Experimental Study On Protective Effect Of Caspase Inhibitor Z-VAD-fmk On Mice With Inhalation Injury

Objective:Inhalation injury is one of main reasons of death in the early stage of burn patients,the mechanism of pathophysiology is closely related to apoptosis.Cysteinyl aspartate specific protease(caspase) is the protease family which can lead to apoptosis and play a key role during the process of apoptosis,we could eliminate the apoptosis and protect the lung function through inhibiting the activity of caspase.This experiment is to observe the effect of caspase inhibitor(z-VAD-fmk)on apoptosis and expression of Bcl-2 and Bax in mice lungs with inhalation injury and provide an theoretical evidence for clinical treatment.Methods:72 BALB/c mice were made to moderate and severe inhalation injury by the device of inhalation injury,then divided them into control group(n=36) and treatment group(n=36) randomly,6 time points of 2 h,6 h,12 h,24 h,48 h and 72 h were set in two groups separately,The treatment group were given z-VAD-fmk 6mg/kg by intraperitoneal injection.For the control group,the same dose of 0.9% saline was applied using the same method in treatment group.The mice were killed and the lungs were immediately removed separately at the time points mentioned above,observed the change of organization structure routinely by the pathological sections and the expression of Bcl-2 and Bax by immunohistochemical method and calculated apoptosis index(AI).Results:1.The results of pathological sections:the lungs of control group can be found the vasculars in lung interstitium became expansion and congestion locally, pneumonocyte became swollen at 2 h;lung interstitium became congestion and swollen diffusely,neutrophils and lymphocytes infiltrated into alveolar space and the structure of alveoli of lung destroyed,we found red cells in alveoli of lung and alveolar epithelial cell fell off irregularity at 6-12 h.the changes were obvious at 24 h, except the changes mentioned above,we also found fibroplasia in lung interstitium and pulmonary collapse locally and lung interstitium thickening obviously;the changes improved at 48-72 h.Compared with the control guoup,the treatment group after injury alleviated in varying degrees. 2.The results of TUNEL:Apoptosis participated the earlier period injury of lungs after inhalation injury,the mice in the control group were found apoptosis at 2 h,the peak occurred at 24 h.Compared with the control guoup,the AI of the treatment group did not decrease significantly at 2 h and had no statistical differences(P>0.05). The results after 6 h had statistical differences(P<0.05),the AI of every time point after 12 h had significant difference(P<0.01).3.The result of immunohistochemical:Bcl-2 and Bax both expressed after inhalation injury,Bcl-2 expressed weakly and Bax expressed highly positive in control group, z-VAD-fmk could up-regulate the expression of Bcl-2 and down-regulate the expression of Bax in treatment group.Conclusion:1.After inhalation injury,the lung displayed that pneumonocyte became swollen,the structure of alveoli of lung destroyed and inflammatory cells infiltration. the treatment group after injury alleviated in varying degrees.2.z-VAD-fmk could up-regulate the expression of Bcl-2 and down-regulate the expression of Bax and change the ratio of Bcl-2/Bax.3.z-VAD-fmk could degrade AI after inhalation injury.