Comparative analysis of hypertensive nephrosclerosis in animal models of hypertension and its relevance to human pathology. Glomerulopathy

Current research on hypertension utilizes more than fifty animal models that rely mainly on stable increases in systolic blood pressure. In experimental hypertension, grading or scoring of glomerulopathy in the majority of studies is based on a wide range of opinion-based histological changes that do not necessarily comply with lesional descriptors for glomerular injury that are well-established in clinical pathology. Here, we provide a critical appraisal of experimental hypertensive glomerulopathy with the same approach used to assess hypertensive glomerulopathy in humans. Four hypertensive models with varying pathogenesis were analyzed–chronic angiotensin II infused mice, mice expressing active human renin in the liver (TTRhRen), spontaneously hypertensive rats (SHR), and Goldblatt two-kidney one-clip rats (2K1C). Analysis of glomerulopathy utilized the same criteria applied in humans–hyalinosis, focal segmental glomerulosclerosis (FSGS), ischemic, hypertrophic and solidified glomeruli, or global glomerulosclerosis (GGS). Data from animal models were compared to human reference values. Kidneys in TTRhRen mice, SHR and the nonclipped kidneys in 2K1C rats had no sign of hyalinosis, FSGS or GGS. Glomerulopathy in these groups was limited to variations in mesangial and capillary compartment volumes, with mild increases in collagen deposition. Histopathology in angiotensin II infused mice corresponded to mesangioproliferative glomerulonephritis, but not hypertensive glomerulosclerosis. The number of nephrons was significantly reduced in TTRhRen mice and SHR, but did not correlate with severity of glomerulopathy. The most substantial human-like glomerulosclerotic lesions, including FSGS, ischemic obsolescent glomeruli and GGS, were found in the clipped kidneys of 2K1C rats. The comparison of affected kidneys to healthy control in animals produces lesion values that are numerically impressive but correspond to mild damage if compared to humans. Animal studies should be standardized by employing the criteria and classifications established in human pathology to make experimental and human data fully comparable for comprehensive analysis and model improvements.

MicroRNA-214-3p in the Kidney Contributes to the Development of Hypertension

BACKGROUND

In spite of extensive study, the mechanisms for salt sensitivity of BP in humans and rodent models remain poorly understood. Several microRNAs (miRNAs) have been associated with hypertension, but few have been shown to contribute to its development.

METHODS

We examined miRNA expression profiles in human kidney biopsy samples and rat models using small RNA deep sequencing. To inhibit an miRNA specifically in the kidney in conscious, freely moving rats, we placed indwelling catheters to allow both renal interstitial administration of a specific anti-miR and measurement of BP. A rat with heterozygous disruption of the gene encoding endothelial nitric oxide synthase (eNOS) was developed. We used bioinformatic analysis to evaluate the relationship between 283 BP-associated human single-nucleotide polymorphisms (SNPs) and 1870 human miRNA precursors, as well as other molecular and cellular methods.

RESULTS

Compared with salt-insensitive SS.13BN26 rats, Dahl salt-sensitive (SS) rats showed an upregulation of miR-214-3p, encoded by a gene in the SS.13BN26 congenic region. Kidney-specific inhibition of miR-214-3p significantly attenuated salt-induced hypertension and albuminuria in SS rats. miR-214-3p directly targeted eNOS. The effect of miR-214-3p inhibition on hypertension and albuminuria was abrogated in SS rats with heterozygous loss of eNOS. Human kidney biopsy specimens from patients with hypertension or hypertensive nephrosclerosis showed upregulation of miR-214-3p; the gene encoding miR-214-3p was one of several differentially expressed miRNA genes located in proximity to human BP-associated SNPs.

CONCLUSIONS

Renal miR-214-3p plays a functional and potentially genetic role in the development of hypertension, which might be mediated in part by targeting eNOS.

Cell adhesion molecule-1 shedding induces apoptosis of renal epithelial cells and exacerbates human nephropathies

Chronic kidney disease (CKD) is an important problem throughout the world, associated with the increase of blood urea nitrogen (BUN) and serum creatinine (sCre) and with renal tubular injuries. It is crucial to elucidate the molecular mechanisms of renal injuries to identify the new therapeutics and early diagnostic methods. We focused on cell adhesion molecule-1 (CADM1) protein. CADM1, its isoform SP4, is expressed in the epithelial cells of various tissues, including renal distal tubules, localized on the lateral cell membrane, mediates cell-cell adhesion via trans-homophilic binding, and interacts with various proteins. We previously reported that its expression was downregulated by post-proteolytic cleavage (α- and β-shedding) in pulmonary diseases. To investigate whether CADM1 α-shedding occurs in human nephropathies, we performed Western blotting and immunohistochemical analysis of specimens with arterionephrosclerosis (AS) and diabetic nephropathy (DN) from autopsied kidneys. CADM1 α-shedding was induced in AS and DN kidneys and derived from the decrease in full-length CADM1 (FL-CADM1) and increase of the COOH-terminal fragment (α-CTF). In particular, the reduced FL-CADM1 level was correlated with tubular and tubulointerstitial injuries and the increases in BUN and sCre levels. Apoptosis of renal tubular epithelial cells (TECs) was promoted in both nephropathies, and it was significantly correlated with the decrease in the FL-CADM1. Furthermore, FL-CADM1 knockdown by small interfering RNA downregulated anti-apoptotic Bcl-2 protein and promoted apoptosis of cultured renal TECs. The present study suggests that the reduction of FL-CADM1 leads to renal TEC apoptosis and could exacerbate renal tubular and tubulointerstitial injuries, which contribute to the development of CKD.

Experimental Inhibition of Periostin Attenuates Kidney Fibrosis

BACKGROUND

Periostin is responsible for tissue regeneration, fibrosis, and wound healing via its interaction with integrin. Recently, the role of periostin has been shown to contribute to fibrosis in chronic kidney disease. We investigated the role of periostin and the effect of periostin blockade in renal fibrogenesis.

METHODS

We investigated the function of periostin in vivo in wild-type and periostin-null mice (Postn-KO) in a unilateral ureteral obstruction (UUO) model. For the in vitro experiments, primary cultured inner medullary collecting duct cells from the wild-type and Postn-KO mice were used.

RESULTS

Periostin expression was strongly induced by UUO in the wild-type mice. UUO induced renal fibrosis and morphological changes in the obstructed kidney of wild-type mice, whereas global knockout of periostin reduced fibrosis induced by UUO and improved kidney structure. Fibrosis- and inflammation-related mRNA were significantly induced in the wild-type mice and were decreased in the Postn-KO mice. Additionally, α-smooth muscle actin expression was increased following the administration of recombinant periostin in vitro. The effect of periostin blockade was examined using 2 methods. The integrin blockade peptide decreased fibrosis-related gene expression in in vitro experiments. Anti-periostin polyclonal antibody attenuated renal fibrosis induced by UUO through changes in transforming growth factor-β signaling and the inflammatory and apoptotic pathways.

CONCLUSION

Periostin is a marker of renal fibrosis and may augment the progression of fibrogenesis as an extracellular matrix protein. Periostin blockade effectively attenuated renal fibrogenesis. Thus, periostin inhibition may be a therapeutic strategy for the amelioration of renal disease progression.

Comparison of Clinical Trajectories before Initiation of Renal Replacement Therapy between Diabetic Nephropathy and Nephrosclerosis on the KDIGO Guidelines Heat Map

This study investigated differences between the clinical trajectories of diabetic nephropathy and nephrosclerosis using the Kidney Disease: Improving Global Outcomes (KDIGO) heat map and the clinical characteristics between the two diseases at RRT initiation. This single-center, retrospective study enrolled 100 patients whose estimated glomerular filtration rate (eGFR) was ≥45 mL/min/1.73 m(2) at their first visit and who were initiated on RRT. Fifty consecutive patients were assigned to each of the diabetic nephropathy and nephrosclerosis groups. All data for simultaneously measured eGFR and urinary albumin to creatinine ratio (UACR) were collected from first visit to RRT initiation and were plotted on the KDIGO heat map. Diabetic nephropathy was characterized by higher blood pressure and UACR and lower age, eGFR, and serum albumin levels compared with nephrosclerosis at RRT initiation. The vast majority of patients with diabetic nephropathy and eGFR < 60 mL/min/1.73 m(2) had concomitant macroalbuminuria, whereas for patients with nephrosclerosis, even when eGFR was <45 mL/min/1.73 m(2), many still had normoalbuminuria or microalbuminuria. The rate of decline of eGFR was significantly faster in the diabetic nephropathy group than that in the nephrosclerosis group. The clinical trajectories of diabetic nephropathy and nephrosclerosis differed markedly on the KDIGO heat map.

GQ5 Hinders Renal Fibrosis in Obstructive Nephropathy by Selectively Inhibiting TGF-β-Induced Smad3 Phosphorylation

TGF-β1, via Smad-dependent or Smad-independent signaling, has a central role in the pathogenesis of renal fibrosis. This pathway has been recognized as a potential target for antifibrotic therapy. Here, we identified GQ5, a small molecular phenolic compound isolated from the dried resin of Toxicodendron vernicifluum, as a potent and selective inhibitor of TGF-β1-induced Smad3 phosphorylation. In TGF-β1-stimulated renal tubular epithelial cells and interstitial fibroblast cells, GQ5 inhibited the interaction of Smad3 with TGF-β type I receptor (TβRI) by blocking binding of Smad3 to SARA, suppressed subsequent phosphorylation of Smad3, reduced nuclear translocation of Smad2, Smad3, and Smad4, and downregulated the transcription of major fibrotic genes such as α-smooth muscle actin (α-SMA), collagen I, and fibronectin. Notably, intraperitoneal administration of GQ5 in rats immediately after unilateral ureteral obstruction (UUO) selectively inhibited Smad3 phosphorylation in UUO kidneys, suppressed renal expression of α-SMA, collagen I, and fibronectin, and resulted in impressive renal protection after obstructive injury. Late administration of GQ5 also effectively attenuated fibrotic lesions in obstructive nephropathy. In conclusion, our results suggest that GQ5 hinders renal fibrosis in rats by selective inhibition of TGF-β1-induced Smad3 phosphorylation.

Failed Tubule Recovery, AKI-CKD Transition, and Kidney Disease Progression

The transition of AKI to CKD has major clinical significance. As reviewed here, recent studies show that a subpopulation of dedifferentiated, proliferating tubules recovering from AKI undergo pathologic growth arrest, fail to redifferentiate, and become atrophic. These abnormal tubules exhibit persistent, unregulated, and progressively increasing profibrotic signaling along multiple pathways. Paracrine products derived therefrom perturb normal interactions between peritubular capillary endothelium and pericyte-like fibroblasts, leading to myofibroblast transformation, proliferation, and fibrosis as well as capillary disintegration and rarefaction. Although signals from injured endothelium and inflammatory/immune cells also contribute, tubule injury alone is sufficient to produce the interstitial pathology required for fibrosis. Localized hypoxia produced by microvascular pathology may also prevent tubule recovery. However, fibrosis is not intrinsically progressive, and microvascular pathology develops strictly around damaged tubules; thus, additional deterioration of kidney structure after the transition of AKI to CKD requires new acute injury or other mechanisms of progression. Indeed, experiments using an acute-on-chronic injury model suggest that additional loss of parenchyma caused by failed repair of AKI in kidneys with prior renal mass reduction triggers hemodynamically mediated processes that damage glomeruli to cause progression. Continued investigation of these pathologic mechanisms should reveal options for preventing renal disease progression after AKI.

Intrarenal and Urinary Th9 and Th22 Cytokine Gene Expression in Lupus Nephritis

OBJECTIVE

We studied the urinary sediment mRNA level of Th9- and Th22-related cytokines in patients with systemic lupus erythematosus (SLE).

METHODS

We quantified urinary mRNA levels of interleukin (IL) 9, IL-10, IL-22, and their corresponding transcription factors in 73 patients with active lupus nephritis, 13 patients with hypertensive nephrosclerosis (HTN), and 25 healthy subjects.

RESULTS

There was no detectable IL-9 mRNA in all samples. Patients with proliferative lupus nephritis had significantly lower urinary IL-22 mRNA levels than those with nonproliferative nephritis (2.2 ± 5.4 vs 8.6 ± 20.0 copies, p = 0.019), and urinary IL-22 mRNA level inversely correlated with the histological activity index (r = -0.427, p < 0.0001). In contrast, patients with lupus nephritis had significantly higher urinary IL-10 mRNA levels than patients with HTN (7.8 ± 18.5 vs 1.9 ± 4.0 copies, p = 0.012), and urinary IL-10 mRNA levels correlated with its intrarenal mRNA levels (r = 0.337, p = 0.004) and SLE disease activity index (r = 0.277, p = 0.018). Urinary IL-10 mRNA level was significantly lower among patients who achieved complete remission than those with partial remission or no response (4.1 ± 6.5 vs 14.1 ± 28.0 copies, p = 0.036).

CONCLUSION

Urinary IL-22 mRNA level is decreased in patients with SLE with proliferative nephritis, while urinary IL-10 mRNA levels correlates with its intrarenal mRNA level and disease activity. Urinary IL-10 mRNA levels may also predict treatment response. These results suggest that urinary mRNA levels of IL-10 and IL-22 might be used as biomarkers for assessing disease activity and risk stratification in lupus nephritis.

Increased expression of p21WAF1/CIP1 in kidney proximal tubules mediates fibrosis

Tissue fibrosis is a major cause of death in developed countries. It commonly occurs after either acute or chronic injury and affects diverse organs, including the heart, liver, lung, and kidney. Using the renal ablation model of chronic kidney disease, we previously found that the development of progressive renal fibrosis was dependent on p21(WAF1/Cip1) expression; the genetic knockout of the p21 gene greatly alleviated this disease. In the present study, we expanded on this observation and report that fibrosis induced by two different acute injuries to the kidney is also dependent on p21. In addition, when p21 expression was restricted only to the proximal tubule, fibrosis after injury was induced in the whole organ. One molecular fibrogenic switch we describe is transforming growth factor-β induction, which occurred in vivo and in cultured kidney cells exposed to adenovirus expressing p21. Our data suggests that fibrosis is p21 dependent and that preventing p21 induction after stress could be a novel therapeutic target.

Syndecan-4 knockout leads to reduced extracellular transglutaminase-2 and protects against tubulointerstitial fibrosis

Transglutaminase type 2 (TG2) is an extracellular matrix crosslinking enzyme with a pivotal role in kidney fibrosis. The interaction of TG2 with the heparan sulfate proteoglycan syndecan-4 (Sdc4) regulates the cell surface trafficking, localization, and activity of TG2 in vitro but remains unstudied in vivo. We tested the hypothesis that Sdc4 is required for cell surface targeting of TG2 and the development of kidney fibrosis in CKD. Wild-type and Sdc4-null mice were subjected to unilateral ureteric obstruction and aristolochic acid nephropathy (AAN) as experimental models of kidney fibrosis. Analysis of renal scarring by Masson trichrome staining, kidney hydroxyproline levels, and collagen immunofluorescence demonstrated progressive fibrosis associated with increases in extracellular TG2 and TG activity in the tubulointerstitium in both models. Knockout of Sdc-4 reduced these effects and prevented AAN-induced increases in total and active TGF-β1. In wild-type mice subjected to AAN, extracellular TG2 colocalized with Sdc4 in the tubular interstitium and basement membrane, where TG2 also colocalized with heparan sulfate chains. Heparitinase I, which selectively cleaves heparan sulfate, completely abolished extracellular TG2 in normal and diseased kidney sections. In conclusion, the lack of Sdc4 heparan sulfate chains in the kidneys of Sdc4-null mice abrogates injury-induced externalization of TG2, thereby preventing profibrotic crosslinking of extracellular matrix and recruitment of large latent TGF-β1. This finding suggests that targeting the TG2-Sdc4 interaction may provide a specific interventional strategy for the treatment of CKD.

Increased renal iron accumulation in hypertensive nephropathy of salt-loaded hypertensive rats

Although iron is reported to be associated with the pathogenesis of chronic kidney disease, it is unknown whether iron participates in the pathophysiology of nephrosclerosis. Here, we investigate whether iron is involved in the development of hypertensive nephropathy and the effects of iron restriction on nephrosclerosis in salt- loaded stroke-prone spontaneously hypertensive rats (SHRSP). SHRSP were given either a normal or high-salt diet for 8 weeks. Another subset of SHRSP were fed a high-salt with iron-restricted diet. SHRSP given a high-salt diet developed severe hypertension and nephrosclerosis. As a result, survival rate was decreased after 8 weeks diet. Importantly, massive iron accumulation and increased iron content were observed in the kidneys of salt-loaded SHRSP, along with increased superoxide production, urinary 8-Hydroxy-2′-deoxyguanosine excretion, and urinary iron excretion; however, these changes were markedly attenuated by iron restriction. Of interest, expression of cellular iron transport proteins, transferrin receptor 1 and divalent metal transporter 1, was increased in the tubules of salt-loaded SHRSP. Notably, iron restriction attenuated the development of severe hypertension and nephrosclerosis, thereby improving survival rate in salt-loaded SHRSP. Taken together, these results suggest a novel mechanism by which iron plays a role in the development of hypertensive nephropathy and establish the effects of iron restriction on salt-induced nephrosclerosis.

Plasticity of renal erythropoietin-producing cells governs fibrosis

CKD progresses with fibrosis and erythropoietin (Epo)-dependent anemia, leading to increased cardiovascular complications, but the mechanisms linking Epo-dependent anemia and fibrosis remain unclear. Here, we show that the cellular phenotype of renal Epo-producing cells (REPs) alternates between a physiologic Epo-producing state and a pathologic fibrogenic state in response to microenvironmental signals. In a novel mouse model, unilateral ureteral obstruction-induced inflammatory milieu activated NFκB and Smad signaling pathways in REPs, rapidly repressed the Epo-producing potential of REPs, and led to myofibroblast transformation of these cells. Moreover, we developed a unique Cre-based cell-fate tracing method that marked current and/or previous Epo-producing cells and revealed that the majority of myofibroblasts are derived from REPs. Genetic induction of NFκB activity selectively in REPs resulted in myofibroblastic transformation, indicating that NFκB signaling elicits a phenotypic switch. Reversing the unilateral ureteral obstruction-induced inflammatory microenvironment restored the Epo-producing potential and the physiologic phenotype of REPs. This phenotypic reversion was accelerated by anti-inflammatory therapy. These findings demonstrate that REPs possess cellular plasticity, and suggest that the phenotypic transition of REPs to myofibroblasts, modulated by inflammatory molecules, underlies the connection between anemia and renal fibrosis in CKD.

ADAMTS13--more than just TMA and TTP

ADAMTS13 (a disintegrin-like and metalloprotease with thrombospondin type-1 motifs 13) has been shown to be of major pathophysiological importance for thrombotic microangiopathy (TMA) in the setting of thrombocytic thrombocytopenic purpura (TTP) when either lacking (inherited TTP) or if antibodies against ADAMTS13 are present (acquired TTP). A potential pathophysiological role of ADAMTS13 has also been postulated in other diseases i.e. myocardial infarction, atrial fibrillation and diabetic angiopathy. Recent data provides evidence, however, for a completely different role of ADAMTS13 in vascular physiology and pathophysiology. In the present issue of Nephrology Dialysis and Transplantation, Bockmeyer et al. documented a physiological expression of ADAMTS13 in arteriolar vascular smooth muscle cells (VSMCs) which is maintained in the early, so-called benign nephrosclerosis, i.e. under conditions of early hypertensive vascular damage, and is completely lost if the damage proceeds to late, fibrotic stages of vascular injury. Thus, the recent report identifies ADAMTS13 as a new marker for the contractile phenotype of VSMC which is maintained in the early, hyalinotic phase of vascular damage, but is lost in later, more fibrotic stages of benign nephrosclerosis. This finding adds a novel and potentially important aspect to the unsolved and underestimated problem of benign or hypertensive nephrosclerosis.

[Molecular factors of angiogenesis in renal tissue of patients with chronic glomerulonephritis: association with nephrosclerosis and anemia]

AIM

To study correlations between accumulation of angiogenesis molecular factors (hypoxia-inducible factor-1alpha - HIF-1alpha, vascular endothelial growth factor - VEGF, thrombospondin - TSP-1) in kidney biopsy tissue from chronic glomerulonephritis (CGN) patients and severity of nephrosclerosis, obliteration of renal capillary bed, filtration dysfunction and anemia.

MATERIAL AND METHODS

We examined 22 patients with marked proteinuria (2.77; 5.7, mean 4.2 g/ day). Half of the patients had nephrotic syndrome. Glomerular filtration rate (GFR) by Cochroft-Golt formula was 68 (53;84) ml/min/1.73 m2. According to renal biopsy findings, CGN was detected in 19 patients, 2 patients had lupus nephritis (LN), 1 patient had renal amyloidosis. Nineteen CGN patients were divided into two groups by nephrosclerosis severity: group 1-7 patients with moderate nephrosclerosis, group 2-12 patients with severe nephrosclerosis. Cryostate sections of renal biopsy tissue samples were studied immunohistochemically using monoclonal antibodies to HIF-1alpha, VEGF, TSP-1, CD34. The reaction intensity was assessed by 6-point scale semiquantitative method.

RESULTS

Response to HIF-1alpha was stronger in the tubular epithelium than in glomeruli. No correlation was observed between accumulation of HIF-1alpha in the glomeruli and tubular epithelium. Intensity of glomerular staining correlated with severity of proteinuria (Rs = 0.63, p < 0.05), intensity of HIF-1alpha accumulation in tubular epithelium correlated with duration of the kidney disease (Rs = 0.74, p < 0.001), duration of persistent arterial hypertension (Rs = 0.68, p < 0.05) and severity of nephrosclerosis. VEGF and TSP-1 were found in equal quantity both in the glomeruli and renal interstitium. CGN patients with marked nephrosclerosis had lower accumulation of VEGF and higher TSP-1 in the interstitium. No correlation was found between intensity of tubular epithelium response to HIF-1alpha and accumulation of VEGF in the interstitium. Patients with severe nephrosclerosis demonstrated weaker staining of tubulointerstitium to CD34, reflecting the degree of its vascularisation. Significant correlation between CD34 and expression of HIF-1alpha, VEGF, TSP-1 was not registered. In patients with low intensity of tubular epithelial staining to HIF-1alpha (less than 2 points) anemia was detected in 63% versus 18% in patients with more intensive accumulation.

CONCLUSION

CGN progression is associated with development of renal tubulointerstitial ischemia. High tubular production of HIF-1alpha was not accompanied with activation of VEGF accumulation in renal interstitium but was associated with reduced risk of anemia in CGN patients with manifest nephrosclerosis.

Parenchymal injury in remnant-kidney model may be linked to apoptosis of renal cells mediated by nitric oxide

BACKGROUND

The importance of apoptotic cell death in the pathogenesis of progressive renal sclerosis has been well established. While activity of vasorelaxant nitric oxide is conceivable in the remnant hyperfiltrating kidney and nitric oxide has been reported to cause apoptosis, we postulated that this mechanism of cell death may be operating in progressive renal fibrosis.

METHODS

The intensity of apoptosis in glomerular and tubular cells was assessed (light microscopy, TUNEL method) in the remnant-kidney model of progressive renal fibrosis in rats undergoing 5/6 nephrectomy. Numbers of apoptotic cells were correlated with expression of mRNA for inducible nitric oxide synthase (iNOS; RT-PCR in situ), generation of nitrite in renal tissue, an index of glomerulosclerosis, proteinuria and creatinine clearance. A control group of 5/6 nephrectomized rats received an iNOS inhibitor, L-NAME, in drinking water during the 4 weeks after nephrectomy.

RESULTS

Number of apoptotic cells gradually increased in experimental rats both in glomeruli and tubules, until termination of the study 3 months after 5/6 nephrectomy. At 3 months postinduction, the intensity of tubular cell apoptosis was significantly correlated with creatinine clearance (p<0.05), while glomerular cell apoptosis was correlated with the index of glomerulosclerosis, also at 3 months (p<0.0025). Along with the apoptosis, the levels of iNOS mRNA for, and generation of, nitrite in renal tissue had risen until termination of the study. The generation of nitrites correlated with the number of apoptotic glomerular cells (p<0.025). Treatment with the iNOS inhibitor resulted in a significant reduction in number of apoptotic cells (p<0.01).

CONCLUSIONS

Apoptotic depletion of renal tubular and glomerular cells linked to activity of iNOS may contribute to progression of chronic kidney tissue injury in the 5/6 nephrectomy model.

Age Trends of Renal Arteriolar Hyalinization Explored with the Aid of Serial Sections

BACKGROUND

Hyalinized renal arterioles (Hy) can be counted per unit area of PAS-stained paraffin sections. The percentages of nephrons having hyalinized afferent and efferent arterioles can be assessed in serial sections.

METHODS

Slides of renal tissue were assessed for Hy in 559 basal forensic autopsies, i.e. those with no condition known to correlate with hypertension. Serial sections in a series of 20 cases were used to measure afferent and efferent arterioles and determine formulas to relate afferent and efferent arterioles to Hy. The formulas were used in the 559 cases to assess the trends on age of Hy in terms of percentage of affected nephrons.

RESULTS

Hy increased rapidly from ages 15 to 34 years, but stabilized from ages 35 to 102 years at levels implying afferent arterioles of about 2/5 of nephrons and efferent arterioles of about 1/5. Most of the nephrons in the kidney were deduced to be supplied by hyalinized afferent arterioles in nearly half of all subjects from ages 35 to 102 years, and the rates were the same at all ages.

CONCLUSION

These data provide for the first time provisional estimates for the prevalence of Hy to be used as baselines for biopsy comparisons. Failure of numerous kidneys to enter end-stage nephrosclerosis in spite of several decades of involvement by hyalinization in half or more of their arterioles does not support the view that hyalinization induces ischemic nephron atrophy.

[Expression of p27 in rat kidney with unilateral ureteral obstruction and the therapeutic effect of enalapril]

OBJECTIVE

To explore the effect of p27 in the renal tubule on the process of renal interstitial fibrosis caused by unilateral ureteral obstruction (UUO) in rats, and to examine the expression changes of p27 after enalapril intervention and to interpret the anti-fibrotic mechanism.

METHODS

Ninety rats were randomly divided into the sham-operated group (SOR), UUO group,and UUO+enalapril treatment group [enalapril: 10 mg/(kg.d)]. The rats of each group were respectively sacrificed on 7, 14, 21 days post-operatively. The renal pathological changes were dynamically observed by HE. The expression and dynamic changes of p27 were detected by immunohistochemistry. The level of p27 mRNA were detected by RT-PCR.

RESULTS

The expression of p27 in renal tubular epithelial cells and p27 mRNA were strongly positive in the SOR group. With degree of interstitial fibrosis aggravating, the expression of p27 mRNA was gradually reducing. Enalapril could improve the expression of p27 on the 14th and 21st days after the UUO.

CONCLUSION

(1) This study supports a causative role of p27 in the formation of fibrosis of renal mesenchyme in rats with UUO. (2) The anti-fibrotic mechanism of enalapril is partly the improvement of p27 expression.

[P21 expression in renal interstitial fibrosis and regulative effect of enalapril]

OBJECTIVE

To investigate the expression of P21 in renal interstitial fibrosis rats and the effect of enalapril on it.

METHODS

Sprague Dawley rats were randomly divided into 3 groups: a sham operation group,a unilateral urethral obstruction group, and an enalapril treatment group. The expression of P21 in renal tubular epithelial cells on the process was detected by immunohistochemistry at different time spots (7, 14, 21 d after UUO, sham-surgery or enalapril treatment). The expression of p21 mRNA was detected by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

Seven days after the surgery, significant differences were found in P21 expression between UUO and SOR renal tubular cells. With degree of interstitial fibrosis aggravating, P21 expression increased. Enalapril can inhibit its expression.

CONCLUSION

In the kidney of UUO rats, P21 expression increased and enalapril possessed significant inhibitory effects on the procedure. P21 may participate in the pathogenesis of renal tubule-interstitial fibrosis.

Renal vascular sclerosis is associated with inherited thrombophilias

Vascular sclerosis is often seen in renal biopsies. It is usually associated with diabetes mellitus, hypertension, smoking, etc. However, whether inherited thrombophilic states such as factor V gene mutation, prothrombin gene mutation, and methylenetetrahydrofolate reductase (MTHFR) gene mutation are associated with the vascular sclerosis is not known. Renal biopsies that showed vascular disease were grouped into five groups: (1) diabetic patients, (2) hypertensive patients, (3) diabetic and hypertensive patients, (4) smokers, and (5) vascular sclerosis of unknown etiology (idiopathic renal disease). Renal biopsies with no vascular sclerosis were used as controls. Frozen tissue was analyzed for factor V Leiden mutation, prothrombin G20210A mutation, and MTHFR C677T. Factor V Leiden mutation and prothrombin G20210A mutation was not seen in patients with diabetes, hypertension, or smoking, whereas MTHFR C677T polymorphism in these groups was not significant, compared to the controls. In the idiopathic renal disease group, three of the 17 patients (17.6%) had prothrombin G20210A mutation, two of the 17 patients (11.8%) had the factor V Leiden mutation, and five of the 17 (29.4%) were homozygous for the MTHFR C677T polymorphism. When the data were evaluated as a whole, 10 mutations were found in 17 patients (P<0.0005 compared to controls) or eight of the 17 patients (47%) were observed to have at least one of the three forms of inherited thrombophilia (P<0.001 compared to controls). These findings indicate that renal vascular lesions, in the absence of diabetes, hypertension, or smoking appears to be associated with inherited thrombophilias.

Angiotensin II formation in the kidney and nephrosclerosis in Ren-2 hypertensive rats

BACKGROUND

Ren-2 transgenic hypertensive rats develop malignant hypertensive nephrosclerosis despite low to normal plasma angiotensin II and suppressed renal renin. We tested the hypothesis that local angiotensin II formation occurs at sites of renal vascular and interstitial injury in this model.

METHODS

Heterozygous Ren-2 transgenic rats were compared with normotensive Sprague-Dawley-Hannover control rats and Ren-2 transgenic rats treated with a very low dose of an angiotensin II type 1 (AT1) receptor antagonist, 1 mg/kg/day losartan, for 4 weeks. Blood pressure measurements, quantifications of urinary albumin, plasma and tissue angiotensin II as well as immunohistochemical analyses were performed.

RESULTS

Systolic blood pressure was not affected by losartan during the study but intra-arterial recordings revealed a decrease of blood pressure. Losartan reduced albumin excretion, cell proliferation, macrophage influx, collagen I and collagen IV deposition. Plasma angiotensin II was decreased, while kidney tissue angiotensin II content was increased in Ren-2 transgenic rats compared with control rats. In Ren-2 transgenic rats, juxtaglomerular renin and angiotensin II staining were reduced, but there was a marked angiotensin II staining at foci of tubulo-interstitial fibrosis and at proliferative malignant vascular lesions.

CONCLUSION

We conclude that local angiotensin II formation is increased in proliferative or fibrotic kidney lesions in the Ren-2 transgenic rat. Local angiotensin II formation may help to explain why the AT1 receptor antagonist prevents or ameliorates this transgenic model of malignant nephrosclerosis despite low to normal plasma angiotensin II and suppressed renal renin.

[Effect of perindopril on renal interstitial fibrosis of hypertension in rats]

OBJECTIVE

To explore the effect of perindopril on renal interstitial fibrosis of spontaneously hypertensive rats and on the expression of transforming growth factor-beta1.

METHODS

Spontaneously hypertensive rats at the age of 9 weeks were randomly assigned to 2 groups: Spontaneously hypertensive rats (SHR, vehicle once daily, n = 10) and Treament-SHR (T-SHR, perindopril, 4 mg/(kg x d), per day PO, n = 10). Wistar-Kyoto rats (WKY, n = 7) were served as controls. After 10 weeks of treatment, the serum concentration of TGF-beta1, collagen type I, III and TGF-beta1 in the renal interstitum and renal mRNA levels of TGF-beta1 were detected.

RESULTS

There were no significant differences in the serum TGF-beta1 levels among the 3 groups (P > 0.05). Immunohistochemical studies revealed a significant interstitial accumulation of collagens I, III and TGF-beta1 in SHR compared with those in WKY (P < 0.01 or P < 0.05). These changes in SHR were significantly ameliorated by the administration of perindopril (P < 0.01 or P < 0.05). In SHR, renal TGF-beta1 mRNA expression was increased significantly compared with that in WKY (P < 0.01), but perindopril decreased it to the normal levels of WKY (P > 0.05). The increased expression of TGF-beta1 was blocked by perindopril. The expressions of collagens I and III in renal interstitum significantly correlated with the accumulation of TGF-beta1 in the renal (r = 0. 734, r = 0.762, respectively; P < 0.01).

CONCLUSION

The tubulointerstitial fibrosis of spontaneously hypertensive rats is mediated by an increased level of TGF-beta1 in the renal tissue, and perindopril may decrease the expression of TGF-beta1 to ameliorate the tubulointerstitial fibrosis.

[Expression of p27 in renal interstital fibrosis in rats induced by unilateral ureteral obstruction]

OBJECTIVE

To explore the role of p27 in the renal tubule on the process of renal interstitial fibrosis caused by unilateral ureteral obstruction (UUO) in rats.

METHODS

Rats were killed at the 7th, 14th, 21st days after UUO or sham-surgery. The protein expression of p27 in renal tubule was detected by immuohistochemistry at each time point.

RESULTS

At the 7th day after the surgery, no noticeable abnormalities of p27 expression were found in renal tubular cells between UUO and the sham operated surgery. At the 14th and 21st days after UUO, the p27 expressions in renal tubular cells obviously decreased compared with those after the sham operated surgery.

CONCLUSION

The p27 expression has no noticeable changes in the early UUO rats, and then it was significantly reduced with the renal interstitial fibrosis progressing.

Multifactorial determination of hypertensive nephroangiosclerosis

Essential hypertension causes renal injury. Hypertensive nephroangiosclerosis (HN) or hypertensive nephropathy are terms most commonly used to describe this renal pathology. Although specific histological lesions occurring in affected kidneys are well known, pathogenesis of hypertension-related renal scarring is not completely understood. Evidence exists to support the theory that other factors such as aging, black race or smoking, beside blood pressure, contribute to the development and progression of HN. Metabolic disturbances, cocaine and nonsteroidal anti-inflammatory drug abuse, ochratoxin A exposure, dietary salt intake, heavy metal toxicity, hantavirus infection and perinatal programming are also considered risk factors. Renal susceptibility genes may determine whether hypertension-induced progressive renal damage occurs and how severe it is. Determination of all risk factors may identify patients at high risk of renal failure and help tailor an appropriate management. In the present paper, the knowledge available on this clinically important objective is discussed.

Lipid profile before and after renal transplantation--a longitudinal study

BACKGROUND

The data on lipid profile in renal transplant recipients from the Indian subcontinent is scant.

METHODS

Lipid profile was studied in 30 consecutive patients of end stage renal disease before renal transplantation (0 month) and prospectively posttransplantation at 1, 3, and 6 months. The results were compared with 30, age and sex matched, healthy controls. All the patients received triple immunosuppression (prednisolone, azathioprine and cyclosporine).

RESULTS

Pretransplantation, the hypertriglyceridemia and hypercholesterolemia was present in 20% and 7% of the patients and the difference (elevation) in the mean values of various lipid fractions was not significant compared to healthy controls except a fall in HDL (p < .01). After renal transplantation, there was a significant elevation in the mean values of total cholesterol, triglycerides, VLDL, and LDL cholesterol at 1, 3, and 6 months. HDL cholesterol levels remained significantly lower as compared to healthy controls. Although, the mean values of serum triglycerides and cholesterol were significantly higher in diabetic end stage renal disease compared to nondiabetic ESRD, however there was insignificant difference in the lipid profile amongst diabetic and nondiabetic renal allograft recipients.

CONCLUSION

Our data shows distinct elevation in the lipids and lipoproteins after renal transplantation and immunosuppressive drugs seem to be the culprit.

Prostacyclin-deficient mice develop ischemic renal disorders, including nephrosclerosis and renal infarction

BACKGROUND

Prostacyclin (PGI2) is a short-lived endogenous inhibitor of platelet aggregation and a potent vasodilator and regulator of the growth of vascular smooth muscle cells. To study the role of PGI2 in the vascular system in vivo, PGI2-deficient (PGID) mice were established by genetic disruption of the PGI2 synthase gene.

METHODS AND RESULTS

PGI2 synthase-null mice were generated by replacing the exons of PGI2 synthase gene that encodes for the catalytic site of the enzyme with a neomycin resistance gene. In these mice, PGI2 levels in the plasma, kidneys, and lungs were reduced, whereas thromboxane and prostaglandin E2 levels became elevated. Blood pressure and the amounts of urea nitrogen and creatinine in plasma of the PGID mice were significantly higher than those of wild-type mice (P<0.05). They developed progressive morphological abnormalities in the kidneys, accompanied by atrophy, surface irregularity, fibrosis, cyst, arterial sclerosis, and hypertrophy of vessel walls. Thickening of the thoracic aortic media and adventitia were observed in aged PGID mice. Importantly, these phenotypes have not been reported in PGI2 receptor-deficient mice.

CONCLUSIONS

PGI2 deficiency resulted in the development of vascular disorders with the thickening of vascular walls and interstitial fibrosis, especially in mouse kidneys. The findings demonstrated in vivo that PGI2 is important in the homeostasis of blood vessels. Our established PGID mice are useful for studies on the initiation and development of vascular diseases, such as ischemic renal disorders with arterial sclerosis and infarction, and also for studies on the novel signaling pathway of PGI2.

Proteinuria in patients with arterial/arteriolar nephrosclerosis

Controversy exists regarding the level of proteinuria in patients with nephrosclerosis.

MATERIAL AND METHODS

We retrospectively examined the clinical parameters of 67 patients with the histologic diagnosis of nephrosclerosis defined as arteriolar hyalinization and/or arterial intimal fibrosis in the absence of other findings in an adequate renal biopsy. Biopsies were performed for clinical indications and were submitted to Cedars-Sinai Pathology Department from January 1994 to March 1999.

RESULTS

The mean age and blood pressure (+/- SD) was 60 +/- 17 years, and 139 +/- 19/80 +/- 12 mmHg. Mean serum creatinine was 2.3 +/- 1.3 mg/dl and 24-hour urinary protein excretion was 0.94 +/- 0.73 g, 66% had < or = 1 g/day, 25% had > 1 but < or = 2 g/day, 6% had > 2 g but < 3 g/day and 1 patient had nephrotic range proteinuria. Twelve patients had no history of hypertension. They had a mean blood pressure of 121 +/- 8/76 +/- 8. Their mean serum creatinine was 1.5 +/- 0.6 mg/dl and their mean 24-hour urinary protein excretion was 0.78 +/- 0.43 g.

CONCLUSIONS

Our data do not confirm that of Innes et al. [1993] who reported proteinuria > 1.5 g/day in 40% and nephrotic syndrome in 22% of patients with nephrosclerosis; systemic hypertension may not be a prerequisite for the development of nephrosclerosis.

[Effect of astragalus-angelica mixture on osteopontin expression in rats with chronic nephrosclerosis]

OBJECTIVE

To observe the effect of Astragalus-Angelica Mixture (AAM) on osteopontin (OPN) expression in rats with chronic nephrosclerosis.

METHODS

Chronic nephrosclerosis model rats induced by repeated intraperitoneal injection of puromycin were randomly divided into the model group, AAM group and Irbesartan (an antagonist of angiotensin) group. The experimental course lasted 12 weeks. Blood and urine samples were examined by biochemical method. Kidney tissue was taken for pathological stain and immunohistochemical method and was applied to examine OPN expression, mononuclear macrophage, laminin in extracellular matrix and decorin expressions.

RESULTS

AAM showed the effects of decreasing urinary protein and improving renal function similar to that of Irbesartan. It also could alleviate the pathological damage of kidney tissue, especially in decreasing renal tubular mesenchymal damage index. The accumulation of decorin and laminin in the mesenchymal extracellular matrix significantly decreased. Renal tubular OPN expression and mesenchymal infiltration of mononuclear macrophage decreased significantly and in a positive correlated manner (r = 0.885, P < 0.01).

CONCLUSION

AAM has similar renal protective action to that of Irbesartan, this action may be related to the inhibition of up-regulated OPN expression.

Iron deposition in renal biopsy specimens from patients with kidney diseases

This study was performed to investigate the correlation between clinical parameters and grading of iron deposition in renal biopsy specimens from 102 patients with various kidney diseases. Iron deposition in renal tissues was detected by Berlin blue staining. The extent of iron staining was semiquantitatively graded as negative (Fe(-)), grade 0, or positive (Fe(+)), including faint, grade 1; moderate, grade 2; or severe, grade 3, by light microscopy. Thirty-four of 102 patients (33%) showed positive iron staining. Fe(+) patients had various renal diseases, mainly consisting of 12 patients with immunoglobulin A nephropathy and 5 patients with benign nephrosclerosis. Mean arterial pressure (MAP), serum creatinine (sCr) levels, incidence of hematuria, and urinary N-acetylbeta-D-glucosaminidase (u-NAG) levels in Fe(+) patients were significantly greater than those in Fe(-) patients, and u-NAG levels correlated positively with the extent of iron deposition. Study patients were tentatively divided into two groups according to the extent of iron deposition: group A, patients with grades 2 and 3 staining, and group B, patients with grades 0 and 1 staining. In group A, MAP, sCr level, urinary protein excretion, and the incidence of hematuria were significantly greater than in group B. Our results suggest that the amount of iron deposition in renal tissue may contribute to the progression of chronic renal disease and may be an early and sensitive indicator of renal damage in certain renal diseases.

Oxidative stress and renal dysfunction in salt-sensitive hypertension

Hypertension is a risk factor for the development of end-stage renal disease. The mechanisms underlying hypertensive nephropathy are poorly understood. There is evidence, however, that in hypertension there is an accumulation of partially reduced oxygen and its derivatives, known collectively as reactive oxygen species, which may contribute to progressive renal dysfunction. In the present study, we assess the contribution of oxidative stress in the development of salt-dependent hypertensive nephrosclerosis. Going beyond previous end point studies, which inferred renal function either indirectly or only qualitatively, we have determined oxidative stress concurrently with direct and quantitative measurements of renal function (via inulin and p-aminohippuric acid clearances). Moreover, in this time-dependent study, the measurements have been taken under low- as well as high-salt diets. As was expected from previous studies, in the Dahl salt-sensitive rat, a high-salt diet (8% NaCl) resulted in the development of hypertension, in a decreased glomerular filtration rate, and in a decreased renal plasma flow as compared with the normotensive control, the Dahl salt-resistant rat. In addition, however, we found clear evidence for the accumulation of reactive oxygen species in renal tissue homogenates of Dahl salt-sensitive rats on the high-salt diet. Our time-dependent protocol also indicated that renal oxidative stress follows, in time, the development of hypertension. We also found that after 2 weeks of increased salt loading, Dahl salt-sensitive rats excreted less cyclic guanosine monophosphate and NO(x) than Dahl salt-resistant rats on the same diet. It is known that urinary cyclic guanosine monophosphate and NO(x) represent the activity and stable derivatives of renal NO., respectively, and that they closely correlate with renal vascular resistance. Therefore, our results suggest that, in the Dahl salt-sensitive rat, increased oxidative stress is associated with salt-dependent hypertensive nephrosclerosis and that decreased NO. bioavailability may represent a common factor responsible for the vascular and glomerular dysfunction.

Comparison of cross-sectional renal function measurements in African Americans with hypertensive nephrosclerosis and of primary formulas to estimate glomerular filtration rate

Renal function measurements were obtained in 1,703 African Americans with presumed hypertensive nephrosclerosis who were screened for entry into the African-American Study of Hypertension and Kidney Disease (AASK). We examined the effect of race on relationships involving renal variables by comparing African Americans enrolled into the AASK with non-African Americans enrolled into the Modification of Diet in Renal Disease (MDRD) study. We examined the effect of gender on renal variables by comparing African American men and women. We compared various methods for estimating glomerular filtration rate (GFR) with iodine 125-labeled ((125)I)-iothalamate GFR. AASK data were also used to derive a new formula for estimating GFR in African Americans. After adjusting for age, sex, and baseline GFR, African American patients on the AASK study were heavier and had larger body surface areas and body mass indices than either MDRD African Americans or non-African Americans. African Americans had greater serum creatinine levels and urinary creatinine excretions for any given level of GFR. Mean GFR was greater in African American men than African American women (59.7 versus 51.7 mL/min/1.73 m(2)), although serum creatinine levels were also greater in men (1.91 versus 1.73 mg/dL). Seventy-eight percent of women with serum creatinine levels between 1.2 and 1.5 mg/dL had GFRs less than 65 mL/min/1.73 m(2). For African Americans in the AASK, GFR was overestimated by the 24-hour creatinine clearance and underestimated by the Cockcroft-Gault formula. A prediction formula developed in the MDRD study more accurately predicted GFR in AASK patients than these measurements. AASK data were also used to derive a new five-term formula for estimating GFR that was slightly more accurate in the African Americans in the AASK than the MDRD formula (median percentage of error, 12.4% for the MDRD formula versus 12.1% for the AASK formula). Important differences exist in renal variables between African Americans and non-African Americans and between African American men and African American women. Formulas using demographic data and readily measured serum values estimate (125)I-iothalamate GFR.

[Experimental study on effect of bushen qingli huoxue treatment on glomerular extracellular matrix of remnant kidney in rats]

OBJECTIVE

To study the effect of Bushen Qingli Huoxue (BQH) treatment on glomerular extracellular matrix (ECM) and in retarding glomerular sclerosis in rats and to explore the mechanism and key of regulation.

METHODS

Animal model was established by 5/6 nephrectomy and the study was carried out by using immune histochemical and pathological methods. Treatment of BQH started 1 week after operation.

RESULTS

After being treated with BQH, the serum creatinine (SCr), blood urea nitrogen (BUN) and urinary protein excretion reduced markedly. Pathological examination showed accumulation of ingredients of glomerular ECM such as type I, IV collagen and laminin decreased significantly, the number of glomerular cells and proliferation cell nuclear antigen positive cells also decreased obviously, and showed that the glomerular sclerosis was retarded. The effect of BQH was similar to that of Enapril, but superior to that of Enapril in reducing BUN and SCr.

CONCLUSION

BQH has the effects of reducing ECM accumulation, improving renal function and retarding glomerular sclerosis.

What is 'nephrosclerosis'? lessons from the US, Japan, and Mexico

BACKGROUND

Selected features of 'nephrosclerosis' can be quantitated morphometrically in renal histology at autopsy. Specimens are available from Japan, Mexico, and the US (blacks and whites).

METHODS

Autopsies of men and women aged 15-79 years provided renal samples for paraffin sectioning. These were assembled in New Orleans for objective evaluation after standardized staining with PAS-Alcian blue and interspersion with each other. Obsolescence of glomeruli, interstitial fibrosis, fibroplastic intimal thickenings of arteries, and arteriolar hyalinization, as operationally defined, were measured by objective morphometry.

RESULTS

Obsolescence of glomeruli and interstitial fibrosis displayed the expected correlation with arterial intimal fibroplasia, but failed to confirm any direct association with arteriolar hyalinization. Some of the variation of 'nephrosclerosis', within and between populations, cannot be fully explained by microvascular defects.

CONCLUSIONS

Arterial intimal fibroplasia appeared to promote 'nephrosclerosis', in the sense of fibrous replacement of atrophied nephrons, but arteriolar hyalinization did not. Hyaline deposits in arterioles may offer little or no threat to the integrity of the affected nephrons. 'Nephrosclerosis' appears to be multifactorial; it may be, in part, a consequence of fibroplasia in microscopic arteries causing ischaemic injury to scattered nephrons, but may also be a confluence of basically separate conditions, only some of which are known.

Disposition of [G-(3)H]paclitaxel and cremophor EL in a patient with severely impaired renal function

In the present work, we studied the pharmacokinetics and metabolic disposition of [G-(3)H]paclitaxel in a female patient with recurrent ovarian cancer and severe renal impairment (creatinine clearance: approximately 20 ml/min) due to chronic hypertension and prior cisplatin treatment. During six 3-weekly courses of paclitaxel at a dose level of 157.5 mg/m(2) (viz. a 10% dose reduction), the renal function remained stable. Pharmacokinetic evaluation revealed a reproducible and surprisingly high paclitaxel area under the plasma concentration-time curve of 26.0 +/- 1.11 microM.h (mean +/- S.D.; n = 6; c.v. = 4.29%), and a terminal disposition half-life of approximately 29 h. Both parameters are substantially increased ( approximately 1.5-fold) when compared with kinetic data obtained from patients with normal renal function. The cumulative urinary excretion of the parent drug was consistently low and averaged 1.58 +/- 0.417% (+/- S.D.) of the dose. Total fecal excretion (measured in one course) was 52.9% of the delivered radioactivity, and mainly comprised known mono- and dihydroxylated metabolites, with unchanged paclitaxel accounting for only 6.18%. The plasma area under the plasma concentration-time curve of the paclitaxel vehicle Cremophor EL, which can profoundly alter the kinetics of paclitaxel, was 114.9 +/- 5.39 microl.h/ml, and not different from historic data in patients with normal or mild renal dysfunction. Urinary excretion of Cremophor EL was less than 0.1% of the total amount administered. These data indicate that the substantial increase in systemic exposure of the patient to paclitaxel relates to decreased renal metabolism and/or urinary elimination of polar radioactive species, most likely lacking an intact taxane ring fragment.

Effects of angiotensin inhibitors on renal injury and angiotensin receptor expression in early hypertensive nephrosclerosis

Angiotensin converting enzyme inhibitors (ACEI) are known to inhibit the progression of established renal failure. The aim of this study was to compare the efficacy of an ACEI and an AT1 receptor antagonist (AT1R-Ant) in preventing the development of renal disease, at an early stage of hypertensive nephrosclerosis. SHRSP/Izm rats (n = 61) were treated from 10 wk until 22 wk with the ACEI delapril (40 mg/kg/d) or the AT1R-Ant candesartan cilexetil (1 mg/kg/d). Proteinuria, and structural/ultrastructural changes were assessed at 14 and 22 wk. Treatment with either agent resulted in reductions in blood pressure and cardiovascular hypertrophy. Neither proteinuria nor major renal histological changes were evident at 14 wk. At 22 wk, however, proteinuria accompanied by nephrosclerotic changes was seen in the untreated SHRSP/Izm. Treatment with either ACEI or AT1R-Ant resulted in similar reductions in proteinuria (untreated, 32.2 +/- 7.4; delapril-treated, 5.5 +/- 1.2; candesartan-treated, 3.9 +/- 0.3 mg/100 g/d). Prominent sclerosis of small-to-medium sized renal arteries was seen in the untreated SHRSP/Izm at 22 wk, but was similarly attenuated by the ACEI and AT1R-Ant. The glomerular ultrastructure was comparable between the two groups. No significant changes in renal AT1a or AT1b receptor subtype mRNA expression were seen throughout the course of the study. In contrast, a decrease in AT2 receptor mRNA was seen in the drug-treated groups at 14 wk but not at 22 wk. These results suggest that both ACEI and AT1R-Ant have similar efficacy in attenuating the onset of renal injury in early hypertensive nephrosclerosis, and that treatment with either agent is associated with a transient decrease in AT2 receptor mRNA expression.

Vascular endothelin-1 gene expression and synthesis and effect on renal type I collagen synthesis and nephroangiosclerosis during nitric oxide synthase inhibition in rats

BACKGROUND

The progression of hypertension during NO deficiency is associated with renal vascular fibrosis due to increased extracellular matrix (mainly collagen I) formation. The purpose of the present study was to investigate whether endothelin-1 (ET-1) is involved in this pathophysiological process.

METHODS AND RESULTS

Treatment of rats for 4 weeks with the NO synthase inhibitor Nomega-nitro-L-arginine methyl ester (L-NAME) 50 mg. kg-1. d-1 increased systolic blood pressure to 159+/-12 mm Hg. In animals treated with L-NAME, histological evaluation of renal sections revealed an increased formation of extracellular matrix (Masson's trichrome), and specifically of collagens (Sirius red). A part of this fibrosis was attributed to abnormal collagen I presence, because mRNA expression of the collagen I alpha1 chain (reverse transcription-polymerase chain reaction) and procollagen I formation (radioimmunoassay) were increased 3- and 2.5-fold, respectively, in the renal resistance vessels of hypertensive animals. In subsequent experiments, we examined whether ET-1 was involved in activation of collagen I formation. mRNA expression (RNase protection assay) of preproET-1 and ET-1 content (radioimmunoassay) were 10-fold and 3-fold increased, respectively, in renal microvessels of rats treated with L-NAME. Interestingly, in these vessels, ET-1 (immunostaining) was colocalized with sudanophilic lesions. Bosentan, an ET receptor antagonist (20 mg. kg-1. d-1), coadministered with L-NAME canceled the increased mRNA expression and synthesis of collagen I and attenuated the severity of renal vascular lesions without affecting L-NAME-induced high blood pressure.

CONCLUSIONS

These data demonstrate that ET-1 synthesis is increased in renal microvessels when NO production is suppressed. In this model of hypertension, ET-1 is a major activator of collagen I formation in renal resistance vessels and participates in the development of renal fibrosis without affecting systolic blood pressure.

The long-term prognosis of benign nephrosclerosis accompanied by focal glomerulosclerosis and renal cortical interstitial fibrosis, designated so-called decompensated benign nephrosclerosis by Fahr, Bohle and Ratscheck

The long-term prognosis of decompensated benign nephrosclerosis (DBN) was investigated by a retrospective analysis of the fate of 170 patients with this disease, which yielded the following results: 1) DBN carries a particularly poor prognosis. The renal survival rate (RSR) was 35.9% at 5 years and 23.6% at 10 years. The prognosis is therefore worse than that of any other primary glomerulopathy, with the exception of rapidly progressive glomerulonephritis. 2) DBN mainly affects males (sex ratio 5:1) and differs in this respect, among others, from focal sclerosing glomerulonephritis, in which the male:female ratio is 1.2:1. 3) The prognosis for females is no better than for males. 4) The severity of proteinuria at the time of biopsy has no influence on the prognosis. 5) The prognosis is particularly poor in cases in which the serum creatinine concentration is already elevated to more than 2.0 mg% at the time of biopsy. We conclude from these findings that not only the blood pressure, but also the serum creatinine concentration, should be assessed at regular intervals in all hypertensive individuals, so that DBN can be treated at an early stage, when it is still amenable to treatment.

[Copper and zinc metabolic derangement in patients with chronic pyelonephritis developing nephrosclerosis and renal insufficiency]

Cu and Zn levels were measured (nuclear-absorption spectrophotometry) in the blood and urine from patients with chronic pyelonephritis (CP) in emergence of nephrosclerosis and renal insufficiency. CP patients were found to develop hypercupremia as early as initial stages of nephrosclerosis when renal insufficiency was not apparent. Blood Zn was low, especially in development of chronic renal insufficiency. Cu and Zn disbolism may contribute to formation of sclerotic lesions in the kidneys and to development of chronic renal insufficiency. Assay for Cu and Zn is proposed for early diagnosis of nephrosclerosis and provides objective clinical control over the disease course to make timely correction of the detected defects and valid prognosis.

Involvement of angiotensin II in cardiovascular and renal injury: effects of an AT1-receptor antagonist on gene expression and the cellular phenotype

OBJECTIVES

We investigated the effects of an angiotensin II type 1 (AT1)-receptor antagonist on experimental cardiac hypertrophy, vascular thickening and nephrosclerosis, in order to determine the involvement of this receptor in the development of cardiovascular and renal damage.

DESIGN

Accumulating evidence indicates that various growth-related genes, growth factors and extracellular matrix components play a central part in the pathogenesis and development of cardiovascular and renal diseases, either by regulating cell growth and migration or by promoting tissue fibrosis.

MATERIALS AND METHODS

Stroke-prone spontaneously hypertensive rats were given candesartan cilexetil, a specific non-peptide AT1-receptor antagonist, for 10 weeks, and cardiac phenotypic and fibrosis-related gene expression and aortic and mesenteric arterial gene expressions were determined. Balloon-injured carotid arteries and deoxycorticosterone acetate (DOCA)-salt hypertensive rats were also similarly examined.

RESULTS

Treatment of hypertensive rats with an AT1-receptor antagonist led to the regression of cardiac hypertrophy, suppression of cardiac phenotypic changes to a fetal phenotype and an increase in fibrosis-related gene expression in the hypertrophied heart. Balloon injury-induced neointima formation in the rat carotid artery was prevented by the AT1-receptor antagonist, which was associated with the inhibition of the induction of proto-oncogenes such as c-fos, c-jun and Egr-1 and of increased fibronectin gene expression. Furthermore, the AT1-receptor antagonist prevented either the phenotypic modulation of glomerular cells or an increase in transforming growth factor-beta 1 expression in an experimental model of nephrosclerosis.

CONCLUSIONS

AT1-receptor antagonists in vivo potently inhibit the expression of the growth-related and extracellular matrix genes, as well as cellular phenotypic modulation. These molecular effects of the AT1-receptor antagonist may contribute to their protective effects on cardiovascular and renal diseases.

Effect of 2,3-dimercaptosuccinic acid on nephrosclerosis in the Dahl rat. I. Role of reactive oxygen species

2,3-Dimercaptosuccinic acid (DMSA), a sulfhydryl-containing chelator, has previously been shown to reduce mean blood pressure in lead-treated rats. In the present study we have demonstrated that DMSA (0.5% for 5 days every 2 weeks) also reduces mean blood pressure in the Dahl salt-sensitive (SS) rat. Six-week-old Dahl SS and salt resistant (SR) rats were placed on a 0.3% NaCl diet for two weeks, followed by an 8% NaCl diet for four weeks. Eight SS and 8 SR rats remained untreated while 8 SS and 8 SR rats were treated with DMSA. DMSA treatment ameliorated the mean blood pressure rise in the Dahl SS rats (141 +/- 5 vs. 120 +/- 4 mm Hg at 6 weeks, P < 0.001). Nephrosclerosis was severe in untreated SS rats but absent in treated SS rats as well as in both treated and untreated SR rats. Reactive oxygen species formation, as assessed by kidney cortex content of malondialdehyde (MDA) and immunohistochemical demonstration of nitrotyrosine (a byproduct of peroxynitrite) in interlobular arteries, was increased in Dahl SS rats, but abolished by DMSA (MDA 9.65 +/- 0.33 nmol/g wet wt, untreated SS, vs. 6.46 +/- 0.51, treated SS, P < 0.001). The anti-nephrosclerotic action of DMSA was clearly disproportionate to the reduction in blood pressure. We conclude that the effect of DMSA was related instead to the reactive oxygen species scavenging properties of the thiol groups.

Significance of increased accumulation of type VI collagen and transforming growth factor beta 1 in tubulointerstitial damage in hypertensive nephrosclerosis: an immunohistochemical study

The distribution of type VI collagen and transforming growth factor beta 1 (TGF beta 1) was studied by immunohistochemistry in 12 renal biopsy specimens of hypertensive nephrosclerosis and five control cases. In control kidneys, the immunostaining of type VI collagen was found in the mesangium, glomerular basement membrane and tubular basement membrane. For TGF beta 1, mesangium, glomerular basement membrane, tubular basement membrane and tubular epithelial cells stained positively in the control kidneys. In contrast to the control cases, markedly increased immunostaining for both type VI collagen and TGF beta 1 was consistently observed in tubulointerstitial damage in hypertensive nephrosclerosis. These immunohistochemical findings provide the evidence for a parallel increase of both type VI collagen and TGF beta 1 during the process of tubulointerstitial injury in hypertensive nephrosclerosis. From the results of the present study, it is speculated that TGF beta 1 may contribute to the tubulointerstitial injury by stimulating increased synthesis of various extracellular matrix including type VI collagen.

An index of plasma refilling in hemodialysis patients

During hemodialysis therapy, a large amount of water is removed from the patient's blood in a short time; however, blood pressure remains stable in most patients. As water is removed, the circulating serum proteins become more concentrated, resulting in a marked increase in the driving force which pulls water from the extravascular space into the blood vessels, by a process called plasma refilling. However, since a method for studying plasma refilling has not previously been proposed, it is not known what determines the plasma refilling capacity of hemodialysis patients. To evaluate the plasma refilling capacity of patients, we propose here a method for calculating an index of plasma refilling capacity, which we have called the plasma-refilling coefficient (Kr). In 14 patients receiving maintenance hemodialysis therapy, total serum protein was measured before hemodialysis, and hematocrits were measured hourly during hemodialysis. From the changes in the hematocrits, we estimated the changes in the circulating plasma volume and in the intracapillary oncotic pressure at each time point. The water removal rate was also measured hourly. From these values, we calculated Kr. An averaged volume of 2,692 +/- 219 ml of water was removed from each patient resulting in a decrease in the estimated circulating blood volume, while the hematocrit and the estimated intracapillary oncotic pressure increased gradually. Kr calculated after 1 h of hemodialysis varied widely between patients, 140.3-1,744.2 ml/mm Hg/h, and decreased gradually as water removal continued. The average Kr of 14 patients was 698.9 +/- 15.2 ml/mm Hg/h at the beginning of water removal, and it decreased to 405.3 +/- 75.4, 203.9 +/- 39.5, 130.2 +/- 20.5 and 93.9 +/- 14.3 each hour thereafter. The index of plasma refilling proposed in this paper is useful for examining capillary water permeability and the degree of plasma refilling in hemodialysis patients.

Effects of glycosaminoglycans on the glomerular changes induced by Adriamycin

Glycosaminoglycans can stimulate the synthesis of glomerular basement membrane (GBM) proteins by glomerular cells and correct biochemical alterations of the GBM. In this study we examine the effects of heparin and low-molecular-weight heparin (LMWH) on glomerular permeability to proteins and glomerular structure in Adriamycin-treated rats. One Adriamycin dose of 5 mg/kg body weight was administered i.v. to 38 female Wistar rats. Eleven animals were also treated with heparin (250 U) administered s.c. twice daily and 7 with LMWH 6 mg/kg body weight administered s.c. twice daily. Urine samples were collected before and 30 and 60 days after the beginning of treatment to quantify albumin excretion and to characterize urinary proteins by gel filtration and electrophoresis in sodium dodecyl sulfate polyacrylamide gels. Blood samples were also collected on day 60 from these rats to estimate renal permeability by gel filtration; the rats were then killed and the kidneys removed for histological analysis. Heparin administration caused a reduction in urinary albumin excretion and in the incidence of segmental glomerulosclerosis in Adriamycin-treated rats. However, heparin did not modify the selectivity of the GBM to proteins of different molecular weights. These data suggest that the effect of heparin on albuminuria may be due to changes in the negative GBM charges induced by this drug.

Expression of vascular endothelial growth factor in renal vascular disease and renal allografts

Vascular endothelial growth factor (VEGF) is a dimeric glycoprotein that exerts a proliferative effect specifically on endothelial cells. VEGF can increase vascular permeability and collagenase activity, is chemotactic for monocytes, and may dilate blood vessels. It can be induced by phorbol ester and cAMP in both mesenchymal and epithelial cells. In vitro cell culture experiments suggest that VEGF is upregulated by oxygen deprivation. In this study we tested whether in vivo acute and/or chronic reduction of renal blood flow by vascular obstruction would result in increased expression of VEGF mRNA and protein. Three normal kidneys, five human kidneys with narrowing of preglomerular vessels by vascular rejection or by vasculitis, and eight kidneys with nephrosclerosis and/or diabetic nephropathy were examined. In situ hybridization with 35S-labelled riboprobes showed a pronounced expression of VEGF mRNA in acutely hypoxic proximal and distal tubules of both the cortex and medulla; VEGF protein was demonstrated in the epithelia of these tubules by immunohistochemistry. In kidneys with chronically reduced blood flow, the majority of atrophic tubules were negative for VEGF mRNA and protein, although interstitial cells expressed VEGF mRNA. In arcuate arteries showing intimal and adventitial fibrosis, some medial smooth muscle cells were positive for VEGF mRNA. In glomeruli with segmental sclerosis, viable podocytes showed a prominent signal for VEGF mRNA. Mesangial cells did not express VEGF in the cases studied. It is possible that hypoxia itself led to the upregulation of VEGF in tubular epithelia and vascular smooth muscle cells. The vasodilatory and permeability-promoting effects of the endothelial growth factor produced by damaged tubular epithelia may constitute a mechanism to alleviate a decrease in blood flow and substrate availability and to re-establish vascular integrity.

Immunohistochemical detection of fibronectin in early and advanced atherosclerosis

Fibronectin is known to be involved in the pathogenesis of atherosclerosis. We therefore applied paraffin-section immunohistochemistry, which permits detailed morphological analysis of the tissue distribution of fibronectin, in order to evaluate the alterations of fibronectin in terms of quantity and localization during the progression of atherosclerosis in humans. In 48/60 (80%) cases (p < 0.005) with early atherosclerotic lesions we found intense fibronectin staining presenting a distribution in continuous fibrils in the subendothelium around the fibrous plaque. The total amount of fibronectin was elevated. In 51/60 (85%) cases (p < 0.001) presenting advanced or complicated atherosclerotic lesions, the characteristic distribution of fibronectin in continuous fibrils was interrupted, fibronectin strands were fragmented and in regions where the sclerotic process was complete, fibronectin seemed to be almost absent. These findings reveal that fibronectin during atherosclerosis plays a role similar to that reported during the wound healing process and demonstrate a close relationship between quantity and topographical distribution of fibronectin and evolution of atherosclerosis. Further studies are required to determine whether fibronectin could be used as a marker for evaluation of the severity of atherosclerotic lesions.

[Morphologic characteristics of nephrosclerosis: electron microscopic, immunohistochemical and histospectrophotometric study]

Combined study of nephrosclerosis revealed profound alterations of both extracellular matrix (ECM) and tubular epithelium. ECM alterations manifested in the accumulation in the stroma of I and III types of collagen, fibronectin, considerable increase of collagen IV and laminin.

Glomerular expression of type III and type IV collagens in benign nephrosclerosis: immunohistochemical and in situ hybridization study

The development of glomerular sclerosis in benign nephrosclerosis (BNS) was studied. We investigated the intraglomerular expression of type III and IV collagens and their mRNAs by immunohistochemistry and by the in situ hybridization method. Formalin-fixed paraffin sections from 28 patients with BNS and 10 control cases were stained by the avidin-biotin complex (ABC) method using monoclonal antibodies for human type III and IV collagens. In the course of the sclerotic process of the glomerulus in BNS, the glomerular staining intensity of type IV collagen increased. The strongest staining was observed in the glomerulus at the early sclerotic stage, and intensity decreased slightly at the later stages. Although type III collagen was absent in normal and nonsclerotic glomeruli, peripheral regions of the sclerotic glomeruli were positive at the early sclerotic stage. Later, type III collagen was diffusely observed in the completely hyalinized glomeruli. The expression of type III and type IV collagen mRNAs was detected in the glomeruli of BNS by the non-radioactive in situ hybridization method using thymine-thymine (T-T) dimerized synthetic oligonucleotides. The number of mRNA positive cells for type III and type IV collagens increased at the presclerotic and early sclerotic stages. But these cells gradually decreased in number as glomerular sclerosis developed. We concluded that type III collagen was presumably synthesized by the intraglomerular cells and may contribute to the development of glomerular sclerosis in BNS along with type IV collagen.

[Immunohistochemical study on the extracellular matrix components in various renal diseases]

In order to clarify considerable alterations of the extracellular matrix components in various renal diseases, monoclonal antibodies against type IV collagen (IV col), 200-KD laminin (200-KD Lam), 400-KD laminin (400-KD Lam) and heparan sulfate proteoglycan (HSPG) were applied to 142 renal biopsy specimens for the indirect immunofluorescence. These subjects included 5 cases with 1 hour specimen in the transplanted kidney, 32 minimal change nephrotic syndrome (MCNS), 30 mesangial proliferative glomerulonephritis (PGN), 2 focal segmental glomerulosclerosis (FGS), 21 membranous nephropathy (MN), 9 membranoproliferative glomerulonephritis (MPGN), 2 poststreptococcal acute glomerulonephritis (PSAGN), 13 diabetic nephropathy (DN), 16 lupus nephritis (LN), 9 diffuse sclerosing glomerulonephritis (DSGN), 2 amyloid kidney and 1 granulomatous nephropathy in sarcoidosis. In the transplanted kidney, the staining intensity of IV col was stronger than that of 200-KD Lam, 400-KD Lam and HSPG in general. IV col was predominantly distributed throughout the mesangium area and less along the glomerular basement membrane (GBM). The positive stainings with 200-KD Lam along the GBM and that with 400-KD Lam in the mesangium area were weakly recognized. HSPG was mainly detected along the GBM in the linear fashion. In MCNS, the distribution of the extracellular matrix components was mostly identical to that in the transplanted kidney. In the group of the glomerulonephritis showed the proliferations of mesangial cells, such as PGN and MPGN, the staining intensity of both IV col and 400-KD Lam, particularly in the latter, was remarkably increased in the sclerotic lesions. In MN, the thickened GBM was strongly stained with both IV col and 200-KD Lam, and the stainings of 200-KD Lam were more intensive. And still more, by the double labelling method performed for the couple of IV col and immunoglobulins, the correlation between glomerular capillary walls and/or mesangial areas and immunoglobulins deposits became more clear. These findings suggest as follows: (1) both IV col and 400-KD Lam, in particular 400-KD Lam, are possibly involved in the process of glomerulosclerosis: (2) both IV col and 200-KD Lam, in particular 200-KD Lam, are greatly involved in the process of new basement membrane-like materials formation in MN.