Biosynthesis of the regulatory oxysterol, 5-cholesten-3β,25-diol 3-sulfate, in hepatocytes

Abstract

Cellular cholesterol homeostasis is maintained through coordinated regulation of cholesterol synthesis, degradation, and secretion. Nuclear receptors for oxygenated cholesterol derivatives (oxysterols) are known to play key roles in the regulation of cholesterol homeostasis. We recently identified a sulfated oxysterol, 5-cholesten-3b,25-diol 3-sulfate (25HC3S), that is localized to liver nuclei. The present study reports a biosynthetic pathway for 25HC3S in hepatocytes. Assays using mitochondria isolated from rats and sterol 27-hydroxylase (Cyp27A1) gene knockout mice indicated that 25-hydroxycholesterol (25HC) is synthesized by CYP27A1. Incubation of cholesterol or 25HC with mitochondrial and cytosolic fractions in the presence of 3 ¶-phosphoadenosyl 5 ¶-phosphosulfate resulted in the synthesis of 25HC3S. Real-time RT-PCR and Western blot analysis showed the presence of insulin-regulated hydroxycholesterol sulfotransferase 2B1b (SULT2B1b) in hepatocytes. 25HC3S, but not 25HC, decreased SULT2B1b mRNA and protein levels. Specific small interfering RNA decreased SULT2B1b mRNA, protein, and activity levels. These findings demonstrate that mitochondria synthesize 25HC, which is subsequently 3b-sulfated to form 25HC3S.-Li, X., W. M. Pandak, S. K. Erickson, Y. Ma, L. Yin, P. Hylemon, and S. Ren. Biosynthesis of the regulatory oxysterol, 5-cholesten-3b,25-diol 3-sulfate, in hepatocytes.

Knockout of mouse Cyp3a gene enhances synthesis of cholesterol and bile acid in the liver

“…25-Hydroxy-cholesterol and other oxysterols suppress cholesterol biosynthesis by suppressing proteolytic activation of SREBP-2 ( 23 ). Although 25-hydroxy-cholesterol is also produced by microsomal cholesterol 25-hydroxylase ( 42 ), mitochondrial CYP27A1 ( 43,44 ), and nonenzymatic autoxidation of cholesterol ( 45 ), results of the present study showed that levels of 25-hydroxy-cholesterol in the livers of Cyp3a Ϫ / Ϫ mice were signifi cantly lower than those in WT mice ( Table 1 ). Therefore, it is suggested that defi ciency of CYP3A leads to reduction of 25-hydroxy-cholesterol synthesis, resulting in activation of SREBP-2.…”

25-Hydroxycholesterol-3-sulfate attenuates inflammatory response via PPARγ signaling in human THP-1 macrophages

“…THP-1 macrophages express SULT2B1b and are able to synthesize 25HC3S (38). It has been reported by our laboratory that the expression is dramatically upregulated by insulin and downregulated by 25HC3S in both hepatocytes (36) and macrophages (38). In vitro, only 5% of our added 25HC3S entered the cells.…”

“…Macrophages are able to synthesize this oxysterol (38). This oxysterol appears to be synthesized from 25-hydroxycholesterol (25HC) by sterol sulfotransferase-2B1b (SULT2B1b) (36). Overexpression of SULT2B1 impairs the response of oxysterol receptor liver X receptor (LXR) to multiple oxysterol ligands.…”

Bile acids as regulatory molecules

“…It also is capable of carrying out further oxidation of the 27-hydroxy group to yield a C-27 carboxyl group. Finally, this enzyme also has the ability to 25-hydroxylate cholesterol, yielding a potentially important regulatory oxysterol, 25-hydroxycholesterol ( 37 ). 25-Hydroxycholestrol can be further metabolized in hepatocytes to 25-hydroxycholesterol-3-sulfate.…”