Expression of interferon-gamma in the lens exacerbates anterior uveitis and induces retinal degenerative changes in transgenic Lewis rats

Advances in Genome Editing and Application to the Generation of Genetically Modified Rat Models

The rat has been extensively used as a small animal model. Many genetically engineered rat models have emerged in the last two decades, and the advent of gene-specific nucleases has accelerated their generation in recent years. This review covers the techniques and advances used to generate genetically engineered rat lines and their application to the development of rat models more broadly, such as conditional knockouts and reporter gene strains. In addition, genome-editing techniques that remain to be explored in the rat are discussed. The review also focuses more particularly on two areas in which extensive work has been done: human genetic diseases and immune system analysis. Models are thoroughly described in these two areas and highlight the competitive advantages of rat models over available corresponding mouse versions. The objective of this review is to provide a comprehensive description of the advantages and potential of rat models for addressing specific scientific questions and to characterize the best genome-engineering tools for developing new projects.

Autoimmunity to neuroretina in the concurrent absence of IFN-γ and IL-17A is mediated by a GM-CSF-driven eosinophilic inflammation

IFN-γ and IL-17A can each elicit ocular autoimmunity independently of the other. Since absence of IFN-γ or IL-17A individually failed to abolish pathology of experimental autoimmune uveitis (EAU), we examined EAU development in the absence of both these cytokines. Ifng-/-Il17a-/- mice were fully susceptible to EAU with a characteristic eosinophilic ocular infiltrate, as opposed to a mononuclear infiltrate in WT mice. Retinal pathology in double-deficient mice was ameliorated when eosinophils were genetically absent or their migration was blocked, supporting a pathogenic role for eosinophils in EAU in the concurrent absence of IFN-γ and IL-17A. In EAU-challenged Ifng-/-Il17a-/- mice, ocular infiltrates contained increased GM-CSF-producing CD4+ T cells, and supernatants of retinal antigen-stimulated splenocytes contained enhanced levels of GM-CSF that contributed to activation and migration of eosinophils in vitro. Systemic or local blockade of GM-CSF ameliorated EAU in Ifng-/-Il17a-/- mice, reduced eosinophil peroxidase levels in the eye and in the serum and decreased eosinophil infiltration to the eye. These results support the interpretation that, in the concurrent absence of IFN-γ and IL-17A, GM-CSF takes on a major role as an inflammatory effector cytokine and drives an eosinophil-dominant pathology. Our findings may impact therapeutic strategies aiming to target IFN-γ and IL-17A in autoimmune uveitis.

Optical Coherence Tomography Angiography for Evaluation of Retinal Vascular Changes in Patients with Psoriasis according to Disease Severity

OBJECTIVES

To investigate foveal avascular zone (FAZ) area and retinal vascular density (VD) in patients with psoriasis according to disease severity using optical coherence tomography angiography (OCTA).

METHODS

Twenty-seven patients with mild psoriasis (Group 1), 28 with moderate to severe psoriasis (Group 2) and 30 healthy controls (Group 3) were evaluated with OCTA. Foveal and parafoveal VD and FAZ area were measured and compared.

RESULTS

FAZ values were significantly higher in Group 2 (0.20 ± 0.1, 0.31 ± 0.07, 0.20 ± 0.09; P < .001, respectively.). The mean VD value were significantly lower in the deep capillary plexus in parafoveal area in Group 2 (35.5 ± 8.7, 28.7 ± 4.6, 35.0 ± 3.5; P < .001, respectively.). These changes showed significant correlation with Psoriasis Area and Severity Index (PASI) scores of patients.

CONCLUSIONS

Our results suggest that OCTA may have a future role as alert of potentially more severe disease in cases clinically classified as mild disease.

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.

Suppressor of cytokine signaling 1 (SOCS1) mitigates anterior uveitis and confers protection against ocular HSV-1 infection

Immunological responses to pathogens are stringently regulated in the eye to prevent excessive inflammation that damage ocular tissues and compromise vision. Suppressors of cytokine signaling (SOCS) regulate intensity/duration of inflammatory responses. We have used SOCS1-deficient mice and retina-specific SOCS1 transgenic rats to investigate roles of SOCS1 in ocular herpes simplex virus (HSV-1) infection and non-infectious uveitis. We also genetically engineered cell-penetrating SOCS proteins (membrane-translocating sequence (MTS)-SOCS1, MTS-SOCS3) and examined whether they can be used to inhibit inflammatory cytokines. Overexpression of SOCS1 in transgenic rat eyes attenuated ocular HSV-1 infection while SOCS1-deficient mice developed severe non-infectious anterior uveitis, suggesting that SOCS1 may contribute to mechanism of ocular immune privilege by regulating trafficking of inflammatory cells into ocular tissues. Furthermore, MTS-SOCS1 inhibited IFN-γ-induced signal transducers and activators of transcription 1 (STAT1) activation by macrophages while MTS-SOCS3 suppressed expansion of pathogenic Th17 cells that mediate uveitis, indicating that MTS-SOCS proteins maybe used to treat ocular inflammatory diseases of infectious or autoimmune etiology.

Relationship between retinal sensitivity and disease activity in patients with psoriasis vulgaris

OBJECTIVES

Psoriasis is a hyperproliferative chronic inflammatory skin disease of unknown etiology and ocular structures and visual pathways can also be affected during the course of this disease. Subclinical optic neuritis has previously been observed in psoriatic patients in visual evoked potential studies. This trial was designed to evaluate retinal sensitivity in patients with psoriasis vulgaris.

METHODS

A total of 40 eyes of 40 patients with chronic plaque-type psoriasis and 40 eyes of 40 age- and sex-matched control subjects were included in this study. The diagnosis of psoriasis was confirmed by skin biopsy. The severity was determined using the Psoriasis Area and Severity Index and the duration of the disease was recorded. After a full ophthalmological examination, including tests for color vision and pupil reactions, the visual field of each subject was assessed using both standard achromatic perimetry and short wavelength automated perimetry.

RESULTS

The mean Psoriasis Area and Severity Index was 22.05±6.40'. There were no significant differences in the visual field parameters of subjects versus controls using either method. There were correlations between disease severity and the mean deviations in standard achromatic perimetry and short wavelength automated perimetry and between disease severity and the corrected pattern standard deviation and pattern standard deviation of short wavelength automated perimetry (r = -0.363, r = -0.399, r = 0.515 and r = 0.369, respectively).

CONCLUSIONS

Retinal sensitivity appears to be affected by the severity of psoriasis vulgaris.

Interferon-gamma (IFN-γ)-mediated retinal ganglion cell death in human tyrosinase T cell receptor transgenic mouse

We have recently demonstrated the characterization of human tyrosinase TCR bearing h3T-A2 transgenic mouse model, which exhibits spontaneous autoimmune vitiligo and retinal dysfunction. The purpose of current study was to determine the role of T cells and IFN-γ in retina dysfunction and retinal ganglion cell (RGC) death using this model. RGC function was measured by pattern electroretinograms (ERGs) in response to contrast reversal of patterned visual stimuli. RGCs were visualized by fluorogold retrograde-labeling. Expression of CD3, IFN-γ, GFAP, and caspases was measured by immunohistochemistry and Western blotting. All functional and structural changes were measured in 12-month-old h3T-A2 mice and compared with age-matched HLA-A2 wild-type mice. Both pattern-ERGs (42%, p = 0.03) and RGC numbers (37%, p = 0.0001) were reduced in h3T-A2 mice when compared with wild-type mice. The level of CD3 expression was increased in h3T-A2 mice (h3T-A2: 174 ± 27% vs. HLA-A2: 100%; p = 0.04). The levels of effector cytokine IFN-γ were also increased significantly in h3T-A2 mice (h3T-A2: 189 ± 11% vs. HLA-A2: 100%; p = 0.023). Both CD3 and IFN-γ immunostaining were increased in nerve fiber (NF) and RGC layers of h3T-A2 mice. In addition, we have seen a robust increase in GFAP staining in h3T-A2 mice (mainly localized to NF layer), which was substantially reduced in IFN-γ ((-/-)) knockout h3T-A2 mice. We also have seen an up-regulation of caspase-3 and -9 in h3T-A2 mice. Based on our data we conclude that h3T-A2 transgenic mice exhibit visual defects that are mostly associated with the inner retinal layers and RGC function. This novel h3T-A2 transgenic mouse model provides opportunity to understand RGC pathology and test neuroprotective strategies to rescue RGCs.

Chronic intraocular inflammation and development of retinal degenerative disease

Elevated levels of inflammatory cytokines in the vitreous of patients with chronic intraocular inflammatory (uveitis) have long been suspected to contribute to the pathogenesis of retinal degenerative diseases. However, direct connection between chronic inflammation and development of retinal degenerative diseases has been difficult to establish because we lack an appropriate animal model of co-existing chronic intraocular inflammation and neurodegeneration. This report discusses new developments in immunological and diabetic research that suggest that persistent secretion of pro-inflammatory cytokines during uveitis might induce insulin resistance and retinal degenerative changes that contribute to the pathogenesis of Diabetic Retinopathy (DR), a retinal dystrophy of significant public health importance.

Suppressor of cytokine signaling-1 (SOCS1) inhibits lymphocyte recruitment into the retina and protects SOCS1 transgenic rats and mice from ocular inflammation

PURPOSE

Suppressors of cytokine signaling (SOCS) proteins regulate the intensity and duration of cytokine signals and defective expression of SOCS1 and SOCS3 has been reported in a number of human diseases. The purpose of this study was to investigate the role of SOCS1 in intraocular inflammatory diseases (uveitis) and whether SOCS1 expression is defective in patients with ocular inflammatory diseases.

METHODS

Blood from patients with scleritis or healthy human volunteers was analyzed for SOCS expression by RNase protection assay and RT-PCR. The authors generated SOCS1 transgenic rats and mice (SOCS1-Tg), induced experimental autoimmune uveoretinitis (EAU) by active immunization with interphotoreceptor retinal binding protein or adoptive transfer of uveitogenic T cells, and investigated effects of SOCS1 overexpression on EAU. SOCS1-mediated protection of retinal cells from apoptosis was assessed by annexin V staining.

RESULTS

Induction of cytokine-induced SH2 protein was comparable between patients and volunteers, whereas 80% of lymphocytes from patients with scleritis failed to induce SOCS1 in response to IL-2. Compared with wild-type littermates, SOCS1-Tg rats/mice developed less severe EAU. Constitutive overexpression of SOCS1 in retina inhibited expression of chemokines (CCL17, CCL20, CXCL9, CXCL10), reduced Th17/Th1 expansion, and inhibited recruitment of inflammatory cells into the retina. The authors also show that SOCS1 protected retinal cells from staurosporine as well as H₂O₂-induced apoptosis.

CONCLUSIONS

Defective expression of SOCS1 in patients with scleritis, taken together with SOCS1-mediated protection of neuroretinal cells from apoptosis, suggest that SOCS1 has neuroprotective function in the retina, implying that administration of SOCS1 mimetic peptides may be useful in treating uveitis or scleritis.

Anticytokine therapy, particularly anti-IFN-gamma, in Th1-mediated autoimmune diseases

Anticytokine therapy was proposed in 1974 in Nature, in which it was stated that hyperproduced interferon can cause autoimmune disease and anti-interferon can be therapeutic. In 1989, the use of antibodies to tumor necrosis factor-alpha in combination with antibodies to certain types of interferon was proposed to treat various autoimmune diseases, including AIDS. The first anticytokine therapy was conducted in 1975. Anti-interferon-gamma has brought improved and often striking results in the treatment of various T-helper 1-mediated autoimmune diseases, including inflammatory skin diseases. Anti-interferon-gamma may be a universal treatment for these conditions. In AIDS and other virus-induced autoimmune diseases, the virus may stimulate cytokines (interferons), which increase, rather than halt, viral replication. Tumor necrosis factor-alpha inhibitors have also shown good clinical results, however, they may result in complications and are ineffective in some autoimmune diseases.

STAT3 in CD4+ T helper cell differentiation and inflammatory diseases

Jak/STAT pathways influence cell-fate decisions made by differentiating naïve T cells, regulate the intensity and duration of inflammatory responses and are implicated in pathogenic mechanisms of a number of chronic inflammatory diseases. Among the STATs, the STAT3 protein has emerged as an important determinant of whether the naïve T cell differentiates into regulatory (Treg) or an inflammatory (Th17) T cell lineage. STAT3 also has potent anti-inflammatory effects and regulates critical cellular processes such as, cell growth, apoptosis and transcription of inflammatory genes. Dysregulation of STAT3 pathway has therefore been implicated in the development of chronic inflammatory diseases, as well as, a number of malignant and neurodegenerative diseases. This review focuses on recent findings regarding the role of STAT3 in immunity, with particular emphasis on T cell lineage specification and disease etiology. New insights from animal models of uveitis, multiple sclerosis and inflammatory bowel diseases are discussed as exemplars of critical roles that STAT3 pathways play in inflammatory diseases and on how inhibiting STAT3 can be exploited to mitigate pathogenic autoimmunity.

Suppressors of cytokine-signaling proteins induce insulin resistance in the retina and promote survival of retinal cells

OBJECTIVE

Suppressors of cytokine signaling (SOCS) are implicated in the etiology of diabetes, obesity, and metabolic syndrome. Here, we show that some SOCS members are induced, while others are constitutively expressed, in retina and examine whether persistent elevation of SOCS levels in retina by chronic inflammation or cellular stress predisposes to developing insulin resistance in retina, a condition implicated in diabetic retinopathy.

RESEARCH DESIGN AND METHODS

SOCS-mediated insulin resistance and neuroprotection in retina were investigated in 1) an experimental uveitis model, 2) SOCS1 transgenic rats, 3) insulin-deficient diabetic rats, 4) retinal cells depleted of SOCS6 or overexpressing SOCS1/SOCS3, and 5) oxidative stress and light-induced retinal degeneration models.

RESULTS

We show that constitutive expression of SOCS6 protein in retinal neurons may improve glucose metabolism, while elevated SOCS1/SOCS3 expression during uveitis induces insulin resistance in neuroretina. SOCS-mediated insulin resistance, as indicated by its inhibition of basally active phosphoinositide 3-kinase/AKT signaling in retina, is validated in retina-specific SOCS1 transgenic rats and retinal cells overexpressing SOCS1/SOCS3. We further show that the SOCS3 level is elevated in retina by oxidative stress, metabolic stress of insulin-deficient diabetes, or light-induced retinal damage and protects ganglion cells from apoptosis, suggesting that upregulation of SOCS3 may be a common physiologic response of neuroretinal cells to cellular stress.

CONCLUSIONS

Our data suggest two-sided roles of SOCS proteins in retina. Whereas SOCS proteins may improve glucose metabolism, mitigate deleterious effects of inflammation, and promote neuroprotection, persistent SOCS3 expression caused by chronic inflammation or cellular stress can induce insulin resistance and inhibit neurotrophic factors, such as ciliary neurotrophic factor, leukemia inhibitory factor, and insulin, that are essential for retinal cell survival.

Anticytokine therapy, especially anti-interferon-gamma, as a pathogenetic treatment in TH-1 autoimmune diseases

We pioneered anticytokine therapy (ACT) in 1974 and 1989, proposing to remove interferon (IFN) and tumor necrosis factor (TNF)-alpha together with IFNs to treat various autoimmune diseases, including AIDS. This hypothesis was confirmed in different laboratories and opened a new line to produce and test different anticytokines. We have had good, sometimes striking results treating various Th1-mediated autoimmune diseases, including inflammatory skin diseases, using anti-IFN-gamma and sometimes anti-TNF-alpha. Anti-IFN-gamma may be a universal treatment for these conditions. Because TNF-alpha inhibitors, now successfully used in certain autoimmune disorders, have many severe side effects, there are opportunities for the development of other ACT and TNF-alpha antagonists with fewer side effects.

Inhibition of IFN-gamma as a method of treatment of various autoimmune diseases, including skin diseases

We pioneered anticytokine therapy (ACT) for autoimmune diseases (ADs). In 1974, we proposed that hyperproduced interferon (IFN) can bring AD and anti-IFN can be therapeutic. In 1989, we proposed removing tumor necrosis factor (TNF)-alpha together with certain types of IFN to treat various ADs. We found IFN in patients with different ADs and conducted the first clinical trial of ACT in 1975. Anti-IFN-gamma and anti-TNF-alpha work in similar ways, but the latter brings serious complications in some patients. We obtained good, sometimes striking, therapeutic effects treating many different Th-1-mediated ADs with anti-IFN-gamma, including rheumatoid arthritis, multiple sclerosis (MS), corneal transplant rejection, and various autoimmune skin diseases such as psoriasis, alopecia areata, vitiligo, acne vulgaris, and others. Anti-IFN-gamma was in some ways superior to anti-TNF-alpha, which was ineffective in MS. Anti-IFN-gamma therapy holds great promise for treating many Th-1 ADs, especially skin diseases.

Interferon-γ induces regression of epithelial cell carcinoma: critical roles of IRF-1 and ICSBP transcription factors

We have developed an epithelial cell carcinoma model for studying efficacy of IFNgamma gene therapy and have identified components of IFNgamma-signaling pathway responsible for its direct anti-tumor actions. The tumor results from ectopic expression of SV40 Large T-Antigen (SV40 T-Ag) oncogene in lens of transgenic mouse (alphaT3) and complete regression of the tumor is induced by targeting expression of IFNgamma into malignant lens cells. Inflammatory cells are absent in lens of alphaT3 or DT (co-expressing IFNgamma and SV40-T-Antigen) mice and the transformed lens cells are non-immunogenic, suggesting non-involvement of immunologic cells. We show that IFNgamma has direct growth-inhibitory effects on tumor cells, induces death of tumor cells by apoptosis and that these effects are mediated by two transcription factors, IRF-1 (interferon-regulatory factor-1) and ICSBP (interferon-consensus sequence-binding protein) induced by IFNgamma. Furthermore, stable transfection with ICSBP or IRF-1 construct inhibits lens carcinoma cell growth by upregulating Caspase-1, p21(WAF1) and p27 expression. In contrast, tumor progression in alphaT3 lens correlates with inhibition of IRF-1 and ICSBP expression. Our results suggest that IFNgamma gene therapy maybe effective in malignant diseases for which DNA tumor viruses are etiologic agents and that antitumor actions of IRF-1/ICSBP can be exploited therapeutically to circumvent adverse clinical effects associated with IFN therapy.

Transgenic modifications of the rat genome

The laboratory rat (R. norvegicus) is a very important experimental animal in several fields of biomedical research. This review describes the various techniques that have been used to generate transgenic rats: classical DNA microinjection and more recently described techniques such as lentiviral vector-mediated DNA transfer into early embryos, sperm-mediated transgenesis, embryo cloning by nuclear transfer and germline mutagenesis. It will also cover techniques associated to transgenesis such as sperm cryopreservation, embryo freezing and determination of zygosity. The availability of several technologies allowing genetic manipulation in the rat coupled to genomic data will allow biomedical research to fully benefit from the rat as an experimental animal.