Seminar: Retinal Pigment Epithelial Cell Bystander Effects Contribute to AMD Pathology

Barbel Rohrer, the SmartState Endowed Chair in Gene and Pharmacological Treatment Of Retinal Degenerative Diseases at Medical University South Carolina will be delivering a seminar on “Retinal Pigment Epithelial Cell Bystander Effects Contribute to AMD pathology” on Wednesday, April 18th at 12:00 Noon in the  Moran Eye Center auditorium.

Abstract: Retinal pigment epithelium damage in age-related macular degeneration is triggered in many different locations, suggesting that damage occurs in susceptible areas, while delaying damage in more resilient areas. I will be describing experiments to distinguish two different mechanisms that would mediate the bystander effect: transfer of a signal to the recipient cells by exosomes; or the spread of information by means of communication via gap junctions.

Seminar: Polarity, Signaling and Cross-talk In The Outer Retina

Enrique Rodriguez Flyer

Enrique Javier Rodriguez-Boulan, Charles and Margaret Dyson Professor Professor of Cell Biology, Neurosciences and Physiology at the Margaret Dyson Vision Research Institute, Department of Ophthalmology at Weill Cornell Medical College will be delivering a seminar on Polarity, Signaling and Cross-talk In The Outer Retina on Wednesday, April 8th at Noon in the the Moran Eye Center auditorium.

Abstract: The polarized structure and function of Retinal Pigment Epithelium (RPE) is key to all of its retinal and choroid supporting functions, as well as for its roles in retinal development. Some of the mechanisms responsible for the reversed polarity of RPE have recently emerged. For example, we have shown that RPE cells lack a basolateral sorting adaptor present in most other epithelial cells. Recent work also suggests that RPE cells play a key role in the terminal differentiation and maintenance of photoreceptors and choroid. I will discuss a project we recently started that aims to build an in vitro model of the outer retina, initially focusing on co- culturing RPE and choroid endothelium. Finally, I will discuss the development of a drug that binds and removes lipofuscin bisretinoids from RPE with the ultimate goal of providing a new therapeutic angle for lipofuscin-induced retinal degenerations

Thy-1 Expressed In CNV And Increased In migrating Choroidal ECs In Human Neovascular AMD

Haibo Wang

This abstract was presented today at the 2014 Association for Research in Vision and Opthalmology (ARVO) meetings in Orlando, Florida by Haibo Wang, Yanchao Jiang and M. Elizabeth Hartnett.

Thy-1 regulates VEGF-induced choroidal endothelial cell migration 

Dept of Ophthalmology, John A. Moran Eye Center, The University of Utah-Salt Lake City. 

Purpose: Choroidal endothelial cell (CEC) activation and migration precede the development of choroidal neovascularization in neovascular AMD. Thy-1 is a cell surface protein expressed on different cells, including neurons and endothelial cells. As a glycosylphosphatidylinositol (GPI)-anchored glycoprotein, Thy-1 is located in lipid raft microdomains within the cell membrane, which brings Thy-1 into proximity of signaling molecules including cytoplasmic tyrosine kinases that can modulate adhesive and migratory events. In the retina, Thy-1 is well known as a retinal ganglion cell marker. Given the possibility that Thy-1 might be expressed in CECs, we addressed the hypothesis that upregulated Thy-1 in CECs by age-related stresses contributes to CEC migration.

Methods: Western blots of Thy-1 were determined in retinal pigment epithelial cells (RPE) and CECs. By real time quantitative PCR, Thy-1 mRNA was measured in CECs treated with vascular endothelial growth factor (VEGF) (20 ng/ml), CCL11 (100 ng/ml) or PBS for 24 hours, or in RPE/choroids from young (<40 yrs) and old (>60 yrs) donor eyes. Immunohistochemistry of Thy-1 was performed in posterior globe sections of human retina/RPE/choroids in the maculas of young and old donor eyes with or without AMD.  Colabeling with VE-cadherin was used to identify CECs. CECs transfected with Thy-1 siRNA or control siRNA were stimulated with VEGF, and CEC migration and phosphorylation of VEGF receptor 2 (VEGFR2) were measured. Statistics were performed using ANOVA.

Results:  Thy-1was highly expressed in CECs but not in RPE.  Thy-1 staining was not only detected in the retinal ganglion cell layer, but also in the choroid, and colocalized to a greater extent with VE-cadherin labeled CECs in sections from donors with AMD compared to age-matched controls without AMD.  Thy-1 mRNA was significantly increased in CECs treated with VEGF or CCL11 (p<0.05 vs. PBS) and greater in RPE/choroids from aged donor eyes (p<0.001 vs. young).  Knockdown of Thy-1 in CECs by siRNA transfection significantly inhibited VEGF-induced CEC migration (p<0.001) and VEGFR2 activation.

Conclusions: Thy-1is expressed in CECs and its expression is upregulated by stresses associated with neovascular AMD, including elderly age and increased VEGF.  Upregulated Thy-1 in CECs contributes to VEGF-induced VEGFR2 activation and CEC migration. Future studies into the potential role of Thy-1 in neovascular AMD are being considered. 

Interesting Article: Mechanism of RPE Cell Death in α-Crystallin Deficient Mice: A Novel and Critical Role for MRP1-Mediated GSH Efflux

RPE

I ran across an interesting paper in PLOS One published back in March of 2012 by Parameswaran G. Sreekumar, Christine Spee, Stephen J. Ryan, Susan P. C. Cole, Ram Kannan and David R. Hinton.  This manuscript looks at a mechanism of retinal pigment epithelium (RPE) cell death with notable findings identifying therapeutic targets for disorders that involve the RPE cells.

The authors tested whether α-crystallin has a protective effect that is influenced by changes in glutathione (GSH) content while exploring the mechanism of glutathione efflux from the cells.  Interestingly, they found that the multiple multidrug resistance proteins (MRP) were expressed in RPE, particularly MRP1 and that it is MRP1 that mediates GSH (reduced form) and GSSG (oxidized form) efflux from the RPE cells.  In addition, they noted that inhibition of MRP1 makes RPE cells resistant to oxidative stress induced cell death pathways and conversely, over expression of MRP1 renders them more susceptible to oxidatively induced cell death pathways. Finally the authors note that α-crystallin’s antiapoptotic function is mediated by both GSH and MRP1.

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