IKappaB-kinase/nuclear factor-kappaB signaling prevents thermal injury-induced gut damage by inhibiting c-Jun NH2-terminal kinase activation

Abstract

Objective: The molecular mechanism of major burn-induced gut damage is not clear. This study is to determine whether IkappaB-kinase (IKK)/nuclear factor-kappaB signaling in intestinal mucosa maintains gut function through the regulation of the c-Jun NH2-terminal kinase (JNK) and p38 phosphorylation.

Design: Prospective, experimental study.

Setting: Research laboratory at a university hospital.

Subjects: Thermal injury models in mice.

Interventions: Conditional intestinal epithelial cell IKKbeta knockout (Vil-Cre/Ikkbeta(F/Delta) mice and control (Ikkbeta(F/Delta) mice were subjected to 30% total body surface area third-degree burn. JNK inhibitor (SP600125) or p38 inhibitor (SB203580) was given to mice immediately after burn injury.

Measurements and main results: Thermal injury induced a significant increase of intestinal permeability, nuclear factor-kappaB DNA-binding activity, phosphorylated JNK, phosphorylated p38, and caspase 3 expression of intestinal mucosa in Vil-Cre/Ikkbeta(F/Delta) mice compared with those of Ikkbeta(F/Delta) mice. BCL-xL and cellular FLICE inhibitory protein, but not GADD45beta (growth arrest and DNA damage-inducing protein beta), cellular inhibitor of apoptosis 1, Bfl-1, or TRAIL, messenger RNA expression was significantly decreased in Vil-Cre/Ikkbeta(F/Delta) mice compared with that of Ikkbeta(F/Delta) mice. SP600125 decreased intestinal permeability and increased phosphorylated p38 and tumor necrosis factor receptor-associated factor 2 expression of intestinal mucosa in Vil-Cre/Ikkbeta(F/Delta) mice. SB203580 treatment enhanced thermal injury-induced gut damage in Vil-Cre/Ikkbeta(F/Delta) mice.

Conclusions: Thermal injury induces nuclear factor-kappaB activation of intestinal mucosa and IKK protects intestinal mucosa from thermal injury-induced gut damage. IKK blocks caspase 3 expression by up-regulating BCL-xL and cellular FLICE inhibitory protein expression. IKK inhibits JNK and p38 but not p44/42 phosphorylation of intestinal mucosa. JNK inhibition increases p38 and tumor necrosis factor receptor-associated factor 2 expression and decreases thermal injury-induced gut damage. Taken together with the enhanced thermal injury-induced gut damage by p38 inhibition, we conclude that IKK maintains gut function by inhibiting JNK phosphorylation, which suppresses p38 phosphorylation and induces gut damage.