adenosine-kinase and Edema

Chronic inflammatory diseases, such as arthritis and rheumatoid arthritis, remain major health problems worldwide. We previously demonstrated that adenosine kinase inhibitors (AKIs) exhibit antiinflammatory effects by inhibiting TNF-alpha production, neutrophil accumulation, and edema formation. Although adenosine receptor agonists produce similar effects, AKIs showed the antiinflammatory activity without the cardiovascular side effects that prevented the development of adenosine receptor specific agonists. However, previously described potent AKIs, such as 5-iodotubercidin, are nucleosides which have the potential to undergo in vivo 5'-O-phosphorylation and therefore produce cytotoxicity. In an effort to eliminate toxicities produced by phosphorylated nucleosides, l-lyxofuranosyl analogues of tubercidin were tested as potential AKIs since the opposite stereochemical orientation of the CH(2)OH was expected to eliminate intracellular phosphorylation. Described herein are the discovery of a new series of AKIs based on alpha-l-lyxofuranosyl nucleosides, their SAR, as well as the antiinflammatory activity of the lead compound GP790 (IC(50) = 0.47 nM, 47% inhibition of paw swelling at 10 mg/kg in rat carrageenan paw edema model). In addition, a study showing that in the skin lesion model the antiinflammatory activity is reversed by an A2 selective adenosine receptor antagonist 3,7-dimethyl-1-propargyl xanthine [correction of propylxanthine] (DMPX) is also described.

Topics: Adenosine Kinase; Animals; Anti-Inflammatory Agents, Non-Steroidal; Dose-Response Relationship, Drug; Edema; Leukocyte Count; Neutrophils; Nucleosides; Phosphorylation; Purinergic P1 Receptor Antagonists; Rats; Skin; Structure-Activity Relationship; Theobromine

Adenosine kinase (AK; EC 2.7.1.20) is a key intracellular enzyme regulating intra-and extracellular concentrations of adenosine (ADO), an endogenous neuromodulator, antinociceptive, and anti-inflammatory autocoid. AK inhibition provides a means of potentiating local tissue concentrations of endogenous ADO, and AK inhibitors may have therapeutic potential as analgesic and anti-inflammatory agents. The effects of ABT-702, a novel, potent (IC(50) = 1.7 nM), and selective non-nucleoside AK inhibitor were examined in rat models of nociception and acute inflammation. ABT-702 was orally effective and fully efficacious to suppress nociception in a spectrum of pain models in the rat, including carrageenan-induced thermal hyperalgesia, the formalin test of persistent pain, and models of nerve injury-induced and diabetic neuropathic pain (tactile allodynia after L5/L6 spinal nerve ligation or streptozotocin injection, respectively.) ABT-702 was especially potent at relieving inflammatory thermal hyperalgesia (ED(50) = 5 micromol/kg p.o.). ABT-702 was also effective in the carrageenan-induced paw edema model of acute inflammation (ED(50) = 70 micromol/kg p.o.). The antinociceptive and anti-inflammatory effects of ABT-702 were blocked by selective ADO receptor antagonists, consistent with endogenous ADO accumulation and ADO receptor activation as a mechanism of action. The antinociceptive effects of ABT-702 were not blocked by the opioid antagonist naloxone. In addition, ABT-702 showed less potential to develop tolerance to its antinociceptive effects compared with morphine. ABT-702 had no significant effect on rotorod performance or heart rate (at 30-300 micromol/kg p.o.), mean arterial pressure (at 30-100 micromol/kg p.o.), or exploratory locomotor activity (at

Topics: Adenosine Kinase; Administration, Oral; Analgesics, Non-Narcotic; Animals; Anti-Inflammatory Agents, Non-Steroidal; Diabetes Mellitus, Experimental; Edema; Enzyme Inhibitors; Formaldehyde; Hemodynamics; Hyperalgesia; Male; Morpholines; Motor Activity; Pain; Pyrimidines; Rats; Rats, Sprague-Dawley; Receptors, Purinergic P1; Streptozocin

Spinal administration of an adenosine kinase inhibitor, alone or in combination with an adenosine deaminase inhibitor, produces antinociception in inflammatory pain tests. In the present study, we examined the antinociceptive and anti-inflammatory effects produced by the peripheral (intraplantar) administration of 5'-amino-5'-deoxyadenosine (an adenosine kinase inhibitor), 2'-deoxycoformycin (an adenosine deaminase inhibitor), and combinations of both agents in the carrageenan-induced thermal hyperalgesia and paw oedema model in the rat. When injected in the ipsilateral paw immediately prior to carrageenan injection, both agents produced antinociception only at the highest dose (1 micromol), whereas a reduction in paw swelling was evident at a lower dose (300 nmol). Significant augmentation in both the antinociceptive and anti-inflammatory effects was seen when 5'-amino-5'-deoxyadenosine and 2'-deoxycoformycin were co-administered in equimolar doses at all dose levels. Both effects were mediated via activation of adenosine receptors, as indicated by blockade by an adenosine receptor antagonist. When administered into the contralateral paw, 1 micromol 5'-amino-5'-deoxyadenosine+1 micromol 2'-deoxycoformycin produced prominent antinociception, indicating a systemic drug activity. There was only a modest reduction in paw oedema in the carrageenan-injected (ipsilateral) paw, suggesting that much of this activity was locally mediated. Reversal of systemic effects on thermal thresholds by an intrathecal adenosine receptor antagonist implicates a spinal site of action in this instance. An ipsilateral administration of 1 micromol 5'-amino-5'-deoxyadenosine, but not 1 micromol 2'-deoxycoformycin, reduced carrageenan-induced c-Fos expression in the spinal dorsal horn, and this was further reduced by the peripheral co-injection of the two agents. These results provide evidence for a predominantly spinal antinociceptive effect and a predominantly peripheral anti-inflammatory effect produced by inhibitors of adenosine kinase and adenosine deaminase.

Topics: Adenosine Deaminase; Adenosine Deaminase Inhibitors; Adenosine Kinase; Analgesics; Animals; Anti-Inflammatory Agents; Caffeine; Carrageenan; Central Nervous System Stimulants; Deoxyadenosines; Dose-Response Relationship, Drug; Drug Synergism; Edema; Enzyme Inhibitors; Hindlimb; Hyperalgesia; Injections, Spinal; Male; Nociceptors; Pain; Pentostatin; Proto-Oncogene Proteins c-fos; Purinergic P1 Receptor Antagonists; Rats; Rats, Sprague-Dawley; Spinal Cord; Theobromine; Time Factors

The present study used plethysmometry to examine oedema following local injection of selective adenosine A(1), A(2) and A(3) receptor agonists and inhibitors of adenosine metabolism into the hindpaw of the rat. N(6)-Cyclopentyladenosine and L-N(6)-phenylisopropyladenosine (A(1)), 2-[p(2-carboxyethyl) phenethylamino]-5'-N-ethylcarboxamidoadenosine hydrochloride (CGS21680) (A(2A)) and N(6)-benzyl-5'-N-ethylcarboxamido adenosine (N(6)-B-NECA) (A(3)) all produced an increase in paw volume (N(6)N(6)-cyclopentyladenosine, L-N(6)CGS21680). At the highest dose, each agent also produced a systemically mediated suppression of oedema. Oedema by N(6)-cyclopentyladenosine was blocked by caffeine, 8-cyclopentyl-1,3-dimethylxanthine and enprofylline. Oedema by CGS21680 was blocked by caffeine and 8-cyclopentyl-1, 3-dimethylxanthine. Oedema by N(6)-B-NECA was blocked by enprofylline, but not by caffeine or 8-cyclopentyl-1, 3-dimethylxanthine, or by systemic administration of MRS 1191. Oedema by both N(6)-cyclopentyladenosine and N(6)-B-NECA was blocked by mepyramine, ketanserin and phentolamine, but that by CGS21680 was not. The adenosine kinase inhibitor 5'-amino-5'-deoxyadenosine and the adenosine deaminase inhibitor 2'-deoxycoformycin produced only a limited increase in paw volume, and this was blocked by caffeine. This study demonstrates an acute paw oedema response following local administration of adenosine A(1), A(2) and A(3) receptor agonists, which likely results from different mechanisms of action in each case.

Topics: Acute Disease; Adenosine; Adenosine Deaminase Inhibitors; Adenosine Kinase; Animals; Caffeine; Drug Interactions; Edema; Enzyme Inhibitors; Histamine H1 Antagonists; Male; Phenethylamines; Purinergic P1 Receptor Agonists; Purinergic P1 Receptor Antagonists; Pyrilamine; Rats; Rats, Sprague-Dawley; Receptor, Adenosine A3

Adenosine inhibits neutrophil function, but also causes cardiovascular side effects when administered systemically. To regulate local adenosine concentrations and minimize toxicity, a novel adenosine kinase inhibitor, GP-1-515, was tested in several acute inflammation models in rats. GP-1-515 inhibited carrageenan-induced rat paw swelling in a dose-dependent manner (maximum inhibition, 47 +/- 3%). In a rat skin lesion model, GP-1-515 significantly reduced cutaneous neutrophil infiltration following an intradermal injection of carrageenan or zymosan-activated plasma, or induction of a reverse passive Arthus reaction. This action appeared to be mediated by endogenous adenosine, inasmuch as a specific A2 adenosine receptor antagonist reversed the effect. GP-1-515 also decreased vascular leakage induced by carrageenan (which is partly neutrophil dependent) and by the neutrophil-independent mediators histamine and bradykinin. Inhibition of leakage was reversed by co-administration of adenosine receptor antagonist. Treatment with anti-inflammatory doses of GP-1-515 had no effect on heart rate or blood pressure. In conclusion, GP-1-515 significantly reduced both neutrophil infiltration and vascular leakage through the release of endogenous adenosine without evidence of cardiovascular side effects.

Topics: Adenosine Kinase; Animals; Anti-Inflammatory Agents, Non-Steroidal; Capillary Permeability; Carrageenan; Chemotaxis, Leukocyte; Edema; Hemodynamics; Male; Neutrophils; Rats; Rats, Inbred Strains; Ribonucleosides; Skin Diseases