Neuroprotective action of synthetic steroids with oxygen bridge. Activity on GABAA receptor

- We characterize 7 conformational analogs of allopregnanolone (A)/pregnanolone (P).
- Four steroids affected the binding to the GABAA receptor similar to A or P.
- 3β-HSD activity in brain tissue showed regional and steroid dependency.
- Neuroprotection was observed in hypoxia-induced brain injury.
- Two of the oxygen bridged steroids could be potential therapeutic substances.

Allopregnanolone (A) and pregnanolone (P) are able to modify neural activities acting through the GABAA receptor complex. This capacity makes them useful as anticonvulsant, anxiolytic, or anti-stress compounds. In this study, the performance of seven synthetic steroids (SS) analogous of A or P containing an intramolecular oxygen bridge was evaluated using different assays. Competition assays showed that compounds 1, 5, 6 and 7 affected the binding of specific ligands for the GABAA receptor in a way similar to that of A and P, whereas compounds 3 and 4 stimulated [3H]-flunitrazepam and reduced [35S]-TBPS binding. The enzyme 3β-hydroxysteroid dehydrogenase (3β-HSD) produces the precursor for A and P, and its activity is regulated by steroids. The action of several SS on 3β-HSD activity was tested in different tissues. All SS analyzed inhibit its activity, but compound 5 was the least effective. Finally, the neuroprotective role of two SS was evaluated in cerebral cortex and hippocampus cultures subjected to hypoxia. Glial fibrillary acidic protein (GFAP) increase was prevented by A, P, and compounds 3 and 5. Only A, P and compound 5 prevented neurofilament (NF160/200) decrease in hippocampus cultures, whereas A and compound 5 partially prevented NF200 and NF160 decreases respectively in cerebral cortex cultures. A prevented microtubule associated protein (MAP 2b) decrease in cerebral cortex cultures, while in hippocampus cultures only compounds 3 and 5 had effect. All steroids prevented MAP 2c decrease in both brain regions.