Electrophysiologic and Morphologic Strain Differences in a Low-Dose NaIO3-Induced Retinal Pigment Epithelium Damage Model

Deletion of the stress response protein REDD1 prevents sodium iodate-induced RPE damage and photoreceptor loss

Age-related macular degeneration (AMD) is a leading cause of blindness in elderly populations, yet the molecular events that initiate the early retinal defects that lead to visual function deficits remain poorly understood. The studies here explored a role for the stress response protein Regulated in Development and DNA damage response 1 (REDD1) in the development of retinal pathology by using the oxidant stressor sodium iodate (NaIO3) to model dry AMD in mice. REDD1 protein abundance was increased in the retinal pigmented epithelium (RPE) and retina of mice administered NaIO3. In wild-type REDD1+/+ mice, reactive oxygen species (ROS) levels were robustly increased in the outer retinal layers 1 day after NaIO3 administration, with focal areas of increased ROS seen throughout the outer retina after 7 days. In contrast with REDD1+/+ mice, ROS levels were blunted in REDD1-/- mice after NaIO3 administration. REDD1 was also required for upregulated expression of pro-inflammatory factors in the RPE/retina and immune cell activation in the outer retina following NaIO3 administration. In REDD1+/+ mice, NaIO3 reduced RPE65 and rhodopsin levels in the RPE and photoreceptor layers, respectively. Unlike REDD1+/+ mice, REDD1-/- mice did not exhibit disrupted RPE integrity, retinal degeneration, or photoreceptor thinning. Overall, REDD1 deletion was sufficient to prevent retinal oxidative stress, RPE damage, immune cell activation, and photoreceptor loss in response to NaIO3. The findings support a potential role for REDD1 in the development of retinal complications in the context of dry AMD.

Systemic Sodium Iodate Injection as a Model for Expanding Geographic Atrophy

Purpose

Geographic atrophy (GA), an advanced form of dry age-related macular degeneration (AMD), has limited treatment options. This study introduces a novel mouse model featuring an expanding GA patch that can be used to test mechanisms and therapeutics.

Methods

C57Bl/6J male mice (n = 96) aged 9-10 weeks received an intraperitoneal (IP) injection of 20 mg/kg sodium iodate (NaIO3). In vivo confocal scanning laser ophthalmoscope (cSLO) and optical coherence tomography imaging were done at one, four, eight, and 16 weeks after injection, with GA area measurements taken at weeks 8 and 16. Mice were euthanized on weeks 8 and 16 for histological analysis.

Results

Administration of 20 mg/kg intraperitoneal NaIO3 caused variable damage levels. Approximately 22% of cases showed damage (speckled autofluorescence) covering 35% to 90% of the 102° field of view cSLO image at one week after injection. These mice developed an expanding patch of GA by week 8, with a mean 1.45-fold increase in area by week 16. This region showed complete photoreceptor and retinal pigment epithelium loss and complement activation at the atrophy edge, whereas the inner retina remained undamaged. Mice with less damage (48% of cases) only developed incomplete outer retinal degeneration, and mice with more damage (30% of cases) had too much GA for measurable expansion.

Conclusions

Although expanding GA formed in only 22% of mice, the model's simplicity and predictability for GA development via one-week post-injection imaging make it suitable for GA therapeutic experimentation.

Translational Relevance

This murine model provides a valuable tool for testing GA therapies, mirroring clinical endpoints relevant to human trials.

Loss of Pigment Epithelium Derived Factor Sensitizes C57BL/6J Mice to Light-Induced Retinal Damage

Purpose

Pigment epithelium-derived factor (PEDF) is a neurotrophic glycoprotein secreted by the retinal pigment epithelium (RPE) that supports retinal photoreceptor health. Deficits in PEDF are associated with increased inflammation and retinal degeneration in aging and diabetic retinopathy. We hypothesized that light-induced stress in C57BL/6J mice deficient in PEDF would lead to increased retinal neuronal and RPE defects, impaired expression of neurotrophic factor Insulin-like growth factor 1 (IGF-1), and overactivation of Galectin-3-mediated inflammatory signaling.

Methods

C57BL/6J mice expressing the RPE65 M450/M450 allele were crossed to PEDF KO/KO and wildtype (PEDF +/+) littermates. Mice were exposed to 50,000 lux light for 5 hours to initiate acute damage. Changes in visual function outcomes were tracked via electroretinogram (ERG), confocal scanning laser ophthalmoscopy(cSLO), and spectral domain optical coherence tomography (SD-OCT) on days 3, 5, and 7 post-light exposure. Gene and protein expression of Galectin-3 were measured by digital drop PCR (ddPCR) and western blot. To further investigate the role of galectin-3 on visual outcomes and PEDF expression after damage, we also used a small-molecule inhibitor to reduce its activity.

Results

Following light damage, PEDF KO/KO mice showed more severe retinal thinning, impaired visual function (reduced a-, b-, and c-wave amplitudes), and increased Galectin-3 expressing immune cell infiltration compared to PEDF +/+. PEDF KO/KO mice had suppressed damage-associated increases in IGF-1 expression. Additionally, baseline Galectin-3 mRNA and protein expression were reduced in PEDF KO/KO mice compared to PEDF +/+. However, after light damage, Galectin-3 expression decreases in PEDF +/+ mice but increases in PEDF KO/KO mice without reaching PEDF +/+ levels. Galectin-3 inhibition worsens retinal degeneration, reduces PEDF expression in PEDF +/+ mice, and mimics the effects seen in PEDF knockouts.

Conclusions

Loss of PEDF alone does not elicit functional defects in C57BL/6J mice. However, under light stress, PEDF deficiency significantly increases severe retinal degeneration, visual deficits, Galectin-3 expression, and suppression of IGF-1 than PEDF +/+. PEDF deficiency reduced baseline expression of Galectin-3, and pharmacological inhibition of Galectin-3 worsens outcomes and suppresses PEDF expression in PEDF +/+, suggesting a novel co-regulatory relationship between the two proteins in mitigating light-induced retinal damage.

The protective role of Cordyceps cicadae and its active ingredient myriocin against sodium iodate-induced age-related macular degeneration via an anti-necroptotic TNF-RIPK1/3 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Cordyceps cicadae (C.cicadae), named "Chan Hua", an anamorph of Isaria cicadae Miquel, is an entomogenous complex formed by fungi parasitizing on the larvae of cicadas and belongs to the Claviciptaceae family and the genus Codyceps, which traditionally holds a significant place in Chinese ethnopharmacology, specifically for eye clarity and as a remedy for age-related ocular conditions. The underlying mechanisms contributing to its eyesight enhancement and potential effectiveness against Age-related macular degeneration (AMD) remain unexplored.

AIM OF THE STUDY

This study aims to elucidate the protective role of C.cicadae and its active ingredient, Myriocin (Myr), against AMD.

MATERIALS AND METHODS

A chemical inducer was employed to make retinal pigment epithelium (RPE) damage in vitro and in vivo. The key ingredients of C.cicadae and their related mechanisms for anti-AMD were studied through bioinformatic analysis and molecular biological approaches.

RESULTS

Myr was identified through high-performance liquid chromatography (HPLC) as an active ingredient in C.cicadae, and demonstrated a protective effect on RPE cells, reducing the structural damage and cell death induced by sodium iodate (SI). Further, Myr reduced eyelid secretions in AMD mice and restored their retinal structure and function. The differentially expressed genes (DEGs) in Myr treatment are primarily associated with TNF and Necroptosis signaling pathways. Molecular docking indicated a strong affinity between TNF and Myr. Myr inhibited the TNF signaling pathway thereby reducing the expression of inflammatory factors in ARPE-19 cells. Additionally, Myr had consistent action with the necroptosis inhibitor Necrostatin-1 (Nec-1), inhibited the RIPK1/RIPK3/MLKL pathway thereby protecting ARPE-19 cells.

CONCLUSION

The findings present Myr, as a potent protector against SI-induced AMD, predominantly through modulation of the TNF-RIPK1/RIPK3/MLKL signaling pathway, offering the insights of therapeutic C.cicadae as viable candidates for AMD treatment.

Acetylcholine regulates the melanogenesis of retinal pigment epithelia cells via a cAMP-dependent pathway: A non-neuronal function of cholinergic system in retina

The turnover rate of melanogenesis in retinal pigment epithelium (RPE) and its molecular signaling remain unclear. This study aimed to investigate the role of cholinergic signaling in the process of melanogenesis of cultured RPE cells. Here, a human retinal pigment epithelia cell line, ARPE-19 cell, was used to study the process of melanogenesis. The mRNA and protein expressions of cholinergic molecules, e.g., acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and melanogenic molecules i.e., tyrosinase (TYR), microphthalmia-associated transcription factor (MITF), and melanin pigment were measured during melanogenesis of cultured ARPE-19 cells. Forskolin (a cAMP inducing agent), acetylcholine (ACh) and bethanechol (Bch; a muscarinic AChR agonist) were used to induce melanogenesis in the cultures. Muscarinic acetylcholine receptor (mAChR) antagonists were employed to identify the receptor subtype. During melanogenesis of ARPE-19 cells, the mRNA and protein expressions of cholinergic molecules, e.g., AChE and BChE, were increased along with melanogenic molecules, i.e., TYR, MITF and melanin pigment. Forskolin, ACh, and Bch induced an upregulation of melanogenesis in cultured ARPE-19 cultures: the induction was parallel to an increase of AChE expression. The Bch-induced enzymatic activities and mRNA levels of AChE and TYR were fully blocked by the treatments of gallamine (a M2 specific antagonist), tropicamide (a M4 specific antagonist) and atropine (non-specific antagonist for mAChRs). Cholinergic signaling via M2/M4 mAChRs regulates melanogenesis in cultured ARPE-19 cells through a cAMP-dependent pathway. This study provides insights into the regulation of RPE cell melanogenesis via a non-neuronal function of cholinergic system.

Optimizing the sodium iodate model: Effects of dose, gender, and age

Sodium iodate (NaIO3) is a commonly used model for age-related macular degeneration (AMD), but its rapid and severe induction of retinal pigment epithelial (RPE) and photoreceptor degeneration can lead to the premature dismissal of potentially effective therapeutics. Additionally, little is known about how sex and age affect the retinal response to NaIO3. This study aims to establish a less severe yet reproducible regimen by testing low doses of NaIO3 while considering age- and sex-related effects, enabling a broader range of therapeutic evaluations. In this study, young (3-5 months) and old (18-24 months) male and female C57Bl/6J mice were given an intraperitoneal (IP) injection of 15, 20, or 25 mg/kg NaIO3. Damage assessment one week post-injection included in vivo imaging, histological examination, and qRT-PCR analysis. The results revealed that young mice showed no damage at 15 mg/kg IP NaIO3, with varying degrees of damage observed at 20 mg/kg. At 25 mg/kg, most young mice displayed widespread retinal damage, with females exhibiting less retinal thinning than males. In contrast, older mice at 20 and 25 mg/kg displayed a more patchy degeneration pattern, outer retinal undulations, and greater variability in degeneration than the young mice. The most effective model for minimizing damage while maintaining consistency utilizes young female mice injected with 25 mg/kg NaIO3. The observed sex- and age-related differences underscore the importance of considering these variables in research, aligning with the National Institutes of Health's guidance. While the model does not fully replicate the complexity of AMD, these findings enhance its utility as a valuable tool for testing RPE/photoreceptor protective or replacement therapies.

Age-Related RPE changes in Wildtype C57BL/6J Mice between 2 and 32 Months

Purpose

This study provides a systematic evaluation of age-related changes in RPE cell structure and function using a morphometric approach. We aim to better capture nuanced predictive changes in cell heterogeneity that reflect loss of RPE integrity during normal aging. Using C57BL6/J mice ranging from P60-P730, we sought to evaluate how regional changes in RPE shape reflect incremental losses in RPE cell function with advancing age. We hypothesize that tracking global morphological changes in RPE is predictive of functional defects over time.

Methods

We tested three groups of C57BL/6J mice (young: P60-180; Middle-aged: P365-729; aged: 730+) for function and structural defects using electroretinograms, immunofluorescence, and phagocytosis assays.

Results

The largest changes in RPE morphology were evident between the young and aged groups, while the middle-aged group exhibited smaller but notable region-specific differences. We observed a 1.9-fold increase in cytoplasmic alpha-catenin expression specifically in the central-medial region of the eye between the young and aged group. There was an 8-fold increase in subretinal, IBA-1-positive immune cell recruitment and a significant decrease in visual function in aged mice compared to young mice. Functional defects in the RPE corroborated by changes in RPE phagocytotic capacity.

Conclusions

The marked increase of cytoplasmic alpha-catenin expression and subretinal immune cell deposition, and decreased visual output coincide with regional changes in RPE cell morphometrics when stratified by age. These cumulative changes in the RPE morphology showed predictive regional patterns of stress associated with loss of RPE integrity.

Pentosan Polysulfate Sodium Causes Diminished Function and Subtle Morphological Changes in Retina and RPE of Mice

Purpose

There are numerous reports of a distinctive maculopathy in adults exposed to pentosan polysulfate sodium (PPS), a drug prescribed to treat bladder discomfort associated with interstitial cystitis. We tested whether PPS treatment of mice injures RPE or retina to provide insight into the etiology of the human condition.

Methods

Mice were fed PPS-supplemented chow over 14 months. RPE and retinal function was assessed by electroretinography (ERG) regularly. Following euthanasia, one eye was used for sagittal sectioning and histology, the contralateral for RPE flatmounting. ZO-1 positive RPE cell borders were imaged using confocal microscopy and cell morphology was analyzed using CellProfiler.

Results

After 10 months of PPS treatment, we observed diminution of mean scotopic c-wave amplitudes. By 11 months, we additionally observed diminutions of mean scotopic a- and b-wave amplitudes. Analysis of flatmounts revealed altered RPE cell morphology and morphometrics in PPS-treated mice, including increased mean en face cell area and geometric eccentricity, decreased RPE cell solidity and extent, and cytosolic translocation of alpha-catenin, all markers of RPE cell stress. Sex and regional differences were seen in RPE flatmount measures. Shortened photoreceptor outer segments were also observed.

Conclusions

PPS treatment reduced RPE and later retina function as measured by ERG, consistent with a primary RPE injury. Post-mortem analysis revealed extensive RPE pleomorphism and polymegathism and modest photoreceptor changes. We conclude that PPS treatment of mice causes slowly progressing RPE and photoreceptor damage and thus may provide a useful model for some retinal pathologies.

Regulated cell death pathways in the sodium iodate model: Insights and implications for AMD

The sodium iodate (NaIO3) model of increased oxidative stress recapitulates dry AMD features such as patchy RPE loss, secondary photoreceptors, and underlying choriocapillaris death, allowing longitudinal evaluation of the retinal structure. Due to the time- and dose-dependent degeneration observed in diverse animal models, this preclinical model has become one of the most studied models. The events leading to RPE cell death post- NaIO3 injection have been extensively studied, and here we have reviewed different modalities of cell death, including apoptosis, necroptosis, ferroptosis, and pyroptosis with a particular focus on findings associated with in vivo and in vitro NaIO3 studies on RPE cell death. Because the fundamental cause of vision loss in patients with dry AMD is the death of these same cells affected by NaIO3, studies using NaIO3 can provide valuable insights into RPE and photoreceptor cell death mechanisms and can help understand mechanisms behind RPE degeneration in AMD.

Choroidal Mast Cells and Pathophysiology of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) remains a leading cause of vision loss in elderly patients. Its etiology and progression are, however, deeply intertwined with various cellular and molecular interactions within the retina and choroid. Among the key cellular players least studied are choroidal mast cells, with important roles in immune and allergic responses. Here, we will review what is known regarding the pathophysiology of AMD and expand on the recently proposed intricate roles of choroidal mast cells and their activation in outer retinal degeneration and AMD pathogenesis. We will focus on choroidal mast cell activation, the release of their bioactive mediators, and potential impact on ocular oxidative stress, inflammation, and overall retinal and choroidal health. We propose an important role for thrombospondin-1 (TSP1), a major ocular angioinflammatory factor, in regulation of choroidal mast cell homeostasis and activation in AMD pathogenesis. Drawing from limited studies, this review underscores the need for further comprehensive studies aimed at understanding the precise roles changes in TSP1 levels and choroidal mast cell activity play in pathophysiology of AMD. We will also propose potential therapeutic strategies targeting these regulatory pathways, and highlighting the promise they hold for curbing AMD progression through modulation of mast cell activity. In conclusion, the evolving understanding of the role of choroidal mast cells in AMD pathogenesis will not only offer deeper insights into the underlying mechanisms but will also offer opportunities for development of novel preventive strategies.

Integration of human stem cell-derived in vitro systems and mouse preclinical models identifies complex pathophysiologic mechanisms in retinal dystrophy

Rare DRAM2 coding variants cause retinal dystrophy with early macular involvement via unknown mechanisms. We found that DRAM2 is ubiquitously expressed in the human eye and expression changes were observed in eyes with more common maculopathy such as Age-related Macular Degeneration (AMD). To gain insights into pathogenicity of DRAM2-related retinopathy, we used a combination of in vitro and in vivo models. We found that DRAM2 loss in human pluripotent stem cell (hPSC)-derived retinal organoids caused the presence of additional mesenchymal cells. Interestingly, Dram2 loss in mice also caused increased proliferation of cells from the choroid in vitro and exacerbated choroidal neovascular lesions in vivo. Furthermore, we observed that DRAM2 loss in human retinal pigment epithelial (RPE) cells resulted in increased susceptibility to stress-induced cell death in vitro and that Dram2 loss in mice caused age-related photoreceptor degeneration. This highlights the complexity of DRAM2 function, as its loss in choroidal cells provided a proliferative advantage, whereas its loss in post-mitotic cells, such as photoreceptor and RPE cells, increased degeneration susceptibility. Different models such as human pluripotent stem cell-derived systems and mice can be leveraged to study and model human retinal dystrophies; however, cell type and species-specific expression must be taken into account when selecting relevant systems.

Oxidative Model of Retinal Neurodegeneration Induced by Sodium Iodate: Morphofunctional Assessment of the Visual Pathway

Sodium iodate (NaIO3) has been shown to cause severe oxidative stress damage to retinal pigment epithelium cells. This results in the indirect death of photoreceptors, leading to a loss of visual capabilities. The aim of this work is the morphological and functional characterization of the retina and the visual pathway of an animal model of retinal neurodegeneration induced by oxidative stress. Following a single intraperitoneal dose of NaIO3 (65 mg/kg) to C57BL/6J mice with a mutation in the Opn4 gene (Opn4-/-), behavioral and electroretinographic tests were performed up to 42 days after administration, as well as retinal immunohistochemistry at day 57. A near total loss of the pupillary reflex was observed at 3 days, as well as an early deterioration of visual acuity. Behavioral tests showed a late loss of light sensitivity. Full-field electroretinogram recordings displayed a progressive and marked decrease in wave amplitude, disappearing completely at 14 days. A reduction in the amplitude of the visual evoked potentials was observed, but not their total disappearance. Immunohistochemistry showed structural alterations in the outer retinal layers. Our results show that NaIO3 causes severe structural and functional damage to the retina. Therefore, the current model can be presented as a powerful tool for the study of new therapies for the prevention or treatment of retinal pathologies mediated by oxidative stress.

SIRT6 overexpression in the nucleus protects mouse retinal pigment epithelium from oxidative stress

Retinal pigment epithelium (RPE) is essential for the survival of retinal photoreceptors. To study retinal degeneration, sodium iodate (NaIO3) has been used to cause oxidative stress-induced RPE death followed by photoreceptor degeneration. However, analyses of RPE damage itself are still limited. Here, we characterized NaIO3-induced RPE damage, which was divided into three regions: periphery with normal-shaped RPE, transitional zone with elongated cells, and center with severely damaged or lost RPE. Elongated cells in the transitional zone exhibited molecular characteristics of epithelial-mesenchymal transition. Central RPE was more susceptible to stresses than peripheral RPE. Under stresses, SIRT6, an NAD+-dependent protein deacylase, rapidly translocated from the nucleus to the cytoplasm and colocalized with stress granule factor G3BP1, leading to nuclear SIRT6 depletion. To overcome this SIRT6 depletion, SIRT6 overexpression was induced in the nucleus in transgenic mice, which protected RPE from NaIO3 and partially preserved catalase expression. These results demonstrate topological differences of mouse RPE and warrant further exploring SIRT6 as a potential target for protecting RPE from oxidative stress-induced damage.

Dependence of Retinal Pigment Epithelium Integrity on the NRF2-Heme Oxygenase-1 Axis

Purpose

Tight junctions (TJs) form the structural basis of retinal pigment epithelium (RPE) barrier functions. Although oxidative stress contributes to age-related macular degeneration, it is unclear how RPE TJ integrity is controlled by redox balance. In this study, we investigated the protective roles of nuclear factor erythroid 2–related factor 2 (NRF2), a transcription factor, and heme oxygenase-1 (HO1), a heme-degrading enzyme encoded by the NRF2 target gene HMOX1.

Methods

ARPE19 cell cultures and mice, including wild-type, Nrf2^−/−, and RPE-specific NRF2-deficient mice, were treated with chemicals that impose oxidative stress or impact heme metabolism. In addition, NRF2 and HO1 expression in ARPE19 cells was knocked down by siRNA. TJ integrity was examined by anti–zonula occludens-1 staining of cultured cells or flatmount RPE tissues from mice. RPE barrier functions were evaluated by transepithelium electrical resistance in ARPE19 cells and immunofluorescence staining for albumin or dextran in eye histological sections.

Results

TJ structures and RPE barrier functions were compromised due to oxidant exposure and NRF2 deficiency but were rescued by HO1 inducer. Furthermore, treatment with HO1 inhibitor or heme precursor is destructive to TJ structures and RPE barrier properties. Interestingly, both NRF2 and HO1 were upregulated under oxidative stress, probably as an adaptive response to mitigate oxidant-inflicted damages.

Conclusions

Our data indicate that the NRF2–HO1 axis protects TJ integrity and RPE barrier functions by driving heme degradation.

Noninvasive Ophthalmic Imaging Measures Retinal Degeneration and Vision Deficits in Ndufs4-/- Mouse Model of Mitochondrial Complex I Deficiency

Purpose

To characterize postnatal ocular pathology in a Ndufs4^−/− mouse model of complex I deficiency using noninvasive retinal imaging and visual testing.

Methods

Ndufs4^−/− mice and wild-type (WT) littermates were analyzed at 3, 5, and 7 weeks postnatal. Retinal morphology was visualized by optical coherence tomography (OCT). OCT images were analyzed for changes in retinal thickness and reflectivity profiles. Visual function was assessed by electroretinogram (ERG) and optomotor reflex (OMR).

Results

Ndufs4^−/− animals have normal OCT morphology at weaning and develop inner plexiform layer atrophy over weeks 5 to 7. Outer retinal layers show hyporeflectivity of the external limiting membrane (ELM) and photoreceptor ellipsoid zone (EZ). Retinal function is impaired at 3 weeks, with profound deficits in b-wave, a-wave, and oscillatory potential amplitudes. The b-wave and oscillatory potential implicit times are delayed, but the a-wave implicit time is unaffected. Ndufs4^−/− animals have normal OMR at 3 weeks and present with increasing acuity and contrast OMR deficits at 5 and 7 weeks. Physiological thinning of inner retinal layers, attenuation of ELM reflectivity, and attenuation of ERG b- and a-wave amplitudes occur in WT C57BL/6 littermates between weeks 3 and 7.

Conclusions

Noninvasive ocular imaging captures early-onset retinal degeneration in Ndufs4^−/− mice and is a tractable approach for investigating retinal pathology subsequent to complex I deficiency.

Translational Relevance

Ophthalmic imaging captures clinically relevant measures of retinal disease in a fast-progressing mouse model of complex I deficiency consistent with human Leigh syndrome.

Fine Tuning of an Oxidative Stress Model with Sodium Iodate Revealed Protective Effect of NF-κB Inhibition and Sex-Specific Difference in Susceptibility of the Retinal Pigment Epithelium

Oxidative stress of the retinal pigment epithelium (RPE) is a major risk factor for age-related macular degeneration (AMD). As a dry AMD model via oxidative stress, sodium iodate (NaIO₃), which is primarily toxic to the RPE, has often been used at a high dose to cause RPE death for studying photoreceptor degeneration. Thus, characterization of RPE damage by a low dose of NaIO₃ is still limited. To quantify RPE damage caused by NaIO₃ in mice, we recently developed a morphometric method using RPE flat-mounts. Here, we report that NaIO₃ has a narrow range of dose–effect correlation at 11–18 mg/kg body weight in male C57BL/6J mice. We evaluated the usefulness of our quantification method in two experimental settings. First, we tested the effect of NF-κB inhibition on NaIO₃-induced RPE damage in male C57BL/6J mice. IKKβ inhibitor BAY 651942 suppressed upregulation of NF-κB targets and protected the RPE from oxidative stress. Second, we tested sex-specific differences in NaIO₃-induced RPE damage in C57BL/6J mice using a low dose near the threshold. NaIO₃ caused more severe RPE damage in female mice than in male mice. These results demonstrate the usefulness of the quantification method and the importance of fine-tuning of the NaIO₃ dose. The results also show the therapeutic potential of IKKβ inhibition for oxidative stress-related RPE diseases, and reveal previously-unrecognized sex-specific differences in RPE susceptibility to oxidative stress.

Nanoprotection Against Retinal Pigment Epithelium Degeneration via Ferroptosis Inhibition

Lethal oxidative stress and ferrous ion accumulation-mediated degeneration/death in retinal pigment epithelium (RPE) exert an indispensable impact on retinal degenerative diseases with irreversible visual impairment, especially in age-related macular degeneration (AMD), but corresponding pathogenesis-oriented medical intervention remains controversial. In this study, the potent iron-binding nanoscale Prussian blue analogue KCa[Fe^III (CN)₆ ] (CaPB) with high biocompatibility is designed to inhibit RPE death and subsequently photoreceptor cell degeneration. In mice, CaPB effectively prevents RPE degeneration and ultimately fulfills superior therapeutic outcomes upon a single intravitreal injection: significant rescue of retinal structures and visual function. Through high-throughput RNA sequencing and sophisticated biochemistry evaluations, the findings initially unveil that CaPB nanoparticles protect against RPE degradation by inhibiting ferroptotic cell fate. Together with the facile, large-scale preparations and in vivo biosafety, it is believed that the synthesized CaPB therapeutic nanoparticles are promising for future clinical treatment of diverse retinal diseases involving pathological iron-dependent ferroptosis, including AMD.