Thymosin β4 inhibits PDGF-BB induced activation, proliferation, and migration of human hepatic stellate cells via its actin-binding domain

ABSTRACT

Objectives: Hepatic stellate cells (HSC) trans-differentiation is central to the development of liver fibrosis, marked by the expression of pro-fibrogenic genes and the proliferation and migration of activated HSC. Therefore, preventing and/or reverting the activation, proliferation, and migration of HSC may lead to new therapies for treating fibrosis/cirrhosis. Thymosin β4 (Tβ4) inhibits PDGF-BB-induced fibrogenesis, proliferation and migration of HSC by blocking Akt phosphorylation. Here, we utilized Tβ4-derived peptides: amino-terminal-Ac-SDKPDMAEIEKFDKS (1-15aa) and actin-binding-LKKTETQ (17-23aa) to investigate the molecular mechanisms in the anti-fibrogenic actions of Tβ4.

Methods: We used RT-PCR, Western blot, and proliferation and migration assays in early passages of human HSC cultures treated with PDGF-BB and/or Tβ4 peptides.

Results: We showed that 17-23aa but not 1-15aa inhibited PDGF-BB-dependent up-regulation of PDGFβ receptor, α-SMA, and collagen 1. It also blunted the phosphorylation of Akt at T 308 and S473, resulting in the inhibition of phosphorylation of PRAS40, and HSC proliferation and migration. Interestingly, 1-15aa blocked Akt phosphorylation at S473, but not T308 by inhibiting mTOR phosphorylation, thus, it did not have any effect on HSC proliferation and migration.

Conclusion: These findings suggest that while 1-15aa has a minor effect on Akt phosphorylation, the anti-fibrogenic actions of Tβ4 are exerted via 17-23aa.

KEYWORDS:

• Hepatic fibrosis
• hepatic stellate cells
• akt pathway
• thymosin beta 4

Author contributions

MR led and conceptualized the project; RS designed and performed experiments and wrote the manuscript; KRG designed and performed the experiments and revised the manuscript.

Acknowledgments

This work was presented in part at the 5th International Symposium on Thymosins in Health and Disease (2017) in Washington, DC. Tβ4 peptides used for this work were a kind gift from RegeneRx. We thank Dr. Allan L. Goldstein for his encouragement and advice.

Declaration of interest

No potential conflict of interest was reported by the authors.

The primer sequences used for quantitative PCR amplification.

Additional information

Funding

This work is supported by the NIH grants RO1 10541 (to M. Rojkind) and 1K01 AA025140–01 (to K. Reyes-Gordillo). This paper has been published as part of a supplement issue covering the proceedings of the Fifth International Symposium on Thymosins in Health and Disease and is funded by SciClone Pharmaceuticals