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Mark M Huycke

Publications and source records attributed to Mark M Huycke.

11 recordsLinked to original sources
PubMed2005

Variable phenotypes of enterocolitis in interleukin 10-deficient mice monoassociated with two different commensal bacteria.

BACKGROUND & AIMS: To explore the hypothesis that selective immune responses to distinct components of the intestinal microflora induce intestinal inflammation, we characterized disease kinetics and bacterial antigen-specific T-cell responses in ex germ-free interleukin 10 -/- and wild-type control mice monoassociated with Enterococcus faecalis , Escherichia coli , or Pseudomonas fluorescens . METHODS: Colitis was measured by using blinded histological scores and spontaneous interleukin 12 secretion from colonic strip culture supernatants. Interferon gamma secretion was measured from mesenteric or caudal lymph node CD4 + T cells stimulated with bacterial lysate-pulsed antigen-presenting cells. Luminal bacterial concentrations were measured by culture and quantitative polymerase chain reaction. RESULTS: Escherichia coli induced mild cecal inflammation after 3 weeks of monoassociation in interleukin 10 -/- mice. In contrast, Enterococcus faecalis-monoassociated interleukin 10 -/- mice developed distal colitis at 10-12 weeks that was progressively more severe and associated with duodenal inflammation and obstruction by 30 weeks. Neither bacterial strain induced inflammation in wild-type mice, and germ-free and Pseudomonas fluorescens-monoassociated interleukin 10 -/- mice remained disease free. CD4 + T cells from Enterococcus faecalis- or Escherichia coli-monoassociated interleukin 10 -/- mice selectively produced higher levels of interferon gamma and interleukin 4 when stimulated with antigen-presenting cells pulsed with the bacterial species that induced disease; these immune responses preceded the onset of histological inflammation in Enterococcus faecalis -monoassociated mice. Luminal bacterial concentrations did not explain regional differences in inflammation. CONCLUSIONS: Different commensal bacterial species selectively initiate immune-mediated intestinal inflammation with distinctly different kinetics and anatomic distribution in the same host.

Animals↗
PubMed2004

Bacteria-induced intestinal cancer in mice with disrupted Gpx1 and Gpx2 genes.

Two glutathione peroxidase (GPX) isozymes, GPX-1 and GPX-2 (GPX-GI), are the major enzymes that reduce hydroperoxides in intestinal epithelium. We have previously demonstrated that targeted disruption of both the Gpx1 and Gpx2 genes (GPX-DKO) results in a high incidence of ileocolitis in mice raised under conventional conditions, which include the harboring of Helicobacter species [non-specific-pathogen-free (non-SPF) conditions]. In this study, we have characterized GPX-DKO mice that have microflora-associated intestinal cancers, which are correlated with increased intestinal pathology/inflammation. We found that GPX-DKO mice raised under germ-free conditions have virtually no pathology or tumors. After colonizing germ-free mice with commensal microflora without any known pathogens (SPF), <9% of GPX-DKO mice develop tumors in the ileum or the colon. However, about one-fourth of GPX-DKO mice raised under non-SPF conditions from birth or transferred from SPF conditions at weaning have predominantly ileal tumors. Nearly 30% of tumors are cancerous; most are invasive adenocarcinomas and a few signet-ring cell carcinomas. On the basis of these results, we conclude that GPX-DKO mice are highly susceptible to bacteria-associated inflammation and cancer. The sensitivity exhibited in these mice suggests that peroxidative stress plays an important role in ileal and colonic pathology and inflammation, which can lead to tumorigenesis.

Animals↗
PubMed2004

Commensal bacteria, redox stress, and colorectal cancer: mechanisms and models.

The potential role for commensal bacteria in colorectal carcinogenesis is explored in this review. Most colorectal cancers (CRCs) occur sporadically and arise from the gradual accumulation of mutations in genes regulating cell growth and DNA repair. Genetic mutations followed by clonal selection result in the transformation of normal cells into malignant derivatives. Numerous toxicological effects of colonic bacteria have been reported. However, those recognized as damaging epithelial cell DNA are most easily reconciled with the currently understood genetic basis for sporadic CRC. Thus, we focus on mechanisms by which particular commensal bacteria may convert dietary procarcinogens into DNA damaging agents (e.g., ethanol and heterocyclic amines) or directly generate carcinogens (e.g., fecapentaenes). Although these and other metabolic activities have yet to be linked directly to sporadic CRC, several lines of investigation are reviewed to highlight difficulties and progress in the area. Particular focus is given to commensal bacteria that alter the epithelial redox environment, such as production of oxygen radicals by Enterococcus faecalis or production of hydrogen sulfide by sulfate-reducing bacteria (SRB). Super-oxide-producing E. faecalis has conclusively been shown to cause colonic epithelial cell DNA damage. Though SRB-derived hydrogen sulfide (H(2)S) has not been reported thus far to induce DNA damage or function as a carcinogen, recent data demonstrate that this reductant activates molecular pathways implicated in CRC. These observations combined with evidence that SRB carriage may be genetically encoded evoke a working model that incorporates multifactorial gene-environment interactions that appear to underlie the development of sporadic CRC.

Animals↗
PubMed2004

Effects of iron and phytic acid on production of extracellular radicals by Enterococcus faecalis.

Enterococcus faecalis is a human intestinal commensal that produces extracellular superoxide, hydrogen peroxide, and hydroxyl radical while colonizing the intestinal tract. To determine whether dietary factors implicated in colorectal cancer affect oxidant production by E. faecalis, radicals were measured in rats colonized with this microorganism while on diets supplemented with iron or phytic acid. Hydroxyl radical activity was measured by assaying for aromatic hydroxylation products of D-phenylalanine using reverse-phase high-performance liquid chromatography and electrochemical detection. In vitro, as expected, iron enhanced, and phytic acid decreased, hydroxyl radical formation by E. faecalis. For rats colonized with E. faecalis given supplemental dietary iron (740 mg elemental iron as ferric phosphate per kg diet) or phytic acid (1.2% w/w), no differences were found in concentrations of urinary ortho- or meta- isomers of D-phenylalanine compared to rats on a basal diet. Aqueous radicals in colonic contents were further assessed ex vivo by electron spin resonance using 5,5-dimethyl-1-pyrroline-N-oxide as a spin trap. Mixtures of thiyl (sulfur-centered) and oxygen-centered radicals were detected across all diets. In vitro, similar spectra were observed when E. faecalis was incubated with hydrogen sulfide, air-oxidized cysteine, or an alkylsulfide, as typical sulfur-containing compounds that might occur in colonic contents. In conclusion, intestinal colonization with E. faecalis in a rat model generates both thiyl and oxygen-centered radicals in colonic contents. Radical formation, however, was not significantly altered by short-term dietary supplementation with iron or phytic acid.

Animals↗
PubMed2003

Outbreak of invasive Aspergillus infection in surgical patients, associated with a contaminated air-handling system.

An outbreak of Aspergillus infection at a tertiary care hospital was identified among inpatients who had amputation wounds, peritonitis, allograft nephritis, or mediastinitis. During a 2-year period, 6 patients were identified, all of whom had Aspergillus species recovered from samples from normally sterile sites. All cases clustered in the operating theater during a single 12-day period. To assess operating theater air quality, particle counts were measured as surrogate markers for Aspergillus conidia. A substantial increase in the proportion of airborne particles > or =3 microm in size (range, 3-fold to 1000-fold) was observed in many operating rooms. A confined space video camera identified moisture and contamination of insulating material in ductwork and variable airflow volume units downstream of final filters. No additional invasive Aspergillus wound infections were identified after the operating theater air-handling systems were remediated, suggesting that this unusual outbreak was due to the deterioration of insulating material in variable airflow volume units.

Air Conditioning↗
PubMed2002

In vivo production of hydroxyl radical by Enterococcus faecalis colonizing the intestinal tract using aromatic hydroxylation.

Enterococcus faecalis is an intestinal commensal that produces extracellular superoxide (O(2)(*-)) through autoxidation of membrane-associated demethylmenaquinone. To assess free radical production by E. faecalis in vivo, intestinal tracts of rats were colonized using wild-type E. faecalis or a mutant strain with attenuated O(2)(*-) production. Ex vivo electron paramagnetic resonance spin trapping study of colonic contents (mean +/- SD) showed 1.4 +/- 1.5 and 0.094 +/- 0.24 microM 5,5-dimethyl-1-pyrroline-N-oxide-hydroxyl radical adduct/gm stool for rats colonized with wild-type and mutant strains, respectively (p = .002). In vivo hydroxyl radical production was further assayed by aromatic hydroxylation using phenyl N-tert-butylnitrone (PBN) and D-phenylalanine. Hydroxylated PBN and D-phenylalanine products were recovered from stool (microM/gm colonic contents/10(9) colony forming units) and urine (microM/h/ml), respectively, and quantified using electrochemical detection. Hydroxylated (OH) PBNs and isomeric tyrosines (hydroxylated phenylalanine) were significantly increased (mean +/- SD) for rats colonized with wild-type E. faecalis (2-OH PBN, 63 +/- 58; 3-OH PBN, 63 +/- 84; ortho-tyrosine, 31 +/- 27; meta-tyrosine, 17 +/- 14) compared to the mutant strain (2-OH PBN, 2.5 +/- 7.3 (p < .001); 3-OH PBN, 3.9 +/- 12.3 (p = .01); ortho-tyrosine, 1.9 +/- 6.0 (p < .001); meta-tyrosine, 1.5 +/- 3.4 (p = .03)). Similar differences were observed following in vitro incubations of these bacteria with aromatic targets. These results confirm in vivo production of hydroxyl radical by E. faecalis colonizing the intestine, and indicate this bacterium may be a potent source of oxidative stress on the intestinal epithelium.

Animals↗
PubMed2002

Enterococcus faecalis produces extracellular superoxide and hydrogen peroxide that damages colonic epithelial cell DNA.

Enterococcus faecalis is a commensal microorganism of the human intestinal tract that produces substantial extracellular superoxide (O(-)(2)), and derivative reactive oxygen species such as H(2)O(2) and hydroxyl radical, through autoxidation of membrane-associated demethylmenaquinone. Because these oxidants may be important as a cause of chromosomal instability (CIN) associated with sporadic adenomatous polyps and colorectal cancer, the ability of E.faecalis to damage eukaryotic cell DNA was examined using the alkaline lysis single cell gel electrophoresis (comet) assay. Both Chinese hamster ovary and HT-29 intestinal epithelial cells showed increased DNA damage after co-incubation with wild-type E. faecalis strain OG1RF, but not a transposon-inactivated mutant with attenuated extracellular O(-)(2) production. E. faecalis-mediated DNA damage was prevented by catalase, but not manganese superoxide dismutase, indicating H(2)O(2) arising from O(-)(2) was the genotoxin. In a rat model of intestinal colonization, OG1RF resulted in significantly higher stool concentrations of H(2)O(2) and 5,5-dimethyl-1-pyrroline N-oxide adducts of hydroxyl and thiyl radicals, as identified by electron spin resonance-spin trapping, compared with rats colonized with a mutant strain having attenuated O(-)(2) production. Using the comet assay, luminal cells from the colon of rats colonized with O(-)(2)-producing E. faecalis showed significantly increased DNA damage compared with control rats colonized with the mutant. These findings suggest a potentially profound role for extracellular free radical production by E. faecalis in promoting CIN associated with sporadic adenomatous polyps and colorectal cancer.

Animals↗
PubMed2002

Viral agents as biological weapons and agents of bioterrorism.

Multiple viral agents have been classified by the CDC as potential weapons of mass destruction or agents for biologic terrorism. Agents such as smallpox, viral hemorrhagic fever viruses, agents of viral encephalitis, and others are of concern because they are highly infectious and relatively easy to produce. Although dispersion might be difficult, the risk is magnified by the fact that large populations are susceptible to these agents and only limited treatment and vaccination strategies exist. Although the risk of large-scale bioterrorism using viral agents is small, public health programs and health care providers must be prepared for this potentially devastating impact on public health.

Arenaviridae Infections↗
PubMed2002

Unconventional biological threats and the molecular biological response to biological threats.

This article concludes this symposium on potential agents of warfare and terrorism with discussion of 3 topics. First, influenza A virus is discussed as a potential biological weapon. Although it does not receive much attention in this role, the potential for mass casualties and public panic certainly exist if an epidemic of a virulent influenza A virus were initiated. Second, agroterrorism, terrorism directed at livestock or poultry or crops, is briefly discussed. Finally, the potential role of techniques of modern molecular biology to create new agents for bioterrorism or enhance the terrorist potential of available agents, and the known roles of these techniques in defense against biological warfare or terrorism are discussed.

Agriculture↗
PubMed2002

Smallpox in the post-eradication era.

Smallpox is a recently extinct human viral infection for which herd immunity has rapidly waned. The threat of smallpox during a bioterrorist event using caches of virus outside reference repositories would lead to epidemics of great and predictable mortality. The result would be short-term societal chaos. Control of smallpox requires vaccination and quarantine, the same measures that eliminated this disease in the 1970's. Extensive coordination and planning would be needed among the healthcare infrastructure, law enforcement agencies and political leadership for effective responses to this public health threat. Despite this challenge, we must remind ourselves that smallpox transmission and vaccinia effectiveness are well understood. Strategies that successfully eradicated smallpox 25 years ago, if appropriately implemented again, would undoubtedly lead to its elimination once again.

Bioterrorism↗