@article{gookin_chiang_allen_armstrong_stauffer_finnegan_murtaugh_2006, title={NF-kappa B-mediated expression of iNOS promotes epithelial defense against infection by Cryptosporidium parvum in neonatal piglets}, volume={290}, ISSN={["1522-1547"]}, DOI={10.1152/ajpgi.00460.2004}, abstractNote={Cryptosporidium sp. parasitizes intestinal epithelium, resulting in enterocyte loss, villous atrophy, and malabsorptive diarrhea. We have shown that mucosal expression of inducible nitric oxide (NO) synthase (iNOS) is increased in infected piglets and that inhibition of iNOS in vitro has no short-term effect on barrier function. NO exerts inhibitory effects on a variety of pathogens; nevertheless, the specific sites of iNOS expression, pathways of iNOS induction, and mechanism of NO action in cryptosporidiosis remain unclear. Using an in vivo model of Cryptosporidium parvum infection, we have examined the location, mechanism of induction, specificity, and consequence of iNOS expression in neonatal piglets. In acute C. parvum infection, iNOS expression predominated in the villous epithelium, was NF-κB dependent, and was not restricted to infected enterocytes. Ongoing treatment of infected piglets with a selective iNOS inhibitor resulted in significant increases in villous epithelial parasitism and oocyst excretion but was not detrimental to maintenance of mucosal barrier function. Intensified parasitism could not be attributed to attenuated fluid loss or changes in epithelial proliferation or replacement rate, inasmuch as iNOS inhibition did not alter severity of diarrhea, piglet hydration, Cl−secretion, or kinetics of bromodeoxyuridine-labeled enterocytes. These findings suggest that induction of iNOS represents a nonspecific response of the epithelium that mediates enterocyte defense against C. parvum infection. iNOS did not contribute to the pathogenic sequelae of C. parvum infection.}, number={1}, journal={AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY}, author={Gookin, JL and Chiang, S and Allen, J and Armstrong, MU and Stauffer, SH and Finnegan, C and Murtaugh, MP}, year={2006}, month={Jan}, pages={G164–G174} }
 @article{zadrozny_stauffer_armstrong_jones_gookin_2006, title={Neutrophils do not mediate the pathophysiological sequelae of Cryptosporidium parvum infection in neonatal piglets}, volume={74}, ISSN={["1098-5522"]}, url={http://europepmc.org/abstract/med/16988224}, DOI={10.1128/IAI.00153-06}, abstractNote={ABSTRACT
          
            Cryptosporidium parvum
            is a minimally invasive protozoal pathogen of intestinal epithelium that results in villus atrophy, mucosal lipid peroxidation, diarrhea, and diminished barrier function. Influx of neutrophils is a consistent feature of human and animal cryptosporidiosis, and yet their contribution to the pathological sequelae of infection has not been investigated. Accordingly, we used an established neonatal piglet model of
            C. parvum
            infection to examine the role of neutrophils in disease pathogenesis by inhibiting their recruitment and activation in vivo using a monoclonal anti-CD18 antibody. Infected piglets were treated daily with anti-CD18 or isotype control immunoglobulin G and euthanized at peak infection, at which time neutrophil infiltrates, lipid peroxidation, severity of infection, and intestinal barrier function were quantified.
            C. parvum
            infection resulted in a significant increase in mucosal neutrophil myeloperoxidase activity that was prevented by treatment of piglets with anti-CD18 antibody. Neutrophil recruitment was dependent on mucosal superoxide formation (prevented by treatment of infected piglets with superoxide dismutase). Neutrophils did not contribute to peroxynitrite formation or peroxidative injury of
            C. parvum
            -infected mucosa and had no impact on the severity of epithelial infection, villus atrophy, or diarrhea. The presence of neutrophils in
            C. parvum
            -infected mucosa was associated with enhanced barrier function that could not be attributed to mucosal elaboration of prostaglandins or stimulation of their synthesis. These studies are the first to demonstrate that neutrophilic inflammation arising in response to infection by a noninvasive epithelial pathogen results in physiologic rather than pathological effects in vivo.
          }, number={10}, journal={INFECTION AND IMMUNITY}, author={Zadrozny, Leah M. and Stauffer, Stephen H. and Armstrong, Martha U. and Jones, Samuel L. and Gookin, Jody L.}, year={2006}, month={Oct}, pages={5497–5505} }
 @article{gookin_allen_chiang_duckett_armstrong_2005, title={Local peroxynitrite formation contributes to early control of Cryptosporidium parvum infection}, volume={73}, ISSN={["0019-9567"]}, DOI={10.1128/IAI.73.7.3929-3936.2005}, abstractNote={ABSTRACT
          
            In intestinal inflammation, mucosal injury is often exacerbated by the reaction of NO with neutrophil-derived superoxide to form the potent oxidant peroxynitrite. Peroxynitrite also has antimicrobial properties that aid in the killing mechanism of macrophages and neutrophils.
            Cryptosporidium parvum
            parasitizes intestinal epithelium, resulting in loss of epithelial cells and mucosal inflammation. Synthesis of NO is significantly increased and arises from the induced expression of inducible nitric oxide synthase (iNOS) by the infected epithelium. Inhibition of iNOS results in intensified epithelial parasitism and oocyst excretion. We hypothesized that formation of peroxynitrite is restricted to sites of iNOS expression by the epithelium and contributes to host defense in
            C. parvum
            infection. Accordingly, the location and biological effects of peroxynitrite formation were examined in neonatal piglets infected with
            C. parvum
            . Infected piglets were treated daily with a selective iNOS inhibitor [
            L
            -N6-(1-iminoethyl)-lysine] or one of two peroxynitrite scavengers [5,10,15,20-tetrakis(
            N
            -methyl-4′-pyridyl)porphyrinato iron(III) or uric acid] or received vehicle. At peak infection, peroxynitrite formation was restricted to sites of iNOS expression by parasitized epithelium and lamina propria of the apical villi. Peroxynitrite formation was dependent on iNOS activity and was inhibited by treatment with peroxynitrite scavengers. Scavengers increased the number of intracellular parasites and the number of infected epithelial cells present per villus and significantly exacerbated oocyst excretion. Recovery from infection was not delayed by ongoing treatment with scavenger. The present results are the first to demonstrate an in vivo role for peroxynitrite formation in acute mucosal defense against a noninvasive intestinal epithelial pathogen.
          }, number={7}, journal={INFECTION AND IMMUNITY}, author={Gookin, JL and Allen, J and Chiang, S and Duckett, L and Armstrong, MU}, year={2005}, month={Jul}, pages={3929–3936} }
 @article{gookin_duckett_armstrong_stauffer_finnegan_murtaugh_argenzio_2004, title={Nitric oxide synthase stimulates prostaglandin synthesis and barrier function in C-parvum-infected porcine ileum}, volume={287}, ISSN={["0193-1857"]}, DOI={10.1152/ajpgi.00413.2003}, abstractNote={Cell culture models implicate increased nitric oxide (NO) synthesis as a cause of mucosal hyperpermeability in intestinal epithelial infection. NO may also mediate a multitude of subepithelial events, including activation of cyclooxygenases. We examined whether NO promotes barrier function via prostaglandin synthesis using Cryptosporidium parvum-infected ileal epithelium in residence with an intact submucosa. Expression of NO synthase (NOS) isoforms was examined by real-time RT-PCR of ileal mucosa from control and C. parvum-infected piglets. The isoforms mediating and mechanism of NO action on barrier function were assessed by measuring transepithelial resistance (TER) and eicosanoid synthesis by ileal mucosa mounted in Ussing chambers in the presence of selective and nonselective NOS inhibitors and after rescue with exogenous prostaglandins. C. parvum infection results in induction of mucosal inducible NOS (iNOS), increased synthesis of NO and PGE2, and increased mucosal permeability. Nonselective inhibition of NOS ( NG-nitro-l-arginine methyl ester) inhibited prostaglandin synthesis, resulting in further increases in paracellular permeability. Baseline permeability was restored in the absence of NO by exogenous PGE2. Selective inhibition of iNOS [l- N6-(1-iminoethyl)-l-lysine] accounted for ∼50% of NOS-dependent PGE2synthesis and TER. Using an entire intestinal mucosa, we have demonstrated for the first time that NO serves as a proximal mediator of PGE2synthesis and barrier function in C. parvum infection. Expression of iNOS by infected mucosa was without detriment to overall barrier function and may serve to promote clearance of infected enterocytes.}, number={3}, journal={AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY}, author={Gookin, JL and Duckett, LL and Armstrong, MU and Stauffer, SH and Finnegan, CP and Murtaugh, MP and Argenzio, RA}, year={2004}, month={Sep}, pages={G571–G581} }
 @article{hunt_fu_armstrong_rennix_webster_galanko_chen_weaver_argenzio_rhoads_2002, title={Oral bovine serum concentrate improves cryptosporidial enteritis in calves}, volume={51}, ISSN={["0031-3998"]}, DOI={10.1203/00006450-200203000-00017}, abstractNote={Cryptosporidium parvum produces a prolonged watery diarrhea unresponsive to conventional antimicrobials. Because of reported efficacy of antibody-based immunotherapy, we studied the effect of inexpensive, commercially available oral bovine serum concentrate (BSC) in experimental cryptosporidiosis. Twenty-four calves were treated with 57 g/d BSC (n = 12) or soy protein (n = 12) added to their standard whey protein-based milk replacer (227 g/2 L twice daily). Of the 24, 9 were also treated with l-glutamine (GLN), 8 g/L (50 mM) in the milk (5 calves in the BSC group and 4 in the soy group). Animals were inoculated with 108 cryptosporidium oocysts per os on d 8 of life and received oral rehydration on d 12–14. Eight uninfected controls were treated with BSC or soy protein. Fecal and urine volume and urinary Cr-EDTA excretion were measured. Animals were killed on d 18 of life. Cryptosporidiosis induced severe watery diarrhea lasting >9 d and produced a 25% increase in intestinal permeability, a 33% decrease in villous surface area, and a 40% reduction in mucosal lactase specific activity. Glutamine treatment had no effect on the diarrhea or any of the intestinal tests; and therefore pooled data were used to compare the 12 calves treated with BSC with the 12 treated with soy. In animals receiving BSC, peak diarrheal volume and intestinal permeability were reduced 33%, fewer oocysts were shed, intestinal crypts were significantly deeper, and villous surface area returned to normal by 9 d after infection (all p ≤ 0.05). BSC should be studied as a treatment for human cryptosporidiosis.}, number={3}, journal={PEDIATRIC RESEARCH}, author={Hunt, E and Fu, Q and Armstrong, MU and Rennix, DK and Webster, DW and Galanko, JA and Chen, WN and Weaver, EM and Argenzio, RA and Rhoads, JM}, year={2002}, month={Mar}, pages={370–376} }
 @article{argenzio_armstrong_blikslager_rhoads_1997, title={Peptide YY inhibits intestinal Cl- secretion in experimental porcine cryptosporidiosis through a prostaglandin-activated neural pathway}, volume={283}, number={2}, journal={Journal of Pharmacology and Experimental Therapeutics}, author={Argenzio, R. A. and Armstrong, M. U. and Blikslager, A. and Rhoads, J. M.}, year={1997}, pages={692–697} }