No abstract

Norgestrel, a progesterone analogue, has demonstrated neuroprotective effects in a mouse model of retinitis pigmentosa. Neuroprotection is achieved in part through Norgestrels anti-inflammatory properties, alleviating detrimental microglial activity. Gliosis is a feature of many neurodegenerative diseases of the retina, including retinitis pigmentosa. Müller glia, a type of macroglia found in the retina, are major contributors of gliosis, characterized by the upregulation of glial fibrillary acidic protein (GFAP). Microglia-Müller glia crosstalk has been implicated in the initiation of gliosis. In the rd10 retina, increased microglial activity and gliotic events are observed prior to the onset of photoreceptor loss. We hypothesized that Norgestrels dampening effects on harmful microglial activity would consequently impact on gliosis. In the current study, we explore the role of microglia-Müller glia crosstalk in degeneration and Norgestrel-mediated neuroprotection in the rd10 retina. Norgestrels neuroprotective effects in the rd10 retina coincide with significant decreases in both microglial activity and Müller cell gliosis. Using a Müller glial cell line, rMC-1, and isolated microglia, we show that rd10 microglia stimulate GFAP production in rMC-1 cells. Norgestrel attenuates gliosis through direct actions on both microglia and Müller glia. Norgestrel reduces the release of harmful stimuli from microglia, such as interferon-γ, which might otherwise signal to Müller glia and stimulate gliosis. We propose that Norgestrel also targets Müller cell gliosis directly, by limiting the availability of pSTAT3, a known transcription factor for GFAP. These findings highlight an important aspect to Norgestrels neuroprotective effects in the diseased retina, in combating Müller cell gliosis.

Changes in the adrenal and thyroid axes in critically ill patients are accentuated by increasing disease severity. However, the relationship of gonadal axis suppression to severity of illness is not well defined. We evaluated serial serum levels of LH, FSH, and testosterone (T) in 59 men and 42 postmenopausal women admitted to critical care units with a spectrum of disease severity. Patients were grouped according to severity of illness by the Acute Physiologic and Chronic Health Evaluation II (APACHE II) scores and by survival. Patients with surgery, renal or hepatic failure, alcohol abuse, endocrine disease, or head trauma were excluded to avoid these confounding factors. In men, mean admission serum T levels in all groups were lower than in healthy controls (P < 0.005). In addition, T levels in men with severe illness (APACHE > 15) were lower than in men with relatively mild (APACHE < 10; P < 0.01) or moderate illness (APACHE 10-15; P < 0.05). These differences were accentuated as hospitalization progressed. In postmenopausal women and men, nadir serum FSH but not LH levels during hospitalization were lower in patients with APACHE greater than 15 than in patients with APACHE scores of 10-15 or less than 15 (P < 0.05). Grouping patients by survival yielded similar results. Analysis of drug effects, age, and PRL did not explain these relationships. We conclude that the degree of both central and peripheral suppression of the reproductive axis in acute illness is related to disease severity. This suppression could not be attributed to other factors known to alter the reproductive axis independently from critical illness (e.g. age, drugs, head trauma, hepatic failure, etc.). These findings further document a general endocrine response to acute illness involving several axes which is graded according to disease severity.

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No abstract

Retinitis pigmentosa (RP) is one of the most common retinal degenerative conditions affecting people worldwide, and is currently incurable. It is characterized by the progressive loss of photoreceptors, in which the death of rod cells leads to the secondary death of cone cells; the cause of eventual blindness. As rod cells die, retinal-oxygen metabolism becomes perturbed, leading to increased levels of reactive oxygen species (ROS) and thus oxidative stress; a key factor in the secondary death of cones. In this study, norgestrel, an FDA-approved synthetic analog of progesterone, was found to be a powerful neuroprotective antioxidant, preventing light-induced ROS in photoreceptor cells, and subsequent cell death. Norgestrel also prevented light-induced photoreceptor morphological changes that were associated with ROS production, and that are characteristic of RP. Further investigation showed that norgestrel acts via post-translational modulation of the major antioxidant transcription factor Nrf2; bringing about its phosphorylation, subsequent nuclear translocation, and increased levels of its effector protein superoxide dismutase 2 (SOD2). In summary, these results demonstrate significant protection of photoreceptor cells from oxidative stress, and underscore the potential of norgestrel as a therapeutic option for RP.

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 (PGRMC1) 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 PGRMC1 inhibition by AG205 (1 μm) showed this rise to be PGRMC1-dependent, primarily utilizing calcium from extracellular sources, for blockade of L-type calcium channels by verapamil (50 μm) prevented a Norgestrel-induced calcium influx in stressed cells. Calcium influx was also shown to be bFGF-dependent, for siRNA knock down of bFGF prevented Norgestrel-PGRMC1 induced changes in cytosolic calcium. Notably, we demonstrate PGRMC1-activation is necessary for Norgestrel-induced bFGF upregulation. We propose that Norgestrel protects through the following pathway: binding to and activating PGRMC1 expressed on the surface of photoreceptor cells, PGRMC1 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.

Retinitis pigmentosa (RP) is a group of hereditary retinal diseases, characterised by photoreceptor cell loss. Despite a substantial understanding of the mechanisms leading to cell death, an effective therapeutic strategy is sought. Our laboratory has previously demonstrated the neuroprotective properties of Norgestrel, a progesterone analogue, in the degenerating retina, mediated in part by the neurotrophic factor basic fibroblast growth factor (bFGF). In other retinal studies, we have also presented a pro‐survival role for reactive oxygen species (ROS), downstream of bFGF. Thus, we hypothesized that Norgestrel utilises bFGF‐driven ROS production to promote photoreceptor survival. Using the 661W photoreceptor‐like cell line, we now show that Norgestrel, working through progesterone receptor membrane complex 1 (PGRMC1); generates an early burst of pro‐survival bFGF‐induced ROS. Using the rd10 mouse model of RP, we confirm that Norgestrel induces a similar early pro‐survival increase in retinal ROS. Norgestrel‐driven protection in the rd10 retina was attenuated in the presence of antioxidants. This study therefore presents an essential role for ROS signalling in Norgestrel‐mediated neuroprotection in vitro and demonstrates that Norgestrel employs a similar pro‐survival mechanism in the degenerating retina.