Paneth cell dysfunction in radiation injury and radio-mitigation by human α-defensin 5

Abstract

IntroductionThe mechanism underlying radiation-induced gut microbiota dysbiosis is undefined. This study examined the effect of radiation on the intestinal Paneth cell α-defensin expression and its impact on microbiota composition and mucosal tissue injury and evaluated the radio-mitigative effect of human α-defensin 5 (HD5).MethodsAdult mice were subjected to total body irradiation, and Paneth cell α-defensin expression was evaluated by measuring α-defensin mRNA by RT-PCR and α-defensin peptide levels by mass spectrometry. Vascular-to-luminal flux of FITC-inulin was measured to evaluate intestinal mucosal permeability and endotoxemia by measuring plasma lipopolysaccharide. HD5 was administered in a liquid diet 24 hours before or after irradiation. Gut microbiota was analyzed by 16S rRNA sequencing. Intestinal epithelial junctions were analyzed by immunofluorescence confocal microscopy and mucosal inflammatory response by cytokine expression. Systemic inflammation was evaluated by measuring plasma cytokine levels.ResultsIonizing radiation reduced the Paneth cell α-defensin expression and depleted α-defensin peptides in the intestinal lumen. α-Defensin down-regulation was associated with the time-dependent alteration of gut microbiota composition, increased gut permeability, and endotoxemia. Administration of human α-defensin 5 (HD5) in the diet 24 hours before irradiation (prophylactic) significantly blocked radiation-induced gut microbiota dysbiosis, disruption of intestinal epithelial tight junction and adherens junction, mucosal barrier dysfunction, and mucosal inflammatory response. HD5, administered 24 hours after irradiation (treatment), reversed radiation-induced microbiota dysbiosis, tight junction and adherens junction disruption, and barrier dysfunction. Furthermore, HD5 treatment also prevents and reverses radiation-induced endotoxemia and systemic inflammation.ConclusionThese data demonstrate that radiation induces Paneth cell dysfunction in the intestine, and HD5 feeding prevents and mitigates radiation-induced intestinal mucosal injury, endotoxemia, and systemic inflammation.

Spatial Proteomics Reveals Alcohol-Induced Damages to the Crypts and Villi of the Mouse Small Intestine

“…On the other hand, downregulation of antimicrobial proteins such as Defa20, Defa23, Defa29, and Dmbt1 was observed in the present study, which agrees well with a previous study that production of α-defensins is notably decreased by Paneth cells in a chronic alcoholic hepatitis mouse model . The decrease in the levels of α-defensins was linked to changes in the gut microbiota over time, enhanced gut permeability, and the presence of endotoxins . However, another important antimicrobial enzyme characteristic of Paneth cell–lysozyme did not change upon alcohol treatment, indicating that the Paneth cell population remains stable and the downregulation of defensins is unlikely a result of Paneth cell death.…”

“… 6 The decrease in the levels of α-defensins was linked to changes in the gut microbiota over time, enhanced gut permeability, and the presence of endotoxins. 22 However, another important antimicrobial enzyme characteristic of Paneth cell–lysozyme did not change upon alcohol treatment, indicating that the Paneth cell population remains stable and the downregulation of defensins is unlikely a result of Paneth cell death. In villi, alcohol also upregulates proteins associated with lipid metabolism.…”

Human α-Defensin 51–9 and Human β-Defensin 2 Improve Metabolic Parameters and Gut Barrier Function in Mice Fed a Western-Style Diet

“…Wendler et al [ 83 ] demonstrated that reduced β-defensin 1 (hBD1 red ) was proteolytically degraded into different fragments, which exhibited increased antimicrobial activity and inhibited growth of Bifidobacterium breve . Nevertheless, oral administration of HD5 has been shown to provide therapeutic effects, as treatment with modified HD5 1–9 fragment D3 regulated appetite in obese mice [ 37 ], and oral administration of HD5 improved glucose tolerance [ 34 ], gut barrier function, and microbiota composition in mice after radiation-induced injury [ 84 ]. Similarly, intranasal treatment of hBD2 improved experimental asthma [ 85 ] and oral hBD2 administration ameliorated alcohol-associated liver disease in mice [ 40 ].…”