Klotho supplementation ameliorates blood pressure and renal function in DBA/2-pcy mice, a model of polycystic kidney disease.

Klotho interacts with various membrane proteins such as receptors for transforming growth factor-ß (TGF-ß) and insulin-like growth factor (IGF). Renal expression of klotho is diminished in polycystic kidney disease (PKD). In the present study, the effects of klotho supplementation on PKD were assessed. Recombinant human klotho protein (10 µg·kg-1·day-1) or a vehicle was administered daily by subcutaneous injection to 6-wk-old mice with PKD (DBA/2-pcy). Blood pressure was measured using tail-cuff methods. After 2 mo, mice were killed, and the kidneys were harvested for analysis. Exogenous klotho protein supplementation reduced kidney weight, cystic area, systolic blood pressure, renal angiotensin II levels, and 8-epi-PGF2α excretion (P < 0.05). Klotho protein supplementation enhanced glomerular filtration rate, renal expression of superoxide dismutase, and klotho itself (P < 0.05). Klotho supplementation attenuated renal expressions of TGF-ß and collagen type I and diminished renal abundance of Twist, phosphorylated Akt, and mammalian target of rapamycin (P < 0.05). Pathological examination revealed that klotho decreased the fibrosis index and nuclear staining of Smad in PKD kidneys (P < 0.05). Our data indicate that klotho protein supplementation ameliorates the renin-angiotensin system, reducing blood pressure in PKD mice. Furthermore, the present results implicate klotho supplementation in the suppression of Akt/mammalian target of rapamycin signaling, slowing cystic expansion. Finally, our findings suggest that klotho protein supplementation attenuated fibrosis at least partly by inhibiting epithelial mesenchymal transition in PKD.

Interactions between Host PPARs and Gut Microbiota in Health and Disease.

The human gastrointestinal tract is inhabited by many types of microbiota, including bacteria, viruses, and fungi. Dysregulations of their microenvironment are associated with various health problems, not only limited to gastrointestinal disorders, such as inflammatory bowel disease, but to impacts beyond the intestine. For example, intestinal microbiota can affect the liver in non-alcoholic fatty liver disease, visceral adipose tissue during adipogenesis, and the heart in atherosclerosis. The factors contributing to these pathogeneses involve the gut microbiota and the effector organs of the host, and everything in between. The nuclear receptor peroxisome proliferator-activated receptors (PPARs) are pivotal for the modulation of many of the pathogeneses mentioned above. It is, therefore, conceivable that, in the process of host-microbiota interactions, PPARs play important roles. In this review, we focus on the interactions between host PPARs in different organs and gut microbiota and their impacts on maintaining health and various diseases.

PPARγ activation mitigates glucocorticoid receptor-induced excessive lipolysis in adipocytes via homeostatic crosstalk.

Proper balance between lipolysis and lipogenesis in adipocytes determines the release of free fatty acids (FFA) and glycerol, which is crucial for whole body lipid homeostasis. Although, dysregulation of lipid homeostasis contributes to various metabolic complications such as insulin resistance, the regulatory mechanism remains elusive. This study clarified the individual and combined roles for glucocorticoid receptor (GCR) and peroxisome proliferator-activated receptor (PPAR)γ pathways in lipid metabolism of adipocytes. In mature 3T3-L1 adipocytes, GCR activation using dexamethasone upregulated adipose triglyceride lipase (ATGL) and downregulated phosphoenolpyruvate carboxykinase (PEPCK), resulting in enhanced glycerol release into the medium. In contrast, PPARγ ligand pioglitazone modestly upregulated ATGL and hormone sensitive lipase (HSL), but markedly enhanced PEPCK and glycerol kinase (GK), thereby suppressed glycerol release. Dexamethasone showed permissive like effect on PPARγ target genes including perilipin A and aP2, therefore co-administration of dexamethasone and pioglitazone demonstrated synergistic upregulation of these enzymes excepting PEPCK, of which downregulation by dexamethasone was abolished by pioglitazone to the level above control. Thus, the excessive glycerol release was prevented as the net outcome of the co-administration. Consistently, the bodipy stain demonstrated that dexamethasone reduced the amount of cytosolic lipid, which was preserved in co-treated adipocytes. Moreover, silencing of PPARγ suppressed the synergistic effects of co-treatment on the lipolytic and lipogenic genes, and therefore the GCR pathway indeed involves PPARγ. In conclusion, crosstalk between GCR and PPARγ is largely synergistic but counter-regulatory in lipogenic genes, of which enhancement prevents excessive glycerol and possibly FFA release by glucocorticoids into the circulation.

Effect of a SGLT2 inhibitor on the systemic and intrarenal renin-angiotensin system in subtotally nephrectomized rats.

We aimed to examine the effects of a sodium glucose co-transporter 2 (SGLT2) inhibitor on systemic and intrarenal renin-angiotensin system (RAS) in subtotally nephrectomized non-diabetic rats, a model of chronic kidney disease (CKD). Oral administration of the selective SGLT2 inhibitor, TA-1887 (10 mg/kg/day), for 10 weeks induced glycosuria. However, plasma renin activity, plasma angiotensinogen levels, kidney angiotensin II contents and renal injury were not significantly affected by TA-1887. These data indicate that chronic treatment with an SGLT2 inhibitor does not activate the systemic and intrarenal RAS in subjects with non-diabetic CKD.

Add-On Effect of Angiotensin Receptor Blockade (Candesartan) on Clinical Remission in Active IgA Nephropathy Patients Treated with Steroid Pulse Therapy and Tonsillectomy: a Randomized, Parallel-Group Comparison Trial.

BACKGROUND/AIMS: Angiotensin receptor blockers (ARBs) may be beneficial for clinical remission during conventional therapy with tonsillectomy and steroid pulse (TSP) for active IgA nephropathy. METHODS: Seventy-seven patients with active IgA nephropathy were randomly assigned to the control arm with conventional regimen (TSP followed by oral prednisolone) (n = 37) or the ARB arm with conventional regimen plus ARB candesartan for the first 6 months (n = 40). Patients not achieving proteinuria remission at 12 months in either arm were administered candesartan, which was titrated until the 24-month follow-up. The primary endpoints were remission of proteinuria (< 0.3 g/gCr) and hematuria at 12 months. RESULTS: Baseline proteinuria (g/g Cr) were comparable between the control and ARB arm (1.02 vs. 0.97, P = 0.97). Similarly, cumulative remission rates at 6, 12, and 24 months were comparable between the control and ARB arms (37.8% vs. 35% [P = 0.80], 48.7% vs. 38.5% [P = 0.37], 71.4% vs. 51.3% [P = 0.08]). Proteinuria, which was slightly worse in the control arm than in the ARB arm at 6 months, was comparable afterwards (0.20 vs. 0.23 g/g Cr at 12 months; 0.12 vs. 0.13 g/g Cr at 24 months). Significant reductions observed in urinary angiotensinogen were almost comparable between the two treatment arms at both 6 and 12 months. CONCLUSION: Early candesartan treatment combined with TSP may not benefit clinical remission regardless of the blood pressure. ARB titration later during the treatment might provide benefit for patients with active IgA nephropathy.

Independent regulation of renin-angiotensin-aldosterone system in the kidney.

Renin-angiotensin-aldosterone system (RAAS) plays important roles in regulating renal hemodynamics and functions, as well as in the pathophysiology of hypertension and renal disease. In the kidney, angiotensin II (Ang II) production is controlled by independent multiple mechanisms. Ang II is compartmentalized in the renal interstitial fluid with much higher concentrations than those existing in the circulation. Inappropriate activation of the intrarenal RAAS is an important contributor to the pathogenesis of hypertension and renal injury. It has been revealed that intrarenal Ang II levels are predominantly regulated by angiotensinogen and therefore, urinary angiotensinogen could be a biomarker for intrarenal Ang II generation. In addition, recent studies have demonstrated that aldosterone contributes to the progression of renal injury via direct actions on glomerular podocytes, mesangial cells, proximal tubular cells and tubulo-interstitial fibroblasts through the activation of locally expressed mineralocorticoid receptor. Thus, it now appears that intrarenal RAAS is independently regulated and its inappropriate activation contributes to the pathogenesis of the development of hypertension and renal disease. This short review article will focus on the independent regulation of the intrarenal RAAS with an emphasis on the specific role of angiotensinogen.

Altered Circadian Timing System-Mediated Non-Dipping Pattern of Blood Pressure and Associated Cardiovascular Disorders in Metabolic and Kidney Diseases.

The morning surge in blood pressure (BP) coincides with increased cardiovascular (CV) events. This strongly suggests that an altered circadian rhythm of BP plays a crucial role in the development of CV disease (CVD). A disrupted circadian rhythm of BP, such as the non-dipping type of hypertension (i.e., absence of nocturnal BP decline), is frequently observed in metabolic disorders and chronic kidney disease (CKD). The circadian timing system, controlled by the central clock in the suprachiasmatic nucleus of the hypothalamus and/or by peripheral clocks in the heart, vasculature, and kidneys, modulates the 24 h oscillation of BP. However, little information is available regarding the molecular and cellular mechanisms of an altered circadian timing system-mediated disrupted dipping pattern of BP in metabolic disorders and CKD that can lead to the development of CV events. A more thorough understanding of this pathogenesis could provide novel therapeutic strategies for the management of CVD. This short review will address our and others' recent findings on the molecular mechanisms that may affect the dipping pattern of BP in metabolic dysfunction and kidney disease and its association with CV disorders.

Klotho suppresses the renin-angiotensin system in adriamycin nephropathy.

BACKGROUNDS: Klotho protein interacts with the transforming growth factor ß (TGF-ß) receptor and Wnt, which contribute to the progression of renal disease, inhibiting their signals. Renal and circulating klotho levels are diminished in chronic kidney disease. METHODS: Experiments were performed to assess whether supplementation of klotho protein could have protective effects on the kidney. Rats were injected with adriamycin (5 mg/kg) and divided into three groups: those treated with vehicle, those treated with klotho protein and those treated with klotho plus 4-benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione (TDZD). Rats without adriamycin treatment were used as a control. RESULTS: Adriamycin reduced the serum klotho concentration and renal expression of klotho and E-cadherin. Adriamycin also increased the renal expression of Wnt, TGF-ß, and angiotensinogen, as well as the renal abundance of ß-catenin and angiotensin II. Klotho supplementation suppressed adriamycin-induced elevations of ß-catenin and angiotensin II with sustained Wnt expression. Combined treatment with klotho and TDZD reversed the klotho-induced improvements in the renal abundance of ß-catenin and angiotensin II as well as the expression of TGF-ß and angiotensinogen without affecting E-cadherin. CONCLUSIONS: Our data indicate that Wnt is involved in the pathogenesis of adriamycin nephropathy. Furthermore, klotho supplementation inhibited Wnt signaling, ameliorating renal angiotensin II. Finally, klotho protein appears to suppress epithelial-mesenchymal transition by inhibiting TGF-ß and Wnt signaling.

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.

Urinary Angiotensinogen Could Be a Prognostic Marker of the Renoprotection of Olmesartan in Metabolic Syndrome Patients.

This study was performed to demonstrate urinary angiotensinogen as a potential prognostic marker of the albuminuria reduction effects of olmesartan in patients with metabolic syndrome. In 24 patients (eight women, 57.88 ± 2.00 years), 5-40 mg/day of olmesartan were given. Urinary concentrations of albumin and angiotensinogen (normalized by urinary concentrations of creatinine) and plasma renin activity were measured before and after the 12- and 24-week marks of olmesartan treatment. Olmesartan treatment increased plasma renin activity and decreased urinary albumin and urinary angiotensinogen significantly (p < 0.05). Based on the % change in urinary albumin, patients were divided into two groups, responders (<-50%) and non-responders (≥-50%), and a logistic analysis of urinary angiotensinogen before treatment showed the area under the curve as 0.694. When the cutoff value of urinary angiotensinogen before the treatment of 13.9 µg/g Cr was used, the maximum Youden index (0.500, specificity: 11/12 = 91.7% and sensitivity: 7/12 = 58.3%) was obtained. When all patients were re-divided into two groups, those with higher values of urinary angiotensinogen before the treatment (Group H, n = 16) and those with lower values, Group H showed significantly decreased urinary albumin (p < 0.05). Therefore, urinary angiotensinogen could be a prognostic marker of the albuminuria reduction effects of olmesartan in patients with metabolic syndrome.

Role of the renal sympathetic nerve in renal glucose metabolism during the development of type 2 diabetes in rats.

AIMS/HYPOTHESIS: Recent clinical studies have shown that renal sympathetic denervation (RDX) improves glucose metabolism in patients with resistant hypertension. We aimed to elucidate the potential contribution of the renal sympathetic nervous system to glucose metabolism during the development of type 2 diabetes. METHODS: Uninephrectomised diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats underwent RDX at 25 weeks of age and were followed up to 46 weeks of age. RESULTS: RDX decreased plasma and renal tissue noradrenaline (norepinephrine) levels and BP. RDX also improved glucose metabolism and insulin sensitivity, which was associated with increased in vivo glucose uptake by peripheral tissues. Furthermore, RDX suppressed overexpression of sodium-glucose cotransporter 2 (Sglt2 [also known as Slc5a2]) in renal tissues, which was followed by an augmentation of glycosuria in type 2 diabetic OLETF rats. Similar improvements in glucose metabolism after RDX were observed in young OLETF rats at the prediabetic stage (21 weeks of age) without changing BP. CONCLUSIONS/INTERPRETATION: Here, we propose the new concept of a connection between renal glucose metabolism and the renal sympathetic nervous system during the development of type 2 diabetes. Our data demonstrate that RDX exerts beneficial effects on glucose metabolism by an increase in tissue glucose uptake and glycosuria induced by Sglt2 suppression. These data have provided a new insight not only into the treatment of hypertensive type 2 diabetic patients, but also the pathophysiology of insulin resistance manifested by sympathetic hyperactivity.

Changes in urinary angiotensinogen posttreatment in pediatric IgA nephropathy patients.

BACKGROUND: Recently, we demonstrated that urinary angiotensinogen (AGT) levels are increased and reflect intrarenal renin-angiotensin system (RAS) status in pediatric patients with chronic glomerulonephritis. Therefore, this study was performed to test the hypothesis that urinary AGT (UAGT) levels provide a specific index of intrarenal RAS status associated with RAS blockade treatment in pediatric IgA nephropathy (IgAN) patients. METHODS: We measured plasma and UAGT levels and urinary transforming growth factor beta (TGF-ß) levels, after which we performed immunohistochemical analysis of AGT, angiotensin II (Ang II), and TGF-ß in 24 pediatric IgAN patients treated with RAS blockades for 2 years. Paired tests were used to analyze the changes from baseline to study end. RESULTS: Although there was no change in plasma AGT levels, UAGT and TGF-ß levels were significantly decreased after RAS blockade, which was accompanied by the expression levels of AGT, Ang II, and TGF-ß, as well as the magnitude of glomerular injury. Baseline UAGT levels positively correlated with diastolic blood pressure, urinary protein levels, scores for mesangial hypercellularity, and the expression levels of AGT, Ang II, and TGF-ß in renal tissues. CONCLUSIONS: These data indicate that UAGT is a useful biomarker of intrarenal RAS activation, which is associated with glomerular injury during RAS blockade in pediatric IgAN patients.

Anti-albuminuric effects of spironolactone in patients with type 2 diabetic nephropathy: a multicenter, randomized clinical trial.

BACKGROUND: Several studies have demonstrated that spironolactone has an anti-albuminuric property in diabetic nephropathy. As an adverse event, spironolactone often induces the elevation of creatinine levels with hypotension and hyperkalemia. Therefore, we aimed to evaluate the efficacy and safety of spironolactone in Japanese patients with type 2 diabetes treated with either angiotensin-converting enzyme inhibitors or angiotensin receptor blockers. METHODS: Fifty-two Japanese patients with diabetic nephropathy and albuminuria (100 mg/gCr-2000 mg/gCr) treated with renin-angiotensin system (RAS) blockade were enrolled in a prospective, randomized, open-label study. The patients were subjected to add-on treatment with spironolactone 25 mg once daily and compared with matched controls for 8 weeks. The primary outcome was a reduction in the rate of albuminuria at 8 weeks compared with the baseline value. This study was registered with UMIN Clinical Trials Registry (000008016). RESULTS: Albuminuria was reduced by 33 % (95 % confidence interval: 22-54; P = 0.0002) at 8 weeks with spironolactone. In the spironolactone group, blood pressure tended to lower and the estimated glomerular filtration rate (eGFR) was significantly decreased compared to those in the control group. When adjusted by systolic blood pressure and eGFR, spironolactone treatment still showed a significant effect on albuminuria reduction in a linear mixed model (coefficient ± standard error; 514.4 ± 137.6 mg/gCr, P < 0.0005). No patient was excluded from the study because of hyperkalemia. CONCLUSIONS: Spironolactone reduced albuminuria along with conventional RAS inhibitors in patients with diabetic nephropathy. Our study suggests that spironolactone exerts anti-albuminuric effects independent of systemic hemodynamic alterations.

ROCK/NF-κB axis-dependent augmentation of angiotensinogen by angiotensin II in primary-cultured preglomerular vascular smooth muscle cells.

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.

Deletion of the angiotensin II type 1 receptor-associated protein enhances renal sodium reabsorption and exacerbates angiotensin II-mediated hypertension.

Angiotensin II type 1 receptor (AT1R)-associated protein (ATRAP) promotes AT1R internalization along with suppression of pathological activation of tissue AT1R signaling. However, the functional significance of ATRAP in renal sodium handling and blood pressure regulation under pathological stimuli is not fully resolved. Here we show the blood pressure of mice with a gene-targeted disruption of ATRAP was comparable to that of wild-type mice at baseline. However, in ATRAP-knockout mice, angiotensin II-induced hypertension was exacerbated and the extent of positive sodium balance was increased by angiotensin II. Renal expression of the sodium-proton antiporter 3, a major sodium transporter in the proximal tubules, urinary pH, renal angiotensinogen production, and angiotensin II content was unaffected. Stimulation of the renal expression and activity of the epithelial sodium channel (ENaC), a major sodium transporter in the distal tubules, was significantly enhanced by chronic angiotensin II infusion. The circulating and urinary aldosterone levels were comparable. The blood pressure response and renal ENaC expression by aldosterone were not affected. Thus, ATRAP deficiency exacerbated angiotensin II-mediated hypertension by pathological activation of renal tubular AT1R by angiotensin II. This directly stimulates ENaC in the distal tubules and enhances sodium retention in an aldosterone-independent manner.

The effectiveness of relugolix compared with leuprorelin for preoperative therapy before laparoscopic myomectomy in premenopausal women, diagnosed with uterine fibroids: protocol for a randomized controlled study (MyLacR study).

BACKGROUND: The oral gonadotropin-releasing hormone antagonist relugolix, which temporarily stops menstruation, is used to treat heavy menstrual bleeding, pelvic pressure, and low back pain in women with uterine fibroids. Treatment can also help women recover from low hemoglobin levels and possibly shrink the fibroids. However, evidence of preoperative use of relugolix before laparoscopic myomectomy is limited. Nevertheless, the treatment could reduce interoperative blood loss, decrease the risk of developing postoperative anemia, and shorten the operative time. Thus, we aim to test whether 12-week preoperative treatment with relugolix (40 mg orally, once daily) is similar to or not worse than leuprorelin (one injection every 4 weeks) to reduce intraoperative blood loss. METHODS: Efficacy and safety of preoperative administration of drugs will be studied in a multi-center, randomized, open-label, parallel-group, noninferiority trial enrolling premenopausal women ≥ 20 years of age, diagnosed with uterine fibroids and scheduled for laparoscopic myomectomy. Participants (n = 80) will be recruited in the clinical setting of participating institutions. The minimization method (predefined factors: presence or absence of fibroids ≥ 9 cm and the International Federation of Gynecology and Obstetrics [FIGO] type 1-5 fibroids) with randomization is used in a 1:1 allocation. Relugolix is a 40-mg oral tablet taken once a day before a meal, for 12 weeks, up to the day before surgery. Leuprorelin is a 1.88 mg, or 3.75 mg subcutaneous injection, given in three 4-week intervals during patient visits before the surgery. For the primary outcome measure of intraoperative bleeding, the blood flow is collected from the body cavity, surgical sponges, and collection bag and measured in milliliters. Secondary outcome measures are hemoglobin levels, myoma size, other surgical outcomes, and quality-of-life questionnaire responses (Kupperman Konenki Shogai Index and Uterine Fibroid Symptoms-Quality of Life). DISCUSSION: Real-world evidence will be collected in a clinical setting to use pre-treatment with an oral gonadotropin-releasing hormone antagonist to reduce intraoperative bleeding in women who undergo laparoscopic myomectomy. TRIAL REGISTRATION: jRCTs031210564 was registered on 19 January 2022 in the Japan Registry of Clinical Trials ( https://jrct.niph.go.jp ).

Renal sympathetic denervation suppresses de novo podocyte injury and albuminuria in rats with aortic regurgitation.

BACKGROUND: The presence of chronic kidney disease is a significant independent risk factor for poor prognosis in patients with chronic heart failure. However, the mechanisms and mediators underlying this interaction are poorly understood. In this study, we tested our hypothesis that chronic cardiac volume overload leads to de novo renal dysfunction by coactivating the sympathetic nervous system and renin-angiotensin system in the kidney. We also examined the therapeutic potential of renal denervation and renin-angiotensin system inhibition to suppress renal injury in chronic heart failure. METHODS AND RESULTS: Sprague-Dawley rats underwent aortic regurgitation and were treated for 6 months with vehicle, olmesartan (an angiotensin II receptor blocker), or hydralazine. At 6 months, albuminuria and glomerular podocyte injury were significantly increased in aortic regurgitation rats. These changes were associated with increased urinary angiotensinogen excretion, kidney angiotensin II and norepinephrine (NE) levels, and enhanced angiotensinogen and angiotensin type 1a receptor gene expression and oxidative stress in renal cortical tissues. Aortic regurgitation rats with renal denervation had decreased albuminuria and glomerular podocyte injury, which were associated with reduced kidney NE, angiotensinogen, angiotensin II, and oxidative stress. Renal denervation combined with olmesartan prevented podocyte injury and albuminuria induced by aortic regurgitation. CONCLUSIONS: In this chronic cardiac volume-overload animal model, activation of the sympathetic nervous system augments kidney renin-angiotensin system and oxidative stress, which act as crucial cardiorenal mediators. Renal denervation and olmesartan prevent the onset and progression of renal injury, providing new insight into the treatment of cardiorenal syndrome.

Augmented intrarenal and urinary angiotensinogen in hypertension and chronic kidney disease.

Activated intrarenal renin-angiotensin system plays a cardinal role in the pathogenesis of hypertension and chronic kidney disease. Angiotensinogen is the only known substrate for renin, which is the rate-limiting enzyme of the renin-angiotensin system. Because the levels of angiotensinogen are close to the Michaelis-Menten constant values for renin, angiotensinogen levels as well as renin levels can control the renin-angiotensin system activity, and thus, upregulation of angiotensinogen leads to an increase in the angiotensin II levels and ultimately increases blood pressure. Recent studies using experimental animal models have documented the involvement of angiotensinogen in the intrarenal renin-angiotensin system activation and development of hypertension. Enhanced intrarenal angiotensinogen mRNA and/or protein levels were observed in experimental models of hypertension and chronic kidney disease, supporting the important roles of angiotensinogen in the development and the progression of hypertension and chronic kidney disease. Urinary excretion rates of angiotensinogen provide a specific index of the intrarenal renin-angiotensin system status in angiotensin II-infused rats. Also, a direct quantitative method has been developed recently to measure urinary angiotensinogen using human angiotensinogen enzyme-linked immunosorbent assay. These data prompted us to measure urinary angiotensinogen in patients with hypertension and chronic kidney disease, and investigate correlations with clinical parameters. This short article will focus on the role of the augmented intrarenal angiotensinogen in the pathophysiology of hypertension and chronic kidney disease. In addition, the potential of urinary angiotensinogen as a novel biomarker of the intrarenal renin-angiotensin system status in hypertension and chronic kidney disease will be also discussed.

Activation of the renin-angiotensin system by a low-salt diet does not augment intratubular angiotensinogen and angiotensin II in rats.

In angiotensin II (ANG II) infusion hypertension, there is an augmentation of intratubular angiotensinogen (AGT) and ANG II leading to increased urinary AGT and ANG II excretion rates associated with tissue injury. However, the changes in urinary AGT and ANG II excretion rates and markers of renal injury during physiologically induced stimulation of the renin-angiotensin system (RAS) by a low-salt diet remain unclear. Male Sprague-Dawley rats received a low-salt diet (0.03% NaCl; n = 6) and normal-salt diet (0.3% NaCl, n = 6) for 13 days. Low-salt diet rats had markedly higher plasma renin activity and plasma ANG II levels. Kidney cortex renin mRNA, kidney AGT mRNA, and AGT immunoreactivity were not different; however, medullary renin mRNA, kidney renin content, and kidney ANG II levels were significantly elevated by the low-salt diet. Kidney renin immunoreactivity was also markedly increased in juxtaglomerular apparati and in cortical and medullary collecting ducts. Urinary AGT excretion rates and urinary ANG II excretion rates were not augmented by the low-salt diet. The low-salt diet caused mild renal fibrosis in glomeruli and the tubulointerstitium, but no other signs of kidney injury were evident. These results indicate that, in contrast to the response in ANG II infusion hypertension, the elevated plasma and intrarenal ANG II levels caused by physiological stimulation of RAS are not reflected by increased urinary AGT or ANG II excretion rates or the development of renal injury.

Interferon-γ biphasically regulates angiotensinogen expression via a JAK-STAT pathway and suppressor of cytokine signaling 1 (SOCS1) in renal proximal tubular cells.

Renal inflammation modulates angiotensinogen (AGT) production in renal proximal tubular cells (RPTCs) via inflammatory cytokines, including interleukin-6, tumor necrosis factor α, and interferon-γ (IFN-γ). Among these, the effects of IFN-γ on AGT regulation in RPTCs are incompletely delineated. This study aimed to elucidate mechanisms by which IFN-γ regulates AGT expression in RPTCs. RPTCs were incubated with or without IFN-γ up to 48 h. AGT expression, STAT1 and STAT3 activities, and SOCS1 expression were evaluated. RNA interference studies against STAT1, SOCS1, and STAT3 were performed to elucidate a signaling cascade. IFN-γ decreased AGT expression at 6 h (0.61±0.05, ratio to control) and 12 h (0.47±0.03). In contrast, longer exposure for 24 and 48 h increased AGT expression (1.76±0.18, EC(50)=3.4 ng/ml, and 1.45±0.08, respectively). IFN-γ treatment for 6 h strongly induced STAT1 phosphorylation and SOCS1 augmentation, and decreased STAT3 activity. However, STAT1 phosphorylation and SOCS1 augmentation waned at 24 h, while STAT3 activity increased. RNA interference studies revealed that activation of STAT1-SOCS1 axis decreased STAT3 activity. Thus, IFN-γ biphasically regulates AGT expression in RPTCs via STAT3 activity modulated by STAT1-SOCS1 axis, suggesting the STAT1-SOCS1 axis is important in IFN-γ-induced activation of the intrarenal renin-angiotensin system.