Role of tissue angiotensin II in myocardial remodelling induced by mechanical stress

In an in vivo study, spontaneously hypertensive rats (SHR) were treated with an angiotensin II (Ang II) type 1 receptor antagonist of candesartan or hydralazine. Untreated SHR progressively developed severe hypertension, and treatment with candesartan or hydralazine decreased blood pressure. Candesartan reduced left ventricular (LV) weight, LV wall thickness, transverse myocyte diameter, the relative amount of V3 myosin heavy chain, and interstitial fibrosis, while treatment with hydralazine slightly prevented an increase in LV wall thickness, but did not exert a significant reduction on other parameters. In an in vitro study, neonatal rat cardiomyocytes were cultured on deformable silicone dishes. Stretching cardiomyocytes activated second messengers such as protein kinase C, Raf-1 kinase, and mitogen-activated protein (MAP) kinase, increasing protein synthesis, enhancing endothelin (ET)-1 release, activating the Na+/H+ ion exchanger. Moreover, pretreatment with candesartan diminished an increase in phenylalanine incorporation, MAP kinase activity, and c-fos gene expression induced by the stretching of cardiomyocytes. This suggests that the cardiac renin-angiotensin system is linked to the formation of pressure-overload hypertrophy and that Ang II increases the growth of cardiomyocytes by an autocrine mechanism. Finally, we examined the signalling pathways leading to MAP kinase activation both in cardiac myocytes and in cardiac fibroblasts. Ang II-evoked signal transduction pathways differed between cell types. In cardiac fibroblasts, Ang II activated MAP kinase through a pathway including the Gbetagamma subunit of Gi protein, Src, Shc, Grb2, and Ras, while Gq and protein kinase C were important in cardiac myocytes.     

Angiotensin II type 1 receptor blocker attenuates myocardial remodeling and preserves diastolic function in diabetic heart.

Blockade of the renin-angiotensin system reduces cardiovascular morbidity and mortality in diabetic patients. Angiotensin II (Ang II) plays an important role in the structural and functional abnormalities of the diabetic heart. We investigated whether or not Ang II type 1 receptor blocker (ARB) could attenuate left ventricular (LV) remodeling in male mice with diabetes mellitus (DM) induced by the injection of streptozotocin (200 mg/kg, i.p.). Diabetic mice were treated with candesartan (1 mg/kg/day; DM+Candesartan, n=7) or vehicle (DM+Vehicle, n=7) for 8 weeks. Heart rate and aortic blood pressure were comparable between the groups. Normal systolic function was preserved in diabetic mice. In contrast, diastolic function was impaired in DM+Vehicle and was improved in DM+Candesartan, as assessed by the deceleration time of the peak velocity of transmitral diastolic flow (40.3+/-0.3 vs. 37.3+/-0.5 ms, p<0.01) and the time needed for relaxation of 50% maximal LV pressure to baseline value (tau; 10.6+/-0.7 vs. 8.7+/-0.6 ms, p<0.05) without significant changes in heart rate and aortic blood pressure. Improvement of LV diastolic function was accompanied by the attenuation of myocyte hypertrophy, interstitial fibrosis and apoptosis in association with the expression of connective tissue growth factor (CTGF) and myocardial oxidative stress. Moreover, candesartan directly inhibited Ang II-mediated induction of CTGF in cultured cardiac fibroblasts. ARB might be beneficial to prevent cardiac abnormalities in DM.     

Increased AT2R protein expression but not increased apoptosis during cardioprotection induced by AT1R blockade

BACKGROUND: The angiotensin II type 2 receptor (AT2R) is considered to be antigrowth and to mediate apoptosis in several cell types. Whether AT2R upregulation, associated with angiotensin II type 1 receptor (AT1R) blockade and cardioprotection after ischemia-reperfusion (IR), might not result in increased cardiomyocyte (CM) apoptosis has not been documented. OBJECTIVES: To determine whether increased AT2R protein expression, during AT1R blockade after acute IR, is associated with no increase in CM apoptosis. MATERIALS AND METHODS: The recovery of left ventricular (LV) mechanical function after acute IR (30 min of ischemia, 40 min of reperfusion) was measured in isolated Langendorff rat hearts following pretreatment with the AT1R antagonist candesartan (CN) (CN 10 nmol/L) for 40 min before ischemia. The authors established with an initial dose-response curve using escalating concentrations of CN that 10 nmol/L abrogated vasoconstriction induced by angiotensin II (0.1 mmol/L). AT1R and AT2R protein expression (Western immunoblot), CM apoptosis (terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate nick end-labelling assay and nuclear morphology) and apoptotic markers (Bax, Bcl-2, caspase-3, p53) were assessed in LV tissue. RESULTS: Compared with IR controls, CN improved peak systolic pressure, LV developed pressure and positive dp/dt, and increased AT2R (not AT1R) protein, but did not change the level of apoptosis or the expression of Bax, Bcl-2, caspase-3 or p53. CN also increased AT2R protein after ischemia alone but did not change CM apoptosis or expression of the markers. CONCLUSIONS: Increased AT2R protein expression during AT1R blockade after IR in the isolated Langendorff rat heart is associated with cardioprotection but no increase in CM apoptosis.     

Angiotensin II plays an important role in maintaining blood pressure in postmenopausal women receiving hormone replacement therapy

BACKGROUND: We investigated the role of angiotensin (Ang) II in maintaining blood pressure (BP) by administering a small dose of candesartan, an Ang II type 1 receptor antagonist, in postmenopausal women receiving long-term hormone replacement therapy (HRT). METHODS: A single dose of 2 mg of candesartan was administered orally to 13 normotensive postmenopausal women receiving HRT (continuous combined conjugated estrogen and medroxyprogesterone acetate orally; HRT group) and 13 normotensive postmenopausal women not receiving HRT (control group). Both BP and heart rate (HR) were measured at baseline and at 1, 2, 3, 4, 5, and 6 h after administration. Plasma renin activity (PRA) and Ang I, Ang II, and bradykinin concentrations were measured at baseline and 4 h after the administration of candesartan. RESULTS: Candesartan lowered the BP and raised the HR in both groups. However, the decrease in BP was significantly greater in the HRT group than in the control group (P < .05), whereas no significant difference in the change in HR was observed between the two groups. In the HRT group, significant increases were found in PRA, Ang I, and Ang II (all P < .05) and a significant decrease in bradykinin (P < .01) with candesartan treatment. In the control group, candesartan as associated with an increase in PRA (P < .05) but not in Ang I, Ang II, or bradykinin. CONCLUSIONS: Based on our study results, Ang II plays an important role in maintaining BP in normotensive postmenopausal women receiving HRT. Maintenance of BP may be dependent on the balance between the hypertensive effect of Ang II and the hypotensive effect of bradykinin.     

Angiotensin II and norepinephrine release: interaction and effects on the heart

BACKGROUND: Angiotensin (Ang) II may enhance the influence of the sympathetic nervous system at various levels by facilitating norepinephrine (NE) release. We investigated whether such an interaction is evident in the human heart and whether it has an impact on left ventricular (LV) structure. METHODS AND RESULTS: Ang I and Ang II concentrations were determined in arterial and coronary sinus (CS) plasma samples in a group of normotensive (n = 10) and hypertensive (n = 18) subjects. Total systemic and cardiac NE spillover was measured using isotope dilution methodology and LV structure by echocardiography. Arterial and CS concentrations of Ang I and Ang II were similar in both groups (Ang II CS, 5.8 +/- 4.0 versus 3.7 +/- 3.1 fmol/ml; P = not significant), as was the Ang II/Ang I ratio (CS, 0.56 +/- 0.17 versus 0.54 +/- 0.22 fmol/fmol; P = not significant). Total systemic (223 +/- 145 versus 374 +/- 149 ng/min; P < 0.05) and cardiac NE spillover (11.7 +/- 6.3 versus 19.4 +/- 10.5 ng/min; P < 0.05) were increased in hypertensive patients, as was LV mass index (LVMI) (86.7 +/- 14.7 versus 117.2 +/- 19.4 g/m; P < 0.001). LVMI correlated with cardiac NE spillover (r = 0.47; P < 0.02). No correlation was evident between CS Ang II and cardiac NE spillover (r = 0.001; P = not significant) or LVMI (r = -0.20; P = not significant). Arterial Ang II tended to correlate with total systemic NE spillover (r = 0.34; P = 0.081). When hypertensive subjects were divided into two groups with either high or low CS Ang II concentration, cardiac NE spillover and LVMI did not differ between the two groups. CONCLUSION: These findings suggest a growth-promoting effect of increased cardiac sympathetic tone on cardiomyocytes in hypertensive patients, but do not support the notion of a significant role of Ang II for norepinephrine release and LV hypertrophy in the hypertensive human heart.     

Orally administered benidipine and manidipine prevent ischemia-reperfusion injury in the rat heart.

BACKGROUND: The present study was designed to investigate whether orally administered benidipine and manidipine protect the myocardium from ischemia - reperfusion injury. METHODS AND RESULTS: Each drug (1, 3 or 10 mg/kg) was administered orally once daily for 1 week. The isolated rat heart model (Langendorff perfusion) was used, and each heart was subjected to global ischemia at 37 degrees C for 40 min followed by reperfusion. Post-ischemic recovery of left ventricular (LV) function (measured as developed pressure (LVDP), dP/dt max and end-diastolic pressure) was compared with a control group. Creatine kinase (CK) leakage was also measured. Post-ischemic recovery of LVDP and LV dP/dt max were significantly increased by 3 mg/kg benidipine (LVDP: 87.5+/-10.1 vs 64.6+/-11.9%; LV dP/dt max: 97.8+/-10.4 vs 70.2+/-15.7%; p<0.05). CK leakage was significantly lower than in the control group (39.4+/-7.5 vs 61.1 +/-9.8 IU per 15 min per kg; p<0.05). Manidipine produced significant recoveries in LVDP and dP/dt max at a dose of 1 mg/kg (LVDP: 93.7+/-16.5% vs 53.4+/-9.5%; dP/dt max: 104.2+/-21.9% vs 55.5+/-15.5%; p<0.05). CK leakage was also significantly reduced at the same dose (50.0+/-18.3 vs 80.1+/-14.0 IU per 15 min per kg; p<0.05). CONCLUSIONS: Orally administered benidipine and manidipine exerted significant cardioprotective effects against ischemia - reperfusion injury.     

Increased AT(2)R protein expression but not increased apoptosis during cardioprotection induced by AT(1)R blockade

BACKGROUND: The angiotensin II type 2 receptor (AT2R) is considered to be antigrowth and to mediate apoptosis in several cell types. Whether AT2R upregulation, associated with angiotensin II type 1 receptor (AT1R) blockade and cardioprotection after ischemia-reperfusion (IR), might not result in increased cardiomyocyte (CM) apoptosis has not been documented. OBJECTIVES: To determine whether increased AT2R protein expression, during AT1R blockade after acute IR, is associated with no increase in CM apoptosis. MATERIALS AND METHODS: The recovery of left ventricular (LV) mechanical function after acute IR (30 min of ischemia, 40 min of reperfusion) was measured in isolated Langendorff rat hearts following pretreatment with the AT1R antagonist candesartan (CN) (CN 10 nmol/L) for 40 min before ischemia. The authors established with an initial dose-response curve using escalating concentrations of CN that 10 nmol/L abrogated vasoconstriction induced by angiotensin II (0.1 mol/L). AT1R and AT2R protein expression (Western immunoblot), CM apoptosis (terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate nick end-labelling assay and nuclear morphology) and apoptotic markers (Bax, Bcl-2, caspase-3, p53) were assessed in LV tissue. RESULTS: Compared with IR controls, CN improved peak systolic pressure, LV developed pressure and positive dp/dt, and increased AT2R (not AT1R) protein, but did not change the level of apoptosis or the expression of Bax, Bcl-2, caspase-3 or p53. CN also increased AT2R protein after ischemia alone but did not change CM apoptosis or expression of the markers. CONCLUSIONS: Increased AT2R protein expression during AT1R blockade after IR in the isolated Langendorff rat heart is associated with cardioprotection but no increase in CM apoptosis.     

Appraisal of the role of angiotensin II and aldosterone in ventricular myocyte apoptosis in adult normotensive rat

Despite previous observations on isolated ventricular myocytes, there are still few evidences that angiotensin II induces cardiomyocyte apoptosis in vivo. The possibility that aldosterone, the final hormone of the renin-angiotensin-aldosterone system under Ang II control, can stimulate cardiac apoptosis has not yet been explored. Angiotensin II or aldosterone (1mg/kg each) were infused in adult normotensive rats for different times, and the number of apoptotic ventricular myocyte nuclei was quantified by the TUNEL method, along with caspase-3 activation. The role of angiotensin II type 1 receptor in vivo was assessed by selective blockade with valsartan and ex vivo by binding experiments. In addition, myocytes in primary culture were incubated with Ang II or aldosterone in presence of spironolactone. Continuous infusion of Ang II induced a rapid, AT(1)-mediated increase of apoptotic cardiomyocyte nuclei (from 14+/-9 to 188+/-35 TdT-labeled nuclei/10(6) after 3h, P<0.005) and of activated caspase-3, that normalized after 24h. The normalization was associated with a down-regulation of myocardial AT(1) receptors. Aldosterone stimulated cardiomyocyte apoptosis both in vivo and in isolated cells, to a similar extent as Ang II. The maximal apoptotic rate reported here ( approximately 0.02%) and the transient effect of Ang II suggest that myocyte loss by apoptosis is limited in the present model. The data on aldosterone-induced ventricular myocyte apoptosis deserve further attention to delineate the role of aldosterone in cell death and offer possible mechanistic explanations on the benefits afforded by aldosterone receptor antagonists in heart failure.     

Cardiac dysfunction in the Goto-Kakizaki rat

METHODS: Both isolated perfused hearts and isolated ventricular myocytes from GK and matched control Wistar rat hearts were studied. Percent myocyte twitch shortening (%TS) and corresponding intracellular calcium transients (indo-1 fluorescence ratio, R) were measured over a range of stimulation frequencies (0.5-2.5 Hz; 32 degrees C, n = 16-24 cells). In isolated Langendorff-perfused hearts, we measured systolic LV pressure (LVP(max)), left ventricular end diastolic pressure (LVEDP), maximal rate of LV pressure rise (LV dP/dt(max)) and fall (LV dP/dt(min)) and isovolumic LV relaxation (exponential time constant, T) both at baseline and during brief (10 minutes) hypoxia. RESULTS: The %TS and corresponding indo-1 R were similar between GK and control myocytes at all stimulation frequencies (e.g. at 2.5 Hz: % TS = 8.6 +/- 0.77 and 8.2 +/- 0.19; R = 0.19 +/- 0.009 and 0.18 +/- 0.018, GK and control respectively, P = NS). Similarly, there were no significant differences in baseline LVP(max) (129 +/- 6.2 and 135 +/- 9.6 mmHg; GK and control respectively, P = NS), LV dP/dt(max) (3169.5 +/- 165.80 and 3390.6 +/- 232.60 mmHg/s; GK and control respectively, P = NS), LV dP/dt(min) or T (24 +/- 0.7 and 25 +/- 0.6 ms, GK and control respectively, P = NS). During 10 min hypoxia, LV dP/dt(max) decreased significantly more, and LVEDP and T increased significantly more, in GK compared to control hearts (LV dP/dt(max): 668.90 +/- 32.8 versus 1027.10 +/- 84.0 mmHg/s; LVEDP: 21.4 +/- 4.3 versus 11.6 +/- 0.6 mmHg; T: 102 +/- 13.8 versus 56 +/- 3.0 ms; GK versus control respectively; all P < 0.05). These abnormalities in GK hearts were reversed with acute addition of insulin (0.01 i. u./ml) to the perfusion buffer. CONCLUSION: The GK model of Type II diabetes displays a mild cardiomyopathy evident as exaggerated diastolic dysfunction during hypoxia. The mechanism is likely to involve substrate deficiency. Experimental study of cardiac function in the diabetic heart has focussed mostly on models of Type I diabetes. We studied cardiac function in the Goto-Kakizaki (GK) rat, an inbred model of spontaneous non-obese, Type II diabetes.     

Caspase-dependent and serine protease-dependent DNA fragmentation of myocytes in the ischemia-reperfused rabbit heart: these inhibitors do not reduce infarct size

Some infarcted myocytes undergo caspase-dependent DNA fragmentation, but serine protease-dependent DNA fragmentation may also be involved. There is controversy regarding whether caspase inhibitors can reduce infarct size, so the present study investigated whether serine protease inhibitor can reduce the DNA fragmentation of infarcted myocytes and whether serine protease or caspase inhibitors attenuates myocardial infarct size in Japanese white rabbits without collateral circulation. Rabbits were subjected to 30-min coronary occlusion followed by 48-h reperfusion. A vehicle (dimethylsulfoxide, control group, n=8) or Z-Val-Ala-Asp(Ome)-CH2F (ZVAD-fmk, a caspase inhibitor, ZVAD group, 0.8 mg/kg iv at 20 min before coronary occlusion and 0.8 mg/kg at 90 min after reperfusion, n=8) or 3,4-dichloroisocoumarin (DCI, a serine protease inhibitor, 2 mg/kg iv at 20 min before coronary occlusion, DCI group, n=8) was administered. Animals were killed at 48h after reperfusion for the detection of myocardial infarct size and at 4h after reperfusion for the detection of dUTP nick end-labeling (TUNEL)-positive myocytes, the electrophoretic pattern of DNA fragmentation and ultrastructural analysis. The left ventricle (LV) was excised and sliced. The myocardial infarct size as a percentage of the area at risk was assessed by triphenyltetrazolium chloride staining. DNA fragmentation was assessed by in situ TUNEL at the light microscopic level. ZVAD and DCI significantly reduced the mean blood pressure during reperfusion without affecting heart rate. There was no significant difference in the % area at risk (AAR) of LV among the 3 groups (control: 26.3+/-3.0%; ZVAD: 25.6+/-2.6%; DCI: 25.6+/-2.0%). The % infarct size as a percentage of the AAR in the ZVAD group (41.3+/-4.5%) and the DCI group (50.4+/-3.8%) was not significantly different from the control group (43.5+/-4.5%). However, the percent DNA fragmentation in the infarcted area in the ZVAD (3.5+/-0.8%) and DCI groups (4.2+/-0.9%) was significantly reduced compared with the control group (10.7+/-1.9%). The DNA ladder pattern observed in the control group was attenuated in both the ZVAD and DCI groups. There was no difference in electron microscopic changes among the 3 groups. Serine protease-dependent DNA fragmentation is present in infarcted myocytes, in addition to caspase-dependent DNA fragmentation, but an infarct-size reducing effect was not observed with either of these inhibitors.     

In vivo inhibition of angiotensin receptors in the rat kidney by candesartan cilexetil: a comparison with losartan

The present study examined the in vivo effects of candesartan cilexetil compared with losartan on angiotensin II (Ang II) receptor binding in the rat kidney after oral administration. Male Sprague-Dawley rats (250 to 300 g) were gavaged with candesartan cilexetil or losartan in doses of 0.1, 0.3, 1, 3, 10, or 30 mg/kg, or corresponding vehicle. Rats were killed at 0, 1, 2, 8, or 24 h after drug administration, trunk blood collected, and kidneys removed. The effects of candesartan cilexetil and losartan on Ang II receptor binding were determined by quantitative in vitro autoradiography using the radioligand [125I]-[Sar1,Ile8] Ang II. Ang II receptor binding in the kidney was mainly due to AT1 receptors with high levels of binding localized to the inner stripe of the outer medulla and glomeruli in cortical regions. Candesartan cilexetil (0.1 to 30 mg/kg) inhibited Ang II receptor binding to all anatomical sites of the kidney, in a dose-dependent manner. Losartan (0.1 to 30 mg/kg) also produced dose-dependent inhibition of Ang II receptor binding but was approximately 10- to 30-fold less potent than candesartan cilexetil. Inhibition of Ang II receptor binding was near maximal about 1 h after administration of candesartan cilexetil (10 mg/kg) or losartan (10 mg/kg), with both drugs producing persistent blockade at 24 h despite plasma renin activity and plasma drug concentrations returning to near normal levels. In vitro, candesartan, losartan, and EXP3174 (1 x 10(-10) to 1 x 10(-5) mol/L) displaced [125I]-[Sar1,Ile8] Ang II binding from AT1 receptors in the kidney in a concentration-dependent manner with a rank order of potency of candesartan > EXP3174 > losartan. The concentration required to displace 50% of radioligand binding (IC50) by candesartan, EXP3174, and losartan was 0.9+/-0.1 nmol/L, 3.4+/-0.4 nmol/L, and 8.9+/-1.1 nmol/L, respectively. In conclusion, the findings of the present study suggest that candesartan cilexetil is more potent than losartan in antagonizing AT1 receptors in the kidney in vivo. Nonetheless, both candesartan cilexetil and losartan produce rapid, complete, and sustained blockade of AT1 receptors in the rat kidney. Tissue blockade of Ang II receptors in target organs, such as the kidney, may contribute to the beneficial effects of Ang II receptor antagonists as antihypertensive agents.     

Neuronal nitric oxide synthase is up-regulated by angiotensin II and attenuates NADPH oxidase activity and facilitates relaxation in murine left ventricular myocytes

Angiotensin II (Ang II) is critical in myocardial pathogenesis, mostly via stimulating NADPH oxidase. Neuronal nitric oxide synthase (nNOS) has recently been shown to play important roles in modulating myocardial oxidative stress and contractility. Here, we examine whether nNOS is regulated by Ang II and affects NADPH oxidase production of intracellular reactive oxygen species (ROS(i)) and contractile function in left ventricular (LV) myocytes. Our results showed that Ang II induced biphasic effects on ROS(i) and LV myocyte relaxation (TR(50)) without affecting the amplitude of sarcomere shortening and L-type Ca(2+) current density: TR(50) was prolonged at 30 min but was shortened after 3h (or after Ang II treatment in vivo). Correspondingly, ROS(i) was increased, followed by a reduction to control level. Quantitative RT-PCR and immunoblotting experiments showed that Ang II (3h) increased the mRNA and protein expression of nNOS and increased NO production (nitrite assay) in LV myocyte homogenates, suggesting that nNOS activity may be enhanced and involved in mediating the effects of Ang II. Indeed, n(omega)-nitro-l-arginine methyl ester (l-NAME) or a selective nNOS inhibitor, S-methyl-l-thiocitrulline (SMTC) increased NADPH oxidase production of superoxide/ROS(i) and abolished faster myocyte relaxation induced by Ang II. The positive lusitropic effect of Ang II was not mediated by PKA-, CaMKII-dependent signaling or peroxynitrite. Conversely, inhibition of cGMP/PKG pathway abolished the Ang II-induced faster relaxation by reducing phospholamban (PLN) Ser(16) phosphorylation. Taken together, these results clearly demonstrate that myocardial nNOS is up-regulated by Ang II and functions as an early adaptive mechanism to attenuate NADPH oxidase activity and facilitate myocardial relaxation.     

Angiotensin II type 1 receptor antagonist decreases plasma levels of tumor necrosis factor alpha, interleukin-6 and soluble adhesion molecules in patients with chronic heart failure

OBJECTIVES: To evaluate the effects of an angiotensin (Ang II) type 1 receptor antagonist on immune markers in patients with congestive heart failure (CHF). BACKGROUND: Ang II stimulates production of immune factors via the Ang II type 1 receptor in vitro, and the long-term effects of Ang II type 1 receptor antagonists on plasma markers of immune activation are unknown in patients with CHF. METHODS: Twenty-three patients with mild to moderate CHF with left ventricular dysfunction were randomly divided into two groups: treatment with Ang II type 1 receptor (candesartan cilexetil) (n = 14) or placebo (n = 9). We measured plasma levels of immune factors such as tumor necrosis factor alpha (TNFalpha), interleukin-6 (IL-6), soluble intercellular adhesion molecule-1 (sICAM-1) and soluble vascular cell adhesion molecule-1 (sVCAM-1). We also measured plasma levels of the neurohumoral factors such as atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) and cyclic guanosine monophosphate (cGMP), a biological marker of ANP and BNP. RESULTS: Plasma levels of TNFalpha, IL-6, sICAM-1 and sVCAM-1 were increased in the 23 CHF patients compared with normal subjects and significantly decreased after 14 weeks of candesartan cilexetil treatment, but did not change in the placebo group. Plasma levels of BNP, which is a marker of ventricular injury, significantly decreased, and the molar ratio of plasma cGMP to cardiac natriuretic peptides (ANP + BNP) was significantly increased after candesartan cilexetil treatment, but did not change in the placebo group. CONCLUSIONS: These findings suggest that 14 weeks of treatment with an Ang II type 1 receptor antagonist (candesartan cilexetil) decreased plasma levels of the immune markers such as TNFalpha, IL-6, sICAM-1 and sVCAM-1 and that it improved the biological compensatory action of endogenous cardiac natriuretic peptides in patients with mild to moderate CHF.     

压力超负荷下bcl—2、bax蛋白对兔左室细胞凋亡的影响

目的：探讨超负荷时兔左室心肌细胞bcl-2和bax蛋白表达对兔左室心肌细胞凋亡的影响。方法：采取末端脱核苷酸转移酶介导的dUTP－生物素平移末端标记（TUNEL）技术和链酶亲和素－生物素－过氧化物酶复合物（SABC）免疫组化方法，观察持续压力超负荷下免左室心肌凋亡的动态变化及bcl-2和bax蛋白的表达。结果：对照组出现极少量凋亡细胞，表达少量bcl-2蛋白，不表达bax蛋白。术后凋亡阳性心肌细胞数和bcl-2蛋白阳性表达心肌细胞数迅速增加，两者在心衰组最高，凋亡阳性心肌细胞数在术后第3天多于术后第7天。左室心肌细胞仅在术后第1组和心衰组表达bax蛋白。结论：在持续压力负荷所致心力衰竭的全过程，bcl-2蛋白都以与了抑制心肌细胞凋亡的调节，bax蛋白可能只以与了心肌细胞凋亡的启动。     

Disparate systemic and renal blocking properties of angiotensin II antagonists during exogenous angiotensin II administration: implications for treatment

Generation of angiotensin II (Ang II) contributes to the pathogenesis of cardiovascular diseases. Owing to the existence of high levels of Ang II within the kidney, blockade of the intrarenal Ang II levels may be important since long term outcome seems not only to be related to blood pressure per se. This was a prospective, randomized, double-blind, placebo-controlled study, with crossover design. We examined in 13 patients with mild to moderate hypertension the specific systemic and renal blocking properties of two different Ang II receptor blockers during a wide range of Ang II concentrations, 24 h post dose. The effects were evaluated after 4 weeks treatment with candesartan cilexetil (16 mg OD), losartan (50 mg OD) and placebo using clearance techniques. Candesartan reduced the 24 h blood pressure better than losartan (138(*)/87+/-12/8 vs 145/89+/-12/7 mmHg, (*)P<0.05 vs losartan) and placebo. Despite the lower blood pressure, candesartan attenuated the Ang II-induced response on ERPF and RVR markedly better than losartan or placebo. The GFR decreased, as expected, with placebo, but remained stable with candesartan. The present study demonstrates that in hypertensive patients candesartan and to a lesser degree losartan are effective in blocking the systemic and renal effects of Ang II during a wide range of Ang II infusion rates. Interestingly, 24 h post dose, candesartan effectively diminished the change in ERPF as well as GFR. This sustained renal effect of candesartan may be of importance, especially in pathophysiological circumstances in which (high renal levels of) Ang II contributes to cardiovascular damage.     

β1-AR阻断剂联合β2-AR激动剂对心肌梗死大鼠心功能的影响及机制

目的 观察美托洛尔与特布他林联用对心梗大鼠心功能的影响,从心肌细胞凋亡及氧化应激角度探讨其机制.方法 结扎冠状动脉前降支制备心梗大鼠模型,随机分为美托洛尔组(M 组)、特布他林组(T 组)、联合治疗组(L 组)和安慰剂组(A 组),另选一组为假手术组(S 组),每组8 只.术后1 周灌胃给药,M 组给予美托洛尔20 mg/kg,T 组给予特布他林2 mg/kg,L 组给予美托洛尔和特布他林,剂量同上,A 组给予等量生理盐水,S 组不予处理.生理盐水及药物皆为2 次/d 灌胃.8 周后行超声心动图、血流动力学、心肌组织GSH/GSSG、bax/bcl-2 蛋白测定.结果 ①用药组LVEDD、LVESD 较A 组明显降低(P＜0.05),EF、FS 明显升高(P＜0.05),T 组与L 组较M 组进一步改善(P＜0.05).②用药组LVEDP 较A 组明显降低(P＜0.05),LVSP、±dp/dt 明显升高(P＜0.05),L 组较M 组进一步改善(P＜0.05),T 组LVEDP 较M 组明显降低(P＜0.05).③用药组谷光甘肽(GSH)较A 组明显升高(P＜0.01),氧化型谷光甘肽(GSSG)明显降低(P＜0.01),L 组较单药治疗组进一步改善(P＜0.05),T 组与M 组相比,GSH 明显升高(P＜0.05).④用药组bcl-2 较A 组明显升高(P＜0.01),bax 明显降低(P＜0.01),T 组与L 组bax 水平接近(P=0.141),两组较M 组明显降低(P＜0.05),L 组bcl-2 水平与S 组接近(P=0.453),两单药治疗组bcl-2 差异无统计学意义(P=0.132),均显著低于L 组,L 组bcl-2/bax 明显高于T 组,T 组bcl-2/bax 明显高于M 组.结论 特布他林对心梗后大鼠心功能及心室重构的改善作用优于美托洛尔,二者联用改善作用进一步增强.其相关机制可能与改善心肌组织氧化应激、明显减轻心肌细胞凋亡有关.     

Aldosterone receptor antagonism induces reverse remodeling when added to angiotensin receptor blockade in chronic heart failure.

OBJECTIVES: The objective of this study was to determine if adding spironolactone to an angiotensin II receptor blocker improves left ventricular (LV) function, mass, and volumes in chronic heart failure. BACKGROUND: Add-on spironolactone therapy substantially improves clinical outcomes among patients with severe heart failure (HF) on standard therapy. However, the value of combining spironolactone with an angiotensin II receptor blocker on LV reverse remodeling in mild-to-moderate systolic HF is unclear. METHODS: Fifty-one systolic HF patients with left ventricular ejection fraction (LVEF) <40% were randomly assigned to receive 1-year treatment of candesartan and spironolactone (combination group) or candesartan and placebo (control group). Reverse remodeling was assessed by serial cardiac magnetic resonance imaging and echocardiographic tissue Doppler imaging (TDI). RESULTS: There were significant improvements in LVEF (35 +/- 3% vs. 26 +/- 2%, p < 0.01) and reduction of LV end-diastolic volume index (121 +/- 16 ml/m2 vs. 155 +/- 14 ml/m2, p = 0.001), end-systolic volume index (88 +/- 17 ml/m2 vs. 120 +/- 15 ml/m2, p < 0.0005), and LV mass index (81 +/- 6 g/m2 vs. 93 +/- 6 g/m2, p = 0.002) in the combination group at 1 year. In addition, there was significant increase in peak basal systolic velocity and strain by TDI, decrease in index of filling pressure, and increase in cyclic variation integrated backscatter. In the control group, there were no significant changes in all these parameters after 1 year. CONCLUSIONS: The addition of spironolactone to candesartan has significant beneficial effects on LV reverse remodeling in patients with mild-to-moderate chronic systolic HF.     

The impact of angiotensin-converting enzyme inhibitor therapy on the extracellular collagen matrix during left ventricular assist device support in patients with end-stage heart failure.

OBJECTIVES: We hypothesized that angiotensin-converting enzyme inhibition (ACE-I) during left ventricular assist device (LVAD) support in patients with end-stage heart failure prevents potentially deleterious effects on the extracellular matrix. BACKGROUND: Left ventricular assist device-induced mechanical unloading increases myocardial collagen and stiffness and may contribute to the low rate of recovery. METHODS: Heart samples obtained before and after LVAD implantation were divided into groups depending on whether the patients received (n = 7) or did not receive (control; n = 15) ACE-I. At transplant, ex vivo pressure-volume relationships were measured and chamber and myocardial stiffness constants determined. Myocardial tissue content of angiotensin (Ang) I and II, matrix metalloproteinase (MMP)-1, tissue inhibitor of MMPs (TIMP)-1, and total and cross-linked collagen was measured. RESULTS: Duration of support was comparable between ACE-I and control subjects (96 +/- 65 days vs. 109 +/- 22 days). Pre-LVAD Ang I and II and total and cross-linked collagen were similar between groups. Post-LVAD, Ang II was reduced in the ACE-I group but increased in control subjects (181 +/- 7 fmol/g vs. 262 +/- 41 fmol/g; p < 0.05). Similarly, cross-linked collagen decreased during LVAD support in the ACE-I group. Left ventricular (LV) mass and myocardial stiffness were lower in the ACE-I group. ACE-I normalized the LV and right ventricular (RV) MMP-1/TIMP-1 ratio. Collagen content and characteristics of the RV were not affected by ACE-I. CONCLUSIONS: ACE-I therapy was associated with decreased Ang II, myocardial collagen content, and myocardial stiffness during LVAD support. This is the first demonstration of a pharmacologic therapy that can impact myocardial properties during mechanical unloading, and it could foster new lines of investigation in strategies of enhancing myocardial recovery during LVAD support.