Silibinin attenuates TGF-ß2-induced fibrogenic changes in human trabecular meshwork cells by targeting JAK2/STAT3 and PI3K/AKT signaling pathways.

Transforming growth factor-ß2 (TGF-ß2) induced fibrogenic changes in human trabecular meshwork (HTM) cells have been implicated in trabecular meshwork (TM) damage and intraocular pressure (IOP) elevation in primary open-angle glaucoma (POAG) patients. Silibinin (SIL) exhibited anti-fibrotic properties in various organs and tissues. This study aimed to assess the effects of SIL on the TGF-ß2-treated HTM cells and to elucidate the underlying mechanisms. Our study found that SIL effectively inhibited HTM cell proliferation, attenuated TGF-ß2-induced cell migration, and mitigated TGF-ß2-induced reorganization of both actin and vimentin filaments. Moreover, SIL suppressed the expressions of fibronectin (FN), collagen type I alpha 1 chain (COL1A1), and alpha-smooth muscle actin (α-SMA) in the TGF-ß2-treated HTM cells. RNA sequencing indicated that SIL interfered with the phosphoinositide 3-kinase (PI3K)/protein kinase B (PKB, also known as AKT) signaling pathway, extracellular matrix (ECM)-receptor interaction, and focal adhesion in the TGF-ß2-treated HTM cells. Western blotting demonstrated SIL inhibited the activation of Janus kinase 2 (JAK2)/signal transducers and activators of transcription 3 (STAT3) and the downstream PI3K/AKT signaling pathways induced by TGF-ß2, potentially contributing to its inhibitory effects on ECM protein production in the TGF-ß2-treated HTM cells. Our study demonstrated the ability of SIL to inhibit TGF-ß2-induced fibrogenic changes in HTM cells. SIL could be a potential IOP-lowering agent by reducing the fibrotic changes in the TM tissue of POAG patients, which warrants further investigation through additional animal and clinical studies.

TGF-ß2 enhances glycolysis in chondrocytes via TßRI/p-Smad3 signaling pathway.

Chondrocytes rely heavily on glycolysis to maintain the metabolic homeostasis and cartilage matrix turnover. Glycolysis in chondrocytes is remodeled by diverse biochemical and biomechanical factors due to the sporty joint microenvironment. Transforming growth factor-ß2 (TGF-ß2), one of the most abundant TGF-ß superfamily members in chondrocytes, has increasingly attracted attention in cartilage physiology and pathology. Although previous studies have emphasized the importance of TGF-ß superfamily members on cell metabolism, whether and how TGF-ß2 modulates glycolysis in chondrocytes remains elusive. In the current study, we investigated the effects of TGF-ß2 on glycolysis in chondrocytes and explored the underlying biomechanisms. The results showed that TGF-ß2 could enhance glycolysis in chondrocytes by increasing glucose consumption, up-regulating liver-type ATP-dependent 6-phosphofructokinase (Pfkl) expression, and boosting lactate production. The TGF-ß2 signal entered chondrocytes via TGF-ß receptor type I (TßRI), and activated p-Smad3 signaling to regulate the glycolytic pathway. Subsequent experiments employing specific inhibitors of TßRI and p-Smad3 further substantiated the role of TGF-ß2 in enhancement of glycolysis via TßRI/p-Smad3 axis in chondrocytes. The results provide new understanding of the metabolic homeostasis in chondrocytes induced by TGF-ß superfamily and might shed light on the prevention and treatment of related osteoarticular diseases.

Bone morphogenetic protein-6 suppresses TGF-ß2-induced epithelial-mesenchymal transition in retinal pigment epithelium.

AIM: To evaluate the effect of bone morphogenetic protein-6 (BMP-6) on transforming growth factor (TGF)-ß2-induced epithelial-mesenchymal transition (EMT) in retinal pigment epithelium (RPE). METHODS: Adult retinal pigment epithelial cell line (ARPE-19) were randomly divided into control, TGF-ß2 (5 µg/L), and BMP-6 small interfering RNA (siRNA) group. The cell morphology was observed by microscopy, and the cell migration ability were detected by Transwell chamber. The EMT-related indexes and BMP-6 protein levels were detected by Western blotting. Furthermore, a BMP-6 overexpression plasmid was constructed and RPE cells were divided into the control group, TGF-ß2+empty plasmid group, BMP-6 overexpression group, and TGF-ß2+BMP-6 overexpression group. The EMT-related indexes and extracellular regulated protein kinases (ERK) protein levels were detected. RESULTS: Compared with the control group, the migration of RPE cells in the TGF-ß2 group was significantly enhanced. TGF-ß2 increased the protein expression levels of α-smooth muscle actin (α-SMA), fibronectin and vimentin but significantly decreased the protein levels of E-cadherin and BMP-6 (P<0.05) in RPE. Similarly, the migration of RPE cells in the BMP-6 siRNA group was also significantly enhanced. BMP-6 siRNA increased the protein expression levels of α-SMA, fibronectin and vimentin but significantly decreased the protein expression levels of E-cadherin (P<0.05). Overexpression of BMP-6 inhibited the migration of RPE cells induced by TGF-ß2 and prevented TGF-ß2 from affecting EMT-related biomarkers (P<0.05). CONCLUSION: BMP-6 prevents the EMT in RPE cells induced by TGF-ß2, which may provide a theoretical basis for the prevention and treatment of proliferative vitreoretinopathy.