Asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA) and L-arginine in patients with arteriogenic and non-arteriogenic erectile dysfunction.

The plasma concentration of asymmetrical dimethylarginine (ADMA), an inhibitor of nitric oxide synthase, has been linked to endothelial dysfunction. We investigated the relation between ADMA, symmetric dimethylarginine (SDMA) and L-arginine concentrations and erectile dysfunction. We compared plasma levels of ADMA, SDMA and L-arginine in 61 men in good health with erectile dysfunction of arteriogenic and non-arteriogenic origin. Diagnosis of erectile dysfunction was based on the International Index of Erectile Function Score and its aetiology was classified with penile echo-colour-Doppler in basal condition and after intracavernous injection of prostaglandin E1. The ADMA and SDMA concentrations were significantly higher in men with arteriogenic erectile dysfunction compared with those with erectile dysfunction of non-arteriogenic origin (p < 0.05) and the concentrations in both subgroups were significantly higher than in controls (p < 0.001). There was a negative correlation between ADMA and International Index of Erectile Function Score only in arteriogenic erectile dysfunction subgroup. L-arginine did not differ significantly neither between the two erectile dysfunction subgroups (p > 0.05) nor between each of the two erectile dysfunction subgroups and controls (p > 0.05). The L-arginine/ADMA and the L-arginine/SDMA ratios in arteriogenic erectile dysfunction subgroups were significantly lower than both in controls (p < 0.05) and in non-arteriogenic erectile dysfunction patients (p < 0.05); the two ratios in non-arteriogenic erectile dysfunction patients did not differ from those in the controls (p > 0.05). We conclude that ADMA and SDMA concentrations are significantly higher and L-arginine/ADMA ratio lower in patients who have arteriogenic erectile dysfunction compared with both patients with non-arteriogenic erectile dysfunction and controls. The negative correlation between ADMA and severity of erectile dysfunction is present only in patients with arteriogenic erectile dysfunction. This study supports the importance to always distinguish arteriogenic from non-arteriogenic erectile dysfunction patients to study the complicate erectogenic mechanisms that lead to erectile dysfunction and also to provide potential therapeutic agents for patients with arteriogenic erectile dysfunction.

Thyroid peroxidase as toxicity target for dithiocarbamates.

In vivo ethylenebisdithiocarbamates and ETU are toxic to the thyroid gland. Since the molecular target of these compounds is thought to be thyroid peroxidase (TPO) which catalyzes the transfer of iodine to thyroglobulin, we examined the effect of these compounds on peroxidative activity in Chinese hamster ovary (CHO) cells transfected with the human TPO gene. The activity was inhibited by 50 microM ETU, 5 microM ziram and 5 microM zineb, the last-mentioned effect being irreversible in the absence of iodide. Thiram had no effect. By contrast, the iodinating activity of TPO was blocked only by 5 microM ETU and 50 microM zineb but not by the other compounds. The effect on TPO-catalysed iodination could explain the differences in thyrotoxicity of these compounds in vivo.

NF-kappaB activation by triphenyltin triggers apoptosis in HL-60 cells.

Trisubstituted organotin pesticides are lethal for different cell types. In this study we investigated whether triphenyltin chloride (TPT) causes apoptosis in HL-60 promyelocytic cells and, if so, by what mechanisms. We report that 5 microM TPT increased intracellular Ca2+ in HL-60 cells within seconds; concomitantly actin depolymerization was detected 30 s and 1 min after the treatment. This was followed 15 min later by NF-kappaB activation, and apoptotic bodies and DNA fragmentation were evident after 3 and 6 h, respectively. At these times TPT also induced the release of tumor necrosis factor-alpha (TNF-alpha). Prior treatment of the cells with a polyclonal antibody to human TNF-alpha abolished TPT-induced DNA fragmentation, which suggests that the ultimate effect of TPT may be mediated by TNF-alpha. Prior treatment of the cells with 100 microM pyrrolidine dithiocarbamate, an antioxidant and potent inhibitor of NF-kappaB activation, prevented actin depolymerization, NF-kappaB activation, and DNA fragmentation, although it did not affect TPT-induced Ca2+ mobilization. These findings suggest that TPT increases intracellular Ca2+, alters actin polymerization and the cytoskeleton, and induces NF-kappaB activation, TNF-alpha synthesis, DNA degradation, and apoptosis. Reactive oxygen species seem to be essential to NF-kappaB activation, TNF-alpha synthesis, and the subsequent steps.

Effect of pesticide mixtures on in vitro nervous cells: comparison with single pesticides.

The toxicity of dimethoate, azinphos-methyl, diazinon, pirimiphos methyl, organophosphorus insecticides, and benomyl (a benzimidazole fungicide) singly and in mixture was studied in a human neuroblastoma cell line, SH-SY5Y. The cells were incubated for 30 min and 4 h with pesticides at concentrations ranging from 0.4 to 100 micrograms/ml, or with the same compounds mixed as follows: (a) dimethoate-diazinon-azinphos; (b) benomyl-pirimiphos; (c) all together. Pesticides in the mixtures were at the same concentration used when tested singly. Diazinon, azinphos-methyl and pirimiphos, but not dimethoate and benomyl, inhibited acetylcholine esterase (AchE) activity, whereas all the compounds inhibited protein synthesis in the following order: benomyl > azinphos > diazinon >> pirimiphos = dimethoate. The mixtures showed a toxicity on AchE activity at a maximum equal to that of the most active compound in the mixture. On the contrary, the mixture were more toxic than the single compounds on protein synthesis, and in certain cases potentiation occurred. Therefore, we can conclude that it is not feasible to predict the toxicity of pesticide mixtures on the basis of the results of the toxicity of single components.

Effect of 25-hydroxycholesterol, 26-hydroxycholesterol and its analogue, 26-aminocholesterol, on protein content, protein synthesis and LDH leakage in mouse epidermal cells.

The cytotoxicity of 25-hydroxycholesterol, 26-hydroxycholesterol and its analogue, 26-aminocholesterol was investigated in murine epidermal cell line, HEL-30. Lactate dehydrogenase (LDH) leakage, protein synthesis and protein content were determined after exposure of cell monolayers to the compounds ranging from 0.1-200 microM for 2, 6, or 24 h. 26-Aminocholesterol affected all the parameters studied time and concentration dependently; 25-hydroxycholesterol and 26-hydroxycholesterol were not toxic for HEL-30 cells. The cellular target for 26-aminocholesterol was primarily the membrane, since the LDH leakage was already detectable 10 min after exposure. On the other hand, for the other two oxysterols a protective role on this structure might be postulated. In fact 25-hydroxycholesterol and 26-hydroxycholesterol decreased the natural LDH leakage due to the ageing of the culture. In addition, 20 microM 25-hydroxycholesterol reversed the effect of moderately lytic doses of 26-aminocholesterol and Triton X-100, but not of sodium dodecyl sulfate.

Effect of short-term cyclosporine administration in rats on renin-angiotensin and thromboxane A2: possible relevance to the reduction in glomerular filtration rate.

A short-term treatment with Cyclosporine A (CyA) induces a decrease in glomerular filtration rate (GFR), promptly reversible after withdrawal of the drug. Several lines of evidence are now available as to indicate that this phenomenon is dependent on a hemodynamic perturbation resulting in a renal vasoconstriction. With the present work we have examined the relationship between the reduction in GFR which follows a short-term administration of CyA in rats and the biochemical changes in renin-angiotensin system and renal arachidonic acid metabolism. Our results show that CyA administration (25 mg/kg/day) for 45 days stimulates renin-angiotensin system with an increase in plasma renin activity. These changes are not accompanied by a parallel increase in the renal synthesis of vasodilatory prostaglandin E2 and prostacyclin as it occurs in other conditions of renin-angiotensin stimulation. At variance glomerular synthesis and urinary excretion of thromboxane A2 (TxA2) are increased progressively during CyA treatment. These changes in renal Tx precede the increase in serum creatinine and the decrease in GFR thus indicating that TxA2 might be an additional factor potentiating the effect of angiotensin II on glomerular hemodynamics. In conclusion the early reduction in GFR which follows daily administration of CyA in rats might be the result of a synergic action of angiotensin II and TxA2 on vascular tone and mesangial contraction which is not modulated by an increase in glomerular vasodilatory prostaglandins. If this explanation may be applied to early reduction in GFR observed in humans treated with CyA before tubular toxicity develops needs to be investigated further.

Cyclosporin-induced endothelial cell injury.

The administration of Cyclosporin-A (CyA) to animals and humans may induce an arteriolar damage. It has also been reported that CyA in some instances may cause an hemolytic uremic-like syndrome. This is a syndrome of vascular damage with thrombotic occlusions of the microcirculation. Endothelial injury is considered the first event in the pathogenetic cascade leading to hemolytic-uremic syndrome. We have used bovine aortic endothelial cells in culture to address the issue of CyA-induced arteriolar damage. Exposure of endothelial cells to different concentrations of CyA induced a time- and dose-dependent cell injury in vitro. The damage induced by CyA was characterized by an early cell detachment from culture substrate followed by cell lysis as documented by the increase in lactate dehydrogenase (LDH) and 51Cr release. Both detachment and lysis were negligible after short-term incubation of 1 microM CyA with endothelial cells. One micromolar CyA only induced lysis if incubations were prolonged above 6 hours. Ten and 50 microM CyA both induced marked endothelial cell detachment and lysis; lysis started 3 hours after incubation of endothelial cells with CyA and was maximal at the end of 24 hours incubation. CyA-induced injury was associated with dose- and time-dependent increase in prostacyclin and thromboxane A2 release by endothelial cells exposed to CyA independently from the concentrations of CyA used. CyA-induced generation of prostacyclin and thromboxane A2 was inhibited when the incubations were performed in the presence of aspirin (500 microM). These studies indicate that CyA exerts a direct cytotoxic effect on endothelial cells and might help in understanding the pathogenesis of CyA-induced vascular damage.

Acute cyclosporine A nephrotoxicity in rats: which role for renin-angiotensin system and glomerular prostaglandins?

Cyclosporine A (CsA) is a recently introduced immunosuppressive agent that represents a significant advance in the clinical control of graft rejection. However despite the remarkable effectiveness, one of the limiting factors to a more extensive use of CsA appears to be its nephrotoxicity. CsA is reported to induce a tubular epithelial damage whereas histological examination of glomeruli does not reveal abnormalities unless particularly high doses of the drug are used. On the other hand a decrease in glomerular filtration rate (GFR) has been reported in association with acute administration of CsA. Relatively few studies are available to compare structural and functional abnormalities in the same animals after an acute administration of CsA. Here we evaluated morphological abnormalities and renal function in the same animals treated for 20 days with CsA. Moreover in the attempt to find a link between tubular damage and decrease in GFR we studied the effect of CsA on the renin-angiotensin system as well as on glomerular synthesis of prostacyclin (PGI2) and prostaglandin E2 (PGE2). Our results confirmed that CsA induces a focal damage of tubular epithelial cells with isometric vacuolization of cytoplasm. No glomerular or vascular changes have been detected at histological examination. Serum creatinine was significantly elevated after 20 days of treatment, whereas creatinine clearance showed a progressive tendency to decrease without reaching a statistical significance. Plasma renin activity was found to progressively increase during CsA administration, whereas the synthesis of PGI2 and PGE2 by isolated glomeruli was not modified in CsA-treated animals in respect to animals receiving the solvent alone.(ABSTRACT TRUNCATED AT 250 WORDS)