generating enzymes, (4) do ACE inhibitors and AT(1) receptor antagonists exert local effects that are renin-angiotensin system independent (thereby incorrectly leading to the conclusion that they interfere with the local generation or effects of angiotensin II), and (5) to what degree do differences in tissue angiotensin generation underlie the association between cardiovascular diseases and renin-angiotensin system gene polymorphisms?

Prorenin uptake in the heart: a prerequisite for local angiotensin generation?

Interference with locally generated angiotensin II most likely underlies the beneficial effects of renin-angiotensin system blockers in cardiac disorders. Since renin is not synthesized in the heart, this enzyme must be sequestered from the circulation in order to allow angiotensin generation at cardiac tissue sites. This review addresses the various ways through which circulating (i.e., kidney-derived) renin may reach cardiac tissue sites, considering in particular the possibility that prorenin, the inactive precursor of renin, is involved in cardiac angiotensin generation, as the plasma concentrations of prorenin are tenfold higher than those of renin. Renin and prorenin diffuse into the cardiac interstitial space and bind to cardiac (pro)renin receptors/renin-binding proteins. One of these receptors is the mannose 6-phosphate/insulin-like growth factor II receptor. This receptor not only binds mannose 6-phosphate-containing ligands like renin and prorenin, it also internalizes these enzymes, and activates prorenin intracellularly. This process possibly represents (pro)renin clearance, since intracellular angiotensin generation could not be demonstrated following (pro)renin uptake by cardiomyocytes. Angiotensin II-mediated myocyte proliferation did occur when incubating cardiomyocytes with prorenin plus angiotensionogen. The effects of prorenin plus angiotensinogen were comparable to those of 100nmol/l angiotensin II, although the angiotensin II levels in the medium during exposure of the cells to prorenin plus angiotensinogen were <1nmol/l. This suggests that cardiac angiotensin II generation by circulating renin occurs predominantly on the cell surface. The presence of ACE and/or renin on the cell membrane, in the microenvironment of angiotensin receptors, would allow maximal efficiency of local angiotensin II generation, i.e., immediate binding of angiotensin II to its receptors with minimal loss into the extracellular space.

Decreased susceptibility of cardiac function to hypoxia-reoxygenation in renin-angiotensinogen transgenic rats

We tested the hypothesis that the renin-angiotensin system (RAS) protects the contractile function of the myocardium against the damaging effect of hypoxia-reoxygenation. For this purpose, the contractility of isolated papillary muscles from wild-type (WT) rats and from rats expressing human renin and angiotensinogen as transgenes (TGR) was compared. After 15 min of hypoxia, peak force (PF) was decreased to 24 +/- 5% of the normoxic values in TGR (n = 10) and to 18 +/- 1% in WT rats (n = 12). PF and relaxation rates recovered completely in TGR but not in WT rats during 45 min of reoxygenation. Improved contractility of the papillary muscles from TGR during hypoxia-reoxygenation correlated with increased glutathione peroxidase activities and creatine kinase (CK)-MB and CK-BB isoenzyme levels. On the other hand, inhibition of the RAS with ramipril (1 mg/kg body wt for 3 wk) in WT animals resulted in deterioration of the contractile function of the papillary muscles during reoxygenation compared with untreated rats. These findings suggest that activation of the RAS protects contractile function of the cardiac muscle against hypoxia-reoxygenation, possibly through changes in CK isoenzymes and enhanced antioxidant capacity.

Enhanced responses of blood pressure, renal function, and aldosterone to angiotensin I in the DD genotype are blunted by low sodium intake

Angiotensin-converting enzyme (ACE) activity is increased in the DD genotype, but the functional significance for renal function is unknown. Blunted responses of BP and proteinuria to ACE inhibition among DD renal patients during periods of high sodium intake were reported. It was therefore hypothesized that sodium status affects the phenotype in the ACE I/D polymorphism. The effects of angiotensin I (AngI) and AngII among 27 healthy subjects, with both low (50 mmol sodium/d) and liberal (200 mmol sodium/d) sodium intakes, were studied. Baseline mean arterial pressure (MAP) values, renal hemodynamic parameters, and renin-angiotensin system parameters were similar for all genotypes with either sodium intake level. With liberal sodium intake, the increases in MAP, renal vascular resistance, and aldosterone levels during AngI infusion (8 ng/kg per min) were significantly higher for the DD genotype, compared with the ID and II genotypes (all parameters presented as percent changes +/- 95% confidence intervals), with mean MAP increases of 22 +/- 2% (DD genotype), 13 +/- 5% (ID genotype), and 12 +/- 6% (II genotype) (P < 0.05), mean increases in renal vascular resistance of 100.1 +/- 19.7% (DD genotype), 73.0 +/- 16.3% (ID genotype), and 63.2 +/- 16.9% (II genotype) (P < 0.05), and increases in aldosterone levels of 650 +/- 189% (DD genotype), 343 +/- 71% (ID genotype), and 254 +/- 99% (II genotype) (P < 0.05). Also, the decrease in GFR was more pronounced for the DD genotype, with mean decreases of 17.9 +/- 4.7% (DD genotype), 8.8 +/- 3.4% (ID genotype), and 6.4 +/- 5.9% (II genotype) (P < 0.05). The effective renal plasma flow, plasma AngII concentration, and plasma renin activity values were similar for the genotypes. In contrast, with low sodium intake, the responses to AngI were similar for all genotypes. The responses to AngII were also similar for all genotypes, with either sodium intake level. In conclusion, the responses of MAP, renal hemodynamic parameters, and aldosterone concentrations to AngI are enhanced for the DD genotype with liberal but not low sodium intake. These results support the presence of gene-environment interactions between ACE genotypes and dietary sodium intake.