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The synthetic progesterone N orgestrel is neuroprotective in stressed photoreceptor‐like cells and retinal explants, mediating its effects via basic fibroblast growth factor, protein kinase A and glycogen synthase kinase 3β signalling
Author(s) -
Wyse Jackson Alice C.,
Cotter Thomas G.
Publication year - 2016
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/ejn.13166
Subject(s) - neuroprotection , basic fibroblast growth factor , ex vivo , microbiology and biotechnology , protein kinase a , biology , downregulation and upregulation , endocrinology , kinase , medicine , chemistry , growth factor , biochemistry , pharmacology , in vitro , receptor , gene
The synthetic progesterone Norgestrel has been shown to have proven neuroprotective efficacy in two distinct models of retinitis pigmentosa: the rd10/rd10 (B6. CXBI ‐Pde6b rd10 /J) mouse model and the Balb/c light‐damage model. However, the cellular mechanism underlying this neuroprotection is still largely unknown. Therefore, this study aimed to examine the downstream signalling pathways associated with Norgestrel both in vitro and ex vivo . In this work, we identify the potential of Norgestrel to rescue stressed 661W photoreceptor‐like cells and ex vivo retinal explants from cell death over 24 h. Norgestel is thought to work through an upregulation of neuroprotective basic fibroblast growth factor ( bFGF ). Analysis of 661W cells in vitro by real‐time polymerase chain reaction (rt‐ PCR ), enzyme‐linked immunosorbent assay ( ELISA ) and Western blotting revealed an upregulation of bFGF in response to Norgestrel over 6 h. Specific si RNA knockdown of bFGF abrogated the protective properties of Norgestrel on damaged photoreceptors, thus highlighting the crucial importance of bFGF in Norgestrel‐mediated protection. Furthermore, Norgestrel initiated a bFGF ‐dependent inactivation of glycogen synthase kinase 3β ( GSK 3β) through phosphorylation at serine 9. The effects of Norgestrel on GSK 3β were dependent on protein kinase A ( PKA ) pathway activation. Specific inhibition of both the PKA and GSK 3β pathways prevented Norgestrel‐mediated neuroprotection of stressed photoreceptor cells in vitro . Involvement of the PKA pathway following Norgestrel treatment was also confirmed ex vivo . Therefore, these results indicate that the protective efficacy of Norgestrel is, at least in part, due to the bFGF ‐mediated activation of the PKA pathway, with subsequent inactivation of GSK3β.