Inotropic response of the rat heart during development and regression of triiodothyronine-induced hypertrophy

The inotropic response of rat hearts in vivo was tested by infusion of 2 mmol/kg/h calcium chloride after 14 days of daily 3,3',5-triiodo-L-thyronine (T3) treatment and 14 days following discontinuation of T3 treatment. The hyperthyroid state was characterized by marked cardiac hypertrophy (57% increase in the heart weight/body weight ratio) which was more pronounced in the right ventricle (63% increase). Heart rate and cardiac output index were elevated by 56 and 63%, respectively, and total peripheral resistance was reduced by 40%. Left ventricular systolic pressure (LVSP) was elevated by 15%, the maximal rate of rise in left ventricular pressure (LV dp/dtmax) by 106%, and LV pressure-volume performance by 192%. Right ventricular systolic pressure (RVSP) was elevated by 71%, RV dp/dtmax by 126%, and RV pressure-volume performance by 371%. Intravenous infusion of calcium induced an elevation in heart rate and LV dp/dtmax, the increase of the latter was less pronounced than in the control heart. After 14 days subsequent to discontinuation of T3 treatment, there was a regression of cardiac hypertrophy. However, the LV was still hypertrophied by 12% and the RV by 24%. Heart rate and contractility were normal. The pressure-volume performance of both LV and RV was still enhanced by 24 and 18%, respectively. The inotropic response of the LV to calcium infusion was similar to that of the normal heart. Thus, 14 days after discontinuation of T3 treatment, the regression of cardiac hypertrophy was not complete, although heart rate and contractility as well as the inotropic response to calcium, were normal. The remaining cardiac hypertrophy correlated with the still existing elevation in the pressure-volume performance.     

Inhibition of c-Src protects paraquat induced microvascular endothelial injury by modulating caveolin-1 phosphorylation and caveolae mediated transcellular permeability

The mechanisms underlying paraquat induced acute lung injury (ALI) is still not clear. C-Src plays an important role in the regulation of microvascular endothelial barrier function and the pathogenesis of ALI. In the present study, we found that paraquat induced cell toxicity and an increase of reactive oxygen species (ROS) in endothelium. Paraquat exposure also induced significant increase of caveolin-1 phosphorylation, caveolae trafficking and albumin permeability in endothelial monolayers. C-Src depletion by siRNA significantly attenuate paraquat induced cell toxicity, caveolin-1 phosphorylation, caveolae formation and endothelial hyperpermeability. N-acetylcysteine (NAC) failed to protect endothelial monolayers against paraquat induced toxicity. Thus, our findings suggest that paraquat exposure increases paracellular endothelial permeability by increasing caveolin-1 phosphorylation in a c-Src dependant manner. The depletion of c-Src might protect microvascular endothelial function by regulating caveolin-1 phosphorylation and caveolae trafficking during paraquat exposure, and might have potential therapeutic effects on paraquat induced ALI.     

辛伐他汀对内皮素-1诱导氧活性物质介导心肌细胞肥大的抑制作用

目的　探讨辛伐他汀对内皮素 1 (endothelin 1 ,ET 1 )诱导的氧活性物质 (reactiveoxygenspecies,ROS)产生和心肌细胞肥大的抑制作用。方法　用原代培养的新生大鼠心肌细胞进行实验。细胞内荧光信号用荧光倒置显微镜检测。细胞内ROS水平用ROS敏感的荧光探针 2 ,7 dichlorofluo rescindictate(DCF DA)来反应 ,细胞内RNA含量用RNA敏感的荧光探针碘化丙啶 (propidiumiodide ,PI)来测定。用考马斯亮蓝法测定细胞内总蛋白含量。用图像分析软件 (Leica图像分析软件 )测细胞表面积。结果　①ET 1浓度依赖性地使心肌细胞内DCF DA的荧光信号增加和心肌细胞肥大。过氧化氢酶 (catalase ,CAT ,0 2U·L- 1 )抑制ET 1 (1× 1 0 - 8mol·L- 1 )诱导的心肌细胞内DCF DA的荧光信号的增加和心肌细胞肥大。②辛伐他汀对ET 1诱导的心肌细胞内DCF DA的荧光信号增强和心肌细胞肥大产生剂量依赖性的抑制作用。结论　ET 1能够使心肌细胞产生ROS和ROS依赖的心肌细胞肥大 ,辛伐他汀能抑制ET 1诱导的ROS依赖的心肌细胞肥大。     

The adenine nucleotide translocator: regulation and function during myocardial development and hypertrophy

1. The present review focuses on the adenine nucleotide translocator (ANT), which facilitates exchange of cytosolic ADP for mitochondrial ATP. This protein serves a central role in regulating cellular oxidative capacity. 2. The ANT, a nuclear-encoded mitochondrial protein, is developmentally regulated and, thus, accumulates within the mitochondrial membrane during maturation. 3. Accumulation of ANT parallels changes in kinetics of myocardial respiration determined from 31P magnetic resonance spectroscopy studies. 4. Thyroid hormone modulates developmental transitions in ANT content, as well as respiratory control patterns. These transitions are linked to quantitative ANT changes, not to alterations in functionality at individual exchanger sites. 5. Developmental programming for ANT and parallel alterations in oxidative phosphorylation kinetics are relevant to the heart, which exhibits remodelling in response to pathological processes. Maladaptive hearts exhibiting ANT deficits demonstrate ADP-dependent respiratory kinetics similar to the newborn heart. Thus, ANT deficits and alterations in mitochondrial respiratory function may contribute to the pathogenesis of myocardial remodelling and heart failure.     

Assessment of sarcoplasmic reticulum Ca2+-uptake during the development of left ventricular hypertrophy

Cardiac sarcoplasmic reticulum (SR) sequesters Ca(2+) and plays a crucial role in the regulation of intracellular Ca(2+). Its functional properties are central to the excitation-contraction cycle of cardiac muscle. In this study, we hypothesized that alterations in SR function occur during the development of left ventricular (LV) hypertrophy. LV hypertrophy was produced in Lewis rats by the one-kidney, one-clip (1K1C) procedure. LV tissues were obtained from 1K1C rats 1 week (mild, N=7), 4 weeks (moderate, N=7), and 8 weeks (severe, N=7) post-surgery and from the corresponding age-matched, sham-operated controls (N=7 at each stage). In all of these rats, the ratio of LV weight (g) to body weight (kg) was determined and considered as an index for LV hypertrophy. In addition, the ratio of lung weight (g) to body weight (kg) was determined and considered as an index for pulmonary congestion and heart failure. In each LV specimen, SR Ca(2+)-uptake and tissue Ca(2+)-ATPase (CAA) level were determined. In 1K1C rats, LV hypertrophy increased by 21, 40, and 90% at 1, 4, and 8 weeks post-surgery, respectively, compared to the age-matched, sham-operated rats, whereas pulmonary congestion did not occur at 1 and 4 weeks but increased significantly by about 21% at 8 weeks. Further, both SR Ca(2+)-uptake and immunodetectable CAA level did not change at 1 week, increased (54%) to the same extent at 4 weeks, and decreased (42%) by approximately the same extent at 8 weeks in 1K1C rats compared to the age-matched, sham-operated rats. In summary, as LV hypertrophy evolved, Ca(2+)-uptake and CAA expression did not change in the early, increased in the moderate, and then declined in the later stages of hypertrophy development. The increase in Ca(2+)-uptake and CAA expression suggests, at the cellular level, a compensatory response to LV hypertrophy, while the decline at later stages indicates the transition to heart failure.     

Modulation of adrenergic receptors during left ventricular hypertrophy development and after regression by captopril.

The objective of this study was to analyze adrenergic receptors during cardiac hypertrophy development, after establishment of cardiac hypertrophy and after regression of cardiac hypertrophy by an angiotensin-converting enzyme inhibitor. Left ventricular hypertrophy (LVH) was induced by abdominal aortic stenosis. After surgery, plasma norepinephrine concentrations (PNE) and left ventricular adrenergic receptors from rat hearts subjected to aortic stenosis were assessed during cardiac hypertrophy development (at 3, 7, 15, and 30 days of aortic stenosis), once cardiac hypertrophy had been established (7 and 14 weeks after the stenosis) and after regression of cardiac hypertrophy by an antihypertensive dose (200 mg/kg/day) of captopril. The presence of LVH was observed from day 7 after stenosis. PNE had significantly increased after 15 days but returned to control values 30 days after surgery. The density of alpha1-adrenoceptors was found to decrease with development of hypertrophy. Once hypertrophy had been established, 7 weeks from stenosis, PNE was not different from control; however, the density of alpha1-adrenoceptors continued to diminish, whereas PNE and the density of beta-adrenoceptors were no different from control values. Fourteen weeks after stenosis, a significant decrease in PNE was recorded, and no change in alpha1- but an increase in beta-adrenoceptors was observed. LVH was reversed by treatment with captopril; PNE was similar in control and stenosed treated animals. The density of alpha1-adrenoceptors was decreased when compared with control animals, and no change in the density of beta-adrenoceptors was observed with treatment. In conclusion, a decrease of alpha1-adrenoceptors was associated with LVH development and earlier stages of established cardiac hypertrophy. Later stages of established cardiac hypertrophy were characterized by no change in alpha1- and an increase in beta-adrenoceptors. Treatment with captopril induced LVH regression and decreased the number of alpha1-adrenoceptors without any change in beta-adrenoceptors.     

缺血/再灌注过程中心肌细胞自噬研究进展

自噬是一种广泛存在于真核细胞中的生命现象,心肌细胞营养缺乏、缺血/再灌注损伤、心衰等均可诱发细胞自噬。缺血/再灌注过程中的心肌细胞自噬可以维持心肌细胞稳态、减少细胞缺失,但是自噬作用也可导致心肌细胞死亡。     

Increase in caveolae and caveolin-1 expression modulates agonist-induced contraction and store- and receptor-operated Ca2 + entry in pulmonary arteries of pulmonary hypertensive rats

Caveolin-1 (Cav-1) is a major component protein associated with caveolae in the plasma membrane and has been identified as a regulator of store-operated Ca^2 + entry (SOCE) and receptor-operated Ca^2 + entry (ROCE). However, the contributions of caveolae/Cav-1 of pulmonary arterial smooth muscle cells (PASMCs) to the altered Ca^2 + signaling pathways in pulmonary arteries (PAs) during pulmonary hypertension (PH) have not been fully characterized. The present study quantified caveolae number and Cav-1 expression, and determined the effects of caveolae disruption on ET-1, cyclopiazonic acid (CPA) and 1-Oleoyl-2-acetyl-glycerol (OAG)-induced contraction in PAs and Ca^2 + influx in PASMCs of chronic hypoxia (CH)- and monocrotaline (MCT)-induced PH rats. We found that the number of caveolae, and the Cav-1 mRNA and protein levels were increased significantly in PASMCs in both PH models. Disruption of caveolae by cholesterol depletion with methyl-β-cyclodextrin (MβCD) significantly inhibited the contractile response to ET-1, CPA and OAG in PAs of control rats. ET-1, SOCE and ROCE-mediated contractile responses were enhanced, and their susceptibility to MβCD suppression was potentiated in the two PH models. MβCD-induced inhibition was reversed by cholesterol repletion. Introduction of Cav-1 scaffolding domain peptide to mimic Cav-1 upregulation caused significant increase in CPA- and OAG-induced Ca^2 + entry in PASMCs of control, CH and MCT-treated groups. Our results suggest that the increase in caveolae and Cav-1 expression in PH contributes to the enhanced agonist-induced contraction of PA via modulation of SOCE and ROCE; and targeting caveolae/Cav-1 in PASMCs may provide a novel therapeutic strategy for the treatment of PH.     

Caveolin-1在载脂蛋白E基因敲除小鼠动脉粥样硬化形成中的变化

目的：探讨caveolin-1在apoE基因敲除小鼠动脉粥样硬化形成过程中的变化。方法：取正常和apoE基因敲除小鼠(品系均为C57BL／6J)作为研究对象，分别观察不同周龄apoE基因敲除小鼠血清甘油三酯、总胆固醇、低密度脂蛋白、高密度脂蛋白的含量及主动脉横断面积、斑块面积的变化。免疫组织化学染色法对caveolin-1进行半定量及定位分析，Western-blotting检测caveolin-1在主动脉的表达。结果：apoE基因敲除小鼠的血清甘油三酯、总胆固醇、低密度脂蛋白水平与对照组比较显著升高，并随小鼠周龄增加而升高；斑块面积及斑块面积与主动脉面积的比值也随小鼠周龄增加而增大。免疫组织化学染色法显示，caveolin-1在实验组血管内膜表达呈阳性减弱，其程度随周龄增加有减少趋势。免疫印迹检测显示实验组caveolin-1的表达与对照组比较有所减弱，并与小鼠周龄呈负相关。结论：apoE基因敲除小鼠主动脉内皮细胞caveolin-1表达下调，可能与其动脉粥样硬化形成有关。     

Qiliqiangxin inhibits the development of cardiac hypertrophy, remodeling, and dysfunction during 4 weeks of pressure overload in mice

Qiliqiangxin (QL), a traditional Chinese medicine, has been used in the treatment of chronic heart failure. However, whether QL can benefit cardiac remodeling in the hypertensive state is unknown. We here examined the effects of QL on the development of cardiac hypertrophy through comparing those of losartan in C57BL/6 mice underlying transverse aorta constriction for 4 weeks. QL and losartan were administrated at 0.6 mg and 13.4 mg·kg·d, respectively. Cardiac hypertrophy, function, and remodeling were evaluated by echocardiography, catheterization, histology, and examination of specific gene expression and ERK phosphorylation. Cardiac apoptosis, autophagy, tumor necrosis factor α/insulin-like growth factor-1, and angiotensin II type 1 receptor expression and especially the proliferation of cardiomyocytes and phosphorylation of ErbB receptors were examined in vivo to elucidate the mechanisms. Transverse aorta constriction for 2 weeks resulted in a significant cardiac hypertrophy, which was significantly suppressed by either QL or losartan treatment. At 4 weeks after transverse aorta constriction, although the development of cardiac dysfunction and remodeling and the increases in apoptosis, autophagy, tumor necrosis factor α/insulin-like growth factor-1, and angiotensin II type 1 receptor expression were abrogated comparably between QL and losartan treatments, QL, but not losartan, enhanced proliferation of cardiomyocytes, which was paralleled with dowregulation of CCAAT/enhancer-binding protein β, upregulation of CBP/p300-interacting transactivator with ED-rich carboxy-terminal domain 4, and increases in ErbB2 and ErbB4 phosphorylation. Furthermore, inhibition of either ErbB2 or CBP/p300-interacting transactivator with ED-rich carboxy-terminal domain 4 abolished the cardiac protective effects of QL. Thus, QL inhibits myocardial inflammation and cardiomyocyte death and promotes cardiomyocyte proliferation, leading to an ameliorated cardiac remodeling and function in a mouse model of pressure overload. The possible mechanisms may involve inhibition of angiotensin II type 1 receptor and activation of ErbB receptors.     

Cell biology of caveolae and caveolin

Originally described in the 1950s caveolae are morphologically identifiable as small omega-shaped plasma membrane invaginations present in most cell types. Caveolae are particularly abundant in adipocytes, fibroblasts, type 1 pneumocytes, endothelial and epithelial cells as well as in smooth and striated muscle cells. The first proposed function for caveolae was that of mediating the internalisation and transendothelial trafficking of solutes. Caveolae have been the object of intense research since the discovery of a biochemical marker protein, caveolin, in the early 1990s. Three genes encoding for caveolins have been characterised in mammals. Caveolins (18-24 kDa) are integral membrane proteins that constitute the major protein component of caveolar membrane in vivo. In addition to a structural role of caveolins in the formation of caveolae, caveolin protein interacts directly, and in a regulated manner, with a number of signalling molecules. We present here a general overview of the current knowledge on the structural role of caveolin in caveolae formation, and implication of caveolin in the control of cell signalling.     

Roles of TRP channels in the development of cardiac hypertrophy

Cardiac hypertrophy is induced by various stresses such as hypertension and myocardial infarction. It is believed that hypertrophy is adaptive in the early phase but becomes maladaptive in the late phase. Cardiac hypertrophy develops heart failure when the heart is exposed persistently to the stresses. The increase in intracellular Ca(2+) ([Ca(2+)](i)) plays an important role in the development of hypertrophy. It is generally thought that the increase in [Ca(2+)](i) for hypertrophy occurs via G(q)-stimulated production of inositol-1,4,5-trisphosphate (IP(3)) and IP(3)-mediated release of Ca(2+) from intracellular store. However, several groups recently reported that canonical transient receptor potential (TRPC) channels are responsible for the increase in [Ca(2+)](i). Among them, three TRPC subtypes (TRPC3/TRPC6/TRPC7) are activated by another G(q)-mediated second messenger, diacylglycerol. Although several groups independently demonstrated that TRPC channels mediate receptor-stimulated and pressure overload-induced hypertrophy, there is discrepancy of which subtypes of TRPC channels predominantly mediate hypertrophy. However, there is consensus that TRPC-mediated Ca(2+) influx is essential for hypertrophy. As TRPC channels participate in pathological hypertrophy, but not physiological contraction and the relaxation cycle, TPRC channels are a new target for the treatment of hypertrophy.     

Ethanol-induced cardiac hypertrophy: correlation between development and the excretion of adrenal catecholamines

The progression of cardiac hypertrophy and the effects on adrenal medullary catecholamine content and release were determined in rats given ethanol, in conjunction with a supplementary diet, by gavage, every eight hours for periods up to 96 hours. Ethanol caused a marked depletion of adrenal medullary adrenaline content which fell to about 25 percent of control after the full time course. During this time, there were two- to fourfold increases in urinary noradrenaline content and five- to tenfold increases in urinary adrenaline. Cardiac hypertrophy, with increases in protein content and tissue weight of both ventricles, was evident at 24 hours of intoxication. By 96 hours of treatment these markers had increased more than 20% over control values. Proportional heart weight increases per day correlated significantly with daily urinary catecholamine excretion, providing support for the hypothesis that ethanol induced cardiac hypertrophy in the rat results from catecholaminergic stimulation, primarily of adrenal medullary origin.     

Ranolazine inhibits an oxidative stress-induced increase in myocyte sodium and calcium loading during simulated-demand ischemia

Ranolazine inhibits the late Na current and is proposed to reduce angina by decreasing [Na]i during ischemia, thereby reducing Ca influx via Na/Ca exchange (NCX). We sought to test this hypothesis and to determine whether oxidative stress during simulated-demand ischemia activates the late Na current. We measured [Ca]i and [Na]i in rabbit ventricular myocytes by flow cytometry during metabolic inhibition (MI) with 2 mM cyanide and 0 mM glucose at 37 degrees C plus pacing (P) at 0.5 Hz (P-MI), and in P-MI + 1, 10, or 50 microM ranolazine. In the clinically relevant concentration range (1-10 microM), ranolazine decreased Na and Ca loading and the development of myocyte contracture. P-MI caused an increase in fluorescence of the oxidative radical probe CM-H2DCFDA, which was inhibited by the radical scavenger Tiron 20 mM. The NCX inhibitor KB-R7943 (10 microM) and Tiron 20 mM reduced the rise in [Ca]i during P-MI and eliminated the effect of 10 microM ranolazine on [Ca]i. These results indicate that oxidative stress increases the late Na current during MI. Inhibition of the resulting increase in Na and Ca loading and contracture seems to account for the observed antiischemia effects of ranolazine.     

Toxicity of 3′3-ditrifluormethyldiphenyl diselenide administered during intra-uterine development of rats

The aim of this study was to assess the effects of the organoselenium compound, 3′3-ditrifluormethyldiphenyl diselenide [(F₃CPhSe)₂], during the intra-uterine development of Wistar rats. Dams were given repeated doses of 1, 5 or 10 mg/kg (F₃CPhSe)₂ by intragastric route on gestation days 6–15, and cesarean sections were performed on day 20 of pregnancy. The numbers of implantation sites, living and dead fetuses and resorptions were recorded. Fetuses were weighed and stained with Alizarin red S for skeletal evaluation. The placental morphology was also evaluated. In 1 mg/kg (F₃CPhSe)₂ group, neither maternal toxicity nor prenatal growth retardation was observed. Conversely, in 5 and 10 mg/kg groups, there was a decrease in maternal weight gain during pregnancy indicating that (F₃CPhSe)₂ was maternally toxic, without affecting fetuses weight and length. (F₃CPhSe)₂ caused some morphological alterations in placenta of 5 and 10 mg/kg-exposed dams. Results also showed that skeletal variations were produced by (F₃CPhSe)₂ only at doses (10 mg/kg) in which a marked embryolethality was found. We conclude that (F₃CPhSe)₂ was toxic to the dams and induced embryofeto-toxicity at doses equal to 10 mg/kg.     

Phosphoinositide-3 kinase signaling in cardiac hypertrophy and heart failure

Heart failure, a major symptom in the progression of cardiac hypertrophy, is a critical risk factor for cardiac death. A large body of research has investigated cardioprotective mechanisms that prevent or minimize hypertrophy, identifying a variety of specific peptide hormones, growth factors, and cytokines with cardioprotective properties. Recent investigation of the downstream effector pathways for these growth factors has identified molecules involved in the progression of cardiac hypertrophy and heart failure, including phosphoinositide 3-kinase (PI3K), Akt and mammalian target of rapamycin (mTOR). Using genetically modified transgenic or knockout mice and adenoviral targeting to manipulate expression or function in experimental models of heart failure, several investigators have demonstrated that the PI3K-Akt pathway regulates cardiomyocyte size, survival, angiogenesis, and inflammation in both physiological and pathological cardiac hypertrophy. In this review, we discuss the reciprocal regulation of PI3K, Akt and mTOR in cardiomyocytes and their association with cardiac disease.