Constantina Heltianu

Relationship of eNOS gene variants to diseases that have in common an endothelial cell dysfunction

The endothelial cell (EC) dysfunction is a common characteristic of various pathologies that include atherosclerosis, hypertension, and Fabrys disease. Aware of the role of eNO and ACE in EC dysfunction, we questioned whether polymorphism of eNOS and/or ACE gene may be a common denominator in these pathologies. Patients with CHD (108), HT (109), Fabrys disease (37) and healthy subjects (control, 141) were genotyped for the eNOSG894T by RFLP‐PCR technique and for eNOS4b/a, and ACEI/D polymorphisms by PCR amplification. The results of these studies were statistically evaluated. Compared to controls, the frequency of the eNOSG894T (T allele) was higher in CHD (P=0.03) and Fabry (P=0.01), while the eNOS4b/a (a allele) in CHD (P=0.01) and HT patients (P=0.01). The proportion of the ACEI/D was similar in all subjects. In CHD patients at “low risk” of atherogenic factors, the frequency of the T and a alleles of eNOS gene was high (P=0.03 and 0.02, respectively). Carriers of the T allele of eNOSG894T were over‐represented (P=0.04) in Fabry subgroup with renal failure. Compared to women, the eNOS894T alleles were more frequent (P=0.03) in men with CHD and HT, whereas ACE I/D in men (P=0.03) with HT. These findings suggest: (i) the frequency of eNOSG894T and/or eNOS4b/a is significantly associated with coronary dysfunction; (ii) eNOS4b/a confers a relatively high risk of hypertension in subjects with atherogenic risk factors; (iii) the frequency of eNOSG894T is high in Fabry hemizygotes with renal complications. Therefore, eNOS gene polymorphism represent a frequent risk factor for vascular abnormalities in CHD, HT and Fabrys disease, afflictions which have in common, the endothelial dysfunction.

Protein and fatty acid composition of caveolae from apical plasmalemma of aortic endothelial cells

Abstract In endothelial cells (EC), caveolae or plasmalemmal vesicles (PVs) represent a structurally and biochemically specialized membrane microdomain. Since few data are available on the biochemical composition of PVs of large vessel endothelium, we have designed experiments to isolate this domain and to analyze its chemical components. A highly purified apical membrane fraction was obtained from cultured bovine aortic EC by using cationic colloidal silica (silica-ap), or the EC were surface-radioiodinated and a cell homogenate was prepared. Detergent treatment (Triton X-100; TX) and mechanical disruption of both the silica-ap fraction and cell homogenate followed by ultracentrifugation on a sucrose gradient gave detergent-soluble and detergent-insoluble membranous fractions. The lowest density TX-insoluble fraction appeared morphologically as distinct vesicles (caveolae; 60 nm average diameter; PVs fraction). Biochemical characterization of the PVs fraction (by comparison with the soluble fraction) revealed the presence, at high concentration, of specific caveolar markers, viz., caveolin (both isoforms, the 24-kDa form being conspicuously more abundant) and Ca2+-ATPase. By contrast, angiotensin-converting enzyme and alkaline phosphodiesterase were present almost exclusively in the TX-soluble fraction. The glycoproteins in the PVs fraction were of apparent molecular weights 52, 68, 95, and 114 kDa. Analysis of the fatty acid composition revealed more palmitoleic and stearic acid in the PVs fraction then in the TX-soluble fraction. Thus, in comparison with the plasmalemma proper, the PVs fraction (1) is detergent-insoluble; (2) contains caveolin in two isoforms; (3) contains Ca2+-ATPase at high concentration; (4) contains a set of specific glycoproteins; and (5) is enriched in palmitoleic and stearic acids.

Identification of gene variants in NOS3, ET-1 and RAS that confer risk and protection against microangiopathy in type 2 diabetic obese subjects.

The study aim was to investigate NOS3 VNTR, NOS3 G894T, EDN1 C8002T, ACE I/D, AGT M235T and AGTR1 A1166C in nonobese and obese T2DM patients, and their interaction with the incidence of microangiopathy. T2DM subjects (n=250; 166 nonobese, and 84 obese) were genotyped for the gene variants by PCR/RFLP. The interaction of these polymorphisms with obesity and their contribution to microangiopathy were analyzed by multivariate regression analysis. A higher frequency of NOS3 4a allele was found in obese (P=0.027) vs. nonobese subjects. ACE D (P=0.009) and AGT 235T (P=0.026) alleles were associated with the reduced risk of diabetic nephropathy in nonobese and obese patients, respectively. In obese subjects, NOS3 4a (P=0.011) had a converse effect to NOS3 894T (P=0.043), and EDN1 8002T (P=0.035) on the prevalence of combined microangiopathy (neuropathy/retinopathy/nephropathy) vs. microangiopathy-negative subjects. The study indicates association of RAS variants with obesity and nephropathy, and an opposite effect of NOS3 VNTR and NOS3 G894T on the occurrence of combined microangiopathy.

Evidence for thyroxine transport by the lung and heart capillary endothelium

The uptake and transport of carrier-bound thyroxine by the endothelium were investigated by perfusing through the heart and lung of young rats radiolabeled thyroxine bound to prealbumin ([125I]T4Pa) or serum ([125I]T4S). In addition these complexes were tagged to 5-nm gold particles to obtain quantitative (radioassay) and qualitative (autoradiography) data from the same experiment. The complexes (prewarmed at 37 degrees) were perfused in situ at various concentrations (1 to 50 muCi/ml) for time intervals ranging from 5 to 30 min. After thorough washing of the unbound probe, tissue fragments were either measured for total uptake in a gamma counter or processed for electron microscopy autoradiography. The results showed that both the lung and heart take up [125I]T4 complexes by a process that is saturable at low hormone concentration; uptake is completed by free T4 and Pa. In specimens perfused with double-labeled complexes (iodinated and tagged to gold) autoradiography revealed that silver grains and gold particles colocalize predominantly on endothelial plasmalemmal vesicles. The probe appeared first in vesicles open to the capillary lumen (5 min) and further on in vesicles apparently free within the cytoplasm or open to the abluminal front. At 30 min, only silver grains seem to be present in the pericapillary space, on the alveolar epithelial cells, as well as on the nucleus and mitochondria of heart myocytes. The findings suggest that (1) T4Pa uptake by the endothelial cell (EC) is a specific process (possibly via specific binding sites); (2) T4Pa is taken up and transported across capillary EC by plasmalemmal vesicles; (3) in the pericapillary space T4 seems to dissociate from its carrier.

Immunological detection of an analogue of the erythroid protein 4.1 in endothelial cells.

Endothelial cells (EC) of arterial and venous origin were investigated by indirect immunofluorescence and immunoautoradiography for the presence of red cell membrane 4.1-like protein. By immunofluorescence, EC exhibited a relatively uniform fluorescent staining sometimes of a reticular pattern, distributed over the entire cell. All controls were negative. Immunoblot analysis of EC revealed a cross reactive band of a molecular weight comparable to that of the erythrocyte band 4.1. These findings indicate that endothelial cells of arterial and venous origin express a polypeptide immunologically related to the erythrocyte protein 4.1, which may play an important role in membrane-cytoskeleton interactions.

Role of Nitric Oxide Synthase Family in Diabetic Neuropathy

Diabetes mellitus is one of the most common chronic diseases and a major health problem in nearly all countries. Its prevalence has risen sharply worldwide during the past few decades. The increase in its prevalence is largely due to an epidemic of type 2 diabetes (T2DM) but also the type 1 diabetes (T1DM) incidence is rising all over the world. The “classical” microvascular complications of both types of diabetes are represented by diabetic retinopathy, diabetic renal disease, and diabetic polyneuropathy (DPN). The latter has known to be heterogeneous regarding symptoms, pattern of neurologic involvement, and progression in time, pathologic alterations, and underlying mechanisms. DPN results from the direct damage of peripheral nerve components and of the associated vasa nervorum. The main contributor to the DPN development is the cumulative effect of chronic hyperglycemia - duration of diabetes and level of metabolic control. Apart the major role of hyperglycemia one of the most important factor is nitric oxide (NO) system. The NO production and local release are dramatically changed and contribute to the DPN development. The process takes place by the modulation of the nitric oxide synthase (NOS) enzymes responsible for NO synthesis by the diabetic milieu. While the decline in NO bioavailability is due to the decrease in neuronal (NOS1) and endothelial (NOS3) expression, the increase of local NO levels with the formation of peroxynitrites arises from the upregulation of inducible (NOS2) protein. Thus, NOS genes became natural candidates for the study of DPN genetics. In comparison with the other diabetes microvascular complications, data regarding the genetic background of DPN are rather scarce, particularly for NOS genes. The aim of this review is to present the pathogenesis of DPN in both type 1 and type 2 diabetes and the effect of the NOS genes-NOS enzymes-NO system.

Genetic Determinants of Microvascular Complications in Type 1 Diabetes

Diabetes mellitus is one of the most prevalent chronic diseases of modern societies and a major health problem in nearly all countries. Its prevalence has risen sharply worldwide during the past few decades (Amos et al., 1997; Shaw et al., 2010). Moreover, predictions show that diabetes prevalence will continue to rise, reaching epidemic proportions by 2030: 7.7% of world population, representing 439 million adults worldwide (Shaw et al., 2010). This increase is largely due to the epidemic of obesity and consequent type 2 diabetes (T2DM). However, the incidence of type 1 diabetes (T1DM) is also rising all over the world (DiaMond Project Group, 2006; Maahs et al., 2010). Recent data for Europe (Patterson et al., 2009) predict the doubling of new cases of T1DM between 2005 and 2020 in children younger than 5 years and an increase of 70% in children younger than 15 years, old. Despite major progresses in T1DM treatment during the past decades, mortality in T1DM patients continues to be much higher than in general population, with wide variations in mortality rates between countries. In Europe, these variations are not explained by the country T1DM incidence rate or its gross domestic product, but are greatly influenced by the presence of its chronic complications, especially diabetic renal disease (Groop et al., 2009; Patterson et al., 2007). In fact, much of the health burden related to T1DM is created by its chronic vascular complications, involving both large (macrovascular) and small (microvascular) blood vessels. Many genetic, metabolic and hemodynamic factors are involved in the genesis of diabetic vascular complications. However, major epidemiological and interventional studies showed that chronic hyperglycemia is the main contributor to diabetic tissue damage (DCCT Research Group, 1993). If the degree of metabolic control remains the main risk factor for the development of diabetic chronic complications, an important contribution can be attributed to genetic risk factors, some of them common for all microvascular complications (diabetic retinopathy, neuropathy, and renal disease) and some specific for each of them (Cimponeriu et al., 2010). Additional factors are represented by some accelerators such as hypertension and dyslipidemia. In the following pages, we present briefly the pathogenesis type 1 diabetes and its chronic microvascular complications. The main information of the genetic background in T1DM with particular focus on gene variants having strong impact on endothelial dysfunction as the key factor in the development of microvascular disorders are also summarized.