Figure 1.

Ionizing radiation down-regulates Paneth cell α-defensins, alters gut microbiota, increases gut permeability, and leads to endotoxemia. Adult mice were exposed to ionizing radiation (IR) or sham-treated (0 hour). Intestinal α-defensin expression (A-F), microbiota composition (G-I), mucosal permeability (J), and plasma LPS (K) were analyzed at varying times after irradiation (post-IR). (A-C) RNA preparations from the ileum and colon were analyzed for Defa5 (A, B) and Defa6 (C) mRNA by RT-qPCR. Zero-hour values represent the sham-treated group. Values are mean ± sem (n = 6); *p<0.05 for significant difference from “0 h” value. (D-F) Colonic luminal flushing from Sham-treated and irradiated mice at 24 hours after irradiation were analyzed for overall α-defensins (D), DEFA5 (E), and DEFA21 (F) by mass spectrometry. Values are mean ± sem (n = 6); **p<0.01, ***p<0.001 for significant difference from corresponding “Sham” values. (G-I) At varying times after irradiation, DNA preparations from colonic luminal flushing were analyzed for selected microbiota taxa by RT-qPCR. Results of Firmicutes/Bacteroidetes or F/B ratio (G), Enterobacteriaceae (H), and E. coli (I) by mass spectrometry. Zero-hour values represent the sham-treated group. Values are mean ± sem (n = 4); *p<0.05, **p<0.01 for significant difference from corresponding “0 h” values. (J) At varying times after irradiation, colonic mucosal permeability in vivo was evaluated by measuring the vascular-to-luminal flux of FITC-inulin. Zero-hour values represent the sham-treated group. Values are mean ± sem (n = 6); *p<0.05 for significant difference from corresponding “0 h” value. (K) Plasma LPS levels were measured at varying times after irradiation. Zero-hour values represent the sham-treated group. Values are mean ± sem (n = 6); *p<0.05 for significant difference from corresponding “0 h” value.