Biology subjects

Burkitt, M. D.

Publications and source records attributed to Burkitt, M. D..

3 recordsLinked to original sources

bioRxiv2019

Long-term iron deficiency and iron supplementation exacerbate acute DSS-induced colitis and are associated with significant dysbiosis

Patients taking oral iron supplementation often suffer from gastrointestinal side effects. We have previously shown that acute alterations in oral iron exacerbate dextran sodium sulphate (DSS) induced colitis and are associated with dysbiosis. As patients take iron supplementation for long periods, we asked whether this too would influence colitis and the microbiome. We assessed the impact of long-term changes in dietary iron, by feeding chow containing 100ppm, 200ppm and 400ppm (reflecting a deficient, normal or supplemented diet, respectively) for up to 9 weeks to female wild-type C57BL/6 (WT) mice in presence or absence of chronic colitis, or acute colitis induced after 8 weeks, induced by DSS. Assessment was made based on (i) clinical and histological severity of colitis, and (ii) faecal microbial diversity, as assessed by sequencing the V4 region of 16S rRNA. In mice with long term changes to their dietary iron, reduced iron intake (100ppm iron diet) was associated with increased weight loss and histology scoring in the acute colitis model. Chronic colitis was not influenced by altering dietary iron however there was a clear change in the faecal microbiome in the 100 and 400ppm iron DSS-treated groups and in controls consuming the 400ppm iron diet. Proteobacteria levels increased significantly at day-63 compared to baseline and Bacteroidetes levels decreased in the 400ppm iron DSS group at day-63 compared to baseline; mirroring our previously published work in acute colitis. Long term dietary iron alterations clearly affects gut microbiota signatures but do not appear to exacerbate chronic colitis. However, acute colitis is exacerbated by changes in dietary iron. More work is needed to understand the impact of iron supplementation of the pathologenesis of IBD and rise that possiblity that the change in the microbiome, in patients with colitis, is a consequence of the increase in luminal iron and not simply the presence of colitis.

pathology↗

bioRxiv2019

Macrophage-specific NF-kappa B activation dynamics can segregate inflammatory bowel disease patients

The heterogeneous nature of inflammatory bowel disease (IBD) presents challenges, particularly when choosing therapy. Activation of the NF-{kappa}B transcription factor is a highly-regulated, dynamic event in IBD pathogenesis. We expressed the human NF-{kappa}B/p65 subunit in blood-derived macrophages, using lentivirus. Confocal imaging of p65 activation revealed that a higher proportion of macrophages from Crohns patients responded to lipid-A compared to controls. In contrast, cells from ulcerative colitis (UC) patients exhibited a shorter duration of p65 nuclear localisation compared to healthy controls and Crohns donors. Using a similar lentivirus approach, NF-{kappa}B-regulated luciferase was expressed in patient macrophages, isolated from frozen peripheral blood mononuclear cell samples. Following activation, samples could be segregated into three clusters based on the NF-{kappa}B-regulated luciferase response. The majority of UC samples appeared in hypo-responsive cluster 1, with Crohns patients representing the majority of hyper-responsive cluster 3. A positive correlation was seen between NF-{kappa}B-induced luciferase activity and cytokine levels released to medium from stimulated macrophages, but not in serum or biopsy. Analysis of macrophage cytokine responses and patient metadata revealed a strong correlation between Crohns patients who smoked and hyper-activation of p65. These in vitro dynamic assays of NF-{kappa}B activation in blood-derived macrophages segregate IBD patients into groups with different phenotypes and therefore may help determine response to therapy. Significance statementThis manuscript describes two dynamic assays of NF-{kappa}B activation in blood-derived macrophages that can segregate IBD patients into groups with different phenotypes. For the first time we introduce the use of dynamic measurements of a transcription factor activation as a method to stratify patients and we are confident that our approach will lead in future to early patient stratification and prediction of treatment outcome.

immunology↗

bioRxiv2018

Oral iron exacerbates colitis and influences the intestinal microbiome

Inflammatory bowel disease (IBD) is associated with anaemia and oral iron replacement to correct this can be problematic, intensifying inflammation and tissue damage. The intestinal microbiota also plays a key role in the pathogenesis of IBD, and iron supplementation likely influences gut bacterial diversity in patients with IBD. Here, we assessed the impact of dietary iron, using chow diets containing either 100, 200 or 400 ppm, fed ad libitum to adult female C57BL/6 mice in the presence or absence of colitis induced using dextran sulfate sodium (DSS), on (i) clinical and histological severity of acute DSS-induced colitis, and (ii) faecal microbial diversity, as assessed by sequencing the V4 region of 16S rRNA. Increasing or decreasing dietary iron concentration from the standard 200 ppm exacerbated both clinical and histological severity of DSS-induced colitis. DSS-treated mice provided only half the standard levels of iron ad libitum (i.e. chow containing 100 ppm iron) lost more body weight than those receiving double the amount of standard iron (i.e. 400 ppm); p<0.01. Faecal calprotectin levels were significantly increased in the presence of colitis in those consuming 100 ppm iron at day 8 (5.94-fold) versus day-10 group (4.14-fold) (p<0.05), and for the 400 ppm day-8 group (8.17-fold) versus day-10 group (4.44-fold) (p<0.001). In the presence of colitis, dietary iron at 400 ppm resulted in a significant reduction in faecal abundance of Firmicutes and Bacteroidetes, and increase of Proteobacteria, changes which were not observed with lower dietary intake of iron at 100 ppm. Overall, altering dietary iron intake exacerbated DSS-induced colitis; increasing the iron content of the diet also led to changes in intestinal bacteria diversity and composition after colitis was induced with DSS.

physiology↗