S. M. Alaish1, D. R. Shores2, A. Zhang1, M. Wang1, H. Jia1, W. Fulton1, C. Sodhi1, D. J. Hackam1 1Johns Hopkins University School Of Medicine,Pediatric Surgery/Surgery,Baltimore, MD, USA 2Johns Hopkins University School Of Medicine,Pediatric Gastroenterology/Pediatrics,Baltimore, MD, USA
Introduction: Short bowel syndrome (SBS) causes an intestinal dysbiosis and increased intestinal permeability which can lead to sepsis and even death. As an iron-sequestering protein in the antibacterial innate immune response, Lipocalin-2 (LCN2) prevents bacterial iron uptake and controls bacterial growth. In a mouse model, we have previously shown that LCN2 mRNA and protein increase in the intestine following 75% small bowel resection. We now hypothesize that LCN2 may serve as a potential defense mechanism in the intestine against the dysbiosis that occurs in SBS and tested this by evaluating the outcome of LCN2-/- mice exposed to a model of SBS.
Methods: Under an ACUC-approved protocol, we performed a 75% small bowel resection (SBR) on both C57BL/6J (n=6) and LCN2-/- (C57BL/6J background) (n=6) mice, which mimics the extensive resection seen in SBS patients. Sham-operated C57Bl/6J (n=6) and LCN2 -/- (n=6) mice served as controls. Mice were weighed daily. On postoperative day 6, the mice were injected with BrdU. 24 hours later, the mice were gavage fed FITC-Dextran, serum was collected, intestinal permeability was assayed, and the mice then underwent euthanasia. Intestinal tissue was collected and processed for staining. Statistical analysis was performed using ANOVA with p<0.05 considered significant.
Results:LCN2 -/- mice exposed to SBR lost significantly more weight than shams (p<0.05) but significantly less than wild-type SBR mice (p<0.05). Similarly, intestinal permeability was increased in LCN2 -/- SBR mice as compared to shams (p<0.05) but less than wild-type SBR mice (p<0.05), while enterocyte proliferation was similar for the LCN2-/- SBR mice and the wild-type SBR mice. Strikingly, survival was significantly greater in the LCN2-/- SBR mice as compared to the wild-type SBR mice (87.5% vs. 56.1%, p<0.05), suggesting that in disagreement with our original hypothesis, the presence of LCN2 exerts pro-weight loss and pro-permeability effects that contribute to increased mortality, and which are reversed in LCN2 -/- mice.
Conclusion:Contrary to our hypothesis, LCN2 exerts surprising, deleterious effects on gut permeability and weight loss in mice, contributing to increased mortality, in a mouse model of short bowel resection. Such effects may reflect the pro-inflammatory role of LCN2 which has been observed in other systems, and suggest that LCN2 inhibition may offer a novel therapeutic approach for gut protection in children with SBS.