Judith Attias

The angiotensin-converting enzyme inhibitor, fosinopril, and the angiotensin II receptor antagonist, losartan, inhibit LDL oxidation and attenuate atherosclerosis independent of lowering blood pressure in apolipoprotein E deficient mice

OBJECTIVE To investigate the possible mechanisms of the antiatherosclerotic effects of the angiotensin-converting enzyme (ACE) inhibitor, fosinopril, in apolipoprotein (apo) E deficient mice. METHODS Apo E deficient (E0) mice at the age of 8 weeks received either placebo or a high dose (25 mg/kg/d) of fosinopril supplemented in their drinking water. RESULTS After 12 weeks of treatment, fosinopril reduced the aortic lesion size by 70%, compared with the placebo group. At this dosage, fosinopril significantly reduced blood pressure from 93 +/- 2 mmHg before treatment to 70 +/- 2 mmHg at the end of the treatment period (P < 0.005). Fosinopril also increased the resistance of the mice plasma low density lipoprotein (LDL) to CuSO4-induced oxidation, as shown by a 90% reduction in the LDL content of malondialdehyde (MDA) and also by a prolongation of the lag time required for the initiation of LDL oxidation (from 100 min in the placebo-treated mice to more than 240 min in the fosinopril-treated mice; P < 0.001). In addition, fosinopril inhibited CuSO4-induced oxidation of LDL that was obtained from the aortas of the treated mice, as shown by an 18% and 37% reduction in the LDL content of lipid peroxides and hydroperoxy-cholesterol linoleate, respectively, compared with the placebo-treated mice (P < 0.01). A low dosage of fosinopril (5 mg/kg/d) that was still adequate to reduce their plasma ACE activity and LDL propensity to lipid peroxidation was insufficient to lower their blood pressure. This dosage also reduced the aortic lesion size in the apo E deficient mice by 40% (P < 0.01). CONCLUSIONS The antiatherogenic effects of fosinopril in apo E deficient mice are due not only to blood pressure reduction but also to the direct inhibition of angiotensin II-dependent effects, which are probably also associated with the inhibition of LDL oxidation.

Antiatherosclerotic and antioxidative effects of captopril in apolipoprotein E-deficient mice

The effect of the angiotensin-converting enzyme (ACE) inhibitor, captopril, on the development of atherosclerosis was determined in the apolipoprotein (apo) E-deficient mice. These mice develop severe hypercholesterolemia and extensive atherosclerotic lesions on chow diet, similar to those found in humans. Furthermore, in these mice, accelerated atherosclerosis is associated with increased plasma lipid peroxidation, a phenomenon that may play a crucial role in the buildup of the atherosclerotic lesions. Mice received either placebo or 50 mg/kg/day of captopril. After 12 weeks of treatment, captopril reduced the aortic-lesion area by 70% compared with that of the placebo-treated group. Captopril also increased the resistance of low-density lipoprotein (LDL) to CuSO4-induced oxidative stress, as shown by a significant reduction in the LDL content of malondialdehyde (MDA) by 30%, as well as by the prolongation of the lag time required for LDL oxidation from 55 min in the placebo-treated mice to 70 min in the captopril-treated mice, and reduction of the maximum LDL oxidation at 150 min by 35%. In vitro studies demonstrated that preincubation of LDL with captopril, inhibited the onset of CuSO4-induced LDL peroxidation up to 120 min, and reduced the LDL content of MDA by 90%. We conclude that captopril attenuates atherosclerosis in the apo E-deficient mice, and this phenomenon may be related to its inhibitory effect on the plasma LDL oxidation.

Angiotensin II atherogenicity in apolipoprotein E deficient mice is associated with increased cellular cholesterol biosynthesis

Angiotensin II (Ang II) was shown to be an important risk factor for accelerated atherosclerosis. Inhibition of Ang II action on the arterial wall by blocking its production with angiotensin converting enzyme (ACE) inhibitors, or by blocking binding to its receptors on cells with antagonists was shown to attenuate atherogenesis in animal model of atherosclerosis. We questioned whether Ang II atherogenicity is related to a stimulatory effect of Ang II on macrophage cholesterol biosynthesis. Angiotensin II injected intraperitoneally once a day (0.1 ml of 10(-7) M per mouse) for a period of 30 days, to the apolipoprotein E deficient mice increased the atherosclerotic lesion area by 95% (P < 0.01 vs. control), compared to placebo-injected mice, with no significant effect on blood pressure or on plasma cholesterol levels. On using mouse peritoneal macrophages (MPMs) that were harvested after intraperitoneally injection of Ang II, an increased rate of cellular cholesterol biosynthesis (measured as incorporation of [3H]acetate into cholesterol) by up to 90% (P < 0.01 vs. control) was observed. In mice treated with the ACE inhibitor, Fosinopril (25 mg/kg per day) a reduction in their MPMs cholesterol synthesis by up to 70% (P < 0.01 vs. control) was obtained. In vitro studies in human monocyte-derived macrophages (HMDM), in MPMs from control BALB/c mice, and in J-774 A.1 macrophage-like cell line demonstrated up to 44, 34 and 30% stimulation of macrophage cholesterol biosynthesis, respectively, following cell incubation with 10(-7) M Ang II for 18 h at 37 degrees C. The stimulatory effect of Ang II on macrophage cholesterol biosynthesis could be related to its interaction with the macrophage AT1 receptor, as Losartan (10(-5) M), an AT1 blocker, but not PD 123319 (10(-5) M), an AT2 blocker, prevented the stimulatory effect on macrophage cholesterol synthesis. Furthermore, in cells that lack the AT1 receptor (RAW macrophages), Ang II did not increase cellular cholesterol synthesis. Ang II increased macrophage 3-hydroxy-3-methyl glutaryl CoA (HMG CoA) reductase mRNA levels in a dose dependent manner in J-774 A.1 macrophages and in MPM. Losartan, the AT1 receptor antagonist clearly attenuated this mRNA induction. We thus conclude that Ang II stimulation of macrophage cholesterol biosynthesis is related to its interaction with the AT1 receptor, followed by stimulation of macrophage HMG CoA reductase gene expression, which leads to increased cellular cholesterol biosynthesis, and can possibly result in macrophage cholesterol accumulation and foam cell formation.

Attenuation of atherosclerosis in apolipoprotein E-deficient mice by ramipril is dissociated from its antihypertensive effect and from potentiation of bradykinin.

We investigated the mechanism of the antiatherosclerotic effect of the angiotensin-converting enzyme (ACE) inhibitor, ramipril, in the apolipoprotein (apo) E-deficient mice. Mice that received a high dose (5 mg/kg/day) of ramipril supplemented in their drinking water for 10 weeks showed reduced aortic lesion size by 75% compared with placebo-treated mice. At this dosage, ramipril significantly reduced blood pressure from 95+/-5 mm Hg before treatment to 68+/-4 mm Hg at the end of the treatment period. Ramipril also increased the resistance of the mouse low-density lipoprotein (LDL) to CuSO4-induced oxidation, as shown by a prolongation of the lag time required for the initiation of LDL oxidation from 90 min in the placebo-treated mice to >180 min in the ramipril-treated mice. Similarly, a reduction in the maximal LDL-associated conjugated dienes after 180 min of oxidation by 250% in comparison with placebo-treated mice was noted. Ramipril (1 mg/kg/day) that was still adequate to reduce their plasma ACE activity and LDL propensity to lipid peroxidation was insufficient to reduce their blood pressure. This dosage also inhibited the progression of atherosclerosis in the apo E-deficient mice by 74%. The contribution of bradykinin potentiation to the ACE-inhibitor action was assessed by cotreatment of ramipril with the bradykinin B2-receptor antagonist, icatibant (HOE-140, 0.5 mg/kg given subcutaneously twice a day) for a period of 10 weeks. HOE-140 had no effects on ACE activity, LDL lipid peroxidation, blood pressure, or atherosclerosis. In combination with ramipril, no additional effect of HOE-140 on LDL oxidation or on atherosclerosis was noted in comparison with ramipril treatment alone. We thus conclude that the antiatherogenic effect of ramipril in E(0) mice is independent of blood pressure reduction and is not mediated by bradykinin. It seems, therefore, that most of its antiatherosclerotic and antioxidative effects are mediated through the inhibition of angiotensin II production.

Cardiac Troponin I Elevation in Hospitalized Patients Without Acute Coronary Syndromes

Increase of cardiac troponins occurs in a variety of clinical situations in the absence of an acute coronary syndrome (ACS). Few data exist regarding the incidence, clinical characteristics, and predictive value of various cardiac diagnostic tests and outcome of patients with a non-ACS-related troponin increase. We studied 883 consecutive hospitalized patients with increased cardiac troponin I levels. The discharge diagnosis was reclassified and troponin increase attributed to ACS or another process. Clinical data and results of cardiac diagnostic tests were collected. Patients were followed for a median of 30 months. Three hundred eleven patients were classified as having a non-ACS-related troponin increase (35.2%). An alternative explanation for troponin increase was found in 99% of these patients. Troponin level had poor accuracy in discriminating patients with and without ACS (area under the receiver operating characteristics curve 0.63). Coronary angiography was frequently unhelpful in excluding a non-ACS-related troponin increase because 77% of patients in the non-ACS group had significant flow-limiting coronary artery disease. Patients with non-ACS-related troponin increase had significantly higher in-hospital (hazard ratio 2.8, 95% confidence interval 2.0 to 3.8) and long-term (hazard ratio 2.0, 95% confidence interval 1.6 to 2.5) mortalities compared with patients with ACS. In conclusion, cardiac troponin level is frequently increased in hospitalized patients in the absence of an ACS and portends poor short- and long-term outcomes. Most of these patients have an alternative explanation for cardiac troponin increase. Cardiac diagnostic procedures are frequently unhelpful in excluding a non-ACS-related troponin increase.

Alcohol Poisoning and Venous Hyperoxia

ABSTRACT Venous PCO2 and PO2 in the presence of normal arterial PCO2 and PO2 in patients with alcoholic intoxication have not been previously evaluated. The objective of this study was to compare arterial and venous blood gases in patients with alcoholic intoxication and healthy controls. Sixteen patients with alcoholic intoxication and 20 controls underwent simultaneous blood sampling from a radial artery and an antecubital vein for acid-base analysis. Osmolality and ethanol blood concentration was estimated. Elevated venous pO2 were found in 56% of patients with alcoholic poisoning compared with 15% of controls. A formula was found describing possible arterio-venous shunt accounting for elevated venous pO2 and enabling calculation of the relevant venous carbon dioxide content and CO2 product. The values of the venous pO2 and arterio-venous shunt were more significant in the alcohol group than in controls (p = 0.002, p = 0.001, respectively). Percentage of patients with a-v shunts was significantly higher in the alcohol group (81%) than in controls (25%) (p = 0.002, OR 2.6, 95% CI 0.13–6.52). The relevant venous CO2 and CO2 product had the non-significant trend to be higher in the alcohol group. In conclusion, this study reports ethanol-induced venous pO2 and pCO2 elevation. This may be associated with the effects of tissue perfusion stealing and high oxygen consumption. On the other hand, possible beneficial consequences may occur: acceleration of alcohol elimination and reduction of alcohol-induced tissue damage.