Vitamin B3 modulates mitochondrial vulnerability and prevents glaucoma in aged mice

Excitatory and inhibitory neurotransmitter alterations with advancing age and injury in the mouse retina

Increasing age and elevated intraocular pressure (IOP) are the two major risk factors for glaucoma, the most common cause of irreversible blindness worldwide. Accumulating evidence is pointing to metabolic failure predisposing to neuronal loss with advancing age and IOP injury. Many neurotransmitters are synthesized from endogenous metabolites and are essential for correct cell to cell signaling along the visual pathways. We performed detailed, small molecule metabolomic profiling of the aging mouse retina and further explored the impact of IOP elevation at different ages. The resultant metabolomic profiles showed clear discrimination between young and middle-aged retinas and these changes are accentuated following eye pressure elevation. Alterations in glutamate and Gamma-aminobutyric acid (GABA) related metabolites were the most apparent changes with advancing age with further reductions in GABA and related pathways after IOP elevation. These changes were further confirmed using immunohistochemistry and patch-clamp electrophysiological recording experiments.

"Optic nerve of steel": A case of very high intraocular pressures with markedly little visual field progression over years

Purpose

We report a case of pseudoexfoliation glaucoma with exceedingly high intraocular pressures (IOP) but limited visual field progression despite poor adherence with treatment over a 7-year period.

Observation

A 67-year-old Eastern European female presented to the emergency room with an IOP of 52 mmHg OD and exam findings consistent with pseudoexfoliation glaucoma. Subsequent testing demonstrated superior and inferior arcuate deficits on Humphrey visual field (HVF) testing and corresponding thinning of optic nerve OD. The patient was very inconsistent with topical glaucoma medications, and after undergoing selective laser trabeculoplasty she was lost to follow-up without any additional treatment. She returned one year later with an IOP of 59 mmHg, but remarkably stable HVF. The patient refused to restart glaucoma drops and elected instead to proceed with a trabeculectomy OD, which was successfully performed, with the final visual acuity of 20/25 and IOP of 20 mmHg OD. The patient was again lost to follow-up for three years. Her IOP was 40 mmHg OD on return to clinic, but her glaucoma testing revealed very little progression. She decided to pursue placement of glaucoma drainage device (Baerveldt 350) OD, and her IOP was 18 mmHg OD after 6 months on no medications. The patient was lost to follow-up thereafter.

Conclusions

The limited visual field progression with chronically high IOP over years strongly argues in favor of IOP-independent mechanisms contributing to pathophysiology of glaucoma. This case also highlights the importance of longitudinal monitoring and tailoring glaucoma therapy holistically to individual patient circumstances.

Dysfunctional one-carbon metabolism identifies vitamins B6, B9, B12, and choline as neuroprotective in glaucoma

Glaucoma, characterized by the loss of retinal ganglion cells (RGCs), is a leading cause of blindness for which there are no neuroprotective therapies. To explore observations of elevated homocysteine in glaucoma, we elevate vitreous homocysteine, which increases RGC death by 6% following ocular hypertension. Genetic association with higher homocysteine does not affect glaucoma-associated outcomes from the UK Biobank and serum homocysteine levels have no effect on glaucomatous visual field progression. This supports a hypothesis in which elevated homocysteine is a pathogenic, rather than causative, feature of glaucoma. Further exploration of homocysteine metabolism in glaucoma animal models demonstrates early and sustained dysregulation of genes involved in one-carbon metabolism and the interaction of essential cofactors and precursors (B6, B9, B12, and choline) in whole retina and optic nerve head and RGCs. Supplementing these provides neuroprotection in an acute model and prevents neurodegeneration and protects visual function in a chronic model of glaucoma.

TLR4 deficiency does not alter glaucomatous progression in a mouse model of chronic glaucoma

Glaucoma is a leading cause of irreversible blindness worldwide. Toll-like receptor 4 (TLR4) is a pattern-recognition transmembrane receptor that induces neuroinflammatory processes in response to injury. Tlr4 is highly expressed in ocular tissues and is known to modulate inflammatory processes in both anterior and posterior segment tissues. TLR4 activation can lead to mitochondrial dysfunction and metabolic deficits in inflammatory disorders. Due to its effects on inflammation and metabolism, TLR4 is a candidate to participate in glaucoma pathogenesis. It has been suggested as a therapeutic target based on studies using acute models, such as experimentally raising IOP to ischemia-inducing levels. Nevertheless, its role in chronic glaucoma needs further evaluation. In the current study, we investigated the role of TLR4 in an inherited mouse model of chronic glaucoma, DBA/2J. To do this, we analyzed the effect of Tlr4 knockout (Tlr4-/-) on glaucoma in DBA/2J mice. Our studies found no significant differences in intraocular pressure, iris disease, or glaucomatous progression in Tlr4-/- compared to Tlr4+/+ DBA/2J mice. Our data do not support a role for TLR4 as a treatment target in chronic glaucoma.

B vitamins as adjunct therapies for depressive disorder

The rising prevalence of depressive disorder worldwide requires better interventional avenues. B vitamins are gaining increasing interest as potential therapeutic approaches in this context given current evidence for a bidirectional association between B vitamin deficiency and depressive disorder. We discuss how B vitamins and B vitamin-associated probiotic supplementation may represent an effective adjunctive treatment for depression, and highlight the key metabolic mechanisms involved. We also provide a perspective on the future of this field and advocate for further high-quality clinical trials to assess the benefits of B vitamins in this context and optimize their clinical implementation.

Accelerated Epigenetic Aging Is Associated with Faster Glaucoma Progression: A DNA Methylation Study

PURPOSE

To investigate the association between epigenetic age acceleration and glaucoma progression.

DESIGN

Retrospective cohort study.

PARTICIPANTS

A total of 100 patients with primary open-angle glaucoma (POAG) with fast progression and 100 patients with POAG with slow progression.

METHODS

Patients were classified as fast or slow progressors based on rates of change in standard automated perimetry (SAP) mean deviation (MD) and retinal nerve fiber layer (RNFL) thickness. Epigenetic age was calculated using the Horvath, Hannum, PhenoAge, and GrimAge clocks from DNA methylation profiles obtained from blood samples. Age acceleration was defined as the residual from a linear regression of epigenetic age on chronologic age, with positive values suggesting faster biological aging. Multivariable logistic regression models estimated the association between age acceleration and likelihood of fast progression, adjusting for confounders.

MAIN OUTCOME MEASURES

Difference in epigenetic age acceleration between fast and slow glaucoma progressors.

RESULTS

The mean rate of SAP MD change in the fastest progressing eye was -1.06 dB/year (95% confidence interval [CI], -1.28 to -0.85 dB/year) for fast progressors compared with -0.10 dB/year (95% CI, -0.16 to -0.04 dB/year) for slow progressors (P < 0.001). For RNFL thickness, corresponding values were -1.60 μm/year (95% CI, -1.97 to -1.23 μm/year) and -0.76 μm/year (95% CI, -1.04 to -0.48 μm/year), respectively (P < 0.001). Fast progressors demonstrated significantly greater age acceleration compared with slow progressors for the Horvath clock (mean difference, 2.93 years; 95% CI, 1.48-4.39 years; P < 0.001) and Hannum clock (mean difference, 1.24 years; 95% CI, 0.03-2.46 years; P = 0.045). In multivariable models, each year of Horvath age acceleration was associated with 15% higher odds of fast progression (odds ratio, 1.15; 95% CI, 1.07-1.23; P < 0.001). Hannum and GrimAge clocks also showed significant associations with fast progression. The association between age acceleration and fast progression was stronger in those with relatively low IOP during follow-up.

CONCLUSIONS

Accelerated epigenetic aging was associated with faster glaucoma progression. These findings suggest that faster biological age, as reflected in DNA methylation, may increase optic nerve susceptibility to damage, highlighting epigenetic age as a potential prognostic biomarker.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Pyruvate and related energetic metabolites modulate resilience against high genetic risk for glaucoma

A glaucoma polygenic risk score (PRS) can effectively identify disease risk, but some individuals with high PRS do not develop glaucoma. Factors contributing to this resilience remain unclear. Using 4,658 glaucoma cases and 113,040 controls in a cross-sectional study of the UK Biobank, we investigated whether plasma metabolites enhanced glaucoma prediction and if a metabolomic signature of resilience in high-genetic-risk individuals existed. Logistic regression models incorporating 168 NMR-based metabolites into PRS-based glaucoma assessments were developed, with multiple comparison corrections applied. While metabolites weakly predicted glaucoma (Area Under the Curve = 0.579), they offered marginal prediction improvement in PRS-only-based models (p=0.004). We identified a metabolomic signature associated with resilience in the top glaucoma PRS decile, with elevated glycolysis-related metabolites-lactate (p=8.8E-12), pyruvate (p=1.9E-10), and citrate (p=0.02)-linked to reduced glaucoma prevalence. These metabolites combined significantly modified the PRS-glaucoma relationship (Pinteraction = 0.011). Higher total resilience metabolite levels within the highest PRS quartile corresponded to lower glaucoma prevalence (Odds Ratiohighest vs. lowest total resilience metabolite quartile=0.71, 95% Confidence Interval = 0.64-0.80). As pyruvate is a foundational metabolite linking glycolysis to tricarboxylic acid cycle metabolism and ATP generation, we pursued experimental validation for this putative resilience biomarker in a human-relevant Mus musculus glaucoma model. Dietary pyruvate mitigated elevated intraocular pressure (p=0.002) and optic nerve damage (p<0.0003) in Lmx1bV265D mice. These findings highlight the protective role of pyruvate-related metabolism against glaucoma and suggest potential avenues for therapeutic intervention.

Valproic acid prevents NMDA-induced retinal degeneration in marmosets

Valproic acid (VPA) is a prescribed drug widely used for treatment of epilepsy, mood disorders, migraines and neuropathic pain. Accumulating evidence suggests that VPA possess neuroprotective properties. Glaucoma, one of the leading causes of vision loss in the world, is characterized by progressive degeneration of retinal ganglion cells (RGCs) and their axons. Intravitreal injection of N-methyl-D-aspartate (NMDA) is well studied in rodents as an acute model of RGC death. In the present study, we first investigated whether NMDA induced retinal degeneration in non-human primate common marmosets as the structure and function of the eye is similar to that of humans. We found that NMDA had no effects on intraocular pressure but induced retinal degeneration by using optical coherence tomography and multifocal electroretinogram, both of which are non-invasive methods. In addition, VPA treatment suppressed acute retinal degeneration and ameliorated visual impairment in marmosets. Our findings raise intriguing possibilities that VPA may be useful for preventing RGC death and suggest that the marmoset is a useful animal model for studying glaucoma.

Profiling of the Peripheral Blood Mononuclear Cells Proteome by Shotgun Proteomics Identifies Alterations of Immune System Components, Proteolytic Balance, Autophagy, and Mitochondrial Metabolism in Glaucoma Subjects

Glaucoma is a chronic optic neuropathy and is the second cause of irreversible blindness worldwide. Although the pathogenesis of the disease is not fully understood, the death of retinal ganglion cells and degeneration of the optic nerve are likely promoted by a combination of local and systemic factors. Growing attention has been paid to nonintraocular pressure risk factors, including mechanisms of inflammation and neuroinflammation. Phenotypical and molecular alterations of circulating immune cells, in particular, lymphocyte subsets, have been documented in murine models of glaucoma and in human subjects. Very recently, oxygen consumption rate and nicotinamide adenine dinucleotide levels of human peripheral blood mononuclear cells (PBMC) have been proposed as biomarkers of disease progression, thus suggesting that immune cells of glaucoma subjects present severe molecular and metabolic alterations. In this framework, this pilot study aimed to be the first to characterize global proteome perturbations of PBMC of patients with primary open-angle glaucoma (POAG) compared to nonglaucomatous controls (control) by shotgun proteomics. The approach identified >4,500 proteins and a total of 435 differentially expressed proteins between POAG and control subjects. Clustering and rationalization of proteomic data sets and immunodetection of selected proteins by Western blotting highlighted significant alterations of immune system compartments (i.e., complement factors, regulators of immune functions, and lymphocyte activation) and pathways serving key roles for immune system such as proteolysis (i.e., matrix metalloproteinases and their inhibitors), autophagy (i.e., beclin-1 and LC3B), cell proliferation (Bcl2), mitochondrial (i.e., sirtuin), and energetic/redox metabolism (i.e., NADK). Based on these findings, this proteomic study suggests that circulating immune cells suffer from heterogeneous alterations of central pathways involved in cell metabolism and homeostasis. Larger, properly designed studies are required to confirm specifically how immune cellular alterations may be involved in the pathogenesis of both neuroinflammation and glaucomatous disease.

Neuroprotection beyond intraocular pressure: game changer or quiet addiction

The topic of neuroprotection in glaucoma and age-related macular degeneration (AMD) is well disseminated in the literature. However, the problem is providing ophthalmologists with clear, evidence-based messages to draw on. This review examines the landscape of neuroprotective therapies for glaucoma and AMD. While promising neuroprotective agents, such as citicoline and nicotinamide, have been explored for their potential to mitigate neurodegeneration in glaucoma, robust clinical evidence validating their efficacy remains limited and there is a need for further large-scale, long-term studies to substantiate the neuroprotective effects of these agents. Maintaining low intraocular pressure plays a vital role in preventing neuronal death in glaucoma. AMD has traditionally been considered a disease affecting the outer retinal layers; however, growing evidence suggests that the inner layers are also involved. Neuroprotection is an emerging area of research, with strategies focusing on alleviating oxidative stress, inflammation and apoptosis. A reassessment of clinical endpoints and methodologies in neuroprotection research is critical to better evaluate the efficacy of these therapies in glaucoma and AMD.

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.

Cellular senescence and glaucoma

Cellular senescence, a characteristic feature of the aging process, is induced by diverse stressors. In recent years, glaucoma has emerged as a blinding ocular disease intricately linked to cellular senescence. The principal pathways implicated are oxidative stress, mitochondrial dysfunction, DNA damage, autophagy impairment, and the secretion of various senescence- associated secretory phenotype factors. Research on glaucoma-associated cellular senescence predominantly centers around the increased resistance of the aqueous humor outflow pathway, which is attributed to the senescence of the trabecular meshwork and Schlemm's canal. Additionally, it focuses on the mechanisms underlying retinal ganglion cell senescence in glaucoma and the corresponding intervention measures. Given that cell senescence represents an irreversible phase preceding cell death, an in-depth investigation into its mechanisms in the pathogenesis and progression of glaucoma, particularly by specifically blocking the signal transduction of cell senescence, holds the potential to decrease the outflow resistance of aqueous humor. This, in turn, could provide a novel avenue for safeguarding the optic nerve in glaucoma.

Targeted Neuroprotection of Retinal Ganglion Cells Via AAV2-hSyn-NGF Gene Therapy in Glaucoma Models

Purpose

The purpose of this study was to evaluate the neuroprotective effects of delivering nerve growth factor (NGF) to retinal ganglion cells (RGCs) through adeno-associated virus serotype 2 (AAV2) carrying a neuronal-specific human synapsin (hSyn) promoter.

Methods

AAV2-hSyn-NGF was injected intravitreally in three glaucoma models: optic nerve crush (ONC), microbead-induced ocular hypertension (MB), and genetic glaucoma model (DBA). Quantitative polymerase chain reaction (qPCR) and enzyme-linked immunosorbent assay (ELISA) determined the optimal injection concentration of AAV vector. Flow cytometry monitored immune responses. Transduction efficiency was quantified using green fluorescent protein (GFP) co-localization with RGC-specific marker RNA-binding protein with multiple splicing (RBPMS). The RGCs' density, retinal nerve fiber density, ganglion cell complex thickness, and positive scotopic threshold response (pSTR) were measured to assess structural and functional outcomes of the RGCs. Non-parametric Mann-Whitney U tests or Kruskal-Wallis tests were utilized to ascertain the statistical significance (P < 0.05).

Results

The optimal concentration of AAV vector for intravitreal injection was determined to be 1 × 1010 vector particles (VPs) per eye. The use of the hSyn promoter significantly enhanced targeting specificity to RGCs, resulting in a transduction efficiency of 46.64% ± 2.18%. Administration of AAV2-hSyn-NGF effectively preserved the RGCs' density, nerve fiber layer integrity, and the thickness of ganglion cell complex, while maintaining the RGCs' function across three glaucoma models. Furthermore, this gene delivery system did not elicit detectable immune responses or structural damage to the retina.

Conclusions

The AAV2-hSyn-NGF gene therapy offers a safe and effective neuroprotective strategy for RGCs across multiple glaucoma models, making it a promising candidate for future clinical trials in patients with glaucoma.

Vitamin K1 Alleviates Retinal Inflammation Following Acute Ocular Hypertension by Modulating Microglial Ferroptosis

Purpose

Glaucoma is the leading cause of irreversible blindness worldwide and encompasses a group of diseases characterized by optic nerve atrophy and visual field defects. Acute intraocular pressure (IOP) elevation is a key driver of retinal inflammation and optic nerve damage, often accompanied by microglial activation and dysregulated ferroptosis pathways. Vitamin K1, a fat-soluble vitamin, possesses anti-inflammatory and antioxidant properties, and has the potential to regulate ferroptosis. However, its mechanisms in alleviating retinal inflammation following acute IOP elevation remain unclear.

Methods

In vivo, we established a mouse model of acute ocular hypertension to evaluate the protective effects of vitamin K1 on the retina and visual function. Transcriptome sequencing was used to explore the underlying mechanisms by which vitamin K1 exerts its effects. Immunofluorescence and Western blot were used to assess retinal inflammation and observe ferroptosis in microglia. In vitro, we developed a BV2 cell OGDR model to investigate the regulatory effects of vitamin K1 on iron metabolism and inflammation in microglia.

Results

Our findings demonstrated that acute IOP elevation led to microglial activation, along with iron overload and ferroptosis in microglia. Further analyses revealed that microglial ferroptosis was accompanied by an upregulation of inflammatory cytokine gene expression and protein levels. Vitamin K1 intervention, however, inhibited microglial ferroptosis, alleviated retinal inflammation, minimized retinal ganglion cell (RGC) loss, and protected visual function.

Conclusions

In conclusion, this study demonstrates that vitamin K1 exerts a protective effect by modulating microglial ferroptosis, thereby alleviating acute ocular hypertension-induced retinal inflammation.

Astrocytes in the mouse brain respond bilaterally to unilateral retinal neurodegeneration

Glaucomatous optic neuropathy, or glaucoma, is the world's primary cause of irreversible blindness. Glaucoma is comorbid with other neurodegenerative diseases, but how it might impact the environment of the full central nervous system to increase neurodegenerative vulnerability is unknown. Two neurodegenerative events occur early in the optic nerve, the structural link between the retina and brain: loss of anterograde transport in retinal ganglion cell (RGC) axons and early alterations in astrocyte structure and function. Here, we used whole-mount tissue clearing of full mouse brains to image RGC anterograde transport function and astrocyte responses across retinorecipient regions early in a unilateral microbead occlusion model of glaucoma. Using light sheet imaging, we found that RGC projections terminating specifically in the accessory optic tract are the first to lose transport function. Although degeneration was induced in one retina, astrocytes in both brain hemispheres responded to transport loss in a retinotopic pattern that mirrored the degenerating RGCs. A subpopulation of these astrocytes in contact with large descending blood vessels were immunopositive for LCN2, a marker associated with astrocyte reactivity. Together, these data suggest that even early stages of unilateral glaucoma have broad impacts on the health of astrocytes across both hemispheres of the brain, implying a glial mechanism behind neurodegenerative comorbidity in glaucoma.

Energetic diversity in retinal ganglion cells is modulated by neuronal activity and correlates with resilience to degeneration

Neuronal function requires high energy expenditure that is likely customized to meet specific signaling demands. However, little is known about diversity of metabolic homeostasis among divergently-functioning types of neurons. To this end, we examined retinal ganglion cells (RGCs), a population of closely related, yet electrophysiologically distinct excitatory projection neurons. Using in vivo 2-photon imaging to measure ATP with single cell resolution, we identified differential homeostatic energy maintenance in the RGC population that correspond to distinct RGC types. In the presence of circuit activity, the most active RGC type (Alpha RGCs), had lower homeostatic ATP levels than other types and exhibited the greatest magnitude of ATP decline when ATP synthesis was inhibited. By simultaneously manipulating circuit activity and mitochondrial function, we found that while oxidative phosphorylation was required to meet ATP demands during circuit activity, it was expendable to maintain resting ATP levels. We also examined ATP signatures associated with survival and injury response after axotomy and report a correlation between low homeostatic ATP and increased survival. In addition, we observed transient ATP increases in RGCs following axon injury. Together, these findings identify diversity of energy handling capabilities of dynamically active neurons with implications for neuronal resilience.

Pyruvate and Related Energetic Metabolites Modulate Resilience Against High Genetic Risk for Glaucoma

A glaucoma polygenic risk score (PRS) can effectively identify disease risk, but some individuals with high PRS do not develop glaucoma. Factors contributing to this resilience remain unclear. Using 4,658 glaucoma cases and 113,040 controls in a cross-sectional study of the UK Biobank, we investigated whether plasma metabolites enhanced glaucoma prediction and if a metabolomic signature of resilience in high-genetic-risk individuals existed. Logistic regression models incorporating 168 NMR-based metabolites into PRS-based glaucoma assessments were developed, with multiple comparison corrections applied. While metabolites weakly predicted glaucoma (Area Under the Curve=0.579), they offered marginal prediction improvement in PRS-only-based models (P=0.004). We identified a metabolomic signature associated with resilience in the top glaucoma PRS decile, with elevated glycolysis-related metabolites-lactate (P=8.8E-12), pyruvate (P=1.9E-10), and citrate (P=0.02)-linked to reduced glaucoma prevalence. These metabolites combined significantly modified the PRS-glaucoma relationship (P interaction =0.011). Higher total resilience metabolite levels within the highest PRS quartile corresponded to lower glaucoma prevalence (Odds Ratio highest vs. lowest total resilience metabolite quartile =0.71, 95% Confidence Interval=0.64-0.80). As pyruvate is a foundational metabolite linking glycolysis to tricarboxylic acid cycle metabolism and ATP generation, we pursued experimental validation for this putative resilience biomarker in a human-relevant Mus musculus glaucoma model. Dietary pyruvate mitigated elevated intraocular pressure (P=0.002) and optic nerve damage (P<0.0003) in Lmx1b V265D mice. These findings highlight the protective role of pyruvate-related metabolism against glaucoma and suggest potential avenues for therapeutic intervention.

Oral nicotinic acid administration effect on lipids, thyroid hormones, and oxidative stress in intact adult dogs

BACKGROUND

Nicotinic acid (niacin, Vitamin B3) is one of the most effective medicines for improving high-density lipoprotein concentrations. Obesity and related diseases are life-threatening to dogs. This study investigated the niacin effect on triglyceride, cholesterol, lipoproteins, thyroid hormones, oxidative stress, and lipid peroxidation in intact adult dogs. Blood samples were taken from seven healthy, intact adult dogs as a control group (day 0). Then, the animals received 1000 mg/dog of oral nicotinic acid tab daily for 42 days, and blood sampling was performed on days 14, 28, 42, and 56.

RESULT

The results showed an increasing trend in high-density lipoprotein (HDL) concentration. The highest HDL concentration (138.85 ± 43.72 mg/dl) was related to day 56; the HDL level followed a statistically significant increase between day 14 and 56. Unlike HDL, there was a decreasing trend in low-density lipoprotein (LDL) concentration. The lowest LDL concentration (21.85 ± 18.60 mg/dl) was related to day 56. The concentration of apolipoprotein A-I (apoA1) was significantly increased during the study. The highest concentration of apoA1 (1.66 ± 0.06 g/l) was on day 42. There was a significant increase in apoA1 concentrations between days 0 and 14, 42, and 56. The apoA1 was significantly increased between days 14 and 42 and 56. The apoA1 followed a statistically significant increase between days 28 and 42. Changes in thyroid hormone levels did not show any constant increasing or decreasing trend. On day 14, a decreasing trend in the concentrations of TT4, FT4, and T3 was observed. However, an increasing trend was detected in the concentrations of TT4, FT4, and T3 on days 28 and 42. However, the increase in the concentrations of TT4 and FT4 was less than that on day 0. After treatment (day 56), a decreasing trend was observed in thyroid hormone concentrations. The negative correlation was detected between apoA1 and triiodothyronine (T3), total thyroxine T4 (TT4)), and free T4 (FT4) concentrations on day 42. Furthermore, a significant negative relationship was observed between HDL and T4 on day 42. However, the relationship between triglyceride and T3 was statistically positive on day 14. There was an increasing trend in serum total antioxidant capacity (TAC). The highest TAC concentration (3.83 ± 0.62 µmol /l) was on day 56; however, the malondialdehyde (MDA) concentration was decreased during the study. The total antioxidant level followed a statistically significant increase between days 0 and 56 compared to days 14 and 42.

CONCLUSION

The study demonstrated the efficacy of nicotinic acid in improving serum HDL, apoA1, and TAC, as well as decreasing serum MDA and LDL concentrations.

Evaluating the impact of caloric restriction, body mass index and exercise on primary open-angle glaucoma: A review

This literature review evaluates any possible links between primary open-angle glaucoma (POAG) and caloric restriction (CR), body mass index (BMI), and exercise, aiming to map the extent of the literature. Its primary objective is to recognise the nature and breadth of research evidence, identify possible gaps in these topics and develop future studies. The databases searched were MEDLINE (PudMed), Scopus and ScienceDirect, in April 2023 for articles published in English, with no date restriction. A total of 447 search results were retrieved. Of these, 73 were related to CR, 249 to BMI, and 125 to exercise. Records identified included systematic reviews, meta-analyses, randomised controlled trials, cohort studies and animal studies. CR has been shown to halt the degeneration of retinal ganglion cells and protect against various glaucomatous processes in animal models. Low BMI has been shown to be associated with an increased risk of POAG and a faster rate of visual field deterioration in POAG. However, the association between high BMI and POAG is not consistent. Exercise has been shown to cause mechanical, vascular, and neurobiological changes affecting the pathophysiology of POAG. The present review helps identify key characteristics and factors relating to the impacts of CR, BMI, or exercise on POAG.

Genetic and pharmacological correction of impaired mitophagy in retinal ganglion cells rescues glaucomatous neurodegeneration

Progressive loss of retinal ganglion cells (RGCs) and degeneration of optic nerve axons are the pathological hallmarks of glaucoma. Ocular hypertension (OHT) and mitochondrial dysfunction are linked to neurodegeneration and vision loss in glaucoma. However, the exact mechanism of mitochondrial dysfunction leading to glaucomatous neurodegeneration is poorly understood. Using multiple mouse models of OHT and human eyes from normal and glaucoma donors, we show that OHT induces impaired mitophagy in RGCs, resulting in the accumulation of dysfunctional mitochondria and contributing to glaucomatous neurodegeneration. Using mitophagy reporter mice, we show that impaired mitophagy precedes glaucomatous neurodegeneration. Notably, the pharmacological rescue of impaired mitophagy via Torin-2 or genetic upregulation of RGC-specific Parkin expression restores the structural and functional integrity of RGCs and their axons in mouse models of glaucoma and ex-vivo human retinal-explant cultures. Our study indicates that impaired mitophagy contributes to mitochondrial dysfunction and oxidative stress, leading to glaucomatous neurodegeneration. Enhancing mitophagy in RGCs represents a promising therapeutic strategy to prevent glaucomatous neurodegeneration.

Senolytic Treatment Alleviates Corneal Allograft Rejection Through Upregulation of Angiotensin-Converting Enzyme 2 (ACE2)

Purpose

Allograft rejection remains a major cause of failure in high-risk corneal transplants, but the underlying mechanisms are not fully understood. This study aimed to investigate the contribution of transplantation stress-induced cellular senescence to corneal allograft rejection and to elucidate the associated molecular mechanisms.

Methods

Age-matched murine corneal transplantation models were established. Cellular senescence was evaluated using senescence-associated β-galactosidase (SA-β-Gal) staining, western blot, and immunofluorescence staining. The role of cellular senescence in corneal allograft rejection was analyzed using p16 knockout mice and adoptive transfer experiments. Senolytic treatment with ABT-263 was administered intraperitoneally to evaluate its effects on corneal allograft rejection. RNA sequencing and pharmacological approaches were employed to identify the underlying mechanisms.

Results

Surgical injury induced a senescence-like phenotype in both donor corneas and recipient corneal beds, characterized by an increased accumulation of SA-β-Gal-positive cells in the corneal endothelium and stroma and elevated expression of senescence markers p16 and p21. Using genetic and adoptive transfer models, transplantation stress-induced senescence was shown to exacerbate corneal allograft rejection. Importantly, clearance of senescent cells by ABT-263 significantly suppressed ocular alloresponses and immune rejection. Mechanistically, RNA sequencing and loss-of-function experiments demonstrated that the anti-rejection effects of senolytic treatment were closely dependent on angiotensin-converting enzyme 2 (ACE2).

Conclusions

These findings highlight transplantation stress-induced senescence as a pivotal pathogenic factor in corneal allograft rejection. Senolytic therapy emerges as a potential novel strategy to mitigate transplant rejection and improve corneal allograft survival.

Retinal Protection of New Nutraceutical Formulation

Background/Objectives: Retinal ganglion cell (RGC) protection represents an unmet need in glaucoma. This study assessed the neuroprotective, antioxidant, and anti-inflammatory effect of a new nutraceutical formulation named Epicolin, based on citicoline, homotaurine, epigallocatechin-3-gallate, forskolin, and vitamins, through in vitro and in vivo studies. Methods: The neuroprotective effect of Epicolin or its single components, and Epicolin compared to an untreated control and two marketed formulations [Formulation G (FG) and N (FN)], was evaluated in neuroblastoma cells (SH-SY5Y) challenged with staurosporine. The antioxidant potential and the scavenging activity of Epicolin compared to the untreated control, and FG and FN, was evaluated in SH-SY5Y cells and through oxygen radical absorbance capacity acellular assay, respectively. Moreover, the protective effect against hypoxic damage was evaluated in Muller cells (MIO-M1) subjected to hypoxia. The efficacy of Epicolin was also evaluated in DBA/2J glaucomatous mice through the use of a pattern electroretinogram (PERG), immunostaining, and real-time PCR. Results: Among the nutraceutical formulations tested, only Epicolin showed a significant neuroprotective effect on SH-SY5Y attributable to the synergistic action of its single ingredients. As for antioxidant and scavenging activity, Epicolin showed a higher efficacy compared to FG and FN. Furthermore, Epicolin showed the same protective effect on MIO-M1 cells reducing HIF-1α expression. Finally, Epicolin treatment on DBA/2J mice protected the RGCs from loss of function, as demonstrated by PERG analysis, and attenuated their death by enhancing brain-derived neurotrophic factor (BDNF) and reducing interleukin-1 beta (IL-1β) and tumor necrosis factor-alpha (TNF-α) expression. Conclusions: Epicolin, due to its neuroprotective, antioxidant, and anti-inflammatory properties, represents a promising potential treatment for glaucoma.

A Reduction in Mitophagy Is Associated with Glaucomatous Neurodegeneration in Rodent Models of Glaucoma

Glaucoma is a heterogenous group of optic neuropathies characterized by the degeneration of optic nerve axons and the progressive loss of retinal ganglion cells (RGCs), which could ultimately lead to vision loss. Elevated intraocular pressure (IOP) is a major risk factor in the development of glaucoma, and reducing IOP remains the main therapeutic strategy. Endothelin-1 (ET-1), a potent vasoactive peptide, has been shown to produce neurodegenerative effects in animal models of glaucoma. However, the detailed mechanisms underlying ET-1-mediated neurodegeneration in glaucoma are not completely understood. In the current study, using a Seahorse Mitostress assay, we report that ET-1 treatment for 4 h and 24 h time points causes a significant decline in various parameters of mitochondrial function, including ATP production, maximal respiration, and spare respiratory capacity in cultured RGCs. This compromise in mitochondrial function could trigger activation of mitophagy as a quality control mechanism to restore RGC health. Contrary to our expectation, we observed a decrease in mitophagy following ET-1 treatment for 24 h in cultured RGCs. Using Morrison's model of ocular hypertension in rats, we investigated here, for the first time, changes in mitophagosome formation by analyzing the co-localization of LC-3B and TOM20 in RGCs. We also injected ET-1 (24 h) into transgenic GFP-LC3 mice to analyze the formation of mitophagosomes in vivo. In Morrison's model of ocular hypertension, as well as in ET-1 injected GFP-LC3 mice, we found a decrease in co-localization of LC3 and TOM20, indicating reduced mitophagy. Taken together, these results demonstrate that both ocular hypertension and ET-1 administration in rats and mice lead to reduced mitophagy, thus predisposing RGCs to neurodegeneration.

Gene therapy for glaucoma: Targeting key mechanisms

Glaucoma is a group of optic neuropathies characterised by progressive retinal ganglion cell (RGC) degeneration and is the leading cause of irreversible blindness worldwide. Current treatments for glaucoma focus on reducing intraocular pressure (IOP) with topical medications. However, many patients do not achieve sufficient IOP reductions with such treatments. Patient compliance to dosing schedules also poses a significant challenge, further limiting their effectiveness. While surgical options exist for resistant cases, these are invasive and carry risks of complications. Thus, there is a critical need for better strategies to prevent irreversible vision loss in glaucoma. Gene therapy holds significant promise in this regard, offering potential long-term solutions by targeting the disease's underlying causes at a molecular level. Gene therapy strategies for glaucoma primarily target the two key hallmarks of the disease: elevated IOP and RGC death. This review explores key mechanisms underlying these hallmarks and discusses the current state of gene therapies targeting them. In terms of IOP reduction, this review covers strategies aimed at enhancing extracellular matrix turnover in the conventional outflow pathway, targeting fibrosis, regulating aqueous humor production, and targeting myocilin for gene-specific therapy. Neuroprotective strategies explored include targeting neurotrophic factors and their receptors, reducing oxidative stress and mitochondrial dysfunction, and preventing Wallerian degeneration. This review also briefly highlights key research priorities for advancing gene therapies for glaucoma through the clinical pipeline, such as refining delivery vectors and improving transgene regulation. Addressing these priorities will be essential for translating advancements from preclinical models into effective clinical therapies for glaucoma.

Decoding senescence of aging single cells at the nexus of biomaterials, microfluidics, and spatial omics

Aging has profound effects on the body, most notably an increase in the prevalence of several diseases. An important aging hallmark is the presence of senescent cells that no longer multiply nor die off properly. Another characteristic is an altered immune system that fails to properly self-surveil. In this multi-player aging process, cellular senescence induces a change in the secretory phenotype, known as senescence-associated secretory phenotype (SASP), of many cells with the intention of recruiting immune cells to accelerate the clearance of these damaged senescent cells. However, the SASP phenotype results in inducing secondary senescence of nearby cells, resulting in those cells becoming senescent, and improper immune activation resulting in a state of chronic inflammation, called inflammaging, in many diseases. Senescence in immune cells, termed immunosenescence, results in further dysregulation of the immune system. An interdisciplinary approach is needed to physiologically assess aging changes of the immune system at the cellular and tissue level. Thus, the intersection of biomaterials, microfluidics, and spatial omics has great potential to collectively model aging and immunosenescence. Each of these approaches mimics unique aspects of the body undergoes as a part of aging. This perspective highlights the key aspects of how biomaterials provide non-cellular cues to cell aging, microfluidics recapitulate flow-induced and multi-cellular dynamics, and spatial omics analyses dissect the coordination of several biomarkers of senescence as a function of cell interactions in distinct tissue environments. An overview of how senescence and immune dysregulation play a role in organ aging, cancer, wound healing, Alzheimer's, and osteoporosis is included. To illuminate the societal impact of aging, an increasing trend in anti-senescence and anti-aging interventions, including pharmacological interventions, medical procedures, and lifestyle changes is discussed, including further context of senescence.

Engineered bio-functional material-based nerve guide conduits for optic nerve regeneration: a view from the cellular perspective, challenges and the future outlook

Nerve injuries can be tantamount to severe impairment, standard treatment such as the use of autograft or surgery comes with complications and confers a shortened relief. The mechanism relevant to the regeneration of the optic nerve seems yet to be fully uncovered. The prevailing rate of vision loss as a result of direct or indirect insult on the optic nerve is alarming. Currently, the use of nerve guide conduits (NGC) to some extent has proven reliable especially in rodents and among the peripheral nervous system, a promising ground for regeneration and functional recovery, however in the optic nerve, this NGC function seems quite unfamous. The insufficient NGC application and the unabridged regeneration of the optic nerve could be a result of the limited information on cellular and molecular activities. This review seeks to tackle two major factors (i) the cellular and molecular activity involved in traumatic optic neuropathy and (ii) the NGC application for the optic nerve regeneration. The understanding of cellular and molecular concepts encompassed, ocular inflammation, extrinsic signaling and intrinsic signaling for axon growth, mobile zinc role, Ca2+ factor associated with the optic nerve, alternative therapies from nanotechnology based on the molecular information and finally the nanotechnological outlook encompassing applicable biomaterials and the use of NGC for regeneration. The challenges and future outlook regarding optic nerve regenerations are also discussed. Upon the many approaches used, the comprehensive role of the cellular and molecular mechanism may set grounds for the efficient application of the NGC for optic nerve regeneration.

The role of nicotinamide riboside in the preservation of retinal ganglion cells using an in vitro glutamate-induced excitotoxicity model

Delaying or preventing the loss of retinal ganglion cells (RGCs) in glaucoma is needed for vision preservation. Glutamate-mediated neurotoxicity arises from the excessive stimulation of N-methyl-D-aspartate membrane receptors by glutamate. This overstimulation, occurring specifically in RGCs, triggers a progressive deterioration of the optic nerve that ultimately leads to the vision loss in glaucoma. Our previous investigation demonstrated that nicotinamide riboside (NR) effectively preserved RGCs in multiple mouse models of glaucoma. To investigate the precise role of NR concerning RGCs which remains uncertain, a glutamate-induced excitotoxicity RGCs damage model was established using R28 cells in this study. Results showed that NR treatment could not only prevent the decrease in cell viability but also effectively inhibit the apoptosis of R28 cells induced by glutamate, as proven by flow cytometry and expression of key pro-apoptotic proteins. Additionally, it significantly attenuated oxidative stress induced by glutamate, as evaluated by the production of inflammatory factors, reactive oxygen species (ROS) and mitochondrial ROS (mtROS). Furthermore, NR elevated the intracellular nicotinamide adenine dinucleotide (NAD+) levels in R28 cells. Lastly, we used RNA-seq to reveal the underlying mechanism of NR protection. Combining the results of RNA-seq and Western blot, we found that NR also restored the decreased protein expression of sirtuin 1 (SIRT1) and peroxisome proliferator-activated receptor-gamma coactivator (PGC1α) induced by glutamate. These findings strongly indicated that NR exhibits a protective effect against R28 cell apoptosis in a glutamate-induced excitotoxicity RGCs damage model. This protective effect is likely mediated through the activation of the SIRT1/PGC1α pathway, achieved by increasing intracellular NAD + levels.

Single-cell profiling of trabecular meshwork identifies mitochondrial dysfunction in a glaucoma model that is protected by vitamin B3 treatment

Since the trabecular meshwork (TM) is central to intraocular pressure (IOP) regulation and glaucoma, a deeper understanding of its genomic landscape is needed. We present a multimodal, single-cell resolution analysis of mouse limbal cells (includes TM). In total, we sequenced 9,394 wild-type TM cell transcriptomes. We discovered three TM cell subtypes with characteristic signature genes validated by immunofluorescence on tissue sections and whole-mounts. The subtypes are robust, being detected in datasets for two diverse mouse strains and in independent data from two institutions. Results show compartmentalized enrichment of critical pathways in specific TM cell subtypes. Distinctive signatures include increased expression of genes responsible for 1) extracellular matrix structure and metabolism (TM1 subtype), 2) secreted ligand signaling to support Schlemm's canal cells (TM2), and 3) contractile and mitochondrial/metabolic activity (TM3). ATAC-sequencing data identified active transcription factors in TM cells, including LMX1B. Mutations in LMX1B cause high IOP and glaucoma. LMX1B is emerging as a key transcription factor for normal mitochondrial function and its expression is much higher in TM3 cells than other limbal cells. To understand the role of LMX1B in TM function and glaucoma, we single-cell sequenced limbal cells from Lmx1b V265D/+ mutant mice. In V265D/+ mice, TM3 cells were uniquely affected by pronounced mitochondrial pathway changes. This supports a primary role of mitochondrial dysfunction within TM3 cells in initiating the IOP elevation that causes glaucoma in these mice. Importantly, treatment with vitamin B 3 (nicotinamide), to enhance mitochondrial function and metabolic resilience, significantly protected Lmx1b mutant mice from IOP elevation.

Glaucoma-inducing retinal ganglion cell degeneration alters diurnal rhythm of key molecular components of the central clock and locomotor activity in mice

Glaucoma is a chronic optic neuropathy characterized by the progressive degeneration of retinal ganglion cells (RGC). These cells play a crucial role in transmitting visual and non-visual information to brain regions, including the suprachiasmatic nucleus (SCN), responsible for synchronizing biological rhythms. To understand how glaucoma affects circadian rhythm synchronization, we investigated potential changes in the molecular clock machinery in the SCN. We found that the progressive increase in intraocular pressure (IOP) negatively correlated with spontaneous locomotor activity (SLA). Transcriptome analysis revealed significant alterations in the SCN of glaucomatous mice, including downregulation of genes associated with circadian rhythms. In fact, we showed a loss of diurnal oscillation in the expression of vasoactive intestinal peptide (Vip), its receptor (Vipr2), and period 1 (Per1) in the SCN of glaucomatous mice. These findings were supported by the 7-h phase shift in the peak expression of arginine vasopressin (Avp) in the SCN of mice with glaucoma. Despite maintaining a 24-h period under both light/dark (LD) and constant dark (DD) conditions, glaucomatous mice exhibited altered SLA rhythms, characterized by decreased amplitude. Taken altogether, our findings provide evidence of how glaucoma affects the regulation of the central circadian clock and its consequence on the regulation of circadian rhythms.

Glaucoma and dietary links: insights from high-salt intake, the Mediterranean diet, and specific nutrients

Glaucoma, a prevalent and potentially blinding eye disease, is linked to a variety of factors, including elevated intraocular pressure, optic nerve damage, and oxidative stress. In recent years, dietary habits, as a controllable lifestyle factor, have received increasing attention in the prevention and treatment of glaucoma. The purpose of this review was to investigate the effects of dietary factors on glaucoma, with a particular emphasis on two common dietary patterns: the high-salt diet and the Mediterranean diet. In addition, we investigated the association between many particular nutrients (including omega-3 fatty acids, vitamins, caffeine, and minerals) and glaucoma to fully assess the potential involvement of dietary variables in glaucoma pathogenesis, prevention, and treatment. This article reveals the importance of dietary components in glaucoma prevention and explores prospective possibilities for future research by conducting a comprehensive review of previous scientific studies.

IOP-induced blood-retinal barrier compromise contributes to RGC death in glaucoma

The integrity of the blood-retinal barrier (BRB) has been largely unexplored in glaucoma. We reveal that elevated intraocular pressure (IOP) partially compromises the BRB in two human-relevant inherited mouse models of glaucoma (DBA/2J and Lmx1bV265D). Experimentally increasing IOP in mouse eyes further confirms this. Notably, the compromise induces subtle leakage, happening without bleeding or detected endothelial cell junction disruption, and it precedes neurodegeneration. Leakage occurs from peripheral veins in the retinal ganglion cell layer with a concomitant loss of the transcytosis inhibitor MFSD2A. Importantly, stabilizing β-catenin in retinal endothelial cells prevents both vascular leakage and neurodegeneration in the DBA/2J model. The occurrence of leakage in all 3 high IOP models indicates that BRB compromise may be a common, yet overlooked, mechanism in glaucoma. These findings suggest that IOP-induced BRB compromise plays a critical role in glaucoma, offering a new therapeutic target.

Systematic Review and Meta-Analysis on the Association Between Daily Niacin Intake and Glaucoma

BACKGROUND

Glaucoma is a progressive optic neuropathy, characterised by a complex pathophysiology, with mitochondrial dysfunction playing a significant role in the cellular damage and apoptosis of ganglion cells. Niacin is a precursor to several molecules acting as coenzymes in the mitochondrial production of ATP, in DNA repair and in the reduction of reactive oxygen species. The objective of this systematic review is to assess the impact of daily niacin intake on glaucoma.

METHODS

Case-control and cohort studies regarding niacin and glaucoma, indexed in PubMed, Web of Science, Cochrane and Scopus, were included. Other study methodologies, studies regarding niacin in other ocular disease or other nutrients in glaucoma were excluded. Bias was assessed using the Newcastle-Ottawa Scale. The study protocol was registered in the PROSPERO database (no. CRD42024578889).

RESULTS

Five case-control studies were included. In the pooled analysis, a significantly higher proportion of patients with high niacin consumption was found in the group without glaucoma compared to those with glaucoma as defined by ISGEO criteria (p-value < 0.00001; OR = 0.66, 95% CI 0.55-0.79) or as defined by retinal imaging (p-value = 0.02; OR = 0.63, 95% CI 0.43-0.94).

CONCLUSIONS

Daily dietary intake of niacin is significantly lower in patients with glaucoma compared to the general population. Given different average daily intakes of niacin in these populations, different glaucoma definitions and several confounding variables which weaken the associations, large sample, standardised randomised controlled trials are needed to confirm the potential benefits of niacin in glaucoma.

Accelerated Epigenetic Aging is Associated with Faster Glaucoma Progression: A DNA Methylation Study

Purpose

To investigate the association between epigenetic age acceleration and glaucoma progression.

Design

Retrospective cohort study.

Participants

100 primary open-angle glaucoma (POAG) patients with fast progression and 100 POAG patients with slow progression.

Methods

Subjects were classified as fast or slow progressors based on rates of change in standard automated perimetry (SAP) mean deviation (MD) and retinal nerve fiber layer (RNFL) thickness. Epigenetic age was calculated using the Horvath, Hannum, PhenoAge, and GrimAge clocks from DNA methylation profiles obtained from blood samples. Age acceleration (AgeAccel) was defined as the residual from a linear regression of epigenetic age on chronologic age, with positive values suggesting faster biological aging. Multivariable logistic regression models estimated the association between AgeAccel and likelihood of fast progression, adjusting for confounders.

Main Outcome Measures

Difference in epigenetic age acceleration between fast and slow glaucoma progressors.

Results

The mean rate of SAP MD change in the fastest progressing eye was -1.06 dB/year (95% CI: -1.28 to -0.85) for fast progressors compared to -0.10 dB/year (95% CI: -0.16 to -0.04) for slow progressors (P<0.001). For RNFL thickness, corresponding values were -1.60 μm/year (95% CI: -1.97 to -1.23) and -0.76 μm/year (95% CI: -1.04 to -0.48), respectively (P<0.001). Fast progressors demonstrated significantly greater age acceleration compared to slow progressors for the Horvath clock (mean difference = 2.93 years, 95% CI: 1.48 to 4.39, P<0.001) and Hannum clock (mean difference = 1.24 years, 95% CI: 0.03 to 2.46, P=0.045). In multivariable models, each year of Horvath AgeAccel was associated with 15% higher odds of fast progression (OR 1.15, 95% CI 1.07-1.23, P<0.001), after adjusting for sex, race, intraocular pressure, central corneal thickness, baseline disease severity, smoking status and follow-up time. Hannum and GrimAge clocks also showed significant associations with fast progression. The association between AgeAccel and fast progression was stronger in subjects with relatively low IOP during follow-up.

Conclusion

Accelerated epigenetic aging was associated with faster glaucoma progression. These findings suggest that faster biological age, as reflected in DNA methylation, may increase optic nerve susceptibility to damage, highlighting epigenetic age as a potential prognostic biomarker.

Minocycline Administration Does Not Have an Effect on Retinal Ganglion Cell Survival in a Murine Model of Ocular Hypertension

This study aims to investigate two key aspects in a mouse model of ocular hypertension (OHT): first, the time course of retinal ganglion cell (RGC) death and the parallel activation of caspase-3 (a-Casp3+ cells) to narrow the therapeutic window; and second, the effect of caspase-3 and microglia inhibition by minocycline on RGC rescue in this model. RGC loss after OHT induction was significant at day 7 and progressed to 30 days. However, anatomical RGC death was preceded by significant Casp3 activation on day 3. Microglial inhibition by minocycline did not alter the course of OHT or rescue RGCs but resulted in a decrease in a-Casp3+ cells and phagocytic and total microglia. Therefore, RGC death commitment occurs earlier than their loss of Brn3a expression, microglial cells do not exacerbate RGC loss, and while this death is primarily apoptotic, apoptosis inhibition does not rescue RGCs, suggesting that alternative death pathways play a role in glaucomatous injury.

Glial Cell Activation and Immune Responses in Glaucoma: A Systematic Review of Human Postmortem Studies of the Retina and Optic Nerve

Although researched extensively the understanding regarding mechanisms underlying glaucoma pathogenesis remains limited. Further, the exact mechanism behind neuronal death remains elusive. The role of neuroinflammation in retinal ganglion cell (RGC) death has been prominently theorised. This review provides a comprehensive summary of neuroinflammatory responses in glaucoma. A systematic search of Medline and Embase for articles published up to 8th March 2023 yielded 32 studies using post-mortem tissues from glaucoma patients. The raw data were extracted from tables and text to calculate the standardized mean differences (SMDs). These studies utilized post-mortem tissues from glaucoma patients, totalling 490 samples, compared with 380 control samples. Among the included studies, 27 reported glial cell activation based on changes to cellular morphology and molecular staining. Molecular changes were predominantly attributed to astrocytes (62.5%) and microglia (15.6%), with some involvement of Muller cells. These glial cell changes included amoeboid microglial cells with increased CD45 or HLA-DR intensity and hypertrophied astrocytes with increased glial fibrillary acidic protein labelling. Further, changes to extracellular matrix proteins like collagen, galectin, and tenascin-C suggested glial cells' influence on structural changes in the optic nerve head. The activation of DAMPs-driven immune response and the classical complement cascade was reported and found to be associated with activated glial cells in glaucomatous tissue. Increased pro-inflammatory markers such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) were also linked to glial cells. Glial cell activation was also associated with mitochondrial, vascular, metabolic and antioxidant component disruptions. Association of the activated glial cells with pro-inflammatory responses, dysregulation of homeostatic components and antigen presentation indicates that glial cell responses influence glaucoma progression. However, the exact mechanism triggering these responses and underlying interactions remains unexplored. This necessitates further research using human samples for an increased understanding of the precise role of neuroinflammation in glaucoma progression.

Translational Research and Therapies for Neuroprotection and Regeneration of the Optic Nerve and Retina: A Narrative Review

Most retinal and optic nerve diseases pose significant threats to vision, primarily due to irreversible retinal neuronal cell death, a permanent change, which is a critical factor in their pathogenesis. Conditions such as glaucoma, retinitis pigmentosa, diabetic retinopathy, and age-related macular degeneration are the top four leading causes of blindness among the elderly in Japan. While standard treatments-including reduction in intraocular pressure, anti-vascular endothelial growth factor therapies, and retinal photocoagulation-can partially delay disease progression, their therapeutic effects remain limited. To address these shortcomings, a range of neuroprotective and regenerative therapies, aimed at preventing retinal neuronal cell loss, have been extensively studied and increasingly integrated into clinical practice over the last two decades. Several of these neuroprotective therapies have achieved on-label usage worldwide. This narrative review introduces several neuroprotective and regenerative therapies for retinal and optic nerve diseases that have been successfully translated into clinical practice, providing foundational knowledge and success stories that serve as valuable references for researchers in the field.

Advances in Neuroprotection in Glaucoma: Pharmacological Strategies and Emerging Technologies

Glaucoma is a major global health concern and the leading cause of irreversible blindness worldwide, characterized by the progressive degeneration of retinal ganglion cells (RGCs) and their axons. This review focuses on the need for neuroprotective strategies in glaucoma management, addressing the limitations of current treatments that primarily target intraocular pressure (IOP) reduction. Despite effective IOP management, many patients continue to experience RGC degeneration, leading to irreversible blindness. This review provides an overview of both pharmacological interventions and emerging technologies aimed at directly protecting RGCs and the optic nerve, independent of IOP reduction. Pharmacological agents such as brimonidine, neurotrophic factors, memantine, Ginkgo biloba extract, citicoline, nicotinamide, insulin, and resveratrol show promise in preclinical and early clinical studies for their neuroprotective properties. Emerging technologies, including stem cell therapy, gene therapy, mitochondrial-targeted therapies, and nanotechnologies, offer innovative approaches for neuroprotection and regeneration of damaged RGCs. While these interventions hold significant potential, further research and clinical trials are necessary to confirm their efficacy and establish their role in clinical practice. This review highlights the multifaceted nature of neuroprotection in glaucoma, aiming to guide future research and clinical practice toward more effective management of glaucoma-induced neurodegeneration.

Uncovering the impact and mechanisms of air pollution on eye and ear health in China

Increasing air pollution could undermine human health, but the causal link between air pollution and eye and ear health has not been well-studied. Based on four-week-level records of eye and ear health over 1991-2015 provided by the China Health and Nutrition Survey, we estimate the causal effect of air pollution on eye and ear health. Using two-stage least squares estimation, we find that eye or ear disease possibility rises 1.48% for a 10 μg/m3 increase in four-week average PM2.5 concentration. The impacts can last about 28 weeks and will be insignificant afterward. Females, individuals aged 60 years and over, with high exposure environments, relatively poor economic foundations, and low knowledge levels are more vulnerable to such negative influences. Behavioral channels like more smoking activities and less sleeping activities could partly explain this detrimental effect. Our findings enlighten how to minimize the impact of air pollution and protect public health.

Differential protection by nicotinamide in a mouse model of glaucoma DBA/2J revealed by second-harmonic generation microscopy

Glaucoma is a blinding disease where the retinal ganglion cells and their axons degenerate. Degradation of axonal microtubules is thought to play a critical role in the pathogenesis, but the mechanism is unknown. Here we investigate whether microtubule disruption in glaucoma can be alleviated by metabolic rescue. The integrity of axonal microtubules and the morphology of the retinal nerve fibers were evaluated by second-harmonic generation microscopy in a mouse model of glaucoma, DBA/2J, which received a dietary supplement of nicotinamide (NAM) for reducing metabolic stress. It was compared with control DBA/2J, which did not receive NAM, and non-glaucomatous DBA/2J-Gpnmb+. We found that the morphology of the retinal nerve fibers, but not axonal microtubules, are significantly protected by NAM. The decoupling is analogous to microtubule deficit, a glaucoma pathology in which axonal microtubules exhibit rapid degradation compared to the morphology of the retinal nerve fibers. Understanding microtubule deficit could provide insights into the divergent responses to NAM. From co-registered images of second-harmonic generation and immunofluorescence, it was determined that microtubule deficit was not due to a shortage of tubulins. Furthermore, microtubule deficit colocalized with the sectors in which the retinal ganglion cells were disconnected from the brain, suggesting that microtubule disruption is associated with axonal transport deficit in glaucoma. Together, our data suggests significant role axonal microtubules play in glaucomatous degeneration, offering a new opportunity for neuroprotection.

The potential impact of a vegetarian diet on glaucoma

Treatment of primary open-angle glaucoma has centered on the lowering of intraocular pressure that damages the optic nerve; however, this strategy is not uniformly successful, especially in normal tension glaucoma, and there is interest in antioxidant, anti-inflammatory, and other neuroprotective strategies. Vegetarian diets are known to be rich in antioxidant and anti-inflammatory components and have a number of established health benefits. Thus, it would be reasonable to assume that vegetarian diets would be beneficial in glaucoma, but this approach has not been well studied. We examine the possible role of vegetarian diets and their components in the incidence and progression of glaucoma.

The effects of light emitting diodes on mitochondrial function and cellular viability of M-1 cell and mouse CD1 brain cortex neurons

The invention of Light Emitting Diode (LED) revolutionized energy-efficient illumination, but concerns persist regarding the potential harm of blue light to our eyes. In this study, we scrutinized the impact of LED light characteristics on eyes using two cell types: M-1 (rich in mitochondria) and CD-1 (neuronal). Variations in color rendering index (CRI) and correlated color temperature (CCT) were investigated, alongside exposure durations ranging from 0 to 24 hours. The findings illuminated the potential benefits of high-quality LED lighting, characterized by a high CRI and low CCT, which emits a greater proportion of red light. This form of lighting was associated with enhanced cell proliferation, elevated ATP levels, and reduced oxidative stress. In contrast, LEDs with low CRI and high CCT exhibited adverse effects, diminishing cell viability and increasing oxidative stress. These results suggest that high-quality LED lighting may have neuroprotective potential as a treatment option, such as for retinal ganglion cells.

Oral nicotinamide provides robust, dose-dependent structural and metabolic neuroprotection of retinal ganglion cells in experimental glaucoma

A compromised capacity to maintain NAD pools is recognized as a key underlying pathophysiological feature of neurodegenerative diseases. NAD acts as a substrate in major cell functions including mitochondrial homeostasis, cell signalling, axonal transport, axon/Wallerian degeneration, and neuronal energy supply. Dendritic degeneration is an early marker of neuronal stress and precedes cell loss. However, little is known about dendritic structural preservation in pathologic environments and remodelling in mature neurons. Retinal ganglion cell dendritic atrophy is an early pathological feature in animal models of the disease and has been demonstrated in port-mortem human glaucoma samples. Here we report that a nicotinamide (a precursor to NAD through the NAD salvage pathway) enriched diet provides robust retinal ganglion cell dendritic protection and preserves dendritic structure in a rat model of experimental glaucoma. Metabolomic analysis of optic nerve samples from the same animals demonstrates that nicotinamide provides robust metabolic neuroprotection in glaucoma. Advances in our understanding of retinal ganglion cell metabolic profiles shed light on the energetic shift that triggers early neuronal changes in neurodegenerative diseases. As nicotinamide can improve visual function short term in existing glaucoma patients, we hypothesize that a portion of this visual recovery may be due to dendritic preservation in stressed, but not yet fully degenerated, retinal ganglion cells.

NAD+ and Niacin Supplementation as Possible Treatments for Glaucoma and Age-Related Macular Degeneration: A Narrative Review

Glaucoma and age-related macular degeneration (AMD) are progressive retinal diseases characterized by increased oxidative stress, inflammation, and mitochondrial dysfunction. This review investigates the potential therapeutic benefits of NAD+ and niacin supplementation in managing glaucoma and AMD. A literature search was conducted encompassing keywords such as "niacin", "NAD", "glaucoma", "AMD", and "therapeutics". NAD+ depletion is associated with increased oxidative stress and mitochondrial dysfunction in glaucoma and AMD. Niacin, a precursor to NAD+, has shown promise in replenishing NAD+ levels, improving choroidal blood flow, and reducing oxidative damage. Animal studies in glaucoma models indicate that nicotinamide (NAM) supplementation preserves RGC density and function. Large-scale population-based studies indicate an inverse correlation between niacin intake and glaucoma prevalence, suggesting a preventative role. Randomized controlled trials assessing niacin supplementation showed significant improvements in visual field sensitivity and inner retinal function, with a dose-dependent relationship. In AMD, nicotinamide supplementation may improve rod cell function and protect against oxidative stress-induced damage. Cross-sectional studies reveal that individuals with AMD have a lower dietary intake of niacin. Further studies suggest niacin's role in improving choroidal blood flow and dilating retinal arterioles, potentially mitigating ischemic damage and oxidative stress in AMD. Beyond current management strategies, NAD+ and niacin supplementation may offer novel therapeutic avenues for glaucoma and AMD. Further research is warranted to elucidate their efficacy and safety in clinical settings.

AAV-NDI1 Therapy Provides Significant Benefit to Murine and Cellular Models of Glaucoma

Glaucoma, a leading cause of blindness, is a multifactorial condition that leads to progressive loss of retinal ganglion cells (RGCs) and vision. Therapeutic interventions based on reducing ocular hypertension are not always successful. Emerging features of glaucoma include mitochondrial dysfunction and oxidative stress. In the current study, NDI1-based gene therapy, which improves mitochondrial function and reduces reactive oxygen species, was delivered intraocularly via an adeno-associated viral vector (AAV). This AAV-NDI1 therapy protected RGCs from cell death in treated (1552.4 ± 994.0 RGCs/mm2) versus control eyes (1184.4 ± 978.4 RGCs/mm2, p < 0.05) in aged DBA/2J mice, a murine model of glaucoma. The photonegative responses (PhNRs) of RGCs were also improved in treated (6.4 ± 3.3 µV) versus control eyes (5.0 ± 3.1 µV, p < 0.05) in these mice. AAV-NDI1 also provided benefits in glaucomatous human lamina cribrosa (LC) cells by significantly increasing basal and maximal oxygen consumption rates and ATP production in these cells. Similarly, NDI1 therapy significantly protected H2O2-insulted primary porcine LC cells from oxidative stress. This study highlights the potential utility of NDI1 therapies and the benefits of improving mitochondrial function in the treatment of glaucoma.

Drug-Induced Liver Injury During a Glaucoma Neuroprotection Clinical Trial

ABSTRACT

There are several ongoing, worldwide clinical trials with a cumulative target enrollment of over 1300 participants on the role of nicotinamide (a specific form of vitamin B3) as a therapeutic neuroprotective treatment for glaucoma. We describe a serious adverse event of drug-induced liver injury (DILI) likely related to the use of 3 g/day nicotinamide in a glaucoma clinical trial (clinicaltrials.gov identifier: NCT05695027) based in the United States. This report is important to share with the medical community, as other participants in glaucoma nicotinamide trials globally may have similar adverse events and many patients are using nicotinamide as a health supplement without medical supervision. We recommend that investigators, physicians, and patients remain vigilant about DILI as they seek novel vision-preserving neuroprotective therapies.

Peripheral blood mononuclear cell respiratory function is associated with progressive glaucomatous vision loss

Intraocular pressure (IOP) is currently the only modifiable risk factor for glaucoma and all licensed treatments lower IOP. However, many patients continue to lose vision despite IOP-lowering treatment. Identifying biomarkers for progressive vision loss would have considerable clinical utility. We demonstrate that lower peripheral blood mononuclear cell (PBMC) oxygen consumption rate (OCR) is strongly associated with faster visual field (VF) progression in patients treated by lowering IOP (P < 0.001, 229 eyes of 139 participants), explaining 13% of variance in the rate of progression. In a separate reference cohort of untreated patients with glaucoma (213 eyes of 213 participants), IOP explained 16% of VF progression variance. OCR is lower in patients with glaucoma (n = 168) than in controls (n = 50; P < 0.001) and is lower in patients with low baseline IOP (n = 99) than those with high baseline IOP (n = 69; P < 0.01). PBMC nicotinamide adenine dinucleotide (NAD) levels are lower in patients with glaucoma (n = 29) compared to controls (n = 25; P < 0.001) and strongly associated with OCR (P < 0.001). Our results support PBMC OCR and NAD levels as new biomarkers for progressive glaucoma.

Nicotinamide: Bright Potential in Glaucoma Management

BACKGROUND

Glaucoma is a major cause of incurable ocular morbidity and poses significant challenges in its management due to the limited treatment options and potential adverse effects. Nicotinamide, a naturally occurring diet-rich nutrient, has emerged as a promising therapeutic agent for glaucoma, offering neuroprotective effects and the potential modulation of intraocular pressure (IOP) regulation pathways. This comprehensive review sought to analyze the current literature on nicotinamide in glaucoma management, exploring its mechanisms of action, efficacy, and safety profile.

METHODS

A systematic search of the PubMed database was conducted to identify relevant records on the therapeutic actions of nicotinamide in ocular hypertension and glaucoma. Publications evaluating nicotinamide's effects on retinal ganglion cells (RGCs), optic nerve function, IOP regulation, and neuroinflammatory pathways were included.

RESULTS

The literature review revealed the preclinical evidence supporting nicotinamide's neuroprotective effects on RGCs, the preservation of optic nerve integrity, and the modulation of glaucoma-associated neuroinflammation. Additionally, nicotinamide may exert IOP-lowering effects through its influence on ocular blood flow and aqueous humor dynamics.

CONCLUSIONS

Nicotinamide holds promise as a novel therapeutic approach in glaucoma management, offering potential neuroprotective and IOP-lowering effects. The authors recommend more research to determine the nicotinamide efficacy, safe dosing parameters, and any long-term safety concerns in glaucoma patients.