Comparative proteomics reveals concordant and discordant biochemical effects of caffeine versus epigallocatechin-3-gallate in human endothelial cells.

Caffeine and epigallocatechin-3-gallate (EGCG) are the most abundant bioactive chemicals found in coffee and tea, respectively. While they are known to regulate normal physiology and body homeostasis, their biochemical effects, particularly at cellular and subcellular levels, remain under-investigated. We thus performed comparative proteomics study followed by bioinformatics analyses to investigate differential biochemical effects of these two chemicals on human endothelial cells. EA.hy926 cells were incubated with 100 μM caffeine or EGCG for 24-h and then subjected to label-free quantitative proteomics using nanoLC-ESI-Qq-TOF MS/MS compared to the control cells. A total of 142 and 152 significantly altered proteins were identified in caffeine-exposed and EGCG-exposed cells, respectively. Among these, 86 were the common changes found in both caffeine-exposed and EGCG-exposed cells. Bioinformatics revealed that both caffeine and EGCG mostly affected ribosomal proteins involving protein synthesis for membrane destination and secretion (e.g., SRP-dependent cotranslational protein targeting to membrane, protein targeting to endoplasmic reticulum, nuclear-transcribed mRNA catabolic process, nonsense-mediated decay, etc.). While the down-regulated proteins were similar in both groups, the up-regulated proteins in the EGCG-exposed cells highlighted the promoting effects of EGCG on actin-crosslink formation, glycolysis and ubiquitin-proteasome activity. These concordant and discordant changes in cellular proteome of human endothelial cells induced by caffeine and EGCG are useful for better understanding of biochemical/physiological effects of these two bioactive chemicals.