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Chronic treatment with the mitochodrial peptide humanin prevents age-related myocardial fibrosis in mice

第一作者:Qin, Q

期刊: AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, 2018; 315 (无)

Cardiac fibrosis is a biological process that increases with age and contributes to myocardial dysfunction. Humanin (HN) is an endogenous mitochondria-derived peptide that has cytoprotective effects and reduces oxidative stress. The present study aimed to test the hypothesis that chronic supplementation of exogenous FIN in middle-aged mice could prevent and reverse cardiac fibrosis and apoptosis in the aging heart. Female C57BL/6N mice at 18 mo of age received 14-mo intraperitoneal injections of vehicle (old group; n = 6) or HN analog (HNG; 4 mg/kg 2 times/wk, old + HNG group, n = 8) and were euthanized at 32 mo of age. C57BL/6N female mice (young group, n = 5) at 5 mo of age were used as young controls. HNG treatment significantly increased the ratio of cardiomyocytes to fibroblasts in aging hearts, as shown by the percentage of each cell type in randomly chosen fields after immunofluorescence staining. Furthermore, the increased collagen deposition in aged hearts was significantly reduced after HNG treatment, as indicated by picrosirius red staining. HNG treatment also reduced in aging mice cardiac fibroblast proliferation (5'-bromo-2-deoxyuridine staining) and attenuated transforming growth factor-beta(1), fibroblast growth factor-2, and matrix metalloproteinase-2 expression (immunohistochemistry or real-time PCR). Myocardial apoptosis was inhibited in HNG-treated aged mice (TUNEL staining). To decipher the pathway involved in the attenuation of the myocardial fibrosis by HNG, Western blot analysis was done and showed that HNG upregulated the Akt/glycogen synthase kinase-3 beta pathway in aged mice. Exogenous HNG treatment attenuated myocardial fibrosis and apoptosis in aged mice. The results of the present study suggest a role for the mitochondria- derived peptide HN in the cardioprotection associated with aging. NEW & NOTEWORTHY Cardiac fibrosis is a biological process that increases with age and contributes to myocardial dysfunction. Humanin is an endogenous mitochondria-derived peptide that has cytoprotective effects and reduces oxidative stress. Here, we demonstrate, for the first time, that exogenous humanin treatment attenuated myocardial fibrosis and apoptosis in aging mice. We also detected upregulated Akt/glycogen synthase kinase-3 beta pathway in humanin analog-treated mice, which might be the mechanism involved in the cardioprotective effect of humanin analog in aging mice.

IF:4.05

Atheroprone flow enhances the endothelial-to-mesenchymal transition

第一作者:Lai, BC

期刊: AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, 2018; 315 (无)

The endothelial-to-mesenchymal transition (EndoMT) is a cellular process featuring decreased expression of endothelial marker genes but increased expression of mesenchymal marker genes. The EndoMT is involved in endothelial dysfunction and the pathogenesis of atherosclerosis. To investigate the dynamic expression of EndoMT genes in vascular endothelial cells under atheroprotective pulsatile shear stress (PS) and atheroprone oscillatory shear stress (OS), we analyzed RNA sequencing data from multitimepoint shear-stress experiments. This unbiased analysis involving next-generation sequencing confirmed that PS and OS had an opposite effect in regulating EndoMT genes. Further experimental validations with H2O2 and gain- and loss-of-function approaches indicated that reactive oxygen species are involved in OS-induced EndoMT, whereas AMP-activated protein kinase and sirtuin-1 could inhibit OS-induced EndoMT. Furthermore, compared with PS, OS increased the DNA methylation of the promoter regions of von Willebrand factor, CD31, and cadherin 5 genes but decreased that of cadherin 2, fibroblast-specific protein 1, and vimentin. The translational implication of the present study builds on the ability of the antidiabetic drug metfomin and cholesterol-lowering drug atorvastatin to suppress the EndoMT in cultured endothelial cells and in mouse aortas. NEW & NOTEWORTHY Our RNA sequencing data provided a genome-wide and unbiased view of' the shear stress regulation of the endothelial-to-mesenchymal transition (EndoMT) in the endothelium. Furthermore, epigenetic regulation (e.g., DNA methylation) is a key mechanism involved in shear stress-regulated EndoMT. The translational implication of this study is that cardiovascular medications such as statins and metformin have similar beneficial effects as that of atheroprotective flow by mitigating EndoMT.

IF:4.05

Facilitated Ca2+ homeostasis and attenuated myocardial autophagy contribute to alleviation of diabetic cardiomyopathy after bariatric surgery

第一作者:Huang, X

期刊: AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, 2018; 315 (无)

Bariatric surgery has been reported to relieve diabetic cardiomyopathy (DCM) effectively. However, the mechanisms remain largely unknown. To determine the effects of bariatric surgery on DCM via modulation of myocardial Ca2+ homeostasis and autophagy, sleeve gastrectomy (SG). duodenal-jejunal bypass (DJB), and sham surgeries were performed in diabetic rats induced by high-fat diet and a low dose of streptozotocin. Cardiac remodeling was assessed by a series of morphometric and histological analyses. Transthoracic echocardiography and hemodynamic measurements were performed to determine cardiac function. Ca2+ homeostasis was evaluated by measuring Ca2+ transients with fura-2 AM in isolated ventricular myocytes along with detection of the abundance of Ca2+ regulatory proteins in the myocardium. Myocardial autophagic flux was determined by expression of autophagy-related proteins in the absence and presence of chloroquine. Both SG and DJB surgery alleviated DCM morphologically and functionally. Ca2+ transients exhibited a significantly higher amplitude and faster decay after SG and DJB, which could he partially explained by increased expression of ryanodine receptor 2, sarco(endo)plasmic reticulum Ca2+-2ATPase, 12.6-kDa FK506-binding protein, and hyperphosphorylation of phospholamban. In addition, a lower level of light chain 3B and higher level of p62 were detected after both SG and DJB, which was not reversed by chloroquine treatment and associated with activated mammalian target of rapamycin and attenuated AMP-activated protein kinase signaling pathway. Collectively, these results provided evidence that bariatric surgery could alleviate DCM effectively, which may result, at least in part, from facilitated Ca2+ homeostasis and attenuated autophagy, suggesting a potential choice for treatment of DCM when properly implemented. NEW & NOTEWORTHY The present study is the first to investigate the modulation of myocardial Ca2+ homeostasis and autophagy after bariatric surgery and to examine its effects on diabetic cardiomyopathy. Bariatric surgery-could facilitate myocardial Ca2+ homeostasis and attenuate myocardial autophagy, contributing to the alleviation of cardiomyopathy morphologically and functionally in a diabetic rat model.

IF:4.05

Maternal high-fat diet acts on the brain to induce baroreflex dysfunction and sensitization of angiotensin II-induced hypertension in adult offspring

第一作者:Zhang, YP

期刊: AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, 2018; 314 (无)

Accumulating evidence indicates that maternal high-fat diet (HFD) is associated with metabolic syndrome and cardiovascular disease in adult offspring. The present study tested the hypothesis that maternal HFD modulates the brain renin-angiotensin system (RAS), oxidative stress, and proinflammatory cytokines that alter angiotensin II (ANG II) and TNF-alpha actions and sensitize the ANG II-elicited hypertensive response in adult offspring. All offspring were cross fostered by dams on the same or opposite diet to yield the following four groups: offspring from normal-fat control diet-fed dams suckled by control diet-fed dams (OCC group) or by HFD-fed dams (OCH group) and offspring from HFD-fed dams fed a HFD suckled by control diet-fed dams (OHC group) or by HFD-fed dams (OHH group). RT-PCR analyses of the lamina terminalis and paraventricular nucleus indicated upregulation of mRNA expression of several RAS components, NADPH oxidase, and proinflammatory cytokines in 10-wk-old male offspring of dams fed a HFD during either pregnancy, lactation, or both (OHC, OCH, and OHH groups). These offspring also showed decreased cardiac baroreflex sensitivity and increased pressor responses to intracerebroventricular microinjection of either ANG II or TNF-alpha. Furthermore, chronic systemic infusion of ANG II resulted in enhanced upregulation of mRNA expression of RAS components, NADPH oxidase, and proinflammatory cytokines in the lamina terminalis and paraventricular nucleus and an augmented hypertensive response in the OHC, OCH, and OHH groups compared with the OCC group. The results suggest that maternal HFD blunts cardiac baroreflex function and enhances pressor responses to ANG II or proinflammatory cytokines through upregulation of the brain RAS, oxidative stress, and inflammation. NEW & NOTEWORTHY The results of our study indicate that a maternal high-fat diet during either pregnancy or lactation is sufficient for perinatal programming of sensitization for hypertension, which is associated with hyperreactivity of central cardiovascular nuclei that, in all likelihood, involves elevated expression of the renin-angiotensin system, NADPH oxidase. and proinflammatory cytokines. The present study demonstrates, for the first time, the central mechanism underlying maternal high-fat diet sensitization of the hypertensive response in adult offspring.

IF:4.05

Chronic stimulation of the sigma-1 receptor ameliorates autonomic nerve dysfunction and atrial fibrillation susceptibility in a rat model of depression

第一作者:Liu, X

期刊: AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, 2018; 315 (无)

The present study-aimed to assess the effect of sigma-1 receptor (S1R) stimulation on autonomic nerve dysfunction and susceptibility to atrial fibrillation (AF) in a rat depression model. Male rats were randomly divided into one of the following four treatment groups: saline [control (CTL)]; saline + intragastric administration of SA4503, an agonist of SIR (CTS); chronic unpredictable mild stress (CUMS) to produce depression (MDD); and CUMS + intragastric administration of SA4503 (MDS). Depression-like behaviors, such as reduced sucrose preference, decreased body weight gain, and increased immobility time during forced swimming, improved in the MDS group after 4 wk of SA4503 treatment. Compared with rats in the CTL group, rats in the MDD group showed significantly augmented sympathetic activity, reduced parasympathetic activity, decreased heart rate variability, and lowered S1R expression in the atrium and hippocampus (all P < 0.01). However, rats in the MDS group showed mitigated aforementioned alterations and improved electrical remodeling compared with rats in the MDD group (all P < 0.01). Furthermore, rats in the MDS group showed shortened activation latencies, increased effective refractory periods, and lowered frequency of AF incidence duration and fibrosis compared with rats in the MDD group (all P < 0.01). The results indicate that S1R stimulation reduces sympathetic activity and susceptibility to AF by improving depressive behaviors, modulating cardiac autonomic nerve balance, lightening nerve remodeling, and upregulating SIR and ion channel protein expression. NEW & NOTEWORTHY Chronic stimulation of the sigma-1 receptor (S1R) ameliorates depression-induced autonomic nerve dys-function by modulating the imbalance between overactivated sympathetic activity and decreased vagal activity. Chronic S1R stimulation alleviates atrial electrical remodeling, fibrosis, and susceptibility to atrial fibrillation (AF). The S1R agonist may target the underlying mechanisms related to AF occurrence. The results indicate that the S1R could be a potential clinical target for atrial arrhythmia, especially when it is combined with major depressive disorders.

IF:4.05

Novel role of PKR in palmitate-induced Sirt1 inactivation and endothelial cell senescence

第一作者:Li, YP

期刊: AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, 2018; 315 (无)

Endothelial cell senescence is regarded as a vital characteristic of cardiovascular diseases. Elevated palmitate (PA) is an independent risk factor of cardiovascular diseases. but its role in endothelial cell senescence is currently unknown. During the course of studying the prosenescent role of PA, we discovered a key role of dsRNA-dependent protein kinase [protein kinase R (PKR)] in endothelial senescence. Exposure of human umbilical vein endothelial cells (HUVECs) to PA-induced cell senescence is characterized by increased levels of senescence-associated beta-galactose glucosidase activity, excessive production of reactive oxygen species production. impaired cellular proliferation, and G(1) phase arrest. This phenomenon is associated with an increase of PKR autophosphorylation and decreased activity of sirtuin 1 (Sirt1), a pivotal antisenescent factor. PKR inactivation by PKR siRNA or its phosphorylation inhibitor 2-aminopurine significantly attenuated PA-induced HUVEC senescence by reversing Sirt1 activity and its downstream signaling. Moreover, to study the regulatory mechanism between PKR and Sirt1, we found that PKR promotes JNK activation to inhibit Sirt1 activity and that this effect could be reversed by the JNK inhibitor SP600125. These findings provide evidence that PKR mediates PA-induced HUVEC senescence by inhibiting Sirt1 signaling. Our study provides novel insights into the actions and mechanisms of PKR in endothelial senescence. NEW & NOTEWORTHY This study first provides a novel observation that dsRNA-dependent protein kinase (PKR) mediates palmitate-induced sirtuin 1 inactivation and subsequent human umbilical vein endothelial cell senescence. Most importantly, these new findings will provide a potential therapeutic strategy to improve free fatty acid-induced endothelial senescence by targeting PKR in cardiovascular diseases.

IF:4.05

Antifibrotic cardioprotection of berberine via downregulating myocardial IGF-1 receptor-regulated MMP-2/MMP-9 expression in diabetic rats

第一作者:Li, GH

期刊: AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, 2018; 315 (无)

Diabetic cardiac fibrosis increases ventricular stiffness and facilitates the occurrence of diastolic dysfunction. Our previous studies have shown that berberine, a natural alkaloid, attenuates cardiac ischemia-reperfusion injury in diabetic rats. The aim of present study was to investigate the effects of long-term berberine treatment on cardiac remodeling in diabetic rats and the underlying mechanisms. Diabetic rats induced by low-dose streptozotocin injection combined with 8 wk of high-fat diet displayed significant cardiac matrix collagen deposition and dysfunction, whereas berberine administration (200 mg.kg(-1).day(-1), gavage 4 wk) significantly ameliorated cardiac fibrosis and dysfunction and reduced cardiac IGF-1 receptor (IGF-1R) expression in diabetic rats. Interestingly, IGF-1R expression was upregulated in cardiac fibroblasts isolated from diabetic hearts or cultured in high-glucose conditions (30 mM). High glucose treatment or IGF-1R overexpression increased matrix metalloproteinase (MMP)-2/MMP-9 expression, alpha-smooth muscle actin (alpha-SMA), and collagen type I expression in cardiac fibroblasts. In contrast, berberine treatment significantly inhibited IGF-1R expression and exerted an antifibrotic effect in high glucose-cultured cardiac fibroblasts, as manifested by decreased MMP-2/MMP-9, alpha-SMA, and collagen type I expression, whereas IGF-1R siRNA plus berberine treatment did not further enhance this antifibrotic effect compared with berberine treatment alone. Taken together, long-term berberine treatment ameliorates cardiac fibrosis and dysfunction by downregulating IGF-1R expression in cardiac fibroblasts and subsequently reducing MMP-2/MMP-9, alpha-SMA, and collagen type I expression in diabetic hearts. The findings suggest the therapeutic potential of berberine for diabetic cardiomyopathy associated with cardiac fibrosis. NEW & NOTEWORTHY Berberine downregulated IGF-1 receptor expression and matrix metalloproteinase-2/matrix metalloproteinase-9 levels in cardiac fibroblasts and thus inhibited fibroblast differentiation and collagen overproduction in diabetic hearts, suggesting a novel mechanism for antifibrotic cardioprotection of berberine in type 2 diabetes.

IF:4.05

Differential cardiac hypertrophy and signaling pathways in pressure versus volume overload

第一作者:You, JY

期刊: AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, 2018; 314 (无)

Mechanical overload can be classified into pressure overload and volume overload, causing concentric and eccentric cardiac hypertrophy, respectively. Here, we aimed to differentiate the load-mediated signaling pathways involved in pressure versus volume overload cardiac hypertrophy. Pressure or volume overload was imposed on C57BL/6J mice by transverse aortic constriction (TAC) or aortic regurgitation (AR), respectively. After surgery (2 wk), left ventricular structure and function were evaluated by echocardiographic, hemodynamic, and histological analyses. Signaling pathways related to hypertrophy, fibrosis, angiogenesis, and apoptosis were studied by histological analysis, RT-PCR, and Western blot analysis. Although mean wall stress was similar in both TAC and AR mice, systolic wall stress was significantly increased in TAC and diastolic wall stress was mainly elevated in AR. TAC or AR induced concentric or eccentric compensated hypertrophy, respectively. TAC was associated with more significant fibrosis and apoptosis, whereas AR was associated with more significant angiogenesis. MAPK kinase family, beta-arrestin-2, Akt, and Ca2+-related signaling pathways were markedly activated in TAC but mildly upregulated or unchanged in AR. Pressure overload and volume overload induce different phenotypic and molecular adaptations in cardiac hypertrophy. Most load-related signaling pathways assessed in this study predominate in pressure but not volume overload. The stimulus-specific heterogeneity in the signaling pathways requires distinct manipulations for further mechanistic and pharmacological studies. NEW & NOTEWORTHY Using the transverse aortic constriction mouse model and the newly developed aortic regurgitation mouse model, we delineated the prominent differences between concentric and eccentric cardiac hypertrophy on morphological, functional, and molecular levels. Our findings are important for the precise diagnosis and treatment of these two types of cardiac hypertrophy. Listen to this article's corresponding podcast at http://ajpheart.podbean.com/e/chinese-english-language-podcast-on-differentialcardiac-remodeling-in-tac-vs-ar/.

IF:4.05

Mechanism underlying the heart rate dependency of wave reflection in the aorta: a numerical simulation

第一作者:Xiao, HG

期刊: AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, 2018; 314 (无)

Arterial wave reflection has been shown to have a significant dependence on heart rate (HR). However, the underlying mechanisms inherent in the HR dependency of wave reflection have not been well established. This study aimed to investigate the potential mechanisms and role of arterial viscoelasticity using a 55-segment transmission line model of the human arterial tree combined with a fractional viscoelastic model. At varying degrees of viscoelasticity modeled as fractional order parameter alpha, reflection magnitude (RM), reflection index (RI), augmentation index (AIx), and a proposed novel normalized reflection coefficient (Gamma(norm)) were estimated at different HRs from 60 to 100 beats/min with a constant mean flow of 70 ml/s. RM, RI, AIx, and Gamma(norm) at the ascending aorta decreased linearly with increasing HR at all degrees of viscoelasticity. The means +/- SD of the HR dependencies of RM, RI, AIx, and Gamma(norm) were -0.042 +/- 0.004, -0.018 +/- 0.001, -1.93 +/- 0.55%, and -0.037 +/- 0.002 per 10 beats/min, respectively. There was a significant and nonlinear reduction in RM, RI, and Gamma(norm) with increasing alpha at all HRs. In addition, HR and alpha have a more pronounced effect on wave reflection at the aorta than at peripheral arteries. The potential mechanism of the HR dependency of wave reflection was explained by the inverse dependency of the reflection coefficient on frequency, with the harmonics of the pulse waveform moving toward higher frequencies with increasing HR. This HR dependency can be modulated by arterial viscoelasticity. NEW & NOTEWORTHY This in silico study addressed the underlying mechanisms of how heart rate influences arterial wave reflection based on a transmission line model and elucidated the role of arterial viscoelasticity in the dependency of arterial wave reflection on heart rate. This study provides insights into wave reflection as a frequency-dependent phenomenon and demonstrates the validity of using reflection magnitude and reflection index as wave reflection indexes.

IF:4.05

Overexpression of the neuronal human (pro)renin receptor mediates angiotensin II-independent blood pressure regulation in the central nervous system

第一作者:Peng, H

期刊: AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, 2018; 314 (无)

Despite advances in antihypertensive therapeutics, at least 15-20% of hypertensive patients have resistant hypertension through mechanisms that remain poorly understood. In this study, we provide a new mechanism for the regulation of blood pressure (BP) in the central nervous system (CNS) by the (pro) renin receptor (PRR), a recently identified component of the renin-angiotensin system that mediates ANG II formation in the CNS. Although PRR also mediates ANG II-independent signaling, the importance of these pathways in BP regulation is unknown. Here, we developed a unique transgenic mouse model overexpressing human PRR (hPRR) specifically in neurons (Syn-hPRR). Intracerebroventricular infusion of human prorenin caused increased BP in Syn-hPRR mice. This BP response was attenuated by a NADPH oxidase (NOX) inhibitor but not by antihypertensive agents that target the renin-angiotensin system. Using a brain-targeted genetic knockdown approach, we found that NOX4 was the key isoform responsible for the prorenin-induced elevation of BP in Syn-hPRR mice. Moreover, inhibition of ERK significantly attenuated the increase in NOX activity and BP induced by human prorenin. Collectively, our findings indicate that an ANG II-independent, PRR-mediated signaling pathway regulates BP in the CNS by a PRR-ERK-NOX4 mechanism. NEW & NOTEWORTHY This study characterizes a new transgenic mouse model with overexpression of the human (pro) renin receptor in neurons and demonstrated a novel angiotensin II-independent mechanism mediated by human prorenin and the (pro) renin receptor in the central regulation of blood pressure.

IF:4.05

Advanced oxidation protein products aggravate cardiac remodeling via cardiomyocyte apoptosis in chronic kidney disease

第一作者:Feng, WJ

期刊: AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, 2018; 314 (无)

Advanced oxidation protein products (AOPPs) are independent risk factor for various cardiovascular diseases. Cardiomyocyte apoptosis has been implicated as an important mechanism in cardiac remodeling in chronic kidney disease (CKD). However, whether AOPPs affect cardiomyocyte apoptosis and subsequent cardiac remodeling in CKD is still not very clear. Here, we assessed the role of AOPPs in cardiomyocyte apoptosis in CKD. H9C2 rat cardiomyoblast cells were exposed to AOPPs. Apoptotic cells were determined by TUNEL assay. The expression of apoptotic markers (cleaved caspase-3 and Bax), JNK signaling, and endoplasmic reticulum stress were explored. Serum AOPPs were measured in male Sprague-Dawley rats that underwent sham surgery and 5/6 nephrectomy, respectively. In vitro, our findings showed that AOPPs activated JNK signaling and endoplasmic reticulum stress and significantly aggravated H9C2 rat cardiomyoblast cells apoptosis. These effects were partially ameliorated by apocynin with inhibition of oxidative stress. In vivo, serum levels of AOPPs were progressively elevated with the increasing time course in CKD rats compared with sham-operated rats (P < 0.05). Serum AOPP levels were positively associated with cardiomyocyte apoptosis (R-2 = 0.76, P < 0.01). In conclusion, AOPPs aggravate cardiomyocyte apoptosis in vitro, and these effects are partially prevented by apocynin via suppressing JNK signaling and endoplasmic reticulum stress with oxidative stress inhibition. In vivo, AOPPs are increased in the CKD model and may contribute to the cardiac pathogenesis, but at this point it is unclear if that is true. These results suggest that pharmacological approaches to attenuate AOPP-aggravated cardiomyocyte apoptosis may be beneficial to improve cardiac remodeling in CKD. NEW & NOTEWORTHY Here, we present new evidence to show that advanced oxidation protein products aggravate cardiomyocyte apoptosis and subsequent cardiac remodeling via upregulations of JNK signaling and endoplasmic reticulum stress in chronic kidney disease. Such processes are mainly prevented by apocynin via oxidative stress inhibition.

IF:4.05

PPAR-alpha agonists acutely inhibit Ca2+-independent PLA(2) to reduce H2O2-induced contractions in aortae of spontaneously hypertensive rats

第一作者:Chen, H

期刊: AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, 2018; 314 (无)

Hypertension is associated with endothelial dysfunction, which favors the release of endothelium-derived contracting factors, including vasoconstrictor prostanoids and reactive oxygen species. Peroxisome proliferator-activated receptor-alpha (PPAR-alpha) agonists, clinically used as lipid-lowering drugs, possess antioxidant properties and exert beneficial effects in the vascular system. The present study aimed to identify the mechanism(s) underlying the acute effects of the PPAR-alpha agonists Wy14643 and fenofibate on endothelium-dependent contractions, in particular those related to oxidative stress, in the aorta of the spontaneously hypertensive rat (SHR). Aortic rings with and without endothelium of male SHRs and normotensive Wistar-Kyoto rats were suspended in organ chambers for isometric tension measurements and homogenized for enzyme activity assays. Contractions to acetylcholine in quiescent SHR aortae with endothelium were reduced by tiron (superoxide anion scavenger), diethyldithiocarbamic acid (superoxide dismutase inhibitor), and acute treatment with either Wy14643 or fenofibrate. Similarly to contractions evoked by acetylcholine, H2O2-induced increases in tension in SHR aortae involved, in succession, phospholipase A(2) (PLA(2)), cyclooxygenase, and thromboxane-prostanoid receptors. Wy14643 or fenofibrate, by decreasing the activity of endothelial Ca2+-independent PLA(2), attenuated the contractions to H2O2. In conclusion, the increased oxidative stress in the SHR aorta (mainly increased production of H2O2 and its partially reduced product, hydroxyl radical) contributed to acetylcholine-induced, endothelium-dependent contractions; PPAR-alpha agonists likely inhibit the H2O2-mediated contractions by inhibiting endothelial Ca2+-independent PLA(2). The present study highlights the prospective therapeutic effects of PPAR-alpha agonists in improving endothelial function in hypertension and other vascular implications due to oxidative stress. NEW & NOTEWORTHY Peroxisome proliferator-activated receptor-alpha agonists, which are used clinically as lipid-lowering drugs, acutely reduce H2O2-induced contractions in aortae of hypertensive rats by inhibiting the activity of endothelial Ca2+-independent phospholipase A(2). These vascular effects of peroxisome proliferator-activated receptor-alpha agonists suggest that they may help to prevent vascular complications under pathological conditions associated with oxidative stress.

IF:4.05

Dynamical mechanisms of phase-2 early afterdepolarizations in human ventricular myocytes: insights from bifurcation analyses of two mathematical models

第一作者:Kurata, Y

期刊: AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, 2017; 312 (无)

Early afterdepolarization (EAD) is known as a cause of ventricular arrhythmias in long QT syndromes. We theoretically investigated how the rapid (I-Kr) and slow (I-Ks) components of delayed-rectifier K (+) channel currents, L-type Ca2+ channel current (I-CaL), Na+ /Ca2+ exchanger current (I-NCX), Na+ -K+ pump current (I-NaK), intracellular Ca2+ (Ca-i) handling via sarcoplasmic reticulum (SR), and intracellular Na+ concentration (Na-i) contribute to initiation, termination, and modulation of phase-2 EADs, using two human ventricular myocyte models. Bifurcation structures of dynamical behaviors in model cells were explored by calculating equilibrium points, limit cycles (LCs), and bifurcation points as functions of parameters. EADs were reproduced by numerical simulations. The results are summarized as follows: 1) decreasing IKs and/or IKr or increasing ICaL led to EAD generation, to which mid-myocardial cell models were especially susceptible; the parameter regions of EADs overlapped the regions of stable LCs. 2) Two types of EADs (termination mechanisms), IKs activation-dependent and ICaL inactivation-dependent EADs, were detected; IKs was not necessarily required for EAD formation. 3) Inhibiting INCX suppressed EADs via facilitating Ca2+ -dependent ICaL inactivation. 4) Cai dynamics (SR Ca2+ handling) and Nai strongly affected bifurcations and EAD generation in model cells via modulating ICaL, INCX, and INaK. Parameter regions of EADs, often overlapping those of stable LCs, shifted depending on Cai and Nai in stationary and dynamic states. 5) Bradycardia-related induction of EADs was mainly due to decreases in Nai at lower pacing rates. This study demonstrates that bifurcation analysis allows us to understand the dynamical mechanisms of EAD formation more profoundly. NEW & NOTEWORTHY We investigated mechanisms of phase-2 early afterdepolarization (EAD) by bifurcation analyses of human ventricular myocyte (HVM) models. EAD formation in paced HVMs basically depended on bifurcation phenomena in non-paced HVMs, but was strongly affected by intracellular ion concentrations in stationary and dynamic states. EAD generation did not necessarily require I-Ks.

IF:3.57

Association of serum HMGB2 level with MACE at 1 mo of myocardial infarction: Aggravation of myocardial ischemic injury in rats by HMGB2 via ROS

第一作者:Liu, ZH

期刊: AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, 2017; 312 (无)

High-mobility group box (HMGB) family is related to inflammatory diseases. We investigated whether serum HMGB2 levels are related to myocardial infarction (MI) severity and major adverse cardiac events (MACE) during MI. We included 432 consecutive patients with ST-segment elevation myocardial infarction and 312 controls. Serum HMGB2 levels were significantly higher in MI patients than in controls. Increased HMGB2 levels were associated with MACE and negatively with ejection fraction in MI patients. HMGB2 was an independent determinant of MACE in logistic regression analysis. HMGB2 protein (10 mu g) or saline was injected intramyocardially in MI rats, with or without coadministration of the NADPH oxidase inhibitor apocynin. After 72 h, pathological, echocardiographic, and hemodynamic examinations showed that HMGB2 increased infarct size and worsened cardiac function in MI rats. Moreover, HMGB2 administration enhanced reactive oxygen species (ROS) production, cell apoptosis, inflammation, and autophagosome clearance impairment, which were attenuated by coadministration of apocynin or knock down of receptor for advanced glycation end products (RAGE). In conclusion, increased serum HMGB2 levels are associated with MI severity and MACE at 1 mo. HMGB2 promotes myocardial ischemic injury in rats and hypoxic H9C2 cell damage via ROS provoked by RAGE. NEW & NOTEWORTHY We demonstrate that serum high-mobility group box 2 is associated with major adverse cardiac events at 1 mo in myocardial infarction patients. Mechanistically, high-mobility group box 2 promotes reactive oxygen species production via receptor for advanced glycation end products signaling in ischemic myocardium, thereby aggravating cell apoptosis, inflammation, and autophagosome clearance impairment. This study reveals that high-mobility group box 2 is a novel factor enhancing ischemic injury in myocardial infarction.

IF:3.57

The interaction of estrogen and CSE/H2S pathway in the development of atherosclerosis

第一作者:Li, HZ

期刊: AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, 2017; 312 (无)

Both estrogen and hydrogen sulfide (H2S) have been shown to inhibit the development of atherosclerosis. We previously reported that cystathionine gamma-lyase knockout (CSE-KO) male mice develop atherosclerosis earlier than male wild-type (WT) mice. The present study investigated the interaction of CSE/H2S pathway and estrogen on the development of atherosclerosis in female mice. Plasma estrogen levels were significantly lower in female CSE-KO mice than in female WT mice. NaHS treatment had no effect on plasma estrogen levels in both WT and CSE-KO female mice. After CSE-KO and WT female mice were fed with atherogenic diet for 12 wk, plasma lipid levels were significantly increased and triglyceride levels decreased compared with those of control diet-fed mice. Atherogenic diet induced more atherosclerotic lesion, oxidative stress, intracellular adhesion molecule-1 (ICAM-1), and NF-kappa B in CSE-KO mice than in WT mice. Estrogen treatment of atherogenic diet-fed WT mice attenuated hypercholesterolemia, oxidative stress, ICAM-1 expression, and NF-kappa B in WT mice but not in atherogenic diet-fed CSE-KO mice. Furthermore, H2S production in both the liver and vascular tissues was enhanced by estrogen in WT mice but not in CSE-KO mice. It is concluded that the antiatherosclerotic effect of estrogen is mediated by CSE-generated H2S. This study provides new insights into the interaction of H2S and estrogen signaling pathways on the regulation of cardiovascular functions. NEW & NOTEWORTHY Female cystathionine gamma-lyase (CSE)-knockout mice have significantly lower plasma estrogen levels and more severe early atherosclerotic lesion than female wild-type mice. H2S production in liver and vascular tissues is enhanced by estrogen via its stimulatory effect on CSE activity. The antiatherosclerotic effect of estrogen is mediated by CSE-generated H2S.

IF:3.57

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