CXCR5/NRF2 double knockout mice develop retinal degeneration phenotype at early adult age

Polydopamine Nanoparticles as Mimicking RPE Melanin for the Protection of Retinal Cells Against Blue Light-Induced Phototoxicity

Exposure of the eyes to blue light can induce the overproduction of reactive oxygen species (ROS) in the retina and retinal pigment epithelium (RPE) cells, potentially leading to pathological damage of age-related macular degeneration (AMD). While the melanin in RPE cells absorbs blue light and prevents ROS accumulation, the loss and dysfunction of RPE melanin due to age-related changes may contribute to photooxidation toxicity. Herein, a novel approach utilizing a polydopamine-replenishing strategy via a single-dose intravitreal (IVT) injection is presented to protect retinal cells against blue light-induced phototoxicity. To investigate the effects of overexposure to blue light on retinal cells, a blue light exposure Nrf2-deficient mouse model is created, which is susceptible to light-induced retinal lesions. After blue light irradiation, retina degeneration and an overproduction of ROS are observed. The polydopamine-replenishing strategy demonstrated effectiveness in maintaining retinal structural integrity and preventing retina degeneration by reducing ROS production in retinal cells and limiting the phototoxicity of blue light exposure. These findings highlight the potential of polydopamine as a simple and effective replenishment for providing photoprotection against high-energy blue light exposure.

The TAK1/JNK axis participates in adaptive immunity by promoting lymphocyte activation in Nile tilapia

The transforming growth factor beta-activated kinase 1 (TAK1)/c-Jun N-terminal kinase (JNK) axis is an essential MAPK upstream mediator and regulates immune signaling pathways. However, whether the TAK1/JNK axis harnesses the strength in regulation of signal transduction in early vertebrate adaptive immunity is unclear. In this study, by modeling on Nile tilapia (Oreochromis niloticus), we investigated the potential regulatory function of TAK1/JNK axis on lymphocyte-mediated adaptive immune response. Both OnTAK1 and OnJNK exhibited highly conserved sequences and structures relative to their counterparts in other vertebrates. Their mRNA was widely expressed in the immune-associated tissues, while phosphorylation levels in splenic lymphocytes were significantly enhanced on the 4th day post-infection by Edwardsiella piscicida. In addition, OnTAK1 and OnJNK were significantly up-regulated in transcriptional level after activation of lymphocytes in vitro by phorbol 12-myristate 13-acetate plus ionomycin (P + I) or PHA, accompanied by a predominant increase in phosphorylation level. More importantly, inhibition of OnTAK1 activity by specific inhibitor NG25 led to a significant decrease in the phosphorylation level of OnJNK. Furthermore, blocking the activity of OnJNK with specific inhibitor SP600125 resulted in a marked reduction in the expression of T-cell activation markers including IFN-γ, CD122, IL-2, and CD44 during PHA-induced T-cell activation. In summary, these findings indicated that the conserved TAK1/JNK axis in Nile tilapia was involved in adaptive immune responses by regulating the activation of lymphocytes. This study enriched the current knowledge of adaptive immunity in teleost and provided a new perspective for understanding the regulatory mechanism of fish immunity.

Retinoic acid related orphan receptor α is a genetic modifier that rescues retinal degeneration in a mouse model of Stargardt disease and Dry AMD

Degeneration of the macula is associated with several overlapping diseases including age-related macular degeneration (AMD) and Stargardt Disease (STGD). Mutations in ATP Binding Cassette Subfamily A Member 4 (ABCA4) are associated with late-onset dry AMD and early-onset STGD. Additionally, both forms of macular degeneration exhibit deposition of subretinal material and photoreceptor degeneration. Retinoic acid related orphan receptor α (RORA) regulates the AMD inflammation pathway that includes ABCA4, CD59, C3 and C5. In this translational study, we examined the efficacy of RORA at attenuating retinal degeneration and improving the inflammatory response in Abca4 knockout (Abca4-/-) mice. AAV5-hRORA-treated mice showed reduced deposits, restored CD59 expression and attenuated amyloid precursor protein (APP) expression compared with untreated eyes. This molecular rescue correlated with statistically significant improvement in photoreceptor function. This is the first study evaluating the impact of RORA modifier gene therapy on rescuing retinal degeneration. Our studies demonstrate efficacy of RORA in improving STGD and dry AMD-like disease.

Targeting Lipid Metabolism for the Treatment of Age-Related Macular Degeneration: Insights from Preclinical Mouse Models

Age-related macular degeneration (AMD) is a major leading cause of irreversible visual impairment in the world with limited therapeutic interventions. Histological, biochemical, genetic, and epidemiological studies strongly implicate dysregulated lipid metabolism in the retinal pigmented epithelium (RPE) in AMD pathobiology. However, effective therapies targeting lipid metabolism still need to be identified and developed for this blinding disease. To test lipid metabolism-targeting therapies, preclinical AMD mouse models are needed to establish therapeutic efficacy and the role of lipid metabolism in the development of AMD-like pathology. In this review, we provide a comprehensive overview of current AMD mouse models available to researchers that could be used to provide preclinical evidence supporting therapies targeting lipid metabolism for AMD. Based on previous studies of AMD mouse models, we discuss strategies to modulate lipid metabolism as well as examples of studies evaluating lipid-targeting therapeutics to restore lipid processing in the RPE. The use of AMD mouse models may lead to worthy lipid-targeting candidate therapies for clinical trials to prevent the blindness caused by AMD.

Deficiency of C-X-C chemokine receptor type 5 (CXCR5) gene causes dysfunction of retinal pigment epithelium cells

Homeostasis of the retinal pigment epithelium (RPE) is essential for the health and proper function of the retina. Regulation of RPE homeostasis is, however, largely unexplored, yet dysfunction of this process may lead to retinal degenerative diseases, including age-related macular degeneration (AMD). Here, we report that chemokine receptor CXCR5 regulates RPE homeostasis through PI3K/AKT signaling and by suppression of FOXO1 activation. We used primary RPE cells isolated from CXCR5-deficient mice and wild type controls, as well as ex vivo RPE-choroidal-scleral complexes (RCSC) to investigate the regulation of homeostasis. CXCR5 expression in mouse RPE cells was diminished by treatment with hydrogen peroxide. Lack of CXCR5 expression leads to an abnormal cellular shape, pigmentation, decreased expression of the RPE differentiation marker RPE65, an increase in the undifferentiated progenitor marker MITF, and compromised RPE barrier function, as well as compromised cell-to-cell interaction. An increase in epithelial-mesenchymal transition (EMT) markers (αSMA, N-cadherin, and vimentin) was noted in CXCR5-deficient RPE cells both in vitro and in age-progression specimens of CXCR5-/- mice (6, 12, 24-months old). Deregulated autophagy in CXCR5-deficient RPE cells was observed by decreased LC3B-II, increased p62, abnormal autophagosomes, and impaired lysosome enzymatic activity as shown by GFP-LC3-RFP reporter plasmid. Mechanistically, deficiency in CXCR5 resulted in the downregulation of PI3K and AKT signaling, but upregulation and nuclear localization of FOXO1. Additionally, inhibition of PI3K in RPE cells resulted in an increased expression of FOXO1. Inhibition of FOXO1, however, reverts the degradation of ZO-1 caused by CXCR5 deficiency. Collectively, these findings suggest that CXCR5 maintains PI3K/AKT signaling, which controls FOXO1 activation, thereby regulating the expression of genes involved in RPE EMT and autophagy deregulation.

Experimental Models in Neovascular Age Related Macular Degeneration

Neovascular age-related macular degeneration (vAMD), characterized by the neo-vascularization of the retro-foveolar choroid, leads to blindness within few years. This disease depends on angiogenesis mediated by the vascular endothelial growth factor A (VEGF) and to inflammation. The only available treatments consist of monthly intravitreal injections of antibodies directed against VEGF or VEGF/VEGFB/PlGF decoy receptors. Despite their relative efficacy, these drugs only delay progression to blindness and 30% of the patients are insensitive to these treatments. Hence, new therapeutic strategies are urgently needed. Experimental models of vAMD are essential to screen different innovative therapeutics. The currently used in vitro and in vivo models in ophthalmic translational research and their relevance are discussed in this review.