Secreted protein acidic and rich in cysteine (SPARC) exacerbates colonic inflammatory symptoms in dextran sodium sulphate-induced murine colitis

Background Secreted Protein Acidic and Rich in Cysteine (SPARC) is expressed during tissue repair and regulates cellular proliferation, migration and cytokine expression. The aim was to determine if SPARC modifies intestinal inflammation. Methods Wild-type (WT) and SPARC-null (KO) mice received 3% dextran sodium sulphate (DSS) for 7 days. Inflammation was assessed endoscopically, clinically and histologically. IL-1β, IL-4, IL-5, IL-6, IL-10, IL-13, IL-17A, IL-12/IL23p40, TNF-α, IFN-γ, RANTES, MCP-1, MIP-1α, MIP-1β, MIG and TGF-β1 levels were measured by ELISA and cytometric bead array. Inflammatory cells were characterised by CD68, Ly6G, F4/80 and CD11b immunofluorescence staining and regulatory T cells from spleen and mesenteric lymph nodes were assessed by flow cytometry. Results KO mice had less weight loss and diarrhoea with less endoscopic and histological inflammation than WT animals. By day 35, all (n = 13) KO animals completely resolved the inflammation compared to 7 of 14 WT mice (p<0.01). Compared to WTs, KO animals at day 7 had less IL1β (p = 0.025) and MIG (p = 0.031) with higher TGFβ1 (p = 0.017) expression and a greater percentage of FoxP3+ regulatory T cells in the spleen and draining lymph nodes of KO animals (p<0.01). KO mice also had fewer CD68+ and F4/80+ macrophages, Ly6G+ neutrophils and CD11b+ cells infiltrating the inflamed colon. Conclusions Compared to WT, SPARC KO mice had less inflammation with fewer inflammatory cells and more regulatory T cells. Together, with increased TGF-β1 levels, this could aid in the more rapid resolution of inflammation and restoration of the intestinal mucosa suggesting that the presence of SPARC increases intestinal inflammation

Liver iron homeostasis is altered by colonic inflammation and dietary iron

Background Patients with inflammatory bowel diseases (IBD) develop anaemia of inflammation (AI) due to disturbances in iron homeostasis that limits the availability of iron for erythropoiesis. Aims In this study, the effects of colonic inflammation and dietary iron levels on liver iron homeostasis were investigated in a mouse model of colitis. Methods Colonic inflammation was induced by the administration of dextran sodium sulphate (DSS) to mice fed either an iron-supplemented (1%) or control iron (0.01%) diet. Liver and plasma iron concentrations as well as plasma transferrin saturation were measured biochemically. Liver gene expression was determined by real-time PCR and plasma IL-6 levels were measured by ELISA. Results DSS-induced colonic inflammation increased plasma IL-6 levels. Dietary iron supplementation further enhanced colonic inflammation and plasma IL-6 levels (p < 0.0001). Liver iron and plasma transferrin saturation were elevated in dietary iron-supplemented mice. Post-DSS treatment, liver iron levels increased (p < 0.01) and transferrin saturation decreased (p < 0.01) in mice fed the iron-supplemented and control iron diets, consistent with the presence of AI. Liver expression of the iron regulatory genes, hepcidin (Hamp1) and inhibitor of DNA binding 1 (Id1), was upregulated by dietary iron (p < 0.01) but unexpectedly downregulated by DSS treatment (p < 0.05). Smad7 gene expression was decreased in DSStreated mice and Bmp6 expression was increased by dietary iron supplementation (p < 0.001). Dietary iron supplementation decreased the gene expression of the iron importer transferrin receptor 1 (Tfr1), congruent with the iron-dependent regulation of Tfr1 and expression and further diminished by DSS treatment (p < 0.05). Gene expression of the iron importer Zip14 was increased (p < 0.05) whilst that of the iron exporter ferroportin 1A was decreased (p < 0.0001) with DSS treatment, consistent with the retention of iron by the liver. Conclusion The perturbations in iron homeostasis resulting from increased colonic inflammation observed in this study are consistent with AI. The regulatory pathways for the changes seen, however, are unclear. The lack of induction of Hamp1 expression by plasma IL-6 levels suggests that other regulatory signals may impede hepcidin induction by inflammation. A possible candidate is the erythroid signal as increased erythropoietic activity is known to be a strong negative regulator of hepcidin

Colonic interleukin-6 expression is induced by intestinal inflammation and dietary iron

Chronic intestinal inflammation and high dietary iron are associated with a greater risk of developing colorectal cancer. The aim of this study was to investigate the role of IL-6 in iron-induced colonic inflammation and tumourigenesis in a mouse model of colorectal cancer. Methods: Mice, fed either an iron-supplemented (1% carbonyl iron) or control (0.01% iron) diet, were treated with dextran sodium sulphate (DSS) and azoxymethane (AOM) to induce intestinal inflammation and cancer. Intestinal inflammation and tumour development were assessed using high-resolution video endoscopy at multiple time-points. Colonic inflammation and tumours were examined histologically and gene expression by real-time PCR. Results: Seven days post-AOM/DSS treatment, intestinal inflammation was more severe in iron-loaded mice (p < 0.05). Colonic pro-inflammatory cytokines, IL-6, IFN-γ and TNFα gene expression increased with AOM/ DSS treatment confirming the presence of intestinal inflammation (p < 0.05). Dietary iron loading had an additive effect on the gene expression of IL-6 and other members of this family, IL-11 and IL-17a, in AOM/ DSS-treated mice. STAT3 phosphorylation was increased in AOM/DSS treated mice and this was further enhanced with dietary iron loading. Five weeks after AOM/DSS treatment, iron-loaded mice developed a greater number and larger-sized colonic tumours compared to control mice (p < 0.05). Dietary iron-loading also induced an additive effect on tumour IL-6 gene expression in AOM/DSS-treated mice (p < 0.05). Expression of cellular iron import genes DMT1, Zip14a and Tfr1 was increased and cellular export gene ferroportin was reduced in colonic tumours compared to non-tumour tissue from the same animal (p < 0.05), suggesting increased iron uptake by tumours may promote growth. Summary/Conclusions: Dietary iron-loading promoted colonic inflammation and tumour formation. The mechanistic basis for the interaction between iron, inflammation and colorectal cancer may involve IL-6/ STAT3 signalling

TGF-beta superfamily signaling is essential for tooth and hair morphogenesis and differentiation

Members of the transforming growth factor beta (TGF-beta) superfamily of signaling molecules are involved in the regulation of many developmental processes that involve the interaction between mesenchymal and epithelial tissues. Smad7 is a potent inhibitor of many members of the TGF-beta family, notably TGF-beta and activin. In this study, we show that embryonic overexpression of Smad7 in stratified epithelia using a keratin 5 promoter, results in severe morphogenetic defects in skin and teeth and leads to embryonic and perinatal lethality. To further analyze the functions of Smad7 in epithelial tissues of adult mice, we used an expression system that allowed a controlled overexpression of Smad7 in terms of both space and time. Skin defects in adult mice overexpressing Smad7 were characterized by hyper-proliferation and missing expression of early markers of keratinocyte differentiation. Upon Smad7-mediated blockade of TGF-beta superfamily signaling, ameloblasts failed to produce an enamel layer in incisor teeth. In addition, TGF-beta blockade in adult mice altered the pattern of thymic T cell differentiation and the number of thymic T cells was significantly reduced. This study shows that TGF-beta superfamily signaling is essential for development of hair, tooth and T-cells as well as differentiation and proliferation control in adult tissue

High Dose Vitamin D supplementation alters faecal microbiome and predisposes mice to more severe colitis

Vitamin D has been suggested as a possible adjunctive treatment to ameliorate disease severity in human inflammatory bowel disease. In this study, the effects of diets containing high (D++, 10,000 IU/kg), moderate (D+, 2,280 IU/kg) or no vitamin D (D-) on the severity of dextran sodium sulphate (DSS) colitis in female C57Bl/6 mice were investigated. The group on high dose vitamin D (D++) developed the most severe colitis as measured by blinded endoscopic (p < 0.001) and histologic (p < 0.05) assessment, weight loss (p < 0.001), drop in serum albumin (p = 0.05) and increased expression of colonic TNF-α (p < 0.05). Microbiota analysis of faecal DNA showed that the microbial composition of D++ control mice was more similar to that of DSS mice. Serum 25(OH)D3 levels reduced by 63% in the D++ group and 23% in the D+ group after 6 days of DSS treatment. Thus, high dose vitamin D supplementation is associated with a shift to a more inflammatory faecal microbiome and increased susceptibility to colitis, with a fall in circulating vitamin D occurring as a secondary event in response to the inflammatory process

Browsing regime and growth response of Abies alba saplings planted along light gradients

ISSN:1612-4677ISSN:1612-466