Basher Fahmin, Fan Hongkuan, Zingarelli Basilia, Borg Keith T, Luttrell Lou M, Tempel George E, Halushka Perry V, Cook James A
Int J Clin Exp Med. 2008;1(1):32-41. Epub 2008 Jan 20.
Heterotrimeric Gi proteins have been previously implicated in signaling leading to inflammatory mediator production induced by bacterial lipopolysaccharide (LPS). beta-arrestins are ubiquitously expressed proteins that alter G-protein-coupled receptors signaling. beta-arrestin 2 plays a multifaceted role as a scaffold protein in regulating cellular inflammatory responses. Polymorphonuclear leukocytes (PMNs) activated by LPS induce inflammatory responses resulting in organ injury during sepsis. We hypothesized that beta-arrestin 2 is a critical modulator of inflammatory responses in PMNs. To examine the potential role of beta-arrestin 2 in LPS-induced cellular activation, we studied homozygous beta-arrestin 2 (-/-), heterozygous (+/-), and wildtype (+/+) mice. PMNs were stimulated with LPS for 16h. There was increased basal TNFalpha and IL-6 production in the beta-arrestin 2 (-/-) compared to both beta-arrestin 2 (+/-) and (+/+) cells. LPS failed to stimulate TNFalpha production in the beta-arrestin 2 (-/-) PMNs. However, LPS stimulated IL-6 production was increased in the beta-arrestin 2 (-/-) cells compared to (+/+) cells. In subsequent studies, peritoneal PMN recruitment was increased 81% in the beta-arrestin 2 (-/-) mice compared to (+/+) mice (p<0.05). beta-arrestin 2 deficiency resulted in an augmented expression of CD18 and CD62L (p<0.05). In subsequent studies, beta-arrestin 2 (-/-) and (+/+) mice were subjected to cecal ligation and puncture (CLP) and lung was collected and analyzed for myeloperoxidase activity (MPO) as index of PMNs infiltrate. CLP-induced MPO activity was significantly increased (p<0.05) in the beta-arrestin 2 (-/-) compared to (+/+) mice. These studies demonstrate that beta-arrestin 2 is a negative regulator of PMN activation and pulmomary leukosequestration in response to polymicrobial sepsis.
异源三聚体Gi蛋白先前已被证明参与了由细菌脂多糖（LPS）诱导的炎症介质产生的信号传导过程。β-抑制蛋白是普遍表达的蛋白质，可改变G蛋白偶联受体信号传导。β-抑制蛋白2作为一种支架蛋白，在调节细胞炎症反应中发挥多方面作用。被LPS激活的多形核白细胞（PMN）会诱导炎症反应，导致脓毒症期间器官损伤。我们假设β-抑制蛋白2是PMN中炎症反应的关键调节因子。为了研究β-抑制蛋白2在LPS诱导的细胞活化中的潜在作用，我们研究了纯合β-抑制蛋白2（-/-）、杂合（+/-）和野生型（+/+）小鼠。用LPS刺激PMN 16小时。与β-抑制蛋白2（+/-）和（+/+）细胞相比，β-抑制蛋白2（-/-）细胞中的基础肿瘤坏死因子α（TNFα）和白细胞介素6（IL-6）产生增加。LPS未能刺激β-抑制蛋白2（-/-）PMN中的TNFα产生。然而，与（+/+）细胞相比，LPS刺激的β-抑制蛋白2（-/-）细胞中IL-6产生增加。在随后的研究中，与（+/+）小鼠相比，β-抑制蛋白2（-/-）小鼠的腹膜PMN募集增加了81%（p<0.05）。β-抑制蛋白2缺乏导致CD18和CD62L表达增加（p<0.05）。在随后的研究中，对β-抑制蛋白2（-/-）和（+/+）小鼠进行盲肠结扎和穿刺（CLP），收集肺组织并分析髓过氧化物酶活性（MPO），作为PMN浸润的指标。与（+/+）小鼠相比，CLP诱导的β-抑制蛋白2（-/-）小鼠的MPO活性显著增加（p<0.05）。这些研究表明，β-抑制蛋白2是PMN活化和肺部白细胞滞留以应对多微生物脓毒症的负调节因子。
