Physiologic homeostasis after pig-to-human kidney xenotransplantation.

Demand for kidney grafts outpaces supply, limiting kidney transplantation as a treatment for kidney failure. Xenotransplantation has the potential to make kidney transplantation available to many more patients with kidney failure, but the ability of xenografts to support human physiologic homeostasis has not been established. A brain-dead adult decedent underwent bilateral native nephrectomies followed by 10 gene-edited (four gene knockouts, six human transgenes) pig-to-human xenotransplantation. Physiologic parameters and laboratory values were measured for seven days in a critical care setting. Data collection aimed to assess homeostasis by measuring components of the renin-angiotensin-aldosterone system, parathyroid hormone signaling, glomerular filtration rate, and markers of salt and water balance. Mean arterial blood pressure was maintained above 60 mmHg throughout. Pig kidneys secreted renin (post-operative day three to seven mean and standard deviation: 47.3 ± 9 pg/mL). Aldosterone and angiotensin II levels were present (post-operative day three to seven, 57.0 ± 8 pg/mL and 5.4 ± 4.3 pg/mL, respectively) despite plasma renin activity under 0.6 ng/mL/hr. Parathyroid hormone levels followed ionized calcium. Urine output down trended from 37 L to 6 L per day with 4.5 L of electrolyte free water loss on post-operative day six. Aquaporin 2 channels were detected in the apical surface of principal cells, supporting pig kidney response to human vasopressin. Serum creatinine down trended to 0.9 mg/dL by day seven. Glomerular filtration rate ranged 90-240 mL/min by creatinine clearance and single-dose inulin clearance. Thus, in a human decedent model, xenotransplantation of 10 gene-edited pig kidneys provided physiologic balance for seven days. Hence, our in-human study paves the way for future clinical study of pig-to-human kidney xenotransplantation in living persons.

Renin-angiotensin-aldosterone system function in the pig-to-baboon kidney xenotransplantation model.

After pig-to-baboon kidney transplantation, episodes of hypovolemia and hypotension from an unexplained mechanism have been reported. This study evaluated the renin-angiotensin-aldosterone system post-kidney xenotransplantation. Kidneys from genetically-engineered pigs were transplanted into 5 immunosuppressed baboons after the excision of the native kidneys. Immunosuppressive therapy was based on the blockade of the CD40/CD154 costimulation pathway. Plasma renin, angiotensinogen (AGT), angiotensin II (Ang II), aldosterone levels, and urine osmolality and electrolytes were measured in healthy pigs, healthy nonimmunosuppressed baboons, and immunosuppressed baboons with life-supporting pig kidney grafts. After pig kidney transplantation, plasma renin and Ang II levels were not significantly different, although Ang II trended lower, even though plasma AGT and potassium were increased. Plasma aldosterone levels were unchanged. Urine osmolality and sodium concentration were decreased. Even in the presence of increasing AGT and potassium levels, lower plasma Ang II concentrations may be because of reduced, albeit not absent, the reactivity of pig renin to cleave baboon AGT, suggesting an impaired response of the renin-angiotensin-aldosterone system to hypovolemic and hypotensive episodes. The maintenance of aldosterone may be protective. The reduced urine osmolality and sodium concentration reflect the decreased ability of the pig kidney to concentrate urine. These considerations should not prohibit successful clinical pig kidney xenotransplantation.

Genetic Deletion of AT1a Receptor or Na+/H+ Exchanger 3 Selectively in the Proximal Tubules of the Kidney Attenuates Two-Kidney, One-Clip Goldblatt Hypertension in Mice.

The roles of angiotensin II (Ang II) AT1 (AT1a) receptors and its downstream target Na+/H+ exchanger 3 (NHE3) in the proximal tubules in the development of two-kidney, 1-clip (2K1C) Goldblatt hypertension have not been investigated previously. The present study tested the hypothesis that deletion of the AT1a receptor or NHE3 selectively in the proximal tubules of the kidney attenuates the development of 2K1C hypertension using novel mouse models with proximal tubule-specific deletion of AT1a receptors or NHE3. 2K1C Goldblatt hypertension was induced by placing a silver clip (0.12 mm) on the left renal artery for 4 weeks in adult male wild-type (WT), global Agtr1a−/−, proximal tubule (PT)-specific PT-Agtr1a−/− or PT-Nhe3−/− mice, respectively. As expected, telemetry blood pressure increased in a time-dependent manner in WT mice, reaching a maximal response by Week 3 (p < 0.01). 2K1C hypertension in WT mice was associated with increases in renin expression in the clipped kidney and decreases in the nonclipped kidney (p < 0.05). Plasma and kidney Ang II were significantly increased in WT mice with 2K1C hypertension (p < 0.05). Tubulointerstitial fibrotic responses were significantly increased in the clipped kidney (p < 0.01). Whole-body deletion of AT1a receptors completely blocked the development of 2K1C hypertension in Agtr1a−/− mice (p < 0.01 vs. WT). Likewise, proximal tubule-specific deletion of Agtr1a in PT-Agtr1a−/− mice or NHE3 in PT-Nhe3−/− mice also blocked the development of 2K1C hypertension (p < 0.01 vs. WT). Taken together, the present study provides new evidence for a critical role of proximal tubule Ang II/AT1 (AT1a)/NHE3 axis in the development of 2K1C Goldblatt hypertension.

Immunosuppression by Mycophenolate Mofetil Mitigates Intrarenal Angiotensinogen Augmentation in Angiotensin II-Dependent Hypertension.

Augmentation of intrarenal angiotensinogen (AGT) leads to further formation of intrarenal angiotensin II (Ang II) and the development of hypertensive kidney injury. Recent studies demonstrated that macrophages and the enhanced production of pro-inflammatory cytokines can be crucial mediators of renal AGT augmentation in hypertension. Accordingly, this study investigated the effects of immunosuppression by mycophenolate mofetil (MMF) on intrarenal AGT augmentation. Ang II (80 ng/min) was infused with or without daily administration of MMF (50 mg/kg) to Sprague-Dawley rats for 2 weeks. Mean arterial pressure (MAP) in Ang II infused rats was slightly higher (169.7 ± 6.1 mmHg) than the Ang II + MMF group (154.7 ± 2.0 mmHg), but was not statistically different from the Ang II + MMF group. MMF treatment suppressed Ang II-induced renal macrophages and IL-6 elevation. Augmentation of urinary AGT by Ang II infusion was attenuated by MMF treatment (control: 89.3 ± 25.2, Ang II: 1194 ± 305.1, and Ang II + MMF: 389 ± 192.0 ng/day). The augmentation of urinary AGT by Ang II infusion was observed before the onset of proteinuria. Elevated intrarenal AGT mRNA and protein levels in Ang II infused rats were also normalized by the MMF treatment (AGT mRNA, Ang II: 2.5 ± 0.2 and Ang II + MMF: 1.5 ± 0.1, ratio to control). Ang II-induced proteinuria, mesangial expansion and renal tubulointerstitial fibrosis were attenuated by MMF. Furthermore, MMF treatment attenuated the augmentation of intrarenal NLRP3 mRNA, a component of inflammasome. These results indicate that stimulated cytokine production in macrophages contributes to intrarenal AGT augmentation in Ang II-dependent hypertension, which leads to the development of kidney injury.

Angiotensin II biphasically regulates cell differentiation in human iPSC-derived kidney organoids.

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.NEW & NOTEWORTHY This study demonstrates angiotensin II exertion of biphasic effects on cell differentiation through distinct mediatory roles of angiotensin II type 1 receptor and type 2 receptor in human induced pluripotent stem cell-derived kidney organoids, providing a novel strategy to establish and further characterize the developmental potential of the human kidney organoids.

STAT1 regulates interferon-γ-induced angiotensinogen and MCP-1 expression in a bidirectional manner in primary cultured mesangial cells.

OBJECTIVE: Intrarenal interferon-γ significantly contributes to the development of glomerular injury in which angiotensinogen and monocyte chemoattractant protein 1 levels are elevated. However, the exact nature of the role that interferon-γ plays in regulating angiotensinogen and monocyte chemoattractant protein 1 expression has not been fully delineated. Therefore, the aim of this study was to investigate the role that interferon-γ plays in angiotensinogen and monocyte chemoattractant protein 1 expression. METHODS: Primary cultured rat mesangial cells were treated with 0-20 ng/mL interferon-γ for 2, 8 or 24 hours. Expression levels of angiotensinogen, monocyte chemoattractant protein 1, suppressors of cytokine signaling 1, an intracellular suppressor of Janus kinase-signal transducers and activators of transcription signaling and activity of the Janus kinase-signal transducers and activators of transcription pathway were evaluated by reverse transcriptase polymerase chain reaction and western blot analysis. RESULTS: Interferon-γ increased angiotensinogen expression in mesangial cells with maximal augmentation observed following 5 ng/mL interferon-γ at 8 hours of treatment (1.87 ± 0.05, mRNA, relative ratio). Further increases were reduced or absent using higher concentrations of interferon-γ. Following treatments, monocyte chemoattractant protein 1 expression was induced in a linear dose-dependent manner (6.85 ± 0.62-fold by 20 ng/mL interferon-γ at 24 hours). In addition, interferon-γ induced STAT1 phosphorylation and suppressors of cytokine signaling 1 expression in a linear dose-dependent manner. The suppression of STAT1 and suppressors of cytokine signaling 1 expression by small interference RNAs facilitated an increase in interferon-γ-induced angiotensinogen expression, indicating that these two factors negatively regulate angiotensinogen expression. In contrast, the increase in interferon-γ-induced monocyte chemoattractant protein 1 expression was attenuated in STAT1-deficient mesangial cells, suggesting that STAT1 positively regulates monocyte chemoattractant protein 1 expression in mesangial cells. CONCLUSION: These results demonstrate that while interferon-γ increases both angiotensinogen and monocyte chemoattractant protein 1 expression, STAT1 plays an opposing role in the regulation of each factor in mesangial cells.

Blockade of sodium-glucose cotransporter 2 suppresses high glucose-induced angiotensinogen augmentation in renal proximal tubular cells.

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 µM) 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 µM 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 HG-treated 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.

Canagliflozin Prevents Intrarenal Angiotensinogen Augmentation and Mitigates Kidney Injury and Hypertension in Mouse Model of Type 2 Diabetes Mellitus.

BACKGROUND: Hypertension and renal injury are common complications of type 2 diabetes mellitus (T2DM). Hyperglycemia stimulates renal proximal tubular angiotensinogen (AGT) expression via elevated oxidative stress contributing to the development of high blood pressure and diabetic nephropathy. The sodium glucose cotransporter 2 (SGLT2) in proximal tubules is responsible for the majority of glucose reabsorption by renal tubules. We tested the hypothesis that SGLT2 inhibition with canagliflozin (CANA) prevents intrarenal AGT augmentation and ameliorates kidney injury and hypertension in T2DM. METHODS: We induced T2DM in New Zealand obese mice with a high fat diet (DM, 30% fat) with control mice receiving regular fat diet (ND, 4% fat). When DM mice exhibited > 350 mg/dL blood glucose levels, both DM- and ND-fed mice were treated with 10 mg/kg/day CANA or vehicle by oral gavage for 6 weeks. We evaluated intrarenal AGT, blood pressure, and the development of kidney injury. RESULTS: Systolic blood pressure in DM mice (133.9 ± 2.0 mm Hg) was normalized by CANA (113.9 ± 4.0 mm Hg). CANA treatment ameliorated hyperglycemia-associated augmentation of renal AGT mRNA (148 ± 21 copies/ng RNA in DM, and 90 ± 16 copies/ng RNA in DM + CANA) and protein levels as well as elevation of urinary 8-isoprostane levels. Tubular fibrosis in DM mice (3.4 ± 0.9-fold, fibrotic score, ratio to ND) was suppressed by CANA (0.9 ± 0.3-fold). Furthermore, CANA attenuated DM associated increased macrophage infiltration and cell proliferation in kidneys of DM mice. CONCLUSIONS: CANA prevents intrarenal AGT upregulation and oxidative stress and which may mitigate high blood pressure, renal tubular fibrosis, and renal inflammation in T2DM.

Advanced Glycation End Products Stimulate Angiotensinogen Production in Renal Proximal Tubular Cells.

BACKGROUND: Elevated advanced glycation end products (AGE) in diabetes mellitus (DM) are implicated in the progression of DM-associated tissue injury, including diabetic nephropathy. The intrarenal renin-angiotensin system, in particular augmentation of angiotensinogen (AGT) in proximal tubular cells (PTC), plays a crucial role in the development of diabetic nephropathy. This study investigated hypothesis that AGE stimulates AGT production in PTC. MATERIALS AND METHODS: Urinary AGT and AGE levels in streptozotocin-induced DM mice were measured by enzyme-linked immunosorbent assays. AGT expression and secretion were evaluated in cultured rat PTC receiving 0-200 µg/ml AGE-BSA treatments for 24 hours. Furthermore, intracellular signaling pathways activated by AGE were elucidated. RESULTS: DM mice exhibited greater urinary AGT and AGE levels compared to control mice (AGT: 21.6 ± 5.5 ng/day vs. 190.1 ± 57.8 ng/day, AGE: 139.1 ± 21.6 µg/day vs. 332.8 ± 102.7 µg/day). In cultured PTC, treatment with AGE-BSA enhanced AGT mRNA expression (3.43 ± 0.11-fold compared to control), intracellular AGT protein levels (3.60 ± 0.38-fold), and secreted AGT levels (2.11 ± 0.18-fold). On the other hand, AGT levels were not altered in PTC receiving nonglycated BSA. Recombinant soluble AGE receptor, which competes with endogenous AGE receptor, diminished the AGE-induced AGT upregulation, suggesting that AGE-BSA stimulates AGT expression via activation of the AGE receptor. Enhanced phosphorylation of ERK1/2 and c-Jun, but not p38 MAP kinase, were observed in AGE-BSA-treated PTC. AGE-induced AGT augmentation was attenuated by an ERK inhibitor. CONCLUSIONS: The findings indicate that AGE enhances proximal tubular AGT expression via ERK1/2, which can exacerbate the development of diabetic related kidney injury.

2-Methoxyestradiol Reduces Angiotensin II-Induced Hypertension and Renal Dysfunction in Ovariectomized Female and Intact Male Mice.

Cytochrome P450 1B1 protects against angiotensin II (Ang II)-induced hypertension and associated cardiovascular changes in female mice, most likely via production of 2-methoxyestradiol. This study was conducted to determine whether 2-methoxyestradiol ameliorates Ang II-induced hypertension, renal dysfunction, and end-organ damage in intact Cyp1b1-/-, ovariectomized female, and Cyp1b1+/+ male mice. Ang II or vehicle was infused for 2 weeks and administered concurrently with 2-methoxyestradiol. Mice were placed in metabolic cages on day 12 of Ang II infusion for urine collection for 24 hours. 2-Methoxyestradiol reduced Ang II-induced increases in systolic blood pressure, water consumption, urine output, and proteinuria in intact female Cyp1b1-/- and ovariectomized mice. 2-Methoxyestradiol also reduced Ang II-induced increase in blood pressure, water intake, urine output, and proteinuria in Cyp1b1+/+ male mice. Treatment with 2-methoxyestradiol attenuated Ang II-induced end-organ damage in intact Cyp1b1-/- and ovariectomized Cyp1b1+/+ and Cyp1b1-/- female mice and Cyp1b1+/+ male mice. 2-Methoxyestradiol mitigated Ang II-induced increase in urinary excretion of angiotensinogen in intact Cyp1b1-/- and ovariectomized Cyp1b1+/+ and Cyp1b1-/- female mice but not in Cyp1b1+/+ male mice. The G protein-coupled estrogen receptor 1 antagonist G-15 failed to alter Ang II-induced increases in blood pressure and renal function in Cyp1b1+/+ female mice. These data suggest that 2-methoxyestradiol reduces Ang II-induced hypertension and associated end-organ damage in intact Cyp1b1-/-, ovariectomized Cyp1b1+/+ and Cyp1b1-/- female mice, and Cyp1b1+/+ male mice independent of G protein-coupled estrogen receptor 1. Therefore, 2-methoxyestradiol could serve as a therapeutic agent for treating hypertension and associated pathogenesis in postmenopausal females, and in males.

Sympathoinhibitory Effect of Radiofrequency Renal Denervation in Spontaneously Hypertensive Rats With Established Hypertension.

BACKGROUND: Radiofrequency ablation of the renal arteries (RF-ABL) has been shown to decrease blood pressure (BP) in drug-resistant hypertensive patients who receive antihypertensive drug therapy. However, there remain questions regarding how RF-ABL influences BP independent of drug therapy and whether complete renal denervation is necessary to maximally lower BP. To study these questions, we examined the cardiovascular, sympathetic, and renal effects produced by RF-ABL of the proximal renal arteries in spontaneously hypertensive rats (SHR) with established hypertension. METHODS: SHR were instrumented (telemetry) for measurement of systolic/diastolic BP (SBP/DBP). Rats then underwent Sham-ABL or RF-ABL adjacent to the renal ostium and BP was recorded for 8 weeks. Changes in sympathetic activity, 24-hour water/sodium excretion, and levels of urinary angiotensinogen (AGT), plasma renin activity, and kidney renin content (KRC) were measured in SHR. RESULTS: Compared with Sham-ABL, RF-ABL produced a sustained decrease in BP. At 8 weeks, SBP/DBP was 171±6/115±3 and 183±4/129±3mm Hg for RF-ABL and Sham-ABL SHR, respectively. Correlating with the reduction in BP, RF-ABL significantly decreased the low frequency/total and low frequency/high frequency of BP variability and attenuated the hypotensive response to chlorisondamine. Kidney norepinephrine levels were markedly decreased at 8 weeks in RF-ABL vs. Sham-ABL SHR. There were no group differences in 24-hour sodium/water excretion or urinary AGT excretion rate (6 weeks) or plasma renin activity or KRC (8 weeks). In other studies, concurrent RF-ABL plus surgical denervation initially decreased BP to a greater level than RF-ABL alone, but thereafter the reduction in BP between groups was not different. CONCLUSIONS: In hypertensive SHR, bilateral RF-ABL of the proximal renal arteries produced a sustained decease in sympathetic activity and BP without changes in sodium/water excretion or activity of the systemic/renal renin-angiotensin system.

Quantification of intact plasma AGT consisting of oxidized and reduced conformations using a modified ELISA.

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.

Increased angiotensinogen expression, urinary angiotensinogen excretion, and tissue injury in nonclipped kidneys of two-kidney, one-clip hypertensive rats.

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.

6ß-Hydroxytestosterone, a Cytochrome P450 1B1-Testosterone-Metabolite, Mediates Angiotensin II-Induced Renal Dysfunction in Male Mice.

6ß-Hydroxytestosterone, a cytochrome P450 1B1-derived metabolite of testosterone, contributes to the development of angiotensin II-induced hypertension and associated cardiovascular pathophysiology. In view of the critical role of angiotensin II in the maintenance of renal homeostasis, development of hypertension, and end-organ damage, this study was conducted to determine the contribution of 6ß-hydroxytestosterone to angiotensin II actions on water consumption and renal function in male Cyp1b1(+/+) and Cyp1b1(-/-) mice. Castration of Cyp1b1(+/+) mice or Cyp1b1(-/-) gene disruption minimized the angiotensin II-induced increase in water consumption, urine output, proteinuria, and sodium excretion and decreases in urine osmolality. 6ß-Hydroxytestosterone did not alter angiotensin II-induced increases in water intake, urine output, proteinuria, and sodium excretion or decreases in osmolality in Cyp1b1(+/+) mice, but restored these effects of angiotensin II in Cyp1b1(-/-) or castrated Cyp1b1(+/+) mice. Cyp1b1 gene disruption or castration prevented angiotensin II-induced renal fibrosis, oxidative stress, inflammation, urinary excretion of angiotensinogen, expression of angiotensin II type 1 receptor, and angiotensin-converting enzyme. 6ß-Hydroxytestosterone did not alter angiotensin II-induced renal fibrosis, inflammation, oxidative stress, urinary excretion of angiotensinogen, expression of angiotensin II type 1 receptor, or angiotensin-converting enzyme in Cyp1b1(+/+)mice. However, in Cyp1b1(-/-) or castrated Cyp1b1(+/+) mice, it restored these effects of angiotensin II. These data indicate that 6ß-hydroxytestosterone contributes to increased thirst, impairment of renal function, and end-organ injury associated with angiotensin II-induced hypertension in male mice and that cytochrome P450 1B1 could serve as a novel target for treating renal disease and hypertension in male mice.

Renoprotective effects of direct renin inhibition in glomerulonephritis.

The development of glomerulonephritis causes glomerular injury and renal dysfunction and is thought to increase renin release, thus activating the renin-angiotensin system (RAS). The aims of this study were to demonstrate activation of the intrarenal RAS and determine the effects of direct renin inhibition (DRI) on the progression of glomerulonephritis. Rats were treated with anti-Thy1.1 antibody with or without DRI, aliskiren (30 mg/kg/d). In the glomerulonephritic rats, protein, microalbumin excretion levels, urinary angiotensinogen excretion, glomerular expansion score and intrarenal transforming growth factor-ß and plasminogen activator inhibitor-1 mRNA levels were augmented compared with control rats; however, hypertension was not observed in the glomerulonephritic rats, and aliskiren treatment did not modify their blood pressure. The increases in urinary protein (94.7 ± 13.0 mg/d) and microalbumin (7.52 ± 2.6 mg/d) excretion were reduced by aliskiren (43.6 ± 4.5 mg/d of protein and 2.57 ± 0.7 mg/d of microalbumin). Furthermore, the progression of glomerular expansion and elevation of intrarenal transforming growth factor-ß and plasminogen activator inhibitor-1 levels were prevented by aliskiren. Importantly, aliskiren suppressed the augmentation of urinary angiotensinogen levels, the increased angiotensinogen expression in the kidneys and the increases in Ang II levels in renal medulla induced by the anti-Thy1.1 antibody. These results suggest that DRI with aliskiren prevents intrarenal RAS activation leading to mitigation of the development of glomerulonephritis. In addition, the renoprotective effects of DRI on glomerulonephritis occur in a blood pressure-independent manner. Accordingly, treatment with aliskiren may be an effective approach to treat glomerulonephritis and other intrarenal RAS-associated kidney diseases.

Tumor necrosis factor-{alpha} suppresses angiotensinogen expression through formation of a p50/p50 homodimer in human renal proximal tubular cells.

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

Adipose tissue-specific regulation of angiotensinogen in obese humans and mice: impact of nutritional status and adipocyte hypertrophy.

BACKGROUND: The adipose tissue renin-angiotensin system (RAS) has been implicated in the pathophysiology of obesity and dysfunction of adipose tissue. However, neither regulation of angiotensinogen (AGT) expression in adipose tissue nor secretion of adipose tissue-derived AGT has been fully elucidated in humans. METHODS: Human subcutaneous abdominal adipose tissue (SAT) biopsies were performed for 46 subjects with a wide range of body mass index (BMI). Considering the mRNA level of AGT and indices of body fat mass, the amount of adipose tissue-derived AGT secretion (A-AGT-S) was estimated. Using a mouse model of obesity and weight reduction, plasma AGT levels were measured with a newly developed enzyme-linked immunosorbent assay (ELISA), and the contribution of A-AGT-S to plasma AGT levels was assessed. RESULTS: A-AGT-S was substantially increased in obese humans and the value was correlated with the plasma AGT level in mice. A-AGT-S and plasma AGT were higher in obese mice, whereas lower in mice with weight reduction. However, the AGT mRNA levels in the liver, kidney, and aorta were not altered in the mouse models. In both humans and mice, the AGT mRNA levels in mature adipocytes (MAs) were comparable to those in stromal-vascular cells. Coulter Multisizer analyses revealed that AGT mRNA levels in the MAs were inversely correlated with the average size of mature adipocytes. CONCLUSIONS: This study demonstrates that adipose tissue-derived AGT is substantially augmented in obese humans, which may contribute considerably to elevated levels of circulating AGT. Adipose tissue-specific regulation of AGT provides a novel insight into the clinical implications of adipose tissue RAS in human obesity.

Intrarenal mouse renin-angiotensin system during ANG II-induced hypertension and ACE inhibition.

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(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(-1) x min(-1) for 12 days), ACEi only (ACEi = 10, lisinopril, 100 mg/l), 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 +/- 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 II (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). AT(1)R protein (by WB) was increased by ANG II (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 AT(1)R mRNA. In summary, reduced responses of intrarenal tubular renin, ACE, and the AT(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.

Activation of reactive oxygen species and the renin-angiotensin system in IgA nephropathy model mice.

1. Although IgA nephropathy is the most common form of primary glomerulopathy, the detailed mechanisms underlying its development remain uncertain. 2. In the present study, we used male high IgA strain of ddY (HIGA) mice as the IgA nephropathy model and age-matched male BALB/c mice as the control. Recent studies have demonstrated that reactive oxygen species (ROS)-dependent enhancement of the renin-angiotensin system (RAS) plays a potential role in the development and progression of renal injury. Therefore, in the present study we periodically measured the systolic blood pressure (SBP) of mice over the period 21-25 weeks of age and estimated markers for ROS, RAS and renal damage after mice had been killed at 25 weeks of age. 3. Markers for ROS (urinary 8-isoprostane excretion and renal 4-hydroxy-2-nonenal accumulation), RAS (renal angiotensinogen protein expression, urinary angiotensinogen excretion and renal angiotensin II) and renal damage (desmin-positive area and urinary protein excretion), as well as SBP, were significantly increased in HIGA mice compared with control BALB/c mice. 4. The data suggest that both ROS and the RAS are activated at an early phase in IgA nephropathy model mice.

Role of activated intrarenal reactive oxygen species and renin-angiotensin system in IgA nephropathy model mice.

1. Using HIGA (high IgA of ddY) mice as an IgA nephropathy model and BALB/c mice as controls, we demonstrated that reactive oxygen species (ROS) and the renin-angiotensin system (RAS) were activated in kidneys of HIGA mice. However, it was difficult to establish an association between renal damage and changes in ROS and the RAS. Therefore, the present study was performed to determine whether renal injury is associated with changes in ROS and the RAS in HIGA mice. 2. Male HIGA mice were divided into four groups of 10 each: (i) untreated mice (HIGA + null); (ii) mice treated with the angiotensin AT(1) receptor antagonist olmesartan (5 mg/kg per day; HIGA + OLM); (iii) mice treated with the superoxide dismutase mimetic tempol (50 mg/kg per day; HIGA + Tempol); and (iv) mice treated with RAS-independent antihypertensive drugs (30 mg/kg per day hydralazine, 0.6 mg/kg per day reserpine and 12 mg/kg per day hydrochlorothiazide; HIGA + HRH). Mice were treated for 5 weeks. 3. Systolic blood pressure decreased significantly in the HIGA + OLM and HIGA + HRH groups, but not in the HIGA + Tempol group, compared with HIGA + null mice. The expression of two ROS markers (4-hydroxy-2-nonenal and heme oxygenase-1) and angiotensin II as a marker of the RAS decreased significantly in HIGA + OLM and HIGA + Tempol mice, but not in HIGA + HRH mice, compared with HIGA + null mice. As a marker of renal damage, mesangial matrix expansion and the desmin-positive area decreased significantly in the HIGA + OLM and HIGA + Tempol groups, but not in HIGA + HRH group, compared with the HIGA + null group. 4. These data suggest that intrarenal ROS and RAS activation play a pivotal role in the development of IgA nephropathy model mice, from the early phase, independent of blood pressure.