Role of Toll-like receptor 4 in mechanical ventilation-induced increase in pulmonary capillary permeability in diabetic mice

Abstract

Objective To evaluate the role of Toll-like receptor 4 (TLR4) in mechanical ventilationinduced increase in pulmonary capillary permeability in diabetic mice.Methods Two types of mice,aged 8-10 weeks,weighing 20-25 g,were used in this study:free wild type mice (C3H/HeN) and TLR4 gene mutation type (C3H/HeJ).Diabetes was induced by intraperitoneal streptozotocin 150 mg/kg (in citric acid buffer solution 0.1 mol/L) and confirmed by blood glucose level ＞ 16 mmol/L.Each type of diabetic mice was randomly divided into 2 groups (n =14 each):group diabetes + sham operation (group DS) and group diabetes + mechanical ventilation (group DM).The animals were anesthetized with intraperitoneal ketamine,midazolam and atropine.Tracheal intubation was performed and the animals kept spontaneous breathing in group DS.The animals were mechanically ventilated (FiO2 50％,RR 70 bpm,VT 15 ml/kg,PEEP 2 cmH2O) for 4 h in group DM.Arterial blood samples were obtained at 4 h of ventilation for blood gas analysis,PaO2 and PaCO2 were recorded,and NO concentration in the serum was measured.Then the animals were sacrificed and the lungs were removed for determination of W/D lung weight ratio (W/D ratio),content of evans blue (EB),and expression of caveolin-1,endothelial nitric oxide synthase (eNOS) and phosphor-eNOS (p-eNOS) (by Western blot).The ratio of p-eNOS/eNOS was calculated.Results Compared with group DS,PaO2,PaCO2 and p-eNOS/eNOS ratio were significantly decreased,and W/D ratio,EB content and caveolin-1 expression were increased in group DM (P ＜ 0.05).Compared with C3H/HeN mice,W/D ratio,caveolin-1 expression and EB content were significantly decreased,peNOS/eNOS ratio and serum NO concentrations were increased (P ＜ 0.05),and no significant changes in PaO2 and PaCO2 were found in C3H/HeJ mice in group DM (P ＞ 0.05).Conclusion TLR4 increases the pulmonary capillary permeability after mechanical ventilation in diabetic mice through effectively combining with caveolin-1 and reducing NO bioavailability. Key words: Toll-like receptor 4 ; Respiratory distress syndrome, adult; Diabetes mellitus; Capillary permeability