idate loci involved in genetic susceptibility to Crohn’s disease. Mutation or deletion of ATG16L1 results in increased proinflammatory cytokine production, increased susceptibility to experimental colitis, and reduced capability to eradicate invading Prohibitin Modulation of Autophagy bacteria, indicating the importance of autophagy in suppressing intestinal inflammation. Multiple studies have reported mitochondrial dysfunction in Crohn’s disease and ulcerative colitis as well as the dextran sodium sulfate and 2,4,6-trinitrobenzene sulfonic acid models of colitis. Mitochondria are important regulators of autophagy and apoptosis. During normal function of the mitochondrial respiratory chain, reactive oxygen species, which are partially reduced oxygen species such as superoxide radical, hydrogen peroxide, hydroxyl radical, and peroxynitrate, are generated at low levels. Production of ROS is increased when mitochondria are damaged. IBD is associated with increased ROS and decreased antioxidant enzymes in the intestinal mucosa. It is widely accepted that ROS produced as a by-product of respiration as well as exogenous ROS can induce autophagy via mitochondrial damage. Mitochondria are the main source of ROS for regulation of autophagy. In fact, exogenous ROS and the proinflammatory cytokine tumor necrosis factor a, both of which are increased during IBD, promote cellular injury and autophagy via mitochondrial ROS generation. Defects in autophagy result in the accumulation of intracellular ROS and deformed mitochondria. Prohibitin 1 is an evolutionarily conserved, multifunctional 32 kDa protein implicated in cellular processes including the regulation of proliferation, apoptosis, and transcription. PHB is predominantly localized to the mitochondria in intestinal epithelial cells and multiple studies have shown that PHB plays a role in maintaining normal mitochondrial function and morphology. It has been shown that PHB interacts with complex I and subunits of cytochrome c oxidase of the respiratory chain and regulates their assembly. Loss of PHB in mitochondria impairs function of the mitochondrial respiratory chain. One obvious effect of respiratory chain dysfunction is increased oxidant production leading to oxidative stress, which can cause alterations in mitochondrial morphology and membrane potential. Expression of PHB is decreased in mucosal AVL 292 biopsies from ulcerative colitis and Crohn’s disease afflicted patients and in animal models of colitis. Pro-inflammatory cytokines such as TNFa and oxidative stress induced by exogenous H2O2 decrease expression of intestinal epithelial PHB in vivo and in vitro. Restoration of colonic epithelial PHB expression using genetic manipulation or therapeutic delivery to the colon via nanoparticle or adenovirus protected mice from experimental colitis. Our recent data PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/22182644 suggest that epithelial PHB sustains anti-oxidant expression and has anti-inflammatory properties such as reducing TNFa-stimulated NF-kB activation. This is in agreement with emerging data that suggest a role of PHB in combating oxidative stress in multiple cells types. In this study, we investigated the potential role of PHB in modulating 
mitochondrial stress-related autophagy in intestinal epithelial cells. Here, we show that TNFa and IFNc-induced autophagy inversely correlates with PHB protein expression and that gene silencing of PHB induces mitochondrial autophagy via increased intracellular ROS. Inhibition of autophagy during PHB knockdo
