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There has been considerable work on the relationships between nutrition and the immune response, particularly on studies that have focused on adaptive responses. There is increasing recognition of the importance of innate immunity in host protection and initiation of cytokine networks. In this study, we examined the effect of select cocoa flavanols and procyanidins on innate responses in vitro. Peripheral blood mono-nuclear cells (PBMCs), as well as purified monocytes and CD4 and CD8 T cells, were isolated from healthy volunteers and cultured in the presence of cocoa flavanol fractions that differ from another by the degree of flavanol polymerization: short-chain flavanol fraction (SCFF), monomers to pentamers; and long-chain flavanol fraction (LCFF), hexamers to decamers. Parallel investigations were also done with highly purified flavanol monomers and procyanidin dimers. The isolated cells were then challenged with lipopolysaccharide (LPS) with quantitation of activation using CD69 and CD83 expression and analysis of secreted tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6, IL-10, and granulocyte macrophage colony-stimulating factor (GM-CSF). The chain length of flavanol fractions had a significant effect on cytokine release from both unstimulated and LPS-stimulated PBMCs. For example, there was a striking increase of LPS-induced synthesis of IL-1beta, IL-6, IL-10, and TNF-alpha in the presence of LCFF. LCFF and SCFF, in the absence of LPS, stimulated the production of GM-CSF. In addition, LCFF and SCFF increased expression of the B cell markers CD69 and CD83. There were also unique differential responses in the mononuclear cell populations studied. We conclude that the oligomers are potent stimulators of both the innate immune system and early events in adaptive immunity.

Procyanidins extracted from cocoa play a role in the defense against oxidative stress, as well as in vascular and immune functions. We previously reported that pentameric procyanidins isolated from cocoa inhibit the expression of the tyrosine kinase ErbB2 gene, thus slowing the growth of cultured human aortic endothelial cells. We herein investigate the further consequences of such inhibition by cocoa procyanidins, particularly regarding the protein level in phosphorylation patterns and the effects on the proliferation of human dermal microvascular endothelial cells (HDMECs) following angiogenic stimulation with low-level H2O2. We report herein that both the pentameric and octameric procyanidin fractions of cocoa inhibit the proliferation of HDMECs, whereas the pentameric fraction modulates the activity of several crucial proteins in angiogenic signaling by altering their tyrosine phosphorylation. Similar to aortic endothelial cells, the pentameric procyanidin fraction down-regulates the expression of ErbB2 tyrosine kinase in HDMECs. In conclusion, we report evidence suggesting that polyphenols may influence endothelial growth signaling, thus affecting angiogenesis in vitro. If these observations are applicable in vivo, they suggest a beneficial effect for cells overexpressing ErbB2, such as in specific neoplasias

Flavonoids isolated from cocoa have biological activities relevant to oxidant defenses, vascular health, tumor suppression, and immune function. The intake of certain dietary flavonoids, along with other dietary substances such as tocopherols, ascorbate, and carotenoids, is epidemiologically associated with a reduced risk of cardiovascular disease. Flavonoids have also been shown to modulate tumor pathology in vitro and in animal models. We took advantage of the conserved sequences found in tyrosine kinases to study the influence of cocoa fractions and controls on gene expression. We report that the pentameric procyanidin (molecular weight of 1442 daltons) fraction isolated from cocoa was a potent inhibitor of tyrosine kinase ErbB2 expression, a receptor important in angiogenesis regulation. Consistent with this primary observation, the cocoa flavonoid fraction also suppressed human aortic endothelial cell (HAEC) growth and decreased expression of two tyrosine kinases responsive to ErbB2 modulation, namely VEGFR-2/KDR and MapK 11/p38beta2. These inhibitory effects were observed when HAECs were treated with the flavonol fraction (molecular weight 280 daltons) isolated from cocoa, which comprise the structural subunits from which the procyanidin flavonoid subclass is biosynthetically constructed. Down-regulation of ErbB2 and inhibition of HAEC growth by cocoa procyanidins may have several downstream implications, including reduced vascular endothelial growth factor (VEGF) activity and angiogenic activity associated with tumor pathology. These results suggest specific dietary flavonoids are capable of selectively inhibiting ErbB2 and therefore may offer important insight into the design of therapeutic agents that target tumors overexpressing ErbB2.

Evidence suggests that certain flavan-3-ols and procyanidins (FP) can have a positive influence on cardiovascular health. It has been previously reported that FP isolated from cocoa can potentially modulate the level and production of several signaling molecules associated with immune function and inflammation, including several cytokines and eicosanoids. In the present study, we examined whether FP fractions monomers through decamers modulate secretion of the cytokine transforming growth factor (TGF)-beta(1) from resting human peripheral blood mononuclear cells (PBMC). A total of 13 healthy subjects were studied and grouped according to their baseline production of TGF-beta(1). When cells from individuals with low baseline levels of TGF-beta(1) (n = 7) were stimulated by individual FP fractions (25 microg/ml), TGF-beta(1) release was enhanced in the range of 15%-66% over baseline (P < 0.05; monomer, dimer, and tetramer). The low-molecular-weight FP fractions (<or=pentamer) were more effective at augmenting TGF-beta(1) secretion than their larger counterparts (>or=hexamer), with the monomer and dimer inducing the greatest increases (66% and 68%, respectively). In contrast to the above, TGF-beta(1) secretion from high TGF-beta(1) baseline subjects (n = 6) was inhibited by individual FP fractions (P < 0.05; trimer through decamer). The inhibition was most pronounced with trimeric through decameric fractions (28%-42%), and monomers and dimers moderately inhibited TGF-beta(1) release (17% and 23%, respectively). Given the vascular actions associated with TGF-beta(1), we suggest that in healthy individuals, homeostatic modulation of its production by FP offers an additional mechanism by which FP-rich foods can potentially benefit cardiovascular health.