Acetyl salicylic acid induces damage to intestinal epithelial cells by oxidation-related

21 Acetyl salicylic acid (ASA) is one of the most frequently prescribed 22 medications for the secondary prevention of cardiovascular and cerebrovascular events. 23 It has recently been reported to cause small intestinal mucosal injury at a considerably 24 higher rate than previously believed. The aim of this study is to investigate the 25 mechanism by which this occurs using an in vitro small intestine model focusing on the 26 role of oxidative stress and cell permeability. Differentiated Caco-2 exhibits a 27 phenotype similar to human small intestinal epithelium. We measured whether ASA 28 induced the increase of differentiated Caco-2 permeability, the decrease of tight junction 29 (TJ) protein expression, the production of reactive oxygen species (ROS), and the 30 expression of ROS-modified ZO-1 protein. In some experiments, MnTMPyP (a 31 superoxide dismutase mimetic) was used. The non-toxic concentration of ASA 32 decreased transepithelial electrical resistance (TEER) and increased the flux of 33 FITC-conjugated dextran (FD4) across Caco-2 in a time-dependent manner. The same 34 concentration of ASA significantly decreased ZO-1 expression among TJ proteins as 35 assessed by western blot and immunocytochemistry, and increased ROS production and 36 the expression of oxidative stress-modified ZO-1 protein. However, MnTMPyP 37 suppressed the ASA-induced increased intercellular permeability and the ASA-induced 38