Dexmedetomidine Modulates Polarity Switch Of Macrophage To Attenuate Acute Lung Injury Induced By Renal Ischemia Reperfusion

Background and objectiveAcute kidney injury?AKI?induced by renal ischemia reperfusion?RIR?is a common clinical critical disease.The systemic inflammatory response?SIR?induced by AKI often leads to the injury of extra-renal remote organs including brain,lung and heart and so on,which results in a high mortality.The lung is more susceptible to the SIR induced by AKI.due to its extensive microvascular network.And kidney-lung crosstalk is more easily formed when compared to other extra-renal organs.The mortality even reaches 80%when AKI combined with ALI.Perioperative excessive AKI-induced SIR is closely related to the poor prognosis of patients.It is clinically valuable to make effective strategies to attenuate AKI as well as AKI-induced SIR so as to improve the function of remote renal organs,especially the lung.Alveolar macrophages?AMs?plays an important role in maintaining pulmonary system homeostasis.Studies have shown that AMs exerts the functions during the inflammatory initiation,maintenance,resolution,repair and reconstruction of AKI-induced ALI,while different activation states of AMs?pro-inflammatory M1 pattern,anti-inflammatory and tissue-repairing M2 pattern?play the critical role in pathophysiological process and damage repairing of AKI-induced ALI.Therefore,switching macrophages from M1 towards M2 to inhibit inflammatory progression and promote tissue repairing may be an effective treatment strategy for AKI-induced ALI.Dexmedetomidine?Dex?is a highly selective?₂ adrenergic receptor??₂ adrenoceptor,?₂AR?agonist with sedative,analgesic,and anti-sympathetic effect.Recent studies have shown that it has certain anti-inflammatory effects and can improve the prognosis of perioperative patients.Our previous results confirmed that Dex has a renal protective effect on renal ischemia-reperfusion AKI and can also reduce distal lung inflammatory response to attenuate AKI-induced ALI.However the mechanism of anti-inflammatory effect of Dex is less clear,whether the anti-inflammatory effet of Dex related to the regulation of macrophage polarity switching is worth exploring.Therefore,we hypothesize that Dex plays a protective role in AKI-induced ALI via modulating macrophage polarization to inhibite inflammatory response.In this study,C57BL/6J mouse renal ischemia-reperfusion was established as pathological model,focusing on peritoneal macrophages and alveolar macrophages to explore the regulatory effect of Dex on macrophages polarization.Methods1.Effects of dexmedetomidine on systemic inflammatory response and the polarity conversion of peritoneal macrophages after renal ischemia reperfusion in mice15 C57BL/6J mice were randomly divided into three groups?n=5?,Group Sham:laparotomy without renal pedicle occlusion.Group RIR:bilateral renal pedicles was clamped for 60 min with a microvascular clamps.Group Dex+RIR:intraperitoneal inject 25?g/ml Dex15 min prior to bilateral renal ischemia.After surgery or reperfusion 24h,the blood and peritoneal macrophages samples were harvested.Blood analyzer detected the counts of lymphocytes,neutrophils,and monocytes/macrophages.The levels of inflammatory cytokines?TNF-?,IL-1?and IL-10?in serum were detected using ELISA.Western blot was used to detect iNOS and Arg 1,indicating the polarization of macrophages.2.Effects of Dex on AKI induced lung inflammation in ALI and the polarity conversion of AMs60 C57BL/6J mice were divided into two parts?30 per part?,and both parts were randomly divided into five groups?n=6?,Group Sham:laparotomy without renal pedicle occlusion.Group Dex:intraperitoneal inject 25?g/ml Dex 15 min prior to laparotomy without renal pedicle occlusion.Group RIR:bilateral renal pedicles was clamped for 60 min with a microvascular clamps.Group Dex+RIR:intraperitoneal inject 25?g/ml Dex 15 min prior to bilateral renal ischemia.Group Atip+Dex+RIR:intraperitoneal inject 250?g/ml Atip15 min prior to injection of Dex following bilateral renal ischemia.After surgery or reperfusion 24h,the lung tissue and arterial blood were harvested for H&E stain and blood gas analysis,respectively.The bronchoalveolar lavage fluid?BALF?was collected for cell counting.A commercial reagent kit was used to detect multiple cytokines in BALF.Alveolar macrophages were harvested following adhesion purification,immunofluorescence and western blot were used to detected the expression of iNOS and Arg 1.Finally,the lung tissue were lysed and detected using protein microarray detection.Results1.Compared with those in group Sham,the numbers of neutrophils,monocytes and lymphocytes were significantly elevated?p<0.01?,the levels of TNF-?and IL-1?were up-regulated?p<0.01?,M1 marker i NOS was increased and M2 marker Arg 1 was decreased?p<0.01?in group RIR.When compared with those in group RIR,the numbers of neutrophils,monocytes and lymphocytes did not changed?p>0.05?,the levels of TNF-?,IL-1?were down-regulated?p<0.01?,the level of IL-10 increased?p<0.01?,M1 marker iNOS were decreased?p<0.01?as well as M2 marker Arg 1 were increased?p<0.05?in group Dex+RIR.2.Compared with those in group Sham,the lung tissue histopathological score was significantly increased?p<0.01?,the PH value,PaO₂ and PaCO₂ of arterial blood were decreased?p<0.01?,the cell number of bronchoalveolar lavage fluid was increased?p<0.01?,and the alveolar macrophages M1 marker iNOS were increased as well as M2 marker Arg 1were decreased?p<0.01?in group RIR.When compared with those in group RIR,in group Dex+RIR,the lung tissue histopathological score was effectively decreased?p<0.01?,the PH value increased?p<0.01?,the cell number of bronchoalveolar lavage fluid was reduced?p<0.01?,as well as the levels of inflammatory factors TNF-?,IL-1?inflammation-encouraging M1 macrophages produced were down-regulated?p<0.01?,the level of inflammatory factors IL-10,CCL 17 anti-inflammatory and tissue-repairing M2 macrophages produced un-regulated?p<0.01?,the alveolar macrophages M1 marker iNOS were decreased?p<0.01?,meanwhile chemokines?CCL 5,CCL 11,CXCL 1,CXCL 13?and cytokines?CD54,TCA-3,IL-1?,IL-?,IL-2,IL-6,IL-7,IL-15,TNF-?,G-CSF,MIP-1??detected in lung tissue were significantly reduced?p<0.05 or p<0.01?.Compared with those in group Dex+RIR,the lung tissue histopathological score was significantly increased?p<0.01?,the PH value of arterial blood was decreased?p<0.01?,the cell number of bronchoalveolar lavage fluid was increased?p<0.01?in group Atip+Dex+RIR.Conclusion1.Dex inhibits the systemic inflammatory response induced by renal ischemia reperfusion in mice,and the mechanism may be associated with the macrophage polarity modulation.2.Dex alleviates AKI-induced ALI by improving pulmonary inflammatory microenvironment,the mechanism of which is related to the modulation of AMs polarity from M1 to M2 pattern by Dex via activating?₂AR.