Relationship between heme oxygenase-1 expression and autophagy during acute lung injury in septic mice

Abstract

Objective To evaluate the relationship between heme oxygenase-1 (HO-1) expression and autophagy during acute lung injury in septic mice. Methods Forty-eight male C57BL/6 mice, aged 6-8 weeks, weighing 20-25 g, were randomly divided into 4 groups (n=12 each) using a random number table: sham operation group (group SH), sepsis group (group CLP), HO-1 agonist hemin plus sepsis group (group Hemin+ CLP) and HO-1 inhibitor SnPP plus sepsis group (group SnPP+ CLP). Sepsis was induced by cecal ligation and puncture in CLP, Hemin+ CLP and SnPP+ CLP groups.Hemin 50 μmol/kg and SnPP 50 μmol/kg were intraperitoneally injected at 2 h before operation in Hemin+ CLP group and SnPP+ CLP group, respectively.Arterial blood samples were taken at 24 h after operation for blood gas analysis, PaO2 was recorded, and oxygenation index was calculated.Lungs were removed for examination of pathological changes which were scored and for determination of autophagosome count (with an electron microscope), weight/dry weight ratio (W/D ratio) and expression of HO-1, Becling-1 and microtubule-associated protein 1 light chain 3 Ⅱ (LC3 Ⅱ) in lung tissues (by Western blot). Results Compared with group SH, oxygenation index was significantly decreased, and W/D ratio, autophagosome count and pathological scores were increased in CLP, Hemin+ CLP and SnPP+ CLP groups, and the expression of HO-1, Beclin-1 and LC3 Ⅱ was significantly up-regulated in CLP and Hemin+ CLP groups (P<0.05). Compared with group CLP, oxygenation index and autophagosome count were significantly increased, W/D ratio and pathological scores were decreased, and the expression of HO-1, Beclin-1 and LC3 Ⅱ was up-regulated in group Hemin+ CLP, and oxygenation index and autophagosome count were significantly decreased, W/D ratio and pathological scores were increased, and the expression of HO-1, Beclin-1 and LC3 Ⅱ was down-regulated in group SnPP+ CLP (P<0.05). Conclusion Up-regulated expression of HO-1 mediates autophagy, which is involved in the endogenous protective mechanism underlying acute lung injury in septic mice. Key words: Heme oxygenase-l; Autophagy; Sepsis; Respiratory distress syndrome, adult