Iron is neurotoxic in retinal detachment and transferrin confers neuroprotection.

In retinal detachment (RD), photoreceptor death and permanent vision loss are caused by neurosensory retina separating from the retinal pigment epithelium because of subretinal fluid (SRF), and successful surgical reattachment is not predictive of total visual recovery. As retinal iron overload exacerbates cell death in retinal diseases, we assessed iron as a predictive marker and therapeutic target for RD. In the vitreous and SRF from patients with RD, we measured increased iron and transferrin (TF) saturation that is correlated with poor visual recovery. In ex vivo and in vivo RD models, iron induces immediate necrosis and delayed apoptosis. We demonstrate that TF decreases both apoptosis and necroptosis induced by RD, and using RNA sequencing, pathways mediating the neuroprotective effects of TF are identified. Since toxic iron accumulates in RD, we propose TF supplementation as an adjunctive therapy to surgery for improving the visual outcomes of patients with RD.

Progesterone treatment in two rat models of ocular ischemia.

PURPOSE: To determine whether the neurosteroid progesterone, shown to have protective effects in animal models of traumatic brain injury, stroke, and spinal cord injury, is also protective in ocular ischemia animal models. METHODS: Progesterone treatment was tested in two ocular ischemia models in rats: a rodent anterior ischemic optic neuropathy (rAION) model, which induces permanent monocular optic nerve stroke, and the middle cerebral artery occlusion (MCAO) model, which causes transient ischemia in both the retina and brain due to an intraluminal filament that blocks the ophthalmic and middle cerebral arteries. Visual function and retinal histology were assessed to determine whether progesterone attenuated retinal injury in these models. Additionally, behavioral testing and 2% 2,3,5-triphenyltetrazolium chloride (TTC) staining in brains were used to compare progesterone's neuroprotective effects in both retina and brain using the MCAO model. RESULTS: Progesterone treatment showed no effect on visual evoked potential (VEP) reduction and retinal ganglion cell loss in the permanent rAION model. In the transient MCAO model, progesterone treatment reduced (1) electroretinogram (ERG) deficits, (2) MCAO-induced upregulation of glutamine synthetase (GS) and glial fibrillary acidic protein (GFAP), and (3) retinal ganglion cell loss. As expected, progesterone treatment also had significant protective effects in behavioral tests and a reduction in infarct size in the brain. CONCLUSIONS: Progesterone treatment showed protective effects in the retina following MCAO but not rAION injury, which may result from mechanistic differences with injury type and the therapeutic action of progesterone.

Subretinal delivery and electroporation in pigmented and nonpigmented adult mouse eyes.

Subretinal injection offers one of the best ways to deliver many classes of drugs, reagents, cells and treatments to the photoreceptor, Müller, and retinal pigment epithelium (RPE) cells of the retina. Agents delivered to this space are placed within microns of the intended target cell, accumulating to high concentrations because there is no dilution due to transport processes or diffusion. Dilution in the interphotoreceptor space (IPS) is minimal because the IPS volume is only 10-20 µl in the human eye and less than 1 µl in the mouse eye. For gene delivery purposes, we wished to transfect the cells adjacent to the IPS in adult mouse eyes. Others transfect these cells in neonatal rats to study the development of the retina. In both neonates and adults, electroporation is found to be effective. Here we describe the optimization of electroporation conditions for RPE cells in the adult mouse eye with naked plasmids. However, both techniques, subretinal injection and electroporation, present some technical challenges that require skill on the part of the surgeon to prevent untoward damage to the eye. Here we describe methods that we have used for the past 10 years (Johnson et al. Mol Vis 14: 2211-2226, 2008).

Bile acids in treatment of ocular disease.

Bear bile has been included in Asian pharmacopeias for thousands of years in treatment of several diseases, ranging from sore throat to hemorrhoids. The hydrophilic bile acids tauroursodeoxycholic acid (TUDCA) and ursodeoxycholic acid (UDCA) are the major bile acids of bear bile. Both of these are available as synthetic formulations and are approved by the health administrations of several countries for treatment of cirrhosis and gallstones. This review briefly covers the use of bear bile in Traditional Chinese Medicine, bile acid physiology, approved use of UDCA and TUDCA in Western medicine, and recent research exploring their neuroprotective properties, including in models of ocular disease.

Tool from ancient pharmacopoeia prevents vision loss.

PURPOSE: Bear bile has been used in Asia for over 3,000 years to treat visual disorders, yet its therapeutic potential remains unexplored in Western vision research. The purpose of this study was to test whether treatment of mice undergoing retinal degeneration with tauroursodeoxycholic acid (TUDCA), a primary constituent of bear bile, alters the course of degeneration. METHODS: Two retinal degeneration models were tested: the rd10 mouse, which has a point mutation in the gene encoding the beta subunit of rod phosphodiesterase, and light induced retinal damage (LIRD). For LIRD studies, albino Balb/C adult mice were subcutaneously injected with TUDCA (500 mg/kg body weight) or vehicle (0.15 M NaHCO(3)). Sixteen h later, each mouse received repeat injections. Half of each treatment group was then placed in bright light (10,000 lux) or dim light (200 lux) for seven h. At the end of exposure, animals were transferred to their regular housing. Electroretinograms (ERGs) were assessed 24 h later, mice sacrificed, eyes embedded in paraffin and sectioned, and retina sections assayed for morphology and apoptosis by TUNEL and anti-active caspase-3 immunoreactivity via fluorescent confocal microscopy. A subset of mice were sacrificed 8 and 15 days after exposure and retina sections analyzed for morphology and apoptosis. For rd10 studies, mice were injected subcutaneously with TUDCA or vehicle at postnatal (P) days 6, 9, 12, and 15. At p18, ERGs were recorded, mice were euthanized and eyes were harvested, fixed, and processed. Retinal sections were stained (toluidine blue), and retinal cell layers morphometrically analyzed by light microscopy. Consecutive sections were analyzed for apopotosis as above. RESULTS: By every measure, TUDCA greatly slowed retinal degeneration in LIRD and rd10 mice. ERG a-wave and b-wave amplitudes were greater in mice treated with TUDCA compared to those treated with vehicle. Retinas of TUDCA-treated mice had thicker outer nuclear layers, more photoreceptor cells, and more fully-developed photoreceptor outer segments. Finally, TUDCA treatments dramatically suppressed signs of apoptosis in both models. CONCLUSIONS: Systemic injection of TUDCA, a primary constituent of bear bile, profoundly suppressed apoptosis and preserved function and morphology of photoreceptor cells in two disparate mouse models of retinal degeneration. It may be that bear bile has endured so long in Asian pharmacopeias due to efficacy resulting from this anti-apoptotic and neuroprotective activity of TUDCA. These results also indicate that a systematic, clinical assessment of TUDCA may be warranted.