Nitric oxide mediates apoptosis through formation of peroxynitrite and Fas/Fas-ligand interactions in experimental autoimmune uveitis

Serum GAS6, sAXL, IL-10, NO, and BCL-2 levels are decreased in patients with Behçet's disease

PURPOSE

Behçet's disease (BD) is an autoimmune chronic systemic inflammatory disease characterized by a versatile clinical spectrum. Growth arrest specific protein 6 (GAS6)/soluble AXL (sAXL) signaling pathway draws attention in the resolution of inflammation, and its deficiency is associated with chronic inflammatory, autoimmune diseases, as well as clearance of apoptotic cells by phagocytes - efferocytosis. In this study, it was aimed to investigate whether GAS6/sAXL, interleukin (IL)-10, nitric oxide (NO), and BCL-2 levels were associated with inflammation and efferocytosis contributes to the pathogenesis of BD.

METHODS

A total of 37 Behçet patients with ocular involvement and 30 healthy control subjects were included in this study. GAS6, sAXL, IL-10, NO, and BCL-2 levels were quantified using enzyme-linked immunosorbent assay (ELISA) method.

RESULTS

Serum GAS6, sAXL, IL-10, NO, and BCL-2 levels were significantly lower in patients with BD compared to the controls (P < 0.005, P < 0.001, P < 0.001, P < 0.001, and P < 0.001, respectively). In correlation analysis, research parameters decreased in patients with BD was significantly correlated with each other: GAS6-IL-10 (r = 0.585, P < 0.001), GAS6-BCL-2 (r = 0.541, P < 0.001), sAXL-BCL-2 (r = 0.696, P < 0.001), IL-10-NO (r = 0.717, P < 0.001), IL-10-BCL-2 (r = 0.759, P < 0.001), and NO-BCL-2 (r = 0.541, P < 0.001).

CONCLUSION

In conclusion, decreased serum BCL-2 level may be an indicator of increased apoptosis in these patients and decreased levels of GAS6/sAXL, IL-10, and NO may indicate insufficient clearance of apoptotic bodies released as a result of increased apoptosis in BD patients.

Value of Serum Asymmetric Dimethylarginine (ADMA) As a Novel Biomarker for Uveitis in Behçet's Disease

PURPOSE

To evaluate the serum asymmetric dimethylarginine (ADMA) level as a biomarker for uveitis in Behçet's Disease (BD).

METHODS

In this cross-sectional study, two groups of BD patients were examined: 33 with uveitis and 27 without uveitis. All patients were clinically evaluated, with disease activity measured by Behçet's Disease Current Activity Form (BDCAF) score. They also underwent thorough ophthalmic evaluation, and routine laboratory investigations, including serum ADMA.

RESULTS

Patients with BD who experienced active or inactive uveitis had higher levels of serum ADMA compared to those without uveitis. Anterior (ρ = 0.34, p < 0.01), posterior (ρ = 0.3, p < 0.05), and pan uveitis (ρ = 0.35, p < 0.01) were significantly correlated with serum ADMA levels. However, there was no significant correlation between ADMA and other BD manifestations. ROC curve analysis showed that increased serum ADMA levels in BD patients predicted uveitis with a sensitivity of 61.8%, specificity of 96.2%, and AUC of 0.78(95% CI: 0.66-0.9, p < 0.001).

CONCLUSION

Serum ADMA level can serve as a novel biomarker of uveitis in BD and its severity with good diagnostic accuracy, regardless of its site or activity.

Local Myeloid-Derived Suppressor Cells Impair Progression of Experimental Autoimmune Uveitis by Alleviating Oxidative Stress and Inflammation

Purpose

To evaluate the immune regulatory effect of human cord blood myeloid-derived suppressor cells (MDSCs) in experimental autoimmune uveitis (EAU) models.

Methods

MDSCs (1 × 106) or PBS were injected into established C57BL/6 EAU mice via the subconjunctival route on days 0 and 7. The severity of intraocular inflammation was evaluated for up to 3 weeks. Tissue injury and inflammation were analyzed using immunolabelled staining, real-time PCR, and ELISA. In addition, immune cells in draining lymph nodes (LNs) were quantified using flow cytometry.

Results

After 21 days, the clinical scores and histopathological grades of EAU were lower in the MDSCs group compared with the PBS group. Local administration of MDSCs suppressed the oxidative stress and the expression of TNF-α and IL-1β in the retinal tissues. In addition, it inhibited the activation of pathogenic T helper 1 (Th1) and Th17 cells in draining LNs. MDSCs increased the frequency of CD25+ Foxp3+ regulatory T cells and the mRNA expression of IL-10, as an immune modulator.

Conclusions

MDSCs suppressed inflammation and oxidative stress in the retina and inhibited pathogenic T cells in the LNs in EAU. Therefore, ocular administration of MDSCs has therapeutic potential for uveitis.

Comparative Efficacy of Fish Meal Replacement With Enzymatically Treated Soybean Meal on Growth Performance, Immunity, Oxidative Capacity and Fecal Microbiota in Weaned Pigs

This study investigated the growth performance, immunity, antioxidant capacity and fecal microbiota of weaned pigs by partially or completely replacing dietary fish meal with enzymatically treated soybean meal. A total of 144 piglets (initial body weight of 7.19 ± 0.11 kg) weaned at 28 d were allotted to 3 dietary treatments (6 replicates per treatment): 4% fish meal diet (FM); 2% fishmeal plus 6% enzymatically treated soybean meal (ESBM1); and 6% enzymatically treated soybean meal without fish meal (ESBM2). The experimental period was 28 d, serum was collected at day 14 and day 28 for biochemical parameters analysis, feces was obtained for microbiota analysis at 28d. The body weight, average daily gain and average daily feed intake of piglets in the ESBM2 group were significantly increased compared with those in the FM and ESBM1 groups from 0 to 28 d, respectively (P < 0.05). The diets with enzymatically treated soybean meal in ESBM1 and ESBM2 groups decreased the diarrhea rate (P < 0.05). Compared with FM, ESBM1 and ESBM2 decreased 5-hydroxytryptamine (5-HT) (P < 0.05). ESBM1 decreased diamine oxidase (DAO) and Interleukin 6 (IL-6) compared with FM and ESBM2 (P < 0.05). ESBM1 decreased serum Interleukin 1β (IL-1β) compared with FM at d 14 (P < 0.05). The serum Immunoglobulin E (IgE), secretory curl associated protein 5 (sFRP-5) were higher in ESBM1 compared with FM and ESBM2 (P < 0.05). ESBM2 increased super oxidase dismutase (SOD) level and decreased malondialdehyde (MDA) content compared with FM and ESBM1, the concentration of SOD in ESBM1was higher than that in FM (P < 0.05). ESBM1 decreased cortisol and caspase 3 (Casp-3) (P < 0.05). FM showed a higher content of tri-iodothyronine (T3) (P < 0.05) and a lower thyroxine/ tri-iodothyronine ratio compared with those in the other two groups (P < 0.05). The concentration of leptin was lower in ESBM2 (P < 0.05). ESBM1 had a higher α-diversity than ESBM2 (P < 0.05). The microbiota composition was different among three treatments (difference between FM and ESBM1, p = 0.005; FM and ESBM2, p = 0.009; ESBM1 and ESBM2, p = 0.004). ESBM2 tend to increase the abundance of Firmicutes (P = 0.070) and decrease Bacteroidetes (P = 0.069). ESBM2 decreased the abundance of Parabacteroides and increased SMB53 compared with FM (P < 0.05). The spearman correlation analysis revealed that the abundance of Parabacteroides enriched in FM group was negatively correlated with SOD, Megasphaera enriched in ESBM2 group were positively correlated with SOD. The abundance of Lachnospira enriched in ESBM2 group were negatively correlated with serum concentration of D-lactate, DAO, IL-6, and NO. In conclusion, under the conditions of this study, diet with only ESBM demonstrate the beneficial impact on intestinal microbiota developments, antioxidant capacity as well as growth performance for weaned pigs.

TNF-α in Uveitis: From Bench to Clinic

Uveitis is an inflammation of the iris, ciliary body, vitreous, retina, or choroid, which has been shown to be the first manifestation of numerous systemic diseases. Studies about the immunopathogenesis and treatment of uveitis are helpful to comprehend systemic autoimmune diseases, and delay the progression of systemic autoimmune diseases, respectively. Tumor necrosis factor-alpha (TNF-α), a pleiotropic cytokine, plays a pivotal role in intraocular inflammation based on experimental and clinical data. Evidence of the feasibility of using anti-TNF-α agents for uveitis management has increased. Although there are numerous studies on TNF-α in various autoimmune diseases, the pathological mechanism and research progress of TNF-α in uveitis have not been reviewed. Therefore, the objective of this review is to provide a background on the role of TNF-α in the immunopathogenesis of uveitis, as well as from bench to clinical research progress, to better guide TNF-α-based therapeutics for uveitis.

Association between increased Bcl-2, Fas and FasL levels and inflammation extent in labial salivary glands during primary Sjögren's syndrome

BACKGROUND

Primary Sjögren syndrome (pSS) is a chronic autoimmune disease characterized by epithelial atrophy, mononuclear infiltration in exocrine glands resulting in defective function of these glands. In pSS, atrophy of the epithelium is caused by an increased amount of apoptosis.

OBJECTIVE

The main aim of this study is to investigate the role of the apoptosis-related factors by studying Bcl-2, Fas and FasL expression in relation to the extent of inflammation as well as the effect of therapy on the expression of these mediators.

METHODS

In pSS patients (n=62) documented for their serological and clinical features, Fas, FasL and Bcl-2 plasma levels were assessed using enzyme-linked immunosorbent assays. In the same context, we investigated their expression by immunohistochemistry analysis in the labial salivary glands samples in association with the extent of inflammation.

RESULTS

Interestingly, our results indicated that in pSS patients, the plasmatic Bcl-2, Fas and FasL levels, which appear to be associated with the severity of inflammation and were significantly elevated in comparison to the healthy controls. Moreover, a significant decrease in all these factors was observed in patients after combined corticosteroids-hydroxychloroquine therapy. Importantly, we report a strong positive correlation between Bcl-2 and NO levels. The immunohistochemical staining reveals a strong Bcl-2 expression in infiltrating mononuclear cells and a total absence in the acinar cells. The Bcl-2 level varies according to the severity of the pathology. However, the expression of Fas and FasL was less important and predominantly localized in infiltrating mononuclear cells.

CONCLUSION

Our current study highlights the involvement of Bcl-2, Fas and FasL in pSS glands injury. These factors may act as useful predictor markers of a clinical course in pSS suggesting a novel approach in the pSS patients monitoring.

The Efficacy of Adalimumab as an Initial Treatment in Patients with Behçet's Retinal Vasculitis

Background: No study has evaluated the effectiveness of Adalimumab (ADA) as first-line in treatment-naïve patients with retinal vasculitis due to Behçet’s Uveitis (BU).

Objective: To compare the efficacy of ADA plus conventional therapy and conventional therapy alone as initial treatments in naïve BU patients characterized by retinal vasculitis.

Methods: Medical records of BU patients characterized by retinal vasculitis treated with conventional therapy (CT, refers to glucocorticoid and immunosuppressive agents) alone or ADA plus conventional therapy with at least 6 months of follow-up between February 2015 and June 2020 were analyzed. Only patients who were first diagnosed with BU without previous systemic treatment were reviewed. The retinal vasculitis score based on fluorescein angiography (FA), best-corrected visual acuity, glucocorticoid-sparing effect, the number of relapses and ocular complications were evaluated.

Results: A total of 45 patients (87 eyes) were included. Twenty-four patients (55.33%) in the CT group were treated with conventional therapy and 21 patients (46.67%) in the ADA group were treated with ADA plus conventional therapy. The inflammatory parameters improved in both groups. FA scores showed significantly greater improvement in ADA group than CT group (p < 0.001). The median number of relapses was significantly lower, and the duration of remission was longer in ADA group than CT group (p < 0.001). At the last visit, a significantly better BCVA improvement (p = 0.024), better inflammation control (anterior chamber inflammation p = 0.017 and vitritis p < 0.001) and lower daily glucocorticoid dosage (p = 0.005) were identified in patients received ADA therapy. In CT group, 1 patient suffered hepatitis B and tuberculosis, 1 had growth retardation, 1 patient had with osteoporosis, then followed by other mild AEs (mostly respiratory upper tract infections); while in ADA group, 1 patient experienced a mild pneumonia (n = 1) while milder AEs were represented mostly by respiratory upper tract infections followed by gastrointestinal discomfort.

Conclusion: ADA plus conventional therapy achieved superiority over conventional therapy as initial treatment in naïve BU patients with retinal vasculitis.

Comparative study of adalimumab versus conventional therapy in sight-threatening refractory Behçet's uveitis with vasculitis

BACKGROUND

Anti-tumor necrosis factor-alpha was regarded as an option in treatment of non-infectious uveitis. However, few studies in the far easter region have concentrated on this therapy and current studies have not emphasized the elimination of retinal vasculitis. To compare the effectiveness of adalimumab (ADA) plus conventional therapy (CT) versus CT alone in treating patients with retinal vasculitis (RV) due to refractory Behçet's uveitis (BU).

DESIGN

Retrospective cohort study.

METHODS

Clinical records of BU patients with previously treated but poorly controlled RV were analyzed. Patients were allocated into two groups depending on ADA use. Each group was treated for no less than 6 months between February 2015 and September 2020. The primary outcome parameter was the RV score. Best-corrected visual acuity (BCVA), number of relapses, macular thickness and ocular complications were considered concomitantly.

RESULTS

Forty-two patients (72 eyes) were included; 21 patients were in CT group, and 21 patients were in ADA group. Inflammatory parameters improved in both groups. The improvement in the fluorescein angiography (FA) score and anterior chamber inflammation were significantly better in ADA group than in CT group (P < 0.05). The relapse time was significantly lower in ADA group than in CT group (P = 0.01). Daily glucocorticoid dose tapers were more evident in ADA group than in CT group (P < 0.05). Adverse events were detected in 7 patients (5 had upper respiratory tract infection and 2 had gastrointestinal discomfort) in ADA group; in CT group, upper respiratory infection and recurrent gum swelling were observed in 1 patient each.

CONCLUSION

Our results indicate that ADA plus CT outperforms CT alone in patients with RV due to refractory BU. More agile ADA use in these patients should be considered to achieve optimal treatment.

The role of myeloid-derived suppressor cells in rheumatoid arthritis: An update

Rheumatoid arthritis (RA) is an autoimmune disease that generally affects the joints. In the late stages of the disease, it can be associated with several complications. Although the exact etiology of RA is unknown, various studies have been performed to understand better the immunological mechanisms involved in the pathogenesis of RA. At the onset of the disease, various immune cells migrate to the joints and increase the recruitment of immune cells to the joints by several immunological mediators such as cytokines and chemokines. The function of specific immune cells in RA is well-established. The shift of immune responses to Th1 or Th17 is one of the most essential factors in the development of RA. Myeloid-derived suppressor cells (MDSCs), as a heterogeneous population of myeloid cells, play a regulatory role in the immune system that inhibits T cell activity through several mechanisms. Various studies have been performed on the function of these cells in RA, which in some cases have yielded conflicting results. Therefore, the purpose of this review article is to comprehensively understand the pro-inflammatory and anti-inflammatory functions of MDSCs in the pathogenesis of RA.

The Effects and Mechanism of Quercetin Dietary Supplementation in Streptozotocin-Induced Hyperglycemic Arbor Acre Broilers

Quercetin, a flavonoid found in fruits and vegetables, is widely distributed as a secondary metabolite in the plant kingdom. Oxidative stress plays a role in the pathogenesis of diabetes mellitus (DM). The present study investigated the effects of quercetin dietary supplementation on streptozotocin- (STZ-) induced hyperglycemic Arbor Acre (AA) broilers by determining the levels of fasting blood glucose (FBG), fasting insulin (FINS), biochemical indicators, oxidative stress markers, inflammatory cytokines content, antioxidant enzymes activities in tissues, and mRNA expression of genes relating to the insulin signaling pathway. Three hundred one-day-old healthy AA broilers were randomly assigned into 5 treatments; A, control healthy broilers; B, STZ-induced broilers; C, STZ-induced broiler dietary supplemented with 0.02% quercetin; D, STZ-induced broiler dietary supplemented with 0.04% quercetin; and E, STZ-induced broiler dietary supplemented with 0.06% quercetin. The results showed that quercetin supplementation relieved the side effects of STZ-induced oxidative stress by changing activities of antioxidant enzymes, decreasing malondialdehyde (MDA) and nitric oxide (NO) levels, activating expression of genes relating to PI3K/PKB signaling pathway that modulate glucose metabolism and reduce oxidative damage, thereby decreasing FBG and increasing FINS levels. These findings suggest that quercetin exhibits a protective effect in STZ-induced hyperglycemic AA broilers via decreasing oxidative stress.

Folic acid deficiency and vision: a review

Folic acid (FA), also termed folate, is an essential vitamin for health at all ages since it participates in the biosynthesis of nucleotides, amino acids, neurotransmitters, and certain vitamins. It is therefore crucial for rapidly growing tissues such as those of the fetus. It is becoming clear that FA deficiency and impaired folate pathways are implicated in many diseases of both early life and old age. FA can be transported into the cell by the folate receptor, the reduced folate transporter, and proton-coupled folate transporter. Folate transport proteins are present in certain eye tissues, which explains why FA plays an important role in eye development. The purpose of this literature review is to investigate the evidence relating FA deficiency to eye diseases.

Myeloid-derived suppressor cells and myeloid regulatory cells in cancer and autoimmune disorders

Myeloid-derived suppressor cells (MDSCs) were originally described as a heterogeneous population of immature cells derived from myeloid progenitors with immune-suppressive functions in tumor-bearing hosts. In recent years, increasing number of studies have described various populations of myeloid cells with MDSC-like properties in murine models of cancer and autoimmune diseases. These studies have observed that the populations of MDSCs are increased during inflammation and autoimmune conditions. In addition, MDSCs can effectively suppress T cell responses and modulate the activity of natural killer cells and other myeloid cells. MDSCs have also been implicated in the induction of regulatory T cell production. Furthermore, these cells have the potential to suppress the autoimmune response, thereby limiting tissue injury. Myeloid regulatory cells (Mregs) are recently attracting increasing attention, since they function in proinflammatory and immune suppression in autoimmune diseases, as well as in various types of cancer. Currently, research focus is directed from MDSCs to Mregs in cancer and autoimmune diseases. The present study reviewed the suppressive roles of MDSCs in various autoimmune murine models, the immune modulation of MDSCs to T helper 17 lymphocytes, as well as the proinflammatory and immunosuppressive roles of Mregs in various types of cancer and autoimmune diseases.

Interleukin-6 secreted by bipotential murine oval liver stem cells induces apoptosis of activated hepatic stellate cells by activating NF-κB-inducible nitric oxide synthase signaling

Liver fibrosis is now well recognized as the causative factor for increased mortality from complications associated with liver pathologies. Activated hepatic stellate cells (HSCs) play a critical role in the progression of liver fibrosis. Therefore, targeting these activated HSCs to prevent and (or) treat liver disease is a worthwhile approach to explore. In the present in vitro study, we investigated the use of bipotential murine oval liver cells (BMOL) in regulating the functions of activated HSCs to prevent progression of liver fibrosis. We used a conditioned medium-based approach to study the effect of BMOL cells on activated HSC survival and function. Our data showed that BMOL cells block the contraction of activated HSCs by inducing apoptosis of these cells. We demonstrated that BMOL cells secrete soluble factors, such as interleukin-6 (IL-6), which induced apoptosis of activated HSCs. Using both pharmacological and molecular inhibitor approaches, we further identified that IL-6-mediated activation of NF-κB-iNOS-NO-ROS signaling in activated HSCs plays a critical role in BMOL-cell-mediated apoptosis of activated HSCs. Thus, the present study provides an alternative cell-based therapeutic approach to treat liver fibrosis.

Correlation of inducible nitric oxide synthase (iNOS) inhibition with TNF-α, caspase-1, FasL and TLR-3 in pathogenesis of rabies in mouse model

The role of inflammatory cytokines such as interleukin-1α/β (IL-1α/β), IL-6, IL-10, tumour necrosis factor-alpha (TNF-α), interferons, nitric oxide (NO) and inducible nitric oxide synthase (iNOS) in pathogenesis of rabies is being actively pursued. Presently, levels of certain immune molecules in pathogenesis of rabies in mice have been investigated. CVS strain of rabies infection resulted in early increase in iNOS, TNF-α, caspase-1, Fas ligand (FasL) and toll-like receptor-3 (TLR-3) mRNA levels in brain, and nitric oxide levels in serum. The severity of clinical signs and microscopic lesions largely correlated with NO levels. Aminoguanidine (AG; iNOS inhibitor) decreased NO production with delay in development of clinical signs and increase in survival time. Prolonged survival time correlated with reduced viral load evident by real-time PCR, reduced fluorescent signals of rabies antigen in brain and reduced immunohistochemistry signals in neuronal cytoplasm. These parameters suggested that nitric oxide did influence the rabies virus replication. Inhibition of iNOS by AG administration led to decreased expression of TNF-α, caspase-1, FasL and TLR-3 mRNA levels suggesting that increase in NO levels in rabies virus infection possibly contributed to development of disease through inflammation, apoptosis and immune-evasive mechanisms.

Correlation between Fluorescein Angiographic Findings and Visual Acuity in Behçet Retinal Vasculitis

PURPOSE

To identify significant fluorescein angiographic (FA) characteristics associated with visual acuity (VA) in Behçet retinal vasculitis.

MATERIALS AND METHODS

Retrospective review of 86 eyes of 48 patients (age: 35.6±10.2 years) with Behçet retinal vasculitis were performed. VA and FA findings as well as correlation between them were assessed.

RESULTS

The mean initial VA of eyes with posterior pole-involved vasculitis (63 eyes; 73.3%) was significantly worse than that of those with peripheral vasculitis (23 eye; 26.7%) (logarithm of the minimum angle of resolution VA: 0.554±0.572 vs. 0.078±0.148; p<0.0001). Subgroup analysis revealed a more severe and diffuse pattern of vascular leakage in posterior pole-involved vasculitis compared to peripheral vasculitis (p<0.0001). Retinal vascular leakage (β=0.345; p<0.0001), optic disc hyperfluorescence (β=0.147; p=0.032), and macular leakage (β=0.107; p=0.047) were significantly associated with worse initial VA. During the follow up (mean: 33.3±17.9 months), the change of leakage showed no significant correlation with change of VA in posterior pole-involved vasculitis (τ=0.199, p=0.092).

CONCLUSION

Posterior pole involvement, the degree of retinal vascular leakage, optic disc hyperfluorescence, and macular leakage are significantly associated with VA in Behçet retinal vasculitis.

Nitric oxide and oxidative stress is associated with severity of diabetic retinopathy and retinal structural alterations

BACKGROUND

The aim of the study was to determine plasma nitric oxide (NO) and lipid peroxide (LPO) levels in diabetic retinopathy and its association with severity of disease.

DESIGN

Prospective observational study.

PARTICIPANTS

A total of 60 consecutive cases and 20 healthy controls were included.

METHODS

Severity of retinopathy was graded according to early treatment diabetic retinopathy study (ETDRS) classification. Photoreceptor inner segment ellipsoid band (ISel) disruption and retinal pigment epithelium (RPE) alteration were graded using spectral domain optical coherence tomography. Data were statistically analyzed.

MAIN OUTCOME MEASURES

Plasma thiobarbituric acid reactive substances, NO assay and reduced glutathione (GSH) were measured using standard protocol.

RESULTS

Increased severity of diabetic retinopathy was significantly associated with increase in plasma levels of LPO (P < 0.05), NO (P < 0.001) and decrease in plasma levels of GSH (P < 0.0001), ISel disruption (P < 0.001) and RPE topographic alteration (P < 0.01).

CONCLUSION

Increased plasma NO levels are associated with increased severity of diabetic retinopathy. For the first time, it has been demonstrated that increased plasma LPO, NO and decreased GSH levels are associated with in vivo structural changes in inner segment ellipsoid and RPE.

Macrophages and Uveitis in Experimental Animal Models

Resident and infiltrated macrophages play relevant roles in uveitis as effectors of innate immunity and inductors of acquired immunity. They are major effectors of tissue damage in uveitis and are also considered to be potent antigen-presenting cells. In the last few years, experimental animal models of uveitis have enabled us to enhance our understanding of the leading role of macrophages in eye inflammation processes, including macrophage polarization in experimental autoimmune uveoretinitis and the major role of Toll-like receptor 4 in endotoxin-induced uveitis. This improved knowledge should guide advantageous iterative research to establish mechanisms and possible therapeutic targets for human uveitis resolution.

Role of myeloid-derived suppressor cells in autoimmune disease

Myeloid-derived suppressor cells (MDSCs) represent an important class of immunoregulatory cells that can be activated to suppress T cell functions. These MDSCs can inhibit T cell functions through cell surface interactions and the release of soluble mediators. MDSCs accumulate in the inflamed tissues and lymphoid organs of patients with autoimmune diseases. Much of our knowledge of MDSC function has come from studies involving cancer models, however many recent studies have helped to characterize MDSC involvement in autoimmune diseases. MDSCs are a heterogeneous group of immature myeloid cells with a number of different functions for the suppression of T cell responses. However, we have yet to fully understand their contributions to the development and regulation of autoimmune diseases. A number of studies have described beneficial functions of MDSCs during autoimmune diseases, and thus there appears to be a potential role for MDSCs in the treatment of these diseases. Nevertheless, many questions remain as to the activation, differentiation, and inhibitory functions of MDSCs. This review aims to summarize our current knowledge of MDSC subsets and suppressive functions in tissue-specific autoimmune disorders. We also describe the potential of MDSC-based cell therapy for the treatment of autoimmune diseases and note some of hurdles facing the implementation of this therapy.

Complement expression in retinal pigment epithelial cells is modulated by activated macrophages

Complement activation is involved in a variety of retinal diseases. We have shown previously that a number of complement components and regulators can be produced locally in the eye, and that retinal pigment epithelial (RPE) cells are the major source of complement expression at the retina-choroidal interface. The expression of complement components by RPE cells is regulated by inflammatory cytokines. Under aging or inflammatory conditions, microglia and macrophages accumulate in the subretinal space, where they are in close contact with RPE cells. In this study, we investigated the effect of activated macrophages on complement expression by RPE cells. Mouse RPE cells were treated with the supernatants from un-activated bone marrow-derived macrophages (BM-DMs), the classically activated BM-DMs (M1) and different types of the alternatively activated BM-DMs (M2a by IL-4, M2b by immune complex and lipopolysaccharide (LPS), M2c by IL-10). The expression of inflammatory cytokines and complement genes by RPE cells were determined by real-time RT-PCR. The protein expression of CFB, C3, C1INH, and C1r was examined by Western blot. Our results show that un-stimulated RPE cells express a variety of complement-related genes, and that the expression levels of complement regulators, including C1r, factor H (CFH), DAF1, CD59, C1INH, Crry, and C4BP genes are significantly higher than those of complement component genes (C2, C4, CFB, C3, and C5). Macrophage supernatants increased inflammatory cytokine (IL-1β, IL-6, iNOS), chemokine (CCL2) and complement expression in RPE cells. The supernatants from M0, M2a and M2c macrophages mildly up-regulated (2-3.5-fold) CFB, CFH and C3 gene expression in RPE cells, whereas the supernatants from M1 and M2b macrophages massively increased (10-30-fold) CFB and C3 gene expression in RPE cells. The expression of other genes, including C1r, C2, C4, CFH, Masp1, C1INH, and C4BP in RPE cells was also increased by the supernatants of M1 and M2b macrophages; however, the increment levels were significantly lower than CFB and C3 genes. M1 and M2b macrophage supernatants enhanced CFB (Bb fragment) protein expression and C3 secretion by RPE cells. M1 macrophages may affect complement expression in RPE cells through the STAT1 pathway. Our results suggest that under inflammatory conditions, activated macrophages could promote the alternative pathway of complement activation in the retina via induction of RPE cell CFB and C3 expression.

Role of the retinal vascular endothelial cell in ocular disease

Retinal endothelial cells line the arborizing microvasculature that supplies and drains the neural retina. The anatomical and physiological characteristics of these endothelial cells are consistent with nutritional requirements and protection of a tissue critical to vision. On the one hand, the endothelium must ensure the supply of oxygen and other nutrients to the metabolically active retina, and allow access to circulating cells that maintain the vasculature or survey the retina for the presence of potential pathogens. On the other hand, the endothelium contributes to the blood-retinal barrier that protects the retina by excluding circulating molecular toxins, microorganisms, and pro-inflammatory leukocytes. Features required to fulfill these functions may also predispose to disease processes, such as retinal vascular leakage and neovascularization, and trafficking of microbes and inflammatory cells. Thus, the retinal endothelial cell is a key participant in retinal ischemic vasculopathies that include diabetic retinopathy and retinopathy of prematurity, and retinal inflammation or infection, as occurs in posterior uveitis. Using gene expression and proteomic profiling, it has been possible to explore the molecular phenotype of the human retinal endothelial cell and contribute to understanding of the pathogenesis of these diseases. In addition to providing support for the involvement of well-characterized endothelial molecules, profiling has the power to identify new players in retinal pathologies. Findings may have implications for the design of new biological therapies. Additional progress in this field is anticipated as other technologies, including epigenetic profiling methods, whole transcriptome shotgun sequencing, and metabolomics, are used to study the human retinal endothelial cell.

[Effects of peroxynitrite derived from nitric oxide on cultured bovine ocular explants]

INTRODUCTION

Several studies have reported a significant production of nitric oxide (NO) with peroxynitrite formation in the setting of intraocular inflammation. In a previous study, we showed the cytotoxic effect of nitrites and nitrates, stable metabolites of NO, on the various tissues forming the layers of the eye, with variable degrees of tissue sensitivity. This study aims to investigate the effect of peroxynitrite on whole ocular bovine explants in culture.

METHODS

Healthy ocular bovine eyes, obtained immediately upon enucleation, were dissected and samples were taken from the anterior and posterior segments, and then cultured in DMEM supplemented with 10% fetal bovine serum, 2mM L-glutamine and antibiotics. Cultures were treated with 3-morpholino-sydonimin N-ethyl-carbamide (SIN-1) (molecule which produces NO and superoxide anion O(2)(.-)) at varying concentrations (100 to 500 μM) over 24 hours. After incubation, the explants were fixed in 10% buffered formalin, and histological study was performed.

RESULTS

Most of the structures showed changes on tissue and cellular levels after incubation with the peroxynitrite donor and various responses depending on the concentration used. These observations reflect variable concentration-dependent tissue sensitivity. The epithelia (cornea, iris and ciliary process) showed high sensitivity in comparison with sclera, which developed greater resistance.

CONCLUSION

In all, our results indicate a deleterious effect of peroxynitrite on bovine ocular structures in vitro. This effect is proportional to the concentration used. These results corroborate those reported by other teams and suggest the role of peroxynitrite derived from NO in the ocular lesions observed in the setting of uveitis.

Inflammation-associated nitrotyrosination affects TCR recognition through reduced stability and alteration of the molecular surface of the MHC complex

Nitrotyrosination of proteins, a hallmark of inflammation, may result in the production of MHC-restricted neoantigens that can be recognized by T cells and bypass the constraints of immunological self-tolerance. Here we biochemically and structurally assessed how nitrotyrosination of the lymphocytic choriomeningitis virus (LCMV)-associated immunodominant MHC class I-restricted epitopes gp33 and gp34 alters T cell recognition in the context of both H-2D^b and H-2K^b. Comparative analysis of the crystal structures of H-2K^b/gp34 and H-2K^b/NY-gp34 demonstrated that nitrotyrosination of p3Y in gp34 abrogates a hydrogen bond interaction formed with the H-2K^b residue E152. As a consequence the conformation of the TCR-interacting E152 was profoundly altered in H-2K^b/NY-gp34 when compared to H-2K^b/gp34, thereby modifying the surface of the nitrotyrosinated MHC complex. Furthermore, nitrotyrosination of gp34 resulted in structural over-packing, straining the overall conformation and considerably reducing the stability of the H-2K^b/NY-gp34 MHC complex when compared to H-2K^b/gp34. Our structural analysis also indicates that nitrotyrosination of the main TCR-interacting residue p4Y in gp33 abrogates recognition of H-2D^b/gp33-NY complexes by H-2D^b/gp33-specific T cells through sterical hindrance. In conclusion, this study provides the first structural and biochemical evidence for how MHC class I-restricted nitrotyrosinated neoantigens may enable viral escape and break immune tolerance.

Interplay between innate and adaptive immunity in the development of non-infectious uveitis

In vertebrates, the innate and adaptive immune systems have evolved seamlessly to protect the host by rapidly responding to danger signals, eliminating pathogens and creating immunological memory as well as immunological tolerance to self. The innate immune system harnesses receptors that recognize conserved pathogen patterns and alongside the more specific recognition systems and memory of adaptive immunity, their interplay is evidenced by respective roles during generation and regulation of immune responses. The hallmark of adaptive immunity which requires engagement of innate immunity is an ability to discriminate between self and non-self (and eventually between pathogen and symbiont) as well as peripheral control mechanisms maintaining immunological health and appropriate responses. Loss of control mechanisms and/or regulation of either the adaptive or the innate immune system lead to autoimmunity and autoinflammation respectively. Although autoimmune pathways have been largely studied to date in the context of development of non-infectious intraocular inflammation, the recruitment and activation of innate immunity is required for full expression of the varied phenotypes of non-infectious uveitis. Since autoimmunity and autoinflammation implicate different molecular pathways, even though some convergence occurs, increasing our understanding of their respective roles in the development of uveitis will highlight treatment targets and influence our understanding of immune mechanisms operative in other retinal diseases. Herein, we extrapolate from the basic mechanisms of activation and control of innate and adaptive immunity to how autoinflammatory and autoimmune pathways contribute to disease development in non-infectious uveitis patients.

Increased nitric oxide and vascular endothelial growth factor levels in the aqueous humor of patients with coats' disease

PURPOSE

To determine the aqueous humor levels of nitric oxide (NO) and vascular endothelial growth factor (VEGF) in the eyes of patients with Coats' disease and study the correlation between these levels.

METHODS

Samples of aqueous humor were obtained from 7 patients with Coats' disease and 15 age-matched patients with congenital cataracts as controls. Nitrite and nitrate (NOx), the stable end products of NO, were detected by the Griess reaction, and VEGF levels were assessed by enzyme-linked immunosorbent assay.

RESULTS

The aqueous humor NOx and VEGF levels were elevated in the eyes of patients with Coats' disease compared with those of controls (P=0.001 and P<0.001, respectively). The median NOx level was 55.2 μM (range, 23.0-75.3 μM) in the Coats' disease group and 18.8 μM (range, 8.7-36.2 μM) in the control group. The median VEGF level was 731.7 pg/mL (range, 288.3-1364.3 pg/mL) in the Coats' disease group and 33.3 pg/mL (range, 9.0-96.8 pg/mL) in the control group. No correlation was observed between the aqueous humor concentrations of NOx and VEGF.

CONCLUSIONS

NOx and VEGF are increased but not related in the aqueous humor samples of patients with Coats' disease. NO and VEGF may play roles in the pathogenesis of Coats' disease. Further studies are needed to clearly elucidate the relationship among VEGF, NO, and other cytokines in Coats' disease.

Protective effect of pristane on experimental autoimmune uveitis

This study evaluates the effects of pristane and phytol, two mineral oils with pro-oxidative effects, on the course of experimental autoimmune uveitis. C57BL6 mice were immunized with IRBP1-20 peptide emulsified in CFA and treated five days prior to immunization with phytol or with pristane or with PBS as control. Administration of pristane reduces the incidence and severity of IRBP-induced uveitis as demonstrated by the decrease in vasculitis and inflammatory foci in fundus and by a reduction in histological damages and leukocyte infiltration compared to untreated or phytol-treated mice. The protective effect observed is associated with a decreased activation of peripheral CD4+ and CD8+ T lymphocytes and a decrease in the intensity of the Th1 and Th17 autoimmune response to IRBP in pristane-treated mice compared to control mice, as evidenced by the decreased production of IFNγ and IL17 by IRBP-specific lymphocytes from lymph nodes draining the site of immunization and by the increased production of anti-IRBP IgG1 over IgG2a. In addition, HUVEC and ARPE-19 cells incubated with the sera of mice treated with pristane presented a reduced production of H(2)O(2). The benefit of lowering the systemic oxidative stress by pristane in the course of EAU was confirmed by injecting the antioxidant NAC in IRBP-immunized mice. As pristane, NAC decreased clinical and histological inflammation of the retina and preserved the integrity of the hemato-retinal barrier. Finally, the protective effect of pristane on the development of EAU suggests that some mineral oils may represent a new therapeutic strategy in human uveitis.

Nitric oxide potentiates TNF-α-induced neurotoxicity through suppression of NF-κB

Modulation of enzyme activity through nitrosylation has recently been identified as a new physiological activity of nitric oxide (NO). We hypothesized that NO enhances the TNF-α-induced death of retinal neurons through a suppression of nuclear factor-κB (NF-κB) by nitrosylation. In this study, cells from the RGC-5 line were exposed to different concentrations (2.0, 10, and 50 ng/ml) of TNF-α, and the degree of TNF-α-induced cell death was determined by the WST-8 assay and by flow cytometric measurements of the externalization of phosphatidylserine. The effects of etanercept, a soluble TNFR-Fc fusion protein, and S-nitroso-N-penicillamine (SNAP), an NO donor, on the toxicity were determined. Experiments were also performed to determine whether nitric oxide synthase (NOS) was associated with the toxicity of TNF-α. The activation of NF-κB was determined by the detection of the p65 subunit in the nuclear extracts. Our results showed that exposure of RGC-5 cells to different concentrations of TNF-α significantly decreased the number of living cells in a dose-dependent way. The death was partially due to apoptosis with an externalization of phosphatidylserine, and the death was suppressed by etanercept. Exposure to TNF-α increased the activation of NF-κB and the expression of iNOS. Although NF-κB inhibitors suppressed the increase of iNOS, they also potentiated the TNF-α-induced death. Both L-NAME and aminoguanidine, both NOS inhibitors, rescued the cells from death. In contrast, addition of SNAP caused nitrosylation of the inhibitory κB kinase, and suppressed the NF-κB activation and potentiated the TNF-α-induced neurotoxicity. These results indicate that NO potentiates the neurotoxicity of TNF-α by suppressing NF-κB.

Tolerogenic dendritic cells and myeloid-derived suppressor cells: potential for regulation and therapy of liver auto- and alloimmunity

Organ transplantation is now established as an accepted treatment for end-stage liver disease, acute fulminant hepatic liver failure and hepatocellular carcinoma. While early graft acceptance rates have increased markedly due to improved immunosuppressive drug regimens, rates of late graft failure remain largely unchanged. Recent findings suggest that in addition to alloimmunity, chronic rejection of liver allografts may also reflect de novo autoimmune hepatitis or recurrence of pre-existing hepatic autoimmune disease. Dendritic cell (DC)- based therapy is a promising experimental approach to promotion of transplant tolerance and the treatment of autoimmune diseases. Newly emerging evidence also demonstrates the potential efficacy of myeloid-derived suppressor cells (MDSC) in the antigen (Ag)-specific regulation of T-cell responses. Herein, we discuss current understanding of liver autoimmunity post-transplantation, along with current approaches for the development of tolerogenic DC, and the potential use of MDSC for the development of stable, Ag-specific tolerance.

The induction of reactive oxygen species and loss of mitochondrial Omi/HtrA2 is associated with S-nitrosoglutathione-induced apoptosis in human endothelial cells

The pathophysiological relevance of S-nitrosoglutathione (GSNO)-induced endothelial cell injury remains unclear. The main objective of this study was to elucidate the molecular mechanisms of GSNO-induced oxidative stress in endothelial cells. Morphological evaluation through DAPI staining and propidium iodide (PI) flow cytometry was used to detect apoptosis. In cultured EA.hy926 endothelial cells, exposure to GSNO led to a time- and dose-dependent apoptotic cascade. When intracellular reactive oxygen species (ROS) production was measured in GSNO-treated cells with the fluorescent probes 5-(and-6)-carboxy-2',7'-dichlorofluorescein diacetate, we observed elevated ROS levels and a concomitant loss in mitochondrial membrane potential, indicating that GSNO-induced death signaling is mediated through a ROS-mitochondrial pathway. Importantly, we found that peroxynitrite formation and Omi/HtrA2 release from mitochondria were involved in this phenomenon, whereas changes of death-receptor dependent signaling were not detected in the same context. The inhibition of NADPH oxidase activation and Omi/HtrA2 by a pharmacological approach provided significant protection against caspase-3 activation and GSNO-induced cell death, confirming that GSNO triggers the death cascade in endothelial cells in a mitochondria-dependent manner. Taken together, our results indicate that ROS overproduction and loss of mitochondrial Omi/HtrA2 play a pivotal role in reactive nitrogen species-induced cell death, and the modulation of these pathways can be of significant therapeutic benefit.

Pleiotropic effects of YC-1 selectively inhibit pathological retinal neovascularization and promote physiological revascularization in a mouse model of oxygen-induced retinopathy

Vascular endothelial growth factor (VEGF) and inducible nitric-oxide synthase (iNOS) have been implicated in ischemia-induced retinal neovascularization. Retinal ischemia has been shown to induce VEGF and iNOS expression. It has been postulated that one of the crucial consequences of iNOS expression in the ischemic retina is the inhibition of angiogenesis. Furthermore, iNOS was shown to be overexpressed in Müller cells from patients with diabetic retinopathy. YC-1, a small molecule inhibitor of hypoxia-inducible factor (HIF)-1 alpha, has been shown to inhibit iNOS expression in various tissue models. Our aim was to assess the pleiotropic effects of YC-1 in an oxygen-induced retinopathy (OIR) mouse model and evaluate its therapeutic potential in HIF-1- and iNOS-mediated retinal pathologies. Dual-injections of YC-1 into the neovascular retinas decreased the total retinopathy score, inhibited vaso-obliteration and pathologic tuft formation, and concomitantly promoted physiological retinal revascularization, compared with dimethyl sulfoxide (DMSO)-treated group. Furthermore, YC-1-treated retinas exhibited a marked increase in immunoreactivities for CD31 and von Willebrand factor and displayed significant inhibition in HIF-1alpha protein expression. Furthermore, YC-1 down-regulated VEGF, erythropoietin, endothelin-1, matrix metalloproteinase-9, and iNOS message and protein levels. When hypoxic Müller and neuoroglial cells were treated with YC-1, iNOS mRNA and protein levels were reduced in a dose-dependent fashion. We demonstrate that YC-1 inhibits pathological retinal neovascularization by exhibiting antineovascular activities, which impaired ischemia-induced expression of HIF-1 and its downstream angiogenic molecules. Furthermore, YC-1 enhanced physiological revascularization of the retinal vascular plexuses via the inhibition of iNOS mRNA and protein expressions. The pleiotropic effects of YC-1 allude to its possible use as a promising therapeutic iNOS inhibitor candidate for the treatment of retinal neovascularization.

Para-inflammation in the aging retina

Para-inflammation is a tissue adaptive response to noxious stress or malfunction and has characteristics that are intermediate between basal and inflammatory states (Medzhitov, 2008). The physiological purpose of para-inflammation is to restore tissue functionality and homeostasis. Para-inflammation may become chronic or turn into inflammation if tissue stress or malfunction persists for a sustained period. Chronic para-inflammation contributes to the initiation and progression of many human diseases including obesity, type 2 diabetes, atherosclerosis, and age-related neurodegenerative diseases. Evidence from our studies and the studies of some others suggests that para-inflammation also exists in the aging retina in physiological conditions and might contribute to age-related retinal pathologies. The purpose of this review is to introduce the notion of "para-inflammation" as a state between frank, overt destructive inflammation and the non-inflammatory removal of dead or dying cells by apoptosis, to the retinal community. In diabetes and atherosclerosis, leukocytes particularly monocytes and vascular endothelial cells are constantly under noxious stress due to glycaemic and/or lipidaemic dysregulation. These blood-borne stresses trigger para-inflammatory responses in leukocytes and endothelial cells by up-regulating the expression of adhesion molecules or releasing cytokines/chemokines, which in turn cause abnormal leukocyte-endothelial interactions and ultimately vascular damage. In the aging retina, on the other hand, oxidized lipoproteins and free radicals are considered to be major causes of tissue stress and serve as local triggers for retinal para-inflammation. Microarray analysis has revealed the up-regulation of a large number of inflammatory genes, including genes involved in complement activation and inflammatory cytokine/chemokine production, in the aging retina. Para-inflammatory responses in the neuroretina of aged mice are characterized by microglial activation and subretinal migration, and breakdown of blood-retinal barrier. At the retinal/choroidal interface para-inflammation is manifested by complement activation in Bruch's membrane and RPE cells, and microglia accumulation in subretinal space. With age, para-inflammatory changes have also been observed in the choroidal tissue, evidenced by 1) increased thickness of choroid; 2) increased number of CD45(+)CRIg(+) macrophages; 3) morphological abnormalities in choroidal melanocytes; and 4) fibrosis in choroidal tissue. An increased knowledge of contribution of retinal para-inflammation to various pathological conditions is essential for the better understanding of the pathogenesis of various age-related retinal diseases including diabetic retinopathy, glaucoma and age-related macular degeneration.

Protective effect of intravitreal injection of vasoactive intestinal peptide-loaded liposomes on experimental autoimmune uveoretinitis

PURPOSE

The aim of this study was to investigate the effect of a single intravitreal (i.v.t.) injection of vasoactive intestinal peptide (VIP) loaded in rhodamine-conjugated liposomes (VIP-Rh-Lip) on experimental autoimmune uveoretinitis (EAU).

METHODS

An i.v.t. injection of VIP-Rh-Lip, saline, VIP, or empty-(E)-Rh-Lip was performed simultaneously, either 6 or 12 days after footpad immunization with retinal S-antigen in Lewis rats. Clinical and histologic scores were determined. Immunohistochemistry and cytokine quantification by multiplex enzyme-linked immunosorbent assay were performed in ocular tissues. Systemic immune response was determined at day 20 postimmunization by measuring proliferation and cytokine secretion of cells from inguinal lymph nodes (ILNs) draining the immunization site, specific delayed-type hypersensitivity (DTH), and the serum concentration of cytokines. Ocular and systemic biodistribution of VIP-Rh-Lip was studied in normal and EAU rats by immunofluorescence.

RESULTS

The i.v.t. injection of VIP-Rh-Lip performed during the afferent, but not the efferent, phase of the disease reduced clinical EAU and protected against retinal damage. No effect was observed after saline, E-Rh-Lip, or VIP injection. VIP-Rh-Lip and VIP were detected in intraocular macrophages and in lymphoid organs. In VIP-Rh-Lip-treated eyes, macrophages expressed transforming growth factor-beta2, low levels of major histocompatibility complex class II, and nitric oxide synthase-2. T-cells showed activated caspase-3 with the preservation of photoreceptors. Intraocular levels of interleukin (IL)-2, interferon-gamma (IFN-gamma), IL-17, IL-4, GRO/KC, and CCL5 were reduced with increased IL-13. At the systemic level, treatment reduced retinal soluble autoantigen lymphocyte proliferation, decreased IL-2, and increased IL-10 in ILN cells, and diminished specific DTH and serum concentration of IL-12 and IFN-gamma.

CONCLUSIONS

An i.v.t. injection of VIP-Rh-Lip, performed during the afferent stage of immune response, reduced EAU pathology through the immunomodulation of intraocular macrophages and deviant stimulation of T-cells in ILN. Thus, the encapsulation of VIP within liposomes appears as an effective strategy to deliver VIP into the eye and is an efficient means of the prevention of EAU severity.

Uveitic foveal atrophy: clinical features and associations

OBJECTIVE

To characterize foveal atrophy in a heterogeneous group of patients with uveitis using clinical findings and high-definition (HD) optical coherence tomography (OCT).

DESIGN

Cross-sectional, retrospective case series.

RESULTS

The HD-OCT scans of 140 patients seen in a tertiary referral center were reviewed and 23 patients (33 eyes) with foveal atrophy were identified. All of the patients with foveal atrophy were diagnosed with intermediate uveitis, posterior uveitis, or panuveitis. The status of the photoreceptor layer as visualized with HD-OCT was associated with significant differences in mean visual acuity (P < .001). Clinical findings associated with foveal atrophy included atrophy of the retinal pigment epithelium and choroid (30 eyes [91%]), macular ischemia (13 eyes [39%]), cystoid macular edema (5 eyes [15%]), choroidal neovascularization (4 eyes [12%]), retinal detachment involving the macula (2 eyes [6%]), and serum antiretinal antibodies (2 eyes [6%]).

CONCLUSIONS

Foveal atrophy can be a complication of intraocular inflammation in a variety of uveitic syndromes. The cause of foveal atrophy is multifactorial and may include dysfunction and atrophy of the retinal pigment epithelium and choroid, cystoid macular edema, macular ischemia secondary to occlusive retinal vasculitis, choroidal neovascularization, retinal detachment, and possibly antibody-mediated damage directed against photoreceptors. Careful observation of the photoreceptor layer using HD-OCT may help to identify patients who are at risk for visual loss secondary to foveal atrophy.

Analysis of retinal cellular infiltrate in experimental autoimmune uveoretinitis reveals multiple regulatory cell populations

Experimental autoimmune uveoretinitis (EAU) is an animal model for human intraocular inflammatory disease. EAU is induced in B10.RIII mice by immunization with RBP-3 161-180 peptide and intraperitoneal pertussis toxin and is mediated by CD4(+) T cells that generate a clinically monophasic disease peaking approximately 2 weeks post-immunization. Collagenase digestion of retinal tissue allowed the quantification and characterization of leukocytes in the inflamed retina during disease progression. Using this method we identified three stages of disease. Initially there is a prodromal phase where we found significant changes in the number of leukocytes in the eye as early as 5 days post-immunization. This effect was, in part, non-antigen specific as a small increase in retinal leukocytes was also observed following immunization with OVA peptide. Following the prodrome there is a primary peak of infiltration including both CD4(+) T cells and CD11b(+) cells. This coincides with an early influx of neutrophils and is associated with a peak in IL-17-producing T cells. The neutrophils in the eye are CD11b(+) and Gr1(+) but can be distinguished from other myeloid cells by their high expression of Ly6G. The remaining CD11b(+)Gr1(+) cells can suppress proliferation and are analogous to myeloid derived suppressor cells which are found in tumors. The inflamed eye also contains a considerable proportion of FoxP3(+) regulatory cells. Following peak disease, the retina does not return to its pre-disease phenotype. Instead, fluctuations in infiltrating leukocyte numbers and changes to their relative composition continue, indicating that clinical recovery does not equate to the restoration of a normal retinal leukocyte population.

Blockade of neuronal nitric oxide synthase reduces cone cell death in a model of retinitis pigmentosa

Retinitis pigmentosa (RP) is a group of diseases in which many different mutations cause rod photoreceptor cells to die and then gradually cone photoreceptors die due to progressive oxidative damage. In this study, we have shown that peroxynitrite-induced nitrosative damage also occurs. In the rd1 mouse model of RP, there was increased staining for S-nitrosocysteine and nitrotyrosine protein adducts that are generated by peroxynitrite. Peroxynitrite is generated from nitric oxide (NO) and superoxide radicals. After degeneration of rods, injection of hydroethidine resulted in strong fluorescence in the retina of rd1 mice, indicating high levels of superoxide radicals, and this was reduced, as was nitrotyrosine staining, by apocynin, suggesting that overaction of NADP(H) oxidase is at least partially responsible. Treatment of rd1 mice with a mixture of nitric oxide synthase (NOS) inhibitors markedly reduced S-nitrosocysteine and nitrotyrosine staining and significantly increased cone survival, indicating that NO-derived peroxynitrite contributes to cone cell death. Treatment with 7-nitroindazole, a relatively specific inhibitor of neuronal NOS, also significantly reduced cone cell death, but aminoguanidine, a relatively specific inhibitor of inducible NOS, did not. These data suggest that NO generated by neuronal NOS exacerbates oxidative damage to cones in RP and that combined therapy to reduce NO and oxidative stress should be considered.

Tumour necrosis factor-alpha released by testicular macrophages induces apoptosis of germ cells in autoimmune orchitis

BACKGROUND

Experimental autoimmune orchitis (EAO) is a model of chronic inflammation and infertility useful for studying testicular immune and germ cell (GC) interactions. In this model, EAO was induced in rats by immunization with testicular homogenate and adjuvants; Control (C) rats were injected with adjuvants. EAO was characterized by an interstitial infiltrate of lymphomonocytes and seminiferous tubule damage, moderate 50 days (focal orchitis) and severe 80 days after the first immunization (severe orchitis). Based on the previous results showing that the number of macrophages and apoptotic GC expressing tumour necrosis factor (TNF) receptor 1 increased in EAO, we studied the role of macrophages and TNF-alpha in GC apoptosis.

METHODS AND RESULTS

Conditioned media of testicular macrophages (CMTM) obtained from rats killed on Days 50 and 80 decreased the viability (MTS, P < 0.01) and induced apoptosis (terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labelling, TUNEL) of GC obtained from EAO but not from non-immunized, N rats (P < 0.001). TNF-alpha content (enzyme-linked immunosorbent assay) was significantly higher in the CMTM from EAO versus C rats on Day 80 (P < 0.05). The apoptotic effect of CMTM from Day 80 rats was abrogated by a selective TNF-alpha blocker (Etanercept). Moreover, TNF-alpha in vitro induced GC apoptosis. TNF-alpha expression (by immunofluorescence) was observed in testicular (ED2(+)) and non-resident (ED1(+)) macrophages, the percentage of TNF-alpha(+) macrophages being similar in focal and severe orchitis.

CONCLUSIONS

Results demonstrated that soluble factors released from testicular EAO macrophages induce apoptosis of GC, biased by the local inflammatory environment, and that TNF-alpha is a relevant cytokine involved in testicular damage during severe orchitis.

Conversion of tyrosine to the inflammation-associated analog 3'-nitrotyrosine at either TCR- or MHC-contact positions can profoundly affect recognition of the MHC class I-restricted epitope of lymphocytic choriomeningitis virus glycoprotein 33 by CD8 T cells

Immunohistochemical detection of increased levels of protein-associated nitrotyrosine has become widely used as a surrogate marker of in situ inflammation. However, the potential consequences of protein-associated nitrotyrosine formation in terms of cellular immune recognition has received surprisingly little attention. Using a well-defined I-E(K)-restricted epitope of pigeon cytochrome c, we previously demonstrated that conversion of a single tyrosine residue to nitrotyrosine can have a profound effect on recognition by CD4 T cells. In this study, we used the MHC class I-restricted epitope of lymphocytic choriomeningitis virus glycoprotein (gp33) to demonstrate that conversion of tyrosine to nitrotyrosine can also profoundly affect recognition of MHC class I-restricted epitopes. Conversion of the Y4 residue of the gp33 epitope to nitrotyrosine completely abrogated recognition by gp33-specific T cells from P14 TCR-transgenic mice. In contrast, CD8(+) T cells specific for "nitrated gp33" (NY-gp33) can be readily elicited in C57BL/6 mice after immunization with NY-gp33 peptide. Interestingly, T-T hybridomas specific for NY-gp33 peptide were found to fall into two distinct subsets, being specific for NY-gp33 presented in the context of either H-2D(b) or H-2K(b). This latter result is surprising in light of previous structural studies showing that Y4 comprises a critical TCR-contact residue when presented by H-2D(b) but that the same residue points downward into the peptide-binding groove of the MHC when presented by H-2K(b). Together, these results indicate that nitrotyrosine formation can impact T cell recognition both directly, through alteration of TCR-contact residues, or indirectly, through alterations in MHC-contact positions.

Lack of inducible nitric oxide synthases attenuates leukocyte-endothelial cell interactions in retinal microcirculation

Aim:

To investigate the effect of inducible nitric oxide synthases (iNOS) on inflammatory reactions during endotoxin-induced uveitis (EIU) in mice by studying leukocyte–endothelial cell interactions.

Methods:

EIU was produced in immunosuppressed iNOS^−/− mice and C57BL/6 (normal) mice by footpad injection of lipopolysaccharide. Leukocytes were labelled with acridine orange. Leukocyte rolling in the retinal microcirculation was evaluated in vivo with acridine orange digital fluorography. The number of migrated leukocytes was counted in flat-mounted retina.

Results:

Both leukocyte rolling and migration peaked at 48 h after lipopolysaccharide injection. The maximal numbers of rolling leukocytes in the immunosuppressed iNOS^−/− mouse retina decreased by 98.2% (p<0.001) compared with that in the normal mouse retina at 48 h after lipopolysaccharide injection. In addition, the maximal numbers of migrated leukocytes in the immunosuppressed iNOS^−/− mouse retina decreased by 74.0% (p<0.001) compared with that in the normal mouse retina at 24 h after lipopolysaccharide injection. Furthermore, the diameters of major retinal veins of the immunosuppressed iNOS^−/− group were smaller at both 24 and 48 h after lipopolysaccharide injection than were those of the normal group (p<0.001, respectively).

Conclusions:

A lack of iNOS suppresses leukocyte–endothelial cell interactions in the retinas of mice with EIU. This suggests that iNOS may play a role in the management of patients with uveitis and other inflammatory conditions.

[Neoretinal antigen expression: a comparison of anatomical and clinical features of a murine uveoretinitis model]

PURPOSE

Uveitis is an inflammation involving the retina. The antigens targeted by the experimental models are located in the pigmentary epithelium-photoreceptor complex. To gain insights into the variations in topographic expression of the antigen in the retina, we studied a new mouse model.

MATERIAL

and methods: Stable retinal expression of the influenza virus hemagglutinin (HA) was obtained after intravitreal or subretinal injection of recombinant adeno-associated virus carrying HA (AAV-HA). One month later, we transferred HA-specific T cells, followed by a subcutaneous immunization of the cognate antigen emulsified in CFA. The animals were clinically examined with a slit lamp biomicroscope. Infiltration of donor cells was detected by immunostaining on retina flatmounts with anti-Thy-1.1 antibody, and infiltrating cells were studied using FACS analysis.

RESULTS

Whatever the location of the HA expression, intraocular inflammation was clinically and histologically detected in all animals, between 10 and 15 days after immunization with HA. Lesions were identified with histopathological analysis. The ocular infiltrate was mostly composed of macrophages and HA-specific T cells in different proportions.

CONCLUSIONS

The topographic variations of targeted ocular antigens do not seem to modify the development of inflammatory reactions in our model. By targeting different antigen-presenting cells, ocular infiltrating cells are different.

Protein kinase Czeta (PKCzeta) regulates ocular inflammation and apoptosis in endotoxin-induced uveitis (EIU): signaling molecules involved in EIU resolution by PKCzeta inhibitor and interleukin-13

We show that inhibitory effect of interleukin-13 on endotoxin-induced uveitis in the Lewis rat is dependent on signaling activity of protein kinase Czeta (PKCzeta). To understand the effect of interleukin-13 or PKCzeta inhibitor treatment, the activation status of rat bone marrow-derived macrophages was studied in vitro. At 6 hours, lipopolysaccharide-stimulated macrophages produced tumor necrosis factor-alpha (TNF-alpha) with nuclear factor kappaB (NF-kappaB)/p65 expression. Treatment led to absence of NF-kappaB/p65 expression and low levels of TNF-alpha, suggesting accelerated inactivation of macrophages. At 24 hours after lipopolysaccharide stimulation, nuclear NF-kappaB/p65 decreased and nuclear NF-kappaB/p50 increased, associated with nuclear BCL-3 and a low level of TNF-alpha, indicating onset of spontaneous resolution. Treatment limited PKCzeta cleavage, with expression of nuclear NF-kappaB/p50 and BCL-3 and low nuclear NF-kappaB/p65 promoting macrophage survival, as evidenced by Bcl-2 expression. At 24 hours, intraocular treatment decreased membranous expression of PKCzeta by ocular cells, reduced vascular leakage with low nitric-oxide synthase-2 expression in vascular endothelial cells, and limited inflammatory cell infiltration with decreased intraocular TNF-alpha, interleukin-6, and nitric-oxide synthase-2 mRNA. Importantly, treatment decreased nuclear NF-kappaB/p65, increased transforming growth factor-beta2, and reduced caspase 3 expression in infiltrating macrophages, implying a change of their phenotype within ocular microenvironment. Treatment accelerated endotoxin-induced uveitis resolution through premature apoptosis of neutrophils related to high expression of toll-like receptor 4 and caspase 3.

Photoreceptor mitochondrial oxidative stress in early experimental autoimmune uveoretinitis

AIMS

In early S-antigen induced experimental uveitis (EAU), photoreceptor mitochondrial proteins are nitrated prior to macrophage infiltration of the retina, suggesting that oxidative stress is an initial event in the development of EAU. We attempted to detect the oxidative stress and localise it in the EAU retina.

METHODS

Lewis rats were immunised with S-antigen in complete Freund's adjuvant (CFA). Animals were injected with CFA alone and non-immunised animals served as controls. Immunised and non-immunised animals were killed on day 5 and subsequent days. Isolated retinas were processed for inducible nitric oxide synthase (iNOS), tumour necrosis factor (TNF)alpha, interferon (IFN)gamma, interleukin (IL)Ialpha and CD28 expression by real time polymerase chain reaction. In addition, iNOS was colocalised with cytochrome c oxidase on day 5 of EAU. Oxidative stress was detected by 2', 7'-dichlorodihydrofluorescein diacetate and localised by a mitochondrial specific marker. Leucocyte and T cell infiltration in the retina/choroid was evaluated by immunohistochemistry.

RESULTS

The iNOS, TNFalpha, IFNgamma, IL1alpha and CD28 transcripts were significantly upregulated on day 5 in EAU, and iNOS was colocalised with cytochrome c oxidase in the photoreceptor mitochondria. Oxidative stress was seen primarily in the photoreceptor mitochondria. Occasional T cells were present in the retina at this stage.

CONCLUSIONS

During early EAU, mitochondrial oxidative stress is selectively noted in the photoreceptor inner segments. The oxidative stress appears to result from iNOS upregulation in the photoreceptor mitochondria and cytokine generation in the retina by a few antigen specific infiltrating T cells.

Accumulation of immunosuppressive CD11b+ myeloid cells correlates with the failure to prevent tumor growth in the anterior chamber of the eye

The purpose of these studies is to determine why an immunogenic tumor grows unchecked in the anterior chamber (a.c.) of the eye. The OVA-expressing EL4 tumor, E.G7-OVA, was injected into the a.c. or skin of immunocompetent and immunodeficient mice. Tumor growth and tumor-specific immune responses were monitored. Ocular tumor-infiltrating leukocytes were characterized phenotypically and functionally. Growth of E.G7-OVA was inhibited when limiting numbers of cells were injected in the skin but not in the a.c. of C57BL/6 mice, although both routes primed OVA-specific immune responses, which prevented the growth of a subsequent injection with E.G7-OVA in the skin or opposite eye. Tumor regression was OVA-specific because growth of the parental EL-4 tumor was not inhibited in primed mice. E.G7-OVA growth in the skin was not inhibited in immunodeficient Rag(-/-) or CD8 T cell-deficient mice, suggesting that CD8(+) CTLs mediate tumor elimination. CD8(+) T cell numbers were significantly increased in eyes of mice primed with E.G7-OVA, but few were detected in primary ocular tumors. Nevertheless, growth of E.G7-OVA was retarded in the a.c. of TCR-transgenic OT-I mice, and CD8(+) T cell numbers were increased within eyes, suggesting that tumor-specific CD8(+) CTLs migrated into and controlled primary ocular tumor growth. E.G7-OVA did not lose antigenicity or become immunosuppressive after 13 days of growth in the eye. However, CD11b(+) cells accumulated in primary ocular tumors and contained potent immunosuppressive activity when assayed in vitro. Thus, CD11b(+) cells that accumulate within the eye as tumors develop in the a.c. may contribute to immune evasion by primary ocular tumors by inhibiting CTLs within the eye.

Regulatory T cells control uveoretinitis induced by pathogenic Th1 cells reacting to a specific retinal neoantigen

In many clinical cases, uveitis develops secondary to an infection. This could result from peripheral activation followed by ocular penetration and reactivation of T cells specific for microbial Ags expressed in the retina. To gain insights into the pathophysiology of uveitis, we developed a new mouse model based on stable retinal expression of influenza virus hemagglutinin (HA) neoantigen by adeno-associated virus-mediated gene transfer. One month thereafter, we adoptively transferred HA-specific T cells, which were activated in vitro or in vivo. Intraocular inflammation was clinically and histologically observed in all animals within 15 days. The ocular infiltrate was composed mostly of macrophages and HA-specific T cells with a proinflammatory cytokine profile. Depletion of CD4(+)CD25(+) regulatory T cells exacerbated the disease, whereas HA-specific CD4(+)CD25(+) T cells given i.v. controlled the disease. This novel model should allow to better study the pathophysiology and therapeutic of uveitis.