ACE inhibitor reduces growth factor receptor expression and signaling but also albuminuria through B2-kinin glomerular receptor activation in diabetic rats

Kinins and Kinin Receptors in Cardiovascular and Renal Diseases

This review addresses the physiological role of the kallikrein–kinin system in arteries, heart and kidney and the consequences of kallikrein and kinin actions in diseases affecting these organs, especially ischemic and diabetic diseases. Emphasis is put on pharmacological and genetic studies targeting kallikrein; ACE/kininase II; and the two kinin receptors, B1 (B1R) and B2 (B2R), distinguished through the work of Domenico Regoli and his collaborators. Potential therapeutic interest and limitations of the pharmacological manipulation of B1R or B2R activity in cardiovascular and renal diseases are discussed. This discussion addresses either the activation or inhibition of these receptors, based on recent clinical and experimental studies.

Benazepril hydrochloride improves diabetic nephropathy and decreases proteinuria by decreasing ANGPTL-4 expression

BACKGROUND

This study aimed to investigate the effects of benazepril hydrochloride (BH) on proteinuria and ANGPTL-4 expression in a diabetic nephropathy (DN) rat model.

METHODS

A total of 72 Wistar male rats were randomly divided into three groups: normal control (NC), DN group and BH treatment (BH) groups. The DN model was induced by streptozotocin (STZ). Weight, glucose, proteinuria, biochemical indicators and the kidney weight index were examined at 8, 12 and 16 weeks. In addition, ANGPTL-4 protein and mRNA expressions were assessed by immunohistochemistry and qRT-PCR, respectively. Relationships between ANGPTL-4 and biochemical indicators were investigated using Spearman analysis.

RESULTS

Weight was significantly lower but glucose levels were significantly higher in both the DN and BH groups than in the NC group (P < 0.05). Compared with the DN group, proteinuria, urea, creatinine, triglycerides and total cholesterol levels were decreased, whereas the albumin level was increased after BH treatment (all P < 0.05). Furthermore, BH diminished kidney volume and ameliorated the pathological changes associated with DN. ANGPTL-4 expression was significantly decreased after BH treatment, and ANGPTL-4 expression was highly correlated with biochemical indicators of DN (P < 0.05).

CONCLUSIONS

Benazepril hydrochloride improves DN and decreases proteinuria by decreasing ANGPTL-4 expression.

Effect of calcium channels blockers and inhibitors of the renin-angiotensin system on renal outcomes and mortality in patients suffering from chronic kidney disease: systematic review and meta-analysis

BACKGROUND

The renoprotective effect of inhibitors of renin-angiotensin system (RAS) has been identified through placebo-controlled trials. However, the effect of calcium-channel blockers (CCBs) on renal system is still controversial. Our current meta-analysis includes available evidences to compare the effect of dihydropyridine CCBs and ACEIs or ARBs on renal outcomes and mortality. We also further investigate whether CCBs can be used in combination with inhibitors of RAS to improve the prognosis of patients with chronic kidney disease (CKD).

METHODS AND RESULTS

Electronic databases were searched up to July 2012, for clinical randomized controlled trials, assessing the effect of dihydropyridine CCBs on the incidence of end-stage renal disease (ESRD) and all-cause mortality in contrast to ACEIs or ARBs. Eight clinical trials were included containing 25,647 participants. ESRD showed significantly higher frequency with CCBs therapy compared with ACEIs or ARBs therapy, though blood pressure was decreased similarly in both groups in every trial (OR, 1.25; 95% CI, 1.05-1.48; p = 0.01). In contrast, there was no significant difference in the incidence of all-cause mortality between these two groups, though ACEIs or ARBs exhibited better renoprotective effect compared to CCBs (OR, 0.96; 95% CI, 0.89-1.03; p = 0.24).

CONCLUSIONS

CCBs did not increase all-cause mortality incidence in patients with CKD though they displayed weaker renoprotective, compared to ACEIs or ARBs therapy. Our results suggest the combination of a CCB and an ACEI or ARB should be a preferable antihypertensive therapy in patients with CKD, considering their higher effect in decreasing blood pressure and fewer adverse metabolic problems caused.

Renal kallikrein activation and renoprotection after dual blockade of renin-angiotensin system in diet-induced diabetic nephropathy

PURPOSE

The objective of this study is to investigate the effect of dual blockage of renin-angiotensin system (RAS) on renal kallikrein expression and inflammatory response in diabetic nephropathy (DN).

METHODS

Rats were randomly divided into 5 groups with 10 rats in each group: normal control; DN model induced by high fat and high sucrose diets; and DN treated with either benazepril 10 mg/kg/d, irbesartan 30 mg/kg/d, or both. After 8-week treatment, we examined changes in the kidney histopathology, function and immunohistochemical stain of kallikrein, macrophage marker CD68, and profibrotic markers transforming growth factor- (TGF-) β and α-smooth muscle action (SMA).

RESULTS

DN rats showed enlarged kidneys with glomerulosclerosis, interstitial chronic inflammation and fibrosis, and proteinuria. All the pathological damage and functional impairments were improved after the RAS blockades (all P < 0.05). Compared with monotherapy, combined treatment further alleviated the kidney impairments in parallel to increased tubular immunoreactivity for kallikrein and decreased immunopositive cells for CD68, TGF-β, and α-SMA.

CONCLUSION

The renoprotective effects of the dual RAS blockade in diabetic nephropathy may be attributed to improved tubular kallikrein expression and interstitial inflammatory response.

Genetic manipulation and genetic variation of the kallikrein-kinin system: impact on cardiovascular and renal diseases

Genetic manipulation of the kallikrein-kinin system (KKS) in mice, with either gain or loss of function, and study of human genetic variability in KKS components which has been well documented at the phenotypic and genomic level, have allowed recognizing the physiological role of KKS in health and in disease. This role has been especially documented in the cardiovascular system and the kidney. Kinins are produced at slow rate in most organs in resting condition and/or inactivated quickly. Yet the KKS is involved in arterial function and in renal tubular function. In several pathological situations, kinin production increases, kinin receptor synthesis is upregulated, and kinins play an important role, whether beneficial or detrimental, in disease outcome. In the setting of ischemic, diabetic or hemodynamic aggression, kinin release by tissue kallikrein protects against organ damage, through B2 and/or B1 bradykinin receptor activation, depending on organ and disease. This has been well documented for the ischemic or diabetic heart, kidney and skeletal muscle, where KKS activity reduces oxidative stress, limits necrosis or fibrosis and promotes angiogenesis. On the other hand, in some pathological situations where plasma prekallikrein is inappropriately activated, excess kinin release in local or systemic circulation is detrimental, through oedema or hypotension. Putative therapeutic application of these clinical and experimental findings through current pharmacological development is discussed in the chapter.

Targeting the 'Janus face' of the B2-bradykinin receptor

INTRODUCTION

Kinins are main active mediators of the kallikrein-kinin system (KKS) via bradykinin type 1 inducible (B1R) and type 2 constitutive (B2R) receptors. B2R mediates most physiological bradykinin (BK) responses, including vasodilation, natriuresis, NO, prostaglandins release.

AREAS COVERED

The article summarizes knowledge on kinins, B2R signaling and biological functions; highlights crosstalks between B2R and renin-angiotensin system (RAS). The double role (Janus face) in physiopathology, namely the beneficial protection of the endothelium, which forms the basis for the therapeutical utilization of B2 receptor agonists, on the one side, and the involvement of B2R in inflammation or infection diseases and in pain mechanisms, which justifies the use of B2R antagonists, on the other side, is extensively analyzed.

EXPERT OPINION

For decades, the B2R has been unconsciously activated during angiotensin-converting enzyme inhibitor (ACEI) or angiotensin receptor blocker (ARB) treatments. Whether direct B2R targeting with stable agonists could bring additional therapeutic benefit to RAS inhibition should be investigated. Efficacy, established in experimental models, should be confirmed by translational studies in cardiovascular pathologies, glaucoma, Duchenne cardiopathy and during brain cancer therapy. The other face of B2R is targeted by antagonists already approved to treat hereditary angioedema. The use of antagonists could be extended to other angioedema and efficacy tested against acute pain and inflammatory diseases.

Bradykinin inhibits high glucose- and growth factor-induced collagen synthesis in mesangial cells through the B2-kinin receptor

Mesangial matrix expansion is an early lesion leading to glomeruloclerosis and chronic renal diseases. A beneficial effect is achieved with angiotensin I-converting enzyme inhibitors (ACEI), which also favor bradykinin (BK) B2 receptor (B2R) activation. To define the underlying mechanism, we hypothesized that B2R activation could be a negative regulator of collagen synthesis in mesangial cells (MC). We investigated the effect of BK on collagen synthesis and signaling in MC. Inflammation was evaluated by intercellular adhesion molecule-1 (ICAM-1) expression. BK inhibited collagen I and IV synthesis stimulated by high glucose, epithelial growth factor (EGF), and transforming growth factor-β (TGF-β) but did not alter ICAM-1. Inhibition of collagen synthesis was B2R but not B1R mediated. PKC or phosphatidylinositol 3-kinase (PI3K) inhibitors mimicked the BK effect. B2R activation inhibited TGF-β- and EGF-induced Erk1/2, Smad2/3, Akt S473, and EGFR phosphorylation. A phosphatase inhibitor prevented BK effects. The in vivo impact of B2R on mesangial matrix expansion was assessed in streptozotocin-diabetic rodents. Deletion of B2R increased mesangial matrix expansion and albuminuria in diabetic mice. In diabetic rats, matrix expansion and albuminuria were prevented by ACEI but not by ACEI and B2R antagonist cotreatment. Consistently, the lowered BK content of diabetic glomeruli was restored by ACEI. In conclusion, deficient B2R activation aggravated mesangial matrix expansion in diabetic rodents whereas B2R activation reduced MC collagen synthesis by a mechanism targeting Erk1/2 and Akt, common pathways activated by EGF and TGF-β. Taken together, the data support the hypothesis of an antifibrosing effect of B2R activation.

Durable improvement of renal function after perindopril withdrawal in Lyon hypertensive rats

To determine whether the persistent antihypertensive effect observed after withdrawal of angiotensin-converting enzyme inhibition was specific and whether it was associated with durable improvement of renal function. Lyon hypertensive (LH) rats were treated from 3 and 12 weeks of age with perindopril at the dose of 0.4 (P0.4) or 1.5 (P1.5) mg·kg(-1)·d(-1), with double (hydralazine 75 mg·kg(-1)·d(-1) and hydrochlorothiazide 15 mg·kg(-1)·d(-1)), or triple antihypertensive therapy (reserpine 0.75 mg·kg(-1)·d(-1) was added). Blood pressure (BP) was recorded by telemetry, and renal functions were evaluated in freely moving rats. Despite similar BP reduction after perindopril withdrawal in P0.4 and P1.5 groups, greater decrease in proteinuria was observed in P1.5 group. Double or triple therapy prevented the hypertension of LH rats, but without any persistent antihypertensive or antiproteinuric effect after its withdrawal. Salt load elicited an increase in BP that was similar in untreated LH and both perindopril-pretreated groups (+30 mm Hg), but more pronounced in double therapy–pretreated or triple therapy–pretreated groups (+50 mm Hg). The pressure–natriuresis curve shifted to lower BP levels in P0.4 and P1.5 groups, whereas it was blunted in double and triple therapy groups. Angiotensin-converting enzyme inhibition has a durable renoprotection after treatment withdrawal that is independent of BP lowing.

The kallikrein-kinin system in diabetic nephropathy

Diabetic nephropathy is the major cause of end-stage renal disease worldwide. Although the renin-angiotensin system has been implicated in the pathogenesis of diabetic nephropathy, angiotensin I-converting enzyme inhibitors have a beneficial effect on diabetic nephropathy independently of their effects on blood pressure and plasma angiotensin II levels. This suggests that the kallikrein-kinin system (KKS) is also involved in the disease. To study the role of the KKS in diabetic nephropathy, mice lacking either the bradykinin B1 receptor (B1R) or the bradykinin B2 receptor (B2R) have been commonly used. However, because absence of either receptor causes enhanced expression of the other, it is difficult to determine the precise functions of each receptor. This difficulty has recently been overcome by comparing mice lacking both receptors with mice lacking each receptor. Deletion of both B1R and B2R reduces nitric oxide (NO) production and aggravates renal diabetic phenotypes, relevant to either lack of B1R or B2R, demonstrating that both B1R and B2R exert protective effects on diabetic nephropathy presumably via NO. Here, we review previous epidemiological and experimental studies, and discuss novel insights regarding the therapeutic implications of the importance of the KKS in averting diabetic nephropathy.

The protective effect of Salvia miltiorrhiza in an animal model of early experimentally induced diabetic nephropathy

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetic nephropathy (DN) is the most common cause of end stage renal disease. In this study, the effects of Salvia miltiorrhiza (SM) were studied in an experimental rat model of DN that was induced by streptozotocin (STZ) treatment.

MATERIALS AND METHODS

Diabetes was induced in male Sprague-Dawley rats (290 ± 10 g) by injecting STZ (45 mg/kg) into the tail vein. After development of diabetes, the rats were treated with SM (500 mg/kg) for 8 weeks in order to analyze its renoprotective effect, which was evaluated by means of blood glucose level, urine protein, and the expression of advanced glycation end-products (AGEs), receptor of advanced glycation end-products (RAGE), transforming growth factor β1 (TGF-β1), collagen IV, and monocyte/macrophage (ED-1) infiltration.

RESULTS

High levels of 24-h urinary protein excretion were ameliorated by SM. Moreover, the serum and kidney levels of transforming growth factor β1 (TGF-β1) and the kidney levels of collagen IV, monocytes/macrophages (ED-1) and the receptor for advanced glycation end-products (RAGE), were significantly reduced.

CONCLUSIONS

These findings suggest that SM might inhibit the progression of DN and could be a therapeutic agent for regulating several pharmacological targets for treatment or prevention of DN.

Transcriptional inhibition of progressive renal disease by gene silencing pyrrole-imidazole polyamide targeting of the transforming growth factor-β1 promoter

Pyrrole-imidazole (PI) polyamides are small synthetic molecules that recognize and attach to the minor groove of DNA, thereby inhibiting gene transcription by blocking transcription factor binding. These derivatives can act as gene silencers inhibiting target gene expression under stimulatory conditions such as disease. To evaluate PI polyamides as treatments for the progression of renal diseases, we examined morphological effects, pharmacological properties, and the specificity of PI polyamides targeted to the transforming growth factor (TGF)-β1 promoter during salt-induced hypertensive nephrosclerosis in Dahl salt-sensitive rats. The targeted PI polyamide markedly reduced glomerulosclerosis and interstitial fibrosis without side effects. PI polyamide significantly decreased expression of TGF-β1 and extracellular matrix in the renal cortex. Microarray analysis found that only 3% of the transcripts were affected by PI polyamide, but this included decreased expression of extracellular matrix, TGF-β1-related cytokines, angiogenic, and cell stabilizing factors, proteinases, and renal injury-related factors. Thus, targeted PI polyamides are potential gene silencers for diseases not treatable by current remedies.

Therapeutic advantage of angiotensin-converting enzyme inhibitors in patients with proteinuric chronic kidney disease

Angiotensin-converting enzyme inhibitor (ACEI) or angiotensin receptor blocker (ARB) is recommended for the treatment of hypertension in patients with chronic kidney disease (CKD). The relation of ACEI to renal prognosis was investigated in CKD patients in a retrospective cohort study. The objectives were patients with nondiabetic CKD of stage 4 or below receiving monotherapy with calcium channel blocker (CCB), ACEI, or ARB, and combination therapy. For the endpoint of progression to CKD stage 5, Cox's proportional hazards analysis was conducted with explanatory variables of age, sex, baseline estimated GFR (eGFR), and proteinuria (UP) at the start of the observation period, and final blood pressure (BP) and UP at completion of the observation period. Analyzed patients comprised 131 males and 117 females, with mean age of 47.8 years. Patients were observed for 44.2 months, and the parameters of final SBP, DBP, eGFR, and UP were 127.6 +/- 6.9 mmHg, 77.8 +/- 5.8 mmHg, 38.1 +/- 10.6 ml/min/1.73 m(2), and 1.08 +/- 0.57 g/gCr, respectively, where 42 patients progressed to CKD stage 5. Drugs of CCB, ACEI, and ARB types were administered to 93, 85, and 127 patients, respectively. In the multivariate analysis, extracted common prognostic factors included the baseline eGFR and final UP, the odds ratio of which was 0.876 (every increase by 1 ml/min of eGFR) and 2.229 (every increase by 1 g of UP), respectively. Among drugs in use, ACEI was an independent prognostic factor, whose odds ratio was 0.147. The present study suggests that ACEI is a prognostic factor independent of hypotensive action and UP in CKD patients.

Abnormalities in signaling pathways in diabetic nephropathy

Diabetic nephropathy (DN) is characterized by a plethora of signaling abnormalities that together ultimately result in the clinical and pathologic hallmarks of DN, namely progressive albuminuria followed by a gradual decline in glomerular filtration rate leading to kidney failure, and accompanied by podocyte loss, progressive glomerular sclerosis and, ultimately, progressive tubulointerstitial fibrosis. Over the past few years, the general understanding of the abnormalities in signaling pathways that lead to DN has expanded considerably. In this review, some of the important pathways that appear to be involved in driving this process are discussed, with special emphasis on newer findings and insights. Newer concepts regarding signaling changes in bradykinin, mTOR, JAK/STAT, MCP-1, VEGF, endothelial nitric oxide synthase, activated protein C and other pathways are discussed.

Mouse models of diabetic nephropathy

Diabetic nephropathy is a major cause of ESRD worldwide. Despite its prevalence, a lack of reliable animal models that mimic human disease has delayed the identification of specific factors that cause or predict diabetic nephropathy. The Animal Models of Diabetic Complications Consortium (AMDCC) was created in 2001 by the National Institutes of Health to develop and characterize models of diabetic nephropathy and other complications. This interim report and our online supplement detail the progress made toward that goal, specifically in the development and testing of murine models. Updates are provided on validation criteria for early and advanced diabetic nephropathy, phenotyping methods, the effect of background strain on nephropathy, current best models of diabetic nephropathy, negative models, and views of future directions. AMDCC investigators and other investigators in the field have yet to validate a complete murine model of human diabetic kidney disease. Nonetheless, the critical analysis of existing murine models substantially enhances our understanding of this disease process.

Effect of different antihypertensive treatments on Ras, MAPK and Akt activation in hypertension and diabetes

Ras GTPases function as transducers of extracellular signals regulating many cell functions, and they appear to be involved in the development of hypertension. In the present study, we have investigated whether antihypertensive treatment with ARBs (angiotensin II receptor blockers), ACEi (angiotensin-converting enzyme inhibitors) and diuretics induce changes in Ras activation and in some of its effectors [ERK (extracellular-signal-regulated kinase) and Akt] in lymphocytes from patients with hypertension without or with diabetes. ACEi treatment transiently reduced Ras activation in the first month of treatment, but diuretics induced a sustained increase in Ras activation throughout the 3 months of the study. In patients with hypertension and diabetes, ARB, ACEi and diuretic treatment increased Ras activation only during the first week. ACEi treatment increased phospho-ERK expression during the first week and also in the last 2 months of the study; however, diuretic treatment reduced phospho-ERK expression during the last 2 months of the study. In patients with hypertension and diabetes, antihypertensive treatments did not induce changes in phospho-ERK expression in lymphocytes. ACEi treatment reduced phospho-Akt expression in patients with hypertension and diabetes only in the first month of treatment. In conclusion, these findings show that antihypertensive treatments with ACEi, and diuretics to a lesser extent, modify Ras activation and some of its signalling pathways, although in different directions, whereas ARBs do not appear to have any influence on Ras signalling pathways.

Role of PPARgamma in renoprotection in Type 2 diabetes: molecular mechanisms and therapeutic potential

DN (diabetic nephropathy) is a chronic disease characterized by proteinuria, glomerular hypertrophy, decreased glomerular filtration and renal fibrosis with loss of renal function. DN is the leading cause of ESRD (end-stage renal disease), accounting for millions of deaths worldwide. TZDs (thiazolidinediones) are synthetic ligands of PPARgamma (peroxisome-proliferator-activated receptor gamma), which is involved in many important physiological processes, including adipose differentiation, lipid and glucose metabolism, energy homoeostasis, cell proliferation, inflammation, reproduction and renoprotection. A large body of research over the past decade has revealed that, in addition to their insulin-sensitizing effects, TZDs play an important role in delaying and preventing the progression of chronic kidney disease in Type 2 diabetes. Although PPARgamma activation by TZDs is in general considered beneficial for the amelioration of diabetic renal complications in Type 2 diabetes, the underlying mechanism(s) remains only partially characterized. In this review, we summarize and discuss recent findings regarding the renoprotective effects of PPARgamma in Type 2 diabetes and the potential underlying mechanisms.

The kallikrein-kinin system in health and in diseases of the kidney

Since kallikrein was discovered as a vasodilatory substance in human urine, the kallikrein-kinin system (KKS) has been considered to play a physiological role in controlling blood pressure. Gene targeting experiments in mice in which the KKS has been inactivated to varying degrees have, however, questioned this role, because basal blood pressures are not altered. Rather, these experiments have shown that the KKS has a different and important role in preventing changes associated with normal senescence in mice, and in reducing the nephropathy and accelerated senescence-associated phenotypes induced in mice by diabetes. Other experiments have shown that the KKS suppresses mitochondrial respiration, partly by nitric oxide and prostaglandins, and that this suppression may be a key to understanding how the KKS influences senescence-related diseases. Here we review the logical progression and experimental data leading to these conclusions, and discuss their relevance to human conditions.

Insulin-like growth factor-1 receptor expression masks the antiinflammatory and glucose uptake capacity of insulin in vascular smooth muscle cells

OBJECTIVE

Insulin resistance of vascular smooth muscle cells (VSMCs) has been linked to accelerated atherosclerosis in diabetes; however, the effects of insulin on VSMCs remain controversial. Most VSMC insulin receptors are sequestered into insulin-insensitive hybrids with insulin-like growth factor-1 receptors (IGF1Rs). Thus we hypothesized that regulation of IGF1R expression may impact cellular insulin sensitivity.

METHODS AND RESULTS

IGF1R expression was increased in aortas from diabetic mice. IGF1R overexpression in VSMCs impaired insulin-induced Akt phosphorylation. Conversely, IGF1R downregulation by siRNA allowed assembly of insulin holoreceptors, enhanced insulin-induced phosphorylation of its receptor, Akt, Erk1/2, and further augmented insulin-induced glucose uptake. IGF1R downregulation uncovered an insulin-induced reduction in activation of NF-kappaB and inhibition of MCP-1 upregulation in response to TNF-alpha.

CONCLUSIONS

Downregulation of IGF1R increases the fraction of insulin receptors organized in holoreceptors, which leads to enhanced insulin signaling and unmasks potential antiinflammatory properties of insulin in VSMCs. Therefore, IGF1R, which is susceptible to feedback regulation by its own ligand, may represent a novel target for interventions designed to treat insulin resistance in the vasculature.

New insights into the mechanisms of fibrosis and sclerosis in diabetic nephropathy

Progression of diabetic nephropathy (DN) is manifested by gradual scarring of both the renal glomerulus and tubulointerstitial region. Over the past several years, the general understanding of the pathogenic factors that lead to renal fibrosis in DN has expanded considerably. In this review, some of the important factors that appear to be involved in driving this fibrosing process are discussed, with special emphasis on newer findings and insights. It is now clear that multiple cell types in the kidney contribute to progressive fibrosis in DN. New concepts about bradykinin, TGF-beta and eNOS signaling as well as JAK/STAT activation and the central role of inflammation in both glomerular and tubulointerstitial fibrosis are discussed.

Systemic and local effects of angiotensin II blockade in experimental diabetic nephropathy

INTRODUCTION

Our objective was to evaluate the effect of blocking the renin-angiotensin system (RAS) on the expression of transforming growth factor-beta 1 (TGF-beta1), platelet derived growth factor-B (PDGF-B), tumour necrosis factor-alpha (TNF-alpha) and vascular endothelial growth factor (VEGF) in diabetic kidney glomeruli.

MATERIALS AND METHOD

1) Uninephrectomised streptozotocin induced diabetic rats were treated during eight months with vehicle (CD) or irbesartan (ID). Uninephrectomised non-diabetic rats were used as control group (ND). Protein urinary excretion and morphological renal damage were analysed. Glomerular expression of TGF-beta1, PDGF-B, VEGF and TNF-alpha were evaluated by Western blot and Immunohistochemistry. 2) Isolated glomeruli of diabetic rats were incubated 24-hours in the presence of different doses of irbesartan. Glomerular expression of TGF-beta1, PDGF-B, TNF-alpha and VEGF were determined by Western blot.

RESULTS

ND and ID presented lower renal injury and proteinuria than CD (p<0.05). Glomerular expression of TGF-beta1, PDGF-B, TNF-alpha and VEGF were similar in ND and ID, but lower than in CD (p<0.05). In addition, in isolated diabetic rat glomeruli, irbesartan reduced the content of all these factors.

CONCLUSION

Systemic and local administration of irbesartan lowers glomerular expression of TGF-beta1, PDGF-B, VEGF and TNF-alpha. These data suggest that part of the effect of lowering the expression of these growth factors and cytokines is due to a direct blockade of glomerular RAS.

Renal and metabolic disorders depend on the renin-angiotensin system in Lyon hypertensive rats associated with diabetes

BACKGROUND

In Lyon genetically hypertensive (LH) rats with diabetes, the effects of angiotensin converting enzyme (ACE) inhibition with perindopril on the prevention of dyslipidemia and proteinuria were evaluated by comparison with a nonspecific antihypertensive treatment.

METHODS

Diabetes was induced in 2-day-old male LH rats by intraperitoneal injection of streptozotocin (75 mg/kg). Glucose tolerance (glucose 2 g/kg by gavage), blood pressure (BP), plasma lipids, and urinary protein excretion were studied in: (i) untreated diabetic LH rats, (ii) diabetic LH rats treated from 8 to 16 weeks of age with oral perindopril at a low dose (0.01 mg/kg/day), (iii) similar rats treated with oral perindopril for the same duration at a high dose (1 mg/kg/day), and (iv) similar rats treated for the same duration with a triple therapy regimen consisting of hydralazine, hydrochlorothiazide, and reserpine (75, 15, and 0.75 mg/kg/day, respectively).

RESULTS

The neonatal administration of streptozotocin in LH rats increased nonfasting glycemia and induced a marked glucose intolerance which was accompanied by further increases in BP, plasma cholesterol, and urinary protein excretion. None of the treatments was able to modify glucose tolerance in diabetic LH rats. The low dose of perindopril was ineffective in the prevention of hypertension, dyslipidemia, and proteinuria in diabetic LH rats, while the high dose of perindopril normalized the BP, reduced the plasma lipids, and lowered the proteinuria. However, in spite of significant reduction in BP, the triple therapy failed to improve dyslipidemia and proteinuria; on the contrary, the therapy worsened these two conditions.

CONCLUSIONS

In diabetic LH rats, only ACE inhibition is of benefit to the kidney and lipidemia, thereby demonstrating that antihypertensive regimens may differ in their capacity to protect the target organs and lipid metabolism in a diabetic setting.

Activation of peroxisome proliferator-activated receptor-gamma by curcumin blocks the signaling pathways for PDGF and EGF in hepatic stellate cells

During hepatic fibrogenesis, reduction in the abundance of peroxisome proliferator-activated receptor-gamma (PPARgamma) is accompanied by activation of mitogenic signaling for platelet-derived growth factor (PDGF) and epidermal growth factor (EGF) in hepatic stellate cells (HSCs), the major effector cells. We previously reported that curcumin, the yellow pigment in curry, interrupted PDGF and EGF signaling, stimulated PPARgamma gene expression, and enhanced its activity, leading to inhibition of cell proliferation of activated HSC in vitro and in vivo. The aim of this study was to elucidate the underlying mechanisms. We hypothesized that the enhancement of PPARgamma activity by curcumin might result in the interruption of PDGF and EGF signaling. Our experiments demonstrated that curcumin, with different treatment strategies, showed different efficiencies in the inhibition of PDGF- or EGF-stimulated HSC proliferation. Further experiments observed that curcumin dose dependently reduced gene expression of PDGF and EGF receptors (ie, PDGF-betaR and EGFR), which required PPARgamma activation. The activation of PPARgamma by its agonist suppressed pdgf-betar and egfr expression in HSC. In addition, curcumin reduced the phosphorylation levels of PDGF-betaR and EGFR, as well as their downstream signaling cascades, including ERK1/2 and JNK1/2. Moreover, activation of PPARgamma induced gene expression of glutamate-cysteine ligase, the rate-limiting enzyme in de novo synthesis of the major intracellular antioxidant, glutathione. De novo synthesis of glutathione was required for curcumin to suppress pdgf-betar and egfr expression in activated HSCs. Our results collectively demonstrated that enhancement of PPARgamma activity by curcumin interrupted PDGF and EGF signaling in activated HSCs by reducing the phosphorylation levels of PDGF-betaR and EGFR, and by suppressing the receptor gene expression. These results provide novel insights into the mechanisms of curcumin in the inhibition of HSC activation and the suppression of hepatic fibrogenesis.

Pharmacological blockade of B2-kinin receptor reduces renal protective effect of angiotensin-converting enzyme inhibition in db/db mice model

Diabetic nephropathy (DN) can be delayed by the use of angiotensin-converting enzyme inhibitors (ACEi). The mechanisms of ACEi renal protection are not univocal. To investigate the impact of bradykinin B(2) receptor (B2R) activation during ACE inhibition, type II diabetic mice (C57BLKS db/db) received for 20 wk: 1) ACEi (ramipril) alone, 2) ACEi + HOE-140 (a specific B2R antagonist), 3) HOE-140 alone, or 4) no treatment. The development of DN, defined by an increase in albuminuria and glomerulosclerosis, was largely prevented by ACEi treatment (albuminuria: 980 +/- 130 vs. 2,160 +/- 330 mg/g creatinine; mesangial area: 22.5 +/- 0.5 vs. 27.6 +/- 0.3%). The protective effect of ramipril was markedly attenuated by B2R blockade (albuminuria: 2,790 +/- 680 mg/g creatinine; mesangial area: 30.4 +/- 1.1%), whereas HOE-140 alone significantly increased albuminuria. Despite such benefits, glomerular filtration rate remained unchanged, probably because of the combination of the hypotensive effect of diabetes in this model and the renal hemodynamic action of ramipril. Finally, the renal protective effect of ACEi was associated with a marked decrease in glomerular overexpression of insulin-like growth factor-1 (IGF-1) and transforming growth factor-beta pathways, but also in advanced glycation end product receptors and lipid peroxidation assessed by 4-hydroxy-2-nonenal (4-HNE) adducts. Concomitant blockade of B2R partly restored glomerular overexpression of IGF-1 receptor beta and 4-HNE complexes. These results support the critical role of B2R activation in the mediation of ACEi renal protection against DN and provide the rationale to examine the benefit of B2R activation by itself as a new therapeutic approach for DN.