Splenic monocytes drive pathogenic subretinal inflammation in age-related macular degeneration.

Age-related macular degeneration (AMD) is invariably associated with the chronic accumulation of activated mononuclear phagocytes in the subretinal space. The mononuclear phagocytes are composed of microglial cells but also of monocyte-derived cells, which promote photoreceptor degeneration and choroidal neovascularization. Infiltrating blood monocytes can originate directly from bone marrow, but also from a splenic reservoir, where bone marrow monocytes develop into angiotensin II receptor (ATR1)+ splenic monocytes. The involvement of splenic monocytes in neurodegenerative diseases such as AMD is not well understood. Using acute inflammatory and well-phenotyped AMD models, we demonstrate that angiotensin II mobilizes ATR1+ splenic monocytes, which we show are defined by a transcriptional signature using single-cell RNA sequencing and differ functionally from bone marrow monocytes. Splenic monocytes participate in the chorio-retinal infiltration and their inhibition by ATR1 antagonist and splenectomy reduces the subretinal mononuclear phagocyte accumulation and pathological choroidal neovascularization formation. In aged AMD-risk ApoE2-expressing mice, a chronic AMD model, ATR1 antagonist and splenectomy also inhibit the chronic retinal inflammation and associated cone degeneration that characterizes these mice. Our observation of elevated levels of plasma angiotensin II in AMD patients, suggests that similar events take place in clinical disease and argue for the therapeutic potential of ATR1 antagonists to inhibit splenic monocytes for the treatment of blinding AMD.

FoxP3 expression by retinal pigment epithelial cells: transcription factor with potential relevance for the pathology of age-related macular degeneration.

BACKGROUND: Forkhead-Box-Protein P3 (FoxP3) is a transcription factor and marker of regulatory T cells, converting naive T cells into Tregs that can downregulate the effector function of other T cells. We previously detected the expression of FoxP3 in retinal pigment epithelial (RPE) cells, forming the outer blood-retina barrier of the immune privileged eye. METHODS: We investigated the expression, subcellular localization, and phosphorylation of FoxP3 in RPE cells in vivo and in vitro after treatment with various stressors including age, retinal laser burn, autoimmune inflammation, exposure to cigarette smoke, in addition of IL-1ß and mechanical cell monolayer destruction. Eye tissue from humans, mouse models of retinal degeneration and rats, and ARPE-19, a human RPE cell line for in vitro experiments, underwent immunohistochemical, immunofluorescence staining, and PCR or immunoblot analysis to determine the intracellular localization and phosphorylation of FoxP3. Cytokine expression of stressed cultured RPE cells was investigated by multiplex bead analysis. Depletion of the FoxP3 gene was performed with CRISPR/Cas9 editing. RESULTS: RPE in vivo displayed increased nuclear FoxP3-expression with increases in age and inflammation, long-term exposure of mice to cigarette smoke, or after laser burn injury. The human RPE cell line ARPE-19 constitutively expressed nuclear FoxP3 under non-confluent culture conditions, representing a regulatory phenotype under chronic stress. Confluently grown cells expressed cytosolic FoxP3 that was translocated to the nucleus after treatment with IL-1ß to imitate activated macrophages or after mechanical destruction of the monolayer. Moreover, with depletion of FoxP3, but not of a control gene, by CRISPR/Cas9 gene editing decreased stress resistance of RPE cells. CONCLUSION: Our data suggest that FoxP3 is upregulated by age and under cellular stress and might be important for RPE function.

Hypoxia Inhibits Subretinal Inflammation Resolution Thrombospondin-1 Dependently.

Hypoxia is potentially one of the essential triggers in the pathogenesis of wet age-related macular degeneration (wetAMD), characterized by choroidal neovascularization (CNV) which is driven by the accumulation of subretinal mononuclear phagocytes (MP) that include monocyte-derived cells. Here we show that systemic hypoxia (10% O2) increased subretinal MP infiltration and inhibited inflammation resolution after laser-induced subretinal injury in vivo. Accordingly, hypoxic (2% O2) human monocytes (Mo) resisted elimination by RPE cells in co-culture. In Mos from hypoxic mice, Thrombospondin 1 mRNA (Thbs1) was most downregulated compared to normoxic animals and hypoxia repressed Thbs-1 expression in human monocytes in vitro. Hypoxic ambient air inhibited MP clearance during the resolution phase of laser-injury in wildtype animals, but had no effect on the exaggerated subretinal MP infiltration observed in normoxic Thbs1-/--mice. Recombinant Thrombospondin 1 protein (TSP-1) completely reversed the pathogenic effect of hypoxia in Thbs1-/--mice, and accelerated inflammation resolution and inhibited CNV in wildtype mice. Together, our results demonstrate that systemic hypoxia disturbs TSP-1-dependent subretinal immune suppression and promotes pathogenic subretinal inflammation and can be therapeutically countered by local recombinant TSP-1.

Insulin inhibits inflammation-induced cone death in retinal detachment.

BACKGROUND: Rhegmatogenous retinal detachment (RD) involving the macula is a major cause of visual impairment despite high surgical success rate, mainly because of cone death. RD causes the infiltration of activated immune cells, but it is not clear whether and how infiltrating inflammatory cells contribute to cone cell loss. METHODS: Vitreous samples from patients with RD and from control patients with macular hole were analyzed to characterize the inflammatory response to RD. A mouse model of RD and retinal explants culture were then used to explore the mechanisms leading to cone death. RESULTS: Analysis of vitreous samples confirms that RD induces a marked inflammatory response with increased cytokine and chemokine expression in humans, which is closely mimicked by experimental murine RD. In this model, we corroborate that myeloid cells and T-lymphocytes contribute to cone loss, as the inhibition of their accumulation by Thrombospondin 1 (TSP1) increased cone survival. Using monocyte/retinal co-cultures and TSP1 treatment in RD, we demonstrate that immune cell infiltration downregulates rod-derived cone viability factor (RdCVF), which physiologically regulates glucose uptake in cones. Insulin and the insulin sensitizers rosiglitazone and metformin prevent in part the RD-induced cone loss in vivo, despite the persistence of inflammation CONCLUSION: Our results describe a new mechanism by which inflammation induces cone death in RD, likely through cone starvation due to the downregulation of RdCVF that could be reversed by insulin. Therapeutic inhibition of inflammation and stimulation of glucose availability in cones by insulin signaling might prevent RD-associated cone death until the RD can be surgically repaired and improve visual outcome after RD. TRIAL REGISTRATION: ClinicalTrials.gov NCT03318588.

[On the inflammatory origins of AMD]. / Sur les origines inflammatoires de la DMLA.

Age-related macular degeneration (AMD) is a complex, highly heritable, multifactorial disease caused by the interplay of age and genetic and environmental risk factors. No treatment has yet been found to treat the slowly progressing atrophic form of AMD. All forms of AMD are invariably associated with an accumulation of mononuclear phagocytes (MP) in the subretinal space, a family of cells that include inflammatory and resident macrophages. We here present an overview of the inflammatory process occurring in AMD and discuss the origin of MPs and the consequences of their accumulation in the subretinal space. Finally, we will review the role played by the established risk factors for AMD to promote the switch from beneficial inflammation in early stage to a deleterious inflammation in the advanced stage of the disease.

TITLE: Sur les origines inflammatoires de la DMLA. ABSTRACT: La dégénérescence maculaire liée à l'âge (DMLA) est une maladie multifactorielle hautement héréditaire qui survient chez le sujet âgé et est causée par une combinaison de facteurs de risques génétiques et environnementaux. Les formes atrophiques de la maladie constituent aujourd'hui une impasse thérapeutique. La physiopathologie de la DMLA est invariablement associée à une accumulation dans l'espace sous-rétinien, de phagocytes mononucléés (PM), une famille de cellules qui inclue des macrophages résidents et inflammatoires. Nous aborderons dans cette revue l'ensemble des mécanismes de cette inflammation spécifique, de l'origine des PM aux conséquences de leur accumulation dans l'espace sous-rétinien. Finalement, nous discuterons de l'impact des facteurs de risques génétiques et environnementaux établis de la DMLA sur le passage d'une inflammation bénéfique aux stades précoces de la maladie à une inflammation délétère aux stades avancés.

The 10q26 Risk Haplotype of Age-Related Macular Degeneration Aggravates Subretinal Inflammation by Impairing Monocyte Elimination.

A minor haplotype of the 10q26 locus conveys the strongest genetic risk for age-related macular degeneration (AMD). Here, we examined the mechanisms underlying this susceptibility. We found that monocytes from homozygous carriers of the 10q26 AMD-risk haplotype expressed high amounts of the serine peptidase HTRA1, and HTRA1 located to mononuclear phagocytes (MPs) in eyes of non-carriers with AMD. HTRA1 induced the persistence of monocytes in the subretinal space and exacerbated pathogenic inflammation by hydrolyzing thrombospondin 1 (TSP1), which separated the two CD47-binding sites within TSP1 that are necessary for efficient CD47 activation. This HTRA1-induced inhibition of CD47 signaling induced the expression of pro-inflammatory osteopontin (OPN). OPN expression increased in early monocyte-derived macrophages in 10q26 risk carriers. In models of subretinal inflammation and AMD, OPN deletion or pharmacological inhibition reversed HTRA1-induced pathogenic MP persistence. Our findings argue for the therapeutic potential of CD47 agonists and OPN inhibitors for the treatment of AMD.

VEGF is an autocrine/paracrine neuroprotective factor for injured retinal ganglion neurons.

Vascular endothelial growth factor-A (VEGF) is the angiogenic factor promoting the pathological neovascularization in age-related macular degeneration (AMD) or diabetic macular edema (DME). Evidences have suggested a neurotrophic and neuroprotective role of VEGF, albeit in retina, cellular mechanisms underlying the VEGF neuroprotection remain elusive. Using purified adult retinal ganglion cells (RGCs) in culture, we demonstrated here that VEGF is released by RGCs themselves to promote their own survival, while VEGF neutralization by specific antibodies or traps drastically reduced the RGC survival. These results indicate an autocrine VEGF neuroprotection on RGCs. In parallel, VEGF produced by mixed retinal cells or by mesenchymal stem cells exerted a paracrine neuroprotection on RGCs. Such neuroprotective effect was obtained using the recombinant VEGF-B, suggesting the involvement of VEGF-R1 pathway in VEGF-elicited RGC survival. Finally, glaucomatous patients injected with VEGF traps (ranibizumab or aflibercept) due to either AMD or DME comorbidity, showed a significant reduction of RGC axon fiber layer thickness, consistent with the plausible reduction of the VEGF autocrine stimulation of RGCs. Our results provide evidence of the autocrine neuroprotective function of VEGF on RGCs is crucially involved to preserve injured RGCs such as in glaucomatous patients.

Deletion of the myeloid endothelin-B receptor confers long-term protection from angiotensin II-mediated kidney, eye and vessel injury.

The endothelin system may be an important player in hypertensive end-organ injury as endothelin-1 increases blood pressure and is pro-inflammatory. The immune system is emerging as an important regulator of blood pressure and we have shown that the early hypertensive response to angiotensin-II infusion was amplified in mice deficient of myeloid endothelin-B (ETB) receptors (LysM-CreEdnrblox/lox). Hypothesizing that these mice would display enhanced organ injury, we gave angiotensin-II to LysM-CreEdnrblox/lox and littermate controls (Ednrblox/lox) for six weeks. Unexpectedly, LysM-CreEdnrblox/lox mice were significantly protected from organ injury, with less proteinuria, glomerulosclerosis and inflammation of the kidney compared to controls. In the eye, LysM-CreEdnrblox/lox mice had fewer retinal hemorrhages, less microglial activation and less vessel rarefaction. Cardiac remodeling and dysfunction were similar in both groups at week six but LysM-CreEdnrblox/lox mice had better endothelial function. Although blood pressure was initially higher in LysM-CreEdnrblox/lox mice, this was not sustained. A natriuretic switch at about two weeks, due to enhanced ETB signaling in the kidney, induced a hypertensive reversal. By week six, blood pressure was lower in LysM-CreEdnrblox/lox mice than in controls. At six weeks, macrophages from LysM-CreEdnrblox/lox mice were more anti-inflammatory and had greater phagocytic ability compared to the macrophages of Ednrblox/lox mice. Thus, myeloid cell ETB receptor signaling drives this injury both through amplifying hypertension and by inflammatory polarization of macrophages.

Microglia versus Monocytes: Distinct Roles in Degenerative Diseases of the Retina.

Unlike in the healthy mammalian retina, macrophages in retinal degenerative states are not solely comprised of microglia but may include monocyte-derived recruits. Recent studies have applied transgenics, lineage-tracing, and transcriptomics to help decipher the distinct roles of these two cell types in the diseasesettings of inherited retinal degenerations and age-related macular degeneration.Literature discussed here focuses on the ectopic presence of both macrophage types in the extracellular site surrounding the outer aspect ofphotoreceptor cells (i.e.,the subretinal space), which is crucially involved in the pathobiology. From these studies we propose a working model in which perturbed photoreceptor states cause microglial dominant migration to the subretinal space as a protective response, whereas the abundant presence ofmonocyte-derived cells there instead drives and accelerates pathology. The latter, we propose, is underpinned by specific genetic and nongenetic determinants that lead to a maladaptive macrophage state.

Mo-derived perivascular macrophage recruitment protects against endothelial cell death in retinal vein occlusion.

BACKGROUND: To decipher the role of monocyte-derived macrophages (Mφs) in vascular remodeling of the occluded vein following experimental branch retinal vein occlusion (BRVO). METHODS: The inflammation induced by laser-induced BRVO on mice retina was evaluated at different time points by RT-PCR looking at inflammatory markers mRNA level expression, Icam-1, Cd11b, F4/80, Ccl2, and Ccr2 and by quantification of Iba1-positive macrophage (Mφ) density on Iba1-stained retinal flatmount. Repeated intraperitoneal EdU injection combined with liposome clodronate-induced monocyte (Mo) depletion in wildtype mice was used to differentiate Mo-derived Mφs from resident Mφs. Liposome clodronate Mo-depleted wildtype mice and Ccr2-deficient mice were used to evaluate the role of all CCR2+ and CCR2neg Mo-derived Mφs on EC apoptosis in the occluded vein. RESULTS: cd11b, ICAM-1, F4/80, Ccl2, and Ccr2 mRNA expression were increased 1, 3, and 7 days after vein occlusion. The number of parenchymal (parMφs) and perivascular (vasMφs) macrophages was increased 3 and 7 days after BRVO. The systemic depletion of all circulating Mos decreased significantly the BRVO-induced parMφs and vasMφs macrophage accumulation, while the deletion of CCR2+-inflammatory Mo only diminished the accumulation of parMφs, but not vasMφs. Finally, apoptotic ECs of the vein were more numerous in fully depleted, liposome clodronate-treated mice, than in Ccr2-/- mice that only lack the recruitment of CCR2+ inflammatory Mos. CONCLUSIONS: BRVO triggers the recruitment of blood-derived parMφs and vasMφs. Interestingly, vasMφs accumulation was independent of CCR2. The observation that the inhibition of the recruitment of all infiltrating Mφs increases the vein EC apoptosis, while CCR2 deficiency does not, demonstrates that CCR2neg Mo-derived vasMφs protect the ECs against apoptosis in the occluded vein.

Anoctamin-4 is a bona fide Ca2+-dependent non-selective cation channel.

Changes in cell function occur by specific patterns of intracellular Ca2+, activating Ca2+-sensitive proteins. The anoctamin (TMEM16) protein family has Ca2+-dependent ion channel activity, which provides transmembrane ion transport, and/or Ca2+-dependent phosphatidyl-scramblase activity. Using amino acid sequence analysis combined with measurements of ion channel function, we clarified the so far unknown Ano4 function as Ca2+-dependent, non-selective monovalent cation channel; heterologous Ano4 expression in HEK293 cells elicits Ca2+ activated conductance with weak selectivity of K+ > Na+ > Li+. Endogenously expressed Ca2+-dependent cation channels in the retinal pigment epithelium were identified as Ano4 by KO mouse-derived primary RPE cells and siRNA against Ano4. Exchanging a negatively charged amino acid in the putative pore region (AA702-855) into a positive one (E775K) turns Ano4-elicited currents into Cl- currents evidencing its importance for ion selectivity. The molecular identification of Ano4 as a Ca2+-activated cation channel advances the understanding of its role in Ca2+ signaling.

CD36 Deficiency Inhibits Retinal Inflammation and Retinal Degeneration in Cx3cr1 Knockout Mice.

Background: CD36, a member of the class B scavenger receptor family, participates in Toll-like receptor signaling on mononuclear phagocytes (MP) and can promote sterile pathogenic inflammation. We here analyzed the effect of CD36 deficiency on retinal inflammation and photoreceptor degeneration, the hallmarks of age-related macular degeneration (AMD), that characterize Cx3cr1-/-mice. Methods: We analyzed subretinal MP accumulation, and cone- and rod-degeneration in light-challenged and aged, CD36 competent or deficient, hyper-inflammatory Cx3cr1-/- mice, using histology and immune-stained retinal flatmounts. Monocytes (Mo) were subretinally adoptively transferred to evaluate their elimination rate from the subretinal space and Interleukin 6 (IL-6) secretion from cultured Mo-derived cells (MdCs) of the different mouse strains were analyzed. Results: CD36 deficient Cx3cr1-/- mice were protected against age- and light-induced subretinal inflammation and associated cone and rod degeneration. CD36 deficiency in Cx3cr1-/- MPs inhibited their prolonged survival in the immune-suppressive subretinal space and reduced the exaggerated IL-6 secretion observed in Cx3cr1-/- MPs that we previously showed leads to increased subretinal MP survival. Conclusion:Cd36 deficiency significantly protected hyperinflammatory Cx3cr1-/- mice against subretinal MP accumulation and associated photoreceptor degeneration. The observed CD36-dependent induction of pro-inflammatory IL-6 might be at least partially responsible for the prolonged MP survival in the immune-suppressive environment and its pathological consequences on photoreceptor homeostasis.

Inhibition of Placenta Growth Factor Reduces Subretinal Mononuclear Phagocyte Accumulation in Choroidal Neovascularization.

Purpose: The cellular immune response driven by mononuclear phagocytes (MPs) is crucial for choroidal neovascularization (CNV) progression. Case reports show that a switch from pure anti-vascular endothelial growth factor-A (VEGF-A) intravitreal treatment to aflibercept, a drug with combined anti-VEGF-A and anti-placenta growth factor (PlGF) activity, can be beneficial for patients who do not respond to anti-VEGF-A alone. Since MPs harbor VEGFR1, we hypothesize that the interplay of P1GF/vascular endothelial growth factor receptor 1 (VEGFR1) in immune cells plays a pivotal role for CNV. Methods: CNV was induced with laser, and immune cells and neovascularization were analyzed in vivo and ex vivo. Immunohistochemistry was employed for protein detection. Differential expression of angiogenic factors and macrophage polarization markers were assessed by quantitative PCR (qPCR). One day after laser, intravitreal injection of aflibercept or anti-PlGF was performed. Results: In the early inflammatory phase after laser, Plgf but not Vegfa was significantly upregulated. VEGF-A upregulation is limited to the scar, whereas PlGF shows a wider distribution. M1 (proinflammatory) macrophage markers were upregulated in the early phase of CNV. However, M2 (proangiogenic) markers showed more inconsistent dynamics. We demonstrated that both aflibercept and anti-PlGF treatments decrease the overall amount of activated subretinal MPs, and especially of those expressing PlGF. These data correlated with a reduction in leakage associated to CNV. Aflibercept showed a stronger reduction in both parameters. Conclusions: The results hint at an interplay between PlGF/VEGFR1 and MPs that is important in the early phase of CNV. A combined inhibition of VEGF-A and PlGF is superior to a specific anti-PlGF treatment in terms of subretinal MP recruitment.

Effect of benzalkonium chloride on trabecular meshwork cells in a new in vitro 3D trabecular meshwork model for glaucoma.

PURPOSE: To validate a new culture model of primary human trabecular meshwork cells (p-hTMCs) using Matrigel®, in order to mimic in vitro 3D-TM organization, and to investigate the proinflammatory effect of benzalkonium chloride (BAK) in 3D p-hTMC cultures. METHODS: p-hTMCs, seeded onto Matrigel®-coated inserts were stimulated with BAK (10-4%), dexamethasone (DEX) (10-6M) or transforming growth factor-beta 2 (TGF-ß2) (5ng/ml) for 48h and observed with confocal microscopy. The BAK effect at 10-4% or 5.10-3% on the gene expressions of interleukin-6 (IL-6), interleukin-8 (IL-8) and matrix metalloproteinase (MMP-9) was investigated using qRT-PCR in 2D and 3D p-hTMC cultures. RESULTS: p-hTMCs seeded in Matrigel® were able to organize themselves in a 3D-spatial conformation in the different conditions tested with cross-linked actin network (CLAN) formation in presence of DEX or TGF-ß2 and intercellular space contraction with TGF-ß2. IL-6 and IL-8 gene expressions increased in presence of BAK in 2D and in 3D p-hTMC cultures. BAK 10-4% only showed a tendency to stimulate MMP-9 expression in p-hTMCs after 24h-recovery. CONCLUSIONS: We investigated this new 3D-TM in vitro model in Matrigel® matrix for pathophysiological and toxicological purposes. It appears as a new promising tool for a better understanding of TM behavior in physiological and stress conditions, as well as toxicological evaluations of antiglaucoma eyedrops and preservatives.

Anoctamin2 (TMEM16B) forms the Ca2+-activated Cl- channel in the retinal pigment epithelium.

Chloride channels (Cl channels) play an essential role for the retinal pigment epithelium (RPE). They provide a plasma membrane conductance for Cl- important for transepithelial transport and volume regulation. Ca2+-dependent chloride channels (CaCC) in the RPE were found to adapt Cl- transport to specific needs by increasing intracellular free Ca2+. Although a variety of Cl channels have been identified in the RPE, the molecular identity of the CaCC remains controversial. Sagittal sections of mouse retina were stained against anoctamin2 (Ano2) and analyzed by confocal microscopy. Membrane currents from ARPE-19 cells and primary murine RPE cells were recorded in the whole-cell configuration of the patch-clamp technique. Expression of Ano2 was assessed via immunocytochemistry, PCR and western-blot and down-regulated via siRNA approaches. In the mouse retina, Ano2 was found in the basolateral membrane of the RPE. In primary mouse RPE cells, Ano2 was localized predominantly in the cell membrane. Ano2 mRNA and protein were also detected in rat and primate RPE as well as ARPE-19 cells. Whole-cell currents were elicited by increasing intracellular free Ca2+ via ATP application. These currents were identified as Cl- currents by their reversal potential and blocker sensitivity. Knock-down of Ano2 by siRNA decreased both the Ca2+ dependent chloride conductance and protein expression of Ano2. The biophysical and pharmacological properties of CaCC in ARPE-19 and primary mouse RPE cells resemble those described in previous publications using RPE cells from different species. The siRNA knock-down suggests that Ano2 contributes to Ca2+-dependent chloride conductance in the RPE.

Hyperosmolarity and Benzalkonium Chloride Differently Stimulate Inflammatory Markers in Conjunctiva-Derived Epithelial Cells in vitro.

Tear hyperosmolarity is known to cause ocular surface inflammation in dry eye syndrome. Benzalkonium chloride (BAK), an eyedrop preservative, is known to induce dry eye in long-term-treated patients. Analyzing the modulation of the proinflammatory potential of hyperosmolarity in the presence of BAK on the conjunctiva could give new insights into the effect of this preservative on the disease. In a hyperosmolar model on a conjunctiva-derived cell line, and in the presence of BAK, we evaluated key inflammatory markers [CCL2, IL-8, IL-6, macrophage migration inhibitory factor (MIF) and intercellular adhesion molecule (ICAM)-1] as well as the osmoprotectant element nuclear factor of activated T cells (NFAT)5 using ELISA, RT-qPCR or immunofluorescence staining. Hyperosmolarity highly stimulated CCL2 and NFAT5 in these cells. BAK alone only increased IL-6 expression. The stress-combined condition stimulated CCL2, NFAT5, MIF and IL-8 secretion. ICAM-1 was not modulated by any of the conditions tested. In this model, hyperosmolarity and BAK induced the release of different proinflammatory mediators, and, when combined, they lead to the release of additional inflammatory cytokines. This in vitro study highlights the importance of avoiding long-term ophthalmic treatments containing BAK, as tear film hyperosmolarity can be a result of its detergent action.

Chorioretinal thinning in chronic kidney disease links to inflammation and endothelial dysfunction.

BACKGROUND. Chronic kidney disease (CKD) is strongly associated with cardiovascular disease and there is an established association between vasculopathy affecting the kidney and eye. Optical coherence tomography (OCT) is a novel, rapid method for high-definition imaging of the retina and choroid. Its use in patients at high cardiovascular disease risk remains unexplored. METHODS. We used the new SPECTRALIS OCT machine to examine retinal and retinal nerve fiber layer (RNFL) thickness, macular volume, and choroidal thickness in a prospective cross-sectional study in 150 subjects: 50 patients with hypertension (defined as a documented clinic BP greater than or equal to 140/90 mmHg (prior to starting any treatment) with no underlying cause identified); 50 with CKD (estimated glomerular filtration rate (eGFR) 8-125 ml/min/1.73 m2); and 50 matched healthy controls. We excluded those with diabetes. The same, masked ophthalmologist carried out each study. Plasma IL-6, TNF-α , asymmetric dimethylarginine (ADMA), and endothelin-1 (ET-1), as measures of inflammation and endothelial function, were also assessed. RESULTS. Retinal thickness, macular volume, and choroidal thickness were all reduced in CKD compared with hypertensive and healthy subjects (for retinal thickness and macular volume P < 0.0001 for CKD vs. healthy and for CKD vs. hypertensive subjects; for choroidal thickness P < 0.001 for CKD vs. healthy and for CKD vs. hypertensive subjects). RNFL thickness did not differ between groups. Interestingly, a thinner choroid was associated with a lower eGFR (r = 0.35, P <0.0001) and, in CKD, with proteinuria (r = -0.58, P < 0.001) as well as increased circulating C-reactive protein (r = -0.57, P = 0.0002), IL-6 (r = -0.40, P < 0.01), ADMA (r = -0.37, P = 0.02), and ET-1 (r = -0.44, P < 0.01). Finally, choroidal thinning was associated with renal histological inflammation and arterial stiffness. In a model of hypertension, choroidal thinning was seen only in the presence of renal injury. CONCLUSIONS. Chorioretinal thinning in CKD is associated with lower eGFR and greater proteinuria, but not BP. Larger studies, in more targeted groups of patients, are now needed to clarify whether these eye changes reflect the natural history of CKD. Similarly, the associations with arterial stiffness, inflammation, and endothelial dysfunction warrant further examination. TRIAL REGISTRATION. Registration number at www.clinicalTrials.gov: NCT02132741. SOURCE OF FUNDING. TR was supported by a bursary from the Erasmus Medical Centre, Rotterdam. JJMHvB was supported by a bursary from the Utrecht University. JRC is supported by a Rowling Scholarship. SB was supported by a Wellcome Trust funded clinical research fellowship from the Scottish Translational Medicine and Therapeutics Initiative, and by a Rowling Scholarship, at the time of this work. ND is supported by a British Heart Foundation Intermediate Clinical Research Fellowship (FS/13/30/29994).

Bilateral neuroinflammatory processes in visual pathways induced by unilateral ocular hypertension in the rat.

BACKGROUND: Glaucoma is one of the leading causes of irreversible blindness in the world. The major risk factor is elevated intraocular pressure (IOP) leading to progressive retinal ganglion cell (RGC) death from the optic nerve (ON) to visual pathways in the brain. Glaucoma has been reported to share mechanisms with neurodegenerative disorders. We therefore hypothesize that neuroinflammatory mechanisms in central visual pathways may contribute to the spread of glaucoma disease. The aim of the present study was to analyze the neuroinflammation processes that occur from the pathological retina to the superior colliculi (SCs) in a rat model of unilateral ocular hypertension induced by episcleral vein cauterization (EVC). RESULTS: Six weeks after unilateral (right eye) EVC in male Long-Evans rats, we evaluated both the neurodegenerative process and the neuroinflammatory state in visual pathway tissues. RGCs immunolabeled (Brn3a(+)) in ipsilateral whole flat-mounted retina demonstrated peripheral RGC loss associated with tissue macrophage/microglia activation (CD68(+)). Gene expression analysis of hypertensive and normotensive retinas revealed a significant increase of pro-inflammatory genes such as CCL2, IL-1ß, and Nox2 mRNA expression compared to naïve eyes. Importantly, we found an upregulation of pro-inflammatory markers such as IL-1ß and TNFα and astrocyte and tissue macrophage/microglia activation in hypertensive and normotensive RGC projection sites in the SCs compared to a naïve SC. To understand how neuroinflammation in the hypertensive retina is sufficient to damage both right and left SCs and the normotensive retina, we used an inflammatory model consisting in an unilateral stereotaxic injection of TNFα (25 ng/µl) in the right SC of naïve rats. Two weeks after TNFα injection, using an optomotor test, we observed that rats had visual deficiency in both eyes. Furthermore, both SCs showed an upregulation of genes and proteins for astrocytes, microglia, and pro-inflammatory cytokines, notably IL-1ß. In addition, both retinas exhibited a significant increase of inflammatory markers compared to a naïve retina. CONCLUSIONS: All these data evidence the complex role played by the SCs in the propagation of neuroinflammatory events induced by unilateral ocular hypertension and provide a new insight into the spread of neurodegenerative diseases such as glaucoma.

Intraocular pressure reduction and neuroprotection conferred by bone marrow-derived mesenchymal stem cells in an animal model of glaucoma.

INTRODUCTION: Glaucoma is a sight-threatening retinal neuropathy associated with elevated intraocular pressure (IOP) due to degeneration and fibrosis of the trabecular meshwork (TM). Glaucoma medications aim to reduce IOP without targeting the specific TM pathology, Bone-marrow mesenchymal stem cells (MSCs) are used today in various clinical studies. Here, we investigated the potential of MSCs therapy in an glaucoma-like ocular hypertension (OHT) model and decipher in vitro the effects of MSCs on primary human trabecular meshwork cells. METHODS: Ocular hypertension model was performed by cauterization of 3 episcleral veins (EVC) of Long-Evans male rat eyes. MSCs were isolated from rat bone marrow, amplified in vitro and tagged with quantum dot nanocrystals. Animals were distributed as 1) MSCs group receiving 5.10(5)cells/6µl Minimum Essential Medium and 2) MEM group receiving 6µl MEM (n = 10 each). Injections were performed into the anterior chamber of 20 days-hypertensive eyes and IOP was monitored twice a week for 4 weeks. At the end of experiment, cell distribution in the anterior segment was examined in confocal microscopy on flat mounted corneas. Moreover, we tested in vitro effects of MSCs conditioned medium (MSC-CM) on primary human trabecular meshwork cells (hTM cells) using Akt activation, myosin phosphorylation and TGF-ß2-dependent profibrotic phenotype in hTM cells. RESULTS: We demonstrated a rapid and long-lasting in vivo effect of MSCs transplantation that significantly reduced IOP in hypertensive eyes induced by EVC. MSCs were located to the ciliary processes and the TM. Enumeration of RGCs on whole flat-mounted retina highlighted a protective effect of MSCs on RGCs death. In vitro, MSC-CM promotes: (i) hTM cells survival by activating the antiapoptotic pathway, Akt, (ii) hTM cells relaxation as analyzed by the decrease in myosin phosphorylation and (iii) inhibition of TGF-ß2-dependent profibrotic phenotype acquisition in hTM cells. CONCLUSIONS: MSCs injection in the ocular anterior chamber in a rat model of OHT provides neuroprotective effect in the glaucoma pathophysiology via TM protection. These results demonstrate that MSCs constitute promising tool for treating ocular hypertension and retinal cell degeneration.

Upregulation of P2RX7 in Cx3cr1-Deficient Mononuclear Phagocytes Leads to Increased Interleukin-1ß Secretion and Photoreceptor Neurodegeneration.

Photoreceptor degeneration in age-related macular degeneration (AMD) is associated with an infiltration and chronic accumulation of mononuclear phagocytes (MPs). We have previously shown that Cx3cr1-deficient mice develop age- and stress- related subretinal accumulation of MPs, which is associated with photoreceptor degeneration. Cx3cr1-deficient MPs have been shown to increase neuronal apoptosis through IL-1ß in neuroinflammation of the brain. The reason for increased IL-1ß secretion from Cx3cr1-deficient MPs, and whether IL-1ß is responsible for increased photoreceptor apoptosis in Cx3cr1-deficient mice, has not been elucidated. Here we show that Cx3cr1-deficient MPs express increased surface P2X7 receptor (P2RX7), which stimulates IL-1ß maturation and secretion. P2RX7 and IL-1ß inhibition efficiently blunted Cx3cr1-MP-dependent photoreceptor apoptosis in a monocyte/retina coculture system and in light-induced subretinal inflammation of Cx3cr1-deficient mice in vivo. Our results provide an explanation for increased CX3CR1-dependent IL-1ß secretion and suggest that IL-1ß or P2RX7 inhibition can help inhibit the inflammation-associated photoreceptor cell loss in late AMD, including geographic atrophy, for which no efficient treatment currently exists.