Acidic fibroblast growth factor decreases α-smooth muscle actin expression and induces apoptosis in human normal lung fibroblasts

Abstract

Fibroblast/myofibroblast expansion is critical in the pathogenesis of pulmonary fibrosis. To date, most research has focused on profibrotic mediators, whereas studies on antifibrotic factors are scanty. In this study, we explored the effects of acidic fibroblast growth factor (FGF-1) and FGF-1 plus heparin (FGF-1+H) on fibroblast growth rate, apoptosis, and myofibroblast differentiation. Heparin was used because it participates in FGF-1 signaling. Growth rate was evaluated by WST-1 colorimetric assay, DNA synthesis by [(3)H]thymidine incorporation, and apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and cleaved caspase 3. Expression of alpha-smooth muscle actin (alpha-SMA) was examined by immunocytochemistry, flow cytometry, real-time PCR, and immunoblotting. Despite the induction of DNA synthesis, FGF-1+H significantly reduced fibroblast growth rate. This correlated with a significant increase in apoptosis, evaluated by TUNEL (41.6 +/- 1.4% vs. 12.5 +/- 0.6% from controls; P < 0.01) and cleaved caspase 3 (295 +/- 32 vs. 200 +/- 19 ng/10(6) cells from controls; P < 0.05). Double immunostaining (alpha-SMA-TUNEL) revealed that the levels of induced apoptosis were similar in fibroblasts and myofibroblasts. FGF-1+H inhibited the effect of TGF-beta1 on myofibroblast differentiation. alpha-SMA-positive cells were reduced by immunocytochemistry from 44.5 +/- 6.5% to 10.9 +/- 1.9% and by flow cytometry from 30.6 +/- 2.5% to 7.7 +/- 0.6% (P < 0.01). Also, FGF-1+H significantly inhibited the TGF-beta1 induction of alpha-SMA quantified by real-time PCR and Western blot. This decrease was associated with a 35% reduction in TGF-beta1-induced collagen gel contraction. The effect of FGF-1+H was mediated by a significant decrease of TGF-beta1-induced Smad2 phosphorylation. FGF-1 alone exhibited similar but lower effects. These findings suggest that FGF-1 can have an antifibrogenic role, inducing apoptosis of fibroblasts and inhibiting myofibroblast differentiation.

Colorectal Cancer Cells Activate Adjacent Fibroblasts Resulting in FGF1/FGFR3 Signaling and Increased Invasion

“…Interestingly, during the development of lung fibrosis, FGF1 has recently been shown to inhibit myofibroblast differentiation. 20 This could suggest an autocrine FGF signaling in fibroblasts that might be important also during cancer progression. However, in this study we have only focused on FGF1 signaling effects in cancer cells, and further studies are needed to clarify this field.…”

Transforming Growth Factor–β–Induced Differentiation of Airway Smooth Muscle Cells Is Inhibited by Fibroblast Growth Factor–2

“…FGF-2 may prevent ASM cell differentiation into a more contractile phenotype (maturation), as has been reported for corneal fibroblasts (18) and microvascular pericytes (19). Acidic fibroblast growth factor (FGF-1) also inhibits the TGF-b-stimulated differentiation (or transdifferentiation) of lung epithelial cells and fibroblasts (20,21). We present evidence of the antagonistic effects of FGF-2 on ASM cell differentiation into a more contractile phenotype in response to TGF-b, and show that this inhibitory effect is dissociated from the mitogenic actions of FGF-2.…”

“…The concentrations of IL-6 secreted in control cells or cells treated with FGF-2, TGF-b, or a combination of FGF-2 and TGF-b were 5,631 6 1,009, 10,183 6 2,107, 29,588 6 2,247, and 27,660 6 1,725 pg/ml 21 , respectively (n ¼ 4). Thus, TGFb increased the concentrations of released IL-6 more than fivefold (P , 0.001), but coincubation with FGF-2 exerted no effect on the TGF-b-stimulated production of IL-6 (P .…”

“…Furthermore, we have shown that the incubation of ASM cells with platelet-derived growth factor (PDGF) (25 ng/ml 21 ), another ASM cell mitogen, did not attenuate TGF-b-stimulated increases in either SM22 or calponin expression (P . 0.05; Figures E4a and E4b).…”

Mechanisms of Lung Fibrosis Resolution

“…49 Dedifferentiation of myofibroblasts after fibroblast growth factor-1 administration was associated with reduced Smad2 phosphorylation. These findings support a direct dedifferentiation effect of fibroblast growth factor-1 by antagonizing TGF-b actions, an observation also observed in corneal myofibroblasts.…”