PubMed Health⌕ Search

Biomedical subjects

Anthony Koupparis

Publications and source records attributed to Anthony Koupparis.

5 recordsLinked to original sources
PubMed2006

Sildenafil inhibits the up-regulation of phosphodiesterase type 5 elicited with nicotine and tumour necrosis factor-alpha in cavernosal vascular smooth muscle cells: mediation by superoxide.

OBJECTIVES: To determine whether there is an association between vascular phosphodiesterase type 5 (PDE-5) and NADPH oxidase (NOX) in cavernosal vascular smooth muscle cells (CVSMCs), and to study the actions of the PDE-5 inhibitor sildenafil; the pro-erectile actions of nitric oxide (NO) are reduced by PDE-5 which hydrolyses cGMP to inactive GMP, thus an up-regulation of PDE-5 and over-production of O(2)(-) derived from NOX might promote erectile dysfunction (ED). MATERIALS AND METHODS: To study the effects of nicotine and tumour necrosis factor-alpha (TNF-alpha) on superoxide (O(2)(-)) production and PDE-5 expression, CVSMCs from rabbit penis were incubated with nicotine or TNF-alpha, and superoxide dismutase (SOD), catalase, sildenafil citrate, or apocynin (NADPH inhibitor) for 16 h. The expression of PDE-5 and of glyceraldehyde-3-phosphate dehydrogenase (internal standard) was assessed using Western blotting. O(2)(-) was measured spectrophotometrically. RESULTS: After a 16-h incubation, both nicotine (maximal at 10 microm) and TNF-alpha (10 ng/mL) significantly increased O(2)(-) formation in CVSMCs; this effect was blocked by co-incubating with SOD, catalase, and sildenafil (1 microm). Apocynin also inhibited O(2)(-) formation when added after 16-h incubation with nicotine (10 microm) or TNF-alpha. PDE-5 expression was also significantly increased in CVSMCs incubated with nicotine and TNF-alpha. This effect was negated by 16-h co-incubation with SOD, catalase, apocynin, and sildenafil. CONCLUSIONS: Nicotine and TNF-alpha up-regulate PDE-5 expression in CVSMCs through an a priori up-regulation of NOX and formation of O(2)(-). As PDE-5 hydrolyses cGMP, this effect might 'blunt' the pro-erectile actions of NO. Sildenafil inhibits O(2)(-) formation, and 'normalizes' PDE-5 expression. This represents a novel pathogenic mechanism underlying ED, and a novel mechanism of action of sildenafil.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed2006

Penicillamine administration reverses the inhibitory effect of hyperhomocysteinaemia on endothelium-dependent relaxation and superoxide formation in the aorta of the rabbit.

Although hyperhomocysteinaemia is a risk factor for cardiovascular disease, the mechanisms underlying this association have not been elucidated. It has been demonstrated, however, that copper augments the inhibitory effect of homocysteine on nitric oxide (NO)-mediated relaxation of the rat aorta through increased superoxide formation, which reacts with NO thereby reducing the bioavailability of NO. Since it follows that the administration of a copper chelator may blunt the pathogenic impact of hyperhomocysteinaemia, in vivo, the effect of penicillamine administration on NO-dependent relaxation and superoxide formation in the aortae of hyperhomocysteinaemic rabbits was studied. New Zealand White rabbits were fed a methionine-rich (20 g/kg chow) diet for 1 month+/-penicillamine administered orally (10 mg/kg/day) and aortic relaxation elicited with acetylcholine and superoxide measured. The role of NADPH oxidase was also studied using a range of inhibitors and western analysis of gp47(phox) (a catalytic subunit of NADPH oxidase). The methionine-rich diet markedly increased plasma total homocysteine levels. In hyperhomocysteinaemic rabbits there was a marked reduction of acetylcholine-stimulated relaxation and an increase in superoxide formation that were both inhibited with superoxide dismutase and apocynin, an NADPH oxidase inhibitor. Gp47(phox) expression was also increased in aortae from methionine fed rabbits. Penicillamine administration significantly reduced plasma total copper in methionine-fed rabbits compared to controls. Impaired acetylcholine-stimulated relaxation, increased superoxide formation and increased gp47(phox) expression in aortae from methionine-fed rabbits was reversed by penicillamine administration. These data indicate that hyperhomocysteinaemia augments the formation of arterial superoxide through an increase in NADPH oxidase expression/activity which in turn reduces NO bioavailability. Since these effects were reversed by penicillamine, these data consolidate the hypothesis that copper plays a role in mediating homocysteine-induced vasculopathy.

Acetophenones↗
PubMed2005

Cavernosal dysfunction in a rabbit model of hyperhomocysteinaemia.

OBJECTIVE: To investigate the effect of sustained hyperhomocysteinaemia (HHCy) on cavernosal smooth muscle function in a rabbit model of HHCy, developed using a methionine-enriched diet in which cavernosal responses were characterized, as elevated plasma levels of homocysteine may be a risk factor for vasculogenic erectile dysfunction. MATERIALS AND METHODS: Six New Zealand White rabbits were fed a diet supplemented with methionine (20 g/kg chow) for 4 weeks, while six control animals were fed a standard diet. Cavernosal strips were mounted in an organ bath and relaxation assessed when stimulated with carbachol, sodium nitroprusside (SNP), or noncholinergic, nonadrenergic (NANC)-mediated relaxation to electrical-field stimulation (EFS). Cavernosal tissue cGMP levels were assessed using an enzyme-linked immunosorbent assay, and superoxide (O(2) (.-)) production assessed using an assay of the superoxide dismutase (SOD)-inhibitable reduction of ferricytochrome c. RESULTS: The methionine-rich diet led to an early but sustained HHCy; cavernosal strips from animals after 4 weeks of HHCy had a significantly impaired relaxation response to carbachol, an index of endothelium-dependent nitric oxide (NO)-mediated relaxation. This impairment was reversed by incubating with either SOD or catalase. Relaxation with either SNP, an index of endothelium-independent NO-mediated relaxation, or NANC-mediated EFS-induced relaxation, was unaffected by HHCy. There was a corresponding significant reduction in cavernosal cGMP levels (index of NO activity) in the HHCy group, with a more than five-fold increase in cavernosal tissue O(2) (.-) production. CONCLUSION: Supplementing the diet of rabbits with methionine for 4 weeks caused an early and sustained HHCy and promoted a marked inhibitory effect on endothelium-dependent relaxation and NO formation in isolated corpus cavernosum, an effect mediated by reactive oxygen species.

Animals↗