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Updated: May 15, 2026
Measurement of Fatty Acid β-Oxidation in a Suspension of Freshly Isolated Mouse Hepatocytes
Published on: September 9, 2021
Mouse hepatic oval cells require Met-dependent PI3K to impair TGF-β-induced oxidative stress and apoptosis
Adoración Martínez-Palacián1, Gaelle del Castillo, Amileth Suárez-Causado
1Dep Bioquímica y Biología Molecular II, Facultad de Farmacia, Universidad Complutense, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, IdISSC, Madrid, Spain.
Abstract:
We have previously shown that oval cells harboring a genetically inactivated Met tyrosine kinase (Met(-/-) oval cells) are more sensitive to TGF-β-induced apoptosis than cells expressing a functional Met (Met(flx/flx)), demonstrating that the HGF/Met axis plays a pivotal role in oval cell survival. Here, we have examined the mechanism behind this effect and have found that TGF-β induced a mitochondria-dependent apoptotic cell death in Met(flx/flx) and Met(-/-) oval cells, associated with a marked increase in levels of the BH3-only proteins Bim and Bmf. Bmf plays a key role during TGF-β-mediated apoptosis since knocking down of BMF significantly diminished the apoptotic response in Met(-/-) oval cells. TGF-β also induced oxidative stress accompanied by NADPH oxidase 4 (Nox4) mRNA up-regulation and decreased protein levels of antioxidant enzymes. Antioxidants inhibit both TGF-β-induced caspase 3 activity and Bmf up-regulation, revealing an oxidative stress-dependent Bmf regulation by TGF-β. Notably, oxidative stress-related events were strongly amplified in Met(-/-) oval cells, emphasizing the critical role of Met in promoting survival. Pharmacological inhibition of PI3K did impair HGF-driven protection from TGF-β-induced apoptosis and increased sensitivity of Met(flx/flx) oval cells to TGF-ß by enhancing oxidative stress, reaching apoptotic indices similar to those obtained in Met(-/-) oval cells. Interestingly, both PI3K inhibition and/or knockdown itself resulted in caspase-3 activation and loss of viability in Met(flx/flx) oval cells, whereas no effect was observed in Met(-/-) oval cells. Altogether, results presented here provide solid evidences that both paracrine and autocrine HGF/Met signaling requires PI3K to promote mouse hepatic oval cell survival against TGF-β-induced oxidative stress and apoptosis.
Insights
The HGF/Met axis, crucial for liver oval cell survival, protects against TGF-β-induced apoptosis. This involves PI3K-mediated signaling that combats oxidative stress and Bmf protein upregulation.
Area of Science:
- Cell Biology
- Hepatology
- Molecular Biology
Background:
- The HGF/Met axis is vital for hepatic oval cell survival.
- Met tyrosine kinase signaling influences cellular responses to TGF-β.
- Understanding Met's role in apoptosis is crucial for liver health.
Purpose of the Study:
- To elucidate the mechanism by which the HGF/Met axis promotes oval cell survival against TGF-β-induced apoptosis.
- To investigate the role of oxidative stress and BH3-only proteins in this process.
- To determine the involvement of PI3K signaling in Met-mediated protection.
Main Methods:
- Utilized genetically modified mouse oval cells (Met(-/-) and Met(flx/flx)).
- Assessed TGF-β-induced apoptosis, mitochondrial pathways, and BH3-only protein levels (Bim, Bmf).
- Investigated oxidative stress markers (Nox4), antioxidant enzyme activity, and the effect of PI3K inhibition.
Main Results:
- TGF-β triggers mitochondria-dependent apoptosis, involving Bim and Bmf, with Bmf playing a key role.
- TGF-β induces oxidative stress via Nox4, which regulates Bmf and enhances apoptosis.
- Met signaling, particularly via PI3K, protects against TGF-β-induced apoptosis by mitigating oxidative stress.
Conclusions:
- The HGF/Met axis, through PI3K signaling, is essential for mouse hepatic oval cell survival.
- This protection is mediated by counteracting TGF-β-induced oxidative stress and apoptosis.
- Bmf and oxidative stress are critical components in the TGF-β apoptotic pathway regulated by Met.
