Lack of transketolase-like (TKTL) 1 aggravates murine experimental colitis

Abstract

Transketolase-like (TKTL) 1 indirectly replenishes NADPH preventing damage induced by reactive oxygen species (ROS) formed upon intestinal inflammation. We investigated the function of TKTL1 during murine colitis and ROS detoxification for prevention of tissue damage. Mucosal damage in TKTL1−/− and wild-type (WT) mice was assessed by miniendoscopy and histology during dextran sodium sulfate (DSS) colitis. mRNA levels of interferon (IFN)-γ, inducible nitric oxide synthase (iNOS), interleukin (IL)-6, tumor necrosis factor (TNF), transketolase (TKT), and TKTL2 were determined by PCR and/or Western blotting. To assess oxidative and nitrosative stress nitrosylation, carbonylation and antioxidative enzymes catalase (Cat), superoxide dismutase 1 and 2, as well as glutathione (GSH) were determined. Myeloperoxidase (MPO) was determined for assessment of tissue neutrophils. TKTL1 knockout or DSS treatment did not influence TKT and TKTL2 mRNA or protein expression. Mucosal damage was significantly increased in TKTL1−/− mice indicated by miniendoscopy as well as a significantly shorter colon and more severe histological scores compared with WT mice during DSS colitis. This was associated with higher mRNA levels of IFN-γ, iNOS, IL-6, and TNF. In addition, iNOS protein expression was significantly enhanced in TKTL1−/− mice as well as MPO activity. Protein modification by nitric oxide (nitrotyrosine) was induced in TKTL1−/− mice. However, introduction of carbonyl groups by ROS was not induced in these mice. The expression of SOD1, SOD2, Cat, as well as GSH content was not significantly changed in TKTL1−/− mice. We conclude that induced colitis in TKTL1−/− mice was more severe compared with WT. This indicates a role of TKTL1 during mucosal repair and restoration.