ABSTRACT
Inflammatory bowel disease (IBD) is a group of chronic, relapsing, immunological, inflammatory disorders of the gastrointestinal tract including ulcerative colitis (UC) and Crohn's disease (CD). It has been reported that UC, which is studied using a dextran sodium sulfate (DSS)-induced colitis model, is associated with the production of reactive oxygen species (ROS) and the apoptosis of intestine epithelial cells (IEC). Mitochondrial NADP+-dependent isocitrate dehydrogenase (IDH2) has been reported as an essential enzyme in the mitochondrial antioxidant system via generation of NADPH. Therefore, we evaluated the role of IDH2 in DSS-induced colitis using IDH2-deficient (IDH2-/-) mice. We observed that DSS-induced colitis in IDH2-/- mice was more severe than that in wild-type IDH2+/+ mice. Our results also suggest that IDH2 deficiency exacerbates PUMA-mediated apoptosis, resulting from NF-κB activation regulated by histone deacetylase (HDAC) activity. In addition, DSS-induced colitis is ameliorated by an antioxidant N-acetylcysteine (NAC) through attenuation of oxidative stress, resulting from deficiency of the IDH2 gene. In conclusion, deficiency of IDH2 leads to increased mitochondrial ROS levels, which inhibits HDAC activity, and the activation of NF-κB via acetylation is enhanced by attenuated HDAC activity, which causes PUMA-mediated apoptosis of IEC in DSS-induced colitis. The present study supported the rationale for targeting IDH2 as an important cancer chemoprevention strategy, particularly in the prevention of colorectal cancer.
Subject(s)
Apoptosis , Colitis, Ulcerative/metabolism , Isocitrate Dehydrogenase/genetics , Animals , Apoptosis Regulatory Proteins/metabolism , Colitis, Ulcerative/etiology , Colitis, Ulcerative/genetics , Colitis, Ulcerative/pathology , Dextran Sulfate/toxicity , Histone Deacetylases/metabolism , Isocitrate Dehydrogenase/deficiency , Isocitrate Dehydrogenase/metabolism , Male , Mice , Mice, Inbred C57BL , NF-kappa B/metabolism , Oxidative Stress , Reactive Oxygen Species/metabolism , Tumor Suppressor Proteins/metabolismABSTRACT
Go, a heterotrimeric G-protein, is enriched in brain and neuronal growth cones. Although several reports suggest that Go may be involved in modulation of neuronal differentiation, the precise role of Go is not clear. To investigate the function of Go in neuronal differentiation, we determined the effect of Goalpha, the alpha subunit of Go, on the expression of Ca(v)2.2, the pore-forming unit of N-type calcium channels, at the transcription level. Treatment with cyclic AMP (cAMP), which triggers neurite outgrowth in neuroblastoma F11 cells, increased the mRNA level and the promoter activity of the Ca(v)2.2 gene. Overexpression of Goalpha inhibited neurite extension in F11 cells and simultaneously repressed the stimulatory effect of cAMP on the Ca(v)2.2 gene expression to the basal level. Targeted mutation of the Goalpha gene also increased the level of Ca(v)2.2 in the brain. These results suggest that Go may regulate neuronal differentiation through modulation of gene expression of target genes such as N-type calcium channels.
