The Study Of The Relationship Of Heat Shock Protein (HSP-70) And Lung Damage Under Different Tidal Volume Mechanical Ventilation On Rats

Objective To study the role of heat shock protein (HSP-70) and cytokines in ventilatorinduced lung injury on rats.1)To observe the concentration of heat shock protein(HSP-70) in bronchoalveolar lavage fluid from different tidal volume mechanicalventilated rats.2)To observe the concentrations of interleukin-6(IL-6), macrophageinflammatory protein-2(MIP-2) in bronchoalveolar lavage fluid from different tidalvolume mechanical ventilated rats and analyze the relationship of heat shock protein(HSP-70) and cytokines in ventilator induced lung injured rats.3)To observe therelationship of heat shock protein (HSP-70) and the lung injury score,apoptotic indexunder different tidal volume mechanical ventilated rats.Methods36male SD rats were randomly divided into three groups, according todifferent tidal volume as high tidal volume ventilation with room air inhalation (HV),low tidal volume ventilation with room air inhalation (LV) and room air inhalationwithout mechanical ventilation (N). After anaesthesia and tracheostomy, a cannula wasinserted into the trachea and connected to a ventilator. The rats were spine on a heat padto maintain the body temperature at37degrees Celsius. Then the rats were ventilatedwith different tidal volume(Vt) as HV group(25ml/kg) and LV group(7ml/kg); thecontrol group were spontaneous breathing with room air in single cages. The wholeventilation time is4h; respiratory ratio is1:2. The initial anaesthesia were obtained by10%chloral hydrate(0.3mL/kg)intraperitoneally and were maintained by intraperitoneal 10%chloral hydrate every30minutes. At the end of ventilation the rats were sacrificedand underwent lavaged with NS. The BALF was collected and centrifuged. Thesupernatants were keeped in-80degree in fridge for future use.(1)The sediment wasresuspended and the cells were counted using cell counting board under a microscope.Wright’s staining was used to differentiate the cells.(2) The adapted BCA was used todetermine the concentrations of total protein in bronchial lavage fluid(BALF) from therats. The adapted ELISA was used to determine the concentrations of HSP-70,interlukin(IL-6),macrophage inflammatory protein(MIP-2) in bronchial lavagefluid(BALF) from the rats;(3) HE staining was used to judge the pathologicalchanges of the lung injury score, to assess the degree of lung tissue damage;(4)Terminal deoxynucleotidyl transferase(TdT)-mediated dUTP nick endlabeling(TUNEL) assay was performed on rat lung sections to assess of lung tissue cellsapoptosis index.Result1. The level of differential count of leukocytes and neutrophils from rats underlow or high tidal volume ventilation increased significantly compared with that fromrats of control group(each P<0.05).2.The level of HSP-70,IL-6and MIP-2in BALF andlung injury score, lung apoptotic index from rats under low or high tidal volumeventilation increased significantly compared with that from rats of control group(eachP<0.05).3.The same trend of lung injury score was seen within these above3experimental animals. Worthy to note that the concentrations of IL-6, MIP-2, HSP-70from HV ventilated rats were significantly higher than those from LV ventilatedrats(each P<0.05), so did the lung injury score and apoptotic index.4.In addition,positive correlations were seen between HSP-70level in BALF and lung injury scorefrom HV ventilated rats(P=0.01, r=0.8852).HSP-70also had positive correlation withconcentration of IL-6and MIP-2in BALF(P=0.01,r=0.8538;P=0.01,r=0.8919respectively). Conclusion1)Severe lung injury caused by high tidal volume ventilation could lead toincreased airway epithelial cell injury or necrosis which resulted in the release ofHSP-70from epithelial cells to the airway space and thus enhanced the inflammation ofthe lung. It may aggravate the injury and apoptosis of lung tissue.2) Low tidal volumemechanical ventilation relative high tidal volume mechanical ventilation, lung epithelialcell injury or necrosis lighter HSP-70extracellular release fewer cytokines, mildpulmonary inflammatory response, apoptosis.3) Therefore, mechanical stretch duringmechanical ventilation resulted in pulmonary apoptosis and lung tissue injury togetherwith the releasing of HSP-70from intra-cell into the airway space, accumulatedinflammation cells and cytokines in the airway.