Inhibiting (pro)renin receptor-mediated p38 MAPK signaling decreases hypoxia/reoxygenation-induced apoptosis in H9c2 cells

Metallothionein-2A Protects Cardiomyocytes from Hypoxia/reper-Fusion through Inhibiting p38

The reperfusion of coronary artery blood supply is often accompanied by myocardial hypoxia/reperfusion (H/R) injury, and induced cardiomyocytes apoptosis. The activation of p38 can induce apoptosis, thereby aggravating the myocardial H/R injury. Metallothionein-2A (MT2A) has the functions of anti-apoptosis and protective effect through p38. However, it is not clear that MT2A may protect cardiomyocytes from H/R injury through p38 signaling pathway. Here, we constructed an H/R model for H9c2 cardiomyocytes to explore the protective effect of MT2A on cardiomyocytes apoptosis during the process of H/R through p38 signal pathway. The results revealed that both endogenously overexpressed MT2A and exogenously added MT2A can inhibit the active expression of p-p38 and cleaved caspase-3 under H/R. Based on our results, H/R induced cardiomyocytes apoptosis and activation of p38. And, MT2A can inhibit the active expression of caspase-3 and p38. We found that MT2A can protect cardiomyocytes apoptosis from H/R injury through p38 signaling pathway.

The role of (pro)renin receptor and its soluble form in cardiovascular diseases

The renin-angiotensin system (RAS) is a major classic therapeutic target for cardiovascular diseases. In addition to the circulating RAS, local tissue RAS has been identified in various tissues and plays roles in tissue inflammation and tissue fibrosis. (Pro)renin receptor (PRR) was identified as a new member of RAS in 2002. Studies have demonstrated the effects of PRR and its soluble form in local tissue RAS. Moreover, as an important part of vacuolar H⁺-ATPase, it also contributes to normal lysosome function and cell survival. Evidently, PRR participates in the pathogenesis of cardiovascular diseases and may be a potential therapeutic target of cardiovascular diseases. This review focuses on the effects of PRR and its soluble form on the physiological state, hypertension, myocardial ischemia reperfusion injury, heart failure, metabolic cardiomyopathy, and atherosclerosis. We aimed to investigate the possibilities and challenges of PRR and its soluble form as a new therapeutic target in cardiovascular diseases.

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.

Catecholamine-induced cardiotoxicity: A critical element in the pathophysiology of stroke-induced heart injury

Cerebrovascular diseases such as ischemic stroke, brain hemorrhage, and subarachnoid hemorrhage provoke cardiac complications such as heart failure, neurogenic stress-related cardiomyopathy and Takotsubo cardiomyopathy. With regards to the pathophysiology of stroke-induced heart injury, several mechanisms have been postulated to contribute to this complex interaction between brain and heart, including damage from gut dysbiosis, immune and systematic inflammatory responses, microvesicle- and microRNA-mediated vascular injury and damage from a surge of catecholamines. All these cerebrovascular diseases may trigger pronounced catecholamine surges through diverse ways, including stimulation of hypothalamic-pituitary adrenal axis, dysregulation of autonomic system, and secretion of adrenocorticotropic hormone. Primary catecholamines involved in this pathophysiological response include norepinephrine (NE) and epinephrine. Both are important neurotransmitters that connect the nervous system with the heart, leading to cardiac damage via myocardial ischemia, calcium (Ca²⁺) overload, oxidative stress, and mitochondrial dysfunction. In this review, we will aim to summarize the molecular mechanisms behind catecholamine-induced cardiotoxicity including Ca²⁺ overload, oxidative stress, apoptosis, cardiac hypertrophy, interstitial fibrosis, and inflammation. In addition, we will focus on how synchronization among these pathways evokes cardiotoxicity.

(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.

MicroRNA-148a regulates low-density lipoprotein metabolism by repressing the (pro)renin receptor

High plasma LDL cholesterol (LDL-c) concentration is a major risk factor for atherosclerosis. Hepatic LDL receptor (LDLR) regulates LDL metabolism, and thereby plasma LDL-c concentration. Recently, we have identified the (pro)renin receptor [(P)RR] as a novel regulator of LDL metabolism, which regulates LDLR degradation and hence its protein abundance and activity. In silico analysis suggests that the (P)RR is a target of miR-148a. In this study we determined whether miR-148a could regulate LDL metabolism by regulating (P)RR expression in HepG2 and Huh7 cells. We found that miR-148a suppressed (P)RR expression by binding to the 3’-untranslated regions (3’-UTR) of the (P)RR mRNA. Mutating the binding sites for miR-148a in the 3’-UTR of (P)RR mRNA completely abolished the inhibitory effects of miR-148a on (P)RR expression. In line with our recent findings, reduced (P)RR expression resulted in decreased cellular LDL uptake, likely as a consequence of decreased LDLR protein abundance. Overexpressing the (P)RR prevented miR-148a-induced reduction in LDLR abundance and cellular LDL uptake. Our study supports a new concept that miR-148a is a regulator of (P)RR expression. By reducing (P)RR abundance, miR-148a decreases LDLR protein abundance and consequently cellular LDL uptake.

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 is Involved in Myocardial Damage in Alcoholic Cardiomyopathy

BACKGROUND

(Pro)renin receptor (PRR), a novel member of the renin-angiotensin system, participates in various cardiovascular diseases. However, the role of PRR in alcoholic cardiomyopathy (ACM), which is caused by alcohol intake and manifests as myocardial damage and cardiac dysfunction, remains unclear.

METHODS

PRR gene silencing was achieved by transfecting recombinant adenovirus expressing anti-PRR short hairpin RNA (PRR-shRNA). In vitro, primary rat cardiac fibroblasts (CFs) were cultured with the stimulation of alcohol (200 mM), with or without PRR-shRNA and PD98059. Immunofluorescence, RT-PCR, and Western blot were used to measure the protein and messenger (mRNA) expression of PRR, fibrotic factors, and members of related signaling pathways. In vivo, Wistar rats were fed a diet containing 9% (v/v) alcohol or a normal diet for 3 months, with or without PRR-shRNA. Sirius Red staining, immunohistochemical staining, and toluidine blue staining were used to evaluate myocardial fibrosis, oxidative stress, and inflammation response.

RESULTS

Alcohol markedly increased PRR mRNA and protein expression in a time- and concentration-dependent manner in CFs. The increased expression of fibrotic factors induced by alcohol was prevented by PRR-shRNA and PD98059. Moreover, PRR-shRNA decreased the phosphorylation of extracellular regulated protein kinases (ERK) 1/2 in CFs. Furthermore, PRR-shRNA decreased cardiac fibrosis, reduced oxidative stress, and alleviated inflammation response in the myocardial tissue.

CONCLUSIONS

Our results show that PRR-ERK1/2 signaling was involved in the development of ACM and that PRR could be a new target for the treatment of ACM.

Effects of Irbesartan Pretreatment on Pancreatic β-Cell Apoptosis in STZ-Induced Acute Prediabetic Mice

The current study was performed to investigate the effects and potential effects of irbesartan pretreatment on pancreatic β-cell apoptosis in a streptozotocin- (STZ-) induced acute mouse model of prediabetes. Twenty-four male BALB/C mice (18–22 g) were randomly divided into three groups: normal control group (NC, n = 6), STZ group (STZ, n = 8), and irbesartan + STZ group (IRB + STZ, n = 10). In the IRB + STZ group, mice were administered irbesartan (300 mg/kg per day) by gavage for one week. The STZ group and IRB + STZ group received STZ (80 mg/kg by intraperitoneal (IP) injection once). The NC group received normal saline (80 mg/kg by IP injection once). Fasting blood glucose prior to STZ injection and presacrifice was analysed using samples withdrawn from the caudal vein to confirm the induction of prediabetes. Haematoxylin and eosin staining, immunohistochemical detection of insulin, and apoptosis analysis were performed. Reverse transcription-quantitative polymerase chain reaction was used to detect angiotensin II type 1 receptor (AT1R), caspase-3, and p38 mitogen-activated protein kinase (MAPK) mRNA expression. Blood glucose was significantly higher in the STZ group (9.01 ± 1.1089 vs 4.78 ± 0.7026) and IRB + STZ group (7.86 ± 1.1811 vs 4.78 ± 0.7026) compared with the NC group (P < 0.05). In comparison to the STZ group, the islet cell damage was marginally improved in the IRB + STZ group, and the IRB + STZ group had a significantly lower apoptotic rate than the STZ group (22.42 ± 8.3675 vs 50.86 ± 5.3395, P < 0.001). AT1R expression in the IRB + STZ group was lower than that in the STZ group (1.56 ± 1.2207 vs 3.92 ± 2.4392, P < 0.05). The mRNA expression of caspase-3 in pancreatic tissue was significantly lower in the IRB + STZ group than in the STZ group (0.90 ± 0.7272 vs 1.88 ± 1.0572, P < 0.05). Similarly, the IRB + STZ group also had lower p38MAPK levels than the STZ group (1.16 ± 1.0642 vs 2.55 ± 1.7925, P > 0.05). In conclusion, irbesartan pretreatment improved glucose levels and insulin secretion and decreased islet β-cell apoptosis to protect islet β cells in an STZ-induced acute prediabetic mouse model.

Jujuboside A attenuates norepinephrine-induced apoptosis of H9c2 cardiomyocytes by modulating MAPK and AKT signaling pathways

Cardiomyocyte apoptosis is closely associated with the pathogenesis of heart failure. Jujuboside A (JUA) is a type of saponin isolated from the seeds of Zizyphus jujuba. In traditional Chinese medicine, it is believed that JUA possesses multiple biological effects, including antianxiety, antioxidant and anti‑inflammatory activities. The present study aimed to evaluate the effects of JUA on norepinephrine (NE)‑induced apoptosis of H9c2 cells and to investigate its underlying mechanisms. Rat H9c2 cardiomyocytes were pretreated with JUA and were then exposed to NE as an in vitro model of myocardial apoptosis. A cell viability assay, scanning electron microscopy, transmission electron microscopy, flow cytometry assay, acridine orange/ethidium bromide staining, reverse transcription‑quantitative polymerase chain reaction and western blotting, all revealed that NE induced H9c2 cell apoptosis. The results demonstrated that NE inhibited cell viability, and enhanced cell damage and apoptosis of H9c2 cells. Conversely, pretreatment with JUA was able to reverse NE‑induced decreased cell viability and increased apoptosis. Furthermore, JUA suppressed upregulation of the B‑cell lymphoma 2 (Bcl‑2)‑associated X protein/Bcl‑2 ratio, and inhibited the increased protein expression levels of cleaved caspase‑3 and cleaved caspase‑9 following NE exposure. However, the protein expression levels of cleaved caspase‑12 and cleaved caspase‑8 were not significantly altered following exposure to NE or JUA pretreatment. In addition, in JUA‑pretreated cells, the protein expression levels of phosphorylated (p)‑p38 and p‑c‑Jun N‑terminal kinase were downregulated compared with in NE‑treated cells. Furthermore, JUA regulated the activation of extracellular signal‑regulated kinase (ERK) in NE‑treated cells and significantly increased the expression levels of p‑AKT. Taken together, these data suggested that JUA may protect against NE‑induced apoptosis of cardiomyocytes via modulation of the mitogen‑activated protein kinase and AKT signaling pathways. Therefore, JUA may be considered a potential therapeutic strategy for the treatment of heart disease.

Crosstalk between p38 MAPK and caspase-9 regulates mitochondria-mediated apoptosis induced by tetra-α-(4-carboxyphenoxy) phthalocyanine zinc photodynamic therapy in LoVo cells

Photodynamic therapy (PDT) is considered to be an advancing antitumor technology. PDT using hydrophilic/lipophilic tetra-α-(4-carboxyphenoxy) phthalocyanine zinc (TαPcZn-PDT) has exhibited antitumor activity in Bel-7402 hepatocellular cancer cells. However, the manner in which p38 MAPK and caspase-9 are involved in the regulation of mitochondria-mediated apoptosis in the TαPcZn-PDT-treated LoVo human colon carcinoma cells remains unclear. Therefore, in the present study, a siRNA targeting p38 MAPK (siRNA-p38 MAPK) and the caspase-9 specific inhibitor z-LEHD-fmk were used to examine the crosstalk between p38 MAPK and caspase-9 during mitochondria-mediated apoptosis in the TαPcZn-PDT-treated LoVo cells. The findings revealed that the TαPcZn-PDT treatment of LoVo cells resulted in the induction of apoptosis, the formation of p38 MAPK/caspase-9 complexes, the activation of p38 MAPK, caspase-9, caspase-3 and Bid, the downregulation of Bcl-2, the reduction of mitochondrial membrane potential (ΔΨm), the upregulation of Bax and the release of apoptosis-inducing factor (AIF) and cytochrome c (Cyto c). By contrast, siRNA-p38 MAPK or z-LEHD-fmk both attenuated the effects of TαPcZn-PDT in the LoVo cells. Furthermore, the results revealed that siRNA-p38 MAPK had more significant inhibitory effects on apoptosis and mitochondria compared with the effects of z-LEHD-fmk in TαPcZn-PDT-treated LoVo cells. These findings indicated that p38 MAPK plays the major regulatory role in the crosstalk between p38 MAPK and caspase-9 and that direct interaction between p38 MAPK and caspase-9 may regulate mitochondria-mediated apoptosis in the TαPcZn-PDT-treated LoVo cells.

PTPIP51 regulates mouse cardiac ischemia/reperfusion through mediating the mitochondria-SR junction

Protein tyrosine phosphatase interacting protein 51 (PTPIP51) participates in multiple cellular processes, and dysfunction of PTPIP51 is implicated in diseases such as cancer and neurodegenerative disorders. However, there is no functional evidence showing the physiological or pathological roles of PTPIP51 in the heart. We have therefore investigated the role and mechanisms of PTPIP51 in regulating cardiac function. We found that PTPIP51 was markedly upregulated in ischemia/reperfusion heart. Upregulation of PTPIP51 by adenovirus-mediated overexpression markedly increased the contact of mitochondria-sarcoplasmic reticulum (SR), elevated mitochondrial Ca²⁺ uptake from SR release through mitochondrial Ca²⁺uniporter. Inhibition or knockdown of mitochondrial Ca²⁺uniporter reversed PTPIP51-mediated increase of mitochondrial Ca²⁺ and protected cardiomyocytes against PTPIP51-mediated apoptosis. More importantly, cardiac specific knockdown of PTPIP51 largely reduced myocardium infarction size and heart injury after ischemia/reperfusion. Our study defines a novel and essential function of PTPIP51 in the cardiac ischemia/reperfusion process by mediating mitochondria-SR contact. Downregulation of PTPIP51 improves heart function after ischemia/reperfusion injury, suggesting PTPIP51 as a therapeutic target for ischemic heart diseases.

Fisetin regulates astrocyte migration and proliferation in vitro

Fisetin (3,3′,4′,7-tetrahydroxyflavone) is a plant flavonol found in fruits and vegetables that has been reported to inhibit migration and proliferation in several types of cancer. Reactive astrogliosis involves astrocyte migration and proliferation, and contributes to the formation of glial scars in central nervous system (CNS) disorders. However, the effect of fisetin on the migration and proliferation of astrocytes remains unclear. In this study, we found that fisetin inhibited astrocyte migration in a scratch-wound assay and diminished the phosphorylation of focal adhesion kinase (FAK; Tyr576/577 and paxillin (Tyr118). It also suppressed cell proliferation, as indicated by the decreased number of 5-ethynyl-2′-deoxyuridine (EdU)-positive cells, induced cell cycle arrest in the G1 phase, reduced the percentage of cells in the G2 and S phase (as measured by flow cytometry), and decreased cyclin D1 expression, but had no effect on apoptosis. Fisetin also decreased the phosphorylation levels of Akt and extracellular signal-regulated kinase (Erk)1/2, but had no effect on the phosphorylation of p38 mitogen-activated protein kinase (MAPK). These results indicate that fisetin inhibits aggressive cell phenotypes by suppressing cell migration and proliferation via the Akt/Erk signaling pathway. Fisetin may thus have potential for use as a therapeutic strategy targeting reactive astrocytes, which may lead to the inhibition of glial scar formation in vitro.

Nox4 has a crucial role in uric acid‑induced oxidative stress and apoptosis in renal tubular cells

The purpose of the present study was to evaluate the effects of uric acid in promoting tubular cell apoptosis and verify the role of nicotinamide adenine dinucleotide phosphate oxidase 4 (Nox4)‑induced oxidative stress in this process. HK‑2 cells were used as a human proximal tubular cell model and co‑cultured with various concentrations of uric acid with or without pre‑treatment with the Nox4 inhibitor diphenylene iodonium (DPI). The apoptotic rate and the amount of reactive oxygen species (ROS) were examined by flow cytometry. Furthermore, levels of Nox4, phosphorylated (p)‑P38, p‑extracellular signal‑regulated kinase (ERK), B‑cell lymphoma 2 (Bcl‑2) and Bcl‑2‑extra large (Bax) were detected by western blot analysis. The results showed that treatment with uric acid decreased HK‑2 cell viability and promoted apoptosis in a dose‑dependent manner. This was paralleled with an upregulation of Nox4 as well as ROS overproduction, which activated the phosphorylation of P38/ERK and caused an imbalance of Bax/Bcl‑2 in HK‑2 cells. Of note, inhibition of Nox4 with DPI prevented uric acid‑induced cell injury by suppressing ROS generation and P38/ERK activation. In conclusion, it was demonstrated that elevated uric acid promoted ROS‑induced tubular cell apoptosis by upregulating Nox4 expression. The present study therefore provided possible mechanisms and a potential therapeutic target of uric acid‑induced chronic kidney disease.

Combination of microRNA-21 and microRNA-146a Attenuates Cardiac Dysfunction and Apoptosis During Acute Myocardial Infarction in Mice

Recent studies have revealed the cytoprotective roles of microRNAs (miRNAs) miR-21 and miR-146a against ischemic cardiac injuries. While these studies investigated each of these miRNAs as an independent individual factor, our previous study has suggested the possible interaction between these two miRNAs. The present study was designed to investigate this possibility by evaluating the effects of miR-21 and miR-146a combination on cardiac ischemic injuries and the underlying mechanisms. MiR-21 and miR-146a synergistically decreased apoptosis under ischemia/hypoxic conditions in cardiomyocytes compared with either miR-21 or miR-146a alone. Mice coinjected with agomiR-21 and agomiR-146a had decreased infarct size, increased ejection fraction (EF), and fractional shortening (FS). These effects were greater than those induced by either of the two agomiRs. Furthermore, greater decreases in p38 mitogen-associated protein kinase phosphorylation (p-p38 MAPK) were observed with miR-21: miR-146a combination as compared to application of either of the miRNAs. These data suggest that combination of miR-21 and miR-146a has a greater protective effect against cardiac ischemia/hypoxia-induced apoptosis as compared to these miRNAs applied individually. This synergistic action is mediated by enhanced potency of inhibition of cardiomyocyte apoptosis by the miR-21—PTEN/AKT—p-p38—caspase-3 and miR-146a—TRAF6—p-p38—caspase-3 signal pathways.