PECAM1 and Erythema: L-theanine ameliorated 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced erythema, increased vascular permeability, epidermal and dermal hyperplasia, and neutrophil infiltration via decreasing platelet endothelial cell adhesion molecule (PECAM)-1 expression and the production of pro-inflammatory cytokines including IL-1β, tumor necrosis factor (TNF)-α and cyclooxygenase (COX)-2 [34].