Sildenafil inhibits the formation of superoxide and the expression of gp47 NAD[P]H oxidase induced by the thromboxane A2 mimetic, U46619, in corpus cavernosal smooth muscle cells.
OBJECTIVE
To assess the effect of sildenafil on superoxide formation and p47(phox) (the active subunit of NADPH oxidase) expression in cultured corpus cavernosal smooth muscle cells (CVSMCs).


METHODS
CVSMCs derived from rabbit penis were incubated with U46619 (thromboxane A2 analogue) with or without sildenafil for 1 or 16 h at 37 degrees C. Superoxide dismutase-inhibitable superoxide formation was assessed using the reduction of ferricytochrome c measured spectrophotometrically, and gp47(phox) assessed using Western blot analysis. The role of NAD[P]H oxidase and cGMP was further studied by using specific inhibitors of each.


RESULTS
Superoxide formation was significantly greater in cells incubated with U46619 after 1 and 16 h incubation than in controls, an effect blocked by NADP(H) oxidase inhibitors. These effects of U46619 were inhibited by sildenafil (1 and 10 nmol/L), which in turn were negated by the guanylyl cyclase inhibitor, ODQ; 10 nmol/L sildenafil inhibited p47phox expression induced by U46619.


CONCLUSIONS
Sildenafil is a potent inhibitor of superoxide formation in CVSMCs. This effect is mediated through the inhibition of PDE-5 which in turn augments the inhibitory action of the NO-cGMP axis on NAD[P]H oxidase expression and activity. This mechanism constitutes a new pharmacological action of sildenafil, consolidates the potential role of superoxide in ED, and indicates that thromboxane A(2) may be an important mediator of intrapenile oxidative stress.
Koupparis
Anthony J
AJ
Urology and Bristol Heart Institute, Bristol Royal Infirmary, Bristol, UK. koupps@hotmail.com
Jeremy
Jamie Y
JY
Muzaffar
Saima
S
Persad
Raj
R
Shukla
Nilima
N
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology*; D000818:Animals; D007172:Erectile Dysfunction / Q000378:metabolism; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000378:metabolism; D019255:NADPH Oxidases / Q000378:metabolism*; D010413:Penis / Q000378:metabolism*; D010879:Piperazines / Q000494:pharmacology*; D011687:Purines; D051381:Rats; D000068677:Sildenafil Citrate; D013450:Sulfones; D013481:Superoxides / Q000378:metabolism*; D013928:Thromboxane A2; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
D010879:Piperazines; D011687:Purines; D013450:Sulfones; D014662:Vasoconstrictor Agents; D013481:Superoxides; D013928:Thromboxane A2; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000068677:Sildenafil Citrate; D019255:NADPH Oxidases