P739 Phosphodiesterase 5A expression is up-regulated in vascular endothelium under pro-inflammatory conditions: a newly disclosed anti-inflammatory activity by the omega-3 fatty acid docosahexaenoic acid.

Endothelial inflammatory dysfunction, reflected by reduced NO bioavailability, is recognized as promoting atherosclerosis. NO activates the soluble guanylate cyclase (sGC) and the subsequent generation of cyclic guanosine monophosphate (cGMP), which in turn, serves as a final modulator of vascular relaxation. PDE5A, is a phosphodiesterase that catalyses the hydrolysis of cGMP into GMP, thus curtailing NO signalling and favouring pro-angiogenic effects. The ω-3 fatty acids DHA and eicosapentaenoic acid (EPA) are considered health-promoting nutrients. However, molecular mechanisms underlying their effects remain incompletely understood. Since recent data suggest a role for endothelial phosphodiesterase (PDE)5A in the modulation of endothelial-dependent vasodilation and angiogenesis, we investigated whether inflammatory stimuli known to be involved in the inflammation-mediated endothelial dysfunction and angiogenesis affect the endothelial PDE5A expression, and whether cell exposure to DHA modifies such PDE5A expression.Methods: Human umbilical vein endothelial cells (HUVEC) were treated with inflammatory or pro-angiogenic stimuli interleukin (IL)-1, tumour necrosis factor (TNF), IL-6, vascular endothelial growth factor (VEGF) and phorbol myristate acetate (PMA) for 0-24 hours. After this time, PDE5A expression was assessed by Western analysis, while mRNA expression was investigated by quantitative PCR (qPCR). In a subset of experiments HUVEC were treated with 0-50 μmol/L DHA for 48 hours before stimulation with IL-1, and PDE5A expression was then evaluated by Western analysis and qPCR.Results: PDE5A protein expression increased significantly after stimulation with 10 ng/mL IL-1 and TNF for 12 h (P<0.01 vs control), but not after stimulation with IL-6, PMA and VEGF. At the same concentrations, IL-1 also increased mRNA expression by 40% (P<0.05 vs control). DHA treatment of HUVEC before IL-1 stimulation reduced PDE5A induction at both protein and mRNA levels (P<0.05 vs IL-1).Conclusions: Classical pro-inflammatory - but not specifically pro-angiogenic - stimuli significantly induce PDE5A expression in endothelial cells, thus suggesting the involvement of an inflammatory signaling in the mechanisms leading to PD5A expression. Since PDE5A inhibitors are now approved for use in erectile dysfunction and pulmonary hypertension and have a potential in treating other disease states featuring endothelial dysfunction, downregulating the inflammation-mediated expression of PDE5A by DHA may positively impact the NO/sGC/cGMP axis and reproduce, at least partially, the therapeutic potential of PDE5 inhibitors. [ABSTRACT FROM AUTHOR]