title: Impact of disrupting adenosine A₃ receptors (A₃⁻/⁻ AR) on colonic motility or progression of colitis in the mouse.
abstract: BACKGROUND
  Pharmacological studies suggest that adenosine A₃AR influences motility and colitis. Functional A₃⁻/⁻AR knockout mice were used to prove whether A₃AR activation is involved in modulating either motility or colitis.
  
  
  METHODS
  A₃AR was probed by polymerase chain reaction (PCR) genotyping, Western blot, and immunochemistry. Motility was assessed in vivo by artificial bead-expulsion, stool-frequency, and FITC-dextran transit. Colitis was induced with dextran sodium sulfate (DSS) in A₃⁻/⁻AR or wildtype (WT) age- and sex-matched controls. Progression of colitis was evaluated by histopathology, changes in myeloperoxidase (MPO), colon length, CD4(+) -cells, weight-loss, diarrhea, and the guaiac test.
  
  
  RESULTS
  Goat anti-hu-A₃ antiserum identified a 66 kDa immunogenic band in colon. A₃AR-immunoreactivity is expressed in SYN(+) -nerve varicosities, s-100(+) -glia, and crypt cells, but not 5-HT(+) (EC), CD4(+) (T), tryptase(+) (MC), or muscle cells. A₃AR immunoreactivity in myenteric ganglia of distal colon >> proximal colon by a ratio of 2:1. Intestinal transit and bead expulsion were accelerated in A₃⁻/⁻AR mice compared to WT; stool retention was lower by 40%-60% and stool frequency by 67%. DSS downregulated A₃AR in epithelia. DSS histopathology scores indicated less mucosal damage in AA₃⁻/⁻AR mice than WT. A₃⁻/⁻AR phenotype protected against DSS-induced weight loss, neutrophil (MPO), or CD4(+) -T cell infiltration, colon shortening, change in splenic weight, diarrhea, or occult-fecal blood.
  
  
  CONCLUSIONS
  Functional disruption of A₃AR in A₃⁻/⁻AR mice alters intestinal motility. We postulate that ongoing release of adenosine and activation of presynaptic-inhibitory A₃AR can slow down transit and inhibit the defecation reflex. A₃AR may be involved in gliotransmission. In separate studies, A₃⁻/⁻AR protects against DSS colitis, consistent with a novel hypothesis that A₃AR activation contributes to development of colitis.
authors: Department of Anesthesiology, Ohio State University, Columbus, Ohio.
authors: Tianhua
authors: T
authors: Ren
authors: Iveta
authors: I
authors: Grants
authors: Mazin
authors: M
authors: Alhaj
authors: Matt
authors: M
authors: McKiernan
authors: Marlene
authors: M
authors: Jacobson
authors: Hamdy H
authors: HH
authors: Hassanain
authors: Wendy
authors: W
authors: Frankel
authors: Jacqueline
authors: J
authors: Wunderlich
authors: Fievos L
authors: FL
authors: Christofi
mesh_terms: D000818:Animals; D018791:CD4 Lymphocyte Count; D003092:Colitis / Q000139:chemically induced / Q000473:pathology / Q000503:physiopathology*; D003106:Colon / Q000294:innervation / Q000473:pathology / Q000503:physiopathology*; D003672:Defecation / Q000502:physiology; D016264:Dextran Sulfate; D003967:Diarrhea / Q000503:physiopathology; D005260:Female; D005772:Gastrointestinal Transit / Q000502:physiology*; D005838:Genotype; D051379:Mice; D018345:Mice, Knockout; D009197:Myenteric Plexus / Q000378:metabolism; D009780:Occult Blood; D009929:Organ Size; D009195:Peroxidase / Q000378:metabolism; D043684:Receptor, Adenosine A3 / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D013154:Spleen / Q000473:pathology; D013997:Time Factors; D015431:Weight Loss
chemical_list: D043684:Receptor, Adenosine A3; D016264:Dextran Sulfate; D009195:Peroxidase