Fig. 4: High circulatory iron in Muc2^−/− promotes bacteria survival.

a Increased serum total iron levels and lowered Fe²⁺/Fe³⁺ iron levels in the liver of Muc2^−/− littermates suggests dysregulated iron homeostasis (n = 7–10). Sera were hemolysis free. Data are representative of four independent experiments, Student’s t test. b Liver samples were collected from saline perfused euthanized animals, formalin fixed, paraffin embedded, sectioned, and stained with Prussian blue for iron. Representative Prussian blue-stained liver samples confirm lower iron deposits in Muc2^−/− littermates (n = 4). Representative images are from four independent experiments. Means ± SEM, paired Student’s t test. c ELISA-based serum lipocalin 2 (NGAL) quantification from naïve Muc2^−/− and Muc2^+/+ littermates (n = 10). Graph shows data from one of two independent experiments. d Serum ferritin levels quantification from Muc2^−/− and Muc2^+/+ (n = 5) using ELISA. Graph shows cumulative data from two independent experiments. e Serum transferrin saturation levels from Muc2^−/− and Muc2^+/+ animals (n = 5/experiment); cumulative data shown of two independent experiments. f Reduced bacterial growth in deferoxamine (DFO)-treated Muc2^−/− and Muc2^+/+ littermates serum as compared to untreated control (n = 4). Representative of three independent experiments; paired one-way ANOVA. g Blood samples were collected following LPS challenge at the indicated time points and subjected to total iron quantification using hemolysis-free serum (n = 5). Delayed hypoferremia was recorded in Muc2^−/− littermates. Representative data are from three experiments, paired one-way ANOVA. h Comparative susceptibility to sepsis in Muc2^−/− littermates treated or not with DFO and challenged with 5 mg/kg body weight LPS intraperitoneally. Animals treated with DFO showed reduced weight loss and increased survival compared to the untreated group (n = 6–8). Representative data are from four independent experiments; paired one-way ANOVA. i Comparison of pro-inflammatory cytokines levels in the blood following LPS challenge in DFO treated and untreated Muc2^−/− littermates indicate unregulated attenuated immune response (n = 6). Representative data are from three independent experiments; paired Student’s t test. *p < 0.05, **p < 0.01, and ***p < 0.001.