Inhibition of the Nuclear Receptor RORγ and Interleukin-17A Suppresses Neovascular Retinopathy: Involvement of Immunocompetent Microglia

The adaptive immune system in the retina of diabetics

As the prevalence of diabetes mellitus increases each year, its most common microvascular complication, diabetic retinopathy (DR), is also on the rise. DR is now regarded as an inflammatory disease in which innate immunity plays a crucial role, and a large number of innate immune cells with associated cytokines are involved in the pathologic process of DR. The role of adaptive immunity in DR is seldom mentioned, probably due to the general perception of the immune privileged environment of the retina; however, in recent years there has been a gradual increase in research on the role of adaptive immunity in DR, and with the discovery of the retinal lymphatic system, it seems that the role of adaptive immunity can no longer be ignored. Here, we discuss the immunosuppressive environment of the retina, the phenomenon and potential mechanisms of lymphocyte infiltration in DR, and the role of the adaptive immune system in the diabetic retina, which may point the way for future research.

Alpha-1 antitrypsin reduces inflammation and vasculopathy in mice with oxygen-induced retinopathy

BACKGROUND

Damage to the retinal vasculature is a major cause of vision loss and is influenced by a pro-inflammatory environment within retinal tissue. Alpha-1 antitrypsin (AAT) is a potent inhibitor of serine proteases and has anti-inflammatory properties. We hypothesised that AAT could reduce inflammation and vasculopathy in neovascular retinopathies including oxygen-induced retinopathy (OIR).

METHODS

Litters of C57BL/6J mice were randomised to develop OIR by exposure to high oxygen between postnatal days 7 to 12 resulting in vaso-obliteration (phase I OIR), and then room air from postnatal days 12 to 18 resulting in neovascularisation (phase II OIR). Control mice were exposed to room air. Separate cohorts of mice were administered control vehicle or human AAT (120 mg/kg) by intraperitoneal injection every second day in phase I or phase II OIR.

RESULTS

In phase I OIR, plasma levels of AAT were reduced compared to room air controls, and AAT treatment reduced vaso-obliteration. In phase II OIR, AAT treatment influenced inflammation by reducing the density of ionised calcium binding adaptor protein 1 + cells (microglia/macrophages) and modulating their cell process length and reducing mRNA levels of tumour necrosis factor and monocyte chemoattractant protein-1, but not interleukin-1b and interleukin-6 in retina. Furthermore, AAT treatment reduced retinal neovascularisation, gliosis, vascular endothelial growth factor mRNA and protein expression, and vascular leakage, compared to OIR controls.

CONCLUSIONS

This research demonstrates the vasculo-protective actions of AAT, and thereby the potential of AAT as a therapeutic option for neovascular retinopathies.

The impact of circadian rhythms on retinal immunity

The eye is an immune-protected organ, which is driven by factors such as cytokines, chemicals, light, and mechanical stimuli. The circadian clock is an intrinsic timing mechanism that influences the immune activities, such as immune cell count and activity, as well as inflammatory responses. Recent studies have demonstrated that the eye also possesses an intrinsic circadian rhythm, and this rhythmic regulation participates in ocular immune modulation. In this review, we discuss the immunoregulatory mechanisms of the circadian clock within the eye, and reveal new perspectives for the prevention and treatment of ocular diseases.

Mechanism and therapeutic targets of circulating immune cells in diabetic retinopathy

Diabetic retinopathy (DR) continues to be the leading cause of preventable vision loss among working-aged adults, marked by immune dysregulation within the retinal microenvironment. Typically, the retina is considered as an immune-privileged organ, where circulating immune cells are restricted from entry under normal conditions. However, during the progression of DR, this immune privilege is compromised as circulating immune cells breach the barrier and infiltrate the retina. Increasing evidence suggests that vascular and neuronal degeneration in DR is largely driven by the infiltration of immune cells, particularly neutrophils, monocyte-derived macrophages, and lymphocytes. This review delves into the mechanisms and therapeutic targets associated with these immune cell populations in DR, offering a promising and innovative approach to managing the disease.

IL-17A enhances the inflammatory response of glaucoma through Act1/TRAF6/NF-κB pathway

OBJECTIVES

To investigate the possible roles of Interleukin 17A (IL-17A) and IL-17A neutralizing antibodies (IL-17Ab) in glaucoma and the potential mechanisms.

METHODS

The two glaucoma animal models, chronic ocular hypertension (COH) and N-methyl-D-aspartate (NMDA)-induced retinal ganglion cell (RGC) damage, were established and treated with intravitreal injection of IL-17A or IL-17Ab. Intraocular pressure (IOP) was measured by a rebound tonometer. The retina and RGC injury were evaluated by HE staining, TUNLE assay and Brn3a immunofluorescence staining. The frequency of IL-17A+CD4+T cells in peripheral blood was detected by flow cytometry. The expression of glial fibrillary acidic protein (GFAP) was detected by immunofluorescence staining, Western Blot and qPCR in retina. The RNA and protein expression of Act1/TRAF6/NF-κB were detected by Western Blot and qPCR in retina.

RESULTS

The expression of IL-17A increased in glaucoma models. After intravitreal injection of IL-17A, in the retina, the number of RGCs decreased, the apoptosis of RGCs increased, the Müller cell gliosis was more obvious. In addition, peripheral inflammation aggravated. Whereas the intravitreal injection of IL-17Ab alleviated the relevant manifestations and peripheral inflammation, reduced the gliosis of Müller cells. In the COH model, IOP increased after the injection of IL-17A, while the intravitreal injection of IL-17Ab led to a decrease in IOP. Furthermore, IL-17A promotes the apoptosis of RGCs by binding to IL-17A receptor, activating Act1/TRAF6/NF-κB pathways.

CONCLUSION

IL-17A plays a role in and aggravates RGC damage in glaucoma. IL-17Ab can neutralize the pro-inflammatory effect of IL-17A and have a protective function in glaucoma. These findings reveal the importance of IL-17A in the pathogenesis of glaucoma, which will shed light on a novel direction for the prevention and treatment of glaucoma, and also provide a reference for further research on other retinal diseases.

Interleukin-17A in diabetic retinopathy: The crosstalk of inflammation and angiogenesis

Diabetic retinopathy (DR) is a severe ocular complication of diabetes which can leads to irreversible vision loss in its late-stage. Chronic inflammation results from long-term hyperglycemia contributes to the pathogenesis and progression of DR. In recent years, the interleukin-17 (IL-17) family have attracted the interest of researchers. IL-17A is the most widely explored cytokine in IL-17 family, involved in various acute and chronic inflammatory diseases. Growing body of evidence indicate the role of IL-17A in the pathogenesis of DR. However, the pro-inflammatory and pro-angiogenic effect of IL-17A in DR have not hitherto been reviewed. Gaining an understanding of the pro-inflammatory role of IL-17A, and how IL-17A control/impact angiogenesis pathways in the eye will deepen our understanding of how IL-17A contributes to DR pathogenesis. Herein, we aimed to thoroughly review the pro-inflammatory role of IL-17A in DR, with focus in how IL-17A impact inflammation and angiogenesis crosstalk.

Chrysin alleviates DNA damage to improve disturbed immune homeostasis and pro-angiogenic environment in laser-induced choroidal neovascularization

Choroidal neovascularization (CNV) is a devastating pathology of numerous ocular diseases, such as wet age-related macular degeneration (wAMD), which causes irreversible vision loss. Although anti-vascular endothelial growth factor (VEGF) therapy has been widely used, poor response or no response still exists in some cases, suggesting that there are other components involved in the angiogenic process. Therefore, the underlying mechanism needs to be clarified and new target of anti-angiogenic therapy is urgently needed. It has been demonstrated that damaged retinal pigment epithelium (RPE) cells can activate inflammasome, driving a degenerative tissue environment and an enhanced pro-angiogenic response, which implies that RPE dysfunction may be a hallmark of the pathogenesis. Previously, we have shown that DNA damage can induce RPE dysfunction, triggering senescence-associated secretory phenotype (SASP) and local inflammation. In this study, we identify that chrysin can reduce DNA damage, especially telomere erosion in vitro, thus compromise the dysfunction of RPE and the decreased expression of SASP factor. Importantly, we find that DNA damage of RPE cells is remarkable in laser-induced CNV lesion, resulting in inflammatory response, which can be ameliorated by chrysin, mainly through IL-17 signaling pathway and its downstream signal transducer and activator of transcription 3 (STAT3) activities. In summary, our results indicate the interplay between DNA damage, perturbed RPE homeostasis, inflammatory response and angiogenesis in laser-induced CNV, and more importantly, chrysin may be an effective therapeutic supplement for CNV.

Inhibition of Nuclear Receptor Related Orphan Receptor γ Ameliorates Mechanical Hypersensitivity Through the Suppression of Spinal Microglial Activation

Microglia are crucial in induction of central sensitization under a chronic pain state. Therefore, control of microglial activity is important to ameliorate nociceptive hypersensitivity. The nuclear receptor retinoic acid related orphan receptor γ (RORγ) contributes to the regulation of inflammation-related gene transcription in some immune cells, including T cells and macrophages. Their role and function in regulation of microglial activity and nociceptive transduction have yet to be elaborated. Treatment of cultured microglia with specific RORγ inverse agonists, SR2211 or GSK2981278, significantly suppressed lipopolysaccharide (LPS)-induced mRNA expression of pronociceptive molecules interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor (TNF). Intrathecal treatment of naïve male mice with LPS markedly induced mechanical hypersensitivity and upregulation of ionized calcium-biding adaptor molecule (Iba1) in the spinal dorsal horn, indicating microglial activation. In addition, intrathecal treatment with LPS significantly induced mRNA upregulation of IL-1β and IL-6 in the spinal dorsal horn. These responses were prevented by intrathecal pretreatment with SR2211. In addition, intrathecal administration of SR2211 significantly ameliorated established mechanical hypersensitivity and upregulation of Iba1 immunoreactivity in the spinal dorsal horn of male mice following peripheral sciatic nerve injury. The current findings demonstrate that blockade of RORγ in spinal microglia exerts anti-inflammatory effects, and that RORγ may be an appropriate target for the treatment of chronic pain.

Differential Activities of the Botanical Extract PBI-05204 and Oleandrin on Innate Immune Functions under Viral Challenge Versus Inflammatory Culture Conditions

The Nerium oleander extract PBI 05204 (PBI) and its cardiac glycoside constituent oleandrin have direct anti-viral properties. Their effect on the immune system, however, is largely unknown. We used an in vitro model of human peripheral blood mononuclear cells to document effects under three different culture conditions: normal, challenged with the viral mimetic polyinosinic:polycytidylic acid Poly I:C, and inflamed by lipopolysaccharide (LPS). Cells were evaluated for immune activation marks CD69, CD25, and CD107a, and culture supernatants were tested for cytokines. Both PBI and oleandrin directly activated Natural Killer (NK) cells and monocytes and triggered increased production of cytokines. Under viral mimetic challenge, PBI and oleandrin enhanced the Poly I:C-mediated immune activation of monocytes and NK cells and enhanced production of IFN-γ. Under inflammatory conditions, many cytokines were controlled at similar levels as in cultures treated with PBI and oleandrin without inflammation. PBI triggered higher levels of some cytokines than oleandrin. Both products increased T cell cytotoxic attack on malignant target cells, strongest by PBI. The results show that PBI and oleandrin directly activate innate immune cells, enhance anti-viral immune responses through NK cell activation and IFN-γ levels, and modulate immune responses under inflamed conditions. The potential clinical impact of these activities is discussed.

Effects of medications on hypoxia-inducible factor in the retina: A review

Hypoxia-inducible factor (HIF) plays a critical role in the mechanisms that allow cells to adapt to various oxygen levels in the environment. Specifically, HIF-1⍺ has shown to be widely involved in cellular repair, survival, and energy metabolism. HIF-1⍺ has also been found in increased levels in cancer cells, highlighting the importance of balance in the hypoxic response. Promoting HIF-1⍺ activity as a potential therapy for degenerative diseases and inhibiting HIF-1⍺ as a therapy for pathologies with overactive cell proliferation are actively being explored. Digoxin and metformin, HIF-1⍺ inhibitors, and deferoxamine and ⍺-ketoglutarate analogues, HIF-1⍺ activators, are being studied for application in age-related macular degeneration, diabetic retinopathy, and retinitis pigmentosa. However, these same medications have retinal toxicities that must be assessed before implementation of therapeutic care. Herein, we highlight the duality of therapeutic and toxic potential of HIF-1⍺ that must be carefully assessed prior to its clinical application in retinal disorders.

Retinoic Acid Receptor-Related Orphan Receptors (RORs) in Eye Development and Disease

The retinoic acid receptor-related orphan receptors (RORs) are ligand-mediated transcription factors with important biological roles in regulating circadian rhythms, metabolism, immunity, angiogenesis, inflammation, and development. They belong to the superfamily of nuclear receptors and include three family members: RORα, RORβ, and RORγ. Currently identified ROR ligands include cholesterol and cholesterol derivatives for RORα and RORγ, and stearic acid and all-trans retinoic acid for RORβ. Aberrant signaling of the RORs is involved in the pathogenesis of several human diseases including autoimmune diseases, metabolic disorders, and certain cancers. In the eye, RORs regulate normal development of the lens and the retina, and also contribute to potentially blinding eye diseases, especially retinal vascular diseases. Here, we review the role of RORs in eye development and disease to highlight their potential as druggable targets for therapeutic development in retinal vascular and degenerative diseases.

Neurovascular abnormalities in retinopathy of prematurity and emerging therapies

Blood vessels in the developing retina are formed in concert with neural growth, resulting in functional neurovascular network. Disruption of the neurovascular coordination contributes to the pathogenesis of retinopathy of prematurity (ROP), a potentially blinding retinal neovascular disease in preterm infants that currently lacks an approved drug therapy in the USA. Despite vasculopathy as predominant clinical manifestations, an increasing number of studies revealed complex neurovascular interplays among neurons, glial cells and blood vessels during ROP. Coordinated expression of glia-derived vascular endothelial growth factor (VEGF) in spatio-temporal gradients is pivotal to the formation of well-organized vascular plexuses in the healthy retina, whereas uncoordinated VEGF expression triggers pathological angiogenesis with disorganized vascular tufts in ROP. In contrast with VEGF driving both pathological and physiological angiogenesis, neuron-derived angiogenic factor secretogranin III (Scg3) stringently regulates ROP but not healthy retinal vessels in animal models. Anti-VEGF and anti-Scg3 therapies confer similar high efficacies to alleviate ROP in preclinical studies but are distinct in their disease selectivity and safety. This review discusses neurovascular communication among retinal blood vessels, neurons and glial cells during retinal development and ROP pathogenesis and summarizes the current and emerging therapies to address unmet clinical needs for the disease.

Meningitic Escherichia coli-Induced Interleukin-17A Facilitates Blood-Brain Barrier Disruption via Inhibiting Proteinase 3/Protease-Activated Receptor 2 Axis

Bacterial meningitis is a life-threatening infectious disease with high morbidity and mortality worldwide, among which meningitic Escherichia coli is a common Gram-negative pathogenic bacterium causing meningitis. It can penetrate the blood–brain barrier (BBB), invoke local inflammatory responses and consequently disrupt the integrity of the BBB. Interleukin-17A (IL-17A) is recognized as a pro-inflammatory cytokine that is released during meningitic E. coli infection. It has been reported that IL-17A is involved in several pathological tissue injuries. However, the function of IL-17A in BBB breakdown remains rarely discussed. Here, our study found that E. coli-induced IL-17A led to the degradation of tight junction proteins (TJs) and adherens junction proteins (AJs) in human brain microvascular endothelial cells (hBMECs) through inhibiting protease proteinase 3 (PRTN3)/protease-activated receptor 2 (PAR-2) axis, thus increasing the permeability of BBB. In summary, this study uncovered the involvement of IL-17A in regulating BBB integrity and proposed a novel regulatory mechanism, which could be potential therapeutic targets of E. coli meningitis.

Rocaglamide Prolonged Allograft Survival by Inhibiting Differentiation of Th1/Th17 Cells in Cardiac Transplantation

BACKGROUND

Aglaia (Meliaceae) species are used for treating autoimmune disorders and allergic diseases in Asian countries. Rocaglamide, an extract obtained from Aglaia species, exhibits suppressive effect by regulating the T cell subset balance and cytokine network in cancer. However, whether it can be used in organ transplantation is unknown. In this study, we investigated the antirejection effect and mechanism of action of rocaglamide in a mouse cardiac allograft model.

METHODS

Survival studies were performed by administering mice with phosphate-buffered saline (PBS) (n = 6) and rocaglamide (n = 8). Heart grafts were monitored until they stopped beating. After grafting, the mice were sacrificed on day 7 for histological, mixed lymphocyte reaction (MLR), enzyme-linked immunosorbent assay (ELISA), and flow cytometric analyses.

RESULTS

Rocaglamide administration significantly prolonged the median survival of the grafts from 7 to 25 days compared with PBS treatment (P < 0.001). On posttransplantation day 7, the rocaglamide-treated group showed a significant decrease in the percentage of Th1 cells (7.9 ± 0.9% vs. 1.58 ± 0.5%, P < 0.001) in the lymph nodes and spleen (8.0 ± 2.5% vs. 2.4 ± 1.3%, P < 0.05). Rocaglamide treatment also significantly inhibited the production of Th17 cells (6.4 ± 1.0% vs. 1.8 ± 0.4%, P < 0.01) in the lymph nodes and spleen (5.9 ± 0.3% vs. 2.9 ± 0.8%, P < 0.01). Furthermore, the prolonged survival of the grafts was associated with a significant decrease in IFN-γ and IL-17 levels. Our results also showed that NF-AT activation was inhibited by rocaglamide, which also induced p38 and Jun N-terminal kinase (JNK) phosphorylation in Jurkat T cells. Furthermore, by using inhibitors that suppressed p38 and JNK phosphorylation, rocaglamide-mediated reduction in NF-AT protein levels was prevented.

CONCLUSION

We identified a new immunoregulatory property of rocaglamide, wherein it was found to regulate oxidative stress response and reduce inflammatory cell infiltration and organ injury, which have been associated with the inhibition of NF-AT activation in T cells.

IL-17A injury to retinal ganglion cells is mediated by retinal Müller cells in diabetic retinopathy

Diabetic retinopathy (DR), the most common and serious ocular complication, recently has been perceived as a neurovascular inflammatory disease. However, role of adaptive immune inflammation driven by T lymphocytes in DR is not yet well elucidated. Therefore, this study aimed to clarify the role of interleukin (IL)-17A, a proinflammatory cytokine mainly produced by T lymphocytes, in retinal pathophysiology particularly in retinal neuronal death during DR process. Ins2^Akita (Akita) diabetic mice 12 weeks after the onset of diabetes were used as a DR model. IL-17A-deficient diabetic mice were obtained by hybridization of IL-17A-knockout (IL-17A-KO) mouse with Akita mouse. Primarily cultured retinal Müller cells (RMCs) and retinal ganglion cells (RGCs) were treated with IL-17A in high-glucose (HG) condition. A transwell coculture of RGCs and RMCs whose IL-17 receptor A (IL-17RA) gene had been silenced with IL-17RA-shRNA was exposed to IL-17A in HG condition and the cocultured RGCs were assessed on their survival. Diabetic mice manifested increased retinal microvascular lesions, RMC activation and dysfunction, as well as RGC apoptosis. IL-17A-KO diabetic mice showed reduced retinal microvascular impairments, RMC abnormalities, and RGC apoptosis compared with diabetic mice. RMCs expressed IL-17RA. IL-17A exacerbated HG-induced RMC activation and dysfunction in vitro and silencing IL-17RA gene in RMCs abolished the IL-17A deleterious effects. In contrast, RGCs did not express IL-17RA and IL-17A did not further alter HG-induced RGC death. Notably, IL-17A aggravated HG-induced RGC death in the presence of intact RMCs but not in the presence of RMCs in which IL-17RA gene had been knocked down. These findings establish that IL-17A is actively involved in DR pathophysiology and particularly by RMC mediation it promotes RGC death. Collectively, we propose that antagonizing IL-17RA on RMCs may prevent retinal neuronal death and thereby slow down DR progression.

Myeloid lineage contributes to pathological choroidal neovascularization formation via SOCS3

Background

Pathological neovascularization in neovascular age-related macular degeneration (nAMD) is the leading cause of vision loss in the elderly. Increasing evidence shows that cells of myeloid lineage play important roles in controlling pathological endothelium formation. Suppressor of cytokine signaling 3 (SOCS3) pathway has been linked to neovascularization.

Methods

We utilised a laser-induced choroidal neovascularization (CNV) mouse model to investigate the neovascular aspect of human AMD. In several cell lineage reporter mice, bone marrow chimeric mice and Socs3 loss-of-function (knockout) and gain-of-function (overexpression) mice, immunohistochemistry, confocal, and choroidal explant co-culture with bone marrow-derived macrophage medium were used to study the mechanisms underlying pathological CNV formation via myeloid SOCS3.

Findings

SOCS3 was significantly induced in myeloid lineage cells, which were recruited into the CNV lesion area. Myeloid Socs3 overexpression inhibited laser-induced CNV, reduced myeloid lineage-derived macrophage/microglia recruitment onsite, and attenuated pro-inflammatory factor expression. Moreover, SOCS3 in myeloid regulated vascular sprouting ex vivo in choroid explants and SOCS3 agonist reduced in vivo CNV.

Interpretation

These findings suggest that myeloid lineage cells contributed to pathological CNV formation regulated by SOCS3.

Funding

This project was funded by NIH/NEI (R01EY030140, R01EY029238), BrightFocus Foundation, American Health Assistance Foundation (AHAF), and Boston Children's Hospital Ophthalmology Foundation for YS and the National Institutes of Health/National Heart, Lung and Blood Institute (U01HL098166) for PZ.

The immunological link between neonatal lung and eye disease

Bronchopulmonary dysplasia (BPD) and retinopathy of prematurity (ROP) are two neonatal diseases of major clinical importance, arising in large part as a consequence of supplemental oxygen therapy used to promote the survival of preterm infants. The presence of coincident inflammation in the lungs and eyes of neonates receiving oxygen therapy indicates that a dysregulated immune response serves as a potential common pathogenic factor for both diseases. This review examines the current state of knowledge of immunological dysregulation in BPD and ROP, identifying similarities in the cellular subsets and inflammatory cytokines that are found in the alveoli and retina during the active phase of these diseases, indicating possible mechanistic overlap. In addition, we highlight gaps in the understanding of whether these responses emerge independently in the lung and retina as a consequence of oxygen exposure or arise because of inflammatory spill-over from the lung. As BPD and ROP are anatomically distinct, they are often considered discreet disease entities and are therefore treated separately. We propose that an improved understanding of the relationship between BPD and ROP is key to the identification of novel therapeutic targets to treat or prevent both conditions simultaneously.

IL-17 signaling induces iNOS+ microglia activation in retinal vascular diseases

Activation of microglia and inflammation-mediated vascular damages are suggested to play a decisive role in the pathogenesis of various retinopathies. The inducible nitric oxide synthase (iNOS) was required for activated microglia-mediated injuries. However, the induction mechanism of microglia activation during retinal vascular diseases is still elusive. Here we showed that IL-17 induced microglia activation with high expression of iNOS and promoted the development of retinal vascular diseases. IL-17-dependent activation of the STAT3-iNOS pathway was essentially required for microglia activation, which promoted endothelial cell growth and accelerated vascular leakage and leukostasis via IL-6 in vitro and in vivo. Taken together, our data provide novel mechanistic insights on microglia activation-mediated retinopathy, unveil the specific role of IL-17 on microglia, and define novel therapeutic targets for treating retinal vascular diseases.

ROR: Nuclear Receptor for Melatonin or Not?

Whether the retinoic acid-related orphan receptor (ROR) is a nuclear receptor of melatonin remains controversial. ROR is inextricably linked to melatonin in terms of its expression, function, and mechanism of action. Additionally, studies have illustrated that melatonin functions analogous to ROR ligands, thereby modulating the transcriptional activity of ROR. However, studies supporting these interactions have since been withdrawn. Furthermore, recent crystallographic evidence does not support the view that ROR is a nuclear receptor of melatonin. Some other studies have proposed that melatonin indirectly regulates ROR activity rather than directly binding to ROR. This review aims to delve into the complex relationship of the ROR receptor with melatonin in terms of its structure, expression, function, and mechanism. Thus, we provide the latest evidence and views on direct binding as well as indirect regulation of ROR by melatonin, dissecting both viewpoints in-depth to provide a more comprehensive perspective on this issue.

Blocking the interaction between interleukin-17A and endoplasmic reticulum stress in macrophage attenuates retinal neovascularization in oxygen-induced retinopathy

BACKGROUND

Neovascularization is a leading cause of visual loss typically associated with diabetic retinopathy (DR) and retinopathy of prematurity (ROP). Interleukin-17A (IL-17A) and endoplasmic reticulum (ER) stress both have been demonstrated to play a proangiogenic role in ischemic retinopathies. However, the relationship between IL-17A and ER stress in retinal neovascularization (RNV) under hypoxic conditions and its underlying mechanisms remain unclear.

METHODS

In this study, oxygen-induced retinopathy (OIR) mice model was established and intravitreal injections were conducted. Changes of IL-17A and ER stress markers in retinas and cultured primary bone marrow derived macrophage (BMDM) under normoxic or hypoxic conditions were detected. Western blotting, Real-Time RT-PCR, Immunofluorescence assays were conducted to explore the roles and relationship of IL-17A and ER stress in RNV, as well as its underlying mechanisms.

RESULTS

Compared to that in normal controls, IL-17A and ER stress markers were all remarkably increased under hypoxic conditions both in vivo and in vitro. Neutralization or knock out of IL-17A decreased ER stress. ER stress inhibitor 4-phenylbutyrate (4-PBA), attenuated the production of IL-17A, suggesting a positive feedback loop between IL-17A and ER stress. Inhibition of IL-17A or ER stress decreased areas of nonperfusion and neovascularization in OIR retinas. As TXNIP/NLRP3 pathway activation has been demonstrated to be involved in increased retinal vascular permeability of ischemic retinopathy, we observed that TXNIP/NLRP3 pathway mediated in the interaction between IL-17A and ER stress under hypoxic conditions.

CONCLUSION

The interplay between IL-17A and ER stress contributes to RNV in macrophages via modulation of TXNIP/NLRP3 signaling pathway under hypoxic conditions. The feedback loops may become an innovative and multiple pharmacological therapeutic target for ischemic retinopathy.

Immune-Mediated Retinal Vasculitis in Posterior Uveitis and Experimental Models: The Leukotriene (LT)B4-VEGF Axis

Retinal vascular diseases have distinct, complex and multifactorial pathogeneses yet share several key pathophysiological aspects including inflammation, vascular permeability and neovascularisation. In non-infectious posterior uveitis (NIU), retinal vasculitis involves vessel leakage leading to retinal enlargement, exudation, and macular oedema. Neovascularisation is not a common feature in NIU, however, detection of the major angiogenic factor—vascular endothelial growth factor A (VEGF-A)—in intraocular fluids in animal models of uveitis may be an indication for a role for this cytokine in a highly inflammatory condition. Suppression of VEGF-A by directly targeting the leukotriene B4 (LTB4) receptor (BLT1) pathway indicates a connection between leukotrienes (LTs), which have prominent roles in initiating and propagating inflammatory responses, and VEGF-A in retinal inflammatory diseases. Further research is needed to understand how LTs interact with intraocular cytokines in retinal inflammatory diseases to guide the development of novel therapeutic approaches targeting both inflammatory mediator pathways.

Mesenchymal Stromal Cells Promote Retinal Vascular Repair by Modulating Sema3E and IL-17A in a Model of Ischemic Retinopathy

Ischemic retinopathies (IRs), such as retinopathy of prematurity and diabetic retinopathy, are characterized by an initial phase of microvascular degeneration that results in retinal ischemia, followed by exaggerated pathologic neovascularization (NV). Mesenchymal stromal cells (MSCs) have potent pro-angiogenic and anti-inflammatory properties associated with tissue repair and regeneration, and in this regard exert protection to neurons in ischemic and degenerative conditions; however, the exact mechanisms underlying these functions remain largely unknown. Class III Semaphorins (A–G) are particularly implicated in regulating neural blood supply (as well as neurogenesis) by suppressing angiogenesis and affecting myeloid cell function; this is the case for distinct neuropillin-activating Sema3A as well as PlexinD1-activating Sema3E; but during IR the former Sema3A increases while Sema3E decreases. We investigated whether retinal vascular repair actions of MSCs are exerted by normalizing Semaphorin and downstream cytokines in IR. Intravitreal administration of MSCs or their secretome (MSCs-conditioned media [MSCs-CM]) significantly curtailed vasoobliteration as well as aberrant preretinal NV in a model of oxygen-induced retinopathy (OIR). The vascular repair effects of MSCs-CM in the ischemic retina were associated with restored levels of Sema3E. Vascular benefits of MSCs-CM were reversed by anti-Sema3E; while intravitreal injection of anti-angiogenic recombinant Sema3E (rSema3E) in OIR-subjected mice reproduced effects of MSCs-CM by inhibiting as expected preretinal NV but also by decreasing vasoobliteration. To explain these opposing vascular effects of Sema3E we found in OIR high retinal levels, respectively, of the pro- and anti-angiogenic IL-17A and Sema3A-regulating IL-1β; IL-17A positively affected expression of IL-1β. rSema3E decreased concentrations of these myeloid cell-derived pro-inflammatory cytokines in vitro and in vivo. Importantly, IL-17A suppression by MSCs-CM was abrogated by anti-Sema3E neutralizing antibody. Collectively, our findings provide novel evidence by which MSCs inhibit aberrant NV and diminish vasoobliteration (promoting revascularization) in retinopathy by restoring (at least in part) neuronal Sema3E levels that reduce pathological levels of IL-17A (and in turn other proinflammatory factors) in myeloid cells. The ability of MSCs to generate a microenvironment permissive for vascular regeneration by controlling the production of neuronal factors involved in immunomodulatory activities is a promising opportunity for stem cell therapy in ocular degenerative diseases.

Effects of long non-coding RNA myocardial infarction-associated transcript on retinal neovascularization in a newborn mouse model of oxygen-induced retinopathy

Whether long non-coding RNA myocardial infarction-associated transcript is involved in oxygen-induced retinopathy remains poorly understood. To validate this hypothesis, we established a newborn mouse model of oxygen-induced retinopathy by feeding in an oxygen concentration of 75 ± 2% from postnatal day 8 to postnatal day 12, followed by in normal air. On postnatal day 11, the mice were injected with the myocardial infarction-associated transcript siRNA plasmid via the vitreous cavity to knockdown long non-coding RNA myocardial infarction-associated transcript. Myocardial infarction-associated transcript siRNA transcription significantly inhibited myocardial infarction-associated transcript mRNA expression, reduced the phosphatidylinosital-3-kinase, phosphorylated Akt and vascular endothelial growth factor immunopositivities, protein and mRNA expression, and alleviated the pathological damage to the retina of oxygen-induced retinopathy mouse models. These findings suggest that myocardial infarction-associated transcript is likely involved in the retinal neovascularization in retinopathy of prematurity and that inhibition of myocardial infarction-associated transcript can downregulate phosphatidylinosital-3-kinase, phosphorylated Akt and vascular endothelial growth factor expression levels and inhibit neovascularization. This study was approved by the Animal Ethics Committee of Shengjing Hospital of China Medical University, China (approval No. 2016PS074K) on February 25, 2016.

Hyperbaric oxygen in animal model of rheumatoid arthritis: Analysis Of HIF-1α, ACPA and IL-17a

Antigen and collagen-induced arthritis (ACIA) is animal model of rheumatoid arthritis. The aim of this study was to identify the effect of different doses of hyperbaric oxygen (HBO) exposure in reducing inflammation on ACIA through analysis hypoxia inducible factor-1α (HIF-1α), anticyclic citrullinated peptide antibody (ACPA) and interleukine 17a (IL-17a). 24 male Balb/C mice were divided into 3 groups, 8 mice did not receive HBO exposure as a control group (G1) and 16 mice received HBO exposure as treatment group (G2 and G3). G2 was ACIA which was exposed to HBO 2.4 ATA O2 100% 90 minutes divided by 3 each 30 minutes intervals 2 times 5 minutes breathing with normal air for 10 consecutive days. G3 was ACIA which was exposed to HBO 2.4 ATA O2 100% 90 minutes divided by 3 each 30 minutes intervals 2 times 5 minutes breathing with normal air for 5 consecutive days, break 5 days, 5 consecutive days.ACPA and IL-17a were measured by enzyme-linked immunosorbent assay (ELISA) technique. The expression of HIF-1α was measured by immunohistochemistry technique. There was significant decrease of ACPA levels, IL-17a levels and HIF-1α expression (P< 0.05) in G2 and G3 compared to G1. There was not significant decrease of ACPA levels (P> 0.05), there was significant decrease of IL-17a levels and HIF-1α expression (P<0.05) in G2 compared to G3. G2 was a group with a higher oxygen partial pressure than G3. HBO 2.4 ATAO2 100% 90 minutes divided by 3 each 30 minutes intervals 2 times 5 minutes breathing with normal air for 10 consecutive days more effective in reducing inflammation than exposure 5 consecutive days, break 5 days, 5 consecutive days in ACIA. HBO has therapeutic potential for the treatment of RA.

Radiofrequency irradiation attenuates angiogenesis and inflammation in UVB-induced rosacea in mouse skin

Rosacea is a skin inflammatory condition accompanied by cutaneous signs such as oedema, flushing, erythema, telangiectasia and pustules. Generally, rosacea is triggered by ultraviolet B (UVB) exposure. When exposed to UVB, skin epidermis thickens and produces elevated levels of pro-inflammatory cytokines, especially keratinocyte-related VEGF, a potent angiogenic factor. The upregulations of VEGF expression and its secretion promote the formation of new blood vessels and exacerbates rosacea. In this study, radiofrequency (RF) irradiation reduced keratinocyte proliferation in the epidermal layer, the expressions of pro-inflammatory cytokines, angiogenesis-related inflammatory factors and VEGF in our UVB-induced model of rosacea in vitro and in vivo. RF irradiation attenuated VEGF-induced angiogenesis-associated processes such as tube formation, cell migration and endothelial cell proliferation. Notably, blood vessel densities in the skins of UVB-treated mice and rosacea patients were significantly decreased by RF irradiation. These results provide experimental and molecular evidence regarding the effectiveness of RF irradiation for the treatment of rosacea.

RORγt Inhibitor-SR1001 Halts Retinal Inflammation, Capillary Degeneration, and the Progression of Diabetic Retinopathy

Diabetic retinopathy is a diabetes-mediated retinal microvascular disease that is the leading cause of blindness in the working-age population worldwide. Interleukin (IL)-17A is an inflammatory cytokine that has been previously shown to play a pivotal role in the promotion and progression of diabetic retinopathy. Retinoic acid-related orphan receptor gammaT (RORγt) is a ligand-dependent transcription factor that mediates IL-17A production. However, the role of RORγt in diabetes-mediated retinal inflammation and capillary degeneration, as well as its potential therapeutic attributes for diabetic retinopathy has not yet been determined. In the current study, we examined retinal inflammation and vascular pathology in streptozotocin-induced diabetic mice. We found RORγt expressing cells in the retinal vasculature of diabetic mice. Further, diabetes-mediated retinal inflammation, oxidative stress, and retinal endothelial cell death were all significantly lower in RORγt-/- mice. Finally, when a RORγt small molecule inhibitor (SR1001) was subcutaneously injected into diabetic mice, retinal inflammation and capillary degeneration were ameliorated. These findings establish a pathologic role for RORγt in the onset of diabetic retinopathy and identify a potentially novel therapeutic for this blinding disease.

Cho S, Britton W, S. Kern T, Antonetti DA, Hellström A, E.H. Smith L. Targeting Neurovascular Interaction in Retinal Disorders

The tightly structured neural retina has a unique vascular network comprised of three interconnected plexuses in the inner retina (and choroid for outer retina), which provide oxygen and nutrients to neurons to maintain normal function. Clinical and experimental evidence suggests that neuronal metabolic needs control both normal retinal vascular development and pathological aberrant vascular growth. Particularly, photoreceptors, with the highest density of mitochondria in the body, regulate retinal vascular development by modulating angiogenic and inflammatory factors. Photoreceptor metabolic dysfunction, oxidative stress, and inflammation may cause adaptive but ultimately pathological retinal vascular responses, leading to blindness. Here we focus on the factors involved in neurovascular interactions, which are potential therapeutic targets to decrease energy demand and/or to increase energy production for neovascular retinal disorders.

Circular RNA-ZBTB44 regulates the development of choroidal neovascularization

Rationale: Choroidal neovascularization (CNV) is a major cause of severe vision loss and occurs in many ocular diseases, especially neovascular age-related macular degeneration (nAMD). Circular RNAs (circRNAs) are emerging as a new class of endogenous noncoding RNAs, which have been implicated in the regulation of endothelial cell dysfunction in diabetes mellitus and cancer. In this study, we aimed to determine the role of circRNA-ZBTB44 (cZBTB44) in the pathogenesis of CNV.

Methods: Quantitative polymerase chain reaction was conducted to detect cZBTB44 expression pattern during CNV development. Isolectin B4 staining, hematoxylin and eosin (HE) staining, and choroidal sprouting assay ex vivo were conducted to evaluate the role of cZBTB44 in the development of CNV. Endothelial cell proliferation, migration and tube formation assays were conducted to determine the role of cZBTB44 in angiogenic effect in vitro. Bioinformatics analysis, RNA immunoprecipitation assay, luciferase assay, and in vitro studies were conducted to investigate the mechanism of cZBTB44-mediated CNV development.

Results: cZBTB44 expression was significantly up-regulated in a laser-induced CNV mouse model in vivo and in endothelial cells upon hypoxia stress in vitro. cZBTB44 silencing retarded CNV development, while overexpression of cZBTB44 showed the opposite effects. The role of cZBTB44 in CNV development was confirmed in choroidal sprouting assay ex vivo. cZBTB44 silencing reduced endothelial cell viability, proliferation, migration and tube formation in vitro. cZBTB44 acted as miR-578 sponge to sequester and inhibit miR-578 activity, which led to increased expression of vascular endothelial growth factor A (VEGFA) and vascular cell adhesion molecule-1 (VCAM1). Overexpression of miR-578 mimicked cZBTB44 silencing-mediated anti-angiogenic effects in vivo and in vitro. Furthermore, dysregulated cZBTB44 expression was detected in the clinical samples of nAMD patients.

Conclusions: This study provided novel insights into the molecular pathogenesis of CNV. The cZBTB44-miR-578-VEGFA/VCAM1 axis might be a potential source of novel therapeutic targets for neovascularization-related diseases.

Diabetes induces IL-17A-Act1-FADD-dependent retinal endothelial cell death and capillary degeneration

PURPOSE

Diabetes leads to progressive complications such as diabetic retinopathy, which is the leading cause of blindness within the working-age population worldwide. Interleukin (IL)-17A is a cytokine that promotes and progresses diabetes. The objective of this study was to determine the role of IL-17A in retinal capillary degeneration, and to identify the mechanism that induces retinal endothelial cell death. These are clinically meaningful abnormalities that characterize early-stage non-proliferative diabetic retinopathy.

METHODS

Retinal capillary degeneration was examined in vivo using the streptozotocin (STZ) diabetes murine model. Diabetic-hyperglycemia was sustained for an 8-month period in wild type (C57BL/6) and IL-17A^-/- mice to elucidate the role of IL-17A in retinal capillary degeneration. Further, ex vivo studies were performed in retinal endothelial cells to identify the IL-17A-dependent mechanism that induces cell death.

RESULTS

It was determined that diabetes-induced retinal capillary degeneration was significantly lower in IL-17A^-/- mice. Further, retinal endothelial cell death occurred through an IL-17A/IL-17R ➔ Act1/FADD signaling cascade, which caused caspase-mediated apoptosis.

CONCLUSION

These are the first findings that establish a pathologic role for IL-17A in retinal capillary degeneration. Further, a novel IL-17A-dependent apoptotic mechanism was discovered, which identifies potential therapeutic targets for the early onset of diabetic retinopathy.

Anti-apoptotic effect of interleukin-17 in a mouse model of oxygen-induced retinopathy

Retinopathy of prematurity (ROP) is an important cause of visual loss in children born prematurely. Although the involvement of inflammation in the development of ROP is gaining increasing attention, the role of IL-17A in ROP progress remains unclear. The aim of this study was to assess the levels of IL-17A production in the mice model of oxygen-induced retinopathy (OIR) and elucidate its potential roles. Wild-type (WT) and IL-17A knockout (IL-17A^-/-) mice were exposed to 75% O₂ from postnatal day 7 (P7) to P12. Age-matched controls were maintained in room air. Primary Müller cells isolated from WT or IL-17A^-/- mice retina were co-cultured with 661W cells and exposed to hypoxic conditions. Western blotting and immunofluorescent staining were used to assess the expression of target protein. Apoptosis in OIR retinal sections and 661W cells was detected by TUNEL staining. Results turned out that IL-17A expression was increased and reached a peak at P22 in OIR retina and at 8 h in hypoxic-cultured Müller cells. IL-17A knockout decreased the expression of glial fibrillary acidic protein (GFAP) and mature neurotrophin-3 (NT-3) in retina of OIR mice as well as hypoxic-cultured Müller cells. The NT-3 release induced by IL-17 was prevented by an ERK-specific inhibitor. In addition, more apoptosis cells and higher levels of Bax and cleaved caspase-3 was detected in the retina tissues of IL-17A^-/- OIR and the 661W cells co-cultured with IL-17A^-/- Müller cells. Taken together, our findings suggest that Müller cell was the potential source of IL-17A under the hypoxic conditions. Modulation of the IL-17A/ERK/NT-3 pathway exerts anti-apoptotic effect on photoreceptor cell and may be a novel therapeutic strategy for ROP.

Müller cells in pathological retinal angiogenesis

Müller cells are the major glial cells spanning the entire layer of the retina and maintaining retinal structure. Under pathological conditions, Müller cells are involved in retinal angiogenesis, a process of growing new blood vessels from pre-existing capillaries. In response to hypoxia, high glucose, and inflammation conditions, multiple signaling pathways are activated in Müller cells, followed by the increased production of proangiogenic factors including vascular endothelial growth factor, basic fibroblast growth factor, matrix metalloproteinases, Netrin-4, and angiopoietin-like 4. Expression of antiangiogenic factors is also downregulated in Müller cells. Besides, proliferation and dedifferentiation of Müller cells facilitates retinal angiogenesis. In this review, we summarized molecular mechanisms of Müller cells-related retinal angiogenesis. The potential of Müller cells as a therapeutic target for retinal angiogenesis was also discussed.

Interleukin-17: The Role for Pathological Angiogenesis in Ocular Neovascular Diseases

Ocular neovascular diseases are featured by abnormal angiogenesis in the eye, and they seriously threaten the human visual health. These diseases include proliferative diabetic retinopathy (PDR), age-related macular degeneration (AMD), retinopathy of prematurity (ROP), and retinal vein occlusion (RVO). In fact, ocular neovascular diseases represent the leading causes of vision impairment and blindness worldwide. Ocular neovascularization, the process of pathological vessel formation in eye, underlies ocular neovascular diseases. Cytokines have important regulatory roles in neovascularization through immunological networks. Interleukin (IL)-17, the signature cytokine produced by T helper 17 (Th17) cells, has proven to be involved in ocular neovascularization. However, roles of IL-17 in ocular neovascular diseases still remain controversial. This review provides an overview of the functional roles of IL-17 in ocular neovascular diseases from basic research to clinical evidence by focusing on PDR, AMD, ROP, and RVO. The possible roles of IL-17 in neovascularization are achieved through a regulatory network of cytoskeleton remodeling, vascular endothelial growth factor (VEGF), VEGF-related cytokines, and complement components. Current applications as well as potential therapies targeting IL-17 with genome editing systems are also outlined and discussed. Targeting IL-17 might be a promising therapeutic strategy against ocular neovascular diseases.

Role of aldose reductase in diabetes-induced retinal microglia activation

Diabetes-induced hyperglycemia plays a key pathogenic role in degenerative retinal diseases. In diabetic hyperglycemia, aldose reductase (AR) is elevated and linked to the pathogenesis of diabetic retinopathy (DR) and cataract. Retinal microglia (RMG), the resident immune cells in the retina, are thought to contribute to the proinflammatory phenotype in the diabetic eye. However, we have a limited understanding of the potential role of AR expressed in RMG as a mediator of inflammation in the diabetic retina. Glycated proteins accumulate in diabetes, including Amadori-glycated albumin (AGA) which has been shown to induce a proinflammatory phenotype in various tissues. In this study, we investigated the ability of AGA to stimulate inflammatory changes to RMG and macrophages, and whether AR plays a role in this process. In macrophages, treatment with an AR inhibitor (Sorbinil) or genetic knockdown of AR lowered AGA-induced TNF-α secretion (56% and 40%, respectively) as well as cell migration. In a mouse RMG model, AR inhibition attenuated AGA-induced TNF-α secretion and cell migration (67% and 40%, respectively). To further mimic the diabetic milieu in retina, we cultured RMG under conditions of hypoxia and observed the induction of TNF-α and VEGF protein expression. Downregulation of AR in either a pharmacological or genetic manner prevented hypoxia-induced TNF-α and VEGF expression. In our animal study, increased numbers of RMG observed in streptozotocin (STZ)-induced diabetic retina was substantially lower when diabetes was induced in AR knockout mice. Thus, in vitro and in vivo studies demonstrated that AR is involved in diabetes-induced RMG activation, providing a rationale for targeting AR as a therapeutic strategy for DR.

A journey into the retina: Müller glia commanding survival and death

Müller glial cells (MGCs) are known to participate actively in retinal development and to contribute to homoeostasis through many intracellular mechanisms. As there are no homologous cells in other neuronal tissues, it is certain that retinal health depends on MGCs. These macroglial cells are located at the centre of the columnar subunit and have a great ability to interact with neurons, astrocytes, microglia and endothelial cells in order to modulate different events. Several investigations have focused their attention on the role of MGCs in diabetic retinopathy, a progressive pathology where several insults coexist. As expected, data suggest that MGCs display different responses according to the severity of the stimulus, and therefore trigger distinct events throughout the course of the disease. Here, we describe physiological functions of MGCs and their participation in inflammation, gliosis, synthesis and secretion of trophic and antioxidant factors in the diabetic retina. We invite the reader to consider the protective/deleterious role of MGCs in the early and late stages of the disease. In the light of the results, we open up the discussion around and ask the question: Is it possible that the modulation of a single cell type could improve or even re-establish retinal function after an injury?

Retinal microglia - A key player in healthy and diseased retina

Microglia, the resident immune cells of the brain and retina, are constantly engaged in the surveillance of their surrounding neural tissue. During embryonic development they infiltrate the retinal tissues and participate in the phagocytosis of redundant neurons. The contribution of microglia in maintaining the purposeful and functional histo-architecture of the adult retina is indispensable. Within the retinal microenvironment, robust microglial activation is elicited by subtle changes caused by extrinsic and intrinsic factors. When there is a disturbance in the cell-cell communication between microglia and other retinal cells, for example in retinal injury, the activated microglia can manifest actions that can be detrimental. This is evidenced by activated microglia secreting inflammatory mediators that can further aggravate the retinal injury. Microglial activation as a harbinger of a variety of retinal diseases is well documented by many studies. In addition, a change in the microglial phenotype which may be associated with aging, may predispose the retina to age-related diseases. In light of the above, the focus of this review is to highlight the role played by microglia in the healthy and diseased retina, based on findings of our own work and from that of others.

IL-17 in neonatal health and disease

Over the last few years, scientific interest in the cytokine IL-17A has intensified as its role in human health and disease has been elucidated. Discovered almost a quarter century ago, IL-17A is known to have poor biologic activity when acting alone, but attains robust actions when working synergistically with potent mediators of proinflammatory immune responses, such as IL-6 and IL-8. IL-17A is produced by specialized innate immune cells that protect host barriers from the outside world. Like sentries, these innate immune cells can "sound the alarm" through increased production of IL-17A, causing activation and recruitment of primed neutrophils and monocytes when pathogens escape initial host defenses. In this way, IL-17A promulgates mechanisms responsible for pathogen death and clearance. However, when IL-17A pathways are triggered during fetal development, due to chorioamnionitis or in utero inflammatory conditions, IL-17A can instigate and/or exacerbate fetal inflammatory responses that increase neonatal morbidities and mortality associated with common neonatal conditions such as sepsis, bronchopulmonary dysplasia (BPD), patent ductus arteriosus (PDA), and necrotizing enterocolitis (NEC). This review details the ontogeny of IL-17A in the fetus and newborn, discusses how derangements in its production can lead to pathology, and describes known and evolving therapies that may attenuate IL-17A-mediated human conditions.

Microglia at center stage: a comprehensive review about the versatile and unique residential macrophages of the central nervous system

Microglia cells are the unique residential macrophages of the central nervous system (CNS). They have a special origin, as they derive from the embryonic yolk sac and enter the developing CNS at a very early stage. They play an important role during CNS development and adult homeostasis. They have a major contribution to adult neurogenesis and neuroinflammation. Thus, they participate in the pathogenesis of neurodegenerative diseases and contribute to aging. They play an important role in sustaining and breaking the blood-brain barrier. As innate immune cells, they contribute substantially to the immune response against infectious agents affecting the CNS. They play also a major role in the growth of tumours of the CNS. Microglia are consequently the key cell population linking the nervous and the immune system. This review covers all different aspects of microglia biology and pathology in a comprehensive way.

Foxp3+ Tregs are recruited to the retina to repair pathological angiogenesis

Neovascular retinopathies are major causes of vision loss; yet treatments to prevent the condition are inadequate. The role of regulatory T cells in neovascular retinopathy is unknown. Here we show that in retinopathy regulatory T cells are transiently increased in lymphoid organs and the retina, but decline when neovascularization is established. The decline is prevented following regulatory T cells expansion with an IL-2/anti-IL-2 mAb complex or the adoptive transfer of regulatory T cells. Further, both approaches reduce vasculopathy (vaso-obliteration, neovascularization, vascular leakage) and alter the activation of Tmem119⁺ retinal microglia. Our in vitro studies complement these findings, showing that retinal microglia co-cultured with regulatory T cells exhibit a reduction in co-stimulatory molecules and pro-inflammatory mediators that is attenuated by CTLA-4 blockade. Collectively, we demonstrate that regulatory T cells are recruited to the retina and, when expanded in number, repair the vasculature. Manipulation of regulatory T cell numbers is a previously unrecognized, and promising avenue for therapies to prevent blinding neovascular retinopathies.

The local immune responses in the eye are attenuated to preserve sight. Surprisingly, Deliyanti et al. show that regulatory T cells (Tregs) take an active role in protecting the eye from neovascularization in oxygen-induced retinopathy, and that interventions that augment the retinal Treg numbers reduce neovascular retinopathy in mice.

Apln-CreERT:mT/mG reporter mice as a tool for sprouting angiogenesis study

Background

Angiogenesis is defined as a new blood vessel sprouting from pre-existing vessels, and the sprouting angiogenesis is the start phase of angiogenesis, which is critical for both physiological and pathological processes, such as embryonic development, organ growth, wound healing, tumor growth, diabetic retinopathy and age-related macular degeneration. Better understanding of the mechanisms of sprout angiogenesis will provide a rationale for the treatments of these angiogenesis related diseases.

Methods

mT/mG tool mice are crossed with Apln-CreERT mice to generate Apln-CreERT: mT/mG mice, then we used neonatal retinal angiogenesis model to observe the angiogenic pattern of Apln-CreERT:mT/mG mice compared with Cdh5-CreERT:mT/mG mice. FACS analysis was used to sort eGFP and tdTomato endothelial cells (ECs) for measuring Apelin and Cdh5 expression. Retinal sprouting angiogenesis pattern was also observed at different neonatal time when induced by tamoxifen and at hypoxia condition, as well as in vivo tumor in real-time angiogenesis in a dorsal skinfold window chamber in Apln-CreERT:mT/mG mice.

Results

Apln-CreERT:mT/mG mice exhibited eGFP signal only in the sprouting angiogenesis, with less eGFP expression in the retinal “optic nerve” area than in that of Cdh5-CreERT: mT/mG mice, which might be due to relative mature vessels in the “optic nerve” area. The ECs sorted by FACS confirmed that the Apelin expression level was higher in eGFP ECs than tdTomato ECs of “optic nerve” area. Further we found that GFP-labeled sprouting angiogenesis decreased gradually following tamoxifen administration from P5-P7, but increased significantly during hypoxia in Apln-CreERT:mT/mG mice. At last, using Apln-CreERT:mT/mG mice we found tumor sprouting angiogenesis in dorsal skinfold, but not in the normal skinfold tissue.

Conclusions

Apln-CreERT:mT/mG mouse line is a useful tool to differentiate sprouting angiogenesis from whole blood vessels in the investigation of retinal and tumor sprouting angiogenesis in vivo.

RORα modulates semaphorin 3E transcription and neurovascular interaction in pathological retinal angiogenesis

Pathological proliferation of retinal blood vessels commonly causes vision impairment in proliferative retinopathies, including retinopathy of prematurity. Dysregulated crosstalk between the vasculature and retinal neurons is increasingly recognized as a major factor contributing to the pathogenesis of vascular diseases. Class 3 semaphorins (SEMA3s), a group of neuron-secreted axonal and vascular guidance factors, suppress pathological vascular growth in retinopathy. However, the upstream transcriptional regulators that mediate the function of SEMA3s in vascular growth are poorly understood. Here we showed that retinoic acid receptor-related orphan receptor α (RORα), a nuclear receptor and transcription factor, is a novel transcriptional regulator of SEMA3E-mediated neurovascular coupling in a mouse model of oxygen-induced proliferative retinopathy. We found that genetic deficiency of RORα substantially induced Sema3e expression in retinopathy. Both RORα and SEMA3E were expressed in retinal ganglion cells. RORα directly bound to a specific ROR response element on the promoter of Sema3e and negatively regulated Sema3e promoter-driven luciferase expression. Suppression of Sema3e using adeno-associated virus 2 carrying short hairpin RNA targeting Sema3e promoted disoriented pathological neovascularization and partially abolished the inhibitory vascular effects of RORα deficiency in retinopathy. Our findings suggest that RORα is a novel transcriptional regulator of SEMA3E-mediated neurovascular coupling in pathological retinal angiogenesis.-Sun, Y., Liu, C.-H., Wang, Z., Meng, S. S., Burnim, S. B., SanGiovanni, J. P., Kamenecka, T. M., Solt, L. A., Chen, J. RORα modulates semaphorin 3E transcription and neurovascular interaction in pathological retinal angiogenesis.

Fractalkine-CX3CR1 signaling is critical for progesterone-mediated neuroprotection in the retina

Retinitis pigmentosa (RP) encompasses a group of retinal diseases resulting in photoreceptor loss and blindness. We have previously shown in the rd10 mouse model of RP, that rd10 microglia drive degeneration of viable neurons. Norgestrel, a progesterone analogue, primes viable neurons against potential microglial damage. In the current study we wished to investigate this neuroprotective effect further. We were particularly interested in the role of fractalkine-CX3CR1 signaling, previously shown to mediate photoreceptor-microglia crosstalk and promote survival in the rd10 retina. Norgestrel upregulates fractalkine-CX3CR1 signaling in the rd10 retina, coinciding with photoreceptor survival. We show that Norgestrel-treated photoreceptor-like cells, 661Ws, and C57 explants modulate rd10 microglial activity in co-culture, resulting in increased photoreceptor survival. Assessment of Norgestrel's neuroprotective effects when fractalkine was knocked-down in 661 W cells and release of fractalkine was reduced in rd10 explants confirms a crucial role for fractalkine-CX3CR1 signaling in Norgestrel-mediated neuroprotection. To further understand the role of fractalkine in neuroprotection, we assessed the release of 40 cytokines in fractalkine-treated rd10 microglia and explants. In both cases, treatment with fractalkine reduced a variety of pro-inflammatory cytokines. These findings further our understanding of Norgestrel's neuroprotective properties, capable of modulating harmful microglial activity indirectly through photoreceptors, leading to increased neuroprotection.