Steroid synthesis in rat brain cell cultures

Area of Science:

• Neuroscience
• Cell Biology
• Biochemistry

Background:

• Primary cultures of neonatal rat forebrain glial cells were established.
• These cultures mature into oligodendrocytes and astrocytes.
• Oligodendrocyte differentiation is marked by increased 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) activity.

Purpose of the Study:

• To investigate steroid biosynthesis in cultured rat glial cells.
• To determine if steroid synthesis is associated with oligodendrocyte differentiation.
• To explore the role of cytochrome P-450scc in this process.

Main Methods:

• Glial cell cultures were characterized using immunofluorescence for galactocerebroside (Gal C), myelin basic protein (MBP), and glial fibrillary acidic protein (GFAP).
• Steroid biosynthesis was assessed by incubating cells with [3H]mevalonolactone and measuring radiolabeled cholesterol and pregnenolone metabolites.
• The activity of cytochrome P-450scc was evaluated using specific inhibitors like aminoglutethimide.

Main Results:

• Oligodendrocytes expressed cytochrome P-450scc, an enzyme crucial for steroid synthesis.
• De novo biosynthesis of cholesterol, pregnenolone, and 20-alpha-hydroxysteroids was demonstrated.
• Steroid synthesis correlated with increased CNPase activity, peaking at 3 weeks of culture.
• Dibutyryl cAMP and dexamethasone enhanced steroid synthesis.
• Inhibition of cytochrome P-450scc led to cholesterol accumulation and subsequent 20-OHP production upon blockade release.

Conclusions:

• Normal rat glial cells, particularly oligodendrocytes, are capable of de novo steroid biosynthesis.
• This steroidogenic capacity is linked to oligodendrocyte differentiation.
• The findings provide evidence for the concept of "neurosteroids" produced within the brain.