Anti-inflammatory effect of avenanthramides via NF-κB pathways in C2C12 skeletal muscle cells

Avenanthramides (Avns), the polyphenol compounds found only in oats, have been shown to exhibit anti-inflammatory effects mainly by inhibiting nuclear factor (NF)-kappa B activation in select cell lines. However, the molecular mechanism by which Avns regulate the NF-kappa B pathway is still unclear. The purpose of this study was to investigate (1) the molecular mechanism by which three main fractions of Avns (AvnA, AvnB and AvnC) interact with I kappa B Kinase beta (IKK beta); and (2) whether this interaction results in reduced inflammatory responses in skeletal muscle cells. The protein-ligand docking and molecular dynamics simulation studies suggest that Avns acted as an allosteric inhibitor for modulating IKK beta's affinity for the NF-kappa B complex. Thus, Avns reduced IKK beta kinase activity in response to tert-butyl hydroperoxide (tBHP) stimulation and attenuated tBHP-induced TNF alpha and IL-1 beta mRNA expression. Furthermore, the three-fold increases in cyclooxygenase-2 (COX-2) protein and luciferase activity with tBHP treatment were reduced by 50% with Avns (P < .01), along with decreased prostaglandin E2 levels (P < .01). These data indicate that Avns are potent inhibitors of NF kappa B-mediated inflammatory response due to the downregulation of IKK beta activity in C2C12 cells.