The effect of toll-like receptor 4 on macrophage cytokines during endotoxin induced uveitis

Annexin A1 Mimetic Peptide and Piperlongumine: Anti-Inflammatory Profiles in Endotoxin-Induced Uveitis

Uveitis is one of the main causes of blindness worldwide, and therapeutic alternatives are worthy of study. We investigated the effects of piperlongumine (PL) and/or annexin A1 (AnxA1) mimetic peptide Ac2-26 on endotoxin-induced uveitis (EIU). Rats were inoculated with lipopolysaccharide (LPS) and intraperitoneally treated with Ac2-26 (200 µg), PL (200 and 400 µg), or Ac2-26 + PL after 15 min. Then, 24 h after LPS inoculation, leukocytes in aqueous humor, mononuclear cells, AnxA1, formyl peptide receptor (fpr)1, fpr2, and cyclooxygenase (COX)-2 were evaluated in the ocular tissues, along with inflammatory mediators in the blood and macerated supernatant. Decreased leukocyte influx, levels of inflammatory mediators, and COX-2 expression confirmed the anti-inflammatory actions of the peptide and pointed to the protective effects of PL at higher dosage. However, when PL and Ac2-26 were administered in combination, the inflammatory potential was lost. AnxA1 expression was elevated among groups treated with PL or Ac2-26 + PL but reduced after treatment with Ac2-26. Fpr2 expression was increased only in untreated EIU and Ac2-26 groups. The interaction between Ac2-26 and PL negatively affected the anti-inflammatory action of Ac2-26 or PL. We emphasize that the anti-inflammatory effects of PL can be used as a therapeutic strategy to protect against uveitis.

Effect of LPS on Cytokine Secretion from Peripheral Blood Monocytes in Juvenile Idiopathic Arthritis-Associated Uveitis Patients with Positive Antinuclear Antibody

Objectives

Antinuclear antibody (ANA) positivity is a key finding in JIA-associated uveitis (JIAU), but there are quite a few patients with negative ANA. There is no relevant report on the difference of their clinical manifestations. Previous animal model studies have found that the occurrence of uveitis is related to macrophage activation. In this article, our goal is to investigate changes in the morphology and cytokines of peripheral blood mononuclear cells (PBMCs) in uveitis patients testing positive or negative for ANAs after lipopolysaccharide (LPS) stimulation.

Methods

A total of 30 patients were included in this study (10 in each group). They were divided into three groups (the ANA-positive [ANA+] group, ANA-negative [ANA-] group, and control group). There were ten patients (6 females and 4 males) in each group. Peripheral venous blood was collected into a heparinized tube, and PBMCs were isolated as soon as possible by the Ficoll-Hypaque density gradient separation method. Isolated cells were mixed with RPMI-1640 medium, and the cell concentration was adjusted to ensure that each patient had the same number of cells entering the study. After putting the extracted PBMC into the culture plate, LPS was added carefully to the plate. The cell culture supernatants were collected at 0 h, 3 h, 6 h, 12 h, and 24 h after LPS stimulation to detect the concentrations of IL-6, IL-1, TNF-α, and IL-10. Immunofluorescence was used to discover the deformation of macrophages after LPS stimulation.

Results

The newly isolated cells were approximately round. 6 h after LPS stimulation, the ratio of noncircular cells/circular cells was the highest in the ANA+ group. Unlike IL-10 that has been rising during the observation period, IL-6, IL-1, and TNF-α peaked at 6 h after LPS stimulation.

Conclusion

With LPS motivation, cytokines in the ANA+ group increased the most violently.

A cell-permeable peptide inhibitor of p55PIK signaling alleviates ocular inflammation in mouse models of uveitis

PURPOSE

Previously we developed TAT-N24 as a synthetic cell-permeable peptide inhibitor of p55PIK signaling and demonstrated its anti-inflammatory effects. This study aimed to evaluate the potential of TAT-N24 as a new agent for the treatment of ocular inflammatory diseases.

METHODS

The endotoxin-induced uveitis (EIU) model was established by intravitreal injection of lipopolysaccharide (LPS) in BALB/c mice and experimental autoimmune uveitis (EAU) model was established by subcutaneous injection of a peptide spanning amino acid residues 161-180 of interphotoreceptor retinoid binding protein (IRBP161-180) with complete Freund's adjuvant (CFA) in B10.RIII mice. TAT-N24 was topically administered in EIU model and intraperitoneally administered in EAU model. The severity levels of uveitis were assessed by clinical and histopathological scores. The mRNA levels of inflammatory cytokines in iris-ciliary body (ICB) and retina were analyzed by reverse transcription quantitative polymerase chain reaction (RT-qPCR). The protein levels of inflammatory factors were determined by ELISA or Western blotting.

RESULTS

The results showed that TAT-N24 alleviated clinical signs, decreased inflammatory cell infiltration and the expression of inflammatory cytokines in both EIU and EAU models. Furthermore, protein levels of tumor necrosis factor-alpha (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) in aqueous humor and mRNA and protein levels of NF-κB p65 in the ICB significantly decreased in EIU model. In EAU model, TAT-N24 application induced a significant decrease of IFN-gamma (IFN-γ) and interleukin-17 (IL-17) in the retina, which were secreted by Th1 and Th17 cells, respectively.

CONCLUSION

In conclusion, TAT-N24 suppressed intraocular inflammation in both EIU and EAU models, and the anti-inflammatory effects were mediated by suppressing the expression of inflammatory cytokines by PI3K/NF-κB signaling pathway. TAT-N24 could be potential candidate for the treatment of ocular inflammatory diseases.

The Protective Effect of Low Dose of Lipopolysaccharide Pretreatment on Endotoxin-Induced Uveitis in Rats Is Associated with Downregulation of CSF-1 and Upregulation of LRR-1

Purpose

To observe the effect of low dose of lipopolysaccharide (LPS) pretreatment on the expression of CSF-1 and LRR-1 in rats with endotoxin-induced uveitis (EIU), and to explore the possible role of TLR4.

Method

EIU was induced by a single subcutaneous injection of 200 μg LPS. For the endotoxin tolerance group, the induction of EIU was preceded by a daily subcutaneous injection of 0.1 mg/kg LPS for five days. Clinical scores were graded at 24 h after EIU under a slit lamp microscope. HE stain was performed to observe the histopathology. The concentrations of IL-17, INF-γ, and IL-6 in aqueous humor were quantified with enzyme-linked immunosorbent assay. Real-time PCR, Western blot, and immunofluorescence analysis were used to determine the expression of NF-κB P65 and the activation of CSF-1, LRR-1.

Results

: Low dose of LPS pretreatment produced a suppressive effect by significantly reducing the inflammatory reaction of anterior segment as measured by slit lamp and histopathology. It also significantly reduced the concentrations of IL-17, INF-γ, and IL-6 in aqueous humor and the expression of CSF-1 and NF-κB P65, while increased the expression of LRR-1 compared to the EIU group.

Conclusions

Low dose of LPS pretreatment can ameliorate endotoxin-induced uveitis in rats. This protection may be associated with upregulation of LRR-1 and downregulation of CSF-1, which is regulated by TLR4 signaling pathway.

Regulatory Role of rno-miR-30b-5p in IL-10 and Toll-like Receptor 4 Expressions of T Lymphocytes in Experimental Autoimmune Uveitis In Vitro

Uveitis is a serious eye disease that usually damages young adult's health. MicroRNAs (miRNAs) are a class of small noncoding RNAs which regulate messenger RNA (mRNA) expression. It is predicted that rno-miR-30b-5p can regulate the expressions of interleukin-10 (IL-10) and Toll-like receptor 4 (TLR4). In this study, the regulatory role of rno-miR-30b-5p in IL-10 and TLR4 gene expressions was validated using luciferase activity assay. Further, the inflammatory manifestation of the anterior segment and pathological examination of the eye were explored in experimental autoimmune uveitis (EAU) rats. Meanwhile, the levels of rno-miR-30b-5p in eye tissues, spleen, and lymph nodes were measured using quantitative PCR (Q-PCR). IL-10 and TLR4 in spleen and lymph nodes were further separately determined by using Q-PCR and Enzyme-Linked Immunosorbent Assay (ELISA). Moreover, rno-miR-30b-5p mimic and its inhibitor were separately transfected into purified T cells, and the levels of IL-10 and TLR4 were detected using PCR, flow cytometry, and ELISA techniques. Results indicate that rno-miR-30b-5p was downregulated in spleen, lymph nodes, and eye tissues whereas the expressions of IL-10 and TLR4 at mRNA and protein levels were upregulated. The levels of IL-10 and TLR4 were negatively correlated to rno-miR-30b-5p levels. The result of in vitro cell transfection experiment indicates that IL-10 and TLR4 expressions were inhibited at mRNA and protein levels after T cells incubated with rno-miR-30b-5p mimic. However, the IL-10 and TLR4 mRNA levels were upregulated in purified T cells from spleen and lymph nodes after treatment with miR-30b-5p antagonist. In addition, there was no evident change of IL-10 and TLR4 proteins in spleen and lymph node T cells between EAU control and negative treatment groups. Flow cytometry analysis revealed that rno-miR-30b-5p mimic could reduce the number of both IL-10 and TLR4 positive cells, whereas rno-miR-30b-5p inhibitor could increase the number of IL-10 and TLR4 positive cells. Our study demonstrates that rno-miR-30b-5p influences the development of uveitis by regulating the level of IL-10 and TLR4 positive cells, thereby playing a role in the pathogenesis of uveitis.

Refined Deep-Sea Water Suppresses Inflammatory Responses via the MAPK/AP-1 and NF-κB Signaling Pathway in LPS-Treated RAW 264.7 Macrophage Cells

Atopic dermatitis (AD) is a type of inflammatory skin disease caused by genetics, immune system dysfunction, and environmental stresses. It is, however, still considered to be a refractory disease. Macrophages are inflammatory immune cells that infiltrate the skin and induce inflammation. We investigated the effect of refined deep-sea water (RDSW) on lipopolysaccharide (LPS)-induced inflammatory response in RAW 264.7 macrophage cells. The results showed that RDSW suppressed the expressions of inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2. Furthermore, nitric oxide, a product of iNOS, and prostaglandin (PG) D₂ and PGE₂, products of COX-2, were significantly inhibited by RDSW in a hardness-dependent manner. Moreover, we found that RDSW reversed the release of histamines and regressed the mRNA expressions and production of pro-inflammatory cytokines, such as tumor necrosis factor-α, interleukin (IL)-1β, IL-6, and IL-10, and vascular endothelial growth factor, in a hardness-dependent manner. We also found that the suppressive effect of RDSW on LPS-induced inflammatory responses was regulated by the inhibition of NF-κB nuclear translocation, and ERK 1/2 and JNK 1/2 mediated the suppression of c-Jun and c-Fos expressions. In conclusion, the present investigation suggests the possibility that RDSW may be used to treat and/or prevent inflammatory diseases, including AD.

Resident Macrophages in Muscle Contribute to Development of Hyperalgesia in a Mouse Model of Noninflammatory Muscle Pain

Macrophages play a role in innate immunity within the body, are located in muscle tissue, and can release inflammatory cytokines that sensitize local nociceptors. In this study we investigate the role of resident macrophages in the noninflammatory muscle pain model induced by 2 pH 4.0 preservative-free sterile saline (pH 4.0) injections 5 days apart in the gastrocnemius muscle. We showed that injecting 2 pH 4.0 injections into the gastrocnemius muscle increased the number of local muscle macrophages, and depleting muscle macrophages with clodronate liposomes before acid injections attenuated the hyperalgesia produced by this model. To further examine the contribution of local macrophages to this hyperalgesia, we injected mice intramuscularly with C34, a toll-like receptor 4 (TLR4) antagonist. When given before the first pH 4.0 injection, C34 attenuated the muscle and tactile hyperalgesia produced by the model. However, when given before the second injection C34 had no effect on the development of hyperalgesia. Then to test whether activation of local macrophages sensitizes nociceptors to normally non-nociceptive stimuli we replaced either the first or second acid injection with the immune cell activator lipopolysaccharide, or the inflammatory cytokine interleukin (IL)-6. Injecting LPS or IL-6 instead of the either the first or second pH 4.0 injection resulted in a dose-dependent increase in paw withdrawal responses and decrease in muscle withdrawal thresholds. The highest doses of LPS and IL-6 resulted in development of hyperalgesia bilaterally. The present study showed that resident macrophages in muscle are key to development of chronic muscle pain.

PERSPECTIVE

This article presents evidence for the role of macrophages in the development of chronic muscle pain using a mouse model. These data suggest that macrophages could be a potential therapeutic target to prevent transition of acute to chronic muscle pain particularly in tissue acidosis conditions.

Protective effects of the galectin-1 protein on in vivo and in vitro models of ocular inflammation

PURPOSE

Galectin-1 (Gal-1) is a β-galactoside-binding protein with diverse biological activities in the pathogenesis of inflammation but has been poorly investigated in terms of ocular inflammation. In the present study, we monitored the anti-inflammatory effects of Gal-1 using the in vivo rodent model of endotoxin-induced uveitis (EIU) and in vitro assays with human RPE (ARPE-19) cells.

METHODS

For this purpose, EIU was induced by subcutaneous sterile saline injection of 0.1 ml of lipopolysaccharide (LPS, 1 mg/Kg) in the rat paw, which was maintained under these conditions for 24 h. The therapeutic efficacy of recombinant Gal-1 (rGal-1) was tested in the EIU animals by intraperitoneal inoculation (3 µg/100 µl per animal) 15 min after the LPS injection. In vitro studies were performed using LPS-stimulated ARPE-19 cells (10 μg/ml) for 2, 8, 24 and 48 h, treated or not with rGal-1 (4 μg/ml) or dexamethasone (Dex, 1.0 μM).

RESULTS

Gal-1 treatment attenuated the histopathological manifestation of EIU via the inhibition of polymorphonuclear cells (PMN) infiltration in the eye and by causing an imbalance in adhesion molecule expression and suppressing interleukin (IL)-1β, IL-6, and monocyte chemotactic protein-1 (MCP-1) productions. Immunohistochemical and western blotting analyses revealed significant upregulation of Gal-1 in the eyes induced by EIU after 24 h. In the retina, there was no difference in the Gal-1 expression, which was high in all groups, demonstrating its structural role in this region. To better understand the effects of Gal-1 in the retina, in vitro studies were performed using ARPE-19 cells. Ultrastructural immunocytochemical analyses showed decreased levels of endogenous Gal-1 in LPS-stimulated cells (24 h), while Dex treatment upregulated this protein. The protective effects of rGal-1 on LPS-stimulated cells were associated with the significant reduction of the release of cytokines (IL-8 and IL-6), similar to Dex treatment. Furthermore, rGal-1 and Dex inhibited cyclooxygenase-2 (COX-2) expression in LPS-stimulated cells, as shown by immunofluorescence.

CONCLUSIONS

Overall, this study identified potential roles for Gal-1 in ocular inflammation, especially uveitis, and may lead to future therapeutic approaches.

Micro-concentration Lipopolysaccharide as a Novel Stimulator of Megakaryocytopoiesis that Synergizes with IL-6 for Platelet Production

Lipopolysaccharide (LPS) induces platelet activation and enhances platelet sensitivity to aggregation, which might alter platelet counts. We found that serial doses of micro-concentration LPS significantly increased the platelet count in mice treated with kanamycin, along with increased expression of IL-6 compared with IL-3 and TPO in megakaryocytes obtained from the mouse bone morrow following LPS administration. Furthermore, LPS at lower levels ranging plus IL-6 effectively stimulated CFU-MK formation and increased CD41 expression and megakaryocyte polyploidization. Meanwhile, there was a sustained rise in the percentage of reticulated platelets in the whole blood in response to low-dosage LPS combined with IL-6. In vivo experiments also demonstrated that the administration of LPS combined with IL-6 substantially enhanced the number of circulating platelets in normal and thrombocytopenic mice. Notably, the optimal LPS concentration in combination with IL-6 might be a novel stimulator of TLR4 and IL-6R expression in Dami cell lines, which initially occurs through TLR4-IL-6R crosstalk and then involves the activation of NF-κB and phosphorylation of p38 MAPK. These data suggest a new paradigm for the regulation of megakaryocytopoiesis and platelet production via a synergistic effect of LPS and IL-6, which has the potential to be used for the design of new therapies.

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.

Topical administration of diminazene aceturate decreases inflammation in endotoxin-induced uveitis

PURPOSE

Our previous study demonstrated that an intraperitoneal injection of Diminazene Aceturate (DIZE) attenuated uveitis by activating ocular angiotensin-converting enzyme 2 (ACE2). Here, we investigated the anti-inflammatory effects on the ocular anterior segment of a topical administration of a DIZE solution and explored the downstream target molecules involved in the anti-inflammatory mechanism after ACE2 activation.

METHODS

Endotoxin-induced uveitis (EIU) in rats was induced by a subcutaneous injection of lipopolysaccharides (LPS, 200 μg) in 0.1 ml of sterile saline. DIZE (0.025, 0.05, or 0.1%) and dexamethasone (0.1%) solutions were applied topically (10 μl eyedrops) to both eyes 6X every two hours before and after LPS injection. The inflammation of the ocular anterior segment was observed and the clinical scores were evaluated 24 h after LPS injection. The total protein concentration and levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in the aqueous humor were determined. CD11b-positive cells adjacent to the iris ciliary body (ICB) were stained by immunohistochemistry. The mRNA levels of inflammatory cytokines and mediators, including IL-1β, TNF-α, COX-2, and iNOS or NF-κB subunit p65 in the ICB, were analyzed by real time RT-PCR. The protein expression of NF-κB p65 and the phosphorylated protein of p38 MAPK were detected by western blotting.

RESULTS

A topical administration of DIZE decreased clinical scores and the total protein concentration, as well as TNF-α and IL-6 levels in the aqueous humor. Meanwhile, the mRNA levels of inflammatory cytokines and mediators, including IL-1β, TNF-α, COX-2, and iNOS in the ICB, were downregulated. DIZE reduced the recruitment of CD11b-positive cells adjacent to the ICB. Furthermore, DIZE downregulated the expressions of NF-κB subunit p65 at protein and mRNA levels and inhibited the phosphorylation of p38 MAPK protein in the ICB.

CONCLUSIONS

A topical administration of DIZE suppressed ocular inflammation in EIU and decreased the levels of inflammatory cytokines. DIZE attenuated the activation of NF-κB and p38 MAPK in EIU, which may be associated with ACE2-mediated anti-inflammatory effects. Our data provided further evidence that DIZE may represent a novel class of drug for the management of ocular inflammation.