Research progress of iron metabolism in retinal diseases

Gypenoside A-loaded mPEG-PLGA nanoparticles ameliorate high-glucose-induced retinal microvasculopathy by inhibiting ferroptosis

Diabetic retinopathy (DR) is one of the chronic microvascular complications of type 2 diabetes mellitus (T2DM), which will cause retinal detachment and blindness without ideal therapies. Gypenoside A (GPA) are the main bioactive compound from Gynostemma pentaphyllum, and have various pharmacological effects. However, it suffered from poor bioavailability and potential cardiotoxicity in the clinical application. To overcome those limitations, in this study, nearly spherical nanoparticles (GPA-NP) with a mean particle size of 140.6 ± 22.4 nm were prepared by encapsulating GPA into mPEG-PLGA. This encapsulation efficiency was 84.4 ± 6.9 %, and the drug load was 4.02 %±0.35 %. The results showed that GPA-NP displayed more prolonged GPA release and higher bioavailability in vitro than GPA. GPA-NP obviously reduced the levels of oxidative stress markers and inflammatory cytokines in both retinal tissues of DR mice and high glucose-exposed HRMEC better than GPA alone. Mechanismly, GPA blocked the Nrf2-Keap1 interaction by binding with Kelch domain of Keap1 via alkyl and hydrogen bonds. Therefore, GPA-NP exerted more potent protectivity effects against high glucose-induced retinal microvascular endothelial ferroptosis in vitro and in vivo by activating Nrf2/HO-1/GPX4 pathway. It could be a promising therapeutic agent for preventing DR.

Selective detection of Fe3+ via fluorescent in real sample using aminoanthraquinone resorcin[4]arene-based receptors with logic gate application

Resorcin[4]arene based fluorescent sensors RES-AAQ containing eight anthraquinone groups as binding sites, were developed for very accurate and sensitive detection of Fe3+ metal ion. The motivation for this study lies in the need for advanced sensing techniques for precisely identifying Fe3+ ions. Due to its unique redox properties, Fe3+ plays a crucial role in biological processes, environmental remediation, medical diagnostics, and advanced detection methods. The sensors were extensively characterized using FT-IR, 1H NMR, 13C NMR, and ESI-MS techniques. The absorption spectra revealed significant interactions between RES-AAQ and Fe3+ ions. Fluorescence quenching was observed due to Photoinduced electron transfer (PET). The quenching process was systematically analyzed using Stern-Volmer analysis. Each sensor (L1, L2, L3, L4) demonstrated remarkable detection limits for Fe3+ ions (10.51 nM, 10.48 nM, 10.49 nM, 10.47 nM, respectively) along with substantial binding affinities (binding constants: 9.07x109 M-1, 1.19x109 M-1, 1.49x109 M-1 and 1.03x109 M-1 for L1, L2, L3, and L4, respectively). Traditional, Fe3+ detection methods often suffer from limitations such as complexity, lack of sensitivity, or interference from other metal ions. This research offers highly sensitive fluorescent sensors for Fe3+ detection with potential applications in human blood serum and tap water. Molecular docking, DFT studies, and ESI-MS investigation have been employed to gain insights into the binding interactions between the molecules. The low detection limits, high binding affinity, and real-world applicability highlight the significant advantages of developed sensors compared to existing methods. Additionally, a combinatorial logic gate was constructed to facilitate a proper understanding of the working principle of RES-AAQ.

Serum Iron Status and Retinal Degenerative Diseases: A Mendelian Randomization Study on AMD, RP, and DR

Background: Observational studies have noted that patients with certain retinal degenerative diseases exhibit iron disturbances in the retina or vitreous compared to healthy controls. However, the connection between serum iron status and these diseases remains unclear. This study aims to explore the potential causal relationship between serum iron status biomarkers and the development of age-related macular degeneration (AMD), retinitis pigmentosa (RP), and diabetic retinopathy (DR). Methods: A two-sample Mendelian randomization (MR) analysis was conducted to investigate the causal relationship between serum iron status and several retinal degenerative diseases. Genome-wide association study (GWAS) summary-level data were extracted from public GWAS databases. Inverse-variance weighting (IVW), MR-Egger regressions, Simple model, Weighted median, and Weight mode were used as MR methods. Sensitivity analysis was conducted to confirm the robustness of the results by examining horizontal pleiotropy and heterogeneity through MR-Egger intercept and leave-one-out analysis. Results: The MR analysis revealed causal relationships between genetically predicted serum iron status biomarkers and various retinal diseases. Transferrin was positively associated with the odds of AMD (whether dry or wet) (OR = 1.167, 95% CI = 1.045-1.304, p = 0.006) and wet AMD (OR = 1.194, 95% CI = 1.018-1.402, p = 0.030). Ferritin was negatively associated with the odds of wet AMD (OR = 0.555, 95% CI = 0.333-0.927, p = 0.024). Serum iron (OR = 0.508, 95% CI = 0.260-0.993, p = 0.048) and transferrin saturation (OR = 0.508, 95% CI = 0.260-0.993, p = 0.048) were negatively associated with the odds of RP. Conclusions: These findings provide evidence supporting a potential causal relationship between serum iron status and various retinal degenerative diseases, highlighting a direction for future research into the underlying mechanisms of these diseases.

Recent Advances in Nanomedicine for Ocular Fundus Neovascularization Disease Management

As an indispensable part of the human sensory system, visual acuity may be impaired and even develop into irreversible blindness due to various ocular pathologies. Among ocular diseases, fundus neovascularization diseases (FNDs) are prominent etiologies of visual impairment worldwide. Intravitreal injection of anti-vascular endothelial growth factor drugs remains the primary therapy but is hurdled by common complications and incomplete potency. To renovate the current therapeutic modalities, nanomedicine emerged as the times required, which is endowed with advanced capabilities, able to fulfill the effective ocular fundus drug delivery and achieve precise drug release control, thus further improving the therapeutic effect. This review provides a comprehensive summary of advances in nanomedicine for FND management from state-of-the-art studies. First, the current therapeutic modalities for FNDs are thoroughly introduced, focusing on the key challenges of ocular fundus drug delivery. Second, nanocarriers are comprehensively reviewed for ocular posterior drug delivery based on the nanostructures: polymer-based nanocarriers, lipid-based nanocarriers, and inorganic nanoparticles. Thirdly, the characteristics of the fundus microenvironment, their pathological changes during FNDs, and corresponding strategies for constructing smart nanocarriers are elaborated. Furthermore, the challenges and prospects of nanomedicine for FND management are thoroughly discussed.