Effects Of Targeted Renal Denervation Guided By Renal Nerve Stimulation On Mechanism Of Blood Pressure Regulation In Kidney In Canine

Background:Related animal experiments and preliminary clinical studies have confirmed that Renal Nerve Stimulation(RNS)can be used as a means of mapping renal afferent and efferent nerves.The study found that RNS performed at different sites of the renal artery has different blood pressure(BP)elevation response,moreover,the degree of BP increase induced by RNS has a good positive correlation between the degree of reduction in the office and ambulatory blood pressure of patients after RDN.This suggests that the long-term BP-lowing effects after RDN at sites with different BP responses to RNS may be different.Since the efferent nerves can also be positioned while mapping the afferent nerves by RNS,and the efferent nerves mainly regulate kidney function,and the efferent nerves mainly regulate kidney function,and its activation produces and secretes norepinephrine(NE),which activates the intrarenal RAS system,thereby enhancing the reabsorption of water and sodium in the kidneys.Therefore,there is reason to believe that the BP-lowing effects after RDN may be partly related to changes of Neuro-humoral regulation in the kidney.That is,due to these changes related to improvements of water and sodium reabsorption in kidney,which may contribute to the decrease of blood pressure.It is not clear whether there are differences in the BP-lowing effects after RDN at sites with different BP changes,and to clarify this issue is of great significance for improving the efficacy of RDN.Objective:To investigate the changes and differences of renal humoral regulation after selective renal denervation(RDN)at sites with different BP-elevation responses to renal nerve stimulation(RNS).Methods:Twenty-one dogs with anatomically eligible to perform RNS and RDN were randomly assigned into 3 groups: Sham group(n=7),weak BP-response to RNS ablation group(WRA,n=7)and strong BP-response to RNS ablation group(SRA,n=7).Radiofrequency ablation was performed at the sites with weak or strong BP-responses in WRA or SRA group,respectively.Invasive femoral artery BP was recorded at baseline and 4 weeks after RDN.The levels of Norepinephrine(NE)in kidney was assessed by ELISA;The protein expressions of tyrosine hydroxylase(TH),RAS components and molecules related to water and sodium retention were measured by Western blot or immunohistochemistry.Result:1.There was no significant difference in the number of stimulation or ablation sites between WRA and SRA group.No significant differences at baseline among groups in systolic BP(SBP,P=0.188)and diastolic BP(DBP,P=0.304).2.The SBP/DBP decreased by(14.74±6.09)/(13.12±8.78)mm Hg(P=0.004 and 0.042)in the WRA group and(28.64±6.71)/(20.45±10.80)mm Hg(P<0.001 and=0.001)in SRA group,respectively,compared with the Sham group at 4 weeks after RDN.In addition,the reduction of SBP was greater in SRA group than in WRA group(P=0.002),in contrast,although the reduction trend of DBP was more pronounced in SRA group,there was no statistical difference compared with WRA group(P=0.131).3.Compared with the Sham group,the NE concentration,TH and renin protein expression were significantly reduced in both groups,and all of these reductions were more significant in the SRA group;The expression of angiotensin converting enzyme(ACE),angiotensinogen(AGT),angiotensin ? type 1 receptor(AT1R)was significantly attenuated in both ablation groups,compared with the Sham group,while the ACE2 was significantly up-regulated,Both of these changes are more marked in the SRA group.4.Compared with the Sham group,the protein expression of AQP1 and AQP2 in WRA and SRA decreased to varying degrees regardless of in renal cortex or medulla,and the greatest decrease was observed in SRA group.Compared with Sham group,WRA group The expression of medullary AQP2 and cortical AQP1 also decreased,but did not reach statistical difference;Compared with the sham group,the protein expression of AQP2 in medulla and the AQP1 in cortex in WRA group showed a decreasing trend,but no statistical difference.6.The total protein expression level of NKCC2 was not statistically different among the three groups at 4 weeks after RDN,However,compared with the Sham group,the phosphorylation level of NKCC2 was decreased with different degrees in the WRA group and the SRA group,and the decreasing trend was more significant in SRA.Compared with the Sham group,the NKCC2 enriched in the plasma membrane((mNKCC2)was reduced in different degrees in both group,and the degree in the SRA group was more significant.Conclusion:Selective RDN at sites with different BP-elevation response to RNS can lower blood pressure by reducing renal sympathetic activity,local RAS activity as well as improving renal sodium and water retention,and selective RDN at sites with strong BP-elevation response to RNS could lead to more efficient RDN.