Signalling pathways involved in the expression of Transglutaminase 2 induced by IFNg and TNFa in the small intestine mucosa

BAYARDO, MARIELA; BONDAR, CONSTANZA; CHIRDO, FERNANDO

Oslo

Simposio; 14th International Coeliac Disease Symposium 2011; 2011

 Transglutaminase 2 (TG2) plays important roles in the pathogenesis of Coeliac Disease (CD). The small intestinal mucosa in untreated CD patients contains several proinflammatory cytokines whose signal transduction pathways driving TG2 expression have not been assessed. The aim of this work was to study the signalling pathways involved in TG2 induction in proinflammatory settings in human small intestine. Caco-2 cells were incubated with TNFa, gIFN, IL-6, IL-1, IL-15 for 24h. The analysis of TG2 RNAm level, by qRT-PCR, showed that gIFN was the most potent inducer of TG2 expression (fold increase?fi=18) followed by TNFa (fi=4). While IL-6, IL-1 and IL-15 showed a fi lower than 3. Treatment of Caco-2 cells with TNFa+gIFN showed a synergistic effect on TG2 expression (fi=25,7). Biopsies from untreated CD patients showed statistically higher TG2 levels than control samples. Differences were even higher after TNFa+gIFN incubation showing the synergistic effect. Using a set of inhibitors, we observed that NFkB pathway was central for the induction of TG2 by either TNFa or gIFN, being completely blocked by Sulfasalazine and BAY-117082. Both cytokines also induced separate cascades. The induction of TG2 by TNFa was completely blocked by SB203580 (MAPKp38). Wortmanine (PI3K) and Ly294002 (Akt), blocked the TG2 induction by gIFN. Inhibition of NFkB (sulfosalazine) or Akt (Ly294002) blocked TG2 induction in biopsies from CD or control individuals incubated with TNFa+gIFN. Conclusion. gIFN was the most potent inducer of TG2 expression. Together with TNFa produced a synergistic induction of TG2 which must be considered as part of the pathogenic mechanism of CD. Specific inhibitors selectively blocked signalling pathways involved in the induction of TG2 by TNFa and gIFN. Altogether, this information can be valuable not only on the role of TG2 in the pathogenic mechanisms of disease but also on the therapeutic potential of its pharmacological inhibition.