Jin Shunying, Merchant Michael L, Ritzenthaler Jeffrey D, McLeish Kenneth R, Lederer Eleanor D, Torres-Gonzalez Edilson, Fraig Mostafa, Barati Michelle T, Lentsch Alex B, Roman Jesse, Klein Jon B, Rane Madhavi J
Department of Medicine, University of Louisville, Louisville, Kentucky, United States of America.
Department of Medicine, University of Louisville, Louisville, Kentucky, United States of America; Department of Biochemistry and Molecular Biology, University of Louisville, Louisville, Kentucky, United States of America; Robley Rex VA Medical Center, Zorn Avenue, Louisville, Kentucky, United States of America.
PLoS One. 2015 Apr 7;10(4):e0121637. doi: 10.1371/journal.pone.0121637. eCollection 2015.
Immune-complexes play an important role in the inflammatory diseases of the lung. Neutrophil activation mediates immune-complex (IC) deposition-induced acute lung injury (ALI). Components of gamma amino butyric acid (GABA) signaling, including GABA B receptor 2 (GABABR2), GAD65/67 and the GABA transporter, are present in the lungs and in the neutrophils. However, the role of pulmonary GABABR activation in the context of neutrophil-mediated ALI has not been determined. Thus, the objective of the current study was to determine whether administration of a GABABR agonist, baclofen would ameliorate or exacerbate ALI. We hypothesized that baclofen would regulate IC-induced ALI by preserving pulmonary GABABR expression. Rats were subjected to sham injury or IC-induced ALI and two hours later rats were treated intratracheally with saline or 1 mg/kg baclofen for 2 additional hours and sacrificed. ALI was assessed by vascular leakage, histology, TUNEL, and lung caspase-3 cleavage. ALI increased total protein, tumor necrosis factor α (TNF-α and interleukin-1 receptor associated protein (IL-1R AcP), in the bronchoalveolar lavage fluid (BALF). Moreover, ALI decreased lung GABABR2 expression, increased phospho-p38 MAPK, promoted IκB degradation and increased neutrophil influx in the lung. Administration of baclofen, after initiation of ALI, restored GABABR expression, which was inhibited in the presence of a GABABR antagonist, CGP52432. Baclofen administration activated pulmonary phospho-ERK and inhibited p38 MAPK phosphorylation and IκB degradation. Additionally, baclofen significantly inhibited pro-inflammatory TNF-α and IL-1βAcP release and promoted BAL neutrophil apoptosis. Protective effects of baclofen treatment on ALI were possibly mediated by inhibition of TNF-α- and IL-1β-mediated inflammatory signaling. Interestingly, GABABR2 expression was regulated in the type II pneumocytes in lung tissue sections from lung injured patients, further suggesting a physiological role for GABABR2 in the repair process of lung damage. GABABR2 agonists may play a potential therapeutic role in ALI.
免疫复合物在肺部炎症性疾病中起重要作用。中性粒细胞活化介导免疫复合物（IC）沉积诱导的急性肺损伤（ALI）。γ-氨基丁酸（GABA）信号通路的组成部分，包括GABA B受体2（GABABR2）、谷氨酸脱羧酶65/67（GAD65/67）和GABA转运体，存在于肺和中性粒细胞中。然而，肺GABABR激活在中性粒细胞介导的ALI中的作用尚未确定。因此，本研究的目的是确定给予GABABR激动剂巴氯芬是否会改善或加重ALI。我们假设巴氯芬通过保留肺GABABR表达来调节IC诱导的ALI。将大鼠进行假损伤或IC诱导的ALI，两小时后，大鼠经气管内给予生理盐水或1mg/kg巴氯芬，再持续2小时，然后处死。通过血管渗漏、组织学、TUNEL和肺半胱天冬酶-3裂解来评估ALI。ALI增加了支气管肺泡灌洗液（BALF）中的总蛋白、肿瘤坏死因子α（TNF-α）和白细胞介素-1受体相关蛋白（IL-1R AcP）。此外，ALI降低了肺GABABR2表达，增加了磷酸化p38丝裂原活化蛋白激酶（p38 MAPK），促进了IκB降解，并增加了肺中的中性粒细胞流入。在ALI开始后给予巴氯芬可恢复GABABR表达，而在存在GABABR拮抗剂CGP52432的情况下，该表达受到抑制。给予巴氯芬可激活肺磷酸化细胞外信号调节激酶（ERK），并抑制p38 MAPK磷酸化和IκB降解。此外，巴氯芬显著抑制促炎TNF-α和IL-1βAcP的释放，并促进BAL中性粒细胞凋亡。巴氯芬治疗对ALI的保护作用可能是通过抑制TNF-α和IL-1β介导的炎症信号来介导的。有趣的是，在肺损伤患者的肺组织切片中，II型肺泡上皮细胞中的GABABR2表达受到调节，这进一步表明GABABR2在肺损伤修复过程中具有生理作用。GABABR2激动剂可能在ALI中发挥潜在的治疗作用。
