The
neurosteroid pregnenolone sulfate (PREGS), which is synthesized in glial cells, plays a significant role in learning and memory performance. The aim of this study was to investigate the regulation of expression of the
steroid sulfotransferase SULT2B1a, which catalyzes the conversion of
pregnenolone to PREGS, using the rat C6
glioma cell line. Rat C6
glioma cells expressed the SULT2B1a
isoform, which sulfonates
pregnenolone, but, neither the SULT2B1b
isoform, which catalyzes
cholesterol, nor the prototypical
steroid sulfotransferase SULT2A1 were expressed in these cells. Increasing concentrations of
l-glutamic acid in the presence of
cyclothiazide, which prevents
AMPA receptor desensitization, attenuated SULT2B1a
mRNA expression; however, neither
NMDA nor
kainic acid had a significant effect. Exposure to the synthetic
glutamate analogue alpha-amino-3-hydroxy-5-methyl-4-isoxazole
propionic acid (
AMPA) in the presence of
cyclothiazide also inhibited SULT2B1a expression. Attenuation of SULT2B1a expression by
L-glutamic acid was reversed by the selective
AMPA/
kainate receptor antagonist
2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline (
NBQX), and partially reversed by the specific
neuronal nitric oxide synthase (NOS) inhibitor
7-nitroindazole (7-NI). Induction of inducible NOS by
TNF-alpha in combination with
lipopolysaccharide (LPS) dramatically attenuated SULT2B1a expression; this was partially reversed by the specific inducible NOS inhibitor N(6)-(1-iminoethyl)-L-lysine hydrochloride (L-NIL). Furthermore, exposure to exogenous NO donors inhibited SULT2B1a
mRNA expression, and exposure to
sodium nitroprusside, LPS/
TNF-alpha and
L-glutamic acid in combination with
cyclothiazide increased the production of
nitrite, a stable degradation product of NO. These findings suggest that expression of SULT2B1a, which catalyzes PREGS production, is inhibited by activation of
excitatory amino acid receptors of the
AMPA subtype, via facilitation of intracellular NO signaling.