Bio prolactin 60 kDa is overexpressed in salivary glandular epithelial cells from patients with Sjogren's syndrome

Abstract

Characterization of endogenous synthesis of prolactin (PRL) proteins and their cellular localization in labial salivary glands of patients with Sjogren's syndrome (SS) were achieved. PRL, PRL-receptors (PRL-R), and S100A6 protein were detected by immunohistochemistry. In situ prolactin synthesis was investigated in controls and SS patients by ex vivo incubation of minor salivary glands biopsies and immunoprecipitation assay. Increased PRL- immunoreactivity was found in cytoplasmic acinar epithelial cells in SS patients compared with normal subjects. PRL-R was distributed only in ductal epithelial cells in which S100A6 protein (a PRL-R-associated protein) was also present. PRL, PRL-R, or S100A6-immunoreactivity was not detected in infiltrating mononuclear cells. Immunoprecipitation demonstrated that PRL synthesis occurred in minor salivary glands with increased synthesis of two distinct PRL-like proteins (one major band at 60 kDa and a minor at 16 kDa) in SS glands compared with normal glands. Expression of PRL gene was demonstrated in SS salivary glands using RT-PCR. A positive correlation was found between the presence of PRL-like proteins in acinar epithelial cells of SS patients and clinical extraglandular manifestations. The presence of anti- Ro and anti-La antibodies also positively correlated with a higher percentage of PRL in acinar epithelial cells. In conclusion, PRL-like proteins are synthetized and overexpressed in glandular epithelial cells of labial salivary glands from SS patients and correlate with the aggressiveness of the disease.