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Human cadmium (Cd) exposure is associated with cancers of the lung and kidney. Using cDNA microarray analysis, we have recently reported that the expression of E2F1 is reduced by Cd in human lung fibroblasts, indicating the possibility of G1-phase arrest. To test this hypothesis, we investigated the effects of Cd on the cyclin-dependent kinase (CDK2) and retinoblastoma protein (Rb) regulatory pathways in WI38 human lung fibroblasts. We demonstrate here that G1-phase accumulation was induced by Cd in WI38 (wild-type for p53 and Rb), but not in the SV40 large T antigen-transformed variant WI38-VA13 (p53- and Rb-defective). Cd-induced cell-cycle arrest was associated with a decrease in CDK2 protein and with increase in p21 expression and p53 phosphorylation. Cd treatment caused a distinct increase in the formation of p21-cyclin E-CDK2 complex, as revealed by immunoprecipitation. The level of Rb-E2F1 complexes was increased, and the translocation of E2F1 to the nucleus was decreased by Cd treatment. Consequently, the transcriptional activity of E2F1 and the expression of the E2F1 target genes were also decreased by Cd. These results clearly demonstrate that Cd-mediated G1 arrest in WI38 cells is associated with the suppression of Rb phosphorylation and with the inhibition of E2F1 transcriptional activity.

Herbal medicines are widely used in many countries for the treatment of many diseases. Although the use of herb extracts as alternative medicine is growing, their toxicological properties have not been thoroughly investigated. In this study, we have investigated the effects of water and ethanol extracts of 18 herbs on the hepatic lipid metabolism and steatogenic hepatotoxicity. Ethanol extracts of Cirsium japonicum, Carthamus tinctorius, Rehmanniae glutinosa (preparata), Polygala tenuifolia, Foeniculum vulgare, Polygonum multiflorum, and Acorus gramineus and water extracts of Polygonum multiflorum and Rehmanniae glutinosa induced lipid accumulation in Sk-hep1 human hepatoma cells as determined by Nile red staining. These extracts increased the luciferase activity of sterol regulatory element (SRE) and decreased that of peroxisome proliferator response element (PPRE), indicating the possibilities of enhanced fatty acid synthesis and decreased fatty acid oxidation. To identify the components responsible for the fat accumulation, we tested 50 chemicals isolated from the nine herbs. Apigenin, luteolin, pectolinarin and lupeol from Cirsium japonicum, 8-methoxypsoralen and umbelliferone from Foeniculum vulgare and pomonic acid and jiocerebroside from Rehmanniae glutinosa significantly increased the accumulation of lipid droplets. These results suggest that ethanol extracts of Cirsium japonicum, Carthamus tinctorius, Rehmanniae glutinosa (preparata), Polygala tenuifolia, Foeniculum vulgare, Polygonum multiflorum, and Acorus gramineus and water extracts of Polygonum multiflorum and Rehmanniae glutinosa can cause fatty liver disease by decreasing β-oxidation of fatty acid and increasing lipogenesis.

Non-alcoholic fatty liver disease is associated with inhibited AMP-activated kinase (AMPK) and activation of sterol regulatory element binding protein 1 (SREBP-1). AMPK phosphorylation inhibits SREBP-1, a major transcription factor of de novo lipogenesis, by inhibiting the liver X receptor (LXR) or by direct phosphorylation. Resveratrol, a polyphenol, has regulatory effects on hepatic lipid metabolism as a potent AMPK activator. In this study, we evaluated the anti-steatogenic effects of resveratrol and its derivatives and identified the molecular mechanism in vitro and in vivo. Resveratrol and its derivatives decreased lipid accumulation by free fatty acids (FFA mixture; 0.5 mM, oleic acid:palmitic acid = 2: 1) in H4IIEC3 cells. Synthesized derivatives of resveratrol had lower cytotoxicity than the parental molecule with similar potency. SY-102 suppressed SREBP-1 maturation by T0901317, an LXR agonist, and decreased SRE luciferase activity and the mRNA levels of lipogenic genes. Inhibition of AMPK by pre-treatment with compound C completely blocked the effects of SY-102. To evaluate their efficacy in vivo, mice were fed a high-fat diet for 5 days, and resveratrol or SY-102 was administered orally for the last 2 days. Oral administration of the SY-102 increased AMPK phosphorylation, followed by reduced hepatic triglyceride accumulation to a similar extent as resveratrol. These data demonstrate that SY-102, a synthesized derivative of resveratrol, might provide a promising therapeutic effect against fatty liver disease.