Role of PIAS-regulated SUMOylation of PPARγ in endogenous protective mechanism against endotoxin-induced acute lung injury in mice / 中华麻醉学杂志

ABSTRACT

Objective:To evaluate the role of small ubiquitin-associated modifier (SUMO) E3 ligase (PIAS)-regulated SUMOylation of peroxisome proliferator-activated receptor γ (PPARγ) in the endogenous protective mechanism against endotoxin-induced acute lung injury (ALI) in mice.Methods:Experiment Ⅰ Twenty-four clean-grade wild type male C57BL/6 mice, aged 6-8 weeks, weighing 18-22 g, were divided into 4 groups ( n=6 each) using a random number table method: control group (C group), ALI group, ALI+ PPARγ inducer TZD group (ALI+ T group) and ALI+ TZD+ SUMOylation inhibitor anacardic acid group (ALI+ T+ A group). Lipopolysaccharide (LPS) 15 mg/kg was injected into the tail vein to develop the ALI model. In ALI+ T+ A group, anacardic acid 5 mg/kg was intraperitoneally injected at 1 h before LPS administration. In ALI+ T group and ALI+ T+ A group, TZD 50 mg/kg was intraperitoneally injected at 30 min before LPS administration. The mice were sacrificed at 12 h after LPS administration, and the lung tissues were obtained to examine the pathological changes which were scored and to determine the wet/dry (W/D) weight ratio, and expression of PIAS1, PIAS2, PIAS3 and PIASy protein and mRNA (by Western blot or polymerase chain reaction). Experiment Ⅱ Mouse alveolar macrophages (MH-S cells) were cultured in vitro and divided into 4 groups ( n=5 each) using a random number table method: control group (C group), LPS group, LPS+ PIAS2 siRNA group (L+ P group) and LPS+ Con siRNA group (L+ C group). Cells were routinely cultured in group C. Cells were stimulated with 10 μg/ml LPS to develop the model of endotoxin challenge. PIAS2 siRNA 50 nmol/L and Con siRNA 50 nmol/L were transfected at 48 h before LPS was added in L+ P group and L+ C group, respectively. The cells were collected at 24 h of incubation with LPS to determine the cell viability, levels of M1 and M2 alveolar macrophages (by flow cytometry), expression of PIAS2 and PPARγ (by Western blot), co-expression of PPARγ-SUMO1 (by immunoprecipitation) and expression of tumor necrosis factor-alpha (TNF-α) and interleukin-10 (IL-10) mRNA (by polymerase chain reaction). The ratio of M1/M2 was calculated. Results:Experiment Ⅰ Compared with C group, the lung injury scores and W/D ratio were significantly increased, and the expression of PIAS2 protein and mRNA was up-regulated in the other three groups ( P<0.05). Compared with ALI group, the lung injury scores and W/D ratio were significantly decreased, and the expression of PIAS2 protein and mRNA was up-regulated in ALI+ T group and ALI+ T+ A group ( P<0.05). Compared with ALI+ T group, the lung injury scores and W/D ratio were significantly increased, and the expression of PIAS2 protein and mRNA was down-regulated in ALI+ T+ A group ( P<0.05). There was no significant difference in the expression of PIAS1, PIAS3 and PIASy protein and mRNA in lung tissues among the four groups ( P>0.05). Experiment Ⅱ Compared with C group, the cell viability was significantly decreased, the expression of PPARγ and co-expression of PPARγ-SUMO1 was up-regulated, the levels of M1 and M2 macrophages and M1/M2 ratio were increased, the expression of TNF-α mRNA was up-regulated, and the expression of IL-10 mRNA was down-regulated in the other three groups, and PIAS2 expression was significantly up-regulated in L group and L+ C group ( P<0.05). Compared with L group, the cell viability was significantly decreased, the expression of PIAS2 and PPARγ and PPARγ-SUMO1 co-expression were down-regulated, the M1 macrophage level and M1/M2 ratio were increased, TNF-α mRNA expression was up-regulated, and the expression of IL-10 mRNA was down-regulated in L+ P group ( P<0.05), and no significant change was found in the parameters mentioned above in L+ C group ( P>0.05). Compared with L+ C group, the cell viability was significantly decreased, the expression of PIAS2 and PPARγ and co-expression of PPARγ-SUMO1 were down-regulated, the level of M1 alveolar macrophages and M1/M2 ratio were increased, the expression of TNF-α mRNA was down-regulated, and the expression of IL-10 mRNA was up-regulated in L+ P group ( P<0.05). Conclusions:PIAS2-regulated SUMOylation of PPARγ is the endogenous protective mechanism against endotoxin-induced ALI in mice, which may be related to inhibition of macrophage polarization into M1 type and alleviation of inflammatory responses.