The Protective Effect And Mechanism Of Dexmedetomidine On Inflammatory Response In Mice With Acute Pancreatitis

Severe acute pancreatitis is a clinical subtype of acute pancreatitis.The persistent inflammatory response syndrome triggered by severe acute pancreatitis is closely related to multiple organ failure and mortality.Although significant progress has been made in the comprehensive treatment of acute pancreatitis in recent years,the overall mortality rate at 60 days is still around 6.4%.Studies have shown that in patients with severe acute pancreatitis with persistent inflammatory response syndrome(SIRS),the case fatality rate is 25%,much higher than in patients with transient inflammatory response syndrome.The mortality of severe acute pancreatitis usually occurs in two stages.The first phase is the early period of excessive inflammation.The second stage is the later period of pancreatic necrosis.Generally believed that the early inflammatory response is severe,often caused by multiple organ failure.This stage is the early stage of death of patients with severe acute pancreatitis.Sympathetic nervous system activation and inflammation are inseparable.Recent studies have shown that sympathetic hyperactivity and an increased inflammatory response in the initial stages of acute coronary syndrome(ACS)are associated with adverse outcomes in patients with ACS.Related sepsis studies have also shown that inflammatory stress response is often accompanied by high sympathetic excitement,sustained sympathetic high excitement can lead to multiple system organ damage.Regulating autonomic nervous excitement can effectively reduce the inflammatory response and organ dysfunction.Therefore,to reduce SAP early excessive sympathetic excitation and the resulting inflammatory response is conducive to reduce pancreatic damage and other organ failure.Dexmedetomidine,as a classical α2 adrenergic receptor agonist,is often used clinically to treat sedation and analgesia in critically ill patients.Its sympathetic inhibition can be used to reduce the patient’s stress response.A series of basic and clinical studies have shown that dexmedetomidine plays an inhibitory role in the inflammatory response induced by infection and also has an effect of mitigating inflammatory responses in animal models that mimic shock and ischemia-reperfusion injury.At present,it is generally believed that dexmedetomidine has organ protection effects on multiple organs in the body.In sepsis model rats or sheep,the use of different doses of the alpha 2 receptor agonist clonidine and dexmedetomidine reduced serum norepinephrine concentrations.This has also been demonstrated in human studies using clonidine to reduce norepinephrine levels in patients with HIV,end-stage lung sepsis and necrotizing enterocolitis.In sepsis,the mechanism by which α2-agonists act is to reduce sympathetic excitability and endogenous catecholamine levels,and excessive inflammation is associated with sympathetic excitability.In addition,dexmedetomidine sedation can reduce the serum IL-6,IL-1β,TNF-α levels in major surgery patients,thereby reducing their inflammatory response.Our study will be divided into three parts.In the first part,we will evaluate changes in sympathetic nerve activity in mice with acute pancreatitis.In the second part,we confirmed the role of dexmedetomidine in alleviating the inflammatory response in pancreatitis model mice.In the third part,we explored the mechanisms involved in reducing the inflammatory response in acute pancreatitis model mice.Part one: Changes of sympathetic nerve activity in mice with acute pancreatitisObjective: To observe changes of sympathetic nerve activity in mice with acute pancreatitis.Methods: A model of mild acute pancreatitis was established by intracervical injection of Caerulein and a model of severe acute pancreatitis was established using Caerulein plus LPS.ICR background male mice were randomly divided into 3 groups(n=8),control group,Cae group,Cae + LPS group.Blood samples were collected and norepinephrine levels were measured.The expression of α2 receptor and NET in pancreatic tissue was detected by Western Blot.Results: The expression of NET in pancreatic tissue of two pancreatitis model mice gradually decreased over time.After the establishment of the two models,the expression of α2 receptor in mouse pancreatic tissue was lower than that in the corresponding control group.Serum norepinephrine levels in the two models were higher than those in the corresponding model group.Conclusion: Sympathetic nerve activity was increased in both acute pancreatitis model mice.Part two: Effect of dexmedetomidine on alleviating inflammation in mice with acute pancreatitisObjective: To demonstrate that dexmedetomidine attenuates the inflammatory response in acute pancreatitis model mice by inhibiting sympathetic activity.Methods: The models of mild pancreatitis were established by intraperitoneal injection of Cae and the models of severe acute pancreatitis were established by Cae + LPS.The male ICR mice were randomly divided into 7 groups(n = 8),control group,cae group,Dexmedetomidine 10 ug / kg treatment group,Cae + dexmedetomidine 20 ug / kg treatment group,Cae + LPS group,Cae + LPS + dexmedetomidine 10 ug / kg treatment group,Cae + LPS + dexmedetomidine 20 ug / kg treatment group.Blood samples were collected for the detection of amylase,lipase,inflammatory cytokines and norepinephrine levels.The expression of MPO in pancreatic tissue was detected by Immunohistochemistry and Immunofluorescence.Pancreatic tissues,lung tissue samples were collected for histomorphometry.Results: The levels of serum amylase,lipase,inflammatory cytokines and norepinephrine in the two groups of model mice(Cae group,Cae + LPS group)were lower than that of the corresponding model group at 20 ug / kg dexmedetomidine treatment.In the dexmedetomidine 20 ug / kg treatment group,the histopathological score of the pancreas was lower than that of the model group,and the expression of MPO in the pancreas was also lower than that of the model group.Conclusion: Dexmedetomidine can reduce the inflammatory response in mice with acute pancreatitis and has an organ protective effect on acute pancreatitis in mice.Part three: Mechanism of Dexmedetomidine in Reducing Inflammatory Reaction in Acute Pancreatitis MiceObjective: To investigate the pathways and mechanism of dexmedetomidine in reducing inflammation in mice with acute pancreatitisMethods: Western Blot(WB)and RT-PCR were used to detect the expression of NLRP3,IL-1β in each group.The expression of NET in pancreatic tissue was detected by WB method.Serum norepinephrine levels were measured in each group.Results: After treated with dexmedetomidine 20 ug / kg,the expression of NLRP3 and IL-1β in pancreatic tissues of mice with acute pancreatitis was lower than that of model mice.NET expression in pancreas was also higher than that in model mice.At the same time,serum norepinephrine levels after dexmedetomidine treatment were lower than those in the model group.Conclusion: Dexmedetomidine may reduce the inflammatory response in mice with acute pancreatitis by inhibiting NLRP3 inflammatory body activity and inhibiting sympathetic nerve activity.