Role Of Endoplasmic Reticulum Stress And A_2BR In Renal Fibrosis

BACKGROUND&OBJECTIVE:Renal fibrosis is a common endpoint and major pathological change in the progression of various primary or secondary renal diseases to the terminal stage.Previously,we found that adenosine and its A2BR are closely related to the formation of renal fibrosis,and ER stress is an important link in the process of renal fibrosis,but the specific mechanism is not clear.METHODS:Therefore,we constructed in vivo and in vitro renal fibrosis models to try to confirm the effect of ER stress on renal fibrosis through adenosine 2B receptor(A_2BR)-mediated transforming growth factorβ1（TGF-β1）signaling pathway and interleukin-6（IL-6）signaling pathway and preliminarily elucidate the mechanism of ER stress and A2BR in renal fibrosis.SD rats aged 6–8 weeks were used to establish an animal model using unilateral ureteral ligation;tubular epithelial cells（HK-2）were used for oxygen-glucose deprivation（OGD）to establish a cell model.After successful modeling,changes in C/EBP-homologous protein（CHOP）,adenosine,IL-6,and TGF-β1 were detected.On the cell model,the ER stress inhibitor 4-PBA,ER stress agonist TM,adenosine,and adenosine receptor inhibitor MRS-1754 were used to intervene,respectively,to detect the changes in CHOP,adenosine,IL-6,and TGF-β1and verify the role of adenosine and ER stress in the process of OGD-induced fibrosis.RESULTS:Unilateral ureteral ligation can well establish a renal fibrosis model,causing renal function injury in rats along with increased expression of ER stress protein CHOP,increased adenosine levels,and up-regulation of renal fibrosis-related factors TGF-β1 and IL-6.In the cellular OGD model,adenosine,TGF-β1,IL-6,and CHOP were also increased.In the OGD model,4-PBA,an inhibitor of ER stress,and TM,an ER stress agonist,were intervened,respectively.4-PBA caused down-regulation of CHOP expression,accompanied by a decrease in adenosine production,and was accompanied by a decrease in the renal fibrosis-related factors IL-6 and TGF-β1.TM caused an increase in adenosine production,as did TGF-β1 and IL-6.These results indicate that OGD-induced ER stress can cause disturbances in ATP metabolism leading to increased adenosine production;while ER stress is associated with increased renal fibrosis-related factor TGF-β1,and inflammatory factor IL-6.Addition of the adenosine receptor inhibitor MRS-1754 did not affect CHOP as well as adenosine expression,but reduced IL-6 and TGF-β1 expression.CONCLUSION:Based on the results of the rat UUO model and the HK-2 cell OGD model,the CHOP/adenosine pathway is involved in mediating renal fibrosis.The association between renal fibrosis and ER stress was verified,indicating that ER stress induced an increase in adenosine,while leading to an increase in TGF-β1 and IL-6.