Milk Fat Globule-Epidermal Growth Factor 8 Is Decreased in Intestinal Epithelium of Ulcerative Colitis Patients and Thereby Causes Increased Apoptosis and Impaired Wound Healing

Qiu-Jie Zhao,Yan-Qing Li,Yan-Bo Yu,Xiu-Li Zuo,Yan-Yan Dong

doi:10.2119/molmed.2011.00369

Abstract

Milk fat globule-epidermal growth factor 8 (MFG-E8) plays an important role in maintaining intestinal barrier homeostasis and accelerating intestinal restitution. However, studies of MFG-E8 expression in humans with ulcerative colitis are lacking. We examined MFG-E8 expression in colonic mucosal biopsies from ulcerative colitis patients and healthy controls (n = 26 each) by real-time quantitative polymerase chain reaction (PCR), Western blot analysis and immunohistochemistry. MFG-E8 mRNA and protein expression was lower in ulcerative colitis patients than in controls. MFG-E8 expression was inversely correlated with mucosal inflammatory activity and clinical disease activity in patients. MFG-E8 was present in human intestinal epithelial cells both in vivo and in vitro. Apoptosis induction was also detected in the intestinal epithelium of ulcerative colitis patients by terminal-deoxynucleoitidyl transferase mediated nick-end labeling assay. We used lentiviral vectors encoding human MFG-E8 targeting short hairpin RNA to obtain MFG-E8 knockdown intestinal epithelia cell clones. MFG-E8 knockdown could promote apoptosis in intestinal epithelial cell lines, accompanied by a decrease in level of the antiapoptotic protein B-cell lymphoma 2 (BCL-2) and induction of the proapoptotic protein BCL2-associated protein X (BAX). The addition of recombinant human MFG-E8 led to decreased BAX and cleaved caspase-3 levels and induction of BCL-2 level in intestinal epithelia cells. MFG-E8 knockdown also attenuated wound healing on scratch assay of intestinal epithelial cells. The mRNA level of intestinal trefoid factor 3, a pivotal factor in intestinal epithelial cell migration and restitution, was downregulated with MFG-E8 knockdown. In conclusion, we demonstrated that decreased colonic MFG-E8 expression in patients with ulcerative colitis may be associated with mucosal inflammatory activity and clinical disease activity through basal cell apoptosis and preventing tissue healing in the pathogenesis of ulcerative colitis.

Highlights

Ulcerative colitis (UC) is a chronic and relapsing inflammatory disorder involving the mucosal layer of the colon and rectum [1]
Reverse transcription (RT)-polymerase chain reaction (PCR) analysis revealed that MFGE8 mRNA was abundant in normal intestinal biopsies and lower in inflamed UC biopsies (Figure 1A)
We further demonstrated decrease of Milk fat globule–epidermal growth factor 8 (MFG-E8) and induction of apoptosis in intestinal epithelial cells (IECs) of patients with UC

Summary

Introduction

Ulcerative colitis (UC) is a chronic and relapsing inflammatory disorder involving the mucosal layer of the colon and rectum [1]. UC is characterized by elevated production of proinflammatory mediators, repeated intestinal injury and cell restitution and increased apoptosis of intestinal epithelial cells (IECs), which leads to impaired mucosal barrier function [5,6,7,8]. Milk fat globule–epidermal growth factor 8 (MFG-E8), named lactadherin, BA46 or SED1, is a secreted glycoprotein present in several cell types, including macrophages, mammary epithelial cells and epidermal keratinocytes [9,10,11]. MFG-E8 participates in cell events such as the promotion of mammary gland branching and facilitation of sperm–egg binding [10,15]

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