title: Thymosin-β4 (Tβ4) blunts PDGF-dependent phosphorylation and binding of AKT to actin in hepatic stellate cells.
abstract: Hepatic stellate cell transdifferentiation is a key event in the fibrogenic cascade. Therefore, attempts to prevent and/or revert the myofibroblastic phenotype could result in novel therapeutic approaches to treat liver cirrhosis. The expression of platelet-derived growth factor (PDGF)-β receptor and the proliferative response to platelet-derived growth factor-ββ (PDGF-ββ) are hallmarks of the transdifferentiation of hepatic stellate cells (HSC). In this communication, we investigated whether thymosin-β4 (Tβ4), a chemokine expressed by HSC could prevent PDGF-BB-mediated proliferation and migration of cultured HSC. Using early passages of human HSC, we showed that Tβ4 inhibited cell proliferation and migration and prevented the expression of PDGF-β receptor (PDGF-βr), α-smooth muscle actin and α1(I) collagen mRNAs. Tβ4 also inhibited the reappearance of PDGF-βr after its PDGF-BB-dependent degradation. These PDGF-dependent events were associated with the inhibition of AKT phosphorylation at both T308 and S473 amino acid residues. The lack of AKT phosphorylation was not due to the inhibition of PDGF-βr phosphorylation, the activation of phosphoinositide 3-kinase (PI3K), pyruvate dehydrogenase kinase isozyme 1 (PDK1), and mammalian target of rapamycin (mTOR). We found that PDGF-BB induced AKT binding to actin, and that Tβ4 prevented this effect. Tβ4 also prevented the activation of freshly isolated HSC cultured in the presence of Dulbecco's modified Eagle's medium or Dulbecco's minimal essential medium containing 10% fetal bovine serum. In conclusion, overall, our findings suggest that Tβ4 by sequestering actin prevents binding of AKT, thus inhibiting its phosphorylation. Therefore, Tβ4 has the potential to be an antifibrogenic agent.
authors.affiliation: Department of Biochemistry and Molecular Biology, The George Washington University Medical Center, Washington, DC, USA.
authors.forename: Karina
authors.initials: K
authors.lastname: Reyes-Gordillo
authors.forename: Ruchi
authors.initials: R
authors.lastname: Shah
authors.forename: Anastas
authors.initials: A
authors.lastname: Popratiloff
authors.forename: Sidney
authors.initials: S
authors.lastname: Fu
authors.forename: Anna
authors.initials: A
authors.lastname: Hindle
authors.forename: Frederick
authors.initials: F
authors.lastname: Brody
authors.forename: Marcos
authors.initials: M
authors.lastname: Rojkind
mesh_terms: D000199:Actins / Q000378:metabolism*; D000077214:Becaplermin; D015153:Blotting, Western; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002469:Cell Separation; D054338:Cell Transdifferentiation / Q000187:drug effects / Q000502:physiology*; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D055166:Hepatic Stellate Cells / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D008103:Liver Cirrhosis / Q000378:metabolism; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D020574:Proto-Oncogene Proteins c-sis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013947:Thymosin / Q000378:metabolism* / Q000494:pharmacology; D000099201:Thymosin beta(4)
chemical_list: D000199:Actins; D000077214:Becaplermin; D010982:Platelet-Derived Growth Factor; D051057:Proto-Oncogene Proteins c-akt; D020574:Proto-Oncogene Proteins c-sis; D013947:Thymosin; D000099201:Thymosin beta(4)