Downregulation of miRNA-155-5p contributes to the adipogenic activity of 2-ethylhexyl diphenyl phosphate in 3T3-L1 preadipocytes

2-Ethylhexyl diphenyl phosphate (EHDPP) is a commonly used organophosphorus flame retardant and food packaging material. Because of its high lipophilic and bioaccumulative properties, adipocytes are the primary target of EHDPP. However, the toxicity of EHDPP on preadipocytes and the potential mechanism have not been fully elucidated. MicroRNAs (miRNAs) are thought to be an important mediator that contribute to the toxicity of environmental contaminants. To identify the miRNAs specifically responsible for EHDPP exposure and their role in EGDPP's toxicity in preadipocytes, the adipogenic effects and miRNA expression profiling were performed on 3T3-L1 preadipocytes exposed to EHDPP. EHDPP at concentrations of 1-10 μM promoted adipocyte differentiation, as evidenced by lipid staining, triglyceride content, and expression of adipogenesis markers. MiRNA-seq analysis revealed that 7 differentially expressed miRNAs were recognized under EHDPP exposure, with miR-155-5p being the top down-regulated miRNA. Quantitative reverse transcription PCR (RT-qPCR) analysis showed that miR-155-5p level fell sharply during the first 2 days and continued to fall dose-dependently throughout the EHDPP exposure period. MiR-155-5p inhibition promotes adipocyte differentiation, whereas its overexpression counteracted EHDPP-induced adipogenesis. Luciferase reporter assay identified CCAAT/enhancer-binding protein beta (C/EBPβ) as a target of miR-155-5p in 3T3-L1 preadipocytes in response to EHDPP. Taken together, EHDPP exposure down-regulated miR-155-5p, which then increased C/EBPβ and peroxisome proliferator-activated receptor γ (PPARγ) expression and promoted adipogenesis in preadipocytes.