Platelet-activating factor (PAF) induces wheal and flare skin reactions independent of mast cell degranulation

BACKGROUND

Platelet-activating factor (PAF) causes wheal and flare responses which are abrogated by H1-antihistamines giving rise to the hypothesis that PAF-induced wheal development is secondary to histamine release from dermal mast cells. But is this hypothesis correct?

METHODS

Wheal and flare responses were induced by intradermal injection of PAF, codeine and histamine in 14 healthy volunteers. Dermal histamine and PGD2 contractions were measured using microdialysis.

RESULTS

PAF, unlike histamine and codeine, did not cause a statistically significant rise in mean histamine levels with ten persons showing negligible histamine release. Codeine caused a significant but variable histamine release, ranging from 29 to 282 ng/ml. Codeine, but not PAF or histamine, caused a small but statistically significant release of PGD2.

CONCLUSION

Wheal and flare reactions in human skin induced by PAF are not associated with histamine release and, therefore, appear to be independent of mast cell degranulation.

Tyrosol and hydroxytyrosol are absorbed from moderate and sustained doses of virgin olive oil in humans

OBJECTIVE

To investigate the absorption of tyrosol and hydroxytyrosol from moderate and sustained doses of virgin olive oil consumption. The study also aimed to investigate whether these phenolic compounds could be used as biomarkers of virgin olive oil intake.

DESIGN AND INTERVENTIONS

Ingestion of a single dose of virgin olive oil (50 ml). Thereafter, for a week, participants followed their usual diet which included 25 ml/day of the same virgin olive oil as the source of raw fat.

SETTING

Unitat de Recerca en Farmacologia. Institut Municipal d'Investigació Mèdica (IMIM).

SUBJECTS

Seven healthy volunteers.

RESULTS

An increase in 24 h urine of tyrosol and hydroxytyrosol, after both a single-dose ingestion (50 ml) and short-term consumption (one week, 25 ml/day) of virgin olive oil (P<0.05) was observed. Urinary recoveries for tyrosol were similar after a single dose and after sustained doses of virgin olive oil. Mean recovery values for hydroxytyrosol after sustained doses were 1.5-fold those obtained after a single 50 ml dose.

CONCLUSIONS

Tyrosol and hydroxytyrosol are absorbed from realistic doses of virgin olive oil. With regard to the dose-effect relationship, 24 h urinary tyrosol seems to be a better biomarker of sustained and moderate doses of virgin olive oil consumption than hydroxytyrosol.

Bioavailability of tyrosol, an antioxidant phenolic compound present in wine and olive oil, in humans

Tyrosol is a phenolic compound present in two of the traditional components of the Mediterranean diet: wine and virgin olive oil. The presence of tyrosol has been described in red and white wines. Tyrosol is also present in vermouth and beer. Tyrosol has been shown to be able to exert antioxidant activity in in vitro studies. Oxidation of low-density lipoprotein (LDL) appears to occur predominantly in arterial intima in microdomains sequestered from antioxidants of plasma. The antioxidant content of the LDL particle is critical for its protection. Thus, phenolics, which are able to bind LDL, could be effective in preventing lipid peroxidation and atherosclerotic processes. The ability of tyrosol to bind human LDL has been reported. We have demonstrated the bioavailability of tyrosol in humans from virgin olive oil in its natural form. Urinary tyrosol increased, reaching a peak at 0-4 h after virgin olive oil administration. Men and women showed a different pattern of urinary excretion of tyrosol. Moreover, tyrosol is absorbed in a dose-dependent manner after sustained and moderate doses of virgin olive oil. In summary, our results suggest that tyrosol from wine or virgin olive oil could exert beneficial effects on human health in vivo if its biological properties are confirmed in in vivo studies.

Postprandial effects of wine consumption on lipids and oxidative stress biomarkers

Postprandial lipemia has been recognized as a risk factor for atherosclerosis development. Consuming meals with suitable sources of antioxidants such as red wine reduces postprandial oxidative stress. However, information about the postprandial effects of wine ingestion outside meals on lipids and on in vivo low-density lipoprotein (LDL) oxidation in humans is scarce. The aim of this study was to investigate postprandial changes in lipids and in vivo LDL oxidation after moderate (250 ml) red wine ingestion, before and after sustained wine consumption of 250 ml/day for 4 days. After 4 days of sustained wine consumption a decrease in the LDL/high-density lipoprotein cholesterol ratio was observed after wine ingestion (p = 0.026). On day 4, a decrease in oxidized LDL levels and an increase in the antioxidant enzyme glutathione peroxidase activity (p = 0.025) were observed after wine ingestion. Our results show that consumption of red wine at moderate doses outside meals does not promote oxidative stress. Daily consumption of moderate doses of red wine can improve postprandial lipid profile and oxidative status when wine is ingested outside meals.