Heat Shock Protein 70 Expression And Relation With Cytokines In Ventilator-induced Lung Injury In Rabbit

Objective: To investigate heat shock protein 70(HSP70) expression and the effect of mechanical ventilation with PEEP (positive end expiratory pressure) in a model of ventilator-induced lung injury(VILI). We observed the changes of heart rate, mean arterial blood pressure, plateau airway pressure(Pplat), peak inspiratory pressure(PIP) and arterial blood gas analysis at different time, and to observe the changes of tumor necrosis factor-a(TNF-a), interlukin-1β(IL-1β) and interlukin-6(IL-6) in serum, and to investigate the relation between HSP70 expression and serum inflammatory cytokine levels. We also investigated the relation HSP70 and inhibitor-Kappa B-a (IκB-α) expression.Methods: Thirty healthy male adult rabbits weighted 2.2 3.2kg were divided into three groups at random, large tidal volume ventilation +3cmH₂O PEEP(PEEP), large tidal volume ventilation +0cm H₂O PEEP(ZEEP) and control group,ventilated in normal tidal volume (NVC). All animals were subsequently ventilated for 4 hours. After 4 hours, rabbits were killed by exsanguination. (1) Heart rate, mean arterial blood pressure, plateau airway pressure and peak Inspiratory pressure were detected and arterial blood gas analysis were analyzed at different time of mechanical ventilation. (2)Lung histopathology was assessed and compared among three groups. The wet to dry ratio(W/D) of lung tissue were measured. (3)TNF-a, IL-1β and IL-6 levels in blood at different time of mechanical ventilation were assayed by using radioimmunoassay(RIA) methods. (4)Methods of immunohistochemistry were used to study the expression of HSP70 in lung tissue among three groups.(5)Expression of HSP70 and I-KBa in lungtissue were detected by using Westem-blot methods.Results: (l)After injured ventilation (large tidal volume ventilation+Ocm H2OPEEP, ZEEP group) for 4 hours, Histopathology showed alveolar and interstitial edema and many inflammatory cell infiltration, and ventilation with PEEP, the histopathologic injury of lung were alleviated. (2)The W/D of lung tissue increased after injured ventilation, and ventilation with PEEP, the W/D of lung tissue decreased. (3)After injured ventilation 4 hours, the heart rate, mean arterial blood pressure and artery oxygen blood pressure(PC>2) decreased significantly. Ventilation with PEEP can increase heart rate, mean arterial blood pressure and PO2 significantly. (4)The levels of TNF-a, IL-ip and IL-6 were increased distinctly in blood, and there was a significant lower levels of TNF-a, IL-ip and IL-6 in the blood of the mechanical ventilation with PEEP. (5)After injured ventilation for 4 hours, there was a significant higher expression of HSP70 in lung tissue. (6)There were no significant differences between the protein levels of IkB-oi among three groups. (7)In the ZEEP group, high HSP70 expression levels were correlated inversely with TNF-a, IL-ip and IL-6 levels, and the level of MB-a was positively correlated to the HSP70 expression level.Conclusion: (Dlnjured ventilation (large tidal volume ventilation+0cmH2O PEEP, ZEEP group) can induce or increase an inflammatory response in the lung, i.e. ventilator-induced lung injury, called biotrauma. (2)After injured ventilation, histopathology showed alveolar and interstitial edema and many inflammatory cell infiltration. (3)Injured ventilation can significantly increased HSP70 expression levels in the lung. (4)HSP70 can inhibit Inflammatory reaction by reducing the production of proinflammatory cytokines. (5)HSP70 inhibit Inflammatory reaction by inhibition of I-KBa degradation. This degradation isnecessary for NF-kB activation and induces transcription of TNF-a, IL-ip and IL-6. (6)Mechanical ventilation with PEEP can protect the lung against ventilator-induced lung injury by alleviating the histopathologic injury of lung and reducing the production of TNF-a, IL-lf3 and IL-6.