GP-1-515

Adenosine is a potent anti-inflammatory mediator. Through elevation of endogenous adenosine concentrations the adenosine kinase inhibitor GP515 might serve to down-regulate local inflammatory responses. In the present study we investigated the effect of systemic GP515 in the nonacute model of dextran sulfate sodium (DSS)-induced colitis. The clinical score, colon length, histologic score, colon cytokine production, and spleen weight from mice with DSS-induced colitis (3.5% DSS in drinking water for 11 days) receiving GP515 treatment were determined and compared with untreated control mice. Splenocytes were analyzed for phenotype, interferon-gamma (IFNgamma) production, and CD69 expression. First, GP515 treatment resulted in a significant improvement of clinical score (weight loss, stool consistency, and bleeding) and of histologic score. Second, colon shortening, an indirect parameter for the degree of inflammation, was decreased, consistent with a decreased IFNgamma concentration in the colonic tissue. Third, spleen weight was reduced in GP515-treated DSS mice. And fourth, IFNgamma synthesis and CD69 expression, as a marker for early cell activation, of ex vivo-stimulated splenocytes were suppressed in the GP515-treated DSS mice. These studies show that GP515 is effective in the therapy of DSS-induced colitis. One potential mechanism of action is the suppression of IFNgamma synthesis and CD69 expression. Adenosine kinase inhibition forms a pharmacologic target that should be further investigated for chronic inflammatory bowel disease.

To determine actions of the prototype adenosine-regulating agent, acadesine (5-amino-1-[beta-D-ribofuranosyl]imidazole-4-carboxamideriboside; AICAR), on intestinal barrier function after hemorrhagic shock and fluid resuscitation, three series of experiments were performed to measure functional (series 1: intestinal permeability and intramural blood flow), structural (series 2: histology), and biochemical (series 3: tissue concentrations of adenine nucleotides and metabolites) changes.

Prospective, controlled animal study.

University laboratory; juvenile crossbred pigs of either gender.

Either AICAR or its saline vehicle were intravenously administered 30 mins before 40% hemorrhage. After 1 hr shock, shed blood plus crystalloid was administered for resuscitation. Data were collected for 1 hr thereafter.

In series 1, permeability of the ileum was measured by assaying the portal venous concentration of fluorescein-labeled dextran after placement of this tracer in the lumen. In addition, serosal and mucosal blood flow were monitored with laser-Doppler probes. With vehicle, hemorrhage and resuscitation increased the dextran concentration three-fold and decreased blood flow 50% of the baseline values (both p < .05). AICAR attenuated the permeability increase (p < .05) and attenuated mucosa, but not serosal, ischemia (p < .05). Similar effects were observed with a structurally dissimilar compound-- 4-amino-1-(5-amino-5-deoxy-1-beta-D-ribofuranosyl)-3-bromo-pyrazolo [3,4-d] pyrimidine, a specific adenosine kinase inhibitor-as well as continuous intra-arterial infusion of adenosine. In series 2, AICAR ameliorated the mucosal damage caused by shock/resuscitation (p < .05). In series 3, AICAR increased ileal tissue adenine nucleotides and metabolites during the shock period (p < .05).

AICAR attenuated gut permeability changes, increased mucosal perfusion, and increased tissue adenine nucleotides, which is consistent with preserved intestinal barrier function after hemorrhage and fluid resuscitation. In context with previous studies from this laboratory, these results provide further evidence for a role for adenosine as an endogenous anti-inflammatory autacoid after shock and trauma. Further study is needed to determine the therapeutic potential of adenosine-regulating agents in resuscitation fluids.