Intravitreal Injection Of Lipopolysaccharide Research Articles

MiR-27a-3p promotes inflammatory response in infectious endophthalmitis via targeting TSC1

Infectious endophthalmitis (IE) poses a significant threat to vision. This study aimed to explore the impact of microRNA (miR)-27a-3p on inflammation in IE. A rat model was developed through intravitreal injection of lipopolysaccharide. Clinical and demographic data were collected for 54 participants: 31 diagnosed with IE and 23 non-infectious patients with idiopathic macular holes. Expression levels of miR-27a-3p and inflammatory genes were quantified via reverse transcription quantitative polymerase chain reaction. Concentrations of inflammatory cytokines in human vitreous samples were measured using enzyme-linked immunosorbent assay. In vitro studies were conducted to explore the target gene of miR-27a-3p. The final animal experiments further verified the role of miR-27a-3p and tuberous sclerosis complex (TSC)1 in inflammatory responses. Results showed that miR-27a-3p was elevated in LPS-treated rats and IE patients. Thirty-one IE patients were divided into the High (n = 15) and Low (n = 16) groups according to the expression of miR-27a-3p. No significant differences were observed in baseline clinical and demographic characteristics between the control and IE patient groups. Pro-inflammatory cytokine mRNA levels and concentrations were notably increased in both LPS-treated rats and the High group of patients. Besides, results showed that TSC1 is a target gene of miR-27a-3p. Moreover, TSC1 inhibition promoted inflammation in rat vitreous samples. In summary, our findings suggested that miR-27a-3p exacerbated inflammatory responses in IE though targeting TSC1, offering novel insights for potential therapeutic strategies targeting miR-27a-3p in the clinical management of IE.

Intravenous 3K3A-Activated Protein C Inhibits Murine Ocular Inflammation and Suppresses Ocular Choroidal Neovascularization

Introduction: Choroidal neovascularization (CNV) is characterized by the growth of newly formed abnormal blood vessels from the choroid extending into the neurosensory retina, leading to vision loss. CNV is a common cause of visual impairment in neovascular age-related macular degeneration (nAMD) patients. Current treatments failed to stop the continuity of the neurodegenerative process. Despite the urgency, no neuroprotective agent has been found yet to treat AMD and other neurodegenerative ocular diseases. 3K3A-activated protein C (APC) is a cell-signaling analog of the endogenous blood serine protease APC. Preclinical studies showed that circulating plasma 3K3A-APC readily crosses the blood-brain barrier (BBB) and reaches neurons due to EPCR-dependent transport. In rodent models of stroke, brain injury, and neurodegenerative disorders, 3K3A-APC exerts neuroprotective, anti-inflammatory, and vasculoprotective activities. Due to its pleiotropic effects, 3K3A-APC has advanced to clinical trial stages for treating acute brain damage and chronic neurodegenerative diseases, which share similarities with retinal neurodegenerative disorders. Notably, the retina is part of the central nervous system (CNS), and the blood-retina barrier shares functional and structural similarities with the BBB. We previously demonstrated that intraocular administration of 3K3A-APC functions as a pleiotropic cytoprotective molecule within the retina, reducing ocular inflammation, suppressing CNV growth, and exhibiting promising therapeutic potential as a neuroprotective agent for treating ocular disorders. Intraocular administration is commonly utilized for delivering therapeutics to treat retinal conditions. However, safety concerns, the burden on the healthcare system, and patient comfort may indicate that systemic administration of 3K3A-APC is a beneficial alternative. Aim: To determine whether intravenously injecting 3K3A-APC into mice tails will cross the blood-retina barrier, induce anti-inflammatory activities in the retina, and suppress CNV. Methods: The efficacy of systemic administration of 3K3A-APC was evaluated using two C57BL/6J murine models: the LPS-induced ocular inflammation and the laser-induced CNV model. CNV was triggered by laser and ocular inflammation was triggered by intravitreal injection of lipopolysaccharide (LPS). Murine recombinant 3K3A-APC was administered systemically via tail injection. Fluorescein isothiocyanate (FITC)-dextran perfusion followed by retinal flatmount staining with anti-CD11b was used to assess inflammatory co-localization of cells to retinal vessels. FITC-dextran perfusion followed by retinal pigment epithelium (RPE)-choroid flatmount was used to assess CNV vascular penetration using 3D confocal imaging. Results: LPS injection triggered robust inflammatory cell infiltration in both the anterior and posterior chambers of the eyes. Systemic administration of 3K3A-APC (0.5 mg/kg, 1 and 4 hours post-LPS) significantly inhibited ocular inflammation. Immunostaining performed 24 hours post LPS revealed that 3K3A-APC reduced the number of CD11b+ monocyte and their extravasation into the retinal parenchyma (Figure). In the laser-induced CNV model, systemic administration of 0.2 mg/kg 3K3A-APC was applied one hour and four days post-laser. Evaluation of retinal specimens ten days post-laser showed that 3K3A-APC treatment significantly suppressed CNV growth, attenuated the abnormal growth of blood vessels from the choroid into the sensory retina, and decreased myeloid cell recruitment to the RPE-choroid area. Conclusion: Our study reveals that systemically administered 3K3A-APC effectively inhibits ocular inflammation and reduces CNV formation. Drawing insights from the neuroprotective activities of 3K3A-APC in the brain and CNS and recognizing the retina, particularly the macula, as an extension of the brain, we propose 3K3A-APC as a potential neuroprotective treatment for AMD and other neurodegenerative retinal pathologies. Given the established safety of systemic 3K3A-APC administration in phase 2 clinical trials for ischemic stroke, our findings support further exploring 3K3A-APC as a novel therapeutic approach in ophthalmology. Further research is warranted to elucidate fully the mechanisms underlying 3K3A-APC's beneficial effects on the retina.

Intravitreal injection of mitochondrial DNA induces cell damage and retinal dysfunction in rats

BackgroundRetinal neurodegeneration is induced by a variety of environmental insults and stresses, but the exact mechanisms are unclear. In the present study, we explored the involvement of cytosolic mitochondrial DNA (mtDNA), resulting in the cGAS-STING dependent inflammatory response and apoptosis in retinal damage in vivo.MethodsRetinal injury was induced with white light or intravitreal injection of lipopolysaccharide (LPS). After light- or LPS-induced injury, the amount of cytosolic mtDNA in the retina was detected by PCR. The mtDNA was isolated and used to transfect retinas in vivo. WB and real-time PCR were used to evaluate the activation of cGAS-STING pathway and the levels of apoptosis-associated protein at different times after mtDNA injection. Retinal cell apoptosis rate was detected by TUNEL staining. Full-field electroretinography (ERG) was used to assess the retinal function.ResultsLight injury and the intravitreal injection of LPS both caused the leakage of mtDNA into the cytoplasm in retinal tissue. After the transfection of mtDNA in vivo, the levels of cGAS, STING, and IFN-β mRNAs and the protein levels of STING, phosph-TBK1, phospho-IRF3, and IFN-β were upregulated. mtDNA injection also induced the activation of caspase 3 and caspase 9. BAX and BAK were increased at both the mRNA and protein levels. The release of cytochrome c from the mitochondria to the cytosol was increased after mtDNA injection. The wave amplitudes on ERG decreased and retinal cell apoptosis was detected after mtDNA injection.ConclusionsCytosolic mtDNA triggers an inflammatory response. It also promotes apoptosis and the dysfunction of the retina.

SHP-1 suppresses endotoxin-induced uveitis by inhibiting the TAK1/JNK pathway.

We investigated how Src‐homology 2‐domain phosphatase‐1 (SHP‐1) regulates the inflammatory response in endotoxin‐induced uveitis (EIU), and the signalling pathways involved. One week after intravitreal injection of short hairpin RNA targeting SHP‐1 or SHP‐1 overexpression lentivirus in rats, we induced ocular inflammation with an intravitreal injection of lipopolysaccharide (LPS). We then assessed the extent of inflammation and performed full‐field electroretinography. The concentrations and retinal expression of various inflammatory mediators were examined with enzyme‐linked immunosorbent assays and Western blotting, respectively. SHP‐1 overexpression and knockdown were induced in Müller cells to study the role of SHP‐1 in the LPS‐induced inflammatory response in vitro. Retinal SHP‐1 expression was up‐regulated by LPS. SHP‐1 knockdown exacerbated LPS‐induced retinal dysfunction and increased the levels of proinflammatory mediators in the retina, which was abrogated by a c‐Jun N‐terminal kinase (JNK) inhibitor (SP600125). SHP‐1 overexpression had the opposite effects. In Müller cells, the LPS‐induced inflammatory response was enhanced by SHP‐1 knockdown and suppressed by SHP‐1 overexpression. SHP‐1 negatively regulated the activation of the transforming growth factor‐β‐activated kinase‐1 (TAK1)/JNK pathway, but not the nuclear factor‐κB pathway. These results indicate that SHP‐1 represses EIU, at least in part, by inhibiting the TAK1/JNK pathway and suggest that SHP‐1 is a potential therapeutic target for uveitis.

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

PurposePreviously 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. MethodsThe 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. ResultsThe 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. ConclusionIn 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.

Synthetic Glucocorticoid-Induced Leucine Zipper Peptide Inhibits Lipopolysaccharide-Induced Ocular Inflammation in Rats

Purpose: To demonstrate the anti-inflammatory action of a synthetic glucocorticoid-induced leucine zipper (GILZ^98–134) peptide (GILZ-p) in a model of endotoxin-induced uveitis (EIU) in rats. Methods: The EIU model was induced in Sprague Dawley rats with an intravitreal injection of lipopolysaccharide (LPS). Synthetic GILZ-p was injected intravitreally 6 h after the LPS injection. To evaluate the anti-inflammatory effects of GILZ-p, the inflammatory response in the anterior chamber and iris of the rat eyes was evaluated with a slitlamp microscope on days 0, 1, 2, 3, and 4 after GILZ-p injection. The retinal expression of inflammatory cytokines was measured on days 0, 1, 2, 3, and 4 after GILZ-p injection. Müller cell gliosis was also detected at planned time points after GILZ-p injection. Results: Anterior segment inflammation peaked at 24 h after LPS injection in the EIU model. Compared with the controls, intravitreal GILZ-p significantly suppressed LPS-induced anterior segment inflammation in the EIU rats. The levels of retinal inflammatory factors IL-1β, TNF-α, MCP-1, and ICAM-1 were simultaneously reduced by the intravitreal GILZ-p injection. The expression of vimentin in the EIU retina was significantly reduced by GILZ-p, and the downregulated aquaporin 4 in the EIU retina was significantly restored by GILZ-p. Conclusion: The synthetic GILZ-p inhibited the inflammatory reaction in the EIU model and may have utility in the treatment of inflammatory ocular disease.

Lipocalin 2 Suppresses Ocular Inflammation by Inhibiting the Activation of NF-κβ Pathway in Endotoxin-Induced Uveitis

Background/Aims: Lipocalin 2 (LCN2), an important mediator of a variety of cellular processes, is involved in regulating the inflammatory response, but its roles in different inflammatory diseases are controversial. Because the role of LCN2 in ocular inflammation has been unclear until now, we explored the function of LCN2 in lipopolysaccharide (LPS)-induced ocular inflammation in vivo and in vitro. Methods: Endotoxin-induced uveitis (EIU) was induced in male Sprague Dawley rats by the intravitreal injection of LPS. The expression and location of LCN2 in the retina were detected with western blotting and immunohistochemistry, respectively. We determined the clinical scores for anterior inflammation, quantified the infiltrated inflammatory cells, and measured the pro-inflammatory factors to determine the anti-inflammatory effects of LCN2 in EIU eyes. Cultured primary rat Müller cells were stimulated with LPS and the expression and secretion of LCN2 were measured with real-time PCR, western blotting, and an ELISA. After Müller cells were cotreated with LPS and LCN2 or PBS, the expression and secretion of TNF-α, IL-6, and MCP-1 were examined with realtime PCR, western blotting, and ELISAs. Western blotting and immunofluorescence were used to detect the phosphorylation and cellular distribution of nuclear factor kappaB (NF-κB) subunit p65. Results: In EIU, the expression of LCN2 was significantly upregulated in the retina, especially in the outer nuclear layer (mainly composed of Müller cells). LPS stimulation of cultured Müller cells also markedly elevated LCN2 expression. Intravitreal injection of LCN2 significantly reduced the clinical scores, inflammatory infiltration, and protein leakage in EIU, which correlated with the reduced levels of proinflammatory factors in the aqueous humor and retina. LCN2 treatment also reduced the expression and secretion of TNF-α, IL-6, and MCP-1 in LPS-stimulated Müller cells. LCN2 inhibited the inflammatory response by inhibiting the phosphorylation and translocation of NF-κB p65. Conclusions: LCN2 protects against ocular inflammation, at least in part, by negatively regulating the activation of the NF-κB signaling pathway. LCN2 may be a promising anti-inflammatory therapy for ocular diseases, such as uveitis.

The effect of endothelin receptor antagonists in the endotoxin-induced uveitis rabbit model

Purpose: To investigate the effect of Bosentan (non-selective endothelin receptor antagonist) and BQ123 (ETA receptor antagonist) on intraocular inflammation in an endotoxin-induced uveitis (EIU) rabbit model.Methods: Uveitis was induced by intravitreal injection of lipopolysaccharide (LPS). The animals were divided into 7 groups and there were six rabbits in each group (saline, saline and ethanol, bosentan, BQ123, lipopolysaccharide (LPS), bosentan and LPS, BQ123 and LPS-injected groups). Bosentan and BQ123 were applied before LPS injection. Aqueous humour was collected at 24th hour post-injections and enucleation was performed for the evaluation of histopathological changes.Results: BQ123 decreased clinical score, cell counts and protein amount more than bosentan and it was significant for cell counts (p = 0.018). Bosentan significantly diminished inflammatory reactions more than BQ123 as shown in histopathological specimens (p = 0.002).Conclusions: ETA receptor blockage is effective on uveitis treatment by its protective effect on blood aqueous barrier.

Glucocorticoid-induced leucine zipper overexpression inhibits lipopolysaccharide-induced retinal inflammation in rats

Glucocorticoid-induced leucine zipper (GILZ) mediates several effects of glucocorticoids and has important anti-inflammatory properties. Here, we explored the role of GILZ in inhibiting retinal inflammation. Endotoxin-induced uveitis (EIU) was established in rats by intravitreal injection of lipopolysaccharide (LPS). GILZ levels decreased in the EIU retina after LPS injection. Retinal GILZ was downregulated by recombinant lentivirus-delivered short-hairpin RNA targeting GILZ (shRNA-GILZ-rLV) and upregulated by recombinant lentivirus-mediated GILZ overexpression (Oe-GILZ-rLV). GILZ silencing attenuated the anti-inflammatory effects of intravitreal injection of triamcinolone acetonide (TA) in the EIU retina, as demonstrated by increased retinal interleukin (IL)-1β, monocyte chemoattractant protein (MCP)-1and intercellular cell adhesion molecule-1 expression at 18 h after TA injection. A Bio-Plex cytokine assay and western blotting demonstrated that GILZ overexpression inhibited the effects of LPS, downregulating retinal IL-1β, MCP-1, MIP-1α, and IL-17 and inhibiting LPS-induced activation of the retinal toll-like receptor 4–myeloid differentiation factor 88 signaling pathway. At 48 and 72 h after LPS injection, the clinical score of inflammation was significantly lower in Oe-GILZ-rLV–transfected eyes than in blank-rLV–transfected eyes. Histological examination showed a 67.85% reduction of infiltrating inflammatory cells in the anterior chamber and a 58.97% reduction in vitreous cavity of Oe-GILZ-rLV transfected eyes at 48 h after LPS injection. Taken together, our results suggest that GILZ is a novel therapeutic target for the treatment of retinal inflammatory diseases.

ATF4 is a novel regulator of MCP-1 in microvascular endothelial cells.

BackgroundMonocyte chemoattractant protein-1 (MCP-1) is a major chemokine that recruits monocyte/macrophage to the site of tissue injury and plays a critical role in microvascular complications of diabetes. However, the mechanisms underlying the regulation of MCP-1 are not fully understood. The present study aims to explore the role of activating transcription factor 4 (ATF4), an ER stress-inducible transcription factor, in regulation of MCP-1 expression and production in brain and retinal microvascular endothelial cells.MethodsFor in vitro study, primary brain microvascular endothelial cells isolated from ATF4 knockout mice or mouse retinal endothelial cells were treated with lipopolysaccharide (LPS) to induce MCP-1 expression. ATF4 expression/function was manipulated by adenoviruses expressing wild type ATF4 (Ad-ATF4) or a dominant negative mutant of the protein (Ad-ATF4DN). For in vivo study, MCP-1 expression was induced by intravitreal injection of LPS or Ad-ATF4 in heterozygous ATF4 knockout or wild type mice.ResultsLPS treatment induced a dose- and time-dependent increase in ATF4 expression, ER stress and MCP-1 production in brain and retinal microvascular endothelial cells. Overexpression of ATF4 in endothelial cells significantly increased the secretion of MCP-1 and promoted THP-1 monocyte-endothelial cell adhesion. Conditioned medium from ATF4-overexpressiing endothelial cells significantly enhanced THP-1 cell migration. Consistently, intravitreal injection of Ad-ATF4 remarkably enhanced retinal levels of MCP-1 and promoted inflammatory cell infiltration into the vitreous and retina. In contrast, LPS-induced MCP-1 upregulation was markedly attenuated in ATF4-deficient endothelial cells and in retinas of ATF4 knockout mice, suggesting that ATF4 is essential for LPS-induced MCP-1 production in endothelial cells and in the retina. Mechanistically, overexpression of ATF4 enhanced, while inhibition of ATF4, attenuated the basal and LPS-stimulated phosphorylation of NF-κB, P38, and JNK. Furthermore, pharmacological inhibition of NF-κB, P38, or JNK significantly reduced ATF4-stimulated MCP-1 secretion from endothelial cells.ConclusionsTaken together, our results suggest a critical role of ATF4 in the regulation of MCP-1 production in retinal and brain microvascular endothelial cells, which may contribute to inflammation-related endothelial injury in diseases such as diabetic retinopathy.

Caveolin-1 increases proinflammatory chemoattractants and blood-retinal barrier breakdown but decreases leukocyte recruitment in inflammation.

Caveolin-1 (Cav-1), the signature protein of caveolae, modulates inflammatory responses, and innate immunity. However, Cav-1's role in retinal inflammation has not been rigorously tested. In this study, we examined the effect of Cav-1 ablation on the sensitivity of the retina to inflammation. Cav-1 knockout (KO) mice were challenged by intravitreal injection of lipopolysaccharide (LPS) and inflammatory cell recruitment was assessed by flow cytometry and immunohistochemistry. Leukostasis was assessed in retinal flatmounts after perfusion with FITC-labeled Concanavalin A (FITC-ConA). Chemoattractants were measured by multiplex immunoassays. Blood-retinal barrier (BRB) breakdown was assessed quantitatively by a FITC-dextran permeability assay. The ratio of extravascular to total immune cells was determined by CD45 immunohistochemistry of retinal flatmounts. Inflammatory challenge resulted in significant blunting of proinflammatory cytokine (monocyte chemoattractant protein-1 [MCP-1/CCL2], CXCL1/KC, IL-6, and IL-1β) responses as well as reduced inflammatory BRB breakdown in Cav-1 KO retinas. Paradoxically, Cav-1 deficiency resulted in significantly increased recruitment of immune cells compared with controls as well as increased leukostasis. A similar ratio of extravascular/total leukocytes were found in Cav-1 KO and wild-type (WT) retinas suggesting that Cav-1 deficient leukocytes were as competent to extravasate as those from WT mice. We found increased levels of circulating immune cells in naïve (not challenged with LPS) Cav-1 KO mice compared with controls. Caveolin-1 paradoxically modulates inflammatory signaling and leukocyte infiltration through distinct mechanisms. We hypothesize that Cav-1 expression may enhance inflammatory signaling while at the same time supporting the physical properties of the BRB.

Adaptive Müller cell responses to microglial activation mediate neuroprotection and coordinate inflammation in the retina

PurposeMicroglia and Müller cells are prominent participants in retinal responses to injury and disease that shape eventual tissue adaptation or damage. This investigation examined how microglia and Müller cells interact with each other following initial microglial activation.MethodsMouse Müller cells were cultured alone, or co-cultured with activated or unactivated retinal microglia, and their morphological, molecular, and functional responses were evaluated. Müller cell-feedback signaling to microglia was studied using Müller cell-conditioned media. Corroborative in vivo analyses of retinal microglia-Müller cell interactions in the mouse retina were also performed.ResultsOur results demonstrate that Müller cells exposed to activated microglia, relative to those cultured alone or with unactivated microglia, exhibit marked alterations in cell morphology and gene expression that differed from those seen in chronic gliosis. These Müller cells demonstrated in vitro (1) an upregulation of growth factors such as GDNF and LIF, and provide neuroprotection to photoreceptor cells, (2) increased pro-inflammatory factor production, which in turn increased microglial activation in a positive feedback loop, and (3) upregulated chemokine and adhesion protein expression, which allowed Müller cells to attract and adhere to microglia. In vivo activation of microglia by intravitreal injection of lipopolysaccharide (LPS) also induced increased Müller cell-microglia adhesion, indicating that activated microglia may translocate intraretinally in a radial direction using Müller cell processes as an adhesive scaffold.ConclusionOur findings demonstrate that activated microglia are able to influence Müller cells directly, and initiate a program of bidirectional microglia-Müller cell signaling that can mediate adaptive responses within the retina following injury. In the acute aftermath following initial microglia activation, Müller cell responses may serve to augment initial inflammatory responses across retinal lamina and to guide the intraretinal mobilization of migratory microglia using chemotactic cues and adhesive cell contacts. Understanding adaptive microglia-Müller cell interactions in injury responses can help discover therapeutic cellular targets for intervention in retinal disease.

The Anti-inflammatory Effects ofCurcuma longaandBerberis aristatain Endotoxin-Induced Uveitis in Rabbits

To investigate the anti-inflammatory effect of topical application of Curcuma longa (C. longa) and Berberis aristata (B. aristata) aqueous extracts on experimental uveitis in the rabbit. Anterior uveitis was induced in rabbits by intravitreal injection of lipopolysaccharide from Escherichia coli after pretreatment with C. longa and B. aristata aqueous extracts. Subsequently, the anti-inflammatory activity of C. longa and B. aristata was evaluated by grading the clinical signs and histopathologic changes and estimating the inflammatory cell count, protein, and TNF-alpha levels in the aqueous humor. The anterior segment inflammation in the control group was significantly higher than in both the extract-treated groups, as observed by clinical and histopathologic grading. The inflammatory cell count in the control group was 30.75 +/- 7.33 x 10(5) cells/mL, whereas it was 2.39 +/- 0.59 x 10(5) (P < 0.001 vs. control) and 11.56 +/- 2.44 x 10(5) (P = 0.001 vs. control) cells/mL in the C. longa- and B. aristata-treated groups, respectively. The protein content of the aqueous humor was 18.14 +/- 4.98, 3.16 +/- 0.55 (P < 0.001 vs. control), and 8.24 +/- 1.42 (P < 0.01 vs. control) mg/mL in the control, C. longa-, and B. aristata-treated groups, respectively. The aqueous TNF-alpha level in the control group was 976.29 +/- 66.38 pg/mL and was 311.96 +/- 28.50 (P < 0.0001 vs. control) and 654.09 +/- 47.66 (P < 0.001vs. control) pg/mL in the C. longa- and B. aristata-treated groups, respectively. Topical instillation of aqueous extracts of C. longa and B. aristata showed potent anti-inflammatory activity against endotoxin-induced uveitis in rabbits.

Direct, real-time, simultaneous monitoring of intravitreal nitric oxide and oxygen in endotoxin-induced uveitis in rabbits

Nitric oxide (NO) plays a critical role in the pathogenesis of endotoxin-induced uveitis (EIU). Since NO is a labile free radical, it is difficult to examine the dynamics of NO directly in vivo. In this study, we established a system for direct monitoring of the dynamics of NO and partial pressure of oxygen ( pO 2) in EIU in rabbits. The currents (calculated concentrations) of NO and pO 2 in the vitreous were monitored after the intravitreal injection of lipopolysaccharide (LPS). In addition, the protein concentrations and nitrite levels in the aqueous humor were analyzed. The eyes were enucleated, and a histologic study was performed on their posterior segments. The tissue slices were also immunostained with anti-nitrotyrosine as a marker of peroxinitrite and/or nitrogen-related oxidants. The NO level decreased temporarily after LPS injection and then increased from 1 to 7 h. pO 2 increased temporarily for about 30 min after LPS injection. The change in NO current was inversely proportional to pO 2 after LPS injection and vice versa. The protein concentration and nitrite level after LPS injection increased significantly. These changes were suppressed by pretreatment with N G-nitro- l-arginine-methyl-ester. Immunohistochemical study showed enhanced immunoreactivity of nitrotyrosine in the inflamed retina. Since nitrotyrosine was detected, it appears that NO readily reacts with oxygen to produce cytotoxic species, peroxynitrite, and/or nitrogen-related oxidants. This process may be related to the retinal injury in EIU. This monitoring system can provide useful information on dynamic changes in intravitreal NO and pO 2 for understanding EIU.

Coinduction of Nitric Oxide Synthase and Arginine Metabolic Enzymes in Endotoxin-induced Uveitis Rats

The regulation of expression of the arginine-recycling enzymes and arginase isoforms in association with inducible nitric oxide synthase (iNOS) in the eye of endotoxin-induced uveitis (EIU) rats is investigated. An animal model of EIU was created in Wistar rats by intravitreal injection of lipopolysaccharide (LPS). mRNAs for argininosuccinate synthase (AS) and arginase I as well as for iNOS, measured by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR), were induced in the eye of EIU rats. iNOS mRNA increased markedly 3hr after injection, reached a maximum at 6–12hr, and then decreased at 24hr. AS mRNA remained little change at 3hr and increased maximally at 6hr (by about 3.3-fold), whereas arginase I mRNA increased later and reached a maximum at 12hr (by about 4.2-fold). iNOS, AS, and arginase I proteins were also induced. AL and arginase II mRNAs remained little changed. In immunohistochemical analysis, iNOS, AS and arginase I were almost colocalized in infiltrated inflammatory cells in the vitreous, iris, ciliary body and inner layers of the retina. In conclusion, AS and arginase I are coinduced with iNOS in infiltrated inflammatory cells in the eyes of EIU rats, and may regulate NO production by changing intracellular concentration of arginine.

Role and Regulation of IL-8 and MCP-1 in LPS-induced Uveitis in Rabbits

Intravitreal injection of lipopolysaccharide (LPS) induces leukocyte infiltration and protein leakage into the aqueous humor. In the present study, we investigated the role of IL-8 and MCP-1 and regulation of these chemokines by TNFα and IL-1 in LPS-induced uveitis in rabbits. After intravitreal injection of LPS, generation of IL-8 in the aqueous humor showed a biphasic pattern with the first peak at 12 hr and the second one at 24 hr, while MCP-1 was produced in a monophasic pattern and peaked at 24 hr. Immunohistochemistry showed that ciliary epithelial cells and infiltrating leukocytes were the producing cells of IL-8 and MCP-1. Administration of anti-IL-8 IgG suppressed by 66% the peak levels of LPS-induced aqueous neutrophil counts at 24 hr but did not suppress aqueous mononuclear cell counts or protein levels. anti-MCP-1 IgG inhibited aqueous mononuclear cell counts by 41% and protein levels by 28%, but did not inhibit aqueous neutrophil counts.The levels of LPS-induced aqueous IL-8 and MCP-1 at 12 hr were inhibited by anti-TNFα mAb but not by an IL-1 receptor antagonist (IL-1Ra), while concentrations of the two chemokines at 24 hr were inhibited by both anti-TNFα mAb and IL-1Ra. A combination of anti-TNFα mAb and rrIL-1Ra had an additive effect on the 24 hr-chemokine levels and inhibited up to 90% chemokine production.Taken together, our results show that IL-8 mediates neutrophil infiltration, while MCP-1 mediates mononuclear cell infiltration and protein leakage in LPS-induced uveitis in rabbits. Levels of aqueous IL-8 and MCP-1 at 12 hr are regulated by TNFα, while levels at 24 hr are regulated by TNFα and IL-1.

Involvement of TNF α, IL-1β and IL-1 Receptor Antagonist in LPS-induced Rabbit Uveitis

The objective of the study was to investigate involvement of TNFα, IL-1β and IL-1 receptor antagonist (IL-1Ra) in lipopolysaccharide (LPS)-induced uveitis. Intravitreal injection of LPS (100 ng) to rabbits induced a massive leukocyte infiltration and protein leakage into the aqueous humor. Aqueous leukocyte counts and protein levels reached a peak 24 hr after this injection. The peak concentrations of aqueous TNFα (230±37 pg ml-1, at 9 hr) and IL-1β (185±80 pg ml-1, at 18 hr) preceded peak levels of aqueous leukocyte counts and protein levels. In contrast, the levels of aqueous IL-1Ra peaked at 48 hr (12239±1964 pg ml-1) and a fairly high concentration of IL-1Ra remained when the inflammatory reactions subsided. Immunohistochemistry and leukocyte-depletion studies showed that infiltrating leukocytes were the major cellular sources of aqueous TNFα, IL-1β and IL-1Ra. Intravitreal injection of homologous TNFα (0.1–1.5 μg) or IL-1β (0.5–5 ng) reproduced a rapid leukocyte infiltration and protein leakage. Administration of anti-TNFα mAb (10 μg) suppressed the number of LPS-induced infiltrating neutrophils by 50%, mononuclear cells by 58%, and protein leakage by 42%. Administration of rabbit IL-1Ra (10 μg) also suppressed neutrophil influx by 78%, however, neither mononuclear cell influx nor protein leakage was inhibited by rabbit IL-1Ra. Co-administration of the two inhibitors enhanced inhibition of neutrophil infiltration to 88%, and protein leakage to 64%. We conclude that TNFα and IL-1β are the principal mediators of LPS-induced uveitis. Our observations also suggest that endogenous IL-1Ra may down-regulate inflammatory reactions.