Prolonged oleic acid exposure impairs Caco-2 cell differentiation and tight junction integrity

Proliferation to differentiation transition (PDT) of the intestinal epithelium is a critical step in intestinal homeostasis. Disruption of PDT balance can contribute to the onset and progression of systemic diseases. Consumption of high-fat diet (HFD) is known to promote systemic inflammation, in part due to the associated intestinal barrier permeabilization. This could be due to alterations in tight junction (TJ) formation and/or altered function during the process of stem cell differentiation into mature enterocytes. To investigate this potential mechanism, this study investigated the effects of exposure to oleic acid (OA), a fatty acid abundant in HFD, on Caco-2 cell differentiation. Caco-2 cells were incubated with 0.2-1.6 mM OA for 6 h/day, during the 10-21 days period involved in the transition of undifferentiated Caco-2 cells into mature enterocytes. We assessed time-dependent changes in markers of cell differentiation, monolayer permeability, and parameters of TJ structure and dynamics. We observed that OA: (1) altered barrier formation, as assessed by measuring the monolayer transepithelial electrical resistance; (2) decreased levels of the TJ proteins ZO-1 and claudin-1; and (3) activated signaling cascades/events leading to TJ opening, i.e. ERK1/2, NF-κB, and myosin light chain (MLC) phosphorylation, and (4) caused alterations in redox homeostasis. These findings suggest that prolonged exposure to OA has a disruptive effect on the transition of Caco-2 cells into fully differentiated enterocytes. This can in part explain the permeabilization of the intestinal barrier and systemic inflammation associated with regular HFD consumption.