A putative role of micro RNA in regulation of cholesterol 7α-hydroxylase expression in human hepatocytes

Kwang-Hoon Song; Tiangang Li; Erika Owsley; John Y. L. Chiang

doi:10.1194/jlr.M004531

A putative role of micro RNA in regulation of cholesterol 7α-hydroxylase expression in human hepatocytes[S]

Department of Integrative Medical Sciences, Northeastern Ohio Universities Colleges of Medicine and Pharmacy, Rootstown, OH 44272

1To whom correspondence should be addressed. e-mail: jchiang{at}neoucom.edu

Abstract

Cholesterol 7α-hydroxylase (CYP7A1) plays a critical role in regulation of bile acid synthesis in the liver. CYP7A1 mRNAs have very short half-lives, and bile acids destabilize CYP7A1 mRNA via the 3′-untranslated region (3′-UTR). However, the underlying mechanism of translational regulation of CYP7A1 mRNA remains unknown. Screening of a human micro RNA (miRNA) microarray has identified five differentially expressed miRNAs in human primary hepatocytes treated with chenodeoxycholic acid, GW4064, or fibroblast growth factor (FGF)19. These compounds also significantly induced the expression of miR-122a, a liver-specific and the predominant miRNA in human hepatocytes. The putative recognition sequences for miR-122a and miR-422a were localized in the 3′-UTR of human CYP7A1 mRNA. The miR-122a and miR-422a mimics inhibited, whereas their inhibitors stimulated CYP7A1 mRNA expression. These miRNAs specifically inhibited the activity of the CYP7A1-3′-UTR reporter plasmids, and mutations of miRNA binding sites in 3′-UTR abrogated miRNA inhibition of reporter activity. These results suggest that miR-122a and miR-422a may destabilize CYP7A1 mRNA to inhibit CYP7A1 expression. However, these miRNAs did not play a role in mediating FGF19 inhibition of CYP7A1 transcription. Under certain conditions, miRNA may reduce CYP7A1 mRNA stability to inhibit bile acid synthesis, and the miR-122a antagomirs may stimulate bile acid synthesis to reduce serum cholesterol and triglycerides.

Footnotes

Abbreviations:

Apobec

apolipoprotein B editing enzyme

CDCA

chenodeoxycholic acid

CYP7A1

cholesterol 7α-hydroxylase

CYP8B1

sterol 12α-hydroxylase

ERK

extracellular signal-regulated kinase

FGF

fibroblast growth factor

FGFR4

fibroblast growth factor 15 receptor 4

FXR

farnesoid X receptor

I-mir

miRNA inhibitor

MAPK

mitogen-activated protein kinase

miRNA

micro RNA

miR

miRNA mimic

PHH

primary human hepatocyte

SLC7A1

solute carrier 7A1

3′-UTR

3′-untranslated region
This study is supported by the National Institutes of Health grants DK44442 and DK58379. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the National Institutes of Health.
↵[S] The online version of this article (available at http://www.jlr.org) contains supplementary data in the form of four figure.