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To the Editor: Several wildlife-associated zoonotic agents have played a major role in the emergence of diseases in humans (1). However, diseases can also emerge in wildlife as a result [...]

Objective: To examine the proliferative effect of of raloxifene on human umbilical-vein endothelial cells (HUVECs), and to investigate whether there is an associated increased expression of some key regulators of the cell cycle. Design: Cell culture for different incubation times. Setting: University research laboratory. Patient(s): Sources of HUVECs. Intervention(s): Measurement of cell proliferation, of protein levels of cyclin A, cyclin B1, cyclin D1, cyclin-dependent protein kinase (CDK) 2, CDK4, and p27Kip1, and of messenger RNA expression of cyclin A, cyclin B1, and p27Kip1. Main Outcome Measure(s): Cell proliferation was measured by the 3-(4.5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, the bromo-2′-deoxyuridine assay, and the sodium 3′-[1-(phenylaminocarbonyl)-3,4-tetrazolium]-bis (4-methoxy-6-nitro) benzene sulfonic acid hydrate assay. Changes in protein expression were measured by immunoblotting, and modifications in gene expression were measured by quantitative real-time polymerase chain reaction. Result(s): Both 1 nM and 10 nM of either E2 or raloxifene achieved a similar increase in cell proliferation. The pure antiestrogen ICI 182780 only blocked the E2-induced proliferative effect. Western blot experiments detected an increase in the expression of only cyclin A and B1, and a decreasing trend for p27Kip1. Enhancements in gene expression were observed in response to E2 and raloxifene for cyclin A and B1. No significant changes were found for p27Kip1. The ICI 182780 effectively abrogated the increased gene expression associated with E2 for cyclin B1, but not for cyclin A. In contrast, ICI 182780 was ineffective in the case of raloxifene. Conclusion(s): Raloxifene increased the proliferation of HUVECs in association with enhanced gene expression of cyclins A and B1. [Copyright &y& Elsevier]

Abstract: Objective: Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide (NO) synthase, is a novel cardiovascular risk factor produced by endothelial cells. ADMA levels are mainly regulated by the activity of dimethylarginine dimethylaminohydrolases (DDAH). Endothelial release of ADMA is increased in the presence of oxidized LDL cholesterol (oxLDL), whereas estrogens stimulate NO production by endothelial cells by increasing both expression and activity of NO synthase and by reducing ADMA levels. Thus, the aim of the present study was to evaluate the estradiol effects on the DDAH/ADMA/NO pathway in cultured human umbilical vein endothelial cells (HUVEC) exposed to LDL. Methods: After 24 h of exposure to various treatments, culture medium was collected to measure NO production by using an amperometric sensor specific for NO, and to measure dimethylarginines by high-performance liquid chromatography (HPLC). DDAH-I and II mRNA expression and protein content were quantified by real-time PCR assay and immunoblotting, respectively. Results: Exposure of HUVEC to 100 μg/mL oxLDL, but not to 100 μg/mL of native LDL (nLDL), reduced DDAH-II expression at both the mRNA as well as the protein levels, which in turn increased ADMA levels and reduced NO production. Estradiol (1 nM) alone increased DDAH-II mRNA and protein expression, which reduced ADMA levels and increased NO production. In cells exposed to estradiol in combination with either nLDL or oxLDL, levels of DDAH-II, ADMA, and NO were the same as those for estradiol alone. Conclusion: Estradiol completely reverses the effects induced by oxLDL on the DDAH/ADMA/NO pathway. [Copyright &y& Elsevier]

We investigated the effect of a therapeutic dose of raloxifene on the plasma levels of myeloperoxidase and F2α-isoprostanes, two markers of oxidative stress recently described as reliable indicators of coronary heart disease. Contrary to changes described in the literature for estrogens (E), raloxifene did not modify the levels of either myeloproxidase or F2α-isoprostanes after 3 or 6 months of treatment. [Copyright &y& Elsevier]

Estradiol (E(2)) acts on the endothelium to promote vasodilatation through the release of several compounds, including prostanoids, which are products of arachidonic acid metabolism. Among these, prostacyclin (PGI2) and thromboxane A2 (TXA2) exert opposite effects on vascular tone. The role of different estrogen receptors (ERs) in the PGI2/TXA2 balance, however, has not been fully elucidated. Our study sought to uncover whether E(2) enhances basal production of PGI2 or TXA2 in cultured human umbilical vein endothelial cells (HUVECs), to analyze the enzymatic mechanisms involved, and to evaluate the different roles of both types of ERs (ERalpha and ERbeta). HUVECs were exposed to E(2), selective ERalpha (1,3,5-tris(4-hydroxyphenyl)-4-propyl-1h-pyrazole, PPT) or ERbeta (diarylpropionitrile, DPN) agonists and antagonists (unspecific: ICI 182 780; specific for ERalpha: methyl-piperidino-pyrazole, MPP). PGI2 and TXA2 production was measured by ELISA. Expression of phospholipases, cyclooxygenases (COX-1 and COX-2), PGI2 synthase (PGIS), and thromboxane synthase (TXAS) was analyzed by western blot and quantitative RT-PCR. E(2) (1-100 nM) dose dependently increased PGI2 production (up to 50%), without affecting TXA2 production. COX-1 and PGIS protein and gene expressions were increased, whereas COX-2, phospholipases, and TXAS expression remained unaltered. All these effects were mediated through ERalpha, since they were produced not only in the presence of E(2), but also in that of PPT, while they were abolished in the presence of MPP. In conclusion, E(2), acting through ERalpha, up-regulates COX-1 and PGIS expression, thus directing prostanoid balance toward increased PGI2 production.