title: Isorhamnetin attenuates liver fibrosis by inhibiting TGF-β/Smad signaling and relieving oxidative stress.
abstract: Hepatic fibrosis is considered integral to the progression of chronic liver diseases, leading to the development of cirrhosis and hepatocellular carcinoma. Activation of hepatic stellate cells (HSCs) is the dominant event in hepatic fibrogenesis. We investigated the ability of isorhamnetin, the 3'-O-methylated metabolite of quercetin, to protect against hepatic fibrosis in vitro and in vivo. Isorhamnetin inhibited transforming growth factor (TGF)-β1-induced expression of α-smooth muscle actin (α-SMA), plasminogen activator inhibitor-1 (PAI-1), and collagen in primary murine HSCs and LX-2 cells. The TGF-β1- or Smad-induced luciferase reporter activity of Smad binding elements was significantly decreased by isorhamnetin with a concomitant decrease in Smad2/3 phosphorylation. Isorhamnetin increased the nuclear translocation of Nrf2 in HSCs and increased antioxidant response element reporter gene activity. Furthermore, isorhamnetin blocked TGF-β1-induced reactive oxygen species production. The specific role of Nrf2 in isorhamnetin-mediated suppression of PAI-1 and phosphorylated Smad3 was verified using a siRNA against Nrf2. To examine the anti-fibrotic effect of isorhamnetin in vivo, liver fibrosis was induced by CCl4 in mice. Isorhamnetin significantly prevented CCl4-induced increases in serum alanine transaminase and aspartate transaminase levels, and caused histopathological changes characterized by decreases in hepatic degeneration, inflammatory cell infiltration, and collagen accumulation. Moreover, isorhamnetin markedly decreased the expression of phosphorylated Smad3, TGF-β1, α-SMA, and PAI-1. Isorhamnetin attenuated the CCl4-induced increase in the number of 4-hydroxynonenal and nitrotyrosine-positive cells, and prevented glutathione depletion. We propose that isorhamnetin inhibits the TGF-β/Smad signaling pathway and relieves oxidative stress, thus inhibiting HSC activation and preventing liver fibrosis.
authors.affiliation: College of Pharmacy, Chosun University, Gwangju 61452, Republic of Korea.
authors.forename: Ji Hye
authors.initials: JH
authors.lastname: Yang
authors.affiliation: MRC-GHF, College of Korean Medicine, Daegu Haany University, Gyeongsan, Gyeongsangbuk-do 38610, Republic of Korea.
authors.forename: Sang Chan
authors.initials: SC
authors.lastname: Kim
authors.affiliation: College of Pharmacy, Chosun University, Gwangju 61452, Republic of Korea.
authors.forename: Kyu Min
authors.initials: KM
authors.lastname: Kim
authors.affiliation: College of Pharmacy, Chosun University, Gwangju 61452, Republic of Korea.
authors.forename: Chang Ho
authors.initials: CH
authors.lastname: Jang
authors.affiliation: College of Pharmacy, Chosun University, Gwangju 61452, Republic of Korea.
authors.forename: Sam Seok
authors.initials: SS
authors.lastname: Cho
authors.affiliation: College of Pharmacy, Chosun University, Gwangju 61452, Republic of Korea.
authors.forename: Seung Jung
authors.initials: SJ
authors.lastname: Kim
authors.affiliation: MRC-GHF, College of Korean Medicine, Daegu Haany University, Gyeongsan, Gyeongsangbuk-do 38610, Republic of Korea.
authors.forename: Sae Kwang
authors.initials: SK
authors.lastname: Ku
authors.affiliation: MRC-GHF, College of Korean Medicine, Daegu Haany University, Gyeongsan, Gyeongsangbuk-do 38610, Republic of Korea.
authors.forename: Il Je
authors.initials: IJ
authors.lastname: Cho
authors.affiliation: College of Pharmacy, Chosun University, Gwangju 61452, Republic of Korea. Electronic address: shki@chosun.ac.kr.
authors.forename: Sung Hwan
authors.initials: SH
authors.lastname: Ki
mesh_terms: D000818:Animals; D002460:Cell Line; D055166:Hepatic Stellate Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D006801:Humans; D008103:Liver Cirrhosis / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D051267:NF-E2-Related Factor 2 / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects*; D011794:Quercetin / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D015398:Signal Transduction / Q000187:drug effects*; D051785:Smad Proteins / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism*
chemical_list: D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D051785:Smad Proteins; D016212:Transforming Growth Factor beta; C047368:3-methylquercetin; D011794:Quercetin
keywords: Hepatic stellate cells; Isorhamnetin; Liver fibrosis; Oxidative stress; Smad; TGF-β