ABSTRACT
4,4'-Isopropylidenediphenol (bisphenol A, BPA), a chemical substance that is widely used mainly as a monomer in the production of polycarbonates, in epoxy resins, and in thermal papers, is suspected to cause epigenetic modifications with potentially toxic consequences. Due to its negative health effects, BPA is banned in several products and is replaced by other bisphenols such as bisphenol S and bisphenol F. The present study examined the effects of BPA, bisphenol S, bisphenol F, p,p'-oxybisphenol, and the BPA metabolite BPA ß-d-glucuronide on the expression of a set of microRNAs (miRNAs) as well as long interspersed nuclear element-1 methylation in human lung fibroblast and Caco-2 cells. The results demonstrated a significant modulation of the expression of different miRNAs in both cell lines including miR-24, miR-155, miR-21, and miR-146a, known for their regulatory functions of cell cycle, metabolism, and inflammation. At concentrations between 0.001 and 10 µg/ml, especially the data of miR-155 and miR-24 displayed non-monotonous and often significant dose-response curves that were U- or bell-shaped for different substances. Additionally, BPA ß-d-glucuronide also exerted significant changes in the miRNA expression. miRNA prediction analysis indicated effects on multiple molecular pathways with relevance for toxicity. Besides, long interspersed nuclear element-1 methylation, a marker for the global DNA methylation status, was significantly modulated by two concentrations of BPA and p,p'-oxybisphenol. This pilot study suggests that various bisphenols, including BPA ß-d-glucuronide, affect epigenetic mechanisms, especially miRNAs. These results should stimulate extended toxicological studies of multiple bisphenols and a potential use of miRNAs as markers.
ABSTRACT
AIM: We investigated different bioactive compounds including epigallocatechin gallate (EGCG), anthocyanidin, resveratrol, phloretin, spermidine, butyrate, and ß-hydroxybutyrate with regard to their effect on SIRT3 via NRF2 and modulation of the proinflammatory senescence-associated secretory phenotype (SASP) in senescence induced 3T3-L1 preadipocytes. METHODS: For induction of senescence, 3T3-L1 preadipocytes were incubated with bromodeoxyuridine (BrdU) for 8 days. Cell cycle inhibition was observed, and ß-galactosidase activity was measured. After BrdU treatment, cells were treated with different bioactive compounds in various concentrations for 96 h. ELISA was used for determining proinflammatory cytokine IL6 in SASP cells. RESULTS: CDKN1a increased significantly after BrdU incubation compared to untreated control (p < 0.01). All secondary plant ingredients used for treatment, but not anthocyanidin 50 µM, decrease CDKN1a expression (p < 0.05), whereas most endogenous substances did not attenuate CDKN1a. IL6 secretion positively correlated with CDKN1a (p < 0.01), whereas EGCG could diminish both, IL6 and CDKN1a with the strongest effect (p < 0.01). Although NRF2 positively correlated with SIRT3 activation (p < 0.05), only resveratrol (p < 0.01) and anthocyanidin (p < 0.05) could activate NRF2 significantly. Solely anthocyanidin 50 µM (p < 0.05) and 100 µM (p < 0.01) and EGCG 50 µM (p < 0.01) could increase SIRT3 expression. Activation of SIRT3 with EGCG correlated with lowered IL6 secretion significantly (p < 0.05) but not with anthocyanidin. CONCLUSION: Accumulation of senescent cells in adipose tissue plays an important role in obesity and age-related diseases. SIRT3, located in the mitochondria, can regulate ROS via different pathways. Thus, targeting SIRT3 activating compounds such as EGCG may delay senescence of cells and senescence induced inflammatory processes.
