Showing papers by "Sabina Passamonti published in 2009"

Bioavailability of flavonoids: a review of their membrane transport and the function of bilitranslocase in animal and plant organisms.

Abstract: Fruits and vegetables are rich in flavonoids, and ample epidemiological data show that diets rich in fruits and vegetables confer protection against cardiovascular, neurodegenerative and inflammatory diseases, and cancer. However, flavonoid bioavailability is reportedly very low in mammals and the molecular mechanisms of their action are still poorly known. This review focuses on membrane transport of flavonoids, a critical determinant of their bioavailability. Cellular influx and efflux transporters are reviewed for their involvement in the absorption of flavonoids from the gastro-intestinal tract and their subsequent tissue distribution. A focus on the mammalian bilirubin transporter bilitranslocase (TCDB 2.A.65.1.1) provides further insight into flavonoid bioavailability and its relationship with plasma bilirubin (an endogenous antioxidant). The general function of bilitranslocase as a flavonoid membrane transporter is further demonstrated by the occurrence of a plant homologue in organs (petals, berries) where flavonoid biosynthesis is most active. Bilitranslocase appears associated with sub-cellular membrane compartments and operates as a flavonoid membrane transporter.

Identification and localization of the bilitranslocase homologue in white grape berries (Vitis vinifera L.) during ripening

Abstract: A homologue of the mammalian bilirubin transporter bilitranslocase (BTL) (TCDB 2A6511), able to perform an apparent secondary active transport of flavonoids, has previously been found in carnation petals and red grape berries In the present work, a BTL homologue was also shown in white berries from Vitis vinifera L cv Tocai/Friulano, using anti-sequence antibodies specific for rat liver BTL This transporter, similarly to what found in red grape, was localized in the first layers of the epidermal tissue and in the vascular bundle cells of the mesocarp In addition, a strong immunochemical reaction was detected in the placental tissue and particularly in peripheral integuments of the seed The protein was expressed during the last maturation stages in both skin and pulp tissues and exhibited an apparent molecular mass of c 31 kDa Furthermore, the transport activity of such a carrier, measured as bromosulphophthalein (BSP) uptake, was detected in berry pulp microsomes, where it was inhibited by specific anti-BTL antibodies The BTL homologue activity exhibited higher values, for both K(m) and V(max), than those found in the red cultivar Moreover, two non-pigmented flavonoids, such as quercetin (a flavonol) and eriodictyol (a flavanone), inhibited the uptake of BSP in an uncompetitive manner Such results strengthen the hypothesis that this BTL homologue acts as a carrier involved also in the membrane transport of colourless flavonoids and demonstrate the presence of such a carrier in different organs and tissues

Cellular antioxidant activity of bilirubin in the human endothelial cell line EA.hy 926 is mediated by bilitranslocase

Abstract: . The latter can be ascribed to an efficientamplification cycle whereby bilirubin, acting as antioxi-dant, is itself oxidized to biliverdin and then recycled backto bilirubin by NADPH-dependent biliverdin reductase.Bilitranslocase, a bilirubin-specific membrane carrier thatmediates cellular uptake of bilirubin, has recently beenfound in the vascular endothelium. However, the levels ofalbumin-free bilirubin in plasma and tissues are only 10to 50 nM. Therefore, the objective of this study was to elu-cidate the antioxidant activity of low concentrations ofbilirubin and the involvement of bilitranslocase-medi-ated plasma membrane transport in human endothelialcells.

Presence of bilitranslocase in the vascular system and its role in the vasodilatation activity of anthocyanins

Abstract: Background Flavonoids are well known for their vasodilatation activity. Their mechanism of action is still to be elucidated. Bilitranslocase is a bilirubin-specific membrane carrier that is also responsible for the ATP-independent transport of flavonoids across the cell membrane [1]. Recently, the expression of bilitranslocase in the endothelium has been characterized [2]. The aim of the study was to examine the possible role of bilitranslocase in the vasodilatation activity of flavonoids. As a source of flavonoids we used bilberries, which are abundant in anthocyanins that show strong affinity for bilitranslocase.