Tissue-Nonspecific Alkaline Phosphatase Maintains the Intestinal Microenvironment in Mouse Experimental Sepsis

Mikaela A. Barbour*, Allison L. Brichacek, Divine C. Nwafor and Candice M. Brown, Departments of Neuroscience and Microbiology, Immunology, and Cell Biology; Center for Basic and Translational Stroke Research, West Virginia University School of Medicine, Morgantown, WV 26506

Field (Broad Category): Medical Sciences (Biological & Biochemical Sciences) 

Student’s Major: Biology 

Over 1.7 million people in the US develop sepsis each year. Sepsis—a systemic response to infection— increases intestinal inflammation and permeability by disrupting the intestinal microenvironment. Despite being the leading cause of death in intensive care units, there are currently no FDA-approved targeted treatments for sepsis, and many current treatments for infection further interfere with the intestinal microenvironment. Tissue-nonspecific alkaline phosphatase (TNAP) is an enzyme found in many body tissues, and although its exact function is unclear, increased TNAP levels have been observed in septic patients’ blood samples. We hypothesized that TNAP depletion in endothelial cells would increase intestinal inflammation and permeability and disrupt microbial balance in experimental sepsis. Experimental sepsis was induced with cecal ligation and puncture in mice with conditional TNAP deletion in endothelial cells— VE-cKO mice—as well as littermate control mice. Sham surgery animals had similar abdominal incisions, but their cecums were left intact. Small intestine segments (duodenum, jejunum, and ileum) and lung tissue were collected 24 hours post-surgery. Both genotypes showed increased alkaline phosphatase enzyme activity and pro-inflammatory cytokine interleukin (IL)-6 levels in the intestines post-sepsis. However, VEcKO septic mice had higher bacterial load in the ileum, examined on brain-heart infusion media plates, compared to controls. MALDI-TOF mass spectrometry was used to identify bacteria from representative plates. While both genotypes showed clinically relevant bacteria, VE-cKO mice had greater species diversity. These results indicate that endothelial-specific TNAP may have a crucial role in maintaining microbial homeostasis in the gut after sepsis. 

Funding: 

Program/mechanism supporting research/creative efforts: WVU's Research Apprenticeship Program (RAP) & accompanying HONR 297-level course