Calprotectin is a
calcium binding protein produced by leukocytes, macrophages and epithelial cells, and its levels in several tissues increase during
infections and in many inflamed areas, suggesting that it may be an
indicator of inflammatory activity.
Osteopontin is a prominent phosphorylated
glycoprotein in bone matrix, having
calcium binding capacity. Recently, it has been reported that
calprotectin and
osteopontin are present in
urinary stones (pathological mineralized masses in the body), and that these
proteins may be involved in their formation.
Dental calculus formed by mineralization of
dental plaque is an inflammatory factor which may contribute to
periodontal disease. It contains many organic components involved in mineralization. We recently found
osteopontin molecules in human
dental calculus and suggested that the components of its matrix may be similar to those of
urinary stones. In this study, we investigated the presence of
calprotectin in human
dental calculus by immunohistochemical and immunoblotting analyses using a specific antibody for
calprotectin. After fixation and demineralization of dental
calculi adhered to tooth roots, sections embedded in
paraffin were immunoreacted with the antibody for
calprotectin and positive immunostaining for
calprotectin was observed.
Dental calculus proteins were then extracted with
EDTA and separated by electrophoresis on 15%
polyacrylamide gels. By immunoblotting analysis, 3 or 4 bands were observed at 11, 14.5, 22-25, 28 or 36.5 kDa and these patterns corresponded to those of
calprotectin subunits. When non-immune rabbit serum was used instead of
calprotectin-specific antibody as a negative control, no immunoreactivity was observed. These findings indicate that
calprotectin is associated not only with antibacterial action but also with
calcium binding capacity during
dental calculus formation.