1 Department of Medical Oncology, City of Hope National Medical Center, Duarte 91010; 2 Division of Digestive Diseases, Department of Medicine, and 3 Division of Gastroenterology and Nutrition, Department of Pediatrics, University of California School of Medicine, Los Angeles 90019; 2 Department of Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles 90024; and 4 Division of Medical Genetics, Department of Pathology, Cedars-Sinai Medical Center, Los Angeles, California 90048
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ABSTRACT |
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Glutathione peroxidase (GPX)-1 and gastrointestinal (GI) epithelium-specific GPX (GPX-GI), encoded by Gpx1 and Gpx2, provide most GPX activity in GI epithelium. Although homozygous mice deficient in either the Gpx1 or Gpx2 gene appeared to be normal under standard housing conditions, homozygous mice deficient in both genes, double-knockout (KO) mice, had symptoms and pathology consistent with inflammatory bowel disease. These symptoms included a high incidence of perianal ulceration, growth retardation that started around weaning, and hypothermia that resembled that observed in calorie-restricted mice, even though the double-KO mice in our study were allowed to eat ad libitum. The growth retardation and hypothermia were components of cachexia, which is fatal in a high percentage of mice. Histological examination revealed that the double-KO mice had a high incidence of mucosal inflammation in the ileum and colon but not in the jejunum. Elevated levels of myeloperoxidase activity and lipid hydroperoxides were also detected in colon mucosa of these homozygous double-KO mice. These results suggest that GPX is essential for the prevention of the inflammatory response in intestinal mucosa.
inflammatory bowel disease; lipid hydroperoxides; growth retardation; hypothermia; mitochondrial superoxide dismutase
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INTRODUCTION |
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SELENIUM-DEPENDENT GLUTATHIONE PEROXIDASES (GPXs) are the major selenoprotein-containing gene family in mammals. The GPXs include four selenium-dependent hydroperoxide-reducing isozymes: GPX-1, gastrointestinal (GI) epithelium-specific GPX (GPX-GI), the secreted plasma GPX (GPX-P), and monomeric phospholipid hydroperoxide GPX (PHGPX), which are encoded by the Gpx1, Gpx2, Gpx3, and Gpx4 genes, respectively. The GPX-1 and GPX-GI isozymes have very similar properties, such as substrate specificity and cytosolic localization (4, 9). They both reduce H2O2 and fatty acid hydroperoxides very efficiently and reduce lipid hydroperoxides poorly. Unlike the ubiquitous GPX-1, GPX-GI is expressed only in epithelium, most highly in the gastrointestinal epithelium. Although GPX-P and PHGPX are also present in the GI tract (5, 30), GPX-P is secreted extracellularly, and PHGPX has a substrate specificity distinct from these two cytosolic isozymes. GPX-1 and GPX-GI contribute almost all of the intracellular H2O2-reducing activity in the GI tract.
Little is known about the physiological roles of the GPX isozymes. The best available evidence points to GPX-1 having anti-inflammatory activity in animal studies. We observed that Gpx1-knockout (KO) mice were more susceptible to myocarditis than wild-type mice after infection with Coxsackie virus (3). Because the viral antibody titers in Gpx1-KO mice are about one-fifth of those found in wild-type mice, this suggests that, in addition to enhanced susceptibility to inflammation, humoral immune responses may also be impaired in homozygous Gpx1-KO mice. Additionally, the Gpx1-KO mice are more susceptible to neutrophil-caused liver injury induced by combined treatment with lipopolysaccharide and galactosamine (21). The kidneys of Gpx1-transgenic mice are more resistant to renal ischemia/reperfusion injury, and these Gpx1-transgenic mouse kidneys have less neutrophil infiltration (20). Neutrophils, also called polymorphonuclear leukocytes, are often referred to as inflammatory cells because they play an important role in inflammation and natural immunity and function to eliminate microbes and necrotic tissues. These results suggest that GPX-1 in heart, liver, and kidney can prevent oxidative injury from the immune/inflammatory response.
We have recently generated homozygous Gpx2-KO mice and have
not observed any differential responses from wild-type mice under normal housing conditions and after exposure to limited types of
treatment such as -irradiation to examine crypt regeneration (8). Because the epithelium of the GI tract has high-level coexpression of two very similar isozymes, GPX-1 and GPX-GI, the lack
of phenotype in both unchallenged homozygous Gpx1-KO
(7, 8, 16) and Gpx2-KO mice suggests a
functional redundancy of these two genes in the GI tract. However,
these two genes appear to be expressed differentially within the
epithelium: the Gpx1 gene is predominately expressed in the
villus, whereas the Gpx2 gene is preferentially expressed in
the crypt (6, 9, 30, 34). This suggests that expression of
these two genes may be complementary rather than completely redundant.
To investigate the physiological functions of GPX in intestinal epithelial cells, we have generated homozygous double-KO mice deficient in both Gpx1 and Gpx2 gene expression. These double-KO mice have symptoms and histopathology consistent with inflammatory bowel disease (IBD). The three-fourths-KO mice with only a single Gpx1 allele are more prone to inflammation compared with the reciprocal three-fourths-KO mice with a single Gpx2 allele. These results suggest that these two genes are not functionally redundant. In this study, we have provided the first evidence suggesting that both GPX-1 and GPX-GI have anti-inflammatory activity in the intestinal mucosa. These homozygous double-KO mice may provide a novel animal model in which to study the pathogenesis of IBD.
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EXPERIMENTAL PROCEDURES |
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Generation and maintenance of double-KO mice deficient in both Gpx1 and Gpx2 gene expression. Gpx1-KO mice were generated by Ye-Shih Ho (Wayne State University, Detroit, MI) (16) as C57BL/6J (B6) and 129Sv/J hybrids. The generation of Gpx2-KO mice as B6 and 129S3 hybrids at the City of Hope (COH; Duarte, CA) Transgenic Mouse Core has been described previously (8). These mice were housed at the COH Animal Resources Center in ventilated cage racks (Allentown Caging Equipment, Allentown, NJ). We have followed protocols approved by the COH Research Animal Care Committee, which abides by NIH guidelines, to perform all of the animal studies described in this paper. Sentinel mice housed in the cage containing bedding from the double-KO mice tested positive for Helicobacter hepaticus, H. typhlonicus, and H. rodentium by PCR that was performed by the Missouri University Research Animal Diagnostic and Investigative Lab (Columbia, MO). The mice were free of parasites and microorganisms including Salmonella sp., Mycoplasma pulmonis, and Pasteurella pneumotropica. They had no serum antibodies to M. pulmonis or to known murine viruses including Sendai, mouse hepatitis, pneumonia of mice, ectromelia, retrovirus type 3, GDVII (mouse polio), parvovirus, epidemic diarrhea of infant mice virus, and lymphocytic choriomeningitis. All mice had free access to water and a laboratory rodent diet (chow 5001, Purina Mills, Richmond, IN) that contained 23% protein, 4.5% fat, 6% fiber, and 0.28 ppm selenium as provided by the manufacturer (http://www.labdiet.com). If mice were emaciated, we were obligated to supplement the diet with Nutri-Cal (EVSCO Pharmaceuticals, Brena, NJ), which has 0.7% protein, 34.5% fat, and 3.8% fiber and is enriched with vitamins A and E. One to two milliliters of Nutri-Cal paste was added on top of the chow every other day. This was a preferred diet judging from the immediate consumption on application.
Tail DNA was used for genotyping of Gpx1- and Gpx2-KO mice by either Southern blot or PCR analysis. For Southern blot analysis, 10 µg of DNA was digested with BamH I or Apa I to determine the genotype of Gpx1 and Gpx2, respectively. After overnight digestion, DNA was resolved on a 0.75% agarose gel, transferred to a ZetaProbe membrane (Bio-Rad, Richmond, CA), and probed with a 32P-labeled and random-primed 3' EcoR I fragment of mouse Gpx1 cDNA and mouse Gpx2 exon 2 cDNA. The Southern blot was analyzed by phosphorimaging (Molecular Dynamics, Sunnyvale, CA) (8). The PCR primers for the wild-type Gpx1 allele were mPX101F (5'-AAGGAGGTGCAGGCGGCTGTGAGCG-3') and GPX15 (5'-ACCGTTCACCTTGCACTTCTC-3') to amplify an ~600-bp DNA fragment. The primers for the Gpx1-KO allele were pPNTpgk1 (5'-CAGTTTCATAGCCTGAAGAACGAGAT-3') and GPX15 to amplify an ~200-bp DNA fragment. The primers for the wild-type Gpx2 allele were MPX206 (5'-CCCACCTGTCTAGAGGACTTA-3') and MPXin09 (5'-TCCATGCCAACGTAGTGATT-3') to amplify an ~600-bp DNA fragment. The primers for the Gpx2 allele were MPXin09 and pNTpgk1 to amplify an ~400-bp DNA fragment. pPNTpgk1 is from the mouse phosphoglycerate kinase poly(A) signal that follows the neomycin phosphotransferase (neo) coding sequence. Both alleles were amplified in the same reaction tubes.Metabolic studies. Rectal temperature was measured with a Thermalert mouse probe (TH-8; Physitemp Instrument, Clifton, NJ) between 6:00 and 8:00 AM for mice under normal housing conditions. To quantify the food and water consumption and feces and urine excretion, mice were placed in metabolic cages with wire grid floors for 24 h. This setting appeared to be stressful for the double-KO mice, as shown by a frequent hunched-over appearance and the presence of loose stools.
Histology of small and large intestine from mice with altered Gpx1, Gpx2, or Sod2 gene expression. The mice with altered Gpx1 and Gpx2 genes were killed by halothane overdose (Halocarbon Labs, North Augusta, SC). After the luminal contents were removed, sections of jejunum, ileum, colon, and rectum were rinsed with PBS and then fixed in 10% buffered formalin or Bouin's fixative for 2-3 h. The fixed GI tissues from homozygous Sod2-KO [deficient in the Mn-superoxide dismutase (SOD) gene] B6D2F2 mice, 15-19 days of age, were obtained from Charles J. Epstein (University of California, San Francisco, CA) (18). The tissues were then dehydrated in ethanol, embedded in paraffin, and sectioned onto slides. The tissue sections were stained with hematoxylin and eosin alone or in combination with the periodic acid-Schiff reagent.
GPX, myeloperoxidase, and lipid hydroperoxide assays. The GPX activity was determined on intestinal and colonic epithelium from 42- to 47-day-old mice. Jejunal and ileal epithelium was isolated from the proximal and the distal one-third of small intestine as described previously (8). GPX activity was measured with 60 µM H2O2 and 3 mM GSH at pH 7.3. Myeloperoxidase (MPO) activity was determined with the enzyme that catalyzes the oxidation of 3,3',5,5'-tetramethylbenzidine by H2O2 to yield a chromogen that can be measured at absorbance (A)655 (13). Elevation of lipid hydroperoxide (LPO) levels were measured colorimetrically with a commercial kit (LPO assay kit; Cayman, Ann Arbor, MI). This assay measures the hydroperoxide-driven production of thiocyanate ion, which is detected at A500, with a sensitivity of 0.25-5 nmol hydroperoxide. Mice 40 days of age were used for this assay. LPO levels were measured after the intestinal lumen was flushed with Ca2+- and Mg2+-free PBS. Two-tenths of a gram of jejunum, ileum, or colon was homogenized in 2 ml of ice-cold water. Fifty microliters were taken for protein assay. The remainder of the sample was extracted with methanol and chloroform and measured for LPO spectrophotometrically at A500, following the manufacturer's recommendation. The protein concentration was determined with a BCA assay (Pierce Chemical, Rockford, IL), with BSA as the standard. Statistical analysis was performed with a two-tailed Student's t-test using Excel (Microsoft Office 97, Professional Edition). A P value <0.05 was considered significant.
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RESULTS |
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Generation of double-KO mice.
Homozygous Gpx1-KO and Gpx2-KO mice
were bred to generate heterozygous double-KO mice. These heterozygous
double-KO mice were bred to each other; one-sixteenth of the offspring
were homozygous double-KO mice as determined by Southern blot (Fig.
1A). One-fourth of the mice
were three-fourths-KOs, with either a single Gpx1 or
Gpx2 allele. These double-KO and three-fourths-KO mice were then used as breeders to generate double-KO mice. The number of the
double-KO mice agreed with the predicted value from Mendelian genetics,
suggesting that there was no prenatal selection. Similar numbers of
male and female offspring were obtained, suggesting that there was no
gender selection. Fertile male and female double-KO mice were raised
but were considered high-risk breeders because of their health
problems.
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Weight gain and gross phenotypes of double-KO mice.
The homozygous double-KO mice gained weight more slowly than mice of
other genotypes or stopped gaining weight completely starting around 16 days of age. Figure 2A shows
the typical growth of individual mice in a litter. Among the eight
pups, two double-KO mice had the same body weight as their littermates
until weaning. In a cohort of 33 double-KO mice, 32 showed growth
retardation onset between 16 and 26 days of age. The last mouse started
to show growth retardation at 30 days of age. Other symptoms often associated with these homozygous double-KO mice included perianal ulceration (shown in Fig. 2B) as well as anal mucus
discharge, diarrhea, and hypothermia. One or more of these symptoms
occurred as early as 14 days of age. Approximately 40% of the
double-KO mice died or were euthanized because of presumed imminent
death, which was judged by their emaciated body condition between 20 and 36 days of age. Autopsies revealed diarrheal stool in edematous colons. No macroscopic or microscopic abnormality was seen in other
major organs.
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Inflammation of the small intestine, colon, and rectum.
Histological analysis was performed on cross sections of stomach,
jejunum, ileum, colon, and rectum after staining with
hematoxylin and eosin as shown in Fig. 4.
Cross sections from two representative 24-day-old littermates, a
homozygous double-KO and a three-fourths-KO with a Gpx2
allele, were compared. The three-fourths-KO mouse had normal histology
in the GI tract. In contrast, the double-KO mouse had severe
inflammation involving the ileum and colon, whereas the jejunum and
stomach were unaffected. The inflammation was limited to the mucosa and
was rarely transmural. Crypt abscesses were prevalent in ileum, colon,
and rectum. These histological features of a mixed inflammatory cell
infiltrate, mucin depletion, and occasional crypt distortion are
features consistent with human ulcerative colitis.
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Increase of MPO activity and LPO in double-KO mice.
MPO is a granulocyte-specific enzyme (13). Because
neutrophils are the predominant granulocytes to mediate mucosal injury, the MPO assay has been used for quantification of neutrophil
infiltration in intestinal mucosa. As shown in Fig.
5, a higher level of MPO activity was
detected in the colonic mucosa of double-KO mice compared with that in
other genotypes. Inflammation is associated with increased lipid
peroxidation. Increased reactive oxygen metabolites have been
associated with IBD (2, 27). Because GPX reduces hydroperoxides, we also determined LPO levels in the lower GI tract.
The double-KO mice had higher levels of LPO in the ileum and colon, but
not jejunum, compared with those in mice with one or two Gpx
alleles (Fig. 6). The levels of LPO were
in reverse proportion to the levels of GPX activity in the ileum and
colon but not jejunum.
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DISCUSSION |
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We have generated a line of mice deficient in two isozymes that are present in intestinal epithelial cells, GPX-1 and GPX-GI, and have provided evidence indicating that these two isozymes contribute nearly all of the GSH-dependent, H2O2-reducing activity in the distal gastrointestinal epithelium. This was demonstrated by the decreasing GPX activity in the intestinal epithelium in those mice with a decreasing number of Gpx1 and Gpx2 alleles. The homozygous double-KO mice had almost no GPX activity in the mucosa of their distal GI tracts.
The expression pattern of Gpx1 and Gpx2 genes differs in different regions of the GI tract. Although both Gpx1 and Gpx2 mRNA are present in jejunal epithelium (8), unlike Gpx1 mRNA which is translated into GPX-1 efficiently, the Gpx2 mRNA does not appear to be translated into GPX-GI efficiently in this region. Also, GPX-1 may be compensating for the lack of GPX-GI in the epithelium of the small intestine but not the large intestine. We conclude this from the following observations: 1) the same level of GPX activity was detected in mice with heterozygous and homozygous deletions of the Gpx2 allele, 2) a higher level of GPX-1 was detected in homozygous Gpx2-KO intestine compared with that in wild-type mice as determined by immunoprecipitation (8, 9), and 3) the same level of GPX-GI was detected in Gpx1-KO and wild-type mouse intestinal mucosa. These observations suggest that the Gpx1 gene can compensate for the lack of Gpx2 gene expression but not vice versa. Alternatively, this implies that Gpx2 mRNA may be competing for the limiting translational machinery for selenoprotein synthesis because GPX-GI has approximately one-third the specific activity of GPX-1, and the same GPX level is detected in colonic mucosa of wild-type control and heterozygous double-KO mice.
The first sign of abnormality that we observed in these double-KO mice
was growth retardation. Weight loss can be caused by either decreased
caloric intake or an increase in cachectic cytokine levels, such as
tumor necrosis factor-, interleukin (IL)-1, or IL-6, during
inflammation (19). Because these double-KO mice ingested
amounts of food similar to those ingested by the control mice, the
weight loss was most likely due to an increase in inflammatory cytokines. Small mammals, including mice, that are experiencing caloric
restriction can lower body temperature to conserve energy, inducing
hypothermia (12, 22). Therefore, cachexia and hypothermia are related pathophysiologically.
GPX activity in the crypt epithelium appears to be most important in the prevention of inflammation. The frequency of IBD-like pathology is inversely correlated with the GPX activity level; nearly all of the homozygous double-KO mice had classic symptoms of IBD, and very few of the wild-type and heterozygous double-KO mice had IBD-like symptoms. Because the three-fourths-KO mice with one Gpx1 allele are more prone to IBD-like pathology compared with those with one Gpx2 allele, this suggests that GPX-GI, which is predominantly expressed in the crypt epithelium, is more protective than GPX-1, which is predominately expressed in mature epithelial cells.
Increased MPO activity and LPO levels in the double-KO mice suggest that GPX prevents neutrophil-activated tissue injury. Neutrophils are the predominant granulocytes in the mediation of mucosal injury, and MPO is a granulocyte-specific enzyme (13, 29). A significantly higher amount of MPO activity was detected in the double-KO mice than in those mice that had at least one copy of the Gpx1 or Gpx2 gene. Because the cytotoxic activity mediated by neutrophils is produced by the respiratory burst that generates reactive oxygen species, we have also determined the level of lipid peroxidation in the mouse GI tract. Significantly higher levels of LPO were detected in the ilea of homozygous double-KO mice than in three-fourths-KO mice. Higher LPO levels were also found in the colons of homozygous double-KO mice than in heterozygous double-KO mice. These results suggest that the inflammatory injury is contributed by activated neutrophils and that GPX protects against such injury. It is possible that mice deficient in both Gpx1 and Gpx2 genes and phagocyte NADPH oxidase activity will not have colitis because this NADPH oxidase generates a large number of oxidants, including H2O2, in neutrophils (17, 31).
Hydroperoxides, but not superoxide, appear to mediate the IBD-like symptoms. Mice deficient in the Sod2 gene were found to be hypothermic and very short-lived (18, 24). These Sod2-KO mice had impaired mitochondrial enzymes in the oxidative phosphorylation reaction chain (26, 33) and thus were not able to convert food into metabolic energy efficiently. However, these mice did not have an IBD histology. This shows that there is a unique role for GPX activity as a major mediator of inflammation in the GI tract. However, whether H2O2 or fatty acid hydroperoxides mediates the inflammation is not known because GPX can reduce both.
In addition to the weakened host anti-inflammatory response, bacterial colonization appears to play an important role in the pathogenesis of IBD-like symptoms. Our mouse colonies were naturally infected with several Helicobacter species. These pathogen-associated IBD symptoms have been observed mainly in immune-deficient mice (11, 23), and the IBD symptoms present in immunocompetent mice are infrequent and affect only older mice (10, 11, 32). The progression of disease in the double-KO mice at the time of weaning is consistent with the timing of bacterial colonization. Mammals are born without microorganisms. Increases and alterations in intestinal bacterial species occur during the first month after birth (25). Changes in bacterial flora are likely to result from decreases in protective IgA levels and other bactericidal components present in milk or solid food, which alter luminal pH (14, 25, 28). To confirm this hypothesis regarding the role of bacteria, germ-free double-KO mice must be derived to further examine IBD pathology.
Among many existing IBD animal models, the most unique feature of our GPX double-KO mice is the early onset and prevalence of colitis. The most aggressive IBD symptoms to date have previously been reported in IL-10 deficient mice, which develop symptoms at 4 wk of age. Other mouse models, such as those expressing a dominant-negative N-cadherin or mice deficient in the multiple drug resistance gene mdr1a, develop colitis-like symptoms after 12 and 20 wk of age (15, 25, 28). Histological analysis shows that homozygous GPX double-KO mice have inflammation starting in the distal colon as early as 11 days of age, which was the youngest age analyzed. After weaning, the inflammatory changes progressed from distal to proximal colon and then to ileum.
Although reactive oxygen species are clearly involved in inflammation, current views of the function of antioxidant enzymes suggest that these proteins are passively involved in dissipating toxic oxidative species to avoid damage to DNA, proteins, or membrane lipids. Our double-KO mice provide the first clear evidence supporting a role for cytosolic GPX activity in the prevention of IBD-like pathology. Because IBD patients often have selenium deficiency, dietary supplementation with selenium has been recommended. Understanding the mechanism for GPX protection against IBD-like symptoms may provide new ideas for therapeutic reagents, such as the use of GPX-mimic compounds in addition to standard therapies.
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ACKNOWLEDGEMENTS |
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We thank Sharon Wilczynski, director of the City of Hope (COH) Pathology Core Facility (Los Angeles, CA), for providing advice and help with animal histology slides; Terri Armenta in the COH Animal Resources Center for maintaining the mouse lines; and Charles J. Epstein and Ting-Ting Huang (University of California, San Francisco, CA) for the Sod2-KO mouse tissue.
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FOOTNOTES |
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This work was supported in part by Grant-in-Aid 9960042Y from the American Heart Association Western States (F.-F. Chu), National Institutes of Health Cancer Center Support Grant P30-CA-33572 (City of Hope Beckman Research Institute), and a Veterans Affairs Career Development Award (R. Aranda). Phosphor- Imager was supported by National Science Foundation Grant BIR-9220534.
Address for reprint requests and other correspondence: Fong-Fong Chu, Dept. of Medical Oncology, City of Hope National Medical Center, 1500 E. Duarte Road, Duarte, CA 91010.
The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Received 29 January 2001; accepted in final form 7 May 2001.
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REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
1.
Aranda, R,
Sydora BC,
McAllister PL,
Binder SW,
Yang HY,
Targan SR,
and
Kronenberg M.
Analysis of intestinal lymphocytes in mouse colitis mediated by transfer of CD4+, CD45RBhigh T cells to SCID recipients.
J Immunol
158:
3464-3473,
1997[Abstract].
2.
Babbs, CF.
Oxygen radicals in ulcerative colitis.
Free Radic Biol Med
13:
169-181,
1992[ISI][Medline].
3.
Beck, MA,
Esworthy RS,
Ho YS,
and
Chu FF.
Glutathione peroxidase protects mice from viral-induced myocarditis.
FASEB J
12:
1143-1149,
1998
4.
Chu, FF,
Doroshow JH,
and
Esworthy RS.
Expression, characterization, and tissue distribution of a new cellular selenium-dependent glutathione peroxidase, GSHPx-GI.
J Biol Chem
268:
2571-2576,
1993
5.
Chu, FF,
and
Esworthy RS.
The expression of an intestinal form of glutathione peroxidase (GSHPx-GI) in rat intestinal epithelium.
Arch Biochem Biophys
323:
288-294,
1995[ISI][Medline].
6.
Chu, FF,
Esworthy RS,
Lee L,
and
Wilczynski S.
Retinoic acid induces Gpx2 gene expression in MCF-7 human breast cancer cells.
J Nutr
129:
1846-1854,
1999
7.
Esposito, LA,
Kokoszka JE,
Waymire KG,
Cottrell B,
MacGregor GR,
and
Wallace DC.
Mitochondrial oxidative stress in mice lacking the glutathione peroxidase-1 gene.
Free Radic Biol Med
28:
754-766,
2000[ISI][Medline].
8.
Esworthy, RS,
Mann JR,
Sam M,
and
Chu FF.
Low glutathione peroxidase activity in Gpx1 knockout mice protects jejunum crypts from -irradiation damage.
Am J Physiol Gastrointest Liver Physiol
279:
G426-G436,
2000
9.
Esworthy, RS,
Swiderek KM,
Ho YS,
and
Chu FF.
Selenium-dependent glutathione peroxidase-GI is a major glutathione peroxidase activity in the mucosal epithelium of rodent intestine.
Biochim Biophys Acta
1381:
213-226,
1998[ISI][Medline].
10.
Fox, JG,
Yan L,
Shames B,
Campbell J,
Murphy JC,
and
Li X.
Persistent hepatitis and enterocolitis in germfree mice infected with Helicobacter hepaticus.
Infect Immun
64:
3673-3681,
1996[Abstract].
11.
Franklin, CL,
Riley LK,
Livingston RS,
Beckwith CS,
Hook RR, Jr,
Besch-Williford CL,
Hunziker R,
and
Gorelick PL.
Enteric lesions in SCID mice infected with "Helicobacter typhlonicus," a novel urease-negative Helicobacter species.
Lab Anim Sci
49:
496-505,
1999[Medline].
12.
Gavrilova, O,
Leon LR,
Marcus-Samuels B,
Mason MM,
Castle AL,
Refetoff S,
Vinson C,
and
Reitman ML.
Torpor in mice is induced by both leptin-dependent and -independent mechanisms.
Proc Natl Acad Sci USA
96:
14623-14628,
1999
13.
Grisham, MB,
Benoit JN,
and
Granger DN.
Assessment of leukocyte involvement during ischemia and reperfusion of intestine.
Methods Enzymol
186:
729-742,
1990[Medline].
14.
Hentges, DJ,
Marsh WW,
Petschow BW,
Thal WR,
and
Carter MK.
Influence of infant diets on the ecology of the intestinal tract of human flora-associated mice.
J Pediatr Gastroenterol Nutr
14:
146-152,
1992[ISI][Medline].
15.
Hermiston, ML,
and
Gordon JI.
Inflammatory bowel disease and adenomas in mice expressing a dominant negative N-cadherin.
Science
270:
1203-1207,
1995[Abstract].
16.
Ho, YS,
Magnenat JL,
Bronson RT,
Cao J,
Gargano M,
Sugawara M,
and
Funk CD.
Mice deficient in cellular glutathione peroxidase develop normally and show no increased sensitivity to hyperoxia.
J Biol Chem
272:
16644-16651,
1997
17.
Hsich, E,
Segal BH,
Pagano PJ,
Rey FE,
Paigen B,
Deleonardis J,
Hoyt RF,
Holland SM,
and
Finkel T.
Vascular effects following homozygous disruption of p47(phox): an essential component of NADPH oxidase.
Circulation
101:
1234-1236,
2000
18.
Huang, TT,
Carlson EJ,
Raineri I,
Gillespie AM,
Kozy H,
and
Epstein CJ.
The use of transgenic and mutant mice to study oxygen free radical metabolism.
Ann NY Acad Sci
893:
95-112,
1999
19.
Inui, A.
Cancer anorexia-cachexia syndrome: are neuropeptides the key?
Cancer Res
59:
4493-4501,
1999
20.
Ishibashi, N,
Weisbrot-Lefkowitz M,
Reuhl K,
Inouye M,
and
Mirochnitchenko O.
Modulation of chemokine expression during ischemia/reperfusion in transgenic mice overproducing human glutathione peroxidases.
J Immunol
163:
5666-5667,
1999
21.
Jaeschke, H,
Ho YS,
Fisher MA,
Lawson JA,
and
Farhood A.
Glutathione peroxidase-deficient mice are more susceptible to neutrophil-mediated hepatic parenchymal cell injury during endotoxemia: importance of an intracellular oxidant stress.
Hepatology
29:
443-450,
1999[ISI][Medline].
22.
Lane, MA,
Baer DJ,
Rumpler WV,
Weindruch R,
Ingram DK,
Tilmont EM,
Cutler RG,
and
Roth GS.
Calorie restriction lowers body temperature in rhesus monkeys, consistent with a postulated anti-aging mechanism in rodents.
Proc Natl Acad Sci USA
93:
4159-4164,
1996
23.
Li, X,
Fox JG,
Whary MT,
Yan L,
Shames B,
and
Zhao Z.
SCID/NCr mice naturally infected with Helicobacter hepaticus develop progressive hepatitis, proliferative typhlitis, and colitis.
Infect Immun
66:
5477-5484,
1998
24.
Li, Y,
Huang TT,
Carlson EJ,
Melov S,
Ursell PC,
Olson JL,
Noble LJ,
Yoshimura MP,
Berger C,
Chan PH,
Wallace DC,
and
Epstein CJ.
Dilated cardiomyopathy and neonatal lethality in mutant mice lacking manganese superoxide dismutase.
Nat Genet
11:
376-381,
1995[ISI][Medline].
25.
Madsen, KL,
Doyle JS,
Tavernini MM,
Jewell LD,
Rennie RP,
and
Fedorak RN.
Antibiotic therapy attenuates colitis in interleukin 10 gene-deficient mice.
Gastroenterology
118:
1094-1105,
2000[ISI][Medline].
26.
Melov, S,
Coskun P,
Patel M,
Tuinstra R,
Cottrell B,
Jun AS,
Zastawny TH,
Dizdaroglu M,
Goodman SI,
Huang TT,
Miziorko H,
Epstein CJ,
and
Wallace DC.
Mitochondrial disease in superoxide dismutase 2 mutant mice.
Proc Natl Acad Sci USA
96:
846-851,
1999
27.
Millar, AD,
Rampton DS,
Chander CL,
Claxson AW,
Blades S,
Coumbe A,
Panetta J,
Morris CJ,
and
Blake DR.
Evaluating the antioxidant potential of new treatments for inflammatory bowel disease using a rat model of colitis.
Gut
39:
407-415,
1996[Abstract].
28.
Panwala, CM,
Jones JC,
and
Viney JL.
A novel model of inflammatory bowel disease: mice deficient for the multiple drug resistance gene, mdr1a, spontaneously develop colitis.
J Immunol
161:
5733-5744,
1998
29.
Parkos, CA.
Cell Adhesion and Migration. I. Neutrophil adhesive interactions with intestinal epithelium.
Am J Physiol Gastrointest Liver Physiol
273:
G763-G768,
1997
30.
Tham, DM,
Whitin JC,
Kim KK,
Zhu SX,
and
Cohen HJ.
Expression of extracellular glutathione peroxidase in human and mouse gastrointestinal tract.
Am J Physiol Gastrointest Liver Physiol
275:
G1463-G1471,
1998
31.
Vazquez-Torres, A,
Xu Y,
Jones-Carson J,
Holden DW,
Lucia SM,
Dinauer MC,
Mastroeni P,
and
Fang FC.
Salmonella pathogenicity island 2-dependent evasion of the phagocyte NADPH oxidase.
Science
287:
1655-1658,
2000
32.
Ward, JM,
Anver MR,
Haines DC,
Melhorn JM,
Gorelick P,
Yan L,
and
Fox JG.
Inflammatory large bowel disease in immunodeficient mice naturally infected with Helicobacter hepaticus.
Lab Anim Sci
46:
15-20,
1996[Medline].
33.
Williams, MD,
Van Remmen H,
Conrad CC,
Huang TT,
Epstein CJ,
and
Richardson A.
Increased oxidative damage is correlated to altered mitochondrial function in heterozygous manganese superoxide dismutase knockout mice.
J Biol Chem
273:
28510-28515,
1998
34.
Wingler, K,
Muller C,
Schmehl K,
Florian S,
and
Brigelius-Flohe R.
Gastrointestinal glutathione peroxidase prevents transport of lipid hydroperoxides in CaCo-2 cells.
Gastroenterology
119:
420-430,
2000[ISI][Medline].