Abstract：
BACKGROUND: One of the most common entry gates for systemic infection is the lung. In humans, pulmonary infections can lead to significant neurological impairment, ranging from acute sickness behavior to long-term disorders. Surfactant proteins (SP), essential parts of the pulmonary innate immune defense, have been detected in the brain of rats and humans. Recent evidence suggests that SP-A, the major protein component of surfactant, also plays a functional role in modulating neuroinflammation. This study aimed to determine whether SP-A deficiency affects the inflammatory response in the brain of adult mice during pulmonary infection.
METHODS: Adult male wild-type (WT, n = 72) and SP-A-deficient (SP-A-/-, n = 72) mice were oropharyngeally challenged with lipopolysaccharide (LPS), Pseudomonas aeruginosa (P. aeruginosa), or PBS (control). Both, behavioral assessment and subsequent brain tissue analysis, were performed 24, 48, and 72 h after challenge. The brain concentrations of the pro-inflammatory cytokines TNF-α, IL-6, and IL-1β were determined by ELISA. Quantitative rtPCR was used to detect SP-A mRNA expression in brain homogenates and immunohistochemistry was applied for the detection of SP-A protein expression in brain coronal slices.
RESULTS: SP-A mRNA and histological evidence of protein expression were detected in both the lungs and brains of WT mice, with significantly higher amounts in lung samples. SP-A-/- mice exhibited significantly higher baseline concentrations of brain TNF-α, IL-6, and IL-1β compared to WT mice. Oropharyngeal application of either LPS or P. aeruginosa elicited significantly higher brain levels of TNF-α and IL-1β in SP-A-/- mice compared to WT mice at all time points. In comparison, behavioral impairment as a measure of sickness behavior, was significantly stronger in WT than in SP-A-/- mice, particularly after LPS application.
CONCLUSIONS: SP-A is known for its anti-inflammatory role in the pulmonary immune response to bacterial infection. Recent evidence suggests that in an abdominal sepsis model SP-A deficiency can lead to increased cytokine levels in the brain. Our results extend this perception and provide evidence for an anti-inflammatory role of SP-A in the brain of adult WT mice after pulmonary infection.
METHODS: Adult male wild-type (WT, n = 72) and SP-A-deficient (SP-A-/-, n = 72) mice were oropharyngeally challenged with lipopolysaccharide (LPS), Pseudomonas aeruginosa (P. aeruginosa), or PBS (control). Both, behavioral assessment and subsequent brain tissue analysis, were performed 24, 48, and 72 h after challenge. The brain concentrations of the pro-inflammatory cytokines TNF-α, IL-6, and IL-1β were determined by ELISA. Quantitative rtPCR was used to detect SP-A mRNA expression in brain homogenates and immunohistochemistry was applied for the detection of SP-A protein expression in brain coronal slices.
RESULTS: SP-A mRNA and histological evidence of protein expression were detected in both the lungs and brains of WT mice, with significantly higher amounts in lung samples. SP-A-/- mice exhibited significantly higher baseline concentrations of brain TNF-α, IL-6, and IL-1β compared to WT mice. Oropharyngeal application of either LPS or P. aeruginosa elicited significantly higher brain levels of TNF-α and IL-1β in SP-A-/- mice compared to WT mice at all time points. In comparison, behavioral impairment as a measure of sickness behavior, was significantly stronger in WT than in SP-A-/- mice, particularly after LPS application.
CONCLUSIONS: SP-A is known for its anti-inflammatory role in the pulmonary immune response to bacterial infection. Recent evidence suggests that in an abdominal sepsis model SP-A deficiency can lead to increased cytokine levels in the brain. Our results extend this perception and provide evidence for an anti-inflammatory role of SP-A in the brain of adult WT mice after pulmonary infection.
摘要：
背景：全身感染最常见的进入门之一是肺。在人类中,肺部感染会导致严重的神经功能缺损，从急性疾病行为到长期疾病。表面活性剂蛋白(SP),肺先天免疫防御的重要部分，已经在大鼠和人类的大脑中检测到。最近的证据表明，SP-A，表面活性剂的主要蛋白质成分，在调节神经炎症中也起着功能性作用。这项研究旨在确定SP-A缺乏是否会影响成年小鼠肺部感染期间大脑的炎症反应。
方法：成年雄性野生型（WT，n=72）和SP-A缺陷（SP-A-/-，n=72)小鼠经口咽攻击脂多糖(LPS)，铜绿假单胞菌(P.铜绿假单胞菌)，或PBS（对照）。两者,行为评估和随后的脑组织分析，在攻击后24、48和72小时进行。促炎细胞因子TNF-α的脑浓度，通过ELISA测定IL-6和IL-1β。定量rtPCR用于检测脑匀浆中SP-AmRNA的表达，免疫组织化学用于检测脑冠状切片中SP-A蛋白的表达。
结果：在WT小鼠的肺和大脑中检测到SP-AmRNA和蛋白质表达的组织学证据，在肺样本中含量明显更高。SP-A-/-小鼠表现出显著较高的基线浓度的脑TNF-α，IL-6和IL-1β与WT小鼠相比。在所有时间点,与WT小鼠相比,LPS或铜绿假单胞菌的口咽部应用在SP-A-/-小鼠中引起显著更高的TNF-α和IL-1β的脑水平。相比之下，行为障碍作为疾病行为的一种衡量标准，WT明显强于SP-A-/-小鼠，特别是在应用LPS之后。
结论：SP-A因其对细菌感染的肺部免疫反应的抗炎作用而闻名。最近的证据表明，在腹部败血症模型中，SP-A缺乏可导致脑中细胞因子水平升高。我们的结果扩展了这种认识，并为肺部感染后成年WT小鼠的大脑中SP-A的抗炎作用提供了证据。
方法：成年雄性野生型（WT，n=72）和SP-A缺陷（SP-A-/-，n=72)小鼠经口咽攻击脂多糖(LPS)，铜绿假单胞菌(P.铜绿假单胞菌)，或PBS（对照）。两者,行为评估和随后的脑组织分析，在攻击后24、48和72小时进行。促炎细胞因子TNF-α的脑浓度，通过ELISA测定IL-6和IL-1β。定量rtPCR用于检测脑匀浆中SP-AmRNA的表达，免疫组织化学用于检测脑冠状切片中SP-A蛋白的表达。
结果：在WT小鼠的肺和大脑中检测到SP-AmRNA和蛋白质表达的组织学证据，在肺样本中含量明显更高。SP-A-/-小鼠表现出显著较高的基线浓度的脑TNF-α，IL-6和IL-1β与WT小鼠相比。在所有时间点,与WT小鼠相比,LPS或铜绿假单胞菌的口咽部应用在SP-A-/-小鼠中引起显著更高的TNF-α和IL-1β的脑水平。相比之下，行为障碍作为疾病行为的一种衡量标准，WT明显强于SP-A-/-小鼠，特别是在应用LPS之后。
结论：SP-A因其对细菌感染的肺部免疫反应的抗炎作用而闻名。最近的证据表明，在腹部败血症模型中，SP-A缺乏可导致脑中细胞因子水平升高。我们的结果扩展了这种认识，并为肺部感染后成年WT小鼠的大脑中SP-A的抗炎作用提供了证据。
