DEXAMETHASONE ALTERS MESSENGER-RNA LEVELS BUT NOT SYNTHESIS OF COLLAGENS, FIBRONECTIN, OR LAMININ BY CULTURED RAT FAT-STORING CELLS

Glucocorticoids have been shown to suppress collagen synthesis and gen e expression by fibroblasts. However, little is Known about their effe cts on fat-storing cells, the major matrix-producing cells in liver fi brosis. In this study we investigated the effect of dexamethasone on t he extracellular matrix expression by cultured rat fat-storing cells. Fat-storing cells were isolated from male Wistar rats by collagenase/p ronase digestion and purified by density gradient centrifugation. Pat- storing cells in early primary culture (3-day-old, representing a rela tively quiescent phenotype) and in subculture (one passage, about a-we ek-old, representing an activated phenotype) were treated with 10(-6) mol/L dexamethasone for messenger RNA (mRNA) study or with 10(-8) to 1 0(-6) mol/L dexamethasone for protein study. Expression of collagen ty pe I, III, IV, fibronectin, and laminin was analyzed at the mRNA level by Northern hybridization, and at the protein level by metabolic labe ling and immunoprecipitation. Dexamethasone had a variable effect on t he expression of collagen alpha 1(I) mRNA level. While a tendency for modest suppression was observed (5%-50%) in primary cells, the differe nce was not statistically significant, Variable response was observed in subcultured cells. Collagen alpha 1(III) mRNA level showed a tenden cy for stimulation, Dexamethasone stimulated the expression of collage n alpha 1(IV), fibronectin, and laminin B1 mRNA levels by 1.4-, 2.4-, and 1.6-fold respectively, in primary fat-storing cells. Subcultured c ells showed a similar response, but the magnitude of stimulation was m ore variable than that of primary cells. Unexpectedly, at the protein level dexamethasone had no effect on the expression of these proteins. Our results indicate that glucocorticoids do not possess a net suppre ssive effect on extracellular matrix synthesis by fat-storing cells. B eneficial effects of glucocorticoids may be attributable to other mech anisms of action, such as their anti-inflammatory effect.