An extremely high dose of losartan affords superior renoprotection in the remnant model

Dose and Time Effects of Renin-Angiotensin Inhibitors on Patients With Advanced Stages 4 to 5 of Diabetic Kidney Disease

Context

Limited evidence exists regarding the cumulative dosing and duration impact of renin-angiotensin system inhibitors (RASis) on cardiorenal and mortality outcomes in patients with advanced stages (predominantly in stage 5 and a minority in stage 4) of diabetic kidney disease (DKD).

Objective

To retrospectively investigate whether there are dose- and time-dependent relationships between RASis and cardiorenal and mortality outcomes in this population.

Methods

Using Taiwan's national health insurance data in 2000-2017, we analyzed 2196 RASi users and 2196 propensity-matched nonusers among 8738 patients living with diabetes and newly diagnosed with advanced chronic kidney disease (23% stage 4, 77% stage 5). Cox proportional hazards regression models were used to estimate adjusted hazard ratios (aHRs) and 95% CI.

Results

RASi use was significantly associated with reduced risks of all-cause mortality (aHR, 0.53; 95% CI 0.47-0.60) and cardiovascular mortality (0.68; 0.56-0.83) with the degree of benefit depending on therapeutic dosage and duration, despite a nonsignificant increase in acute kidney injury risk (1.16; 0.98-1.38) and a significant increase in hyperkalemia risk (1.45; 1.19-1.77). Significant differences in proteinuria risk (1.32; 1.21-1.43) were observed, while there were no significant differences in end-stage renal disease risk (1.01; 0.88-1.15) and no dose- or time-response relationships for either end-stage renal disease or proteinuria risks. Sensitivity analyses confirmed cardiovascular and survival benefits, even in patients with stage 5 DKD.

Conclusion

This real-world study suggests that RASi use in advanced stages 4 to 5 DKD may provide dose- and time-dependent cardioprotection and improved survival, without excess renal harms.

Losartan ameliorates renal fibrosis by inhibiting tumor necrosis factor signal pathway

Losartan is widely used in the treatment of chronic kidney disease (CKD) and has achieved good clinical efficacy, but its exact mechanism is not clear. We performed high-throughput sequencing (HTS) technology to screen the potential target of losartan in treating CKD. According to the HTS results, we found that the tumor necrosis factor (TNF) signal pathway was enriched. Therefore, we conducted in vivo and in vitro experiments to verify it. We found that TNF signal pathway was activated in both unilateral ureteral obstruction (UUO) rats and human proximal renal tubular epithelial cells (HK-2) treated with transforming growth factor-β1 (TGF-β1), while losartan can significantly inhibit TNF signal pathway as well as the expression of fibrosis related genes (such as COL-1, α-SMA and Vimentin). These data suggest that losartan may ameliorate renal fibrosis through modulating the TNF pathway.

Antihypertensive treatment with hydrochlorothiazide-hydralazine combination aggravates medial vascular calcification in CKD rats with mineral bone disorder

Background

Arterial stiffness and medial vascular calcification, leading to isolated systolic blood pressure (BP), are major cardiovascular risk factors in patients with chronic kidney disease (CKD) and mineral bone disorders (MBD). The impact of BP on MBD-induced medial vascular calcification in CKD remains uncertain. We investigated whether BP reduction improves arterial stiffness and medial vascular calcification in a rat model of CKD-MBD.

Methods

CKD was induced in Wistar rats by subtotal nephrectomy. Then, MBD was generated by a Ca/P-rich diet with calcitriol supplementation to induce medial vascular calcification. Two antihypertensive treatments were evaluated: (1) the angiotensin AT1 receptor antagonist losartan, and (2) the combination of the thiazide diuretic hydrochlorothiazide and the direct vasodilator hydralazine (HCTZ/HY). After 5 weeks, mean BP (MBP), pulse pressure (PP), and pulse wave velocity (PWV) were determined. Vascular calcification was assessed in the thoracic aorta.

Results

While MBP was similar in CKD-MBD and control CKD rats, PP and PWV were increased in CKD-MBD rats. The heightened arterial stiffness in CKD-MBD rats was associated with diffused medial calcification along the thoracic aorta. Although both losartan and HCTZ/HY reduced MBP in CKD-MBD rats, losartan did not affect PP and PWV nor medial vascular calcification, whereas HCTZ/HY, unexpectedly, further increased arterial stiffness and medial vascular calcification.

Conclusion

In the rat model of CKD-MBD, antihypertensive treatment with losartan did not affect arterial stiffness or medial vascular calcification. However, HCTZ/HY treatment aggravated arterial stiffness and vascular calcification despite a similar reduction of MBP, suggesting a blood pressure-independent mechanism for vascular calcification.

Inflammation in kidney repair: Mechanism and therapeutic potential

The kidney has a remarkable ability of repair after acute kidney injury (AKI). However, when injury is severe or persistent, the repair is incomplete or maladaptive and may lead to chronic kidney disease (CKD). Maladaptive kidney repair involves multiple cell types and multifactorial processes, of which inflammation is a key component. In the process of inflammation, there is a bidirectional interplay between kidney parenchymal cells and the immune system. The extensive and complex crosstalk between renal tubular epithelial cells and interstitial cells, including immune cells, fibroblasts, and endothelial cells, governs the repair and recovery of the injured kidney. Further research in this field is imperative for the discovery of biomarkers and promising therapeutic targets for kidney repair. In this review, we summarize the latest progress in the immune response and inflammation during maladaptive kidney repair, analyzing the interaction between immune cells and intrinsic kidney cells, pointing out the potentialities of inflammation-related pathways as therapeutic targets, and discussing the challenges and future research prospects in this field.

Metformin arrests the progression of established kidney disease in the subtotal nephrectomy model of chronic kidney disease

Metformin, an AMP-activated protein kinase (AMPK) activator, has been shown in previous studies to reduce kidney fibrosis in different models of experimental chronic kidney disease (CKD). However, in all of these studies, the administration of metformin was initiated before the establishment of renal disease, which is a condition that does not typically occur in clinical settings. The aim of the present study was to investigate whether the administration of metformin could arrest the progression of established renal disease in a well-recognized model of CKD, the subtotal kidney nephrectomy (Nx) model. Adult male Munich-Wistar rats underwent either Nx or sham operations. After the surgery (30 days), Nx rats that had systolic blood pressures of >170 mmHg and albuminuria levels of >40 mg/24 h were randomized to a no-treatment condition or to a treatment condition with metformin (300 mg·kg−1·day−1) for a period of either 60 or 120 days. After 60 days of treatment, we did not observe any differences in kidney disease parameters between Nx metformin-treated and untreated rats. However, after 120 days, Nx rats that had been treated with metformin displayed significant reductions in albuminuria levels and in markers of renal fibrosis. These effects were independent of any other effects on blood pressure or glycemia. In addition, treatment with metformin was also able to activate kidney AMPK and therefore improve mitochondrial biogenesis. It was concluded that metformin can arrest the progression of established kidney disease in the Nx model, likely via the activation of AMPK.

Addition of Endothelin A-Receptor Blockade Spoils the Beneficial Effect of Combined Renin-Angiotensin and Soluble Epoxide Hydrolase Inhibition: Studies on the Course of Chronic Kidney Disease in 5/6 Nephrectomized Ren-2 Transgenic Hypertensive Rats

Introduction: Previous studies in Ren-2 transgenic hypertensive rats (TGR) after 5/6 renal ablation (5/6 NX) have shown that besides pharmacological blockade of the renin-angiotensin system (RAS) also increasing kidney tissue epoxyeicosatrienoic acids (EET) levels by blocking soluble epoxide hydrolase (sEH), an enzyme responsible for degradation of EETs, and endothelin type A (ETA) receptor blockade retards chronic kidney disease (CKD) progression. This prompted us to evaluate if this progression will be alleviated by the addition of sEH inhibitor and ETA receptor antagonist to the standard complex blockade of RAS (angiotensin-converting enzyme inhibitor plus angiotensin II type 1 receptor blocker) in rats with established CKD. Methods: The treatment regimens were initiated 6 weeks after 5/6 NX in TGR, and the follow-up period was 60 weeks. Results: The addition of sEH inhibition to RAS blockade improved survival rate, further reduced albuminuria and renal glomerular and kidney tubulointerstitial injury, and attenuated the decline in creatinine clearance – all this as compared with 5/6 NX TGR treated with RAS blockade alone. Addition of ETA receptor antagonist to the combined RAS and sEH blockade not only offered no additional renoprotection but, surprisingly, also abolished the beneficial effects of adding sEH inhibitor to the RAS blockade. Conclusion: These data indicate that pharmacological strategies that combine the blockade of RAS and sEH could be a novel tool to combat the progression of CKD. Any attempts to further extend this therapeutic regimen should be made with extreme caution.

Renoprotection Provided by Additional Diuretic Treatment in Partially Nephrectomized Ren-2 Transgenic Rats Subjected to the Combined RAS and ETA Blockade

Objective

Our previous study in heterozygous Ren-2 transgenic rats (TGR) demonstrated that long-term treatment with endothelin receptor A (ET_A) blocker atrasentan added to the renin-angiotensin system (RAS) blockade had renoprotective effects in a model of chronic kidney disease (CKD) induced by partial nephrectomy. Since ET_A blockade is known to cause edema, we were interested whether diuretic treatment added to this therapy would be beneficial.

Design and Methods

Partial nephrectomy (NX) was performed at the age of 3 months in TGR rats which were subjected to: (i) RAS blockade alone (angiotensin receptor blocker losartan and angiotensin converting enzyme inhibitor trandolapril), (ii) combined RAS (losartan and trandolapril) and ET_A receptor blockade (atrasentan), or (iii) diuretic (hydrochlorothiazide) added to the combined RAS + ET_A blockade for 50 weeks following NX.

Results

At the end of the study systolic blood pressure and cardiac hypertrophy were similarly decreased in all treated groups. Survival was significantly improved by ET_A receptor blockade added to RAS blockade with no further effects of diuretic treatment. However, additional diuretic treatment combined with RAS + ET_A blockade decreased body weight and had beneficial renoprotective effects - reductions of both kidney weight and kidney damage markers. Proteinuria gradually increased in rats treated with RAS blockade alone, while it was substantially lowered by additional ET_A blockade. In rats treated with additional diuretic, proteinuria was progressively reduced throughout the experiment.

Conclusion

A diuretic added to the combined RAS and ET_A blockade has late renoprotective effects in CKD induced by partial nephrectomy in Ren-2 transgenic rats. The diuretic improved: renal function (evaluated as proteinuria and creatinine clearance), renal morphology (kidney mass, glomerular volume), and histological markers of kidney damage (glomerulosclerosis index, tubulointerstitial injury).

Inflammation in Renal Diseases: New and Old Players

Inflammation, a process intimately linked to renal disease, can be defined as a complex network of interactions between renal parenchymal cells and resident immune cells, such as macrophages and dendritic cells, coupled with recruitment of circulating monocytes, lymphocytes, and neutrophils. Once stimulated, these cells activate specialized structures such as Toll-like receptor and Nod-like receptor (NLR). By detecting danger-associated molecules, these receptors can set in motion major innate immunity pathways such as nuclear factor ĸB (NF-ĸB) and NLRP3 inflammasome, causing metabolic reprogramming and phenotype changes of immune and parenchymal cells and triggering the secretion of a number of inflammatory mediators that can cause irreversible tissue damage and functional loss. Growing evidence suggests that this response can be deeply impacted by the crosstalk between the kidneys and other organs, such as the gut. Changes in the composition and/or metabolite production of the gut microbiota can influence inflammation, oxidative stress, and fibrosis, thus offering opportunities to positively manipulate the composition and/or functionality of gut microbiota and, consequentially, ameliorate deleterious consequences of renal diseases. In this review, we summarize the most recent evidence that renal inflammation can be ameliorated by interfering with the gut microbiota through the administration of probiotics, prebiotics, and postbiotics. In addition to these innovative approaches, we address the recent discovery of new targets for drugs long in use in clinical practice. Angiotensin II receptor antagonists, NF-ĸB inhibitors, thiazide diuretics, and antimetabolic drugs can reduce renal macrophage infiltration and slow down the progression of renal disease by mechanisms independent of those usually attributed to these compounds. Allopurinol, an inhibitor of uric acid production, has been shown to decrease renal inflammation by limiting activation of the NLRP3 inflammasome. So far, these protective effects have been shown in experimental studies only. Clinical studies will establish whether these novel strategies can be incorporated into the arsenal of treatments intended to prevent the progression of human disease.

Protective Role of Angiotensin Type 1 Receptor Blockade in 4/6 Nephrectomized Male and Female Rats

Background

Chronic kidney disease associated with serious morbidity and mortality rate while it is affected by renin-angiotensin system. The effects of losartan as angiotensin II Type 1 receptor antagonist on renal functional in 4/6 nephrectomized rats was evaluated.

Methods

Twenty-six male and female Wistar rats underwent 4/6 nephrectomy, and the animals from each gender were randomly divided into two groups which treated with vehicle and losartan (10 mg/kg/day for 1 week). The parameters related to kidney function were measured.

Results

Creatinine (Cr) clearance and urine flow were improved in losartan-treated group significantly (P < 0.05). The serum level of blood urea nitrogen and Cr and kidney tissue damage score and sodium urinary output (U_NaV) did not alter. However, losartan decreased percentage of sodium excretion (E_Na%) in both genders insignificantly.

Conclusions

Losartan may improve renal function in 4/6 nephrectomized male rats.

Nicousamide attenuates renal dysfunction and glomerular injury in remnant kidneys by inhibiting TGF-β1 internalisation and renin activity

Nicousamide has been shown to exert renal protective effects against diabetic nephropathy and has moved to a phase II clinical trial in China for diabetic nephropathy indication. To expand its clinical indications, 5/6-nephrectomised rats were used to mimic glomerular and vascular sclerosis and tubulointerstitial scarring, with subsequent progression towards end-stage renal disease. Adult Wistar rats underwent 5/6 nephrectomy to induce the development of chronic kidney disease, with a sham operation performed as a control. The nephrectomised animals were treated orally with either saline, nicousamide (7.5,15, or 45 mg/kg), benazepril (4 mg/kg), or losartan (10 mg/kg) daily for 20 weeks. At 8, 16, and 20 weeks of treatment, blood pressure was measured in each animal, and blood and urine samples were collected for biochemical analysis, while kidney remnants were collected for histological examination. Levels of fibronectin and transforming growth factor beta 1 (TGF-β1) were measured in kidneys by immunohistochemistry. Renin activity in the plasma was measured by an enzyme-linked immunosorbent assay. The results showed that nicousamide treatment significantly reduced systemic hypertension, proteinuria, and blood urea nitrogen (P < 0.05), effectively alleviated glomerular sclerosis scores and tubulointerstitial injuries in a dose-dependent manner (P < 0.01), and markedly decreased fibronectin and TGF-β1 levels in kidney tissues of the 5/6-nephrectomised animals. In vitro studies suggested that nicousamide could moderately inhibit the renin activity and strongly block the TGF-β1 internalisation into fibroblast cells. In summary, nicousamide may protect from renal failure through dual targeting, which involves a TGF-β1-dependent mechanism and inhibition of renin activity.

Fimasartan attenuates renal ischemia-reperfusion injury by modulating inflammation-related apoptosis

Fimasartan, a new angiotensin II receptor antagonist, reduces myocyte damage and stabilizes atherosclerotic plaque through its anti-inflammatory effect in animal studies. We investigated the protective effects of pretreatment with fimasartan on ischemia-reperfusion injury (IRI) in a mouse model of ischemic renal damage. C57BL/6 mice were pretreated with or without 5 (IR-F5) or 10 (IR-F10) mg/kg/day fimasartan for 3 days. Renal ischemia was induced by clamping bilateral renal vascular pedicles for 30 min. Histology, pro-inflammatory cytokines, and apoptosis assays were evaluated 24 h after IRI. Compared to the untreated group, blood urea nitrogen and serum creatinine levels were significantly lower in the IR-F10 group. IR-F10 kidneys showed less tubular necrosis and interstitial fibrosis than untreated kidneys. The expression of F4/80, a macrophage infiltration marker, and tumor necrosis factor (TNF)-α, decreased in the IR-F10 group. High-dose fimasartan treatment attenuated the upregulation of TNF-α, interleukin (IL)-1β, and IL-6 in ischemic kidneys. Fewer TUNEL positive cells were observed in IR-F10 compared to control mice. Fimasartan caused a significant decrease in caspase-3 activity and the level of Bax, and increased the Bcl-2 level. Fimasartan preserved renal function and tubular architecture from IRI in a mouse ischemic renal injury model. Fimasartan also attenuated upregulation of inflammatory cytokines and decreased apoptosis of renal tubular cells. Our results suggest that fimasartan inhibited the process of tubular injury by preventing apoptosis induced by the inflammatory pathway.

Combined Inhibition of Soluble Epoxide Hydrolase and Renin-Angiotensin System Exhibits Superior Renoprotection to Renin-Angiotensin System Blockade in 5/6 Nephrectomized Ren-2 Transgenic Hypertensive Rats with Established Chronic Kidney Disease

BACKGROUND/AIMS

We found recently that increasing renal epoxyeicosatrienoic acids (EETs) levels by blocking soluble epoxide hydrolase (sEH), an enzyme responsible for EETs degradation, shows renoprotective actions and retards the progression of chronic kidney disease (CKD) in Ren-2 transgenic hypertensive rats (TGR) after 5/6 renal ablation (5/6 NX). This prompted us to examine if additional protection is provided when sEH inhibitor is added to the standard renin-angiotensin system (RAS) blockade, specifically in rats with established CKD.

METHODS

For RAS blockade, an angiotensin-converting enzyme inhibitor along with an angiotensin II type receptor blocker was used. RAS blockade was compared to sEH inhibition added to the RAS blockade. Treatments were initiated 6 weeks after 5/6 NX in TGR and the follow-up period was 60 weeks.

RESULTS

Combined RAS and sEH blockade exhibited additional positive impact on the rat survival rate, further reduced albuminuria, further reduced glomerular and tubulointerstitial injury, and attenuated the decline in creatinine clearance when compared to 5/6 NX TGR subjected to RAS blockade alone. These additional beneficial actions were associated with normalization of the intrarenal EETs deficient and a further reduction of urinary angiotensinogen excretion.

CONCLUSION

This study provides evidence that addition of pharmacological inhibition of sEH to RAS blockade in 5/6 NX TGR enhances renoprotection and retards progression of CKD, notably, when applied at an advanced stage.

Innate And Adaptive Immunity are Progressively Activated in Parallel with Renal Injury in the 5/6 Renal Ablation Model

The mechanisms triggering renal inflammation in chronic kidney disease (CKD) are unclear. We performed a detailed analysis of the time course of innate and adaptive immunity activation in the 5/6 renal ablation (Nx) model. Munich-Wistar rats undergoing Nx were studied 15, 60 and 120 days after ablation. Hypertension, albuminuria, creatinine retention, interstitial expansion and infiltration by macrophages and T-lymphocytes were already evident 15 days after Nx. PCR-array was used to screen for altered gene expression, whereas gene and protein expressions of TLR4, CASP1, IL-1β and NLRP3 were individually assessed. Tlr4, Tlr5, Lbp, Nlrp3, Casp1, Irf7 and Il1b were already upregulated 15 days after Nx, while activation of Tlr2, Tlr7, Tlr9, Nod2, Tnf and Il6 was seen after 60 days post-ablation. The number of genes related to innate or adaptive immunity grew steadily with time. These observations indicate that parallel activation of innate and adaptive immunity antecedes glomerular injury and involves a growing number of intricate signaling pathways, helping to explain the difficulty in detaining renal injury in Nx as CKD advances, and, stressing the need for early treatment. Additionally, these findings may contribute to the search of therapeutic targets specific for advanced phases of CKD.

Suppression of NLRP3 Inflammasome Activation Ameliorates Chronic Kidney Disease-Induced Cardiac Fibrosis and Diastolic Dysfunction

Cardiac fibrosis is a common finding in patients with chronic kidney disease. Here, we investigate the cardio-renal effects of theracurmin, a novel formulation of the polyphenolic compound curcumin, in a rat model of chronic kidney disease. Briefly, Sprague-Dawley rats were randomized to undergo sham or subtotal nephrectomy (SNx) surgery. At 3 weeks post surgery, SNx animals were further randomized to received theracurmin via once daily oral gavage or vehicle for 5 consecutive weeks. At 8 weeks post surgery, cardiac function was assessed via echocardiography and pressure volume loop analysis, followed by LV and renal tissue collection for analysis. SNx animals developed key hallmarks of renal injury including hypertension, proteinuria, elevated blood urea nitrogen, and glomerulosclerosis. Renal injury in SNx animals was also associated with significant diastolic dysfunction, macrophage infiltration, and cardiac NLRP3 inflammasome activation. Treatment of SNx animals with theracurmin improved structural and functional manifestations of cardiac injury associated with renal failure and also attenuated cardiac NLRP3 inflammasome activation and mature IL-1β release. Taken together, our findings suggest a significant role for the NLRP3 inflammasome in renal injury-induced cardiac dysfunction and presents inflammasome attenuation as a unique strategy to prevent adverse cardiac remodeling in the setting of chronic kidney disease.

Differential renal effects of candesartan at high and ultra-high doses in diabetic mice-potential role of the ACE2/AT2R/Mas axis

High doses of Ang II receptor (AT1R) blockers (ARBs) are renoprotective in diabetes. Underlying mechanisms remain unclear. We evaluated whether high/ultra-high doses of candesartan (ARB) up-regulate angiotensin-converting enzyme 2 (ACE2)/Ang II type 2 receptor (AT2R)/Mas receptor [protective axis of the of the renin–angiotensin system (RAS)] in diabetic mice. Systolic blood pressure (SBP), albuminuria and expression/activity of RAS components were assessed in diabetic db/db and control db/+ mice treated with increasing candesartan doses (intermediate, 1 mg/kg/d; high, 5 mg/kg/d; ultra-high, 25 and 75 mg/kg/d; 4 weeks). Lower doses candesartan did not influence SBP, but ultra-high doses reduced SBP in both groups. Plasma glucose and albuminuria were increased in db/db compared with db/+ mice. In diabetic mice treated with intermediate dose candesartan, renal tubular damage and albuminuria were ameliorated and expression of ACE2, AT2R and Mas and activity of ACE2 were increased, effects associated with reduced ERK1/2 phosphorylation, decreased fibrosis and renal protection. Ultra-high doses did not influence the ACE2/AT2R/Mas axis and promoted renal injury with increased renal ERK1/2 activation and exaggerated fibronectin expression in db/db mice. Our study demonstrates dose-related effects of candesartan in diabetic nephropathy: intermediate–high dose candesartan is renoprotective, whereas ultra-high dose candesartan induces renal damage. Molecular processes associated with these effects involve differential modulation of the ACE2/AT2R/Mas axis: intermediate–high dose candesartan up-regulating RAS protective components and attenuating pro-fibrotic processes, and ultra-high doses having opposite effects. These findings suggest novel mechanisms through the protective RAS axis, whereby candesartan may ameliorate diabetic nephropathy. Our findings also highlight potential injurious renal effects of ultra-high dose candesartan in diabetes.

Evaluation of kidney dysfunction and angiotensinogen as an early novel biomarker of intrauterine growth restricted offspring rats

BACKGROUND

Few studies have addressed the growing concerns of chronic kidney diseases in children with intrauterine growth restriction (IUGR). Therefore, the purpose of this study was to evaluate long-term kidney dysfunction and determine if urinary angiotensinogen (AGT) was suitable as a novel early biomarker for kidney dysfunction in IUGR offspring.

METHODS

Pregnant rats underwent bilateral uterine artery ligation, and as a control group, sham surgeries were performed.

RESULTS

The birth weight was reduced, the urinary AGT to creatinine ratio was significantly higher at week 20, and urinary protein levels were significantly higher at week 32 in IUGR rats than in control rats. On the other hand, the histological findings at week 32 revealed long-term kidney dysfunction, more severe glomerulosclerosis, and greater glomerular diameters in IUGR rats. Moreover, AGT mRNA expression and immunohistological staining were significantly increased in IUGR rats; this suggests that the intrarenal renin-angiotensin system (RAS) contributes to renal dysfunction of IUGR offspring.

CONCLUSION

Urinary AGT elevation prior to urinary protein levels suggests that AGT is an early biomarker. At week 32, kidney dysfunction was severe in IUGR rats and intrarenal RAS appeared to be one of the causes.

A Salt-Induced Reno-Cerebral Reflex Activates Renin-Angiotensin Systems and Promotes CKD Progression

Salt intake promotes progression of CKD by uncertain mechanisms. We hypothesized that a salt-induced reno-cerebral reflex activates a renin-angiotensin axis to promote CKD. Sham-operated and 5/6-nephrectomized rats received a normal-salt (0.4%), low-salt (0.02%), or high-salt (4%) diet for 2 weeks. High salt in 5/6-nephrectomized rats increased renal NADPH oxidase, inflammation, BP, and albuminuria. Furthermore, high salt activated the intrarenal and cerebral, but not the systemic, renin-angiotensin axes and increased the activity of renal sympathetic nerves and neurons in the forebrain of these rats. Renal fibrosis was increased 2.2-fold by high versus low salt, but intracerebroventricular tempol, losartan, or clonidine reduced this fibrosis by 65%, 69%, or 59%, respectively, and renal denervation or deafferentation reduced this fibrosis by 43% or 38%, respectively (all P<0.05). Salt-induced fibrosis persisted after normalization of BP with hydralazine. These data suggest that the renal and cerebral renin-angiotensin axes are interlinked by a reno-cerebral reflex that is activated by salt and promotes oxidative stress, fibrosis, and progression of CKD independent of BP.

Brazilian red propolis attenuates hypertension and renal damage in 5/6 renal ablation model

The pathogenic role of inflammation and oxidative stress in chronic kidney disease (CKD) is well known. Anti-inflammatories and antioxidant drugs has demonstrated significant renoprotection in experimental nephropathies. Moreover, the inclusion of natural antioxidants derived from food and herbal extracts (such as polyphenols, curcumin and lycopene) as an adjuvant therapy for slowing CKD progression has been largely tested. Brazilian propolis is a honeybee product, whose anti-inflammatory, antimicrobial and antioxidant effects have been widely shown in models of sepsis, cancer, skin irritation and liver fibrosis. Furthermore, previous studies demonstrated that this compound promotes vasodilation and reduces hypertension. However, potential renoprotective effects of propolis in CKD have never been investigated. The aim of this study was to evaluate the effects of a subtype of Brazilian propolis, the Red Propolis (RP), in the 5/6 renal ablation model (Nx). Adult male Wistar rats underwent Nx and were divided into untreated (Nx) and RP-treated (Nx+RP) groups, after 30 days of surgery; when rats already exhibited marked hypertension and proteinuria. Animals were observed for 90 days from the surgery day, when Nx+RP group showed significant reduction of hypertension, proteinuria, serum creatinine retention, glomerulosclerosis, renal macrophage infiltration and oxidative stress, compared to age-matched untreated Nx rats, which worsened progressively over time. In conclusion, RP treatment attenuated hypertension and structural renal damage in Nx model. Reduction of renal inflammation and oxidative stress could be a plausible mechanism to explain this renoprotection.

Inhibition of soluble epoxide hydrolase is renoprotective in 5/6 nephrectomized Ren-2 transgenic hypertensive rats

1. The aim of the present study was to test the hypothesis that increasing kidney tissue concentrations of epoxyeicosatrienoic acids (EETs) by preventing their degradation to the biologically inactive dihydroxyeicosatrienoic acids (DHETEs) using blockade of soluble epoxide hydrolase (sEH) would attenuate the progression of chronic kidney disease (CKD).

2. Ren-2 transgenic rats (TGR) after 5/6 renal mass reduction (5/6 NX) served as a model of CKD associated with angiotensin (Ang) II-dependent hypertension. Soluble epoxide hydrolase was inhibited using cis-4-[4-(3-adamantan-1-yl-ureido)cyclohexyloxy]benzoic acid (c-AUCB; 3 mg/L drinking water) for 20 weeks after 5/6 NX. Sham-operated normotensive transgene-negative Hannover Sprague-Dawley (HanSD) rats served as controls.

3. When applied in TGR subjected to 5/6 NX, c-AUCB treatment improved survival rate, prevented the increase in blood pressure, retarded the progression of cardiac hypertrophy, reduced proteinuria and the degree of glomerular and tubulointerstitial injury and reduced glomerular volume. All these organ-protective actions were associated with normalization of the intrarenal EETs : DHETEs ratio, an index of the availability of biologically active EETs, to levels observed in sham-operated HanSD rats. There were no significant concurrent changes of increased intrarenal AngII content.

4. Together, these results show that 5/6 NX TGR exhibit a profound deficiency of intrarenal availability of active epoxygenase metabolites (EETs), which probably contributes to the progression of CKD in this model of AngII-dependent hypertension, and that restoration of intrarenal availability of EETs using long-term c-AUCB treatment exhibits substantial renoprotective actions.

Losartan attenuates renal interstitial fibrosis and tubular cell apoptosis in a rat model of obstructive nephropathy

Ureteral obstruction leads to renal injury and progresses to irreversible renal fibrosis, with tubular cell atrophy and apoptosis. There is conflicting evidence concerning whether losartan (an angiotensin II type I receptor antagonist) mitigates renal interstitial fibrosis and renal tubular epithelial cell apoptosis following unilateral ureteral obstruction (UUO) in animal models. The aim of this study was to investigate the effect and mechanism of losartan on renal tubular cell apoptosis and renal fibrosis in a rat model of UUO. The rats were subjected to UUO by ureteral ligation and were treated with dimethyl sulfoxide (control) or losartan. The controls underwent sham surgery. The renal tissues were collected 3, 5, 7 and 14 days after surgery for measurement of various indicators of renal fibrosis. UUO increased the expression levels of α‑smooth muscle actin and collagen I, and the extent of renal tubular fibrosis and apoptosis in a time‑dependent manner. Losartan treatment partially attenuated these responses. Progression of renal interstitial fibrosis was accompanied by phosphorylation of signal transducer and activator of transcription 3 (STAT3) and altered the expression levels of two apoptosis‑related proteins (Bax and Bcl2). Losartan treatment also partially attenuated these responses. The results indicated that losartan attenuated renal fibrosis and renal tubular cell apoptosis in a rat model of UUO. This effect appeared to be mediated by partial blockage of STAT3 phosphorylation.

Inhibition of cellular transdifferentiation by losartan minimizes but does not reverse type 2 diabetes-induced renal fibrosis

HYPOTHESIS/INTRODUCTION

Transformer Growth Factor (TGF-β1) and angiotensin II (AngII) induce epithelial mesenchymal transition (EMT) and myofibroblastic transdifferentiation (MFT) contributing to renal fibrosis. The present study evaluated the capacity of an AT1 receptor blocker (losartan) to induce the regression of pre-existing fibrosis via interference with MFT and EMT in a rat model of type 2 diabetes, and in cultured mesangial cells (MCs) stimulated with high glucose and AngII.

MATERIALS AND METHODS

After 12 weeks of diabetes induction (D12 group), animals showing evidence of nephropathy, were divided in groups untreated for additional 8 weeks (D20 group) and treated for additional 8 weeks with losartan (D20+los group).

RESULTS

D12 animals presented hyperglycemia, insulin resistance, hypertension, proteinuria, increased levels of TGF-β1 and MFT/EMT markers. Losartan stabilized all of these parameters and hindered the progression of fibrosis, but it did not reverse the pre-existing fibrotic manifestations. Losartan reduced TGF-β1 in the tubules, but not in the glomeruli. Stimulated MC exhibited myofibroblast phenotype and capacity for migration, which were completely reversed by losartan.

CONCLUSIONS

Cellular transition may play a role in diabetes-inducing renal fibrogenesis in both AngII-TGF-β1 axis-dependent and independent manners. Losartan was efficient in preventing cells from undergoing further transdifferentiation, but this strategy was not sufficient to induce regression of the pre-existing tissue fibrosis.

Addition of ET(A) receptor blockade increases renoprotection provided by renin-angiotensin system blockade in 5/6 nephrectomized Ren-2 transgenic rats

AIMS

There is evidence that in addition to hypertension and hyperactivity of the renin-angiotensin system (RAS), enhanced intrarenal activity of endothelin (ET) system contributes to the pathophysiology and progression of chronic kidney disease (CKD). This prompted us to examine if this progression would be alleviated by addition of type A ET receptor (ETA) blockade to the standard blockade of RAS.

MAIN METHODS

Ren-2 transgenic rats (TGR) after 5/6 renal ablation (5/6 NX) served as a model of CKD. For RAS inhibition a combination of angiotensin-converting enzyme inhibitor (trandolapril, 6 mg/L drinking water) and angiotensin II type 1 receptor blocker (losartan, 100 mg/L drinking water) was used. Alternatively, ETA receptor blocker (atrasentan, 5 mg·kg(-1)·day(-1) in drinking water) was added to the combined RAS blockade. The follow-up period was 44 weeks after 5/6 NX, and the rats' survival rate, systolic blood pressure (SBP), proteinuria and indices of renal glomerular damage were evaluated.

KEY FINDINGS

The survival rate was at first improved, by either therapeutic regime, however, the efficiency of RAS blockade alone considerably decreased 36 weeks after 5/6 NX: final survival rate of 65% was significantly lower than 91% achieved with combined RAS and ETA receptor blockade. SBP was not affected by the addition of ETA blockade while proteinuria and renal glomerular damage were further reduced.

SIGNIFICANCE

Our data show that a combined RAS and ETA receptor blockade exhibits additional beneficial effects on survival rate and the progression of CKD in 5/6 NX TGR, as compared with RAS inhibition alone.

Effect of treatment on urinary kidney injury molecule-1 in IgA nephropathy

Background

Kidney injury molecule-1 (KIM-1) is a biomarker useful for detecting early tubular damage and has been recently reported as a useful marker for evaluating kidney injury in IgA nephropathy (IgAN). We therefore investigated whether treatment decreases urinary KIM-1 excretion in IgAN.

Methods

We prospectively enrolled 37 patients with biopsy-proven IgAN. Urinary KIM-1 was assessed before and after treatment, which included low salt diet, blood pressure control, pharmacotherapy with angiotensin receptor blockers and/or angiotensin converting enzyme inhibitors, and immunosuppressive agents as necessary. The median treatment duration was 24 months.

Results

Urinary KIM-1/creatinine (Cr) was significantly decreased in patients with IgAN after treatment compared to baseline (P < 0.0001, 1.16 [0.51-1.83] vs 0.26 [0.12-0.65] ng/mg). There was a decrease in the amount of proteinuria after treatment, but it was not statistically significant (P = 0.052, 748.1 [405-1569.7] vs 569.2 [252.2-1114] g/d). Estimated glomerular filtration rate (eGFR) did not change with treatment (P = 0.599, 79.28 ± 30.56 vs 80.98 ± 32.37 ml/min/1.73 m²). Urinary KIM-1 was not correlated with proteinuria baseline or follow up (pre-: R = - 0.100, P = 0.577, post-: R = 0.001, P = 0.993). In patients with higher baseline urinary KIM-1, both urinary KIM-1 level and proteinuria were significantly decreased following treatment.

Conclusions

Treatment decreases urinary KIM-1/Cr in patients with IgAN. It also reduces proteinuria in patients with higher baseline urinary KIM-1. These results suggest a potential role for urinary KIM-1 as a biomarker for predicting treatment response in IgAN, however, further study is needed to verify this.

Effects of chronotherapy of benazepril on the diurnal profile of RAAS and clock genes in the kidney of 5/6 nephrectomy rats

This study investigated the effects of benazepril administered in the morning or evening on the diurnal variation of renin-angiotensin-aldosterone system (RAAS) and clock genes in the kidney. The male Wistar rat models of 5/6 subtotal nephrectomy (STNx) were established. Animals were randomly divided into 4 groups: sham STNx group (control), STNx group, morning benazepril group (MB) and evening benazepril group (EB). Benazepril was intragastrically administered at a dose of 10 mg/kg/day at 07:00 and 19:00 in the MB group and EB group respectively for 12 weeks. All the animals were synchronized to the light:dark cycle of 12:12 for 12 weeks. Systolic blood pressure (SBP), 24-h urinary protein excretion and renal function were measured at 11 weeks. Blood samples and kidneys were collected every 4 h throughout a day to detect the expression pattern of renin activity (RA), angiotensin II (AngII) and aldosterone (Ald) by radioimmunoassay (RIA) and the mRNA expression profile of clock genes (bmal1, dbp and per2) by real-time PCR at 12 weeks. Our results showed that no significant differences were noted in the SBP, 24-h urine protein excretion and renal function between the MB and EB groups. There were no significant differences in average Ald and RA content of a day between the MB group and EB group. The expression peak of bmal1 mRNA was phase-delayed by 4 to 8 h, and the diurnal variation of per2 and dbp mRNA diminished in the MB and EB groups compared with the control and STNx groups. It was concluded when the similar SBP reduction, RAAS inhibition and clock gene profile were achieved with optimal dose of benazepril, morning versus evening dosing of benazepril has the same renoprotection effects.

Regression of albuminuria and hypertension and arrest of severe renal injury by a losartan-hydrochlorothiazide association in a model of very advanced nephropathy

Treatments that effectively prevent chronic kidney disease (CKD) when initiated early often yield disappointing results when started at more advanced phases. We examined the long-term evolution of renal injury in the 5/6 nephrectomy model (Nx) and the effect of an association between an AT-1 receptor blocker, losartan (L), and hydrochlorothiazide (H), shown previously to be effective when started one month after Nx. Adult male Munich-Wistar rats underwent Nx, being divided into four groups: Nx+V, no treatment; Nx+L, receiving L monotherapy; Nx+LH, receiving the L+H association (LH), and Nx+AHHz, treated with the calcium channel blocker, amlodipine, the vascular relaxant, hydralazine, and H. This latter group served to assess the effect of lowering blood pressure (BP). Rats undergoing sham nephrectomy (S) were also studied. In a first protocol, treatments were initiated 60 days after Nx, when CKD is at a relatively early stage. In a second protocol, treatments were started 120 days after Nx, when glomerulosclerosis and interstitial fibrosis are already advanced. In both protocols, L treatment promoted only partial renoprotection, whereas LH brought BP, albuminuria, tubulointerstitial cell proliferation and plasma aldosterone below pretreatment levels, and completely detained progression of renal injury. Despite normalizing BP, the AHHz association failed to prevent renal damage, indicating that the renoprotective effect of LH was not due to a systemic hemodynamic action. These findings are inconsistent with the contention that thiazides are innocuous in advanced CKD. In Nx, LH promotes effective renoprotection even at advanced stages by mechanisms that may involve anti-inflammatory and intrarenal hemodynamic effects, but seem not to require BP normalization.

Renoprotective effects of telmisartan on renal injury in obese Zucker rats

The purpose of the present study was to investigate the renoprotective effect of telmisartan, an angiotensin II receptor antagonist, on the early stages of diabetic nephropathy in obese Zucker rats, which is a type 2-related diabetes mellitus model. Telmisartan 1, 3 or 10 mg/kg/day was orally administered to 7-week-old rats that demonstrated glucose tolerance without albuminuria or proteinuria, for 24 consecutive weeks (Experiment A). In another experiment (Experiment B), oral administration of telmisartan 10 mg/kg/day was initiated at the age of 16 weeks after the rats demonstrated marked proteinuria, and continued for 24 weeks. Telmisartan inhibited the increase in proteinuria and albuminuria in a dose-dependent manner, and the inhibition for all telmisartan groups was statistically significant by the completion of administration (Experiment A). Telmisartan also displayed similar inhibitory effects on proteinuria and albuminuria in Experiment B. Histologically, telmisartan [3 and 10 mg/kg/day] was associated with a significant decrease in the progression of glomerulosclerosis, and significantly improved interstitial cell infiltration, interstitial fibrosis and dilation and atrophy of renal tubules. Furthermore, telmisartan treatment was associated with a tendency towards normalized plasma lipids (total cholesterol and triglyceride). Our results suggest that telmisartan has a definite renoprotective effect against renal injury in type II diabetic nephropathy.

Low dose of hydrochlorothiazide, in combination with angiotensin receptor blocker, reduces blood pressure effectively without adverse effect on glucose and lipid profiles

Previous studies have shown highly effective lowering of blood pressure with thiazide diuretics in combination with angiotensin receptor blockers. However, thiazide diuretics may cause the development of diabetes and abnormal lipid metabolism. Little is known as to whether dysmetabolic potential of thiazide diuretics could be neutralized when adding angiotensin receptor blockers. This study consisted of 26 patients with essential hypertension. Patients were randomized to 24 weeks of treatment with either candesartan, 12 mg monotherapy (n = 13, group A), or hydrochlorothiazide (HCTZ), 6.25 mg in combination with candesartan, 8 mg (n = 13, group B). Before and after treatment, we assessed glucose and lipid profiles including adiponectin, resistin, and active glucagon-like peptide-1 (GLP-1) levels. At baseline, there were no differences in age, body mass index, systolic blood pressure (SBP), and diastolic blood pressure (DBP), as well as plasma levels of hemoglobin A1c, insulin, low-density lipoprotein cholesterol, triglycerides, adiponectin, resistin, and active GLP-1 between the two groups. There were significant reductions in SBP (from 152 ± 10 mmHg at baseline to 134 ± 12 mmHg after treatment) and DBP (from 84 ± 5 mmHg at baseline to 71 ± 8 mmHg after treatment) in group A. There were also significant reductions in SBP (from 148 ± 10 at baseline to 128 ± 7 mmHg after treatment) and DBP (from 90 ± 9 at baseline to 74 ± 12 mmHg after treatment) in group B. There were no differences in reduction of SBP or DBP after 24 weeks of treatment between the two groups. There were no changes of the glucose and lipid profiles, including adiponectin, resistin, insulin, and active GLP-1 levels after 24 weeks of treatment in both groups. A low dose of HCTZ in combination with candesartan reduces blood pressure effectively without adverse effects on the glucose and lipid profiles. Therefore, the combination of thiazide diuretics and angiotensin receptor blockers could assist patients in achieving long-term control of blood pressure with good tolerability.

Podocyte biology in segmental sclerosis and progressive glomerular injury

During the past 2 decades, progress has been made in understanding the biology and mechanisms of podocyte injury and the relationship of these processes to glomerulosclerosis. In addition, studies of human biopsies and animal models have provided insights into the mechanisms of glomerular disease progression and repair. These new developments are critical for establishing better therapeutic guidelines that target specific pathways, which otherwise would lead to irreversible injury.

Combination therapy with an angiotensin II receptor blocker and an HMG-CoA reductase inhibitor in experimental subtotal nephrectomy

BACKGROUND

Angiotensin receptor 1 blockers (ARB) are standard nephroprotective drugs in chronic kidney disease. There is less evidence for a nephroprotective effect of HMG-CoA reductase inhibitors (statins) and much less is known about potential benefits of combination therapy. We evaluated the therapeutic potential of a statin alone or in combination with an ARB in experimental chronic kidney disease.

METHODS

Subtotally nephrectomized (5/6 Nx) rats were treated early with vehicle, losartan, cerivastatin or losartan/cerivastatin. Expression of messenger RNA (mRNA) was assessed by real-time reverse transcription-polymerase chain reaction. Tissue proteins were localized by immunohistochemistry. Nuclear factor-κB (NF-κB) activation was measured in whole kidneys.

RESULTS

In contrast to the sham group, at 6 weeks, vehicle-treated 5/6 Nx rats displayed renal lesions, albuminuria and increased blood pressure, serum creatinine and total kidney NF-κB p65 DNA-binding activity and preproendothelin-1, fibronectin and type I and III collagen mRNA. NF-κB activation correlated with albuminuria and histological renal injury. Losartan or combination therapy preserved renal function, abrogated albuminuria and improved glomerular and interstitial histology. Cerivastatin alone preserved renal function and improved interstitial injury but did not influence albuminuria, glomerular histology or NF-κB activation. Losartan/cerivastatin normalized kidney NF-κB activation and extracellular matrix mRNA expression pattern. The effect of losartan alone on these parameters was less intense. All treatments decreased preproendothelin-1 mRNA and preserved interstitial capillaries.

CONCLUSIONS

In a chronic kidney disease model, early treatment with either an ARB or a statin preserved renal function although the mechanisms differed. Combination therapy with an ARB and a statin did not confer clear-cut advantages on biochemical and histological parameters over ARB alone, although it further improved the kidney NF-κB and gene expression profile.

Increased capillary branching contributes to angiotensin type 1 receptor blocker (ARB)-induced regression of sclerosis

Chronic kidney disease is characterized by progressive glomerulosclerosis and tubulointerstitial fibrosis. High-dose angiotensin type 1 receptor blocker (ARB) or angiotensin-converting enzyme inhibitor can induce regression of existing glomerulosclerosis, at least in part by decreasing matrix accumulation. However, the potential mechanisms of remodeling of capillary loops remain obscure. This study aimed to determine whether capillary branching was augmented in glomeruli with ARB-induced regression of sclerosis. Three-dimensional confocal images were assessed by graph theory analysis to explore the topology of the glomerular capillary network. Compared with normal glomeruli, glomeruli of rats with progressive sclerosis were enlarged but had a significantly reduced number of capillary segments and capillary branch points and decreased complexity of the glomerular network. In contrast, in rats with regression of sclerosis induced by ARB, glomerular enlargement was due to a significantly increased number of glomerular capillary segments and capillary branch points and restored complexity of the capillary network. These data support the theory that capillary growth contributes to regression of sclerosis and is mediated at least in part by ARB-induced increased complexity and branching of capillary segments.

Angiotensin type 1 receptor modulates macrophage polarization and renal injury in obesity

The mechanisms for increased risk of chronic kidney disease (CKD) in obesity remain unclear. The renin-angiotensin system is implicated in the pathogenesis of both adiposity and CKD. We investigated whether the angiotensin type 1 (AT(1)) receptor, composed of dominant AT(1a) and less expressed AT(1b) in wild-type (WT) mice, modulates development and progression of kidney injury in a high-fat diet (HFD)-induced obesity model. WT mice had increased body weight, body fat, and insulin levels and decreased adiponectin levels after 24 wk of a high-fat diet. Identically fed AT(1a) knockout (AT1aKO) mice gained weight similarly to WT mice, but had lower body fat and higher plasma cholesterol. Both obese AT1aKO and obese WT mice had increased visceral fat and kidney macrophage infiltration, with more proinflammatory M1 macrophage markers as well as increased mesangial expansion and tubular vacuolization, compared with lean mice. These abnormalities were heightened in the obese AT1aKO mice, with downregulated M2 macrophage markers and increased macrophage AT(1b) receptor. Treatment with an AT(1) receptor blocker, which affects both AT(1a) and AT(1b), abolished renal macrophage infiltration with inhibition of renal M1 and upregulation of M2 macrophage markers in obese WT mice. Our data suggest obesity accelerates kidney injury, linked to augmented inflammation in adipose and kidney tissues and a proinflammatory shift in macrophage and M1/M2 balance.

Effects of Huanshuai Recipe Oral Liquid on restructuring glomerular microvasculature and expression of vascular endothelial growth factor in subtotal nephrectomized rats

OBJECTIVES

To explore the effects and significance of Huanshuai Recipe Oral Liquid (, HSR), a formula with supplementing qi, nourishing blood and activating blood on restructuring glomerular microvasculature and expression of vascular endothelial growth factor (VEGF) in subtotal nephrectomized (SNX) rats.

METHODS

A total of 76 male Wistar rats were randomly divided into four groups: 16 in the sham-operated group and fed with tap water 10 mL/kg per day; 20 in the model group were operated with 5/6 SNX and fed with tap water 10 mL/ kg per day; 20 SNX rats in the HSR group were treated with HSR 10 mL/kg per day; 20 SNX rats in the losartan group were treated with losartan 40 mg/kg per day. Serum creatinine (SCr) and urinary protein excretion (Upro) were examined at the 2nd, 4th, 8th, and 12th weeks of the treatment, and the remnant kidneys were harvested. Changes in histological microstructure were evaluated using light microscopy, and the expression of VEGF was detected by using ELISA.

RESULTS

Upro, microvasculature injury and glomerulosclerosis were found to be alleviated in HSR and Losartan groups, respectively. The change of VEGF expression showed positive correlation with glomerular capillary area and peritubular capillary number (r=0.448, r=0.422, P<0.01), but negative correlation with that of SCr and Upro (r=-0.592, r=-0.481, P<0.01).

CONCLUSIONS

HSR could regulate the VEGF expression, reduce the loss of microvasculature, which demonstrated similar renal protective effects to losartan in SNX rats. Examination of Chinese herbal medicine influence on VEGF signaling and restructuring renal microvasculature may elucidate the molecular mechanism of renal protection to a certain degree.

The role of renin angiotensin system inhibition in kidney repair

Chronic kidney diseases share common pathogenic mechanisms that, independently from the initial injury, lead to glomerular hyperfiltration, proteinuria, and progressive renal scarring and function loss. Inhibition of the renin angiotensin system (RAS) has been consistently found to reduce or halt the progressive deterioration of renal function through reduction of blood pressure and proteinuria, the two main determinants of renal function decline. In few instances, RAS inhibition may even promote amelioration of the glomerular filtration rate. Animal data suggest that chronic therapy with angiotensin-converting enzyme inhibitors or angiotensin II receptor type I blockers promotes regression of glomerulosclerosis, even in later phases of the disease. In humans, studies investigating the effect of angiotensin II inhibition on renal structural changes have shown inconsistent results, possibly due to small numbers and/or short duration of follow-up. Whether regression of glomerulosclerosis relies on a direct regenerative effect of RAS inhibition or on spontaneous kidney self-repair after the injury has been removed is still unknown. Improved understanding of mechanisms that promote renal regeneration may help in designing specific therapies to prevent the development of end-stage renal disease. This is a desirable goal, considering the economic burden of chronic kidney diseases and their effect on morbidity and mortality.

Kidney regeneration

Neonephrogenesis, the capacity to regenerate renal tissue, is a distinctive feature of fish but not usually of mammals. However, evidence exists for kidney repair in response to insulting agents for animals and human beings. Studies have therefore been designed in the past few years to clarify the cellular and molecular basis of renal repair, with the aim to investigate the potential regenerative capacity of animal and human kidneys. Three main questions are being addressed by this research: whether terminally differentiated cells in adult animal kidneys have regenerative capacity; whether multipotent progenitor cells exist in kidneys; and whether renal repair can be favoured or accelerated by cells of extrarenal origin migrating to the kidney in response to injury. In this Review, we describe evidence of cellular and molecular pathways related to renal repair and regeneration, and review data from animal and human studies that show that the kidney might have regenerative capacity.

Combination therapy with SMP-534 and an angiotensin-converting enzyme inhibitor provides additional renoprotection in 5/6 nephrectomized rats

The number of patients with chronic kidney disease (CKD) has continuously grown worldwide. Treatment with antihypertensive agents reduces the rate of progression of CKD, however, there is still a large unmet need to develop strategies for the treatment of CKD. Although we have previously reported that the antifibrotic agent, SMP-534 inhibits the progression of CKD, it is unknown whether combination therapy with SMP-534 and antihypertensive agent shows additive effects on CKD. In present study, we examined whether combination therapy with SMP-534 and the antihypertensive agent, lisinopril is more effective than single therapy with SMP-534 or lisinopril on five-sixths nephrectomized (5/6Nx) rat model. Combination therapy with SMP-534 (50 mg/kg) and lisinopril (5 mg/kg) significantly decreased urinary albumin excretion, blood urea nitrogen (BUN) and serum creatinine and increased creatinine clearance in 5/6Nx rats. On the other hands, single treatment with SMP-534 or lisinopril did not improve renal function at this dose. In addition, combination therapy with SMP-534 and lisinopril significantly decreased extracellular matrix (ECM) accumulation in renal glomeruli and tubulointerstitial injury. These data suggest that combination therapy with an antifibrotic agent and an antihypertensive agent may offer a new therapeutic option for suppressing the progression of CKD.

Inhibition of angiotensin II receptor 1 limits tumor-associated angiogenesis and attenuates growth of murine melanoma

PURPOSE

We evaluated the involvement of angiotensin II (AngII)-dependent pathways in melanoma growth, through the pharmacological blockage of AT1 receptor by the anti-hypertensive drug losartan (LOS).

RESULTS

We showed immunolabeling for both AngII and the AT1 receptor within the human melanoma microenvironment. Like human melanomas, we showed that murine melanomas also express the AT1 receptor. Growth of murine melanoma, both locally and at distant sites, was limited in mice treated with LOS. The reduction in tumor growth was accompanied by a twofold decrease in tumor-associated microvessel density and by a decrease in CD31 mRNA levels. While no differences were found in the VEGF expression levels in tumors from treated animals, reduction in the expression of the VEGFR1 (Flt-1) at the mRNA and protein levels was observed. We also showed downregulation of mRNA levels of both Flt-4 and its ligand, VEGF-C.

CONCLUSIONS

Together, these results show that blockage of AT1 receptor signaling may be a promising anti-tumor strategy, interfering with angiogenesis by decreasing the expression of angiogenic factor receptors.

Use of angiotensin-converting enzyme inhibitor/angiotensin receptor blocker therapy to reduce cardiovascular events in high-risk patients: part 2

As presented previously in Part 1 of this 2-part article, many long-term clinical trials provide overwhelming evidence of the benefits of angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) across the cardiovascular continuum. Trials also indicate additive or synergistic effects of combination therapy in renal disease and heart failure. Part 2, which is presented here, discusses the extensive interaction of the renin-angiotensin system (RAS) with the cellular and molecular pathophysiology of cardiovascular disease and the cross-continuum effects of ARBs and ACE inhibitors, which raises the possibility that RAS inhibition can offer protection in high-risk patients who do not have symptoms. Although trial evidence supports the effectiveness of monotherapy, the benefits of combined ACE inhibitor/ARB therapy in high-risk patients await confirmation. Ongoing clinical research will provide new and important information regarding the efficacy of specific combination (ACE inhibitor/ARB) therapies.

Unexpected effect of angiotensin AT1 receptor blockade on tubuloglomerular feedback in early subtotal nephrectomy

After subtotal nephrectomy (STN), the remaining nephrons engage in hyperfiltration, which may be facilitated by a reduced sensitivity of the tubuloglomerular feedback (TGF) response to increased distal delivery. However, a muted TGF response would contradict the notion of remnant kidney as a prototype of angiotensin II (ANG II) excess, since ANG II normally sensitizes the TGF response and stimulates proximal reabsorption. We examined the role of ANG II as a modulator of TGF and proximal reabsorption in 7 days after STN in male rats. Single-nephron glomerular filtration rate (SNGFR) and proximal reabsorption (J(prox)) were measured in late proximal collections while perfusing Henle's loop for minimal and maximal TGF stimulation in rats treated with the angiotensin type 1 (AT(1)) receptor blocker losartan or placebo in drinking water for 7 days. Perfusion of Henle's loop yielded a robust TGF response in sham-operated rats. In STN, the feedback responses were highly variable and nil, on average. Paradoxical TGF responses to augmented late proximal flow were confirmed in SNGFR measurements from the early distal nephron. Chronic losartan treatment normalized the average TGF response without reducing the variability. J(prox) was subtly affected by chronic losartan in sham surgery or STN, after controlling for differences in SNGFR. However, when administered acutely into the early S1 segment, losartan potently suppressed J(prox) in STN and sham-operated rats alike. Chronic losartan stabilizes the TGF system in remnant kidneys. This cannot be explained by currently known actions of AT(1) receptors but is commensurate with a salutary effect of an intact TGF system on dynamic autoregulation of intraglomerular flow and pressure.

Effect of unilateral ureteral obstruction and anti-angiotensin II treatment on renal tubule and interstitial cell apoptosis in rats

AIM

To investigate the effects of angiotensin-converting enzyme inhibitor (cilazapril) and angiotensin II type I receptor antagonist (losartan) on tubular and interstitial cell apoptosis and caspase-3 activity in rats with obstructive nephropathy after unilateral ureteral obstruction.

METHODS

Rats with unilateral obstructive nephropathy and sham-operated rats were treated with cilazapril, losartan, or the vehicle (water). Tubular and interstitial cell apoptosis was detected morphologically on hematoxylin and eosin-stained renal specimens and by the terminal deoxynucleotidyl transferase-mediated nick end-labeling. Caspase-3 activity in whole-kidney tissue homogenates was measured colorimetrically.

RESULTS

After unilateral ureter ligation, there was a significant increase in the number of apoptotic tubular and interstitial cells in the obstructed kidney (P=0.049 and P=0.036, respectively, vs sham-operated rats, 10 days after ligation). In rats with unilateral obstructive nephropathy, neither cilazapril nor losartan had an effect on tubular cell apoptosis. However, cilazapril caused a significant increase in the number of renal apoptotic interstitial cells (P=0.019). Caspase-3 activity was not significantly different in rats with unilateral obstructive nephropathy than in sham-operated rats.

CONCLUSION

Rats with unilateral obstructive nephropathy had increased apoptosis of tubular and interstitial cells in comparison with sham-operated rats. Neither cilazapril nor losartan had an effect on tubular cell apoptosis, and cilazapril even increased interstitial cell apoptosis.

Inhibition of the renin-angiotensin system: is more better?

Inhibitors of the renin-angiotensin-aldosterone system (RAS) exert beneficial effects in diabetic nephropathy, but the possibility of regression of existing renal lesions remains to be investigated. Teles et al. tested the effects of the RAS inhibitor losartan in rats starting 10 months after induction of diabetes, when glomerular lesions were already present. They linked the reductions of proteinuria with regression of mesangial expansion. More advanced lesions were not affected. There were no dose-response renal effects of losartan.

Podocyte repopulation contributes to regression of glomerular injury induced by ACE inhibition

Angiotensin-converting enzyme (ACE) inhibition induces glomerular repair in the Munich Wistar Frömter (MWF) rat, a model of spontaneous glomerular injury. In this study, we investigated whether this effect is related to changes in glomerular cell number, particularly of podocytes, which are progressively lost with age. MWF rats with advanced nephropathy were studied at both 40 weeks and after 20 weeks of observation either with or without treatment with the ACE inhibitor lisinopril. Forty-week-old Wistar rats were used as controls. In untreated MWF rats, proteinuria, hypertension, glomerulosclerosis, and renal function worsened, while lisinopril induced regression of both functional and structural changes. Despite glomerular hypercellularity in untreated MWF rats, the number of endothelial cells per glomerulus did not change, and podocyte number even decreased. ACE inhibition halted the progressive increase in glomerular cell number and enhanced endothelial cell volume density. Surprisingly, lisinopril not only halted age-related podocyte loss but also increased the number of glomerular podocytes above baseline, which was associated with an increased number of proliferating Wilms tumor 1-positive cells, loss of cyclin-dependent kinase inhibitor p27 expression, and increased number of parietal podocytes. These data indicate that ACE inhibition restructures glomerular capillary, primarily by restoring the podocyte population in this model of glomerular injury. Increased parietal podocyte number in lisinopril-treated MWF rats suggests that the remodeling of Bowman's capsule epithelial cells contributes to this effect.

Losartan chemistry and its effects via AT1 mechanisms in the kidney

Besides the importance of the renin-angiotensin system (RAS) in the circulation and other organs, the local RAS in the kidney has attracted a great attention in research in last decades. The renal RAS plays an important role in the body fluid homeostasis and long-term cardiovascular regulation. All major components and key enzymes for the establishment of a local RAS as well as two important angiotensin II (Ang II) receptor subtypes, AT1 and AT2 receptors, have been confirmed in the kidney. In additional to renal contribution to the systemic RAS, the intrarenal RAS plays a critical role in the regulation of renal function as well as in the development of kidney disease. Notably, kidney AT1 receptors locating at different cells and compartments inside the kidney are important for normal renal physiological functions and abnormal pathophysiological processes. This mini-review focuses on: 1) the local renal RAS and its receptors, particularly the AT1 receptor and its mechanisms in physiological and pathophysiological processes; and 2) the chemistry of the selective AT1 receptor blocker, losartan, and the potential mechanisms for its actions in the renal RAS-mediated disease.

PAI-1 and kidney fibrosis

Substantial evidence demonstrates a link of increased plasminogen activator inhibitor-1 (PAI-1) and glomerulosclerosis and kidney fibrosis, providing a novel therapeutic option for prevention and treatment of chronic kidney diseases. Several mechanisms contributing to increased PAI-1 will be addressed, including classic key profibrotic factors such as the renin-angiotensin-system (RAS) and transforming growth factor-beta (TGF-b???and novel molecules identified by proteomic analysis, such as thymosin- b4. The fibrotic sequelae caused by increased PAI-1 in kidney depend not only on its classic inhibition of tissue-type and urokinase-type plasminogen activators (tPA and uPA), but also its influence on cell migration.

Regression of glomerular injury by losartan in experimental diabetic nephropathy

Many features of chronic kidney disease may be reversed, but it is unclear whether advanced lesions, such as adhesions of sclerotic glomerular tufts to Bowman's capsule (synechiae), can resolve during treatment. We previously showed, using a renal ablation model, that the renoprotective effect of the AT-1 receptor blocker, losartan, is dose-dependent. Here we determined if moderate and advanced glomerular lesions, associated with streptozotocin-induced diabetes, regress with conventional or high-dose losartan treatment. Using daily insulin injection for 10 months, we maintained diabetic adult male Munich-Wistar rats in a state of moderate hyperglycemia. Following this period, some rats continued to receive insulin with or without conventional or high-dose losartan for an additional 2 months. Diabetic rats pretreated with insulin for 10 months and age-matched non-diabetic rats served as controls. Mesangial expansion was found in the control diabetic rats and was exacerbated in those rats maintained on only insulin for an additional 2 months. Conventional and high-dose losartan treatments reduced this mesangial expansion and the severity of synechiae lesions below that found prior to treatment; however, the frequency of the latter was unchanged. There was no dose-response effect of losartan. Our results show that regression of mesangial expansion and contraction of sclerotic lesions is feasible in the treatment of diabetes, but complete resolution of advanced glomerulosclerosis may be hard to achieve.