Expression of neutrophil gelatinase-associated lipocalin in human salivary glands

Objectives: We performed an observational study of RNA and protein expression in human tissue to examine the distribution of neutrophil gelatinase-associated lipocalin (NGAL) in normal and chronic inflammatory salivary tissues, and to investigate the expression level of NGAL in inflammatory conditions of salivary glands. Methods: Normal salivary gland tissues and tissue samples of salivary glands with chronic sialadenitis were obtained. Expression of NGAL was investigated by reverse transcriptase- polymerase chain reaction, and semiquantitative analysis of these results was also performed. The differential localization and amount of immunoreactivity to NGAL protein was evaluated by immunohistochemistry and Western blot analysis in normal salivary gland tissues and salivary glands with chronic sialadenitis. Results: NGAL messenger RNA transcripts were detected in the tissues from the salivary glands with chronic sialadenitis, but only a small amount was detected in the tissues from the normal salivary glands. A weak expression of NGAL protein was occasionally seen in a few ductal epithelial cells of normal salivary gland tissue. However, in tissue samples from glands with chronic sialadenitis, the NGAL protein was expressed strongly in ductal epithelial cells and infiltrating inflammatory cells. Conclusions: These results imply that NGAL is associated with the regulation of inflammation in salivary glands.