Endothelial cell telomere dysfunction induces senescence and results in vascular and metabolic impairments

In advanced age, increases in oxidative stress and inflammation impair endothelial function, which contributes to the development of cardiovascular disease (CVD). One plausible source of this oxidative stress and inflammation is an increase in the abundance of senescent endothelial cells. Cellular senescence is a cell cycle arrest that occurs in response to various damaging stimuli. In the present study, we tested the hypothesis that advanced age results in endothelial cell telomere dysfunction that induces senescence. In both human and mouse endothelial cells, advanced age resulted in an increased abundance of dysfunctional telomeres, characterized by activation of DNA damage signaling at telomeric DNA. To test whether this results in senescence, we selectively reduced the telomere shelterin protein telomere repeat binding factor 2 (Trf2) from endothelial cells of young mice. Trf2 reduction increased endothelial cell telomere dysfunction and resulted in cellular senescence. Furthermore, induction of endothelial cell telomere dysfunction increased inflammatory signaling and oxidative stress, resulting in impairments in endothelial function. Finally, we demonstrate that endothelial cell telomere dysfunction-induced senescence impairs glucose tolerance. This likely occurs through increases in inflammatory signaling in the liver and adipose tissue, as well as reductions in microvascular density and vasodilation to metabolic stimuli. Cumulatively, the findings of the present study identify age-related telomere dysfunction as a mechanism that leads to endothelial cell senescence. Furthermore, these data provide compelling evidence that senescent endothelial cells contribute to age-related increases in oxidative stress and inflammation that impair arterial and metabolic function.     

Incidence of Friedreich ataxia in Italy estimated from consanguineous marriages

The frequency of consanguineous marriages up to second-cousin degree has been carefully established in the past for each of the 95 Italian provinces using the Archive of about 500,000 dispensations given by the Catholic church for such marriages over a 55-year period. It has therefore been possible to compare the frequency of consanguineous marriages observed among 83 couples of parents of Friedreich patients with the frequency of consanguineous marriages of the same degree in the different Italian provinces during the same years. From these data, an estimate of the incidence of the disease has been obtained for the whole nation (between 1/22,000 and 1/25,000). In Southern Italy, where 16 out of the 18 consanguineous marriages among Friedreich parents are concentrated, the incidence of the disease is similar (between 1/25,000 and 1/28,000). This study indicates that the Archive of consanguinity existing in Italy allows a reliable comparison of the frequency of consanguineous marriages among parents of patients with that of the general population. The same method can therefore be applied to the study of incidence of other autosomal recessive disorders in Italy.     

LOW PROFILE BIOPROSTHESIS FOR CARDIAC VALVE REPLACEMENT: EARLY CLINICAL RESULTS

Between May 1976 and April 1977, 100 patients underwent cardiac valve replacement with a unique low profile glutaraldehyde-treated porcine aortic xenograft. These patients were classified in four groups: Group I, 43 patients who underwent isolated mitral valve replacement (MVR); Group II, 27 patients who had isolated aortic valve replacement (AVR); Group III, 10 patients who had MVR and AVR; and Group IV, 20 patients who had MVR or AVR associated with other cardiac procedures. The operative mortality for Group I was 2.3% (1 of 43) and 15% (3 of 20) in Group IV. The total operative mortality was 4% (4 of 100) and the late mortality was 1.02% (1 of 96 survivors), who died apparently secondary to a cardiac arrhythmia. During a follow-up period extending for 16 months, thromboembolic complications occurred early in the postoperative period in 3% (3 of 100), one patient with neurological residual, and two patients with transient symptoms only. The embolic complications occurred only in Group I. Considering all patients in whom the mitral valves were replaced, the incidence of emboli was 4.9% (3 of 61). The 96 patients did not receive anticoagulant therapy. Reoperation was necessary in one patient because of periprosthetic leak. The incidence of endocarditis was 1.02% (1 of 96 survivors). We recommend anticoagulant therapy for eight to twelve weeks postoperatively in MVR patients after bioprosthetic insertion.     

Malondialdehyde is a biochemical marker of peroxidative damage in the isolated reperfused rat heart

Concentration of MDA in isolated control, ischemic, and reperfused rat hearts was determined by using a new sensitive and reproducible HPLC method on the perchloric acid extract of the freeze-clamped tissues. By means of this HPLC assay for the direct measurements of MDA, concentrations of adenine nucleotide derivatives were also obtained in the same chromatographic run. Under the present experimental conditions, no detectable amount of MDA could be observed in control hearts while ischemic hearts showed 0.009moles/g d. w. of MDA (s. d. = 0.001), this value representing the sensitivity limit of the method employed. On the contrary, reperfused hearts showed 0.118moles/g d.w. of MDA (s.d. = 0.036), thereby indicating that this compound originates from an oxygen free radical-mediated breakdown of phospholipids and demonstrating the existence of quantifiable molecular damage occurring upon reperfusion. On the whole, our data demonstrate that MDA, if properly assayed, is a reliable index of peroxidative injury to biological systems. (Mol Cell Biochem116: 193–196, 1992)Abbreviations Ado Adenosine - d.w. dry weight - HPLC High-Performance Liquid Chromatography - Hyp Hypoxanthine - Ino Inosine - MDA Malondialdehyde - Xan Xanthine     

Bovine seminal ribonuclease: Non-hyperbolic kinetics in the second reaction step

Peroxisomes contain enzymes catalyzing the β-oxidation of fatty acids, which have been purified and partially characterized. Hypolipidemic drugs, including clofibrate, cause a marked proliferation of peroxisomes and a striking increase in the activity of their β-oxidation system. We have compared by sodium dodecyl sulfate—polyacrylamide gel electrophoresis the polypeptide patterns of normal and clofibrate-induced peroxisomes and the purified β-oxidation enzymes. The data allow a tentative identification of the β-oxidation enzymes among the peroxisomal polypeptides; these enzymes constitute only a small part of the protein of normal peroxisomes. A subset of peroxisomal polypeptides, including the β-oxidation enzymes, is preferentially increased by clofibrate.     

Endothelial cell-specific reduction in mTOR ameliorates age-related arterial and metabolic dysfunction

Systemic inhibition of the mammalian target of rapamycin (mTOR) delays aging and many age-related conditions including arterial and metabolic dysfunction. However, the mechanisms and tissues involved in these beneficial effects remain largely unknown. Here, we demonstrate that activation of S6K, a downstream target of mTOR, is increased in arteries with advancing age, and that this occurs preferentially in the endothelium compared with the vascular smooth muscle. Induced endothelial cell-specific deletion of mTOR reduced protein expression by 60–70%. Although this did not significantly alter arterial and metabolic function in young mice, endothelial mTOR reduction reversed arterial stiffening and improved endothelium-dependent dilation (EDD) in old mice, indicating an improvement in age-related arterial dysfunction. Improvement in arterial function in old mice was concomitant with reductions in arterial cellular senescence, inflammation, and oxidative stress. The reduction in endothelial mTOR also improved glucose tolerance in old mice, and this was associated with attenuated hepatic gluconeogenesis and improved lipid tolerance, but was independent of alterations in peripheral insulin sensitivity, pancreatic beta cell function, or fasted plasma lipids in old mice. Lastly, we found that endothelial mTOR reduction suppressed gene expression of senescence and inflammatory markers in endothelial-rich (i.e., lung) and metabolically active organs (i.e., liver and adipose tissue), which may have contributed to the improvement in metabolic function in old mice. This is the first evidence demonstrating that reducing endothelial mTOR in old age improves arterial and metabolic function. These findings have implications for future drug development.     

The oxidation of Delta2, Delta2,4 and Delta4,6 steroids with RuO4

In order to find new ways for the functionalization of the A and B rings of the steroid nucleus, the reaction of 5alpha-androst-2-en-17beta-ol 17-acetate (1), cholesta-2,4-diene (4) and cholesta-4,6-dien-3beta-ol 3-acetate (7) was examined using stoichiometric amounts of ruthenium tetraoxide to yield 1,2-cis diols and/or alpha-hydroxy ketones. The reaction of 5alpha-cholest-2-en-3-ol 3-acetate (9) with ruthenium tetraoxide was also carried out and afforded, apart from an alpha-hydroxy ketone, also a diketone and a seco-dicarboxylic acid. The structures of all new steroids, including stereochemical details, were deduced by analysis of spectral data.     

S100A1 codistributes with synapsin I in discrete brain areas and inhibits the F-actin-bundling activity of synapsin I

The Ca2+-sensor protein S100A1 was recently shown to bind in vitro to synapsins, a family of synaptic vesicle phosphoproteins involved in the regulation of neurotransmitter release. In this paper, we analyzed the distribution of S100A1 and synapsin I in the CNS and investigated the effects of the S100A1/synapsin binding on the synapsin functional properties. Subcellular fractionation of rat brain homogenate revealed that S100A1 is present in the soluble fraction of isolated nerve endings. Confocal laser scanning microscopy and immunogold immunocytochemistry demonstrated that S100A1 and synapsin codistribute in a subpopulation (5-20%) of nerve terminals in the mouse cerebral and cerebellar cortices. By forming heterocomplexes with either dephosphorylated or phosphorylated synapsin I, S100A1 caused a dose- and Ca2+-dependent inhibition of synapsin-induced F-actin bundling and abolished synapsin dimerization, without affecting the binding of synapsin to F-actin, G-actin or synaptic vesicles. These data indicate that: (i) synapsins and S100A1 can interact in the nerve terminals where they are coexpresssed; (ii) S100A1 is unable to bind to SV-associated synapsin I and may function as a cytoplasmic store of monomeric synapsin I; and (iii) synapsin dimerization and interaction with S100A1 are mutually exclusive, suggesting an involvement of S100A1 in the Ca2+-dependent regulation of synaptic vesicle trafficking.