Regulation of adenosine system at the onset of peritonitis.
BACKGROUND
Adenosine, a potent regulator of inflammation, is produced under stressful conditions due to degradation of ATP/ADP by the ectoenzymes CD39 and CD73. Adenosine is rapidly degraded by adenosine deaminase (ADA) or phosphorylated in the cell by adenosine kinase (AK). From four known receptors to adenosine, A(1) (A(1)R) promotes inflammation by a G(i)-coupled receptor. We have previously shown that A(1)R is up-regulated in the first hours following bacterial inoculation. The aim of the current study is to characterize the inflammatory mediators that regulate adenosine-metabolizing enzymes and A(1)R at the onset of peritonitis.


METHODS
Peritonitis was induced in CD1 mice by intraperitoneal injection of Escherichia coli. TNFalpha and IL-6 levels were determined in peritoneal fluid by enzyme-linked immunosorbent assay. Adenosine-metabolizing enzymes and the A(1)R mRNA or protein levels were analyzed by quantitative PCR or by Western blot analysis, respectively.


RESULTS
We found that CD39 and CD73 were up-regulated in response to bacterial stimuli (6-fold the basal levels), while AK and ADA mRNA levels were down-regulated. Cytokine production and leukocyte recruitment were enhanced (2.5-fold) by treatment with an A(1)R agonist (2-chloro-N(6)-cyclopentyladenosine, 0.1 mg/kg) and reduced (2.5-3-fold) by the A(1)R antagonist (8-cyclopentyl-1, 3-dipropylxanthine, 1 mg/kg). In contrast to lipopolysaccharide, IL-1, TNF and IFNgamma, only low IL-6 levels (0.01 ng/ml), in the presence of its soluble IL-6R (sIL-6R), were found to promote A(1)R expression on mesothelial cells. In mice, administration of neutralizing antibody to IL-6R or soluble gp130-Fc (sgp130-Fc) blocked peritoneal A(1)R up-regulation following inoculation.


CONCLUSIONS
Bacterial products induce the production of adenosine by up-regulation of CD39 and CD73. Low IL-6-sIL-6R up-regulates the A(1)R to promote efficient inflammatory response against invading microorganisms.
Nakav
Sigal
S
Department of Clinical Biochemistry, Soroka Medical University Center and Ben-Gurion University of the Negev, Beer-Sheva 84101, Israel.
Naamani
Oshri
O
Chaimovitz
Cidio
C
Shaked
Gad
G
Czeiger
David
D
Zlotnik
Moshe
M
Douvdevani
Amos
A
D015720:5'-Nucleotidase / Q000378:metabolism; D000241:Adenosine / Q000378:metabolism*; D000243:Adenosine Deaminase / Q000378:metabolism*; D000248:Adenosine Kinase / Q000378:metabolism*; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D001081:Apyrase / Q000378:metabolism; D004195:Disease Models, Animal; D004926:Escherichia coli; D007274:Injections, Intraperitoneal; D015850:Interleukin-6 / Q000378:metabolism; D051379:Mice; D008815:Mice, Inbred Strains; D010538:Peritonitis / Q000378:metabolism* / Q000382:microbiology; D019947:Receptors, Interleukin-6 / Q000378:metabolism; D018047:Receptors, Purinergic P1 / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D015703:Antigens, CD; D015850:Interleukin-6; D019947:Receptors, Interleukin-6; D018047:Receptors, Purinergic P1; D014409:Tumor Necrosis Factor-alpha; D000248:Adenosine Kinase; D015720:5'-Nucleotidase; D000243:Adenosine Deaminase; D001081:Apyrase; C067869:CD39 antigen; D000241:Adenosine