Antonioli L, Fornai M, Awwad O, Giustarini G, Pellegrini C, Tuccori M, Caputi V, Qesari M, Castagliuolo I, Brun P, Giron M C, Scarpignato C, Blandizzi C, Colucci R
Division of Pharmacology and Chemotherapy, Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy.
Br J Pharmacol. 2014 Mar;171(5):1314-29. doi: 10.1111/bph.12539.
Adenosine A(2B) receptors regulate several physiological enteric functions. However, their role in the pathophysiology of intestinal dysmotility associated with inflammation has not been elucidated. Hence, we investigated the expression of A2B receptors in rat colon and their role in the control of cholinergic motility in the presence of bowel inflammation.
Colitis was induced by 2,4-dinitrobenzenesulfonic acid (DNBS). Colonic A(2B) receptor expression and localization were examined by RT-PCR and immunofluorescence. The interaction between A(2B) receptors and adenosine deaminase was assayed by immunoprecipitation. The role of A(2B) receptors in the control of colonic motility was examined in functional experiments on longitudinal muscle preparations (LMPs).
A(2B) receptor mRNA was present in colon from both normal and DNBS-treated rats but levels were increased in the latter. A(2B) receptors were predominantly located in the neuromuscular layer, but, in the presence of colitis, were increased mainly in longitudinal muscle. Functionally, the A(2B) receptor antagonist MRS 1754 enhanced both electrically-evoked and carbachol-induced cholinergic contractions in normal LMPs, but was less effective in inflamed tissues. The A(2B) receptor agonist NECA decreased colonic cholinergic motility, with increased efficacy in inflamed LMP. Immunoprecipitation and functional tests revealed a link between A(2B) receptors and adenosine deaminase, which colocalize in the neuromuscular compartment.
Under normal conditions, endogenous adenosine modulates colonic motility via A2B receptors located in the neuromuscular compartment. In the presence of colitis, this inhibitory control is impaired due to a link between A2B receptors and adenosine deaminase, which catabolizes adenosine, thus preventing A(2B) receptor activation.
腺苷A(2B)受体调节多种肠道生理功能。然而，其在与炎症相关的肠道运动障碍病理生理学中的作用尚未阐明。因此，我们研究了A2B受体在大鼠结肠中的表达及其在肠道炎症状态下对胆碱能运动控制的作用。
用2,4-二硝基苯磺酸（DNBS）诱导结肠炎。通过逆转录聚合酶链反应（RT-PCR）和免疫荧光检测结肠A(2B)受体的表达和定位。通过免疫沉淀法检测A(2B)受体与腺苷脱氨酶之间的相互作用。在纵向肌条制备物（LMPs）的功能实验中研究A(2B)受体在结肠运动控制中的作用。
正常大鼠和经DNBS处理的大鼠结肠中均存在A(2B)受体mRNA，但后者水平升高。A(2B)受体主要位于神经肌肉层，但在结肠炎状态下，主要在纵行肌中增加。在功能上，A(2B)受体拮抗剂MRS 1754增强了正常LMPs中电刺激诱发的和卡巴胆碱诱导的胆碱能收缩，但在炎症组织中效果较差。A(2B)受体激动剂NECA降低结肠胆碱能运动，在炎症LMP中效力增加。免疫沉淀和功能测试揭示了A(2B)受体与腺苷脱氨酶之间的联系，它们共定位于神经肌肉区室。
在正常情况下，内源性腺苷通过位于神经肌肉区室的A2B受体调节结肠运动。在结肠炎状态下，由于A2B受体与分解腺苷的腺苷脱氨酶之间的联系，这种抑制性控制受损，从而阻止A(2B)受体激活。
