22R-Hydroxycholesterol induces differentiation of human NT2 precursor (Ntera2/D1 teratocarcinoma) cells.

Recently, we have shown that 22R-hydroxycholesterol, a steroid intermediate in the pathway of pregnenolone formation from cholesterol, is present at lower levels in Alzheimer's disease (AD) hippocampus and frontal cortex tissue specimens than in age-matched controls, and that this substance protects against cell death induced by amyloid beta-peptide in both rat sympathetic nerve pheochromocytoma (PC12) and differentiated human Ntera2/D1 teratocarcinoma neurons. Herein we report that 22R-hydroxycholesterol inhibits the proliferation of human Ntera2/D1 teratocarcinoma precursor cells (NT2) and induces these cells to differentiate into "neuron-like" or "astrocyte-like" cells. 22R-Hydroxycholesterol-induced differentiation of NT2 cells is associated with increases in the expression of neurofilament protein NF200, the cytoskeletal proteins microtubule-associated protein type II (MAP2) a and MAP2b, glial fibrillary acidic protein (GFAP) and glial cell line-derived neurotrophic factor receptor-alpha 2 (GFRalpha2). These effects of 22R-hydroxycholesterol are considered to be stereospecific because its enantiomer 22S-hydroxycholesterol and other steroids failed to induce differentiation of NT2 cells. 22R-Hydroxycholesterol was found to lack specific binding for numerous receptors, including all steroid receptors tested. However, using a cholesterol protein binding blot assay we demonstrated the presence of a 22R-hydroxycholesterol-binding protein in NT2 cells distinct from the human oxysterol receptors liver X receptor LXRalpha and beta.