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Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide (NO) synthase. ADMA accumulation, mainly due to a decreased dimethylarginine dimethylaminohydrolase (DDAH) activity, has been related to the development of cardiovascular diseases. We investigate whether estradiol prevents the changes induced by oxidized low density lipoprotein (oxLDL) on the DDAH/ADMA/NO pathway in human umbilical artery endothelial cells (HUAEC). HUAEC were exposed to estradiol, native LDL (nLDL), oxLDL and their combinations for 24 h. In some experiments, cells were also exposed to the unspecific estrogen receptor (ER) antagonist ICI 182780, the specific ERα antagonist MPP or specific agonists for ERα, ERβ and GPER. ADMA concentration was measured by HPLC and concentration of NO by amperometry. Protein expression and DDAH activity were measured by immunoblotting and an enzymatic method, respectively. oxLDL, but not nLDL, increased ADMA concentration with a concomitant decrease on DDAH activity. oxLDL reduced eNOS protein and NO production. Estradiol alone had no effects on DDAH/ADMA/NO pathway, but increased the attenuated endothelial NO production induced by oxLDL by reduction in ADMA and preventing loss of eNOS protein levels. ICI 182780 and MPP completely abolished these effects of estradiol on oxLDL-exposed cells. ERα agonist, but not ERβ and GPER agonists, mirrored estradiol effects on NO production. In conclusion, estradiol restores (1) DDAH activity, and therefore ADMA levels, and (2) NO production impaired by oxLDL in HUAEC acting through ERα.

Nervous tissue, central and peripheral, is, as any other, subject to variations in oxygen tension, and to the attack of different xenobiotics; these situations may promote the generation of activated oxygen species of free radical character. Results are presented showing that the content of total glutathione (GSH) in brain is 10-fold that found in the sciatic nerve of the rat (2620 vs. 261 nmol/g wet weight, respectively). The existence of a relatively high superoxide dismutase activity in peripheral nervous tissue, when compared with brain or liver, in combination with the DT-diaphorase activity detected in the sciatic nerve might represent an effective defense mechanism against quinone toxicity, as is also discussed. Nervous tissue, both central and peripheral lack Se-independent GSH peroxidase activity. Finally, the activities of other glutathione-related enzymes studied in the sciatic nerve are very low, when compared with the central nervous tissue, thus suggesting a higher susceptibility of peripheral tissue to oxidative stress damage, since GSH concentration and/or any GSH-related enzymatic activities, e.g. GSH peroxidase or glutathione disulfide reductase, might become limiting.

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.

The present work tries to establish the antioxidant capacity of the peripheral nervous tissue of the rat, in terms of the enzymatic activities present in this tissue that either prevent the formation of activated species as the semiquinone radical (DT-diaphorase), protect against activated oxygen species (superoxide dismutase, glutathione peroxidase), conjugate natural toxic products or xenobiotics (glutathione S-transferases, especially the activity conjugating 4-hydroxy-nonenal), or complete the glutathione system metabolism (glutathione disulfide reductase, γ-glutamyl transpeptidase). All the activities studied are lower in this tissue than they are in liver, except for γ-glutamyl transpeptidase. The relevance of the results obtained and its possible relationship with different neuropathies is discussed. It is concluded that the peripheral nervous tissue is by far less protected than the liver against oxidative damage.

We have studied the biochemical and immunohistochemical changes of DT-diaphorase in diethylstilbestrol (DES)-induced hamster kidney tumours and human biopsies from normal kidneys and renal clear cell carcinoma. The activities of primary and secondary antioxidants in these hamster and human tissues are also reported. DT-diaphorase is decreased in the different subcellular fractions of hamster and human tissues. In hamster kidney the activities of the one-electron quinone reductases show a nearly two-fold increase. Immunohistochemical findings confirm the decrease in DT-diaphorase in hamster and human tissues. This image is of special interest in the case of nephroblastoma (Wilms' tumour), since it has been proposed that the DES-induced tumour is a 'nephroblastoma-like' one. Primary anti oxidant enzymatic activities, i.e. superoxide dismutase and glutathione peroxidase, are increased in hamster kidney bearing DES-induced tumours and decreased in human renal clear cell carcinoma. Glutathione disulphide reductase is decreased in hamster and human tumours. The role of these enzymatic activities in the carcinogenic process is also discussed.