Pj. Daniels et al., Cytokine-mediated stimulation of laminin expression and cell-growth arrestin a human submandibular gland duct-cell line (HSG), ARCH ORAL B, 44(7), 1999, pp. 603-615
Increased expression of laminin and various cytokines, including interferon
-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha) has been de
monstrated in minor salivary glands from patients with Sjogren's syndrome.
Previous reports state that exposure of a human salivary-gland cell line (H
SG) to IFN-gamma results in cellular changes similar to those in vivo Sjogr
en's syndrome. To begin studies of the cause of increased laminin expressio
n in salivary glands in Sjogren's syndrome and laminin's role in the pathol
ogical process, the effects of IFN-gamma on laminin expression and growth o
f HSG cells were examined here. Subconfluent cultures of HSG cells were tre
ated or not with IFN-gamma (1000 units/ml) for 1, 3 or 6 days. Immunoprecip
itation showed that the expression of cell-associated laminin was significa
ntly greater in IFN-gamma-treated cells at 3 or 6 days than in untreated ce
lls, while no significant differences in laminin counts precipitated from t
he media were evident among any of the IFN-gamma-treated or untreated sampl
es. Western blot analysis strongly suggested that this immunoprecipitated p
roduct is a dimer of the beta- and gamma-chains of laminin. Intracellular l
aminin was demonstrated immunocytochemically in a distinct, perinuclear pat
tern in both cytokine-treated and untreated cells. However, only faint stai
ning for type IV collagen. and no staining for fibronectin were evident in
untreated and cytokine-treated cells. An RNase protection assay showed only
slight upregulation of the laminin beta-chain mRNA at 3 days, but no signi
ficant difference at 6 days of treatment. Taken together, these data sugges
t enhanced accumulation of a dimer of laminin beta- and gamma-chains in the
cytoplasm of cytokine-treated HSG cells. However, mRNA for glyceraldehyde
3-phosphate dehydrogenase was significantly reduced at 6 days of treatment,
suggestive of cytokine-mediated metabolic abnormalities. IFN-gamma treatme
nt also resulted in significant reductions in cell numbers over time, in ag
reement with previous reports. Treatment of HSG cells for 3 days with IFN-g
amma (1000 U/ml) and TNF-alpha (70 U/ml) resulted in no significant changes
in cell proliferation or laminin protein and/or mRNA species compared to c
ells treated with IFN-gamma alone. Karyotype analysis of HSG cells revealed
human chromosomes with triploid chromosome numbers and rearrangements, cha
racteristic of transformed cells. These data demonstrate that IFN-gamma inc
reases the amount of intracellular laminin beta gamma dimers while decreasi
ng cell growth. Further studies are required to define an interaction betwe
en laminin expression and the growth and viability of HSG cells. (C) 1999 E
lsevier Science Ltd. All rights reserved.