A proteomic analysis of procyanidin B2 isolated from cocoa against oxidized low-density lipoprotein-induced lipid-laden macrophage formation was performed. Of ≈400 detected proteins, 12 were differentially expressed as a result of B2 treatment. They were subsequently identified by liquid chromatography-electrospray ionization-tandem mass spectrometry and the SWISS-PROT database.
Further reverse transcriptase-polymerase chain reaction and Western blot analysis revealed that B2 strongly inhibited arachidonic acid inflammatory reactions, apoptosis, and their coupled mitogen-activated protein kinase and NF-κB pathways. To highlight proteins or genes with similar expressed patterns and similarly biological function induced by B2 in lipid-laden macrophages, a cluster and Kyoto Encyclopedia of Genes and Genomes pathway analysis were performed. The data were mapped to multiple pathways. Further validation of the bioinformatic results revealed that activation of Wnt signaling may contribute to the cardioprotection of B2.
The differentially expressed genes and proteins mentioned above induced by B2 are through regulating nuclear transcription factors, activating peroxisome proliferator-activated receptor-gamma and inhibiting AP-1 mRNA expressions. These in vitro data help to interpret the beneficial effects of B2 in reducing the risk of atherosclerosis after consumption of flavonoid-rich foods. Many differentially expressed genes induced by B2 help to uncover novel targets and may help to target disease interactions in atherosclerosis in the future.