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Purpose: Vital dyes have become a clinical standard during vitrectomy to visualize anatomical structures. It was the aim of this study to test the effect of two vital dyes (AV 17-M with 5% mannitol and MBB Dual) on different intraocular cells, to see whetherin vitrotest can be used as reliable preclinical testing tool. Methods: Cell morphology was assessed via phase contrast pictures, cell viability via MTS assay and total cell amount via crystal violet staining. ARPE19 and 661W cells were chosen for toxicology testing at different exposure times (60 seconds, 15 minutes and 30 minutes). Vital dyes were completely removed after the staining period. Results: Treatment with AV 17-M changed the morphology and the cell number at every time point investigated on ARPE19 and 661 W cells. ARPE19 cells treated with AV 17-M or MBB Dual displayed only a slight or no decrease in cell viability after the three different exposure times. AV-17 without medium to simulate a possible intraoperative use after fluid-air exchange showed a decrease in viability of 6%, 24% and 14%. A difference in cell density of 21%, 46% and 34% was noted after CV staining for AV 17-M, MBB Dual led to a decrease of 2%, 16% and 3% after 30 minutes compared to BSS. AV 17-M directly applied on 661W decreased viability significantly by 18% after 60 seconds, 33% after 15 minutes and 40% after 30 minutes. Cell density of 661W cells exposed relevant negative effects; after incubation of 60 seconds with AV 17-M, the cell amount was significantly lowered by 41% and MBB Dual by 12%. After 15 minutes, a loss of 48% cell amount was detected with AV 17-M and after 30 min 51%. MBB Dual led to 37% loss after 15 minutes and to 28% loss after 30 minutes. Conclusion: AV 17-M with 5% mannitol has a negative effect on different ocular cells. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

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 μ m) showed this rise to be PGRMC1-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- 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. [ABSTRACT FROM AUTHOR]

The synthetic progesterone Norgestrel has been shown to have proven neuroprotective efficacy in two distinct models of retinitis pigmentosa: the rd10/rd10 (B6. CXBI-Pde6brd10/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 ( GSK3β) through phosphorylation at serine 9. The effects of Norgestrel on GSK3β were dependent on protein kinase A ( PKA) pathway activation. Specific inhibition of both the PKA and GSK3β 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. [ABSTRACT FROM AUTHOR]

The loss of photoreceptors is the defining characteristic of many retinal degenerative diseases, but the mechanisms that regulate photoreceptor cell death are not fully understood. Here we have used the 661W cone photoreceptor cell line to ask whether exposure to the terminal complement complex C5b-9 induces cell death and/or modulates the sensitivity of these cells to other cellular stressors. 661W cone photoreceptors were exposed to complete normal human serum following antibody blockade of CD59. Apoptosis induction was assessed morphologically, by flow cytometry, and on western blotting by probing for cleaved PARP and activated caspase-3. Necroptosis was assessed by flow cytometry and Sirtuin 2 inhibition using 2-cyano-3-[5-(2,5-dichlorophenyl)-2-furyl]- N-5-quinolinylacrylamide (AGK2). The sensitivity of 661W cells to ionomycin, staurosporine, peroxide and chelerythrine was also investigated, with or without prior formation of C5b-9. 661W cells underwent apoptotic cell death following exposure to C5b-9, as judged by poly(ADP-ribose) polymerase 1 cleavage and activation of caspase-3. We also observed apoptotic cell death in response to staurosporine, but 661W cells were resistant to both ionomycin and peroxide. Interestingly, C5b-9 significantly increased 661W sensitivity to staurosporine-induced apoptosis and necroptosis. These studies show that low levels of C5b-9 on 661W cells can induce apoptosis, and that C5b-9 specifically sensitizes 661W cells to certain apoptotic and necroptotic pathways. Our observations provide new insight into the potential role of the complement system in photoreceptor loss, with implications for the molecular aetiology of retinal disease. [ABSTRACT FROM AUTHOR]

Retinitis pigmentosa (RP) is an inherited form of retinal degeneration characterized by primary rod photoreceptor cell death followed by cone loss. Mutations in several genes linked to the disease cause increased levels of cyclic guanosine monophosphate (cGMP) and calcium ion influxes. The purpose of this project was to develop a new in vitro photoreceptor degeneration model for molecular studies of RP. 661W cells were genetically modified to stably express the neural retina leucine zipper (NRL) transcription factor. One clone (661W-A11) was selected based on the expression of Nrl target genes. 661W-A11 showed a significant increase in expression of rod-specific genes but not of cone-specific genes, compared with 661W cells. Zaprinast was used to inhibit phosphodiesterase 6 (PDE6) activity to mimic photoreceptor degeneration in vitro. The activation of cell death pathways resulting from PDE6 inhibition was confirmed by detection of decreased viability and increased intracellular cGMP and calcium, as well as activation of protein kinase G (PKG) and calpains. In this new in vitro system, we validated the effects of previously published neuroprotective drugs. The 661W-A11 cells may serve as a new model for molecular studies of RP and for high-throughput drug screening. [ABSTRACT FROM AUTHOR]

Evaluating cell death is essential when investigating neurodegeneration and neuroprotection in the retina. Cell death assays provide us with a means to identify and quantify dying cells in a population. Terminal dUTP nick end-labeling (TUNEL) is one method used for the identification of dying cells. This technique is based upon the enzymatic incorporation of fluorescently tagged DNA base pairs to fragmented DNA. In this chapter, we describe two different techniques employing TUNEL. The first method uses TUNEL to analyze cell death in cultured retinal explants by fluorescence microscopy. The second technique describes a method for measuring cell death in a retinal cell line by flow cytometry.

In 2001, a transformed cell line RGC-5 was developed from the rat retina that was thought to be of retinal ganglion cell origin. Since that time many investigators have used this line in a wide variety of studies to understand better retinal ganglion cell activity, cell signaling, and neuroprotection. Recently, a publication emerged that claimed that this RGC-5 cell line was derived from mouse and not rat, and other studies also indicated the expression of certain proteins that typically were not associated with retinal ganglion cells. This certainly came as a shock not only to the originators of this cell line, but also to others who have been using this as an in vitro model of rat retinal ganglion cells. As a result, we undertook experiments to determine if the RGC-5 cell line currently in use may have been mischaracterized. We, indeed, found that the RGC-5 cell line was of mouse and not rat origin, as was claimed originally in the original research report. We further determined whether these cells were of retinal ganglion origin. Our findings showed conclusively that RGC-5 cells were, indeed, of mouse origin and, using additional cytogenetic profile testing, karyotyping, and genetic and protein profiling, we concluded that these cells were not of retinal ganglion cell origin, but were the cell line 661W, a mouse SV-40 T antigen transformed photoreceptor cell line. The 661W cell line also was present in the laboratory of the originating laboratory and probably resulted in cross-contamination. The present study reviews some of the errors that were made in misidentifying the RGC-5 cell line and offers some insight as to how this may have happened, and ways one can avoid mischaracterization of a potentially important cell line.