Abstract
Secretory leukocyte protease inhibitor (SLPI) is a well-known protease inhibitor. Its function is thought to be protease/protease-inhibitor balance. Free proteolytic activity, mainly pancreatic elastase, anionic trypsin and granulocytic elastase, has been demonstrated in faecal extracts from patients with ulcerative colitis. We wanted to verify that SLPI is actually secreted from normal human colonic mucosa. Also, we wanted to ascertain whether studies of SLPI secretion based on punch biopsies were dependent on biopsy area or on biopsy circumference. Normal colonic mucosa was sampled during surgery for colonic cancer. A total of 36 samples from four patients were used. Mucosa preparation was carried out using a punch biopsy technique, and samples of 3, 4 and 6 mm diameter were used. All media contained SLPI at varying concentrations. When expressed in terms of the sample area, the secretion per millimetre-squared seemed to decrease with increasing area. When calculated as secretion per circumference, secretion seemed to be constant. In conclusion, SLPI was secreted from normal human colonic mucosa. The SLPI secretion seemed dependent on the circumference of the biopsy rather than on the area of the biopsy.
Highlights
Secretory leukocyte protease inhibitor (SLPI) is a 12 kDa non-glycosylated acid-stable antiprotease
SLPI is a protease secreted by a variety of mucosal cells
We verified that SLPI is found in the medium from cultured normal human colonic mucosa
Summary
Secretory leukocyte protease inhibitor (SLPI) is a 12 kDa non-glycosylated acid-stable antiprotease. Its amino acid sequence was elucidated in 1986.1 Its inhibitory activity against leukocytic as well as pancreatic elastase, cathepsin G, trypsin and chymotrypsin is well known.[1,2,3,4] It was first found in cervical secretions[5] and has since been found on a variety of different cell surfaces. It appears in large quantities in parotid secretions[6] as well as in bronchial secretions.[7,8] Its role is thought to be mainly the modulation of the inflammatory process. Both antibacterial and antiviral properties have been reported.[9,10,11,12] Increased concentrations have been reported in pneumonia among the elderly.[1 3]
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