Cyclooxygenase-2 expression in the eyes of cats with and without uveitis

OBJECTIVE To characterize the distribution and intensity of cyclooxygenase (COX)-2 expression in the eyes of cats with and without uveitis and to determine whether COX-2 expression is correlated with severity of inflammation. SAMPLES Archived ocular tissue specimens from 51 cats with and 10 cats without ocular disease. PROCEDURES Specimens from only 1 eye were evaluated for each cat. Specimens were stained with H&E stain or immunohistochemical stain for detection of COX-2 and reviewed. For each eye, the type, severity, and distribution of inflammation and the distribution and intensity of COX-2 expression were determined for the uvea and other ocular tissues. Correlation between COX-2 expression and inflammation severity was also assessed. RESULTS COX-2 was not expressed in any nondiseased eye. Of the 51 diseased eyes, 20 had histologic evidence of lymphocytic-plasmacytic uveitis, 13 had neutrophilic uveitis, 11 had diffuse iris melanoma with uveitis, and 7 had diffuse iris melanoma without uveitis. Of the 44 eyes with uveitis, COX-2 was detected in the uvea of 16, including 11 eyes with lymphocytic-plasmacytic uveitis, 4 with neutrophilic uveitis, and 1 with diffuse iris melanoma-induced uveitis. Inflammation was severe, moderate, or mild in 10, 5, and 1 of those eyes, respectively. Cyclooxygenase-2 was detected in the cornea of 21 eyes with uveitis and 1 eye with diffuse iris melanoma without uveitis. Uveitis severity was positively correlated with COX-2 expression in both the uvea and cornea. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that COX-2 is an inflammatory mediator in feline uveitis but not diffuse iris melanoma.

CD73 Expressed on γδ T Cells Shapes Their Regulatory Effect in Experimental Autoimmune Uveitis

γδ T cells can either enhance or inhibit an adaptive immune response, but the mechanisms involved are not fully understood. Given that CD73 is the main enzyme responsible for conversion of AMP into the immunosuppressive molecule adenosine, we investigated its role in the regulatory function of γδ T cells in experimental autoimmune uveitis (EAU). We found that γδ T cells expressed different amounts of CD73 during the different stages of EAU and that low CD73 expression on γδ T cells correlated with enhanced Th17 response-promoting activity. Functional comparison of CD73-deficient and wild-type B6 (CD73+/+) mice showed that failure to express CD73 decreased both the enhancing and suppressive effects of γδ T cells on EAU. We also demonstrated that γδ T cells expressed different amounts of CD73 when activated by different pathways, which enabled them to either enhance or inhibit an adaptive immune response. Our results demonstrate that targeting CD73 expression on γδ T cells may allow us to manipulate their pro- or anti-inflammatory effect on Th17 responses.

Association between polymorphism of the vitamin D metabolism gene CYP27B1 and HLA-B27-associated uveitis. Is a state of relative immunodeficiency pathogenic in HLA B27-positive uveitis?

Objective

Polymorphisms of the vitamin D metabolism gene CYP27B1 showed associations with multiple autoimmune diseases. The aim of this study was to investigate a possible association between the rs703842 A>G polymorphism of the CYP27B1 gene and HLA-B27-associated uveitis.

Design

One hundred fifty-nine patients with HLA-B27-associated uveitis, 138 HLA-B27-negative controls and 100 HLA-B27-positive controls were recruited for this retrospective case-control study. Main outcome parameters were genotype distribution and allelic frequencies determined by polymerase chain reaction.

Results

Carriers of the rs703842G allele were found significantly more often in patients with HLA-B27-associated uveitis than in HLA-B27-positive controls (p = 0.03). Between patients and HLA-B27-negative controls no significant difference in the genotype distribution of the rs703842 A>G polymorphism was found (p = 0.97).

Conclusions

Our data suggest that the rs703842 A>G polymorphism may play a role in HLA-B27-associated uveitis.

Contribution of T cell subset analysis in induced sputum in diagnosing ocular sarcoidosis

OBJECTIVE

The aim of this study was to establish a correlation between the diagnosis of ocular sarcoidosis and the presence of an elevated CD4/CD8 ratio in the induced sputum(IS) of patients with uveitis and no other systemic symptoms.

METHODS

This retrospective chart review study included all newly diagnosed uveitis patients treated between 1998-2006. IS examinations and determination of angiotensin-converting enzyme (ACE) levels were carried out. A CD4/CD8 ratio > 2.5 and an ACE level > 145 Cd/ml/min were considered abnormal. The etiology of uveitis was retrieved from the medical records.

RESULTS

Twenty males and 26 females (mean age 47 +/- 16.1 years) were enrolled. The CD4/CD8 ratio was elevated in 26 (56.5%) patients, and five (10.9%) were diagnosed as having sarcoidosis by the end of follow-up. The sensitivity and specificity of the T lymphocytes CD4/CD8 ratio in diagnosing sarcoidosis were 100% and 48.8%, respectively. CD4/CD8 ratios were not significantly different between the sarcoid and non-sarcoid groups (p > 0.05), but the former tended to have higher levels (p = 0.0991). The mean ACE level of the sarcoid patients was significantly higher than that of the non-sarcoid patients (p < 0.001).

CONCLUSION

CD4/CD8 lymphocytes ratios obtained by IS were sensitive in uveitis patients with concomitant sarcoidosis, suggesting that analysis of T cells subsets in IS may rule out an etiology of sarcoidosis in newly diagnosed uveitis patients.

Aldose reductase deficiency protects from autoimmune- and endotoxin-induced uveitis in mice

PURPOSE

To investigate the effect of aldose reductase (AR) deficiency in protecting the chronic experimental autoimmune (EAU) and acute endotoxin-induced uveitis (EIU) in c57BL/6 mice.

METHODS

The WT and AR-null (ARKO) mice were immunized with human interphotoreceptor retinoid-binding peptide (hIRPB-1-20), to induce EAU, or were injected subcutaneously with lipopolysaccharide (LPS; 100 μg) to induce EIU. The mice were killed on day 21 for EAU and at 24 hours for EIU, when the disease was at its peak, and the eyes were immediately enucleated for histologic and biochemical studies. Spleen-derived T-lymphocytes were used to study the antigen-specific immune response in vitro and in vivo.

RESULTS

In WT-EAU mice, severe damage to the retinal wall, especially to the photoreceptor layer was observed, corresponding to a pathologic score of ∼2, which was significantly prevented in the ARKO or AR inhibitor-treated mice. The levels of cytokines and chemokines increased markedly in the whole-eye homogenates of WT-EAU mice, but not in ARKO-EAU mice. Further, expression of inflammatory marker proteins such as inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2, tumor necrosis factor (TNF)-α, and vascular cell adhesion molecule (VCAM)-1 was increased in the WT-EIU mouse eyes but not in the ARKO-EIU eyes. The T cells proliferated vigorously when exposed to the hIRPB antigen in vitro and secreted various cytokines and chemokines, which were significantly inhibited in the T cells isolated from the ARKO mice.

CONCLUSIONS

These findings suggest that AR-deficiency/inhibition protects against acute as well as chronic forms of ocular inflammatory complications such as uveitis.

Understanding the role of aldose reductase in ocular inflammation

Aldose reductase, although identified initially as a glucose-reducing enzyme via polyol pathway, is believed to be an important component of antioxidant defense system as well as a key mediator of oxidative stress-induced molecular signaling. The dual role played by AR has made it a very important enzyme for the regulation of not only the cellular redox state by detoxifying the reactive lipid-aldehydes generated by lipid peroxidation which is crucial in the cellular homeostasis, but also in the regulation of molecular signaling cascade that may regulate oxidative stress-induced cytotoxic events. Search for the new molecular targets to restrain the oxidative stress-induced inflammation has resulted in the identification of AR as an unanticipated mediator of oxidative stress-induced signaling. Although, in last one decade or so AR has been implicated in various inflammation-related diseases conditions ranging from diabetes, sepsis, cancer, cardiovascular and ocular inflammation, however, a critical evaluation of the clinical efficacy of AR inhibitors awaits a better understanding of the role of AR in regulating inflammation, especially in ocular inflammation.

Lack of inducible nitric oxide synthases attenuates leukocyte-endothelial cell interactions in retinal microcirculation

Aim:

To investigate the effect of inducible nitric oxide synthases (iNOS) on inflammatory reactions during endotoxin-induced uveitis (EIU) in mice by studying leukocyte–endothelial cell interactions.

Methods:

EIU was produced in immunosuppressed iNOS^−/− mice and C57BL/6 (normal) mice by footpad injection of lipopolysaccharide. Leukocytes were labelled with acridine orange. Leukocyte rolling in the retinal microcirculation was evaluated in vivo with acridine orange digital fluorography. The number of migrated leukocytes was counted in flat-mounted retina.

Results:

Both leukocyte rolling and migration peaked at 48 h after lipopolysaccharide injection. The maximal numbers of rolling leukocytes in the immunosuppressed iNOS^−/− mouse retina decreased by 98.2% (p<0.001) compared with that in the normal mouse retina at 48 h after lipopolysaccharide injection. In addition, the maximal numbers of migrated leukocytes in the immunosuppressed iNOS^−/− mouse retina decreased by 74.0% (p<0.001) compared with that in the normal mouse retina at 24 h after lipopolysaccharide injection. Furthermore, the diameters of major retinal veins of the immunosuppressed iNOS^−/− group were smaller at both 24 and 48 h after lipopolysaccharide injection than were those of the normal group (p<0.001, respectively).

Conclusions:

A lack of iNOS suppresses leukocyte–endothelial cell interactions in the retinas of mice with EIU. This suggests that iNOS may play a role in the management of patients with uveitis and other inflammatory conditions.

Levels and Activation of Matrix Metalloproteinases in Aqueous Humor Are Elevated in Uveitis-Related Secondary Glaucoma

PURPOSE

To measure the levels of matrix metalloproteinase (MMP)-2 and tissue inhibitors of metalloproteinases (TIMP)-2 and to study the expression pattern and molecular forms of MMP-2, 8, 9, 13, and 14 and TIMP-1 and 2 in aqueous humor samples in cases of uveitis-related secondary glaucoma (USG) with a history of up to 20 years by comparison with primary open-angle glaucoma (POAG) and cataracts.

METHODS

33 aqueous humor samples were collected during intraocular surgery. MMP-2 and TIMP-2 levels were analyzed by enzyme-linked immunosorbent assay. Molecular forms and activation degrees of MMPs and TIMPs were analyzed by Western immunoblotting and zymography. The results were related to the clinical data.

RESULTS

Enzyme-linked immunosorbent assay measurements of both MMP-2 and TIMP-2 were statistically significantly increased in the USG samples relative to POAG and cataracts (P=0.002). In Western blotting all the MMPs showed increased expression and conversion to their active forms in USG, whereas in the POAG and cataract samples MMPs were found mainly in their latent forms. MMP-8, 9, 13, and 14 showed statistically significantly elevated expression in USG relative to POAG and cataracts on densitometric scanning of Western blots. On zymography, MMP-2 and 9 activation was significantly enhanced in USG compared with POAG and cataracts.

CONCLUSIONS

Increased expression of MMPs and their conversion to active forms is characteristics of the aqueous humor in USG, even with a very long history. This emphasizes the fact that increased MMP expression reflects inflammatory disease activity and is probably associated with the development of USG and its complications. Although intraocular pressure is elevated in both glaucoma types, MMP expression in POAG more closely resembles that in cataracts, and therefore the role of MMPs in USG differs very markedly from that in POAG.

Phospholipase D1 is up-regulated in the retina of Lewis rats with experimental autoimmune uveoretinitis

To investigate whether phospholipase D1 (PLD1) is involved in autoimmune damage to the eyes, we used Western blotting and immunohistochemistry to examine the expression and distribution of PLD1 in the retinas of Lewis rats with experimental autoimmune uveoretinitis (EAU). Western blot analysis showed that the level of expression of PLD1 was significantly increased in EAU-affected retinas compared to that of control. Immunohistochemical analysis showed that ganglion cells and Muller cells, which express PLD1 weakly in the normal retina, showed increased expression of PLD1 in EAU-affected retinas; some ED1-immunopositive cells were also immunopositive for PLD1 in lesions at post-immunization days 14 and 21. These results suggest that the increased expression of PLD1 in inflammatory cells exacerbates an autoimmune response in EAU, while its expression in ganglion cells limits cell loss by activation of survival factors in eyes with autoimmune injury.

Inhibition of MMP-dependent chemotaxis and amelioration of experimental autoimmune uveitis with a selective metalloproteinase-2 and -9 inhibitor

The chemotaxis of inflammatory cells depends on proteolytic disruption of extracellular matrix components. The metalloproteinases (MMP)-2 and -9 enable T-lymphocytes to pass through basement membranes. Selective inhibition of only MMP-2 and -9 almost completely abolished the ability of lymphocytes to digest collagen. The chemotaxis of lymphocytes was reduced 40%. In our in-vivo model of experimental autoimmune uveitis (EAU), 46% of the animals in the treated group remained disease-free, whereas all animals in the control group developed EAU. The mean activity of the disease was also statistically significantly reduced. The data suggest that selective MMP-2 and -9 inhibition might be a treatment option.

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)-alpha, and IL-1beta mRNA was determined by real time PCR. The concentration of nitrate plus nitrite, and levels of IL-6 and TNF-alpha 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.

Pertussis toxin enhances Th1 responses by stimulation of dendritic cells

Pertussis toxin (PTX) has been widely used as an adjuvant to induce Th1-mediated organ-specific autoimmune diseases in animal models. However, the cellular and molecular mechanisms remain to be defined. In this study, we showed that dendritic cells (DC) stimulated with PTX (PTX-DC) were able to substitute for PTX to promote experimental autoimmune uveitis (EAU). EAU induced by PTX-DC revealed a typical Th1 response, characterized by high uveitogenic retinal Ag interphotoreceptor retinoid-binding protein (IRBP)-specific IFN-gamma and IL-12 production in the draining lymph nodes, as well as increased levels of anti-IRBP IgG2a and decreased levels of anti-IRBP IgG1 in the serum of IRBP-immunized mice. Furthermore, PTX-DC preferentially induced T cells to produce the Th1 cytokine, IFN-gamma. After being stimulated with PTX, DC exhibited up-regulation of MHC class II, CD80, CD86, CD40, and DEC205. PTX-DC had also increased allostimulatory capacity and IL-12 and TNF-alpha production. Serum IL-12 was increased in naive mice that received PTX-DC i.p. In addition, PTX activated extracellular signal-regulated kinase in DC. Following the inhibition of extracellular signal-regulated kinase signaling, the maturation of PTX-DC was reduced. Subsequently, the ability of PTX-DC to promote IFN-gamma production by T cells in vitro and to induce EAU in vivo was blocked. The results suggest that PTX might exert an adjuvant effect on DC to promote their maturation and the production of proinflammatory cytokines, thereby eliciting a Th1 response.

[Effect of bacteriophage on the lipid peroxidation process and antioxidant protective enzymes in experimental uveitis]

Experimental uveitis features distinct hyperlipoperoxidation in damaged eye tissues, blood serum and the liver. The activity of antioxidant defense (AOD) enzymes decreases in tissues and blood of experimental animals whereas catalase compensatorily activates in hepatic tissue. Experimental therapy of uveitis with gentamycin and bacteriophage results in reducing hyperlipoperoxidation, increased activity of AOD enzymes but no complete normalization is observed. This manifested in preservation of inflammations to a certain degree.

Down-regulation of NOSII gene expression by iontophoresis of anti-sense oligonucleotide in endotoxin-induced uveitis

Transcorneoscleral iontophoresis was used to enhance ocular penetration of a 21-bp NH(2) protected anti-NOSII oligonucleotides (ODNs) (fluorescein or infrared-41 labeled) in Lewis rats. Both histochemical localization and acrylamide sequencing gels were used. To evaluate the potential to down-regulate NOSII expression in the rat model of endotoxin-induced uveitis (EIU), anti-sense NOSII ODN, scrambled ODN or saline were iontophorezed into these animals' eyes. Iontophoresis facilitated the penetration of intact ODNs into the intraocular tissues of the rat eye and only the eyes receiving ODNs and electrical current demonstrated intact ODNs within the ocular tissues of both segments of the eye. Iontophoresis of anti-NOSII ODN significantly down-regulated the expression of NOSII expression in iris/ciliary body compared to the saline or scrambled ODN treated eyes. Nitrite production was also significantly reduced in the anti-NOSII applied eyes compared to those treated with saline. Using this system, intraocular delivery of ODNs can be significantly enhanced increasing the potential for successful gene therapy for human eye diseases.

Induced sputum for identifying sarcoidosis in patients with uveitis

OBJECTIVE

To evaluate the value of the induced sputum technique in diagnosing sarcoidosis as the cause of uveitis.

DESIGN

Comparative case series.

PARTICIPANTS

Seventeen patients with uveitis. Two control groups were used. The first included 10 patients with sarcoid without uveitis; the second included 5 healthy volunteers.

TESTING

Sputum was induced by a 20-minute inhalation of 3.5% saline using an ultrasonic nebulizer. Samples were studied by differential counts of 200 cells on cytopreps stained by Giemsa. T lymphocyte subset analyses were done by fluorescence-activated cell sorter using the monoclonal antibodies CD4 (T helper cells) and CD8 (T suppressor-cytotoxic cells). Angiotensin-converting enzyme (ACE) serum levels were obtained.

MAIN OUTCOME MEASURES

A CD4/CD8 ratio >2.5 and an ACE level >145 microl/ml/minute were considered to be abnormal.

RESULTS

The difference in the CD4/CD8 ratios in the induced sputum examination between the group of patients with an elevated ACE level and the group of patients with an ACE level within normal limits was statistically significant (P = 0.0001).

CONCLUSIONS

The induced sputum examination showed increased CD4/CD8 ratios in patients with uveitis who also had elevated ACE levels, suggesting the presence of sarcoidosis.

Extracellular signal-regulated kinase activation predominantly in Müller cells of retina with endotoxin-induced uveitis

PURPOSE

To evaluate the consequences of mitogen-activated protein kinase (MAPK)-mediated signaling in retinas with endotoxin-induced uveitis (EIU).

METHODS

EIU was induced with footpad inoculation of lipopolysaccharide (LPS). To identify the expression and activity of extracellular signal-regulated kinase (ERK), c-Jun NH2-terminal kinase (JNK), and p38, Western blot analysis and immunohistochemistry (IHC) were performed using antibodies against these kinases and phosphorylated forms. To evaluate the ERK mRNA expression level, semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) was performed. To identify cell species that express phosphorylated (p)-ERK, simultaneous demonstration of p-ERK and glial fibrillary acidic protein (GFAP) was performed with combined IHC and in situ hybridization. Dexamethasone (Dex) was used to reduce the LPS-induced inflammatory stimulus, and changes in p-ERK expression were evaluated by Western blot analysis after treatment.

RESULTS

Only p-ERK among the phosphorylated MAPKs increased after LPS stimulation, according to Western blot analysis. p-ERK increased after LPS injection, whereas both the Western blot and RT-PCR studies showed no apparent changes in ERK-1 and -2 expression. IHC revealed that strong p-ERK-positive staining initially appeared in the Müller cell bodies. Thereafter p-ERK immunostaining was also observed transiently in the radial processes of the Müller cells. The double-labeling study revealed that almost all Müller cells were positive for GFAP and p-ERK. Dex treatment substantially reduced expression of p-ERK, beginning 12 hours after treatment.

CONCLUSIONS

The present study suggests that LPS stimulation activates ERK in Müller cells, whereas the total amount of ERK is unchanged. Because the LPS-induced p-ERK level was reduced by Dex treatment, its expression seems to be associated with ocular inflammatory stimulus. Because the inflammatory stimulus elicited in EIU upregulated ERK activity in Müller cells, activated Müller cells may play a crucial role in protecting retinal cells from such inflammation.

Nitration of manganese superoxide dismutase during ocular inflammation

Reactive nitrogen species, in particular, peroxynitrite (ONOO(-)) have been proposed to play an important role in the pathogenesis of endotoxin-induced uveitis (EIU). Tyrosine nitration by ONOO(-) has been shown in other model systems to inhibit the activity of the superoxide anion quenching enyzme, manganese superoxide dismutase (MnSOD), perhaps contributing to progression of disease. In this study, it is confirmed through immunoanalysis that nitrated proteins are produced during EIU, and furthermore, that MnSOD is a target of nitration during the inflammatory response. In addition, through microsequencing analyses, nitrated albumin--apparent in both control and EIU eyes--was identified. Positive immunostaining of nitrated proteins was seen in the ciliary epithelium, inflammatory cells, and protein exudate of eyes from rats injected with endotoxin. Incubation of nitrotyrosine immunoprecipitates from the iris and ciliary body (ICB) with a polyclonal antibody against MnSOD revealed that nitrated MnSOD was present only in the ICB of EIU rats. When the total activity of the enzyme was examined, it was observed that despite the presence of nitrated MnSOD, activity was increased relative to control. Analysis of MnSOD mRNA and protein from the ICB of both groups demonstrated an increase in mRNA expression and consequently a three- to five-fold increase in MnSOD protein in EIU rats as compared to control rats. Further examination of MnSOD protein expression through immunohistochemistry noted enhanced immunostaining in the ciliary epithelium of eyes of EIU rats. Additional investigation of a 70 kDa band apparent in nitrotyrosine immunoprecipitates from the ICB of control and EIU rats revealed that the plasma protein albumin is nitrated as well. This protein is present as a result of the breakdown of the blood-aqueous barrier during inflammation. In summary, two endogenous nitration targets, albumin and MnSOD, were identified. Nitrated MnSOD appears to be specifically targeted to the ICB during inflammation, underscoring the importance of the interface in EIU. Furthermore, the expression and activity of the enzyme is increased in the ICB during EIU, perhaps regulating reactive nitrogen species produced within the cells. This study implicates ONOO(-) in the pathogenesis of EIU and imparts the putative role MnSOD plays in disease resolution.

Neutrophil accumulation correlates with type IV collagenase/gelatinase activity in endotoxin induced uveitis

BACKGROUND/AIM

Anterior uveitis is a common inflammatory ocular disease characterised by protein accumulation and leucocyte infiltration in the anterior chamber. The aim of this study was to determine the expression of gelatinases in the aqueous humour (AH) and uvea in an animal model of endotoxin induced uveitis (EIU).

METHODS

EIU was established in Lewis rats following an intraperitoneal injection of lipopolysaccharide (LPS). AH and ocular tissue were obtained from control animals and those with EIU over a 1 week time course and the samples analysed immunohistochemically and by gelatin zymography.

RESULTS

Matrix metalloproteinase (MMP) 2 and 9 levels were elevated in rat AH over a 1 week time course. MMP-2 and MMP-9 levels peaked at the time of maximum uveal inflammation, before returning to baseline levels as the inflammation subsided. MMP-9 was detected in the latent and functionally active form. Total protein extracted from inflamed rat uveal tissue displayed no significant gelatinolytic modulation throughout the time course of EIU. Anterior chamber neutrophils and ciliary body epithelial cells were the most abundant source of the gelatinases.

CONCLUSION

This study has revealed a correlation between infiltrating neutrophils and the presence of elevated gelatinases in EIU. The results suggest that these proteolytically active enzymes may be important mediators of the inflammatory response and contribute to matrix remodelling observed in uveitis. Furthermore, the excess production of MMPs may be a mechanism by which leucocytes, such as neutrophils, gain access to uveal tissue and AH. Therapeutic strategies aimed at reducing MMP activity may be of some benefit in the treatment of uveitis.

Expression of serine protease inhibitor 3 in ocular tissues in endotoxin-induced uveitis in rat

PURPOSE

To ascribe the serine protease inhibitor 3 (SPI-3) as an ocular acute inflammatory molecule and to clarify its producing cells in an endotoxin-induced uveitis (EIU) model.

METHODS

Male Wistar rats were injected with lipopolysaccharide (LPS), and the expression of SPI-3 mRNA in the ocular tissues was examined by in situ hybridization (ISH) and Northern blot analysis. A combination of ISH and immunohistochemistry (IHC) were performed to prove the colocalization of SPI-3 mRNA and either glial fibrillary acidic protein (GFAP) or OX-42. The expression of phosphorylated STAT3 (pSTAT3) was demonstrated by IHC and Western blot after LPS injection. The colocalization of SPI-3 mRNA and pSTAT3 was finally examined by the double labeling of ISH and IHC.

RESULTS

After LPS injection, the expression of SPI-3 mRNA in ocular tissues was quickly upregulated and reached a peak between 12 and 24 hours after injection. An intense mRNA signal was observed in epithelial cells of the iris and ciliary body and the innermost retinal layer. In the retina, SPI-3 mRNA was colocalized with GFAP, demonstrating that the cells expressing SPI-3 mRNA were astrocytes. After LPS treatment, SPI-3 mRNA and pSTAT3 were colocalized in retinal astrocytes, and pSTAT3 expression appeared slightly earlier than that of SPI-3 mRNA.

CONCLUSIONS

Ocular inflammation induced the transient expression of SPI-3 mRNA in retinal astrocytes and epithelial cells in the iris and ciliary body, particularly during early phase of the inflammation. Simultaneously, the activation of STAT3 (phosphorylation of STAT3) occurred slightly earlier in astrocytes. This supports the previous in vitro results that SPI-3 expression is induced in a STAT3-mediated manner. SPI-3 may have some crucial roles in preventing some degenerative proteolysis, which is induced by inflammatory stimuli.

Pertussis toxin inhibits induction of tissue-specific autoimmune disease by disrupting G protein-coupled signals

Pertussis toxin (PTX) has been used for many years as an adjuvant that promotes development of tissue-specific experimental autoimmune diseases such as experimental autoimmune encephalomyelitis, experimental autoimmune uveitis (EAU), and others. Enhancement of vascular permeability and of Th1 responses have been implicated in this effect. Here we report a surprising observation that, in a primed system, PTX can completely block the development of EAU. Disease was induced in B10.RIII mice by adoptive transfer of uveitogenic T cells, or by immunization with a uveitogenic peptide. A single injection of PTX concurrently with infusion of the uveitogenic T cells, or two injections 7 and 10 days after active immunization, completely blocked development of EAU. EAU also was prevented by a 1-h incubation in vitro of the uveitogenic T cells with PTX before infusing them into recipients. Uveitogenic T cells treated with PTX in vitro and lymphoid cells from mice treated with PTX in vivo failed to migrate to chemokines in a standard chemotaxis assay. Neither the isolated B-oligomer subunit of PTX that lacks ADP ribosyltransferase activity nor the related cholera toxin that ADP-ribosylates G(s) (but not G(i)) proteins blocked EAU induction or migration to chemokines. We conclude that PTX present at the time of cell migration to the target organ prevents EAU, and propose that it does so at least in part by disrupting signaling through G(i) protein-coupled receptors. Thus, the net effect of PTX on autoimmune disease would represent an integration of enhancing and inhibitory effects.

[Metabolic state of the other eye in post-traumatic uveitis]

Biochemical analysis of the paired eye lacrimal fluid lipid peroxides (diene conjugates, Schiff's bases, TBA-active products), antioxidant enzymes (catalase, superoxide dismutase), dehydrogenases (lactate and malate dehydrogenases), and lactic and pyruvic acids was carried out during the early and remote posttraumatic period in 468 patients after perforating injuries to the eye. Signs of activation of lipid peroxidation, antioxidants, dehydrogenases, and of glycolysis intensification were detected. These changes corresponded to the results of analysis of lacrimal fluid of the injured eye and depended on the severity of injury, time elapsed after it, and severity and course of posttraumatic uveitis. The author claims that the detected metabolic shifts in the lacrimal fluid of paired eye are involved in the pathogenesis of posttraumatic uveitis.

The matrix metalloproteinase inhibitor BB-1101 prevents experimental autoimmune uveoretinitis (EAU)

EAU is characterized by breakdown of the blood-retinal barrier and extravasation of leucocytes into retinal tissue leading to destruction of photoreceptor cells. Matrix metalloproteinases (MMP) have been implicated in trafficking of cells into tissues, but their role in inflammatory eye disease is unclear. A synthetic MMP inhibitor, BB-1101, was administered subcutaneously, from either day 0 or day 7, to Lewis rats challenged with bovine S-antigen to induce EAU. When given up to day 14, BB-1101 reduced the incidence of disease and delayed the day of onset of clinical disease. When administered from day 7 until day 21, EAU was completely abrogated. A quantitative polymerase chain reaction (PCR) assay showed an increase of both matrilysin (MMP-7), neutrophil collagenase (MMP-8) and macrophage metalloproteinase (MMP-12) in retinas from EAU animals compared with naive controls. These enzymes are produced by activated leucocytes and act on components of the basement membrane. These results therefore implicate these MMP as integral to the development of pathology in EAU.

Differential expression of nitric oxide synthase in experimental uveoretinitis

PURPOSE

To investigate the site and the cellular source of inducible nitric oxide synthase (iNOS) expression in human S-antigen peptide-induced experimental autoimmune uveoretinitis (EAU).

METHODS

Twenty-one Lewis rats were sensitized with human S-antigen peptides. Three rats were killed each consecutive day from day 6 through day 12 after sensitization. Frozen sections of the enucleated eyes were analyzed for iNOS by the dual immunohistochemical method. Primary antibodies included rabbit anti-mouse iNOS combined with anti-human endothelium NOS, anti-rat lysosomal protein (ED1), or anti-rat major histocompatibility complex class II molecule (OX6) monoclonal antibodies. Secondary antibodies were fluorescein-conjugated anti-mouse IgG and streptavidin rhodamine-labeled anti-rabbit IgG. The adjacent sections were separately stained with ED1, iNOS, and glial fibrillary acidic protein (GFAP). The mouse macrophage cell line RAW 264.7 was exposed to either interferon (IFN)gamma/lipopolysaccharide (LPS) or S-antigen and to interphotoreceptor retinoid-binding protein (IRBP), myelin basic protein, and bovine serum albumin for 12 hours. Cells were harvested for detection of iNOS expression by northern blot analysis hybridization and detection of protein by immunohistochemistry.

RESULTS

In the retina of eyes with EAU, ED1+/iNOS+ and OX6+/iNOS+ cells were first detected on day 9 after sensitization. These iNOS+ cells increased in number on subsequent days in parallel with the increasing severity of retinal damage. Most of the cells localized around the outer retina. In contrast, a large number of ED1+ and OX6+ cells that were localized in the uvea and conjunctiva were negative for iNOS. Retinal pigment epithelial cells did not stain for iNOS. Macrophages exposed to IFNgamma/LPS, S-antigen, and IRBP showed expression of iNOS mRNA and the protein.

CONCLUSIONS

Macrophages are an important source of NO production in eyes with EAU. These macrophages preferentially express iNOS in the retina. Such a differential expression of iNOS by the macrophages appears to be related to retinal soluble proteins.

Retinal expression of a neo-self antigen, beta-galactosidase, is not tolerogenic and creates a target for autoimmune uveoretinitis

Recent studies revealing active mechanisms of immune privilege in neural tissues have diminished the putative role of passive tolerance. To examine the significance of Ag localization in the retina on immune privilege, the immune responses of transgenic mice expressing high and low levels of beta-galactosidase (beta-gal) in the photoreceptor cells of the retina were compared with those of normal mice and those of mice expressing moderate levels of beta-gal systemically. Immunization with beta-gal induced experimental autoimmune uveoretinitis indistinguishable from that induced by known photoreceptor cell autoantigens, including destruction of photoreceptor cells, in transgenic mice with high level retinal expression. Retinal expression had no apparent effect on the immune responses to beta-gal, showing that tolerance was not elicited by levels of retinal beta-gal sufficient to serve as a target for autoimmune disease. Mice with systemic expression exhibited reduced lymphoproliferative responses following immunization with beta-gal and did not develop autoimmune disease. T cells prepared from normal mice immunized with beta-gal transferred experimental autoimmune uveoretinitis to the transgenic mice with high level retinal beta-gal expression, but no disease was found in mice with systemic transgene expression under these conditions. The results of our experiments are most consistent with sequestration being the primary mechanism of retinal immune privilege. The results also show that beta-gal can serve as an immunopathogenic neural autoantigen, and that T cells raised by immunization of normal mice with a foreign Ag can be immunopathogenic in certain transgenic recipients.

Improved myeloperoxidase assay for quantitation of neutrophil influx in a rat model of endotoxin-induced uveitis

Previously described models of endotoxin-induced uveitis quantify neutrophil influx into the eye using biochemical or direct cell count methods that result in an underestimation of ocular leukocyte accumulation following the inflammatory stimulus. We have optimized the rat model of endotoxin-induced uveitis by first overcoming interference in the biochemical assay of myeloperoxidase due to endogenous ocular reductants and cellular constituents containing free thiol functional groups. This was accomplished by simultaneously 1) extensively diluting soluble, interfering substances and 2) blocking tissue sulfhydril functional groups during tissue homogenization. Uveitis was induced in rats by subplantar injection of endotoxin. Twenty-four hours later, eyes were enucleated, homogenized, fractionated, and myeloperoxidase activity of neutrophils sedimenting with the membranous pellet was extracted. Previously published extraction procedures yielded only 40% of total assayable myeloperoxidase activity. Optimal recovery of myeloperoxidase activity (>twofold increase) was achieved only with two sequential extractions using 50 mM phosphate buffer (pH 7.4) containing 10 mM N-ethylmaleimide, and subsequent solubilization of myeloperoxidase activity by extraction with 0.5% hexadecyltrimethylammonium bromide in 50 mM phosphate buffer (pH 6.0). This modified extraction procedure and optimized myeloperoxidase assay conditions (300 microM hydrogen peroxide and 1.5 mM o-dianisidine) were then used to enhance the uveitis model. Maximum ocular neutrophil accumulation was observed at endotoxin doses of 100-200 microg. Total ocular neutrophil infiltrations ranged from 250,000 to 800,000 cells/globe. This leukocyte influx was inhibited dose-dependently by topical ocular administration of dexamethasone, with half-maximal inhibition observed at a concentration of 0.01%, w/v. Further validated by the correlation of biochemical results with histological evaluation, the refined methodology described in this report has application in assessing the ophthalmic therapeutic potential of antiinflammatory agents.

Nitric oxide accelerates the onset and increases the severity of experimental autoimmune uveoretinitis through an IFN-gamma-dependent mechanism

The production of large amounts of nitric oxide (NO) by inducible nitric oxide synthase (iNOS) has been described as a double-edged sword eliciting pro- or anti-inflammatory effects in different immune situations. Our aim, therefore, was to investigate its role in experimental autoimmune uveoretinitis (EAU), a model of ocular inflammation, induced in the Lewis rat following a single footpad injection of retinal Ags. iNOS enzyme was not detected in the normal Lewis rat eye, but was strongly expressed by infiltrating ED1+ macrophages during the acute inflammatory stages of EAU. Treating immunized animals with L-arginine increased urinary NO metabolite (NOx) levels, accelerated the inflammatory response, and increased disease severity, whereas treatment with the NOS inhibitor, N(G)-nitro-L-arginine methyl ester, reduced NOx excretion, delayed the onset, and reduced the clinical signs of EAU. Reverse transcription-PCR analysis of ocular tissue from untreated and treated animals detected iNOS mRNA at all stages of disease, and expression was up-regulated during peak disease. L-arginine treatment enhanced cytokine mRNA expression, particularly of IFN-gamma, which was detected earlier than in control animals, corresponding with the more rapid onset of disease and increased disease severity observed in this group. N(G)-nitro-L-arginine methyl ester had little or no effect on iNOS or inflammatory cytokine mRNA expression. These results suggest NO is central to the pathogenesis of EAU and highlight the importance of the macrophage as an effector cell in what is considered a CD4+ T cell-dependent disease. Furthermore, this study demonstrates the therapeutic potential of NOS inhibitors in the treatment of inflammatory and autoimmune mediated disease.

Cellular localisation and dynamics of nitric oxide synthase expression in the rat anterior segment during endotoxin-induced uveitis

The present study examined the temporal pattern and cellular localisation of nitric oxide synthase in Endotoxin-Induced Uveitis (EIU). Lewis rats (n=40) received a single footpad injection of 200 microg of bacterial lipopolysaccharide. Animals were killed at 0, 2, 4, 6, 12, 24, 48 and 72 hr after injection and ocular tissues prepared as iris-ciliary body wholemounts or frozen sections of the anterior segment. The expression of constitutive nitric oxide synthase (cNOS) and inducible nitric oxide synthase (iNOS) was investigated at all time points by immunohistochemistry. A further group of animals (n=6) were killed at the peak of the disease (12 hr) and the cellular co-localisation of iNOS on resident and infiltrating immune cells was investigated by double immunohistochemistry utilising the biotinylated monoclonal antibodies ED1, ED2 and Ox6. Expression of cNOS on iris vessels did not alter during the course of EIU. Quantitative analysis of iris-ciliary body wholemounts revealed the first evidence of iNOS+ at 2 hr which increased dramatically at 4 and 6 hr with a peak at 12 hr. The expression of iNOS in the early phase of the disease (2-6 hr) was associated with small round marginating and newly extravasated cells that on morphological criteria were most likely neutrophils and monocytes. At 12 hr, cells of more mixed morphologies began to express iNOS and double labelling revealed 70% of these cells were also ED1(+) (a lysosomal antigen present in monocytes/macrophages and dendritic cells), 52% were Ox6(+) (MHC class II) (dendritic cells, activated macrophages and some T-cells) and 19% were ED2(+) (pan-specific resident tissue macrophages). Expressed in an alternative manner, 10% of the total ED1(+) cell population, 11% of the ED2(+) cells and 44% of Ox6(+) cells co-expressed iNOS. Expression of iNOS decreased significantly by 24 hr to near baseline levels and was absent by 48 and 72 hr. Within the ciliary processes iNOS+ dendriform cells were noted at 6 hr and accumulations of many small round iNOS+ cells were present at 12 hr. The ciliary epithelium did not at any time express iNOS at the protein level detectable by immunohistochemistry. The results of this study suggest that iNOS expression early in EIU is associated with infiltrating or newly recruited neutrophils and monocytes/macrophages in the iris whereas later in the disease resident tissue macrophages and MHC class II+ cells (activated macrophages and putative dendritic cells) in the iris and ciliary body may synthesise nitric oxide. The role of this late phase of nitric oxide synthesis may include lymphocytostasis and immunosuppression as proposed in other tissue sites. The outcome of the present study may help in planning therapeutic strategies using NOS inhibitors.

Concomitant treatment with a 5-lipoxygenase inhibitor improves the anti-inflammatory effect of the inhibition of nitric oxide synthase during the early phase of endotoxin-induced uveitis in the rabbit

Nitric oxide (NO) synthase inhibitors, such as NG-nitro-L-arginine methyl ester (L-NAME), have been shown to attenuate endotoxin-induced uveitis (EIU) but they could increase leukocyte adhesion to the vascular endothelium. We hypothesize that a concomitant treatment with the 5-lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA) in 50% dimethylsulfoxide (DMSO, a hydroxyl radical scavenger) could improve the anti-inflammatory activity of L-NAME. EIU was induced in albino rabbits by intravitreal injection of 100 ng lipopolysaccharide. Animals were treated with multiple intraperitoneal injections of 50% DMSO in phosphate-buffered saline (PBS), NDGA (10 mg/kg) in 50% DMSO, L-NAME (50 mg/ kg) in PBS, or the combination NDGA+L-NAME. Uveitis was assessed by slit lamp examination, protein levels in aqueous humor, and myeloperoxidase (MPO) activity in the iris/ciliary body 6 h after induction. Nitrite, leukotriene B4 (LTB4), prostaglandin E2 (PGE2), platelet-activating factor (PAF) and interleukin-1 beta (IL-1 beta) levels in aqueous humor were also determined. NDGA or L-NAME alone did not show a significant reduction of uveitis intensity, although a significant decrease in MPO or in proteins was found, respectively. The combination NDGA+L-NAME significantly reduced the uveitis intensity, MPO in the iris/ciliary body, and the levels of nitrites, LTB4, PGE2, and PAF in aqueous humor. IL-1 beta levels were lower than the detection limit of the radioimmunoassay in all treatment groups. We conclude that concomitant treatment with NDGA in DMSO improves the anti-inflammatory activity of L-NAME during the early phase of EIU, suggesting that the inhibition of NO synthesis could enhance leukocyte infiltration and the release of oxygen free radicals.

Expression of inducible nitric oxide synthase in the eye from endotoxin-induced uveitis rats

PURPOSE

Inducible nitric oxide (NO) synthase (iNOS) has been implicated in the pathogenesis of endotoxin-induced uveitis (EIU). This study was undertaken to localize the cells, in the eye, which express iNOS during EIU in the rat.

METHODS

EIU was induced in Lewis rats by a single foot pad injection of 150 micrograms lipopolysaccharide (LPS) from Salmonella typhimurium. At different time intervals after LPS injection, the authors evaluated ocular inflammation (slit lamp observation), iNOS localization by in situ hybridization, and comparison of OX-42- and ED1-positive cell appearance and of glial response by specific immunohistochemistry.

RESULTS

iNOS mRNA was not detected in the iris-ciliary body nor in the retina of control rats. It was detected strongly in the epithelial cells of the iris-ciliary body at 6 hours and also in stromal cells of the ciliary processes at 16 hours after LPS injection. In the neuroretina, iNOS mRNA was observed in the inner layers 16 hours after LPS injection. iNOS-positive cells were also present on the vitreous at this time. At 6 and approximately 16 hours after LPS injection, immunohistochemistry experiments revealed a large number of OX-42- and ED1-positive cells (microglia, macrophages, or polymorphonuclear leukocytes) colocalized in part with some iNOS-positive cells in the ciliary body and in the retina. Furthermore, expression of iNOS in Müller cells cannot be excluded.

CONCLUSIONS

These observations confirm that subcutaneous injection of endotoxin dramatically induces NOS mRNA expression in the eye, and they demonstrate that epithelial cells of the iris-ciliary body and cells infiltrating the anterior segment of the eye and the retina are the major source of NO. These results support the hypothesis that both inflammatory and resident ocular cells are involved in iNOS expression during EIU.

[Serum adenosine deaminase and angiotensin converting enzyme activity in patients with endogenous uveitis]

Serum activity of adenosine deaminase (ADA) and angiotensin converting enzyme (ACE) was investigated in 32 patients with sarcoidosis, 22 patients with Behçet's disease, 22 patients with Vogt-Koyanagi-Harada's (VKH) disease and 253 healthy controls. In healthy controls, the ADA level was significantly higher in females than in males (p < 0.01). In patients with sarcoidosis, the serum ADA level was significantly higher in both males and females than in the controls (p < 0.01). In patients with Behçet's disease, the serum ADA level was significantly higher than in the controls (p < 0.01) in males only. In VKH disease, the serum ADA level showed no significant difference from the normal controls. Significant elevation of the serum ACE activity was observed only in patients with sarcoidosis (p < 0.01). Serum ACE activity was therefore considered to be more specific to sarcoidosis than serum ADA activity.

Chemoattractant and neutrophil degranulation activities related to interleukin-8 in vitreous fluid in uveitis and vitreoretinal disorders

PURPOSE

To investigate whether the cytokine interleukin-8 (IL-8), a strong chemoattractant and activator for neutrophils, is responsible for neutrophil infiltration and degranulation in the eye in uveitis.

METHODS

IL-8 and elastase were measured with specific enzyme-linked immunoassays in vitreous fluid samples obtained from 69 patients with various uveitis entities. Vitreous fluid of nonuveitis patients and eye bank eyes served as controls. The chemotactic activity of vitreous fluid was tested with the Boyden chamber technique.

RESULTS

IL-8 was detected in 45% of the vitreous fluid samples from uveitis patients and in 26% of vitreous fluid samples from nonuveitis patients. Vitreous fluid samples with IL-8 levels exceeding 100 pg/ml were chemotactic for neutrophils. This chemotactic activity could be blocked by 41% to 79% with a monoclonal anti-IL-8 antibody. Elastase levels in vitreous fluid of uveitis patients with detectable IL-8 were significantly higher than those in vitreous fluid samples with no detectable IL-8.

CONCLUSION

These results indicate that IL-8 participates in the inflammatory processes in the eye by attracting and degranulating neutrophils. It is suggested that these processes contribute to the pathogenesis of tissue destruction in uveitis.

[Effect of kontrikal on the course of experimental nonspecific phacogenic uveitis]

Nonspecific phacogenic uveitis (NPGU) was simulated in 21 chinchilla rabbits to follow the time course of the blood serum proteolytic activity and the principal protease inhibitors (alpha 1 inhibitor and alpha 2 macroglobulin) in various stages of the inflammatory process. Effects of contrykal, a synthetic protease inhibitor, on these parameters and the course of the inflammation was also under study. The results evidence that i.v. and subconjunctival contrykal administration reduced the periods of NPGU treatment 1.5-2 times.

The lysosomal enzymes of the iris-ciliary body are retained in their organelles and exhibit increased activities during acute uveal inflammation

Acute uveal inflammation, characterised by conjunctival hyperaemia, limbal vascular injection, iritis and aqueous flare, was induced in the rabbit eye by a single intravitreal injection of 10 micrograms of Shigella endotoxin. Twenty-four, 48 and 72 h after endotoxin administration, lysosomal-rich fractions and cytosolic supernatants were prepared from iris-ciliary bodies and the enzymatic activities of some lysosomal hydrolases in these fractions were assayed. Acid phosphatase, aryl sulphatase and N-acetyl-B-D-glucosaminidase exhibited increased activities in the lysosomal preparations from inflamed iris-ciliary bodies, relative to the activities of the same enzymes in lysosomal fractions from normal iris-ciliary bodies. No significant differences in activities were obtained for these enzymes in cytosolic supernatants from normal and inflamed iris-ciliary bodies. The results suggest that during acute ocular inflammation the lysosomal hydrolases are retained in their organelles at an elevated state of activity.

[The kallikrein-kinin system in experimental uveitis]

The author analyzes changes in the activities of the kallikrein-kinin system (KKS) parameters over the course of experimental toxic allergic uveitis induced in 24 animals; the reference group consisted of 8 intact animals. Clinical examinations of the eyes were parallelled by biochemical analyses that revealed a significant activation of the blood serum and vitreous KKS, the degree of this activation correlating with uveitis severity. No normalization of KKS parameters was associated with complete clinical cure, this being possibly due to a chronic course of the condition and thus valuable for pathogenetically oriented therapy.

Role of free radicals in uveitis

In acute inflammation, the tissue damage is generally mediated through polymorphonuclear leukocytes and macrophages. Recent studies on the mechanism of this leukocyte-mediated cytolysis have demonstrated that these cells, on stimulation, release a variety of reactive products. These metabolic products consist of superoxide and hydrogen peroxide, which in turn can form highly reactive species such as hydroxyl radicals. It is believed that these oxygen products play an important role in the tissue damage that occurs in inflammations such as uveitis. The ocular structures contain various antioxidant enzymes that normally protect against free radical mediated injury. In experimental animal models of uveitis, it has been shown that antioxidants and free radical scavengers can function as antiinflammatory agents and can protect the eye from inflammation-mediated tissue damage.

Concentration of angiotensin-converting enzyme in tears of patients with sarcoidosis

The concentration of angiotensin-converting enzyme (ACE) was studied in 39 patients with sarcoidosis, 6 of whom had active uveitis, 7 patients with non-sarcoid uveitis and 36 healthy controls. ACE concentration in tears was also compared with total protein concentration in tears in order to exclude the effect of varying dilution of tears at sampling. Mean tear ACE concentration and ACE/protein ratio were higher in patients with sarcoidosis than in controls. There were no significant differences in tear ACE concentration or ACE/protein ratio between sarcoidosis patients with uveitis and those with no eye involvement. Tear ACE concentration and ACE/protein ratio did not correlate significantly with serum ACE concentration. It is concluded that the mean concentration of tear ACE and ACE/protein ratio are elevated in sarcoidosis, but that this elevation is independent of any eye involvement.

Angiotensin-converting enzyme in sarcoid and chalazion granulomas of the conjunctiva

Angiotensin-converting enzyme (ACE) was studied immunohistochemically in conjunctival biopsies from 6 patients with systemic sarcoidosis, 4 patients with posterior non-sarcoid uveitis and in specimens from 4 patients with chalazion of the eyelid. Specimens with sarcoid granulomas showed intense ACE-positive immunoreactivity in epitheloid cells of the granuloma, whereas chalazion granulomas did not contain ACE-immunoreactivity. There was no difference in staining patterns between specimens without granulomas. Thus immunohistochemical staining for ACE may be of help in differentiating conjunctival granulomatous tissue of a chalazion from sarcoid granuloma.

Angiotensin-converting enzyme activity in human aqueous humor

We measured aqueous angiotensin-converting enzyme (ACE) activity in 37 patients. Patients with granulomatous uveitis and probable sarcoidosis (based on increased serum ACE activity or characteristic radiologic findings) had a significant increase in aqueous ACE activity compared with normal subjects. Aqueous ACE activity was also significantly elevated in patients with sarcoid who had normal serum ACE activity. We believe that measurement of aqueous ACE activity should be considered in patients with uveitis who have normal serum ACE activity and are suspected of having sarcoidosis.

Ascorbic acid inhibits the activity of polymorphonuclear leukocytes in inflamed ocular tissues

Myeloperoxidase (MPO) is present at high levels in polymorphonuclear leukocytes (PMNs) and has been used as a marker to quantify the accumulation of PMNs in inflamed tissues. MPO activity in inflamed ocular tissues was inhibited by aspirates of aqueous humor. This inhibition could be duplicated by the addition of ascorbic acid at concentrations equivalent to those present in the aliquots of aqueous humor. Similarly, aqueous humor and ascorbic acid inhibited MPO from isolated rabbit leukocytes. Therefore, ascorbic acid appears to inhibit the functional activity of the peroxidase in PMNs, thus preventing potential tissue damage by this enzyme when released during leukocyte degranulation in inflammation. Ascorbic acid might fulfill a role as an endogenous anti-inflammatory agent in the eye.

Neutrophil collagenolytic activity in patients with Behçet disease

Studies were made on neutrophil dysfunction in Behçet disease by examining collagenolytic activity in neutrophils. The collagenolytic activity of neutrophil was found to be significantly higher in patients during the attack phase of this disease than in patients during the remission phase, in patients with other forms of uveitis and in normal controls. Collagenase was present in the collagenolytic enzyme, which showed high activity in the attack phase. The molecular weight of this enzyme was similar to that of mammalian neutrophil collagenase.

Immunoassay of serum alpha-1 antitrypsin level in uveitis

The serum alpha-1 antitrypsin level was measured in 60 patients with endogenous uveitis, 27 patients with phacoallergic endophthalmitis, 12 patients with phacolytic glaucoma, and 58 healthy subjects. Thirty-four patients with endogenous uveitis were also followed up for 6 months after treatment, and the serum alpha-1 antitrypsin level was measured again. There was a significant rise in the serum alpha-1 antitrypsin level in cases of endogenous uveitis and phacoallergic endophthalmitis but no alteration in cases of phacolytic glaucoma. Among the patients with endogenous uveitis the level was significantly raised in cases of anterior uveitis, but there was no change in cases of posterior uveitis. A significant rise was seen only in cases of acute anterior uveitis but not in chronic anterior uveitis. The serum alpha-1 antitrypsin level was unaltered in endogenous uveitis despite clinical improvement.

Decreased ecto-5'-nucleotidase activity in rabbit lymphocytes during experimental lens-induced uveitis

An experimental uveitis was produced by immunizing albino and pigmented rabbits with heterologous (rat) lens protein six times at two-week intervals. After sensitization the anterior lens capsules were disrupted in an operation. After operation the rabbits were examined repeatedly with a slit-lamp. On the seventh day after operation the animals were sacrificed and both eyes were enucleated. The inflammatory reaction in the uveal tract was verified histopathologically. Thymus and spleen lymphocytes were purified using BSA-gradients. Ecto-5'-nucleotidase (AMP-ase) activity on the intact lymphocytes was measured biochemically and B-cells were counted using the fluorescent anti-IgG technique. Purified spleen and thymus lymphocytes were also analyzed using transmission electron microscopy. The AMP-ase activity of purified spleen lymphocytes was significantly decreased in albino rabbits suffering from experimental lens-induced uveitis when compared to that observed in control animals. The AMP-ase activity was also decreased in pigmented rabbits suffering from a very mild uveitis. Moreover, a decreased AMP-ase activity was observed in albino rabbits which were only immunized but not operated on and did not show any signs of uveitis. Differences in neither the B-cell proportions nor the ultrastructure of the purified lymphocytes could be observed in any of these experimental groups. It is proposed that the biochemical change in spleen lymphocytes observed in the present work is a reflection of the general immunological state which in certain conditions may lead to uveitis.

Ecto 5'-nucleotidase activity in lymphocytes in cases of uveitis

This study attempts to demonstrate cellular reactivity in cases of uveitis. Lymphocyte AMPase activity was measured in 59 patients with uveitis of different types, all in the active stage. The patients were divided into 3 groups: 1) anterior uveitis with known disease, 2) anterior uveitis with unknown aetiology, and 3) posterior uveitis. The AMPase activity in peripheral lymphocytes from uveitis patients with known disease (group 1) was significantly decreased in comparison to lymphocytes from controls. Patients having endogenous uveitis (unknown aetiology, group 2) showed heterogeneity concerning their enzyme activity, and no significant changes were demonstrated. A subpopulation of patients with very low AMPase activity in the active stage of their disease could be defined. Patients with posterior uveitis showed no change in their lymphocyte AMPase activity. B-cells were also counted in cell suspension to verify that there was no selective change in the B-cells. Cell suspensions from patients with low and normal AMPase activities were studied by the electron microscope and found to have similar proportions of different types of mononuclear cells. Enzyme deficiencies in lymphocytes were associated with immunological disorders and would reflect dysfunction of lymphocytes. The heterogenous results from patients with endogenous uveitis were interpreted as showing cellular reactivity to ocular damage caused by a variety of mechanisms.

Quantification of ocular inflammation: evaluation of polymorphonuclear leucocyte infiltration by measuring myeloperoxidase activity

Myeloperoxidase (MPO) activity was measured in rabbit cornea and iris-ciliary body to quantitate the infiltration and accumulation of polymorphonuclear leucocytes (PMN's) following an inflammatory stimulus. Following injection of clove oil into the cornea, MPO activity could be detected in the cornea at 6 hr, reaching a maximum at 12 hr, and falling to non-detectable levels at 72 hr. MPO activity was only detected in the iris-ciliary body 24 hr after intracorneal clove oil injection. MPO activity in the iris-ciliary body increased in a dose-dependent manner following intravitreal injection of endotoxin. No MPO activity could be detected in cornea. Topical administration of dexamethasone inhibited MPO activity in cornea and iris-ciliary body 24 hr after intracorneal clove oil and intravitreal endotoxin injection, respectively. Measurement of MPO activity in ocular tissues could provide a useful tool to quantitatively evaluate the severity and time course of inflammation.