A Possible Therapeutic Role for Adenosine During Inflammation

Study Overview
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Brief Summary
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The adenosine receptor is known for its anti-inflammatory actions and could therefore be a potential target in the treatment of sepsis and septic shock. Stimulation of the adenosine receptor could potentially lead to a decrease in inflammation and tissue damage. Under normal conditions adenosine is formed either by an intracellular 5'nucleotidase, which dephosphorylates AMP, or by the hydrolysis of S-adenosylhomcysteine by hydrolase. An alternative pathway of AMP degradations is provided by the cytosolic enzyme AMP deaminase (AMPD), which catalyses the irreversible deamination of AMP to inosine monophosphate and ammonia. In humans four AMPD isoforms have been described, named after the source from which they were initially purified; M (muscle), L (liver), E1 and E2 (erythrocyte), encoded by AMPD1, AMPD2 and AMPD3. Approximately 15-20% of Caucasian and African American individuals are heterozygous or homozygous for the 34C>T variant of AMPD1. We hypothesize that healthy volunteers who have the polymorphism for AMPD1 have a less severe inflammatory response to LPS and show less (severe) organ failure. This hypothesis is based on the expected higher levels of adenosine in patients with the AMPD1 polymorphism. This hypothesis is strengthened by the fact that patients with coronary artery disease and the AMPD1 polymorphism show improved cardiovascular survival (Anderson JL et al. J Am Coll Cardiol 2000; 36: 1248-52) possibly based on higher adenosine levels by reduced AMPD activity. Furthermore the polymorphism predicts improved clinical outcome in patients with heart failure (Loh E et al. Circulation 1999) also based on a hypothetical elevation of adenosine. We hypothesize that: The C34T-polymorphism of the enzyme AMP-deaminase leads to a decreased inflammatory respons and thereby a decrease of LPS-induced tissue damage. A second hypothesis is based on the antagonism of the adenosine receptor, by caffeine; Antagonism of the adenosine receptor by caffeine leads to an increased LPS-induced inflammatory reaction and an increase in (subclinical) tissue damage?

Official Title
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A Possible Therapeutic Role for Adenosine During Inflammation

Conditions
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Endotoxemia

Intervention / Treatment
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* Genetic: AMPD1 polymorphism
* Drug: Caffeine infusion
* Drug: placebo


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Healthy male volunteers Exclusion Criteria: Drug-, nicotine-, alcohol abuses Tendency towards fainting Relevant medical history

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 35 Years

Sexes Eligible for Study
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Male

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: 1<br>Endotoxin and AMPD1 polymorphism | Genetic: AMPD1 polymorphism<br>* Endotoxin 2ng/kg to subjects with a AMPD1 polymorphism<br>|
| Experimental: 2<br>Endotoxin and intervention with caffeine | Drug: Caffeine infusion<br>* Endotoxin 2ng/kg combined with caffeine. Caffeine (4mg/kg) is used as an adenosine receptor antagonist.<br>|
| Placebo Comparator: 3<br>Endotoxin combined with placebo | Drug: placebo<br>* Endotoxin 2ng/kg combined with saline infusion (0.9%)<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Hemodynamics; heart rate variability |  | 24 hrs after LPS administration | 
| Markers of Inflammation |  | 24 hrs after LPS administration | 
| Cytokines |  | 24 hrs after LPS administration | 
| Sensitivity to norepinephrine |  | 24 hrs after LPS administration | 
| Endothelial-dependent and independent vasorelaxation |  | 24 hrs after LPS administration | 
| Mediators of Vascular reactivity |  | 24 hrs after LPS administration | 
| Markers of endothelial damage and circulating endothelial cells |  | 24 hrs after LPS administration | 
| Urinary excretion of markers of renal injury |  | 24 hrs after LPS administration | 
| Neurologic testing |  | 24 hrs after LPS administration | 
| Adenosine and related nucleotide concentrations. |  | 24 hrs after LPS administration | 
| Additional blood samples will be drawn for measurement of: TLR-expression, Genetics; micro array analyses and determination of intercellular signalling pathways. |  | 24 hrs after LPS administration | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Endotoxin, Adenosine, Caffeine, AMPD1 polymorphism