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Progesterone analogue protects stressed photoreceptors via bFGF ‐mediated calcium influx
Author(s) -
WyseJackson Alice C.,
Roche Sarah L.,
RuizLopez Ana M.,
Moloney Jennifer N.,
Byrne Ashleigh M.,
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.13445
Subject(s) - calcium , calcium in biology , endocrinology , extracellular , medicine , microbiology and biotechnology , downregulation and upregulation , norgestrel , chemistry , biology , population , biochemistry , environmental health , family planning , gene , research methodology
Retinitis pigmentosa ( RP ) is a degenerative retinal disease leading to photoreceptor cell loss. In 2011, our group identified the synthetic progesterone ‘Norgestrel’ as a potential treatment for RP . Subsequent research showed Norgestrel to work through progesterone receptor membrane component 1 ( PGRMC 1) activation and upregulation of neuroprotective basic fibroblast growth factor ( bFGF ). Using trophic factor deprivation of 661W photoreceptor‐like cells, we aimed to further elucidate the mechanism leading to Norgestrel‐induced neuroprotection. In the present manuscript, we show by flow cytometry and live‐cell immunofluorescence that Norgestrel induces an increase in cytosolic calcium in both healthy and stressed 661Ws over 24 h. Specific PGRMC 1 inhibition by AG 205 (1 μ m ) showed this rise to be PGRMC 1‐dependent, primarily utilizing calcium from extracellular sources, for blockade of L‐type calcium channels by verapamil (50 μ m ) prevented a Norgestrel‐induced calcium influx in stressed cells. Calcium influx was also shown to be bFGF ‐dependent, for si RNA knock down of bFGF prevented Norgestrel‐ PGRMC 1 induced changes in cytosolic calcium. Notably, we demonstrate PGRMC 1‐activation is necessary for Norgestrel‐induced bFGF upregulation. We propose that Norgestrel protects through the following pathway: binding to and activating PGRMC 1 expressed on the surface of photoreceptor cells, PGRMC 1 activation drives bFGF upregulation and subsequent calcium influx. Importantly, raised intracellular calcium is critical to Norgestrel's protective efficacy, for extracellular calcium chelation by EGTA abrogates the protective effects of Norgestrel on stressed 661W cells in vitro .