Calcium-dependent diuretic system in preascitic liver cirrhosis.

BACKGROUND & AIMS: Extracellular Ca(++) activates cell membrane calcium-sensing receptors (CaRs), leading to renal tubule production of prostaglandins E(2) (PGE(2)), which decrease both sodium reabsorption in the thick ascending limb of Henle's loop and free-water reabsorption in collecting ducts. AIMS & METHODS: To assess the activity of this diuretic system in experimental cirrhosis, we evaluated renal function, hormonal status, PGE(2) urinary excretion, and renal tissue concentrations of Na(+)-K(+)-2Cl(-) co-transporters (BSC-1) and CaRs in three groups of rats: one group of controls receiving 5% glucose solution (vehicle) intravenously and two groups of rats with CCl(4)-induced preascitic cirrhosis receiving either vehicle or 0.5mg i.v. Poly-l-Arginine (PolyAg), a CaR-selective agonist. RESULTS: Compared to controls, cirrhotic rats showed reduced urine volume and sodium excretion (p<0.05). Western blot analysis revealed reduced CaRs and increased BSC-1 protein content in kidneys of cirrhotic rats compared with controls (all p<0.01). PolyAg-treated cirrhotic rats had their urine and sodium excretion returned to normal; PolyAg also increased renal plasma flow, PGE(2) urinary excretion, and free-water clearance in cirrhotic rats (all p<0.01 v. untreated cirrhotic animals). CONCLUSIONS: In preascitic cirrhosis, sodium retention may be linked to down-regulation of renal CaRs and up-regulation of tubular sodium-retaining channels. Calcimimetic drugs normalize preascitic sodium retention.

Protective Effects of Pyridoxamine Supplementation in the Early Stages of Diet-Induced Kidney Dysfunction.

Pyridoxamine, a structural analog of vitamin B6 that exerts antiglycative effects, has been proposed as supplementary approach in patients with initial diabetic nephropathy. However, the molecular mechanism(s) underlying its protective role has been so far slightly examined. C57Bl/6J mice were fed with a standard diet (SD) or a diet enriched in fat and fructose (HD) for 12 weeks. After 3 weeks, two subgroups of SD and HD mice started pyridoxamine supplementation (150 mg/kg/day) in the drinking water. HD fed mice showed increased body weight and impaired glucose tolerance, whereas pyridoxamine administration significantly improved insulin sensitivity, but not body weight, and reduced diet-induced increase in serum creatinine and urine albumin. Kidney morphology of HD fed mice showed strong vacuolar degeneration and loss of tubule brush border, associated with a drastic increase in both advanced glycation end products (AGEs) and AGEs receptor (RAGE). These effects were significantly counteracted by pyridoxamine, with consequent reduction of the diet-induced overactivation of NF-kB and Rho/ROCK pathways. Overall, the present study demonstrates for the first time that the administration of the antiglycative compound pyridoxamine can reduce the early stages of diet-dependent kidney injury and dysfunction by interfering at many levels with the profibrotic signaling and inflammatory cascades.

Fructose-derived advanced glycation end-products drive lipogenesis and skeletal muscle reprogramming via SREBP-1c dysregulation in mice.

Advanced Glycation End-Products (AGEs) have been recently related to the onset of metabolic diseases and related complications. Moreover, recent findings indicate that AGEs can endogenously be formed by high dietary sugars, in particular by fructose which is widely used as added sweetener in foods and drinks. The aim of the present study was to investigate the impact of a high-fructose diet and the causal role of fructose-derived AGEs in mice skeletal muscle morphology and metabolism. C57Bl/6J mice were fed a standard diet (SD) or a 60% fructose diet (HFRT) for 12 weeks. Two subgroups of SD and HFRT mice received the anti-glycative compound pyridoxamine (150 mg/kg/day) in the drinking water. At the end of protocol high levels of AGEs were detected in both plasma and gastrocnemius muscle of HFRT mice associated to impaired expression of AGE-detoxifying AGE-receptor 1. In gastrocnemius, AGEs upregulated the lipogenesis by multiple interference on SREBP-1c through downregulation of the SREBP-inhibiting enzyme SIRT-1 and increased glycation of the SREBP-activating protein SCAP. The AGEs-induced SREBP-1c activation affected the expression of myogenic regulatory factors leading to alterations in fiber type composition, associated with reduced mitochondrial efficiency and muscular strength. Interestingly, pyridoxamine inhibited AGEs generation, thus counteracting all the fructose-induced alterations. The unsuspected involvement of diet-derived AGEs in muscle metabolic derangements and proteins reprogramming opens new perspectives in pathogenic mechanisms of metabolic diseases.

Dehydroepiandrosterone prevents oxidative injury induced by transient ischemia/reperfusion in the brain of diabetic rats.

Both chronic hyperglycemia and ischemia/reperfusion (IR) cause an imbalance in the oxidative state of tissues. Normoglycemic and streptozotocin (STZ)-diabetic rats were subjected to bilateral carotid artery occlusion for 30 min followed by reperfusion for 60 min. Rats had either been treated with dehydroepiandrosterone (DHEA) for 7, 14, or 21 days (2 or 4 mg/day per rat) or left untreated. Oxidative state, antioxidant balance, and membrane integrity were evaluated in isolated synaptosomes. IR increased the levels of reactive species and worsened the synaptic function, affecting membrane Na/K-ATPase activity and lactate dehydrogenase release in all rats. The oxidative imbalance was much severer when transient IR was induced in STZ-diabetic rats. DHEA treatment restored H2O2, hydroxyl radical, and reactive oxygen species to close to control levels in normoglycemic rats and significantly reduced the level of all reactive species in STZ-diabetic rats. Moreover, DHEA treatment counteracted the detrimental effect of IR on membrane integrity and function: the increase of lactate dehydrogenase release and the drop in Na/K-ATPase activity were significantly prevented in both normoglycemic and STZ-diabetic rats. The results confirm that DHEA, an adrenal steroid that is synthesized de novo by brain neurons and astrocytes, possesses a multitargeted antioxidant effect. They also show that DHEA treatment is effective in preventing both derangement of the oxidative state and neuronal damage induced by IR in experimental diabetes.

Oxidative and nitrosative stress in brain mitochondria of diabetic rats.

Diabetic encephalopathy, characterized by impaired cognitive functions and neurochemical and structural abnormalities, may involve direct neuronal damage caused by intracellular glucose. The study assesses the direct effect of chronic hyperglycemia on the function of brain mitochondria, the major site of reactive species production, in diabetic streptozotocin (STZ) rats. Oxidative stress plays a central role in diabetic tissue damage. Alongside enhanced reactive oxygen species (ROS) levels, both nitric oxide (NO) levels and mitochondrial nitric oxide synthase expression were found to be increased in mitochondria, whereas glutathione (GSH) peroxidase activity and manganese superoxide dismutase protein content were reduced. GSH was reduced and GSH disulfide (GSSG) was increased in STZ rats. Oxidative and nitrosative stress, by reducing the activity of complexes III, IV and V of the respiratory chain and decreasing ATP levels, might contribute to mitochondrial dysfunction. In summary, this study offers fresh evidence that, besides the vascular-dependent mechanisms of brain dysfunction, oxidative and nitrosative stress, by damaging brain mitochondria, may cause direct injury of neuronal cells.

Osteoclast precursors circulate in the peripheral blood of patients with aggressive multiple myeloma.

Osteolysis resulting in extensive bone damage is a major clinical manifestation of patients with multiple myeloma (MM). The mechanisms of bone resorption in MM are incompletely understood. The final pathway is the generation of activated osteoclasts within bone marrow (BM) microenvironment. To investigate the mechanisms of bone resorption in MM we established an experimental system that, including bone marrow (BM) stromal cells and bone slices, closely mimicks in vitro the in vivo BM microenvironment. Peripheral blood mononuclear cells (PBMC) from nine patients with MM, three monoclonal gammopathy of undetermined significance (MGUS), and nine normal controls were cultured in this system. PBMC from patients with aggressive and bone devastating MM gave rise to multi-nucleated cells with the morphology and phenotype of osteoclasts. These cells induced bone resorption in vitro which was inhibited by the addition of calcitonin. No bone resorption was observed in cultures of PBMC from patients with MM and limited bone damage, with MGUS and from normal subjects. These findings indicate that patients with aggressive MM have a population of circulating precursors that develop into functionally active osteoclast-like cells once they come in contact with the BM microenvironment. These cells may contribute to the wide-spread and generalized bone erosion observed in the patients.

Oxidative stress and eicosanoids in the kidneys of hyperglycemic rats treated with dehydroepiandrosterone.

Oxidative stress plays a crucial role in the pathogenesis of chronic diabetic complications. Normoglycemic and streptozotocin-diabetic rats were treated with dehydroepiandrosterone (DHEA) (4 mg/d per rat) for 3 weeks. At the end of treatment, hydroxynonenal, hydroperoxyeicosatetraenoic acids and antioxidant levels, as well as Na/K-ATPase activity and membrane fatty acids composition were evaluated in kidney homogenates. Chronic hyperglycemia caused a marked increase of both hydroxynonenal and lipoxygenase pathway products and a drop in both GSH levels and membrane Na/K-ATPase activity. DHEA treatment restored the antioxidant levels to close to the control value and considerably reduced hydroxynonenal and hydroperoxyeicosatetraenoic acid levels. Moreover, DHEA counteracted the detrimental effect of hyperglycemia on membrane function: the drop of Na/K-ATPase activity in diabetic animals was significantly inhibited by DHEA treatment. These results show that DHEA reduces oxidative stress and the consequent increase of lipoxygenase pathway products induced by experimental diabetes in rat kidney; they also suggest that, by reducing the inflammatory response to oxidative stress, DHEA treatment might delay the progression of diabetic kidney disease.

Protective effect of dehydroepiandrosterone against copper-induced lipid peroxidation in the rat.

This study investigates the effectiveness and multitargeted activity of dehydroepiandrosterone (DHEA) as antioxidant in vivo. A single dose of DHEA was given IP to male rats. Liver and brain microsomes, and plasma low density lipoprotein (LDL), were isolated from rats sacrificed 17 h later. Liver and brain microsomes were challenged with CuSO(4) and, as index of lipid peroxidation, the production of thiobarbituric acid reactive substances (TBARS) was measaured. Also, plasma low-density lipoprotein (LDL) were challenged with copper and the time course of lipid peroxidation was evaluated following the formation of conjugated dienes. The onset of TBARS generation induced by copper was marked delayed in both liver and brain microsomes from DHEA-treated animals. Also, the resistance of LDL to oxidation, expressed by the duration of the lag-phase of the kinetic curve, was significantly enhanced in DHEA-treated rats. Results indicate that in vivo DHEA supplementation makes subcellular fractions isolated from different tissues and plasma constituents (LDL) more resistant to lipid peroxidation triggered by copper. The antioxidant effect on plasma LDL might be of special relevance to the proposed antiatherogenic activity of DHEA. Moreover, multitargeted antioxidant activity of DHEA might protect tissues from oxygen radicals damage.

Dehydroepiandrosterone protects tissues of streptozotocin-treated rats against oxidative stress.

Chronic hyperglycemia in diabetes determines the overproduction of free radicals, and evidence is increasing that these contribute to the development of diabetic complications. It has recently been reported that dehydroepiandrosterone possesses antioxidant properties; this study evaluates whether, administered daily for three weeks per os, it may provide antioxidant protection in tissues of rats with streptozotocin-induced diabetes. Lipid peroxidation was evaluated on liver, brain and kidney homogenates from diabetic animals, measuring both steady-state concentrations of thiobarbituric acid reactive substances and fluorescent chromolipids. Hyperglycemic rats had higher thiobarbituric acid reactive substances formation and fluorescent chromolipids levels than controls. Dehydroepiandrosterone-treatment (4 mg/day for 3 weeks) protected tissues against lipid peroxidation: liver, kidney and brain homogenates from dehydroepiandrosterone-treated animals showed a significant decrease of both thiobarbituric acid reactive substances and fluorescent chromolipids formation. The effect of dehydroepiandrosterone on the cellular antioxidant defenses was also investigated, as impaired antioxidant enzyme activities were considered proof of oxygen-dependent toxicity. In kidney and liver homogenates, dehydroepiandrosterone treatment restored to near-control values the cytosolic level of reduced glutathione, as well as the enzymatic activities of superoxide-dismutase, glutathione-peroxidase, catalase. In the brain, only an increase of catalase activity was evident (p < .05), which reverted with dehydroepiandrosterone treatment. The results demonstrate that DHEA treatment clearly reduces oxidative stress products in the tissues of streptozotocin-treated rats.

Liver AP-1 activation due to carbon tetrachloride is potentiated by 1,2-dibromoethane but is inhibited by alpha-tocopherol or gadolinium chloride.

Experimental acute intoxication by prooxidant haloalkanes produces marked stimulation of hepatic lipid peroxidation and cytolysis, which is followed by tissue regeneration. Our aim was to clarify the role of oxidative imbalance in the activation of the redox-sensitive transcription factor, activator protein-1 (AP-1), which is involved in tissue repair. Rats were poisoned with a very low concentration of carbon tetrachloride, given alone or in combination with another hepatotoxin, 1,2-dibromoethane, to provide varying extents of oxidative damage. The level of AP-1-DNA binding was analyzed by electrophoretic mobility shift assay on liver extracts, obtained from rats killed 6 h after poisoning. Stimulation of lipid peroxidation and AP-1 upregulation were already established when the hepatic damage due to carbon tetrachloride +/-1,2-dibromoethane was beginning to appear. Rat supplementation with the antioxidant vitamin E completely inhibited AP-1 upregulation, thus supporting a causative role of membrane lipid oxidation in the observed modulation of the transcription factor. Moreover, activation of Kupffer cells appears to be a crucial step in the increased AP-1 binding to DNA, the latter being largely prevented by gadolinium chloride, a macrophage-specific inhibitor.

Dehydroepiandrosterone administration prevents the oxidative damage induced by acute hyperglycemia in rats.

Free radical overproduction contributes to tissue damage induced by acute hyperglycemia. Dehydroepiandrosterone, which has recently been found to have antioxidant properties, was administered i.p. to rats at different doses (10, 50 or 100 mg/kg body weight) 3 h before treatment with dextrose (5 g/kg). Lipid peroxidation was evaluated on liver, brain and kidney homogenates, measuring both steady-state concentrations of thiobarbituric acid reactive substances, and fluorescent chromolipids, evaluated as hydroxynonenal adducts. Formation of thiobarbituric acid reactive substances was significantly higher in hyperglycemic than in normoglycemic animals. Three hours (but not 1 h) dehydroepiandrosterone-pretreatment protected tissues against lipid peroxidation induced by dextrose; both thiobarbituric acid reactive substances and hydroxynonenal adducts in liver, kidney and brain homogenates were significantly lower in dehydroepiandrosterone-pretreated animals. Dehydroepiandrosterone did not modify the cytosolic level of antioxidants, such as alpha-tocopherol or glutathione, nor the activities of glutathione peroxidase, reductase or transferase. The results of this study indicate that the 'in vivo' administration of dehydroepiandrosterone increases tissue resistance to lipid peroxidation triggered by acute hyperglycemia.

Dehydroepiandrosterone prevents lipid peroxidation and cell growth inhibition induced by high glucose concentration in cultured rat mesangial cells.

The oxidative stress induced by high glucose concentration contributes to tissue damage associated with diabetes, including renal injury. Dehydroepiandrosterone (DHEA), the major secretory product of the human adrenal gland, has been shown to possess a multi-targeted antioxidant activity which is also effective against lipid peroxidation induced by high glucose. In this study we evaluated the effect of DHEA on the growth impairment which high glucose concentration induces in cultured rat mesangial cells. Primary cultures of rat mesangial cells were grown for 10 days in media containing either normal (i.e. 5.6 mmol/l) or high (i.e. 30 mmol/l) concentrations of glucose, without or with DHEA at different concentrations. The impairment of cell growth induced by high glucose was reversed by 100 nmol/l and 500 nmol/l DHEA, which had no effect on mesangial cells cultured in media containing glucose at the normal physiological concentration (5.6 mmol/l). In high-glucose cultured mesangial cells, DHEA also attenuated the lipid peroxidation, as measured by thiobarbituric acid reactive substances (TBARS) generation and 4-hydroxynonenal (HNE) concentration, and preserved the cellular content of reduced glutathione as well as the membrane Na+/K+ ATPase activity. The data further support the protective effect of DHEA against oxidative damage induced by high glucose concentrations, and bring into focus its possible effectiveness in preventing chronic complications of diabetes.

Dehydroepiandrosterone protects bovine retinal capillary pericytes against glucose toxicity.

Pericyte loss is an early feature of diabetic retinopathy and represents a key step in the progression of this disease. This study aimed to evaluate the effect of dehydroepiandro-sterone (DHEA) on glucose toxicity in retinal capillary pericytes. Bovine retinal pericytes (BRP) were cultured in a high glucose concentration, with or without DHEA. After 4 days of incubation the number of BRP was significantly reduced by the high glucose concentration. The addition of DHEA to the medium reversed the adverse effect of high glucose: BRP proliferation partially recovered in the presence of 10 nmol/l DHEA, and completely recovered in the presence of DHEA at concentrations equal to or greater than 100 nmol/l. At physiological glucose concentrations, DHEA had no effect on BRP growth. Data show that DHEA, at concentrations similar to those found in human plasma, protects BRP against glucose toxicity. This effect seems specific for DHEA, since its metabolites, 5-en-androstene-3 beta, 17 beta-diol, dihydrotestosterone and estradiol did not alter BRP growth in normal or high glucose media. Various pieces of evidence link the antioxidant properties of DHEA to its protective effect on glucose-induced toxicity in BRP.

Oxidative derangement in rat synaptosomes induced by hyperglycaemia: restorative effect of dehydroepiandrosterone treatment.

Central nervous system damage in diabetes is caused by both cerebral atherosclerosis and the detrimental effect of chronic hyperglycaemia on nervous tissue. Hyperglycaemia is the primer of a series of cascade reactions causing overproduction of free radicals. There is increasing evidence that these reactive molecules contribute to neuronal tissue damage. Dehydroepiandrosterone (DHEA) has been reported to possess antioxidant properties. This study evaluates the oxidative status in the synaptosomal fraction isolated from the brain of streptozotocin-treated rats and the antioxidant effect of DHEA treatment on diabetic rats. Hydroxyl radical generation, hydrogen peroxide content, and the level of the reactive oxygen species was increased (P<0.05) in synaptosomes isolated from streptozotocin-treated rats. The derangement of the oxidative status was confirmed by a low level of reduced glutathione and alpha-tocopherol. DHEA treatment (4 mg per day for 3 weeks, per os) protected the synaptosomes against oxidative damage: synaptosomes from diabetic DHEA-treated rats showed a significant decrease in reactive species (P<0.05) and in the formation of end products of lipid peroxidation, evaluated in terms of fluorescent chromolipid (P<0.01). Moreover, DHEA treatment restored the unsaturated fatty acid content of the membrane and the reduced glutathione and alpha-tocopherol levels to normal levels and restored membrane NaK-ATPase activity close to control levels. The results demonstrate that DHEA supplementation greatly reduces oxidative damage in synaptosomes isolated from diabetic rats and suggest that this neurosteroid may participate in protecting the integrity of synaptic membranes against hyperglycaemia-induced damage.

Dehydroepiandrosterone pretreatment protects rats against the pro-oxidant and necrogenic effects of carbon tetrachloride.

A single intraperitoneal injection of dehydroepiandrosterone (3 beta-hydroxy-5-androsten-17-one, DHEA) 17 hr before carbon tetrachloride (CCl4) poisoning protects rats against liver injury induced by the haloalkane. In liver homogenates, both the increase in malondialdehyde production and the formation of fluorescent lipid peroxidation products are significantly reduced. Also, liver microsomes obtained from DHEA-pretreated rats incubated in vitro with CCl4 are less susceptible to lipid peroxidation than microsomes from normal animals. The release of liver enzymes into the blood is much reduced in DHEA-pretreated rats, confirming a cause-effect relationship between lipid peroxidation and hepatocyte death. Treatment with DHEA inhibits neither glucose-6-phosphate dehydrogenase activity in the cytosol, nor the microsomal mixed function oxidase system (cytochrome P450 content, aminopyrine demethylase and ethoxycoumarin de-ethylase activities). In animals treated with DHEA, the liver content of total glutathione and vitamin E is not modified. These results support the hypothesis that DHEA protects against CCl4-induced liver injury through its own antioxidant activity, rather than by interfering with the metabolism of the toxin or with the tissue level of primary antioxidants.

MEC1 and MEC2: two new cell lines derived from B-chronic lymphocytic leukaemia in prolymphocytoid transformation.

We report the establishment and characterization of two cell lines, MEC1 and MEC2, that grew spontaneously on two subsequent occasions from the peripheral blood (PB) of a patient with B-chronic lymphocytic leukemia (B-CLL) in prolymphocytoid transformation. The patient was EBV-seropositive, his leukemic cells were EBNA negative, but the spontaneously grown cell lines are EBNA-2 positive. In liquid culture MEC1 cells grow adherent to the vessel wall and as tiny clumps; MEC2 cells do not adhere and form large clumps. The doubling time of MEC1 is 40h and of MEC2 is 31h. Both cell lines express the same light (kappa) and heavy chains (mu, delta) as the fresh parental B-CLL cells at the same high intensity, share the expression of mature B cell markers (CD19, CD20, CD21, CD22), differ in the expression of CD23 and FMC7, are CD11a+, CD18+, CD44+, CD49d+, CD54+ and express at high levels both CD80 and CD86. CD5 is negative on MEC1 cells (as on the vast majority of parental cells) and it has been lost by MEC2 cells after several months of culture. The cells have a complex karyotype. The tumour origin of MEC1 and MEC2 has been demonstrated by Southern blot analysis of the IgH loci and by Ig gene DNA sequencing. They use the VH4 Ig family and have not undergone somatic mutations (94.8% homology with germline Ig gene 4-59). Cytofluorographic analysis and RT-PCR reveal that MEC1 and MEC2 overexpress Bcl-2 together with Bax, express large amounts of Bcl-xL and trace amounts of Bcl-xS.

Protective effect of dehydroepiandrosterone against lipid peroxidation in a human liver cell line.

OBJECTIVE: Dehydroepiandrosterone (DHEA) is a widely studied steroid hormone with multi-functional properties. Reports suggest that some of the many activities of DHEA are due to its protective effect against lipid peroxidation. Nevertheless, the antioxidant properties of DHEA are still the subject of debate. The aim was to evaluate whether its two opposed effects on lipid peroxidation reported in the literature may be dependent on schedule and doses used. METHODS: Chang liver cells, a line derived from normal human liver, were grown in media containing either no steroids (control) or DHEA at concentrations ranging from 0.1 micromol/l to 50 micromol/l. At specific times, cultures were halted and cells received a pro-oxidant stimulus (cumene (CuOOH) 0.5 mmol/l), at which time cell viability (by trypan blue staining and lactate dehydrogenase (LDH) release) and thiobarbituric acid reactive substances (TBARS) concentration (spectrophotometrical assay) were evaluated. RESULTS: At concentrations ranging from 0.1 micromol/l to 1 micromol/l, DHEA protects Chang liver cells against lipid peroxidation and/or death induced by cumene. This effect disappears if the concentration is increased to 10 micromol/l; at higher concentrations (50 micromol/l) a pro-oxidant/cytotoxic effect of DHEA appears. CONCLUSIONS: DHEA exhibits two opposed effects on lipid peroxidation; depending on its concentration it acts either to limit or to induce oxidative stress. The threshold concentration at which the pro-oxidant activity of DHEA prevails is not far in excess of that having an antioxidant effect. Either effect of DHEA on lipid peroxidation is only evident after a 'lag-phase'.

Growth inhibition of DMBA-induced rat mammary carcinomas by the antiandrogen flutamide.

Antiandrogens have sporadically been reported to exert antitumor activities in both pre- and post-menopausal breast cancer. To explore the possibility of using the pure antiandrogen flutamide (FLU) in breast cancer therapy, rats bearing DMBA-induced mammary tumors were treated with FLU, dihydrotestosterone (DHT), or FLU plus DHT. FLU was administered orally, at doses comparable to those used in the treatment of prostate cancer patients. FLU-treated animals had a significantly smaller average tumor area than controls from day 11 up to the end of the experiment (day 20). A similar reduction of tumor growth was observed in rats given DHT and in those treated with DHT plus FLU. Plasma levels of LH, FSH, P, 17-OH P, E2 and DHEA measured at the end of experiment did not differ between treated animals and controls. Results demonstrate that the antiandrogen FLU and the full androgen DHT exert similar inhibitory effects on the growth of dimethylbenz(a)anthracene (DMBA)-induced rat mammary tumors. Moreover, data show that plasma steroids levels are unaffected by FLU treatment. This finding rules out any antitumor effect dependent on the reduction of adrenal and gonadal steroidosynthesis, and makes it appear more likely that androgen receptors are involved in the antiproliferative effect of FLU.

NT2 neurons, a classical model for Alzheimer's disease, are highly susceptible to oxidative stress.

We have tested undifferentiated NT2 cells as well as differentiated NT2 neurons (NT2N) for vulnerability to oxidative stress, lipid composition and antioxidant pattern. NT2N, but not NT2 cells, are highly susceptible to oxidative stress elicited by different classic pro-oxidant stimuli. In particular, NT2N cells undergo a high level of oxidative decomposition of omega-3 and omega-6 polyunsaturated fatty acids (PUFA) of membrane phospholipids, as evaluated by monitoring generation of thiobarbituric reactive substances, 4-hydroxynonenal (HNE) and chromolipid fluorescent adducts. NT2N cells exhibit low levels of natural antioxidants such as glutathione (GSH) and alpha-tocopherol and of antioxidant enzymatic activities such as Se-dependent GSH peroxidase and catalase. Accordingly, a direct correlation between lipid peroxidation and irreversible cell damage is suggested by prevention of NT2N cell death by alpha-tocopherol.

Prevention of carbon tetrachloride-induced lipid peroxidation in liver microsomes from dehydroepiandrosterone-pretreated rats.

Dehydroepiandrosterone (DHEA), a lipid soluble steroid, administered to rats (100 mg/kg b.wt) by a single intraperitoneal injection, increases to twice its normal level in the liver microsomes. Microsomes so enriched become resistant to lipid peroxidation induced by incubation with carbon tetrachloride in the presence of a NADPH-regenerating system: also the lipid peroxidation-dependent inactivation of glucose-6-phosphatase and gamma-glutamyl transpetidase due to the haloalkane are prevented. Noteworthy, the liver microsomal drug-metabolizing enzymes and in particular the catalytic activity of cytochrome P450IIE1, responsible for the CCl4-activation, are not impaired by the supplementation with the steroid. Consistently, in DHEA-pretreated microsomes the protein covalent binding of the trichloromethyl radical (CCl3 degrees), is similar to that of not supplemented microsomes treated with CCl4. It thus seems likely that DHEA protects liver microsomes from oxidative damage induced by carbon tetrachloride through its own antioxidant properties rather than inhibiting the metabolism of the toxin.