Experimental Studies On The Therapy Effect Of Synthesized Peptide S247 On Ventilator-induced Lung Injury

Mechanical ventilation has been part of basic life support for patients with acute respiratory failure in intensive care unit within several decades. Several potential drawbacks and complications have been identified early in the use of mechanical ventilation ,Of these, ventilator-induced lung injury (VILI) has recently received much attention in both the experimental and the clinical field . During mechanical ventilation, large tidal volume (VT) and/or high levels of positive end-expiratory pressure results in this permeability type pulmonary oedema with releasing of some cytokines,such as IL-1β,IL-6,MIP-2 and TNF-α,which called"biotrauma".Experimentally and clinically, involvement of inflammatory cytokines in VILI has not been unequivocally demonstrated. Cellular response to mechanical stretch has been increasingly investigated, both on the epithelial and the endothelial side. It is now clear that VILI is essentially involved in severe different mechanisms,RGD Integrins existed in lung cell epithelial play a important role in generating of VILI , which constitute the link between subcellular matrix and cytoskeleton at focal adhesions. Distortions attributable to shear and stretch at the cell–matrix interface result in integrin aggregation that, in turn, induces focal adhesions,mechnical signals convert to biochemistry signals, thus spread through a series of downstream passageways, which at last induces the expression and releasing of some inflammatory factors. S247 is a synthesized peptide constited of arginine , glycocine and aspartate. the compounds can competitivly binding to the RGD sequence of FN and VN and so on in ECM, thus inhibiting ligand binding to the family of integrins which contain the alpha v subunit. As a result ,correlated cytokines expression ,such as MIP-2,TNF-αwill be suppressed .lung injury will be relieved to some extent. The reseach was finished according to the next two parts.Part one. Effect of different ventilatory volume on ventilator-induced lung injury: a study of a rat model of acute lung injuryObjectives: To evaluate the influence of different ventilatory volume on ventilator-induced lung injury in rat .Methods: a total of ninety-two specific-pathogen free Sprague-Dawley rats(250～360g) were randomly divided into control group( group A n=5), Group B( n=15 Vt=10ml·kg-1 ) , Group C ( n=15 Vt=20ml·kg-1 ) , Group D ( n=15 Vt=40ml·kg-1),survival rates at each time point within four hours were observed by another eight rats of each group. Rats were randomly divided into three group again by 1h, 2h and 4h separatedly, rats were inserted tracheal catheter via mouth under urethan injection anesthesia, then receive different volume ventilation, except the control group. Besides arterial blood pressure and heart rate analysis, lung pathology examination, lung water measure, quantity of LDH, total protein, white blood cell and TNF-αin bronchoalveolar lavage fluid were also performed.Results: Hight volume mechanical ventilation result in a substantial morphological change , include increased lung water, pneumorrhagia etc. Compared to the control group and the normal tide volume ventilation group, quantity of LDH, total protein, white blood cell and TNF-αin BALF are all increased in Group C(p<0.05或p<0.01), especially in Group D, and these tendency are basically positively correlated to time. No apparente difference of survival rate analysis exist between group C and group D. Conclusion: Hight volume mechanical ventilation result in severe VILI. 40ml/kg volume mechanical ventilation for 4 hours can be used suitably for next part.Part two. Experimental studies on the therapy effect of synthesized peptide S247 on ventilator-induced lung injuryObjectives:To study the therapeutical effect of synthesized peptide S247 on ventilator-induced lung injury.Methods:A total of 21 SPF Sprague-Dawley male rats were divided into three groups, each consiting of 7 rats: control group(Group C),lung injury group(Group I) and S247 group(Group S). Acute lung injury model were made by high volume mechanical ventilation. Besides the lung pathology examination, lung water measure , total protein level and counts of wbc in bronchoalveolar lavage fluid were performed, concentrations of MIP-2 and TNF-αin BALF were also detected by ELISA. we also detected the expression of integrinαvβ6 by immunohistoch- emical.Result:Differences of the value of wet/dry,total protein level,wbc counts and concentrations of MIP-2 and TNF-αin BALF were significantly existed among the three groups (p<0.05 or p<0.01).but there is no difference between group I and group S of the expression of integrinαvβ6.Conclusion:the potent integrin antagonist S247 may have a therapy effect on VILI through multiple mechanisms, such as inhibiting release of inflammation mediators TNF-αand MIP-2 from injuried lung cells.