Systemic Administration of Pegylated Arginase-1 Attenuates the Progression of Diabetic Retinopathy

Preserving blood-retinal barrier integrity: a path to retinal ganglion cell protection in glaucoma and traumatic optic neuropathy

Retinal ganglion cells (RGCs) are the visual gateway of the brain, with their axons converging to form the optic nerve, making them the most vulnerable target in diseases such as glaucoma and traumatic optic neuropathy (TON). In both diseases, the disruption of the blood-retinal barrier(BRB) is considered an important mechanism that accelerates RGC degeneration and hinders axon regeneration. The BRB consists of the inner blood-retinal barrier (iBRB) and the outer blood-retinal barrier (oBRB), which are maintained by endothelial cells(ECs), pericytes(PCs), and retinal pigment epithelial (RPE), respectively. Their functions include regulating nutrient exchange, oxidative stress, and the immune microenvironment. However, in glaucoma and TON, the structural and functional integrity of the BRB is severely damaged due to mechanical stress, inflammatory reactions, and metabolic disorders. Emerging evidence highlights that BRB disruption leads to heightened vascular permeability, immune cell infiltration, and sustained chronic inflammation, creating a hostile microenvironment for RGC survival. Furthermore, the dynamic interplay and imbalance among ECs, PCs, and glial cells within the neurovascular unit (NVU) are pivotal drivers of BRB destruction, exacerbating RGC apoptosis and limiting optic nerve regeneration. The intricate molecular and cellular mechanisms underlying these processes underscore the BRB's critical role in glaucoma and TON pathophysiology while offering a compelling foundation for therapeutic strategies targeting BRB repair and stabilization. This review provides crucial insights and lays a robust groundwork for advancing research on neural regeneration and innovative optic nerve protective strategies.

Multi-Omics Integration With Machine Learning Identified Early Diabetic Retinopathy, Diabetic Macula Edema and Anti-VEGF Treatment Response

Purpose

Identify optimal metabolic features and pathways across diabetic retinopathy (DR) stages, develop risk models to differentiate diabetic macular edema (DME), and predict anti-vascular endothelial growth factor (anti-VEGF) therapy response.

Methods

We analyzed 108 aqueous humor samples from 78 type 2 diabetes mellitus patients and 30 healthy controls. Ultra-high-performance liquid chromatography-high-resolution-mass-spectrometry detected lipidomics and metabolomics profiles. DME patients received ≥3 anti-VEGF treatments, categorized into strong and weak response groups. Machine learning (ML) screened prospective metabolic features, developing prediction models.

Results

Key metabolic features identified in the metabolomics and lipidomics datasets included n-acetyl isoleucine (odds ratio [OR] = 1.635), cis-aconitic acid (OR = 3.296), and ophthalmic acid (OR = 0.836) for DR. For early-DR, n-acetyl isoleucine (OR = 1.791) and decaethylene glycol (PEG-10) (OR = 0.170) were identified as key markers. L-kynurenine (OR = 0.875), niacinamide (OR = 0.843), and linoleoyl ethanolamine (OR = 0.941) were identified as significant indicators for DME. Trigonelline (OR = 1.441) and 4-methylcatechol-2-sulfate (OR = 1.121) emerged as predictors for strong response to anti-VEGF. Predictive models achieved R² values of 99.9%, 97.7%, 93.9%, and 98.4% for DR, early-DR, DME, and strong response groups in the calibration set, respectively, and validated well with R² values of 96.3%, 96.8%, 79.9%, and 96.3%.

Conclusions

This research used ML to identify differential metabolic features from metabolomics and lipidomics datasets in DR patients. It implies that metabolic indicators can effectively predict early disease progression and potential weak responders to anti-VEGF therapy in DME eyes.

Translational Relevance

The identified metabolic indicators may aid in predicting the early progression of DR and optimizing therapeutic strategies for DME.

Arginine deprivation/citrulline augmentation with ADI-PEG20 as novel therapy for complications in type 2 diabetes

OBJECTIVE

Chronic inflammation and oxidative stress mediate the pathological progression of diabetic complications, like diabetic retinopathy (DR), peripheral neuropathy (DPN) and impaired wound healing. Studies have shown that treatment with a stable form of arginase 1 that reduces l-arginine levels and increases ornithine and urea limits retinal injury and improves visual function in DR. We tested the therapeutic efficacy of PEGylated arginine deiminase (ADI-PEG20) that depletes l-arginine and elevates l-citrulline on diabetic complications in the db/db mouse model of type 2 diabetes (T2D).

METHODS

Mice received intraperitoneal (IP), intramuscular (IM), or intravitreal (IVT) injections of ADI-PEG20 or PEG20 as control. Effects on body weight, fasting blood glucose levels, blood-retinal-barrier (BRB) function, visual acuity, contrast sensitivity, thermal sensitivity, and wound healing were determined. Studies using bone marrow-derived macrophages (BMDM) examined the underlying signaling pathway.

RESULTS

Systemic injections of ADI-PEG20 reduced body weight and blood glucose and decreased oxidative stress and inflammation in db/db retinas. These changes were associated with improved BRB and visual function along with thermal sensitivity and wound healing. IVT injections of either ADI-PEG20, anti-VEGF antibody or their combination also improved BRB and visual function. ADI-PEG20 treatment also prevented LPS/IFNℽ-induced activation of BMDM in vitro as did depletion of l-arginine and elevation of l-citrulline.

CONCLUSIONS/INTERPRETATION

ADI-PEG20 treatment limited signs of DR and DPN and enhanced wound healing in db/db mice. Studies using BMDM suggest that the anti-inflammatory effects of ADI-PEG20 involve blockade of the JAK2-STAT1 signaling pathway via l-arginine depletion and l-citrulline production.

Human umbilical cord derived mesenchymal stem cells overexpressing HO-1 attenuate neural injury and enhance functional recovery by inhibiting inflammation in stroke mice

AIMS

The current evidence demonstrates that mesenchymal stem cells (MSCs) hold therapeutic potential for ischemic stroke. However, it remains unclear how changes in the secretion of MSC cytokines following the overexpression of heme oxygenase-1 (HO-1) impact excessive inflammatory activation in a mouse ischemic stroke model. This study investigated this aspect and provided further insights.

METHODS

The middle cerebral artery occlusion (MCAO) mouse model was established, and subsequent injections of MSC, MSCHO-1 , or PBS solutions of equal volume were administered via the mice's tail vein. Histopathological analysis was conducted on Days 3 and 28 post-MCAO to observe morphological changes in brain slices. mRNA expression levels of various factors, including IL-1β, IL-6, IL-17, TNF-α, IL-1Ra, IL-4, IL-10, TGF-β, were quantified. The effects of MSCHO-1 treatment on neurons, microglia, and astrocytes were observed using immunofluorescence after transplantation. The polarization direction of macrophages/microglia was also detected using flow cytometry.

RESULTS

The results showed that the expression of anti-inflammatory factors in the MSCHO-1 group increased while that of pro-inflammatory factors decreased. Small animal fluorescence studies and immunofluorescence assays showed that the homing function of MSCsHO-1 was unaffected, leading to a substantial accumulation of MSCsHO-1 in the cerebral ischemic region within 24 h. Neurons were less damaged, activation and proliferation of microglia were reduced, and polarization of microglia to the M2 type increased after MSCHO-1 transplantation. Furthermore, after transplantation of MSCsHO-1 , the mortality of mice decreased, and motor function improved significantly.

CONCLUSION

The findings indicate that MSCs overexpressing HO-1 exhibited significant therapeutic effects against hyper-inflammatory injury after stroke in mice, ultimately promoting recovery after ischemic stroke.

Alteration in mitochondrial dynamics promotes the proinflammatory response of microglia and is involved in cerebellar dysfunction of young and aged mice following LPS exposure

Cerebellar dysfunction is implicated in impaired motor coordination and balance, thus disturbing the dynamics of sensorimotor integration. Neuroinflammation and aging could be prominent contributors to cerebellar aberration. Additionally, changes in mitochondrial dynamics may precede microglia activation in several chronic neurodegenerative diseases; however, the underlying mechanism remains largely unknown.Here using LPS (1 mg/kg i.p. for four consecutive days) stimulation in both young (3 months old) and aged (12 months old) mice, followed by molecular analysis on the 21st day, we have explored the correlation between aging and mitochondrial dynamic alteration in the backdrop of chronic neuroinflammation. Following LPS stimulation, we observed microglia activation and subsequent elevation in proinflammatory cytokines (M1; TNF-α, IFN-γ) with NLRP3 activationand a concomitant reduction in the expression of anti-inflammatory markers (M2; YM1, TGF-β1) in the cerebellar tissue of aged mice compared with the young LPS and aged controls. Remarkably, senescence (p21, p27, p53) and epigenetic (HDAC2) markers were found upregulated in the cerebellum tissue of the aged LPS group, suggesting their crucial role in LPS-induced cerebellar deficit. Further, we demonstrated alteration in the antagonistic forces of mitochondrial fusion and fission with increased expression of the mitochondrial fission-related gene [FIS1] and decreased fusion-related genes [MFN1 and MFN2]. We noted increased mtDNA copy number, microglia activation, and inflammatory response of IL1β and IFN-γ post-chronic neuroinflammation in aged LPS group. Our results suggest that the crosstalk between mitochondrial dynamics and altered microglial activation paradigm in chronic neuroinflammatory conditions may be the key to understanding the cerebellar molecular mechanism.