trans-Resveratrol (t-RESV; 1–10 μM), a phenolic component of wines, had no effect on phenylephrine-(PE; 1 μM) and high KCl-(60 mM) induced contractions in endothelium-denuded rat aortic rings. However, it relaxed the contractile response produced by these vasoconstrictor agents in intact rat aorta. The vasorelaxing effects of t-RESV were completely inhibited byN^G-nitro-l-arginine (l-NOARG; 0.1 mM) and methylene blue (10 μM), but they were unaffected by atropine (10 μM) and yohimbine (1 μM). The reversal effect produced by l-NOARG was antagonized byl-arginine but not by d-arginine (0.1 mM).t-RESV (1–10 μM) did not significantly modify rat aorta constitutive nitric-oxide synthase activity. However, this natural compound decreased NADH/NADPH oxidase activity in rat aortic homogenates. In addition, t-RESV (1–10 μM) was ineffective in scavenging superoxide anions (O₂⨪) generated enzymatically by a hypoxanthine/xanthine oxidase (HX/XO) system and/or to inhibit XO. The above data demonstrate that the characteristic endothelium-dependent vasorelaxant effect oft-RESV in rat aorta seems to be caused by the inhibition of vascular NADH/NADPH oxidase and the subsequent decrease of basal cellular O₂⨪ generation and, therefore, of NO biotransformation. Under the assumption that t-RESV exhibits a similar behavior in human blood vessels and bearing in mind that an overactivity of NADH/NADPH oxidase has been found in a number of cardiovascular pathologies, the results obtained in this work suggest that t-RESV could play an important role in the cardioprotective effects induced by the long-term moderate wine consumption.

This study investigated for the first time the effects of the cis isomer of resveratrol (c-RESV) on the responses of inflammatory murine peritoneal macrophages, namely on the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) during the respiratory burst; on the biosynthesis of other mediators of inflammation such prostaglandins; and on the expression of inflammatory genes such as inducible nitric oxide synthase (NOS)-2 and inducible cyclooxygenase (COX)-2. Treatment with 1–100 μM c-RESV significantly inhibited intracellular and extracellular ROS production, and c-RESV at 10–100 μM significantly reduced RNS production. c-RESV at 1–100 μM was ineffective for scavenging superoxide radicals (O₂^•−), generated enzymatically by a hypoxanthine (HX)/xanthine oxidase (XO) system and/or for inhibiting XO activity. However, c-RESV at 10–100 μM decreased nicotinamide adenine dinucleotide/nicotinamide adenine dinucleotide phosphate (NADH/NADPH) oxidase activity in macrophage homogenates. c-RESV at 100 μM decreased NOS-2 and COX-2 mRNA levels in lipopolysaccharide (LPS) interferon gamma (IFN-γ)-treated macrophages. At 10–100 μM, c-RESV also significantly inhibited NOS-2 and COX-2 protein synthesis and decreased prostaglandin E₂ (PGE₂) production. These results indicate that c-RESV at micromolar concentrations significantly attenuates several components of the macrophage response to proinflammatory stimuli (notably, production of O₂^•− and of the proinflammatory mediators NO^• and PGE₂).

The potential vasorelaxant, antioxidant and cyclic nucleotide phosphodiesterase (PDE) inhibitory effects of the citrus-fruit flavonoids naringin and (±)-naringenin were comparatively studied for the first time in this work. (±)-Naringenin (1 μM - 0.3 mM) did not affect the contractile response induced by okadaic acid (OA, 1 μM). However, (±)-naringenin relaxed, in a concentration-dependent manner, the contractions elicited by phenylephrine (PHE, 1 μM) or by a high extracellular KCl concentration (60 mM) in intact rat aortic rings. Mechanical removal of endothelium and/or pretreatment of aorta rings with glibenclamide (GB, 10 μM) or tetraethylammonium (TEA, 2 mM) did not significantly modify the vasorelaxant effects of this flavanone. (±)-Naringenin (10 μM - 0.1 mM) did not alter the basal uptake of ⁴⁵Ca²⁺ but decreased the influx of ⁴⁵Ca²⁺ induced by PHE and KCl in endothelium-containing and endothelium-denuded rat aorta. (±)-Naringenin (10 μM - 0.1 mM) was ineffective to scavenge superoxide radicals (O₂ ^·-) generated by the hypoxanthine (HX)-xanthine oxidase (XO) system and/or to inhibit XO activity. (±)-Naringenin (0.1 mM) significantly increased the production of cGMP and cAMP decreased by PHE (1 μM) and high KCl (60 mM) in cultured rat aortic myocytes. (±)-Naringenin preferentially inhibited calmodulin (CaM)-activated PDE1, PDE4 and PDE5 isolated from bovine aorta with IC₅₀ values of about 45 μM, 60 μM and 68 μM, respectively. In contrast, the 7-rhamnoglucoside of (±)-naringenin, naringin (1 μM - 0.3 mM), was totally inactive in all experiments. These results indicate that the vasorelaxant effects of (±)-naringenin seem to be basically related to the inhibition of PDE1, PDE4 and PDE5 activities. CaM:calmodulin GB:glibenclamide HX:hypoxanthine IBMX:3-isobutyl-1-methylxanthine MLC:myosin light chain NBT:nitroblue tetrazolium O₂ ^·-:superoxide radical OA:okadaic acid PBS:phosphate-buffered saline PDE(s):cyclic nucleotide phosphodiesterase(s) PHE:phenylephrine SOD:superoxide dismutase TEA:tetraethylammonium XO:xanthine oxidase