Nicholas D. Chinskey

Autophagy Activation in the Injured Photoreceptor Inhibits Fas-Mediated Apoptosis

PURPOSE To examine the activation of autophagy and its relationship to Fas-mediated photoreceptor apoptosis during experimental retinal detachment. METHODS Retina-retinal pigment epithelium (RPE) separation was created in Brown-Norway rats by subretinal injection of 1% hyaluronic acid and the intraretinal levels of the autophagy proteins LC3 and Atg5, the time course of LC3-I to LC3-II conversion, and the activation of cathepsins B and D were assayed with Western blot analysis and immunohistochemistry. We measured the ability of a Fas-activating antibody to induce LC3-I to LC3-II conversion in 661W cells, and the in vivo effect of Met12, a small molecule inhibitor of the Fas receptor, on LC3-I to LC3-II conversion and Atg5 expression. Autophagy activation was inhibited using 3-methyladenine (3-MA) or siRNA knockdown of Atg5 and the effect on apoptosis was measured using a caspase 8 activity assay, caspase 8 immunoblots, and photoreceptor TUNEL staining. RESULTS Retina-RPE separation resulted in a Fas-dependent activation of autophagy, with increased Atg5 levels and intraphotoreceptor conversion of LC3-I to LC3-II. Detached retinas had increased levels of autophagosome-associated lysosomal proteases, cathepsins B and D. Inhibition of autophagy by 3-MA or siAtg5 accelerated the time course of caspase 8 activation and photoreceptor TUNEL staining. CONCLUSIONS Autophagy activation occurs in the photoreceptors after retina-RPE separation. This appears to be, at least in part, dependent on Fas receptor activation, and plays a role in regulating the level of photoreceptor apoptosis.

Inhibition of Retinal Detachment-Induced Apoptosis in Photoreceptors by a Small Peptide Inhibitor of the Fas Receptor

Purpose. To test the effect of a small peptide inhibitor (Met12) of the Fas receptor on the activation of extrinsic and intrinsic apoptosis pathways after retinal detachment. Methods. Retinal-RPE separation was created in Brown Norway rats by subretinal injection of 1% hyaluronic acid. Met12, derived from the Fas-binding extracellular domain of the oncoprotein Met, was injected into the subretinal space at the time of separation. A mutant peptide and vehicle administered in a similar fashion acted as inactive controls. The extrinsic apoptotic pathway was induced in 661W cells using a Fas-activating antibody in the presence or absence of Met12. Caspase 3, caspase 8, and caspase 9 activities were measured with calorimetric and luminescent assays in retinal extracts and cell lysates. Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) was performed in retinal sections 3 days after separation. Histology was performed in retinal sections 2 months after retinal detachment. Results. Met12 inhibited Fas-induced caspase 8 activation in 661W cells. Similarly, administration of Met12 into the subretinal space inhibited the activation of caspase 3, caspase 8, and caspase 9 after retinal detachment. This corresponded to a decreased level of TUNEL-positive staining of photoreceptors after retinal-RPE separation in animals that received Met12, but not inactive mutant, peptide treatment. After 2 months, the outer nuclear layer was significantly thicker, and the photoreceptor count was higher in animals treated with subretinal Met12. Conclusions. The small peptide Met12 may serve as a photoreceptor-protective agent in the setting of retinal-RPE separation.

Retinal cell death and current strategies in retinal neuroprotection.

Purpose of review Retinal cell death is the main cause of vision loss in many blinding conditions. Research on the basics of how and why retinal cells die in different diseases provides insights into the development of treatment strategies to prevent or reverse this loss. This review summarizes the literature published on this topic in the last year. Recent findings Apoptosis is generally considered the main pathway by which retinal cells die in response to a range of noxious stimuli. However, inhibiting apoptosis does not completely prevent retinal cell death, as many enter programmed necrosis or necroptosis. Many novel ways of inhibiting apoptosis and necrosis, including blockage of the Fas receptor, neuroprotective peptides and antioxidants, continue to be investigated. Also, additional pathways including autophagy and inflammation are being examined on how they contribute to the loss of retinal cells in different disease models. Summary With more knowledge of how retinal cells die, further advances are being made in prolonging the cell survival. However, even as basic science discoveries remain promising, clinical utility of neuroprotection is still quite limited at this time.

Control of Photoreceptor Autophagy After Retinal Detachment: The Switch From Survival to Death

PURPOSE To examine whether calpain inhibition following retinal detachment would prolong autophagy and result in reduced photoreceptor apoptosis. METHODS Retinal detachments were created in Brown-Norway rats by subretinal injection of 1% hyaluronic acid and simulated in vitro by Fas-receptor activation of 661W cells, a cone cell line. Protein levels of LC3 and autophagy-related gene 5 (Atg5), both of which are involved in the creation of the autophagosome, were assayed by Western blot. Calpain 1, the protease responsible for Atg5 cleavage and transitioning photoreceptors from autophagy to apoptosis, activity was monitored by α-spectrin cleavage. Various calpain inhibitors were added either to the subretinal space or cell culture media. Apoptosis was assessed in vitro by caspase-8 activity assays and in vivo via TUNEL assays. Cell counts were assessed in vivo at 2 months following detachment. RESULTS Following retinal detachment or Fas-receptor activation of 661W cells, there was an increase in Atg5 and LC3-II that peaked at 3 days and decreased by 7-days postdetachment. Calpain 1 activity level peaked at 7 days and was associated with decreased autophagy. Calpain inhibition led to increased autophagy, a decrease in caspase-8 activation, reduced TUNEL-positive photoreceptors, and increased photoreceptor cell survival. CONCLUSIONS Our data suggest that calpain activation, which peaks at 7-days postdetachment, is a key step in triggering photoreceptors to shift from cell survival to death. Prolonging autophagy through calpain inhibition leads to significantly reduced photoreceptor apoptosis and increased cell survival.

Treatment of Subretinal Fluid Associated With Dome-Shaped Macula

Dome-shaped macula is a recently described disorder seen in eyes with myopic posterior staphyloma. Vision loss may accompany sub-macular fluid accumulation, for which no effective treatment has been reported. The authors report the successful treatment of two female patients, aged 34 and 59 years, with chronic exudative macular detachment associated with dome-shaped macula. Symptoms of subretinal fluid had been present for at least 2 years in each case, and the fluid was refractory to multiple intravitreal bevacizumab injections in one eye. After a single session of half-fluence verteporfin photodynamic therapy, the submacular fluid resolved completely in each eye. In one eye, recurrent submacular fluid 2 years later responded partially to repeat photodynamic therapy and completely to focal laser photocoagulation. [Ophthalmic Surg Lasers Imaging Retina. 2013;44:593-595.].

Acute Macular Neuroretinopathy Following Non-Ocular Trauma: A Hypothesis Regarding Pathophysiologic Mechanism.

BACKGROUND AND OBJECTIVE To describe the imaging characteristics and clinical course of acute macular neuroretinopathy (AMN) following non-ocular trauma, and to hypothesize a pathophysiologic mechanism for this syndrome. PATIENTS AND METHODS The records of five patients who developed symptoms and findings suggestive of AMN following trauma to the face or chest were retrospectively reviewed. Optical coherence tomography (OCT), infrared reflectance, fundus autofluorescence, fluorescein and indocyanine green angiography, and multifocal electroretinography were evaluated. RESULTS Visual symptoms started immediately or very soon after non-ocular trauma, and scotomas persisted at last follow-up (2 weeks to 10 years after trauma). OCT imaging performed within days of the trauma demonstrated focal areas of hyper-reflectivity in the outer plexiform and outer nuclear layers with eventual thinning of the outer nuclear layer, as well as variable loss of the ellipsoid and interdigitation zones. CONCLUSION Acute ischemic injury caused by trauma-induced hypotension and/or catecholamine release and involving the deep retinal capillary plexus is the pathogenic mechanism that most plausibly explains trauma-associated AMN.

Inferior oblique myokymia: A unique ocular motility disorder

tinct zones, each with different venous drainage. Between these 2 zones, a watershed developed. After the 2 chorioretinal anastomoses matured, blood flow through the venous tributary that bridged the watershed zone— the tributary connecting the inferotemporal branch retinal vein to the central retinal vein—was very slow (Figure 2B). The slow blood flow made that blood vessel susceptible to venous stasis-induced thrombosis, narrowing, and subsequent partial occlusion. This case illustrates retinal venous remodeling over time in response to modification of the retinal circulation.

Epiretinal Membrane Peeling in Patients With Good Preoperative Vision

Objective: To evaluate the outcomes of patients undergoing removal of an epiretinal membrane (ERM) with good starting visual acuity. Design: Retrospective chart review. Participants: Forty eyes of 40 patients seen at a tertiary, referral-based private practice. Methods: All patients undergoing pars plana vitrectomy with removal of an ERM by a single surgeon (G.K.S.) from the years 2012 to 2014 were evaluated. Patients who were phakic, had a baseline visual acuity of 20/50 or worse, and those who had surgery less than 6 months prior to data collection were excluded. Results: Of the 40 patients included, only 2 (5%) developed a serious postoperative complication. One had a vitreous hemorrhage that cleared without further surgical intervention, and another developed a macula on retinal detachment that required 1 additional procedure. Nineteen (47.5%) had improved best-corrected visual acuity (BCVA), 10 (25%) maintained their initial BCVA, 7 (17.5%) lost 1 to 2 lines, and 4 (10%) lost 3 lines or greater at their last follow-up visit. When looking only at idiopathic ERMs in the group, the results were similar with 48% with improved vision, 29% maintained the initial BCVA, 16% lost 1 to 2 lines, and 6% lost 3 lines or greater. Discussion: Surgery to remove an ERM is a reasonable option for those with significant metamorphopsia and highly symptomatic blurring of central vision, even with good baseline visual acuity.

Rapid Loss of Vision With the Onset of a White Ring Surrounding the Optic Nerve

A white man in his 50s initially presented in the fall of 2015 with “macular changes” noticed by his referring optometrist. The patient was asymptomatic at the time. He had a history of hypertension and non-Hodgkin lymphoma, which was last treated in 2012 without evidence of recurrence. His visual acuity was 20/25 OU, and neither fundus was seen to be abnormal. The vitreous was clear in both eyes. Optical coherence tomography (OCT) revealed vitreomacular adhesion in the right eye and a macular posterior vitreous detachment in the left. The patient was told to follow-up as needed. About 2 months later, the patient called on the telephone to say that he had a new onset of blurry vision and photopsias in the right eye that started about 2 days prior. He denied any recent viral-type illness. An examination revealed that his visual acuity was still 20/25 OU. The anterior segment and the anterior vitreous of his right eye were still clear. However, an examination of the posterior pole of the right eye revealed a light white, deep subretinal/choroidal ring surrounding the optic nerve, with smaller rings around the edge of the larger ring (Figure, A). The left eye still appeared normal. Optical coherence tomography of the right eye revealed loss of the outer retina (more nasal than temporal to the fovea), whereas OCT of the left eye revealed that it was normal (Figure, B). The results of fluorescein angiography and fundus autofluorescence were both unremarkable (data not shown). Fundus photograph A OCT scan B