8-isoprostane F2α up-regulates the expression of type 5 phosphodiesterase in cavernosal vascular smooth muscle cells: inhibition with sildenafil, iloprost, nitric oxide and picotamide.
OBJECTIVE
To explore the possible role of of 8-isoprostane F(2α) (8-IPF(2α) ) in the aetiology of erectile dysfunction (ED), as the over-production of superoxide (O(2)(-)) derived from nicotinamide adenine dinucleotide phosphate (NADPH) oxidase results in the formation of 8-IPF(2α) in vascular tissue, which has similar properties to thromboxane A(2) (TXA(2) ). TXA(2) is vasoconstrictor and up-regulates the expression of NADPH oxidase and phosphodiesterase type 5 (PDE5).


METHODS
Cavernosal vascular smooth muscle cells (CVSMCs) were incubated with 8-IPF(2α) or the TXA(2) analogue, U46619, ±sildenafil, iloprost (a stable prostacyclin [PGI(2) ] analogue) or the nitric oxide (NO) donor NONOate for 16 h. The formation of O(2)(-) was then measured, PDE5 expression assessed using Western blotting and PGI(2) and 8-IPF(2α) formation measured using enzyme-linked immunoassays.


RESULTS
8-IPF(2α) promoted the formation of O(2)(-) , an effect inhibited by apocynin (an NADPH oxidase inhibitor) and up-regulated the expression of PDE5. Under identical incubation conditions, 8-IPF(2α) induced an increase in the formation of 8-IPF(2α) but reduced the formation of PGI(2) . All, these effects were reversed by sildenafil, iloprost, NONOate and picotamide.


CONCLUSIONS
These data show that O(2) (-) derived from NADPH oxidase influences the relative balance of PGI(2) and 8-IPF(2α) in CVSMCs, which in turn alters the degree of PDE5 expression. This is a novel pathogenic mechanism underlying ED and a novel mechanism of action of sildenafil.
Hotston
Matthew
M
Department of Urology and Bristol Heart Institute, University of Bristol, Bristol, UK.
Jeremy
Jamie Y
JY
Persad
Raj
R
Bloor
Jonathon
J
Shukla
Nilima
N
D000818:Animals; D015153:Blotting, Western; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5 / Q000378:metabolism*; D015237:Dinoprost / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D016285:Iloprost / Q000494:pharmacology; D018783:Impotence, Vasculogenic / Q000209:etiology*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D009569:Nitric Oxide; D018384:Oxidative Stress / Q000187:drug effects; D010413:Penis / Q000187:drug effects / Q000378:metabolism*; D058986:Phosphodiesterase 5 Inhibitors / Q000494:pharmacology*; D010795:Phthalic Acids / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D011687:Purines / Q000494:pharmacology; D011817:Rabbits; D000068677:Sildenafil Citrate; D013450:Sulfones / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism; D015854:Up-Regulation
D058986:Phosphodiesterase 5 Inhibitors; D010795:Phthalic Acids; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D013481:Superoxides; C075750:8-epi-prostaglandin F2alpha; D009569:Nitric Oxide; D009249:NADP; C011581:picotamide; D015237:Dinoprost; D000068677:Sildenafil Citrate; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D016285:Iloprost