Regulation Role Of Peripheral Dopamine System In Acute Pancreatitis

Aims:This study focused on the role of dopamine（DA）signaling pathway in acute pancreatitis（AP）and its related mechanisms,to find new therapeutic strategies for AP.Methods:In vitro,CCK was used to stimulate pancreatic acinar cell（PAC）,LPS and IFN-γto stimulate bone marrow-derived macrophage（Mφ）;in vivo,cearulein or L-arginine-induced AP model was built in wild-type,pancreas(Pdx1^+/creDrd2^flox/flox,Drd2^-/-)or myeloid-specific(Lys M^+/creDrd2^flox/flox,Drd2^-/-)Drd2 knockout mice.Change of DA system and the influence of DRD agonist or antagonist on experimental AP was discussed.We used serum amylase,lipase and histological score to assess the severity of AP;western blot to detect Akt-NFκB,NADPH oxidase mediated ROS generation and NLRP3 inflammasome pathways;EMSA to measure NFκB activity;Transwell to investigate Mφand neutrophil migration;flow cytometry and q RT-PCR to detect Mφstatus and function change,the levels of inflammatory cytokines and chemokines,etc.Results:The DA synthetic and metabolic system of PAC were activated but DRD was significantly down-regulated in AP;DRD2 antagonist can block the function of DA in inhibiting the activation of IκBα-NFκB and expression of TNF-α,IL-1β,IL-6 in AP,but DRD1 antagonist cannot;pancreatic specific Drd2^-/-significantly aggravates the pancreatic and lung injury,immune cell infiltration,Akt-NFκB pathway,and TNF-α,IL-1β,IL-6,CCL2,CXCL2 levels in AP;inhibitory effect of DRD2 agonist（Quinpirole）on Akt-NFκB pathway and the inflammatory cytokines in AP was blocked by PP2A antagonist（OA）;DRD2 inhibited the levels of CCL2and CXCL2 in PAC by inhibiting Akt-NFκB pathway via PP2A,and inhibited the migration of Mφand neutrophils.The DA system is activated both in M1 and M2-type Mφ,but DRD decreased in M1 and increased in M2;Mφin AP exhibited M1 subtype;DRD2 activation can inhibit the M1-type Mφand promote M2 in the pancreas;myeloid-specific Drd2^-/-increased the number of M1-type Mφin pancreatic tissue and aggravated AP;Quinpirole didn’t inhibit M1-type Mφfrom Drd2^-/-mice;Quinpirole can significantly reduce the p47^phox translocation to membrane and ROS⁺cell number in M1-type Mφ,inhibit the NFκB and NLRP3 signaling pathway in a dose-dependent manner;the activation of NADPH oxidase,NFκB and NLRP3 pathways in Drd2^-/-M1-type Mφwas significantly increased compared to the wild-type group;Quinpirole can significantly inhibit these phenomena in M1-type Mφof wild type group,but has no significant effect on Drd2^-/-group.Conclusions:In PAC,DRD2 ameliorated inflammatory response by inhibiting Akt-NFκB signaling pathway via PP2A during AP.In Mφ,DRD2 inhibited NADPH oxidase-dependent NFκB and NLRP3inflammasome pathways to inhibit M1-type Mφand promote M2.This study comprehensively elucidated the specific mechanisms of DRD2signaling pathway to reduce AP inflammatory response from two perspectives of PAC and Mφ.