Progesterone receptor signalling in retinal photoreceptor neuroprotection

Abstract

Abstract'Norgestrel', a synthetic form of the female hormone progesterone has been identified as potential drug candidate for the treatment of the degenerative eye disease retinitis pigmentosa. However, to date, no work has looked at the compound's specific cellular target. Therefore, this study aimed to identify the receptor target of Norgestrel and begin to examine its potential mechanism of action in the retina. In this work, we identify and characterize the expression of progesterone receptors present in the C57 wild type and rd10 mouse model of retinitis pigmentosa. Classical progesterone receptors A and B (PR A/B), progesterone receptor membrane components 1 and 2 (PGRMC1, PGRMC2) and membrane progesterone receptors a, b and c were found to be expressed. All receptors excluding PR A/B were also found in the 661W photoreceptor cell line. PGRMC1 is a key regulator of apoptosis and its expression is up-regulated in the degenerating rd10 mouse retina. Activated by Norgestrel through nuclear trafficking, siRNA knock down of PGRMC1 abrogated the protective properties of Norgestrel on damaged photoreceptors. Furthermore, specific inhibition of PGRMC1 by AG205 blocked Norgestrel-induced protection in stressed retinal explants. Therefore, we conclude that PGRMC1 is crucial to the neuroprotective effects of Norgestrel on stressed photoreceptors.

Progesterone Attenuates Microglial-Driven Retinal Degeneration and Stimulates Protective Fractalkine-CX3CR1 Signaling

“…Due to the difficulty in isolating pure photoreceptor primary cultures and in order to assess the interaction between microglia and photoreceptors, we utilized the cone photoreceptor-like 661W cell line. Our group has previously used 661Ws as an in vitro model to study how photoreceptors respond to stressful stimuli and to understand how Norgestrel works in providing neuroprotection [11–13]. …”

“…This cell line was previously validated by this group [11] through real-time quantitative polymerase chain reaction (rt-qPCR) analysis for cone specific opsins; blue cone opsin (Opn1sw) and red/green opsin (Opn1mw). Cells were cultured in Dulbecco’s Modified Eagle’s medium (DMEM) (Sigma) supplemented with 10% fetal calf serum (FCS) and 1% penicillin streptomycin (PS) and maintained at 37°C in a humidified 5% CO 2 atmosphere.…”

“…In 2011, our group showed that the synthetic progestin ‘Norgestrel’ works as a neuroprotective agent in the retina, thus identifying it as a potential treatment for RP [10]. Published studies have since shown that Norgestrel, working through progesterone receptors [11], significantly increases production of basic fibroblast growth factor (bFGF) and leukemia inhibitory factor (LIF) in the retina [10, 12]. These growth factors likely act directly on photoreceptors to provide neuroprotection, through an upregulation of pro-survival and downregulation of apoptotic pathways [13].…”

Neuroprotektion geschädigter Photorezeptoren

“…Um diese Funktionen wahrnehmen zu können, binden die Steroide an spezifische Rezeptoren. So sind sowohl die "nuclear estrogen receptors" (ERα und ERβ) wie auch Rezeptoren für Progesteron in der Netzhaut exprimiert [4,20]. Neben ihren physiologischen Funktionen wirken Steroide zudem protektiv.…”

“…Besonders sind hierbei die schützenden Eigenschaften von 17-Estradiol (E2) und Progesteron hervorzuheben. Beide Steroide wurden im Tiermodell bereits mit Erfolg eingesetzt [20,43]. Zusätzlich wurde gezeigt, dass das synthetische Progesteron-Analog Norgestrel eine gute protektive Wirkung sowohl in induzierten als auch vererbten Modellen der Netzhautdegeneration zeigt [11].…”