25-hydroxy Cholesterol contains six deuterium atoms at the 26, 26, 26, 27, 27, and 27 positions. It is intended for use as an internal standard for the quantification of 25-hydroxy cholesterol by GC-or LC-mass spectrometry. 25-hydroxy Cholesterol is a side-chain substituted oxysterol derived from dietary cholesterol that inhibits the cleavage of sterol regulatory element binding proteins (SREBPs) to suppress endogenous cholesterol synthesis in various cell types.¹It has been implicated in a variety of metabolic events including cholesterol homeostasis and atherosclerosis as well as antitumor activities as it has been shown to induce apoptosis through down-regulation of Bcl-2 expression and activation of caspases.²Immunomodulating capabilities have also been observed as the oxysterol can act as a LXR-RXR ligand coupling cholesterol synthesis to T cell proliferation, can reduce (EC₅₀~ 65 nM) IgA production by B cells in response to IL-2, and can suppress differentiation of monocytes into macrophages.^3,4,5

1.Adams, C.M., Reitz, J., De Brabander, J.K., et al.Cholesterol and 25-hydroxycholesterol inhibit activation of SREBPs by different mechanisms, both involving SCAP and InsigsJ. Biol. Chem.279(50)52772-52780(2004) 2.Bischoff, P.L., Holl, V., Coelho, D., et al.Apoptosis at the interface of immunosuppressive and anticancer activities: The examples of two classes of chemical inducers, oxysterols and alkylating agentsCurr. Med. Chem.7(7)693-713(2000) 3.McDonald, J.G., and Russell, D.W.Editorial: 25-Hydroxycholesterol: A new life in immunologyJournal of Leukocyte Biology88(6)1071-1072(2010) 4.Bauman, D.R., Bitmansour, A.D., McDonald, J.G., et al.25-Hydroxycholesterol secreted by macrophages in response to toll-like receptor activation suppresses immunoglobulin A productionProc. Natl. Acad. Sci. USA106(39)16764-16769(2009) 5.Bensinger, S.J., Bradley, M.N., Joseph, S.B., et al.LXR signaling couples sterol metabolism to proliferation in the acquired immune responseCell13497-111(2008)