PKCδ as a regulator for TGFβ1-induced α-SMA production in a murine nonalcoholic steatohepatitis model

PLoS One. 2013;8(2):e55979. doi: 10.1371/journal.pone.0055979. Epub 2013 Feb 18.

Abstract

The precise mechanism of TGFβ1 signaling in the progression of non-alcoholic steatohepatitis (NASH) has remained unclear. In particular, a potential regulatory mechanism by which PKCδ affects profibrogenic gene expression had never been explored. In this study, therefore, the role of PKCδ in TGFβ1 mediated α-SMA expression was investigated using NASH model mice. In preparation of the NASH model, male C57BL6/J mice were fed a methionine-choline-deficient (MCD) diet for 3 weeks, after which time they were intraperitoneally injected with lipopolysaccharide (LPS). In addition, Tlr4(Lps-d) (CH3/HeJ) mice were used to demonstrate the TGFβ1 signaling's dependency on TLR4 induction. Liver histology and hepatic hepatitis markers were investigated, and hepatic gene expression levels were determined by real-time PCR. Acute liver injury by LPS injection specifically elevated not only α-SMA expression but also phospho-PKCδ in this model. In contrast, Tlr4(Lps-d) (CH3/HeJ) and blockade of TGFβ1 receptor by SB431542 resulted in a significant reduction of PKCδ activation and α-SMA expression. Moreover, the TGFβ1-induced α-SMA production was significantly reduced by a specific PKCδ inhibitor. These findings suggested that PKCδ plays a critical role in TGFβ1-induced α-SMA production in a NASH model. Thus, this was the first demonstration of the involvement of PKCδ in the regulation of α-SMA expression in NASH liver tissues, and the impaired induction of PKCδ phosphorylation by LPS in a steatohepatitis condition. Interestingly, treatment by PKCδ inhibitor caused dramatic reduction of myofibroblast activation, indicating that PKCδ represents a promising target for treating NASH.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetophenones / pharmacology
  • Actins / biosynthesis*
  • Animals
  • Benzopyrans / pharmacology
  • Diet
  • Disease Models, Animal
  • Enzyme Activation / drug effects
  • Fatty Liver / metabolism*
  • Fatty Liver / pathology
  • Lipopolysaccharides / administration & dosage
  • Lipopolysaccharides / pharmacology
  • Liver Cirrhosis / metabolism
  • Male
  • Mice
  • Non-alcoholic Fatty Liver Disease
  • Protein Kinase C-delta / antagonists & inhibitors
  • Protein Kinase C-delta / metabolism*
  • Transforming Growth Factor beta1

Substances

  • Acetophenones
  • Actins
  • Benzopyrans
  • Lipopolysaccharides
  • Transforming Growth Factor beta1
  • alpha-smooth muscle actin, mouse
  • rottlerin
  • Protein Kinase C-delta

Grants and funding

This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Korean Ministry of Education, Science and Technology (2011-0014420). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.