The role of angiotensin II and plasminogen activator inhibitor-1 in progressive glomerulosclerosis

Role of plasminogen activated inhibitor-1 in the pathogenesis of anticoagulant related nephropathy

Anticoagulant related nephropathy (ARN) is the result of glomerular hemorrhage in patients on systemic anticoagulation therapy or underlying coagulopathy. Red blood cells (RBC) that passed through the glomerular filtration barrier form RBC casts in the tubules, increase oxidative stress and result in acute tubular necrosis (ATN). The mechanisms of ARN still not completely discovered. Plasminogen activator inhibitor-1 (PAI-1) plays a significant role in the maintenance of coagulation homeostasis. We developed an animal model to study ARN in 5/6 nephrectomy (5/6NE) rats. The aim of this study was to elucidate the role of PAI-1 in the ARN pathogenesis. 5/6NE rats were treated per os with warfarin (0.75 mg/kg/day) or dabigatran (150 mg/kg/day) alone or in combination with PAI-1 antagonist TM5441 (2.5, 5.0 and 10 mg/kg/day). TM5441 in a dose dependent manner ameliorated anticoagulant-induced increase in serum creatinine in 5/6NE rats. Anticoagulant-associated increase in hematuria was no affected by TM5441. The levels of reactive oxygen species (ROS) in the kidneys were in a dose-dependent manner decreased in 5/6NE rats treated with an anticoagulant and TM5441. Our data demonstrates that PAI-1 may reduce ARN by decreasing ROS in the kidneys. Glomerular hemorrhage is not affected by anti-PAI-1 treatment. These findings indicate that while symptoms of ARN can be reduced by PAI-1 inhibition, the main pathogenesis of ARN - glomerular hemorrhage - cannot be prevented.

[Classical nephroprotection: Renin angiotensin aldosterone system inhibitors]

The role of the renin angiotensin aldosterone system (RAAS) in the pathophysiology of hypertension, cardiovascular disease and kidney disease has been known for years. RAAS inhibitors have been the mainstay of chronic kidney disease (CKD) treatment. Studies have shown that therapy with angiotensin-converting enzyme inhibitors (ACE inhibitors) or angiotensinII receptor blockers (ARBs) reduce the excretion of albuminuria and slow the progression of kidney disease in patients with and without diabetes. In clinical practice, RAAS inhibitors are recommended as the antihypertensive of choice in patients with CKD and albuminuria with or without diabetes. In addition, they have demonstrated cardiovascular benefits beyond blood pressure control. The use of RAAS inhibitors in non-proteinuric nephropathy and advanced CKD is not without controversy. Double blockade of the RAAS is contraindicated. On the other hand, it is essential to know how to titrate doses and avoid side effects, mainly hyperkalaemia.

Alcohol Intoxication and the Postburn Gastrointestinal Hormonal Response

Gastrointestinal hormones are essential in postburn metabolism. Since near 50% of burn victims test positive for blood alcohol levels at hospital admission and have inferior outcomes compared to nonintoxicated burn patients; we hypothesized that the gastrointestinal hormone secretion is compromised in intoxicated burn victims. To test our theory, we quantified gastrointestinal hormones serum levels in a combine ethanol intoxication and burn injury mouse model. Thus, mice received a daily dose of ethanol for 3 days, rested 4 days, and were given ethanol 3 additional days. Mice underwent 15% TBSA scald burn 30 minutes after their last ethanol dose. Serum samples were collected 24 hours after burn injury. Nonintoxicated burned mice exhibited an increase in glucose, insulin, ghrelin, plasminogen activator inhibitor-1, leptin, and resistin by 1.4-, 3-, 13.5-, 6.2-, 9.4-, and 2.4-fold, respectively, compared to sham vehicle mice (P < .05). Burn injury also reduced serum gastric inhibitory polypeptide (GIP) by 32% compared to sham-injured, vehicle-treated mice. Leptin, resistin, glucagon-like peptide-1, as well as insulin, were not different from sham groups when intoxication preceded burn injury. Nevertheless, in burned mice treated with ethanol, gastric inhibitory polypeptide and glucagon serum levels exhibited a significant fold increase of 3.5 and 4.7, respectively. With these results, we conclude that 24 hours after burn injury, mice developed significant changes in gastrointestinal hormones, along with hyperglycemia. Moreover, the combined insult of burn and ethanol intoxication led to additional hormonal changes that may be attributed to a potential pancreatic dysfunction. Further multiday studies are required to investigate the etiology, behavior, and clinical significance of these hormonal changes.

Assessment of the effect of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers in peritoneal dialysis patients: a systematic review and meta-analysis on clinical trials

Background

Renin-angiotensin system inhibitors (RASIs), either angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, are widely used in patients with non-dialysis chronic kidney disease, as a renin-angiotensin system (RAS) blockade has renoprotective effects. Several studies show that preserving residual renal function is important for a better prognosis in peritoneal dialysis (PD) patients. Here, we systematically reviewed the beneficial or harmful effects of RAS blockade in PD patients.

Methods

PubMed, the Cochrane Library, Embase, the Ichushi web databases, and other resources were selected to search clinical guidelines, systematic reviews, and randomized controlled trials (RCT) published before April 14, 2017, using “peritoneal dialysis,” “angiotensin-converting enzyme inhibitors,” “angiotensin II type 1 receptor blockers,” and “randomized controlled trial” as keywords. Desired results were total mortality, technical survival, urine volume, residual renal function calculated byglomerular filtration rate(GFR), cardiovascular events, and anuria progression rate. The study protocol is registered in PROSPERO (International Prospective Register of Systematic Reviews) under the registration number CRD42018104106.

Results

Of a total of 339 studies, eight were identified as suitable for the analysis. Only one study was blinded, whereas the other seven studies were open-label. RASI appeared to preserve residual renal function, GFR (4 studies, 163 participants, mean difference [MD] 0.97 mL/min/1.73 m2, 95% confidence interval [CI] 0.49–1.44), and urine volume (6 studies, 194 participants, MD 142.56 mL 95% CI 25.42–259.69), although there were no beneficial effects of RASI on total mortality, technical survival, cardiovascular events, and anuria rate.

Conclusions

Our analysis found that RASIs contribute to preserving GFR and urine volume in PD patients. As the number of study participants is small, further studies with a larger sample size are required.

Renal Aging: Causes and Consequences

Individuals age >65 years old are the fastest expanding population demographic throughout the developed world. Consequently, more aged patients than before are receiving diagnoses of impaired renal function and nephrosclerosis-age-associated histologic changes in the kidneys. Recent studies have shown that the aged kidney undergoes a range of structural changes and has altered transcriptomic, hemodynamic, and physiologic behavior at rest and in response to renal insults. These changes impair the ability of the kidney to withstand and recover from injury, contributing to the high susceptibility of the aged population to AKI and their increased propensity to develop subsequent progressive CKD. In this review, we examine these features of the aged kidney and explore the various validated and putative pathways contributing to the changes observed with aging in both experimental animal models and humans. We also discuss the potential for additional study to increase understanding of the aged kidney and lead to novel therapeutic strategies.

The emerging role of coagulation proteases in kidney disease

A role of coagulation proteases in kidney disease beyond their function in normal haemostasis and thrombosis has long been suspected, and studies performed in the past 15 years have provided novel insights into the mechanisms involved. The expression of protease-activated receptors (PARs) in renal cells provides a molecular link between coagulation proteases and renal cell function and revitalizes research evaluating the role of haemostasis regulators in renal disease. Renal cell-specific expression and activity of coagulation proteases, their regulators and their receptors are dynamically altered during disease processes. Furthermore, renal inflammation and tissue remodelling are not only associated, but are causally linked with altered coagulation activation and protease-dependent signalling. Intriguingly, coagulation proteases signal through more than one receptor or induce formation of receptor complexes in a cell-specific manner, emphasizing context specificity. Understanding these cell-specific signalosomes and their regulation in kidney disease is crucial to unravelling the pathophysiological relevance of coagulation regulators in renal disease. In addition, the clinical availability of small molecule targeted anticoagulants as well as the development of PAR antagonists increases the need for in-depth knowledge of the mechanisms through which coagulation proteases might regulate renal physiology.

Differential modification of enalapril in the kidneys of lean and 'programmed' obese male young rats

OBJECTIVE

We investigated whether enalapril treatment could have beneficial effects on nutritionally-programmed renal changes in postnatally overfed young rats.

METHODS

Three or 10 male pups per mother were assigned to either the Obese or Lean groups during the first 21 days of life. These pups were treated with enalapril (Obese enalapril, OE; Lean enalapril, LE) or vehicle (Obese control, OC; Lean control, LC) between 15 and 28 days. All pups had their kidneys examined at 29 days.

RESULTS

OC pups weighed more than those in the LC group between 7 and 28 days of age (P<0.05). Enalapril reduced body weights in rats from both the Obese and Lean groups between 22 and 28 days (P<0.05). Renal cell proliferation and apoptosis, glomerulosclerosis, and tubulointerstitial fibrosis were all increased by enalapril (P<0.05). Among the groups, renal cell apoptosis and serum creatinine were the highest in OE pups (P<0.05). Enalapril treatment resulted in contrasting molecular expression profiles involved in renal maturation and repair in the kidneys of the rats from the Lean and Obese groups.

CONCLUSION

Enalapril can differentially modulate renal molecular alterations in lean and postnatally overfed rats and may be not beneficial in obese young male rats.

Activation of renin-angiotensin system is involved in dyslipidemia-mediated renal injuries in apolipoprotein E knockout mice and HK-2 cells

Background

Dyslipidemia and activation of renin-angiotensin system (RAS) contribute to the progression of chronic kidney disease (CKD). This study investigated possible synergistic effects of intrarenal RAS activation with hyperlipidemia in renal injuries.

Methods

Apolipoprotein knockout mice were fed with normal chow diet (control) or high fat diet (HF group) for eight weeks. Human proximal tubular epithelial cell line (HK-2) was treated without (control) or with cholesterol (30 μg/ml) plus 25-hydroxycholesterol (1 μg/ml) (lipid group) for 24 hours. The plasma lipid profile and RAS components were determined by clinical biochemistry assay and radiommunoassay, respectively. Collagen deposition in kidneys was evaluated by Masson-staining. The gene and protein expressions of molecules involved in RAS components and biomarkers of epithelial mesenchymal transition (EMT) were examined by real-time PCR, immunochemical staining, and Western blot.

Results

The mice fed with high-fat diet showed significant hyperlipidemia with collagen deposition in renal tubular interstitium compared to controls. The plasma levels of renin, angiotensin I, and angiotensin II were no difference in two groups. However, the kidneys of HF group showed up-regulated RAS components, which were positively associated with increased plasma levels of triglyceride, total cholesterol, and LDL. These effects were further confirmed by in vitro studies. Lipid loading induced HK-2 cells underwent EMT, which was closely associated with the increased expressions of intracellular RAS components.

Conclusions

Local RAS activation was involved in hyperlipidemia-mediated renal injuries, suggesting that there are synergistic effects resulting from RAS activation with hyperlipidemia that accelerates the progression of CKD.

Postnatal early overnutrition dysregulates the intrarenal renin-angiotensin system and extracellular matrix-linked molecules in juvenile male rats

Overnutrition during the perinatal period has been associated with susceptibility to obesity and related comorbidities. We examined the effects of postnatal early overnutrition on the development of juvenile obesity and the associated renal pathophysiological changes. Three or 10 pups per mother from rat pup litters were assigned to either the overnutrition or control groups during the first 21 days of life. The effects of overfeeding were measured at 28 days. The smaller male litter pups were heavier than the controls between 4 and 28 days after birth (P<.05). By 28 days of age, the kidney weight per body weight ratio decreased in the small litter group (P<.05). Circulating leptin levels increased in the small litter rats (P<.05). Overnutrition had no effect on renal cell proliferation, apoptosis, macrophages and glomerulosclerosis. In the immunoblots and immunohistochemistry, renin and angiotensin II type (AT) 2 receptor expression increased in the overfed rats (P<.05). By contrast, the plasminogen activator inhibitor (PAI)-1 and matrix metalloproteinase (MMP)-9 expression decreased in the overnutrition group (P<.05). The AT 1 receptor, tissue inhibitor of MMP-1, monocyte chemoattractant protein-1, tumor necrosis factor-α, osteopontin and adiponectin expression was not changed. Our data showed that postnatal early overfeeding led to hyperleptinemia, juvenile obesity and the acquired reset of renal maturation. Up-regulation of renin and AT2 and down-regulation of PAI-1 and MMP-9 might contribute to abnormal programming of renal growth in rats exposed to postnatal early overnutrition.

Renin angiotensin signaling in normal pregnancy and preeclampsia

Many reports indicate that there is an increase in almost all of the components of the renin-angiotensin system (RAS) during an uncomplicated pregnancy, but renin activity, angiotensin II, and aldosterone decrease in preeclampsia (PE) for reasons that are unclear. PE is a life-threatening disorder of late pregnancy characterized by hypertension, proteinuria, increased soluble fms-like tyrosine kinase-1, as well as renal and placental morphologic abnormalities. Although a leading cause of maternal and perinatal morbidity and mortality, the pathogenic mechanisms of PE remain largely undefined. Immunologic mechanisms and aberrations of the RAS have been long considered contributors to the disorder. Bridging these two concepts, numerous studies report the presence of the angiotensin II type I receptor agonistic autoantibody (AT(1)-AA) found circulating in preeclamptic women. This autoantibody induces many key features of the disorder through AT(1) receptor signaling, and has been implicated in the pathogenesis of PE. Here we review the functions of the RAS during normal pregnancy and PE, and highlight the role of AT(1)-AA in both animal models and in the human disorder.

Presence of peripheral arterial disease predicts loss of residual renal function in incident CAPD patients

BACKGROUND

Accelerated cardiovascular disease (CVD), including peripheral arterial disease (PAD), is very common in patients with end-stage renal disease. Residual renal function (RRF) is a strong predictor of patient survival that is suggested to be linked to the degree of CVD. However, the relationship between PAD and decline in RRF has not previously been measured.

METHODS

We studied incident continuous ambulatory peritoneal dialysis patients from Peking University Third Hospital. An ankle brachial index of less than 0.9 was used to diagnose PAD. Residual renal function (RRF) was determined as the mean of 24-hour urea and creatinine clearances (glomerular filtration rate). The Cox proportional hazards model was used to identify factors predicting loss of RRF.

RESULTS

The study included 86 patients (age: 61 ± 14 years; men: 51%), 23 of whom had PAD at baseline. Mean follow-up was 19 months (median: 18 months; range: 6 - 30 months). In univariate analysis, baseline PAD, peritonitis during follow-up, inflammation (C-reactive protein), serum uric acid, Ca×P, and serum phosphate were all significantly associated with a greater-than-50% decrease in RRF during follow-up. In multivariate analysis, only baseline PAD, Ca×P, and peritonitis were independently associated with a decline in RRF.

CONCLUSIONS

Our study suggests that PAD may be a clinically important marker of CVD predicting the loss of RRF. It remains to be determined whether interventions aimed at decreasing PAD may also improve renal vascular status and thus slow the rate of RRF decline.

Activation of bone morphogenetic protein 4 signaling leads to glomerulosclerosis that mimics diabetic nephropathy

Diabetic nephropathy (DN) is the most common cause of chronic kidney disease. We have previously reported that Smad1 transcriptionally regulates the expression of extracellular matrix (ECM) proteins in DN. However, little is known about the regulatory mechanisms that induce and activate Smad1. Here, bone morphogenetic protein 4 (Bmp4) was found to up-regulate the expression of Smad1 in mesangial cells and subsequently to phosphorylate Smad1 downstream of the advanced glycation end product-receptor for advanced glycation end product signaling pathway. Moreover, Bmp4 utilized Alk3 and affected the activation of Smad1 and Col4 expressions in mesangial cells. In the diabetic mouse, Bmp4 was remarkably activated in the glomeruli, and the mesangial area was expanded. To elucidate the direct function of Bmp4 action in the kidneys, we generated transgenic mice inducible for the expression of Bmp4. Tamoxifen treatment dramatically induced the expression of Bmp4, especially in the glomeruli of the mice. Notably, in the nondiabetic condition, the mice exhibited not only an expansion of the mesangial area and thickening of the basement membrane but also remarkable albuminuria, which are consistent with the distinct glomerular injuries in DN. ECM protein overexpression and activation of Smad1 in the glomeruli were also observed in the mice. The mesangial expansion in the mice was significantly correlated with albuminuria. Furthermore, the heterozygous Bmp4 knock-out mice inhibited the glomerular injuries compared with wild type mice in diabetic conditions. Here, we show that BMP4 may act as an upstream regulatory molecule for the process of ECM accumulation in DN and thereby reveals a new aspect of the molecular mechanisms involved in DN.

Angiotensinogen Expression Is Enhanced in the Progression of Glomerular Disease

Intrarenal renin-angiotensin system (RAS) activation plays a critical role in the development and progression of renal injury. In the kidney, all of the RAS components are present and intrarenal angiotensin II (Ang II) is formed by multiple independent mechanisms. Angiotensinogen (AGT) is the only known substrate for renin that is a rate-limiting enzyme of the RAS. Recently, enhanced intrarenal AGT levels have been shown to reflect the intrarenal RAS status in hypertension, chronic glomerular disease and diabetic nephropathy. In this review, we focus on AGT expression of the diseased glomeruli in the progression of glomerular disease. An anti-glomerular basement membrane nephritis rat model developed progressive proteinuria and glomerular crescent formation, accompanied by increased macrophage infiltration and glomerular expression of AGT and Ang II. The addition of Ang II type 1 receptor blocker to CC-chemokine recaptor 2 antagonist markedly attenuated the induction of macrophage infiltration, AGT and Ang II, and reduced glomerular crescent formation. Next, the levels of glomerular AGT expression and marker of reactive oxygen species in Zucker diabetic fatty (ZDF) obese rats were higher than those in ZDF lean rats. Hydrogen peroxide (H(2)O(2)) induced an increase in the AGT expression in primary rat mesangial cells. Furthermore, the H(2)O(2)-induced upregulation of AGT was inhibited by a mitogen-activated protein kinase kinase and a c-Jun N-terminal kinase inhibitor. These data suggest the potential contribution of enhanced AGT expression in glomeruli to the intrarenal RAS activation for the development of glomerular disease.

Plasminogen activator inhibitor-1 is an aggregate response factor with pleiotropic effects on cell signaling in vascular disease and the tumor microenvironment

In hemostasis, the serine protease inhibitor (serpin) plasminogen activator inhibitor-1 (PAI-1) functions to stabilize clots via inhibition of tissue plasminogen activator (tPA) with subsequent inhibition of fibrinolysis. In tissues, PAI-1 functions to inhibit extracellular matrix degradation via inhibition of urokinase plasminogen activator (uPA). Elevated levels of PAI-1 in the vasculature and in tissues have long been known to be associated with thrombosis and fibrosis, respectively. However, there is emerging evidence that PAI-1 may participate in the pathophysiology of a number of diseases such as atherosclerosis, restenosis, and cancer. In many of these disease states, the canonical view of PAI-1 as an inhibitor of tPA and uPA cannot fully account for a mechanism whereby PAI-1 contributes to the disease. In these cases, one must consider recent data, which indicates PAI-1 can directly promote pro-proliferative and anti-apoptotic signaling in a variety of cell types. Given the wide variety of inflammatory, hormonal, and metabolic signals that increase PAI-1 expression, it is important to consider mechanisms by which PAI-1 can directly participate in disease etiology.

PPARgamma agonist and angiotensin II receptor antagonist ameliorate renal tubulointerstitial fibrosis

The peroxisome proliferator activated receptor (PPAR)gamma agonist is used as antidiabetic agent with antihyperglycemic and antihyperinsulinemic actions. Beyond these actions, antifibrotic effects have been reported. We examined antifibrotic effects of PPARgamma agonist and interaction with angiotensin receptor antagonist in the unilateral ureteral obstruction (UUO) model. After UUO, mice were divided to four groups: no treatment (CONT), pioglitazone treatment, L158809 treatment, and L158809+ pioglitazone treatment. On day 14, CONT mice showed severe fibrosis and all treated mice showed decreased fibrosis. The immunohistochmistry of PAI-1, F4/80 and p-Smad2 demonstrated that their expressions were increased in CONT group and decreased in the all treated groups compared to CONT. PAI-1 and p-Smad2 determined from Western blotting, among treated groups, was decreased compared to CONT group. The expression of TGF-beta1 from real time RT PCR showed markedly increased in the CONT group and decreased in all treated groups compared to CONT. These data suggest the pioglitazone inhibited tubulointerstitial fibrosis, however, the synergism between pioglitazone and L158809 is not clear. Considering decreased expression of PAI-1 and TGF-beta/Smad2 in the treated groups, PAI-1 and TGF-beta are likely linked to the decreased renal tubulointerstitial fibrosis. According to these results, the PPARgamma agonist might be used in the treatment of renal fibrotic disease.

Angiotensin type 2 receptor actions contribute to angiotensin type 1 receptor blocker effects on kidney fibrosis

Angiotensin type 1 (AT1) receptor blocker (ARB) ameliorates progression of chronic kidney disease. Whether this protection is due solely to blockade of AT1, or whether diversion of angiotensin II from the AT1 to the available AT2 receptor, thus potentially enhancing AT2 receptor effects, is not known. We therefore investigated the role of AT2 receptor in ARB-induced treatment effects in chronic kidney disease. Adult rats underwent 5/6 nephrectomy. Glomerulosclerosis was assessed by renal biopsy 8 wk later, and rats were divided into four groups with equivalent glomerulosclerosis: no further treatment, ARB, AT2 receptor antagonist, or combination. By week 12 after nephrectomy, systolic blood pressure was decreased in all treatment groups, but proteinuria was decreased only with ARB. Glomerulosclerosis increased significantly in AT2 receptor antagonist vs. ARB. Kidney cortical collagen content was decreased in ARB, but increased in untreated 5/6 nephrectomy, AT2 receptor antagonist, and combined groups. Glomerular cell proliferation increased in both untreated 5/6 nephrectomy and AT2 receptor antagonist vs. ARB, and phospho-Erk2 was increased by AT2 receptor antagonist. Plasminogen activator inhibitor-1 mRNA and protein were increased at 12 wk by AT2 receptor antagonist in contrast to decrease with ARB. Podocyte injury is a key component of glomerulosclerosis. We therefore assessed effects of AT1 vs. AT2 blockade on podocytes and interaction with plasminogen activator inhibitor-1. Cultured wild-type podocytes, but not plasminogen activator inhibitor-1 knockout, responded to angiotensin II with increased collagen, an effect that was completely blocked by ARB with lesser effect of AT2 receptor antagonist. We conclude that the benefical effects on glomerular injury achieved with ARB are contributed to not only by blockade of the AT1 receptor, but also by increasing angiotensin effects transduced through the AT2 receptor.

Hemodynamic Maladjustment and Disease Progression in Nephrosis with FSGS

Idiopathic nephrotic syndrome (NS) associated with focal segmental glomerulosclerosis (FSGS) and severe renal function impairment is usually refractory to the conventional treatment and progresses to end-stage renal disease. Herein, we reported 10 patients with NS-FSGS who had initially had CCr 34 +/- 12 mL/min/1.73 m2 (normal 120 mL/min/1.73 m2), FE Mg 7.8 +/- 2.6% (normal 2.2%), 24-h urinary protein 3.1 g (normal <200 mg) and been followed up for over 10 years. The initial intrarenal hemodynamic study revealed a marked elevation of efferent arteriolar resistance (RE 17289 +/- 8636 dyne x s x cm(-5); normal 3000 dyne x s x cm(-5)), intraglomerular hypertension (PG 57 +/- 1 mm Hg; normal 52 mm Hg), hyperfiltration (FF 0.24; normal 0.2), marked reductions in GFR 35 +/- 17 mL/min/1.73 m2, renal plasma flow (RPF 159 +/- 61 mL/min/1.73 m2; normal 600 mL/min/1.73 m2) and peritubular capillary flow (PTCF 123 +/- 57 mL/min/1.73 m2; normal 480 mL/min/1.73 m2). Such a hemodynamic alteration indicated a hemodynamic maladjustment with a preferential constriction at RE. Treatment consists of multidrugs, namely angiotensin converting enzyme inhibitor, calcium channel blocker, antiplatelet and anticoagulant, with or without angiotensin II receptor antagonist. Following the treatment, correction of hemodynamic maladjustment has been achieved which is characterized by reductions in RE 6046 +/- 2191 dyne x s x cm(-5), PG 52 +/- mm Hg, FF 0.19 +/- 0.1 and increments in RPF 341 +/- 118 mL/min/1.73 m2, PTCF 280 +/- 106 mL/min/1.73 m2 and GFR 64 +/- 17 mL/min/1.73 m2. Coinciding with hemodynamic improvement, there has been a steadily increased creatinine clearance and improvement in FE Mg 4.3 +/- 2.6% and suppression of proteinuria 0.29 +/- 0.4 g/24 h after the period of follow-up of greater than 10 years.

Angiotensin II receptor blockade inhibits acute glomerular injuries with the alteration of receptor expression

Angiotensin II receptor blockade (ARB) suppresses the progression of chronic kidney disease. However, the renoprotective effect of ARB in the active phase of glomerulonephritis (GN) has not been evaluated in detail. We examined the alteration of angiotensin II receptors' expression and the action of ARB on acute glomerular injuries in GN. Thy-1 GN was induced in rats that were divided into three groups (n=7, in each group); high dose (3 mg/kg/day) or low dose (0.3 mg/kg/day) olmesartan (Thy-1 GN+HD- or LD-ARB group), and vehicle (Thy-1 GN group). Renal function and histopathology were assessed by week 2. In the Thy-1 GN group, diffuse mesangiolysis and focal aneurysmal ballooning developed by day 3. Marked mesangial proliferation and activation progressed with glomerular epithelial injury. We confirmed that both angiotensin II type 1 receptor (AT1R) and type 2 receptor (AT2R) were expressed on glomerular endothelial, mesangial, epithelial cells, and macrophages, and increased 7 days after disease induction. However, ARB treatment caused a decrease in AT1R and a further increase in AT2R expression in glomeruli. ARB prevented capillary destruction and preserved eNOS expression after diffuse mesangiolysis. Mesangial proliferation and activation was suppressed markedly with low levels of PDGF-B expression. Glomerular desmin expression, which is a marker for injured glomerular epithelial cells, was diminished significantly with retained expression of nephrin and podoplanin. Glomerular macrophage infiltration was also inhibited. Proteinuria was suppressed significantly. Furthermore, these effects of ARB showed dose dependency. These results provide insights that ARB affects individual glomerular cells and macrophages through angiotensin II receptors, with the alteration of both AT1R and AT2R expressions, and leads to inhibition of the acute destructive and proliferative glomerular lesions in GN.

Renal thrombotic microangiopathy after hematopoietic cell transplant: role of GVHD in pathogenesis

BACKGROUND AND OBJECTIVES

Thrombotic microangiopathy (TMA) is a known complication of hematopoietic cell transplantation (HCT). The etiology and diagnosis of TMA in this patient population is often difficult because thrombocytopenia, microangiopathic hemolytic anemia, and kidney injury occur frequently in HCT recipients, and are the result of a variety of insults.

DESIGN, SETTING, PARTICIPANTS & MEASUREMENTS

The authors reviewed renal pathology and clinical data from HCT patients to determine the prevalence of TMA and to identify correlative factors for developing TMA in the kidney. Kidney tissue was evaluated from 314 consecutive autopsies on patients who died after their first HCT (received between 1992 and 1999). Renal pathology was classified into three groups: (1) no renal thrombus (65%), (2) TMA (20%), and (3) isolated thrombosis (15%). Logistic regression models estimated the associations between each histologic category and clinical parameters: donor and recipient gender, patient age, human leukocyte antigen (HLA) matching of the donor and recipient, total body irradiation (TBI), acute graft versus host disease (GVHD), acute kidney injury, medications, and viral infections.

RESULTS

In a multivariate analysis, TMA correlated with acute GVHD grades II to IV, followed by female recipient/male donor, TBI > 1200 cGy, and adenovirus infection. Grades II to IV acute GVHD and female gender were associated with isolated renal thrombus.

CONCLUSIONS

TMA in HCT recipients is associated with acute GVHD grades II to IV, recipient/donor mismatch, TBI > 1200 cGy, and adenovirus infection.

Hypoxia/reoxygenation induces CTGF and PAI-1 in cultured human retinal pigment epithelium cells

Early age-related macular degeneration (AMD) is characterized by thickening of Bruch's membrane due to the accumulation of extracellular matrix (ECM). This finding could be related to hypoxia of the retinal pigment epithelium (RPE). In the present study, we investigated the effects of hypoxia and reoxygenation on the expression of connective tissue growth factor (CTGF), plasminogen activator inhibitor-1 (PAI-1), collagen type IV (Col IV) and fibronectin (Fn) in cultured human RPE cells. Cultured human RPE cells were kept for 12-36h under hypoxic conditions (1% O(2)). Reoxygenation was conducted for 24h. Hypoxia-mediated CTGF and PAI-1 expression were analyzed by using immunohistochemistry, Northern and Western blot analysis. Actinomycin D was added to examine whether hypoxia induces the transcription of CTGF and PAI-1 mRNA. Furthermore, cells were transfected with siRNA against hypoxia-inducible factor-1alpha (HIF-1alpha) and kept under hypoxic conditions. The effects of antioxidants on hypoxia/reoxygenation-mediated CTGF and PAI-1 expression were tested by real-time PCR analysis. Production of Col IV and Fn were investigated by real-time PCR and Western blot analysis. Both hypoxia and hypoxia/reoxygenation increased the expression of CTGF, PAI-1, Col IV and Fn. Actinomycin D prevented the new transcription of CTGF and PAI-1 mRNA by hypoxia. Using siRNA against HIF-1alpha, the hypoxia-mediated increase of CTGF and PAI-1 was inhibited. Antioxidants attenuated the reoxygenation-mediated increase of CTGF and PAI-1. The process of hypoxia/reoxygenation in the RPE may lead to an increase of ECM in the RPE and thus may contribute to the accumulation of ECM in Bruch's membrane.

The functional role of the renin-angiotensin system in pregnancy and preeclampsia

During normal pregnancy, the renin-angiotensin system (RAS) plays a vitally important role in salt balance and subsequent well-being of mother and fetus. In this balance, one must consider not only the classical renal RAS but also that of the uteroplacental unit, where both maternal and fetal tissues contribute to the signaling cascade. Many studies have shown that in normal pregnancy there is an increase in almost all of the components of the RAS. In derangements of pregnancy this delicate equilibrium can become unbalanced. Preeclampsia is one such case. It is a disorder of pregnancy characterized by hypertension, proteinuria and placental abnormalities associated with shallow trophoblast invasion and impaired spiral artery remodeling. Despite being a leading cause of maternal death and a major contributor to maternal and perinatal morbidity, the mechanisms responsible for the pathogenesis of preeclampsia are poorly understood. Immunological mechanisms and the RAS have been long considered to be involved in the development of preeclampsia. Numerous recent studies demonstrate the presence of the angiotensin II type I receptor agonistic autoantibody (AT1-AA). This autoantibody can induce many key features of the disorder and upregulate molecules involved in the pathogenesis of preeclampsia. Here we review the functional role of the RAS during pregnancy and the impact of AT1-AA on preeclampsia.

Genetic polymorphisms of the RAS-cytokine pathway and chronic kidney disease

Chronic kidney disease (CKD) in children is irreversible. It is associated with renal failure progression and atherosclerotic cardiovascular (CV) abnormalities. Nearly 60% of children with CKD are affected since birth with congenital or inherited kidney disorders. Preliminary evidence primarily from adult CKD studies indicates common genetic risk factors for CKD and atherosclerotic CV disease. Although multiple physiologic pathways share common genes for CKD and CV disease, substantial evidence supports our attention to the renin angiotensin system (RAS) and the interlinked inflammatory cascade because they modulate the progressions of renal and CV disease. Gene polymorphisms in the RAS-cytokine pathway, through altered gene expression of inflammatory cytokines, are potential factors that modulate the rate of CKD progression and CV abnormalities in patients with CKD. For studying such hypotheses, the cooperative efforts among scientific groups and the availability of robust and affordable technologies to genotype thousands of single nucleotide polymorphisms (SNPs) across the genome make genome-wide association studies an attractive paradigm for studying polygenic diseases such as CKD. Although attractive, such studies should be interpreted carefully, with a fundamental understanding of their potential weaknesses. Nevertheless, whole-genome association studies for diabetic nephropathy and future studies pertaining to other types of CKD will offer further insight for the development of targeted interventions to treat CKD and associated atherosclerotic CV abnormalities in the pediatric CKD population.

Modulation of glomerulosclerosis

Regardless of the initial injury, the long-term consequence for the patient depends upon the ensuing balance of profibrotic vs reparative modulators activated. The glomerulus has some capacity for repair. Even when sclerosis has developed with accumulation of extracellular matrix, this lesion may be remodeled, with a change in balance between profibrotic and antifibrotic and collagen synthesis vs proteolytic mediators. We will focus here on the interplay between mediators of fibrosis and reparative mechanisms and potential regression of fibrosis. Based on the clinical efficacy of interventions that inhibit angiotensin, we will focus on factors related to the renin-angiotensin system.

Simvastatin inhibits tissue factor and plasminogen activator inhibitor-1 expression of glomerular mesangial cells in hypercholesterolemic rabbits

Tissue factor (TF) and plasminogen activator inhibitor-1 (PAI-1) activity and/or expression are upregulated in hypercholesterolemia. Despite extensive research on anti-thrombotic effect of statins, little is known about their effects on TF and PAI-1 expression in glomerular mesangial cells under hypercholesterolemic condition. Male rabbits were fed on either normal or high-cholesterol diet for 8 weeks. Then cholesterol-fed rabbits were randomly assigned to simvastatin or starch. At the end of 12 weeks, glomerular mesangial cells were collected. The concentrations of TF and PAI-1 mRNA were detected by RT-PCR. The plasma activities of TF and PAI-1 were determined with enzyme linked immunosorbent assay (ELISA) and chromogenic substrate method, respectively. The atherogenic diet caused a consistent increase in serum concentrations of total cholesterol (TC) and serum triglyceride (TG) (p < 0.05), increased TF and PAI-1 mRNA expression in glomerular mesangial cells and plasma activities as compared to the normal diet (p < 0.01). Four-week simvastatin treatment resulted in significant decrease of mesangial TF and PAI-1 mRNA (p < 0.01), and also of the plasma activities of TF (p < 0.05) and PAI-1 (p < 0.01). These results suggest that simvastatin might protect kidney from the formation of microthrombus under hypercholesterolemic condition and might be a possible pathogenesis of obesity-related glomerulopathy.

Angiotensin II-dependent Src and Smad1 signaling pathway is crucial for the development of diabetic nephropathy

Angiotensin II (Ang II) is known to play a pivotal role in the development of diabetic nephropathy. However, the precise mechanism of Ang II-mediated effects on diabetic nephropathy is still unknown. We have reported that Smad1 plays a key role in diabetic mesangial matrix expansion and directly regulates the transcription of type IV collagen (Col4) in vitro and in vivo. Here we examined the effect of Ang II on the expression of Smad1 and mesangial matrix expansion in streptozotocin (STZ)-induced diabetic rats in vivo, using Ang II type 1 receptor blocker, olmesartan. We also examined the signaling mechanism by which Ang II induces mesangial matrix expansion in vitro. Treatment of diabetic rats with low-dose olmesartan for 20 weeks reduced albuminuria and hyperfiltration without affecting blood pressure and inhibited mesangial matrix expansive changes and the expression of Col4 and smooth muscle alpha actin compared with those in untreated rats. Immunohistochemical staining and Western blotting showed that the increased expression of Smad1, phospho-Smad1, and phospho-Src was inhibited by olmesartan. Ang II induced Col4 synthesis and increased expression of phospho-Src and phospho-Smad1 in cultured mesangial cells, which was blocked by olmesartan. PP2, a Src tyrosine kinase inhibitor, and overexpression of dominant negative Src also reduced the phosphorylation of Smad1. Moreover, addition of small-interfering RNA against Src significantly reduced the phosphorylation of Smad1 and synthesis of Col4. Taken together, these results indicate that Ang II can regulate the development of mesangial matrix expansion in the early phase of diabetic nephropathy through Src and Smad1.

Improving outcomes in renal disease

CKD is a silent medical problem that requires laboratory analysis to make an early diagnosis. Early aggressive management of diabetes mellitus, hypertension, and dyslipidemia are vital. Awareness and management of the frequent complications also improve ESRD outcomes. Ongoing consultation with the nephrology team, including a renal dietitian, is important for delaying disease progression and improving patient quality of life.

The clot thickens

Vascular sclerosis has been linked to many risk factors, including smoking, family history, low birth weight, and hypertension. In interesting studies, Goforth et al. show an increased rate of mutations in thrombophilic molecules in patients with vascular sclerosis in renal biopsies, suggesting yet another mechanism.

Evidence for renoprotection by blockade of the renin-angiotensin-aldosterone system in hypertension and diabetes

The incidence of end-stage renal disease (ESRD) is rising worldwide, accompanied by corresponding increases in the risk of morbidity and mortality. Underlying this trend are increasing rates of hypertension and diabetes mellitus, the two most common causes of ESRD. In addition to the adverse haemodynamic effects of hypertension on the kidney, elevated blood pressure (BP) can activate components of the renin-angiotensin-aldosterone system (RAAS), which, in turn, activate mediators of inflammation, oxidative stress, cell growth, and matrix accumulation. Lowering BP reduces the risk of cardiovascular events and renal damage. Accumulating evidence from clinical and laboratory studies suggests that interrupting the RAAS with therapies such as angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, and aldosterone receptor blockers can interfere with the mechanisms that promote diabetic and non-diabetic renal damage. Moreover, clinical trials of RAAS blockade have demonstrated reductions in microalbuminuria, a predictor of increased cardiorenal risk and overt nephropathy in patients with and without diabetes and/or hypertension. In this way, agents that block the RAAS should be considered the drugs of first choice as they provide enhanced renoprotection compared with other classes of antihypertensive agents such as calcium channel blockers and beta-blockers.

Chronic blockade of the angiotensin II receptor has a differential effect on adipose and vascular PAI-1 in OLETF rats

Angiotensinogen (AGT) and plasminogen activator inhibitor-1 (PAI-1) are expressed in both vascular and adipose tissues. Angiotensin II (AG II) has an adipogenic effect and increases PAI-1 expression. To evaluate the chronic effects of AG II type 1 receptor (AT(1)R) antagonism on adipose mass and PAI-1 expression in vascular and adipose tissues, losartan (30mg/kg/day) was administered to Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a model of type 2 diabetes, for 20 weeks. Adipose mass and regional fat distribution in the abdomen did not change after chronic AT(1)R antagonism in OLETF rats. AGT and PAI-1 mRNA expressions in adipose tissue of OLETF rats were significantly increased compared with Long-Evans Tokushima Otsuka (LETO) rats, the normal control. Chronic losartan therapy further increased the level of adipose AGT in OLETF rats, but did not affect the level of adipose PAI-1 mRNA. In contrast, aortic PAI-1 expression in OLETF rats was attenuated by chronic losartan therapy. Our results have two implications. First, adipose tissue may be an important source of AG II in metabolic syndrome even after chronic losartan therapy. Second, chronic AT(1)R antagonism with losartan causes differential effects on vascular and adipose PAI-1 expression.

Chronic kidney disease in long-term survivors of hematopoietic cell transplantation: epidemiology, pathogenesis, and treatment

High-dose myeloablative hematopoietic cell transplantation is becoming an increasingly common treatment modality for a variety of diseases. Patient survival may be limited by substantial treatment-related toxicities, including chronic kidney disease (CKD). Although the majority of CKD after transplantation is idiopathic, thrombotic microangiopathic syndromes and nephrotic syndrome have been described. Epidemiology, pathogenesis, and potential treatment options for the various clinical syndromes that are associated with CKD in hematopoietic cell transplantation patients is reviewed. As the indications for and the numbers of transplants that are performed worldwide increases, so will the burden of CKD. The nephrologists and oncologists will have to work together to identify patients who are at risk for CKD early to prevent its development and progression to end-stage kidney disease.

Origin of interstitial fibroblasts in an accelerated model of angiotensin II-induced renal fibrosis

To determine whether previous renal injury accelerates the progression of glomerulosclerosis and interstitial fibrosis, we examined the effect of treating rats with angiotensin II after Habu venom injury. After initiating disease, we examined the origin of interstitial myofibroblasts by locating alpha-smooth muscle actin (alpha-SMA)-positive and Na+,K+-ATPase-positive cells relative to interstitial space, tubular epithelial cells, the tubular basement membrane (TBM), and vascular structures. Tubular epithelial-mesenchymal transition was also assessed by examining TBM integrity and by using Texas Red (TR)-dextran in intravital tracking experiments. The staining of alpha-SMA-positive myofibroblasts dramatically increased in peritubular interstitial spaces 48 hours after Habu venom plus angiotensin II, particularly in and around perivascular and periglomerular regions, while tubular epithelial cells were alpha-SMA-negative. Na+,K+-ATPase-positive and TR-dextran-labeled cells were restricted to the tubular epithelium and excluded from the interstitium. By 7 and 14 days, expanded interstitial space contained only alpha-SMA-positive myofibroblasts without TR-dextran endocytic particles. Epithelium of atrophic tubules containing TR-dextran remained confined by surrounding interstitium and myofibroblasts. These studies indicate that early expansion of alpha-SMA-positive cells in the interstitium and loss of tubular area occur via encroachment of interstitial myofibroblasts from perivascular into atrophic tubular spaces rather than via epithelial-mesenchymal transition and migration of tubular cells through the TBM into the interstitium.

Angiotensinogen and Plasminogen Activator Inhibitor-1 Gene Polymorphism in Relation to Renovascular Disease

The present study was designed to evaluate angiotensinogen (AGT) M235T and plasminogen activator inhibitor-1 (PAI-1) (4G/5G) polymorphisims in relation to the occurrence of atherosclerotic renal artery stenosis (ARAS) and recurrent stenosis. In this study, 30 patients were enrolled after angiographic demonstration of ARAS; 100 healthy subjects for AGT polymorphism and 80 healthy subjects for PAI-1 polymorphism were considered the control group. The patients were followed for a mean 46.1 +/- 9.2 months. The patients had significantly higher frequencies of the MT genotype and the T allele than control group (chi(2) = 18.2, p < 0.001 and chi(2) = 11.5 p < 0.001). There were no significant differences in the PAI-1 genotype and allele findings when the data for all patients were compared with that for the controls (chi(2)= 2.45, p = 0.29 and chi(2) = 0.019, p = 0.89). There were no significant differences in the genotype and allele findings for the patients with and without restenosis (p > 0.05). The C-reactive protein (CRP) level was higher in the patients with restenosis than in the patients without restenosis (7.694 +/- 0.39 mg/L and 1.56 +/- 1.08 mg/L) (p = 0.001). Our results suggest that the M235T MT genotype and T allele might be associated with increased risk of atherosclerotic renal artery stenosis. The CRP level might be an independent predictor for recurrent stenosis.

Chronic allograft nephropathy: expression and localization of PAI-1 and PPAR-gamma

BACKGROUND

Chronic allograft nephropathy (CAN) is a major cause of loss of renal allografts. Mechanisms postulated to be involved include sequelae of rejection, warm ischaemia time, drug toxicity, ongoing hypertension and dyslipidaemia. Plasminogen activator inhibitor-1 (PAI-1) is implicated not only in thrombosis, but also in fibrosis, by inhibiting matrix degradation, and is expressed in renal parenchymal cells as well as in macrophages. Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is a member of the steroid receptor superfamily, and plays a major beneficial role in lipid regulation, insulin sensitivity and macrophage function, factors that may play a role in CAN. We therefore studied the expression of these molecules in CAN.

METHODS

All renal biopsy/nephrectomy files from Vanderbilt and Nashville VAMC from a 6 year period were reviewed to identify all renal transplant biopsies or nephrectomies more than 6 months after transplant with CAN. CAN was defined as fibrosis in the graft, vascular, interstitial or glomerular. All cases were scored for severity of fibrosis in vasculature (0-3 scale), glomeruli (% affected with either segmental and/or global sclerosis) and interstitial fibrosis (% of sample affected). PAI-1 and PPAR-gamma immunostaining was assessed on a 0-3 scale in glomeruli, vessels and tubules.

RESULTS

Eighty-two patients with a total of 106 samples met entry criteria. The population consisted of 59 Caucasians and 23 African-Americans; 49 males, 33 females with average age 37.9+/-1.7 years. Average time after transplant at time of biopsy was 60.5+/-4.9 months (range 7-229). Glomerulosclerosis extent in CAN was on average 26.5+/-2.4% compared with 3.6+/-1.2% in normal control kidneys from native kidney cancer nephrectomies and 0% in transplanted kidney biopsies from patients obtained > or =6 months after transplantation without CAN. Native control kidneys showed mild interstitial fibrosis (8.0+/-1.2%), whereas transplant controls showed very minimal fibrosis (2.0+/-2.0%). Interstitial fibrosis in CAN kidneys was on average 47.9+/-2.4%. Glomerular PAI-1 and PPAR-gamma staining scores were markedly increased in CAN (1.8+/-0.1, 2.3+/-0.1, respectively) compared with normal control kidneys from native kidney cancer nephrectomies (PAI-1 0.2+/-0.2 and PPAR-gamma 0.4+/-0.2, P<0.001) and transplanted kidney biopsies from patients obtained > or =6 months after transplantation without CAN (PAI-1 0 and PPAR-gamma 0, P<0.001). Tubular PAI-1 and PPAR-gamma staining scores were 1.9+/-0.1 and 1.9+/-0.1, respectively, and also increased over both native and transplant kidney controls (0.8+/-0.2 for both categories for PAI-1, 1.2+/-0.2 for both categories for PPAR-gamma, respectively). Vascular sclerosis in CAN was 1.0+/-0.1 with increased PAI-1 and PPAR-gamma scores (1.7+/-0.1, 1.2+/-0.1, respectively) compared with controls. Infiltrating macrophages were increased in CAN, and were positive for both PAI-1 and PPAR-gamma. Biopsies with less sclerosis overall showed a trend for less PAI-1 and PPAR-gamma staining.

CONCLUSION

PAI-1 and PPAR-gamma are both increased in CAN compared with non-scarred native or transplant control kidneys. We speculate that altered matrix metabolism and macrophage function might be involved in the development of CAN.

Tubular expression of angiotensin II receptors and their regulation in IgA nephropathy

Enhanced renal expression for the renin-angiotensin system (RAS) is detected in IgA nephropathy (IgAN). Previous data showed an altered glomerular expression of angiotensin II type 1 receptor (AT1R), suggesting a regulatory response to high intrarenal angiotensin II (Ang II) concentration in IgAN. In this study, the expression and regulation of Ang II receptors were examined in human proximal tubular epithelial cells (PTEC) in IgAN. Tubular expression of AT1R and Ang II type 2 receptor (AT2R) was increased in IgAN. In vitro culture experiment showed that the upregulation of Ang II receptors was not due to the direct effect of IgA but the indirect effect after IgA deposition on human mesangial cell. When PTEC were cultured with conditioned culture medium from human mesangial cells activated with IgA, Ang II production was upregulated, leading to inflammation and apoptosis via the AT1R and AT2R, respectively. Sequential expression of Ang II receptors determined the injury of PTEC induced by mediators in the conditioned medium. The initial interaction between Ang II and AT1R activated both protein kinase C and mitogen-activated protein kinase pathways, leading to inflammatory responses. This early AT1R-dependent event was followed by upregulation of AT2R expression and continued Ang II release. The interaction between Ang II and AT2R subsequently led to expression of cleaved poly[ADP-ribose] polymerase through downregulation of the mitogen-activated protein kinase pathway. The data suggest that appropriate control of Ang II receptor activities in PTEC may ameliorate tubulointerstitial injury in IgAN.

Regression of glomerulosclerosis with high-dose angiotensin inhibition is linked to decreased plasminogen activator inhibitor-1

The potential and possible mechanisms for regression of existing glomerulosclerosis by angiotensin II type 1 receptor antagonist (AT1RA) and/or angiotensin I converting enzyme inhibitor (ACEI) were investigated. Adult male Sprague Dawley rats underwent 5/6 nephrectomy (Nx). Glomerulosclerosis was assessed by renal biopsy 8 wk later, and rats were divided into groups with equal biopsy sclerosis and treated for the next 4 wk until they were killed at 12 wk as follows: Control with no further treatment (CONT), high-dose AT1RA, high-dose ACEI, and varying AT1RA+ACEI combinations. Hypertension and proteinuria induced by 5/6 Nx were significantly decreased by all treatments, except high-dose ACEI, which showed persistent proteinuria. High-dose AT1RA and ACEI markedly decreased progression of sclerosis, with -2.3% average decrease in sclerosis from biopsy to autopsy in AT1RA versus 194% increase in CONT (P < 0.0001). Glomerulosclerosis regressed, with less severe lesions at the time when the rats were killed than at biopsy in 62% of AT1RA-treated and 57% of ACEI-treated rats. In contrast, only 17 to 33% of rats in combination groups had regression. Alternatively, these data might be viewed as reflecting halting of progression, as some groups had higher BP and proteinuria. However, this potential confounding effect does not negate the effects to achieve regression of sclerosis in these rats. Regression was not explained by changes in mRNA of TGF-beta1 and matrix metalloproteinase-2 and -9 but was linked to decreased tissue inhibitor of metalloproteinase-1 and plasminogen activator inhibitor-1. It is concluded that angiotensin inhibition mediates regression in part by effects on matrix modulation.

Angiotensinogen and plasminogen activator inhibitor-1 gene polymorphism in relation to chronic allograft dysfunction*

Chronic allograft dysfunction (CAD) is the most common cause of allograft failure in the long-term, and current immunologic strategies have little effect on this condition. The renin-angiotensin system (RAS) plays important roles progression of chronic renal disease. It is thought that plasminogen activator inhibitor-1 (PAI-1) functions in the RAS, in addition to involvement in thrombotic risk and fibrosis. This study investigated possible links between angiotensinogen (AGT) genotypes (M235T/MM, MT, TT) and PAI-1 genotypes (4G4G, 4G5G, 5G5G) and CAD assessments of both types of polymorphism were performed in 82 renal allograft recipients. One hundred healthy subjects were also investigated for AGT polymorphism, and 80 healthy subjects for PAI-1 polymorphism. Genotypes were determined using polymerase chain reaction (PCR) sequence-specific primers, and PCR followed by restriction fragment length polymorphism analysis. Kidney recipients with CAD had significantly lower frequencies of the MM genotype and the M allele than the recipients without CAD (p < 0.05 and <0.001). The transplant recipients with CAD also had significantly lower frequencies of the 5G5G genotype and the 5G allele than those without CAD (p < 0.001 and <0.05). Determination of AGT M235T and PAI-1 genotypes prior to transplantation may help identify patients who at risk for chronic renal transplant dysfunction.

Ineffectiveness of allopurinol in reduction of oxidative stress in diabetic patients; a randomized, double-blind placebo-controlled clinical trial

The objective of this randomized, double-blind placebo-controlled clinical trial was to evaluate the value of allopurinol treatment on reduction of oxidative stress in patients with diabetes type II patients. Forty-one diabetic type II subjects were randomly assigned to two groups. One group (n = 20) received 100 mg allopurinol three times a day for 14 days and the other group (n = 21) received a placebo. Blood and saliva samples were collected before and after intervention for analysis of lipid peroxidation level and total antioxidant power as indices of oxidative stress. At the beginning of the study, the groups were similar based upon age, duration of diabetes, fasting glucose, and HbA1c. Both allopurinol and placebo were effective in reduction of lipid peroxidation and total antioxidant power whether in saliva or plasma in a similar extent. HbA1c and FBS levels did not change through the study neither in case or placebo group. It is concluded that allopurinol therapy is not more effective than placebo in reduction of oxidative stress in diabetic patients. The same trend of changes in blood and saliva shown for oxidative stress indices was interesting and suggests a chance for saliva to be valuable in diagnosis of oxidative stress. However, to elaborate the exact role of allopurinol in diabetes, further large randomized clinical trials are needed.

Hypertensive renal damage: insights from animal models and clinical relevance

Investigations using chronic blood pressure (BP) radiotelemetry in conscious animals have provided substantial insights into the pathophysiology of hypertensive renal damage. Normal renal autoregulation protects the renal microvasculature from significant injury in most patients with primary hypertension, unless BP exceeds a certain threshold, when malignant nephrosclerosis develops. However, if autoregulation is impaired, as in chronic renal disease and/or diabetes models, the threshold for renal damage is lowered and glomerulosclerosis (GS) increases linearly with increasing BP. Modest BP reductions are predicted to prevent malignant nephrosclerosis, but prevention of GS in patients with diabetes and chronic renal disease requires that BP be lowered well into the normotensive range, as recognized in the currently recommended BP goals. When BP load is accurately assessed in these experimental models, renal protection is proportional to the achieved BP reductions, and there is little evidence of BP-independent protection, even with agents that block the renin-angiotensin system (RAS). Recent clinical data also suggest that achieving lower BP targets might be vastly more important than the choice of therapeutic regimens. Nevertheless, because aggressive diuretic use is usually necessary to achieve such BP goals, RAS blockade should be included as initial therapy both for antihypertensive synergy and to minimize the potassium and magnesium depletion associated with diuretics.

Combined therapy of enalapril and losartan attenuates histologic progression in immunoglobulin A nephropathy

BACKGROUND

It has been reported that combined therapy of angiotensin converting enzyme inhibitor and angiotensin receptor blocker significantly decreases proteinuria in immunoglobulin A (IgA) nephropathy. However, histologic alterations following the therapy have not been reported.

METHODS

A total of nine Japanese children with severe proteinuric IgA nephropathy who received a prompt immunosuppressive therapy were enrolled the study, four of whom received a combined therapy of angiotensin converting enzyme inhibitor, enalapril and angiotensin receptor blocker, losartan (Group A), while the remaining five did not (Group B). All underwent renal biopsy before and approximately 12 months after the first renal biopsy.

RESULTS

At presentation, urine protein excretion and the histologic indices of mean activity index, mean chronicity index and tubulointerstitial scores did not show a statistical difference between the two groups: Group A (2.6 +/- 0.6 g/day; mean activity index, 5.0 +/- 1.0; mean chronicity index, 5.0 +/- 1.0; tubulointerstitial scores, 4.3 +/- 1.0) and Group B (2.2 +/- 0.6 g/day; mean activity index, 4.8 +/- 0.8; mean chronicity index, 4.8 +/- 1.3; tubulointerstitial scores, 3.6 +/- 0.5, respectively). All had normal blood pressure and renal function. Urine protein excretion and the activity index decreased at the second renal biopsy, while the chronicity index and the tubulointerstitial scores slightly increased or remained unchanged. In comparison with Group B, a significant suppression in increasing the chronicity index and the tubulointerstitial scores obtained at the second renal biopsy were observed in Group A [Group A: 4.3 +/- 1.2 and 3.0 +/- 0.0, respectively, vs Group B: 6.0 +/- 0.7 and 4.4 +/- 0.9, respectively (P < 0.05)]. One patient in Group B developed chronic renal insufficiency thereafter.

CONCLUSIONS

Although only a small number of patients were examined, these clinical findings suggest that a combined therapy of enalapril and losartan may attenuate histologic progression in at least a proportion of patients with severe proteinuric IgA nephropathy.

Pathophysiology of hypertensive renal damage: implications for therapy

Unlike the majority of patients with uncomplicated hypertension in whom minimal renal damage develops in the absence of severe blood pressure (BP) elevations, patients with diabetic and nondiabetic chronic kidney disease (CKD) exhibit an increased vulnerability to even moderate BP elevations. Investigations in experimental animal models have revealed that this enhanced susceptibility is a consequence of an impairment of the renal autoregulatory mechanisms that normally attenuate the transmission of elevated systemic pressures to the glomeruli in uncomplicated hypertension. The markedly lower BP threshold for renal damage and the steeper slope of relationship between BP and renal damage in such states necessitates that BP be lowered into the normotensive range to prevent progressive renal damage. When BP is accurately measured using radiotelemetry in animal models, the renal protection provided by renin-angiotensin system (RAS) blockade is proportional to the BP reduction with little evidence of BP-independent protection. A critical evaluation of the clinical data also suggests that the BP-independent renoprotection by RAS blockade has been overemphasized and that achieving lower BP targets is more important than the selection of antihypertensive regimens. However, achievement of such BP goals is difficult in CKD patients without aggressive diuresis, because of their proclivity for salt retention. The effectiveness of RAS blockers in lowering BP in patients who have been adequately treated with diuretics, along with their potassium-sparing and magnesium-sparing effects, provides a more compelling rationale for the use of RAS blockade in the treatment of CKD patients than any putative BP-independent renoprotective superiority.

Prevention of obesity and insulin resistance in mice lacking plasminogen activator inhibitor 1

Increased plasminogen activator inhibitor 1 (PAI-1) has been linked to not only thrombosis and fibrosis but also to obesity and insulin resistance. Increased PAI-1 levels have been presumed to be consequent to obesity. We investigated the interrelationships of PAI-1, obesity, and insulin resistance in a high-fat/high-carbohydrate (HF) diet-induced obesity model in wild-type (WT) and PAI-1-deficient mice (PAI-1(-/-)). Obesity and insulin resistance developing in WT mice on an HF diet were completely prevented in mice lacking PAI-1. PAI-1(-/-) mice on an HF diet had increased resting metabolic rates and total energy expenditure compared with WT mice, along with a marked increase in uncoupling protein 3 mRNA expression in skeletal muscle, likely mechanisms contributing to the prevention of obesity. In addition, insulin sensitivity was enhanced significantly in PAI-1(-/-) mice on an HF diet, as shown by euglycemic-hyperinsulinemic clamp studies. Peroxisome proliferator-activated receptor (PPAR)-gamma and adiponectin mRNA, key control molecules in lipid metabolism and insulin sensitivity, were maintained in response to an HF diet in white adipose tissue in PAI-1(-/-) mice, contrasting with downregulation in WT mice. This maintenance of PPAR-gamma and adiponectin may also contribute to the observed maintenance of body weight and insulin sensitivity in PAI-1(-/-) mice. Treatment in WT mice on an HF diet with the angiotensin type 1 receptor antagonist to downregulate PAI-1 indeed inhibited PAI-1 increases and ameliorated diet-induced obesity, hyperglycemia, and hyperinsulinemia. PAI-1 deficiency also enhanced basal and insulin-stimulated glucose uptake in adipose cells in vitro. Our data suggest that PAI-1 may not merely increase in response to obesity and insulin resistance, but may have a direct causal role in obesity and insulin resistance. Inhibition of PAI-1 might provide a novel anti-obesity and anti-insulin resistance treatment.

Activation of a local tissue angiotensin system in podocytes by mechanical strain11See Editorial by Kriz, p. 333

BACKGROUND

Glomerular capillary hypertension, a common denominator in various forms of progressive glomerular disease, results in mechanical distention of the capillary tuft, and subsequent injury of the overlying podocyte layer. The mechanisms by which elevated intraglomerular pressure is translated into a maladaptive podocyte response remain poorly understood. Angiotensin II plays a central role in the pathogenesis of chronic renal injury, largely through its actions on the subtype 1 receptor. Accordingly, we have tested the hypothesis that mechanical strain up-regulates local angiotensin II in podocytes, thereby resulting in a progressive reduction in podocyte number.

METHODS

Conditionally immortalized mouse podocytes were subjected to cyclical stretch of 10% amplitude. Nonstretched podocytes served as controls. Angiotensin II levels were measured in whole cell lysate by competitive enzyme-linked immunosorbent assay (ELISA). Expression of angiotensin II receptors (AT1R, AT2R) was measured by quantitative polymerase chain reaction (PCR) and Western blot analysis. Apoptosis was measured by Hoechst staining. Immunostaining for AT1R was performed in tissue sections from rats with 5/6 remnant kidney disease, a model of glomerular hypertension.

RESULTS

Mechanical strain increased angiotensin II production in podocytes at 24, 48, and 72 hours (P < 0.05 vs. nonstretched controls). Stretching podocytes resulted in a fivefold increase in AT1R mRNA expression at 24 hours and a twofold increase in protein levels vs. controls (P < 0.05), and also an increase in transforming growth hormone-beta (TGF-beta) mRNA expression. AT1R staining was increased in a podocyte distribution in the 5/6 remnant kidney, consistent with our in vitro findings. Mechanical strain resulted in a 2.5-fold increase in apoptosis (P < 0.001 vs. nonstretched controls) in an angiotensin II-dependent fashion.

CONCLUSION

Mechanical strain leads to up-regulation of the AT1R and increased angiotensin II production in conditionally immortalized podocytes. The resulting activation of a local tissue angiotensin system leads to an increase in podocyte apoptosis, mainly in an AT1R-mediated fashion.

Divergent effects of low versus high dose anti-TGF-β antibody in puromycin aminonucleoside nephropathy in rats

BACKGROUND

Transforming growth factor-beta (TGF-beta) modulates immune/inflammatory cells, promotes extracellular matrix (ECM) accumulation, and is increased in fibrotic organs. Here we report the effects of administering a puromycin aminonucleoside nephropathy (PAN)-specific TGF-beta neutralizing antibody on glomerulosclerosis in vivo.

METHODS

Adult male Sprague-Dawley rats underwent uninephrectomy (Nx) followed by intraperitoneal PAN at weeks 2, 6, 7 and 8. Rats were treated with either high (5 mg/kg body weight) (N= 9) or low (0.5 mg/kg body weight) (N= 7) dose TGF-beta antibody intraperitoneally three times weekly until sacrifice at week 10. A PAN untreated control group (N= 7) was dosed with an isotype specific, null antibody. The nephrectomy samples were studied as normal kidney control (NL) (N= 5). Rats undergoing left kidney Nx (N= 5) only were also included as age-matched control. Renal function and morphology were assessed, and molecular studies performed.

RESULTS

Systolic blood pressure was increased in parallel over time in all groups (at 10 weeks, control 137 +/- 10 mm Hg; high 129 +/- 4 mm Hg; low 137 +/- 3 mm Hg) (P= NS). Both TGF-beta antibody treatments decreased renal cortex mRNA expressions similarly for TGF-beta1, TGF-beta2, and collagen III (TGF-beta1, control 0.36 +/- 0.02 mm Hg; high 0.19 +/- 0.01 mm Hg; low 0.19 +/- 0.02 mm Hg; P < 0.01 low and high vs. control; TGF-beta2, control 0.38 +/- 0.03 mm Hg; high 0.19 +/- 0.02 mm Hg; low 0.20 +/- 0.03 mm Hg; P < 0.01 low and high vs. control; and collagen III, control 0.33 +/- 0.01 mm Hg; high 0.14 +/- 0.01 mm Hg; low 0.19 +/- 0.01 mm Hg; P < 0.01 low and high vs. control; P < 0.05 low vs. high, data expressed as mRNA normalized density units vs. 18S RNA). However, only low dose TGF-beta antibody improved renal function and sclerosis measured by serum creatinine and creatinine clearance (serum creatinine, control 2.3 +/- 0.5 mg/dL; high 2.5 +/- 0.5 mg/dL; low 0.8 +/- 0.1 mg/dL; P < 0.05 low vs. control and high; creatinine clearance, control 0.44 +/- 0.11 mL/min; high 0.70 +/- 0.26 mL/min; low 1.34 +/- 0.30 mL/min; P < 0.05 low vs. control, P= NS vs. high). In parallel, sclerosis index (0 to 4+ scale) was improved in low dose (control 2.67 +/- 0.27; high 2.37 +/- 0.30; low 1.78 +/- 0.24; P < 0.05 low vs. control). This improved function and structure was linked to decreased glomerular infiltrating macrophages (0 to 4+ score, control 2.3 +/- 0.2; high 1.8 +/- 0.4; low 0.8 +/- 0.1; P < 0.01 low vs. control; P < 0.05 low vs. high; P= NS high vs. control). Further, plasminogen activator inhibitor-1 (PAI-1) mRNA expression in renal cortex was attenuated after low dose TGF-beta antibody treatment compared to control and high dose group (PAI-1/glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA ratio, NL 0.18 +/- 0.003; control 0.45 +/- 0.03; high 0.40 +/- 0.04; low 0.23 +/- 0.01; P < 0.05 low vs. control and high). Matrix metalloproteinase-9 (MMP-9) activity was maintained at higher levels in kidneys of the low dose TGF-beta antibody-treated group.

CONCLUSION

These results show an in vivo dose-response with an agent that blocks the biologic activity of TGF-beta. Higher dose of TGF-beta antibody was without beneficial effect, suggesting that TGF-beta-mediated effects on PAI-1 and macrophage influx are bimodal and closely regulated. Given that both antibody doses reduced the expression of TGF-beta isoforms and collagen III production, but only low dose ameliorated histologic sclerosis, it appears that pharmacologic effects of anti-TGF-beta antibody on matrix synthesis and degradation are not equivalent.