angiotensinogen and olmesartan

(Pro)renin receptor [(P)RR], a trans-membrane receptor for renin and prorenin, is involved in the local activation of renin-angiotensin system (RAS) in the kidney. However, it remains to be determined whether (P)RR plays a role in the development of ischemic acute kidney injury (AKI).. We examined the abundance of (P)RR, renin/prorenin, angiotensinogen (AGT), AT1 receptor (AT1R), phosphorylation of extracellular signal-regulated protein kinase 1/2 (ERK 1/2) and nuclear factor-κB (NF-κB) by Western blots at 6, 24 and 48 h, and at 7 days after 45-min ischemic injury in rats. Intrarenal angiotensin II (Ang II) levels were determined by radioimmunoassay. We then tested whether the beneficial effects of oral loading of saline solution (1.0 % NaCl) for 7 days prior to ischemic injury were associated with changes in RAS components and ERK 1/2 and NF-κB phosphorylation in the kidney. We also examined the effect of AT1R blocker, olmesartan, on ischemia-induced changes of (P)RR downstream such as AGT and phosphorylation of ERK 1/2.. Renal ischemia increased the abundance of (P)RR protein at 24 h, and peaked at 48 h. (P)RR was mainly stained in the connecting tubules and collecting ducts in control rats, while ischemia increased its immunointensity in the damaged proximal tubules. Renal ischemia increased phosphorylation of ERK 1/2 and NF-κB proteins as early as at 6 h. There was a significant increase in AGT and Ang II levels at 24 and 48 h. Prior saline loading prevented the increase in serum creatinine at 48 h (5.36 ± 1.26 vs. 3.38 ± 1.74 mg/dL, p < 0.05), and suppressed the increases in renal (P)RR, AGT and Ang II contents. Saline drinking also significantly blocked the ischemia-induced increases in phosphorylation of ERK 1/2 and NF-κB. In contrast, although treatment with olmesartan (10 mg/kg/day) for 14 days suppressed an increase of intrarenal AGT, olmesartan did not alleviate ischemic AKI, along with no change of (P)RR and phosphorylated ERK 1/2.. These findings suggest that increased (P)RR is associated with activation of RAS-independent downstream such as ERK 1/2 and NF-κB phosphorylation in the ischemic kidney.

Topics: Acute Kidney Injury; Angiotensin II; Angiotensin II Type 1 Receptor Blockers; Angiotensinogen; Animals; Creatinine; Extracellular Signal-Regulated MAP Kinases; Imidazoles; Ischemia; Kidney Tubules; Male; NF-kappa B; Phosphorylation; Prorenin Receptor; Proton-Translocating ATPases; Rats; Rats, Sprague-Dawley; Receptor, Angiotensin, Type 1; Receptors, Cell Surface; Sodium Chloride; Tetrazoles; Vacuolar Proton-Translocating ATPases

In the intrarenal renin-angiotensin system, angiotensinogen levels are well known to be increased in diabetes, and these enhanced intrarenal angiotensinogen levels may initiate the development and accelerate the progression of diabetic nephropathy. However, the specific localization of the augmented angiotensinogen in proximal tubule segments in diabetes is still unknown. We investigated the detailed localization of angiotensinogen in 3 proximal tubule segments in the diabetic Otsuka Long-Evans Tokushima fatty (OLETF) rats and the control Long-Evans Tokushima Otsuka (LETO) rats. We also prepared OLETF rats treated with angiotensin II type 1 receptor blocker, olmesartan or with a combination of vasodilator agents. Moreover, biopsied samples of human kidney cortex were used to confirm the results of animal studies. We examined the co-localization of angiotensinogen with segment-specific markers by double staining using fluorescence in situ hybridization and/or immunofluorescence. Angiotensinogen mRNA expression was barely detectable in segment 1. In segment 3, the area of angiotensinogen mRNA expression was augmented in the OLETF rats compared with the LETO rats. Angiotensinogen protein expression areas in segments 1 and 3 were also increased in the OLETF rats compared with the LETO rats. Chronic treatment with olmesartan ameliorated these areas of augmented angiotensinogen expression. Biopsied human kidney samples showed similar results. These data suggest that the augmented angiotensinogen mRNA levels in segment 3 and angiotensinogen protein levels in segments 1 and 3 may contribute to the progression of diabetic nephropathy.

Topics: Analysis of Variance; Angiotensin II Type 1 Receptor Blockers; Angiotensinogen; Animals; Diabetes Mellitus; DNA Primers; Fluorescent Antibody Technique; Humans; Imidazoles; Immunohistochemistry; In Situ Hybridization, Fluorescence; Kidney Tubules, Proximal; Male; Rats; Rats, Inbred OLETF; RNA, Messenger; Species Specificity; Tetrazoles; Vasodilator Agents

We examined the possibility that continuous activation of the human brain renin-angiotensin system causes cognitive impairment, using human renin (hRN) and human angiotensinogen (hANG) gene chimeric transgenic (Tg) mice. Cognitive function was evaluated by the shuttle avoidance test once a week from 10 to 20 weeks of age. The avoidance rate in wild-type mice gradually increased. In contrast, the avoidance rate in chimeric hRN/hANG-Tg mice also increased; however, no further increase in avoidance rate was observed from 14 weeks of age, and it decreased thereafter. Cerebral surface blood flow was markedly reduced in 20-week-old hRN/hANG-Tg mice. Superoxide anion production in the brain was already higher in 10-week-old hRN/hANG-Tg mice and further increased thereafter with an increase in NADPH oxidase activity. Moreover, expression of p47(phox) and Nox4 in the brain of hRN/hANG-Tg mice also increased. Administration of an angiotensin II type 1 receptor blocker, olmesartan (5.0 mg/kg per day), attenuated the increase in blood pressure and ameliorated cognitive decline with enhancement of cerebral surface blood flow and a reduction of oxidative stress in hRN/hANG-Tg mice. On the other hand, hydralazine (0.5 mg/kg per day) did not improve the decrease in avoidance rate, and did not influence cerebral surface blood flow or oxidative stress in hRN/hANG-Tg mice, in spite of a similar reduction of blood pressure to that by olmesartan. Moreover, we observed that treatment with Tempol improved impaired cognitive function in hRN/hANG-Tg mice. These results suggest that continuous activation of the brain renin-angiotensin system impairs cognitive function via stimulation of the angiotensin II type 1 receptor with a decrease in cerebral surface blood flow and an increase in oxidative stress.

Topics: Angiotensin II Type 1 Receptor Blockers; Angiotensinogen; Animals; Antioxidants; Blood Pressure; Brain; Cognition; Cyclic N-Oxides; Imidazoles; Male; Mice; Mice, Transgenic; NADPH Oxidase 4; NADPH Oxidases; Oxidative Stress; Receptor, Angiotensin, Type 1; Regional Blood Flow; Renin; Renin-Angiotensin System; Spin Labels; Superoxides; Tetrazoles

The differential roles of circulating and intrarenal renin-angiotensin system (RAS) in glomerulonephritis have not been elucidated. In this study, we investigated the levels of circulating and intrarenal RAS activity and urinary angiotensinogen (AGT) excretion in anti-thymocyte serum (ATS) nephritis induced by an ATS injection (ATS group). The effect of olmesartan, an angiotensin II (ANG II) type 1 receptor blocker (ARB), on the development of nephritis was also examined (ATS+ARB group). In addition, the rats received a saline injection instead of ATS (control group). Mesangial proliferation with transient proteinuria, which peaked at day 7, was significantly increased in the ATS group compared with the control group. The levels of glomerular AGT mRNA, intrarenal ANG II, and urinary AGT excretion in the ATS group were increased significantly at day 7 compared with the control group. Administration of olmesartan (ATS+ARB group) significantly decreased the levels of renal lesions, proteinuria, and intrarenal RAS activity compared with the ATS group. In addition, the levels of urinary AGT excretion correlated with the levels of glomerular damage, urinary protein excretion, and immunoreactivity for AGT and ANG II in kidney. On the other hand, plasma renin activity was significantly lower in the ATS group compared with the control group and significantly higher in the ATS+ARB group than in the ATS group. These data suggest that an increase in kidney-specific RAS activity, which parallels urinary AGT excretion, plays an important role in the development of ATS nephritis.

Topics: Angiotensin II; Angiotensin II Type 1 Receptor Blockers; Angiotensinogen; Animals; Antilymphocyte Serum; Blood Pressure; Gene Expression; Glomerulonephritis, Membranoproliferative; Imidazoles; Kidney; Male; Proteinuria; Rats; Rats, Wistar; Renin; Renin-Angiotensin System; RNA, Messenger; Tetrazoles

Augmented intrarenal ANG II stimulates IL-6, which contributes to renal injury. The expression of intrarenal angiotensinogen (AGT) is enhanced by increased intrarenal ANG II in human renin/human AGT double transgenic mice. ANG II also augments AGT expression in hepatocytes and cardiac myocytes. However, the mechanisms underlying AGT augmentation by ANG II and the contribution of IL-6 to this system are poorly understood. This study was performed in human renal proximal tubular epithelial cells (HRPTECs) to test the hypothesis that IL-6 contributes to the upregulation of AGT expression by ANG II. Human kidney-2 (HK-2) cells, immortalized HRPTECs, were incubated with 10(-7) M ANG II and/or 10 ng/ml IL-6 for up to 24 h. AGT mRNA and protein expressions were measured by real-time RT-PCR and ELISA, respectively. The activities of NF-kappaB and STAT3 were evaluated by Western blotting and EMSA. Stimulation with either ANG II or IL-6 did not significantly alter AGT mRNA or protein expression. In contrast, costimulation with ANG II and IL-6 significantly increased AGT mRNA and protein expressions (1.26 +/- 0.10 and 1.16 +/- 0.13 over control, respectively). Olmesartan, an ANG II type 1 receptor blocker, and an IL-6 receptor antibody individually inhibited this synergistic effect. NF-kappaB was also activated by costimulation with ANG II and IL-6. Phosphorylation and activity of STAT3 were increased by stimulation with IL-6 alone and by costimulation. The present study indicates that IL-6 plays an important role in ANG II-mediated augmentation of AGT expression in human renal proximal tubular cells.

Topics: Angiotensin II; Angiotensinogen; Cells, Cultured; Humans; Imidazoles; Interleukin-6; Kidney Tubules, Proximal; NF-kappa B; RNA, Messenger; STAT3 Transcription Factor; Tetrazoles; Up-Regulation

Topics: Angiotensin II; Angiotensinogen; Animals; Anti-Arrhythmia Agents; Buffers; Captopril; Diabetes Complications; Diabetes Mellitus, Experimental; Diffusion; Free Radical Scavengers; Imidazoles; Kallikreins; Mice; Mice, Transgenic; Myocardial Ischemia; Myocardium; Perfusion; Rats; Renin-Angiotensin System; Ribosomal Protein S6 Kinases, 90-kDa; Species Specificity; Tetrazoles