The Role Of Central (Pro) Renin Receptor In Salt-induced Renal Injury In CKD

Purposes:In addition to directly damaging the kidneys,high-salt also promotes renal injury in chronic kidney disease(CKD)through activating the RAS axis of the brain and kidney.Simultaneously,(pro)renin receptor(PRR),as a member of RAS,can exert local physiological effects through mitogen-activated protein kinase/extracellular regulated protein kinasesl/2(MAPK/ERK1/2)or phosphatidylinositide 3-kinases/protein kinase B(PI3K/Akt)signaling pathway,and angiotensin converting enzyme 1angiotensin Ⅱ-angiotensin type 1(ACE1-ANG Ⅱ-AT1)axis.Studies have shown that central PRR can control blood pressure through sympathetic output nerves.However,whether central PRR can regulate salt-induced CKD kidney injury and its specific mechanism is still unclear.Therefore,we investigate the role of central PRR on renal injury,oxidative stress,inflammation,RAS,sympathetic activity and fibrosis in saltloaded CKD rats in this study.Furthermore,we also investigate the potential mechanism of central PRR on renal injury.Methods:Protocol A,First,we screened out the shRNA that inhibit the central PRR expression in vitro.After the CKD model,which was established by 5/6 nephrectomy,was successfully prepared,intraventricular injection of lentiviruspackaged shRNA was used and a high-salt diet was given for 4 weeks.Finally,central and renal pathologic change was detected after silencing of central PRR.Protocol B,U0126,Wortmannin and Losartan were used to inhibit MAPK/ERK1/2,PI3K/Akt signaling pathway,and ACE1-ANG Ⅱ-AT1 axis in CKD model by continuous central administration and a high-salt diet was given for 4 weeks,respectively.Finally,we investigated the central and renal pathological changes.Results:High-salt diet aggravated kidney damage and fibrosis,increased RAS activation,oxidative stress,and inflammation.After successful inhibition of central PRR expression,the expression of tyrosine hydroxylase in neurons of the rostral ventrolateral medulla of the brain,and the serum,renal norepinephrine levels were decreased,indicating decreased activity of the sympathetic nervous system;while kidney pathological scores,as well as Fibronectin,α-smooth muscle actin,and Collagen I were down-regulated,indicating that inhibition of central PRR can ameliorates renal injury and fibrosis.In addition,renal RAS components such as PRR,Angiotensinogen,and Angiotensin Ⅱ(ANG Ⅱ),pro-inflammatory chemokines(Intercellular cell adhesion molecule-1 and Monocyte chemotactic protein 1),and kidney NADPH oxidase(Nox2 and Nox4)were down-regulated,while renal antioxidant enzymes(Catalase,Glutathione peroxidase 1,and Superoxide dismutase 1)were up-regulated.At the same time,central RAS activation,oxidative stress,and inflammation were diminished.Furthermore,phosphorylation of ERK1/2 and Akt in the brain were inhibited after silencing of central PRR.Central administration of U0126,Wortmannin,and Losartan was performed.The results revealed that these interventions ameliorated kidney damage,inflammation,oxidative stress,fibrosis,and sympathetic nerve activity.However,decreased phosphorylation of ERK1/2 and Akt signaling in the brain had no significant effect on the expression of PRR,but silencing of central PRR PRR can inhibit the phosphorylation of the pathways.It suggested that in addition to ANG Ⅱ,central PRR may affect renal pathology through MAPK/ERK1/2 and PI3K/Akt signaling pathways except ANG Ⅱ.Conclusion:Silencing of central PRR expression can reduce RAS activation,inflammation,and oxidative stress,as well as ameliorate salt-induced renal damage,thereby slowing down the progression of CKD.Central PRR may affect renal pathology through the ANG Ⅱ-dependent and ANG Ⅱ-independent pathways.