Abstract

Objective To compare the roles of Toll-like receptor 4 (TLR4)/NF-κB signal pathway in acute lung injury (ALl) induced by blunt chest trauma and by blunt chest trauma-hemorrhagic shock and resuscitation (double hits) in rats.Methods Forty male Sprague-Dawley rats,aged 8 weeks,weighing 240-280 g,were randomly assigned into 3 equal groups (n =10 each) using a random number table:sham operation group (S group),blunt chest trauma group (T group),and blunt chest trauma and hemorrhagic shock and resuscitation group (group THSR).Lung contusion was induced in anesthetized rats by dropping a 300 g weight onto a precordial protective shield to direct the impact force away from the heart and toward the lungs.Blood was withdrawn via the femoral artery 5 min later until MAP was decreased to 35-45 mmHg within 15 min and maintained at this level for 60 min,followed by resuscitation.At 6 h after the model was established,the arterial blood samples were collected for blood gas analysis and detection of tumor necrosis factor-alpha (TNF-α) concentrations in serum.Oxygenation index (PaO2/FiO2) was calculated.The rats were then sacrificed and pulmonary specimens were obtained for determination of TLR4 expression and NF-κB ac tivity (by immunohistochemistry and Western blot) in lung tissues and for microscopic examination.Results Compared with group S,PaO2 and PaO2/FiO2 were significantly decreased,PaCO2 and TNF-α concentrations in serum were increased,TLR4 expression was up-regulated,and NF-κB activity was enhanced in T and THSR groups (P < 0.05).Compared with group T,PaO2 and PaO2/FiO2 were significantly decreased,PaCO2 and TNF-α concentrations in serum were increased,TLR4 expression was up-regulated,and NF-κcB activity was enhanced in THSR group (P < 0.05).The histopathological damage to lung tissues was aggravated in THSR group as compared with T group.Conclusion The role of TLR-4/NF-κB signal pathway in ALI induced by blunt chest traumahemorrhagic shock and resuscitation (double hits) is significantly stronger than that in ALI induced by blunt chest trauma alone in rats. Key words: Thoracic injury ; Shock, hemorrhagic ; Respiratory distress syndrome, adult; Toll-like receptor 4 ; NF-kappaB

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