The Relationship Between Urinary Angiotensinogen And Intrarenal Renin-angiotensin System Activity

PartⅠThe significance and clinical factors related to the level of urinary angiotensinogen in chronic kidney disease patientsBackgroundSeveral authors have demonstrated that intrarenal angiotensinogen is mainly local-ized to proximal tubule. The angiotensinogen produced in proximal tubule cells seems to be secreted directly into the tubular lumen and converted to angiotensinⅡ(AngⅡ) by renin and angiotensin converting enzyme (ACE). Tubular angiotensinogen has been proposed to be the major intrarenal source for AngⅡ. Because of its molecular size, it seems unlikely that much of the plasma angiotensinogen filters across the glomerular membrane, further supporting the concept that urinary angiotensinogen is mainly secreted by proximal tubule cells, having nothing to with general angiotensinogen. Many animal experiments have demonstrated that there is positive correlation between urinary angiotensinogen and intrarenal angiotensinogen and AngⅡcontent. These data also suggest the potential of urinary angiotensinogen as a marker of intrarenal RAS activity. This study was designed to analyze the clinical factors related to the level of urinary angiotensinogen in chronic kidney disease (CKD) patients.MethodsSeventy-four CKD patients who were hospitalized in Shanghai Zhongshan Hospital between April 2009 and May 2009, had not received angiotensin converting enzyme inhibitor(ACEI) or angiotensinⅡreceptor blocker(ARB) during last two months, and gave informed consent were included in the study. We recorded gender, age, height, body weight, blood pressure, urine routine, renal function, serum electrolytes, urinary protein of 24 hours and urinary sodium. Blood samples were collected at bed rest early in the morning and fresh urine samples were collected after waking up. We measured plasma renin activity, plasma and urinary angiotensinogen, AngⅡand aldosterone by RIA or ELISA in order to determine the clinical factors related to the level of urinary angiotensinogen.ResultsAverage urinary angiotensinogen in 74 chronic kidney disease patients was 209.28±33.99 ng/(mg Cr)[49.48-724.81 ng/(mg Cr)]. Average estimated glomerular filtration rate(eGFR) was 51.34±30.26 ml/min/1.73m2(3.99-163.94 ml/min/1.73m2) and there was negative correlation between urinary angiotensinogen and eGFR(r= -0.56, P<0.01). Average urinary AngⅡwas 134.69±95.09 pg/(mg Cr)[45.73-580.06 pg/(mg Cr)] and there was positive correlation between urinary angiotensinogen and urinary AngⅡ(r= 0.56, P<0.01). Average urinary typeⅣcollagen was 672.91±989.10 ng/(mg Cr)[37.53-6269.48 ng/(mg Cr)] and there was positive correlation between urinary angiotensinogen and urinary type IV collagen(r=0.41, P<0.01). Average urinary soduim was 157.73±76.75 mmol/24h(8.00-425.00 mmol/24h) and there was negative correlation between urinary angiotensinogen and urinary sodium(r=-0.25, P<0.05). Multiple regression analysis indicated that low eGFR(P<0.01), high urinary AngⅡ(P<0.01) and high urinary typeⅣcollagen (P<0.01 correlated significantly with high urinary angiotensinogen. Urinary angiotensinogen did not correlate significantly with plasma renin activity, serum angiotensinogen, plasma AngⅡ, serum and urinary aldosterone, urinary protein of 24 hours, serum sodium, serum potassium, blood pressure, BMI, or gender. Average urinary angiotensinogen in patients whose eGFR were lower than 60 ml/min/1.73m2 was higher than that in patients whose eGFR were higher than 60 ml/min/1.73m2 [254.33±151.38 ng/(mg Cr) vs.143.19±60.10 ng/(mg Cr), P<0.01].ConclusionThere is negative correlation between urinary angiotensinogen and eGFR and there is positive correlation between urinary angiotensinogen and urinary type IV collagen in chronic kidney disease patients.Urinary angiotensinogen maybe a marker of kidney injury, especially chronic kidney injury in chronic kidney disease. PartⅡThe relationship between urinary angiotensinogen and intrarenal renin-angiotensin system activityBackgroundThe crucial role of over-activation of intrarenal renin-angiotensin system (RAS) in the development and progression of chronic kidney disease is widely recognized. Urinary AngⅡincludes focal AngⅡformed intrarenally and part of general AngⅡfiltering across the glomerular membrane. Urinary AngⅡis not a stable marker of intrarenal AngⅡactivity. Many animal experiments have demonstrated that there is positive correlation between urinary angiotensinogen and intrarenal AngⅡactivity and these data also suggest the potential of urinary angiotensinogen as a marker of intrarenal RAS activity. However, most data about urinary angiotensinogen and intrarenal AngⅡactivity derive from animal studies. Studies in humans are lacking, but if results from the preliminary studies are confirmed, urinary angiotensinogen might constitute an invaluable tool for measuring the degree of RAS activation or blockade in individuals with chronic kidney disease, beyond blood pressure, proteinuria and eGFR. This study was designed to analyze the relationship between urinary angiotensinogen and intrarenal AngⅡactivity.MethodsSenenty-there CKD patients who were hospitalized in Shanghai Zhongshan Hospital between April 2009 and May 2009, had not received ACEI or ARB during last two months, and gave informed consent were included in the study. Fresh urine samples were collected after waking up and we measured urinary angiotensinogen by ELISA. Experssion of all the components of intrarenal RAS was assessed by immunohistochemistry staining (IHCS) in order to determine the relationship between urinary angiotensinogen and expression of all the components of intrarenal renin-angiotensin system.ResultsAverage urinary angiotensinogen in 73 chronic kidney disease patients was 210.24±134.65 ng/(mg Cr)[49.48-724.81 ng/(mg Cr)]. Positive IHCS area of intrarenal angiotensinogen was 39.15±19.35%(5.00-88.00%) and there was positive correlation between urinary angiotensinogen and positive IHCS area of intrarenal angiotensinogen (P<0.01). Positive IHCS area of intrarenal AngⅡwas 31.85±19.75% (3.00-81.00%) and there was positive correlation between urinary angiotensinogen and positive IHCS area of intrarenal AngⅡ(P<0.01). Positive IHCS area of intrarenal angiotensinⅡtype 1 receptor (AT1R) was 44.50±16.14%(8.00-88.00%) and there was positive correlation between urinary angiotensinogen and positive IHCS area of intrarenal AT1R (P<0.05). Urinary angiotensinogen did not correlate significantly with positive IHCS area of intrarenal renin and angiotensinⅡtype 2 receptor(AT2R).ConclusionUrinary angiotensinogen can reflect intrarenal agiotensinⅡactivity in chronic kidney disease patients and constitutes an invasive marker of intrarenal RAS activity. PartⅢThe effect of angiotensinⅡreceptor blocker on expression of intrarenal renin-angiotensin systemBackgroundThe kidney is a major target for the RAS, as evidenced by the robust renal expression of the AT1R. Data about the effect of ARB on intrarenal RAS activity is still lacking and there is no evidence to support that urinary angiotensinogen is still a marker of intrarenal RAS activity after the treatment of ARB. This study was designed to analyze whether urinary angiotensinogen is still a marker of intrarenal RAS activity after the treatment of ARB and observe the effect of ARB on expression of intrarenal renin-angiotensin system.MethodsSenenteen CKD patients who were hospitalized in Shanghai Zhongshan Hospital between April 2009 and May 2009, had received ARB for at least two weeks, had not received ACEI during last 2 months, and gave informed consent were included in the study (ARB group). They were matched pair with patients in partⅠaccording to eGFR, urinary protein of 24 hours, urinary sodium and blood pressure (control group). We recorded gender, age, height, body weight, blood pressure, urine routine, renal function, serum electrolytes, urinary protein of 24 hours and urinary sodium. Blood samples were collected at bed rest early in the morning and fresh urine samples were collected after waking up. We measured plasma renin activity, plasma and urinary angiotensinogen, AngⅡand aldosterone by RIA or ELISA and assess experssion of all the components of intrarenal RAS by immunohistochemistry staining in order to determine the relationship between urinary angiotensinogen and expression of all the componenets of intrarenal renin-angiotensin system in ARB group and the difference of general and focal renin-angiotensin system activity between two groups.ResultsAverage urinary angiotensinogen in ARB group was 219.17±211.54 ng/(mg Cr) [17.27-700.47 ng/(mg Cr)]. Positive IHCS area of intrarenal angiotensinogen was 34.76±15.64%(10.00-65.00%) and there was positive correlation between urinary angiotensinogen and positive IHCS area of intrarenal angiotensinogen (P<0.05). Positive IHCS area of intrarenal AngⅡwas 33.76±18.82%(10.00-70.00%) and there was positive correlation between urinary angiotensinogen and positive IHCS area of intrarenal AngⅡ(P<0.05). Positive IHCS area of AT1R was 43.65±26.17% (15.00-92.00%) and there was positive correlation between urinary angiotensinogen and positive IHCS area of intrarenal ATIR (P<0.05). Urinary angiotensinogen did not correlate significantly with positive IHCS area of intrarenal renin and AT2R. Average plasma AngⅡin ARB group was significantly higher than that in control group (63.09±15.14 pg/ml vs.53.66±8.33 pg/ml, P<0.05). Positive IHCS area of intrarenal renin in ARB group was significantly higher than that in control group (48.65±19.58% vs.30.29±24.98%, P<0.05). Positive IHCS area of intrarenal angio-tensinogen, AngⅡand ATIR in ARB group was lower than those in control group, but the difference had no statistical meaning. There was no difference between two groups on eGFR, urinary protein of 24 hours, blood pressure, urinary sodium, plasma renin activity, serum and urinary angiotensinogen, urinary Angll, serum and urinary al-dosterone, or positive IHCS area of intrarenal AT2R.ConclusionUrinary angiotensinogen still can reflect intrarenal angiotensinⅡactivity in chronic kidney disease patients treated by ARB. ARB has different influence on the activity of general and intrarenal RAS. ARB can elevate general angiotensinⅡand probably can inhibit the expression of intrarenal angiotensinⅡ. PartⅣExpression of intrarenal renin-angiotensin system and its relationship with clinical-pathological injury in primary IgA nephropathy patientsBackgroundLittle information is available about the RAS expression and regulation in the human kidney and particularly in kidney diseases and data on the RAS expression and regulation were mostly obtained in animals.These data in humans and in diseased kidneys would be worthwhile being evaluated because changes in general RAS do not closely reflect local expression and regulation of intrarenal RAS. On the contrary, the simultaneous assessment of the expression and regulation of all components of intrarenal RAS is necessary for evaluation of the net effect of the intrarenal RAS activity. Indeed, the effect of RAS activity on the kidney can not be accurately assessed by the measurement of one component alone. This study was designed to analyze expression and regulation of all the components of intrarenal RAS and the relationship between intrarenal AngⅡexpression and clinical-pathological injury index in primary IgA nephropathy patients.MethodsThirty-six biopsy-proved IgA nephropathy patients who were hospitalized in Shanghai Zhongshan Hospital between January 2009 and June 2009, had not received ACEI, ARB, glucocorticoids or immunosuppressive agents, and gave informed consent were included in the study. We recorded gender, age, height, body weight, blood pressure, urine routine, renal function, serum electrolytes, urinary protein of 24 hours and urinary sodium. We assessed pathological injury by semiquantitative Katafuchi score and assessed intrarenal experssion of all the components of the intrerenal RAS by immunohistochemistry staining. We assessed expression and regulation of all the components of intrarenal RAS and the relationship between intrarenal Ang II activity and clinical-pathological injury index in primary IgA nephropathy patients.ResultsPositive IHCS area of intrarenal renin, angiotensinogen and AngⅡwere 26.86±13.66%(7-55%),38.34±9.71%(12-57%) and 32.73±14.74%(6-70%), respectively. There were positive correlation between positive IHCS area of intrarenal renin and positive IHCS area of intrarenal Ang II (P<0.01), positive IHCS area of intrarenal angiotensiongen and positive IHCS area of intrarenal Ang II (P<0.05). Average eGFR in 36 IgA nephropathy patients was 55.92±22.87 ml/min/1.73m2(6.62-92.49 ml/min/1.73m) and there was negative correlation between positive IHCS area of intrarenal AngⅡand eGFR(P<0.01). Average pathological chronicity index in 36 IgA nephropathy patients was 3.06±2.60 (0-10) and there was positive correlation between positive IHCS area of intrarenal AngⅡand pathological chronicity index (P<0.05).ConclusionExpression of intrarenal AngⅡcorrelates positively with expression of intrarenal renin and angiotensinogen in IgA nephropathy. Intrarenal AngⅡactivity plays an important role in kidney fibrosis in IgA nephropathy.