Adenosine A2A Receptor Activities Ameliorate White Matter Lesions Induced By Chronic Hypoperfusion And Modulate Psychomotor Behaviors In Mice

PartⅠEffect of adenosine A_2A receptor activities on white matter lesions induce by chronic hypoperfusion in miceBackground and Objective The dominant neuropathological features of the white matter lesions induced by chronic cerebral hypoperfusion is nerve fibers demyelination,axonal degeneration and proliferation of microglia and astroglia. However, Much less is known about the moleculor pathomechanisms of ischemic white matter lesions. Previous studies support that there are a series of pathophysiological events, including white matter lesions, proliferation of glial, periphery inflammatory cell infiltration and increased production of several inflammatory cytokines in the white matter regions after chronic cerebral hypoperfusion. These evidences indicate that inflammatory reaction is correlated to the white matter lesions induced by chronic cerebral hypoperfusion. As an intermediate product of energy metabolism, adenosine is an important neuromodulator in the central nervous systerm. Adenosine acting at its receptors(A1,A2A A2B andA3) regulates many physiological events and is involved in the development of various diseases..A lot of attention was paied to pharmacotherapy role of A_2A receptor because of the definite finds about the therapy role of A_2A receptor in animal models of some diseases. Previous data show that the protective effect of antagonist of adenosine A_2A receptor in acute ischemic brain injury is mediated by suppressing the abnormal rise of the extracellular glutamate concentration and thereby reducing its excitotoxicy to the neurons. Previous study of our laboratory about white matter lesions induced by chronic cerebral hypoperfusion found that adenosine A_2A receptor knockout aggratate white matter lesion, promote the proliferation and activation of microglia and the proliferation of periphery inflammatory cells. It indicated that adenosine A_2A receptor mediated effect play an important role in the white matter lesions induced by chronic cerebral hypoperfuion. But the exact mechanism is stiil unknown. To further confirm the relationship between adenosine A_2A receptor agonist mediates effect and the inflammatory pathomechanism.of white matter lesions, in the present study we observe the influence of A_2AR agonist on the white matter lesions, proliferation of microglia, periphery inflammatory cell infiltration after chronic cerebral hypoperfusion in the mice. Methods The mouse model of chronic cerebral hypoperfusion was established by stenosis of bilateral carotid artery (BCAS) using 0.18mm diameter microcoils in accordance with Shibata. The variation of local cerebral blood flow was measured by Laser Doppler flowmetry at preoperative and after the BCAS. The model mice of CGS21680 group were intraperitoneal injected the adenosine A_2A receptor agonist CGS21680(0.5mg/kg/d,ip) everyday, up to each deadline time intervals, The model mice of control group were intraperitoneal injected equality volume carrier solution to be control group.We evaluated the cognitive function of model mice of CGS21680 group and control group by Morris maze test at 25d after the surgery. the freezing constinuouse corona- sections at 15d,30d,45d after the surery were done, The white matter lesions,microglia proliferation and periphery periphery inflammatory cell infiltration were examined by Kluver-Barrera staining and Bielschowsky silver staining, anti-MBP,anti-CD11b,anti-CD3 and anti-LY-6G immunohistochemistry. Results 1. the mouse model of chronic cerebral hypoperfusion was successful established by stenosis of bilateral carotid artery (BCAS) using the special microcoils, the mean local CBF values after the operation decreased 29±5.38%,white matter fibers sparseness,fibers loophole to raise and local vacuolization was observed in the the model mice at 15d,30d and 45d after the BCAS by histopathlogy; 2. To compare control group , the escape latency period of the CGS21680 group was obvious prolongation in Morris water maze measurement , but the times of crossing the exact position of the former platform was no significant difference in two groups. 3 . To compare control group , the WM lesions were extenuated in the CGS21680 group by Histopathlogy at 15d,30d and 45d after BCAS. 4. The activated microglia with swollen and hypertropic cell bodies as well as thick and short processes were found in the white matter regions in both two groups at 45d after the surgery. But the number of microglia cells of the CGS21680 group is obvious decreased. 5. The CD3 positive cells were observed in the corpus callosum of the control group at 30d,45d after surgery by immunohistostaining, but the CD3 positive cells were not observed in CGS21680 group. 6. No LY-6G positive cells were observed in the corpus callosum,internal capsule and optic tract white matter regions in both two groups. Conclusion 1.Adenosine A2A receptor agonist CGS21680 suppresses the locomotor activity of mice . 2. Adenosine A2A receptor agonist CGS21680 decreasees the white matter lesion induced by chronic cerebral hypoperfusion. 3. Adenosine A2A receptor agonist CGS21680 inhibites the activation of microglia in white matter leion regions induce by chronic cerebral hypoperfusion. 4. Adenosine A2A receptor agonist CGS21680 inhibites the infiltration of lymphocyte in white matter lesion regions induce by chronic cerebral hypoperfusion. 5. Adenosine A2A receptor agonist CGS21680 decreases the white matter lesion induce by chronic cerebral hypoperfusion relevant to CGS21680 inhibiting inflammatory pathologic processes.PartⅡThe modulatory effect of adenosine A_2A receptors on psychiatric locomotor and mood behavior in miceObjective To explore the effects of the gene knock-out, agonist and antagonist of adenosine A_2A receptor on the locomotor activity, anxiety- and depression-like behavior in mice. Method The mice were divided into adenosine A_2A receptor gene knock-out (A_2A KO) group and their wild-type (WT) littermates group, A_2A receptor agonist CGS21680 (0.5mg/kg i.p.) group, A_2A receptor antagonist SCH58261 (2 mg/kg i.p.) group and their vehicle control group. Open-field test, elevated plus maze and forced swimming test were used to evaluate the locomotor activity, anxiety- and depression-like behavior in mice. Results①Compared with the vehicle group, the total movement distance was shortened and the time staying in the peripheral area increased in open field tes(tP<0.01), the open arm entries and entry time decreased in elevated plus maze(P<0.01), the total immobility time increased in forced swimming test (P<0.01) in CGS21680 group.②Compared with the vehicle group, the total movement distance and the movement distance in the central area were significantly longer in open field test (P<0.01), the total immobility time decreased in forced swimming test (P<0.01) in SCH58261 group. No difference of any parameters was found in elevated plus maze between SCH58261 and the vehicle group(P>0.05).③Compared with WT group, the total movement distance was shortened and the time staying in the peripheral area increased in open field test(P<0.05), the open arm entries and entry time decreased in elevated plus maze(P<0.05) in A_2AKO group. There was no significant difference in forced swimming test between WT and A_2AKO group (P>0.05). Conclusions The spontaneous motility as well as the exploratory behavior were inhibited, the anxiety and depression level was exacerbated by the treatment with the agonist of A_2A receptor. The antagonist of A_2A receptor produced basically the contrary effects. The A_2A receptor gene knock-out has the similar effects with that of the A_2A receptor agonist.