内毒素性急性肺损伤小鼠肺泡巨噬细胞极化时HO-1与PPARγ的关系

Relationship between HO-1 and PPARγduring alveolar macrophage polarization in a mouse model of endotoxin-induced acute lung injury

目的评价内毒素性急性肺损伤(ALI)小鼠肺泡巨噬细胞极化时血红素氧合酶-1(HO-1)与过氧化物酶体增殖物激活受体γ(PPARγ)的关系。方法选择清洁级雄性C57BL/6小鼠30只(野生型小鼠24只和HO-1基因敲除小鼠6只),6~8周龄,体重18~22 g。采用随机数字表法将野生型小鼠分为4组(n=6):对照组(C组)、ALI组、ALI+HO-1激动剂氯高铁血红素(Hemin)组(ALI+H组)和ALI+Hemin+PPARγ拮抗剂T0070907组(ALI+H+T组)。HO-1基因敲除小鼠建立ALI模型为ALI+HO-1-/-组。采用尾静脉注射LPS 15 mg/kg制备内毒素性ALI模型。ALI+H+T组于给予LPS前1 h时腹腔注射T00709071.5 mg/kg;ALI+H组和ALI+H+T组于给予LPS前30 min时腹腔注射Hemin 50 mg/kg。给予LPS 12 h后处死小鼠取肺组织,测定湿重/干重(W/D)比值,观察肺组织病理学结果,并行肺损伤评分;采用流式细胞术检测F4/80+/CD86+标记的M1型肺泡巨噬细胞水平和F4/80+/CD206+标记的M2型肺泡巨噬细胞水平;采用ELISA法测定细胞上清液M1型肺泡巨噬细胞相关基因诱导型一氧化氮合酶(iNOS)和M2型肺泡巨噬细胞相关基因精氨酸酶-1(Arg-1)含量;采用Western blot法测定肺组织HO-1和PPARγ表达。结果与C组比较,其余4组肺损伤评分、肺组织W/D比值、CD86和CD206水平、iNOS和Arg-1含量均升高,PPARγ表达上调,ALI组、ALI+H组和ALI+H+T组肺组织HO-1表达上调(P<0.05)。与ALI组比较,ALI+HO-1-/-组肺损伤评分、肺组织W/D比值、CD86和iNOS水平均升高,CD206和Arg-1水平降低,HO-1和PPARγ表达下调,ALI+H组肺损伤评分、肺组织W/D比值、CD86和iNOS水平均降低,CD206和Arg-1水平升高,HO-1和PPARγ表达上调(P<0.05),ALI+H+T组上述各指标差异无统计学意义(P>0.05)。与ALI+H组比较,ALI+H+T组肺损伤评分、肺组织W/D比值、CD86和iNOS水平均升高,CD206和Arg-1水平降低,PPARγ表达下调(P<0.05),HO-1表达差异无统计学意义(P>0.05)。结论HO-1可通过上调PPARγ的表达,抑制肺泡巨噬细胞向M1型极化,促进其向M2型极化,从而在小鼠内毒性ALI中发挥内源性保护作用。

Objective To evaluate the relationship between heme oxygenase-1(HO-1)and peroxisome proliferator-activated receptorγ(PPARγ)during alveolar macrophage polarization in a mouse model of endotoxin-induced acute lung injury(ALI).Methods Thirty clean-grade male C57BL/6 mice(24 wide-type mice and 6 HO-1 knockout mice),aged 6-8 weeks,weighing 18-22 g,were studied.Wide-type mice were divided into 4 groups(n=6 each)using a random number table method:control group(C group),ALI group,ALI+HO-1 agonist hemin group(ALI+H group),and ALI+hemin+PPARγantagonist T0070907 group(ALI+H+T group).HO-1 knockout mice in which the ALI model was developed served as ALI+HO-1-/-group.ALI model was developed by injecting lipopolysaccharide(LPS)15 mg/kg via the tail vein in anesthetized animals.T00709071.5 mg/kg was intraperitoneally injected at 1 h before LPS administration in ALI+H+T group,and hemin 50 mg/kg was intraperitoneally injected at 30 min before LPS administration in ALI+H group and ALI+H+T group.Mice were sacrificed at 12 h after LPS administration,and lung tissues were obtained to measure the wet to dry weight ratio(W/D ratio),to observe pathological changes which were scored,and to determine the F4/80+/CD86+labeled M1 alveolar macrophages and the F4/80+/CD206+labeled M2 alveolar macrophages(by flow cytometry),contents of M1 macrophage-related genes inducible nitric oxide synthase(iNOS)and M2 macrophage-related genes Arginase-1(Arg-1)(by enzyme-linked immunosorbent assay),and the expression of HO-1 and PPARγ(by Western blot).Results Compared with C group,the lung injury score,W/D ratio,levels of CD86 and CD206,and contents of iNOS and Arg-1 were significantly increased,and PPARγexpression was up-regulated in the other four groups(P<0.05),and HO-1 protein expression was up-regulated in ALI,ALI+H and ALI+H+T groups(P<0.05).Compared with ALI group,the lung injury score,W/D ratio,and levels of CD86 and iNOS were significantly increased,the levels of CD206 and Arg-1 were decreased,and the expression of HO-1 and PPARγwas down-regulated in ALI+HO-1-/-group,the lung injury score,W/D ratio and levels of CD86 and iNOS were significantly decreased,the levels of CD206 and Arg-1 were increased,and the expression of HO-1 and PPARγwas up-regulated in ALI+H group(P<0.05),and no significant change was found in the parameters mentioned above in ALI+H+T group(P>0.05).Compared with ALI+H group,the lung injury score,W/D ratio and levels of CD86 and iNOS were significantly increased,the levels of CD206 and Arg-1 were decreased,the expression of PPARγwas down-regulated(P<0.05),and no significant change was found in the expression of HO-1 in ALI+H+T group(P>0.05).Conclusions HO-1 can up-regulate the expression of PPARγ,inhibit the polarization of alveolar macrophages toward M1 phenotype and promote the polarization toward M2 phenotype,thus playing an endogenous protective role in endotoxin-induced ALI in mice.