The plant alkaloid berberine has been shown to have many beneficial effects on human health. This has led to its use as a treatment for various cancer types, obesity, and diabetes. Moreover, a described barrier-strengthening effect in human cancer cell lines indicates that it might be useful for the treatment of inflammatory bowel disease. Detailed information regarding its effects on intestinal epithelium remains limited. In our current study, we describe the impact of berberine on a non-transformed porcine small intestinal epithelial cell model, IPEC-J2. Incubation of IPEC-J2 monolayers with berberine revealed dose- and time-dependent effects on barrier properties. A viability assay confirmed the specific effect of berberine on the apoptotic pathway, paralleled by the internalization of the sealing tight-junction (TJ) proteins claudin-1, claudin-3, and occludin within 6 h. Hence, the barrier function of the cells was reduced, as shown by the reduced transepithelial electrical resistance and the increased [3H]-D-Mannitol flux. A decrease of claudin-1, claudin-3, and occludin expression was also observed after 24 h, whereas ZO-1 expression was not significantly changed. These data indicate an early effect on both cell viability and barrier integrity, followed by a general effect on TJ architecture. The intracellular co-localization of claudin-1 and occludin or claudin-3 and occludin points to an initial induction of apoptosis accompanied by the internalization of sealing TJ proteins. Although barrier strengthening has been reported in cancerogenic epithelial models, our results show a barrier-weakening action, which represents a new aspect of the effect of berberine on epithelia. These results agree with the known toxic potential of plant alkaloids in general and show that berberine is also capable of exerting adverse effects in the intestinal epithelium.
