Protective Effects Of UW Solutions Modified By Dexmedetomidine,Xenon And Argon On Lung From The Pigs Underwent Cardiac Arrest

Background and purposeRight now,many patients are dying while waiting for a donor lung due to a lack of donor organs.The use of donation after cardiac death（DCD）lungs is one of the effective strategies for solving the problem.The controlled DCD donors are predominant,but a lot of uncontrolled DCD donors are untapped clinical resources due to prolonged warm ischemia time.In addition,the long cold preservation of DCD donor lungs for transfer after acquisition can further impair the quality of donor lungs.Therefore,enhancing the quality of uncontrolled DCD donor lungs can help alleviate the reality of organ shortage.DCD donor lungs suffer from the warm/cold ischemia-reperfusion injury.During warm/cold ischemia,cellular oxidative stress is enhanced and normal physiological functions are impaired.Moreover,necrotic cells may release damage associated molecular patterns（DAMPs）proteins.Reperfusion is an important part of rescuing ischemic cell lesions,but at the same time,it can trigger strong oxidative stress and inflammation,which can further damage lung tissue.Dexmedetomidine（DEX）is a highly selectiveα2 adrenoceptor（α2AR）agonist with cytoprotective effects such as anti-inflammatory and anti-apoptotic.DEX has been shown to have protective effects on various organs.Xenon（Xe）can inhibit N-methyl-D-aspartate（NMDA）receptors and regulate a variety of cellular signaling.Research showed that Xe could reduce ischemia-reperfusion injury during renal transplantation and distal lung injury after renal transplantation.Argon（Ar）can directly interact withγ-aminobutyric acid type A（GABAA）receptors at high pressure to produce anesthetic effects.Animal studies have confirmed that Ar can play a protective role in renal transplantation.Therefore,this study was conducted to investigate the protective effects of DEX,Xe,and Ar in University of Wisconsin solution（UW solution）on DCD donor lungs,with the aim of improving the utilization of clinical DCD donor lungs.Thus reducing the lack of donor lungs.Methods1.Addition of DEX,Xe and Ar to UW solution and establishment of donation after cardiac death model in pigAccording to the experimental grouping,oxygen（O₂）,nitrogen（N₂）,carbon dioxide（CO₂）,Xe and Ar were pre-filled into 5 cylinders.Then,the gases in the cylinders were added to the UW solution（with or without the 0.1 nmol/L DEX）through the gas wash bottle to prepare 6 kinds of organ preservation.The mini-musk pigs were established as cardiac death donor models by cis-atracurium infusion（0.5～1 mg/kg）and single injection of high dose propofol（30～40 mg/kg）to stop their respiration and circulation for a short period.After 60minutes of warm ischemia（WI）,the lungs were harvested and cut into thin slices of about1×2 cm in length and width,and the thickness was no more than 0.5 cm.Some of the slices were immediately fixed in the paraformaldehyde or stored in liquid nitrogen which served as WI group,while the other slices were placed in UW solutions at 4℃for cold ischemia（CI）,in which N₂,DEX,or Xe were added with different proportion.These slices served as WI+CI+N₂ group,WI+CI+DEX group,WI+CI+DEX+30%Xe group,and WI+CI+DEX+50%Xe group,WI+CI+DEX+30%Ar group,WI+CI+DEX+50%Ar group respectively.After CI for 24 hours,these slices were immediately fixed in the paraformaldehyde or stored in liquid nitrogen.2.The effects of UW solutions modified by the DEX/Xe on the lung from the pigs underwent cardiac arrestThe lung tissue sections were stained with HE for pathological score.Apoptosis of lung cells was tested by TUNEL.Cleaved Caspase3 and glutathione peroxidase 4（GPX4）were detected by Western blot.Immunohistochemisty was used to assess the expression of GPX4and high mobility group protein 1（HMGB1）.3.The effects of UW solutions modified by the DEX/Ar on the lung from the pigs underwent cardiac arrestThe Lung tissue sections were subjected to the HE stains for pathological score.Apoptosis of lung cells was tested by TUNEL.Results1.4 pig donor models suffering cardiac arrest were established.2.The effects of UW solutions added by the DEX and the Xe on the lungs from the pigs underwent cardiac arrestCompared with the WI group,the HE staining results of the remaining groups showed no significant damage to the alveolar structure after 24 h of cold ischemia,no significant infiltration of inflammatory cells in the lung,and no obvious change in lung injury score（P>0.05）;The number of TUNEL-positive cells and the expression of Cleaved Caspase3protein in the WI+CI+N₂ group increased noticeably（P<0.05）;The level of GPX4 expression had little variation in lung tissue（P>0.05）;There was a sharp elevation of HMGB1 in the WI+CI+N₂ group（P<0.05）.The number of TUNEL-positive cells noticeably declined in the WI+CI+DEX group,WI+CI+DEX+30%Xe group and WI+CI+DEX+50%Xe group compared with the WI+CI+N₂ group（P<0.001,<0.05,<0.05,respectively）.The expression of HMGB1 was significantly lower（P<0.01）compared with the WI+CI+N₂ group.3.The effects of UW solutions added by the DEX and the Ar on the lungs from the pigs underwent cardiac arrestCompared with the WI group,the HE staining results showed that there was no significant difference in the lung injury scores between the groups（P>0.05）.The number of TUNEL-positive cells was significantly increased in the WI+CI+N₂ group compared with the WI group（P<0.05）.Compared with the WI+CI+N₂ group,the number of TUNEL-positive cells in the WI+CI+DEX group（P<0.05）,WI+CI+DEX+30%Ar group（P<0.05）was significantly reduced.Conclusion1.It is simple and reproducible that a porcine DCD donor lung model is established through intravenous injection of muscle relaxants combined with a single high-dose propofol.Also,it is a good model simulating clinical DCD donors.2.The UW solutions added by DEX,DEX+30%Xe and DEX+50%Xe exert significant cytoprotective effects on porcine DCD donor lung by apoptosis inhibition.DEX+30%Xe modified UW solution exerts cytoprotective effects on porcine DCD donor lung by significantly reducing HMGB1 protein expression.3.DEX or DEX+30%Ar added UW solution could exert cytoprotective effects by inhibiting apoptosis on the porcine DCD donor lung.