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The autotaxin-lysophosphatidic acid (ATX-LPA) signaling pathway plays a role in a variety of autoimmune diseases, such as rheumatoid arthritis or neurodegeneration. A link to the pathogenesis of glaucoma is suggested by an overactive ATX-LPA axis in aqueous humor samples of glaucoma patients. Analysis of such samples suggests that the ATX-LPA axis contributes to the fibrogenic activity and resistance to aqueous humor outflow through the trabecular meshwork. In order to inhibit or modulate this pathway, we developed a new series of ATX-inhibitors containing novel bicyclic and spirocyclic structural motifs. A potent lead compound (\(IC_{50}\) against ATX: 6 nM) with good \(\textit {in vivo}\) PK, favorable \(\textit {in vitro}\) property, and safety profile was generated. This compound leads to lowered LPA levels \(\textit {in vivo}\) after oral administration. Hence, it was suitable for chronic oral treatment in two rodent models of glaucoma, the experimental autoimmune glaucoma (EAG) and the ischemia/reperfusion models. In the EAG model, rats were immunized with an optic nerve antigen homogenate, while controls received sodium chloride. Retinal ischemia/reperfusion (I/R) was induced by elevating the intraocular pressure (IOP) in one eye to 140 mmHg for 60 min, followed by reperfusion, while the other untreated eye served as control. Retinae and optic nerves were evaluated 28 days after EAG or 7 and 14 days after I/R induction. Oral treatment with the optimized ATX-inhibitor lead to reduced retinal ganglion cell (RGC) loss in both glaucoma models. In the optic nerve, the protective effect of ATX inhibition was less effective compared to the retina and only a trend to a weakened neurofilament distortion was detectable. Taken together, these results provide evidence that the dysregulation of the ATX-LPA axis in the aqueous humor of glaucoma patients, in addition to the postulated outflow impairment, might also contribute to RGC loss. The observation that ATX-inhibitor treatment in both glaucoma models did not result in significant IOP increases or decreases after oral treatment indicates that protection from RGC loss due to inhibition of the ATX-LPA axis is independent of an IOP lowering effect.

Neuronal damage and impaired vision in different retinal disorders are induced, among other factors, by ischemia/reperfusion (I/R). Since the mechanisms and the progression of ischemic injury are still not completely clarified, a timeline of this retinal degeneration is needed. In this study, we investigated protein and mRNA alterations at 2, 6, 12, and 24 h as well as 3 and 7 days after ischemia to determine the course of an ischemic insult through the whole retina. Moreover, functional analyses were performed at later stages. We detected a significant functional loss of cells in the inner nuclear layer and photoreceptors at 3 and 7 days. Additionally, the thickness of the whole retina was decreased at these points in time, indicating a severe degradation of all retinal layers. Immunohistological and qRT-PCR analyses of retinal ganglion cells (RGCs), glial cells, AII amacrine, cone and rod bipolar as well as cone and rod photoreceptor cells confirmed this first assumption. Our results show that all investigated cell types were damaged by ischemia induction. Especially RGCs, cone bipolar cells, and photoreceptor cones are very sensitive to I/R. These cells were lost shortly after ischemia induction with a progressive course up to 7 days. In addition, Müller cell gliosis was observed over the entire period of time. These results provide evidence, that I/R induces damage of the whole retina at early stages and increases over time. In conclusion, our study could demonstrate the intense impact of an ischemic injury. The ischemic defect spreads across the whole retina right up to the outer layers in the long-term and thus seems to impair the visual perception already during the stimulus processing. In addition, our findings indicate that the cone pathway seems to be particularly affected by this damage.

Neuronal damage and impaired vision in different retinal disorders are induced, among other factors, by ischemia/reperfusion (I/R). Since the mechanisms and the progression of ischemic injury are still not completely clarified, a timeline of this retinal degeneration is needed. In this study, we investigated protein and mRNA alterations at 2, 6, 12, and 24 h as well as 3 and 7 days after ischemia to determine the course of an ischemic insult through the whole retina. Moreover, functional analyses were performed at later stages. We detected a significant functional loss of cells in the inner nuclear layer and photoreceptors at 3 and 7 days. Additionally, the thickness of the whole retina was decreased at these points in time, indicating a severe degradation of all retinal layers. Immunohistological and qRT-PCR analyses of retinal ganglion cells (RGCs), glial cells, AII amacrine, cone and rod bipolar as well as cone and rod photoreceptor cells confirmed this first assumption. Our results show that all investigated cell types were damaged by ischemia induction. Especially RGCs, cone bipolar cells, and photoreceptor cones are very sensitive to I/R. These cells were lost shortly after ischemia induction with a progressive course up to 7 days. In addition, Müller cell gliosis was observed over the entire period of time. These results provide evidence, that I/R induces damage of the whole retina at early stages and increases over time. In conclusion, our study could demonstrate the intense impact of an ischemic injury. The ischemic defect spreads across the whole retina right up to the outer layers in the long-term and thus seems to impair the visual perception already during the stimulus processing. In addition, our findings indicate that the cone pathway seems to be particularly affected by this damage.

In glaucoma, latest studies revealed an involvement of the complement system with and without an elevated intraocular pressure. In the experimental autoimmune glaucoma model, immunization with antigens, such as S100B, lead to retinal ganglion cell (RGC) loss and optic nerve degeneration after 28 days. Here, we investigated the timeline of progression of the complement system, toll-like-receptor 4 (TLR4), and the transcription factor nucleus factor-kappa B (NF\(\kappa\)B). Therefore, rats were immunized with S100B protein (S100) and analyzed at 3, 7, and 14 days. RGC numbers were comparable at all points in time, whereas a destruction of S100 optic nerves was noted at 14 days. A significant increase of mannose binding lectin (MBL) was observed in S100 retinas at 3 days. Subsequently, significantly more MBL\(^{+}\) cells were seen in S100 optic nerves at 7 and 14 days. Accordingly, C3 was upregulated in S100 retinas at 14 days. An increase of interleukin-1 beta was noted in S100 aqueous humor samples at 7 days. In this study, activation of complement system via the lectin pathway was obvious. However, no TLR4 alterations were noted in S100 retinas and optic nerves. Interestingly, a significant NF\(\kappa\)B increase was observed in S100 retinas at 7 and 14 days. We assume that NF\(\kappa\)B activation might be triggered via MBL leading to glaucomatous damage.

\(\bf Background:\) The oral immunomodulatory agent laquinimod is currently evaluated for multiple sclerosis (MS) treatment. Phase II and III studies demonstrated a reduction of degenerative processes. In addition to anti-inflammatory effects, laquinimod might have neuroprotective properties, but its impact on the visual system, which is often affected by MS, is unknown. The aim of our study was to investigate potential protective effects of laquinimod on the optic nerve and retina in an experimental autoimmune encephalomyelitis (EAE) model. \(\bf Methods:\) We induced EAE in C57/BL6 mice via MOG\(_{35–55}\) immunization. Animals were divided into an untreated EAE group, three EAE groups receiving laquinimod (1, 5, or 25 mg/kg daily), starting the day post-immunization, and a nonimmunized control group. Thirty days post-immunization, scotopic electroretinograms were carried out, and mice were sacrificed for histopathology (HE, LFB), immunohistochemistry (MBP, Iba1, Tmem119, F4/80, GFAP, vimentin, Brn-3a, cleaved caspase 3) of the optic nerve and retina, and retinal qRT-PCR analyses (\(\textit {Brn-3a, Iba1, Tmem119, AMWAP, CD68, GFAP}\)). To evaluate the effect of a therapeutic approach, EAE animals were treated with 25 mg/kg aquinimod from day 16 when 60% of the animals had developed clinical signs of EAE. \(\bf Results:\) Laquinimod reduced neurological EAE symptoms and improved the neuronal electrical output of the inner nuclear layer compared to untreated EAE mice. Furthermore, cellular infiltration, especially recruited phagocytes, and demyelination in the optic nerve were reduced. Microglia were diminished in optic nerve and retina. Retinal macroglial signal was reduced under treatment, whereas in the optic nerve macroglia were not affected. Additionally, laquinimod preserved retinal ganglion cells and reduced apoptosis. A later treatment with laquinimod in a therapeutic approach led to a reduction of clinical signs and to an improved b-wave amplitude. However, no changes in cellular infiltration and demyelination of the optic nerves were observed. Also, the number of retinal ganglion cells remained unaltered. \(\bf Conclusion:\) Fromour study, we deduce neuroprotective and anti-inflammatory effects of laquinimod on the optic nerve and retina in EAE mice, when animals were treated before any clinical signs were noted. Given the fact that the visual system is frequently affected by MS, the agent might be an interesting subject of further neuro-ophthalmic investigations.

Retinal ischemia is an important factor in several eye disorders. To investigate the impact of VEGF inhibitors, as a therapeutic option, we studied these in a retinal ischemia animal model. Therefore, animals received bevacizumab or ranibizumab intravitreally one day after ischemia induction. Via electroretinography, a significant decrease in a- and b-wave amplitudes was detected fourteen days after ischemia, but they were reduced to a lesser extent in the ranibizumab group. Ischemic and bevacizumab retinae displayed fewer retinal ganglion cells (RGCs), while no significant cell loss was noted in the ranibizumab group. Apoptosis was reduced after therapy. More autophagocytotic cells were observed in ischemic and bevacizumab eyes, but not in ranibizumab eyes. Additionally, more microglia, as well as active ones, were revealed in all ischemic groups, but the increase was less prominent under ranibizumab treatment. Fewer cone bipolar cells were detected in ischemic eyes, in contrast to bevacizumab and ranibizumab-treated ones. Our results demonstrate a reduced apoptosis and autophagocytosis rate after ranibizumab treatment. Furthermore, a certain protection was seen regarding functionality, RGC, and bipolar cell availability, as well as microglia activation by ranibizumab treatment after ischemic damage. Thus, ranibizumab could be an option for treatment of retinal ischemic injury.

Analyses of different mRNAs via qRT-PCR. Values are median and interquartile range. Significant differences are marked in bold. (DOCX 16.4 kb)

Retinal ischemia is common in eye disorders, like diabetic retinopathy or retinal vascular occlusion. The goal of this study was to evaluate the potential protective effects of an intravitreally injected vascular endothelia l growth factor (VEGF) inhibitor (ranibizumab) on retinal cells in an ischemia animal model via immunohistochemistry (IF) and quantitative real-time PCR (PCR). A positive binding of ranibizumab to rat VEGF-A was confirmed via dot blot. One eye underwent ischemia and a subgroup received ranibizumab. A significant VEGF increase was detected in aqueous humor of ischemic eyes (p = 0.032), whereas VEGF levels were low in ranibizumab eyes (p = 0.99). Ischemic retinas showed a significantly lower retinal ganglion cell number (RGC; IF Brn 3a: p