Constitutive and regulated secretion of secretory leukocyte proteinase inhibitor by human intestinal epithelial cells.
OBJECTIVE
Epithelial cells participate in immune regulation and mucosal integrity by generating a range of biologically active mediators. In the intestine, little is known about the potential endogenous anti-inflammatory molecules. Secretory leukocyte proteinase inhibitor (SLPI) is a major serine proteinase inhibitor, a potent antibiotic, and thus a potential anti-inflammatory molecule, although it is not known if it is secreted by intestinal epithelial cells.


METHODS
We show, by reverse-transcription polymerase chain reaction, the presence of SLPI messenger RNA in human model intestinal epithelial cell lines (Caco2-BBE, T84, and HT29-Cl.19A) and human jejunum and colon biopsy specimens. The polymerase chain reaction product was cloned and sequenced and is identical to that of SLPI isolated previously from the human parotid gland.


RESULTS
As analyzed by enzyme-linked immunosorbent assay, the constitutive secretion of SLPI occurs in a markedly polarized manner toward the apical surface and is enhanced by inflammatory mediators including tumor necrosis factor alpha and interleukin 1beta (approximately 3.5-fold increase over control value). SLPI release is also stimulated by activation of protein kinase C isoenzymes, but not by activation of adenosine 3',5'-cyclic monophosphate- or Ca(2+)-regulated signaling molecules. SLPI protein is detectable in intestinal lavage fluids collected from normal adult humans. Recombinant SLPI attenuates digestive enzyme (trypsin)- or leukocyte proteinase (elastase)-induced permeability alteration of a model epithelia in a dose-dependent manner. Moreover, SLPI exhibits an antibacterial activity against at least one major intestinal pathogen, Salmonella typhimurium. In contrast, SLPI does not influence epithelial barrier integrity as assessed by transepithelial conductance measurements or electrogenic ion transport.


CONCLUSIONS
These results establish that human intestinal epithelium expresses and apically secretes SLPI, a molecule that may significantly contribute to the protection against attack from inflammatory cells and digestive enzymes, as well as against microbial infection.
Si-Tahar
M
M
Epithelial Pathobiology Unit, Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, Georgia, USA.
Merlin
D
D
Sitaraman
S
S
Madara
J L
JL
D000328:Adult; D001483:Base Sequence; D001692:Biological Transport / Q000502:physiology; D001706:Biopsy; D018938:Caco-2 Cells; D016764:Cell Polarity / Q000502:physiology; D002712:Chlorides / Q000378:metabolism; D003001:Cloning, Molecular; D003106:Colon / Q000201:enzymology / Q000382:microbiology / Q000473:pathology; D018076:DNA, Complementary; D004847:Epithelial Cells / Q000201:enzymology / Q000378:metabolism / Q000382:microbiology; D015870:Gene Expression / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic; D019073:HT29 Cells; D006801:Humans; D066298:In Vitro Techniques; D007408:Intestinal Absorption / Q000502:physiology; D007413:Intestinal Mucosa / Q000201:enzymology* / Q000378:metabolism* / Q000473:pathology; D007583:Jejunum / Q000201:enzymology / Q000382:microbiology / Q000473:pathology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008969:Molecular Sequence Data; D018408:Patch-Clamp Techniques; D011493:Protein Kinase C / Q000378:metabolism; D053491:Proteinase Inhibitory Proteins, Secretory; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D012480:Salmonella Infections / Q000378:metabolism; D012486:Salmonella typhimurium; D053481:Secretory Leukocyte Peptidase Inhibitor; D012697:Serine Endopeptidases / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology
D002712:Chlorides; D018076:DNA, Complementary; D053491:Proteinase Inhibitory Proteins, Secretory; D011506:Proteins; D012333:RNA, Messenger; C506814:SLPI protein, human; D053481:Secretory Leukocyte Peptidase Inhibitor; D011493:Protein Kinase C; D012697:Serine Endopeptidases