Angiotensin converting enzyme inhibition prevents polyploidization of cardiomyocytes in spontaneously hypertensive rats with left ventricular hypertrophy

Loss of FHIT protein expression is related to high proliferation, low apoptosis and worse prognosis in non-small-cell lung cancer

The fragile histidine triad (FHIT) gene, located at chromosome 3p14.2, is deleted in many solid tumors, including lung cancer. Its protein product is presumed to have tumor suppressor function. We investigated the incidence of loss of heterozygosity and loss of FHIT expression in a series of non-small-cell lung carcinomas and its correlation to apoptosis, proliferation index and prognosis. FHIT expression was determined by immunohistochemistry in formalin-fixed paraffin-embedded tissues from 54 squamous cell carcinomas (SCC) and 44 adenocarcinomas (AC) of the lung. DNA from frozen tumor and corresponding normal tissues were analyzed for allelic losses at two loci located internal (D3S1300, D3S1234) and three loci in flanking regions centromeric and telomeric (D3S1210, D3S1312, D3S1313) to the FHIT gene. Apoptosis was detected by terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL). Proliferation index was determined with ki-67 and flow cytometric analysis. We correlated the results with tumor histology, prognosis and some immunohistochemical markers (p53, bcl-2, bax, c-myc, p21(waf1), cyclin-D1). FHIT expression was related to tumor histology: 52 of 54 (96.3%) SCC and 20 of 44 (45.5%) AC were negative for FHIT (P<0.0001). We found LOH at 3p14.2 in 67.8% of the 98 cases: 72.3% of SCC and 61.4% of AC. Loss of FHIT expression was associated with a higher proliferation index (ki-67, P=0.007; flow cytometry, P<0.004) and lower apoptotic index (P=0.018). LOH at FHIT gene were associated to a high proliferation (flow cytometry, P<0.001) and lower apoptotic level (P=0.043). The log-rank test demonstrated a significant inverse correlation (P=0.039) between loss of FHIT expression and patient survival. FHIT plays an important role in the development of non-small-cell lung cancer, particularly in SCC. Loss of FHIT protein is correlated with a high proliferation and low apoptotic index in tumor cells, and is an independent prognostic indicator for the clinical outcome in patients with these tumors.

Genes governing placental development

The placenta is essential for fetal growth because it promotes the delivery of nutrients and oxygen from the maternal circulation. In mice, many gene mutations disrupt formation of the placenta, with specific effects at different times and on different components. Studies of these mutations are beginning to provide insights into both the molecular pathways required for formation of different placental substructures and the nature of intercellular interactions, between trophoblast, mesenchymal and vascular components, that regulate placental development. Conserved gene expression patterns in humans should enable the elucidation of the molecular basis of human placental dysfunction.

Genes regulating embryonic and fetal survival

Embryonic mortality in both farm animals and humans occurs most frequently during the first few weeks after conception. It can be attributed to abnormalities in the earliest developmental processes during embryogenesis that include implantation, maternal recognition of pregnancy, and formation of the placenta and cardiovascular system. The molecular mechanisms that are essential for all of these early processes are being elucidated at a rapid pace using transgenic and gene knockout approaches in mice. Two important general conclusions have emerged from this work. First, placental defects can occur by a number of different molecular mechanisms and can result from defects in the development or function of its trophoblast, mesenchymal or vascular components. Second, placental and cardiovascular functions are intimately linked. Cells of the placenta, for example, produce hormones that have profound effects on maternal and fetal cardiac and vascular function. In addition, development of the two is linked mechanistically through the use of some genes that are essential for development of both. Understanding the molecular basis of these processes should help to address the major limits to the success of embryo transfer, IVF and embryo cloning practices in livestock species.

Effect of chronic angiotensin II inhibition on the cardiovascular system of the normal rat

Previous studies have demonstrated in normal rats that chronic treatment, from weaning to 30 days, with either enalapril or losartan, induced significant changes in cardiovascular structure and function. The present study was performed to assess the effect of either enalapril or losartan on the structure and function of the heart and arteries given to normal rats from weaning until 6 months of age. Animals (n = 48) were divided into three groups: control, enalapril treated, and losartan treated; treated rats received 10 mg/kg/day of drug. Blood pressure, body weight, and water intake were recorded for that time period. DNA, cGMP, collagen, degree of fibrosis, and nitric oxide synthase-NADPH-diaphorase-dependent activity in the heart and arteries were determined. Only significant differences (P < .05) are reported. Blood pressure increased only in control rats (13 +/- 1 mm Hg), enalapril treatment enhanced water intake and reduced the rate of body growth (control, 672.9 +/- 15.4 g; losartan, 692.4 +/- 21.8 g; enalapril, 541.8 +/- 13.8 g). In the heart, DNA (control, 120 +/- 5; losartan, 99 +/- 4; enalapril, 93 +/- 6 microg/100 mg), collagen (control, 2.5 +/- 0.2; enalapril, 1.85 +/- 0.08 microg/100 mg), and fibrosis (control, 3.5 +/- 0.4%; losartan, 2.2 +/- 0.3%; enalapril, 2.1 +/- 0.4%) were reduced by treatment. In the aorta, cGMP (control, 0.15 +/- 0.01; losartan, 0.24 +/- 0.02 pmol/mg), and NADPH-diaphorase (control, 0.114 +/- 0.003; losartan, 0.148 +/- 0.006; enalapril, 0.169 +/- 0.003 as optical density) were enhanced. The enzyme was also higher in the aortic endothelium of treated animals (control, 0.193 +/- 0.010; losartan, 0.228 +/- 0.009; enalapril, 0.278 +/- 0.005). The lower rate of body weight increase, the enhanced water intake, and the reduced cardiac and left ventricular weight attributable to enalapril treatment do not seem to be related to inhibition of the renin-angiotensin system. On the other hand, renin-angiotensin system inhibition induces a protective effect on the heart and aorta through structural and functional changes. Most of this action seems to be exerted through angiotensin II type 1 receptors.

Apoptosis during regression of cardiac hypertrophy in spontaneously hypertensive rats. Temporal regulation and spatial heterogeneity

We previously reported that increased apoptosis participates in the regression of aortic hypertrophy in spontaneously hypertensive rats. To further document the potential role of apoptosis in cardiovascular therapy, we examined apoptosis during regression of hypertrophy in the heart of spontaneously hypertensive rats receiving the antihypertensive drug enalapril (30 mg. kg(-1). d(-1)), losartan (30 mg. kg(-1). d(-1)), nifedipine (35 mg. kg(-1). d(-1)), hydralazine (40 mg. kg(-1). d(-1)), propranolol (50 mg. kg(-1). d(-1)), or hydrochlorothiazide (75 mg. kg(-1). d(-1)) for 1 to 4 weeks, starting at 10 to 11 weeks of age. Systolic blood pressure and heart rate were measured by the tail-cuff method. Markers of apoptosis included oligonucleosomal DNA fragmentation in extracted cardiac DNA or in situ in ventricular cross sections labeled with terminal deoxynucleotidyl transferase. Cardiac DNA synthesis was evaluated by [(3)H]-thymidine incorporation in vivo. All drugs reduced cardiac workload, defined as the product of blood pressure and heart rate, by >20% at 4 weeks. However, only nifedipine, enalapril, losartan, and propranolol reduced cardiac mass (>19%) within 4 weeks. Regression of cardiac hypertrophy was accompanied by a 50% to 300% increase in DNA fragmentation and a >20% reduction in DNA synthesis, resulting in a >20% reduction in cardiac DNA content after 4 weeks. Apoptosis induction occurred early and was transient within 4 weeks of nifedipine, enalapril, or losartan administration. With all regression-inducing drugs, the increase in DNA fragmentation occurred mainly in the subepicardium. Thus, transient induction of apoptosis in the subepicardium appears to be a characteristic feature of the early response to drug-induced regression of cardiac hypertrophy in spontaneously hypertensive rats.

Effect of enalapril treatment on the heart of normal rats

Previous experiments showed that enalapril (EN) treatment as well as enalaprilic acid, when added to the perfusion bath, diminish the inotropic response of the papillary muscles to isoproterenol (ISO). The main objective of this study was to evaluate, in normal rats, the effect of EN on basal contractility and inotropic response to ISO on the whole perfused ventricles (Langendorff preparation). Blood pressure (BP), increase in body weight (IBW), ventricular weight/body weight ratio (R) and concentration of ventricular proteins and DNA were also analyzed. Five groups were studied: EN10: 5 mg/kg/day, 10 days; EN21(L): 5mg/kg/day, 21 days; EN21(H): 15 mg/kg/day, 21 days. C10 and C21 were untreated controls. Cardiac contractility was evaluated by the maximal developed pressure, maximal rate of rise of pressure and maximal velocity of relaxation; no changes were found due to EN treatments either on basal conditions or on ISO stimulation. Significant differences (p<0.05 vs C21) were: lower BP and R in EN21(L) and EN21(H), slower IBW in EN21(H), decreased ventricular DNA in EN21(H). In conclusion, daily treatment for ten or twenty one days with enalapril does not change either basal cardiac contractile performance or inotropic response to ISO in the Langendorff preparation. Longterm treatment with EN seems to modify nuclear processes involved in cardiomyocite DNA content.

Overexpression of Bax protein and enhanced apoptosis in the left ventricle of spontaneously hypertensive rats: effects of AT1 blockade with losartan

An association of increased apoptosis with overactivity of the local angiotensin-converting enzyme has been reported in cells from the left ventricle of adult rats with spontaneous hypertension (SHR). To gain insight into the regulation of cardiac apoptosis in arterial hypertension, we investigated the expression of the proteins Bcl-2 (an inhibitor of apoptosis) and Bax (an inducer of apoptosis) in the left ventricle of 30-week-old normotensive Wistar-Kyoto rats (WKY), SHR, and SHR treated with the angiotensin II type 1 receptor (AT1) antagonist losartan (20 mg x kg(-1) x d(-1)) during 14 weeks before death. The density of apoptotic cells was assessed by direct immunoperoxidase detection of biotin-labeled deoxyuridin nucleotides. The expression of Bcl-2 and Bax was assessed by Western blot analysis. Compared with WKY, untreated SHR exhibited increased (P<0.05) apoptosis, increased (P<0.01) Bax, and similar Bcl-2. The Bcl-2/Bax ratio (an inverse index of cell susceptibility to apoptosis) was lower (P<0.05) in untreated SHR than in WKY. The chronic administration of losartan was associated with the normalization of apoptosis, Bax expression, and the Bcl-2/Bax ratio in treated SHR. No changes in the expression of Bcl-2 were observed in these rats after treatment. No significant changes in the apoptotic density were observed between treated SHR with normal blood pressure and treated SHR with abnormally high blood pressure at the end of the treatment period. These results suggest that an association exists between increased apoptosis and overexpression of Bax oncoprotein in cells from the left ventricle of adult SHR. Chronic blockade of AT1 receptors prevents Bax overexpression and normalizes apoptosis in the left ventricle of SHR independently of its hemodynamic effect. On the basis of our findings, it can be proposed that the interaction of angiotensin II with its AT1 receptors may participate in the stimulation of Bax protein, which in turn renders cells from the left ventricle of SHR more susceptible to apoptosis.

Cardiomyocyte apoptosis and cardiac angiotensin-converting enzyme in spontaneously hypertensive rats

Increased apoptosis has been reported in the heart of rats with spontaneous hypertension and cardiac hypertrophy. This study was designed to investigate the relationship between apoptosis and hypertrophy in cardiomyocytes from the left ventricle of spontaneously hypertensive rats (SHR). In addition, we evaluated whether the development of cardiomyocyte apoptosis is related to blood pressure or to the activity of the local angiotensin-converting enzyme (ACE) in SHR. The study was performed in 16-week-old SHR, 30-week-old untreated SHR, and 30-week-old SHR treated with quinapril (10 mg x kg[-1] x d[-1]) during 14 weeks before they were killed. Cardiomyocyte apoptosis was assessed by direct immunoperoxidase detection of digoxigenin-labeled 3'-hydroxyl ends of DNA. Nuclear polyploidization measured by DNA flow cytometry was used to assess cardiomyocyte hypertrophy. Compared with 16-week-old normotensive Wistar-Kyoto rats, 16-week-old SHR exhibited increased blood pressure (P<.001), increased rate of tetraploidy (P<.05), and similar levels of ACE activity and apoptosis. Compared with 30-week-old Wistar-Kyoto rats, 30-week-old SHR showed increased blood pressure (P<.001), increased ACE activity (P<.05), increased rate of tetraploidy (P<.01), and increased apoptosis (P<.01). Untreated 30-week-old SHR exhibited similar values of blood pressure and tetraploidy and higher ACE activity (P<.05) and apoptosis (P<.001) than 16-week-old SHR. A direct correlation (P<.01) was found between ACE activity and the apoptotic index in untreated 30-week-old SHR. The long-term administration of quinapril was associated with the normalization of ACE activity and apoptosis in treated SHR. These results suggest that the timing and mechanisms responsible for apoptosis and hypertrophy of cardiomyocytes are different in SHR. Whereas hypertrophy seems to be an earlier alteration that develops in parallel with hypertension, apoptosis develops later in association with overactivity of the local ACE. Our data suggest that cell death dysregulation may be a novel target for antihypertensive agents that interfere with the renin-angiotensin system in hypertension.