title: Involvement of nitric oxide on the pathogenesis of irinotecan-induced intestinal mucositis: role of cytokines on inducible nitric oxide synthase activation.
abstract: OBJECTIVE
  Intestinal mucositis and the closely associated diarrhea are common costly side effects of irinotecan. Cytokine modulators, such as thalidomide and pentoxifylline, are found capable of attenuating intestinal mucositis progression. Nitric oxide (NO) seems to be a key mediator of the antineoplastic drug toxicity. The aim of this study was to investigate the role of NO on the pathogenesis of intestinal mucositis, as well as the participation of cytokines upon inducible nitric oxide synthase (iNOS) expression in irinotecan-induced intestinal mucositis.
  
  
  METHODS
  iNOS-knockout (iNOS(-/-)) and C57BL/6 (WT, wild type) animals (n = 5-6) were given either saline or irinotecan (60 mg/kg i.p for 4 days), with or without pretreatment with aminoguanidine (50 mg/kg s.c.), thalidomide (60 mg/kg s.c), infliximab (5 mg/kg i.v.), or pentoxifylline (1.7 mg/kg s.c). On day 5, diarrhea was assessed, and following euthanasia, proximal intestinal samples were obtained for myeloperoxidase (MPO) and iNOS activity, morphometric analysis, western blot and immunohistochemistry to iNOS, cytokine dosage, and for in vitro evaluation of gut contractility.
  
  
  RESULTS
  Irinotecan induced severe diarrhea and intestinal smooth muscle over-contractility, accompanied with histopathological changes. Additionally, increased MPO and iNOS activity and iNOS immunoexpression were found in WT animals treated with irinotecan. The rise in MPO, smooth muscle over-contractility, and diarrhea were abrogated in aminoguanidine-treated and iNOS(-/-) mice. Moreover, through western blot, we verified that infliximab and pentoxifylline significantly inhibited irinotecan-induced iNOS expression. In addition, cytokine concentration was found only partially decreased in irinotecan-treated iNOS(-/-) mice when compared with wild-type animals that were given irinotecan.
  
  
  CONCLUSIONS
  This study suggests a role of nitric oxide in the pathogenesis of irinotecan-induced intestinal mucositis and also provides evidence for the participation of cytokines on iNOS induction.
authors.affiliation: Department of Physiology and Pharmacology, Faculty of Medicine, Federal University of Ceará, Rua Cel Nunes de Melo, 1315 Rodolfo Teófilo, Fortaleza, Ceará 60430-270, Brazil.
authors.forename: Roberto César P
authors.initials: RC
authors.lastname: Lima-Júnior
authors.forename: Aline A
authors.initials: AA
authors.lastname: Figueiredo
authors.forename: Helano C
authors.initials: HC
authors.lastname: Freitas
authors.forename: Maria Luisa P
authors.initials: ML
authors.lastname: Melo
authors.forename: Deysi Viviana T
authors.initials: DV
authors.lastname: Wong
authors.forename: Caio Abner V G
authors.initials: CA
authors.lastname: Leite
authors.forename: Raul P
authors.initials: RP
authors.lastname: Medeiros
authors.forename: Raphael D
authors.initials: RD
authors.lastname: Marques-Neto
authors.forename: Mariana L
authors.initials: ML
authors.lastname: Vale
authors.forename: Gerly Anne C
authors.initials: GA
authors.lastname: Brito
authors.forename: Reinaldo B
authors.initials: RB
authors.lastname: Oriá
authors.forename: Marcellus H L P
authors.initials: MH
authors.lastname: Souza
authors.forename: Fernando Q
authors.initials: FQ
authors.lastname: Cunha
authors.forename: Ronaldo A
authors.initials: RA
authors.lastname: Ribeiro
mesh_terms: D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000633:toxicity; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000633:toxicity; D016207:Cytokines / Q000378:metabolism*; D004195:Disease Models, Animal; D004789:Enzyme Activation; D007150:Immunohistochemistry; D007413:Intestinal Mucosa / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D000077146:Irinotecan; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D052016:Mucositis / Q000139:chemically induced* / Q000378:metabolism / Q000473:pathology; D009569:Nitric Oxide / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism*
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D016207:Cytokines; D009569:Nitric Oxide; D000077146:Irinotecan; D052247:Nitric Oxide Synthase Type II; D002166:Camptothecin