Biomedical subjects

C C Chan

Publications and source records attributed to C C Chan.

At least 73 records · Page 4Linked to original sources

PubMed2001

Etoricoxib (MK-0663): preclinical profile and comparison with other agents that selectively inhibit cyclooxygenase-2.

We report here the preclinical profile of etoricoxib (MK-0663) [5-chloro-2-(6-methylpyridin-3-yl)-3-(4-methylsulfonylphenyl) pyridine], a novel orally active agent that selectively inhibits cyclooxygenase-2 (COX-2), that has been developed for high selectivity in vitro using whole blood assays and sensitive COX-1 enzyme assays at low substrate concentration. Etoricoxib selectively inhibited COX-2 in human whole blood assays in vitro, with an IC(50) value of 1.1 +/- 0.1 microM for COX-2 (LPS-induced prostaglandin E2 synthesis), compared with an IC(50) value of 116 +/- 8 microM for COX-1 (serum thromboxane B2 generation after clotting of the blood). Using the ratio of IC(50) values (COX-1/COX-2), the selectivity ratio for the inhibition of COX-2 by etoricoxib in the human whole blood assay was 106, compared with values of 35, 30, 7.6, 7.3, 2.4, and 2.0 for rofecoxib, valdecoxib, celecoxib, nimesulide, etodolac, and meloxicam, respectively. Etoricoxib did not inhibit platelet or human recombinant COX-1 under most assay conditions (IC(50) > 100 microM). In a highly sensitive assay for COX-1 with U937 microsomes where the arachidonic acid concentration was lowered to 0.1 microM, IC(50) values of 12, 2, 0.25, and 0.05 microM were obtained for etoricoxib, rofecoxib, valdecoxib, and celecoxib, respectively. These differences in potency were in agreement with the dissociation constants (K(i)) for binding to COX-1 as estimated from an assay based on the ability of the compounds to delay the time-dependent inhibition by indomethacin. Etoricoxib was a potent inhibitor in models of carrageenan-induced paw edema (ID(50) = 0.64 mg/kg), carrageenan-induced paw hyperalgesia (ID(50) = 0.34 mg/kg), LPS-induced pyresis (ID(50) = 0.88 mg/kg), and adjuvant-induced arthritis (ID(50) = 0.6 mg/kg/day) in rats, without effects on gastrointestinal permeability up to a dose of 200 mg/kg/day for 10 days. In squirrel monkeys, etoricoxib reversed LPS-induced pyresis by 81% within 2 h of administration at a dose of 3 mg/kg and showed no effect in a fecal 51Cr excretion model of gastropathy at 100 mg/kg/day for 5 days, in contrast to lower doses of diclofenac or naproxen. In summary, etoricoxib represents a novel agent that selectively inhibits COX-2 with 106-fold selectivity in human whole blood assays in vitro and with the lowest potency of inhibition of COX-1 compared with other reported selective agents.

Algorithms↗

PubMed2001

Involvement of apoptosis and interferon-gamma in murine toxoplasmosis.

PURPOSE: A murine toxoplasmosis model has been developed that results in central nervous system (CNS) and ocular inflammation characterized by encephalitis with numerous brain tissue cysts and milder inflammation with rare tissue cysts in the eye after 4 weeks of Toxoplasma gondii infection. In this model IFN gamma and inducible nitric oxide (iNO) are protective against T. gondii infection. In this study, the role of apoptosis in the pathogenesis of toxoplasmosis was investigated. METHODS: C57BL/6 (wild-type mice), B6MRL/lpr, and B6MRL/gld (defective Fas or FasL expression, respectively) mice were infected intraperitoneally with 20 to 30 tissue cysts of the ME-49 strain of T. gondii. Mice were killed at days 0, 14, or 28 after infection. The eyes and brains were harvested for histologic, immunohistochemical, and molecular studies. Analysis included immunostaining for Fas, FasL, Bcl-2, and Bax; in situ apoptosis detection (TUNEL assay); RT-PCR amplification for IFN gamma; and measurement of ocular nitrite levels. The control mice were naïve mice of each strain that received no inoculation or injection. RESULTS: Wild-type mice appeared to constitutively express apoptotic molecules at higher levels in the eye than in the brain. Consequently, during T. gondii infection, apoptosis was greater in the eyes than in the brain. Untreated naïve lpr and gld mice showed no expression of Fas and FasL, respectively. After infection, a slightly higher number of tissue cysts (lpr, 11.8 +/- 2.4; gld, 10.3 +/- 3.4) were found in the brains of the mutants than in the control animals (8.8 +/- 2.9). However, no significant differences between the number of apoptotic cells, inflammatory scores, or number of tissue cysts were noted in the eyes. IFN gamma mRNA in control mice was detected at day 28 after infection, whereas in both mutants, mRNA production occurred earlier, at day 14. Ocular nitrite levels were higher in lpr and gld mice than in wild-type mice. CONCLUSIONS: No significant difference in the degree of ocular inflammation and apoptosis was detected between the wild-type and Fas or FasL mutant mice. However, there was an earlier and subjectively greater expression of IFN gamma in the brain and eye and a higher level of nitrite in the ocular tissue of mutant strains than in the wild type. Multiple factors are likely to be involved in the pathogenesis of ocular toxoplasmosis.

Animals↗

PubMed2001

Hepatic encephalopathy in rats with thioacetamide-induced fulminant hepatic failure: role of endotoxin and tumor necrosis factor-alpha.

BACKGROUND: Hepatic encephalopathy, a complex neuropsychiatric syndrome secondary to acute liver failure, chronic parenchymal liver disease or portal-systemic shunting, may possibly develop through mediators of endotoxin and tumor necrosis factor-alpha (TNF-alpha). However, there are no published data concerning the relationships between the severity of encephalopathy and the plasma levels of endotoxin and TNF-alpha. METHODS: Male Sprague-Dawley rats weighing about 300-350 g were used. Fulminant hepatic failure was induced by intraperitoneal injection ofthioacetamide (350 mg/kg/day) for 3 consecutive days. Severity of encephalopathy was assessed by measuring motor counts using an Opto-Varimex animal activity meter. Plasma levels of endotoxin and TNF-alpha were determined by chromogenic Limulus assay and ELISA method, respectively. RESULTS: Our study revealed that higher plasma levels of endotoxin (> 5.9 pg/ml) and TNF-alpha (> 18.8 pg/ml) were significantly associated with more blunted motor activities in rats with fulminant hepatic failure (p < 0.05). A significant correlation was observed between plasma concentrations of endotoxin and TNF-alpha (r = 0.59, p < 0.001). Plasma levels of endotoxin were weakly correlated with the total movements in an open field (r = -0.34, p = 0.032) and the counts of ambulatory (r = -0.38, p = 0.014) and vertical movements (r = -0.40, p = 0.010). There were no correlations between the motor counts and plasma levels of TNF-alpha (p > 0.05). CONCLUSIONS: In addition to endotoxin and TNF-alpha, other factors may participate in the pathogenesis of hepatic encephalopathy in rats with thioacetamide-induced fulminant hepatic failure.

Animals↗

PubMed2001

Occupational exposure to wood, formaldehyde, and solvents and risk of nasopharyngeal carcinoma.

Our objective was to evaluate the link between occupational exposures to wood dust, formaldehyde, and solvents and the development of nasopharyngeal carcinoma (NPC). A case-control study was conducted among 375 newly diagnosed cases of NPC in Taipei, Taiwan, and 325 community controls matched to cases on sex, age, and geographical residence (99 and 87% response rates, respectively). Most cases (>90%) were diagnosed with WHO Types 2 or 3 (nonkeratinizing and undifferentiated carcinomas), whereas the remaining cases were diagnosed with WHO Type 1 (squamous cell carcinomas). A complete occupational history was obtained via a personal interview and blindly assessed by an industrial hygienist for intensity and probability of exposure to wood dust, formaldehyde, and solvents. Information on socio-demographic characteristics, cigarette smoking, dietary consumption of nitrosamines, and other potential confounding factors was obtained via a personal interview. Blood specimens were tested for human leukocyte antigen class I/II genotypes, polymorphisms in cytochrome P450 2E1 genotype, and various anti-EBV antibodies known to be associated with NPC. Analysis was performed using logistic regression; relative risk (RR) estimates and 95% confidence intervals (CI) were calculated. Individuals exposed to wood dust had an adjusted RR of 1.7 (95% CI = 1.0-3.0). Those exposed to wood dust for >10 years had an adjusted RR of 2.4 (95% CI = 1.1-5.0; p(trend) = 0.02). Risk was strongest for those first exposed before the age of 25 years and those seropositive to EBV. Individuals exposed to formaldehyde were at a more modest and nonsignificant increased risk of NPC (RR = 1.4; 95% CI = 0.93-2.2). Those exposed to formaldehyde for >10 years had an adjusted RR of 1.6 (95% CI = 0.91-2.9). The association between formaldehyde and NPC was stronger in analyses restricted to EBV seropositive individuals (RR = 2.7; 95% CI = 1.2-5.9). However, no dose response was observed with increasing duration or cumulative use. No association was observed between solvent exposure and NPC (RR = 1.2; 95% CI = 0.86-1.7). Occupational exposure to wood dust is likely to be involved in the development of NPC, a finding that is consistent with the known link between wood exposure and nasal adenocarcinomas. Formaldehyde exposure is less clearly linked to NPC, whereas exposure to solvents is unlikely to be involved in NPC pathogenesis.

Adolescent↗

PubMed2000

Synthesis, characterization, and activity of metabolites derived from the cyclooxygenase-2 inhibitor rofecoxib (MK-0966, Vioxx).

Metabolites of the COX-2 inhibitor rofecoxib (MK-0966, Vioxx) were prepared by synthetic or biosynthetic methods. Metabolites include products of oxidation, glucuronidation, reduction and hydrolytic ring opening. Based on an in vitro whole blood assay, none of the known human metabolites of rofecoxib inhibits COX-1 nor contributes significantly to the inhibition of COX-2.

Animals↗

PubMed2000

Fas and Fas ligand expressed on cells of the immune system, not on the target tissue, control induction of experimental autoimmune uveitis.

The Fas-Fas ligand (FasL) interaction is important for maintaining lymphocyte homeostasis by signaling for activation-induced cell death. Mice homozygous for the lpr or gld mutations do not express functional Fas or FasL, respectively, and spontaneously develop progressive autoimmune symptoms. Recent studies implicated expression of FasL on immunologically privileged tissues in protection from immune-mediated damage. Conversely, tissue expression of Fas may facilitate damage. We evaluated the susceptibility of lpr and gld mice to induction of experimental autoimmune uveitis (EAU), a T cell-mediated autoimmune disease induced with retinal Ags, which targets the neural retina. gld as well as lpr mice immunized with a retinal Ag developed disease of lower incidence and severity than wild-type controls. Delayed hypersensitivity responses were not significantly different among immunized gld, lpr, or wild-type mice, although in vitro Ag-specific lymphocyte responses of the mutant mice were lower. To evaluate whether the diminished ability of gld and lpr mice to develop EAU was due to a defect at the level of the tissue or the immune system, radiation bone marrow chimeras constructed between wild-type and mutant mice were immunized to induce EAU. Mutant recipients of wild-type bone marrow, but not wild-type recipients of mutant bone marrow, developed normal disease scores. These results indicate that normal expression of Fas and of FasL on cells of the immune system is important for EAU expression. Unexpectedly, neither lack of Fas nor lack of FasL on the ocular tissues affected expression of EAU.

Animals↗

PubMed2000

Cloning, expression, and up-regulation of inducible rat prostaglandin e synthase during lipopolysaccharide-induced pyresis and adjuvant-induced arthritis.

We have cloned and expressed the inducible form of prostaglandin (PG) E synthase from rat and characterized its regulation of expression in several tissues after in vivo lipopoylsaccharide (LPS) challenge. The rat PGE synthase is 80% identical to the human enzyme at the amino acid level and catalyzes the conversion of PGH(2) to PGE(2) when overexpressed in Chinese hamster ovary K1 (CHO-K1) cells. PGE synthase activity was measured using [(3)H]PGH(2) as substrate and stannous chloride to terminate the reaction and convert all unreacted unstable PGH(2) to PGF(2alpha) before high pressure liquid chromatography analysis. We assessed the induction of PGE synthase in tissues from Harlan Sprague-Dawley rats after LPS-induced pyresis in vivo. Rat PGE synthase was up-regulated at the mRNA level in lung, colon, brain, heart, testis, spleen, and seminal vesicles. Cyclooxygenase (COX)-2 and interleukin 1beta were also up-regulated in these tissues, although to different extents than PGE synthase. PGE synthase and COX-2 were also up-regulated to the greatest extent in a rat model of adjuvant-induced arthritis. The RNA induction of PGE synthase in lung and the adjuvant-treated paw correlated with a 3.8- and 16-fold induction of protein seen in these tissues by immunoblot analysis. Because PGE synthase is a member of the membrane-associated proteins in eicosanoid and glutathione metabolism (MAPEG) family, of which leukotriene (LT) C(4) synthase and 5-lipoxygenase-activating protein are also members, we tested the effect of LTC(4) and the 5-lipoxygenase-activating protein inhibitor MK-886 on PGE synthase activity. LTC(4) and MK-886 were found to inhibit the activity with IC(50) values of 1.2 and 3.2 microm, respectively. The results demonstrate that PGE synthase is up-regulated in vivo after LPS or adjuvant administration and suggest that this is a key enzyme involved in the formation of PGE(2) in COX-2-mediated inflammatory and pyretic responses.

Amino Acid Sequence↗

PubMed2000

Blockade of costimulation through B7/CD28 inhibits experimental autoimmune uveoretinitis, but does not induce long-term tolerance.

It has been reported that costimulation blockade can result in T cell anergy. We investigated the effects of blocking costimulatory molecules in vivo on the development of experimental autoimmune uveoretinitis (EAU), a model for autoimmune uveitis in humans that is induced in mice by immunization with the retinal Ag interphotoreceptor retinoid binding protein. B10.A mice immunized with a uveitogenic regimen of interphotoreceptor retinoid-binding protein were treated with Abs to B7.1 and B7.2 for 2 wk. Evaluation of EAU and immunological responses 1 wk later showed that disease had been abrogated, and cellular responses were suppressed. To determine whether the costimulation blockade resulted in tolerance, adult-thymectomized mice immunized for uveitis and treated with anti-B7 or anti-CD28 were rechallenged for uveitis induction 5 wk after the initial immunization. Although confirmed to be disease free after the initial immunization, both anti-B7- and anti-CD28-treated mice developed severe EAU and elevated cellular responses after the rechallenge, equivalent to those of control mice. We conclude that in this model costimulatory blockade in vivo prevents the development of autoimmune disease, but does not result in long-term tolerance. The data are compatible with the interpretation that B7/CD28 blockade prevents generation of effector, but not of memory, T cells.

Animals↗

PubMed2000

Treatment of chronic digital septic tenosynovitis in 12 horses by modified open annular ligament desmotomy and passive open drainage.

A modified open annular ligament desmotomy followed by passive open drainage was used to treat 12 horses with chronic digital septic tenosynovitis due to trauma in the form of open wounds or self-sealing punctures. The surgical approach included complete transection of the palmar/plantar annular ligament of the fetlock and proximal digital annular ligament, which facilitated the removal of fibrin, selective debridement and synovectomy, followed by lavage of the digital sheath. The incision was partially closed leaving a 2 cm gap open distally to allow for passive open drainage. Gentamicin was administered intrathecally during surgery. Postoperatively the horses received ceftiofur and non-steroidal anti-inflammatory drugs. A sterile bandage was used to protect the wound until the gap had healed completely by second intention. Infection was controlled in 11 of the horses which all returned to their previous levels of work, but one horse was euthanased as a result of the persistence of the infection and financial considerations.

Animals↗

PubMed2000

The behaviour of Al in MSW incinerator fly ash during thermal treatment.

Fly ash from municipal solid waste (MSW) incinerators contains leachable metals, including potentially hazardous heavy metals. The metal content of the fly ash can be reduced by thermal treatment, which vaporizes the volatile metal compounds. After heat treatment of fly ash at 1000 degrees C for 3 h, less metal was able to be leached from the thermally treated ash than from the ash without thermal treatment. Al and Cr were the exceptions. These metals were more soluble in the ash that had been thermally treated. This paper focuses on the leaching behaviour of Al only. Both simple and sequential extraction leaching tests showed that the leachable Al for the heat-treated fly ash is about twice that of the untreated fly ash. The sequential test further revealed that (i) the majority of the leachable Al is associated with Fe-Mn oxides in the fly ash, and (ii) most of the unleachable Al resides in the silicate matrices of the heat-treated and untreated fly ash. Pure chemicals, Al(2)O(3), CaO and CaCl(2), simulating the relevant ingredients in the fly ash, were used for studying their reactions at 1000 degrees C. The aluminum compounds were identified by X-ray Diffraction (XRD). Two new chemical phases produced by the thermal treatment were identified; Ca(AlO(2))(2) and 12CaO.7Al(2)O(3). Their formation suggests a mechanism whereby thermal treatment of fly ash would produce more soluble Al.

Air Pollution↗

PubMed2000

Subject-domain approach to the study of air pollution effects on schoolchildren's illness absence.

In this paper, the authors propose a new statistical modeling technique, the subject-domain approach, which is theoretically proven to be equivalent to the time-domain approach in detecting an association between exposure and response with time trends. The authors use an empirical data set from a school absence monitoring study conducted during the 1994-1995 school year in Taiwan to demonstrate this subject-domain approach's application to environmental epidemiologic studies. Because the subject-domain models can control the influential personal confounding factors in the models, they show greater statistical power than the traditional time-domain approaches in determining the relation between air pollution and illness absences. The authors' models found that the schoolchildren's risks of illness absence were significantly related to acute exposures to nitrogen dioxide and nitrogen oxides with a 1-day lag (p < 0.01) at levels below the World Health Organization's guidelines. By contrast, the authors could not detect significant associations between air pollution and schoolchildren's absenteeism using time-domain approaches. Such findings imply that the models built on subject domain may be a general solution to the problem of the ecologic fallacy, which is commonly encountered in environmental and social epidemiologic studies.

Absenteeism↗

PubMed2000

Copolymer 1 inhibits experimental autoimmune uveoretinitis.

Copolymer 1 (Cop 1) inhibits experimental allergic encephalomyelitis induced by a variety of myelin proteins, but has been found ineffective so far in inhibiting other experimental autoimmune diseases such as diabetes or arthritis. Here, we report for the first time that Cop I inhibits the development of experimental autoimmune uveoretinitis, induced in mice by interphotoreceptor retinoid-binding protein (IRBP). Pooled data of three experiments showed that treatment with Cop 1, at 0.5 mg/mouse, reduced the disease severity by 53% ( p = 0.0002). Cop 1 treatment also inhibited the proliferation and the production of cytokines by lymph node cells in response to IRBP and moderately reduced the antibody response to this antigen. The possible mechanisms of EAU inhibition by Cop 1 are discussed.

Animals↗

PubMed2000

Possible mechanism(s) of arachidonic acid-induced intracellular acidosis in rat cardiac myocytes.

Arachidonic acid (AA) and other nonesterified fatty acids (FAs) have been shown to exert harmful effects during cardiac ischemia. By continuously measuring intracellular pH (pH(i)) changes in neonatal and adult cardiac myocytes, we have found, for the first time, that 10 micromol/L AA induces a substantial intracellular acidosis (0.3 to 0.4 pH units). We have ruled out the possibilities that the AA-induced acidosis is caused by (1) inhibition or stimulation of the pH(i) regulators, (2) protein kinase C activation or the generation of AA metabolites or free radicals, or (3) activation of NADPH oxidase or an inward H(+) current. The AA-induced acidosis fits to a simple diffusion mechanism, as proposed by Kamp and Hamilton (flip-flop model) for artificial phospholipid bilayers. The important properties found in the cardiac myocyte are that (1) the initial rate of acid flux (J(H)) increases with the AA concentration (2 to 50 micromol/L), (2) FAs with a (-)COOH group (eg, AA, oleic acid, and linoleic acid) induce intracellular acidification, but FAs with a (-)COOCH(3) group (eg, AA methyl ester) have little effect on the pH(i), (3) tetradecylamine (FA amine) induces intracellular alkalosis, and, most importantly, (4) both the AA- and tetradecylamine-induced pH(i) changes can be reversed by 0.3% BSA. Because a low concentration of AA (10 micromol/L) can induce a substantial acidosis, the possible involvement of the FA-evoked acidosis in the negative inotropic effect during cardiac ischemia is discussed. The full text of this article is available at http://www. circresaha.org.

Acidosis↗

PubMed2000

Biphasic ocular inflammatory response to endotoxin-induced uveitis in the mouse.

OBJECTIVE: To examine the kinetics and mechanisms of endotoxin-induced uveitis in the mouse. METHODS: C3H/HeN mice were injected subcutaneously with 0.3 mg of Salmonella typhimurium lipopolysaccharide (LPS) in 0.1 mL of phosphate-buffered saline solution or phosphate-buffered saline solution alone in 3 separate experiments; mice were killed after 1, 3, 5, and 7 days. In 2 other separate experiments, mice were killed 1, 3, 6, and 24 hours after LPS injection. All eyes were collected for histological examination, immunohistochemical analyses, aqueous protein level determination, and reverse transcriptase-polymerase chain reaction for ocular interleukin (IL)1alpha, IL-6, tumor necrosis factor alpha, and granulocyte-macrophage colony-stimulating factor messenger RNA (mRNA). Enzyme-linked immunosorbent assay was used to measure tumor necrosis factor alpha and IL-6 levels in aqueous and serum samples. RESULTS: Results were consistent for all experiments. Numbers of ocular inflammatory cells and levels of aqueous protein peaked 1 and 5 days after LPS injection. Control mice did not develop inflammation. Serum and aqueous IL-6 and ocular IL-6 mRNA levels peaked at 1 day and subsided at 3 days. However, ocular IL-1alpha, tumor necrosis factor alpha, and granulocyte-macrophage colony-stimulating factor mRNA appeared, peaked, and subsided at 3, 5, and 7 days, respectively. Predominant infiltrating cells were neutrophils at 1 day and macrophages at 5 days. Although no ocular inflammatory cells were detected before 24 hours after LPS injection, tumor necrosis factor alpha mRNA was noticed at 1 hour, peaked at 3 hours, and disappeared at 6 hours and granulocyte-macrophage colony-stimulating factor mRNA was spotted only at 3 hours after LPS injection. CONCLUSIONS: The ocular inflammatory response to C3H/ HeN mouse endotoxin-induced uveitis is biphasic for 7 days. The first wave appears at day 1 and subsides by day 3. A second, higher peak appears at day 5. The 2 inflammatory waves are related to the kinetics of the different cytokines released in the eye. This is in contrast to the rat monophasic endotoxin-induced uveitis model, which has only one peak of intense inflammation associated with cytokine release. CLINICAL RELEVANCE: A biphasic inflammatory response associated with cytokine release lasting several days is observed in C3H/HeN mice with endotoxin-induced uveitis. Because human anterior uveitis has a tendency to be recurrent in nature, this might be a better experimental model.

Animals↗

PubMed2000

Transgenic expression of an immunologically privileged retinal antigen extraocularly enhances self tolerance and abrogates susceptibility to autoimmune uveitis.

Interphotoreceptor retinoid-binding protein (IRBP) is an immunologically privileged retinal antigen that can elicit experimental autoimmune uveitis (EAU). The nature and extent of tolerance to immunologically privileged self antigens is poorly understood. To investigate whether transgenic expression of IRBP extraocularly enhances tolerance and protects from EAU we prepared mice that express half of the mouse IRBP gene, containing a potent uveitogenic epitope (residues 161 - 180), under control of MHC class II promoter. Transgene mRNA was detectable in many tissues. Transgenic protein was undetectable by conventional assays, but was detected in thymic tissue by lymphocyte proliferation assay after induction of the promoter. Transgenic mice challenged with p161 - 180 did not develop EAU and had reduced immunological responses, but remained susceptible to EAU induced by whole IRBP, that contains additional uveitogenic epitopes. Disease was also induced by wild type T cells specific to p161 - 180. Thus, extraocular expression of a privileged retinal antigen enhances self tolerance, supporting the notion that sequestration contributes to immune privilege. Exceedingly low levels of transgene expression result in tolerance that is both profound and epitope specific, implying anergy or deletion of the endogenous uveitogenic repertoire. The same level of expression is, however, insufficient to tolerize wild-type effector T cells in the periphery.

Amino Acid Sequence↗

PubMed2000

Systemic or mucosal administration of immunostimulatory DNA inhibits early and late phases of murine allergic conjunctivitis.

Seasonal allergic conjunctivitis is one of the most common manifestations of allergic disease, affecting 15 % population in the United States annually. Short ragweed (RW) is a major cause of seasonal allergies. Immunostimulatory DNA sequences (ISS or CpG motifs) can inhibit an on-going Th2/allergic response and induce a de novo Th1 response. In this study, we investigated the ability of these ISS to modulate allergic responses in a RW-induced mouse model of seasonal allergic conjunctivitis. Systemic or mucosal administration of ISS oligonucleotide (ISS-ODN) after RW sensitization inhibited both the immediate hypersensitivity response and the late-phase cellular infiltration and induced a RW-specific Th1 response. ISS-ODN administration suppressed the rise of RW-specific IgE titers after repeated allergen challenge. Furthermore, ISS administration was more effective than dexamethasone in inhibiting the allergic response. Mechanistically, the ISS-induced immunomodulatory effects were abolished when mice were treated with anti-IL-12 neutralizing antibodies, suggesting a pivotal role for type 1 cytokines in the inhibition of both the immediate hypersensitivity and the late-phase cellular infiltration. Thus, ISS-ODN is a novel anti-inflammatory and immunomodulatory agent that significantly inhibits the allergic response and may provide an alternative to the current standard care of ocular allergy.

Administration, Topical↗

PubMed2000

Evaluation of in vivo cytokine expression in EAU-susceptible and resistant rats: a role for IL-10 in resistance?

Messenger RNAs for six cytokines (IL-12p40, IFN-gamma, IL-10, IL-4, TNF-alpha and TGF-beta1) expressed in vivo during development of experimental autoimmune uveitis (EAU) were quantitated by PCR in (uncultured) peripheral lymphoid cells and in the eyes of EAU-susceptible Lewis and EAU resistant F344 rats. Disease was induced by immunization with the R16 peptide of IRBP (in RT1B haplotype rats) or with whole IRBP (in all haplotypes). In the periphery, both Lewis and F 344 expressed similar cytokine patterns. In ocular tissues, however, only Lewis expressed elevated type 1 and inflammatory cytokines (IL-12p40, IFN-gamma and TNF-alpha), coincident with onset and peak of disease. Interestingly, naive F344 rats expressed higher basal levels of IL-10 mRNA in the eyes. To examine the possible involvement of this phenomenon in resistance, basal levels of IL-10 vs susceptibility to IRBP were compared in Lewis, BN, DA. F344 and ACI strains. Lewis, BN and DA were susceptible and had low levels of IL-10 mRNA in eyes. F344 and ACI were resistant and expressed high basal levels of IL-10 mRNA. In an in vitro study, recombinant rat IL-10 (but not human or mouse IL-10) suppressed lymphocyte proliferation and IFN-gamma production by primed lymph node cells of R16 immunized rats, but did not suppress uveitogenic long-term T-cell lines polarized to the Thl phenotype, suggesting that mature effector lymphocytes in the rat may lose their ability to be suppressed by IL-10. We propose that higher expression of the IL-10 gene in ocular tissues in some rat strains may represent a mechanism that contributes to a higher threshold of resistance to EAU, but this threshold may be overcome by a more mature Thl effector with a reduced sensitivity to IL-10.

Animals↗

PubMed2000

Xenopus IRBP, a phylogenetically remote protein, is uveitogenic in Lewis rats.

Mammalian interphotoreceptor retinoid-binding proteins (IRBPs) are highly uveitogenic in Lewis rats. Xenopus laevis IRBP resembles mammalian IRBP in its four-fold structure, and has approximately 70% amino acid sequence identity with the bovine protein. This study investigated the uveitogenicity of recombinant Xenopus IRBP and two of its derived peptides in Lewis rats. Rats immunized with Xenopus IRBP developed uveoretinitis as well as pineal inflammation. The Xenopus molecule was, however, less immunopathogenic than the bovine IRBP. Of the two Xenopus IRBP peptides tested, 1180-1191 was remarkably uveitogenic, whereas sequence 521-540 exhibited low activity. It is assumed, therefore, that as with bovine IRBP, peptide 1180-1191 is the major uveitogenic sequence in Xenopus IRBP. The role individual residues of these peptides play in the immunopathogenic process is discussed. Our data thus demonstrate that despite its being phylogenetically remote, Xenopus IRBP is uveitogenic in Lewis rats

Animals↗