Differential expression of interleukin 1 receptor antagonist isoforms in human intestinal epithelial cells.
OBJECTIVE
Regulatory cytokines mediate intestinal epithelial cell (IEC) participation in mucosal immune responses. The aim of this study was to investigate the expression of secretory and intracellular isoforms of interleukin 1 receptor antagonist (IL-1Ra) in human primary IECs and carcinoma-derived cell lines.


METHODS
Primary IECs were isolated from patients with Crohn's disease or ulcerative colitis and from normal controls. Isoform-specific IL-1Ra messenger RNA (mRNA) and protein were assessed by reverse-transcription polymerase chain reaction and Western blot analysis. Expression during cellular differentiation was determined by in situ immunohistochemistry on sequentially released, native IECs and in vitro differentiated cell lines. Intracellular IL-1Ra I function was analyzed by permanent transfection of Caco-2 cells.


RESULTS
Intracellular IL-1Ra I protein accumulated in surface IECs with extension to the crypts during inflammation. Secretory IL-1Ra and intracellular IL-1Ra II mRNA, but not the corresponding protein, was detected. Transcription of intracellular IL-1Ra I mRNA was significantly up-regulated with inflammation and in vitro by phorbol myristate acetate and interleukin 1beta. In vitro differentiated cells had higher constitutive intracellular IL-1Ra I protein content. Intracellular IL-1Ra I expression in Caco-2 cells decreased IL-1beta-stimulated interleukin 8 secretion.


CONCLUSIONS
Native human IECs and certain cell lines constitutively express intracellular IL-1Ra type I, which is up-regulated by inflammation, inflammatory stimuli, and cellular differentiation. Constitutive expression of this anti-inflammatory cytokine may contribute to mucosal protection.
Böcker
U
U
Center for Gastrointestinal Biology and Disease, Department of Medicine, University of North Carolina, Chapel Hill, North Carolina, USA.
Damião
A
A
Holt
L
L
Han
D S
DS
Jobin
C
C
Panja
A
A
Mayer
L
L
Sartor
R B
RB
D002454:Cell Differentiation; D002460:Cell Line; D005786:Gene Expression Regulation; D006801:Humans; D007249:Inflammation; D053590:Interleukin 1 Receptor Antagonist Protein; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism*; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000096:biosynthesis; D017472:Receptors, Interleukin-1 / Q000037:antagonists & inhibitors*; D012795:Sialoglycoproteins / Q000096:biosynthesis* / Q000235:genetics
C507763:IL1RN protein, human; D053590:Interleukin 1 Receptor Antagonist Protein; D020033:Protein Isoforms; D012333:RNA, Messenger; D017472:Receptors, Interleukin-1; D012795:Sialoglycoproteins