Modulating the anti-inflammatory and barrier protective effects on intestinal epithelial cells utilizing an aqueous Aspalathus linearis extract in vitro

Background

Rooibos is a natural herbal plant containing numerous unique polyphenols which have been associated with certain health benefits. Several of these bioactive constituents have been linked to promoting gut health through its beneficial actions such as anti-inflammatory and anti-spasmodic characteristics.

Purpose

The study aims to compare the anti-inflammatory and barrier protective effects of an unfermented and fermented rooibos aqueous extract on intestinal porcine epithelial cells (IPEC-J2).

Methods

Aqueous extracts of unfermented and fermented rooibos were prepared, and chemical and antioxidant analysis were performed of each extract. Intestinal porcine epithelial cells (IPEC-J2) were pre-treated with either unfermented or fermented aqueous rooibos extracts (0.1 and 0.05 mg/ml) then exposed to 10 µg/ml of Escherichia coli lipopolysaccharide (LPS). Cell viability, protein and gene expression of pro-inflammatory cytokines were investigated to determine the anti-inflammatory effect of both extracts. Barrier integrity of IPEC-J2 was investigated by measuring the Transepithelial electrical resistance (TEER) and quantifying tight junction gene expression.

Results

Both the unfermented and fermented rooibos extracts have significant anti-inflammatory properties by reducing pro-inflammatory cytokine production. Interestingly for certain genes (IL-8, IL-6, IL-1B and CCL20) the fermented extracts, specifically at 0.1 mg/ml, exhibited greater effectiveness by decreasing the expression after LPS-induced inflammation whilst for another gene (TNF-α) the unfermented extract at both concentrations was more efficient in decreasing expression and ultimately protecting the IPEC-J2 cells from inflammation. When evaluating the barrier integrity, 0.1 mg/ml of the unfermented rooibos extract showed the most significant barrier protective effects through upregulation of tight junction proteins, ZO-1, Occludin as well as Claudin-4.

Conclusion

Higher concentration of the fermented rooibos extract prevented the inflammatory response significantly whilst the higher concentration of the unfermented rooibos extract enhanced tight junction expression and protected barrier integrity in LPS-induced inflamed intestinal cells. This is attributed to the differences in the polyphenol content of each extract and demonstrating the unique activity mechanisms of different rooibos extracts to reduce onset of early inflammation.