Endotoxin-induced Uveitis In Rats Research Articles

Inhibition of Hsp90 attenuates inflammation in endotoxin‐induced uveitis

Heat shock protein (Hsp) 90 inhibitors, such as 17-allylamino-17-demethoxy-geldanamycin (17-AAG), constitute promising novel therapeutic agents. We investigated the anti-inflammatory activity of 17-AAG in endotoxin-induced uveitis (EIU) in rats. After the induction of EIU with a footpad injection of lipopolysaccharide (LPS), female Lewis rats received a single intraperitoneal. (i.p.) injection of 17-AAG or vehicle. Twenty-four hours later, the retinas were extracted and assayed for leukocyte adhesion; blood-retinal barrier breakdown; VEGF, TNF-alpha, IL-1beta, and CD14 protein levels; NF-kappaB and HIF-1alpha activity; hsp90 and 70 levels and expression and phosphorylation of the tight junction proteins ZO-1 and occludin. 17-AAG treatment significantly suppressed the LPS-induced increase in retinal leukocyte adhesion; vascular leakage; NF-kappaB, HIF-1alpha, p38, and PI-3K activity; and VEGF, TNF-alpha, and IL-1beta levels. 17-AAG also suppressed phosphorylation of ZO-1 and occludin by inhibiting their association with p38 and PI-3K. Although 17-AAG treatment did not reduce the LPS-induced increase in total CD14 levels in leukocytes, it significantly decreased membrane CD14 levels. These data suggest that Hsp90 inhibition suppresses several cardinal manifestations of endotoxin-induced uveitis in the rat. 17-AAG has demonstrated a favorable safety profile in clinical trials in cancer patients and represents a promising therapeutic agent for the treatment of inflammatory eye diseases.

Preventive and therapeutic anti-inflammatory effects of systemic and topical thalidomide on endotoxin-induced uveitis in rats

The present study examined the outcomes of systemic or topical treatment with thalidomide, a compound that possesses anti-inflammatory, immunomodulatory and anti-angiogenic properties, in rats subjected to endotoxin-induced uveitis (EIU). The effects of thalidomide were evaluated on endotoxin-induced leucocyte and protein infiltration and also on the production of interleukin (IL)-1β and tumour necrosis factor (TNF)-α in rat aqueous humour (AqH). Moreover, the actions of thalidomide were assessed on the cyclooxygenase (COX)-2 and inducible nitric oxide synthase (iNOS) protein expression in retinal tissue. EIU was produced by a hindpaw injection of lipopolysaccharide (LPS), in male Wistar rats. Thalidomide (5, 25 and 50 mg/kg) was administered orally 1 h before LPS injection. In another set of experiments, to evaluate the therapeutic efficacy, 5% thalidomide was applied topically to both eyes at 6, 12 and 18 h after LPS administration. The oral pre-treatment with thalidomide decreased, in a dose-dependent manner, the number of inflammatory cells, the protein concentration, and the levels of IL-1β and TNF-α in the AqH. Similar results were found in the AqH of rats that received a topical application of thalidomide. Furthermore, oral (50 mg/kg) and local (5%) thalidomide treatment also reduced expression of the pro-inflammatory proteins COX-2 and iNOS in the posterior segment of the eye. Thalidomide exhibited marked preventive and curative ocular effects in EIU in rats, a property that might be associated with its ability to inhibit the production of inflammatory cytokines and the expression of COX-2 and iNOS. This assembly of data provides additional molecular and functional insights into beneficial effects of thalidomide as an agent for the management of ocular inflammation.

Captopril suppresses inflammation in endotoxin-induced uveitis in rats

Captopril is an inhibitor of angiotensin-converting enzyme (ACE) that is largely used in the treatment of cardiovascular diseases. Several previous studies have demonstrated that captopril exhibits a wide variety of biological activities, including an anti-inflammatory action, on which we focused our attention. The aim of the present study was to investigate the efficacy of captopril on endotoxin induced uveitis (EIU) in rats. We investigated its effect upon cellular infiltration and protein leakage, as well as on the concentration of tumor necrosis factor-α (TNF-α), nitric oxide (NO), prostaglandin E2 (PGE2), monocyte chemoattractant protein-1 (MCP-1) in the anterior chamber. In addition, we checked its effect on activation of nuclear factor kappa B (NF-κB) in iris and ciliary body (ICB) cells in vivo. EIU was induced in male Lewis rats by a footpad injection of lipopolysaccharide (LPS). One hour after the LPS inoculation, either 1 mg/kg, 10 mg/kg or 100 mg/kg captopril were injected intravenously. 24 h later, the aqueous humor was collected from both eyes, and the number of infiltrating cells and protein concentration in the aqueous humor were determined. Levels of TNF-α, PGE2, NO and MCP-1 were determined by enzyme-linked immunosorbent assay. On some eyes, after enucleation, immunohistochemical staining with a monoclonal antibody against activated NF-κB was performed. Captopril treatment significantly decreased the inflammatory cells infiltration, the level of protein, concentrations of TNF-α, PGE2, NO and MCP-1 in the aqueous humor. The number of activated NF-κB-positive cells was lower in ICB of the rats treated with captopril 3 h after the LPS injection. The present results indicate that captopril suppresses the inflammation in EIU by inhibiting the NF-κB-dependent pathway and the subsequent production of pro-inflammatory mediators.

Suppressive effects of astaxanthin against rat endotoxin-induced uveitis by inhibiting the NF-κB signaling pathway

We investigated the effects of astaxanthin (AST), a carotenoid, on endotoxin-induced uveitis (EIU), and over the course of the disease measured the expression of inflammatory cytokines and chemokines in the presence or absence of AST. EIU was induced in male Lewis rats by footpad injection of lipopolysaccharide (LPS). The animals were randomly divided to 12 groups with eight animals in each. Immediately after the inoculation, AST (1, 10, or 100 mg kg −1) was injected intravenously. Aqueous humour was collected at 6, 12 and 24 hr after LPS inoculation and the number of infiltrating cells in the anterior chamber was counted. In addition, we assayed the concentration of protein, nitric oxide (NO), tumour necrosis factor-α (TNF-α) and prostaglandin E2 (PGE2). Immunohistochemical staining with a monoclonal antibody against activated NF-κB was performed in order to evaluate the effects of AST on NF-κB activation. Rats injected with AST showed a significant decrease in the number of infiltrating cells in the anterior chamber and additionally there was a significantly lower concentration of protein, NO, TNF-α and PGE2 in the aqueous humour. Moreover, even early stages of EIU were suppressed by injection of AST. The number of activated NF-κB-positive cells was lower in iris-ciliary bodies treated with 10 or 100 mg kg −1 AST at 3 hr after LPS injection. These results suggest that AST reduces ocular inflammation in eyes with EIU by downregulating proinflammatory factors and by inhibiting the NF-κB-dependent signaling pathway.

The Effects of Naringin and Naringenin on Endotoxin-Induced Uveitis in Rats

The aim of this study was to investigate the efficacy of naringin and naringenin on endotoxin- induced uveitis (EIU) in rats. EIU was induced in male Lewis rats by a footpad injection of lipopolysaccharide (LPS). The rats were injected intravenously with 0.4, 4, or 40 microg/kg naringin or naringenin. Each compound was administered three times, simultaneously, 30 min before and after the actual LPS injection. The aqueous humor was collected 24 h later from both eyes, and the number of cells infiltrating into the aqueous humor and the aqueous humor protein concentration were measured. The levels of prostaglandin E2 (PGE2) and nitric oxide (NO) were determined. Naringin and naringenin suppressed the development of EIU in a dose-dependent fashion. Both treatments with naringin and naringenin produced reductions in PGE2 and NO concentrations in the aqueous humor. In particular, 40 microM/kg of naringin and naringenin suppressed increases in cell count owing to LPS treatment by 31% and 38%, respectively. The possible mechanism for the antiocular inflammatory effect may be the suppression of PGE2 and NO by naringin and naringenin.

Effects of antiglaucoma drugs timolol and GLC756, a novel dopamine D 2 agonist and D 1 antagonist, on endotoxin-induced-uveitis in rats

Antiglaucoma drugs with anti-inflammatory properties may be of particular value for the long-term treatment of glaucoma since they may reduce the risk for treatment-related inflammatory processes in outer compartments of the eye. The purpose of this study was, to evaluate the effect of systemic and topical administration of GLC756, a novel mixed dopamine D 2 receptor agonist and D 1 receptor antagonist which lowered intraocular pressure in man, and timolol on endotoxin-induced-uveitis (EIU) in rats. For EIU, 8-week-old Lewis rats received an intravenous injection of 160 μg lipopolysaccharide (LPS) from Salmonella typhimurium. GLC756, timolol, or betamethasone, as positive control, were administered either topically (0·4, 0·5, and 0·1%, respectively, 16-times 20 μl eye drops during 48 hr) or systemically (1 mg kg −1 subcutaneously for 5 days). Protein content, released TNF-α, the number of cells as well as cells expressing TNF-α were determined in aqueous humor 48 hr after LPS-injection and served as parameters for inflammation. LPS induced an increase of protein content, infiltrating cells and cells expressing TNF-α in the aqueous humor. Topical and systemic administration of GLC756 and betamethasone, almost completely suppressed the increase of protein content and betamethasone in addition also suppressed the number of cells in aqueous humor. In conclusion, the almost complete suppression of LPS-induced protein increase in aqueous humor by GLC756 suggests an additional anti-inflammatory potential of dopaminergic compounds in glaucoma treatment. Timolol did not show any effect on EIU in rats.

Effects of Caffeic Acid Phenethyl Ester on Endotoxin-Induced Uveitis in Rats

Purpose: Caffeic acid phenethyl ester (CAPE) has antimicrobial, anti-inflammatory, antioxidant, immunomodulatory, and carcinostatic properties. In this study, the efficacy of CAPE in endotoxin-induced uveitis (EIU) in rats is investigated. Methods: EIU was induced by a footpad injection of lipopolysaccharide (LPS). In the treatment group, 10 μ mol/kg CAPE was injected intraperitoneally immediately after LPS injection. At 24 hr after LPS injection, the number of infiltrating cells, protein concentration, and levels of myeloperoxidase (MPO) in aqueous humor; malondialdehyde (MDA), MPO, and total antioxidant levels in serum were determined. Eyes were enucleated for histopathologic evaluation, and, counting inflammatory cells in iris-ciliary body (ICB), the efficacy of treatment was determined. Results: CAPE significantly suppressed LPS-induced increase in the number of inflammatory cells (p = 0.0001), protein concentration (p = 0.0001), and MPO levels (p = 0.0001) in aqueous humor as well as MDA (p = 0.001) and MPO (p = 0.0001) levels in serum. Histopathologic evaluation of ICB showed significant reduction in the inflammatory cell counts in the treatment group (p = 0.0001). Conclusions: CAPE was found efficient in suppressing inflammation and ocular tissue damage induced by LPS in rats.

Anti-inflammatory Effects of Aronia Extract on Rat Endotoxin-Induced Uveitis

Aronia crude extract (ACE) with high levels of polyphenol compounds has been reported to have antioxidative effects in vitro and in vivo. In this study, attention was focused on the antioxidant effect of ACE. The purpose of the present study was to investigate the effect of ACE on endotoxin-induced uveitis (EIU) in rats. In addition, the endotoxin-induced expression of the inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 proteins was investigated in a mouse macrophage cell line (RAW 264.7) treated with ACE in vitro, to clarify the anti-inflammatory effect. EIU was induced in male Lewis rats by a footpad injection of lipopolysaccharide (LPS). Immediately after the LPS inoculation, 1, 10, or 100 mg ACE or 10 mg prednisolone was injected intravenously. After 24 hours, the aqueous humor was collected from both eyes, and the number of infiltrating cells, protein concentration, nitric oxide (NO), prostaglandin (PG)-E2, and TNF-alpha levels in the aqueous humor were determined. RAW 264.7 cells treated with various concentrations of ACE were incubated with 10 mug/mL LPS for 24 hours. Levels of NO, PGE2, and TNF-alpha were determined by an enzyme-linked immunosorbent assay. The expression of iNOS and COX-2 proteins was analyzed by Western blot analysis. The number of inflammatory cells, the protein concentrations, and the levels of NO, PGE2, and TNF-alpha in the aqueous humor in the groups treated with ACE were significantly decreased in a dose-dependent manner. In addition, the anti-inflammatory effect of 100 mg ACE was as strong as that of 10 mg prednisolone. The anti-inflammatory action of ACE was stronger than that of either quercetin or anthocyanin administered alone. ACE also suppressed LPS-induced iNOS and COX-2 protein expressions in RAW 264.7 cells in vitro in a dose-dependent manner. The results suggest that ACE has a dose-dependent anti-ocular inflammatory effect that is due to the direct blocking of the expression of the iNOS and COX-2 enzymes and leads to the suppression of the production of NO, PGE2, and TNF-alpha.

Anti-inflammatory effects of alpha-melanocyte-stimulating hormone against rat endotoxin-induced uveitis and the time course of inflammatory agents in aqueous humor

Purpose: We examined the effects of the immunosuppressive neuropeptide alpha-melanocyte stimulating hormone (α-MSH) on rat endotoxin-induced uveitis, and to measure the expression of inflammatory cytokines and chemokines with and without the α-MSH treatment over the course of the disease. Methods: We injected Lewis rats once with Salmonella typhimurium lipopolysaccharide (LPS) to induce uveitis. The rats were given intravenous injections of 250, 500 or 1000 μg of α-MSH. The eyes were examined over the next 24 h for inflammation. Aqueous humor was collected 6, 12 and 24 h after endotoxin injections and the number of infiltrating cells were counted in anterior chamber. In addition, we assayed the concentration of protein, nitric oxide, TNF-α, IL-6, MCP-1 and MIP-2. Results: Rats injected with α-MSH showed a significant decrease in the number of infiltrating cells in anterior chamber. Moreover, α-MSH-treated rats with endotoxin-induced uveitis (EIU) showed significantly lower concentrations of protein, nitric oxide, proinflammatory cytokines and chemokines in their aqueous humor. Even the early stages of EIU were suppressed by the injection of α-MSH. Conclusions: Our results demonstrate that the immunosuppressive neuropeptide α-MSH inhibits the early induction events of endotoxin-induced inflammation in the eye; therefore, suppresses the subsequent infiltration of cells and intraocular production of inflammatory cytokines and chemokines in eyes. α-MSH has a possibility of being a therapeutic strategy for anterior uveitis.

Effect of human cationic antimicrobial protein 18 Peptide on endotoxin-induced uveitis in rats.

Human cationic antimicrobial protein 18 (hCAP18, 18 kDa) was originally identified in leukocytes on the basis of its antimicrobial activity. The peptide composed of the 27 C-terminal amino acids of hCAP18 (hCAP18(109-135)) binds lipopolysaccharide (LPS). The purpose of the present study was to investigate the effects of hCAP18 peptide on endotoxin-induced uveitis (EIU) in rats. EIU was induced by footpad injection of LPS. Each rat was injected intravenously with 1, 10, or 100 micro g hCAP18 peptide in 0.1 mL of PBS immediately after LPS injection in male Lewis rats. At 24 hours after LPS injection, enzyme-linked immunosorbent assay was performed to evaluate concentrations of protein, nitric oxide (NO), tumor necrosis factor (TNF)-alpha, prostaglandin (PG)-E2, interleukin (IL)-6, monocyte chemoattractant protein (MCP)-1 and macrophage inflammatory protein (MIP)-2 in aqueous humor. Also, EIU was evaluated by counting inflammatory cells in aqueous humor. hCAP18 peptide at 10 and 100 micro g significantly suppressed an LPS-induced increase in the number of inflammatory cells and the levels of protein, NO, TNF-alpha, PGE2, MCP-1, and MIP-2. The anti-inflammatory effect of 10 micro g hCAP18 peptide was as strong as that of 100 micro g hCAP18 peptide. Treatment with 1 micro g hCAP18 peptide did not suppress EIU, compared with the LPS group. The present results indicate that hCAP18 peptide suppresses development of EIU. A possible mechanism for the ocular anti-inflammatory effect of hCAP18 peptide is that it suppresses onset of LPS-triggered inflammatory reactions by binding directly to LPS.

Protective role of heme oxygenase-1 against endotoxin-induced uveitis in rats

Endotoxin-induced uveitis (EIU) is an animal model of acute ocular inflammation. Cytokines, chemokines, and nitric oxide (NO) have been reported to play important roles. We have determined whether heme oxygenase (HO)-1, a heat shock protein, can suppress EIU. EIU was induced by a footpad injection of lipopolysaccharide (LPS) in male Lewis rats. Hemin, an inducer of HO-1, was injected intraperitoneally 1 hr prior to the LPS injection. HO-1 and HO-2 expression in the iris-ciliary body (ICB) was studied by real time PCR and Western blot analysis. The number of infiltrating cells and the protein concentration in the aqueous humor (AqH) were evaluated by microscopy and by protein assay. The expression of inducible nitric oxide synthase (iNOS), interleukin (IL)-6, tumor necrosis factor (TNF)-α, and IL-1β mRNA was determined by real time PCR. The concentration of nitrate plus nitrite, and levels of IL-6 and TNF-α in the AqH were also evaluated by Griess reagents and by enzyme-linked immunosorbent assay, respectively. The expression of HO-1 mRNA and protein, induced by LPS, was enhanced significantly by pre-injection of hemin ( P<0·001). HO-2 was constitutively present in the ICB and was not up-regulated by LPS or by hemin. The number of infiltrating cells and the concentration of protein in the AqH was significantly elevated by LPS injection, and hemin significantly reduced the number of cells and the protein concentration ( P<0·0001). The expression of iNOS and IL-6 mRNA and protein were down-regulated by hemin ( P<0·001). Hemin is effective in inducing HO-1 and in reducing the ocular inflammation induced by LPS probably by down-regulating NO and pro-inflammatory cytokine expression.

Effects of cloricromene, a coumarin derivative, on endotoxin-induced uveitis in Lewis rats.

To investigate the effects of cloricromene, a coumarin derivative, in rats subjected to endotoxin-induced uveitis (EIU). Endotoxin uveitis was induced in male Lewis rats by a single footpad injection of 200 microg lipopolysaccharide (LPS). Cloricromene was topically applied to the rat eye twice at 1 hour before and 7 hours after injection of LPS. A separate group of animals was treated with vehicle. Rats were killed 16 hours after injection and the eyes enucleated for histologic examination and immunohistochemical analysis. The effect of treatment was also evaluated by slit lamp examination, by the number of intraocular inflammatory cells on histologic sections, and by measuring the protein and TNFalpha levels in the aqueous humor. Nitrite and nitrate production was also measured in the aqueous humor. The histopathology of the iris-ciliary body included inflammatory cell infiltration and nuclear modification of vessel endothelial cells. Cloricromene treatment reduced the inflammatory cell infiltration and improved histologic status of the ocular tissue. Immunohistochemical analysis for P-selectin, intracellular adhesion molecule (ICAM)-1, nitrotyrosine, and poly(ADP-ribose) synthetase (PARS) revealed a positive staining in inflammatory cell infiltration from LPS-treated rats. The degree of staining for P-selectin, ICAM-1, nitrotyrosine, and PARS was markedly reduced in tissue sections obtained from LPS-recipient rats that had received cloricromene. Cloricromene strongly inhibited cell infiltration, protein exudation, TNFalpha production, and nitrite-nitrate formation. This study provides the first evidence that cloricromene, a coumarin derivative, attenuates the degree of inflammation and tissue damage associated with EIU in rats.

Suppressive Effects of Histamine H1 Receptor Antagonist Diphenhydramine on the Leukocyte Infiltration during Endotoxin-induced Uveitis

Histamine has been shown to play an important role in the step of leukocyte rolling, the initial step to leukocyte infiltration into an inflamed region. We investigated the roles of histamine in the leukocyte recruitment during endotoxin-induced uveitis (EIU) in vivo using acridine orange digital fluorography. An injection of histamine into the vitreous cavity of a Lewis rat induced leukocyte rolling along the major retinal veins. In other experiments, EIU was induced in Lewis rats by footpad injection of lipopolysaccharide (LPS). Leukocyte rolling was also observed in the retinal veins of EIU rats. To block the histamine H1 receptor, diphenhydramine (DPH) was administered intraperitoneally 15min before the LPS injection. DPH significantly inhibited leukocyte rolling along the major retinal veins of EIU rats, suppressing leukocyte infiltration into the vitreous cavity. The vasodilation in EIU was also significantly suppressed with DPH. Moreover, leukocyte infiltration into aqueous humor was significantly suppressed in DPH-treated rats. Although the inhibitory effects of DPH was less obvious at later time points, addition of DPH every 12hr showed prolonged anti-inflammatory effects up to 48hr after LPS injection. In contrast, protein leakage into the aqueous humor was not suppressed as much as leukocyte infiltration with DPH. These results suggest that histamine would play a pivotal role in leukocyte recruitment during EIU in rats. Blocking the histamine H1 receptor might help to prevent or minimize leukocyte infiltration in uveitis.

The effects of betamethasone derivatives on endotoxin-induced uveitis in guinea pigs.

We reported previously that the betamethasone derivative betamethasone dipropionate behaves as an anti-glucocorticoid in rat endotoxin-induced uveitis (EIU). In the present study, we produced EIU in guinea pigs and investigated the effects of betamethasone dipropionate on the EIU. Male Hartley guinea pigs were used. Glucocorticoids were instilled into the eye. To elicit EIU, lipopolysaccharide (LPS) was injected into the anterior chamber of the eye. Cell numbers in the aqueous humor after LPS injection were determined by flow cytometry. Prostaglandin E2 (PGE2) production after LPS injection into the anterior chamber was also examined. Intracameral injection of LPS (1 microgram/eye) induced cell infiltration into the anterior chamber and PGE2 production. Betamethasone dipropionate inhibited cell infiltration and PGE2 production more strongly than betamethasone. These results suggest that betamethasone dipropionate is a potent glucocorticoid in guinea pigs. Structure-activity relationships of glucocorticoids in the guinea pig EIL model may differ from those in the rat EIU model.

The Effects of Betamethasone Derivatives on Endotoxin-induced Uveitis in Rats

The anti-inflammatory effects of betamethasone and its derivatives (betamethasone 21-phosphate, betamethasone 21-acetate, betamethasone 17-valerate, clobetasol 17-propionate and betamethasone dipropionate) on endotoxin-induced uveitis (EIU) in rats was investigated. Among the compounds examined, betamethasone, betamethasone 21-phosphate, betamethasone 21-acetate and clobetasol 17-propionate strongly inhibited cell infiltration into the aqueous humor in the EIU by instillation into the eye in a dose-dependent manner (0.01–1.0%) and by systemic administration (1 mg kg−1). On the other hand, betamethasone 17-valerate and betamethasone dipropionate showed only weak inhibitory effects or enhancment of cell infiltration by instillation into the eye (0.01–1.0%) and by systemic administration (1 mg kg−1). Combined systemic administration of betamethasone dipropionate and betamethasone reduced the inhibitory effect of betamethasone on cell infiltration and gene expression of IL-1β. In anin vitrointerleukin-8 (IL-8) release assay, betamethasone showed stronger inhibition of the IL-8 release from rat peritoneal exudate cells (PEC) than betamethasone dipropionate, and simultaneous addition of betamethasone dipropionate with betamethasone reduced the inhibitory effect of the latter. These results suggest that the betamethasone derivative betamethasone dipropionate might behave as an anti-glucocorticoid in rats.

Differential tumor necrosis factor and nitric oxide production in retinal Müller glial cells from C3H/HeN and C3H/HeJ mice

Tumor necrosis factor (TNF) and nitric oxide (NO) have been shown to play a role in the pathogenesis of endotoxin-induced uveitis (EIU) in rats. Susceptibility to develop EIU in vivo is correlated with the extent of TNF production by retinal Müller glial cells (RMG). Moreover, RMG cells from the susceptible Lewis rat strain synthesize high amounts of nitrite under in vitro stimulation. Variations in susceptibility to endotoxin are observed among mice strains: C3H/HeN mice are known to be susceptible to develop EIU while C3H/HeJ are refractory. We show here that treatment of RMG cells from both strains with LPS+IFN-γ does not induce TNF synthesis in culture supernatants but produces high amounts of NO only in the supernatants from activated C3H/HeN RMG cells. The addition of TNF in the culture medium containing LPS/IFN-γ further increases nitrite production in C3H/HeN RMG cells and allows the synthesis of low levels of nitrite in C3H/HeJ RMG cells. Addition of a specific NO synthase inhibitor, NG-monomethyl-L-arginine (L-NMMA), blocks NO release. We have previously shown that intraperitoneal injections of the NO synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME) which inhibited nitrite and TNF release in the ocular media reduced EIU in rat. We conclude here that the in vivo susceptibility to develop EIU in mice is correlated with the extent of in vitro nitrite production by RMG cells confirming the implication of NO in the induction of ocular inflammation. The low level of retinal inflammation observed during EIU in C3H/HeN mice compared to rats could be related to the absence of TNF production by RMG cells.

Effects of Antiflammins on Endotoxin-Induced Uveitis in Rats

Antiflammins are phospholipase A2-inhibitory, anti-inflammatory, synthetic oligopeptides derived from the region of the highest amino-acid sequence similarity between uteroglobin and lipocortin I. Endotoxin-induced uveitis is a model for anterior uveitis of the eye, which has been suggested to be induced through phospholipase A2 activation. In a preliminary report we demonstrated that topical administration of antiflammins could inhibit endotoxin-induced uveitis in rats. In this study, the anti-inflammatory effects of antiflammins were compared with those of corticosteroids on endotoxin-induced uveitis as measured by phospholipase A2 enzyme activity, inflammatory cell counts in the aqueous humor, and histopathologic features. Antiflammins are as effective as corticosteroids in their ability to suppress endotoxin-induced uveitis.

Endotoxin-induced uveitis in rats as a model for human disease.

Acute anterior uveitis is a relatively common disease of uncertain aetiology. Its association with a wide variety of systemic disorders including ankylosing spondylitis, Reiter's syndrome, Behcet's disease, juvenile rheumatoid arthritis, psoriatic arthritis, inflammatory bowel disease and sarcoidosis and the prevalence of the HLA antigen B27 (ref. 1) in cases without associated disease have been noted but not explained. In general, animal models for uveitis have not clarified the mechanism of human disease. Most require direct intravitreal injection2 or repeated immunizations with retinal or uveal antigens3. Uveitis does occur in adjuvant arthritis, a syndrome that can be produced in rats by the systemic injection of pepti-doglycan from the cell wall of a variety of Gram-positive bacteria4. The disease, which was initially described following the injection of mycobacteria in mineral oil, has many similarities to Reiter's syndrome5, including the development of eye pathology in as many as 40% of the animals6. As Reiter's syndrome is associated with enteric Gram-negative infections such as Shigella, Salmonella and Yersinia, we sought to produce an arthritis in rats by injecting killed Gram-negative bacteria. Although we have not observed clinical arthritis in these animals, careful histological study has shown the near-universal appearance of uveitis. The studies described below indicate that the eye disease is due to a portion of the bacterial cell wall known as endotoxin or lipopolysaccharide (LPS).