Granzyme B degrades extracellular matrix and promotes inflammation and choroidal neovascularization.

Age-related macular degeneration (AMD) is a common retinal neurodegenerative disease among the elderly. Neovascular AMD (nAMD), a leading cause of AMD-related blindness, involves choroidal neovascularization (CNV), which can be suppressed by anti-angiogenic treatments. However, current CNV treatments do not work in all nAMD patients. Here we investigate a novel target for AMD. Granzyme B (GzmB) is a serine protease that promotes aging, chronic inflammation and vascular permeability through the degradation of the extracellular matrix (ECM) and tight junctions. Extracellular GzmB is increased in retina pigment epithelium (RPE) and mast cells in the choroid of the healthy aging outer retina. It is further increased in donor eyes exhibiting features of nAMD and CNV. Here, we show in RPE-choroidal explant cultures that exogenous GzmB degrades the RPE-choroid ECM, promotes retinal/choroidal inflammation and angiogenesis while diminishing anti-angiogenic factor, thrombospondin-1 (TSP-1). The pharmacological inhibition of either GzmB or mast-cell degranulation significantly reduces choroidal angiogenesis. In line with our in vitro data, GzmB-deficiency reduces the extent of laser-induced CNV lesions and the age-related deterioration of electroretinogram (ERG) responses in mice. These findings suggest that targeting GzmB, a serine protease with no known endogenous inhibitors, may be a potential novel therapeutic approach to suppress CNV in nAMD.

Ergothioneine, a dietary antioxidant improves amyloid beta clearance in the neuroretina of a mouse model of Alzheimer's disease.

Introduction: Ergothioneine (Ergo) is a naturally occurring dietary antioxidant. Ergo uptake is dependent on the transporter, organic cation transporter novel-type 1 (OCTN1) distribution. OCTN1 is highly expressed in blood cells (myeloid lineage cells), brain and ocular tissues that are likely predisposed to oxidative stress. Ergo may protect the brain and eye against oxidative damage and inflammation, however, the underlying mechanism remains unclear. Amyloid beta (Aß) clearance is a complex process mediated by various systems and cell types including vascular transport across the blood-brain barrier, glymphatic drainage, and engulfment and degradation by resident microglia and infiltrating innate immune cells. Impaired Aß clearance is a major cause for Alzheimer's disease (AD). Here we investigated neuroretinas to explore the neuroprotective effect of Ergo in a transgenic AD mouse model. Methods: Age-matched groups of Ergo-treated 5XFAD, non-treated 5XFAD, and C57BL/6J wildtype (WT controls) were used to assess Ergo transporter OCTN1 expression and Aß load along with microglia/macrophage (IBA1) and astrocyte (GFAP) markers in wholemount neuroretinas (n = 26) and eye cross-sections (n = 18). Immunoreactivity was quantified by fluorescence or by semi-quantitative assessments. Results and discussion: OCTN1 immunoreactivity was significantly low in the eye cross-sections of Ergo-treated and non-treated 5XFAD vs. WT controls. Strong Aß labeling, detected in the superficial layers in the wholemounts of Ergo-treated 5XFAD vs. non-treated 5XFAD reflects the existence of an effective Aß clearance system. This was supported by imaging of cross-sections where Aß immunoreactivity was significantly low in the neuroretina of Ergo-treated 5XFAD vs. non-treated 5XFAD. Moreover, semi-quantitative analysis in wholemounts identified a significantly reduced number of large Aß deposits or plaques, and a significantly increased number of IBA1(+)ve blood-derived phagocytic macrophages in Ergo-treated 5XFAD vs. non-treated 5XFAD. In sum, enhanced Aß clearance in Ergo-treated 5XFAD suggests that Ergo uptake may promote Aß clearance possibly by blood-derived phagocytic macrophages and via perivascular drainage.

Granzyme B Contributes to Choroidal Neovascularization and Age-Related Macular Degeneration Through Proteolysis of Thrombospondin-1.

Age-related macular degeneration (AMD) is a leading cause of irreversible central vision loss in the elderly. The pathology of neovascular age-related macular degeneration (nAMD), also known as wet AMD, is associated with an abnormal blood vessel growth in the eye and involves an imbalance of proangiogenic and antiangiogenic factors. Thrombospondin (TSP)-1 and TSP-2 are endogenous matricellular proteins that inhibit angiogenesis. TSP-1 is significantly diminished in eyes with AMD, although the mechanisms involved in its reduction are unknown. Granzyme B (GzmB) is a serine protease with an increased extracellular activity in the outer retina and choroid of human eyes with nAMD-related choroidal neovascularization (CNV). This study investigated whether TSP-1 and TSP-2 are GzmB substrates using in silico and cell-free cleavage assays and explored the relationship between GzmB and TSP-1 in human eyes with nAMD-related CNV and the effect of GzmB on TSP-1 in retinal pigment epithelial culture and an explant choroid sprouting assay (CSA). In this study, TSP-1 and TSP-2 were identified as GzmB substrates. Cell-free cleavage assays substantiated the GzmB proteolysis of TSP-1 and TSP-2 by showing dose-dependent and time-dependent cleavage products. TSP-1 and TSP-2 proteolysis were hindered by the inhibition of GzmB. In the retinal pigment epithelium and choroid of human eyes with CNV, we observed a significant inverse correlation between TSP-1 and GzmB, as indicated by lower TSP-1 and higher GzmB immunoreactivity. In CSA, the vascular sprouting area increased significantly with GzmB treatment and reduced significantly with TSP-1 treatment. Western blot showed significantly reduced expression of TSP-1 in GzmB-treated retinal pigment epithelial cell culture and CSA supernatant compared with that in controls. Together, our findings suggest that the proteolysis of antiangiogenic factors such as TSP-1 by extracellular GzmB might represent a mechanism through which GzmB may contribute to nAMD-related CNV. Future studies are needed to investigate whether pharmacologic inhibition of extracellular GzmB can mitigate nAMD-related CNV by preserving intact TSP-1.

Müller cell degeneration and microglial dysfunction in the Alzheimer's retina.

Amyloid beta (Aß) deposits in the retina of the Alzheimer's disease (AD) eye may provide a useful diagnostic biomarker for AD. This study focused on the relationship of Aß with macroglia and microglia, as these glial cells are hypothesized to play important roles in homeostasis and clearance of Aß in the AD retina. Significantly higher Aß load was found in AD compared to controls, and specifically in the mid-peripheral region. AD retina showed significantly less immunoreactivity against glial fibrillary acidic protein (GFAP) and glutamine synthetase (GS) compared to control eyes. Immunoreactivity against ionized calcium binding adapter molecule-1 (IBA-1), a microglial marker, demonstrated a higher level of microgliosis in AD compared to control retina. Within AD retina, more IBA-1 immunoreactivity was present in the mid-peripheral retina, which contained more Aß than the central AD retina. GFAP co-localized rarely with Aß, while IBA-1 co-localized with Aß in more layers of control than AD donor retina. These results suggest that dysfunction of the Müller and microglial cells may be key features of the AD retina.

Inhalable Thioflavin S for the Detection of Amyloid Beta Deposits in the Retina.

We present an integrated delivery technology herein employing the aerosolized method to repurpose thioflavin S for imaging amyloid beta (Abeta) deposits in the retina as a surrogate of Abeta in the brain for early detection of Alzheimer's disease. The data showed that wild type (WT) mice also have Abeta deposits in the retinae, albeit much less than 5XFAD mice. Further, only in 5XFAD mice, significant Abeta deposits were found associated with retinal ganglion cells (RGCs) in whole-mount and cross-section data. Furthermore, the fluorescent signal depicted from thioflavin S corroborates with Abeta immunohistochemistry staining information. Overall, this probe delivery via inhalation method is also applicable to other Abeta-binding molecules, such as Congo red, curcumin, and thioflavin T. The advantage of imaging retinal amyloid deposits compared to the brain counterparts is that the eye is easily accessible by in vivo imaging and it reduces the effort to design a probe that must cross the formidable blood-brain barrier.

Amyloid Beta Immunoreactivity in the Retinal Ganglion Cell Layer of the Alzheimer's Eye.

Alzheimer's disease (AD) is the most prevalent form of dementia, accounting for 60-70% of all dementias. AD is often under-diagnosed and recognized only at a later, more advanced stage, and this delay in diagnosis has been suggested as a contributing factor in the numerous unsuccessful AD treatment trials. Although there is no known cure for AD, early diagnosis is important for disease management and care. A hallmark of AD is the deposition of amyloid-ß (Aß)-containing senile neuritic plaques and neurofibrillary tangles composed of hyperphosporylated tau in the brain. However, current in vivo methods to quantify Aß in the brain are invasive, requiring radioactive tracers and positron emission tomography. Toward development of alternative methods to assess AD progression, we focus on the retinal manifestation of AD pathology. The retina is an extension of the central nervous system uniquely accessible to light-based, non-invasive ophthalmic imaging. However, earlier studies in human retina indicate that the literature is divided on the presence of Aß in the AD retina. To help resolve this disparity, this study assessed retinal tissues from neuropathologically confirmed AD cases to determine the regional distribution of Aß in retinal wholemounts and to inform on future retinal image studies targeting Aß. Concurrent post-mortem brain tissues were also collected. Neuropathological cortical assessments including neuritic plaque (NP) scores and cerebral amyloid angiopathy (CAA) were correlated with retinal Aß using immunohistochemistry, confocal microscopy, and quantitative image analysis. Aß load was compared between AD and control (non-AD) eyes. Our results indicate that levels of intracellular and extracellular Aß retinal deposits were significantly higher in AD than controls. Mid-peripheral Aß levels were greater than central retina in both AD and control eyes. In AD retina, higher intracellular Aß was associated with lower NP score, while higher extracellular Aß was associated with higher CAA score. Our data support the feasibility of using the retinal tissue to assess ocular Aß as a surrogate measure of Aß in the brain of individuals with AD. Specifically, mid-peripheral retina possesses more Aß deposition than central retina, and thus may be the optimal location for future in vivo ocular imaging.

In vivo Retinal Fluorescence Imaging With Curcumin in an Alzheimer Mouse Model.

Alzheimer's disease (AD) is characterized by amyloid beta (Aß) plaques in the brain detectable by highly invasive in vivo brain imaging or in post-mortem tissues. A non-invasive and inexpensive screening method is needed for early diagnosis of asymptomatic AD patients. The shared developmental origin and similarities with the brain make the retina a suitable surrogate tissue to assess Aß load in AD. Using curcumin, a FluoroProbe that binds to Aß, we labeled and measured the retinal fluorescence in vivo and compared with the immunohistochemical measurements of the brain and retinal Aß load in the APP/PS1 mouse model. In vivo retinal images were acquired every 2 months using custom fluorescence scanning laser ophthalmoscopy (fSLO) after tail vein injections of curcumin in individual mice followed longitudinally from ages 5 to 19 months. At the same time points, 1-2 mice from the same cohort were sacrificed and immunohistochemistry was performed on their brain and retinal tissues. Results demonstrated cortical and retinal Aß immunoreactivity were significantly greater in Tg than WT groups. Age-related increase in retinal Aß immunoreactivity was greater in Tg than WT groups. Retinal Aß immunoreactivity was present in the inner retinal layers and consisted of small speck-like extracellular deposits and intracellular labeling in the cytoplasm of a subset of retinal ganglion cells. In vivo retinal fluorescence with curcumin injection was significantly greater in older mice (11-19 months) than younger mice (5-9 months) in both Tg and WT groups. In vivo retinal fluorescence with curcumin injection was significantly greater in Tg than WT in older mice (ages 11-19 months). Finally, and most importantly, the correlation between in vivo retinal fluorescence with curcumin injection and Aß immunoreactivity in the cortex was stronger in Tg compared to WT groups. Our data reveal that retina and brain of APP/PS1 Tg mice increasingly express Aß with age. In vivo retinal fluorescence with curcumin correlated strongly with cortical Aß immunohistochemistry in Tg mice. These findings suggest that using in vivo fSLO imaging of AD-susceptible retina may be a useful, non-invasive method of detecting Aß in the retina as a surrogate indicator of Aß load in the brain.

Evidence for the activation of pyroptotic and apoptotic pathways in RPE cells associated with NLRP3 inflammasome in the rodent eye.

BACKGROUND: Age-related macular degeneration (AMD) is a devastating eye disease causing irreversible vision loss in the elderly. Retinal pigment epithelium (RPE), the primary cell type that is afflicted in AMD, undergoes programmed cell death in the late stages of the disease. However, the exact mechanisms for RPE degeneration in AMD are still unresolved. The prevailing theories consider that each cell death pathway works independently and without regulation of each other. Building upon our previous work in which we induced a short burst of inflammasome activity in vivo, we now investigate the effects of prolonged inflammasome activity on RPE cell death mechanisms in rats. METHODS: Long-Evans rats received three intravitreal injections of amyloid beta (Aß), once every 4 days, and were sacrificed at day 14. The vitreous samples were collected to assess the levels of secreted cytokines. The inflammasome activity was evaluated by both immunohistochemistry and western blot. The types of RPE cell death mechanisms were determined using specific cell death markers and morphological characterizations. RESULTS: We found robust inflammasome activation evident by enhanced caspase-1 immunoreactivity, augmented NF-κB nuclear translocalization, increased IL-1ß vitreal secretion, and IL-18 protein levels. Moreover, we observed elevated proteolytic cleavage of caspase-3 and gasdermin D, markers for apoptosis and pyroptosis, respectively, in RPE-choroid tissues. There was also a significant reduction in the anti-apoptotic factor, X-linked inhibitor of apoptosis protein, consistent with the overall changes of RPE cells. Morphological analysis showed phenotypic characteristics of pyroptosis including RPE cell swelling. CONCLUSIONS: Our data suggest that two cell death pathways, pyroptosis and apoptosis, were activated in RPE cells after exposure to prolonged inflammasome activation, induced by a drusen component, Aß. The involvement of two distinct cell death pathways in RPE sheds light on the potential interplay between these pathways and provides insights on the future development of therapeutic strategies for AMD.

LAMELLAR HOLE-ASSOCIATED EPIRETINAL PROLIFERATION: A Clinicopathologic Correlation.

PURPOSE: To correlate clinical and optical coherence tomographic features with histopathological and immunohistochemical findings in an eye undergoing surgical excision of lamellar hole-associated epiretinal proliferation (LHEP). METHODS: An eye with a lamellar macular hole and LHEP without a tractional epiretinal membrane component was identified with spectral-domain optical coherence tomographic imaging and underwent pars plana vitrectomy with LHEP and internal limiting membrane peeling and gas tamponade. The surgically excised LHEP specimen was analyzed with histopathological and immunohistochemical staining using flat-mount preparation techniques. Postsurgical outcomes including visual acuity and optical coherence tomographic imaging were reviewed. RESULTS: With spectral-domain optical coherence tomography, the lamellar macular hole was found to be closed with no residual LHEP after the surgery. Visual acuity improved from 20/200 preoperatively to 20/40 at 6 months after the surgery. Histopathological and immunohistochemical analyses of the LHEP specimen revealed retinal glial cells that reacted positively with anti-glial fibrillary acidic protein and anti-glutamine synthetase, a Müller cell-specific antibody. CONCLUSION: Lamellar macular hole with LHEP may demonstrate closure after pars plana vitrectomy with LHEP and internal limiting membrane peeling and gas tamponade. There was considerable improvement in visual acuity. It is possible that LHEP originates from middle retinal layers of the lamellar hole defect because it contains retinal glial cells, specifically Müller cells.

Age-related increases in amyloid beta and membrane attack complex: evidence of inflammasome activation in the rodent eye.

BACKGROUND: The membrane attack complex (MAC) is a key player in the pathogenesis of age-related macular degeneration (AMD) and is a putative activator of the NLRP3 inflammasome. Amyloid beta (Aß), a component of drusen deposits, has also been implicated in inflammasome activation by our work and those of others. However, the interactions of MAC and Aß are still poorly understood, especially their roles in aging and retinal degenerative pathologies. Since inflammasome activation may represent a key cellular pathway underlying age-related chronic inflammation in the eye, the purpose of this study is to identify the effects associated with MAC and inflammasome activation in the retinal pigment epithelium (RPE)/choroid and to evaluate the therapeutic merits of MAC suppression. METHODS: Adult Long-Evans rats were divided into treatment and control groups. Treatment groups received oral aurin tricarboxylic acid complex (ATAC), a MAC inhibitor, in drinking-water, and control groups received drinking-water alone (No ATAC). Groups were sacrificed at 7.5 or 11.5 months, after approximately 40 days of ATAC treatment. To study age-related changes of Aß and MAC in RPE/choroid, naive animals were sacrificed at 2.5, 7.5, and 11.5 months. Eye tissues underwent immunohistochemistry and western blot analysis for MAC, Aß, NF-κB activation, as well as cleaved caspase-1 and IL-18. Vitreal samples were collected and assessed by multiplex assays for secreted levels of IL-18 and IL-1ß. Statistical analyses were performed, and significance level was set at p ≤ 0.05. RESULTS: In vivo studies demonstrated an age-dependent increase in MAC, Aß, and NF-κB activation in the RPE/choroid. Systemic ATAC resulted in a prominent reduction in MAC formation and a concomitant reduction in inflammasome activation measured by cleaved caspase-1 and secreted levels of IL-18 and IL-1ß, but not in NF-κB activation. In vitro studies demonstrated Aß-induced MAC formation on RPE cells. CONCLUSIONS: Age-dependent increases in Aß and MAC are present in the rodent outer retina. Our results suggest that suppressing MAC formation and subsequent inflammasome activation in the RPE/choroid may reduce chronic low-grade inflammation associated with IL-18 and IL-1ß in the outer retina.

CFH Y402H polymorphism is associated with elevated vitreal GM-CSF and choroidal macrophages in the postmortem human eye.

PURPOSE: Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in people 50 years of age or older in developed countries. The homozygous CC genotype in the complement factor H (CFH) Y402H single nucleotide polymorphism (SNP; rs1061170) is widely recognized as a risk factor for the development of AMD. In this study, we examined vitreal levels of granulocyte macrophage colony-stimulating factor (GM-CSF), a hematopoietic cytokine, and macrophages in the choroid of postmortem human eyes genotyped for the CFH Y402H SNP. METHODS: Twenty-two pairs of postmortem, non-diseased, human donor eyes were obtained. The vitreous and retinal tissues of the left eyes were collected for GM-CSF level measurement and CFH Y402H genotyping, respectively. The right eyes were paraffin-embedded and sectioned for immunohistochemistry using a macrophage and microglia marker, CD68. Cell cultures of RPE cells were stimulated with complement C3a, C5a, 4-hydroxynonenal (HNE), or tumor necrosis factor alpha (TNF-α), and GM-CSF expression was measured with a suspension assay or quantitative PCR. RESULTS: Eyes genotyped with the CC or the CT risk variant of the CFH Y402H SNP showed significantly increased levels of GM-CSF in the vitreous compared to eyes with the protective TT variant (mean ± standard error of mean, 607.54±85.83 pg/ml or 656.32±15.20 pg/ml versus 286.69±81.96 pg/ml, p<0.05). The choroid of eye tissues genotyped with the CC variant showed higher levels of CD68 immunoreactivity than the tissues genotyped with the TT variant (p<0.05). The GM-CSF levels detected in the supernatant of RPE cells in culture treated with HNE or TNF-α were significantly higher compared to the non-treated control (145.88±5.06 pg/ml and 149.32±3.76 pg/ml versus 123.27±4.05 pg/ml, p<0.05). Furthermore, the gene expression of GM-CSF detected in the lysate of RPE cells stimulated with complement C3a or C5a showed significantly increased fold changes compared to the non-treated control (C3a: 2.38±0.31 fold, p<0.05; C5a: 2.84±0.54 fold, p<0.01). CONCLUSIONS: Our data showed a relationship between the CFH Y402H polymorphism and GM-CSF levels in the vitreous and accumulation of choroidal macrophages in the postmortem eye. These data suggest that the at-risk variant of the CFH gene may contribute to the dysregulation of proinflammatory cytokines locally in the eye.

NLRP3 inflammasome: activation and regulation in age-related macular degeneration.

Age-related macular degeneration (AMD) is the leading cause of legal blindness in the elderly in industrialized countries. AMD is a multifactorial disease influenced by both genetic and environmental risk factors. Progression of AMD is characterized by an increase in the number and size of drusen, extracellular deposits, which accumulate between the retinal pigment epithelium (RPE) and Bruch's membrane (BM) in outer retina. The major pathways associated with its pathogenesis include oxidative stress and inflammation in the early stages of AMD. Little is known about the interactions among these mechanisms that drive the transition from early to late stages of AMD, such as geographic atrophy (GA) or choroidal neovascularization (CNV). As part of the innate immune system, inflammasome activation has been identified in RPE cells and proposed to be a causal factor for RPE dysfunction and degeneration. Here, we will first review the classic model of inflammasome activation, then discuss the potentials of AMD-related factors to activate the inflammasome in both nonocular immune cells and RPE cells, and finally introduce several novel mechanisms for regulating the inflammasome activity.

Vinpocetine inhibits amyloid-beta induced activation of NF-κB, NLRP3 inflammasome and cytokine production in retinal pigment epithelial cells.

Chronic inflammation is a key pathogenic process in age-related macular degeneration (AMD). Amyloid-beta (Aß) is a constituent of AMD drusen and promotes the activation of NLRP3 inflammasome which facilitates the production of cytokines. We investigated the role of transcription factor NF-κB in the activation of inflammasome in the RPE and the effect of vinpocetine, a dietary supplement with inhibitory effect on NF-κΒ. ARPE19/NF-κB-luciferase reporter cells treated with Aß demonstrated enhanced NF-κB activation that was significantly suppressed by vinpocetine. Intraperitoneal injection of vinpocetine (15 mg/kg) inhibited NF-κB nuclear translocation and reduced the expression and activation of NLRP3, caspase-1, IL-1ß, IL-18, and TNF-α in the RPE of adult rats that received intraocular Αß, as measured by retinal immunohistochemistry and Western blot. Cytokine level in the vitreous was assayed using multiplex suspension arrays and revealed significantly lower concentration of MIP-3α, IL-6, IL-1α, IL-1ß, IL-18, and TNF-α in vinpocetine treated animals. These results suggest that the NF-κB pathway is activated by Aß in the RPE and signals the priming of NLRP3 inflammasome and the expression of pro-inflammatory cytokines including the inflammasome substrates IL-1ß and IL-18. NF-κB inhibition may be an effective approach to stem the chronic inflammatory milieu that underlies the development of AMD. Vinpocetine is a potentially useful anti-inflammatory agent that is well-tolerated in long term use.

Astrocyte and microglial activation in the lateral geniculate nucleus and visual cortex of glaucomatous and optic nerve transected primates.

PURPOSE: To examine early cellular changes, including astrocyte reactivity and microglial activation, in the central nervous system (CNS) after unilateral optic nerve transection (ONT) or ocular hypertension (OHT) in monkeys. METHODS: Unilateral ONT or OHT was achieved in monkeys for periods ranging from two weeks to two months in duration. After intracardial perfusion, sections of the lateral geniculate nucleus (LGN) and visual cortex (V1) were examined by immunohistochemistry for glial fibrillary acidic protein (GFAP) and CD11b, a subunit of the complement 3 receptor and marker of macrophage and microglia cells (MAC-1). Alternate serial sections were evaluated by cytochrome oxidase (CO) histochemistry to assess metabolic activity. RESULTS: Both ONT and OHT caused a reduction in metabolic activity in the treated eye layers of the LGN and V1. GFAP and MAC-1 immunoreactivities were elevated in spatial register with the treated eye layers of the LGN and V1 in ONT animals. In the OHT animals, GFAP, but not MAC-1, immunoreactivity was elevated in spatial register with the treated eye layers of LGN and V1. Thus, during the first weeks after OHT or ONT, loss of metabolic activity was accompanied by astrocyte and microglial activation in the ONT group and astrocyte activation in the OHT animals. CONCLUSIONS: These results suggest that unilateral OHT or ONT triggers separate signaling pathways that promote differential activation of CNS glial populations. Astrocyte reactivity was present in all brains studied and demonstrates the loss of metabolic activity is accompanied by increased GFAP immunoreactivity. Microglial activation was only observed in ONT brains. The lack of microglial activation as late as two months following OHT may represent a time window for early treatment to prevent long-term neuronal loss in the CNS after OHT.

Amyloid-beta deposits lead to retinal degeneration in a mouse model of Alzheimer disease.

PURPOSE: To compare the temporal and spatial expression patterns of amyloid precursor protein (APP), amyloid-beta deposits, inflammatory chemokines, and apoptosis in the retina of a mouse model of Alzheimer disease (AD). METHODS: Retinas of transgenic mice harboring a mutant presenilin (PS1) and a mutant APP gene were processed for TUNEL and immunohistochemistry with antibodies against APP, amyloid-beta, monocyte chemotactic protein (MCP)-1, and F4/80. Comparisons were made between age groups and between transgenic and wild-type congeners. RESULTS: The neuroretina demonstrated age-dependent increases in APP in the ganglion cells (RGCs) and in neurons of the inner nuclear layer (INL). Amyloid-beta demonstrated significant age-dependent deposition in the nerve fiber layer (NFL). TUNEL-positive RGC increased in an age-dependent fashion and in transgenic compared with wild-type congeners. Concomitant overexpression of MCP-1 and intense immunoreactivity for F4/80 suggested that RGCs upregulate MCP-1 in response to amyloid-beta. Activated microglia proliferated in response to MCP-1. In the outer retina, retinal pigment epithelium (RPE) demonstrated moderate age-dependent APP immunoreactivity, but nearby drusenlike deposits were not present. Amyloid-beta was observed in the choriocapillaris of the older animals. CONCLUSIONS: Amyloid-beta deposits accumulate with age in the retina of a transgenic mouse model of AD. The amyloid-beta loads are accompanied by increased immunoreactivity for MCP-1, F4/80, and TUNEL-positive profiles in the RGC layer. The results suggest that amyloid-beta causes neurodegeneration in the retina of the doubly mutant transgenic mouse model of AD.

Complement-associated deposits in the human retina.

PURPOSE: The purpose of this study was to investigate complement activation and associated inflammatory mechanisms in normal, aged human retina. METHODS: Evidence of complement activation and associated mechanisms was assessed in normal human retina (n = 52) using a panel of antibodies directed against membrane attack complex (C5b-9), microglia (CD11b), amyloid precursor protein (APP), scavenger receptor (CD36), and a phytolectin (RCA-I). Fifty-two eyes, categorized into two age groups, were used. Nineteen "younger" eyes (<56 years) and 33 "older" eyes (>69 years) with no history of ocular disease were processed between 4 and 22 hours, with a median delay of 14 hours postmortem. RESULTS: Age-dependent expression was evident in C5b-9, APP, CD11b, and RCA-I, but not CD36, immunoreactivity. Immunoreactivity for C5b-9 was robust in Bruch membrane (BM) and the intercapillary pillars of Bruch. Immunoreactivity for APP was robust in the basal cytoplasm of the retinal pigment epithelium. Immunoreactivity for CD11b was robust on the surface of the retinal pigment epithelial cell, in the choriocapillaris, and in BM. Lectin binding of RCA-I was strong throughout the neuroretina. CONCLUSIONS: Robust immunostaining for APP in older donor eyes suggested that amyloid beta peptides may be one of the triggers of complement activation during the normal aging process. Microglial markers CD11b and RCA-I also increase with age, suggesting a concomitant inflammatory response to C5b-9 deposits in the retinal pigment epithelium, BM, and CC. Immunoreactivity for CD36 was strong in both age groups; the lack of age dependence in this candidate receptor for amyloid beta suggested that complement activation may arise from interactions of amyloid beta with other candidate receptors in normal human retina.

Neurochemical correlates of cortical plasticity after unilateral elevated intraocular pressure in a primate model of glaucoma.

PURPOSE: To examine the time course of changes in the expression patterns of several synaptic plasticity markers in the primary visual cortex after unilateral elevated intraocular pressure (IOP) in a primate model of glaucoma. METHODS: A monkey model of experimental glaucoma was combined with immunohistochemical and histochemical methods to assess changes in expression patterns and metabolic activity of cortical neurons in V1. RESULTS: Experimental unilateral glaucoma altered the spatial and temporal distribution of several neurochemicals associated with cortical plasticity in V1 of the primate. Within-animal comparisons of immunohistochemical studies revealed that GABAa receptor protein and GAP-43 were significantly lower in glaucomatous versus normal eye bands after 2, 4, and 7 months of elevated IOP. SYN immunoreactivity was also lower in the glaucomatous versus the normal eye bands but only at 4 months of elevated IOP. CAMKIIalpha immunoreactivity levels were higher in the glaucomatous versus the normal eye bands. Between-animal comparisons revealed that the levels of GAP-43 and SYN were upregulated, whereas levels of GABAa receptor protein were downregulated, in glaucomatous eyes when compared with levels in the visual cortex of normal animals. CONCLUSIONS: Unilateral elevation of IOP affects both the metabolic activity of cortical neurons and the expressed levels of GAP-43, SYN, GABAa receptor protein, and CAMKIIalpha, as measured immunohistochemically in the primary visual cortex of adult monkeys. Because these neurochemicals are thought to be necessary for synaptic plasticity, their redistribution may support functional recovery of cortical neurons after damage to retinal ganglion cells induced by elevated IOP.

Expression of neuropilin-1 in choroidal neovascular membranes.

BACKGROUND: Neovascularization is a serious consequence of several eye diseases, including age-related macular degeneration. Neovascularization is under the control of proangiogenic factors, such as vascular endothelial growth factor and fibroblast growth factor. Recent work in our laboratory has focused on other, novel angiogenic factors, such as neuropilin-1, and their potential role in neovascularization. The purpose of this study was to investigate the role of neuropilin-1 in choroidal neovascularization (CNV). METHODS: We examined the localization of neuropilin-1 by immunohistochemistry in nine choroidal neovascular membranes (CNVMs) surgically excised from four patients with age-related macular degeneration who had not undergone laser photocoagulation, four with idiopathic CNV and one with ocular histoplasmosis. We also stained the membranes for markers of endothelial and retinal pigment epithelial cells. Controls included omission of primary antibody, use of an irrelevant primary antibody, and neuropilin-1 staining of the posterior sclera, choroid and retina of four healthy donor eyes. RESULTS: Neuropilin-1 was present in eight of the nine CNVMs. It was localized mainly to the plasma membrane. The more vascular membranes and those consisting of a larger number of retinal pigment epithelial cells were associated with greater neuropilin-1 staining. Neuropilin-1 was not seen in the posterior segment of the four healthy eyes. INTERPRETATION: Neuropilin-1 appears to play an active role in CNV. Further study is needed to establish a causal relation.