Figure 1

Proteasome inhibition reverses the pro-fibrotic effects of TGF-β in dermal fibroblasts. Fibroblasts were cultured in the presence of TGF-β (10 ng/mL) or bortezomib (1 μM) or both (TGF-β was added 1 hour after bortezomib) or were left untreated for the indicated amount of time (a-c) or for 48 hours (d, e). mRNA levels for COL1A1 (a), COL1A2 (b), and TIMP-1 (c) were assessed by quantitative polymerase chain reaction and normalized to HsEEF1A1 mRNA levels. The increase in treated cells relative to untreated cells is shown in (a-c). The bars represent the mean ± standard deviation of two independent experiments; *P < 0.05, **P < 0.005, and ***P < 0.0005 in comparison with untreated cells. Type I collagen present in culture supernatants was quantified by immunoblotting (d) and TIMP-1 by enzyme-linked immunosorbent assay (e). Bars represent the increase in protein levels in treated cells relative to untreated cells. A representative identification of type I collagen protein by Western blotting is inserted in (d). Bort, bortezomib; COL1A, collagen 1A1; TGF-β, transforming growth factor-beta; TIMP-1, tissue inhibitor of matrix metalloproteinase-1; UT, untreated.