Biomedical subjects
Publications and source records attributed to C C Chan.
Extensive SAR has been established in the alkoxy lactone series and this has lead to the discovery of DFP (5,5-dimethyl-3-(2-propoxy)-4-methanesulfonylphenyl)-2(5H)-furanon e), a potent COX-2 inhibitor exhibiting in vivo efficacy in all models studied.
The development of a COX-2 inhibitor rofecoxib (MK 966, Vioxx) is described. It is essentially equipotent to indomethacin both in vitro and in vivo but without the ulcerogenic side effect due to COX-1 inhibition.
A series of novel 2-alkoxy, 2-thioalkoxy and 2-amino-3-(4-methylsulfonyl)phenylpyridines has been synthesized and shown to be highly potent and selective cyclooxygenase-2 (COX-2) inhibitors. Structure-activity relationship studies have demonstrated that central pyridine ring substituents play an important role in the COX-2 potency, selectivity vs the COX-1 enzyme, and oral activity.
Fabry disease is an X-linked metabolic disorder caused by a deficiency of alpha-galactosidase A (alpha-Gal A). The enzyme defect leads to the systemic accumulation of glycosphingolipids with alpha-galactosyl moieties consisting predominantly of globotriaosylceramide (Gb3). In patients with this disorder, glycolipid deposition in endothelial cells leads to renal failure and cardiac and cerebrovascular disease. Recently, we generated alpha-Gal A gene knockout mouse lines and described the phenotype of 10-week-old mice. In the present study, we characterize the progression of the disease with aging and explore the effects of bone marrow transplantation (BMT) on the phenotype. Histopathological analysis of alpha-Gal A -/0 mice revealed subclinical lesions in the Kupffer cells in the liver and macrophages in the skin with no gross lesions in the endothelial cells. Gb3 accumulation and pathological lesions in the affected organs increased with age. Treatment with BMT from the wild-type mice resulted in the clearance of accumulated Gb3 in the liver, spleen, and heart with concomitant elevation of alpha-Gal A activity. These findings suggest that BMT may have a potential role in the management of patients with Fabry disease.
Explore the source record for details and available documents.
Cyclopentenones containing a 4-(methylsulfonyl)phenyl group in the 3-position and a phenyl ring in the 2-position are selective inhibitors of cyclooxygenase-2 (COX-2). The selectivity for COX-2 over COX-1 is dramatically improved by substituting the 2-phenyl group with halogens in the meta position or by replacing the phenyl ring with a 2- or 3-pyridyl ring. Thus the 3,5-difluorophenyl derivative 7 (L-776,967) and the 3-pyridyl derivative 13 (L-784,506) are particularly interesting as potential antiinflammatory agents with reduced side-effect profiles. Both exhibit good oral bioavailability and are potent in standard models of pain, fever, and inflammation yet have a much reduced effect on the GI integrity of rats compared to standard nonsteroidal antiflammatory drugs.
Many human and mouse tumor antigens are normal, nonmutated tissue differentiation antigens. Consequently, immunization with these "self" antigens could induce autoimmunity. When we tried to induce immune responses to five mouse melanocyte differentiation antigens, gp100, MART-1, tyrosinase, and tyrosinase-related proteins (TRP) 1 and TRP-2, we observed striking depigmentation and melanocyte destruction only in the skin of mice inoculated with a vaccinia virus encoding mouse TRP-1. These mice rejected a lethal challenge of B16 melanoma, indicating the immune response against TRP-1 could destroy both normal and malignant melanocytes. Cytotoxic T lymphocytes specific for TRP-1 could not be detected in depigmented mice, but high titers of IgG anti-TRP-1 antibodies were present. Experiments with knockout mice revealed an absolute dependence on major histocompatibility complex class II, but not major histocompatibility complex class I, for the induction of both vitiligo and tumor protection. Together, these results suggest that the deliberate induction of self-reactivity using a recombinant viral vector can lead to tumor destruction, and that in this model, CD4(+) T lymphocytes are an integral part of this process. Vaccine strategies targeting tissue differentiation antigens may be valuable in cancers arising from nonessential cells and organs such as melanocytes, prostate, testis, breast, and ovary.
Protein tyrosine phosphatase-1B (PTP-1B) has been implicated in the negative regulation of insulin signaling. Disruption of the mouse homolog of the gene encoding PTP-1B yielded healthy mice that, in the fed state, had blood glucose concentrations that were slightly lower and concentrations of circulating insulin that were one-half those of their PTP-1B+/+ littermates. The enhanced insulin sensitivity of the PTP-1B-/- mice was also evident in glucose and insulin tolerance tests. The PTP-1B-/- mice showed increased phosphorylation of the insulin receptor in liver and muscle tissue after insulin injection in comparison to PTP-1B+/+ mice. On a high-fat diet, the PTP-1B-/- and PTP-1B+/- mice were resistant to weight gain and remained insulin sensitive, whereas the PTP-1B+/+ mice rapidly gained weight and became insulin resistant. These results demonstrate that PTP-1B has a major role in modulating both insulin sensitivity and fuel metabolism, thereby establishing it as a potential therapeutic target in the treatment of type 2 diabetes and obesity.
Protection from the development of experimental autoimmune uveitis (EAU) can be induced by feeding mice interphotoreceptor retinoid binding protein before uveitogenic challenge with the same protein. Two different regimens are equally effective in inducing protective tolerance, although they seem to do so through different mechanisms: one involving regulatory cytokines (IL-4, IL-10, and TGF-beta), and the other with minimal involvement of cytokines. Here we studied the importance of IL-4 and IL-10 for the development of oral tolerance using mice genetically engineered to lack either one or both of these cytokines. In these animals we were able to protect against EAU only through the regimen inducing cytokine-independent tolerance. When these animals were fed a regimen that in the wild-type animal is thought to predominantly induce regulatory cells and is associated with cytokine secretion, they were not protected from EAU. Interestingly, both regimens were associated with reduced IL-2 production and proliferation in response to interphotoreceptor retinoid binding protein. These findings indicate that both IL-4 and IL-10 are required for induction of protective oral tolerance dependent on regulatory cytokines, and that one cytokine cannot substitute for the other in this process. These data also underscore the fact that oral tolerance, manifested as suppression of proliferation and IL-2 production, is not synonymous with protection from disease.
Female patients suffering from autoimmune uveitis are reported to experience a temporary remission during pregnancy. Experimental autoimmune uveitis (EAU) is a model for human uveitis. Here we examine the effect of pregnancy on the development of EAU and its associated immunological responses. Susceptible C57BL/6 mice were immunized with interphotoreceptor retinoid-binding protein (IRBP). EAU scores and Ag-specific responses were evaluated 21 days later. Mice immunized during pregnancy developed significantly less EAU than nonpregnant controls. Their lymph node cells and splenocytes produced a distinct pattern of cytokines in response to IRBP: reduced IFN-gamma and IL-12 p40, but unchanged levels of TNF-alpha, IL-4, IL-5, and IL-10. Anti-IRBP Ab isotypes revealed an up-regulation of IgG1, indicating a possible Th2 bias at the humoral level. Ag-specific proliferation and delayed hypersensitivity, as well as mitogen-induced IFN-gamma production, remained undiminished, arguing against an overall immune deficit. Interestingly, pregnant mice that received an infusion of IRBP-primed lymphoid cells from nonpregnant donors also developed reduced EAU, suggesting that pregnancy suppresses not only the generation, but also the function of mature uveitogenic effector T cells. Pregnant mice at the time of immunization exhibited elevated levels of TGF-beta, but not of IL-10, in the serum. We suggest that protection from EAU during pregnancy is due primarily to a selective reduction of Ag-specific Th1 responses with only marginal enhancement of Th2 function, and that these effects may in part be secondary to elevated systemic levels of TGF-beta.
Substituted heterocyclic analogs in the Flosulide class were investigated as potential selective cyclooxygenase-2 inhibitors. 6-(4-Ethyl-2-thiazolylthio)-5-methanesulfonamido-3H-isobe nzofuran-1-one 14 was found to be the optimal compound in the series with superior in vitro and in vivo activities.
Pathogenic effector T cells in experimental autoimmune uveitis (EAU) are T helper type 1-like, and interleukin (IL)-12 is required for their generation and function. Therefore, we expected that IL-12 administration would have disease-enhancing effects. Mice were immunized with a uveitogenic regimen of the retinal antigen interphotoreceptor retinoid-binding protein, treated with IL-12 (100 ng/d for 5 d), and EAU was assessed by histopathology. Unexpectedly, IL-12 treatment failed to enhance EAU in resistant strains and downregulated disease in susceptible strains. Only treatment during the first, but not during the second, week after immunization was consistently protective. High levels of interferon gamma (IFN-gamma) were present in the serum during IL-12 treatment, but subsequent antigen-specific IFN-gamma production in protected mice was diminished, as were IL-5 production, lymph node cell proliferation, and serum antibody levels. Treated mice had fewer cells and evidence of enhanced apoptosis in the draining lymph nodes. Unlike wild-type mice, IFN-gamma-deficient, inducible nitric oxide synthase (iNOS)-deficient, and Bcl-2(lck) transgenic mice were poorly protected by IL-12, whereas IL-10-deficient mice were protected. We conclude that administration of IL-12 aborts disease by curtailing development of uveitogenic effector T cells. The data are compatible with the interpretation that IL-12 induces systemic hyperinduction of IFN-gamma, causing activation of iNOS and production of NO, which mediates protection at least in part by triggering Bcl-2 regulated apoptotic deletion of the antigen-specific T cells as they are being primed.
A total elemental analysis was performed on a municipal solid waste (MSW) fly ash sample, before and after it was treated at 1000 degrees C, to reveal the metal distribution between the volatile matter and the ash residue. Metals such as Pb, Zn, Cd, and to a lesser degree, Cr, Mn and Ni, were volatilized. Addition of chlorinating agents generally increased the volatility of certain elements. More acid resistant compounds were formed in the ash residue after the heat treatment using CaCl2 as a chlorinating agent. The efficiencies of volatilization of the metals, using Cl2 as a chlorinating agent, were generally higher compared with using CaCl2. However, CaCl2 was found to be a more selective chlorinating agent for volatilizing the heavy metals of concern, i.e., Pb, Cd, Zn and Cu. The efficiencies of volatilization of the recovered metals were approximately proportional to their standard free-energy changes (delta G(o) for the corresponding chlorination reactions.
OBJECTIVE: Retinal angioma frequently occurs in von Hippel-Lindau (VHL) disease. However, VHL gene alterations have not been documented in retinal angiomas. METHODS: Using tissue microdissection and polymerase chain reaction amplification, we have analyzed 7 retinal angiomas associated with VHL disease for loss of heterozygosity of the VHL gene. In addition, vascular endothelial growth factor expression was evaluated in these tumors by immunohistochemistry and in situ hybridization. RESULTS: All 6 informative retinal angiomas showed loss of heterozygosity of the VHL gene. Loss of heterozygosity was detected in vacuolated "stromal" cells, but not in vascular cells or reactive glial tissue. Vascular endothelial growth factor protein and messenger RNA were also present in vacuolated "stromal" cells. CONCLUSIONS: These findings suggest that vacuolated "stromal" cells represent the true neoplastic component in retinal angioma. These cells express vascular endothelial growth factor and therefore may be responsible for abundant neovascularization of retinal angioma.
Primary intraocular lymphoma is almost always a central nervous system B-cell non-Hodgkin lymphoma. Primary intraocular lymphoma is commonly diagnosed by demonstrating lymphoma cells in the vitreous or cerebrospinal fluid. An interleukin (IL) 10 to IL-6 ratio greater than 1.0 in these fluids and the detection of immunoglobulin gene rearrangement are useful adjuncts in the diagnosis of primary intraocular lymphoma. We report a case of primary intraocular lymphoma diagnosed by chorioretinal biopsy in which no malignant cells were identified in the vitreous and in which the IL-10 to IL-6 ratio was less than 1.0. The detection of IgH gene rearrangement heterogeneity in the tumor cells by polymerase chain reaction, a high tumor mitotic figure rate, and the rapid onset of multiple brain lesions suggest an aggressive malignant neoplasm.
This study investigated the effect of vasopressin on portal-systemic collaterals in portal hypertensive rats and the influence of nitric oxide (NO) and prostaglandin on the responsiveness of collateral vessels to vasopressin. The vascular responsiveness to graded concentrations of vasopressin was tested with or without the incubation of n(omega)-nitro-L-arginine (NNA) (100 micromol/L) and/or indomethacin (10 micromol/L) in perfused collateral vascular beds of rats with portal hypertension induced by partial portal vein ligation. In addition, concentration-response curves to vasopressin with incubation of a vasopressin V(1) receptor antagonist d(CH(2))(5)Tyr(Me) arginine vasopressin and concentration-response curves to a V(2) receptor agonist 1-desamino-8-D-arginine vasopressin were performed. Vasopressin significantly increased the perfusion pressure of collaterals, and this effect was suppressed by the addition of the V(1) receptor antagonist. Perfusion with the V(2) receptor agonist had no effect on the collaterals. Incubation with NNA, indomethacin, or both significantly potentiated the response of collaterals to vasopressin. In addition, the pressor response to vasopressin in the combination group was significantly higher than that in the NNA-alone group. The results show that vasopressin produces a direct vasoconstrictive effect on the portal-systemic collaterals of portal hypertensive rats. This effect is mediated by the vasopressin V(1,) but not V(2), receptors. The attenuation of the response to vasopressin by NO and prostaglandin suggest a function role of both mediators in the regulation of the portal-systemic collateral circulation in portal hypertensive rats.
Interferon-gamma (IFN-gamma) is a pleiotropic cytokine that has been implicated in immunopathogenic mechanisms of a number of inflammatory diseases of autoimmune or infectious disease etiology. However, its exact role is still a matter of debate. In experimental mouse models, IFN-gamma has been shown to exacerbate autoimmune thyroiditis, insulin-dependent diabetes mellitus, and autoimmune neuritis while it confers protection against experimental allergic encephalomyelitis and experimental uveitis. In this study, we generated transgenic rats with constitutive expression of IFN-gamma in the eye to study its paracrine effects and to investigate whether local production of IFN-gamma also confers protection against uveitis in the rat species. We show here that chronic exposure of ocular cells to IFN-gamma results in apoptotic death of retinal ganglion cells, development of chronic choroiditis, formation of retinal in-foldings, and activation of proinflammatory genes. In contrast to its protective systemic effect in the mouse, constitutive secretion of IFN-gamma in the rat eye was found to predispose the development of severe anterior uveitis and induction of retinal degenerative processes that impair visual acuity. Our data underscore the danger in extrapolation of cytokine effects in the mouse to humans without corroborating evidence in other species.
Cell adhesion molecules are critical for the homing and migration of leukocytes into inflamed tissues. We investigated the role of ICAM-1 and LFA-1 in a previously described experimental model of ragweed (Rw)-induced allergic conjunctivitis. SWR/J mice were treated intraperitoneally 6 and 1 h prior to topical challenge with Rw with injections of anti-ICAM-1 monoclonal antibody (mAb), anti-LFA-1 mAb, both anti-ICAM-1 and anti-LFA-mAbs, or rat IgG. Blocking ICAM-1 or LFA-1 reduced the clinical signs of allergic conjunctivitis. Treatment with anti-ICAM-1 or anti-LFA-1 mAbs also significantly inhibited cellular infiltration into the conjunctiva. The greatest inhibitory effect was achieved with the combination of antibodies against both cell adhesion molecules. Since antibodies against ICAM-1 and LFA-1 significantly inhibit the development of the clinical and histologic signs of allergic conjunctivitis, they may be useful for treating patients with ocular allergy.