Effect of endosulfan and bisphenol A on the expression of SUMO and UBC9.

This study was designed to investigate possible interference of Xenobiotics with SUMOylation in eukaryotic cells. To begin with, we docked 71 chemical structures from PubChem with human SUMO1 and UBC9 protein structures using Auto Dock 4.2 and Hex 6.3 and selected five compounds for binding studies in Surface Plasmon Resonance (SPR) with human SUMO1. In SPR studies, only endosulfan showed binding to SUMO1 (Kd1.313 × 10-4 M). Further, we treated HePG2 and differentiated 3T3-L1 cells with endosulfan/bisphenol A/perfluorooctanoic acid (PFOA) to test induction of oxidative stress and SUMO isoform/UBC9 expression. Treatment with these compounds resulted in higher levels of nitric oxide (NO), NOS2A mRNA, and reactive oxygen species (ROS) associated with decreased NADPH levels. Additionally, treatment with these chemicals resulted in elevated mRNA levels of IL-6 and IL-1ß in 3T3-L1 cells. In HePG2 cells, endosulfan treatment resulted in elevated mRNA levels of SUMO1, 3 and UBC9, whereas, treatment with bisphenol A resulted in increased mRNA of SUMO2, 3 and UBC9. Treatment with PFOA resulted in elevated mRNA levels of SUMO2. Apart from influencing the gene expression, endosulfan caused decrease in SUMO1-Sumoylation of few proteins. We propose that one reason for the severe health consequences of exposure to endosulfan/bisphenol could be due to induction of oxidative stress and modulation in SUMO and UBC9 gene expression.

Developing an in vitro screening assay platform for evaluation of antifibrotic drugs using precision-cut liver slices.

BACKGROUND: Precision-cut liver slices present different cell types of liver in a physiological context, and they have been explored as effective in vitro model systems to study liver fibrosis. Inducing fibrosis in the liver slices using toxicants like carbon tetrachloride is of less relevance to human disease conditions. Our aim for this study was to establish physiologically relevant conditions in vitro to induce fibrotic phenotypes in the liver slices. RESULTS: Precision-cut liver slices of 150 µm thickness were obtained from female C57BL/6 J mice. The slices were cultured for 24 hours in media containing a cocktail of 10 nM each of TGF-ß, PDGF, 5 µM each of lysophosphatidic acid and sphingosine 1 phosphate and 0.2 µg/ml of lipopolysaccharide along with 500 µM of palmitate and were analyzed for triglyceride accumulation, stress and inflammation, myofibroblast activation and extracellular matrix (ECM) accumulation. Incubation with the cocktail resulted in increased triglyceride accumulation, a hallmark of steatosis. The levels of Acta2, a hallmark of myofibroblast activation and the levels of inflammatory genes (IL-6, TNF-α and C-reactive protein) were significantly elevated. In addition, this treatment resulted in increased levels of ECM markers - collagen, lumican and fibronectin. CONCLUSIONS: This study reports the experimental conditions required to induce fibrosis associated with steatohepatitis using physiologically relevant inducers. The system presented here captures various aspects of the fibrosis process like steatosis, inflammation, stellate cell activation and ECM accumulation and serves as a platform to study the liver fibrosis in vitro and to screen small molecules for their antifibrotic activity.