Changes of Serum Inflammatory Molecules and Their Relationships with Visual Function in Retinitis Pigmentosa

Ocular and Serum Profiles of Inflammatory Molecules Associated With Retinitis Pigmentosa

Purpose

To investigate the profiles and correlations between local and systemic inflammatory molecules in patients with retinitis pigmentosa (RP).

Methods

The paired samples of aqueous humor and serum were collected from 36 eyes of 36 typical patients with RP and 25 eyes of age-matched patients with cataracts. The concentration of cytokines/chemokines was evaluated by a multiplexed immunoarray (Q-Plex). The correlations between ocular and serum inflammatory molecules and their association with visual function were analyzed.

Results

The aqueous levels of IL-6, Eotaxin, GROα, I-309, IL-8, IP-10, MCP-1, MCP-2, RANTES, and TARC were significantly elevated in patients with RP compared to controls (all P < 0.05). The detection rate of aqueous IL-23 was higher in patients with RP (27.8%) compared with controls (0%). In patients with RP, Spearman correlation test demonstrated positive correlations for IL-23, I-309, IL-8, and RANTES between aqueous and serum expression levels (IL-23: ⍴ = 0.8604, P < 0.0001; I-309: ρ = 0.4172, P = 0.0113; IL-8: ρ = 0.3325, P = 0.0476; RANTES: ρ = 0.6685, P < 0.0001). In addition, higher aqueous IL-23 was associated with faster visual acuity loss in 10 patients with RP with detected aqueous IL-23 (ρ = 0.4119 and P = 0.0264). Multiple factor analysis confirmed that aqueous and serum IL-23 were associated with visual acuity loss in patients with RP.

Conclusions

These findings suggest that ocular and systemic inflammatory responses have a close interaction in patients with RP. Further longitudinal studies with larger cohorts are needed to explore the correlation between specific inflammatory pathways and the progression of RP.

Translational Relevance

This study demonstrates the local-systemic interaction of immune responses in patients with RP.

Molecular mechanisms underlying inherited photoreceptor degeneration as targets for therapeutic intervention

Retinitis pigmentosa (RP) is a form of retinal degeneration characterized by primary degeneration of rod photoreceptors followed by a secondary cone loss that leads to vision impairment and finally blindness. This is a rare disease with mutations in several genes and high genetic heterogeneity. A challenging effort has been the characterization of the molecular mechanisms underlying photoreceptor cell death during the progression of the disease. Some of the cell death pathways have been identified and comprise stress events found in several neurodegenerative diseases such as oxidative stress, inflammation, calcium imbalance and endoplasmic reticulum stress. Other cell death mechanisms appear more relevant to photoreceptor cells, such as high levels of cGMP and metabolic changes. Here we review some of the cell death pathways characterized in the RP mutant retina and discuss preclinical studies of therapeutic approaches targeting the molecular outcomes that lead to photoreceptor cell demise.

Immunology of Retinitis Pigmentosa and Gene Therapy-Associated Uveitis

The underlying immune state of inherited retinal degenerations (IRDs) and retinitis pigmentosa (RP) has been an emerging area of interest, wherein the consequences have never been greater given the widespread recognition of gene therapy-associated uveitis (GTU) in gene therapy clinical trials. Whereas some evidence suggests that the adaptive immune system may play a role, the majority of studies indicate that the innate immune system is likely the primary driver of neuroinflammation in RP. During retinal degeneration, discrete mechanisms activate resident microglia and promote infiltrating macrophages that can either be protective or detrimental to photoreceptor cell death. This persistent stimulation of innate immunity, overlaid by the introduction of viral antigens as part of gene therapy, has the potential to trigger a complex microglia/macrophage-driven proinflammatory state. A better understanding of the immune pathophysiology in IRD and GTU will be necessary to improve the success of developing novel treatments for IRDs.

Lutein combined with EGCG improved retinitis pigmentosa against N-methyl-N nitrosourea-induced

In order to investigate the synergistic improving effect of lutein (LUT) and epigallocatechin-3-gallate (EGCG) treatment on retinitis pigmentosa (RP), an N-methyl-N-nitrosourea (MNU)-induced mouse model was conducted in the present study. Compared to the LUT alone treatment group, in the LUT combined with EGCG (LUT-EGCG) treatment group, the accumulation content of LUT was significantly increased by 50.24% in the liver. The morphological results indicated that LUT-EGCG treatment significantly improved the retina structure with the thickness of the outer nuclear layer restored to 185.28 ± 0.29 μm, showing no significant difference compared to the control group. The LUT-EGCG treatment also increased the production of short-chain fatty acids, such as acetic and propionic acids. Compared with the LUT alone treatment, the LUT-EGCG treatment significantly increased the relative abundance of Lachnospiraceae and Helicobacteraceae. RT-qPCR results indicated that LUT-EGCG treatment significantly increased the antiapoptotic gene Bcl-2 expression. In addition, the expression of IL-6 was significantly down-regulated in the LUT-EGCG group, while there was no significance in NF-κβ, TNF-α, IL-1β, and IL-18 compared with the LUT group. Correlation analysis supported the conclusion that LUT combined with EGCG may improve RP by modulating antiapoptotic gene expression and regulating the abundance of gut microbiota. However, the underlying mechanism still needs further research.

CRB1-Associated Retinal Dystrophy Patients Have Expanded Lewis Glycoantigen-Positive T Cells

Purpose

Eye inflammation may occur in patients with inherited retinal dystrophies (IRDs) and is seen frequently in IRDs associated with mutations in the CRB1 gene. The purpose of this study was to determine the types of inflammatory cells involved in IRDs, by deep profiling the composition of peripheral blood mononuclear cells of patients with a CRB1-associated IRD.

Methods

This study included 33 patients with an IRD with confirmed CRB1 mutations and 32 healthy controls. A 43-parameter flow cytometry analysis was performed on peripheral blood mononuclear cells isolated from venous blood. FlowSOM and manual Boolean combination gating were used to identify and quantify immune cell subsets.

Results

Comparing patients with controls revealed a significant increase in patients in the abundance of circulating CD4+ T cells and CD8+ T cells that express sialyl Lewis X antigen. Furthermore, we detected a decrease in plasmacytoid dendritic cells and an IgA+CD24+CD38+ transitional B-cell subset in patients with an IRD.

Conclusions

Patients with a CRB1-associated IRD show marked changes in blood leukocyte composition, affecting lymphocyte and dendritic cell populations. These results implicate inflammatory pathways in the disease manifestations of IRDs.

The New Era of Therapeutic Strategies for the Treatment of Retinitis Pigmentosa: A Narrative Review of Pathomolecular Mechanisms for the Development of Cell-Based Therapies

Retinitis pigmentosa, defined more properly as cone-rod dystrophy, is a paradigm of inherited diffuse retinal dystrophies, one of the rare diseases with the highest prevalence in the worldwide population and one of the main causes of low vision in the pediatric and elderly age groups. Advancements in and the understanding of molecular biology and gene-editing technologies have raised interest in laying the foundation for new therapeutic strategies for rare diseases. As a consequence, new possibilities for clinicians and patients are arising due to the feasibility of treating such a devastating disorder, reducing its complications. The scope of this review focuses on the pathomolecular mechanisms underlying RP better to understand the prospects of its treatment using innovative approaches.

Inflammation and retinal degenerative diseases

Vision is an ability that depends on the precise structure and functioning of the retina. Any kind of stress or injury can disrupt the retinal architecture and leads to vision impairment, vision loss, and blindness. Immune system and immune response function maintain homeostasis in the microenvironment. Several genetic, metabolic, and environmental factors may alter retinal homeostasis, and these events may initiate various inflammatory cascades. The prolonged inflammatory state may contribute to the initiation and development of retinal disorders such as glaucoma, age-related macular degeneration, diabetic retinopathy, and retinitis pigmentosa, which pose a threat to vision. In the current review, we attempted to provide sufficient evidence on the role of inflammation in these retinal disorders. Moreover, this review paves the way to focus on therapeutic targets of the disease, which are found to be promising.

Cataract surgery in patients with retinitis pigmentosa: systematic review

Retinitis pigmentosa (RP) is an inherited bilateral retinal degenerative disease with an incidence of 1 in 4000 people. RP affects more than 1 million individuals worldwide. Although night blindness and restricted visual field are the most typical symptoms of these individuals, generalized vision loss due to cataracts can be expected in the latter stages of the disease. It has been demonstrated that posterior subcapsular cataract is the most prevalent cataract in younger individuals with RP, as opposed to age-related cataracts. Although most ophthalmologists may have a negative view of cataract surgery in patients with RP, it appears that it can play an important role in the visual restoration of patients with RP. However, there are concerns about performing cataract surgery for patients with RP. Herein, a systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses on databases of MEDLINE and Scopus.

Neuroinflammation in retinitis pigmentosa: Therapies targeting the innate immune system

Retinitis pigmentosa (RP) is an important cause of irreversible blindness worldwide and lacks effective treatment strategies. Although mutations are the primary cause of RP, research over the past decades has shown that neuroinflammation is an important cause of RP progression. Due to the abnormal activation of immunity, continuous sterile inflammation results in neuron loss and structural destruction. Therapies targeting inflammation have shown their potential to attenuate photoreceptor degeneration in preclinical models. Regardless of variations in genetic background, inflammatory modulation is emerging as an important role in the treatment of RP. We summarize the evidence for the role of inflammation in RP and mention therapeutic strategies where available, focusing on the modulation of innate immune signals, including TNFα signaling, TLR signaling, NLRP3 inflammasome activation, chemokine signaling and JAK/STAT signaling. In addition, we describe epigenetic regulation, the gut microbiome and herbal agents as prospective treatment strategies for RP in recent advances.

Immunological consequences of compromised ocular immune privilege accelerate retinal degeneration in retinitis pigmentosa

Background

Retinitis pigmentosa (RP) is a hereditary retinal disease which leads to visual impairment. The onset and progression of RP has physiological consequences that affects the ocular environment. Some of the key non-genetic factors which hasten the retinal degeneration in RP include oxidative stress, hypoxia and ocular inflammation. In this study, we investigated the status of the ocular immune privilege during retinal degeneration and the effect of ocular immune changes on the peripheral immune system in RP. We assessed the peripheral blood mononuclear cell stimulation by retinal antigens and their immune response status in RP patients. Subsequently, we examined alterations in ocular immune privilege machineries which may contribute to ocular inflammation and disease progression in rd1 mouse model.

Results

In RP patients, we observed a suppressed anti-inflammatory response to self-retinal antigens, thereby indicating a deviated response to self-antigens. The ocular milieu in rd1 mouse model indicated a significant decrease in immune suppressive ligands and cytokine TGF-B1, and higher pro-inflammatory ocular protein levels. Further, blood–retinal-barrier breakdown due to decrease in the expression of tight junction proteins was observed. The retinal breach potentiated pro-inflammatory peripheral immune activation against retinal antigens and caused infiltration of the peripheral immune cells into the ocular tissue.

Conclusions

Our studies with RP patients and rd1 mouse model suggest that immunological consequences in RP is a contributing factor in the progression of retinal degeneration. The ocular inflammation in the RP alters the ocular immune privilege mechanisms and peripheral immune response. These aberrations in turn create an auto-reactive immune environment and accelerate retinal degeneration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02528-x.

Increased H3K27 trimethylation contributes to cone survival in a mouse model of cone dystrophy

Inherited retinal diseases (IRDs) are a heterogeneous group of blinding disorders, which result in dysfunction or death of the light-sensing cone and rod photoreceptors. Despite individual IRDs (Inherited retinal disease) being rare, collectively, they affect up to 1:2000 people worldwide, causing a significant socioeconomic burden, especially when cone-mediated central vision is affected. This study uses the Pde6c^cpfl1 mouse model of achromatopsia, a cone-specific vision loss IRD (Inherited retinal disease), to investigate the potential gene-independent therapeutic benefits of a histone demethylase inhibitor GSK-J4 on cone cell survival. We investigated the effects of GSK-J4 treatment on cone cell survival in vivo and ex vivo and changes in cone-specific gene expression via single-cell RNA sequencing. A single intravitreal GSK-J4 injection led to transcriptional changes in pathways involved in mitochondrial dysfunction, endoplasmic reticulum stress, among other key epigenetic pathways, highlighting the complex interplay between methylation and acetylation in healthy and diseased cones. Furthermore, continuous administration of GSK-J4 in retinal explants increased cone survival. Our results suggest that IRD (Inherited retinal disease)-affected cones respond positively to epigenetic modulation of histones, indicating the potential of this approach in developing a broad class of novel therapies to slow cone degeneration.

Evaluation of photoreceptor-directed fibroblasts derived from retinitis pigmentosa patients with defects in the EYS gene: a possible cost-effective cellular model for mechanism-oriented drug

Background

The most common gene responsible for autosomal recessive retinitis pigmentosa (RP) is EYS. The manner of decay of genetically defective EYS gene transcripts varies depending on the type of mutation using our cellular model, which consists of induced photoreceptor-directed fibroblasts from EYS-RP patients (EYS-RP cells). However, disease-specific profiles have not been clarified in EYS-RP cells. Herein we investigated comprehensive gene expression patterns and restoration of altered expression by low molecular weight molecules in EYS-RP cells.

Methods

Using induced photoreceptor-like cells by CRX, RAX, NeuroD, and OTX2, we employed qRT-PCR and DNA microarray analysis to compare expression levels of disease-related genes in EYS-RP cells. We investigated the effect of antiapoptotic or anti-endoplasmic reticulum (ER) stress/antioxidant reagents on the restoration of altered gene expression.

Results

Expression levels of phototransduction-related genes (blue opsin, rhodopsin, S-antigen, GNAT1, GNAT2) were lower in EYS-RP cells. CRYGD was extracted by global gene expression analysis, as a downregulated, retina-related and apoptosis-, endoplasmic reticulum (ER) stress- or aging-related gene. Pathway enrichment analysis suggested that “complement and coagulation cascades,” “ECM-receptor interaction” and “PI3K-Akt signaling pathway” could be involved in EYS-RP-associated pathogenesis. Among the matching/overlapping genes involved in those pathways, F2R was suggested as an EYS-RP-associated gene. The downregulation of CRYGD and F2R was completely restored by additional 4-PBA, an inhibitor of ER stress, and partially restored by metformin or NAC. In addition, 4-PBA normalized the expression level of cleaved caspase-3.

Conclusions

Our cellular model may reflect the ER stress-mediated degenerative retina and serve as a pathogenesis-oriented cost-effective rescue strategy for RP patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02827-x.

NUTRARET: Effect of 2-Year Nutraceutical Supplementation on Redox Status and Visual Function of Patients With Retinitis Pigmentosa: A Randomized, Double-Blind, Placebo-Controlled Trial

Oxidative stress plays a major role in the pathogenesis of retinitis pigmentosa (RP). The main goal of this study was to evaluate the effect of 2-year nutritional intervention with antioxidant nutraceuticals on the visual function of RP patients. Secondly, we assessed how nutritional intervention affected ocular and systemic redox status. We carried out a randomized, double-blind, placebo-controlled study. Thirty-one patients with RP participated in the study. RP patients randomly received either a mixture of nutraceuticals (NUT) containing folic acid, vitamin B6, vitamin A, zinc, copper, selenium, lutein, and zeaxanthin or placebo daily for 2 years. At baseline and after 2-year of the nutritional supplementation, visual function, dietetic-nutritional evaluations, serum concentration of nutraceuticals, plasma and aqueous humor concentration of several markers of redox status and inflammation were assessed. Retinal function and structure were assessed by multifocal electroretinogram (mfERG), spectral domain-optical coherence tomography (SD-OCT) and automated visual field (VF) tests. Nutritional status was estimated with validated questionnaires. Total antioxidant capacity, extracellular superoxide dismutase (SOD3), catalase (CAT), and glutathione peroxidase (GPx) activities, protein carbonyl adducts (CAR) content, thiobarbituric acid reactive substances (TBARS) formation (as indicator of lipid peroxidation), metabolites of the nitric oxide (NOX) and cytokine (interleukin 6 and tumor necrosis factor alpha) concentrations were assessed by biochemical and immunological techniques in aqueous humor or/and blood. Bayesian approach was performed to determine the probability of an effect. Region of practical equivalence (ROPE) was used. At baseline, Bayesian analysis revealed a high probability of an altered ocular redox status and to a lesser extent systemic redox status in RP patients compared to controls. Twenty-five patients (10 in the treated arm and 15 in the placebo arm) completed the nutritional intervention. After 2 years of supplementation, patients who received NUT presented better retinal responses (mfERG responses) compared to patients who received placebo. Besides, patients who received NUT showed better ocular antioxidant response (SOD3 activity) and lower oxidative damage (CAR) than those who received placebo. This study suggested that long-term NUT supplementation could slow down visual impairment and ameliorate ocular oxidative stress.

Circulating inflammatory monocytes oppose microglia and contribute to cone cell death in retinitis pigmentosa

Retinitis pigmentosa (RP) is an intractable inherited disease that primarily affects the rods through gene mutations followed by secondary cone degeneration. This cone-related dysfunction can lead to impairment of daily life activities, and ultimately blindness in patients with RP. Paradoxically, microglial neuroinflammation contributes to both protection against and progression of RP, but it is unclear which population(s) - tissue-resident microglia and/or peripheral monocyte-derived macrophages (mφ) - are implicated in the progression of the disease. Here we show that circulating blood inflammatory monocytes (IMo) are key effector cells that mediate cone cell death in RP. Attenuation of IMo and peripherally engrafted mφ by Ccl2 deficiency or immune modulation via intravenous nano-particle treatment suppressed cone cell death in rd10 mice, an animal model of RP. In contrast, the depletion of resident microglia by a colony-stimulating factor 1 receptor inhibitor exacerbated cone cell death in the same model. In human patients with RP, IMo was increased and correlated with disease progression. These results suggest that peripheral IMo is a potential target to delay cone cell death and prevent blindness in RP.

The Role of Inflammation in Retinal Neurodegeneration and Degenerative Diseases

Retinal neurodegeneration is predominantly reported as the apoptosis or impaired function of the photoreceptors. Retinal degeneration is a major causative factor of irreversible vision loss leading to blindness. In recent years, retinal degenerative diseases have been investigated and many genes and genetic defects have been elucidated by many of the causative factors. An enormous amount of research has been performed to determine the pathogenesis of retinal degenerative conditions and to formulate the treatment modalities that are the critical requirements in this current scenario. Encouraging results have been obtained using gene therapy. We provide a narrative review of the various studies performed to date on the role of inflammation in human retinal degenerative diseases such as age-related macular degeneration, inherited retinal dystrophies, retinitis pigmentosa, Stargardt macular dystrophy, and Leber congenital amaurosis. In addition, we have highlighted the pivotal role of various inflammatory mechanisms in the progress of retinal degeneration. This review also offers an assessment of various therapeutic approaches, including gene-therapies and stem-cell-based therapies, for degenerative retinal diseases.

Neutrophil-lymphocyte ratio as a predictor of slow gait speed in older adults: The Rugao Longitudinal Aging Study

BACKGROUND

Few studies have investigated the association of the neutrophil-to-lymphocyte ratio (NLR) with gait speed, but whether the NLR is predictive of slow gait speed in older adults remains unknown. The aim of this study is to examine the association of NLR levels with risk of slow gait speed development in older adults.

METHODS

Overall, 1753 participants (53.11% male, aged 60-92 years, with a mean age of 77.01 ± 4.27 years) from the second wave of the Rugao Longitudinal Aging Study were included. The second wave was recognized as the baseline in this study. Gait speed was measured using a 5-m walk test at baseline and at the 3.5-year follow-up. A slow gait speed was considered a walking speed less than 0.8 m/s. The NLR was calculated based on absolute blood neutrophil and lymphocyte counts. Logistic regression models were used to investigate the association between NLR levels and slow gait speed.

RESULTS

In the cross-sectional analysis, 394 individuals were identified as having slow gait speed. We found that increased NLR levels were associated with a higher risk of slow gait speed in older adults with and without comorbidities (P-value <0.05). During the 3.5-year follow-up period, 440 individuals had developed new-onset slowness. After confounding factors were controlled, increased NLR levels were significantly and independently associated with an increased risk of slow gait speed among older adults with (odds ratio [OR] 3.82, 95% confidence interval [CI] 1.87-7.89) and without (OR 3.29, 95% CI: 1.54-7.10) comorbidities.

CONCLUSION

The NLR is an inexpensive and easily obtainable inflammatory biomarker that robustly and independently predicts slow gait speed risk in older adults.

Retinal Inflammation, Cell Death and Inherited Retinal Dystrophies

Inherited retinal dystrophies (IRDs) are a group of retinal disorders that cause progressive and severe loss of vision because of retinal cell death, mainly photoreceptor cells. IRDs include retinitis pigmentosa (RP), the most common IRD. IRDs present a genetic and clinical heterogeneity that makes it difficult to achieve proper treatment. The progression of IRDs is influenced, among other factors, by the activation of the immune cells (microglia, macrophages, etc.) and the release of inflammatory molecules such as chemokines and cytokines. Upregulation of tumor necrosis factor alpha (TNFα), a pro-inflammatory cytokine, is found in IRDs. This cytokine may influence photoreceptor cell death. Different cell death mechanisms are proposed, including apoptosis, necroptosis, pyroptosis, autophagy, excessive activation of calpains, or parthanatos for photoreceptor cell death. Some of these cell death mechanisms are linked to TNFα upregulation and inflammation. Therapeutic approaches that reduce retinal inflammation have emerged as useful therapies for slowing down the progression of IRDs. We focused this review on the relationship between retinal inflammation and the different cell death mechanisms involved in RP. We also reviewed the main anti-inflammatory therapies for the treatment of IRDs.

A Review of Complicated Cataract in Retinitis Pigmentosa: Pathogenesis and Cataract Surgery

Retinitis pigmentosa (RP) is a set of inherited retinal degenerative diseases that affect photoreceptor and retinal pigment epithelial cells (RPEs), possibly associated with some ocular complications, including cataract. The complicated cataract formation is most likely the result of RP-related inflammation response, and the most common morphology category is posterior subcapsular cataract (PSC). Despite the absence of curative pharmacologic treatment, phacoemulsification with intraocular lens implantation to deal with opacification in the lens is preferred due to the considerable visual outcomes. However, the incidence of intraocular and postoperative complications is higher in RP patients than those without, including intraoperative phototoxic retinal damage, posterior capsular opacification (PCO), capsular contraction syndrome (CCS), pseudophakic cystoid macular edema (PCME), increased postoperative intraocular pressure (IOP), and intraocular lens (IOL) dislocation. Hence, it needs much attention to surgery progress and close follow-up. In this review, we discuss the current understanding of RP patients with complicated cataracts from morphology to potential pathogenesis to cataract surgical procedure and provide a concise description and the recommended management of related surgery complications to broaden the knowledge and lower the latent risks to yield better clinical outcomes.