Biology subjects

Probert, C. S.

Publications and source records attributed to Probert, C. S..

3 recordsLinked to original sources

bioRxiv2024

Identification of novel bone-resorption markers by osteoclasts in vitro and in vivo

Bone resorption involves dissolution of mineral and enzymatic degradation of bone matrix. The primary enzyme is cathepsin K but other proteases including matrix metalloproteinases are involved. Some cleavage products of cathepsin K have been partially identified, including crossed-linked telopeptides of type I collagen. However, the pathway of type I bone collagen degradation has not been fully elucidated. The aim of this study was to comprehensively characterise the entire complement of bone breakdown products resulting from osteoclast action under controlled conditions in vitro. Complete characterisation of these breakdown products will advance understanding of osteoclast biology and has the potential to reveal new biomarkers of bone resorption. We analysed extracellular media from osteoclasts cultured on dentine substrates, using untargeted liquid chromatography mass spectrometry. We discovered 22 breakdown products resulting from osteoclastic action. These products were peptide fragment sequences that mapped to various collagen proteins present in bone and dentine matrix. Nine peptide fragments mapped exclusively to collagen I alpha-1 chain (COL1A1), the most abundant protein in bone. Analysis of the reported cleavage sites in the COL1A1 protein sequence indicated 7/9 COL1A1-specific fragments not explained by known proteolytic events. We subsequently showed that 14 of the fragment products were present in human serum and/or urine from metabolomic datasets obtained from patients with the inherited metabolic disease alkaptonuria (serum) and lung cancer (urine). Two products were at higher concentration (P <0.05, fold change >2) in urine from patients with bone metastasis (29/112) from the lung cancer cohort. The range of collagen peptide fragments we discovered as a direct result of osteoclast activity indicates a complexity of bone resorption pathways not previously known. Monitoring the concentrations of these novel bone markers in biofluids has the potential to capture multiple pathways of bone resorption activity beyond the existing assays based on Cathepsin K. Lay summaryBreakdown of bone tissue is performed by specialised bone cells called osteoclasts in a process known as bone resorption. Knowledge of specific molecules produced from osteoclasts acting on bone is important for a) understanding bone resorption in health and disease, and b) clinical tests of bone resorption from measurement of these breakdown products. Here we aimed to characterise the entire complement of bone breakdown products resulting from osteoclast action under controlled conditions in the laboratory. We found a total of 22 breakdown products produced from osteoclasts cultured on wafers of dentine, a tissue with almost identical composition to bone. Analysis of the structures of these products revealed fragments of varying size produced from digestion of specific proteins present in bone. We then showed that 14/22 bone protein fragments observed in our cell culture experiments were also present in human blood and/or urine. In our analysis of urine from patients with lung cancer, we found that two of the protein fragments we identified were higher in a subset (29/112) of patients with bone metastasis. Our findings provide new insights into the mechanisms of bone resorption and show the potential for monitoring the range of urine bone protein fragments in bone disorders.

biochemistry↗

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↗

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↗