title: Giardia intestinalis escapes oxidative stress by colonizing the small intestine: A molecular hypothesis.
abstract: Giardia intestinalis is the microaerophilic protozoon causing giardiasis, a common infectious intestinal disease. Giardia possesses an O(2) -scavenging activity likely essential for survival in the host. We report that Giardia trophozoites express the O(2) -detoxifying flavodiiron protein (FDP), detected by immunoblotting, and are able to reduce O(2) to H(2) O rapidly (∼3 μM O(2) × min × 10(6) cells at 37 °C) and with high affinity (C(50) = 3.4 ± 0.7 μM O(2)). Following a short-term (minutes) exposure to H(2) O(2) ≥ 100 μM, the O(2) consumption by the parasites is irreversibly impaired, and the FDP undergoes a degradation, prevented by the proteasome-inhibitor MG132. Instead, H(2) O(2) does not cause degradation or inactivation of the isolated FDP. On the basis of the elevated susceptibility of Giardia to oxidative stress, we hypothesize that the parasite preferentially colonizes the small intestine since, compared with colon, it is characterized by a greater capacity for redox buffering and a lower propensity to oxidative stress.
authors.affiliation: Department of Biochemical Sciences, CNR Institute of Molecular Biology and Pathology and Istituto Pasteur-Fondazione Cenci Bolognetti, Sapienza University of Rome, Rome, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Mastronicola
authors.forename: Alessandro
authors.initials: A
authors.lastname: Giuffrè
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Testa
authors.forename: Antonella
authors.initials: A
authors.lastname: Mura
authors.forename: Elena
authors.initials: E
authors.lastname: Forte
authors.forename: Eugenio
authors.initials: E
authors.lastname: Bordi
authors.forename: Leopoldo Paolo
authors.initials: LP
authors.lastname: Pucillo
authors.forename: Pier Luigi
authors.initials: PL
authors.lastname: Fiori
authors.forename: Paolo
authors.initials: P
authors.lastname: Sarti
mesh_terms: D000818:Animals; D016829:Giardia lamblia / Q000502:physiology*; D006861:Hydrogen Peroxide / Q000378:metabolism; D007421:Intestine, Small / Q000469:parasitology*; D018384:Oxidative Stress; D010101:Oxygen Consumption
chemical_list: D006861:Hydrogen Peroxide