Previously, we demonstrated that protein kinase D (PKD) plays a protective role during H2O2-induced intestinal cell death. Here, we Sought to determine whether this effect is mediated by nuclear factor kappa B (NF-kappa B) and mitogen-activated protein kinases (MAPKs). Treatment with H2O2 activated NF-kappa B in RIE-1 cells; H2O2 also induced the translocation of NF-kappa B p65 as well as phosphorylation of IKB-alpha. PKD1 siRNA inhibited H2O2-induced activation, translocation of NF-kappa B, and phosphorylation of IKB-alpha. We also found that overexpression of wild type PKD1 attenuated H2O2-induced phosphorylation of p38 MAN and its upstream activator, MAPK kinase (MKK) 3/6, whereas the phosphorylation was increased by PKD1 siRNA or kinase-dead PKD1. Phosphorylation of neither extracellular signal-regulated kinases (ERK) 1/2 nor c-Jun N-terminal kinases (JNK) was altered by PKD1 plasmids or siRNA. Our findings suggest that PKD protects intestinal cells through up-regulation of NF-kappa B and down-Fegulation of p38 MAPK. (C) 2008 Elsevier Inc. All rights reserved.