Caco-2 cells (clone HTB-37) were obtained from the Leibniz Institute DSMZ-German Collection of Microorganisms Cell Cultures (Braunschweig, Germany), and primary human umbilical vein endothelial cells (HUVECs) from pooled donors were obtained from Lonza (Basel, Switzerland). Caco-2 cells were cultured in a T75 cm2 cell culture flask in 12 mL Dulbecco’s Modified Eagle Medium (DMEM) containing 20% fetal calf serum (FCS), 1% nonessential amino acids (NEAAs), 2 mM glutamine, and 100 U/mL penicillin, as well as 100 µg/mL streptomycin (Caco-2 culture medium), in a humidified incubator at 37 °C and 95% CO2. Subculturing was conducted after the cell layer reached ~80% confluency, usually every seven days. For subculturing, Caco-2 cells were washed with 10 mL PBS without magnesium or calcium before they were treated with 5 mL Accutase® (Merck, Darmstadt, Germany) for a maximum of 15 min or until all cells were detached. The enzymatic reaction was stopped with 8 mL Caco-2 culture medium, and the cells were centrifuged at 300 rcf for 5 min. Caco-2 cells were counted and 0.25 × 106 viable cells were seeded in a new T75 cm2 cell culture flask in 12 mL Caco-2 culture medium. All solutions, except for Accutase (room temperature), were warmed to 37 °C before use. Caco-2 cells were not used for more than 20 passages. HUVECs were handled similarly, with a few exceptions. The HUVECs were fed with 15 mL endothelial cell growth medium, with all supplements from Promocell (Heidelberg, Germany) including 2% FCS (HUVEC culture medium). In addition, the HUVECs were detached with Accutase solution for 5 min, and cells were only used from passages 2 to 6.