Molecular interactions of vasoactive systems in cardiovascular damage

Decreased Tissue Kallikrein Levels and the Risk of Ischemic Stroke: A Community-Based Cross-Sectional Study in China

AIM

Tissue kallikrein (TK) exerts protective effects on cardiac cerebrovascular diseases (CCVDs). Changes in TK level in plasma are associated with ischemic stroke and coronary artery disease (CAD); however, a causal correlation could not be established. Therefore, we investigated the association between TK levels and CCVDs in a community-based cross-sectional study in China.

METHODS

A total of 6043 subjects (4242 men and 1801 women) were enrolled in this community-based cross-sectional study. Then, TK levels were measured using an enzyme-linked immunosorbent assay kit. Multivariate linear regression model and logistic regression were used to assess the correlations between TK levels and CCVDs. Subsequently, the receiver operating characteristic (ROC) curve was drawn to assess the value of TK level in evaluating the risk of ischemic stroke. Finally, the influence of various medications was evaluated on TK levels.

RESULTS

The TK level was significantly lower in subjects with ischemic stroke (P < 0.001) and hypertension (P < 0.001) and negatively associated with ischemic stroke (P < 0.001) but not associated with hypertension, coronary heart disease, and diabetes compared to the traditional risk factors. The diagnostic accuracy for ischemic stroke, as quantified by the area under the curve, was 0.892 (95% CI, 0.884-0.900) for TK level, deeming it as a promising assessment tool. Moreover, no appreciable influence of various drugs therapy was found in TK levels (P = 0.222) except for those taking antilipemic agents.

CONCLUSION

TK is a strong and independent endogenous protective factor against ischemic stroke in the Chinese population and could be a promising biomarker for the risk of ischemic stroke.

Angiotensin II receptor type 1 - An update on structure, expression and pathology

The AT₁ receptor, a major effector of the renin-angiotensin system, has been extensively studied in the context of cardiovascular and renal disease. Moreover, angiotensin receptor blockers, sartans, are among the most frequently prescribed drugs for the treatment of hypertension, chronic heart failure and chronic kidney disease. However, precise molecular insights into the structure of this important drug target have not been available until recently. In this context, seminal studies have now revealed exciting new insights into the structure and biased signaling of the receptor and may thus foster the development of novel therapeutic approaches to enhance the efficacy of pharmacological angiotensin receptor antagonism or to enable therapeutic induction of biased receptor activity. In this review, we will therefore highlight these and other seminal publications to summarize the current understanding of the tertiary structure, ligand binding properties and downstream signal transduction of the AT₁ receptor.

Role of the Renin-Angiotensin-Aldosterone System in Dystrophin-Deficient Cardiomyopathy

Dystrophin-deficient cardiomyopathy (DDC) is currently the leading cause of death in patients with dystrophinopathies. Targeting myocardial fibrosis (MF) has become a major therapeutic goal in order to prevent the occurrence of DDC. We aimed to review and summarize the current evidence about the role of the renin-angiotensin-aldosterone system (RAAS) in the development and perpetuation of MF in DCC. We conducted a comprehensive search of peer-reviewed English literature on PubMed about this subject. We found increasing preclinical evidence from studies in animal models during the last 20 years pointing out a central role of RAAS in the development of MF in DDC. Local tissue RAAS acts directly mainly through its main fibrotic component angiotensin II (ANG2) and its transducer receptor (AT1R) and downstream TGF-b pathway. Additionally, it modulates the actions of most of the remaining pro-fibrotic factors involved in DDC. Despite limited clinical evidence, RAAS blockade constitutes the most studied, available and promising therapeutic strategy against MF and DDC. Conclusion: Based on the evidence reviewed, it would be recommendable to start RAAS blockade therapy through angiotensin converter enzyme inhibitors (ACEI) or AT1R blockers (ARBs) alone or in combination with mineralocorticoid receptor antagonists (MRa) at the youngest age after the diagnosis of dystrophinopathies, in order to delay the occurrence or slow the progression of MF, even before the detection of any cardiovascular alteration.

MicroRNA-325-3p protects the heart after myocardial infarction by inhibiting RIPK3 and programmed necrosis in mice

BACKGROUND

Receptor-interacting serine-threonine kinase 3 (RIPK3)-mediated necroptosis has been implicated in the progression of myocardial infarction (MI), but the underlying mechanisms, particularly whether microRNAs (miRNAs) are involved, remain largely unknown.

RESULTS

A microarray analysis was used to screen for miR-325-3p expression in myocardial tissues from MI mice, and the expression was confirmed with qRT-PCR. The levels of myocardial enzymes were measured using commercial kits, and an echocardiography system was utilized for the detection of cardiac function parameters. The pathological features and infarction sizes of cardiac tissues were examined using H&E, TCC and Masson's trichrome staining, and the amount of cell apoptosis was determined using an in situ TUNEL assay. Cardiomyocytes were isolated and then subjected to hypoxia induction in vitro. The expression of the RIPK1, RIPK3 and phosphorylated MLKL (p-MLKL) proteins was measured using a Western blot. The mouse cardiomyocyte cell viability was analyzed by an MTT assay. The mRNA target of miR-325-3p was predicted using TargetScan v7.2 and then validated using a dual-luciferase reporter assay. The overexpression of miR-325-3p evidently decreased the expression levels of lactate dehydrogenase (LDH), phosphocreatine kinase (CK), superoxide dismutase (SOD) and malondialdehyde (MDA), inhibited left ventricular end-diastolic diameter (LVEDD) and left ventricular end-systolic diameter (LVESD), and promoted left ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVES). In addition, miR-325-3p overexpression attenuated the degree of injury to the cardiac tissue, decreased the infarct sizes and downregulated the expression of the necrosis-related proteins RIPK1, RIPK3 and p-MLKL.

CONCLUSIONS

The RIPK1/RIPK3/p-MLKL axis-induced necroptosis that occurred during MI was mediated by a miRNA module, miR-325-3p, which can effectively ameliorate the symptoms of MI by suppressing the expression of RIPK3.

Angiotensinogen-M235T as a risk factor for myocardial infarction in Asian populations: a genetic association study and a bioinformatics approach

Aim

To investigate if there is an association between M235T polymorphism of angiotensinogen gene and myocardial infarction (MI) risk and perform a meta-analysis and an in silico approach.

Methods

This case-control study included 340 participants (155 MI patients and 185 controls) examined at Kashan University of Medical Sciences (Kashan, Iran) between 2013 and 2015. Meta-analysis included 25 studies with 6334 MI patients and 6711 controls. Bioinformatics tools were applied to evaluate the impact of M235T polymorphism on angiotensinogen function and structure.

Results

Genetic association study revealed a significant association between TT genotype (odds ratio [OR] 2.08, 95% confidence interval [CI] 1.08-4.00, P = 0.029) and T allele (OR 1.45, 95% CI 1.06-1.99, P = 0.021) and MI risk. Meta-analysis also revealed a significant association between M235T polymorphism and MI risk in allelic (OR 1.55, 95% CI 1.10-2.18, P = 0.012) and recessive (OR 1.69, 95% CI 1.13-2.53, P = 0.010) models within Asian population. In silico-analysis revealed that M235T fundamentally changed the function of angiotensinogen (score 32; expected accuracy 66%).

Conclusions

Our study suggests that M235T polymorphism might be a helpful biomarker for screening of susceptible individuals for MI in Asian population.

Leptin regulates ACE activity in mice

Leptin is a hormone related to metabolism. It also influences blood pressure, but the mechanisms triggered in this process are not yet elucidated. Angiotensin-I converting enzyme (ACE) regulates cardiovascular functions and recently has been associated with metabolism control and obesity. Here, we used ob/ob mice, a model lacking leptin, to answer the question whether ACE and leptin could interact to influence blood pressure, thereby linking the renin-angiotensin system and obesity. These mice are obese and diabetic but have normal 24 h mean arterial pressure. Our results show that plasma and lung ACE activities as well as ACE mRNA expression were significantly decreased in ob/ob mice. In agreement with these findings, the hypotensive effect produced by enalapril administration was attenuated in the obese mice. Plasma renin, angiotensinogen, angiotensin I, bradykinin, and angiotensin 1-7 were increased, whereas plasma angiotensin II concentration was unchanged in obese mice. Chronic infusion of leptin increased renin activity and angiotensin II concentration in both groups and increased ACE activity in ob/ob mice. Acute leptin infusion restored ACE activity in leptin-deficient mice. Moreover, the effect of an ACE inhibitor on blood pressure was not changed in ob/+ mice during leptin treatment but increased four times in obese mice. In summary, our findings show that the renin-angiotensin system is altered in ob/ob mice, with markedly reduced ACE activity, which suggests a possible connection between the renin-angiotensin system and leptin. These results point to an important interplay between the angiotensinergic and the leptinergic systems, which may play a role in the pathogenesis of obesity, hypertension, and metabolic syndrome.

Tissue renin-angiotensin-aldosterone systems: Targets for pharmacological therapy

The renin-angiotensin-aldosterone system is one of the most important systems in cardiovascular control and in the pathogenesis of cardiovascular diseases. Therefore, it is already a very successful drug target for the therapy of these diseases. However, angiotensins are generated not only in the plasma but also locally in tissues from precursors and substrates either locally expressed or imported from the circulation. In most areas of the brain, only locally generated angiotensins can exert effects on their receptors owing to the blood-brain barrier. Other tissue renin-angiotensin-aldosterone systems are found in cardiovascular organs such as kidney, heart, and vessels and play important roles in the function of these organs and in the deleterious actions of hypertension and diabetes on these tissues. Novel components with mostly opposite actions to the classical renin-angiotensin-aldosterone systems have been described and need functional characterization to evaluate their suitability as novel drug targets.

Hypertrophy and fibrosis in the cardiomyopathy of uremia--beyond coronary heart disease

Cardiac disease is the leading cause of death in uremic patients. In contrast to previous opinion, coronary events account for a relatively small proportion of cardiac deaths, the most common causes being sudden death and heart failure. Against this background the current text will discuss noncoronary cardiac pathology, specifically the pathogenesis and the morphological findings caused by (pathological) cardiac hypertrophy, cardiac interstitial fibrosis and microvascular disease.

Effects of angiotensin-converting enzyme inhibitor on expression of TGFb1 and TGFRⅡmRNA, Smad3 and Smad7 on CCl4-inducing rat hepatic fibrogenesis

AIM: To assess the effects of an angiotensin-converting enzyme inhibitor, perindopril on preventing hepatic fibrosis induced by CCl₄ in rats and to investigate the alternation of the expression of transforming growth factor-beta1 (TGFb1) and its receptor Ⅱ (TGFRⅡ) and smads on liver tissues.

METHODS: 80 Wistar rats were randomly allocated into five groups: group A was healthy controls, groups B and C were hepatic fibrotic models induced by carbon tetrachloride (CCl₄), groups D and E were models treated with perindopril starting at the first and fourth week since rat exposured CCl₄. Except for group A, rats were subcutaneously injected with CCl₄ for eight weeks. Rats in groups A, B and D were killed at eighth week, and rats in groups C and E were sacrificed at twelveth week. The blood and liver of rats were collected for further determinations. The effects of perindopril on hepatic fibrosis were evaluated by detecting the level of TGFb1 and TGFRⅡmRNA by RT-PCR. And the expression and its localization of Smad3 and Smad7 in liver tissue by an immunohistochemical staining. The liver histopathology was also examined by HE staining and an electron microscope.

RESULTS: Contrasted to the groups B and C, the level of TGFb1, TGFRⅡ mRNA and the expression of Smad3 were significantly decreased in groups D and E, and the expression of Smad7 was also significantly increased in liver of the two groups (P < 0.05 or P < 0.01). The expression of TGFb1 and TGFRbⅡmRNA, Smad3 and Smad7 were not different between groups B and C (P > 0.05), but there was a significant difference between groups D and E (P < 0.05). Compared with model groups, the histological changes of fibrosis and the dynamic ultrastructureal alterations in rats treated with perindopril were also obviously improved (P < 0.05).

CONCLUSION: The angiotensin-converting enzyme inhibitor, perindopril has a protective effect on liver injury and can ameliorate hepatic fibrosis in rats induced by CCl₄. The mechanisms of perindopril anti-fibrosis may be associated with their effects of down-regulating TGFb1 and TGFRⅡ mRNA and smad3, up-regulating Smad7 and result in suppressing the activation of hepatic stellate cells.