EPA suppressed selenoprotein P expression via SREBP-1c.
A, efficiency of Srebf1 siRNA. H4IIEC3 cells were transfected with Srebf1 siRNAs or a negative control (NC) siRNA at 48 h. Knockdown efficiency was assessed by real-time PCR. Expression values were normalized to Actb mRNA. Data represent mean ± S.D. (error bars) (n = 4). ***, p < 0.001 versus negative control siRNA-treated cells. B, protein levels in the presence of the SREBP-1c overexpression vector. H4IIEC3 cells were transfected with the pCMV7-precursor SREBP-1c (pSREBP-1c) or the pCMV7-mature SREBP-1c (mSREBP-1c) vector or the pCMV7 empty vector at 24 h. SREBP-1c protein levels were then assessed by Western blotting. C, SELENOP promoter activity transfected with the precursor SREBP-1c or mature SREBP-1c vector. H4IIEC3 cells were co-transfected with the expression vectors for SREBP-1c, SELENOP promoter reporter, and control reporter at 48 h and then treated with 0.25 mm EPA for 24 h. Data represent mean ± S.D. (error bars) (n = 3–4). *, p < 0.05; ***, p < 0.001; N.S., not significant, versus vehicle-treated cells.