In vitro cytotoxic effect of wheat gliadin-derived peptides on the Caco-2 intestinal cell line is associated with intracellular oxidative imbalance: implications for coeliac disease
Coeliac disease (CD) is an inflammatory disorder of the upper small intestine in which gluten acts as an essential factor in its pathogenesis. Although it is generally accepted that cereal protein activation of the immune system is involved in CD progression, a non-immunomediated cytotoxic activity of gliadin-derived peptides on the jejunal/duodenal tract cannot be excluded. In this work, considering that (a) little has been reported about the intracellular metabolic events associated with gliadin toxicity, and (b) an important role for free radicals in a number of gastrointestinal disease has been demonstrated, we investigated the in vitro effects of gliadin-derived peptides on redox metabolism of Caco-2 intestinal cells during a kinetic study in which cells were exposed to peptic–tryptic digest of bread wheat up to 48 h. We found that the antiproliferative effects displayed by gliadin exposure was associated with intracellular oxidative imbalance, characterised by an increased presence of lipid peroxides, an augmented oxidised (GSSG)/reduced (GSH) glutathione ratio and a loss in protein-bound sulfhydryl groups. Significant structural perturbations of the cell plasma membrane were also detected. Additional experiments performed by using the specific GSH-depleting agent buthionine sulfoximine provide evidence that the extent of gliadin-induced cell growth arrest critically depends upon the ‘basal’ redox profile of the enterocytes. On the whole, these findings seem to suggest that, besides the adoption of a strictly gluten-free diet, the possibility for an adjuvant therapy with antioxidants may be considered for CD patients.
