| Objective: Hypertension has become a global healthy problem.About 1/3 adults in the world are suffering from hypertension.It is estimated that only about 972 million people have hypertension in 2000 in the world and it will increase to 1 billion and 560 million by 2025.Hypertension can cause several organ damage.Hypertension can cause damage in various structures of renal tissue,including renal blood vessels,glomeruli and tubulointerstitium.It can also bring loss of podocytes,epithelial mesenchymal transition and renal tubulointerstitial fibrosis.Therefore,there is a close relationship between hypertension and renal injury.Recently,Studies have shown that the development of hypertension is associated with many high risk factors.It is also related to excessive activation of sympathetic nerves system,oxidative stress and activation of RAS system.Renal sympathetic nerve(RDN)has been an important method to treat hypertension.The purpose of this study is to explore the effect of RDN on blood pressure and renal function in spontaneously hypertensive rats and its possible mechanisms through basic experiments.Methods: Part I.SHR rats were randomly divided into 4 groups: sham group and 0.5 ml phenol group,1ml phenol group and 1.5ml phenol group.RDN was performed at the 13 week.Blood pressure was measured every week before and after operation.After 4 weeks,all rats were sacrificed.Plasma norepinephrine content was measured.Histology of renal artery and renal nerve in HE,Masson and PAS staining and TH and NF200 immunohistochemically staining were measured.Part II.SHR and WKY rats were randomly divided into 3 groups: SHR sham group,SHR-RDN group and WKY-RDN group,RDN was performed at the same time.Blood pressure was measured before and after surgery.Twenty weeks later,all rats were sacrificed.Plasma,urine,renal artery,renal tissue and hypothalamus were collected for further study.Part III.SHR rats were divided into four groups: sham group,RDN group,RDN+DIZE group and RDN+MLN-4760 group.RDN and intracerebroventricular infusion of DIZE and MLN-4760 were performed at the 13 weeks.Blood pressure was measured before and after surgery.4 weeks later,all rats were sacrificed.Plasma,renal tissue and hypothalamus were collected for further detection.Results: Part I.Only one rat was died of intestinal obstruction in the 1.5ml phenol group.Four weeks after RDN operation,the systolic blood pressure(SBP)of 1.5ml phenol group increased gradually(P < 0.01),while SBP of 1ml phenol group decreased significantly(P < 0.01),when compared with the sham group.There was also no difference in the renal NE content among the sham group,the 0.5ml phenol group and the 1.5ml phenol group(P > 0.05)except the 1ml phenol group(P < 0.01).The sham group had normal renal nerve.There was mild injury in renal nerve in 0.5ml phenol group.While 1ml group and 1.5ml phenol group showed moderate to severe injury in renal nerves with moderate infiltration of inflammatory cells,nuclear vacuolization,nuclear atrophy and the normal structure of some neural cells disappeared.Renal nerve injury score among sham group,1ml phenol group and 1.5ml phenol group were compared(0.44±0.3 vs 3.46±0.3 vs 3.66±0.2,P < 0.01).It showed that 1ml phenol could successfully remove renal sympathetic nerve and reduce blood pressure,which successfully establish the RDN model with little damage in the renal artery.Part II: Compared with the sham group,SBP was decreased significantly at 17,21,25,29 weeks,respectively,in SHR-RDN group(P < 0.05),but it was gradually increased at 33 weeks(P > 0.05).The level of PRA,Ang II,ALD and NADPH in the plasma were significantly decreased(P < 0.05),while e NOS and NO were significantly increased(P < 0.05).24 h proteinuria in the urine was significantly decreased(P < 0.001).Glomerular sclerosis significantly reduced and glomerular score(GS)decreased significantly in SHR-RDN group compared with SHR-sham group(P < 0.01).Tubulointerstitial fibrosis was significantly reduced and interstitial fibrosis area(P < 0.01).Paraventricular nucleus TH positive cells were significantly decreased(P < 0.001).It is indicated that RDN can delay blood pressure but can not reduce blood pressure totally.RDN could significantly reduce sympathetic nerve activity and oxidative stress in PVN and plasma.It can be attributed to the reason that RDN delay the progression of hypertension and improve the tubulointerstitial fibrosis and glomerulosclerosis.Part III: Compared with the RDN group,SBP was decreased significantly in RDN+DIZE group(168 ± 8.1 vs 151.8 ± 13.6,P < 0.05),while SBP was increased significantly in RDN+MLN-4760 group(168 ± 8.1 vs 182.6 ± 7.1,P < 0.05).Immunofluorescence and WB: Compared with the sham group,the expression of ACE2 and Mas in hypothalamus was significantly increased in RDN group(P < 0.05),while ACE1 and AT1 R were significantly decreased in PVN of hypothalamus(P < 0.05).ACE2 and Mas showed high expression in PVN in RDN-DIZE group when compared with RDN group(1.58 ± 0.026 vs 1.76 ± 0.027;1.57 ± 0.026 vs 2.313 ± 0.037,respectively,P < 0.05),while ACE1 and AT1 R further reduced(P < 0.05).ACE1 and AT1 R showed high expression in PVN in RDN-MLN-4760 group when compared with RDN group(1.58 ± 0.026 vs 0.5 ± 0.021;1.57 ± 0.026 vs 1.195 ± 0.015,respectively,P < 0.05).when compared with the RDN group,glomerulosclerosis in the kidney was significantly reduced in the RDN-DIZE group and the GS was significantly decreased(1.42 ± 0.25 vs 0.44 ± 0.27,P < 0.05).While glomerulosclerosis was aggravated in the RDN-MLN-4760 and GS increased significantly(1.42±0.25 vs 1.65±0.30,P < 0.05).it indicated that activation of ACE2 in the PVN can delay blood pressure and alleviate glomerular sclerosis.Conclusions: The RDN model can be successfully established by chemical phenol method with 1ml phenol in SHR.RDN can delay the progress of hypertension in SHR and improve the renal function.The mechanism is related to the inhibition of the sympathetic activity in the central nervous system,reduction of oxidative stress and the high expression of ACE2 in PVN of the hypothalamus. |
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