Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.4.2.8 (hypoxanthine-guanine phosphoribosyltransferase)
 2,527 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Chronic inhalation of crystalline silica can produce lung tumors in rats whereas this has not been shown for amorphous silica. At present the mechanisms underlying this rat lung tumor response are unknown, although a significant role for chronic inflammation and cell proliferation has been postulated. To examine the processes that may contribute to the development of rat lung tumors after silica exposure, we characterized the effects of subchronic inhalation of amorphous and crystalline silica in rats. Rats were exposed for 6 h/day, on 5 days/week, for up to 13 weeks to 3 mg/m(3) crystalline or 50 mg/m(3) amorphous silica. The effects on the lung were characterized after 6.5 and 13 weeks of exposure as well as after 3 and 8 months of recovery. Exposure concentrations were selected to induce high pulmonary inflammatory-cell responses by both compounds. Endpoints characterized after silica exposure included mutation in the HPRT gene of isolated alveolar cells in an ex vivo assay, changes in bronchoalveolar lavage fluid markers of cellular and biochemical lung injury and inflammation, expression of mRNA for the chemokine MIP-2, and detection of oxidative DNA damage. Lung burdens of silica were also determined. After 13 weeks of exposure, lavage neutrophils were increased from 0.26% (controls) to 47 and 55% of total lavaged cells for crystalline and amorphous silica, with significantly greater lavage neutrophil numbers after amorphous silica (9.3 x 10(7) PMNs) compared to crystalline silica (6.5 x 10(7) PMNs). Lung burdens were 819 and 882 microg for crystalline and amorphous silica, respectively. BAL fluid levels of LDH as an indicator of cytotoxicity were twice as high for amorphous silica compared to those of crystalline silica, at the end of exposure. All parameters remained increased for crystalline silica and decreased rapidly for amorphous silica in the 8-month recovery period. Increased MIP-2 expression was observed at the end of the exposure period for both amorphous and crystalline silica. After 8 months of recovery, those markers remained elevated in crystalline silica-exposed rats, whereas amorphous silica-exposed rats were not significantly different from controls. A significant increase in HPRT mutation frequency in alveolar epithelial cells was detected immediately after 13 weeks of exposure to crystalline, but not to amorphous silica. A significant increase in TUNEL staining was detected in macrophages and terminal bronchiolar epithelial cells of amorphous silica-exposed rats at the end of the exposure period; however, crystalline silica produced far less staining. The observation that genotoxic effects in alveolar epithelial cells occurred only after crystalline but not amorphous silica exposure, despite a high degree of inflammatory-cell response after subchronic exposure to both types of silica, suggests that in addition to an inflammatory response, particle biopersistence, solubility, and direct or indirect epithelial cell cytotoxicity may be key factors for the induction of either mutagenic events or target cell death.
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PMID:Pulmonary chemokine and mutagenic responses in rats after subchronic inhalation of amorphous and crystalline silica. 1091 Oct

Interleukin-8 (IL-8) is a chemokine for neutrophils and an angiogenic factor. Human tumors that express IL-8 may exhibit intense neutrophil infiltration and increased vascularization. Mutatect cells are a murine fibrosarcoma that can be grown as subcutaneous tumors in syngeneic C57BL/6 mice. Since neutrophils are a source of cytotoxic and genotoxic species, we constructed Mutatect cell lines that constitutively express human IL-8 to explore the involvement of neutrophils in tumor biology and genetic instability. An IL-8/neo expression plasmid was stably transfected into Mutatect MC17-51 cells and clone MIL-4 was isolated. Tumors initiated with 5x10(5) MIL-4 cells grew very slowly compared with tumors from pure MC17-51 cells or from 0.5 to 4x10(5) MIL-4 cells mixed with 5x10(5) MC17-51 cells. Over 95% of cells recovered from slow-growing pure MIL-4 tumors lost the transgene as measured by loss of (i) resistance to G418, (ii) expression of IL-8 protein and (iii) IL-8-specific DNA sequences. When tumors from mixed cell types were examined, loss of the transgene did not occur; rather, IL-8 producing cells appeared to have some growth advantage. The neutrophil content of tumors (as measured by myeloperoxidase) was directly proportional to the level of IL-8 expressed at the time tumors were excised. As reported earlier, the frequency of mutations at the hypoxanthine phosphoribosyltransferase locus was also directly proportional to neutrophil content. To explain some of these biological findings, we postulate that early in development of pure MIL-4 tumors, genotoxic/cytotoxic neutrophils are attracted by IL-8, which in turn leads to loss of the transgene and to localized cytotoxicity of IL-8 producing cells. In mixed tumors, where the initial IL-8 concentration may be lower, tumors might become established more readily because fewer neutrophils may be attracted. This relatively simple experimental paradigm has revealed some of the complex biological changes that can occur as a result of IL-8 in tumors.
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PMID:Constitutive expression of interleukin-8 by Mutatect cells markedly affects their tumor biology. 1118 44

Neutrophils represent a potential source of genotoxic reactive oxygen and nitrogen species in the tumor microenvironment. Using Mutatect cell lines, which can form subcutaneous tumors in syngeneic C57BL/6 mice, we have previously established that the number of spontaneously infiltrating neutrophils correlates with the number of mutations at the hypoxanthine phosphoribosyltransferase (Hprt) locus. We now describe the properties of four lines that express different levels of the neutrophil chemokine, interleukin-8 (IL-8), from a tetracycline (TET)-responsive promoter. In a series involving 45 animals, IL-8-expressing lines produced tumors with a higher neutrophil content than the control line. Analysis of the 45 tumors revealed that the neutrophil level again strongly correlated with hprt mutant frequency (MF) (P<.0001, r=0.88). Administration of TET was effective in lowering the neutrophil content of low IL-8-expressing tumors, but not high IL-8-expressing tumors. Although the IL-8 transgene was stable in all lines in vitro, high IL-8-expressing lines completely lost the transgene in vivo whereas low IL-8-expressing lines showed no evidence of transgene instability. These results provide further evidence, based on the study of an endogenous gene (hprt) and an IL-8 transgene, that neutrophils may contribute to genetic instability in tumors.
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PMID:Expression of interleukin-8 promotes neutrophil infiltration and genetic instability in mutatect tumors. 1122 49

A variety of commercial DNA arrays specific for humans and rodents are widely available; however, microarrays containing well-characterized genes to study pathway-specific gene expression are not as accessible for domestic animals, such as cattle, sheep and pigs. Therefore, a small-scale application-targeted bovine immune-endocrine cDNA array was developed to evaluate genetic pathways involved in the immune-endocrine axis of cattle during periods of altered homeostasis provoked by physiological or environmental stressors, such as infection, vaccination or disease. For this purpose, 167 cDNA sequences corresponding to immune, endocrine and inflammatory response genes were collected and categorized. Positive controls included 5 housekeeping genes (glyceraldehydes-3-phosphate dehydrogenase, hypoxanthine phosphoribosyltransferase, ribosomal protein L19, beta-actin, beta2-microglobulin) and bovine genomic DNA. Negative controls were a bacterial gene (Rhodococcus equi 17-kDa virulence-associated protein) and a partial sequence of the plasmid pACYC177. In addition, RNA extracted from un-stimulated, as well as superantigen (Staphylococcus aureus enterotoxin-A, S. aureus Cowan Pansorbin Cells) and mitogen-stimulated (LPS, ConA) bovine blood leukocytes was mixed, reverse transcribed and PCR amplified using gene-specific primers. The endocrine-associated genes were amplified from cDNA derived from un-stimulated bovine hypothalamus, pituitary, adrenal and thyroid gland tissues. The array was constructed in 4 repeating grids of 180 duplicated spots by coupling the PCR amplified 213-630 bp gene fragments onto poly-l-lysine coated glass slides. The bovine immune-endocrine arrays were standardized and preliminary gene expression profiles generated using Cy3 and Cy5 labelled cDNA from un-stimulated and ConA (5 microg/ml) stimulated PBMC of 4 healthy Holstein cows (2-4 replicate arrays/cow) in a time course study. Mononuclear cell-derived cytokine and chemokine (IL-2, IL-1alpha, TNFalpha, IFN-gamma, TGFbeta-1, MCP-1, MCP-2 and MIP-3alpha) mRNA exhibited a repeatable and consistently low expression in un-stimulated cells and at least a two-fold increased expression following 6 and 24 h ConA stimulation as compared to 0 h un-stimulated controls. In contrast, expression of antigen presenting molecules, MHC-DR, MHC-DQ and MHC-DY, were consistently at least two-fold lower following 6 and 24 h ConA stimulation. The only endocrine gene with differential expression following ConA stimulation was prolactin. Additionally, due to the high level of genetic homology between ovine, swine and bovine genes, RNA similarly acquired from sheep and pigs was evaluated and similar gene expression patterns were noted. These data demonstrate that this application-targeted array containing a set of well characterized genes can be used to determine the relative gene expression corresponding to immune-endocrine responses of cattle and related species, sheep and pigs.
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PMID:Construction and application of a bovine immune-endocrine cDNA microarray. 1526 89