Effects of intravenous ABT-870 (iron (III)-hydroxide oligosaccharide) on mean arterial pressure and heart rate in the anaesthetized beagle: comparison with other iron-containing haematinic agents

Iron-deficiency anaemia, a complication of end-stage renal disease (ESRD), is often treated with parenteral iron therapies that have been shown to produce dose-limiting hypotension in patients. ABT-870 (iron-(III)-hydroxide-oligosaccharide) is comprised of elemental iron complexed with oligosaccharide, a composition that we hypothesised would allow the hypotensive effects of parenteral iron therapy to be overcome, thus allowing a rapid rate of infusion to be well tolerated. Mean arterial pressure (MAP) and heart rate (HR) were monitored in anaesthetized dogs following the infusion of ABT-870 and iron sucrose administered at doses of 7.1 and 21.3 mg/kg using a rapid 30 s infusion. ABT-870 and iron sucrose were also monitored at doses of 7.1, 21.3 and 50 mg/kg administered over a 10 min period. Sodium ferric gluconate complex (SFGC) was administered in an identical fashion at doses of 12.5 and 31.2 mg/kg. A 30 s rapid infusion of ABT-870 at doses of 7.1 and 14.3 mg/kg or a 10 min infusion of ABT-870 at doses of 7.1 and 21.3 mg/kg produced little effect on MAP and HR. Infusion of the highest dose of ABT-870 (50 mg/kg) produced no consistent hypotension, but did produce an increase in HR (maximal increase 35 +/- 9 b.p.m.), an effect that lasted only 15 min. A 30 s rapid infusion of iron sucrose at 7.1 mg/kg produced modest increases in MAP and HR (5 +/- 1 mmHg and 5 +/- 2 b.p.m., respectively). However, rapid infusion of iron sucrose at 14.3 mg/kg produced hypotension (to -8 +/- 1 mmHg below baseline) and exerted variable, biphasic effects on HR ranging from -16 to +50 b.p.m. Although 10 min infusion of iron sucrose at 7.1 mg/kg exerted little effect on MAP and HR, at doses of 21.3 and 50 mg/kg iron sucrose elicited a profound dose-dependent decrease in MAP (-34 +/- 11 and -83 +/- 5 mmHg, respectively) and a pronounced increase in HR ranging from 32 to 49 b.p.m. above baseline. A 10 min infusion of SFGC at doses of 12.5 and 31.2 mg/kg produced a dose-dependent decrease in MAP (-28 +/- 18 and -67 +/- 12 mmHg below baseline) and a marked increase in HR (26 +/- 11 and 94 +/- 15 b.p.m. above baseline). In conclusion, unlike iron sucrose and SFGC, high doses of ABT-870 failed to exert consistent hypotensive effects. These data demonstrate that ABT-870 may have a substantial therapeutic window and considerable clinical potential for iron-replacement therapy.     

Endothelin ETA receptor antagonism does not attenuate angiotensin II-induced cardiac hypertrophy in vivo in rats

1. Angiotensin (Ang) II causes cardiac hypertrophy in vitro and in vivo. It also stimulates the release of endothelin (ET)-1. Endothelin-1 induces hypertrophy of cardiomyocytes in vitro. 2. In the present study, we examined whether the cardiac hypertrophic action of AngII in vivo was mediated by ET-1 via ETA receptors. We also determined whether arginine vasopressin (AVP), another ET-1 stimulator, could cause cardiac hypertrophy in vivo through an ET-1-dependent pathway. 3. In Sprague-Dawley rats (n = 8 per group), we determined whether the orally administered ETA receptor antagonist BMS 193884 could attenuate the cardiac hypertrophic effect of: (i) i.v. AngII infusion at either 100 or 200 ng/kg per min, i.v., for 1 week; (ii) AngII infusion at 100 ng/kg per min, i.v., for 2 weeks; and (iii) AVP infusion at either 2 or 10 ng/kg per min, i.v., for 1 week. Mean arterial pressure and heart rate were also measured. 4. Infusion with AngII for both 1 and 2 weeks increased left ventricular weight. Only AngII infusion at 200 ng/kg per min for 1 week increased blood pressure. Endothelin ETA receptor blockade did not attenuate the left ventricular hypertrophy, even though it reduced the hypertensive effect of AngII. Arginine vasopressin increased blood pressure, but did not cause cardiac hypertrophy. 5. We showed that AngII can cause cardiac hypertrophy through a direct, blood pressure-independent effect on the heart. Endothelin-1 did not mediate the cardiac hypertrophic effect of AngII through ETA receptors. This may indicate the involvement of ETB receptors in this model of cardiac hypertrophy. Arginine vasopressin did not cause cardiac hypertrophy in vivo.     

亚降压剂量雷米普利预防高血压心肌肥厚的机制

目的　探讨亚降压剂量雷米普利的抗氧化作用对其抗高血压心肌肥厚作用的影响。方法　采用腹主动脉缩窄法制备大鼠高血压心肌肥厚模型。观察一氧化氮合酶抑制剂Ｎ Ｌ 精氨酸（６ｍｇ·ｋｇ－１·ｄ－１）和ＶｉｔＥ（２００Ｕ·ｄ－１）对雷米普利（１００μｇ·ｋｇ－１·ｄ－１）抗心肌肥厚的影响,以及心肌超氧化物歧化酶（ＳＯＤ）、一氧化氮代谢物（ＮＯ２－）等指标的变化。结果　给予雷米普利后８ｗｋ,与对照组比较心肌肥厚减轻而血压无明显降低,ＮＯ２－含量和ＳＯＤ活性明显提高,脂质过氧化物减少。ＶｉｔＥ能增强上述大部分作用,而Ｎ Ｌ 精氨酸能逆转此增强作用。结论　亚降压剂量雷米普利有抗心肌肥厚的作用,ＶｉｔＥ对此有增强作用,其机制与增强心肌抗氧化能力有关。     

Effect of sodium houttuyfonate on myocardial hypertrophy in mice and rats

Objectives The aim of the study was to determine the effect of sodium houttuyfonate on myocardial hypertrophy and its mechanism of action in mice and rats. Methods A mouse model of myocardial hypertrophy was established by subcutaneous injection with isoproterenol. Mice were randomly divided into five groups: normal control; isoproterenol control; isoproterenol plus metoprolol; isoproterenol plus low‐ and high‐dose sodium houttuyfonate. A rat model of myocardial hypertrophy was established by intraperitoneal injection with l ‐thyroxine. Rats were randomly divided into five groups: normal control; l ‐thyroxine control; l ‐thyroxine plus captopril; l ‐thyroxine plus low‐ and high‐dose sodium houttuyfonate. At the end of the experiments, the left ventricular weight index and heart weight index were determined in mice and rats, the size of cardiomyocytes was measured in rats and the concentrations of cAMP in plasma and angiotensin II in ventricular tissue of mice were detected by radioimmunoassay. The endothelin‐1 concentration was measured by radioimmunoassay and the hydroxyproline content was measured by a digestive method in ventricular tissue of rats. Key findings After 7–9 days of treatment, sodium houttuyfonate significantly reduced the left ventricular weight index and heart weight index in mice and rats with myocardial hypertrophy, decreased the size of cardiomyocytes in rats, and reduced the content of cAMP and angiotensin II in mice with myocardial hypertrophy. It also decreased the endothelin‐1 concentration and the hydroxyproline content in ventricular tissue in rats. Conclusions Sodium houttuyfonate can inhibit myocardial hypertrophy in mouse and rat models by restricting the activity of the sympathetic nervous system and decreasing the levels of angiotensin II and endothelin‐1 in ventricular tissue.     

A distinct AMP‐activated protein kinase phosphorylation site characterizes cardiac hypertrophy induced by l‐thyroxine and angiotensin II

1. The purpose of the present study was to evaluate differences in the AMP‐activated protein kinase (AMPK) phosphorylation sites in cardiac hypertrophy induced by l ‐thyroxine and angiotensin (Ang) II. 2. Cardiac hypertrophy was induced in wild‐type and AMPKα2‐knockout mice by treatment with 1 mg/kg, i.p., thyroxine or 1.44 mg/kg per day AngII for 14 days. The phenotype of the hypertrophy was evaluated using echocardiographic measurments and histological analyses. The phosphorylation of AMPK at α‐Ser^485/491 and α‐Thr¹⁷² was determined by western blot analysis. 3. In wild‐type mice, the phosphorylation of AMPKα‐Ser^485/491 was significantly elevated in the AngII‐treated group, but not in the thyroxine‐reated group, compared with the vehicle control group. In contrast, the phosphorylation of AMPKα‐Thr¹⁷² was significantly increased by thyroxine, but not AngII, treatment compared with the vehicle control group. Furthermore, knockout of the AMPKα2 subunit abolished phosphorylation at the α‐Ser^485/491 site and significantly suppressed phosphorylation at the α‐Thr¹⁷² site, resulting in alleviation of thyroxine‐ but not AngII‐induced hypertrophy. 4. In conclusion, l ‐thyroxine and AngII induce the phosphorylation of distinct sites of AMPK in cardiac hypertrophy. Phosphorylation of AMPK α‐Thr¹⁷² may contribute to thyroxine‐induced cardiac hypertrophy.     

水杉总黄酮抗实验性心肌肥厚作用的研究

目的　研究水杉总黄酮对实验性心肌肥厚的作用及其机制。方法　采用腹腔动 静脉造瘘建立大鼠容量超负荷心肌肥厚模型 ,水杉总黄酮灌胃给药 ,持续 5wk后 ,测定心室肌细胞内Ca2 +浓度、血浆和心肌AngⅡ、心肌MDA及SOD。结果　水杉总黄酮剂量依赖性地减轻大鼠心脏重量 ,抑制心室RNA和蛋白质合成 ,降低心室肌细胞内Ca2 +浓度和心室AngⅡ、MDA含量 ,增加SOD活性。 结论　水杉总黄酮可预防容量超负荷大鼠心肌肥厚的形成 ,其机制可能与拮抗心脏局部RAS ,减轻Ca2 +超负荷以及抗氧化作用有关     

牛磺酸对大鼠心肌成纤维细胞增殖的影响

观察牛磺酸(taurine，Tau)在血管紧张素II(angiotensin II，Ang II)诱导新生大鼠心肌成纤维细胞(cardiac fibroblast，CFb)增殖过程中对一氧化氮(nitric oxide，NO)及蛋白激酶C alpha(p-PKCα)的影响，以探讨牛磺酸抑制CFb增殖的信号转导途径。胰酶消化法分离培养新生大鼠CFb，用Ang II诱导促进其增殖，采用MTT法检测细胞增殖；ELISA法测定I型胶原、 III型胶原的含量；流式细胞仪检测细胞周期；硝酸还原酶法检测细胞上清液NO含量；Western blotting法检测p-PKCα含量。牛磺酸(40、 80和160 mmol·L^-1)可抑制Ang II诱导的CFb增殖及I型胶原、III型胶原合成增加(P<0.05，P<0.01)，并使细胞G₀/G₁期百分率增加，S期细胞百分率降低(P<0.05，P<0.01)。牛磺酸明显抑制p-PKCα的蛋白表达， 提高CFb NO含量， 与Ang II组比较差别具有明显统计学意义(P<0.05， P<0.01)。牛磺酸通过降低p-PKCα的表达而提高CFb NO的含量，使CFb的增殖和胶原合成受到抑制。     

Celecoxib,but not rofecoxib or naproxen,attenuates cardiac hypertrophy and fibrosis induced in vitro by angiotensin and aldosterone

1. Cyclo‐oxygenase (COX)‐2 inhibitors and other non‐steroidal anti‐inflammatory drugs (NSAIDs) have been implicated in increased cardiovascular events. However, the direct effects of these drugs on cardiac function have not been explored extensively. Given the important role of the renin–angiotensin–aldosterone system (RAAS) in cardiac remodelling, we sought to determine the effect of COX‐2 inhibitors and non‐specific (NS‐) NSAIDs on RAAS‐induced cardiac hypertrophy and fibrosis in neonatal rat cardiac myocytes (NCM) and fibroblasts (NCF) isolated from 1–2‐day‐old Sprague‐Dawley rat pups. 2. The NCM were pretreated for 2 h with COX‐2 inhibitors (celecoxib or rofecoxib) or NS‐NSAIDs (naproxen; all at 0.1–10 μmol/L) before being stimulated with 10 μmol/L aldosterone for 72 h or with 0.1 μmol/L angiotensin (Ang) II for 60 h. Hypertrophy of NCM was assessed by [³H]‐leucine incorporation. 3. The NCF were pretreated with COX‐2 inhibitors or naproxen as described for NCM before being stimulated with 0.1 μmol/L AngII for 48 h. Collagen synthesis was subsequently assayed by [³H]‐proline incorporation. 4. Pooled cryopreserved male and female rat hepatocytes were treated with or without COX‐2 inhibitors for 1 h before 1 nmol/L aldosterone (～540 pg/mL) was added to all wells. Cells were incubated for a further 60 min and culture media harvested by centrifugation. Human hepatic HepG2 cells were treated with compounds with or without serum starvation for 48 h. All cells were pretreated with COX‐2 inhibitors for 2 h before the addition of aldosterone. Cell culture media were harvested after a further 3, 18, 24 or 48 h incubation. Aldosterone concentrations in the culture media were determined by enzyme immunoassay. 5. Aldosterone‐ and AngII‐stimulated NCM hypertrophy was inhibited by celecoxib, but not by rofecoxib or naproxen. In NCF, AngII‐stimulated collagen synthesis was inhibited by celecoxib and, to a lesser extent, by rofecoxib, whereas naproxen had no effect. The COX‐2 inhibitors inhibited aldosterone uptake and/or metabolism by rat hepatocytes, but had no effect in human hepatic HepG2 cells. 6. These results demonstrate a potential antiremodelling effect of selective COX‐2 inhibitors in the setting of RAAS stimulation in cardiac cells, whereas naproxen has no effect.     

Angiotensin II type 1 receptor blockade attenuates gefitinib-induced cardiac hypertrophy via adjusting angiotensin II-mediated oxidative stress and JNK/P38 MAPK pathway in a rat model

Gefitinib is a tyrosine kinase inhibitor (TKI) of the epidermal growth factor receptor (EGFR), used for the treatment of advanced or metastatic non-small cell lung cancer. Recently, studies proved that Gefitinib-induced cardiotoxicity through induction of oxidative stress leads to cardiac hypertrophy. The current study was conducted to understand the mechanisms underlying gefitinib-induced cardiac hypertrophy through studying the roles of angiotensin II (AngII), oxidative stress, and mitogen-activated protein kinase (MAPK) pathway. Male Wistar albino rats were treated with valsartan, gefitinib, or both for four weeks. Blood samples were collected for AngII and cardiac markers measurement, and hearts were harvested for histological study and biochemical analysis. Gefitinib caused histological changes in the cardiac tissues and increased levels of cardiac hypertrophy markers, AngII and its receptors. Blocking of AngII type 1 receptor (AT1R) via valsartan protected hearts and normalized cardiac markers, AngII levels, and the expression of its receptors during gefitinib treatment. valsartan attenuated gefitinib-induced NADPH oxidase and oxidative stress leading to down-regulation of JNK/p38-MAPK pathway. Collectively, AT1R blockade adjusted AngII-induced NADPH oxidase and JNK/p38-MAPK leading to attenuation of gefitinib-induced cardiac hypertrophy. This study found a pivotal role of AngII/AT1R signaling in gefitinib-induced cardiac hypertrophy, which may provide novel approaches in the management of EGFRIs-induced cardiotoxicity.     

Effects of prostaglandins and nitric oxide on the renal effects of angiotensin II in the anaesthetized rat

1. The potential influences of nitric oxide (NO) and prostaglandins on the renal effects of angiotensin II (Ang II) have been investigated in the captopril-treated anaesthetized rat by examining the effect of indomethacin or the NO synthase inhibitor, N^ω-nitro-L-arginine methyl ester (L-NAME), on the renal responses obtained during infusion of Ang II directly into the renal circulation.
2. Intrarenal artery (i.r.a.) infusion of Ang II (1–30 ng kg⁻¹ min⁻¹) elicited a dose-dependent decrease in renal vascular conductance (RVC; −38±3% at 30 ng kg⁻¹ min⁻¹; P<0.01) and increase in filtration fraction (FF; +49±8%; P<0.05) in the absence of any change in carotid mean arterial blood pressure (MBP). Urine output (Uv), absolute (UNaV) and fractional sodium excretion (FENa), and glomerular filtration rate (GFR) were unchanged during infusion of Ang II 1–30 ng kg⁻¹ min⁻¹ (+6±17%, +11±17%, +22±23%, and −5±9%, respectively, at 30 ng kg⁻¹ min⁻¹). At higher doses, Ang II (100 and 300 ng kg⁻¹ min⁻¹) induced further decreases in RVC, but with associated increases in MBP, Uv and UNaV.
3. Pretreatment with indomethacin (10 mg kg⁻¹ i.v.) had no significant effect on basal renal function, or on the Ang II-induced reduction in RVC (−25±7% vs −38±3% at Ang II 30 ng kg⁻¹ min⁻¹). In the presence of indomethacin, Ang II tended to cause a dose-dependent decrease in GFR (−38±10% at 30 ng kg⁻¹ min⁻¹); however, this effect was not statistically significant (P=0.078) when evaluated over the dose range of 1–30 ng kg⁻¹ min⁻¹, and was not accompanied by any significant changes in Uv, UNaV or FENa (−21±12%, −18±16% and +36±38%, respectively).
4. Pretreatment with L-NAME (10 μg kg⁻¹ min⁻¹ i.v.) tended to reduce basal RVC (control −11.8±1.4, +L-NAME −7.9±1.8 ml min⁻¹ mmHg⁻¹×10⁻²), and significantly increased basal FF (control +15.9±0.8, +L-NAME +31.0±3.7%). In the presence of L-NAME, renal vasoconstrictor responses to Ang II were not significantly modified (−38±3% vs −35±13% at 30 ng kg⁻¹ min⁻¹), but Ang II now induced dose-dependent decreases in GFR, Uv and UNaV (−51±11%, −41±14% and −31±17%, respectively, at an infusion rate of Ang II, 30 ng kg⁻¹ min⁻¹). When evaluated over the range of 1–30 ng kg⁻¹ min⁻¹, the effect of Ang II on GFR and Uv were statistically significant (P<0.05), but on UNaV did not quite achieve statistical significance (P=0.066). However, there was no associated change in FENa observed, suggesting a non-tubular site of interaction between Ang II and NO.
5. In contrast to its effects after pretreatment with L-NAME alone, Ang II (1–30 ng kg⁻¹ min⁻¹) failed to reduce renal vascular conductance in rats pretreated with the combination of L-NAME and the selective angiotensin AT₁ receptor antagonist, {"type":"entrez-nucleotide","attrs":{"text":"GR117289","term_id":"238364164","term_text":"GR117289"}}GR117289 (1 mg kg⁻¹ i.v.). This suggests that the renal vascular effects of Ang II are mediated through AT₁ receptors. Over the same dose range, Ang II also failed to significantly reduce GFR or Uv.
6. In conclusion, the renal haemodynamic effects of Ang II in the rat kidney appear to be modulated by cyclooxygenase-derived prostaglandins and NO. The precise site(s) of such an interaction cannot be determined from the present data, but the data suggest complex interactions at the level of the glomerulus.

     

Effects of enalapril and hydrochlorothiazide on the salt-induced cardiac and renal hypertrophy in normotensive rats

Recent studies have shown that, not only in hypertensive animals but even in normotensive rats, dietary salt (sodium chloride) produces a dose-related increase in the left ventricular and renal mass. In the present study the effects of the angiotensin converting enzyme inhibitor (ACEI) enalapril and the thiazide-type diuretic, hydrochlorothiazide, on the development of the salt-induced left ventricular and kidney hypertrophy were examined in normotensive Wistar-Kyoto and Wistar rats. A high intake of sodium chloride (6% of the dry weight of the chow to mimic the level found in many human food items) during eight weeks produced a marked increase in the mass of the left ventricle and the kidneys in both rat strains with little or no effect on blood pressure. The cardiac hypertrophy correlated strongly with the renal hypertrophy. These salt-induced changes in the heart and in the kidneys were completely blocked by hydrochlorothiazide, while enalapril was devoid of any significant effects during the high-salt diet. However, during a low-salt diet enalapril, but not hydrochlorothiazide, effectively lowered the blood pressure and decreased the left ventricular mass of the normotensive rats. There was a 3- to 4-fold increase in the urinary excretion of calcium during the high intake of sodium chloride. Hydrochlorothiazide decreased the urinary excretion of calcium even during the low salt diet, and it completely blocked the salt-induced hypercalciuria. Enalapril had no significant effect on the urinary calcium excretion. During the low-salt diet hydrochlorothiazide increased the calcium and decreased the potassium concentration in the heart while enalapril increased the phosphorus concentration.In conclusion, a high intake of sodium chloride produced hypertrophy both in the heart and in the kidneys, even in the absence of a rise in blood pressure. Salt also remarkably increased the urinary calcium excretion. These harmful effects of salt were blocked by the thiazide diuretic hydrochlorothiazide but not by the ACEI enalapril. However, this study does not allow to make any direct comparison between the effects of enalapril and hydrochlorothiazide. Correspondence to: E. Mervaala at the above address     

L-精氨酸-NO途径抑制血管紧张素Ⅱ诱导的心肌细胞肥大反应

目的探讨L-精氨酸(L-arginine,L-Arg)对心肌细胞血管紧张素Ⅱ受体(angiotensin Ⅱ receptor,ATR)及丝裂原活化蛋白激酶(mitogen-activated protein kinase,MAPK)表达的影响,进而阐述L-Arg对病理性心肌肥大的影响作用及相关机制。方法用血管紧张素Ⅱ(angiotensinⅡ,ATⅡ)、ATR抑制剂、L-Arg和(或)L-NAME(L-硝基精氨酸甲酯)分别作用于心肌细胞,然后以[3H]-亮氨酸参入法检测细胞蛋白合成速率、比色法检测一氧化氮(NO)生成量、RT-PCR及Western blot检测ATR及p38MAPK的表达水平。结果①给予L-Arg可缓解ATⅡ引起的心肌细胞NO合成量下降,减弱血管紧张素Ⅱ-1型受体(angiotensin receptor type1,ATR1)表达及下调p38MAPK蛋白磷酸化水平,并降低心肌细胞蛋白合成速率给予ATⅡ或L-Arg均未影响血管紧张素Ⅱ-2受体(angiotensin receptor type 2,ATP2)的表达水平;②心肌ATR1表达水平及p38MAPK蛋白磷酸化水平均与NO合成量之间存在线性负相关。多元逐步回归分析显示在ATR1与ATR2中,仅ATR1的表达水平与p38MAPK蛋白磷酸化水平之间存在回归关系。结论①L-Arg可致心肌细胞NO合成量增加,后者可抑制ATR1介导的p38MAPK蛋白磷酸化水平上调,进而抑制心肌细胞肥大反应;②ATR2未参与上述过程。     

MicroRNA-214 contributes to Ang II-induced cardiac hypertrophy by targeting SIRT3 to provoke mitochondrial malfunction

Reduction of expression and activity of sirtuin 3 (SIRT3) contributes to the pathogenesis of cardiomyopathy via inducing mitochondrial injury and energy metabolism disorder. However, development of effective ways and agents to modulate SIRT3 remains a big challenge. In this study we explored the upstream suppressor of SIRT3 in angiotensin II (Ang II)-induced cardiac hypertrophy in mice. We first found that SIRT3 deficiency exacerbated Ang II-induced cardiac hypertrophy, and resulted in the development of spontaneous heart failure. Since miRNAs play crucial roles in the pathogenesis of cardiac hypertrophy, we performed miRNA sequencing on myocardium tissues from Ang II-infused Sirt3^−/− and wild type mice, and identified microRNA-214 (miR-214) was significantly up-regulated in Ang II-infused mice. Similar results were also obtained in Ang II-treated neonatal mouse cardiomyocytes (NMCMs). Using dual-luciferase reporter assay we demonstrated that SIRT3 was a direct target of miR-214. Overexpression of miR-214 in vitro and in vivo decreased the expression of SIRT3, which resulted in extensive mitochondrial damages, thereby facilitating the onset of hypertrophy. In contrast, knockdown of miR-214 counteracted Ang II-induced detrimental effects via restoring SIRT3, and ameliorated mitochondrial morphology and respiratory activity. Collectively, these results demonstrate that miR-214 participates in Ang II-induced cardiac hypertrophy by directly suppressing SIRT3, and subsequently leading to mitochondrial malfunction, suggesting the potential of miR-214 as a promising intervention target for antihypertrophic therapy.     

氢氯噻嗪和吲哒帕胺逆转自发性高血压大鼠心肌肥厚及对心肌中eNOS表达的影响

目的研究氢氯噻嗪和吲哒帕胺对肥厚心肌及心肌中内皮型一氧化氮合酶(endothelial n itric oxide synthase,eNOS)表达的影响,从而探讨其逆转心肌肥厚可能的分子机制。方法15只成年♀SHR随机分为对照组、氢氯噻嗪组、吲哒帕胺组。治疗前、开始至结束时每周测血压1次。4wk后处死动物,取左心室称重后,计算左心室重与体重的比值,采用天狼猩红染色分析心肌间质和血管壁胶原分布。采用W estern B lot法检测心肌eNOS蛋白质表达。结果治疗组动物收缩压及左心室重与体重比均明显低于对照组。心肌经天狼猩红染色后见治疗组心肌结构基本正常,与对照组相比未见明显的胶原沉积。并且治疗组在蛋白质水平上调心肌eNOS的表达(P<0.05)。结论吲哒帕胺或氢氯噻嗪可逆转自发性高血压大鼠(spontaneous hypertensive rats,SHR)左室肥厚、改善心肌纤维化从而起到保护心脏的作用,可能与其促进心肌中eNOS的表达有关。     

氢氯噻嗪和吲哒帕胺逆转自发性高血压大鼠心肌肥厚及促进心肌中内皮型一氧化氮合酶的表达

目的：研究氢氯噻嗪和吲哒帕胺对肥厚心肌及心肌中内皮型一氧化氮合酶（endothelial nitric oxide synthase，eNOS）表达的影响，从而探讨其逆转心肌肥厚可能的分子机制。方法：15只成年雌性自发性高血压大鼠（SHR）随机分为对照组、氢氯噻嗪组、吲哒帕胺组。治疗前、开始至结束时每周测血压1次。4周后处死动物，取左心室称重后，计算左心室重与体重的比值，采用天狼猩红染色分析心肌间质和血管壁胶原分布。采用Westem Blot法检测心肌eNOS蛋白质表达。结果：治疗组动物收缩压及左心室重与体重比均明显低于对照组。心肌经天狼猩红染色后见治疗组心肌结构基本正常，与对照组相比未见明显的胶原沉积。并且治疗组在蛋白质水平显著上调心肌eNOS的表达（P〈0．05）。结论：吲哒帕胺或氢氯噻嗪治疗自发性高血压可逆转左室肥厚、上调心肌eNOS、改善心肌纤维化从而起到保护心脏的作用。     

Metformin attenuates ventricular hypertrophy by activating the AMP-activated protein kinase-endothelial nitric oxide synthase pathway in rats

1. Metformin is an activator of AMP‐activated protein kinase (AMPK). Recent studies suggest that pharmacological activation of AMPK inhibits cardiac hypertrophy. In the present study, we examined whether long‐term treatment with metformin could attenuate ventricular hypertrophy in a rat model. The potential involvement of nitric oxide (NO) in the effects of metformin was also investigated. 2. Ventricular hypertrophy was established in rats by transaortic constriction (TAC). Starting 1 week after the TAC procedure, rats were treated with metformin (300 mg/kg per day, p.o.), N^G‐nitro‐l‐ arginine methyl ester (l ‐NAME; 50 mg/kg per day, p.o.) or both for 8 weeks prior to the assessment of haemodynamic function and cardiac hypertrophy. 3. Cultured cardiomyocytes were used to examine the effects of metformin on the AMPK–endothelial NO synthase (eNOS) pathway. Cells were exposed to angiotensin (Ang) II (10^?6 mol/L) for 24 h under serum‐free conditions in the presence or absence of metformin (10^?3 mol/L), compound C (10^?6 mol/L), l ‐NAME (10^?6 mol/L) or their combination. The rate of incorporation of [³H]‐leucine was determined, western blotting analyses of AMPK–eNOS, neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) were undertaken and the concentration of NO in culture media was determined. 4. Transaortic constriction resulted in significant haemodynamic dysfunction and ventricular hypertrophy. Myocardial fibrosis was also evident. Treatment with metformin improved haemodynamic function and significantly attenuated ventricular hypertrophy. Most of the effects of metformin were abolished by concomitant l ‐NAME treatment. l ‐NAME on its own had no effect on haemodynamic function and ventricular hypertrophy in TAC rats. 5. In cardiomyocytes, metformin inhibited AngII‐induced protein synthesis, an effect that was suppressed by the AMPK inhibitor compound C or the eNOS inhibitor l ‐NAME. The improvement in cardiac structure and function following metformin treatment was associated with enhanced phosphorylation of AMPK and eNOS and increased NO production. 6. The findings of the present study indicate that long‐term treatment with metformin could attenuate ventricular hypertrophy induced by pressure overload via activation of AMPK and a downstream signalling pathway involving eNOS–NO.     

KMUP-1 attenuates isoprenaline-induced cardiac hypertrophy in rats through NO/cGMP/PKG and ERK1/2/calcineurin A pathways

Background and purpose:

To determine whether KMUP-1, a novel xanthine-based derivative, attenuates isoprenaline (ISO)-induced cardiac hypertrophy in rats, and if so, whether the anti-hypertrophic effect is mediated by the nitric oxide (NO) pathway.

Experimental approach:

In vivo, cardiac hypertrophy was induced by injection of ISO (5 mg·kg⁻¹·day⁻¹, s.c.) for 10 days in Wistar rats. In the treatment group, KMUP-1 was administered 1 h before ISO. After 10 days, effects of KMUP-1 on survival, cardiac hypertrophy and fibrosis, the NO/guanosine 3′5′-cyclic monophosphate (cGMP)/protein kinase G (PKG) and hypertrophy signalling pathways [calcineurin A and extracellular signal-regulated kinase (ERK)1/2] were examined. To investigate the role of nitric oxide synthase (NOS) in the effects of KMUP-1, a NOS inhibitor, N^ω-nitro-L-arginine (L-NNA) was co-administered with KMUP-1. In vitro, anti-hypertrophic effects of KMUP-1 were studied in ISO-induced hypertrophic neonatal rat cardiomyocytes.

Key results:

In vivo, KMUP-1 pretreatment attenuated the cardiac hypertrophy and fibrosis and improved the survival of ISO-treated rats. Plasma NOx (nitrite and nitrate) and cardiac endothelial NOS, cGMP and PKG were all increased by KMUP-1. The activation of hypertrophic signalling by calcineurin A and ERK1/2 in ISO-treated rats was also attenuated by KMUP-1. All these effects of KMUP-1 were inhibited by simultaneous administration of L-NNA. Similarly, in vitro, KMUP-1 attenuated hypertrophic responses and signalling induced by ISO in neonatal rat cardiomyocytes.

Conclusions and implications:

KMUP-1 attenuates the cardiac hypertrophy in rats induced by administration of ISO. These effects are mediated, at least in part, by NOS activation. This novel agent, which targets the NO/cGMP pathway, has a potential role in the prevention of cardiac hypertrophy.