Linoorbitides and enterolactone mitigate inflammation-induced oxidative stress and loss of intestinal epithelial barrier integrity

Abstract

Barrier integrity dysfunction and oxidative stress are considered hallmarks of inflammatory bowel disease (IBD) pathogenesis. Their mitigation continues to be a drug discovery target in IBD. Natural products may aid treatment of chronic inflammatory diseases, but their use in IBD requires a better understanding of whether individual bioactives may positively modulate disease course. This study investigated the ability of flax linoorbitides (LOBs) and enterolactone (ENL), to mitigate inflammation-induced loss of intestinal epithelial barrier integrity and oxidative stress in vitro. TNF-α with INF-γ and lipopolysaccharide (LPS) induced an inflammatory response in HCT-8 monoculture and Caco-2/RAW-264.7 coculture, respectively. Trans-Epithelial Electrical Resistance (TEER) and Lucifer Yellow rejection for barrier permeability were assessed in differentiated monolayers in the presence and absence of LOBs and ENL. Additionally, RAW 264.7 cells were used to assess protective effects upon induction of oxidative stress. In HCT-8 model, 200 nM of LOB-J, LOB-A, and ENL mitigated the inflammation-induced reduction in TEER with relative TEER values of 108.6%, 63.2%, and 64.2%, respectively, at 24 h relative to time zero. Similarly, at 24 h Caco-2/RAW-264.7 coculture TEER values ranged from ~200% - 243.4% for LOB-A, LOB-J, LOB-ACEJ, and ENL relative to TEER values of untreated cells. ENL and LOBs reduced malondialdehyde (MDA) lipid peroxidation in RAW 264.7 cells upon induction with lipopolysaccharide (LPS). ENL, but not LOBs, caused an increase in zona occludins 1 (ZO-1) protein expression in HCT-8 cells exposed to an inflammatory stimulus to levels comparable to negative control. Our results demonstrate after an inflammatory insult that ENL and the tested LOBs protect intestinal barrier integrity and reduce oxidative stress damage. In conclusion, use of different flax bioactives in the treatment of IBD warrants further investigation.

Keywords: Barrier integrity; IBD; Natural products; Oxidative stress.