(HEPATOLOGY 2010.) To date, it has been believed that the activation of hepatic stellate cells (HSCs) plays a pivotal role in the development of liver fibrosis.1–5 In reaction to liver injury by virus, chemicals, drugs, ischemia, or metabolic disorder, HSCs undergo phenotypic changes from a quiescent stage to an activated stage. SMP30 is a 34-kDa aging marker protein that has high expression levels in the liver, kidney, and lung MAPK inhibitor and decreases with the aging process.6–8 SMP30 contains gluconolactonase activity, which is involved in L-ascorbic acid (vitamin C) biosynthesis.8 Moreover, previous

studies have shown that SMP30 prevents the apoptosis and necrosis of hepatocytes.9–11 According to our previous data,12 Smad3 knockout (KO) mice showed significantly increased levels of SMP30 and attenuated liver fibrosis as compared with WT mice. These data suggest the possibility that Smad3 expression might be related to SMP30 expression levels. The transforming growth factor beta (TGF-β)/Smad3 pathway

is believed to be the most important pathway in the activation of quiescent HSCs to myofibroblasts.12, 13 The induction of collagen expression is mediated by the nuclear translocation of these phosphorylated Smads complexes composed of phosphorylated Smad2 (p-Smad2), phosphorylated Smad3 (p-Smad3), and Smad4.14–16 In contrast to the TGF-β/Smads signaling pathway activating HSCs, peroxisome proliferators-activated receptor-γ (PPAR-γ) has recently been identified Ferrostatin-1 cost as an important negative regulator in HSCs activation.17–20 PPAR-γ expression levels and activity are markedly down-regulated during the HSC activation process.17–21 Furthermore, stimulation of PPAR-γ not only inhibits HSC activation but also induces a phenotypic switch from activated HSCs to quiescent HSCs.19–22 Our previous unpublished

data revealed significantly increased PPAR-γ levels and an elevated number of hypertrophic HSC in the liver of aged SMP30 KO mice compared with that of same-aged WT mice. Taken together, these results suggest the possibility that SMP30 may act on TGF-β/Smad3 signaling and PPAR-γ expression. In order to ascertain the role of SMP30 in liver fibrosis, the present study was performed using SMP30 KO mice. α-SMA, smooth muscle actin; CCl4, carbon tetrachloride; 4��8C HPLC, high-performance liquid chromatography; HSC, hepatic stellate cell; KO, knockout; PPAR-γ, peroxisome proliferator-activated receptor-gamma; ROS, reactive oxygen species; RT-PCR, reverse transcription-polymerase chain reaction; SMP30, senescence marker protein 30; TGF-β, transforming growth factor beta; WT, wildtype. SMP30 KO mice were created as described.10 The WT C57BL/6 mice and SMP30 KO mice were housed and bred in a room at 22 ± 3°C, relative humidity 50 ± 10%, a 12-hour light-dark cycle, and were given food and water ad libitum. The genomic DNA was purified from mouse tail tissue using a combination of several procedures found in the literature.