CCAAT/enhancer-binding protein β is involved in the breed-dependent transcriptional regulation of 3β-hydroxysteroid dehydrogenase/Δ(5)-Δ(4)-isomerase in adrenal gland of preweaning piglets

Abstract

The enzyme 3β-hydroxysteroid dehydrogenase/Δ(5)-Δ(4)-isomerase (3β-HSD) catalyzes the biosynthesis of all steroid hormones. The molecular mechanisms regulating porcine adrenal 3β-HSD expression in different breeds are still poorly understood. In this study, we aimed to compare the expression of 3β-HSD between preweaning purebred Large White (LW) and Erhualian (EHL) piglets and to explore the potential factors regulating 3β-HSD transcription. EHL had significantly higher serum levels of cortisol (P<0.01) and testosterone (P<0.01), which were associated with significantly higher expression of 3β-HSD mRNA (P<0.01) and protein (P<0.05) in the adrenal gland, compared with LW piglets. The 5' flanking region of the porcine 3β-HSD gene showed significant sequence variations between breeds, and the sequence of EHL demonstrated an elevated promoter activity (P<0.05) in luciferase reporter gene assay. Higher adrenal expression of 3β-HSD in EHL was accompanied with higher CCAAT/enhancer binding protein β (C/EBPβ) expression (P<0.05), enriched histone H3 acetylation (P<0.05) and C/EBPβ binding to 3β-HSD promoter (P<0.05). In addition, higher androgen receptor (AR) (P=0.06) and lower glucocorticoid receptor (GR) (P<0.05) were detected in EHL. Co-immunoprecipitation analysis revealed interactions of C/EBPβ with both AR and GR. These results indicate that the C/EBPβ binding to 3β-HSD promoter is responsible, at least in part, for the breed-dependent 3β-HSD expression in adrenal gland of piglets. The sequence variations of 3β-HSD promoter and the interactions of AR and/or GR with C/EBPβ may also participate in the regulation.

Keywords: 3β-HSD; 3β-hydroxysteroid dehydrogenase/Δ(5)-Δ(4)-isomerase; AGP; AR; ARE; Adrenal gland; C/EBPβ; CCAAT/enhancer binding protein β; COX-2; ChIP; DAX-1; EHL; Erhualian; FXR; GATA-6; GR; GRE; LW; Large White; NET; PPIA; Pig; SF-1; STAT5A; STAT5B; StAR; androgen receptor; androgen response element; chromatin immunoprecipitation; cyclooxygenase 2; dosage-sensitive sex reversal adrenal hypoplasia congenita critical region on the X chromosome gene 1; farnesoid X receptor; glucocorticoid receptor; glucocorticoid response element; norepinephrine transporter; peptidylprolyl isomerase A; signal transducer and activator of transcription protein 5A; signal transducer and activator of transcription protein 5B; steroidogenic acute regulatory protein; steroidogenic factor 1; transcription factor GATA-6; α1-acid glycoprotein.