Crosstalk of protein clearance, inflammasome, and Ca2+ channels in retinal pigment epithelium derived from age-related macular degeneration patients

Melatonin protects RPE cells from necroptosis and NLRP3 activation via promoting SERCA2-related intracellular Ca2+ homeostasis

BACKGROUND

Melatonin is an antioxidant that also has anti-inflammatory effects. It has been reported to delay the progression of age-related macular degeneration (AMD), however, the mechanism has not been fully recognized.

PURPOSE

The aim of the present study was to investigate the effects of melatonin on sodium iodate (SI)-induced retinal degeneration and elucidate the specific mechanisms, then, provide novel targets in AMD treatment.

METHODS

Retinal degeneration mouse model and in vitro retinal pigment epithelium (RPE) death model were established by SI treatment. Melatonin was administrated intraperitoneally at a concentration of 20, 40 or 80 mg/kg for in vivo study or treated at 48 h before SI treatment. To confirm the therapeutic effects of melatonin on mouse, the retinal structure and visual function were evaluated. The specific cell death rates were determined by CCK-8 assay, PI staining and protein level of RIPK3. The cytosolic or mitochondrial calcium levels were determined by Fluo-4AM or Rhod-2AM staining. Mitochondrial functions including mitochondrial dynamics, mitochondrial membrane potential, or mitochondrial permeability pore opening were evaluated. The proteins involved in endoplasmic reticulum (ER) stress were measured by western blot assay while the genes expression in calcium signaling pathway were measured by RT-qPCR.

RESULTS

We show that melatonin protects RPE cells from necroptosis and NLRP3 inflammasome activation induced by SI. Mechanistically, melatonin suppresses ER stress and intracellular calcium overload triggered by SI through restoring the function of SERCA2. Silencing of SERCA2 or blocking of melatonin receptors inhibit the protective effects of melatonin. Melatonin reduces mitochondrial Ca2+ levels and restores mitochondrial membrane potential. Constant mitochondrial Ca2+ overload directly promote cell necroptosis through mitochondrial fission. Inhibition of mitochondrial fission by Mdivi-1 prevent necroptosis induced by SI without altering the level of mitochondrial Ca2+.

CONCLUSIONS

The results confirmed that melatonin protects RPE cells from SI-induced injury by regulates MT2/SERCA2/Ca2+ axis. This study highlighted the potential of melatonin in the treatment of AMD and elucidated the mechanism and signaling pathway that mediate the protective effects.

Ion channels research in hPSC-RPE cells: bridging benchwork to clinical applications

Ion channels in retinal pigment epithelial (RPE) cells are crucial for retinal health and vision functions. Defects in such channels are intricately associated with the development of various retinopathies that cause blindness. Human pluripotent stem cells (hPSC)-derived RPE cells, including those from human-induced pluripotent stem cells (hiPSC) and human embryonic stem cells (hESC), have been used as in vitro models for investigating pathogenic mechanisms and screening potential therapeutic strategies for retinopathies. Therefore, the cellular status of hPSC-RPE cells, including maturity and physiologic functions, have been widely explored. Particularly, research on ion channels in hPSC-RPE cells can lead to the development of more stable models upon which robust investigations and clinical safety assessments can be performed. Moreover, the use of patient-specific hiPSC-RPE cells has significantly accelerated the clinical translation of gene therapy for retinal channelopathies, such as bestrophinopathies. This review consolidates current research on ion channels in hPSC-RPE cells, specifically Kir7.1, Bestrophin-1, CLC-2, and CaV1.3, providing a foundation for future research.

Oxidative Stress and Inflammation-Related mRNAs Are Elevated in Serum of a Finnish Wet AMD Cohort

Purpose

Localized diseases can be affected by and affect the systemic environment via blood circulation. In this study, we explored the differences in circulating serum mRNAs between patients with wet AMD (wAMD) and controls.

Methods

Blood samples were obtained from 60 Finnish patients with wAMD and 64 controls. After serum preparation and RNA sequencing, the count data was examined for differentially expressed genes (DEGs) and further checked for enriched molecular pathways and ontology terms as well as links to clinical data.

Results

We found many DEGs and some enriched pathways, including the inflammation and cell survival-associated pathway tumour necrosis factor alpha (TNF-α) signaling via nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). The related DEGs were oxidized low-density lipoprotein receptor 1 (OLR1), salt inducible kinase 1 (SIK1), and coagulation factor III (F3). DEGs from degradative macular and retinal processes were also examined, many of which were also related to cardiovascular disease and maintenance. Additionally, DEG counts were inspected in relation to clinical and anti-VEGF treatment parameters, and glutamine amidotransferase-like class 1 domain-containing 3A (GATD3A) levels were found to be significantly lower in patients with wAMD treated with anti-VEGF.

Conclusions

Differentially expressed systemic mRNAs that are linked to mitochondrial function, oxidative stress, and inflammation may have a role in the pathology of wAMD. Our observations provide new data for the understanding of the progression of wAMD.

The impact of 25-hydroxyvitamin D and calcium on risk of age-related macular degeneration: a Mendelian randomization study

BACKGROUND

The relationships between 25-hydroxyvitamin D [25(OH)D] and calcium and age-related macular degeneration (AMD) are unclear.

OBJECTIVES

This study aimed to investigate the causal role of 25(OH)D concentrations, calcium concentrations, and dietary supplements use of vitamin D and calcium on risk of AMD and its subtypes.

METHODS

Independent genetic variants associated with 25(OH)D and calcium concentrations were used as instrumental variables in published genome-wide association studies (GWASs) of European ancestry. The bidirectional 2-sample Mendelian randomization (MR) analyses were performed using summary-level data from the UK Biobank and FinnGen datasets. Sensitivity analyses were conducted to ensure the robustness of the MR results. The meta-analyses were conducted using both fixed-effect and random-effect models to provide comprehensive and reliable estimates.

RESULTS

A standard deviation increase in calcium concentrations was linked to a 14%, 17%, and 13% reduction in the likelihood of developing AMD (95% confidence interval [CI]: 0.77, 0.97), wet AMD (95% CI: 0.73, 0.95), and dry AMD (95% CI: 0.75, 1.00), respectively. No significant causal relationships were detected between genetically predicted 25(OH)D concentrations and AMD and its subtypes (all P > 0.05). The combined analyses showed that higher calcium concentrations were associated with a reduced risk of overall AMD, with an odds ratio of 0.89 (95% CI: 0.81, 0.98).

CONCLUSIONS

This study provides evidence supporting the causal relationship between calcium concentrations and risk of AMD and its subtypes, which may have important implications for the prevention, monitoring, and treatment of AMD.

The effects of time restricted feeding on age-related changes in the mouse retina

Dietary modifications such as caloric restriction (CR) and intermittent fasting (IF) have gained popularity due to their proven health benefits in aged populations. In time restricted feeding (TRF), a form of intermittent fasting, the amount of time for food intake is regulated without restricting the caloric intake. TRF is beneficial for the central nervous system to support brain health in the context of aging. Therefore, we here ask whether TRF also exerts beneficial effects in the aged retina. We compared aged mice (24 months) on a TRF paradigm (access to food for six hours per day) for either 6 or 12 months against young control mice (8 months) and aged control mice on an ad libitum diet. We examined changes in the retina at the functional (electroretinography), structural (histology and fluorescein angiograms) and molecular (gene expression) level. TRF treatment showed amelioration of age-related reductions in both scotopic and photopic b-wave amplitudes suggesting benefits for retinal interneuron signaling. TRF did not affect age-related signs of retinal inflammation or microglial activation at either the molecular or histological level. Our data indicate that TRF helps preserve some aspects of retinal function that are decreased with aging, adding to our understanding of the health benefits that altered feeding patterns may confer.

Natural L-type calcium channels antagonists from Chinese medicine

L-type calcium channels (LTCCs), the largest subfamily of voltage-gated calcium channels (VGCCs), are the main channels for Ca2+ influx during extracellular excitation. LTCCs are widely present in excitable cells, especially cardiac and cardiovascular smooth muscle cells, and participate in various Ca2+-dependent processes. LTCCs have been considered as worthy drug target for cardiovascular, neurological and psychological diseases for decades. Natural products from Traditional Chinese medicine (TCM) have shown the potential as new drugs for the treatment of LTCCs related diseases. In this review, the basic structure, function of LTCCs, and the related human diseases caused by structural or functional abnormalities of LTCCs, and the natural LTCCs antagonist and their potential usages were summarized.

Sequential Fabrication of a Three-Layer Retina-like Structure

Tissue engineering is considered a promising approach to treating advanced degenerative maculopathies such as nonexudative age-related macular degeneration (AMD), the leading cause of blindness worldwide. The retina consists of several hierarchical tissue layers, each of which is supported by a layer underneath. Each of these layers has a different morphology and requires distinct conditions for proper assembly. In fact, a prerequisite step for the assembly of each of these layers is the organization of the layer underneath. Advanced retinal degeneration includes degeneration of the other retina layers, including the choroid, the retinal pigmented epithelium (RPE), and the photoreceptors. Here, we report a step-by-step fabrication process of a three-layer retina-like structure. The process included the 3D printing of a choroid-like structure in an extracellular matrix (ECM) hydrogel, followed by deposition of the RPE monolayer. After the formation of the blood vessel-RPE interface, the photoreceptor cells were deposited to interact with the RPE layer. At the end of the fabrication process, each layer was characterized for its morphology and expression of specific markers, and the integration of the three-layer retina was evaluated. We envision that such a retina-like structure may be able to attenuate the deterioration of a degenerated retina and improve engraftment and regeneration. This retinal implant may potentially be suitable for a spectrum of macular degenerative diseases for which there are currently no cures and may save millions from complete blindness.