Renal angiotensin I-converting enzyme-deficient mice are protected against aristolochic acid nephropathy.

The renal renin-angiotensin system (RAS) is involved in the development of chronic kidney disease. Here, we investigated whether mice with reduced renal angiotensin I-converting enzyme (ACE-/-) are protected against aristolochic acid nephropathy (AAN). To further elucidate potential molecular mechanisms, we assessed the renal abundances of several major RAS components. AAN was induced using aristolochic acid I (AAI). Glomerular filtration rate (GFR) was determined using inulin clearance and renal protein abundances of renin, angiotensinogen, angiotensin I-converting enzyme (ACE) 2, and Mas receptor (Mas) were determined in ACE-/- and C57BL/6J control mice by Western blot analyses. Renal ACE activity was determined using a colorimetric assay and renal angiotensin (Ang) (1-7) concentration was determined by ELISA. GFR was similar in vehicle-treated mice of both strains. AAI decreased GFR in controls but not in ACE-/- mice. Furthermore, AAI decreased renal ACE activity in controls but not in ACE-/- mice. Vehicle-treated ACE-/- mice had significantly higher renal ACE2 and Mas protein abundances than controls. AAI decreased renal ACE2 protein abundance in both strains. Furthermore, AAI increased renal Mas protein abundance, although the latter effect did not reach statistical significance in the ACE-/- mice. Renal Ang(1-7) concentration was similar in vehicle-treated mice of both strains. AAI increased renal Ang(1-7) concentration in the ACE-/- mice but not in the controls. Mice with reduced renal ACE are protected against AAN. Our data suggest that in the face of renal ACE deficiency, AAI may activate the ACE2/Ang(1-7)/Mas axis, which in turn may deploy its reno-protective effects.

Urinary Angiotensinogen and Renin Excretion are Associated with Chronic Kidney Disease.

BACKGROUND/AIMS: Several studies sought to identify new biomarkers for chronic kidney disease (CKD). As the renal renin-angiotensin system is activated in CKD, urinary angiotensinogen or renin excretion may be suitable candidates. We tested whether urinary angiotensinogen or renin excretion is elevated in CKD and whether these parameters are associated with estimated glomerular filtration rate (eGFR). We further tested whether urinary angiotensinogen or renin excretion may convey additional information beyond that provided by albuminuria. METHODS: We measured urinary and plasma angiotensinogen, renin, albumin and creatinine in 177 CKD patients from the Greifswald Approach to Individualized Medicine project and in 283 healthy controls from the Study of Health in Pomerania. The urinary excretion of specific proteins is given as protein-to-creatinine ratio. Receiver operating characteristic (ROC) curves, spearman correlation coefficients and linear regression models were calculated. RESULTS: Urinary angiotensinogen [2,511 (196-31,909) vs. 18.6 (8.3-44.0) pmol/g, *P<0.01] and renin excretion [0.311 (0.135-1.155) vs. 0.069 (0.045-0.148) pmol/g, *P<0.01] were significantly higher in CKD patients than in healthy controls. The area under the ROC curve was significantly larger when urinary angiotensinogen, renin and albumin excretion were combined than with urinary albumin excretion alone. Urinary angiotensinogen (ß-coefficient -2.405, standard error 0.117, P<0.01) and renin excretion (ß-coefficient -0.793, standard error 0.061, P<0.01) were inversely associated with eGFR. Adjustment for albuminuria, age, sex, systolic blood pressure and body mass index did not significantly affect the results. CONCLUSION: Urinary angiotensinogen and renin excretion are elevated in CKD patients. Both parameters are negatively associated with eGFR and these associations are independent of urinary albumin excretion. In CKD patients urinary angiotensinogen and renin excretion may convey additional information beyond that provided by albuminuria.

Iloprost, Prostaglandin E1, and Papaverine Relax Human Mesenteric Arteries With Similar Potency.

OBJECTIVE: Nonocclusive mesenteric ischemia (NOMI) is accompanied by mesenteric artery spasms that are at least in part due to endothelin system activation. Acute treatment includes intra-arterial infusion of vasodilators such as iloprost, prostaglandin E1 (PGE1), and papaverine. Their effectiveness is not well characterized in human mesenteric arteries. We directly compared their potency to relax isolated human mesenteric arteries. To explore the potential of Rock inhibition to treat mesenteric artery spasms, we tested if endothelin-1 (ET-1)-induced mesenteric artery constrictions depend on rho kinase (Rock). METHODS: Mesenteric artery segments were obtained from patients who underwent elective abdominal surgery. Vasodilator concentration-response curves were recorded from ET-1-preconstricted vessels by small vessel myography. Rock expression was investigated by Western blot and the potency of Rock inhibition to blunt ET-1-induced mesenteric artery constriction was tested. RESULTS: Iloprost, PGE1, and papaverine similarly reduced vascular tone to 20% to 30% of ET-1-induced wall tension. In human mesenteric arteries, logEC50 was significantly less for iloprost than for PGE1 or papaverine. Respective logEC50 values were -7.72 ±â€Š0.08 mol/L, -6.58 ±â€Š0.17 mol/L, and -6.73 ±â€Š0.19 mol/L in 150 µm to 300 µm lumen diameter arteries. These vessels were also more sensitive to iloprost than 500 µm to 1,000 µm lumen diameter arteries (logEC50 -7.29 ±â€Š0.07 mol/L). Rock1 and Rock2 were expressed in human mesenteric arteries but Rock inhibition did not significantly affect ET-1-induced vasoconstrictions. CONCLUSIONS: Iloprost, PGE1, and papaverine have a similar potency to relax mesenteric arteries. Our data suggest that iloprost but not Rock inhibition may be particularly useful to treat ET-1-induced spasms of distal mesenteric arteries.