Fig. 2

Serotonin induces autophagy. a HepG2 and SK-Hep1 cells were treated with indicated concentrations of serotonin for 24 h. Cells were lysed and 50 μg proteins were immunoblotted with indicated antibodies. b HepG2 and SK-Hep1 cells were grown on coverslips in 6-well plates and treated with 0.2 and 0.5 mM serotonin, or pre-treated with 3-MA for 8 h followed by 0.5 mM serotonin for 24 h. Cells were stained with Cyto-ID green fluorescence reagent as to determine autophagy. Cells were observed under an OlympusBX60 fluorescent microscope and photographed. c HepG2 and SK-Hep1 cells were grown in 6-well plates and treated with serotonin or 3-MA alone for 30 h, or pre-treated with 3-MA for 8 h followed by serotonin for 24 h as indicated, and cell lysates immunoblotted with anti-LC3β I/II and anti-GAPDH antibodies. d HepG2 cells were grown on coverslips in 6-well plates and treated with serotonin or 3-MA alone for 30 h or pre-treated with 3-MA for 8 h followed by serotonin treatment for 24 h as indicated. Cells were further treated with 100 μM OA for 24 h and stained with Oil Red O stain, and slides were observed under a light microscope using 40X objective and photographed (left panel). The number of Oil-Red-O-stained lipid droplets present in the steatotic cells (n = 10) were measured and plotted (right panel). Data are expressed as the mean ± S.D. *** p < 0.001 compared to OA; ^{# # #} p < 0.001 compared to Serot. 3-MA- 3-Methyladenine. Serot. - Serotonin. OA - Oleic acid