Fibroblast growth factor 21 alleviates idiopathic pulmonary fibrosis by inhibiting PI3K-AKT-mTOR signaling and stimulating autophagy

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive pulmonary disease with an unclear pathogenesis and no available specific drug treatment. The principal etiological factors are lung inflammation caused by environmental factors, damage to alveolar epithelial cells, leading to epithelial-mesenchymal transition (EMT), and the abnormal proliferation of fibroblasts. Here, we have demonstrated that fibroblast growth factor 21 (FGF21) ameliorates IPF via the autophagy pathway. We administered FGF21 to bleomycin (BLM)-treated mice, which ameliorated their defects in lung function, reduced the accumulation of collagen, restored tissue structure, reduced the deposition of hydroxyproline, reduced the expression of collagen I and α-SMA and increased the expression of E-cadherin. The expression of LC3BII and the number of autophagosomes were significantly higher in the lungs. The expression of AKT and mTOR was significantly reduced by FGF21 treatment. We also determined the effects of FGF21 in A549 cells treated with TGF-β, and found that FGF21 significantly inhibits activation of the AKT signaling pathway, thereby reducing TGF-β-induced EMT and preventing the uncontrolled proliferation of fibroblasts. We conclude that FGF21 ameliorates IPF by inhibiting the PI3K-AKT-mTOR signaling pathway and activating autophagy, which provides a theoretical basis for FGF21 to be used for the treatment of IPF.

Effective fraction of Gualou-Xiebai-Banxia decoction inhibits the apoptosis of myocardial cells induced by ox-LDL via FGF21/FGFR1/βKlotho-FRS2α signal pathway

ETHNOPHARMACOLOGICAL RELEVANCE

The Gualou-Xiebai-Banxia decoction (GXBD), a classical traditional Chinese medicine (TCM) formula, has beneficial effects in turbid phlegm obstruction syndrome, a type of coronary heart disease (CHD). However, the underlying mechanism and effective constituents of GXBD remain elusive. Our previous studies have shown that the effective constituents of GXBD may be enriched in the n-butanol fraction (GXB-N) and water fraction (GXB-W), the targets of which remain unknown.

AIM OF THE STUDY

To investigate whether GXB-N and GXB-W protect myocardial cells (MCs) via fibroblast growth factor 21 (FGF21) signaling and, if so, to elucidate the underlying mechanisms. Furthermore, to investigate the targets of GXB-N and GXB-W as potential therapeutic targets for cardiovascular disease (CVD).

MATERIALS AND METHODS

Cell viability and apoptosis were assayed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays, respectively. The content of FGF21 in the medium was measured using enzyme-linked immunosorbent assay (ELISA). Protein expression was detected using immunofluorescence and western blotting.

RESULTS

Apoptosis increased markedly in MCs exposed to oxidized low density lipoprotein (ox-LDL) 100 μg/mL, with increased expression of FGF21, FGFR1 and βKlotho, phosphorylation of fibroblast receptor substrate 2α (FRS2α) was suppressed. Following incubation with GXB-N and GXB-W 200 μg/mL, the expression of FGF21, FGFR1, and βKlotho and the phosphorylation of FRS2α were increased.

CONCLUSION

Ox-LDL may inhibit the phosphorylation of FRS2α, inducing considerable FGF21 resistance and resulting in MC apoptosis. GXB-N and GXB-W restored and enhanced FGF21 sensitivity in MCs, consequently rescuing cells from ox-LDL-induced apoptosis. The FGF21-FRS2α signal pathway may be part action targets of these two effective fractions of GXBD.

Dynamic folding modulation generates FGF21 variant against diabetes

Fibroblast growth factor 21 (FGF21) is a regulator of glucose and lipid metabolism. It has been widely considered as a promising candidate for the treatment of type 2 diabetes mellitus (T2DM) and other related metabolic disorders. However, lack of structural and dynamic information has limited FGF21-based drug development. Here, using nuclear magnetic resonance (NMR) spectroscopy, we determine the structure of FGF21 and find that its non-canonical flexible β-trefoil conformation affects the folding of β2-β3 hairpin and further overall protein stability. To modulate folding dynamics, we designed an FGF21-FGF19 chimera, FGF21SS . As expected, FGF21SS shows better thermostability without inducing hepatocyte proliferation. Functional characterization of FGF21SS shows its better insulin sensitivity, reduced inflammation in 3T3-L1 adipocytes, and lower blood glucose and insulin levels in ob/ob mice compared with wild type. Our dynamics-based rational design provides a promising approach for FGF21-based therapeutic development against T2DM.