Chronic use of β₂-adrenoceptor agonists as a monotherapy in asthma is associated with a loss of disease control and an increased risk of mortality. Herein, we tested the hypothesis that β₂-adrenoceptor agonists, including formoterol, promote biased, β-arrestin (Arr) 2–dependent activation of the mitogen-activated protein kinases, ERK1/2, in human airway epithelial cells and, thereby, effect changes in gene expression that could contribute to their adverse clinical outcomes. Three airway epithelial cell models were used: the BEAS-2B cell line, human primary bronchial epithelial cells (HBEC) grown in submersion culture, and HBEC that were highly differentiated at an air-liquid interface. Unexpectedly, treatment of all epithelial cell models with formoterol decreased basal ERK1/2 phosphorylation. This was mediated by cAMP-dependent protein kinase and involved the inactivation of C-rapidly-activated fibrosarcoma, which attenuated downstream ERK1/2 activity, and the induction of dual-specificity phosphatase 1. Formoterol also inhibited the basal expression of early growth response-1, an ERK1/2-regulated gene that controls cell growth and repair in the airways. Neither carvedilol, a β₂-adrenoceptor agonist biased toward βArr2, nor formoterol promoted ERK1/2 phosphorylation in BEAS-2B cells, although β₂-adrenoceptor desensitization was compromised in ARRB2-deficient cells. Collectively, these results contest the hypothesis that formoterol activates ERK1/2 in airway epithelia by nucleating a βArr2 signaling complex; instead, they indicate that β₂-adrenoceptor agonists inhibit constitutive ERK1/2 activity in a cAMP-dependent manner. These findings are the antithesis of results obtained using acutely challenged native and engineered HEK293 cells, which have been used extensively to study mechanisms of ERK1/2 activation, and highlight the cell type dependence of β₂-adrenoceptor–mediated signaling.

中文翻译：

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β2-肾上腺素受体激动剂通过经典的、cAMP 驱动的信号传导促进人气道上皮细胞中细胞外信号调节的激酶 1/2 去磷酸化，独立于 β-抑制蛋白 2

长期使用的β ₂ -肾上腺素受体激动剂，如哮喘单一疗法与疾病控制的损失和死亡的风险增加相关联。在此，我们检验了β _{2 -}肾上腺素能受体激动剂（包括福莫特罗）促进偏向、β-抑制蛋白 (Arr) 2 依赖于人气道上皮细胞中丝裂原活化蛋白激酶 ERK1/2 的激活，从而影响基因表达的变化，这可能导致其不利的临床结果。使用了三种气道上皮细胞模型：BEAS-2B 细胞系、在浸没培养中生长的人原代支气管上皮细胞 (HBEC) 和在气液界面高度分化的 HBEC。出乎意料的是，用福莫特罗处理所有上皮细胞模型都降低了基础 ERK1/2 磷酸化。这是由 cAMP 依赖性蛋白激酶介导的，涉及 C 快速激活的纤维肉瘤的失活，从而减弱下游 ERK1/2 的活性，并诱导双特异性磷酸酶 1。福莫特罗还抑制了早期生长反应的基础表达—— 1、ERK1/2 调控的基因，控制气道中的细胞生长和修复。无论是卡维地洛，β ₂肾上腺素受体激动剂偏向于β Arr2，福莫特罗也不会促进 BEAS-2B 细胞中的 ERK1/2 磷酸化，尽管β ₂肾上腺素受体脱敏在ARRB2 缺陷细胞中受到损害。总的来说，这些结果反驳了福莫特罗通过使β Arr2 信号复合物成核来激活气道上皮细胞中 ERK1/2的假设。相反，它们表明β _{2 -}肾上腺素能受体激动剂抑制以 cAMP 依赖性方式组成型 ERK1/2 活性。这些发现是使用急性挑战天然和工程改造的HEK293细胞，其已被广泛用于ERK1 / 2激活的研究机构所获得的结果的对立面，并突出显示的细胞类型依赖性β ₂ -肾上腺素受体介导的信号。