Blood-brain barrier transport and neuroprotective potential of blackberry-digested polyphenols: an in vitro study. Homo sapiens

Purpose: Epidemiological and intervention studies have attempted to link the health effects of a diet rich in fruits and vegetables with the consumption of polyphenols and their impact in neurodegenerative diseases. Studies have shown that polyphenols can cross the intestinal barrier and reach concentrations in the bloodstream able to exert effects in vivo. However, the effective uptake of polyphenols in the brain is still regarded with some reservations. Here we describe a combination of approaches to examine the putative transport of blackberry-digested polyphenols (BDP) across the blood-brain barrier (BBB) and ultimate evaluation of their beneficial effects. Methods: BDP was obtained by in vitro digestion of blackberry extract and BDP major aglycones (hBDP) were obtained by enzymatic hydrolysis. Chemical characterization and BBB permeability of extracts were evaluated by LC-Orbitrap MS. BBB permeability and cytoprotection of both extracts was assessed in HBMEC monolayers. Neuroprotective potential of BDP was assessed in NT2-derived 3D co-cultures of neurons and astrocytes and in mouse cerebellar granule cells. Microarray analysis of BDP-modulated genes was evaluated in SK-N-MC cells. Results: Components from BDP and hBDP proven to be BBB permeable. Physiologically-relevant concentrations of both extracts were cytoprotective at endothelial level and BDP revealed to be neuroprotective in advanced cell models. The major canonical pathways involved in the neuroprotective effect of BDP were unveiled, comprising mTOR signaling and the unfolded protein response pathway. Genes like ASNS and ATF5 emerged as novel BDP modulated targets. Conclusions: BBB permeability of BDP and hBDP components reinforce the health benefits of a diet rich in polyphenols in neurodegerative disorders context. Our results suggest some novel pathways and genes that may be involved in the neuroprotective mechanism of the BDP polyphenol components. Overall design: Microarray analysis was performed on SK-N-MC cells incubated with in vitro digested extracts of commercial blackberry (BB) or of wild blackberry - Rubus vagabundus (RV) for 24h, with or without post-incubation with a stress inducer - hydrogen peroxide (S) . Control SK-N-MC cells were also analyzed (C). This experiment was performed three times, so three independent biological replicates per treatment were included in the microarray analysis.