Preventive effect of chrysin on experimental autoimmune uveitis triggered by injection of human IRBP peptide 1-20 in mice

Role of microglia/macrophage polarisation in intraocular diseases (Review)

Macrophages form a crucial component of the innate immune system, and their activation is indispensable for various aspects of immune and inflammatory processes, tissue repair, and maintenance of the balance of the body's state. Macrophages are found in all ocular tissues, spanning from the front surface, including the cornea, to the posterior pole, represented by the choroid/sclera. The neural retina is also populated by specialised resident macrophages called microglia. The plasticity of microglia/macrophages allows them to adopt different activation states in response to changes in the tissue microenvironment. When exposed to various factors, microglia/macrophages polarise into distinct phenotypes, each exhibiting unique characteristics and roles. Furthermore, extensive research has indicated a close association between microglia/macrophage polarisation and the development and reversal of various intraocular diseases. The present article provides a review of the recent findings on the association between microglia/macrophage polarisation and ocular pathological processes (including autoimmune uveitis, optic neuritis, sympathetic ophthalmia, retinitis pigmentosa, glaucoma, proliferative vitreoretinopathy, subretinal fibrosis, uveal melanoma, ischaemic optic neuropathy, retinopathy of prematurity and choroidal neovascularization). The paradoxical role of microglia/macrophage polarisation in retinopathy of prematurity is also discussed. Several studies have shown that microglia/macrophages are involved in the pathology of ocular diseases. However, it is required to further explore the relevant mechanisms and regulatory processes. The relationship between the functional diversity displayed by microglia/macrophage polarisation and intraocular diseases may provide a new direction for the treatment of intraocular diseases.

A de novo missense mutation in MPP2 confers an increased risk of Vogt-Koyanagi-Harada disease as shown by trio-based whole-exome sequencing

Vogt-Koyanagi-Harada (VKH) disease is a leading cause of blindness in young and middle-aged people. However, the etiology of VKH disease remains unclear. Here, we performed the first trio-based whole-exome sequencing study, which enrolled 25 VKH patients and 50 controls, followed by a study of 2081 VKH patients from a Han Chinese population to uncover detrimental mutations. A total of 15 de novo mutations in VKH patients were identified, with one of the most important being the membrane palmitoylated protein 2 (MPP2) p.K315N (MPP2-N315) mutation. The MPP2-N315 mutation was highly deleterious according to bioinformatic predictions. Additionally, this mutation appears rare, being absent from the 1000 Genome Project and Genome Aggregation Database, and it is highly conserved in 10 species, including humans and mice. Subsequent studies showed that pathological phenotypes and retinal vascular leakage were aggravated in MPP2-N315 mutation knock-in or MPP2-N315 adeno-associated virus-treated mice with experimental autoimmune uveitis (EAU). In vitro, we used clustered regularly interspaced short palindromic repeats (CRISPR‒Cas9) gene editing technology to delete intrinsic MPP2 before overexpressing wild-type MPP2 or MPP2-N315. Levels of cytokines, such as IL-1β, IL-17E, and vascular endothelial growth factor A, were increased, and barrier function was destroyed in the MPP2-N315 mutant ARPE19 cells. Mechanistically, the MPP2-N315 mutation had a stronger ability to directly bind to ANXA2 than MPP2-K315, as shown by LC‒MS/MS and Co-IP, and resulted in activation of the ERK3/IL-17E pathway. Overall, our results demonstrated that the MPP2-K315N mutation may increase susceptibility to VKH disease.

Exploration of natural flavones' bioactivity and bioavailability in chronic inflammation induced-type-2 diabetes mellitus

Diabetes, being the most widespread illness, poses a serious threat to global public health. It seems that inflammation plays a critical role in the pathophysiology of diabetes. This review aims to demonstrate a probable link between type 2 diabetes mellitus (T2DM) and chronic inflammation during its development. Additionally, the current review examined the bioactivity of natural flavones and the possible molecular mechanisms by which they influence diabetes and inflammation. While natural flavones possess remarkable anti-diabetic and anti-inflammatory bioactivities, their therapeutic use is limited by the low oral bioavailability. Several factors contribute to the low bioavailability, including poor water solubility, food interaction, and unsatisfied metabolic behaviors, while the diseases (diabetes, inflammation, etc.) causing even less bioavailability. Throughout the years, different strategies have been developed to boost flavones' bioavailability, including structural alteration, biological transformation, and innovative drug delivery system design. This review addresses current advancements in improving the bioavailability of flavonoids in general, and flavones in particular. Clinical trials were also analyzed to provide insight into the potential application of flavonoids in diabetes and inflammatory therapies.

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.

Comprehensive Grading System for Experimental Autoimmune Uveitis in Mice

Experimental autoimmune uveitis (EAU) is the most commonly used animal model to study the progression of chronic uveitis and to test various therapies to treat the disease. However, to accurately evaluate the effectiveness of such treatments, a grading system that combines the latest imaging techniques with definitive quantitative grading thresholds is required. This study aimed to develop a comprehensive grading system that objectively evaluates EAU progression in C57BL/6J mice. EAU was induced following immunisation with interphotoreceptor retinoid-binding protein (IRBP) and pertussis toxin. Weekly fundus and optical coherence tomography (OCT) images were acquired over 12 weeks using a Micron IV imaging system. Each mouse was graded (between 0 to 4) based on changes seen on both the fundus (optic disc, retinal blood vessels and retinal tissue) and OCT (vitreous and retinal layers) images. A total EAU response (with a maximum score of 48) was calculated for each mouse based on the sum of the individual scores each week. Analysis of the clinical scores depicted a gradual increase in inflammatory signs including optic disc and vascular swelling, leukocyte infiltration in the vitreous, lesions in the retina and formation of granulomas and hyper-reflective foci in the retinal layers in EAU mice, with most signs reaching a plateau towards the end of the study period. Development of these signs into sight-threatening complications such as optic disc atrophy, structural damage to the retina and subretinal oedema were noted in 80-90% of mice suggesting consistent disease induction. Overall, a comprehensive and objective grading system encompassing all pathologies occurring in EAU mice was developed to enhance the preclinical evaluation of novel uveitis treatments.

NLRP3 Attenuates Intraocular Inflammation by Inhibiting AIM2-Mediated Pyroptosis Through the Phosphorylated Salt-Inducible Kinase 1/Sterol Regulatory Element Binding Transcription Factor 1 Pathway

OBJECTIVE

The NLRP3 inflammasome has been shown to be involved in the development of uveitis, but the exact mechanism remains elusive. This study was undertaken to explore the role of NLRP3 in the development of uveitis.

METHODS

First, Nlrp3-deficient mice were used to study the role of NLRP3 in experimental autoimmune diseases, such as experimental autoimmune uveitis (EAU) and experimental autoimmune encephalomyelitis (EAE). Next, the gathering of ASC, activation of caspase 1 and gasdermin D, and secretion of lactate dehydrogenase and interleukin-1β were detected to confirm macrophage pyroptosis and AIM2 activation in the Nlrp3^-/- mice. Additionally, RNA sequencing and chromatin immunoprecipitation-polymerase chain reaction were used to investigate the phosphorylated salt-inducible kinase 1 (p-SIK1)/sterol regulatory element binding transcription factor 1 (SREBF1) pathway, which regulates the transcription of Aim2. Finally, overexpression of Nlrp3 was applied to treat EAU.

RESULTS

Surprisingly, our findings show that NLRP3 plays an antiinflammatory role in 2 models of EAU and EAE. Additionally, macrophages show an increased M1 activation and pyroptosis in Nlrp3^-/- mice. Further experiments indicate that this pyroptosis of macrophages was mediated by the up-regulated transcription of Aim2 as a result of Nlrp3 deficiency. In mechanistic studies, Nlrp3 deficiency was implicated in the down-regulation of p-SIK1 and subsequently the up-regulation of SREBF1, which binds to Aim2 and then promotes the latter's transcription. Finally, Aim2 deficiency, RNA silencing of Aim2 or Srebf1, and overexpression of Nlrp3 resulted in attenuated inflammation of EAU.

CONCLUSION

Our data demonstrate that NLRP3 inhibits AIM2 inflammasome-mediated EAU by regulating the p-SIK1/SREBF1 pathway, highlighting the therapeutic potential of targeting Nlrp3.

Long-acting acid-sensitive ketal-linked dexamethasone microcrystals for treating experimental autoimmune uveitis

Corticosteroids have for some time been used as first-line drugs for the topical treatment of noninfectious uveitis, but poor ocular bioavailability and the rapid clearance of eye drops necessitate frequent dosing, reducing patient compliance. In this study, we used an acid-sensitive stearoxyl-ketal-dexamethasone pro-drug microcrystals (SKD MCs), which is consistently safe and effective in the control of uveitis inflammation in rats. We used a rat model of experimental autoimmune uveitis (EAU) to evaluate the effects of SKD MCs in terms of clinical manifestations, molecular biology, pathological histology, and visual electrophysiology compared to dexamethasone sodium phosphate injection or phosphate-buffered saline. SKD MCs significantly reduced inflammation in EAU, improved the ability to suppress inflammatory cytokines and to protect retinal function, and significantly reduced retinal microglia activation, with no increase in intraocular pressure throughout the treatment. Our results indicate that the SKD MCs formulation holds promise as a new strategy for the treatment of noninfectious uveitis and potentially other ocular inflammatory diseases.

Single subcutaneous injection of the minocycline nanocomposite-loaded thermosensitive hydrogel for the effective attenuation of experimental autoimmune uveitis

Autoimmune uveitis induces a serious pathological and inflammatory response in the retina/choroid and results in vision impairment and blindness. Here, we report a minocycline (Mino) nanocomposite-loaded hydrogel offering a high drug payload and sustained drug release for the effective control of ocular inflammation via a single subcutaneous injection. In the presence of divalent cations (i.e., Ca²⁺), Mino was found to co-assemble with a phosphorylated peptide (i.e., NapGFFpY) via electrostatic interaction and consequently generating Mino nanocomposite. The drug entrapment efficiency (EE) of the Mino nanocomposite varied from 29.93±0.76% to 67.90±6.57%, depending on different component concentrations. After incorporation into 30 wt% poly (D,L-lactide)-b-poly (ethylene glycol)-b-poly (D,L-lactide) (PDLLA-PEG-PDLLA) thermosensitive hydrogel, the resulting Mino nanocomposite-loaded hydrogel provided a sustained drug release over 21 days. In the experimental autoimmune uveitis (EAU) rat model, a single subcutaneous injection of the Mino nanocomposite-loaded hydrogel effectively alleviated ocular inflammation in a dose-dependent manner. As indicated by optical coherence tomography (OCT) and electroretinogram (ERG) measurements, the Mino nanocomposite-loaded hydrogel treatment not only remarkably reduced destruction of the retina by EAU, but also greatly rescued retinal functions. Moreover, the proposed Mino nanocomposite-loaded hydrogel exerted its therapeutic effect on EAU primarily through a significant reduction of the influx of leukocytes and Th17 cells as well as suppression of microglia activation and apoptosis in the retina. Overall, the proposed Mino nanocomposite-loaded hydrogel might be a promising strategy for the clinical management of EAU.

Immune Stimulating Outcome of Chrysin and γ-Irradiation via Apoptotic Activation Against Solid Ehrlich Carcinoma Bearing Mice

The rising interest in innovative methods of cancer immunotherapy has prompted research into the immunomodulatory mechanisms of natural and synthetic substances. The goal of this study was to assess chrysin immune-stimulating and pro-apoptotic effects on tumor growth and cell susceptibility to ionizing radiation in order to improve cancer therapy. Chrysin (20 mg/kg/day) was intraperitoneally injected to mice bearing 1 cm³ solid tumor of Ehrlich ascites carcinoma (EAC) for 21 consecutive days. Mice were whole body exposed to 1 Gy of gamma radiation (2 fractionated dose 0.5 Gy each). Treatment with chrysin dramatically reduces tumor proliferation in EAC mice; furthermore, IFN-γ activity is significantly reduced when compared to EAC mice. When compared to EAC mice, the expression of TNF-α, free radicals, and nitric oxide (NO) levels were considerably reduced, along with improvements in apoptotic regulators (caspase-3 activity). Moreover, the histopathological investigation confirms the improvement exerted by chrysin even in the EAC mice group or the EAC + R group. What is more, exposure to gamma radiation sustained the modulatory effect of chrysin on tumor when compared with EAC + Ch mice. Hence, chrysin might represent a potential therapeutic strategy for increasing the radiation response of solid tumor.

Role of the AMPK signalling pathway in the aetiopathogenesis of ocular diseases

BACKGROUND

AMP-activated protein kinase (AMPK) plays a precise role as a master regulator of cellular energy homeostasis. AMPK is activated in response to the signalling cues that exhaust cellular ATP levels such as hypoxia, ischaemia, glucose depletion and heat shock. As a central regulator of both lipid and glucose metabolism, AMPK is considered to be a potential therapeutic target for the treatment of various diseases, including eye disorders.

OBJECTIVE

To review all the shreds of evidence concerning the role of the AMPK signalling pathway in the pathogenesis of ocular diseases.

METHOD

Scientific data search and review of available information evaluating the influence of AMPK signalling on ocular diseases.

RESULTS

Review highlights the significance of AMPK signalling in the aetiopathogenesis of ocular diseases, including cataract, glaucoma, diabetic retinopathy, retinoblastoma, age-related macular degeneration, corneal diseases, etc. The review also provides the information on the AMPK-associated pathways with reference to ocular disease, which includes mitochondrial biogenesis, autophagy and regulation of inflammatory response.

CONCLUSION

The study concludes the role of AMPK in ocular diseases. There is growing interest in the therapeutic utilization of the AMPK pathway for ocular disease treatment. Furthermore, inhibition of AMPK signalling might represent more pertinent strategy than AMPK activation for ocular disease treatment. Such information will guide the development of more effective AMPK modulators for ocular diseases.[Formula: see text].

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.

An updated review on the versatile role of chrysin in neurological diseases: Chemistry, pharmacology, and drug delivery approaches

Neurological diseases are responsible for a large number of morbidities and mortalities in the world. Flavonoids are phytochemicals that possess various health-promoting impacts. Chrysin, a natural flavonoid isolated from diverse fruits, vegetables, and even mushrooms, has several pharmacological activities comprising antioxidant, anti-inflammatory, antiapoptotic, anticancer, and neuroprotective effects. The current study was designed to review the relationship between chrysin administration and neurological complications by discussing the feasible mechanism and signaling pathways. Herein, we mentioned the sources, pharmacological properties, chemistry, and drug delivery systems associated with chrysin pharmacotherapy. The role of chrysin was discussed in depression, anxiety, neuroinflammation, Alzheimer's disease, Parkinson's disease, Huntington's disease, epilepsy, cerebral ischemia, spinal cord injury, neuropathy, Multiple Sclerosis, and Guillain-Barré Syndrome. The findings indicate that chrysin has protective effects against neurological conditions by modulating oxidative stress, inflammation, and apoptosis in animal models. However, more studies should be done to clear the neuroprotective effects of chrysin.

The Immunomodulatory Effects of Honey and Associated Flavonoids in Cancer

Honey has exerted a high impact in the field of alternative medicine over many centuries. In addition to its wound healing, anti-microbial and antioxidant properties, several lines of evidence have highlighted the efficiency of honey and associated bioactive constituents as anti-tumor agents against a range of cancer types. Mechanistically, honey was shown to inhibit cancer cell growth through its pro-apoptotic, anti-proliferative and anti-metastatic effects. However, the potential of honey to regulate anti-tumor immune responses is relatively unexplored. A small number of in vitro and in vivo studies have demonstrated the ability of honey to modulate the immune system by inducing immunostimulatory as well as anti-inflammatory effects. In the present review, we summarize the findings from different studies that aimed to investigate the immunomodulatory properties of honey and its flavonoid components in relation to cancer. While these studies provide promising data, additional research is needed to further elucidate the immunomodulatory properties of honey, and to enable its utilization as an adjuvant therapy in cancer.

High Ambient Temperature Aggravates Experimental Autoimmune Uveitis Symptoms

Whether ambient temperature influences immune responses leading to uveitis is unknown. We thus tested whether ambient temperature affects the symptoms of experimental autoimmune uveitis (EAU) in mice and investigated possible mechanisms. C57BL/6 mice were kept at a normal (22°C) or high temperature (30°C) housing conditions for 2 weeks and were then immunized with human interphotoreceptor retinoid-binding protein (IRBP651–670) peptide to induce EAU. Histological changes were monitored to evaluate the severity of uveitis. Frequency of Th1 cells and Th17 cells was measured by flow cytometry (FCM). The expression of IFN-γ and IL-17A mRNA was measured by real-time qPCR. The generation of neutrophil extracellular traps (NETs) was quantified by enzyme-linked immunosorbent assay (ELISA). Differential metabolites in the plasma of the mice kept in the aforementioned two ambient temperatures were measured via ultra-high-performance liquid chromatography triple quadrupole mass spectrometry quadrupole time of flight mass spectrometry (UHPLC-QQQ/MS). The differential metabolites identified were used to evaluate their effects on differentiation of Th1 and Th17 cells and generation of NETs in vitro. The results showed that EAU mice kept at high temperature experienced a more severe histopathological manifestation of uveitis than mice kept at a normal temperature. A significantly increased frequency of Th1 and Th17 cells in association with an upregulated expression of IFN-γ and IL-17A mRNA was observed in the splenic lymphocytes and retinas of EAU mice in high temperature. The expression of NETs as evidenced by myeloperoxidase (MPO) and neutrophil elastase (NE), was significantly elevated in serum and supernatants of neutrophils from EAU mice kept at high temperature compared to the normal temperature group. The metabolites in the plasma from EAU mice, fumaric acid and succinic acid, were markedly increased in the high temperature group and could induce the generation of NETs via the NADPH oxidase-dependent pathway, but did not influence the frequency of Th1 and Th17 cells. Our findings suggest that an increased ambient temperature is a risk factor for the development of uveitis. This is associated with the induction of Th1 and Th17 cells as well as the generation of NETs which could be mediated by the NADPH oxidase-dependent pathway.

Chrysin prevents lipopolysaccharide-induced acute lung injury in mice by suppressing the IRE1α/TXNIP/NLRP3 pathway

Acute lung injury (ALI) remains a serious challenge in the intensive care unit. Inflammation plays a key role in the progression of ALI. Chrysin (CHR) is a natural flavonoid with anti-inflammatory functions. We investigated the anti-inflammatory effects in a mouse model of ALI induced by lipopolysaccharide (LPS), and identified the underlying mechanisms of its action. Following CHR administration, mice were challenged with LPS intratracheally for 6 h to induce ALI. Compared to mice challenged with LPS alone, the presence of CHR showed a reduction in the development of lung injuries, as confirmed by histopathological observation. Pre-treatment with CHR attenuated inflammation by reducing the production of myeloperosidase (MPO), and pro-inflammatory cytokine levels in the lung and bronchoalveolar lavage fluid (BALF). Furthermore, CHR improved lung edema by reducing the vascular permeability, as demonstrated by less evans blue staining in the lung tissue and low levels of protein in BALF. In addition, our results proved that CHR improved the antioxidant capacity by increasing the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in the lung tissue. Results of western blot assays suggested that CHR suppressed the LPS-induced expression of glucose-regulated protein 78 (GRP78) and phosphorylated inositol-requiring enzyme 1α (p-IRE1α). We also found that CHR suppressed the expression of thioredoxin interaction protein (TXNIP), nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) and cleaved caspase-1. In conclusion, CHR improved vascular permeability and mitigated the inflammatory response of lung tissue by suppressing the IRE1α/TXNIP/NLRP3 pathway, thereby alleviating LPS-induced ALI in the lungs of mice.

Tregs in Autoimmune Uveitis

Uveitis is a chronic disease with relapsing and remitting ocular attack, which requires corticosteroids and systemic immunosuppression to prevent severe vision loss. Classically, uveitis is referred to an autoimmune disease, mediated by pro-inflammatory Th17 cells and immunosuppressive CD4+CD25+FoxP3+ T-regulatory cells (Tregs). More and more evidence indicates that Tregs are involved in development, resolution, and remission of uveitis. Clinically, many researchers have conducted quantitative and functional analyses of peripheral blood from patients with different subtypes of uveitis, in an attempt to find the changing rules of Tregs. Consistently, using the experimental autoimmune uveitis (EAU) model, researchers have explored the development and resolution mechanism of uveitis in many aspects. In addition, many drug and Tregs therapy investigations have yielded encouraging results. In this chapter, we introduced the current understanding of Tregs, summarized the clinical changes in the number and function of patients with uveitis and the immune mechanism of Tregs involved in EAU model, as well as discussed the progress and shortcomings of Tregs-related drug therapy and Tregs therapy. Although the exact mechanism of Tregs-mediated uveitis protection remains to be elucidated, the strategy of Tregs regulation may provide a specific and meaningful way for the prevention and treatment of uveitis.

Quantitative proteomic analysis of rat retina with experimental autoimmune uveitis based on tandem mass tag (TMT) peptide labeling coupled with LC-MS/MS

Uveitis is a recurrent, inflammatory eye disease that occurs in the retina, iris, ciliary body and choroid. Currently, the detailed mechanism is still unclear. Proteomics can offer a powerful set of tools for the direct high-throughput study and a key contribution to the understanding of protein functions. This approach can also allow us to compare the protein profiling of the cells in healthy and diseased states that can be used to identify proteins associated with disease development and progression. In the present study, we first established an autoimmune uveitis (EAU) rat model. On day 12 after immunization, we isolated the rat retinas from both normal and EAU animals to collect total proteins. Using tandem mass tag (TMT) peptide labeling coupled with LC-MS/MS quantitative proteomics technique, we identified the differentially expressed proteins in EAU rat retinas, performed bioinformatics analyses, validated the expression of the COX1, NADH1, C3, and C9 proteins, and determined the adenosine triphosphate (ATP) levels. The results indicated that there were 190 upregulated and 103 downregulated proteins in EAU rat retinas. Bioinformatics analysis revealed the differentially expressed proteins were mainly involved in acute inflammatory response, visual perception and eye photoreceptor cell differentiation that were mainly related to complement and coagulation cascades, phagosome, PI3K-Akt signaling, and metabolic pathways. In conclusion, based on the TMT-based quantitative proteomics technique, the differentially expressed proteins in EAU rat retinas were mainly associated with complement and coagulation cascades and metabolic pathways. Our findings will facilitate the understanding of the pathogenesis of uveitis and will be useful for subsequent studies.

Small molecules targeting RORγt inhibit autoimmune disease by suppressing Th17 cell differentiation

Th17 cells, a lymphocyte subpopulation that is characterized by the expression of the transcription factor "retinoic acid receptor-related orphan receptor gamma-t" (RORγt), plays an important role in the pathogenesis of autoimmune disease. The current study was set up to discover novel and non-steroidal small-molecule inverse agonists of RORγt and to determine their effects on autoimmune disease. Structure-based virtual screening (SBVS) was used to find compounds targeting RORγt. Flow cytometry was used to detect the Th17 cell differentiation. Inverse agonists were intraperitoneally administered to mice undergoing experimental autoimmune uveitis (EAU), experimental autoimmune encephalomyelitis (EAE) or type 1 diabetes. The effects of the inverse agonists were evaluated by clinical or histopathological scoring. Among 1.3 million compounds screened, CQMU151 and CQMU152 were found to inhibit Th17 cell differentiation without affecting the differentiation of Th1 and Treg lineages (both P = 0.001). These compounds also reduced the severity of EAU (P = 0.01 and 0.013) and functional studies showed that they reduced the number of Th17 cell and the expression of IL-17(Th17), but not IFN-γ(Th1) and TGF-β(Treg) in mouse retinas. Further studies showed that these compounds may reduce the expression of p-STAT3 by reducing the positive feedback loop of IL-17/IL-6/STAT3. These compounds also reduced the impaired blood-retinal barrier function by upregulating the expression of tight junction proteins. These compounds were also found to reduce the severity of EAE and type 1 diabetes. Our results showed that RORγt inverse agonists may inhibit the development of autoimmune diseases and may provide new clues for the treatment of Th17-mediated immune diseases.

Cytotoxic effect of specific T cells from mice with experimental autoimmune uveitis on murine photoreceptor cells

AIM

To investigate the cytotoxic effect of specific T cells from mice with experimental autoimmune uveitis (EAU) as well as their secreted interferon (IFN)-γ and interleukin (IL)-17A on murine photoreceptor (661W) cells.

METHODS

An EAU model was established in female mice by injection of interphotoreceptor retinoid binding protein (IRBP) emulsion supplemented with complete Freund's adjuvant (CFA) and Mycobacterium tuberculosis (TB). On day 12 after induction of EAU, specific T cells from spleen and lymph node tissues were isolated and cultured for 4d and the levels of IFN-γ and IL-17A in the supernatants were determined by enzyme-linked immunosorbent assays (ELISAs). T cells and their supernatants were added to 661W cells to observe the alteration of cell morphology; IFN-γ and IL-17A were separately added to 661W cells to observe the effect of IFN-γ and IL-17A on cell proliferation.

RESULTS

The levels of IFN-γ and IL-17A in the T cell supernatants were 1568.64±38.79 pg/mL and 1456.57±46.98 pg/mL, respectively. The supernatants apparently inhibited 661W cell proliferation (P<0.05). T cells could also attach to the surface of 661W cells, and IFN-γ showed a more serious cytotoxic effect on 661W cells than IL-17A, inhibiting cell proliferation (P<0.01).

CONCLUSION

IFN-γ and IL-17A from T cells of EAU mice model can exert cytotoxic effects on murine photoreceptor cell proliferation, and IFN-γ shows more serious cytotoxic effects on murine photoreceptor cells than IL-17A.

Chrysin Attenuates the NLRP3 Inflammasome Cascade to Reduce Synovitis and Pain in KOA Rats

Purpose

Our recent reports have revealed that inhibiting NLRP3 activation reduces synovial inflammation and fibrosis in knee osteoarthritis (KOA). Synovial inflammation is involved the entire process of KOA and promotes the progression of KOA. Natural flavonoid Chrysin from Scutellariae Radix, a traditional Chinese medicine, exhibits multifarious biological activities and potentially has protective activity against osteoarthritis. However, the mechanism of Chrysin in the treatment of synovial inflammation remains elusive. The purpose of our research was to explore the anti-inflammatory effects of Chrysin on KOA, which was induced by monoiodoacetic acid (MIA) in rats by targeting the NLRP3 inflammasome in the hopes of identifying an effective drug to treat KOA.

Methods

The MIA-induced KOA model was used to evaluate the cold pain threshold and paw withdrawal threshold (PWT) of joints after MIA (40 mg/mL) injection into the knee joints. Microscopically, we used LPS (5 ug/mL) and ATP (4 mmol/L) to stimulate fibroblast-like synovial cells (FLSs) to explore the underlying mechanisms and effects of Chrysin. Two staining methods, H&E and Sirius Red, were applied to assess histopathological changes in synovial membranes. Cellular signal transduction was determined by qRT-PCR and WB. Cytokine expression (inflammatory cytokines and pain-related cytokines) was detected by ELISA. The degree of chronic inflammatory pain was evaluated by c-Fos immunofluorescence.

Results

The results showed that Chrysin not only attenuated synovial inflammation but also reduced the secretion of pain-related factors and increased the PWT and cold pain threshold in rats. Chrysin also inhibited NLRP3 inflammasome activation and increased IL-1β levels to alleviate the synovitis.

Conclusion

Chrysin can relieve knee synovial inflammation and improve pain behavior in KOA rats, which may be related to the ability of Chrysin to inhibit NLRP3 inflammasome activation. Therefore, Chrysin may be developed as a new drug for the treatment of KOA.

Analysis of the role of palmitoleic acid in acute anterior uveitis

PURPOSE

To study the role of palmitoleic acid (PA) in the pathogenesis of acute anterior uveitis (AAU).

METHODS

PA levels in feces from AAU patients were measured by gas chromatography coupled with a mass spectrometer (GC-MS) and compared with samples obtained from healthy individuals. Enzyme linked immunosorbent assay (ELISA) and flow cytometry (FCM) were used to assess the effect of PA on dendritic cells (DCs) and CD4⁺T cells obtained from mice, AAU patients and healthy individuals. C57BL/6 mice were fed with PA or vehicle and experimental autoimmune uveitis (EAU) was induced with a human retinal IRBP651-670 peptide. Disease severity of EAU was evaluated by clinical manifestation and histology. Differentiation of splenic Type 1 helper T cells (Th1) and Th17 cells was evaluated by FCM. Tandem mass tag (TMT)-based proteomics analysis was used to identify differentially expressed proteins following incubation of DCs with PA.

RESULTS

The fecal concentration of PA was increased in AAU patients as compared with healthy individuals. In vitro, PA promoted apoptosis of DCs and inhibited the secretion of TNF-α from mouse bone-marrow-derived dendritic cells (BMDCs) as well as in DCs from AAU patients and healthy individuals. It only decreased DCs surface marker expression and IL-12p70 secretion in BMDCs and healthy individuals DCs but not in AAU patient DCs. PA-treated BMDCs inhibited Th cell differentiation from mouse naïve CD4⁺T cells and IL-17 and IFN-γ secretion in co-culture supernatants. PA also inhibited the differentiation of Th cells and secretion of IFN-γ and IL-17 in CD4⁺T cells from mice, AAU patients and healthy individuals. In vivo, PA-treated EAU mice showed milder clinical and histopathological intraocular manifestations as compared with the control group. PA feeding inhibited differentiation of splenic Th17 cells, whereas Th1 cells were not affected. Up to 30 upregulated and 77 downregulated proteins were identified when comparing PA-treated DCs with controls.

CONCLUSION

An increased expression of fecal PA was observed in AAU patients. PA was shown to have immunoregulatory effects on DCs and CD4⁺T cells and attenuated disease severity in EAU mice.

Chrysin Reduces Oxidative Stress but Does Not Affect Polyol Pathway in the Lenses of Type 1 Diabetic Rats

Prolonged hyperglycemia is one of the main causes of reactive oxygen species and free radicals generation in diabetes which may affect various organs, including the eye. Oxidative damage to proteins and lipids in the eye lens could lead to cataract formation. To cope with oxidative stress, the endogenous antioxidative system may be supported by the supplementation of exogenous antioxidants. The aim of this study was to evaluate the effect of chrysin, a natural flavonoid, on oxidative stress and polyol pathway-related markers in the lenses of streptozotocin-induced type 1 male diabetic rats. Chrysin at doses of 50 and 100 mg/kg was administered by gavage for 28 days. This treatment resulted in a decrease in antioxidative enzymes activity and oxidative stress index. Moreover, chrysin administration elevated the reduced glutathione level in the lenses. A decrease in the markers linked to oxidative damage to proteins and lipids in the lenses was noted, especially after treatment with 50 mg/kg of chrysin. Neither of the chrysin doses affected glycemia-related markers in the serum or altered parameters related to the polyol pathway and advanced glycation end-products level in the lenses of diabetic rats. Upon obtaining results, it can be concluded that chrysin reveals antioxidative activity in the lenses but shows no antihyperglycemic or antiglycation properties.

Therapeutic potential of aryl hydrocarbon receptor in autoimmunity

Aryl hydrocarbon receptor (AhR), a type of transcriptional factor, is widely expressed in immune cells. The activation of AhR signaling pathway depends on its ligands, which exist in environment and can also be produced by metabolism. Normal expressions of AhR and AhR-mediated signaling may be essential for immune responses, and effects of AhR signaling on the development and function of innate and adaptive immune cells have also been revealed in previous studies. Recent studies also indicate that aberrant AhR signaling may be related to autoimmune diseases, including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), multiple sclerosis (MS), autoimmune uveitis (AU), autoimmune diabetes, Behcet's disease (BD) and myasthenia gravis (MG). Moreover, administration of AhR ligands or drugs has been proven effective for improving pathological outcomes in some autoimmune diseases or models. In this review, we summarize the effects of AhR on several innate and adaptive immune cells associated with autoimmunity, and the mechanism on how AhR participates in autoimmune diseases. In addition, we also discuss therapeutic potential and application prospect of AhR in autoimmune diseases, so as to provide valuable information for exploring novel and effective approaches to autoimmune disease treatments.

Aryl Hydrocarbon Receptor Regulates Apoptosis and Inflammation in a Murine Model of Experimental Autoimmune Uveitis

Uveitis is characterized as a common cause of blindness worldwide. Aryl hydrocarbon receptor (AhR), a ligand-activated nuclear receptor, has been implicated to play a role in human uveitis, although the exact mechanisms remain poorly understood. The purpose of this study was to enhance our knowledge concerning the role of AhR during intraocular inflammation. We immunized wild-type and AhR-knockout C57BL/6J mice with IRBP_651–670 to induce experimental autoimmune uveitis (EAU). Disease severity was evaluated with both clinical and histopathological grading. Blood–retinal barrier (BRB) integrity was tested by Evans blue and tight junction proteins qualifications. Apoptosis was measured using TdT-mediated dUTP nick end labeling staining. Macrophage/microglia activation and polarization were studied by immunofluorescence and Western blot. Following EAU induction, AhR^−/− mice had more severe clinical and histopathological manifestations of uveitis than AhR^+/+ mice. Increased vascular permeability and apoptotic cells were observed in AhR^−/− EAU mice when compared with AhR^+/+ EAU mice. In addition, AhR^−/− EAU mice showed evidence of a significantly increased macrophage/microglia cells and a stronger polarization from the M2 to the M1 phenotype as compared to AhR^+/+ EAU mice. The levels of pro-inflammatory cytokines including tumor necrosis factor-α (TNF-α), interleukin (IL)-6, and IL-1β were increased in AhR^−/− EAU mice, which was associated with the activation of NF-κB and signal transducers and activators of transcription (STAT) pathways. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), an agonist of AhR, caused a significant decrease in the clinical and histopathological manifestations, preserved BRB integrity, reduced apoptotic cells, inhibited macrophage/microglia activation, and shifted their polarization from M1 toward M2. Moreover, decreased expression of pro-inflammatory cytokines including TNF-α, IL-6, and IL-1β and inhibition of NF-κB and STAT pathways were found in EAU mice following TCDD treatment. In conclusion, AhR activation with TCDD exhibits an immunomodulatory effect by reducing BRB breakdown, inhibiting retinal cell apoptosis, and reducing pro-inflammatory cytokine expression during EAU. The underlying mechanism may involve the modulation of macrophages/microglia polarization and the downregulation of NF-κB and STAT pathways.