Relationship Between Endoplasmic Reticulum Stress In Epicardial Adipose Tissue And Atrial Fibrosis In Patients With Atrial Fibrillation

BackgroundAtrial fibrillation(AF)is one of the arrhythmias with the highest risk of serious complications.Its mechanism has not been fully elucidated.Recent studies show that epicardial adipose tissue(EAT)is closely linked to the occurrence and maintenance of atrial fibrillation.EAT may cause atrial inflammatory response and fibrosis,which is essential for atrial fibrillation.Then there are more and more researches on the relationship between EAT and atrial fibrillation.Some scholars have proposed that the dysfunction of eat may affect atrial electrical signal conduction through fat infiltration,and promote atrial fibrillation through paracrine adipokines,inflammatory factors which promote the occurrence and maintenance of atrial fibrillation by Inflammation and fibrosis factors.However,through literature search,we found that studies on the role of EAT in atrial fibrillation mostly focus on the correlation between the two,and the specific mechanism of what causes EAT dysfunction and how to activate downstream pathways is still unclear.The preliminary experiments in this study found that there may be endoplasmic reticulum stress in eat of patients with atrial fibrillation.The activation of EAT related pathway may be the possible cause of inflammatory and fibrosis response,which can induce and maintain atrial fibrillation.Objectives1.Compare the expression levels of ERS related proteins in EAT of AF patients with pericardial adipose tissue,subcutaneous adipose tissue of AF patients and EAT of sinus rhythm patients,and to determine whether there is excessive activation of ERS in EAT of AF patients.2.Compare the level of fibrosis fat infiltration in left atrial appendage tissue of AF patients and SR patients,as well as the transcription levels of adipokines,inflammatory factors and fibrogenic factors in EAT in those two groups,and to clarify the correlation between the transcription levels of different ERS protein and the transcription levels of different cytokines in EAT of AF patients.MethodsFrom October 2018 to October 2020,hospitalized patients with valvular heart disease in our department were divided into AF group(n=15)and SR group(n=15).EAT,PAT,SAT of AF patients and EAT of SR patients were obtained.1.Sirius red staining was used to evaluate the fibrosis level of eat in patients with AF and SR;2.Real-time quantitative PCR was used to detect the expression of inositol requiring kinase 1α(IRE1α),X-box binding protein 1(XBP1),binding immunoglobulin protein(BIP)and protein kinase R-like ER kinase(PERK),C/EBP homologous protein(CHOP),activating transcription factor 6(ATF6)and eukaryotic initiation factor 2α(e IF2α)in EAT,PAT,SAT of AF patients and EAT of SR patients.Western blot was used to detect the protein levels of IRE1 α,PERK,XBP1,Bip,PERK,CHOP,ATF6 and e IF2α in EAT,PAT,SAT in patients with AF and EAT in patients with SR patients;3.Adiponectin,leptin,tumor necrosis factor(TNF),matrix metalloproteinase 2(MMP-2),matrix metalloproteinase 7(MMP-7),interleukin-1β(IL-1β),monocyte chemotactic protein-1(MCP-1),interleukin-6(IL-6),interleukin-8(IL-8),C-reactive protein(CRP),transforming growth factor-β(TGF-β),angiotensinogen(AGT),angiotensin converting enzyme(ACE),chymase and cathepsin G of EAT in patients with AF and SR were detected by Real-time quantitative PCR.4.Correlation analysis was used to evaluate the correlation between ERS protein and cytokine transcription.Results1.No significant difference showed in general clinical data between AF group and SR group(P>0.05).2.Sirius red staining showed that the levels of myocardial fibrosis in EAT of AF group were higher than those in SR group.3、IRE1α,XBP1 and Bip in EAT of AF group have higher transcriptional levels than those in EAT of SR group(P<0.05),PERK,CHOP,ATF6 and e IF2α in EAT of AF group have similar transcriptional levels with those in EAT of SR group(P>0.05).IRE1 α,XBP1 and Bip in EAT of AF group have higher protein levels than those in EAT of SR group(P<0.05),PERK、CHOP、ATF6、e IF2α in EAT of AF group have similar protein levels with those in EAT of SR group(P>0.05).4.IRE1 α,XBP1 and Bi P in EAT of AF group have higher transcriptional levels than those in PAT and SAT of AF group(P<0.05),PERK,CHOP,ATF6 and e IF2 α in EAT of AF group have similar transcriptional levels with those in PAT and SAT of AF group(P>0.05).IRE1 α,XBP1 and Bip in EAT of AF group have higher protein levels than those in PAT and SAT of AF group(P<0.05).PERK,CHOP,ATF6 and e IF2 α have similar protein levels with those in PAT and SAT of AF group(P>0.05).5.Adiponectin and leptin in EAT of AF group have higher transcriptional levels than those in EAT of SR group(P<0.05).IL-1β and TNF-α in EAT of AF group have higher transcriptional levels than those in EAT of SR group(P<0.05).IL-6,IL-8,MCP-1 and CRP in EAT of AF group have similar transcriptional levels with those in EAT of SR group(P>0.05).TGF-β and MMP-2 in EAT of AF patients have higher transcriptional levels than those in EAT of SR group(P<0.05).MMP-7 in EAT of AF group have similar transcriptional levels with those in EAT of SR group(P>0.05).AGT and chymase have higher transcriptional levels than those in EAT of SR group(P<0.05).ACE and tissue proteinase G have similar transcriptional levels with those in EAT of SR group(P> 0.05).6.The transcriptional level of XBP1 has positive correlation with the transcriptional levels of TNF-α,chymase and AGT in EAT of AF patients(P<0.05),and no correlation with the transcriptional levels of IL-1β,TGF-β and MMP-2 in EAT of AF patients(P>0.05).The transcriptional level of Bip has positive correlation with the transcriptional levels of chymase,IL-1β and TNF-α in EAT of AF patients(P<0.05),and no correlation with the transcriptional level of AGT,TGF-β and MMP-2 in EAT of AF patients(P>0.05).The transcriptional level of IRE1α has positive correlation with the transcriptional level of TGF-β in EAT of AF patients(P<0.05),and no correlation with the transcriptional levels of IL-1β,TNF-α,AGT,chymase and MMP-2 in EAT of AF patients(P>0.05).7.The transcriptional level of chymase has positive correlation with the transcriptional level of TGF-β in EAT of AF patients(P<0.05),and no correlation with the transcriptional levels of IL-1β,TNF-α and MMP-2 in EAT of AF patients(P>0.05).The transcriptional level of AGT has positive correlation with the transcriptional level of TNF-α in EAT of AF patients(P<0.05),and no correlation with the transcriptional levels of IL-1β,TGF-β and MMP-2 in EAT of AF patients(P>0.05).Conclusions1.The levels of many ERS related proteins,including p-IRE1α,IRE1α,XBP1 and Bip,were significantly increased In eat of AF patients,suggesting that the classical pathways of ERS were activated in different degrees in EAT of AF patients;2.The expression levels of IRE1α,XBP1,BIP in EAT of AF patients were correlated with the up-regulated transcription levels of IL-1β,TNF-α,and other inflammatory factors and fibrotic factors in EAT.The up-regulated transcription levels of chymase,AGT and other genes involved in the synthesis of angiotensin Ⅱ in EAT of AF patients,suggested that the pro-inflammatory and fibrotic response of EAT were closely related to the occurrence and maintenance of atrial fibrillation.