(Pro)renin receptor expression in myocardial infarction in transgenic mice expressing rat tonin

Metabolomic study on the protective effect of isoorientin against myocardial infarction

Myocardial infarction has become one of the largest threats to human life. Myocardial ischemia and hypoxia caused by myocardial infarction are important causes of myocardial cell injury. Compared with chemical drugs, botanical drugs that are natural antioxidants have relatively few toxic side effects. Isoorientin (ISO), a C-glucosyl flavone with a chemical nomenclature, exists in the human diet and has antioxidant and anti-inflammatory effects in other diseases. However, its role in myocardial infarction has not been reported. In this study, we investigated the effects of ISO administration on cardiac function in mice after myocardial infarction, on ROS levels in H9C2 myocardial cells after hypoxia in vitro, and on metabolomic changes in mice after myocardial infarction. We found that ISO improved cardiac function in mice after myocardial infarction and inhibited hypoxia-induced oxidative stress injury in H9C2 cells in vitro. We also found through metabolomic analysis and KEGG enrichment analysis that ISO significantly changed metabolic pathways in mice after myocardial infarction, including histidine metabolism, arachidonic acid metabolism, renin secretion and other pathways. These results lay a foundation for further exploration of the protective effect of ISO against myocardial infarction and the development of related drugs.

Cardiovascular aspects of the (pro)renin receptor: Function and significance

Cardiovascular diseases (CVDs), including all types of disorders related to the heart or blood vessels, are the major public health problems and the leading causes of mortality globally. (Pro)renin receptor (PRR), a single transmembrane protein, is present in cardiomyocytes, vascular smooth muscle cells, and endothelial cells. PRR plays an essential role in cardiovascular homeostasis by regulating the renin-angiotensin system and several intracellular signals such as mitogen-activated protein kinase signaling and wnt/β-catenin signaling in various cardiovascular cells. This review discusses the current evidence for the pathophysiological roles of the cardiac and vascular PRR. Activation of PRR in cardiomyocytes may contribute to myocardial ischemia/reperfusion injury, cardiac hypertrophy, diabetic or alcoholic cardiomyopathy, salt-induced heart damage, and heart failure. Activation of PRR promotes vascular smooth muscle cell proliferation, endothelial cell dysfunction, neovascularization, and the progress of vascular diseases. In addition, phenotypes of animals transgenic for PRR and the hypertensive actions of PRR in the brain and kidney and the soluble PRR are also discussed. Targeting PRR in local tissues may offer benefits for patients with CVDs, including heart injury, atherosclerosis, and hypertension.

(Pro)renin receptor contributes to hypoxia/reoxygenation-induced apoptosis and autophagy in myocardial cells via the beta-catenin signaling pathway

(Pro)renin receptor (PRR) contributes to regulating many physiological and pathological processes; however, the role of PRR-mediated signaling pathways in myocardial ischemia/reperfusion injury (IRI) remains unclear. In this study, we used an in vitro model of hypoxia/reoxygenation (H/R) to mimic IRI and carried out PRR knockdown by siRNA and PRR overexpression using cDNA in H9c2 cells. Cell proliferation activity was examined by MTT and Cell Counting Kit-8 (CCK-8) assays. Apoptosis-related factors, autophagy markers and beta-catenin pathway activity were assessed by real-time PCR and western blotting. After 24 h of hypoxia followed by 2 h of reoxygenation, the expression levels of PRR, LC3B-I/II, Beclin1, cleaved caspase-3, cleaved caspase-9 and Bax were upregulated, suggesting that apoptosis and autophagy were increased in H9c2 cells. Contrary to the effects of PRR downregulation, the overexpression of PRR inhibited proliferation, induced apoptosis, increased the expression of pro-apoptotic factors and autophagy markers, and promoted activation of the beta-catenin pathway. Furthermore, all these effects were reversed by treatment with the beta-catenin antagonist DKK-1. Thus, we concluded that PRR activation can trigger H/R-induced apoptosis and autophagy in H9c2 cells through the beta-catenin signaling pathway, which may provide new therapeutic targets for the prevention and treatment of myocardial IRI.

The (pro)renin receptor in health and disease

The (pro)renin receptor ((P)RR) was first identified as a single-transmembrane receptor in human kidneys and initially attracted attention owing to its potential role as a regulator of the tissue renin-angiotensin system (RAS). Subsequent studies found that the (P)RR is widely distributed in organs throughout the body, including the kidneys, heart, brain, eyes, placenta and the immune system, and has multifaceted functions in vivo. The (P)RR has roles in various physiological processes, such as the cell cycle, autophagy, acid-base balance, energy metabolism, embryonic development, T cell homeostasis, water balance, blood pressure regulation, cardiac remodelling and maintenance of podocyte structure. These roles of the (P)RR are mediated by its effects on important biological systems and pathways including the tissue RAS, vacuolar H⁺-ATPase, Wnt, partitioning defective homologue (Par) and tyrosine phosphorylation. In addition, the (P)RR has been reported to contribute to the pathogenesis of diseases such as fibrosis, hypertension, pre-eclampsia, diabetic microangiopathy, acute kidney injury, cardiovascular disease, cancer and obesity. Current evidence suggests that the (P)RR has key roles in the normal development and maintenance of vital organs and that dysfunction of the (P)RR is associated with diseases that are characterized by a disruption of the homeostasis of physiological functions.

(Pro)renin receptor-mediated myocardial injury, apoptosis, and inflammatory response in rats with diabetic cardiomyopathy

Excessive activation of the renin-angiotensin system (RAS) in diabetic cardiomyopathy (DCM) provokes a series of structural and functional abnormalities, and causes ventricular remodeling and heart failure in diabetes. (Pro)renin receptor (PRR) is a component of the RAS and has been reported to be up-regulated in some cardiovascular diseases. Furthermore, PRR blockade in some cardiovascular diseases, such as myocardial infarction and hypertension, has been demonstrated to reverse their pathogenesis. However, there have been few studies about the function of PRR in the pathogenesis of DCM. In this study, we hypothesized that PRR is involved in the pathogenesis of DCM and mediates myocardial injury in DCM. To explore the role of PRR in DCM, we evaluated the effects of PRR overexpression and knockdown on the DCM phenotype in vivo and in vitro The results show that PRR overexpression exacerbates myocardial injury and the inflammatory response in rats with DCM. Conversely, PRR knockdown alleviates myocardial fibrosis, apoptosis, and the inflammatory response, reversing the cardiac dysfunction in rats with DCM. In cell experiments, PRR overexpression also up-regulated the protein expression of collagen I and fibronectin, aggravated the inflammatory response, and increased the production of reactive oxygen species, whereas PRR knockdown had the opposite effect. Thus, PRR mediates myocardial injury, apoptosis, and the inflammatory response, likely through a PRR/extracellular signal-regulated kinase/reactive oxygen species pathway.

Tonin Overexpression in Mice Diminishes Sympathetic Autonomic Modulation and Alters Angiotensin Type 1 Receptor Response

Background: Tonin, a serine-protease that forms Angiotensin II (AngII) from angiotensinogen, is increased in failing human heart samples. Increased blood pressure (BP) and decreased heart rate (HR) variabilities are associated with higher risk of cardiovascular morbidity. Losartan has been used to reduce hypertension and, therefore, lowers the risk of fatal and non-fatal cardiovascular events. Determination of tonin's impact on BP and HR variabilities as well as the impact of losartan remain questions to be elucidated.

Aim: Evaluation of cardiovascular autonomic profile in transgenic mice overexpressing the rat tonin enzyme TGM'(rton) and the impact of AT1 receptor blocker, losartan.

Methods: Male C57BL/6 (WT) and TGM'(rTon) mice were cannulated for recording BP (Windaq, 4 MHz) for 30 min at baseline and 30 min after losartan injection (20 mg/kg). BP and HR variabilities were analyzed in time and frequency domain method. Low-frequency (LF) and high-frequency (HF) components were identified for sympathetic and parasympathetic modulations analysis. Ang I, AngII, and Ang1-7 were quantified by high performance liquid chromatography method. The total enzymatic activity for AngI, AngII, and Ang1-7 formation was evaluated in the heart and plasma by Liquid chromatography mass spectrometry (LC-MS/MS).

Results: At the baseline TGM'(rTon) exhibited higher BP, lower cardiac LF, higher cardiac HF, lower LF/HF, and lower alpha index than wild type (WT). After losartan injection, TGM'(rTon) mice presented an additional decrease in cardiac LF and increase in HF in relation to baseline and WT. In the vasculature, losartan caused decreased in BP and LF of systolic BP in WT mice in relation to its baseline. A similar effect was observed in the BP of TGM'(rTon) mice; however, LF of systolic BP increased compared to baseline. Our data also indicates that AT1R receptor signaling has been altered in TGM’(rTon)mice. Interestingly, the dynamics of the renin-angiotensin system kinetics change, favoring production of Ang1-7.

Conclusion: Autonomic evaluation of TGM’(rTon) mice indicates an unclear prognosis for diseases that affect the heart. HR variability in TGM’(rTon) mice indicates high risk of morbidity, and sympathetic and parasympathetic modulation indicate low risk of morbidity. The low risk of morbidity could be the biased production of Ang1-7 in the heart and circulation; however, the altered response of AT1R in the TGM’(rTon) remains to be elucidated, as well aswhether that signaling is pro-protection or pro-pathology.

Uric acid induced inflammatory responses in endothelial cells via up-regulating(pro)renin receptor

Hyperuricemia is an important risk factor for vascular inflammation, yet the potential mechanisms of uric acid (UA) in endothelial cells are not well understood. UA has been found to stimulate renin-angiotensin system (RAS) activation in human umbilical vein endothelial cells (HUVECs). (Pro)renin receptor ((P)RR) is widely expressed in endothelial cells and able to induce RAS activation. Whether UA-induced endothelial cell inflammation is via up-regulating (P)RR remained unknown. Primary HUVECs were cultured and treated with UA, under the condition of (P)RR or AT1 silencing. The degree of inflammation in HUVECs was determined by Real-time PCR and monocyte adhesion assay. The protein levels of (P)RR were determined by western blotting or immunofluorescence. Probenecid was used to block UA re-absorption in this study. Adhesion of monocytes to HUVECs was elucidated by microfluidic chip. We found (P)RR is up-regulated in HUVECs following UA stimulation. UA promoted vascular inflammation, which was characterized by up-regulating of cytokines and enhanced monocyte adhesion. Silencing of (P)RR alleviated UA-induced vascular inflammation. Probenecid treatment abolished UA-induced vascular inflammation in HUVECs via suppressing (P)RR up-regulation. This finding was further verified by using microfluidic chip. Our findings indicate that (P)RR plays a critical role in endothelial inflammation in response to UA stimulation.