Expression of genes encoding kinin receptors in peripheral blood mononuclear cells from patients with acute coronary syndromes

Unraveling the Pivotal Role of Bradykinin in ACE Inhibitor Activity

Historically, the first described effect of an angiotensin converting enzyme (ACE) inhibitor was an increased activity of bradykinin, one of the substrates of ACE. However, in the subsequent years, molecular models describing the mechanism of action of ACE inhibitors in decreasing blood pressure and cardiovascular risk have focused mostly on the renin-angiotensin system. Nonetheless, over the last 20 years, the importance of bradykinin in regulating vasodilation, natriuresis, oxidative stress, fibrinolysis, inflammation, and apoptosis has become clearer. The affinity of ACE appears to be higher for bradykinin than for angiotensin I, thereby suggesting that ACE inhibitors may be more effective inhibitors of bradykinin degradation than of angiotensin II production. Data describing the effect of ACE inhibition on bradykinin signaling support the hypothesis that the most cardioprotective benefits attributed to ACE inhibition may be due to increased bradykinin signaling rather than to decreased angiotensin II signaling, especially when high dosages of ACE inhibitors are considered. In particular, modulation of bradykinin in the endothelium appears to be a major target of ACE inhibition. These new mechanistic concepts may lead to further development of strategies enhancing the bradykinin signaling.

Galectin-3 and plasma cytokines in patients with acute myocardial infarction

OBJECTIVE

To investigate the concentrations of plasma cytokines and Galectin-3 (Gal-3) as inflammatory markers in patients with acute myocardial infarction (AMI).

METHODS

The study population consisted of 29 patients with AMI and 29 healthy control subjects. We measured Gal-3, tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) levels in plasma using enzyme-linked immunosorbent assays (ELISAs). We measured levels of C-reactive protein (CRP) via the nephelometric method.

RESULTS

Patients with AMI showed significantly higher plasma Gal-3, TNF-α, and IL-6 levels compared with controls. Gal-3 levels were positively and significantly correlated with plasma IL-6, TNF-α, and CRP levels in the control and patient groups.

CONCLUSION

Our findings suggest that Gal-3 can be a new circulating biomarker of inflammation associated with AMI.

Biotechnological Fluorescent Ligands of the Bradykinin B1 Receptor: Protein Ligands for a Peptide Receptor

The bradykinin (BK) B1 receptor (B1R) is a peculiar G protein coupled receptor that is strongly regulated to the point of being inducible in immunopathology. Limited clinical evidence suggests that its expression in peripheral blood mononuclear cells is a biomarker of active inflammatory states. In an effort to develop a novel imaging/diagnostic tool, we report the rational design and testing of a fusion protein that is a ligand of the human B1R but not likely to label peptidases. This ligand is composed of a fluorescent protein (FP) (enhanced green FP [EGFP] or mCherry) prolonged at its N-terminus by a spacer peptide and a classical peptide agonist or antagonist (des-Arg9-BK, [Leu8]des-Arg9-BK, respectively). The design of the spacer-ligand joint peptide was validated by a competition assay for [3H]Lys-des-Arg9-BK binding to the human B1R applied to 4 synthetic peptides of 18 or 19 residues. The labeling of B1R-expressing cells with EGFP or mCherry fused with 7 of such peptides was performed in parallel (microscopy). Both assays indicated that the best design was FP-(Asn-Gly)n-Lys-des-Arg9-BK; n = 15 was superior to n = 5, suggesting benefits from minimizing steric hindrance between the FP and the receptor. Cell labeling concerned mostly plasma membranes and was inhibited by a B1R antagonist. EGFP-(Asn-Gly)15-Lys-des-Arg9-BK competed for the binding of [3H]Lys-des-Arg9-BK to human recombinant B1R, being only 10-fold less potent than the unlabeled form of Lys-des-Arg9-BK to do so. The fusion protein did not label HEK 293a cells expressing recombinant human BK B2 receptors or angiotensin converting enzyme. This study identifies a modular C-terminal sequence that can be adapted to protein cargoes, conferring high affinity for the BK B1R, with possible applications in diagnostic cytofluorometry, histology and drug delivery (e.g., in oncology).

Expression of the genes encoding kinin receptors are increased in human carotid atherosclerotic plaques

There is increasing evidence showing that inflammation occurs in atherosclerosis and contributes to the formation of atherosclerotic plaques. As important inflammatory peptides, kinins are increased in inflammation, eliciting vasodilation, increasing vascular permeability and recruiting inflammatory cells to the injury sites by activating specific receptors, B1 and B2. The two receptors have been reported to increase in inflammation, but their expressions remain to be defined in human carotid atherosclerotic plaques (CAP). In order to assess the gene expression of kinin receptors in human CAP, 47 CAP specimens were collected from patients undergoing endarterectomy and classified into stable and unstable plaque groups, respectively, with 10 mesenteric arteries used as controls. Total mRNA of B1R and B2R was extracted from CAPs and their levels were determined using reverse transcription-polymerase chain reaction. The expression of B1R and B2R mRNA was significantly upregulated in human CAPs compared to the control arteries. In the unstable plaques, the ratios of B1R to the β-actin mRNA level were significantly increased relative to the stable plaques. However, no notable differences were observed in the ratios of B2R to β-actin in mRNA expression between the stable and unstable plaques. The present study suggests that kinin-mediated inflammation involves the formation of atherosclerotic plaque and B1R plays an important role in plaque instability, indicating that kinin receptors can be used as potential targets for future therapeutic interventions.

Diagnostic potential of differentially expressed Homer1, IL-1β, and TNF-α in coronary artery disease

Increasing evidences suggest that inflammation plays an important role in the pathogenesis of coronary artery disease (CAD). Numerous inflammatory cytokines and related genes mediate adverse cardiovascular events in patients with CAD, such as interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and Homer in the present study. The study was carried out on 163 CAD patients at different stages and 68 controls. The gene expression of Homer1, Homer2, Homer3, IL-1β, and TNF-α in the peripheral blood leukocytes were measured by real-time polymerase chain reaction. The mRNA levels of Homer1, IL-1β, and TNF-α in CAD patients were significantly higher than those in the control group, but not Homer2 and Homer3. However, there was no considerable difference in the mRNA levels of Homer1, IL-1β, and TNF-α among AMI, UAP, and SAP three subgroups of CAD. The receiver operating characteristic (ROC) curves showed that Homer1 had a better diagnostic value for UAP patients compared with IL-1β and TNF-α. Like IL-1β and TNF-α, Homer1 may also be an important participant of atherosclerotic plaque development and eventually rupture. The results of the present study may provide an important basis for diagnosing CAD patients, and provide new therapeutic targets for CAD.

Differential gene expression of bradykinin receptors 1 and 2 in peripheral monocytes from patients with essential hypertension

Bradykinin participates in various hypertensive processes, exerted via its type 1 and type 2 receptors (BKR1 and BKR2). The aim of the study was to investigate BKR1 and BK2R gene expression in peripheral monocytes in patients with essential hypertension compared with healthy individuals. Seventeen hypertensive patients (9 males, age 56 ± 7 years) and 12 healthy individuals (7 males, age 55 ± 6) participated. Mononuclear cells isolated using anti-CD14+ antibodies and mRNAs of BKR1 and BKR2 were estimated by real-time quantitative reverse transcription-PCR. Both BKR1 and BKR2 showed significantly upregulated gene expression in the group of hypertensive patients. Specifically, BKR1 gene expression was 142.1 ± 42.2 in hypertensives versus 20.2 ± 8 in controls (P = 0.024) and BKR2 was 1222.2 ± 361.6 in hypertensives versus 259.5 ± 99.1 in controls (P = 0.038). Antihypertensive treatment resulted in a decrease in BKR1 (from 142.1 ± 42.2 to 55.2 ± 17.1, P = 0.065) and in BKR2 (from 1222.2 ± 361.6 to 256.8 ± 81.8, P = 0.014) gene expression. BKR1 and BKR2 gene expression on peripheral monocytes is upregulated in essential hypertension. This may lead to functional changes in monocytes and contribute to the development of target organ damage in hypertensive patients.

Distribution and expression of B2-kinin receptor on human leukocyte subsets in young adults and elderly using flow cytometry

The kallikrein-kinin system has been investigated in many experimental models. Dysregulations of the KKS are likely to be involved in pathologies such as inflammation, cancer and cardiovascular diseases. Previous works on the human KKS mostly rely on gene polymorphism and mRNA expression. In order to assess the KKS in human at the protein level, we have developed an approach based on flow cytometric analysis of leukocytes. Whole blood samples were collected and erythrocytes were lysed. Permeabilised leukocytes were incubated with anti-B2R (IgG2b), anti-IgG2b-PE, anti-CD3-PerCP (lymphocytes) and anti-CD14-APC (monocytes) antibodies. FACScalibur analyzed fluorescence intensities. Results were expressed as per cent of B2R-positive cells in each leukocyte subset and as B2R fluorescence intensity per positive cell. Detection of the B2R protein by this methodology was validated by (i) correlation with Western blotting using two different B2R antibodies, (ii) BK-induced Erk activation, (iii) B2R mRNA expression. The methodology was then applied to evaluate variations of B2R expression in a population including young healthy, elderly healthy, and elderly treated hypertensive men and women. In the young healthy subjects, B2R distribution was: monocytes>polymorphonuclear neutrophils (PMN)>lymphocytes and no difference with gender was observed. Moreover, no difference was observed on PMN B2R expression. B2R expression remained unchanged in the elderly healthy or hypertensive men. By contrast, monocytes and lymphocytes B2R expressions were decreased in the elderly healthy women. Finally, FACS analysis of B2R expression on leukocytes subsets provides single cell quantification of B2R expression allowing comparison of cellular sub-populations. This approach provides a new efficient tool to investigate B2R profiling of immune system in pathological states.

Kinins in cardiac inflammation and regeneration: insights from ischemic and diabetic cardiomyopathy

The kallikrein-kinin system (KKS) is a system of vasoactive peptides, the kinins, involved in different aspects of remodeling, inflammation and angiogenesis. Kinins mediate their actions through two receptors, B1R and B2R. It is increasingly recognized that the KKS is involved in the inflammatory processes of the heart. Evidence shows that the B2R is beneficial in myocardial diseases, protecting from inflammation, fibrosis and apoptosis, while B1R shows a proinflammatory character contributing to the disease progression by increasing the production of cytokines and stimulating the migration of immune cells. Furthermore, novel important actions of the KKS and its receptors contribute to neovascularization and recruitment of endothelial progenitor cells in ischemic areas and endothelial dysfunction. The kinin receptors could therefore constitute potential therapeutic targets in the treatment of myocardial ischemia and diabetic cardiomyopathy.