PKCd as a Regulator for TGFb1-Induced a-SMA Production in a Murine Nonalcoholic Steatohepatitis Model

The precise mechanism of TGFb1 signaling in the progression of non-alcoholic steatohepatitis (NASH) has remained unclear. In particular, a potential regulatory mechanism by which PKCd affects profibrogenic gene expression had never been explored. In this study, therefore, the role of PKCd in TGFb1 mediated a-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, Tlr4Lps-d (CH3/HeJ) mice were used to demonstrate the TGFb1 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 a-SMA expression but also phospho-PKCd in this model. In contrast, Tlr4Lps-d (CH3/ HeJ) and blockade of TGFb1 receptor by SB431542 resulted in a significant reduction of PKCd activation and a-SMA expression. Moreover, the TGFb1-induced a-SMA production was significantly reduced by a specific PKCd inhibitor. These findings suggested that PKCd plays a critical role in TGFb1-induced a-SMA production in a NASH model. Thus, this was the first demonstration of the involvement of PKCd in the regulation of a-SMA expression in NASH liver tissues, and the impaired induction of PKCd phosphorylation by LPS in a steatohepatitis condition. Interestingly, treatment by PKCd inhibito