KF-24345

Spinally delivered adenosine receptor agonists and its analogs have recently been shown to have antinociceptive effects.However, the mechanisms by which adenosine produces antinociception are not clear.Therefore, the present study evaluated the modulating effect of adenosine A₁ receptor agonist, KF24345, R-PIA injected intrathecally (I.T.) on the tactile-allodynia, associated with cerebrospinal fluid (CSF) - glutamate release induced by injection of GABA_A receptor antagonist, bicuculine (BIC).The microdialysis probe and polyethylene tube (PE-10) were intrathecally implanted into lumbar segment under halothane anesthesia in forty-five Sprague-Dawley rats.After three days, rats were divided into six groups; (i) Control (saline), (ii) and (iii) KF24345 at doses of 10 μg and 100 μg, (iv) R-PIA at doses of 10 nM, (v) 10 nM R-PIA plus 300 nM aminophylline, and (vi) 100 μg KF24345 plus 300 nM aminophylline.The tactile-allodynia was evaluated by touch-evoked agitation (TEA) which scored 0 (no response to hair touching at lumbar level) to 3 (strong agitation appeared).Using an intrathecal microdialysis, glutamate concentration in cerebrospinal fluid (CSF-Glu) was periodically (10 min intervals) determined simultaneously by a HPLC-ECD.Intrathecal BIC injection evoked a transient strong agitation (TEA score: 4.7 at 10 min, 1.0 at 30 min), associated with increased CSF-Glu (70 % at 10 min.).KF24345 and R-PIA attenuated such increases of TEA and CSF-Glu dose-dependently.Such action of KF24345 (100 nM) was reversed by codelivery of aminophylline (300 nM).Base on the present study, it is clearly demonstrated that KF24345, R-PIA can prevent allodynia in a dose-dependent manner.This attenuating effect was reversed by adenosine A₁ receptor antagonist, suggesting R-PIA has a potent anti-allodynic effect via inhibiting adenosine A₁ receptor activity at spinal cord.In addition, the microdialysis study demonstrated that R-PIA attenuates increased spinal glutamate release evoked by allodynia through presynaptic inhibition of primary afferent input.

Adenosine protects against cellular damage and dysfunction under several adverse conditions, including inflammation. We examined the effects of KF24345, a novel adenosine uptake inhibitor, on inflammatory diseases to investigate whether the adenosine uptake inhibition is useful for the treatment of inflammation. KF24345 inhibited adenosine uptake into washed erythrocytes (in vitro) and sampled blood cells from mice after its oral administration (in vivo). KF24345 significantly suppressed lipopolysaccharide-induced tumor necrosis factor-alpha production and leukopenia in mice, and the effects of KF24345 were abolished by the treatment with a non-selective or an A(2A)-selective adenosine receptor antagonist. In the experimental glomerulonephritis induced in mice by anti-glomerular basement membrane antiserum, KF24345 significantly inhibited proteinuria and glomerular damage without exhibiting the side effects observed following the treatment with prednisolone and cyclophosphamide. In addition, KF24345 ameliorated the severity of experimental acute pancreatitis induced by cerulein or choline-deficient and ethionine-supplemented diet in mice, and it decreased mortality accompanying severe acute pancreatitis. The anti-pancreatitis effects of KF24345 were abolished by the treatment with a non-selective or an A(2A)-selective adenosine receptor antagonist. These results suggest that KF24345 and adenosine uptake inhibitors can be a new therapeutic approach for various inflammatory diseases, including glomerulonephritis and acute pancreatitis.