title: Interferon-gamma and nitric oxide synthase 2 mediate the aggregation of resident adherent peritoneal exudate cells: implications for the host response to pathogens.
abstract: Interferon-gamma (Ifnγ), a key macrophage activating cytokine, plays pleiotropic roles in host immunity. In this study, the ability of Ifnγ to induce the aggregation of resident mouse adherent peritoneal exudate cells (APECs), consisting primarily of macrophages, was investigated. Cell-cell interactions involve adhesion molecules and, upon addition of Ifnγ, CD11b re-localizes preferentially to the sites of interaction on APECs. A functional role of CD11b in enhancing aggregation is demonstrated using Reopro, a blocking reagent, and siRNA to Cd11b. Studies with NG-methyl-L-arginine (LNMA), an inhibitor of Nitric oxide synthase (Nos), NO donors, e.g., S-nitroso-N-acetyl-DL-penicillamine (SNAP) or Diethylenetriamine/nitric oxide adduct (DETA/NO), and Nos2-/- mice identified Nitric oxide (NO) induced by Ifnγ as a key regulator of aggregation of APECs. Further studies with Nos2-/- APECs revealed that some Ifnγ responses are independent of NO: induction of MHC class II and CD80. On the other hand, Nos2 derived NO is important for other functions: motility, phagocytosis, morphology and aggregation. Studies with cytoskeleton depolymerizing agents revealed that Ifnγ and NO mediate the cortical stabilization of Actin and Tubulin which contribute to aggregation of APECs. The biological relevance of aggregation of APECs was delineated using infection experiments with Salmonella Typhimurium (S. Typhimurium). APECs from orally infected, but not uninfected, mice produce high amounts of NO and aggregate upon ex vivo culture in a Nos2-dependent manner. Importantly, aggregated APECs induced by Ifnγ contain fewer intracellular S. Typhimurium compared to their single counterparts post infection. Further experiments with LNMA or Reopro revealed that both NO and CD11b are important for aggregation; in addition, NO is bactericidal. Overall, this study elucidates novel roles for Ifnγ and Nos2 in regulating Actin, Tubulin, CD11b, motility and morphology during the aggregation response of APECs. The implications of aggregation or "group behavior" of APECs are discussed in the context of host resistance to infectious organisms.
authors.affiliation: Department of Biochemistry, Indian Institute of Science, Bangalore, India.
authors.forename: Bhagawat S
authors.initials: BS
authors.lastname: Chandrasekar
authors.affiliation: Department of Biochemistry, Indian Institute of Science, Bangalore, India.
authors.forename: Shikha
authors.initials: S
authors.lastname: Yadav
authors.affiliation: Department of Biochemistry, Indian Institute of Science, Bangalore, India.
authors.forename: Emmanuel S
authors.initials: ES
authors.lastname: Victor
authors.affiliation: Department of Biochemistry, Indian Institute of Science, Bangalore, India.
authors.forename: Shamik
authors.initials: S
authors.lastname: Majumdar
authors.affiliation: Department of Biochemistry, Indian Institute of Science, Bangalore, India.
authors.forename: Mukta
authors.initials: M
authors.lastname: Deobagkar-Lele
authors.affiliation: Department of Biochemistry, Indian Institute of Science, Bangalore, India.
authors.forename: Nitin
authors.initials: N
authors.lastname: Wadhwa
authors.affiliation: Centre for Infectious Disease Research (CIDR), Indian Institute of Science, Bangalore, India.
authors.forename: Santosh
authors.initials: S
authors.lastname: Podder
authors.affiliation: Department of Biochemistry, Indian Institute of Science, Bangalore, India.
authors.forename: Mrinmoy
authors.initials: M
authors.lastname: Das
authors.affiliation: Department of Biochemistry, Indian Institute of Science, Bangalore, India; Centre for Infectious Disease Research (CIDR), Indian Institute of Science, Bangalore, India.
authors.forename: Dipankar
authors.initials: D
authors.lastname: Nandi
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D039481:CD11b Antigen / Q000378:metabolism; D002448:Cell Adhesion / Q000187:drug effects; D002449:Cell Aggregation / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology; D054884:Host-Pathogen Interactions / Q000187:drug effects*; D007371:Interferon-gamma / Q000494:pharmacology*; D008264:Macrophages / Q000166:cytology / Q000187:drug effects; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000172:deficiency / Q000378:metabolism*; D010529:Peritoneal Cavity / Q000166:cytology* / Q000382:microbiology; D055550:Protein Stability / Q000187:drug effects; D012486:Salmonella typhimurium / Q000502:physiology*; D014404:Tubulin / Q000378:metabolism
chemical_list: D000199:Actins; D039481:CD11b Antigen; D014404:Tubulin; D009569:Nitric Oxide; D007371:Interferon-gamma; D052247:Nitric Oxide Synthase Type II