Hepatic fibrosis is the first stage of liver disease, and can progress to a chronic status, such as cirrhosis or hepatocellular carcinoma. Excessive production of extracellular matrix (ECM) components plays an important role in the development of fibrosis. Mechanistically, transforming growth factor beta (TGFβ)-induced phosphorylation of Smad is thought to be a key signaling pathway in the development of liver fibrosis. Although the natural isoquinoline alkaloid oxoglaucine (1,2,9,10-tetramethoxy-7H-dibenzo(de,g)quinolin-7-one) exerts numerous beneficial effects, including anti-cancer, anti-inflammatory, and anti-osteoarthritic effects in diverse cell types, the effects of oxoglaucine on liver fibrosis and fibrogenic gene expression have not been fully elucidated. The aim of this study is to evaluate the signaling pathway and antifibrotic activity of isoquinoline alkaloid oxoglaucine in TFGβ-induced hepatic fibrosis in vitro. Using Hepa1c1c7 cells and primary hepatocytes, we demonstrated that oxoglaucine treatment resulted in inhibition of the expression of fibrosis markers such as collagen, fibronectin, and alpha-SMA. Subsequent experiments showed that oxoglaucine suppressed TGFβ-induced phosphorylation of Smad2 and reactive oxygen species (ROS) generation, without altering cell proliferation. We further determined that the increase in Smad7 by oxoglaucine treatment is responsible for the inhibition of Smad2 phosphorylation and the anti-fibrogenic effects. These findings indicate that oxoglaucine plays a crucial role in suppression of fibrosis in hepatocytes, thereby making it a potential drug candidate for treatment of liver fibrosis.

27-Hydroxycholesterol (27OHC), an endogenous oxysterol, has been implicated in various physiological processes, including regulation of estrogen receptor activity and lipid metabolism. However, studies on how 27OHC affects the metabolic changes associated with lipogenesis inhibition in the liver remain limited. This study aimed to investigate the systemic effects of 27OHC on hepatocytes through a comparative proteomic analysis of the proteomes in the 27OHC-treated AML12 cells. Ingenuity Pathway Analysis revealed significant downregulation of certain metabolic pathways, such as cholesterol biosynthesis and glycolysis, which are highly associated with lipid metabolism, following 27OHC treatment. Furthermore, in vitro biochemical analysis revealed significant inhibition of the expression of genes associated with the mevalonate pathway and a decrease in the total cellular cholesterol levels in AML12 cells and primary hepatocytes following 27OHC treatment. In addition, it was observed that 27OHC significantly reduced the transcripts levels of critical glycolytic enzymes such as aldolase, phosphofructokinase, and pyruvate kinase. This inhibition resulted in decreased lactate production and extracellular acidification (ECAR), indicating suppression of glycolytic flux. Concurrently, we proved that downregulation of reactive oxygen species generation and HIF-1α expression following 27OHC treatment partially contributed to glycolysis inhibition. Overall, we demonstrated the inhibitory effects of 27OHC on the hepatic mevalonate pathway and glycolysis, revealing a novel mechanism by which 27OHC regulates lipid metabolism. As the accumulation of cholesterol and lipids promotes hepatic fatty liver disease and increased glycolysis contributes to triacylglycerol maturation, the suppressive effects of 27OHC on hepatic lipid and glucose metabolism may contribute to protect against fatty liver development.