Effects of antihypertensive drugs on glomerular morphology

Glomerular hyperfiltration and hypertrophy: an evaluation of maximum values in pathological indicators to discriminate "diseased" from "normal"

The success of sodium-glucose cotransporter 2 inhibitors and bariatric surgery in patients with chronic kidney disease has highlighted the importance of glomerular hyperfiltration and hypertrophy in the progression of kidney disease. Sustained glomerular hyperfiltration and hypertrophy can lead to glomerular injury and progressive kidney damage. This article explores the relationship between obesity and chronic kidney disease, focusing on the roles of glomerular hyperfiltration and hypertrophy as hallmarks of obesity-related kidney disease. The pathological mechanisms underlying this association include adipose tissue inflammation, dyslipidemia, insulin resistance, chronic systemic inflammation, oxidative stress, and overactivation of the sympathetic nervous system, as well as the renin-angiotensin aldosterone system. This article explains how glomerular hyperfiltration results from increased renal blood flow and intraglomerular hypertension, inducing mechanical stress on the filtration barrier and post-filtration structures. Injured glomeruli increase in size before sclerosing and collapsing. Therefore, using extreme values, such as the maximal glomerular diameter, could improve the understanding of the data distribution and allow for better kidney failure predictions. This review provides important insights into the mechanisms underlying glomerular hyperfiltration and hypertrophy and highlights the need for further research using glomerular size, including maximum glomerular profile, calculated using needle biopsy specimens.

Impact of visceral fat area in patients with chronic kidney disease

Longitudinal studies evaluating the association between visceral fat area (VFA) and kidney function decline in patients with chronic kidney disease (CKD) are limited, and little is known about VFA interactions contributing to the kidney prognosis (e.g. interactions between VFA ≥ 100 cm² and age, sex, and CKD category). In this study, we stratified patients with CKD according to VFA category, as well as age, sex, CKD category, hyperglycemia, and diabetes mellitus, and determined the ability of obesity-related indicators (body mass index, waist circumference, subcutaneous fat area, visceral-to-subcutaneous fat ratio) to predict the renal prognosis. Kidney outcomes (≥ 50% estimated glomerular filtration rate decline or end-stage kidney disease) were examined in 200 patients with CKD (median follow-up, 12.3 years). On multivariable Cox analysis, an increase in VFA (10-cm² increase) was significantly associated with kidney outcomes in the entire cohort, and VFA was significantly associated with kidney disease progression even in the VFA < 100 cm² sub-cohort. Interestingly, the hazard ratio (HR) was higher for VFA (10-cm² increase) than for the VFA ≥ 100 cm² sub-cohort (HR 1.33 vs. 1.07). Overall, VFA was found to be the most versatile obesity-related indicator associated with kidney disease progression. VFA was associated with the primary outcome in the sub-cohorts of CKD stages 1-2, hyperglycemia, and diabetes mellitus. A high VFA was a significant kidney prognostic factor in the entire CKD cohort, with greater significance in patients with VFA < 100 cm² than in patients with VFA ≥ 100 cm². Our results may provide new insights into strategies for treating CKD.

Effects of amnion derived mesenchymal stem cells on fibrosis in a 5/6 nephrectomy model in rats

Chronic kidney disease (CKD) is characterized by disruption of the glomerulus, tubule and vascular structures by renal fibrosis. Mesenchymal stem cells (MSC) ameliorate CKD. We investigated the effects of human amnion derived MSC (hAMSC) on fibrosis using expression of transforming growth factor beta (TGF-β), collagen type I (COL-1) and bone morphogenetic protein (BMP-7). We also investigated levels of urinary creatinine and nitrogen in CKD. We used a 5/6 nephrectomy (5/6 Nx) induced CKD model. We used 36 rats in six groups of six animals: sham group, 5/6 Nx group, 15 days after 5/6 Nx (5/6 Nx + 15) group, 30 days after 5/6 Nx (5/6 Nx + 30) group, transfer of hAMSC 15 days after 5/6 Nx (5/6 Nx + hAMSC + 15) group and transfer of hAMSC 30 days after 5/6 Nx (5/6 Nx + hAMSC + 30) group. We isolated 10⁶ hAMSC from the amnion and transplanted them via the rat tail vein into the 5/6 Nx + hAMSC + 15 and 5/6 Nx + hAMSC + 30 groups. We measured the expression of BMP-7, COL-1 and TGF-β using western blot and immunohistochemistry, and their gene expressions were analyzed by quantitative real time PCR. TGF-β and COL-1 protein, and gene expressions were increased in the 5/6 Nx +30 group compared to the 5/6 Nx + hAMSC + 30 group. Conversely, both protein and gene expression of BMP-7 was increased in 5/6 Nx + hAMSC + 30 group compared to the 5/6 Nx groups. Increased TGF-β together with decreased BMP-7 expression may cause fibrosis by epithelial-mesenchymal transition due to chronic renal injury. Increased COL-1 levels cause accumulation of extracellular matrix in CKD. Levels of urea, creatinine and nitrogen were increased significantly in 5/6 Nx + 15 and 5/6 Nx + 30 groups compared to the hAMSC groups. We found that hAMSC ameliorate CKD.

Sex Differences in Time-Series Changes in Pseudo-R2 Values Regarding Hyperuricemia in Relation to the Kidney Prognosis

Studies on sex differences in time-series changes in pseudo-R² values regarding hyperuricemia (HU) in relation to the kidney prognosis among patients with chronic kidney disease (CKD) are scant. The kidney prognosis was evaluated in 200 patients with CKD (median follow-up, 12.3 years). Survival analyses and logistic regression analyses were conducted, generating time-series pseudo-R² values. We used four definitions of HU according to serum uric acid (SUA) levels (HU6, SUA ≥ 6.0 mg/dL; HU7, SUA ≥ 7.0 mg/dL; HU8, SUA ≥ 8.0 mg/dL) and antihyperuricemic agent use to calculate the mean and percentage of the change in pseudo-R² values from the 6th year until the end of the study (6Y–End Mean and 6Y–End Change, respectively). The multivariable Cox regression analysis showed that HU7 was significantly associated with kidney outcomes. When stratified by sex, the 6Y–End Mean was clearly higher in women than in men for all HU definitions, with the highest value (0.1755) obtained for HU7 in women. The pseudo-R² values for HU6 in women showed an increasing pattern, with a 6Y–End Change of 11.4%/year. Thus, it may be clinically meaningful to consider sex differences in the time-series pseudo-R² values regarding HU and kidney outcomes.

Visceral to subcutaneous fat ratio as an indicator of a ≥30% eGFR decline in chronic kidney disease

Whether the visceral-to-subcutaneous fat ratio (V/S ratio) is associated with renal prognosis in patients with chronic kidney disease (CKD) remains unclear. Furthermore, little is known about the effect of sex and the absolute amount of visceral fat accumulation such as visceral fat area (VFA) ≥100 cm² on the V/S ratio in relation to renal prognosis. In this study, 200 patients with CKD were evaluated for renal prognosis. Survival analyses and logistic regression analyses were conducted, generating time-series pseudo-R² values. The mean and percent change of the pseudo-R² values from the 6^th year to the 10^th year (6Y–10Y Mean and 6Y–10Y Change, respectively) were calculated for determining the cut-off points for the medium-term renal prognosis. Multivariate Cox regression analysis revealed that the V/S ratio was significantly associated with renal outcomes and that the VFA category (VFA ≥ 100 cm²) had significant interactions with the V/S ratio regarding renal prognosis. The hazard ratio (HR) of the V/S ratio was higher in the sub-cohort of VFA < 100 cm² than in the sub-cohort of VFA ≥ 100 cm² (HR: 6.42 vs. 1.00). Regarding sex differences, a strong association was noted between the V/S ratio and renal prognosis in women but not in men (HR: 2.40 vs. 1.10). On the other hand, 6Y–10Y Mean of the pseudo-R² values indicated differences in the cut-off points of the V/S ratio between men and women (V/S ratio: 0.75 vs. 0.5). Our findings indicate that it may be clinically meaningful to consider the differences in sex and the amount of VFA ≥100 cm² for the V/S ratio in relation to renal outcomes in patients with CKD. The 6Y–10Y Mean of the pseudo-R² values contributed to determining the cut-off points of the V/S ratio according to the sex difference.

Maximum Glomerular Diameter and Oxford MEST-C Score in IgA Nephropathy: The Significance of Time-Series Changes in Pseudo-R2 Values in Relation to Renal Outcomes

The progression of immunoglobulin A nephropathy (IgAN) is currently assessed using the Oxford MEST-C score, which uses five indicators (mesangial and endocapillary hypercellularity, segmental sclerosis, interstitial fibrosis/tubular atrophy, and the presence of crescents) but has not yet included any risk factors related to glomerular size. Therefore, we tested whether adding another indicator, maximal glomerular diameter (Max GD), would improve the prognostic ability of this scoring system. The data of 101 adult patients diagnosed with IgAN between March 2002 and September 2004 were reviewed. We used McFadden’s pseudo-R² and the corrected Akaike information criterion to assess model fit and the concordance (C)-statistic to assess discriminatory ability. A 10 μm increase in Max GD was significantly associated with a composite outcome (≥50% decline in the estimated glomerular filtration rate or end-stage renal disease). The receiver operating characteristic analysis determined the cut-off for high vs. low Max GD at 245.9 μm, and adding high Max GD to the MEST-C score significantly improved the model’s discrimination of renal outcomes at 5 and ≥10 years. Thus, including the Max GD in the Oxford classification of IgAN might increase its robustness and provide a more comprehensive prognostic system for clinical settings.

Early, but not late therapy with a vasopressin V1a-antagonist ameliorates the development of renal damage after 5/6 nephrectomy

Introduction. Vasopressin, mainly through the V1a-receptor, is thought to be a major player in the maintenance of hyperfiltration. Its inhibition could therefore lead to a decrease in progression of chronic renal failure.To this end, the effect of the vasopressin V1a-receptor-selective antagonist, YM218, was studied on proteinuria and focal glomerulosclerosis in early and late intervention after 5/6 nephrectomy in rats, and compared with an angiotensin-converting enzyme inhibitor (ACE-I).

Materials and methods. After 5/6 nephrectomy, early intervention was performed between week 2 and 10 thereafter with the V1a-receptor-selective antagonist (VRA, 10 mg/kg/day, n=10), enalapril (ACE-I, 10 mg/kg/day, n=9), or vehicle (n=8). Late intervention was performed in another group between week 6 and 12 with VRA (10 mg/kg/day, n=7), lisinopril (ACE-I, 5 mg/kg/day, n=7), or vehicle (n=7).

Results. In early intervention, proteinuria and focal glomerulosclerosis were significantly decreased by VRA compared to vehicle (44 7% and 59+8% respectively). ACE-I significantly decreased proteinuria (67 7%) and a trend towards a decrease in focal glomerulosclerosis was observed (30 18%). In late intervention, VRA did not decrease proteinuria and focal glomerulosclerosis compared to vehicle (21 20% and 0%, respectively),ACE-I significantly lowered proteinuria (92 2%) and a focal glomerulosclerosis (69+1%) lowering trend was observed.

Conclusion. These results indicate that VRA may protect against early progression of renal injury after 5/6 nephrectomy, whereas its effectiveness seems limited in established renal damage.

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.

The role of a low glomerular density and being overweight in the etiology of proteinuria in CKD patients without known glomerular diseases

BACKGROUND

Among the proteinuric patients with chronic kidney disease (CKD) who undergo a renal biopsy, we sometimes encounter those who cannot be classified as having a known primary or secondary glomerular disease. The pathogenesis and pathophysiology of these CKD patients have not been sufficiently elucidated.

METHODS

We recruited 34 proteinuric patients without known glomerular diseases. The glomerular volumes (GV) of the biopsy specimens from those patients were determined by a morphometric analysis. Glomerular hypertrophy (GH) was defined as having more than 3.6 × 10(6) μm(3). The patients were divided in two groups: those with GH (Group 1) and those without GH (Group 2). We compared the clinical and pathological parameters between Group 1 and Group 2, and among the three groups of patients: non-obese, overweight and obese group.

RESULTS

The patients with Group 1 had significantly higher values for the proportion of males, the body mass index (BMI), uric acid and significantly lower values for the glomerular density (GD). Of note, a multivariate regression analysis revealed that sex, the BMI and GD were significant factors correlated with the mean GV. The values for the mean GV were significantly higher in the overweight and obese groups as compared to the non-obese group, and the values for the GD were significantly lower in the obese group than in the non-obese group.

CONCLUSIONS

We identified a subgroup of patients who were characterized as having a high BMI and GV, and a low GD among the proteinuric CKD patients without known glomerular diseases.

Severe renal mass reduction impairs recovery and promotes fibrosis after AKI

Preexisting CKD may affect the severity of and/or recovery from AKI. We assessed the impact of prior graded normotensive renal mass reduction on ischemia-reperfusion-induced AKI. Rats underwent 40 minutes of ischemia 2 weeks after right uninephrectomy and surgical excision of both poles of the left kidney (75% reduction of renal mass), right uninephrectomy (50% reduction of renal mass), or sham reduction of renal mass. The severity of AKI was comparable among groups, which was reflected by similarly increased serum creatinine (SCr; approximately 4.5 mg/dl) at 2 days, tubule necrosis at 3 days, and vimentin-expressing regenerating tubules at 7 days postischemia-reperfusion. However, SCr remained elevated compared with preischemia-reperfusion values, and more tubules failed to differentiate during late recovery 4 weeks after ischemia-reperfusion in rats with 75% renal mass reduction relative to other groups. Tubules that failed to differentiate continued to produce vimentin, exhibited vicarious proliferative signaling, and expressed less vascular endothelial growth factor but more profibrotic peptides. The disproportionate failure of regenerating tubules to redifferentiate in rats with 75% renal mass reduction associated with more severe capillary rarefaction and greater tubulointerstitial fibrosis. Furthermore, initially normotensive rats with 75% renal mass reduction developed hypertension and proteinuria, 2-4 weeks postischemia-reperfusion. In summary, severe (>50%) renal mass reduction disproportionately compromised tubule repair, diminished capillary density, and promoted fibrosis with hypertension after ischemia-reperfusion-induced AKI in rats, suggesting that accelerated declines of renal function may occur after AKI in patients with preexisting CKD.

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.

Seliciclib inhibits renal hypertrophy but not fibrosis in the rat following subtotal nephrectomy

BACKGROUND

5/6 subtotal nephrectomy (SNx) is a non-immune stimulus used to induce renal fibrosis. The ability of seliciclib, a cyclin-dependent kinase inhibitor, to reduce kidney hypertrophy and extracellular matrix (ECM) deposition has been examined in the SNx rat.

METHODS

Wistar rats were subjected to SNx under isoflurane anaesthesia. The acute effect of seliciclib 28 mg/kg (5 days) on compensatory renal growth (CRG), kidney protein and DNA was determined. In chronic studies albuminuria, hypertension and GFR were monitored. Ki67, apoptag and α-smooth muscle actin were determined by immunohistochemistry together with Masson's trichrome staining. The effect of a maximum non-hypotensive dose of seliciclib 28 mg/kg (8 weeks) was determined.

RESULTS

Acutely, the remnant kidney developed CRG. Seliciclib 28 mg/kg inhibited both CRG by 45% and increased kidney protein by 48% without affecting increased kidney DNA. Chronically, SNx rats developed albuminuria, hypertension, low GFR with increased tubulointerstitial cell proliferation, apoptosis, myofibroblast accumulation and enhanced ECM deposition. Seliciclib 28 mg/kg (8 weeks) had no effect on either renal function or renal pathology. Plasma concentrations of seliciclib exceeded 5 µM throughout the study.

CONCLUSIONS

Despite inhibition of early renal hypertrophy, a maximum non-hypotensive dose of seliciclib 28 mg/kg had no impact on the progression of kidney fibrosis in the SNx rat.

Overweight and obesity accelerate the progression of IgA nephropathy: prognostic utility of a combination of BMI and histopathological parameters

BACKGROUND

Although more than 40 years have passed since IgA nephropathy (IgAN) was first reported, predicting the renal outcome of individual IgAN patients remains difficult. Emerging epidemiologic evidence indicates that overweight and obesity are risk factors for end-stage renal disease. We aimed to elucidate the outcome of overweight IgAN patients and improve our ability to predict the progression of IgAN based on a combination of body mass index (BMI) and histopathological parameters, including maximal glomerular area (Max GA).

METHODS

Forty-three adult IgAN patients whose estimated glomerular filtration rate was ≥50 ml/min/1.73 m(2) were enrolled in this study. Renal biopsy specimens were evaluated according to the Oxford classification of IgAN. A Kaplan-Meier analysis and the multivariate Cox proportional hazards method were used to evaluate 10-year kidney survival and the impact of covariates. The ability of factors to predict the progression of IgAN was evaluated by their diagnostic odds ratio (DOR).

RESULTS

A BMI ≥25 kg/m(2) was found to be an independent predictor of a ≥1.5-fold increase in serum creatinine value (DOR 7.4). The combination of BMI ≥25 kg/m(2), Max GA ≥42,900 μm(2), and presence of mesangial hypercellularity (Oxford M1) optimally raised predictive power for disease progression of IgAN (DOR 26.0).

CONCLUSION

A combination of BMI ≥25 kg/m(2), the Oxford classification M1, and a Max GA ≥42,900 μm(2) can serve as a predictor of long-term renal outcome of IgAN.

Maximal glomerular diameter as a 10-year prognostic indicator for IgA nephropathy

BACKGROUND

Although there have been many reports on clinicopathological studies of immunoglobulin A nephropathy (IgAN), reliable outcome predictors are still lacking. We therefore assessed maximal glomerular diameter (Max GD), an indicator of glomerular size, as a predictor of the long-term evolution of renal histopathology.

METHODS

Forty-three adult patients, diagnosed with IgAN, who had estimated glomerular filtration rate (eGFR) ≥50 mL/min/1.73 m(2), were enrolled in this study. Prognostic variables for renal survival were examined by using the multivariate Cox proportional hazards method. The optimal cut-off value of Max GD was 242.3 μm (AUC = 0.78, sensitivity = 62.5%, specificity = 81.5%) by using receiver operating characteristics analysis. In order to assess the characteristics of glomerular hypertrophy, we divided the cases into two groups according to the Max GD value (Group A, ≥242 μm; Group B, <242 μm). Renal survival was also assessed by Kaplan-Meier curves with the log-rank test.

RESULTS

The Max GD was significantly correlated with age, body mass index and serum triglyceride levels at the time of renal biopsy. During the 10-year follow-up period, the Max GD was significantly correlated with eGFR decline per year, and proteinuria, but not with hematuria. A multiple regression analysis by the Cox method adjusted for age, sex and eGFR showed that the Max GD values were significantly associated with a 1.5-fold increase in serum creatinine (Cr) values (hazard ratio = 1.04, P = 0.03). Renal function in 66.7% of the patients whose Max GD was ≥242 μm had at least a 1.5-fold increase in their serum Cr value at the 10-year follow-up examination (log-rank, P = 0.003).

CONCLUSIONS

The results of this study suggest that Max GD is a simple quantitative prognostic indicator of the disease progression in IgAN patients.

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.

Combined inhibition of 20-hydroxyeicosatetraenoic acid formation and of epoxyeicosatrienoic acids degradation attenuates hypertension and hypertension-induced end-organ damage in Ren-2 transgenic rats

Recent studies have shown that the renal CYP450 (cytochrome P450) metabolites of AA (arachidonic acid), the vasoconstrictor 20-HETE (20-hydroxyeicosatetraenoic acid) and the vasodilator EETs (epoxyeicosatrienoic acids), play an important role in the pathophysiology of AngII (angiotensin II)-dependent forms of hypertension and the associated target organ damage. The present studies were performed in Ren-2 renin transgenic rats (TGR) to evaluate the effects of chronic selective inhibition of 20-HETE formation or elevation of the level of EETs, alone or in combination, on the course of hypertension and hypertension-associated end-organ damage. Both young (30 days of age) prehypertensive TGR and adult (190 days of age) TGR with established hypertension were examined. Normotensive HanSD (Hannover Sprague-Dawley) rats served as controls. The rats were treated with N-methylsulfonyl-12,12-dibromododec-11-enamide to inhibit 20-HETE formation and/or with N-cyclohexyl-N-dodecyl urea to inhibit soluble epoxide hydrolase and prevent degradation of EETs. Inhibition in TGR of 20-HETE formation combined with enhanced bioavailability of EETs attenuated the development of hypertension, cardiac hypertrophy, proteinuria, glomerular hypertrophy and sclerosis as well as renal tubulointerstitial injury. This was also associated with attenuation of the responsiveness of the systemic and renal vascular beds to AngII without modifying their responses to noradrenaline (norepinephrine). Our findings suggest that altered production and/or action of 20-HETE and EETs plays a permissive role in the development of hypertension and hypertension-associated end-organ damage in this model of AngII-dependent hypertension. This information provides a basis for a search for new therapeutic approaches for the treatment of hypertension.

Changes seen in the aging kidney and the effect of blocking the renin—angiotensin system

Background: The objective was to evaluate structural changes of glomeruli during aging and the role of chronic renin—angiotensin system inhibition (RASi) on these changes; starting RASi on Wistar rats at two different moments: the first group after weaning and the second at the midpoint of their lifespan (12 months).

Methods: Thirty rats were divided, after weaning, into three groups of 10: group 1: control (C); group 2 : 30 mg/kg/day losartan (L); group 3 : 10 mg/kg/day enalapril (E). At 18 months, rats were placed in metabolic cages to evaluate proteinuria, then killed. Another group of 24 rats, 12 months old, were divided into three groups of eight: group 1: C; group 2: L; group 3: E. At 18 months the same procedure described above was carried out. Finally, a third group of 20 rats was studied as healthy controls and killed: 10 rats at 7 months and ten at 12 months of age. Tissue samples were collected after sacrifice. To evaluate glomerular fibrotic changes, both focal and periglomerular sclerosis, and mesangial matrix expansion, a scoring scale was established. We also evaluated anti-α-SM-actin and anti-collagen-III immunolabeling. Glomerular area was measured using an image analyzer.

Results: Proteinuria and serum creatinine increased with age but were reduced in treated animals. Main glomerular changes present in 18-month-old rats were reduced by half in treated animals. Glomerular area showed significant increase with normal aging and all treatment strategies protected against it.

Conclusion: RAS plays a central role in natural process of renal aging, probably by producing effects influencing the biology of aging, the effects of which can be attenuated by RASi.

Dietary protein causes a decline in the glomerular filtration rate of the remnant kidney mediated by metabolic acidosis and endothelin receptors

Dietary casein promotes a progressive decline in the glomerular filtration rate (GFR) of remnant kidneys associated with metabolic acidosis and an endothelin-mediated increase in renal acidification. We tested whether diets that affect the acid-base status contributes to the decline of GFR through endothelin receptors in rats with a remnant kidney. Rats on a casein diet had metabolic acidosis at baseline and developed a progressive decline in GFR after renal mass reduction. Dietary sodium bicarbonate but not sodium chloride ameliorated metabolic acidosis and prevented the decrease in GFR but only after the sodium bicarbonate-induced increase in blood pressure was treated. Dietary soy protein did not induce baseline metabolic acidosis and rats with remnant kidney on a soy diet had no decrease in their GFR. By contrast, rats with a remnant kidney on soy protein given dietary acid developed metabolic acidosis and a decreased GFR. This decline in GFR was prevented in either case by endothelin A but not endothelin A/B receptor antagonism. Our study suggests that the casein-induced decline in GFR of the remnant kidney is mediated by metabolic acidosis through endothelin A receptors.

The Perfusion Pressure in Non–Heart-Beating Donors May Expand the Glomeruli

INTRODUCTION

We have observed expanded glomeruli in biopsies of kidneys from non-heart-beating donors (NHBDs). We sought to determine the differences in glomerular size between NHBDs and brain-dead donors and to assess whether glomerular size impacted graft outcome.

METHODS

We estimated the glomerular area using the maximal planar area (MPA) method in 198 pretransplant biopsies from 119 donors: 54 (45.4%) NHBDs and 65 (54.6%) brain-dead donors. Donor data and graft outcomes were correlated with MPA and percentage of glomerulosclerosis. The range of follow-up was 1 to 3 years. Uni- and multivariate analyses were performed.

RESULTS

MPA was larger among NHBDs. MPA and GS both significantly correlated with donor age. The association between MPA and age was independent of nephron loss (ie; GS). Increased glomerular size was only observed among donors younger than 50 years. Graft survival and function were not independently associated with MPA. Donor age was a better predictor of graft outcome.

CONCLUSIONS

The perfusion pressure used in NHBDs may expand the glomeruli, but this maneuver does not have any effect on graft outcome. Among donors without severe changes, glomerular size increment shows a limit around the sixth decade of life. In our study, MPA was not an independent predictor of graft survival or function.

Factors influencing the progression of renal damage in patients with unilateral renal agenesis and remnant kidney

BACKGROUND

Although some studies have shown that the risk to develop proteinuria and renal insufficiency is increased in patients with a remnant kidney (RK) or unilateral renal agenesis (URA), other patients maintain normal renal function and negative proteinuria, and the reasons to explain these different outcomes are not known.

METHODS

We performed a retrospective study of 54 patients with a severe reduction in renal mass (33 patients with URA and 21 with RK). Follow-up was 100 +/- 72 months.

RESULTS

Twenty patients (group 1) showed normal renal function at presentation, whereas the 34 remaining (group 2) had proteinuria, and some of them renal insufficiency. Group 2 patients were older and had a higher blood pressure and BMI than group 1 patients. Eleven patients of group 1 remained normal throughout follow-up (group 1A), whereas the remaining 9 developed proteinuria/renal insufficiency (group 1B). BMI at presentation was significantly higher in group 1B: 27 +/- 3.6 kg/m(2) versus 21.6 +/- 2.6 kg/m(2), and BMI was the only factor statistically associated with the risk to develop proteinuria/renal insufficiency in group 1. Among group 2 patients, renal function remained stable in 20 (group 2A), and deteriorated (>50% increase of baseline serum creatinine) in the remaining 14 patients (group 2B). BMI at presentation and treatment with ACEI during follow-up were the only factors statistically associated with the risk for renal failure progression among group 2 patients.

CONCLUSION

Overweight plays a fundamental role in the appearance of proteinuria and renal damage in patients with severe renal mass reduction.

The role of the renin angiotensin system in chronic renal disease

End-stage renal disease (ESRD) is a costly and debilitating condition affecting 250,000 patients in the United States. The incidence of ESRD has doubled in the past 10 years and is expected to continue to increase well into the next century as our population ages. Over the past 20 years investigative efforts have been focused on defining the pathophysiological basis of chronic renal disease and on therapeutic interventions designed to prevent its progression to renal failure. Several experimental models of progressive renal disease have been developed and used to examine potential mechanisms which may contribute to the pathophysiology of renal failure. Data from these studies indicate that the renin-angiotensin system (RAS) contributes significantly to the pathophysiology of renal disease in the experimental models examined. Data from clinical studies also indicates that the RAS contributes to the progression of renal disease in man as well. While our knowledge in this area is far from complete, numerous experimental and clinical studies have demonstrated that the blockade of the RAS has a distinct advantage in preventing the progression of renal insufficiency to complete renal failure.

Blood pressure lability and glomerulosclerosis after normotensive 5/6 renal mass reduction in the rat

BACKGROUND

Hypertension plays a major role in the progression of both experimental and clinical chronic renal disease. However, the pathogenesis of the more slowly developing glomerulosclerosis that is seen even in the absence of overt hypertension, both in renal mass reduction models and in humans with chronic renal disease, remains controversial.

METHODS

The relationship of such glomerulosclerosis to the ambient blood pressure profiles was examined in the normotensive approximately 5/6 surgical excision rat remnant kidney model. Blood pressure was radiotelemetrically monitored at 10-minute intervals for 15 to 16 weeks ( approximately 15,000 blood pressure readings) in untreated rats (N= 13), or those treated with enalapril (N= 8), amlodipine (N= 9), or a combination of hydralazine, reserpine, and hydrochlorothiazide (N= 10).

RESULTS

Even in these normotensive rats (systolic blood pressure <140 mm Hg), % glomerulosclerosis was significantly correlated with the overall average systolic blood pressure (r= 0.62, P < 0.0001; N= 40). However, much stronger correlations were observed between glomerulosclerosis and the % systolic blood pressure readings >150 mm Hg (r= 0.77, P < 0.0001) and the standard deviation of the average systolic blood pressure (r= 0.87, P < 0.0001).

CONCLUSION

These data indicate that pressure dependent injury mechanisms continue to contribute to glomerular injury even within the "normotensive" blood pressure range in rats with reduced renal mass. This most likely represents the consequence of the impairment of protective renal autoregulation and enhanced glomerular transmission of the blood pressure fluctuations into the hypertensive range characteristic of the conscious state in both experimental animals and in humans. Such pathophysiology supports the need for more aggressive and around-the-clock blood pressure control in chronic renal disease.

Hypertension but Not Sodium Intake Determines Progression of Renal Failure in Experimentally Uremic Rats

BACKGROUND/AIMS

High sodium intake is implicated in contributing to progression of chronic renal failure. We studied the effect of high sodium consumption on progression of rat experimental renal failure while sodium-induced hypertension was pharmacologically controlled.

METHODS

64 Sprague-Dawley rats underwent 5/6 nephrectomy. Subsequently, they were divided in three groups which were fed either low, normal, or high sodium diet. Only the high sodium-consuming group developed hypertension. This group was further divided in two subgroups in which hypertension was either untreated or titrated to normotension by hydralazine alone or with propranolol.

RESULTS

Sequential GFR values did not differ between the respective normotensive groups. Survival downslopes of all three normotensive groups (including the pharmacologically treated, high sodium-consuming subgroup) were also similar, extending over 10 weeks. By contrast, pharmacologically untreated animals exhibited severe hypertension and 100% mortality within 3 weeks. In all experimental groups, 24-hour urinary sodium excretion paralleled sodium intake. Proteinuria rose similarly and significantly in all animals on high sodium. A significant correlation between 24-hour sodium and proteinuria was evident throughout the experimental period.

CONCLUSIONS

(1) In 5/6 nephrectomized rats, renal function deterioration was not affected by dietary sodium, provided hypertension was pharmacologically controlled. (2) Enhanced proteinuria secondary to high sodium consumption had no adverse effect on progression of renal failure in this model.

Global heterogeneity of glomerular volume distribution in early diabetic nephropathy

BACKGROUND

Morphologic characteristics in early stage of nephropathy of noninsulin-dependent diabetes mellitus (NIDDM) have not been determined despite the fact thatdiagnosis in this stage of the disease is important for the prognosis. We hypothesized that heterogeneity in glomerular volume-distribution may be a sensitive index of early stage of diabetic nephropathy in NIDDM.

METHODS

In spontaneous diabetic rats [Otsuka Long-Evans Tokushima Fatty (OLETF) rat (N= 5)] of 27 to 28 weeks, an experimental model of early diabetic nephropathy in human NIDDDM and age-matched control rats [Long Evans Tokushima Lean (LETO) rat (N= 5)], we completely filled the kidney with contrast medium. Glomeruli were visualized as three-dimensional images using x-ray micro-computed tomography (micro-CT). Glomerular volumes (N= 400 in each kidney) were directly measured and evaluated as absolute volume and normalized values to kidney weight and body weight. Scattering of glomerular volume-distribution was evaluated as coefficient variation (CV) (SD/mean).

RESULTS

The CV was significantly larger in OLETF rat (0.195) comparing to LETO rat (0.146, P < 0.01). This difference was even consistent under the normalization to kidney weight and body weight. Absolute glomerular volume was larger in OLETF rat compared to LETO rat (P < 0.005); however, when glomerular volume was normalized, this variable was comparable between two groups.

CONCLUSION

We visualized three-dimensional glomerular images in the early stages of diabetic nephropathy using micro-CT and quantified the heterogeneity in glomerular volume distribution throughout the cortex by direct measurement of the individual. We propose that heterogeneity in glomerular volume distribution is a sensitive parameter to ascertain early diabetic nephropathy in NIDDM.

Glomerular hemodynamic changes associated with arteriolar lesions and tubulointerstitial inflammation

Glomerular hemodynamic adaptations to loss of renal mass are thought to be the initiating factor of progression to renal failure; however, tubulointerstitial (TI) injury correlates better with progression than with glomerular damage. Thus, it is conceivable that tubulointerstitial alterations participate in the pathophysiology of renal disease progression by modifying the adaptive responses of glomerular hemodynamics. In experimental models of progressive renal disease, suppressing tubulointerstitial inflammatory cell infiltration with anti-inflammatory drugs reduces renal damage despite persistence of systemic hypertension. In recent studies in rats with subtotal renal ablation, we found that treatment with polysulphate pentosan (PPS) and with mycophenolate mofetil (MMF) prevented proteinuria, glomerular hypertension, and hyperfiltration, despite persisting arterial hypertension due to higher afferent resistance. In addition, arteriolopathy was significantly attenuated by MMF, suggesting preservation of vascular structure and function. Association of vascular injury of afferent arterioles, glomerular hemodynamic changes, and renal lesions has been described in other conditions such as hyperuricemia, protein overload, fawn-hooded rats, and aging spontaneously hypertensive rats (SHR). Arteriolopathy results in a maladaptive function that permits the transmission of systemic hypertension to glomerular capillaries. Glomerular hypertension results in mechanical damage to the capillary wall and increased filtration of proteins to tubular lumen. Enhanced tubular reabsorption induces synthesis of proinflammatory and profibrotic factors, resulting in tubulointerstitial inflammation and fibrosis. In conditions in which there is overactivity of the renin-angiotensin system (RAS), such as mild hyperuricemia and protein overload, arteriolopathy is associated with increased glomerular pressure and reduced glomerular plasma flow that results in post-glomerular ischemia and tubulointerstitial injury.

Evaluation of the effects of inhibition of angiotensin converting enzyme with enalapril in dogs with induced chronic renal insufficiency

OBJECTIVE

To determine whether the angiotensin converting enzyme inhibitor enalapril would lower systemic arterial and glomerular capillary pressure and reduce the magnitude of renal injury in a canine model of renal insufficiency.

ANIMALS

18 adult dogs that had renal mass reduced by partial nephrectomy.

PROCEDURE

After surgical reduction of renal mass and baseline measurements, dogs in 2 equal groups received either placebo (group 1) or enalapril (0.5 mg/kg, PO, q 12 h; group 2) for 6 months.

RESULTS

Values for systemic mean arterial blood pressure determined by indirect and direct measurement after 3 and 6 months of treatment, respectively, were significantly lower in group 2 than in group 1. During treatment, monthly urine protein-to-creatinine ratios were consistently lower in group 2 than in group 1, although values were significantly different only at 3 months. At 6 months, significant reduction in glomerular capillary pressure in group 2 was detected, compared with group 1, but glomerular filtration rate in group 2 was not compromised. Glomerular hypertrophy, assessed by measurement of planar surface area of glomeruli, was similar in both groups. Glomerular and tubulointerstitial lesions were significantly less in group 2, compared with group 1.

CONCLUSIONS AND CLINICAL RELEVANCE

Data suggest that inhibition of angiotensin converting enzyme was effective in modulating progressive renal injury, which was associated with reduction of glomerular and systemic hypertension and proteinuria but not glomerular hypertrophy. Inhibition of angiotensin converting enzyme may be effective for modulating progression of renal disease in dogs.

Animal models of FSGS: lessons for pathogenesis and treatment

Glomerulosclerosis in a heterogeneous pattern, ie, focal and segmental glomerulosclerosis (FSGS), is a common endpoint in a variety of settings, including idiopathic FSGS, and scarring secondary to other renal or systemic diseases. These different causes contribute to the diverse clinical outcomes of histological focal sclerosis, and the varying histologic manifestations of sclerosis. Numerous models have been established in the rat that aim to mirror the various elements of human glomerulosclerosis. With the availability of knockout gene technology, many, but not all of these models have been translated to mouse species. This review will focus on the remnant kidney model, the podocyte injury models of puromycin aminonucleoside or adriamycin injection, and examples of newly developed genetic models, such as knockout of CD2 associated protein (CD2AP).

Low protein diet mediated renoprotection in remnant kidneys: Renal autoregulatory versus hypertrophic mechanisms

BACKGROUND

The mechanism of low protein diet conferred renoprotection in the ablation model remains controversial. Blockade of glomerular hypertrophy, reduced preglomerular vasodilation, and preserved autoregulation have all been postulated. The potential differential impact of calcium channel blockers on these mechanisms and glomerulosclerosis was examined.

METHODS

Rats with 5/6 renal ablation received either a 25% standard protein diet, an 8% low protein diet and a low protein diet with either verapamil or amlodipine. Renal autoregulatory and morphometric studies were performed at 3 weeks before the development of significant injury, and the assessment of glomerulosclerosis after 7 weeks of continuous blood pressure radiotelemetry in additional rats.

RESULTS

The preserved renal autoregulation in low protein rats was abolished by both calcium channel blockers, with the impairment being either comparable to (low protein + verapamil) or greater than the standard protein rats (low protein + amlodipine). Neither calcium channel blocker blocked the inhibitory effects of low protein diet on renal blood flow, kidney weight, and glomerular volume. Results (mean +/- SE) for glomerular volume (microm-3x 10(-6)): low protein (N = 11), 1.6 +/- 0.1; low protein + verapamil (N = 10), 1.7 +/- 0.1; low protein + amlodipine (N = 12), 1.7 +/- 0.2; versus standard protein (N = 10), 2.2 +/- 0.1; P < 0.05. Only amlodipine, but not verapamil, reduced average systolic blood pressure (143 +/- 2 mm Hg versus low protein rats, 168 +/- 5 mm Hg, and standard rats, 170 +/- 6 mm Hg; P < 0.01). Nevertheless, the glomeruloprotection seen in low protein (N = 15) as compared to standard protein (N = 14) rats (9%+/- 3% versus 28%+/- 6% glomerulosclerosis; P < 0.01) was abolished in both low protein + verapamil (N = 14, 32%+/- 7%) and low protein + amlodipine rats (N = 16, 27%+/- 7%).

CONCLUSIONS

Preservation of renal autoregulation and not inhibition of hypertrophy is the critical component in low protein diet-conferred glomeruloprotection.

Differential evolution of blood pressure and renal lesions after RAS blockade in Lyon hypertensive rats

The present work aimed to assess, in Lyon hypertensive (LH) rats, whether an early and prolonged inhibition of the renin-angiotensin system (RAS) could result in a blood pressure (BP) lowering and nephroprotection that persist after its withdrawal. Male LH rats received orally from 3 to 12 wk of age either an angiotensin-converting enzyme inhibitor perindopril at the doses of 0.4 and 3 mg x kg(-1) x day(-1) or an AT(1) receptor antagonist losartan at the dose of 10 mg x kg(-1) x day(-1). BP, histological changes in the kidney, and urinary protein excretion were examined during and 10 wk after cessation of the treatments. Both perindopril and losartan decreased BP, prevented renal lesions, and limited urinary protein excretion. After cessation of the treatment, BP returned to the level of never-treated LH rats in rats having received 3 mg x kg(-1) x day(-1) of perindopril while it remained slightly lower in those treated with 0.4 mg x kg(-1) x day(-1) of perindopril or with losartan. This lack of marked persistent antihypertensive effect contrasted with a durable decrease in urinary protein excretion and improvement of the renal histological lesions. In conclusion, it is possible to separate the BP-lowering effects of RAS blockade from those on glomerulosclerosis and urinary protein excretion.

Angiotensin II induces apoptosis in rat glomerular epithelial cells

ANG II has been shown to modulate kidney cell growth and contribute to the pathobiology of glomerulosclerosis. Glomerular visceral epithelial cell (GEC) injury or loss is considered to play a pivotal role in the initiation and progression of glomerulosclerosis. In the present study, we investigated the effect of ANG II on GEC apoptosis. Rat GECs were incubated with increasing doses of ANG II for variable time periods. Apoptosis was evaluated by cell nucleus staining and DNA fragmentation assay. ANG II induced GEC apoptosis in a dose- and time-dependent manner. The proapoptotic effect was attenuated by the ANG II receptor type 1 antagonist losartan or the ANG II receptor type 2 antagonist PD-123319 and was completely blocked by incubation with the combined antagonists. Moreover, ANG II stimulated transforming growth factor (TGF)-beta1 production as measured by ELISA. GECs exposed to TGF-beta1 demonstrated a dose- and time-dependent increase in apoptosis. ANG II-induced apoptosis was significantly inhibited by addition of anti-TGF-beta1 antibody. ANG II also upregulated the expression of Fas, FasL, and Bax and downregulated the expression of Bcl-2 in GECs. These studies suggest that ANG II induces GEC apoptosis by a mechanism involving TGF-beta1 expression that may, importantly, contribute to the pathogenesis of glomerulosclerosis.

Molecular mechanisms of renal allograft fibrosis

BACKGROUND

Chronic graft nephropathy (CGN) remains the leading cause of renal allograft loss after the first year following transplantation. Histologically it is characterized by glomerulosclerosis, intimal hyperplasia and interstitial fibrosis. The pathogenesis is unclear, but is likely to involve both immunological and non-immunological factors. Despite improvements in short-term graft survival rates, new immunosuppressive regimens have made no impact on CGN.

METHODS

A review of the current literature on renal transplantation, novel immunosuppression regimens and advances in the molecular pathogenesis of renal allograft fibrosis was performed.

RESULTS AND CONCLUSION

Recent advances in understanding of the underlying molecular mechanisms involved suggest autocrine secretion of cytokines and growth factors, especially transforming growth factor beta, are associated with a change in fibroblast phenotype leading to the deposition of extracellular matrix. Repeated insults trigger upregulation of the tissue inhibitors of matrix metalloproteinases, favouring accumulation of extracellular matrix. To date, no drug has proved effective in inhibiting or reducing allograft fibrosis. The deleterious consequences of chronic immunosuppression on the development of such fibrosis are now recognized; newer immunosuppressive drugs, including rapamycin and mycophenolate mofetil, reduce profibrotic gene expression in both experimental and clinical settings, and offer potential strategies for prolonging allograft survival.

Renal protective effects of chronic exercise and antihypertensive therapy in hypertensive rats with chronic renal failure

OBJECTIVES

Patients with chronic renal failure are restricted to mild physical activity and tend to a lack of exercise. However, there have been few reports regarding the influence of chronic exercise on the progression of renal disease. Similarly, there are few animal models concerned with the effect of exercise training on improving renal function. Therefore, we assessed the renal effects of moderate chronic treadmill exercise in a remnant kidney model of spontaneously hypertensive rats (SHR) with chronic renal failure. We also assessed the effects of exercise and antihypertensive therapy on renal function.

DESIGN AND METHODS

Eight-week-old SHR were subjected to 5/6 nephrectomy by removal of the left kidney and excision of two-thirds of the right kidney. The rats were divided into four groups: (i) no exercise (Non-EX); (ii) moderate exercise with treadmill running (20 m/min, 0 grade incline for 60 min) (EX); (iii) EX with an angiotensin converting enzyme (ACE) inhibitor, enalapril (2 mg/kg per day, i.p.); and (iv) EX with an angiotensin receptor antagonist, losartan (5 mg/kg per day, i.p.), for 4 weeks.

RESULTS

Chronic EX significantly attenuated the increase in proteinuria (P < 0.01) and significantly protected against increases in the index of glomerular sclerosis (IGS). Both enalapril and losartan with EX significantly decreased blood pressure (P < 0.001), and further decreased the IGS. In the stepwise multiple regression analysis, only antihypertensive drug remained in the model as a significant predictor of IGS (P < 0.0001). In contrast, exercise, antihypertensive drug and mean systolic blood pressure (weeks 1-4) remained in the model as a significant predictors of mean proteinuria (weeks 1-4) (all P < 0.0001).

CONCLUSIONS

These results suggest that exercise does not worsen renal function and has renal-protective effects in this model of rats. Moreover, the antihypertensive therapy has additional renal-protective effects in this model of rats.

Pentosan polysulfate prevents glomerular hypertension and structural injury despite persisting hypertension in 5/6 nephrectomy rats

Five/six nephrectomy induces systemic and glomerular hypertension, glomerulosclerosis, proteinuria, and tubulointerstitial fibrosis. Polysulfate pentosan (PPS) decreases mesangial proliferation and extracellular matrix accumulation. The aim of this study was to determine whether PPS prevents glomerular hemodynamic changes and renal damage. Micropuncture studies were performed in three groups of eight male Wistar rats. Two groups included rats with 5/6 nephrectomy-one of which was treated with PPS in drinking water (100 mg/kg body wt) and the second of which received normal drinking water-and the third group consisted of normal rats that served as controls. Five/six nephrectomy produced systemic hypertension, a 50% reduction in GFR, and a 67% increase in single-nephron GFR due to elevated glomerular pressure and single-nephron plasma flow as well as proteinuria. Hypertension persisted in PPS-treated animals. Despite a similar reduction in GFR, PPS prevented the rise in single-nephron GFR, glomerular capillary hydrostatic pressure, and proteinuria. By morphometry, glomerular volume was increased by 46% and mesangial area by 94%. Fractional glomerular capillary area decreased by 24%. PPS prevented these changes. Tubular dilatation, epithelial cell atrophy, and increased interstitial area were largely prevented by PPS, as was the interstitial inflammatory infiltrate. These results suggest that the renal protection conferred by PPS was mediated both by prevention of glomerular hypertension as well as suppression of the inflammatory response. It was postulated that this was partly due to the preservation of a greater fraction of functional nephrons.

Renal vascular resistance properties and glomerular protection in early established SHR hypertension

OBJECTIVE

To characterize the in vivo vascular properties of the spontaneously hypertensive rat (SHR) renal vascular bed by examining vascular conductance/resistance responsiveness to vasoactive agents in vivo and determining whether the filtration surface area of glomerular capillaries is reduced.

DESIGN AND METHODS

in vivo renal blood flow responses to intrarenally administered angiotensin II, phenylephrine and acetylcholine were compared in 10-week-old SHR and Wistar-Kyoto (WKY) rats using a wide range of doses from near threshold to near maximal effect. Unbiased stereological techniques and high-resolution light microscopy were used to estimate the surface area and length of glomerular capillaries, and evidence of capillary damage.

RESULTS

The SHR renal bed demonstrated significantly enhanced dose-vascular resistance responses to vasoconstrictors. For vascular conductance and calculated radius of resistance vessels, the SHR curves were significantly lower across the full dilator-constrictor range examined, but the dose-related changes were similar to those of WKY rats. There were only modest enhancements of the renal blood flow responses in the SHR, evident only when renal blood flow was reduced by more than 50% SHR and WKY rats did not differ in mean glomerular capillary surface area (0.13+/-0.02 mm2 and 0.14+/-0.02 mm2, respectively) or length (5.76+/-0.85 mm and 5.48+/-0.90 mm, respectively) nor was there evidence of glomerular capillary damage in either strain.

CONCLUSIONS

The renal vascular bed of the SHR in vivo exhibits reduced vascular conductance across a wide vasomotor range, compatible with findings in other vascular beds. We have further shown no evidence of reduced glomerular capillary surface area or damage. These findings are compatible with the hypothesis that the reduced conductance of the SHR pre-glomerular vasculature increases the aorta-capillary pressure gradient thus protecting the glomerular capillaries from systemic hypertension at this age.

Renal cortical remodelling by NO-synthesis blockers in rats is prevented by angiotensin-converting enzyme inhibitor and calcium channel blocker

The cortical remodelling was studied when chronically nitric oxide synthesis (NOs) blockade (L-NAME-induced) hypertensive rats are simultaneously treated, or not, with angiotensin-converting enzyme inhibitor or calcium channel blocker. Four groups of eight rats each were studied as follows: Control (C), L-NAME (L), L-NAME+Enalapril (L+E) and L-NAME+Verapamil (L+V). The systolic blood pressure (SBP) was weekly recorded. The cortex of the left kidneys was analysed according to the vertical section design. The volume-weighted mean glomerular volume (VWGV) was made through the "point-sampled intercepts" method. Enalapril and verapamil were efficient in reducing the SBP in rats submitted to NOs blockade. Glomeruli had considerable alterations in L group rats (glomerular hypertrophy or sclerosis) and tubular atrophy. The VWGV was 100% greater in L group rats than in the C group rats, while it was 30% smaller in L+E and L+V groups than in L group. The tubular volume was 30-50% greater, while the tubular length was 20-30% smaller in the L group than in the other groups. The renal cortical region showed glomerular sclerosis/hypertrophy and tubular remodelling in rats with NOs blockade that was efficiently prevented with the simultaneous treatment with enalapril or verapamil.

Impaired renal autoregulation: implications for the genesis of hypertension and hypertension-induced renal injury

In summary, autoregulation of the renal vasculature provides a mechanism by which renal function is maintained relatively constant despite variations in systemic blood pressure. This system also provides a means for changes in blood pressure to occur without causing inappropriate alterations in urinary NaCl excretion. Alterations in the autoregulatory response can have clinical consequences. Increased activity of the TGF mechanism may be causally related to the development of some forms of hypertension. Decreased activity of TGF or an impaired myogenic response may help explain the increased susceptibility that certain patient groups exhibit toward hypertension-induced renal injury. The aggressive treatment of hypertension in patients with impaired renal autoregulation may be associated with an increase in the serum creatinine concentration. As long as this increase is neither excessive nor progressive, physicians should not be dissuaded from trying to achieve newly established blood pressure goals.

Attenuating effect of a semipurified alcohol extract of soy protein on glomerular injury in spontaneous hypercholesterolemic male Imai rats

We investigated whether soy protein's alcohol-extractable components (SPEs; mainly consisting of isoflavones) have the ability to attenuate glomerular injury in male Imai rats of a spontaneous focal segmental glomerulosclerosis model. Male Imai rats were fed a casein-based diet with and without SPEs. Group 1 (Cont) was fed a standard diet without additional SPEs, and groups 2 (SPE-1) and 3 (SPE-2) were fed a standard diet supplemented with a semipurified alcohol extract of soy protein, 0.05 and 0.10 g/100 g of diet, respectively. Body weight, urinary protein level, serum constituents, and systolic blood pressure were evaluated every 4 weeks from 12 through 28 weeks of age. At 28 weeks of age, rats were studied morphologically. Growth rates were not different among the three groups throughout the experiment. SPE-supplemented diets resulted in less proteinuria and less hyperlipidemia. The decline in renal function shown by blood urea nitrogen and creatinine clearance was less marked in the animals fed the SPE-supplemented diets. Each SPE-supplemented diet equally induced less glomerular hypertrophy and less renal histological damage compared with nonsupplemented diets. The present study showed a beneficial effect of a semipurified alcohol extract of soy protein on glomerular disease.

Gene expression in rats with renal disease treated with the angiotensin II receptor antagonist, eprosartan

The role of ANG II on renal and cardiac gene expression of matrix proteins was studied in rats with progressive renal disease. Induction of renal failure by five-sixths nephrectomy of Sprague-Dawley rats resulted in hypertension (163 +/- 19 vs. control pressures of 108 +/- 6 mmHg), proteinuria (83 +/- 47 vs. 14 +/- 2 mg/day), and increased renal expression of fibronectin, thrombospondin, collagen I and III, transforming growth factor-beta (TGF-beta), and plasminogen activator inhibitor-1 (PAI-1) mRNA. Treatment with the ANG II receptor antagonist, eprosartan (60 mg. kg(-1).day(-1)), lowered blood pressure (95 +/- 5 mmHg) and proteinuria (19 +/- 8 mg/d) and abrogated the increased TGF-beta, fibronectin, thrombospondin, collagens I and III, and PAI-1 mRNA expression. An increase in left ventricular weight was observed in five-sixths nephrectomized rats (0.13 +/- 0.01 vs. 0.08 +/- 0.01 g/100 g body wt), a response that was inhibited by eprosartan treatment (0.10 +/- 0.01 g/100 g). Left ventricular expression of TGF-beta and fibronectin was also increased in rats with renal disease; however, the small decreases in expression observed in eprosartan-treated rats did not reach statistical significance. These data suggest that eprosartan may be beneficial in progressive renal disease and that the mechanism of action includes inhibition of cytokine production in addition to antihypertensive activity.

Influence of the timing of initiating antihypertensive therapy in hypertensive rats with renal failure

The important contribution of hypertension to the progression of renal failure is well realized. However, it have been less discussed which drugs are suitable for the different stages of progressive renal failure. The present study examined the effects of timing of antihypertensive therapy using calcium channel blocker and angiotensin converting enzyme inhibitor in 5/6 nephrectomized spontaneously hypertensive rats (SHRs). Forty male 6 week old SHRs were divided into 5 groups (n=8 in each group), and they were placed on a high salt diet after 5/6 nephrectomy. Group 1, high salt diet without any drug. Group 2 received 0.2 mg/kg/day of amlodipine and group 3 received 0.2 mg/kg/day of enalapril mixed in the high salt diet from week 6 respectively. Similarly group 4 received the same doses of amlodipine, and group 5 received the same doses of enalapril from week 10. Each drug protected from increasing blood pressure in 4 groups, and no significant difference was observed between the effects of amlodipine and enalapril. Proteinuria was reduced with both drugs. In histopathological evaluation, glomerulosclerosis was controlled only in group 2, and arterio/olosclerosis was significantly suppressed in all treated groups except group 5. From these results, both amlodipine and enalapril are renal protective in early stage of renal failure with hypertension. However, in advanced stage of renal failure, amlodipine is superior in its renal protective effect.

Characteristics of progressive renal disease

Virtually all renal diseases progress to terminal renal failure relatively independently of the initial disease. Arresting the rate of the deterioration of kidney failure has a great impact on reducing the number of patients reaching the stage of expensive renal replacement therapy. Understanding the mechanisms of the progression of kidney disease has greatly been improved during recent years. The nature of the progressive renal damage with various etiologies includes various well-known factors where hemodynamics, renin-angiotensin system (RAS) and progressive proteinuria play the central roles. Proteinuria has to be shown as an independent risk factor for renal disease progression. Also, disturbances in lipid metabolism as well as the later structural lesions contribute to the progression. Various modalities have been used for the prevention of progressive renal disease, e.g. low-protein diet, antihypertensive therapy, antifibrotic therapy. Many recent experimental and clinical studies have shown that besides the systemic blood pressure lowering effect, RAS blocking agents provide renal protective effects via direct, hemodynamic, and indirect, non-hemodynamic, pathways: (1) lowering intraglomerular capillary hydraulic pressure, and increasing the glomerular ultrafiltration coefficient; (2) lowering proteinuria; (3) lowering hyperlipidemia; (4) diminishing kidney growth; (5) diminishing infiltration of macrophages; (6) downregulation of proinflammatory cytokines. Therefore, RAS blocking agents are widely prescribed not only for antihypertensive but also for renoprotective purposes in diabetic and non-diabetic nephropathies.

Methods for estimating the volume of individual glomeruli

Methods for estimating the volume of individual glomeruli.

BACKGROUND

The Cavalieri and maximal planar area (MPA) methods are commonly used to measure the volume of individual glomeruli. Previous studies have suggested that the MPA method, which is less laborious, yields values that are much greater than those obtained by the Cavalieri method. The current study re-examined the relationship of MPA and Cavalieri values for glomerular volume in humans and rats.

METHODS

Both methods were used to measure the volume of 1201 glomeruli from 58 humans and 281 glomeruli from 15 rats. Tissue was embedded in Epon. Further mathematical analysis was performed to assess the extent to which deviation of glomeruli from spherical shape affects the relationship of values obtained by the MPA and Cavalieri methods.

RESULTS

MPA values exceeded Cavalieri values by an average of only 14 +/- 22% in humans and 6 +/- 16% in rats. The relationship of MPA to Cavalieri values was similar in individual humans and rats, with widely varying values for average glomerular volume. Neither the development of sclerosis nor the loss of any connection to a tubule affected the relationship of the MPA and Cavalieri values for the volume of individual glomeruli. Mathematical analysis showed that MPA values would not exceed Cavalieri values if glomeruli had ellipsoidal rather than spherical shape.

CONCLUSION

Similar values for glomerular volume are obtained using the Cavalieri and MPA methods in humans and rats.

A clinicopathological study of IgA nephropathy in renal transplant recipients: beneficial effect of angiotensin-converting enzyme inhibitor

BACKGROUND

Prolonging the survival of transplant kidneys is a major task of modern nephrology. It has recently been shown that deteriorating renal function and substantial graft loss were observed in 55% of renal allograft recipients with recurrent IgA nephropathy (IgAN) at long-term follow-up. To gain a useful insight into the therapeutic approach towards protecting allograft kidneys from deteriorating graft function, we compared the histological characteristics of post-transplant IgAN to primary IgAN and investigated the effects of an ACE inhibitor.

METHODS

Twenty-one patients with post-transplant IgAN and 63 patients with primary IgAN were included in the histopathological study. The effectiveness of angiotensin-converting enzyme (ACE) inhibitor treatment in post-transplant IgAN was also studied in 10 patients.

RESULTS

The prevalence of glomeruli with adhesions and/or cellular crescents in primary IgAN was significantly greater than in post-transplant IgAN (P<0.05), but the proportion of glomeruli with segmental sclerosis was similar in both groups. The rate of global obsolescence, and the degree of interstitial fibrosis in post-transplant IgAN were significantly greater than in primary IgAN (P<0.05). The degree of glomerular obsolescence and the severity of interstitial fibrosis correlated with the severity of glomerular lesion in primary IgAN, but not in post-transplant IgAN. In primary IgAN, glomerular diameter significantly correlated with the proportions of glomerular obsolescence, but not in post-transplant IgAN, suggesting that allograft kidneys may be in a hyperfiltration state. Both the blood pressure and the urinary protein excretion significantly improved after ACE-inhibitor treatment (P<0.001).

CONCLUSION

In post-transplant IgAN, histopathological lesions indicative of acute inflammatory insults were suppressed, and glomerular hypertrophy, which may relate to haemodynamic burden such as hyperfiltration, was prominent. Preliminary study of ACE-inhibitor treatment in 10 patients showed favourable effects. A future long-term follow-up study is required to establish the effectiveness of ACE inhibitors in treatment of post-transplant IgAN.

Lack of evidence of blood pressure-independent protection by renin-angiotensin system blockade after renal ablation

BACKGROUND

The superiority of renin-angiotensin system (RAS) blockade in providing renoprotection has been attributed to class-specific blood pressure "(BP)-independent" mechanisms. However, the conventional BP measurement methodology on which such conclusions are based is inherently limited for an accurate assessment of the fluctuating ambient BP profiles. The present studies were undertaken to rigorously examine the relationship of renoprotection to the antihypertensive effects of RAS blockade using chronic BP radiotelemetry in the 5/6 renal ablation model.

METHODS

Rats with 5/6 renal ablation received either no treatment, the angiotensin-converting enzyme inhibitor benazepril at a dose of 25, 50, and 100 mg/L; or the angiotensin receptor antagonist losartan at a dose of 50, 120, and 180 mg/L of drinking H2O; and were followed for seven weeks.

RESULTS

Glomerulosclerosis (GS) at sacrifice (approximately 7 weeks) demonstrated a close correlation with the average systolic BP in untreated (r = 0.76, N = 20), benazepril-treated (r = 0.80, N = 33), losartan-treated (r = 0.83, N = 32), or all animals combined (r = 0.81, N = 85, P < 0.0001 for all correlations). The slope of the relationship between GS and BP (percentage of increase in GS/mm Hg increase in BP) in untreated rats (0.7 +/- 0.14) was not significantly altered by either benazepril (0.96 +/- 0.13) or losartan (0.60 +/- 0.08), indicating that RAS blockade, by either agent, resulted in renoprotection that was proportionate to the achieved BP reductions.

CONCLUSIONS

These data demonstrate that RAS blockade provides renoprotection in the rat remnant kidney model of progressive GS, primarily through "BP-dependent" and not "BP-independent" mechanisms.