25(S)-27 hydroxy Cholesterol is a stereoisomer of the endogenous oxysterol 27-hydroxy cholesterol. 27-hydroxy Cholesterol is a sterol 27-hydroxylase-mediated cholesterol hydroxylation product involved in activating LXRα and LXRβ and potently suppressing cholesterol biosynthesis [1,2].
Liver X receptors (LXRs) belong to the nuclear receptor superfamily member. LXRs are ligand-activated transcription factors containing two LXR isoforms termed as α and β. LXRs play central roles in the transcriptional control of lipid metabolism. LXRs function as nuclear cholesterol sensors that are activated in response to elevated intracellular cholesterol levels in multiple cell types. Activation of LXRs induces the expression of the genes involved in cholesterol absorption, transport, efflux, and excretion. LXRs are potential targets for a variety of diseases, such as hypertriglyceridemia [3]. LXRs have also been involved in modulating immune and inflammatory responses in macrophages [3].
25(S)-27 hydroxy Cholesterol was the less predominant-occurring (~20%) stereoisomer of the endogenous oxysterol 27-hydroxy cholesterol. 27-hydroxy Cholesterol activated LXRα and LXRβ with the EC50 values of 85 and 71 nM, respectively [1,2].
References:
[1] Fu, X. ,Menke, J.G.,Chen, Y., et al. 27-Hydroxycholesterol is an endogenous ligand for liver X receptor in cholesterol-loaded cells. The Journal of Biological Chemisty 276(42), 38378-38387 (2001).
[2] Javitt, N. B. 25R,26-Hydroxycholesterol revisited: Synthesis, metabolism, and biologic roles. Journal of Lipid Research 43, 665-670 (2002).
[3] Zelcer N, Tontonoz P. Liver X receptors as integrators of metabolic and inflammatory signaling[J]. The Journal of clinical investigation, 2006, 116(3): 607-614.