Activity of the glutathione peroxidase 2. Differences in the selenium dependent expression between colon and small intestine

Background Selenium Se is an essential element which is involved in various biological processes in nearly all tissues of animals and human, e.g. protection against oxidative stress in the cardiovascular system, and may play a role in cancer protection. It is incorporated in the proteome in the form of the genetically encoded amino acid selenocysteine, which is the characteristic component of the selenoproteins. Materials and Methods We investigated the expression of the selenoenzyme GPx 2 which is predominantly present in the tissues of the gastrointestinal tract such as the small intestine and therefore named gastrointestinal glutathione peroxidase. Rats were fed with a Se adequate or Se deficient diet and GPx 2 was assessed by means of enzyme activity with respect to the Se concentration in tissues of the colon and small intestine. Se quantification was carried out by means of graphite furnace atom absorption spectrometry and 2D gel electrophoresis was applied to investigate the expression of the proteins of the small intestine tissue samples. Results Twenty eight differences could be distinguished in the protein spot distribution of the 2D gels of the homogenates. The GPx 2 activity in the Se deficient rat colon samples was 6.8 fold lower than in the Se adequate rats in contrast to 1.2 fold lower levels between the corresponding samples in the small intestine. Conclusion This finding might explain the different susceptibility of the colon and the small intestine to cancer and support the theory of the protective effect of selenium in the gastrointestinal trac

Infliximab in moderately severe glucocorticoid resistant ulcerative colitis: a randomised controlled trial

Background: Tumour necrosis factor production is increased in the mucosa of patients with active ulcerative colitis. The benefits of infliximab in Crohn’s disease are established. We investigated its efficacy in ulcerative colitis. Methods: We conducted a randomised placebo controlled trial of infliximab (5 mg/kg) in the treatment of glucocorticoid resistant ulcerative colitis. Infusions were given at weeks 0 and 2. Disease activity and quality of life were recorded over eight weeks of follow up. Remission was defined as an ulcerative colitis symptom score (UCSS) of ⩽2 and/or Baron score of 0 at week 6. Patients not in remission were offered open label infliximab 10 mg/kg and reviewed two weeks later. Results: After two weeks, there was no statistically significant difference between the infliximab and placebo groups in the proportion of patients with a Baron score of 0 (13% (3/23) v 5% (1/19) (95% confidence interval (CI) −9% to 24%); p=0.74). After six weeks, remission (UCSS ⩽2) rates were 39% (9/23) versus 30% (6/20) (95% CI −19 to 34%; p=0.76). The median improvement in UCSS was 3 for the infliximab group and 2.5 for the placebo group (p=0.82, Mann-Whitney U test). A Baron score of 0 was likely in either group (26% (6/23) v 30% (6/20) (95% CI −30% to 23%); p=0.96). Improvement in the IBDQ and EuroQol was not significantly different between the groups (p=0.22 and 0.3, respectively, Mann-Whitney U test). Twenty eligible patients were given open labelled infusions. Remission was achieved in 3/11 (27%) patients initially treated with infliximab and in 1/9 (11%) patients treated with placebo. Conclusion: These data do not support the use of infliximab in the management of moderately active glucocorticoid resistant ulcerative colitis

Mechanism and function of DNA replication-independent DNA-protein crosslink repair via the SUMO-RNF4 pathway

DNA‐protein crosslinks (DPCs) obstruct essential DNA transactions, posing a serious threat to genome stability and functionality. DPCs are proteolytically processed in a ubiquitin‐ and DNA replication‐dependent manner by SPRTN and the proteasome but can also be resolved via targeted SUMOylation. However, the mechanistic basis of SUMO‐mediated DPC resolution and its interplay with replication‐coupled DPC repair remain unclear. Here, we show that the SUMO‐targeted ubiquitin ligase RNF4 defines a major pathway for ubiquitylation and proteasomal clearance of SUMOylated DPCs in the absence of DNA replication. Importantly, SUMO modifications of DPCs neither stimulate nor inhibit their rapid DNA replication‐coupled proteolysis. Instead, DPC SUMOylation provides a critical salvage mechanism to remove DPCs formed after DNA replication, as DPCs on duplex DNA do not activate interphase DNA damage checkpoints. Consequently, in the absence of the SUMO‐RNF4 pathway cells are able to enter mitosis with a high load of unresolved DPCs, leading to defective chromosome segregation and cell death. Collectively, these findings provide mechanistic insights into SUMO‐driven pathways underlying replication‐independent DPC resolution and highlight their critical importance in maintaining chromosome stability and cellular fitness