Probiotics potentiate IL-6 production in IL-1β-treated Caco-2 cells through a heat shock-dependent mechanism

IL-6 may exert anti-inflammatory and protective effects in intestinal mucosa and enterocytes. The influence of probiotics on mucosal and enterocyte IL-6 production is not known. We tested the hypothesis that the probiotic bacteria Lactobacillus paracasei and Lactobacillus plantarum regulate IL-6 production in intestinal epithelial cells. Cultured Caco-2 cells were treated with 1 ng/ml of IL-1β in the absence or presence of different concentrations of L. paracasei or L. plantarum followed by measurement of IL-6 production. The role of heat shock response was examined by determining the expression of heat shock protein 70 (hsp70) and hsp27, by downregulating their expression with small interfering RNA (siRNA), or by treating cells with quercetin. Treatment of the Caco-2 cells with IL-1β resulted in increased IL-6 production, confirming previous reports from this laboratory. Probiotics alone did not influence IL-6 production, but the addition of probitoics to IL-1β-treated cells resulted in a substantial augmentation of IL-6 production. Treatment of the Caco-2 cells with live L. paracasei increased cellular levels of hsp70 and hsp27 and the potentiating effect on IL-6 production was inhibited by quercetin and by hsp70 or hsp27 siRNA. Results suggest that probiotics may enhance IL-6 production in enterocytes subjected to an inflammatory stimulus and that this effect may, at least in part, be heat shock dependent.