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Angiotensinogen (AGT) expression in renal proximal tubular cells (RPTCs) and intrarenal tumor necrosis factor-[alpha] (TNF-[alpha]) levels are increased in hypertension and renal diseases However, the contribution of TNF-[alpha] to AGT expression in RPTCs has not been established. Therefore, the objective of the present study was to determine influence of TNF-[alpha] on AGT expression in RPTCs. Human kidney-2 (HK-2) cells, immortalized human RPTCs, were treated with several concentrations of TNF-[alpha] up to 24 h. AGT mRNA and protein expression were evaluated by RT-PCR and ELISA, respectively. Activation of nuclear factor-[kappa]B (NF-[kappa]B) by TNF-[alpha] was evaluated by Western blot analysis, immunocytochemistry, and electrophoretic mobility shift assay (EMSA). TNF-[alpha] suppressed AGT mRNA expression in a dose- and time-dependent manner. Maximum AGT mRNA reduction was caused by 40 ng/ml of TNF-[alpha] (0.52 [+ or -] 0.09, ratio to control, at 24 h) and at 24 h (0.66 [+ or -] 0.05, ratio to control, by 10 ng/ml TNF-[alpha]). TNF-[alpha] reduced AGT protein accumulation in the medium between 8 and 24 h (0.62 [+ or -] 0.13 by 40 ng/ml TNF-[alpha], ratio to control). TNF-[alpha] activated and induced translocalization of p50 and p65, which are NF-[kappa]B subunits. Elevated formation of p50/p65 and p50/p50 dimers by TNF-[alpha] were observed by EMSA and supershift assay. Gene silencing of p50, but not p65, attenuated the effect of TNF-[alpha] on reduction of AGT expression in RPTCs. These results indicate that TNF-[alpha] suppresses AGT expression through p50/p50 homodimer formation in human RPTCs, suggesting a possible counteracting mechanism that limits excessive intrarenal AGT production. nuclear factor-[kappa]B; human kidney-2 doi: 10.1152/ajpcell.00078.2010.

Am J Physiol Renal Physiol 298: F150-F157, 2010. First published October 21, 2009; doi:10.1152/ajprenal.00477.2009.--Angiotensin-converting enzyme (ACE) inhibition (ACEi) ameliorates the development of hypertension and the intrarenal ANG II augmentation in ANG II-infused mice. To determine if these effects are associated with changes in the mouse intrarenal renin-angiotensin system, the expression of angiotensinogen (AGT), renin, ACE, angiotensin type 1 receptor ([AT.sub.1]R) mRNA (by quanitative RT-PCR) and protein [by Western blot (WB) and/or immunohistochemistry (IHC)] were analyzed. C57BL/6J male mice (9-12 wk old) were distributed as controls (n = 10), ANG II infused (ANG II = 8,400 ng x [kg.sup.-1] x [min.sup.-1] for 12 days), ACEi only (ACEi = 10, lisinopril, 100 mg/1), and ANG II infused + ACEi (ANG II + ACEi = 11). When compared with controls (1.00), AGT protein (by WB) was increased by ANG II (1.29 [+ or -] 0.13, P < 0.05), and this was not prevented by ACEi (ACEi + ANG II, 1.31 [+ or -] 0.14, P < 0.05). ACE protein (by WB) was increased by ANG II (1.21 [+ or -] 0.08, P < 0.05), and it was reduced by ACEi alone (0.88 [+ or -] 0.07, P < 0.05) or in combination with ANG II (0.80 [+ or -] 0.07, P < 0.05). [AT.sub.1]R protein (by WB) was increased by ANG II (1.27 [+ or -] 0.06, P < 0.05) and ACEi (1.17 [+ or -] 0.06, P < 0.05) but not ANG II + ACEi [1.15 [+ or -] 0.06, not significant (NS)]. Tubular renin protein (semiquantified by IHC) was increased by ANG II (1.49 [+ or -] 0.23, P < 0.05) and ACEi (1.57 [+ or -] 0.15, P < 0.05), but not ANG II + ACEi (1.10 [+ or -] 0.15, NS). No significant changes were observed in AGT, ACE, or [AT.sub.1]R mRNA. In summary, reduced responses of intrarenal tubular renin, ACE, and the [AT.sub.1]R protein to the stimulatory effects of chronic ANG II infusions, in the presence of ACEi, are associated with the effects of this treatment to ameliorate augmentations in blood pressure and intrarenal ANG II content during ANG II-induced hypertension. angiotensin-converting enzyme; angiotensinogen; renin; lisinopril

The objectives of this study were to determine the effects of chronic angiotensin II (ANG II) infusions on ANG II content and angiotensinogen expression in the mouse kidney and the role of the angiotensin II type 1 receptor ([AT.sub.1]R) in mediating these changes. C57BL/6J male mice were subjected to ANG II infusions at doses of 400 or 1,000 ng x [kg.sup.-1] x [min.sup.-1] either alone or with an [AT.sub.1]R blocker (olmesartan; 3 mg x [kg.sup.-1] x [min.sup.-1]) for 12 days. Systolic and mean arterial pressures were determined by tail-cuff plethysmography and radiotelemetry. On day 13, blood and kidneys were collected for ANG II determinations by radioimmunoanalysis and intrarenal angiotensinogen expression studies by quantitative RT-PCR, Western blotting, and immunohistochemistry. ANG II infusions at the low dose elicited progressive increases in systolic blood pressure (135 [+ or -] 2.5 mmHg). In contrast, the high dose induced a rapid increase (152 [+ or -] 2.5, P < 0.05 vs. controls, 109 [+ or -] 2.8). Renal ANG II content was increased by ANG II infusions at the low dose (1,203 [+ or -] 253 fmol/g) and the high dose (1,258 [+ or -] 173) vs. controls (499 [+ or -] 40, P < 0.05). Kidney angiotensinogen mRNA and protein were increased only by the low dose to 1.13 [+ or -] 0.02 and 1.26 [+ or -] 0.10, respectively, over controls (1.00, P < 0.05). These effects were not observed in mice infused at the high dose and those receiving olmesartan. The results indicate that chronic ANG II infusions augment mouse intrarenal ANG II content with [AT.sub.1]R-dependent uptake occurring at both doses, but only the low dose of infusion, which elicited a slow progressive response, causes an [AT.sub.1]R-dependent increase in intrarenal angiotensinogen expression. telemetry; mouse kidney; hypertension

Augmented intrarenal ANG II stimulates 1L-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.sup.-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-[kappa]B 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 [+ or -] 0.10 and 1.16 [+ or -] 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-[kappa]B was also activated by costimulation with ANG II and 1L-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. angiotensinogen; kidney; renin-angiotensin system; cytokines

We recently reported that urinary excretion rates of angiotensinogen provide a specific index of the intrarenal renin-angiotensin system status in angiotensin II-dependent hypertensive rats. Angiotensinogen concentrations in mouse plasma are thought to be much lower than those in rat plasma; however, detailed information is deficient due to lack of direct quantitative measurements of rodent angiotensinogen. To elucidate this issue, we have developed a quantitative method for measurement of rodent angiotensinogen using a sandwich-type ELISA. The standard curve for mouse and rat angiotensinogen exhibited a high linearity at 0.16-10 and 0.08-5 ng/ml, respectively, with correlation coefficients >0.99. While plasma angiotensinogen concentrations of male high serum IgA (HIGA) mice (IgA nephritis model animals, 1,308 [+ or -] 47 ng/ml; n = 10) were lower than those of control BALB/c mice (1,620 [+ or -] 384; n = 12), urinary angiotensinogen concentrations of HIGA mice (14.6 [+ or -] 1.5 ng/ml; n = 34) were higher than those of BALB/c mice (4.6 [+ or -] 0.1; n = 2). In a similar manner, while plasma angiotensinogen concentrations of Zucker diabetic fatty (ZDF) obese rats (type 2 diabetic model animals, 1,789 [+ or -] 50 ng/ml; n = 5) were lower than those of control ZDF lean rats (2,296 [+ or -] 47; n = 5), urinary angiotensinogen concentrations of ZDF obese rats (88.2 [+ or -] 11.4 ng/ml; n = 15) were higher than those of ZDF lean rats (31.3 [+ or -] 1.9; n = 15). These data indicate that plasma and urinary angiotensinogen concentrations are less in mice than rats. However, these data suggest that urinary angiotensinogen levels are different from plasma angiotensinogen levels in rodents. The development of rodent angiotensinogen ELISA allows quantitative comparisons in mouse and rat angiotensinogen levels in models of hypertension and cardiovascular and kidney diseases. enzyme-linked immunosorbent assay; renin-angiotensin system; plasma; urine; mouse; rat

We recently reported that urinary excretion rates of angiotensinogen ([U.sub.AGT]) provide a specific index of intrarenal renin-angiotensin (ANG) system (RAS) status in ANG If-dependent hypertensive rats. When this is shown to be applicable to human subjects, a diagnostic test to identify those hypertensive patients most likely to respond to an RAS blockade could provide useful information to allow a mechanistic rationale for selection of an optimized approach to treatment of hypertensive patients. However, simple and accurate methods to measure human angiotensinogen (hAGT) are unavailable. For future studies of human subjects, we developed antibodies and a sensitive and specific quantification system for hAGT using a sandwich ELISA. We raised two antibodies against hAGT: a mouse monoclonal antibody and a rabbit polyclonal antibody. The standard curve of this ELISA exhibited a high linearity (0.31-20 ng/ml). The correlation coefficient was >0.99. Plasma angiotensinogen concentrations of healthy volunteers ranged from 28 to 71 [micro]g/ml (n = 10). The ratio of [U.sub.AGT] to urinary creatinine concentration ranged from 5.0 to 30 [micro]g/g (n = 7). Intra- and interassay coefficients of variation ranged from 4.4 to 5.5% and from 4.3 to 7.0%, respectively. This ELISA system had no cross-reactivity with major proteins in proteinuric urine samples, such as human albumin, immunoglobulin, or transferrin. Moreover, the cross-reactivity of the system with angiotensin peptides was also negligible. This hAGT ELISA will be a useful tool to investigate the relationship of [U.sub.AGT] and reactivity to antihypertensive drugs in hypertensive patients. renin-angiotensin system; plasma; urine

This study was performed in transgenic mice to test the hypothesis that the selective intrarenal overproduction of ANG II increases intrarenal mouse (m) angiotensinogen (AGT) expression. We used the following three groups: 1) single transgenic mice (group A, n = 14) expressing human (h) AGT only in the kidney, 2) double-transgenic mice (group D, n = 13) expressing human renin systemically in addition to hAGT only in the kidney, and 3) wild-type (group W, n = 12) mice. Exogenous hAGT protein is inactive in group A because endogenous mouse renin cannot cleave hAGT to ANG I because of a high species specificity. All mice were monitored from 12 to 18 wk of age. Systolic blood pressure progressively increased from 116 [+ or -] 5 mmHg (12 wk) to 140 [+ or -] 7 (18 wk) in group D. This increase was not observed in groups A or W. Intrarenal hAGT levels were similar in groups A and D; however, hAGT was not detectable in kidneys of group W. Kidney ANG II levels were increased in group D (216 [+ or -] 43 fmol/g) compared with groups A (117 [+ or -] 16) and W (118 [+ or -] 17). However, plasma ANG II concentrations were similar among the three groups. Endogenous renal mAGT mRNA was increased significantly in group D (1.46 [+ or -] 0.19, ratio) compared with groupsA (0.97 [+ or -]0.12) and W (1.00 [+ or -] 0.08). Endogenous renal mAGT protein was also significantly increased in group D compared with groups A and W. Interstitial collagen-positive area, interstitial macrophage/monocyte infiltration, and afferent arteriolar wall thickness were increased significantly in group D compared with groups A and W. These data indicate for the first time that the selective stimulation of intrarenal production of ANG II from hAGT augments endogenous intrarenal mAGT mRNA and protein expression. hypertension; transgenic mouse; angiotensin II; renal injury

Human kidney organoid technology holds promise for novel kidney disease treatment strategies and utility in pharmacological and basic science. Given the crucial roles of the intrarenal renin-angiotensin system (RAS) and angiotensin II (ANG II) in the progression of kidney development and injury, we investigated the expression of RAS components and effects of ANG II on cell differentiation in human kidney organoids. Human induced pluripotent stem cell-derived kidney organoids were induced using a modified 18-day Takasato protocol. Gene expression analysis by digital PCR and immunostaining demonstrated the formation of renal compartments and expression of RAS components. The ANG II type 1 receptor (AT1R) was strongly expressed in the early phase of organoid development (around day 0), whereas ANG II type 2 receptor (AT2R) expression levels peaked on day 5. Thus, the organoids were treated with 100 nM ANG II in the early phase on days 0-5 (ANG II-E) or during the middle phase on days 5-10 (ANG II-M). ANG II-E was observed to decrease levels of marker genes for renal tubules and proximal tubules, and the downregulation of renal tubules was inhibited by an AT1R antagonist. In contrast, ANG II-M increased levels of markers for podocytes, the ureteric tip, and the nephrogenic mesenchyme, and an AT2R blocker attenuated the ANG II-M-induced augmentation of podocyte formation. These findings demonstrate RAS expression and ANG II exertion of biphasic effects on cell differentiation through distinct mediatory roles of AT1R and AT2R, providing a novel strategy to establish and further characterize the developmental potential of human induced pluripotent stem cell-derived kidney organoids. [ABSTRACT FROM AUTHOR]

Renal proximal tubular angiotensinogen (AGT) is increased by hyperglycemia (HG) in diabetes mellitus, which augments intrarenal angiotensin II formation, contributing to the development of hypertension and kidney injury. Sodium-glucose cotransporter 2 (SGLT2) is abundantly expressed in proximal tubular cells (PTCs). The present study investigated the effects of canagliflozin (CANA), a SGLT2 inhibitor, on HG-induced AGT elevation in cultured PTCs. Mouse PTCs were treated with 5-25 mM glucose. CANA (0-10 œM) was applied 1 h before glucose treatment. Glucose (10 mM) increased AGT mRNA and protein levels at 12 h (3.06 ± 0.48-fold in protein), and 1 and 10 œM CANA as well as SGLT2 shRNA attenuated the AGT augmentation. CANA did not suppress the elevated AGT levels induced by 25 mM glucose. Increased AGT expression induced by treatment with pyruvate, a glucose metabolite that does not require SGLT2 for uptake, was not attenuated by CANA. In HG-treated PTCs, intracellular reactive oxygen species levels were elevated compared with baseline (4.24 ± 0.23-fold), and these were also inhibited by CANA. Furthermore, tempol, an antioxidant, attenuated AGT upregulation in HGtreated PTCs. HG-induced AGT upregulation was not inhibited by an angiotensin II receptor antagonist, indicating that HG stimulates AGT expression in an angiotensin II-independent manner. These results indicate that enhanced glucose entry via SGLT2 into PTCs elevates intracellular reactive oxygen species generation by stimulation of glycolysis and consequent AGT augmentation. SGLT2 blockade limits HG-induced AGT stimulation, thus reducing the development of kidney injury in diabetes mellitus. [ABSTRACT FROM AUTHOR]

Increased dietary salt triggers oxidative stress and kidney injury in salt-sensitive hypertension; however, the mechanism for sensing increased extracellular Na+ concentration ([Na+]) remains unclear. A Na+-activated Na+ channel (Na sensor) described in the brain operates as a sensor of extracellular fluid [Na+]; nonetheless, its presence in the kidney has not been established. In the present study, we demonstrated the gene expression of the Na sensor by RT-PCR and Western blotting in the Sprague- Dawley rat kidney. Using immunofluorescence, the Na sensor was localized to the luminal side in tubular epithelial cells of collecting ducts colocalizing with aquaporin-2, a marker of principal cells, and in thick ascending limb, colocalizing with the glycoprotein Tamm- Horsfall. To determine the effect of a high-salt diet (HSD) on Na sensor gene expression, we quantified its transcript and protein levels primarily in renal medullas from control rats and rats subjected to 8% NaCl for 7 days (n = 5). HSD increased Na sensor expression levels (mRNA: from 1.2 ± 0.2 to 5.1 ± 1.3 au; protein: from 0.98 ± 0.15 to 1.74 ± 0.28 au P < 0.05) in the kidney medulla, but not in the cortex. These data indicate that rat kidney epithelial cells of the thick ascending limb and principal cells of the collecting duct possess a Na sensor that is upregulated by HSD, suggesting an important role in monitoring changes in tubular fluid [Na+]. [ABSTRACT FROM AUTHOR]

Alterations in the balance between ANG II/ACE and ANG 1-7/ACE2 in ANG II-dependent hypertension could reduce the generation of ANG 1-7 and contribute further to increased intrarenal ANG II. Upregulation of collecting duct (CD) renin may lead to increased ANG II formation during ANG II-dependent hypertension, thus contributing to this imbalance. We measured ANG I, ANG II, and ANG 1-7 contents, angiotensin-converting enzyme (ACE) and ACE2 gene expression, and renin activity in the renal cortex and medulla in the clipped kidneys (CK) and nonclipped kidneys (NCK) of 2K1C rats. After 3 wk of unilateral renal clipping, systolic blood pressure and plasma renin activity increased in 2K1C rats (n = 11) compared with sham rats (n = 9). Renal medullary angiotensin peptide levels were increased in 2K1C rats [ANG I: (CK = 171 ± 4; NCK = 251 ± 8 vs. sham = 55 ± 3 pg/g protein; P < 0.05); ANG II: (CK = 558 ± 79; NCK = 328 ± 18 vs. sham = 94 ± 7 pg/g protein; P < 0.001)]; and ANG 1-7 levels decreased (CK = 18 ± 2; NCK = 19 ± 2 pg/g vs. sham = 63 ± 10 pg/g; P < 0.001). In renal medullas of both kidneys of 2K1C rats, ACE mRNA levels and activity increased but ACE2 decreased. In further studies, we compared renal ACE and ACE2 mRNA levels and their activities from chronic ANG II-infused (n = 6) and sham-operated rats (n = 5). Although the ACE mRNA levels did not differ between ANG II rats and sham rats, the ANG II rats exhibited greater ACE activity and reduced ACE2 mRNA levels and activity. Renal medullary renin activity was similar in the CK and NCK of 2K1C rats but higher compared with sham. Thus, the differential regulation of ACE and ACE2 along with the upregulation of CD renin in both the CK and NCK in 2K1C hypertensive rats indicates that they are independent of perfusion pressure and contribute to the altered content of intrarenal ANG II and ANG 1-7. [ABSTRACT FROM AUTHOR]

Angiotensin-converting enzyme (ACE) inhibition (ACEi) ameliorates the development of hypertension and the intrarenal ANG II augmentation in ANG Il-infused mice. To determine if these effects are associated with changes in the mouse intrarenal renin-angiotensin system, the expression of angiotensinogen (AGT), renin, ACE, angiotensin type I receptor (AT1R) mRNA (by quanitative RT-PCR) and protein [by Western blot (WB) and/or immunohistochemistry (IHC)] were analyzed. C57BL/6J male mice (9-12 wk old) were distributed as controls (n = 10), ANG II infused (ANG II = 8,400 ng∙kg-1∙min-1 for 12 days), ACEi only (ACEi = 10, lisinopril, 100 mg/I), and ANG 11 infused + ACEi (ANG 11 + ACEi = Ii). When compared with controls (1.00), AGT protein (by WB) was increased by ANG 11 (1.29 ± 0.13, P < 0.05), and this was not prevented by ACEi (ACEi + ANG II, 1.31 ± 0.14, P <0.05). ACE protein (by WB) was increased by ANG 11(1.21 ± 0.08, P < 0.05), and it was reduced by ACEi alone (0.88 ± 0.07, P < 0.05) or in combination with ANG II (0.80 ± 0.07, P < 0.05). AT1R protein (by WB) was increased by ANG 11(1.27 ± 0.06, P < 0.05) and ACEi (1.17 ± 0.06, P < 0.05) but not ANG II + ACEi [1.15 ± 0.06, not significant (NS)]. Tubular renin protein (semiquantified by IHC) was increased by ANG II (1.49 ± 0.23, P < 0.05) and ACEi (1.57 ± 0.15, P < 0.05), but not ANG II + ACEi (1.10 ± 0.15, NS). No significant changes were observed in AGT, ACE, or AT1R mRNA. In summary, reduced responses of intrarenal tubular renin, ACE, and the AT1R protein to the stimulatory effects of chronic ANG II infusions, in the presence of ACEi, are associated with the effects of this treatment to ameliorate augmentations in blood pressure and intrarenal ANG II content during ANG Il-induced hypertension. [ABSTRACT FROM AUTHOR]

The objectives of this study were to determine the effects of chronic angiotensin H (ANG II) infusions on ANG II content and angiotensinogen expression in the mouse kidney and the role of the angiotensin II type 1 receptor (AT1R) in mediating these changes. C57BL/6J male mice were subjected to ANG II infusions at doses of 400 or 1,000 ng·kg-1 min-1 either alone or with an AT1R blocker (olmesartan; 3 mg·kg-1·day-1) for 12 days. Systolic and mean arterial pressures were determined by tail-cuff plethysmography and radiotelemetry. On day 13, blood and kidneys were collected for ANG H determinations by radioimmunoanalysis and intra-renal angiotensinogen expression studies by quantitative RT-PCR, Western blotting, and immunohistochemistry. ANG II infusions at the low dose elicited progressive increases in systolic blood pressure (135 ± 2.5 mmHg). In contrast, the high dose induced a rapid increase (152 ± 2.5, P <0.05 vs. controls, 109 ± 2.8). Renal ANG II content was increased by ANG II infusions at the low dose (1,203 ± 253 fmol/g) and the high dose (1,258 ± 173) vs. controls (499 ± 40, P < 0.05). Kidney angiotensinogen mRNA and protein were increased only by the low dose to 1.13 ± 0.02 and 1.26 ± 0.10, respectively, over controls (1.00, P < 0.05). These effects were not observed in mice infused at the high dose and those receiving olmesartan. The results indicate that chronic ANG II infusions augment mouse intrarenal ANG II content with AT1R-dependent uptake occurring at both doses, but only the low dose of infusion, which elicited a slow progressive response, causes an AT1R-dependent increase in intrarenal angiotensinogen expression. [ABSTRACT FROM AUTHOR]

The pleiotropic actions of the renin-angiotensin system (RAS) depend on the availability of angiotensinogen (AGT) which generates angiotensin I (ANG I) when cleaved by renin. Thus, quantification of the intact AGT (iAGT) concentrations is important to evaluate the actual renin substrate available. The iAGT conformation exists as oxidized AGT (oxi-AGT) and reduced AGT (red-AGT) in a disulfide bond, and oxi-AGT has a higher affinity for renin, which may exacerbate RAS-associated diseases. Accordingly, we determined iAGT, oxi-AGT, and red-AGT levels in plasma from rats and mice. Blood samples were obtained by cardiac puncture and then immediately mixed with an inhibitor solution containing a renin inhibitor. Total AGT (tAGT) levels were measured by tAGT ELISA which detects both cleaved and iAGT. iAGT levels were determined by iAGT ELISA which was found to only detect red-AGT. Thus, it was necessary to treat samples with dithiothreitol, a reducing agent, to quantify total iAGT concentration. tAGT levels in rat and mouse plasma were 1,839 ± 139 and 1,082 ± 77 ng/ml, respectively. iAGT levels were 53% of tAGT in rat plasma but only 22% in mouse plasma, probably reflecting the greater plasma renin activity in mice. The ratios of oxi-AGT and red-AGT were ∼4:1 (rat) and 16:1 (mouse). Plasma iAGT consists of oxi-AGT and red-AGT, suggesting that oxidative stress can influence ANG I generation by the AGT conformation switch. Furthermore, the lower availability of plasma iAGT in mice suggests that it may serve as a limiting factor in ANG I formation in this species., (Copyright © 2016 the American Physiological Society.)

In angiotensin II (ANG II)-dependent hypertension, there is an angiotensin type 1 receptor-dependent amplification mechanism enhancing intrarenal angiotensinogen (AGT) formation and secretion in the tubular fluid. To evaluate the role of increased arterial pressure, AGT mRNA, protein expression, and urinary AGT (uAGT) excretion and tissue injury were assessed in both kidneys of two-kidney, one-clip Sprague-Dawley hypertensive rats subjected to left renal arterial clipping (0.25-mm gap). By 18-21 days, systolic arterial pressure increased to 180 ± 3 mmHg, and uAGT increased. Water intake, body weights, 24-h urine volumes, and sodium excretion were similar. In separate measurements of renal function in anesthetized rats, renal plasma flow and glomerular filtration rate were similar in clipped and nonclipped kidneys and not different from those in sham rats, indicating that the perfusion pressure to the clipped kidneys remained within the autoregulatory range. The nonclipped kidneys exhibited increased urine flow and sodium excretion. The uAGT excretion was significantly greater in nonclipped kidneys compared with clipped and sham kidneys. AGT mRNA was 2.15-fold greater in the nonclipped kidneys compared with sham (1.0 ± 0.1) or clipped (0.98 ± 0.15) kidneys. AGT protein levels were also greater in the nonclipped kidneys. The nonclipped kidneys exhibited greater glomerular expansion and immune cell infiltration, medullary fibrosis, and cellular proliferation than the clipped kidneys. Because both kidneys have elevated ANG II levels, the greater tissue injury in the nonclipped kidneys indicates that an increased arterial pressure synergizes with increased intrarenal ANG II to stimulate AGT production and exert greater renal injury., (Copyright © 2016 the American Physiological Society.)

The development of ANG II-dependent hypertension involves increased infiltration of macrophages (MΦ) and T cells into the kidney and the consequent elevation of intrarenal cytokines including IL-6, which facilitates the progression of hypertension and associated kidney injury. Intrarenal renin-angiotensin system (RAS) activation, including proximal tubular angiotensinogen (AGT) stimulation, has also been regarded as a cardinal mechanism contributing to these diseases. However, the interaction between immune cells and intrarenal RAS activation has not been fully delineated. Therefore, the present study investigated whether ANG II-treated MΦ induce AGT upregulation in renal proximal tubular cells (PTCs). MΦ were treated with 0-10(-6) M ANG II for up to 48 h. PTCs were incubated with the collected medium from MΦ. In ANG II-treated MΦ, IL-6 mRNA and protein levels were increased (1.86 ± 0.14, protein level, ratio to control); moreover, IL-6 levels were higher than TNF-α and IL-1β in culture medium isolated from ANG II-treated MΦ. Elevated AGT expression (1.69 ± 0.04, ratio to control) accompanied by phosphorylated STAT3 were observed in PTCs that received culture medium from ANG II-treated MΦ. The addition of a neutralizing IL-6 antibody to the collected medium attenuated phosphorylation of STAT3 and AGT augmentation in PTCs. Furthermore, a JAK2 inhibitor also suppressed STAT3 phosphorylation and AGT augmentation in PTCs. These results demonstrate that ANG II-induced IL-6 elevation in MΦ enhances activation of the JAK-STAT pathway and consequent AGT upregulation in PTCs, suggesting involvement of an immune response in driving intrarenal RAS activity., (Copyright © 2016 the American Physiological Society.)

In angiotensin II (ANG II)-dependent hypertension, the augmented intrarenal ANG II constricts the renal microvasculature and stimulates Rho kinase (ROCK), which modulates vascular contractile responses. Rho may also stimulate angiotensinogen (AGT) expression in preglomerular vascular smooth muscle cells (VSMCs), but this has not been established. Therefore, the aims of this study were to determine the direct interactions between Rho and ANG II in regulating AGT and other renin-angiotensin system (RAS) components and to elucidate the roles of the ROCK/NF-κB axis in the ANG II-induced AGT augmentation in primary cultures of preglomerular VSMCs. We first demonstrated that these preglomerular VSMCs express renin, AGT, angiotensin-converting enzyme, and ANG II type 1 (AT1) receptors. Furthermore, incubation with ANG II (100 pmol/l for 24 h) increased AGT mRNA (1.42 ± 0.03, ratio to control) and protein (1.68 ± 0.05, ratio to control) expression levels, intracellular ANG II levels, and NF-κB activity. In contrast, the ANG II treatment did not alter AT1a and AT1b mRNA levels in the cells. Treatment with H-1152 (ROCK inhibitor, 10 nmol/l) and ROCK1 small interfering (si) RNA suppressed the ANG II-induced AGT augmentation and the upregulation and translocalization of p65 into nuclei. Functional studies showed that ROCK exerted a greater influence on afferent arteriole responses to ANG II in rats subjected to chronic ANG II infusions. These results indicate that ROCK is involved in NF-κB activation and the ROCK/NF-κB axis contributes to ANG II-induced AGT upregulation, leading to intracellular ANG II augmentation.