Wang Wei, Chen Ning-Yuan, Ren Dewei, Davies Jonathan, Philip Kemly, Eltzschig Holger K, Blackburn Michael R, Akkanti Bindu, Karmouty-Quintana Harry, Weng Tingting
Department of Thoracic Surgery, Renmin Hospital of Wuhan University, Wuhan, China.
Department of Biochemistry and Molecular Biology, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX, United States.
Front Mol Biosci. 2021 Mar 10;8:636678. doi: 10.3389/fmolb.2021.636678. eCollection 2021.
Acute respiratory distress syndrome (ARDS) is a clinical presentation of acute lung injury (ALI) with often fatal lung complication. Adenosine, a nucleoside generated following cellular stress provides protective effects in acute injury. The levels of extracellular adenosine can be depleted by equilibrative nucleoside transporters (ENTs). ENT inhibition by pharmaceutical agent dipyridamole promotes extracellular adenosine accumulation and is protective in ARDS. However, the therapeutic potential of dipyridamole in acute lung injury has not yet been evaluated. Adenosine acts on three adenosine receptors, the adenosine A1 (Adora1), A2a (Adora2a), the A2b (Adora2b) or the adenosine A3 (Adora 3) receptor. Accumulation of adenosine is usually required to stimulate the low-affinity Adora2b receptor. In order to investigate the effect of adenosine accumulation and the contribution of epithelial-specific ENT2 or adora2b expression in experimental ALI, dipyridamole, and epithelial specific ENT2 or Adora2b deficient mice were utilized. MLE12 cells were used to probe downstream Adora2b signaling. Adenosine receptors, transporters, and targets were determined in ARDS lungs. ENT2 is mainly expressed in alveolar epithelial cells and is negatively regulated by hypoxia following tissue injury. Enhancing adenosine levels with ENT1/ENT2 inhibitor dipyridamole at a time when bleomycin-induced ALI was present, reduced further injury. Mice pretreated with the ADORA2B agonist BAY 60-6583 were protected from bleomycin-induced ALI by reducing vascular leakage (558.6 ± 50.4 vs. 379.9 ± 70.4, < 0.05), total bronchoalveolar lavage fluid cell numbers (17.9 ± 1.8 to 13.4 ± 1.4 e4, < 0.05), and neutrophil infiltration (6.42 ± 0.25 vs. 3.94 ± 0.29, < 0.05). While mice lacking in AECs were no longer protected by dipyridamole. We also identified occludin and focal adhesion kinase as downstream targets of ADORA2B, thus providing a novel mechanism for adenosine-mediated barrier protection. Similarly, we also observed similar enhanced ADORA2B (3.33 ± 0.67 to 16.12 ± 5.89, < 0.05) and decreased occludin (81.2 ± 0.3 to 13.3 ± 0.4, < 0.05) levels in human Acute respiratory distress syndrome lungs. We have highlighted a role of dipyridamole and adenosine signaling in preventing or treating ALI and identified Ent2 and Adora2b as key mediators in important for the resolution of ALI.
急性呼吸窘迫综合征（ARDS）是急性肺损伤（ALI）的一种临床表现，常伴有致命的肺部并发症。腺苷是细胞应激后产生的一种核苷，在急性损伤中具有保护作用。细胞外腺苷水平可被平衡核苷转运体（ENTs）消耗。药物双嘧达莫对ENT的抑制作用可促进细胞外腺苷的积累，对ARDS具有保护作用。然而，双嘧达莫在急性肺损伤中的治疗潜力尚未得到评估。腺苷作用于三种腺苷受体，即腺苷A1（Adora1）、A2a（Adora2a）、A2b（Adora2b）或腺苷A3（Adora 3）受体。通常需要腺苷的积累来刺激低亲和力的Adora2b受体。为了研究腺苷积累的作用以及上皮特异性ENT2或adora2b表达在实验性ALI中的作用，使用了双嘧达莫以及上皮特异性ENT2或Adora2b缺陷小鼠。MLE12细胞用于探究Adora2b信号的下游情况。在ARDS肺中测定腺苷受体、转运体和靶点。ENT2主要表达于肺泡上皮细胞，在组织损伤后受缺氧负调控。在博来霉素诱导的ALI出现时，用ENT1/ENT2抑制剂双嘧达莫提高腺苷水平可减轻进一步损伤。用ADORA2B激动剂BAY 60-6583预处理的小鼠可免受博来霉素诱导的ALI影响，表现为血管渗漏减少（558.6±50.4对379.9±70.4，<0.05）、支气管肺泡灌洗液细胞总数减少（17.9±1.8至13.4±1.4×10⁴，<0.05）以及中性粒细胞浸润减少（6.42±0.25对3.94±0.29，<0.05）。而缺乏肺泡上皮细胞的小鼠不再受到双嘧达莫的保护。我们还确定了闭合蛋白和粘着斑激酶是ADORA2B的下游靶点，从而为腺苷介导的屏障保护提供了一种新机制。同样，我们在人类急性呼吸窘迫综合征肺中也观察到类似的ADORA2B增强（3.33±0.67至16.12±5.89，<0.05）和闭合蛋白水平降低（81.2±0.3至13.3±0.4，<0.05）。我们强调了双嘧达莫和腺苷信号在预防或治疗ALI中的作用，并确定Ent2和Adora2b是ALI消退的关键介质。
