Nicotinamide provides neuroprotection in glaucoma by protecting against mitochondrial and metabolic dysfunction

Nicotinamide adenine dinucleotide (NAD) is a REDOX cofactor and metabolite essential for neuronal survival. Glaucoma is a common neurodegenerative disease in which neuronal levels of NAD decline. We assess the effects of nicotinamide (a precursor to NAD) on retinal ganglion cells (the affected neuron in glaucoma) in normal physiological conditions and across a range of glaucoma relevant insults including mitochondrial stress and axon degenerative insults. We demonstrate retinal ganglion cell somal, axonal, and dendritic neuroprotection by nicotinamide in rodent models which represent isolated ocular hypertensive, axon degenerative, and mitochondrial degenerative insults. We performed metabolomics enriched for small molecular weight metabolites for the retina, optic nerve, and superior colliculus which demonstrates that ocular hypertension induces widespread metabolic disruption, including consistent changes to α-ketoglutaric acid, creatine/creatinine, homocysteine, and glycerophosphocholine. This metabolic disruption is prevented by nicotinamide. Nicotinamide provides further neuroprotective effects by increasing oxidative phosphorylation, buffering and preventing metabolic stress, and increasing mitochondrial size and motility whilst simultaneously dampening action potential firing frequency. These data support continued determination of the utility of long-term nicotinamide treatment as a neuroprotective therapy for human glaucoma.

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Nicotinamide is neuroprotective in cell and animal models that recapitulate isolated features of glaucoma.

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Systemic nicotinamide administration has limited molecular side-effects on visual system tissue under basal conditions.

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Nicotinamide provides a robust reversal in the disease metabolic profile of glaucomatous animals.

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Nicotinamide increases oxidative phosphorylation, buffers and prevents metabolic stress, and increases mitochondrial size.

Targeting Diet and Exercise for Neuroprotection and Neurorecovery in Glaucoma

Glaucoma is a leading cause of blindness worldwide. In glaucoma, a progressive dysfunction and death of retinal ganglion cells occurs, eliminating transfer of visual information to the brain. Currently, the only available therapies target the lowering of intraocular pressure, but many patients continue to lose vision. Emerging pre-clinical and clinical evidence suggests that metabolic deficiencies and defects may play an important role in glaucoma pathophysiology. While pre-clinical studies in animal models have begun to mechanistically uncover these metabolic changes, some existing clinical evidence already points to potential benefits in maintaining metabolic fitness. Modifying diet and exercise can be implemented by patients as an adjunct to intraocular pressure lowering, which may be of therapeutic benefit to retinal ganglion cells in glaucoma.

Retinal Ganglion Cell Degeneration in a Rat Magnetic Bead Model of Ocular Hypertensive Glaucoma

Purpose

Glaucoma remains a leading cause of irreversible blindness worldwide. Animal glaucoma models replicate high intraocular pressure, a risk factor for glaucoma, to induce retinal ganglion cell (RGC) degeneration. We describe an inducible, magnetic bead model in the Brown Norway rat in which we are able to determine degeneration across multiple RGC compartments at a time point that is appropriate for investigating neurodegenerative events and potential treatment effects.

Methods

We induced ocular hypertension through injection of magnetic microspheres into the anterior chamber of Brown Norway rats; un-operated (naïve) rats served as controls. Intraocular pressure was recorded, and eye diameter measurements were taken before surgery and at the terminal end points. We assessed RGC degeneration and vascular changes through immunofluorescence, and axon transport to terminal brain thalami through intravitreal injection of fluorophore-conjugated cholera toxin subunit β.

Results

We observed clinically relevant features of disease accompanying RGC cell somal, axonal, and dendritic loss. RGC axonal dysfunction persisted along the trajectory of the cell into the terminal brain thalami, with clear disruption at the optic nerve head. We also observed vascular compromise consistent with human disease, as well as an expansion of global eye size with ocular hypertension.

Conclusions

The magnetic bead model in the Brown Norway rat recapitulates many clinically relevant disease features of human glaucoma, including degeneration across multiple RGC compartments. Eye expansion is likely a result of rodent scleral elasticity, and we caution that this should be considered when assessing retinal density measurements.

Translational Relevance

This model offers a disease-relevant platform that will allow for assessment of glaucoma-relevant therapeutics.

When Is a Control Not a Control? Reactive Microglia Occur Throughout the Control Contralateral Pathway of Retinal Ganglion Cell Projections in Experimental Glaucoma

Purpose

Animal models show retinal ganglion cell (RGC) injuries that replicate features of glaucoma and the contralateral eye is commonly used as an internal control. There is significant crossover of RGC axons from the ipsilateral to the contralateral side at the level of the optic chiasm, which may confound findings when damage is restricted to one eye. The effect of unilateral glaucoma on neuroinflammatory damage to the contralateral pathway of RGC projections has largely been unexplored.

Methods

Ocular hypertensive glaucoma was induced unilaterally or bilaterally in the rat and RGC neurodegenerative events were assessed. Neuroinflammation was quantified in the retina, optic nerve head, optic nerve, lateral geniculate nucleus, and superior colliculus by high-resolution imaging, and in the retina by flow cytometry and protein arrays.

Results

After ocular hypertensive stress, peripheral monocytes enter the retina and microglia become reactive. This effect is more marked in animals with bilateral ocular hypertensive glaucoma. In rats where glaucoma was induced unilaterally, there was significant microglia activation in the contralateral (control) eye. Microglial activation extended into the optic nerve and terminal visual thalami, where it was similar across hemispheres in unilateral ocular hypertension.

Conclusions

These data suggest that caution is warranted when using the contralateral eye as a control and in comparing visual thalami in unilateral models of glaucoma.

Translational Relevance

The use of a contralateral eye as a control may confound the discovery of human-relevant mechanism and treatments in animal models. We also identify neuroinflammatory protein responses that warrant further investigation as potential disease-modifiable targets.

Retinal ganglion cell degeneration correlates with hippocampal spine loss in experimental Alzheimer's disease

Neuronal dendritic and synaptic pruning are early features of neurodegenerative diseases, including Alzheimer’s disease. In addition to brain pathology, amyloid plaque deposition, microglial activation, and cell loss occur in the retinas of human patients and animal models of Alzheimer’s disease. Retinal ganglion cells, the output neurons of the retina, are vulnerable to damage in neurodegenerative diseases and are a potential opportunity for non-invasive clinical diagnosis and monitoring of Alzheimer’s progression. However, the extent of retinal involvement in Alzheimer’s models and how well this reflects brain pathology is unclear. Here we have quantified changes in retinal ganglion cells dendritic structure and hippocampal dendritic spines in three well-studied Alzheimer’s mouse models, Tg2576, 3xTg-AD and APP^NL-G-F. Dendritic complexity of DiOlistically labelled retinal ganglion cells from retinal explants was reduced in all three models in an age-, gender-, and receptive field-dependent manner. DiOlistically labelled hippocampal slices showed spine loss in CA1 apical dendrites in all three Alzheimer’s models, mirroring the early stages of neurodegeneration as seen in the retina. Morphological classification showed that loss of thin spines predominated in all. The demonstration that retinal ganglion cells dendritic field reduction occurs in parallel with hippocampal dendritic spine loss in all three Alzheimer’s models provide compelling support for the use of retinal neurodegeneration. As retinal dendritic changes are within the optical range of current clinical imaging systems (for example optical coherence tomography), our study makes a case for imaging the retina as a non-invasive way to diagnose disease and monitor progression in Alzheimer’s disease.

Complement peptide C3a receptor 1 promotes optic nerve degeneration in DBA/2J mice

BACKGROUND

The risk of glaucoma increases significantly with age and exposure to elevated intraocular pressure, two factors linked with neuroinflammation. The complement cascade is a complex immune process with many bioactive end-products, including mediators of inflammation. Complement cascade activation has been shown in glaucoma patients and models of glaucoma. However, the function of complement-mediated inflammation in glaucoma is largely untested. Here, the complement peptide C3a receptor 1 was genetically disrupted in DBA/2J mice, an ocular hypertensive model of glaucoma, to test its contribution to neurodegeneration.

METHODS

A null allele of C3ar1 was backcrossed into DBA/2J mice. Development of iris disease, ocular hypertension, optic nerve degeneration, retinal ganglion cell activity, loss of RGCs, and myeloid cell infiltration in C3ar1-deficient and sufficient DBA/2J mice were compared across multiple ages. RNA sequencing was performed on microglia from primary culture to determine global effects of C3ar1 on microglia gene expression.

RESULTS

Deficiency in C3ar1 lowered the risk of degeneration in ocular hypertensive mice without affecting intraocular pressure elevation at 10.5 months of age. Differences were found in the percentage of mice affected, but not in individual characteristics of disease progression. The protective effect of C3ar1 deficiency was then overcome by additional aging and ocular hypertensive injury. Microglia and other myeloid-derived cells were the primary cells identified that express C3ar1. In the absence of C3ar1, microglial expression of genes associated with neuroinflammation and other immune functions were differentially expressed compared to WT. A network analysis of these data suggested that the IL10 signaling pathway is a major interaction partner of C3AR1 signaling in microglia.

CONCLUSIONS

C3AR1 was identified as a damaging neuroinflammatory factor. These data help suggest complement activation causes glaucomatous neurodegeneration through multiple mechanisms, including inflammation. Microglia and infiltrating myeloid cells expressed high levels of C3ar1 and are the primary candidates to mediate its effects. C3AR1 appeared to be a major regulator of microglia reactivity and neuroinflammatory function due to its interaction with IL10 signaling and other immune related pathways. Targeting myeloid-derived cells and C3AR1 signaling with therapies is expected to add to or improve neuroprotective therapeutic strategies.

Potential Therapeutic Benefit of NAD+ Supplementation for Glaucoma and Age-Related Macular Degeneration

Glaucoma and age-related macular degeneration are leading causes of irreversible blindness worldwide with significant health and societal burdens. To date, no clinical cures are available and treatments target only the manageable symptoms and risk factors (but do not remediate the underlying pathology of the disease). Both diseases are neurodegenerative in their pathology of the retina and as such many of the events that trigger cell dysfunction, degeneration, and eventual loss are due to mitochondrial dysfunction, inflammation, and oxidative stress. Here, we critically review how a decreased bioavailability of nicotinamide adenine dinucleotide (NAD; a crucial metabolite in healthy and disease states) may underpin many of these aberrant mechanisms. We propose how exogenous sources of NAD may become a therapeutic standard for the treatment of these conditions.

OPA1 deficiency accelerates hippocampal synaptic remodelling and age-related deficits in learning and memory

A healthy mitochondrial network is essential for the maintenance of neuronal synaptic integrity. Mitochondrial and metabolic dysfunction contributes to the pathogenesis of many neurodegenerative diseases including dementia. OPA1 is the master regulator of mitochondrial fusion and fission and is likely to play an important role during neurodegenerative events. To explore this, we quantified hippocampal dendritic and synaptic integrity and the learning and memory performance of aged Opa1 haploinsufficient mice carrying the Opa1Q285X mutation (B6; C3-Opa1Q285STOP ; Opa1+/- ). We demonstrate that heterozygous loss of Opa1 results in premature age-related loss of spines in hippocampal pyramidal CA1 neurons and a reduction in synaptic density in the hippocampus. This loss is associated with subtle memory deficits in both spatial novelty and object recognition. We hypothesize that metabolic failure to maintain normal neuronal activity at the level of a single spine leads to premature age-related memory deficits. These results highlight the importance of mitochondrial homeostasis for maintenance of neuronal function during ageing.

Ocular hypertension suppresses homeostatic gene expression in optic nerve head microglia of DBA/2 J mice

Glaucoma is the leading cause of irreversible vision loss. Ocular hypertension is a major risk factor for glaucoma and recent work has demonstrated critical early neuroinflammatory insults occur in the optic nerve head following ocular hypertension. Microglia and infiltrating monocytes are likely candidates to drive these neuroinflammatory insults. However, the exact molecular identity / transcriptomic profile of microglia following ocular hypertensive insults is unknown. To elucidate the molecular identity of microglia after long-term exposure to ocular hypertension, we used a mouse model of glaucoma (DBA/2 J). We performed RNA-sequencing of microglia mRNA from the optic nerve head at a time point following ocular hypertensive insults, but preceding detectable neurodegeneration (with microglia identified as being CD45^lo/CD11b⁺/CD11c⁻). Furthermore, RNA-sequencing was performed on optic nerve head microglia from mice treated with radiation therapy, a potent therapy preventing neuroinflammatory insults. Transcriptomic profiling of optic nerve head microglia mRNA identifies metabolic priming with marked changes in mitochondrial gene expression, and changes to phagocytosis, inflammatory, and sensome pathways. The data predict that many functions of microglia that help maintain tissue homeostasis are affected. Comparative analysis of these data with data from previously published whole optic nerve head tissue or monocyte-only samples from DBA/2 J mice demonstrate that many of the neuroinflammatory signatures in these data sets arise from infiltrating monocytes and not reactive microglia. Finally, our data demonstrate that prophylactic radiation therapy of DBA/2 J mice potently abolishes these microglia metabolic transcriptomic changes at the same time points. Together, our data provide a unique resource for the community to help drive further hypothesis generation and testing in glaucoma.

Midget retinal ganglion cell dendritic and mitochondrial degeneration is an early feature of human glaucoma

Glaucoma is characterized by the progressive dysfunction and loss of retinal ganglion cells. However, the earliest degenerative events that occur in human glaucoma are relatively unknown. Work in animal models has demonstrated that retinal ganglion cell dendrites remodel and atrophy prior to the loss of the cell soma. Whether this occurs in human glaucoma has yet to be elucidated. Serial block face scanning electron microscopy is well established as a method to determine neuronal connectivity at high resolution but so far has only been performed in normal retina from animal models. To assess the structure-function relationship of early human glaucomatous neurodegeneration, regions of inner retina assessed to have none-to-moderate loss of retinal ganglion cell number were processed using serial block face scanning electron microscopy (n = 4 normal retinas, n = 4 glaucoma retinas). This allowed detailed 3D reconstruction of retinal ganglion cells and their intracellular components at a nanometre scale. In our datasets, retinal ganglion cell dendrites degenerate early in human glaucoma, with remodelling and redistribution of the mitochondria. We assessed the relationship between visual sensitivity and retinal ganglion cell density and discovered that this only partially conformed to predicted models of structure-function relationships, which may be affected by these early neurodegenerative changes. In this study, human glaucomatous retinal ganglion cells demonstrate compartmentalized degenerative changes as observed in animal models. Importantly, in these models, many of these changes have been demonstrated to be reversible, increasing the likelihood of translation to viable therapies for human glaucoma.

Inhibition of monocyte-like cell extravasation protects from neurodegeneration in DBA/2J glaucoma

BACKGROUND

Glaucoma is characterized by the progressive dysfunction and loss of retinal ganglion cells. Recent work in animal models suggests that a critical neuroinflammatory event damages retinal ganglion cell axons in the optic nerve head during ocular hypertensive injury. We previously demonstrated that monocyte-like cells enter the optic nerve head in an ocular hypertensive mouse model of glaucoma (DBA/2 J), but their roles, if any, in mediating axon damage remain unclear.

METHODS

To understand the function of these infiltrating monocyte-like cells, we used RNA-sequencing to profile their transcriptomes. Based on their pro-inflammatory molecular signatures, we hypothesized and confirmed that monocyte-platelet interactions occur in glaucomatous tissue. Furthermore, to test monocyte function we used two approaches to inhibit their entry into the optic nerve head: (1) treatment with DS-SILY, a peptidoglycan that acts as a barrier to platelet adhesion to the vessel wall and to monocytes, and (2) genetic targeting of Itgam (CD11b, an immune cell receptor that enables immune cell extravasation).

RESULTS

Monocyte specific RNA-sequencing identified novel neuroinflammatory pathways early in glaucoma pathogenesis. Targeting these processes pharmacologically (DS-SILY) or genetically (Itgam / CD11b knockout) reduced monocyte entry and provided neuroprotection in DBA/2 J eyes.

CONCLUSIONS

These data demonstrate a key role of monocyte-like cell extravasation in glaucoma and demonstrate that modulating neuroinflammatory processes can significantly lessen optic nerve injury.

Digestion of the glycosaminoglycan extracellular matrix by chondroitinase ABC supports retinal ganglion cell dendritic preservation in a rodent model of experimental glaucoma

Retinal ganglion cell dendritic atrophy is an early feature of glaucoma, and the recovery of retinal ganglion cell dendrites is a viable option for vision improvement in glaucoma. Retinal ganglion cell neurites are surrounded by a specialised glycosaminoglycan extracellular matrix which inhibits dendritic plasticity. Since digestion of the extracellular matrix by chondroitinase ABC has been reported to have neuro-regenerative and neuro-plastic effects within the central nervous system, we explored its potential for dendritic recovery in a rat model of ocular hypertension. Chondroitinase ABC was administrated intravitreally 1 week after ocular hypertension (a time point where dendritic atrophy has already occurred). Retinal ganglion cell dendritic morphology was unaffected by chondroitinase ABC in normal retina. In ocular hypertensive eyes retinal ganglion cells showed significantly decreased dendritic length and area under the Sholl curve with atrophy confined to higher order dendrites. These changes were not observed in chondroitinase ABC injected eyes despite similar total retinal ganglion cell loss (i.e. dendritic protection of surviving retinal ganglion cells). These data suggest that glycosaminoglycan digestion could have a therapeutic role in mitigating the effects of elevated pressure on retinal ganglion cell dendritic structure in glaucoma.

Synthesis of cationic alkylated chitosans and an investigation of their rheological properties and interaction with anionic surfactant

Two methods were used to alkylate high M_W chitosan with glycidyltrimethylammonium chloride (GTAC) in order to produce chitosan derivatives that are water-soluble throughout the pH range. In addition, a novel chitosan derivative was created by alkylating one of the products with the GTAC analogue Quab 342 containing C12 alkyl chains. The phase behaviour and rheological characteristics of the chitosan derivatives were studied in the presence of anionic surfactant. The derivatives were found to form soluble complexes at low and high SDS concentrations and that the Quab 342 derivative was able to form gels.

Nicotinamide treatment robustly protects from inherited mouse glaucoma

Nicotinamide adenine dinucleotide (NAD) is a key molecule in several cellular processes and is essential for healthy mitochondrial metabolism. We recently reported that mitochondrial dysfunction is among the very first changes to occur within retinal ganglion cells during initiation of glaucoma in DBA/2J mice. Furthermore, we demonstrated that an age-dependent decline of NAD contributes to mitochondrial dysfunction and vulnerability to glaucoma. The decrease in NAD renders retinal ganglion cells vulnerable to a metabolic crisis following periods of high intraocular pressure. Treating mice with the NAD precursor nicotinamide (the amide form of vitamin B₃) inhibited many age- and high intraocular pressure- dependent changes with the highest tested dose decreasing the likelihood of developing glaucoma by ∼10-fold. In this communication, we present further evidence of the neuroprotective effects of nicotinamide against glaucoma in mice, including its prevention of optic nerve excavation and axon loss as assessed by histologic analysis and axon counting. We also show analyses of age- and intraocular pressure- dependent changes in transcripts of NAD producing enzymes within retinal ganglion cells and that nicotinamide treatment prevents these transcriptomic changes.

Glaucoma as a Metabolic Optic Neuropathy: Making the Case for Nicotinamide Treatment in Glaucoma

Mitochondrial dysfunction may be an important, if not essential, component of human glaucoma. Using transcriptomics followed by molecular and neurobiological techniques, we have recently demonstrated that mitochondrial dysfunction within retinal ganglion cells is an early feature in the DBA/2J mouse model of inherited glaucoma. Guided by these findings, we discovered that the retinal level of nicotinamide adenine dinucleotide (NAD, a key molecule for mitochondrial health) declines in an age-dependent manner. We hypothesized that this decline in NAD renders retinal ganglion cells susceptible to damage during periods of elevated intraocular pressure. To replete NAD levels in this glaucoma, we administered nicotinamide (the amide of vitamin B3). At the lowest dose tested, nicotinamide robustly protected from glaucoma (~70% of eyes had no detectable glaucomatous neurodegeneration). At this dose, nicotinamide had no influence on intraocular pressure and so its effect was neuroprotective. At the highest dose tested, 93% of eyes had no detectable glaucoma. This represents a ~10-fold decrease in the risk of developing glaucoma. At this dose, intraocular pressure still became elevated but there was a reduction in the degree of elevation showing an additional benefit. Thus, nicotinamide is unexpectedly potent at preventing this glaucoma and is an attractive option for glaucoma therapeutics. Our findings demonstrate the promise for both preventing and treating glaucoma by interventions that bolster metabolism during increasing age and during periods of elevated intraocular pressure. Nicotinamide prevents age-related declines in NAD (a decline that occurs in different genetic contexts and species). NAD precursors are reported to protect from a variety of neurodegenerative conditions. Thus, nicotinamide may provide a much needed neuroprotective treatment against human glaucoma. This manuscript summarizes human data implicating mitochondria in glaucoma, and argues for studies to further assess the safety and efficacy of nicotinamide in human glaucoma care.

Synthesis, characterisation and physicochemical properties of hydrophobically modified inulin using long-chain fatty acyl chlorides

A series of inulin derivatives were synthesized in aqueous solution using acyl chlorides with varying alkyl chain length (C10-C16). They were characterised using a number of techniques including MALDI TOF-MS, ¹H NMR and FTIR and their degree of substitution determined. The solution properties of the hydrophobically modified inulins were investigated using dye solubilisation and surface tension and it was confirmed that the molecules aggregated in solution above a critical concentration (critical aggregation concentration, CAC). The value of the CAC was found to be reasonably consistent between the different techniques and was shown to decrease with increasing hydrophobe chain length. It was found that the C10, C12 and C14 derivatives formed stable oil-in-water emulsions and the emulsion droplet size decreased with increasing alkyl chain length. The C16 derivative was not able to produce stable oil-in-water emulsions; however, it was able to form stable water-in-oil emulsions. The fact that the derivatives are able to form micellar-like aggregates and stabilise emulsions makes them suitable candidates for the encapsulation and delivery of active compounds with potential application in food, cosmetic, personal care and pharmaceutical formulations.

Early immune responses are independent of RGC dysfunction in glaucoma with complement component C3 being protective

Various immune response pathways are altered during early, predegenerative stages of glaucoma; however, whether the early immune responses occur secondarily to or independently of neuronal dysfunction is unclear. To investigate this relationship, we used the Wlds allele, which protects from axon dysfunction. We demonstrate that DBA/2J.Wlds mice develop high intraocular pressure (IOP) but are protected from retinal ganglion cell (RGC) dysfunction and neuroglial changes that otherwise occur early in DBA/2J glaucoma. Despite this, immune pathways are still altered in DBA/2J.Wlds mice. This suggests that immune changes are not secondary to RGC dysfunction or altered neuroglial interactions, but may be directly induced by the increased strain imposed by high IOP. One early immune response following IOP elevation is up-regulation of complement C3 in astrocytes of DBA/2J and DBA/2J.Wlds mice. Unexpectedly, because the disruption of other complement components, such as C1Q, is protective in glaucoma, C3 deficiency significantly increased the number of DBA/2J eyes with nerve damage and RGC loss at an early time point after IOP elevation. Transcriptional profiling of C3-deficient cultured astrocytes implicated EGFR signaling as a hub in C3-dependent responses. Treatment with AG1478, an EGFR inhibitor, also significantly increased the number of DBA/2J eyes with glaucoma at the same early time point. These findings suggest that C3 protects from early glaucomatous damage, a process that may involve EGFR signaling and other immune responses in the optic nerve head. Therefore, therapies that target specific components of the complement cascade, rather than global inhibition, may be more applicable for treating human glaucoma.

GlyCAM1 negatively regulates monocyte entry into the optic nerve head and contributes to radiation-based protection in glaucoma

BACKGROUND

We previously reported a profound long-term neuroprotection subsequent to a single radiation-therapy in the DBA/2J mouse model of glaucoma. This neuroprotection prevents entry of monocyte-like immune cells into the optic nerve head during glaucoma. Gene expression studies in radiation-treated mice implicated Glycam1 in this protection. Glycam1 encodes a proteoglycan ligand for L-selectin and is an excellent candidate to modulate immune cell entry into the eye. Here, we experimentally test the hypothesis that radiation-induced over-expression of Glycam1 is a key component of the neuroprotection.

METHODS

We generated a null allele of Glycam1 on a DBA/2J background. Gene and protein expression of Glycam1, monocyte entry into the optic nerve head, retinal ganglion cell death, and axon loss in the optic nerve were assessed.

RESULTS

Radiation therapy potently inhibits monocyte entry into the optic nerve head and prevents retinal ganglion cell death and axon loss. DBA/2J mice carrying a null allele of Glycam1 show increased monocyte entry and increased retinal ganglion cell death and axon loss following radiation therapy, but the majority of optic nerves were still protected by radiation therapy.

CONCLUSIONS

Although GlyCAM1 is an L-selectin ligand, its roles in immunity are not yet fully defined. The current study demonstrates a partial role for GlyCAM1 in radiation-mediated protection. Furthermore, our results clearly show that GlyCAM1 levels modulate immune cell entry from the vasculature into neural tissues. As Glycam1 deficiency has a more profound effect on cell entry than on neurodegeneration, further experiments are needed to precisely define the role of monocyte entry in DBA/2J glaucoma. Nevertheless, GlyCAM1's function as a negative regulator of extravasation may lead to novel therapeutic strategies for an array of common conditions involving inflammation.

Nicotinamide and WLDS Act Together to Prevent Neurodegeneration in Glaucoma

Glaucoma is a complex neurodegenerative disease characterized by progressive visual dysfunction leading to vision loss. Retinal ganglion cells are the primary affected neuronal population, with a critical insult damaging their axons in the optic nerve head. This insult is typically secondary to harmfully high levels of intraocular pressure (IOP). We have previously determined that early mitochondrial abnormalities within retinal ganglion cells lead to neuronal dysfunction, with age-related declines in NAD (NAD⁺ and NADH) rendering retinal ganglion cell mitochondria vulnerable to IOP-dependent stresses. The Wallerian degeneration slow allele, Wld^S, decreases the vulnerability of retinal ganglion cells in eyes with elevated IOP, but the exact mechanism(s) of protection from glaucoma are not determined. Here, we demonstrate that Wld^S increases retinal NAD levels. Coupled with nicotinamide administration (an NAD precursor), it robustly protects from glaucomatous neurodegeneration in a mouse model of glaucoma (94% of eyes having no glaucoma, more than Wld^S or nicotinamide alone). Importantly, nicotinamide and Wld^S protect somal, synaptic, and axonal compartments, prevent loss of anterograde axoplasmic transport, and protect from visual dysfunction as assessed by pattern electroretinogram. Boosting NAD production generally benefits major compartments of retinal ganglion cells, and may be of value in other complex, age-related, axonopathies where multiple neuronal compartments are ultimately affected.

Neuroinflammation in glaucoma: A new opportunity

Mounting evidence suggests neuroinflammation is a key process in glaucoma, yet the precise roles are not known. Understanding these complex processes, which may also be a key in other common neurodegenerations such as Alzheimer's disease, will lead to targeted therapeutics for a disease that affects as many as 80 million people worldwide. Here, we define neuroinflammation as any immune-relevant response by a variety of cell types including astrocytes, microglia, and peripherally derived cells occurring in the optic nerve head and/or retina. In this review article, we first discuss clinical evidence for neuroinflammation in glaucoma and define neuroinflammation in glaucoma. We then review the inflammatory pathways that have been associated with glaucoma. Finally, we set out key research directions that we believe will greatly advance our understanding of the role of neuroinflammation in glaucoma. This review arose from a discussion of neuroinflammation in glaucoma at the 2015 meeting of The Lasker/IRRF Initiative for Innovation in Vision Science. This manuscript sets out to summarize one of these sessions; "Inflammation and Glaucomatous Neurodegeneration", as well as to review the current state of the literature surrounding neuroinflammation in glaucoma.

Vitamin B3 modulates mitochondrial vulnerability and prevents glaucoma in aged mice

Glaucomas are neurodegenerative diseases that cause vision loss, especially in the elderly. The mechanisms initiating glaucoma and driving neuronal vulnerability during normal aging are unknown. Studying glaucoma-prone mice, we show that mitochondrial abnormalities are an early driver of neuronal dysfunction, occurring before detectable degeneration. Retinal levels of nicotinamide adenine dinucleotide (NAD+, a key molecule in energy and redox metabolism) decrease with age and render aging neurons vulnerable to disease-related insults. Oral administration of the NAD+ precursor nicotinamide (vitamin B3), and/or gene therapy (driving expression of Nmnat1, a key NAD+-producing enzyme), was protective both prophylactically and as an intervention. At the highest dose tested, 93% of eyes did not develop glaucoma. This supports therapeutic use of vitamin B3 in glaucoma and potentially other age-related neurodegenerations.

Inhibition of the classical pathway of the complement cascade prevents early dendritic and synaptic degeneration in glaucoma

Background

Glaucoma is a complex, multifactorial disease characterised by the loss of retinal ganglion cells and their axons leading to a decrease in visual function. The earliest events that damage retinal ganglion cells in glaucoma are currently unknown. Retinal ganglion cell death appears to be compartmentalised, with soma, dendrite and axon changes potentially occurring through different mechanisms. There is mounting evidence from other neurodegenerative diseases suggesting that neuronal dendrites undergo a prolonged period of atrophy, including the pruning of synapses, prior to cell loss. In addition, recent evidence has shown the role of the complement cascade in synaptic pruning in glaucoma and other diseases.

Results

Using a genetic (DBA/2J mouse) and an inducible (rat microbead) model of glaucoma we first demonstrate that there is loss of retinal ganglion cell synapses and dendrites at time points that precede axon or soma loss. We next determine the role of complement component 1 (C1) in early synaptic loss and dendritic atrophy during glaucoma. Using a genetic knockout of C1qa (D2.C1qa^-/- mouse) or pharmacological inhibition of C1 (in the rat bead model) we show that inhibition of C1 is sufficient to preserve dendritic and synaptic architecture.

Conclusions

This study further supports assessing the potential for complement-modulating therapeutics for the prevention of retinal ganglion cell degeneration in glaucoma.

Abstract P1-01-11: Nuclear immunohistochemical IKK-ϵexpression in flat epithelial atypia (FEA) of the breast: A predictor of ipsilateral ADH, in-situ or invasive malignancy?

Background:Flat Epithelial Atypia of the breast (FEA) is associated with in situ and invasive low grade neoplasia. However, the role of excision after FEA on biopsy is controversial as rates of upgrading to atypical ductal hyperplasia (ADH), ductal carcinoma in situ (DCIS) or invasive carcinoma in subsequent excision are relatively low. Problems include difficulties in inter-observer reproducibility and lack of morphologic or immunohistochemistry (IHC) tools that better identify cases at risk for concurrent ADH/Carcinoma. Nuclear image analysis may be useful, but is not widely available. IKK-ϵ, part of the NF-kB activating pathway, is absent in normal breast epithelium and non atypical (usual) ductal hyperplasia, but is over-expressed in >30% of breast cancers. In addition, in our experience ADH/DCIS shows IKK-ϵ staining, mostly cytoplasmic. Of note, in prostate cancer, nuclear accumulation of IKK-ϵ has been described in hormone sensitive prostate disease while cytoplasmic accumulation is associated with metastatic progression. No previous studies of IKK-ϵ levels in FEA are reported. Here we report IKK-ϵ status in FEA and correlation with ipsilateral, synchronous ADH, DCIS or invasive carcinoma.

Method: Resection specimens from 61 patients with diagnosis of FEA were retrieved. Presence of ADH/carcinoma and laterality (ipsi or contralateral) was recorded. Synchronous neoplasia was defined as ADH, DCIS or invasive carcinoma diagnosed within 6 months of the diagnosis of FEA. Presence of FEA was confirmed by three observers using strict morphologic criteria. IHC for IKK-ϵ was performed using ABCAM, rabbit anti-IKK-ϵ (ab7891) and pH 6 citrate buffer heat-induced epitope retrieval for 20 minutes. IHC slides were scanned and FEA regions captured for blind scoring of nuclear and cytoplasmic staining. Cut off for positive nuclear staining was 10% and cytoplasmic staining was graded as negative, weak, moderate or strong positive.

Results:40 patients had ipsilateral synchronous ADH/carcinoma, and 21 did not. Within these groups, 6 patients had contralateral ADH/carcinoma (2 with and 4 without ipsilateral neoplasia). While cytoplasmic staining showed no difference between the groups, nuclear positivity was more frequent in cases with ipsilateral synchronous ADH/carcinoma, χ2(1, N = 61) = 5.1, p = .025 (Table 1). In contrast, there was no correlation between IKK-ϵ staining and ADH/carcinoma in the opposite breast (p=.25).

Table 1Nuclear IKK-eSynchronous Ipsilateral ADH/DCIS/Carcinoma Negative (%)Positive (%)TotalNegative10 (48)11 (52)21Positive10 (25)30 (75)40

Conclusion:Nuclear IKK-ϵ staining may prove useful in predicting synchronous ipsilateral ADH or malignancy in cases of FEA in biopsy material. Given its more frequent association with ipsilateral synchronous ADH/carcinoma, IKK-ϵ nuclear expression in FEA may represent a step in continuous local oncogenesis rather than a general marker of risk. Given the pleiotropic role of IKK-ϵ in growth and survival, the significance of the shift from nuclear staining in FEA to cytoplasmic staining in ADH/DCIS may reflect different signaling pathways and requires further investigation. Further validation of our findings in larger cohorts is necessary.

Citation Format: Williams PA, Parra-Herran CE, Ayroud Y, Islam S, Gravel DH, Robertson SJ, Pratt C. Nuclear immunohistochemical IKK-ϵexpression in flat epithelial atypia (FEA) of the breast: A predictor of ipsilateral ADH, in-situ or invasive malignancy?. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P1-01-11.

Orexigenic Gene Expression in Late Gestation Ovine Foetal Hypothalamus is Sensitive to Maternal Undernutrition and Realimentation

Adverse nutritional effects on developing foetal hypothalamic appetitive pathways may contribute to programmed hyperphagia and obesity in intra-uterine growth-restricted, low birth weight offspring. In the present study, for the first time, hypothalamic gene expression for primary orexigenic and anorexigenic genes was examined in late gestation ovine foetuses (130 days; term=145 days) whose mothers were undernourished (UN) or well-nourished (C) throughout pregnancy, or transferred from UN to C on day 90 (UN-C). Pregnancies resulted from singleton embryo transfer into adolescent growing ewes. Body weight, carcass fat content and perirenal adipose tissue (PAT) mass were all lower for UN (n=9) than C (n=7) and intermediate for UN-C foetuses (n=6), with no effect of sex. PAT leptin gene expression (by the reverse transcriptase-polymerase chain reaction) was lower in UN than C and UN-C groups, and lower in males than females. Gene expression (by in situ hybridisation with radiolabelled riboprobes) in the arcuate nucleus was greater in UN than C foetuses for neuropeptide Y (NPY), agouti-related peptide (AGRP) and leptin receptor (OBRb) but not different for pro-opiomelanocortin and cocaine- and amphetamine-regulated transcript. Gene expression in UN-C foetuses was intermediate for NPY and AGRP and not different from C foetuses for OBRb. Gene expression for NPY, AGRP and OBRb correlated negatively with foetal carcass fat content and with PAT leptin gene expression across all groups. Males had greater mRNA expression for AGRP than females, with NPY and OBRb showing similar trends. Therefore, maternal undernutrition throughout pregnancy increased orexigenic gene expression in the late gestation foetal hypothalamus, and expression levels were largely normalised by improved maternal nutrition in the last third of pregnancy. These findings may have implications for avoiding or correcting prenatal programming of postnatal hyperphagia and obesity.