Transforming growth factor-β1 reduces apoptosis via autophagy activation in hepatic stellate cells

Abstract

Autophagy is a metabolic process that is important in fibrogenesis, in which cellular components are degraded by lysosomal machinery. Transforming growth factor β1 (TGF-β1) is a potent fibrogenic cytokine involved in liver fibrosis; however, it remains elusive whether autophagy is regulated by TGF-β1 in this process. In the present study, the function of TGF-β1-mediated autophagy in the proliferation and apoptosis of hepatic stellate cells (HSCs) was investigated. A rat HSC cell line (HSC-T6) was incubated with or without TGF-β1 followed by bafilomycin A1, and microtubule-associated proteins 1A/1B light chain 3 (LC3) small interfering (si)RNA was used to inhibit autophagy in order to assess the association between TGF-β1 and autophagy. HSC-T6 cell transient transfection was accomplished with a pLVX-AcGFP-N1-rLC3B-encoding plasmid. An MTS assay and flow cytometry were utilized to detect proliferation and apoptosis of HSC-T6 cells. Quantitative polymerase chain reaction, immunofluorescence and western blot analysis were used to detect the presence of activation markers. Proliferation was increased and apoptosis was reduced in HSC-T6 cells treated with TGF-β1 compared with cells subjected to serum deprivation. However, when HSC-T6 cells were treated with bafilomycin A1 and LC3 siRNA, increased apoptosis and reduced proliferation were observed. In addition, protein and mRNA expression levels of the autophagy marker LC3 were significantly increased. GFP-LC3 punctate markings were more prolific following TGF-β1 treatment of HSC-T6 cells, indicating that TGF-β1 may rescue HSC-T6 cells from serum deprivation and reduce apoptosis via autophagy induction. The present study elucidated the possible functions of TGF-β1-mediated autophagy in the pathological process of liver fibrosis.

Autophagy and the unfolded protein response promote profibrotic effects of TGF-β1 in human lung fibroblasts

“…The TGF-␤ 1 superfamily has an essential role in lung disease associated with tissue and ECM remodeling, including IPF (12,23,28,35,51,55,57). TGF-␤ 1 can promote autophagy in different cell types, including human heart and lung fibroblasts, a response that we have shown promotes the synthesis of ECM proteins (9,14,15,46). There is no direct evidence for TGF-␤ 1 -associated modulation of the UPR in lung cells, despite there being evidence linking UPR activation with lung fibrosis (10,32).…”

“…TGF-␤ 1 also inhibits starvation-induced autophagy in HAFs and cells of the annulus fibrosus of intervertebral disks (42,43). Conversely, TGF-␤ 1 can induce autophagy in association with fibrosis in liver and kidney cells (9,14). At present, the context-and tissue-specific role of TGF-␤ 1 in regulating autophagy and pathogenic features associated with fibrogenesis is unclear.…”

“…Diverse results from studies that dissect the role of specific autophagy regulator (ATG) proteins confer disparate effects with respect to wound repair and tissue remodeling. In some cases, autophagy can facilitate fibrosis (9,14), but it appears to be downregulated in IPF lungs (3,40,43), whereas it may be increased in asthma (46,58). Studies of liver fibrosis indicate that chemically induced liver injury causes hepatic stellate cell activation and promotes lipid catabolism and the loss of lysosomal lipids, which reduces liver fibrosis, particularly in steatosis-related cirrhosis (26).…”

Odontogenic infection by Porphyromonas gingivalis exacerbates fibrosis in NASH via hepatic stellate cell activation

“…Stimulation of PAR2-TGF-β1 pathway caused by P.g.-infection induces HSC activation. In addition to Smad signaling, phosphorylation of ERK1/2, which is reported directly/indirectly to be upregulated by TGF-signaling, was also examined 14,[16][17][18][19] . P.g.-infection induced activation of Smad2, Smad3, and ERK1/2.…”

The role of ZFP580, a novel zinc finger protein, in TGF-mediated cytoprotection against chemical hypoxia-induced apoptosis in H9c2 cardiac myocytes

“…TGF-β1 is a multifunctional cytokine that regulates apoptosis in a cell type-specific and context-dependent manner, with proapoptotic or anti-apoptotic actions depending on the target cell type and the pathophysiologic milieu (8–10). Despite its proapoptotic role in several cell types, TGF-β1 demonstrated cardioprotective effects during reperfusion injury or cardiac inflammatory disease in myocytes (11–13), and exerted an anti-apoptotic role in hypoxia-reoxygenation-induced myocardial cell injury (12,14,15). …”