Spironolactone prevents early renal injury in streptozotocin-induced diabetic rats

Eplerenone potentiates the antiproteinuric effects of enalapril in experimental nephrotic syndrome

Nephrotic syndrome (NS) is a clinical state characterized by massive proteinuria and edema. It is believed that nephrin and podocin are involved in the development of proteinuria. The proteinuria and effects of eplerenone alone or combined with enalapril on nephrin/podocin abundance in rats with NS have not yet been studied. Therefore, the present study was designed to examine the early (beginning 2 days before NS induction) and late (beginning 2 wk after NS induction) effects of eplerenone and enalapril, alone or combined, on proteinuria and nephrin/podocin abundance in rats with adriamycin-induced NS. Adriamycin caused a significant increase in daily protein excretion (UprV; from 26.96 ± 3.43 to 958.57 ± 56.7 mg/day, P < 0.001) and cumulative proteinuria [from 900.33 ± 135.5 to 22,490.62 ± 931.26 mg ( P < 0.001)] during 6 wk. Early treatment with enalapril significantly decreased UprV from 958.6 ± 56.7 to 600.31 ± 65.13 mg/day ( P < 0.001) and cumulative proteinuria to 12,842.37 ± 1,798.17 mg/6 wk ( P < 0.001). Similarly, early treatment with eplerenone produced a profound antiproteinuric effect: UprV decreased from 958.57 ± 56.7 to 593.38 ± 21.83 mg/day, P < 0.001, and cumulative proteinuria to 16,601.84 ± 1,334.31 mg/6 wk; P < 0.001. An additive effect was obtained when enalapril and eplerenone were combined: UprV decreased from 958.57 ± 56.69 to 424.17 ± 38.54 mg/day, P < 0.001, and cumulative protein excretion declined to 10,252.88 ± 1,011.3 mg/6 wk, P < 0.001. These antiproteinuric effects were associated with substantial preservation of glomerular nephrin and podocin. In contrast, late treatment with either enalapril or eplerenone alone or combined mildly decreased UprV and cumulative proteinuria. Thus pretreatment with eplerenone or enalapril is effective in reducing daily and cumulative protein excretion and preservation of nephrin/podocin. More profound antiproteinuric effects were obtained when enalapril and eplerenone were combined.

Spironolactone suppresses peritubular capillary loss and prevents deoxycorticosterone acetate/salt-induced tubulointerstitial fibrosis

We examined whether and how peritubular capillary (PTC) loss in the renal cortex contributes to the development of deoxycorticosterone acetate (DOCA)/salt-induced tubulointerstitial fibrosis. Uninephrectomized rats provided with 0.9% NaCl/0.3% KCl drinking solution ad libitum were divided into control, DOCA, and spironolactone groups, which were administered vehicle, DOCA alone, and DOCA plus spironolactone for 1 (initial phase) and 4 weeks (delayed phase), respectively. Exposure to DOCA initiated a sequence of events that initially involved reduced PTC density, followed by a delayed response that involved further reduced PTC density, development of tubulointerstitial fibrosis and hypertension, enhanced expression of transforming growth factor-beta1 and connective tissue growth factor, and impaired renal function. Concomitant with the reduced PTC density, the 2 hypoxia-responsive angiogenic factors (vascular endothelial growth factor and hypoxia-inducible factor-1alpha) and the antiangiogenic factor (thrombospondin-1) were upregulated in cortical tubular cells of the DOCA group during the 2 phases and only in the delayed phase, respectively. In the DOCA group, PTC endothelial cell apoptosis was enhanced during the 2 phases, and PTC endothelial cell proliferation was inhibited in the delayed phase. In accordance with upregulation of thrombospondin-1, p53 expression was enhanced in the DOCA group in the delayed phase. The initial and delayed effects of DOCA were blocked in the spironolactone group. We conclude that exposure to DOCA initially caused the reduced PTC density associated with enhanced apoptosis independent of thrombospondin-1, which induced tubulointerstitial fibrosis via p53-mediated thrombospondin-1 activation, and spironolactone conversely corrected the effects of DOCA to prevent fibrosis.

The role of aldosterone blockade in murine lupus nephritis

Background

The purpose of this study was to examine the effect of aldosterone receptor blockade on the immunopathogenesis and progression of nephritis in the (NZB × NZW) F₁ murine lupus model.

Methods

Female NZB/W F₁ mice (11 weeks old) were treated daily with 25 or 50 mg/kg oral spironolactone or vehicle. Proteinuria, renal function, and serum autoantibody levels were monitored. Renal histopathology, immune complex deposition, and immunohistochemistry were analyzed at various time points. Targeted microarray analysis was performed on renal tissue, with subsequent real-time PCR analysis of several differentially expressed genes.

Results

Treatment with spironolactone was well tolerated by the mice throughout the course of their disease progression, with no significant differences in azotemia or serum potassium levels between vehicle-treated and spironolactone-treated animals. By 36 weeks of age, fewer spironolactone-treated mice developed nephrotic range proteinuria as compared with the control mice (control 70.8%, 25 mg/kg spironolactone 51.3%, and 50 mg/kg spironolactone 48.6%). Compared with control mice, mice treated with 25 mg/kg spironolactone had significantly lower serum anti-single-stranded DNA levels (2,042 μg/ml versus 1,036 μg/ml; P = 0.03) and anti-double-stranded DNA levels (3,433 μg/ml versus 614 μg/ml; P = 0.05). Spironolactone-treated mice exhibited decreased histopathologic evidence of inflammation and tissue damage, as compared with control mice. Additionally, spironolactone treatment resulted in decreased expression in the kidney of several inflammatory and proapoptotic genes, including those encoding interferon-γ, B lymphocyte stimulator (BlyS), tumor necrosis factor related apoptosis inducing ligand (TRAIL), tumor necrosis factor related weak inducer of apoptosis (TWEAK), and Fas ligand.

Conclusion

Aldosterone receptor blockade is safe and well tolerated in progressive murine lupus nephritis, and it results in decreased levels of clinical proteinuria, lower serum levels of autoantibodies, and decreased kidney damage. It appears to modulate inflammatory changes during the progression of glomerulonephritis and may also have a previously undescribed role in attenuating apoptosis.

Beneficial effects of spironolactone on glomerular injury in streptozotocin-induced diabetic rats

INTRODUCTION

To investigate the beneficial effects of spironolactone (SPL) on glomerular injury in streptozotocin (STZ)-induced diabetic rats and the possible mechanism.

METHODS AND RESULTS

STZ-induced diabetic rats were divided into control group, STZ group, and SPL group. Glomerular morphology was observed by light microscopy after the rats were sacrificed after 30 days treatment. The mRNA expressions of transforming growth factor-beta 1 (TGF-beta1) and type-1 plasminogen activator inhibitor (PAI-1) in renal cortex were measured by transcription-polymerase chain reaction (RT-PCR). The protein expressions of PAI-1, fibronectin (FN) and TGF-beta1 were detected by western blotting and immunohistochemistry respectively. In addition, levels of malondialdehyde (MDA) and the activity of antioxidants including superoxide diamutase (SOD), glutathione peroxidase (GSH-PX) in the cortex of kidney were measured.

RESULTS

In untreated diabetic rats, the glomerular volume, the expression of FN and the urinary albumin excretion increased. The mRNA and protein expression of PAI-1 and TGF-beta1 significantly increased in the STZ group. Treatment with SPL partially reversed these changes. Meanwhile, elevated MDA levels as well as decreased SOD and GSH-PX activities in the cortex of kidney were significantly ameliorated in the treated group.

CONCLUSION

SPL ameliorates the glomerular injury in STZ-induced early diabetic renal injury, which is closely related with the reduction of PAI-1 and TGF-beta1 expression and the attenuation of oxidative stress.

Aldosterone and end-organ damage

Aldosterone concentrations are inappropriately high in many patients with hypertension, as well as in an increasing number of individuals with metabolic syndrome and sleep apnoea. A growing body of evidence suggests that aldosterone and/or activation of the MR (mineralocorticoid receptor) contributes to cardiovascular remodelling and renal injury in these conditions. In addition to causing sodium retention and increased blood pressure, MR activation induces oxidative stress, endothelial dysfunction, inflammation and subsequent fibrosis. The MR may be activated by aldosterone and cortisol or via transactivation by the AT(1) (angiotenin II type 1) receptor through a mechanism involving the EGFR (epidermal growth factor receptor) and MAPK (mitogen-activated protein kinase) pathway. In addition, aldosterone can generate rapid non-genomic effects in the heart and vasculature. MR antagonism reduces mortality in patients with CHF (congestive heart failure) and following myocardial infarction. MR antagonism improves endothelial function in patients with CHF, reduces circulating biomarkers of cardiac fibrosis in CHF or following myocardial infarction, reduces blood pressure in resistant hypertension and decreases albuminuria in hypertensive and diabetic patients. In contrast, whereas adrenalectomy improves glucose homoeostasis in hyperaldosteronism, MR antagonism may worsen glucose homoeostasis and impairs endothelial function in diabetes, suggesting a possible detrimental effect of aldosterone via non-genomic pathways.

Insulin's impact on renal sodium transport and blood pressure in health, obesity, and diabetes

Insulin has been shown to have antinatriuretic actions in humans and animal models. Moreover, endogenous hyperinsulinemia and insulin infusion have been correlated to increased blood pressure in some models. In this review, we present the current state of understanding with regard to the regulation of the major renal sodium transporters by insulin in the kidney. Several groups, using primarily cell culture, have demonstrated that insulin can directly increase activity of the epithelial sodium channel, the sodium-phosphate cotransporter, the sodium-hydrogen exchanger type III, and Na-K-ATPase. We and others have demonstrated alterations in the expression at the protein level of many of these same proteins with insulin infusion or in hyperinsulinemic models. We also discuss how this regulation is perturbed in type I and type II diabetes mellitus. Finally, we discuss a potential role for regulation of insulin receptor signaling in the kidney in contributing to sodium balance and blood pressure.

Pharmacological management of renal fibrotic disease

Chronic kidney diseases frequently advance to end-stage renal failure, and the number of patients affected is steadily increasing worldwide. At the molecular level, progression of renal insufficiency correlates closely with ongoing pathological matrix protein expansion (i.e., renal fibrosis), in a manner independent of the underlying disorder. Overactivity of the renin-angiotensin system and of the TGF-beta system have been identified as key mediators of kidney matrix accumulation, and are principal targets in the management of chronic renal disease. This review provides a recent overview of the therapeutic options that are clinically established, and of novel molecular strategies that will approach clinical practice in the near future.

Aldosterone up-regulates production of plasminogen activator inhibitor-1 by renal mesangial cells

In vivo studies have demonstrated that aldosterone is an independent contributor to glomerulosclerosis. In the present study, we have investigated whether aldosterone itself mediated glomerulosclerosis, as angiotensin II (Ang II) did, by inducing cultured renal mesangial cells to produce plasminogen activator inhibitor-1 (PAI-1), and whether these effects were mediated by aldosterone-induced increase in transforming growth factor beta(1) (TGF-beta(1)) expression and cellular reactive oxygen species (ROS) activity. Quiescent rat mesangial cells were treated by aldosterone alone or by combination of aldosterone and spironolactone, Ang II, neutralizing antibody to TGF-beta(1) or antioxidant Nacetylcysteme (NAC). This study indicate that aldosterone can increase PAI-1 mRNA and protein expression by cultured mesangial cells alone, which is independent of aldosterone-induced increases in TGF-beta(1) expression and cellular ROS. The effects on PAI-1, TGF-beta(1) and ROS generation were markedly attenuated by spironolactone, a mineralocorticoid receptor antagonist, which demonstrate that mineralocorticoid receptor (MR) may play a role in mediating these effects of aldosterone.

Mechanisms of disease: The role of aldosterone in kidney damage and clinical benefits of its blockade

In the past 10 years, many widely accepted concepts relating to aldosterone production and its pathogenetic role have changed. We now know that aldosterone is produced not only by the zona glomerulosa of the adrenal cortex, but also in the heart, blood vessels, kidney and brain; such extra-epithelial production occurs mainly during tissue repair. Also, increased aldosterone levels contribute to vessel inflammation, oxidative stress, endothelial dysfunction and organ damage. As such, aldosterone has a key role in the development of myocardial fibrosis. Anti-aldosterone treatment has proven effective in patients with heart failure. Experimental evidence regarding the role of aldosterone in kidney damage has accumulated. Aldosterone infusion can counteract the beneficial effects of treatment with angiotensin-converting-enzyme inhibitors, causing more-severe proteinuria and an increased number of vascular and glomerular lesions; treatment with aldosterone antagonists can reverse these alterations. Preliminary observations in pilot studies in humans confirm the experimental findings, supporting the hypothesis that aldosterone antagonists are renoprotective in clinical practice. Studies in larger populations with longer follow-up are needed to confirm this theory.

Effect of combining ACE inhibition with aldosterone blockade on proteinuria and renal damage in experimental nephrosis

Aldosterone has pro-fibrotic properties and is a potential target for additional intervention in patients with chronic renal disease showing resistance to therapy during treatment with angiotensin-converting enzyme inhibitors (ACEi). Combining ACEi and aldosterone receptor blockade (aldoRB) in proteinuric renal disease reduces proteinuria, but effects on proteinuria-induced renal damage are unknown. We studied the effect of ACEi/aldoRB in adriamycin nephrosis (AN). Six weeks after injection of adriamycin in Wistar rats, randomized treatment with vehicle (VEH, n=8), aldoRB (n=12), ACEi (n=10), or a combination of ACEi/aldoRB (n=14) was given for 12 weeks. Healthy rats served as controls (n=6). Renal damage was quantified by markers of tubular injury (osteopontin (OPN) and kidney injury molecule-1 (Kim-1)), pre-fibrotic lesions (alpha-smooth muscle actin (SMA)), interstitial fibrosis (IF), and focal glomerulosclerosis (FGS). In AN animals, proteinuria was increased compared with controls. ACEi and ACEi/aldoRB significantly reduced proteinuria compared with VEH, whereas aldoRB monotherapy was without effect. Blood pressure was reduced in ACEi and ACEi/aldoRB compared with VEH and aldoRB. OPN and Kim-1 were increased in AN animals, but significantly reduced by ACEi/aldoRB. Treatment with ACEi and ACEi/aldoRB prevented an increase of SMA, IF, and FGS. In conclusion, ACEi/aldoRB effectively reduced proteinuria and markers of tubular injury and prevented renal damage in this rat model of chronic proteinuria-induced renal damage.

Inflammation and diabetic nephropathy

Diabetic nephropathy has become the main cause of renal failure, but unfortunately the intimate mechanisms leading to the development and progression of renal injury are not yet fully known. Activated innate immunity and inflammation are relevant factors in the pathogenesis of diabetes. Moreover, different inflammatory molecules, including chemokines, adhesion molecules, and proinflammatory cytokines, may be critical factors in the development of microvascular diabetic complications, including nephropathy. This new pathogenic perspective leads to important therapeutic considerations, with new pathogenic pathways becoming important therapeutic targets that can be translated into clinical treatments for diabetic nephropathy.

Spironolactone in type 2 diabetic nephropathy: Effects on proteinuria, blood pressure and renal function

OBJECTIVE

To study the effects of addition of spironolactone to angiotensin-converting enzyme (ACE) inhibition or angiotensin II (AngII) receptor antagonism on proteinuria, blood pressure (BP) and renal function in overt type 2 diabetic nephropathy.

DESIGN

A placebo-controlled, double-blind, parallel-group trial in patients from two outpatient clinics with a follow-up of 1 year.

METHODS

Type 2 diabetic patients with macroalbuminuria, despite long-term use of an ACE inhibitor or AngII receptor blocker were allocated to spironolactone, 25-50 mg once daily (n = 29) or placebo (n = 30). Urinary albumin to creatinine ratio, BP and biochemical parameters were measured at regular intervals.

RESULTS

Five patients of the spironolactone and one of the placebo group developed hyperkalemia and had to be excluded. Compared to other patients their baseline serum creatinine [161 (123-248) versus 88 (72-170) micromol/l] and potassium concentrations (4.7 +/- 0.3 versus 4.2 +/- 0.2 mmol/l) were elevated (P < 0.001). Albuminuria decreased by 40.6% [95% confidence interval (CI) 23.4-57.8%] and BP by 7 mmHg (2-12 mmHg)/3 mmHg (1-6 mmHg) with spironolactone, but did not change with placebo. Estimated glomerular filtration rate (eGFR) during the 1-year follow-up declined on average by 12.9 ml/min per 1.73 m (9.5-16.5 ml/min per 1.73 m) in the spironolactone and by 4.9 ml/min per 1.73 m (0.8-8.9 ml/min per 1.73 m) in the placebo group (P = 0.004). This decline was progressive in the placebo but leveled off in the spironolactone group. In the spironolactone group changes in albuminuria and GFR were correlated (r = 0.48, P = 0.007).

CONCLUSION

Addition of spironolactone to an ACE inhibitor or AngII receptor blocker is associated with a marked and sustained antiproteinuric effect, which in part relates to the more pronounced reduction in GFR.

Enhanced aldosterone signaling in the early nephropathy of rats with metabolic syndrome: possible contribution of fat-derived factors

Metabolic syndrome is an important risk factor for proteinuria and chronic kidney disease independent of diabetes and hypertension; however, the underlying mechanisms have not been elucidated. Aldosterone is implicated in target organ injury of obesity-related disorders. This study investigated the role of aldosterone in the early nephropathy of 17-wk-old SHR/NDmcr-cp, a rat model of metabolic syndrome. Proteinuria was prominent in SHR/NDmcr-cp compared with nonobese SHR, which was accompanied by podocyte injury as evidenced by foot process effacement, induction of desmin and attenuation of nephrin. Serum aldosterone level, renal and glomerular expressions of aldosterone effector kinase Sgk1, and oxidative stress markers all were elevated in SHR/NDmcr-cp. Mineralocorticoid receptors were expressed in glomerular podocytes. Eplerenone, a selective aldosterone blocker, effectively improved podocyte damage, proteinuria, Sgk1, and oxidant stress. An antioxidant tempol also alleviated podocyte impairment and proteinuria, along with inhibition of Sgk1. As for the mechanisms of aldosterone excess, visceral adipocytes that were isolated from SHR/NDmcr-cp secreted substances that stimulate aldosterone production in adrenocortical cells. The aldosterone-releasing activity of adipocytes was not inhibited by candesartan. Adipocytes from nonobese SHR did not show such activity. In conclusion, SHR/NDmcr-cp exhibit enhanced aldosterone signaling, podocyte injury, and proteinuria, which are ameliorated by eplerenone or tempol. The data also suggest that adipocyte-derived factors other than angiotensin II might contribute to the aldosterone excess of this model.

Mineralocorticoid receptor antagonist reduces renal injury in rodent models of types 1 and 2 diabetes mellitus

To determine whether mineralocorticoid receptor (MR) activation plays a role in diabetic renal injury and whether this role differs in types 1 and 2 diabetes mellitus, we examined the effect of a MR antagonist on renal injury in rodent models of type 1 (streptozotocin-treated rat) and type 2 (db/db mouse) diabetes. We studied three groups of 8-wk-old, uninephrectomized Wistar rats for 4 wk: diabetic streptozotocin- (55 mg/kg) treated rats (n = 11), diabetic streptozotocin-treated rats receiving the MR antagonist eplerenone (n = 15), and nondiabetic rats (n = 9). In addition, we studied three groups of 8-wk-old mice for 16 wk: diabetic db/db mice (n = 10), diabetic db/db mice treated with eplerenone (n = 8), and nondiabetic, db/+ littermates (n = 11). Diabetic rats and mice developed albuminuria and histopathological evidence of renal injury, including glomerular hypertrophy, mesangial expansion, and tubulointerstitial injury as well as increased renal cortical levels of MR protein, MR mRNA, TGFbeta mRNA, and osteopontin mRNA. All of these changes were significantly reduced by treatment with eplerenone except for the elevated MR levels. The beneficial effects of eplerenone were not attributable to changes in blood pressure or glycemia. In summary, MR expression was increased in kidneys of diabetic rodents, and MR antagonists effectively reduced diabetic renal injury irrespective of the species or specific cause of the diabetes. Thus, these data suggest that MR activation is a critical factor in the early pathogenesis of renal disease in both type 1 and type 2 diabetes mellitus.

Mineralocorticoid receptor antagonist spironolactone prevents pig serum-induced hepatic fibrosis in rats

Mineralocorticoid receptor (MR) antagonist spironolactone (SPL) is an effective agent for prevention of cardiovascular injury. However, whether and how SPL ameliorates hepatic fibrosis in rats is unknown. Pig serum (PS) (0.5 mL, twice a week, ip) or vehicle-administered rats for 12 weeks were used as rats with hepatic fibrosis or control rats, respectively. Rats given PS were treated with SPL (50 mg/kg/day, sc) for 12 weeks. Hepatic fibrosis, using picro-sirius red staining and determination of hydroxyproline content, immunohistochemistries of alpha-smooth muscle actin (alpha-SMA)-positive hepatic stellate cells (HSCs), Na/H exchange isoform-1 (NHE-1) protein, CYP11B2 aldosterone synthase protein for liver tissues, and plasma aldosterone concentrations were compared among the 3 groups of rats. Rats given PS alone exhibited hepatic fibrosis as well as increases in the number of the alpha-SMA-positive HSCs and NHE-1 protein expression in HSCs and hepatocytes, all of which were suppressed by SPL. Rats given PS alone revealed increased CYP11B2 protein expression in HSCs and hepatocytes, which was not inhibited by SPL. Plasma aldosterone concentrations were significantly greater in rats given PS and SPL than in control rats and rats given PS alone, although they were not different between control rats and rats given PS alone. PS-induced hepatic fibrosis together with HSC activation and NHE-1 protein expression occurs via MRs, and SPL ameliorates hepatic fibrosis presumably via the inhibition of HSC activation and NHE-1 protein expression in PS-induced liver injuries. The aldosterone produced in the injured liver contributes to the PS-induced hepatic fibrosis.

Renoprotective Effect of Breviscapine through Suppression of Renal Macrophage Recruitment in Streptozotocin-Induced Diabetic Rats

BACKGROUND/AIMS

Experimental and clinical evidence has consistently demonstrated that renal macrophage infiltration is one of the most important events for the progression of diabetic nephropathy. Breviscapine is a flavonoid extracted from the Chinese herb Erigeron breviscapus. Previously, it was shown that treatment with breviscapine attenuated renal injury in the diabetic rats. The purpose of this study is to investigate whether the renoprotective effect of breviscapine is through suppression of renal macrophage recruitment in diabetic rats.

METHODS

Diabetes was induced bystreptozotocin injection, and breviscapine was administered orally at a dose of 20 mg/kg/day for 8 weeks. Control rats received vehicle or breviscapine with the same schedule.

RESULTS

Breviscapine treatment markedly inhibited both an increase of albuminuria and glomeruli hypertrophy and tubulointerstitial injury without modifying mean arterial blood pressure and creatinine clearance. Levels of malondialdehyde and protein kinase C activities were markedly higher and antioxidant enzyme activities such as superoxide dismutase, catalase as well as glutathione peroxidase were significantly lower in the kidneys of diabetic rats than of the control group, breviscapine administration markedly remitted these changes. ED-1-positive cells and expression of intercellular adhesion molecule-1 (ICAM-1) and monocyte chemoattractant protein-1 (MCP-1) in glomeruli and tubulointerstitium were all markedly elevated but were significantly reduced by breviscapine. Western blot analysis noted that the expression of transforming growth factor beta1 protein was increased 1.8-fold in the kidney in diabetic rats, breviscapine treatment could reduce increased expression of TGF-beta1 protein by 47%.

CONCLUSION

This study describes a novel mechanism by which breviscapine confers a renoprotective effect.

Spironolactone ameliorates renal injury and connective tissue growth factor expression in type II diabetic rats

Administration of spironolactone provides a beneficial effect in various animal models of renal injury. In this study, we investigated whether spironolactone prevents the progression of diabetic nephropathy through reduction of connective tissue growth factor (CTGF) synthesis in type II diabetic rats. In addition, we evaluated the effect of aldosterone and spironolactone on CTGF and collagen production in cultured cells. Renal functional and morphologic changes were examined in Otsuka Long-Evans Tokushima Fatty rats with or without spironolactone treatment (20 mg/kg/day) for 8 months, as well as in non-diabetic age-matched Long-Evans Tokushima Otsuka rats. Spironolactone treatment did not induce any significant differences in body weight, kidney/body weight ratio, serum creatinine concentration, blood glucose levels, or systolic blood pressure. However, urinary protein and albumin excretion were significantly decreased in the spironolactone treatment group, which was associated with amelioration of glomerulosclerosis. In addition, renal CTGF, collagen synthesis demonstrated marked decreases in the spironolactone treatment group. In cultured MC and PTC, aldosterone induced significant increases in CTGF gene expression and protein synthesis associated with increased collagen synthesis, which was abolished by prior treatment with spironolactone. However, aldosterone treatment did not induce transforming growth factor (TGF)-beta1 overproduction, and inhibition of TGF-beta1 by neutralization of TGF-beta1 protein did not significantly prevent aldosterone-induced CTGF production. These results suggest that the antifibrotic effects of spironolactone may be mediated by CTGF through a TGF-beta1-independent pathway in this animal model of diabetic nephropathy.

Aldosterone infusion with high-NaCl diet increases blood pressure in obese but not lean Zucker rats

Insulin-resistant, obese Zucker rats have blunted pressure natriuresis and are mildly hypertensive. This may involve inappropriate regulation of the renin-angiotensin-aldosterone system. To evaluate mechanisms underlying this defect, we employed the model of aldosterone escape. Male lean (L) and obese (O) Zucker rats were infused with aldosterone (2.8 mug/g body wt(3/4)) via osmotic minipump while being fed a 0.02% NaCl diet (LS). After 4 days, six rats of each type were switched to a high-NaCl (HS) diet (4%) for 4 additional days. Mean arterial blood pressure measured by radiotelemetry was significantly increased by the HS diet only in obese rats (final mean mmHg): 104 (LLS), 99 (LHS), 103 (OLS), and 115 (OHS). Obese rats had relatively increased renal cortical abundance of the bumetanide-sensitive Na-K-2Cl cotransporter (NKCC2) and whole kidney alpha- and beta-ENaC (epithelial sodium channel) relative to lean rats. However, band density for the thiazide-sensitive (Na-Cl) cotransporter (NCC) was similarly reduced by HS in lean and obese rats ( approximately 50%). Obese rats had relatively reduced creatinine clearances and plasma renin activities, effects exacerbated by HS. Furthermore, HS resulted in a 129% increase in urinary nitrates plus nitrites excretion in lean rats and led to, in contrast, a 46% reduction in obese rats. Plasma sodium and potassium concentrations were increased by HS in obese but not lean rats. Thus we demonstrate an impaired response to aldosterone infusion in obese relative to lean Zucker rats. This impairment may involve increased sodium reabsorption via NKCC2 or ENaC, decreased glomerular filtration rate, and/or nitric oxide bioavailability.

Spironolactone prevents diabetic nephropathy through an anti-inflammatory mechanism in type 2 diabetic rats

Aldosterone induces myocardial fibrosis and vascular inflammation via proinflammatory and profibrotic cytokines. The effect of spironolactone on renal inflammation and renal function was investigated in type 2 diabetic rats. For define the molecular mechanism of spironolactone, the effect of spironolactone on the synthesis of monocyte chemotactic peptide-1 (MCP-1) and its upstream transcription factor, NF-kappaB, was evaluated in cultured mesangial cells and proximal tubular cells. There were no changes in blood glucose concentration or BP after spironolactone treatment. Spironolactone treatment significantly reduced urinary albumin excretion and ameliorated glomerulosclerosis. Urinary levels of MCP-1 were significantly increased concurrently with renal expression of MCP-1, macrophage migration inhibitory factor, and macrophage infiltration. Spironolactone treatment significantly inhibited urinary excretion of MCP-1 as well as renal MCP-1 and migration inhibitory factor expression and macrophage infiltration. In addition, aldosterone induced upregulation of MCP-1 expression and NF-kappaB transcriptional activity in cultured cells, and spironolactone reduced both NF-kappaB activation and MCP-1 synthesis. Furthermore, NF-kappaB inhibition abolished aldosterone-induced MCP-1 production. Overall, these findings suggest that aldosterone-induced NF-kappaB activation leads to activation of proinflammatory cytokines, ultimately leading to renal injury in this model. These data suggest that mineralocorticoid blockade may be a potential therapeutic target in diabetic nephropathy.

Plasminogen activator inhibitor-1 deficiency protects against aldosterone-induced glomerular injury

This study tests the hypothesis that plasminogen activator inhibitor-1 (PAI-1) contributes to aldosterone-induced renal and cardiac injury. The effects of 12-week aldosterone (2.8 microg/day)/salt (1% drinking water) versus vehicle/salt on renal and cardiac histology and mRNA expression were determined in wild-type (WT) and PAI-1 deficient (PAI-1(-/-)) mice. Systolic blood pressure was similar in aldosterone-infused WT and PAI-1(-/-) mice until 12 weeks, when it was significantly higher in the WT mice. At 12 weeks, urine volume, sodium excretion, and sodium/potassium ratio were similarly increased in the two aldosterone-infused groups. In contrast, urine albumin excretion was greater in aldosterone-infused WT mice (mean+/-s.d.: 699.0+/-873.0 microg/24 h) compared to vehicle-infused WT (23.6+/-9.0 microg/24 h, P=0.003) or aldosterone-infused PAI-1(-/-) mice (131.6+/-110.6 microg/24 h, P=0.007). Aldosterone increased glomerular area to a greater extent in WT (4651+/-577 versus 3278+/-488 microm2/glomerulus in vehicle-infused WT, P<0.001) than in PAI-1(-/-) mice (3713+/-705 microm2/glomerulus, P=0.001 versus aldosterone-infused WT), with corresponding mesangial expansion. Renal collagen content was also increased in aldosterone-infused WT versus PAI-1(-/-) mice. In WT mice, aldosterone increased renal mRNA expression of PAI-1, collagen I, collagen III, osteopontin, fibronectin, monocyte chemoattractant protein-1 (MCP-1), and F4/80 (all P<0.05), but not transforming growth factor beta (TGF-beta). In PAI-1(-/-) mice, aldosterone increased renal expression of collagen I, osteopontin, fibronectin, and MCP-1, and tended to increase collagen III. Renal osteopontin expression was diminished in aldosterone-treated PAI-1(-/-) compared to aldosterone-treated WT mice (P=0.05). Aldosterone induced cardiac hypertrophy but not fibrosis in WT and PAI-1(-/-) mice. PAI-1 contributes to aldosterone-induced glomerular injury.

Role of aldosterone in diabetic nephropathy

In the last 10 years, many studies have focused on the non-classical action of aldosterone. One of the most important new aspects of aldosterone is its pathogenic role as proinflammatory and profibrotic molecules. It has been reported that aldosterone induces myocardial fibrosis and vascular inflammation through up-regulation of various proinflammatory and profibrotic cytokines. We investigated the effect of aldosterone and spironolactone, which is a non-selective mineralocorticoid receptor antagonist, on monocyte chemoattractant peptide (MCP-1) and collagen synthesis in cultured mesangial and tubular epithelial cells. In addition, to evaluate the effect of spironolactone on diabetic nephropathy, we used Otsuka Long-Evans Tokushima Fatty (OLETF) rats which are known type 2 diabetic animal models. Spironolactone treatment did not induce any significant change in blood glucose levels and blood pressure. However, spironolactone therapy significantly inhibited urinary albumin and MCP-1 excretion. Spironolactone treatment also suppressed renal mRNA expression for MCP-1, macrophage migration inhibitory factor (MIF) as well as intrarenal protein synthesis for ED-1 and MIF. Morphologically, spironolactone treatment significantly prevented glomerulosclerosis, collagen deposition and connective tissue growth factor (CTGF) expression in diabetic rats. In cultured cell experiments, aldosterone directly increased the MCP-1, collagen secretion and spironolactone treatment abolished aldosterone-induced MCP-1 and collagen synthesis. Surprisingly, aldosterone treatment did not induce any significant change in TGFbeta1 gene transcription. Finally, we found that NF-kB activity was increased after stimulation with aldosterone and spironolactone therapy inhibited their activation. In addition, prior treatment with pyrrolidine dithiocarbamate (PDTC), which is a NF-KB inhibitor, inhibited aldosterone-induced MCP-1 protein secretion. These results suggest that aldosterone blockade could play a role in preventing the progression of diabetic nephropathy via anti-inflammatory and antifibrotic mechanisms.

Plasminogen activator inhibitor-1 and diabetic nephropathy

Diabetic nephropathy is characterized by excessive accumulation of extracellular matrix (ECM) in the kidney. Decreased ECM degradation as well as increased ECM synthesis plays an important role in ECM remodeling that favours tissue fibrosis. Plasminogen activator (PA)/plasmin/PA inhibitor (PAI) system is involved in ECM degradation and PAI-1 plays a critical role in ECM remodeling in the kidney. Normal human kidneys do not express PAI-1 but PAI-1 is overexpressed in pathologic conditions associated with renal fibrosis including diabetic nephropathy. Reactive oxygen species mediate PAI-1 up-regulation in renal cells cultured under high glucose, hypoxia, and TGF-beta1. Recent studies utilizing PAI-1 deficient mice suggest that PAI-1 induce ECM deposition in diabetic kidney through increased ECM synthesis by TGF-beta1 up-regulation as well as through decreased ECM degradation by suppression of plasmin and MMP-2 activity.

Azelnidipine Down-Regulates Renal Angiotensin-Converting Enzyme and Mineralocorticoid Receptor mRNA in Diabetic Hypertensive Rats

Effects of a new lipophilic L-type calcium channel blocker, azelnidipine, on the expression of molecular components of the renin-angiotensin-aldosterone system (RAAS) were assessed. Male Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a model of diabetes with hypertension, and their lean littermates, Long-Evans Tokushima Otsuka (LETO) rats, were treated with azelnidipine for 2 weeks. The renal cortical mineralocorticoid receptor mRNA in OLETF was higher than in LETO, but was suppressed (P<0.05) by azelnidipine. Renal cortical angiotensin-converting enzyme mRNA of OLETF was lower than that of LETO rats, and it was further suppressed by azelnidipine (P<0.05). Azelnidipine can down-regulate the gene expression of molecular components of RAAS.

Beneficial impact of spironolactone in diabetic nephropathy

BACKGROUND

Aldosterone has been suggested to play a role in the initiation and progression of diabetic nephropathy. Currently recommended treatment with angiotensin-converting enzyme (ACE) inhibitors or angiotensin II receptor blockers [renin-angiotensin system (RAS) blockade] does not suppress circulating aldosterone sufficiently. We therefore aimed to evaluate the short-term effect of aldosterone antagonism with spironolactone on albuminuria and blood pressure in diabetic nephropathy.

METHODS

Twenty Caucasian type 1 diabetic patients with persistent macroalbuminuria despite antihypertensive treatment, including RAS blockade, completed this double-masked, randomized cross-over trial. Patients were treated in random order with spironolactone 25 mg once daily and matched placebo for two months, respectively, on top of usual antihypertensive treatment. After each treatment period albuminuria, 24-hour blood pressure, and glomerular filtration rate (GFR) were determined.

RESULTS

Spironolactone on top of usual antihypertensive treatment induced a 30% (95% CI 17 to 41) reduction in albuminuria from [geometric mean (95% CI)] 831 (624 to 1106) mg/24-hour on placebo treatment (P < 0.001), and a reduction in fractional albumin clearance of 35% (20 to 46, P < 0.001). Twenty-four-hour blood pressure showed an insignificant reduction of [mean reduction (95% CI)] 8 (-1 to 17)/3 (-0.2 to 7) mm Hg (P < 0.10). There was an insignificant reversible reduction in GFR during treatment with spironolactone. On spironolactone treatment, one patient was excluded due to hyperkalemia (plasma potassium 5.7 mmol/L) and one due to orthostatic dizziness. Otherwise treatment was well tolerated.

CONCLUSION

Our results suggest that spironolactone treatment on top of recommended antihypertensive treatment reduces blood pressure and may offer additional renoprotection in type 1 diabetic patients with diabetic nephropathy.

Renocortical mRNA expression of vasoactive factors during spironolactone protective effect in chronic cyclosporine nephrotoxicity

We showed that spironolactone reduced structural damage and prevented renal dysfunction in chronic cyclosporine (CsA) nephrotoxicity. These findings evidenced an aldosterone renal vascular effect under this condition. To investigate aldosterone’s role in modulating renal vascular tone, renocortical vasoactive pathways mRNA levels in chronic CsA nephrotoxicity as well as spironolactone’s effect on renal function in acute CsA nephrotoxicity were evaluated. Two experimental sets were designed. For chronic nephrotoxicity, rats fed with low-sodium diet were divided into groups receiving vehicle, spironolactone (Sp), CsA, and CsA+Sp, for 21 days. Creatinine clearance, survival percentage, and renocortical mRNA levels of pro-renin, angiotensinogen (Ang), angiotensin receptors (AT1A, AT1B, and AT2), preproendothelin, endothelin receptors (ETA, ETB), cyclooxygenase-2 (COX-2), and adenosine receptors (Ad1, Ad2A, Ad2B, and Ad3) were analyzed. For acute nephrotoxicity, similar groups fed with a standard chow diet for 7 days were included. Serum potassium and sodium, glomerular filtration rate (GFR), and renal blood flow (RBF) were determined. In chronic model, CsA produced pro-renin and ET upregulation, altered adenosine receptors expression, and reduced Ang, AT1A, AT1B, ETB, and COX-2 mRNA levels. Spironolactone protective effect in chronic nephrotoxicity was associated with prevention of pro-renin upregulation and increased AT2, together with ETBreduction. In acute nephrotoxicity, spironolactone completely prevented GFR and RBF reduction induced by CsA. Our results suggest that aldosterone contributes to renal vasoconstriction observed in CsA nephrotoxicity and that renoprotection conferred by spironolactone was related to modification of renocortical vasoactive pathways expression, in which pro-renin normalization was the most evident change in chronic nephropathy. Finally, our data point to spironolactone as a potential treatment to reduce CsA nephrotoxicity in transplant patients.

Prevention of early renal injury by mycophenolate mofetil and its mechanism in experimental diabetes

Previously it was shown that treatment with mycophenolate mofetil (MMF) attenuated renal inflammation and glomerular injury in a model of diabetes. However, the mechanism involved in the renoprotective effects of MMF in experimental diabetes has not been clearly delineated. Diabetes was induced by injection of streptozotocin (STZ) after uninephrectomy. Diabetic animals received no treatment or treatment with MMF (10 mg/kg once daily by gastric gavage) for 8 weeks, non-diabetic rats served as controls. Level of malondialdehyde (MDA) in renal tissue and urine as well as the activity of antioxidant enzymes (AOE) in renal tissue was determined. Renal injury was evaluated. Immunohistochemistry for ED-1 macrophages marker, intercellular adhesion molecule-1 (ICAM-1) and monocyte chemoattractant protein-1 (MCP-1) was performed. Expression of transforming growth factor (TGF)-beta1 protein was determined by Western blotting analysis. Treatment with MMF had no effect on blood glucose level, but did prevent increased urinary albumin excretion and glomerular damage in diabetic rats. Oxidative stress was reduced by MMF treatment, as indicated by a reduction in MDA level in renal tissue and urine. Activity of AOE such as glutathione peroxidase (GSH-PX) was markedly elevated while superoxide dismutase (SOD) and catalase (CAT) were not changed by MMF treatment. In diabetic animals receiving no treatment, there were increases in ED-1-positive cells, ICAM-1 expression and MCP-1 expression in glomeruli and tubulointerstitium, which were effectively suppressed by MMF treatment. Western blotting analysis showed that the expression of TGF-beta1 protein was increased by 1.92-fold in renal tissue in diabetic rats, and MMF treatment significantly reduced the increased expression of TGF-beta1 protein by 45%. Our data suggest that MMF treatment ameliorates early renal injury via the inhibition of oxidative stress and overexpression of ICAM-1, MCP-1 and TGF-beta1 in renal tissue in diabetic rats.

Increased Expression of Mineralocorticoid Effector Mechanisms in Kidney Biopsies of Patients With Heavy Proteinuria

Background— Aldosterone has emerged as a deleterious hormone in the heart, with mineralocorticoid receptor (MR) blockade reducing mortality in patients with severe heart failure. There is also experimental evidence that aldosterone contributes to the development of nephrosclerosis and renal fibrosis in rodent models, but little is known of its role in clinical renal disease.

Methods and Results— We quantified MR, serum- and glucocorticoid-regulated kinase 1 (sgk1), and mRNA expression of inflammatory mediators such as macrophage chemoattractant protein-1 (MCP-1), transforming growth factor-β1, and interleukin-6 in 95 human kidney biopsies in patients with renal failure and mild to marked proteinuria of diverse etiologic origins. We measured renal function, serum aldosterone, urinary MCP-1 protein excretion, and the amount of chronic renal damage. Macrophage invasion was quantified by CD68 and vascularization by CD34 immunostaining. Serum aldosterone correlated negatively with creatinine clearance ( P <0.01) and positively with renal scarring ( P <0.05) but did not correlate with MR mRNA expression or proteinuria. Patients with heavy albuminuria (>2 g/24 h; n=15) had the most renal scarring and the lowest endothelial CD34 staining. This group showed a significant 5-fold increase in MR, a 2.5-fold increase in sgk1 expression and a significant increase in inflammatory mediators (7-fold increase in MCP-1, 3-fold increase in transforming growth factor-β1, and 2-fold increase in interleukin-6 mRNA). Urinary MCP-1 protein excretion and renal macrophage invasion were significantly increased in patients with heavy albuminuria.

Conclusions— These studies support animal data linking aldosterone/MR activation to renal inflammation and proteinuria. Further studies are urgently required to assess the potential beneficial effects of MR antagonism in patients with renal disease.

Beneficial effects of adding spironolactone to recommended antihypertensive treatment in diabetic nephropathy: a randomized, double-masked, cross-over study

OBJECTIVE

The objective of this study was to evaluate the safety and short-term effect of adding spironolactone to conventional antihypertensive treatment including diuretics and maximally recommended doses of an ACE inhibitor or an angiotensin II receptor blocker (ARB) on albuminuria and blood pressure in type 2 diabetic patients with nephropathy.

RESEARCH DESIGN AND METHODS

Twenty-one type 2 diabetic patients with nephropathy were enrolled in a randomized, double-masked, cross-over study. Patients were treated in random order with spironolactone 25 mg once daily and matched placebo for 8 weeks, respectively, in addition to ongoing antihypertensive treatment including diuretics and maximally recommended doses of an ACE inhibitor and/or an ARB. At the end of each treatment period, albuminuria, 24-h ambulatory blood pressure (ABP), and glomerular filtration rate (GFR) were determined.

RESULTS

During the addition of placebo, values were as follows: albuminuria (geometric mean [range]) 1,566 [655-7,762] mg/24 h, ABP (mean +/- SE) 138 +/- 3/71 +/- 1 mmHg, and GFR (mean +/- SE) 74 +/- 6 ml/min per 1.73 m2. During the addition of spironolactone, albuminuria was reduced by 33% (95% CI 25-41) (P < 0.001), fractional clearance of albumin by 40% (24-53) (P < 0.001), and 24-h ABP by 6 mmHg (2-10) for systolic and 4 mmHg (2-6) for diastolic (P < 0.001 for both). The change in albuminuria did not correlate with the change in systolic 24-h ABP (r = 0.19, P = 0.42) or diastolic 24-h ABP (r = 0.01, P = 0.96). Spironolactone treatment induced an insignificant reversible reduction in GFR of 3 ml/min per 1.73 m2 (-0.3 to 6) (P = 0.08). One patient was excluded from the study due to hyperkalemia. Otherwise treatment was well tolerated.

CONCLUSIONS

Our study suggests that spironolactone safely adds to the reno- and cardiovascular protective benefits of treatment with maximally recommended doses of ACE inhibitor and ARB by reducing albuminuria and blood pressure in type 2 diabetic patients with nephropathy.

Reactive oxygen species mediate high glucose-induced plasminogen activator inhibitor-1 up-regulation in mesangial cells and in diabetic kidney

BACKGROUND

Plasminogen activator inhibitor-1 (PAI-1) plays an important role in remodeling of extracellular matrix (ECM) in the glomeruli. PAI-1 is up-regulated by high glucose and is overexpressed in diabetic kidney. Since reactive oxygen species (ROS) mediate ECM accumulation in diabetic glomeruli and was recently found to mediate transforming growth factor-beta1 (TGF-beta1)-induced PAI-1 up-regulation in glomerular mesangial cells, we examined the role of ROS in high glucose-induced PAI-1 expression in cultured glomerular mesangial cells and in streptozotocin-induced diabetic rat glomeruli.

METHODS

Growth arrested and synchronized primary rat mesangial cells were treated with different concentrations of glucose in the presence or absence of N-acetylcysteine (NAC) or trolox, or after cellular reduced form of glutathione (GSH) depleted with DL-buthionine-(S,R)-sulfoximine (BSO). Taurine was administered to diabetic rats from 2 days to 4 weeks after streptozotocin injection. Urinary protein excretion, glomerular volume, and fractional mesangial area were measured as markers of renal injury and lipid peroxide (LPO) as an oxidative stress marker. PAI-1 mRNA expression was measured by Northern blot analysis in mesangial cells and reverse transcription-polymerase chain reaction (RT-PCR) in glomeruli, PAI-1 protein by Western blot analysis and enzyme-linked immunosorbent assay (ELISA), and plasmin activity by fluorometry.

RESULTS

High glucose significantly increased PAI-1 mRNA and protein expression and decreased plasmin activity in mesangial cells. Equimolar concentrations of l-glucose or mannitol did not affect PAI-1 expression. BSO pretreatment significantly increased basal PAI-1 expression and amplified the response to high glucose. NAC effectively inhibited high glucose-induced, but not basal, PAI-1 expression. Reduced plasmin activity in mesangial cells by high glucose was rescued by antioxidants. Anti-TGF-beta antibody inhibited both high glucose- and H(2)O(2)-induced PAI-1 up-regulation. Taurine significantly reduced plasma LPO, glomerular PAI-1 expression, glomerular volume, fractional mesangial area, and proteinuria in streptozotocin-induced diabetic rats.

CONCLUSION

These results demonstrate that ROS mediate high glucose-induced up-regulation of PAI-1 expression in cultured mesangial cells and in diabetic glomeruli. Since both high glucose and TGF-beta1 induce cellular ROS and ROS mediate both high glucose- and TGF-beta1-induced PAI-1, ROS appear to amplify TGF-beta1 signaling in high glucose-induced PAI-1 up-regulation. Antioxidants can prevent accumulation of ECM protein in diabetic glomeruli partly by abrogating up-regulation of PAI-1 and suppression of plasmin activity.

Differing Effects of Mineralocorticoid Receptor–Dependent and –Independent Potassium-Sparing Diuretics on Fibrinolytic Balance

This study tests the hypothesis that spironolactone influences plasminogen activator inhibitor-1 (PAI-1) concentrations through mineralocorticoid receptor antagonism rather than through changes in potassium. Effects of spironolactone (50 mg per day) and triamterene (50 mg per day) on fibrinolytic balance were compared in 18 normotensive and 20 hypertensive subjects pretreated with hydrochlorothiazide (HCTZ; 12.5 mg per day). Blood pressure and serum potassium were similar in spironolactone and triamterene treatment groups. The effect of the 2 drugs on the renin-angiotensin-aldosterone system was also similar. In contrast, spironolactone and triamterene exerted opposing effects on PAI-1 antigen ( P =0.006 for drug effect). In normotensive subjects, triamterene (from 10.1±7.8 to 16.9±9.9 ng/mL at 9 am , P =0.019; from 7.6±5.4 to 11.5±7.3 ng/mL at 11 am , P =0.027; from 9.3±7.7 to 13.7±8.5 ng/mL for average of all time points, P =0.054) but not spironolactone significantly increased PAI-1 antigen. In hypertensive subjects, spironolactone significantly decreased PAI-1 antigen (from 22.0±23.4 to 16.7±19.0 ng/mL at 10 am , P =0.041; from 17.5±21.7 to 12.7±16.8 ng/mL at 11 am , P =0.043; from 20.3±22.6 to 16.6±19.7 ng/mL for average of all time points, P =0.014), whereas there was no effect of triamterene. Only spironolactone significantly decreased the molar ratio of PAI-1 to tissue-type plasminogen activator (t-PA) in hypertensive subjects. By regression analysis, predictors of mean PAI-1 response were spironolactone versus triamterene ( P =0.014), hypertension ( P =0.002), and PAI-1 response to HCTZ ( P =0.019), with a trend for aldosterone ( P =0.061). Mineralocorticoid receptor antagonism prevents the effect of activation of the renin-angiotensin-aldosterone system on PAI-1 antigen in normotensive subjects and improves fibrinolytic balance in hypertensive subjects through a potassium-independent mechanism.

New insights into the pathophysiology of diabetic nephropathy: from haemodynamics to molecular pathology

Although debated for many years whether haemodynamic or structural changes are more important in the development of diabetic nephropathy, it is now clear that these processes are interwoven and present two sides of one coin. On a molecular level, hyperglycaemia and proteins altered by high blood glucose such as Amadori products and advanced glycation end-products (AGEs) are key players in the development of diabetic nephropathy. Recent evidence suggests that an increase in reactive oxygen species (ROS) formation induced by high glucose-mediated activation of the mitochondrial electron-transport chain is an early event in the development of diabetic complications. A variety of growth factors and cytokines are then induced through complex signal transduction pathways involving protein kinase C, mitogen-activated protein kinases, and the transcription factor NF-kappaB. High glucose, AGEs, and ROS act in concert to induce growth factors and cytokines. Particularly, TGF-beta is important in the development of renal hypertrophy and accumulation of extracellular matrix components. Activation of the renin-angiotensin system by high glucose, mechanical stress, and proteinuria with an increase in local formation of angiotensin II (ANG II) causes many of the pathophysiological changes associated with diabetic nephropathy. In fact, it has been shown that angiotensin II is involved in almost every pathophysiological process implicated in the development of diabetic nephropathy (haemodynamic changes, hypertrophy, extracellular matrix accumulation, growth factor/cytokine induction, ROS formation, podocyte damage, proteinuria, interstitial inflammation). Consequently, blocking these deleterious effects of ANG II is an essential part of every therapeutic regiment to prevent and treat diabetic nephropathy. Recent evidence suggests that regression of diabetic nephropathy could be achieved under certain circumstances.