Wang Cairui, Zhou Guopeng, Zeng Zeng
Department of Geriatrics, Peking University First Hospital, Beijing 100034, China.
Department of Geriatrics, Peking University First Hospital, Beijing 100034, China. Email:
Chin Med J (Engl). 2014;127(11):2129-37.
Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are the first steps in the development of multiple organ failure induced by sepsis. A systemic excessive inflammatory reaction is currently the accepted mechanism of the pathogenesis of sepsis. Several studies have suggested a protective role of the peroxisome proliferator activated receptor-β/δ (PPAR-β/δ) in related inflammatory diseases. But the role of PPARβ/δ in ALI remains uncertain. The aim of this study was to investigate the role and possible mechanism of PPARβ/δ in ALI induced by sepsis.
Cecal ligation and puncture (CLP) was used as a sepsis model. Rats were randomly divided into four groups, the control group (CON, n = 6), sham-operation group (SHAM, n = 12), cecal ligation and puncture group (CLP, n = 30), GW501516 group (CLP+GW, n = 25), which underwent CLP and were subcutaneously injected with the PPAR-β/δ agonist GW501516 (0.05 mg/100 g body weight). Survival was monitored to 24 hours after operation. Blood pressure, serum creatinine, blood urea nitrogen, aspartate aminotrasferase and alanine aminotrasferase were measured after CLP. Concentrations of tumor necrosis factor α (TNF-α) and interleukin (IL)-1β in serum were detected by enzyme linked immunosorbent assay (ELISA) kits. Lung tissue samples were stained with H&E and scored according to the degree of inflammation. Bacterial colonies were counted in the peritoneal fluid. Alveolar macrophages were cultured and incubated with GW501516 (0.15 µmol/L) and PPARβ/δ adenovirus and then treated with Lipopolysaccharide (2 µg/ml) for 2 hours. The TNF-α, IL-1β and IL-6 RNA in lung and alveolar macrophages were determined by real-time PCR. Phosphorylation of signal transducer and activator of transcription 3 (STAT3) in lung and alveolar macrophages was detected by Western blotting.
GW501516 significantly increased the survival of septic rats, decreased histological damage of the lungs, reduced inflammatory cytokines in serum and lung tissues of septic rats and did not increase counts of peritoneal bacteria. In vitro, GW501516 and over-expression of PPARβ/δ attenuated gene expression of TNF-α, IL-1β and IL-6 in alveolar macrophages. Both in vivo and in vitro, PPARβ/δ inhibited the phosphorylation of STAT3.
PPARβ/δ plays a protective role in sepsis induced ALI via suppressing excessive inflammation.
急性肺损伤（ALI）和急性呼吸窘迫综合征（ARDS）是脓毒症诱发多器官功能衰竭过程中的起始阶段。全身过度炎症反应是目前公认的脓毒症发病机制。多项研究提示过氧化物酶体增殖物激活受体-β/δ（PPAR-β/δ）在相关炎症性疾病中具有保护作用。但PPARβ/δ在ALI中的作用仍不明确。本研究旨在探讨PPARβ/δ在脓毒症诱导的ALI中的作用及可能机制。
采用盲肠结扎穿孔术（CLP）建立脓毒症模型。将大鼠随机分为四组，即对照组（CON，n = 6）、假手术组（SHAM，n = 12）、盲肠结扎穿孔组（CLP，n = 30）、GW501516组（CLP+GW，n = 25），CLP组大鼠行CLP手术并皮下注射PPAR-β/δ激动剂GW501516（0.05 mg/100 g体重）。术后监测24小时存活率。CLP术后测量血压、血清肌酐、血尿素氮、天冬氨酸转氨酶和丙氨酸转氨酶。采用酶联免疫吸附测定（ELISA）试剂盒检测血清中肿瘤坏死因子α（TNF-α）和白细胞介素（IL）-1β浓度。肺组织样本行苏木精-伊红（H&E）染色并根据炎症程度评分。计数腹腔液中的细菌菌落。培养肺泡巨噬细胞，用GW501516（0.15 µmol/L）和PPARβ/δ腺病毒孵育，然后用脂多糖（2 µg/ml）处理2小时。采用实时聚合酶链反应（PCR）检测肺组织和肺泡巨噬细胞中TNF-α、IL-1β和IL-6的RNA。采用蛋白质印迹法检测肺组织和肺泡巨噬细胞中信号转导子和转录激活子3（STAT3）的磷酸化水平。
GW501516显著提高脓毒症大鼠的存活率，减轻肺组织学损伤，降低脓毒症大鼠血清和肺组织中的炎症细胞因子水平，且不增加腹腔细菌计数。在体外，GW501516和PPARβ/δ过表达减弱肺泡巨噬细胞中TNF-α、IL-1β和IL-6的基因表达。在体内和体外，PPARβ/δ均抑制STAT3的磷酸化。
PPARβ/δ通过抑制过度炎症反应在脓毒症诱导的ALI中发挥保护作用。
