Effects of residual levels of tetracycline on the barrier functions of human intestinal epithelial cells

- The use of antibiotics in food producing animals could result in antimicrobial drug residues in the edible tissues.
- The permeability study revealed that 15 and 150 μg/ml of tetracycline causes intestinal barrier disruption.
- Altered gene expression is observed even at residual level of tetracycline (1.5 μg/ml).
- Translocation of bacteria from apical to basal compartment provides proof of concept to intestinal barrier disruption.

Tetracyclines are frequently used in food-producing animals to treat, control, and prevent microbial diseases. Concerns are raised regarding the effects of residual levels of tetracycline, which may be present in the food supply, for emergence of drug-resistance and transfer of antibiotic-resistance gene in intestinal microbiota. In contrast, no information is available regarding the possible effects of residual tetracycline on the gastrointestinal epithelial layer barrier-disruption. This study investigates the outcome of tetracycline treatment on intestinal epithelial cells integrity. Intestinal epithelial cells (T84) were treated at concentrations of 0.015, 0.15, 1.5, 15 and 150 μg/ml for 48 h in an in vitro cell culture model. The permeability study revealed that 15 and 150 μg/ml of tetracycline causes barrier disruption. Whereas the altered mRNA expression of notch-3, notch-4, claudin-2, claudin-8, claudin-10, claudin-15, gap junction alpha 8 and delta 2 and integrin, alpha 3 and alpha L, which are cell-integrity-related genes starts at 1.5 μg/ml tetracycline after 48 h treatment. Translocation of GFP-labeled bacteria from apical to basal comportment provides proof of concept to intestinal barrier disruption. This study is the first to evaluate whether residual concentrations of tetracycline impact epithelial cell integrity.

This cartoon diagram shows the possible effects of various concentrations of tetracycline on T84 cells. a) Values below the mADI (<1.5 μg/ml) of tetracycline did not alter the barrier function and antibiotics remain in apical compartments, b) The concentration corresponding to the mADI value (1.5 μg/ml) and a concentration above mADI (15 μg/ml) perturbed the epithelial monolayer; barrier function was not totally lost and the majority of tetracycline was still possibly in the apical compartment, and c) 150 μg/ml tetracycline totally compromised the barrier integrity of epithelial cells and could have allowed the majority of the tetracycline to reach the basal compartment.276