The Biochemical changes of Hepatic Lipid Droplets in BALB/ c mice exposed to TCDD

Abstract

Dioxins are highly toxic and persistent halogenated organic pollutants belonging to two families i.e., Polychlorinated Dibenzo-p-Dioxins (PCDDs) and Polychlorinated Dibenzo Furans (PCDFs). Dioxins toxicity is mediated by the Aryl-hydrocarbon Receptor (AhR). 2,3,7,8,-tetrachlorodibenzo-p-dioxin (TCDD) is the most toxic among dioxins showing the highest affinity toward the AhR receptor, and has a Toxic Equivalent Factor (TEF) of 1.0. Dioxins are able to accumulate in fat storage tissue according to its lipophilicity. Liver among other tissues plays the main role in dioxin detoxification since it has a complex enzymatic system, CytochromeP450 (CYPs), and specialized organelle, Lipid Droplets (LDs). It is of necessity to verify the morphologic and molecular effects of TCDD on hepatic LDs in animal model, BALB/c mice. In this work, BALB/c mice were administrated one oral dose of 15µg/Kg/bw of TCDD, and after four sequenced time points, LDs were isolated from liver and described microscopically. Relative quantification in gene expression of dioxin detoxification and oxylipins synthesis genes was detected. The results show differences in gene expression by time intervals, especially in P3 and P4. There is an increasing in expression of AhR, ARNT and CYP1A1 in P3 and P4 in compare with P1 and P2. An obvious accretion/increasing appeared in LOX15, COX2, Plin5, CideC, Ppara and Pparg. In contrast, gene expression of AhR (P1 and P2) and ARNT (P2) decreased in general, and increased briefly in CYP1A1 expression, and no differences were observed in the expression of other genes. In parallel, LDs were isolated, stained with Nile Blue and checked by Fluorescence

microscope to confirm its morphology and integrity. In all time points, a brief increasing in LDs number and proteins concentration were observed in compare with the control. Fluorescence microscope images showed that the size of LDs was almost equal in all samples. Our results shed the light on primary indications for TCDD exposure at the level of gene expression of genes involved in TCDD detoxification, oxylipins and LDs synthesis in a time dependent manner. Here, it seems important to give more concern on TCCD toxicity and its ability to accumulate in LDs and influence on LDs number and its composition of lipid and protein through changes in gene expression. So, more investigations are still needed.