Poster Topical Area: Carotenoids and Retinoids
Poster Board Number: 2
Objectives: Non-alcoholic steatohepatitis (NASH) is characterized by excessive fat accumulation, inflammation, and fibrosis in the liver. The activation of hepatic stellate cells (HSCs) is a critical event of the development of liver fibrosis as they are primarily responsible for the accumulation of extracellular matrix (ECM) in the injured liver. The objective of this study was to evaluate whether fucoxanthin (FCX), a carotenoid present in edible brown seaweeds, can inhibit fibrogenesis in LX-2 cells, a human HSC cell line, as well as primary mouse and human HSCs.
Methods: Cytotoxicity of FCX was measured in LX-2 cells. The effects of the FCX on transforming growth factor β1 (TGFβ1)-induced pro-fibrogenic gene expression and on SMAD3 pathway were determined in LX-2 cells and human primary HSCs using the quantitative realtime PCR and Western blot analysis. The modulatory roles of FCX in the activation of quiescent HSCs to activated HSCs were also evaluated in mouse primary HSCs isolated from C57BL/6J mice.
Results: FCX exhibited cell viability of more than 90% and 75% at a concentration of 2.5 and 5 μM, respectively. TGFβ1 increased mRNA levels of pro-fibrogenic genes, such as α-smooth muscle actin (α-SMA) and procollagen type I α1 (ColaA1), in LX-2 cells and human HSCs. However, FCX significantly abolished the induction. As SMAD3 pathway is known to mediate TGFβ1-induced fibrogenesis in HSCs, we determined whether FCX can regulate SMAD3 activation, i.e., phosphorylation, in LX-2 cells. TGFβ1 stimulated phosphorylation of SMAD3, which was markedly attenuated by FCX. When quiescent mouse primary cells were cultured in an uncoated plastic plate for activation for 4 days, mRNA levels of α-SMA, procollagen genes such as Col1a1, Col3a1, Col6a1, and Col6a3, and tissue inhibitor of metalloproteinases-1 were induced. However, presence of FCX during the activation significantly reduced the mRNA levels. Also, cells treated with FCX displayed more cytoplasmic lipid droplets, a characteristics of quiescent HSCs, than control cells.
Conclusion: The results suggest that FCX exerts anti-fibrogenic effects by preventing TGFβ1-induced pro-fibrogenic gene expression by inhibiting the SMAD3 activation in HSCs and by inhibiting the activation of quiescent HSCs.
Funding source: USDA Hatch CONS00972; USDA Multi-State Hatch CONS00916
University of Connecticut