Witting, P. K. | Search bioRxiv

bioRxiv2020

The role of sodium thiocyanate supplementation during dextran sodium sulphate-stimulated experimental colitis

Ulcerative colitis is a condition characterised by the infiltration of leukocytes into the gastrointestinal wall. Leukocyte-MPO catalyses hypochlorous acid (HOCl) and hypothiocyanous acid (HOSCN) formation from chloride (Cl-) and thiocyanous (SCN-) anions, respectively. While HOCl indiscriminately oxidises biomolecules, HOSCN primarily targets low-molecular weight protein thiols. Oxidative damage mediated by HOSCN may be reversible, potentially decreasing MPO-associated host tissue destruction. This study investigated the effect of SCN- supplementation in a model of acute colitis. Female mice were supplemented dextran sodium sulphate (DSS, 3% w/v) in the presence of 10 mM Cl- or SCN- in drinking water ad libitum, or with salts (NaCl and NaSCN only) or water only (controls). Behavioural studies showed mice tolerated NaSCN and NaCl-treated water with water-seeking frequency. Ion-exchange chromatography showed increased fecal and plasma SCN- levels in thiocyanate supplemented mice; plasma SCN- reached similar fold-increase for smokers. Overall there was no difference in weight loss and clinical score, mucin levels, crypt integrity and extent of cellular infiltration between DSS/SCN- and DSS/Cl- groups. Neutrophil recruitment remained unchanged in DSS-treated mice, as assessed by fecal calprotectin levels. Total thiol and tyrosine phosphatase activity remained unchanged between DSS/Cl- and DSS/SCN- groups, however, colonic tissue showed a trend in decreased 3-chlorotyrosine (1.5-fold reduction, p<0.051) and marked increase in colonic GCLC, the rate-limiting enzyme in glutathione synthesis. These data suggest that SCN- administration can modulate MPO activity towards a HOSCN-specific pathway, however, this does not alter the development of colitis within a DSS murine model.HighlightsSodium thiocyanate (SCN-) supplementation increased plasma and fecal SCN- level.Thiocyanate supplementation diverted HOCl-mediated oxidative damage in mice colon.Thiocyanate supplementation stimulated thiol synthesis in the DSS colitis model.Thiocyanate provides no protection in an acute experimental model of UC.Competing Interest StatementThe authors have declared no competing interest.AbbreviationsCDCrohn’s Disease3-Cl-Tyr3-chlorotyrosineDSSDextran Sodium SulphateGAPDHGlyceraldehyde 3-phosphate dehydrogenaseGCLCGlutamate-Cysteine Ligase Catalytic SubunitGIGastrointestinalGSHGlutathioneGSSGGlutathione DisulfideHOBrHypobromous AcidHOClHypochlorous AcidHCN-Hydrogen; CyanideHOSCNHypothiocyanous AcidIBDInflammatory Bowel DiseaseMPOMyeloperoxidaseNrf2Nuclear factor erythroid 2-related Factor 2PMNsPolymorphonuclear NeutrophilsPTPProtein Tyrosine PhosphatasesROSReactive Oxygen SpeciesSCN-ThiocyanateUCUlcerative ColitisView Full Text

pathology↗

bioRxiv2018

The cyclic nitroxide antioxidant 4-methoxy-TEMPO decreases mycobacterial burden in vivo through host and bacterial targets

Tuberculosis is a chronic inflammatory disease caused by persistent infection with Mycobacterium tuberculosis. The rise of antibiotic resistant strains necessitates the design of novel treatments. Recent evidence shows that not only is M. tuberculosis highly resistant to oxidative killing, it also co-opts host oxidant production to induce phagocyte death facilitating bacterial dissemination. We have targeted this redox environment with the cyclic nitroxide derivative 4-methoxy-TEMPO (MetT) in the zebrafish-M. marinum infection model. MetT inhibited the production of mitochondrial ROS and decreased infection-induced cell death to aid containment of infection. We identify a second mechanism of action whereby stress conditions, including hypoxia, found in the infection microenvironment appear to sensitise M. marinum to killing by MetT both in vitro and in vivo. Together, our study demonstrates MetT inhibited the growth and dissemination of M. marinum through host and bacterial targets.

microbiology↗