A Potential Role of Annexin A5 in Inflammatory Bowel Disease
Kenneth A Friedman, Elaine Lin, Yuanyuan Wu, Andrew Nguyen, Jaya Sunkara, Qiang Liu, Jacob Rand. Montefiore Medical Center, Bronx, NY; CUNY-Queensborough, Queens, NY
Background: The intestine has a remarkable tolerance to resident flora, the details of which are unknown. Annexin A5 (AnxA5) is a protein that protects cell membranes from auto-antibodies by forming a shield, the loss of which is associated with antiphospholipid syndrome. Our previous work has shown that AnxA5 can directly bind lipopolysaccharide (LPS) and block inflammatory response to Gram-negative bacteria. Abnormal down-regulation of AnxA5 in macrophages may result in loss of protection against LPS, leading to immune dysregulation. We hypothesized that AnxA5 expression is decreased in inflammatory bowel disease (IBD) as compared to normal patients.
Design: Paraffin embedded colon or small bowel tissue sections from 13 patients with resections for ulcerative colitis (UC) or Crohn's disease (CD) and 6 sections of control tissue from benign margins in colonic resections were selected and immunohistochemically stained with antibodies to AnxA5 and PGM1 for macrophages. ImageJ (NIH) was used to measure the ratio of macrophage to background staining. Double fluorescent microscopy using green fluorescent protein (GFP) for macrophages and AnxA5, and quantitative PCR were performed in a mouse model of IBD and compared to normal. Statistical analysis was performed using a two-tailed t-test.
Results: Macrophages subadjacent to the colonic epithelium in UC and CD patients had significantly smaller stain ratios for AnxA5 as compared to controls (0.02 vs 0.12, p=0.01), with no significant difference between UC and CD (0.016 vs 0.020, p=0.5). There was also a decrease in GFP+/AnxA5+ macrophages in IBD mice, despite an overall increase in GFP+ cells. Finally, qPCR revealed a 5 fold decrease in AnxA5 expression by LPS-stimulated macrophages from IBD mice, while inflammatory cytokines were overexpressed 6 fold.
Conclusions: This study shows that reduction of expression of AnxA5 by gut macrophages correlates with IBD on histology. The IBD mouse model verifies this reduction along with an increase in inflammatory cytokines. Further exploration is needed to elucidate the role of AnxA5 in the pathogenesis of IBD. To our knowledge, this is the only study to characterize the expression of AnxA5 in human IBD.
Monday, March 4, 2013 9:30 AM
Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 95, Monday Morning