Despite its fundamental role in providing an extensive surface for gas exchange, the alveolar epithelium (AE) serves as an immunological barrier through, e.g., the release of proinflammatory cytokines and secretion of surfactant to prevent alveolar collapse. Thus, AE is important for sustaining lung homeostasis. Extracellular ATP secreted by alveolar epithelial cells (AECs) is involved in physiological and pathological conditions and acts mainly through the activation of purine receptors (P2Rs). When studying P2R-mediated processes, primary isolated type II AECs (piAECs) still represent the gold standard in in vitro research, although their preparation is time-consuming and requires the sacrifice of many animals. Hence, cultivated immortalized and tumor-derived AEC lines may constitute a valuable alternative. In this work, we examined P2R expression and functionality in piAECs, in immortalized and tumor-derived AEC lines with the purpose of gaining a better understanding of purinergic signaling in different cell systems and assisting researchers in the choice of a suitable cell line with a certain P2R in demand. We combined mRNA and protein analysis to evaluate the expression of P2R. For pharmacological testing, we conducted calcium ([Ca²⁺]) measurements and siRNA receptor knockdown. Interestingly, the mRNA and protein levels of P2Y₂, P2Y_6, and P2X₄ were detected on all cell lines. Concerning functionality, P2XR could be narrowed to L2 and piAECs while P2YR were active in all cell lines.

中文翻译：

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肺泡上皮细胞中嘌呤受体表达和功能的分析。

尽管肺泡上皮 (AE) 在提供广泛的气体交换表面方面发挥着基本作用，但它还是通过例如释放促炎细胞因子和分泌表面活性剂来防止肺泡塌陷而充当免疫屏障。因此，AE对于维持肺稳态很重要。肺泡上皮细胞 (AEC) 分泌的细胞外 ATP 参与生理和病理状况，主要通过激活嘌呤受体 (P2R) 起作用。在研究 P2R 介导的过程时，初级分离的 II 型 AEC (piAEC) 仍然代表体外研究的黄金标准，尽管它们的制备耗时且需要牺牲许多动物。因此，培养的永生化和肿瘤衍生的 AEC 系可能是一种有价值的替代品。在这项工作中，我们检查了 piAEC、永生化和肿瘤衍生的 AEC 系中 P2R 的表达和功能，目的是更好地了解不同细胞系统中的嘌呤能信号传导，并帮助研究人员选择具有特定 P2R 需求的合适细胞系。我们结合mRNA和蛋白质分析来评估P2R的表达。对于药理测试，我们进行了钙（[Ca²⁺ ]) 测量和 siRNA 受体敲低。有趣的是，在所有细胞系中都检测到了 P2Y ₂、P2Y ₆和 P2X ₄的 mRNA 和蛋白质水平。关于功能，P2XR 可以缩小到 L2 和 piAEC，而 P2YR 在所有细胞系中都很活跃。