Relationship between HO-1 and PPARγ during alveolar macrophage polarization in a mouse model of endotoxin-induced acute lung injury / 中华麻醉学杂志

ABSTRACT

Objective:To evaluate the relationship between heme oxygenase-1 (HO-1) and peroxisome proliferator-activated receptor γ (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+ PPARγ antagonist 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.T0070907 1.5 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 PPARγ expression 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 PPARγ was 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 PPARγ was 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 PPARγ was 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.