Objective: To observe the effect of electroacupuncture (EA) at "Zusanli"(ST36) pretreatment on lung functions, inflammatory response, and levels of angiotensin-converting enzyme 2 (ACE2) and angiotensin (1-7) ［Ang (1-7)］ in rats with sepsis-induced acute lung injury (ALI), so as to explore its mechanisms underlying improvement of ALI.
Methods: Thirty male SD rats were randomly divided into normal, model and EA groups (n=10 in each group). The sepsis-related ALI model was established by intraperitoneal injection of lipopolysaccharide (LPS, 5 mg/kg). Rats of the EA group received EA (4 Hz/20 Hz, 1-3 mA) stimulation at bilateral ST36 for 30 min, once each day, for 7 days before modeling. The lung functions including forced vital capacity (FVC), forced expiratory volume at 0.1 second (FEV0.1) and FEV0.3 were detected using a respiratory function detector for small animals at 3 h after modeling. The bronchoalveolar lavage fluid (BALF) was collected for assaying the contents of Ang (1-7), tumor necrosis factor-α (TNF-α) and interleukin-1 β (IL-1β) using ELISA. The lung wet/dry weight (W/D) ratio, FEV0.1/FVC, and FEV0.3/FVC were calculated. The histopathological changes of lung tissues were displayed by hematoxylin-eosin (H.E.) staining. The expression of ACE2 and mitochondrial assembly receptor (MasR) mRNAs and proteins in the lung tissue was detected by fluorescence quantitative real-time PCR and Western blot, separately.
Results: Following modeling, the levels of FVC, FEV0.1, FEV0.3, ratio of FEV0.1/FVC and FEV0.3/FVC, content of Ang (1-7) in the BALF, and the expression levels of ACE2 and MasR mRNAs and proteins in the lung tissue were significantly decreased (P<0.01), while the level of W/D ratio and TNF-α and IL-1β contents in the BALF significantly increased (P<0.01) in the model group relevant to the normal group. In comparison with the model group, the levels of FVC, FEV0.1, FEV0.3, ratio of FEV0.1/FVC and FEV0.3/FVC, content of Ang (1-7) in the BALF, and expression levels of ACE2 and MasR mRNAs and proteins in the lung tissue were significantly increased (P<0.05, P<0.01), whereas the level of W/D ratio, and TNF-α and IL-1β contents in the BALF were significantly decreased (P<0.05, P<0.01) in the EA group. H.E. staining showed pulmonary interstitial edema and alveolar septum thickening with severe inflammatory cell infiltration in the model group, which was relatively milder in the EA group.
Conclusion: EA preconditioning at ST36 can improve pulmonary function in sepsis-related ALI rats, which may be related to its effects in inhibiting inflammatory response and up-regulating ACE2 and MasR expression and Ang (1-7) content in the lung tissue.
目的：观察电针“足三里”预处理对脂多糖(LPS)诱导的脓毒症急性肺损伤(ALI)大鼠炎性反应、血管紧张素转化酶2(ACE2)及血管紧张素(1-7)［Ang(1-7)］的影响, 探讨电针对脓毒症ALI的预防作用和可能机制。方法：将30只雄性SD大鼠随机分为正常组、模型组、电针组, 每组10只。采用腹腔注射LPS(5 mg/kg)复制脓毒症ALI大鼠模型。电针组予双侧“足三里”穴电针预处理, 每日1次, 每次30 min, 连续1周后造模。造模3 h后采用小动物呼吸功能检测仪检测大鼠肺功能；ELISA法检测支气管肺泡灌洗液(BALF)中Ang(1-7)、肿瘤坏死因子-α(TNF-α)、白细胞介素-1β(IL-1β)的含量；计算肺湿/干重比(W/D)；HE染色法观察大鼠肺组织病理变化；Western blot法、实时荧光定量PCR法检测肺组织中ACE2、线粒体组装受体(MasR)蛋白和mRNA的表达。结果：与正常组比较, 模型组肺组织可见明显肺间质水肿、肺泡间隔增厚；用力肺活量(FVC)、第0.1秒用力呼气量(FEV0.1)、第0.3秒用力呼气量(FEV0.3)、FEV0.1占FVC之比(FEV0.1/FVC), FEV0.3占FVC之比(FEV0.3/FVC)均显著降低(P<0.01)；BALF内TNF-α、IL-1β含量显著升高(P<0.01), Ang(1-7)含量显著降低(P<0.01)；W/D显著升高(P<0.01)；肺组织内ACE2、MasR蛋白和mRNA表达水平均显著降低(P<0.01)。与模型组比较, 电针组肺间质水肿及肺泡间隔厚度均有改善；FVC、FEV0.1、FEV0.3、FEV0.1/FVC及FEV0.3/FVC均显著升高(P<0.05, P<0.01)；BALF内TNF-α、IL-1β含量显著降低(P<0.01), Ang(1-7)含量显著升高(P<0.01)；W/D显著降低(P<0.05)；肺组织内ACE2、MasR蛋白和mRNA表达水平均显著升高(P<0.05, P<0.01)。结论：电针“足三里”穴预处理对LPS诱导的脓毒症ALI大鼠具有抗炎、降低肺水肿和对肺功能保护的作用, 其机制可能与电针通过上调ACE2和MasR的表达及Ang (1-7)的含量从而抑制炎性反应有关。.
Keywords: Acute lung injury; Angiotensin (1-7); Angiotensin-converting enzyme 2; Electroacupuncture preconditioning; Sepsis; Zusanli (ST36).