Bradykinin inhibition of EGF- and PDGF-induced DNA synthesis in human fibroblasts

Differential Expression of Kinin Receptors in Human Wet and Dry Age-Related Macular Degeneration Retinae

Kinins are vasoactive peptides and mediators of inflammation, which signal through two G protein-coupled receptors, B1 and B2 receptors (B1R, B2R). Recent pre-clinical findings suggest a primary role for B1R in a rat model of wet age-related macular degeneration (AMD). The aim of the present study was to investigate whether kinin receptors are differentially expressed in human wet and dry AMD retinae. The cellular distribution of B1R and B2R was examined by immunofluorescence and in situ hybridization in post-mortem human AMD retinae. The association of B1R with inflammatory proteins (inducible nitric oxide synthase (iNOS) and vascular endothelial growth factor A (VEGFA)), fibrosis markers and glial cells was also studied. While B2R mRNA and protein expression was not affected by AMD, a significant increase of B1R mRNA and immunoreactivity was measured in wet AMD retinae when compared to control and dry AMD retinae. B1R was expressed by Müller cells, astrocytes, microglia and endothelial/vascular smooth muscle cells, and colocalized with iNOS and fibrosis markers, but not with VEGFA. In conclusion, the induction and upregulation of the pro-inflammatory and pro-fibrotic kinin B1R in human wet AMD retinae support previous pre-clinical studies and provide a clinical proof-of-concept that B1R represents an attractive therapeutic target worth exploring in this retinal disease.

Angiotensin II Mediates High Glucose-Induced TGF-β1 and Fibronectin Upregulation in HPMC through Reactive Oxygen Species

Objective

To demonstrate the presence of an independent renin–angiotensin system (RAS) in the peritoneum and to determine the role of locally produced angiotensin (Ang) II in high glucose-induced upregulation of transforming growth factor (TGF)-β1 and fibronectin by human peritoneal mesothelial cells (HPMC).

Methods

In cultured HPMC, the expression of mRNAs for angiotensinogen, angiotensin-converting enzyme (ACE), Ang II type 1 receptor (AT1), and TGF-β1 was evaluated by real-time polymerase chain reaction; ACE, AT1, and fibronectin proteins by Western blot analysis; and Ang I, Ang II, and TGF-β1 proteins by ELISA. Dichlorofluorescein (DCF)-sensitive cellular reactive oxygen species (ROS) were measured by fluorometry.

Results

HPMC constitutively expressed all the components of RAS, and 50 mmol/L D-glucose (high glucose) significantly increased angiotensinogen, ACE, and AT1 mRNAs and ACE, AT1, and Ang II proteins. Ang II increased TGF-β1 and fibronectin protein expression and DCF-sensitive cellular ROS. Losartan prevented Ang II-induced increase in cellular ROS. Both losartan and captopril inhibited high glucose-induced upregulation of TGF-β1 and fibronectin expression in HPMC in a dose-dependent manner. Antioxidant catalase and NADPH oxidase inhibitor diphenyleneiodinium effectively inhibited Ang II-induced TGF-β1 and fibronectin protein expression.

Conclusions

The present data demonstrate that HPMC constitutively express RAS, that Ang II produced by HPMC mediates high glucose-induced upregulation of TGF-β1 and fibronectin expression, and that Ang II-induced TGF-β1 and fibronectin expression in HPMC is mediated by NADPH oxidase-dependent ROS. These data suggest that locally produced Ang II and ROS in the peritoneum may be potential therapeutic targets in peritoneal fibrosis during long-term peritoneal dialysis.

Avoidance of apoptotic death via a hyperploid salvage survival pathway after platinum treatment in high grade serous carcinoma cell line models

The alkylating agent platinum is first-line chemotherapy treatment for high-grade serous carcinomas (HGSC) of tubal-ovarian origin. Platinum compounds cause DNA damage and induce apoptotic cell death in the bulk tumor population. However, subpopulations of tumor cells may exhibit diverging behaviors from the bulk tumor due to an alternate stress response that diverts tumor cells from apoptotic death. In this study, we identified a salvage survival pathway in which G2-arrested tumor cells bypassed apoptosis and progressed through aberrant mitotic events to then emerge as a distinct subpopulation of viable large hyperploid cells but with uncertain long-term propagation potential. Platinum-induced large hyperploid cells were flow sorted and showed rare regrowth capacity as compared to their more proficiently regenerating non-hyperploid counterparts. However, detailed time-lapse microscopy provided direct evidence that these hyperploid cells were mitotically active and could divide successfully to produce viable daughter cells. The hyperploid survival response was observed across different cell lines and utilization of this survival pathway was dependent on the strength of the G2-M checkpoint. Conceivably, this salvage survival strategy may contribute to increased genomic diversity of the regenerating tumor cell line through a coupled hyperploidization and de-polyploidization process that may be relevant for drug resistance.

Angiotensin II Type 1 Receptor Blocker, Fimasartan, Reduces Vascular Smooth Muscle Cell Senescence by Inhibiting the CYR61 Signaling Pathway

BACKGROUND AND OBJECTIVES

Angiotensin II (Ang II) has been suggested to accelerate vascular senescence, however the molecular mechanism(s) remain unknown.

METHODS

We cultured human coronary artery smooth muscle cells (hCSMCs) and treated Ang II and/or fimasartan. Or we transfected adenoviral vectors expressing CYR61 (Ad-CYR61) or antisense CYR61 (Ad-As-CYR61). Cellular senescence was evaluated senescence-associated β-galactosidase (SA-β-gal) assay. The molecular mechanisms were investigated real-time PCR and western blots.

RESULTS

SA-β-gal-positive cells significantly increased in Ang II-treated hCSMCs (5.77±1.43-fold compared with the control). The effect of Ang II was significantly attenuated by pretreatment with the Ang II type 1 receptor blocker, fimasartan (2.00±0.92-fold). The expression of both p53 and p16 senescence regulators was significantly increased by Ang II (p53: 1.39±0.17, p16: 1.19±0.10-fold vs. the control), and inhibited by fimasartan. Cysteine-rich angiogenic protein 61 (CYR61) was rapidly induced by Ang II. Compared with the control, Ad-CYR61-transfected hCSMCs showed significantly increased SA-β-gal-positive cells (3.47±0.65-fold). Upon transfecting Ad-AS-CYR61, Ang II-induced senescence (3.74±0.23-fold) was significantly decreased (1.77±0.60-fold). p53 expression by Ang II was significantly attenuated by Ad-AS-CYR61, whereas p16 expression was not regulated. Ang II activated ERK1/2 and p38 MAPK, which was significantly blocked by fimasartan. ERK and p38 inhibition both regulated Ang II-induced CYR61 expression. However, p53 expression was only regulated by ERK1/2, whereas p16 expression was only attenuated by p38 MAPK.

CONCLUSIONS

Ang II induced vascular senescence by the ERK/p38 MAPK-CYR61 pathway and ARB, fimasartan, protected against Ang II-induced vascular senescence.

Targeting vasoactive peptides for managing calcific aortic valve disease

Calcific aortic valve disease (CAVD) represents a spectrum of disease spanning from milder degrees of calcification of valve leaflets, i.e., aortic sclerosis, to severe calcification i.e., aortic stenosis (AS) with hemodynamic instability. The prevalence of CAVD is increasing rapidly due to the aging of the population, being up to 2.8% among patients over 75 years of age. Even without significant aortic valve stenosis, aortic sclerosis is associated with a 50% increased risk of myocardial infarction and death from cardiovascular causes. To date, there is no pharmacological treatment available to reverse or hinder the progression of CAVD. So far, the cholesterol-lowering therapies (statins) and renin-angiotensin system (RAS) blocking drugs have been the major pharmacological agents investigated for treatment of CAVD. Especially angiotensin receptor blockers (ARB)s and angiotensin convertase enzyme inhibitors (ACEI)s, have been under active investigation in clinical trials, but have proven to be unsuccessful in slowing the progression of CAVD. Several studies have suggested that other vasoactive hormones, including endothelin and apelin systems are also associated with development of AS. In the present review, we discuss the role of vasoactive factors in the pathogenesis of CAVD as novel pharmacological targets for the treatment of aortic valve calcification. Key messages Vasoactive factors are involved in the progression of calcific aortic valve disease. Endothelin and renin-angiotensin systems seem to be most prominent targets for therapeutic interventions in the view of valvular pathogenesis. Circulating vasoactive factors may provide targets for diagnostic tools of calcified aortic valve disease.

Feasibility of fluorescence energy transfer system for imaging the renoprotective effects of aliskiren in diabetic mice

Introduction:

We investigated the feasibility of using a fluorescence resonance energy transfer system to image enzymatic activity in order to evaluate the effects of aliskiren (a direct renin inhibitor) on diabetic nephropathy.

Materials and methods:

First, we induced diabetes in C57BL/6J mice using streptozotocin, then treated them with either aliskiren (25 mg/kg/day) or the angiotensin type 1 receptor blocker valsartan (15 mg/kg/day) for four weeks. Finally, we utilized renin fluorescence resonance energy transfer substrate to assess renin activity.

Results:

Renin activity was much higher in the kidneys of diabetic mice compared to those of the non-diabetic control mice. While aliskiren inhibited this activity, valsartan did not. We noted that production of reactive oxygen species intensified and the bioavailability of nitric oxide diminished in the glomeruli of diabetic mice. Aliskiren and valsartan significantly ameliorated these effects. They suppressed glomerular production of reactive oxygen species and urinary albumin excretion. In fact, urinary albumin excretion in diabetic mice treated with aliskiren or valsartan was lower than that in untreated diabetic mice. Furthermore, aliskiren and valsartan significantly reduced glomerular permeability by maintaining the glomerular endothelial surface layer.

Conclusion:

Fluorescence resonance energy transfer could provide a new tool for evaluating tissue and plasma enzymatic activity.

Increased urinary Smad3 is significantly correlated with glomerular hyperfiltration and a reduced glomerular filtration rate and is a new urinary biomarker for diabetic nephropathy

Background

Diabetic nephropathy is one of the major microvascular complications of diabetes. We investigated the association between urinary Smad3 (usmad3) levels, glomerular hyperfiltration, and the development of nephropathy in patients with type 2 diabetes mellitus (T2DM).

Methods

The usmad3 level was determined by enzyme-linked immunosorbent assay in 245 well-characterised patients with T2DM and 82 healthy control subjects. The associations of the usmad3 level with glomerular hyperfiltration, glucose and lipid profiles, and renal function were evaluated.

Results

The usmad3 level was significantly higher in patients with diabetes than in the control group. The level in the hyperfiltration group was higher than that in the normofiltering group, regardless of whether patients were in the normoalbuminuric or the proteinuria groups. Pearson’s correlation analysis suggested that the usmad3 level was significantly correlated with age, systolic blood pressure, fasting plasma glucose, insulin, C-peptide, glycated haemoglobin, and estimated glomerular filtration rate (eGFR). A multiple linear stepwise regression analysis revealed that usmad3 levels in patients with T2DM and an eGFR ≥90 ml/min/1.73 m² were independently and positively correlated with eGFR, whereas in patients with T2DM and eGFR <90 ml/min/1.73 m², the levels were independently and negatively correlated with eGFR.

Conclusions

The usmad3 level was significantly correlated with biphasic changes in the GFR (both glomerular hyperfiltration and reduced eGFR) in patients with T2DM. Usmad3 may serve as a novel marker for hyperfiltration and for screening patients with T2DM for nephropathy.

Kinin-B1 and B2 receptor activity in proliferation and neural phenotype determination of mouse embryonic stem cells

The kinins bradykinin and des-arg(9) -bradykinin cleaved from kininogen precursors by kallikreins exert their biological actions by stimulating kinin-B2 and B1 receptors, respectively. In vitro models of neural differentiation such as P19 embryonal carcinoma cells and neural progenitor cells have suggested the involvement of B2 receptors in neural differentiation and phenotype determination; however, the involvement of B1 receptors in these processes has not been established. Here, we show that B1 and B2 receptors are differentially expressed in mouse embryonic E14Tg2A stem cells undergoing neural differentiation. Proliferation and differentiation assays, performed in the presence of receptor subtype-selective agonists and antagonists, revealed that B1 receptor activity is required for the proliferation of embryonic and differentiating cells as well as for neuronal maturation at later stages of differentiation, while the B2 receptor acts on neural phenotype choice, promoting neurogenesis over gliogenesis. Besides the elucidation of bradykinin functions in an in vitro model reflecting early embryogenesis and neurogenesis, this study contributes to the understanding of B1 receptor functions in this process.

Involvement of heparan sulfate in the renoprotective effects of imidapril, an angiotensin-converting enzyme inhibitor, in diabetic db/db mice

We investigated the renoprotective effects of imidapril hydrochloride ((-)-(4 S)-3-[(2 S)-2-[[(1 S)-1-ethoxycarbonyl-3-phenylpropyl] amino] propionyl]-1-methyl-2-oxoimidazolidine-4-carboxylic acid hydrochloride, imidapril), an angiotensin-converting enzyme inhibitor, in a diabetic animal model. We used BKS.Cg-+Lepr(db)/+Lepr(db) (db/db) mice, a genetic animal model of obese type 2 diabetes. Diabetic db/db mice suffered from glomerular hyperfiltration, albuminuria and hypoalbuminemia. Oral administration of 5 mg/kg/day of imidapril for 3 weeks suppressed renal hyperfiltration, reduced albuminuria and normalized hypoalbuminemia. Imidapril did not influence body weights, blood pressure or blood glucose concentrations in db/db mice. Urinary excretion of heparan sulfate (HS) in non-treated 11-week-old db/db mice was significantly lower than that in age-matched non-diabetic db/+m mice. HS is a component of HS proteoglycans, which are present in glomerular basement membranes and glycocalyx of cell surfaces. Reduced urinary HS excretion indicated glomerular HS loss in db/db mice. Imidapril increased urinary excretion of HS to concentrations observed in db/+m mice, indicating that imidapril prevented the loss of renal HS. These results suggest that imidapril ameliorates renal hyperfiltration and loss of renal contents of HS. Improvement of filtration function and maintenance of HS, which is an important structural component of glomeruli, may contribute to renoprotective effects of imidapril.

Heterogeneous nuclear ribonucleoproteins F and K mediate insulin inhibition of renal angiotensinogen gene expression and prevention of hypertension and kidney injury in diabetic mice

AIMS/HYPOTHESIS

We investigated whether heterogeneous nuclear ribonucleoproteins F and K (hnRNP F, hnRNP K) mediate insulin inhibition of renal Agt expression and prevention of hypertension and kidney injury in an Akita mouse model of type 1 diabetes.

METHODS

Adult male Akita mice (12 weeks old) were treated with insulin implants and killed at week 16. Untreated non-Akita littermates served as controls. The effects of insulin on blood glucose, systolic BP (SBP), renal proximal tubular cell (RPTC) gene expression and interstitial fibrosis were studied. We also examined immortalised rat RPTCs stably transfected with control plasmid or with plasmid containing rat Agt promoter in vitro.

RESULTS

Insulin treatment normalised blood glucose levels and SBP, inhibited renal AGT expression but enhanced hnRNP F, hnRNP K and angiotensin-converting enzyme-2 expression, attenuated renal hypertrophy and glomerular hyperfiltration and decreased urinary albumin/creatinine ratio, as well as AGT and angiotensin II levels, in Akita mice. In vitro, insulin inhibited Agt but stimulated Hnrnpf and Hnrnpk expression in high-glucose media via p44/42 mitogen-activated protein kinase signalling in RPTCs. Transfection with Hnrnpf or Hnrnpk small interfering RNAs prevented insulin inhibition of Agt expression in RPTCs.

CONCLUSIONS/INTERPRETATION

These data indicate that insulin prevents hypertension and attenuates kidney injury, at least in part, through suppressing renal Agt transcription via upregulation of hnRNP F and hnRNP K expression in diabetic Akita mice. HnRNP F and hnRNP K may be potential targets in the treatment of hypertension and kidney injury in diabetes.

Perfused culture of gingival fibroblasts in a degradable/polar/hydrophobic/ionic polyurethane (D-PHI) scaffold leads to enhanced proliferation and metabolic activity

Periodontal diseases cause the breakdown of the tooth-supporting gingival tissue. In treatments aimed at gingival tissue regeneration, tissue engineering is preferred over the common treatments such as scaling. Perfused (dynamic) culture has been shown to increase cell growth in tissue-engineered scaffolds. Since gingival tissues are highly vascularized, it was desired to investigate the influence of perfusion on the function of human gingival fibroblasts (HGF) when cultured in a degradable/polar/hydrophobic/ionic polyurethane scaffold during the early culture phase (4weeks) of engineering gingival tissues. It was observed that the growth of HGF was continuous over 28days in dynamic culture (3-fold increase, p<0.05), while it was reduced after 14days in static culture (i.e. no flow condition). Cell metabolic activity, as measured by a WST-1 assay, and total protein production show that HGF were in different metabolic states in the dynamic vs. static cultures. Observations from scanning electron microscopy and type I collagen (Col I) production measured by Western blotting suggest that medium perfusion significantly promoted collagen production in HGF after the first 4weeks of culture (p<0.05). The different proliferative and metabolic states for HGF in the perfused scaffolds suggest a different cell phenotype which may favour tissue regeneration.

Cardinal Role of the Intrarenal Renin-Angiotensin System in the Pathogenesis of Diabetic Nephropathy

Diabetes mellitus is one of the most prevalent diseases and is associated with increased incidence of structural and functional derangements in the kidneys, eventually leading to end-stage renal disease in a significant fraction of afflicted individuals. The renoprotective effects of renin-angiotensin system (RAS) blockade have been established; however, the mechanistic pathways have not been fully elucidated. In this review article, the cardinal role of an activated RAS in the pathogenesis of diabetic nephropathy (DN) is discussed with a focus on 4 themes: (1) introduction to RAS cascade, (2) intrarenal RAS in diabetes, (3) clinical outcomes of RAS blockade in DN, and (4) potential of urinary angiotensinogen as an early biomarker of intrarenal RAS status in DN. This review article provides a mechanistic rational supporting the hypothesis that an activated intrarenal RAS contributes to the pathogenesis of DN and that urinary angiotensinogen levels provide an index of intrarenal RAS activity.

Adenosine A(2B) receptor-mediated VEGF induction promotes diabetic glomerulopathy

Diabetic nephropathy ranks as the most devastating kidney disease worldwide. It characterizes in the early onset by glomerular hypertrophy, hyperfiltration and mesangial expansion. Experimental models show that overproduction of vascular endothelial growth factor (VEGF) is a pathogenic condition for podocytopathy; however the mechanisms that regulate this growth factor induction are not clearly identified. We determined that the adenosine A(2B) receptor (A(2B)AR) mediates VEGF overproduction in ex vivo glomeruli exposed to high glucose concentration, requiring PKCα and Erk1/2 activation. The glomerular content of A(2B)AR was concomitantly increased with VEGF at early stages of renal disease in streptozotocin-induced diabetic rats. Further, in vivo administration of an antagonist of A(2B)AR in diabetic rats blocked the glomerular overexpression of VEGF, mesangial cells activation and proteinuria. In addition, we also determined that the accumulation of extracellular adenosine occurs in glomeruli of diabetic rats. Correspondingly, raised urinary adenosine levels were found in diabetic rats. In conclusion, we evidenced that adenosine signaling at the onset of diabetic kidney disease is a pathogenic event that promotes VEGF induction.

Augmented intrarenal and urinary angiotensinogen in hypertension and chronic kidney disease

Activated intrarenal renin-angiotensin system plays a cardinal role in the pathogenesis of hypertension and chronic kidney disease. Angiotensinogen is the only known substrate for renin, which is the rate-limiting enzyme of the renin-angiotensin system. Because the levels of angiotensinogen are close to the Michaelis-Menten constant values for renin, angiotensinogen levels as well as renin levels can control the renin-angiotensin system activity, and thus, upregulation of angiotensinogen leads to an increase in the angiotensin II levels and ultimately increases blood pressure. Recent studies using experimental animal models have documented the involvement of angiotensinogen in the intrarenal renin-angiotensin system activation and development of hypertension. Enhanced intrarenal angiotensinogen mRNA and/or protein levels were observed in experimental models of hypertension and chronic kidney disease, supporting the important roles of angiotensinogen in the development and the progression of hypertension and chronic kidney disease. Urinary excretion rates of angiotensinogen provide a specific index of the intrarenal renin-angiotensin system status in angiotensin II-infused rats. Also, a direct quantitative method has been developed recently to measure urinary angiotensinogen using human angiotensinogen enzyme-linked immunosorbent assay. These data prompted us to measure urinary angiotensinogen in patients with hypertension and chronic kidney disease, and investigate correlations with clinical parameters. This short article will focus on the role of the augmented intrarenal angiotensinogen in the pathophysiology of hypertension and chronic kidney disease. In addition, the potential of urinary angiotensinogen as a novel biomarker of the intrarenal renin-angiotensin system status in hypertension and chronic kidney disease will be also discussed.

Increased susceptibility to hypertensive renal disease in streptozotocin-treated diabetic rats is not modulated by salt intake

AIMS/HYPOTHESIS

In early type 1 diabetes mellitus, renal salt handling is dysregulated, so that the glomerular filtration rate becomes inversely proportional to salt intake. The salt paradox occurs in both humans and rats and, with low salt intake, results in diabetic hyperfiltration. We tested whether increased salt intake could reduce the susceptibility to injury of non-clipped kidneys in diabetic rats with pre-existing Goldblatt hypertension.

METHODS

Male Long-Evans rats were made hypertensive and half were then made diabetic. Blood glucose was maintained at ~20-25 mmol/l by insulin implants. One half of each received only the salt in normal chow (1% by weight) and the other half received added salt in drinking water to equal 2.7% by weight of food intake. Weekly 24 h blood pressure records were acquired by telemetry during the 4-month experiment.

RESULTS

Systolic blood pressure was not affected by diabetes or increased salt intake, alone or together. Autoregulation was highly efficient in the non-clipped kidney of both intact and diabetic rats. Histological examination showed minor injury in the clipped kidney, which did not differ among groups. The non-clipped kidney showed extensive pressure-dependent glomerular and vascular injury in both intact and diabetic rats.

CONCLUSIONS/INTERPRETATION

The relationship between pressure and injury was shifted toward lower blood pressure in diabetic rats, indicating that diabetes increased the susceptibility of the kidney to injury despite preservation of autoregulation. The increased susceptibility was not affected by high salt intake in the diabetic rats, thus disproving the hypothesis.

Bradykinin type-2 receptor expression correlates with age and is subjected to transcriptional regulation

Accumulating work in experimental animals suggests that bradykinin (BK) exerts cardioprotective effects via bradykinin type-2 receptors (BK-2Rs). In human end-stage heart failure, BK-2Rs are significantly downregulated by mechanisms that have remained elusive. Heart tissues from idiopathic dilated cardiomyopathy (IDC; n = 7), coronary heart disease (CHD; n = 6), and normal patients (n = 6) were analyzed by RT-PCR, SSCP, and Western blotting. In normal and IDC hearts, BK-2R expression increased with age, with a lower relative increase in IDC hearts. BK-2R mRNA and protein levels showed a positive linear correlation, suggesting transcriptional regulation. Two known BK-2R promoter polymorphisms, −58T/C and −9/+9, were found to be present in the study population. The allelic frequencies for the C-allele in −58T/C were 0.58 in normal and CHD hearts and 0.81 in IDC hearts. Furthermore, the allelic frequencies for the −9 and +9 alleles were 0.42 and 0.58 in normal hearts and 0.64 and 0.36 in IDC hearts, respectively. All analyzed CHD hearts were homozygous for the −9 allele. Thus, the expression of cardioprotective BK-2Rs in human hearts is increased with age in normal and IDC hearts and may be regulated on the transcriptional level. Moreover, comparison of normal subjects and patients with failing hearts revealed different allelic frequencies in each of two known BK-2R gene polymorphisms.

The platelet-derived growth factor system in renal disease: an emerging role of endogenous inhibitors

The platelet-derived growth factor (PDGF) family consists of four isoforms which are secreted as homodimers (PDGF-AA, PDGF-BB, PDGF-CC and PDGF-DD) or heterodimers (PDGF-AB), and two receptor chains (PDGFR-α and -β). All members of the PDGF system are constitutively or inducibly expressed in renal cells and are involved in the regulation of cell proliferation and migration, the accumulation of extracellular matrix proteins and the secretion of pro- and anti-inflammatory mediators. Particular roles have been identified in mediating mesangioproliferative changes, renal interstitial fibrosis and glomerular angiogenesis. Different endogenous inhibitors of PDGF-induced biological responses exist which affect the activation/deactivation of PDGF isoforms, the activity of the PDGFRs, or which block downstream signaling pathways of the autophosphorylated PDGFRs. The novel endogenous inhibitor nephroblastoma overexpressed gene (NOV, CCN3) reduces PDGF-induced cell proliferation and is downregulated by PDGF isoforms itself. Among all identified inhibitors only few "true" PDGF antagonists have been identified. A better understanding of these inhibitors may aid in the design of novel therapeutic approaches to PDGF-mediated diseases.

Angiotensin-converting enzyme (ACE) 2 overexpression ameliorates glomerular injury in a rat model of diabetic nephropathy: a comparison with ACE inhibition

The reduced expression of angiotensin-converting enzyme (ACE) 2 in the kidneys of animal models and patients with diabetes suggests ACE2 involvement in diabetic nephrology. To explore the renoprotective effects of ACE2 overexpression, ACE inhibition (ACEI) or both on diabetic nephropathy and the potential mechanisms involved, 50 Wistar rats were randomly divided into a normal group that received an injection of sodium citrate buffer and a diabetic model group that received an injection of 60 mg/kg streptozotocin. Eight wks after streptozotocin injection, the diabetic rats were divided into no treatment group, adenoviral (Ad)-ACE2 group, Ad-green flurescent protein (GFP) group, ACEI group receiving benazepril and Ad-ACE2 + ACEI group. Four wks after treatment, physical, biochemical, and renal functional and morphological parameters were measured. An experiment in cultured glomerular mesangial cells was performed to examine the effects of ACE2 on cellular proliferation, oxidative stress and collagen IV synthesis. In comparison with the Ad-GFP group, the Ad-ACE2 group exhibited reduced systolic blood pressure, urinary albumin excretion, creatinine clearance, glomeruli sclerosis index and renal malondialdehyde level; downregulated transforming growth factor (TGF)-β1, vascular endothelial growth factor (VEGF) and collagen IV protein expression; and increased renal superoxide dismutase activity. Ad-ACE2 and ACEI had similar effects, whereas combined use of Ad-ACE2 and ACEI offered no additional benefits. ACE2 transfection attenuated angiotensin (Ang) II-induced glomerular mesangial cell proliferation, oxidative stress and collagen IV protein synthesis. In conclusion, ACE2 exerts a renoprotective effect similar to that of ACEI treatment. Decreased renal Ang II, increased renal Ang-(1-7) levels, and inhibited oxidative stress were the possible mechanisms involved.

New pharmacological treatments for improving renal outcomes in diabetes

Diabetic nephropathy is the most common and most rapidly growing cause of end-stage renal failure in developed countries. Diabetic nephropathy results from complex interactions between genetic, metabolic and hemodynamic factors. Improvements in our understanding of the pathogenesis of fibrosis associated with diabetic kidney disease have led to the identification of several novel targets for the treatment of diabetic nephropathy. Albuminuria is a useful clinical marker of diabetic nephropathy, as it can be used to predict a decline in renal function. A reduction in albuminuria might not, however, be reflective of a protective effect of therapies focused on ameliorating renal fibrosis. Although new strategies for slowing down the progression of several types of renal disease have emerged, the challenge of arresting the relentless progression of diabetic nephropathy remains. In this Review, we discuss novel pharmacological approaches that aim to improve the renal outcomes of diabetic nephropathy, including the use of direct renin inhibitors and statins. We also discuss the promise of using antifibrotic agents to treat diabetic nephropathy. The need for novel biomarkers of diabetic nephropathy is also highlighted.

New insights into the renoprotective actions of the renin inhibitor aliskiren in experimental renal disease

The renin-angiotensin-aldosterone system (RAAS) has a central function in the regulation of blood pressure. Aliskiren, the first direct renin inhibitor to be approved for the treatment of hypertension, blocks the RAAS at its point of activation. As renin inhibition acts at the top of the RAAS cascade, this mechanism has been proposed to offer advantages over existing modes of RAAS blockade. The RAAS is also considered to be a major factor in the pathogenesis of many renal diseases, especially diabetic nephropathy (DN), the main cause of end-stage renal disease. Existing therapies to block the RAAS slow the progression of DN, but they do not halt the disease. Therefore, more effective modes of interventions are needed. Studies to determine the efficacy of aliskiren in human renal disease are in progress. This review summarizes in vivo studies in which the efficacy of aliskiren was tested in experimental models of renal disease, and presents in vitro studies that provide insights into the possible mechanisms by which aliskiren confers renoprotection in animals. These works are discussed in the framework of the intrarenal RAAS and suggest that aliskiren may act by unique renoprotective mechanisms.

Urinary transforming growth factor beta1 in children and adolescents with congenital solitary kidney

The aim of the study was to assess urinary transforming growth factor beta1 (TGF beta1) level in children and adolescents with congenital solitary kidney (CSK), depending on estimated glomerular filtration rate (eGFR) and compensatory overgrowth of the kidney. The study group (I) consisted of 65 children and young adults, 0.5-22 years of age (median 10.0 years) with CSK and no other urinary defects. The control group (C) contained 44 healthy children and adolescents, 0.25-21 years old (median 10.3 years). We used an enzyme-linked immunosorbent assay (ELISA) to determine the urinary level of TGF beta1, the Jaffe method to assess creatinine concentration, and the Schwartz formula to estimate GFR. Kidney length was measured while the patient was in a supine position, and overgrowth (O%) was calculated with reference to the charts. Urinary TGF beta1 level in CSK patients was more than twice as high as that in controls (P < 0.05). Also, eGFR in patients with CSK exceeded the values in the control group (P < 0.01). Compensatory overgrowth of the solitary kidney was found (median 19.44%). Urinary TGF beta1 concentration was positively correlated with eGFR (r = 0.247, P < 0.05), uric acid concentration (r = 0.333, P < 0.01), and percentage of overgrowth (r = 0.338, P < 0.01) and body mass index (BMI) centile (r = 0.274, P < 0.05). We concluded that, although proteinuria and progressive renal insufficiency is not observed in patients with CSK during childhood, the renal haemodynamic changes are present and may be a risk factor for impairment of renal function and hypertension in future life.

Vitamin D and diabetic nephropathy

Diabetic nephropathy (DN) is the most common renal complication of diabetes mellitus and a leading cause of end-stage renal disease. The renin-angiotensin system (RAS) is a major mediator of progressive renal injury in DN, and RAS inhibitors have been used as the mainstay treatment for DN. One major problem limiting the efficacy of the RAS inhibitors is the compensatory renin increase caused by disruption of renin feedback inhibition. Vitamin D negatively regulates the RAS by suppressing renin expression and thus plays a renoprotective role in DN. Diabetic vitamin D receptor-null mutant mice develop more severe renal injuries because of more robust RAS activation. Combination therapy with an RAS inhibitor and a vitamin D analogue markedly ameliorates renal injuries due to blockade of the compensatory renin increase by the analogue. These most recent data demonstrate that vitamin D and its analogues have renoprotective and therapeutic potentials in DN through targeting the RAS.

Combination therapy with AT1 blocker and vitamin D analog markedly ameliorates diabetic nephropathy: blockade of compensatory renin increase

The renin-angiotensin system (RAS) plays a critical role in the development of diabetic nephropathy, and blockade of the RAS is currently used for treatment of diabetic nephropathy. One major problem for the current RAS inhibitors is the compensatory renin increase, which reduces the efficacy of RAS inhibition. We have shown that vitamin D exerts renoprotective actions by transcriptionally suppressing renin. Here we demonstrated that combination therapy with an AT1 receptor blocker and a vitamin D analog markedly ameliorated renal injury in the streptozotocin (STZ)-induced diabetes model due to the blockade of the compensatory renin rise by the vitamin D analog, leading to more effective RAS inhibition. STZ-treated diabetic DBA/2J mice developed progressive albuminuria and glomerulosclerosis within 13 weeks, accompanied by increased intrarenal production of angiotensin (Ang) II, fibronection, TGF-beta, and MCP-1 and decreased expression of slit diaphragm proteins. Treatment of the diabetic mice with losartan or paricalcitol (19-nor-1,25-dihydroxyvitamin D(2), an activated vitamin D analog) alone moderately ameliorated kidney injury; however, combined treatment with losartan and paricalcitol completely prevented albuminuria, restored glomerular filtration barrier structure, and markedly reduced glomerulosclerosis. The combined treatment suppressed the induction of fibronection, TGF-beta, and MCP-1 and reversed the decline of slit diaphragm proteins nephrin, Neph-1, ZO-1, and alpha-actinin-4. These were accompanied by blockade of intrarenal renin and Ang II accumulation induced by hyperglycemia and losartan. These data demonstrate that inhibition of the RAS with combination of vitamin D analogs and RAS inhibitors effectively prevents renal injury in diabetic nephropathy.

Urinary mRNA expression of ACE and ACE2 in human type 2 diabetic nephropathy

AIMS/HYPOTHESIS

The interplay of ACE and type 2 ACE (ACE2) has been recognised as playing an important role in the tissue renin-angiotensin system within the kidney. In the present study, we measured urinary mRNA expression of ACE and ACE2 in patients with type 2 diabetic nephropathy.

METHODS

We studied 50 patients with diabetic nephropathy: 26 were being treated by ACE inhibitor (ACEI) alone (ACEI group), the other 24 by ACEI and angiotensin-receptor blocker (ARB) (ACEI+ARB group). mRNA expression of ACE and ACE2 was measured by real-time quantitative RT-PCR at 0 and 12 weeks. All patients were then followed for 56 weeks.

RESULTS

Proteinuria correlated significantly with urinary ACE (r=0.454, p=0.001) and ACE2 expression (r=0.651, p<0.001). Urinary ACE2 expression correlated with estimated GFR (r= -0.289, p=0.042). In the ACEI group, there was a significant inverse correlation between the rate of GFR decline and urinary ACE2 expression at baseline (r= -0.423, p=0.031) as well as at 12 weeks (r= -0.395, p=0.046). In contrast, there was no significant correlation between the rate of GFR decline and urinary ACE2 expression at baseline or at 12 weeks in the ACEI+ARB group. The rate of GFR decline did not correlate with the baseline urinary ACE expression of either group.

CONCLUSION/INTERPRETATION

There was a relationship between urinary mRNA expression of ACE2 and the degree of proteinuria. The physiological implication and possibility of clinical application of quantifying urinary ACE2 expression require further study.

Angiotensin converting enzyme 2 in the kidney

1

Angiotensin converting enzyme 2 (ACE2) is an important homeostatic component of the renin angiotensin system (RAS). ACE2 both degrades the vasoconstrictor, angiotensin II and generates the potent vasodilator peptide, angiotensin 1–7. These actions counterbalance those of ACE.

2

ACE2 is highly expressed in the healthy kidney, particularly in the proximal tubules, where it colocalizes with ACE and angiotensin receptors.

3

Kidney disease and subtotal nephrectomy is associated with a reduction in renal ACE2 expression, possibly facilitating the damaging effects of angiotensin II in the failing kidney. Acquired or genetic ACE2 deficiency also appears to exacerbate renal damage and albuminuria in experimental models, supporting this hypothesis.

4

ACE2 also has an important role in blood pressure control. Many models of hypertension are associated with reduced ACE2 expression. Although ACE2 KO animals are normotensive, in states associated with activation of the RAS, ACE2 overexpression improves blood pressure control and reduces angiotensin responsiveness.

Overexpression of angiotensinogen increases tubular apoptosis in diabetes

The intrarenal renin-angiotensin system (RAS) plays an important role in the progression of diabetic nephropathy. We have previously reported that mice overexpressing angiotensinogen in renal proximal tubular cells (RPTC) develop hypertension, albuminuria, and renal injury. Here, we investigated whether activation of the intrarenal RAS contributes to apoptosis of RPTC in diabetes. Induction of diabetes with streptozotocin in these transgenic mice led to significant increases in BP, albuminuria, RPTC apoptosis, and proapoptotic gene expression compared with diabetic nontransgenic littermates. Insulin and/or RAS blockers markedly attenuated these changes. Hydralazine prevented hypertension but not albuminuria, RPTC apoptosis, or proapoptotic gene expression. In vitro, high-glucose medium significantly increased apoptosis and caspase-3 activity in rat immortalized RPTC overexpressing angiotensinogen compared with control cells, and these changes were prevented by insulin and/or RAS blockers. In conclusion, intrarenal RAS activation and high glucose may act in concert to increase tubular apoptosis in diabetes, independent of systemic hypertension.

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

Diabetic nephropathy (DN) is associated with increased oxidative stress, overexpression and activation of growth factor receptors, including those for transforming growth factor-β1 (TGF-β-RII), platelet-derived growth factor (PDGF-R), and insulin-like growth factor (IGF1-R). These pathways are believed to represent pathophysiological determinants of DN. Beyond perfect glycemic control, angiotensin-converting enzyme inhibitors (ACEI) are the most efficient treatment to delay glomerulosclerosis. Since their mechanisms of action remain uncertain, we investigated the effect of ACEI on the glomerular expression of these growth factor pathways in a model of streptozotocin-induced diabetes in rats. The early phase of diabetes was found to be associated with an increase in glomerular expression of IGF1-R, PDGF-R, and TGF-β-RII and activation of IRS1, Erk 1/2, and Smad 2/3. These changes were significantly reduced by ACEI treatment. Furthermore, ACEI stimulated glutathione peroxidase activity, suggesting a protective role against oxidative stress. ACEI decreased ANG II production but also increased bradykinin bioavailability by reducing its degradation. Thus the involvement of the bradykinin pathway was investigated using coadministration of HOE-140, a highly specific nonpeptidic B2-kinin receptor antagonist. Almost all the previously described effects of ACEI were abolished by HOE-140, as was the increase in glutathione peroxidase activity. Moreover, the well-established ability of ACEI to reduce albuminuria was also prevented by HOE-140. Taken together, these data demonstrate that, in the early phase of diabetes, ACEI reverse glomerular overexpression and activation of some critical growth factor pathways and increase protection against oxidative stress and that these effects involve B2-kinin receptor activation.

The intrarenal renin-angiotensin system: from physiology to the pathobiology of hypertension and kidney disease

In recent years, the focus of interest on the role of the renin-angiotensin system (RAS) in the pathophysiology of hypertension and organ injury has changed to a major emphasis on the role of the local RAS in specific tissues. In the kidney, all of the RAS components are present and intrarenal angiotensin II (Ang II) is formed by independent multiple mechanisms. Proximal tubular angiotensinogen, collecting duct renin, and tubular angiotensin II type 1 (AT1) receptors are positively augmented by intrarenal Ang II. In addition to the classic RAS pathways, prorenin receptors and chymase are also involved in local Ang II formation in the kidney. Moreover, circulating Ang II is actively internalized into proximal tubular cells by AT1 receptor-dependent mechanisms. Consequently, Ang II is compartmentalized in the renal interstitial fluid and the proximal tubular compartments with much higher concentrations than those existing in the circulation. Recent evidence has also revealed that inappropriate activation of the intrarenal RAS is an important contributor to the pathogenesis of hypertension and renal injury. Thus, it is necessary to understand the mechanisms responsible for independent regulation of the intrarenal RAS. In this review, we will briefly summarize our current understanding of independent regulation of the intrarenal RAS and discuss how inappropriate activation of this system contributes to the development and maintenance of hypertension and renal injury. We will also discuss the impact of antihypertensive agents in preventing the progressive increases in the intrarenal RAS during the development of hypertension and renal injury.

Lovastatin induces the expression of bradykinin type 2 receptors in cultured human coronary artery endothelial cells

Cardioprotective bradykinin type-2 receptors (BK-2Rs) are downregulated in the myocardial endothelium of both human and rat failing hearts. Statins are cardioprotective drugs that reduce the level of plasma cholesterol but also exert cholesterol-independent pleiotropic effects. Here we examined the effect of lovastatin on BK-2R expression in cultured human coronary artery endothelial cells. The effect of lovastatin on the expression of BK receptors in human coronary artery endothelial cells (HCAECs) was examined by real-time PCR, Western blot analysis and immunocytochemistry. Lovastatin induced a time- and concentration-dependent increase in both BK-2R and BK-1R mRNA expression in the cultured HCAECs. Also, the number of functional BK-2Rs capable of inducing BK-mediated NO production and cGMP signaling was increased in the lovastatin-treated HCAECs. Mevalonate, the direct metabolite of HMG-CoA reductase, reversed the effect of lovastatin. Furthermore, lovastatin inhibited Rho activation and a selective inhibitor of Rho-associated kinases, Y-27632, induced a similar increase in BK-2R expression as lovastatin. In contrast, a specific inhibitor of COX-2, NS398, significantly inhibited the lovastatin-induced expression of BK-2Rs. Here we show for the first time that lovastatin induces the expression of BK-2Rs in cultured human coronary artery endothelial cells through a novel cholesterol-independent pleiotropic mechanism that involves RhoA kinase inhibition and COX-2 activation. Thus, reported beneficial effects of statins in cardiovascular diseases may be partly mediated by an increased expression of cardioprotective BK-2Rs in the endothelial cells of the coronary tree. Moreover, the use of COX-2 inhibitors may affect the level of endothelial BK-2Rs in a negative fashion.

Association of somatic and N-domain angiotensin-converting enzymes from Wistar rat tissue with renal dysfunction in diabetes mellitus

Diabetes mellitus (DM) is characterised by alterations in the intrarenal renin-angiotensin system (RAS). Insulin treatment may reverse these changes by an unknown mechanism. We aimed to verify the association between somatic ACE with 136 kDa (sACE) and N-domain ACE with 69 kDa (nACE) from Wistar (W) rat tissue with DM. Three groups were studied: control (CT), insulin treated diabetic (DT) and untreated (D). ACE activity was determined using Hippuryl-His-Leu and Z-Phe-His-Leu as substrates. In D group, urine ACE activity increased for both substrates when compared with CT and DT, despite the decreased activity of renal tissues. Immunostaining of renal tissue demonstrated that ACE is more strongly expressed in the proximal-tubule of D than in the same nephron portion in the other groups. Angiotensin (Ang) 1-7 and Ang II are less expressed in DT group when compared with CT and D. Ang II levels decreased in the D and DT groups showed when compared to the control. Ang 1-7 was detected in all studied groups with low levels in DT. The modulation of angiotensin peptides suggests that sACE, nACE, ACE 2 and NEP could have important functions in renal RAS regulation through a counter-regulatory mechanism to protect the kidney in diabetes mellitus.

Increased expression of profibrotic neutral endopeptidase and bradykinin type 1 receptors in stenotic aortic valves

AIMS

In aortic stenosis (AS), adverse remodelling of the valves may depend on altered local regulation of pro- and antifibrotic systems. We have recently shown that angiotensin-converting enzyme (ACE), which generates profibrotic angiotensin II and inactivates antifibrotic bradykinin (BK), is upregulated in stenotic aortic valves. Here, we analyse the expression of neutral endopeptidase (NEP), another profibrotic and BK-degrading enzyme, and of BK receptors in aortic valves in AS.

METHODS AND RESULTS

Stenotic aortic valves (n = 86) were obtained at valve replacement surgery and control valves (n = 13) at cardiac transplantation. Expression levels of NEP and BK type 1 and 2 receptors (BK-1R and BK-2R) in aortic valves and in isolated valvular myofibroblasts were analysed by real-time PCR and immunohistochemistry, and NEP activity was quantified by autoradiography. NEP, BK-1R, and BK-2R mRNA levels were higher in stenotic than in non-stenotic valves (P < 0.05 for each) and the respective proteins localized to valvular endothelial cells and myofibroblasts. In stenotic valves, the proteolytic activity of NEP was significantly increased (4.5-fold, P < 0.001), and tumour necrosis factor-alpha induced the expression of NEP in cultured myofibroblasts. Finally, treatment of cultured myofibroblasts with an NEP inhibitor (phosphoramidon) downregulated the expression of profibrotic transforming growth factor-beta1, whereas addition of BK decreased the expression of collagens I and III which was reversed by a BK-2R antagonist.

CONCLUSION

NEP activity is increased in stenotic aortic valves in parallel with increased expression of BK-receptors. The upregulation of NEP and BK-1R have the potential to promote valvular fibrosis and remodelling while the increase in BK-2R may represent a compensatory antifibrotic response. These findings add novel pathogenic insight and raise potential new therapeutic targets in AS.

The increased angiotensin II (type 1) receptor density in myocardium of type 2 diabetic patients is prevented by blockade of the renin-angiotensin system

AIMS/HYPOTHESIS

The angiotensin II (type 1) (AT1) receptor mediates many biological effects of the renin-angiotensin system (RAS), leading to remodelling of cardiac tissue. The present study was designed to analyse changes in the function and expression of the AT1 receptor as principal effector of the RAS in myocardium from type 2 diabetic patients compared with non-diabetic myocardium as control. In addition, we determined the effect of treatment with ACE inhibitors or AT1 receptor blockers on expression levels of the receptor in diabetic patients.

METHODS

Gene expression of the AT1 receptor was analysed by quantitative RT-PCR and protein expression was determined by immunoblot analysis in human right atrial myocardium. We investigated functional coupling of the receptors by measuring contractility in isolated trabeculae stimulated with increasing concentrations of angiotensin II.

RESULTS

Diabetic myocardium showed a significant increase in protein expression (170 +/- 16% of control) and median mRNA expression (186% of control) of the AT1 receptor. The additional receptors were functionally coupled, resulting in a stronger inotropic response upon stimulation with angiotensin II (89 +/- 5.5% vs 29 +/- 1.6% in controls), whereas receptor affinity was similar in both groups. However, myocardium from diabetic patients treated with ACE inhibitors or AT1 receptor blockers showed no increase in AT1 receptor expression.

CONCLUSIONS/INTERPRETATION

AT1 receptor expression in myocardium of type 2 diabetic patients is dynamic, depending on the level of glycaemic control and the activity of the RAS. These findings could at least in part explain the strong therapeutic benefit of RAS inhibition in diabetic patients.

Glomerular localization and expression of Angiotensin-converting enzyme 2 and Angiotensin-converting enzyme: implications for albuminuria in diabetes

Angiotensin-converting enzyme 2 (ACE2) expression has been shown to be altered in renal tubules from diabetic mice. This study examined the localization of ACE and ACE2 within the glomerulus of kidneys from control (db/m) and diabetic (db/db) mice and the effect of chronic pharmacologic ACE2 inhibition. ACE2 co-localized with glomerular epithelial cell (podocyte) markers, and its localization within the podocyte was confirmed by immunogold labeling. ACE, by contrast, was seen only in glomerular endothelial cells. By immunohistochemistry, in glomeruli from db/db mice, strong ACE staining was found more frequently than in control mice (db/db 64.6 +/- 6.3 versus db/m 17.8 +/- 3.4%; P < 0.005). By contrast, strong ACE2 staining in glomeruli from diabetic mice was less frequently seen than in controls (db/db 4.3 +/- 2.4 versus db/m 30.6 +/- 13.6%; P < 0.05). For investigation of the significance of reduced glomerular ACE2 expression, db/db mice were treated for 16 wk with a specific ACE2 inhibitor (MLN-4760) alone or combined with telmisartan, a specific angiotensin II type 1 receptor blocker. At the end of the study, glomerular staining for fibronectin, an extracellular matrix protein, was increased in both db/db and db/m mice that were treated with MLN-4760. Urinary albumin excretion (UAE) increased significantly in MLN-4760-treated as compared with vehicle-treated db/db mice (743 +/- 200 versus 247 +/- 53.9 microg albumin/mg creatinine, respectively; P < 0.05), and the concomitant administration of telmisartan completely prevented the increase in UAE associated with the ACE2 inhibitor (161 +/- 56; P < 0.05). It is concluded that ACE2 is localized in the podocyte and that in db/db mice glomerular expression of ACE2 is reduced whereas glomerular ACE expression is increased. The finding that chronic ACE2 inhibition increases UAE suggests that ACE2, likely by modulating the levels of glomerular angiotensin II via its degradation, may be a target for therapeutic interventions that aim to reduce albuminuria and glomerular injury.

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.

Heterogeneous Nuclear Ribonucleoprotein K Modulates Angiotensinogen Gene Expression in Kidney Cells

The present studies aimed to identify the 70-kDa nuclear protein that binds to an insulin-responsive element in the rat angiotensinogen gene promoter and to define its action on angiotensinogen gene expression. Nuclear proteins were isolated from rat kidney proximal tubular cells and subjected to two-dimensional electrophoresis. The 70-kDa nuclear protein was detected by Southwestern blotting and subsequently identified by mass spectrometry, which revealed that it was identical to 65-kDa heterogeneous nuclear ribonucleoprotein K (hnRNP K). hnRNP K bound to the insulin-responsive element of the rat angiotensinogen gene was revealed by a gel mobility shift assay and chromatin immunoprecipitation assay. hnRNP K inhibited angiotensinogen mRNA expression and promoter activity. In contrast, hnRNP K down-expression by small interference RNA enhanced angiotensinogen mRNA expression. Moreover, hnRNP K interacted with hnRNP F in pulldown and co-immunoprecipitation assays. Co-transfection of hnRNP K and hnRNP F further suppressed angiotensinogen mRNA expression. Finally, in vitro and in vivo studies demonstrated that high glucose increases and insulin inhibits hnRNP K expression in rat kidney proximal tubular cells. In conclusion, our experiments revealed that hnRNP K is a nuclear protein that binds to the insulin-responsive element of the rat angiotensinogen gene promoter and modulates angiotensinogen gene transcription in the kidney.

Impact of renin angiotensin system modulation on the hyperfiltration state in type 1 diabetes

The initial stages of diabetic nephropathy are characterized by glomerular hyperfiltration and hypertension, processes that have been linked to initiation and progression of renal disease. Renin angiotensin system (RAS) blockade is commonly used to modify the hyperfiltration state and delay progression of renal disease. Despite this therapy, many patients progress to ESRD, suggesting heterogeneity in the response to RAS modulation. The role of the RAS in the hyperfiltration state in adolescents with uncomplicated type 1 diabetes was examined, segregated on the basis of the presence of hyperfiltration. Baseline renal hemodynamic function was characterized in 22 patients. Eleven patients exhibited glomerular hyperfiltration (GFR>or=135 ml/min), and in the remaining 11 patients, the GFR was <130 ml/min. Renal hemodynamic function was assessed in response to a graded angiotensin II (AngII) infusion during euglycemic conditions and again after 21 d of angiotensin-converting enzyme (ACE) inhibition with enalapril. AngII infusion under euglycemic conditions resulted in a significant decline in GFR and renal plasma flow in the hyperfiltration group but not in the normofiltration group. After ACE inhibition, GFR fell but did not normalize in the hyperfiltration group; the normofiltration group showed no change. These data show significant differences in renal hemodynamic function between hyperfiltering and normofiltering adolescents with type 1 diabetes at baseline, after AngII infusion and ACE inhibition. The response to ACE inhibition and AngII in hyperfiltering patients suggests that vasodilation may complement RAS activation in causing the hyperfiltration state. The interaction between glomerular vasoconstrictors and vasodilators requires examination in future studies.

Effect of rhPDGF-BB on bone turnover during periodontal repair

PURPOSE

Growth factors such as platelet-derived growth factor (PDGF) exert potent effects on wound healing including the regeneration of periodontia. Pyridinoline cross-linked carboxyterminal telopeptide of type I collagen (ICTP) is a well-known biomarker of bone turnover, and as such is a potential indicator of osseous metabolic activity. The objective of this study was to evaluate the release of the ICTP into the periodontal wound fluid (WF) following periodontal reconstructive surgery using local delivery of highly purified recombinant human PDGF (rhPDGF)-BB.

METHODS

Forty-seven human subjects at five treatment centres possessing chronic severe periodontal disease were monitored longitudinally for 24 weeks following PDGF regenerative surgical treatment. Severe periodontal osseous defects were divided into one of three groups and treated at the time of surgery with either: beta-tricalcium phosphate (TCP) osteoconductive scaffold alone (active control), beta-TCP+0.3 mg/ml of rhPDGF-BB, or beta-TCP+1.0 mg/ml of rhPDGF-BB. WF was harvested and analysed for local ICTP levels by radioimmunoassay. Statistical analysis was performed using analysis of variance and an area under the curve analysis (AUC).

RESULTS

The 0.3 and 1.0 mg/ml PDGF-BB treatment groups demonstrated increases in the amount of ICTP released locally for up to 6 weeks. There were statistically significant differences at the week 6 time point between beta-TCP carrier alone group versus 0.3 mg/ml PDGF-BB group (p<0.05) and between beta-TCP alone versus the 1.0 mg/ml PDGF-BB-treated lesions (p<0.03). The AUC analysis revealed no statistical differences amongst groups.

CONCLUSION

This study corroborates the release of ICTP as a measure of active bone turnover following local delivery of PDGF-BB to periodontal osseous defects. The amount of ICTP released from the WF revealed an early increase for all treatment groups. Data from this study suggests that when PDGF-BB is delivered to promote periodontal tissue engineering of tooth-supporting osseous defects, there is a direct effect on ICTP released from the wound.

Effects of Blocking the Renin-Angiotensin System on Expression and Translocation of Protein Kinase C Isoforms in the Kidney of Diabetic Rats

BACKGROUND

High glucose and angiotensin II (Ang II) can activate protein kinase C (PKC) in diabetes mellitus. However, it is not clear which isoform of PKC is activated by glucose or Ang II. Our study focused on the effects of angiotensin blockade, using the angiotensin-converting enzyme inhibitor fosinopril, the Ang II receptor blocker irbesartan and their combination, on the expression and translocation of PKC isoforms alpha and betaII in the renal cortex and medulla in diabetes.

METHODS

Hyperglycemia was induced with streptozotocin and diabetic rats were randomized to 4 groups: diabetic control, irbesartan group (40 mg/kg daily), fosinopril group (40 mg/kg daily) and combination group (irbesartan plus fosinopril, 20 mg/kg daily, respectively); age-matched normal rats served as normal control. After 4 weeks, expression and translocation of PKC-alpha and -betaII in the renal cortex and medulla were assessed by immunohistochemistry and Western immunoblotting.

RESULTS

The expression of PKC-alpha in the membrane and cytosol fractions from the renal cortex was significantly higher in diabetic rats (276.83 +/- 32.44% in membrane, 149.04 +/- 23.42% in cytosol) than that in normal ones. The expression of PKC-betaII in the renal cortex of diabetic rats decreased significantly in the membrane (50.00 +/- 11.68%, p < 0.05) and remained unchanged in the cytosol (94.51 +/- 11.69%, p > 0.05) compared with normal controls. Treatment with irbesartan, fosinopril and their combination partially corrected the abnormalities mentioned above. For the expression of PKC-alpha and -betaII in the medulla, no difference was detected among the 5 groups.

CONCLUSION

The renin-angiotensin system was implicated in the pathogenesis of diabetic nephropathy by regulating the activation of PKC isoforms.

Treatment of severe pulmonary hypertension: a bradykinin receptor 2 agonist B9972 causes reduction of pulmonary artery pressure and right ventricular hypertrophy

Bradykinin is an important modulator of endothelial cell function and has also a powerful cardioprotective effect. Here we report that treatment of severely pulmonary hypertensive rats (that recapitulate several of the physiological and pathological characteristics of the human pulmonary vascular disease, including dramatic right ventricular hypertrophy, pericardial effusion and death) with a newly synthesized long-acting bradykinin B2 receptor agonist B9972 caused reduction of the pulmonary artery pressure (PAP=51+/-2.0 versus 68+/-2.8 of untreated animals) and of right ventricular hypertrophy (Rv/Lv+S=0.55+/-0.02 versus 0.73+/-0.03 of untreated rats) and activation of Akt. Long-term stimulation with B9972 in our animal model of SPH resulted in decreased expression of the B2 receptor in lung vasculature. Treatment with B9972 decreased the number of plexiform lesions in the lungs by inducing cell apoptosis in the obliterated vessels and by restoring caveolin-1 expression. B9972 also promoted eNOS activation. In vitro B9972 caused activation of caspase-3 as well as Erk and induction of prostacyclin production in rat pulmonary microvascular EC. Taken together our data suggest that a stable bradykinin B2 agonist B9972 demonstrates the capacity to reduce severe pulmonary hypertension, right ventricular hypertrophy and induce apoptosis of hyperproliferative cells in pre-capillary pulmonary arterioles.

Temporal renal expression of angiogenic growth factors and their receptors in experimental diabetes: role of the renin-angiotensin system

OBJECTIVE

It has been postulated that vascular endothelial growth factor (VEGF) plays a role in the progression of renal injury. However, the role of other angiogenic factors and their receptors, such as the angiopoietins and Tie2, and in particular their relation to renoprotective therapies, such as agents that interrupt the renin-angiotensin system, have not been studied in the context of diabetes-related renal injury.

DESIGN AND METHODS

Renal expression of VEGF, angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2) and their receptors, VEGF-R2 and Tie-2, were assessed using reverse transcription-polymerase chain reaction, immunohistochemistry and Western blotting, in control and streptozotocin diabetic rats, untreated or receiving the AT1 receptor antagonist, valsartan, or the AT2 receptor antagonist, PD123319.

RESULTS

Diabetes was associated with increased gene and protein expression of VEGF, VEGF-R2, Ang-1, Ang-2 and Tie-2. AT1 receptor antagonism attenuated gene expression of these cytokines and receptors, yet PD123319, which had no effect on blood pressure, reduced VEGF-R2 and Ang-1 gene expression and decreased VEGF, Ang-1 and Ang-2 protein levels.

CONCLUSIONS

In experimental diabetes, there is significant upregulation within the kidney of various angiogenic cytokines and their receptors. Furthermore, the effects of angiotensin II receptor blockade on these parameters is consistent with the VEGF-VEGF-R2 and angiopoietin-Tie-2 axes being modulated in the kidney by haemodynamic factors in the diabetic context.

Increased expression of bradykinin type-1 receptors in endothelium of intramyocardial coronary vessels in human failing hearts

In experimental animals, bradykinin type-1 receptors (BK-1Rs) are induced during inflammation and ischemia, and, by exerting either cardioprotective or cardiotoxic effects, they may contribute to the pathogenesis of heart failure. Nothing is known about the expression of BK-1Rs in human heart failure. Human heart tissue was obtained from excised hearts of patients undergoing cardiac transplantation (n = 13), due to idiopathic dilated cardiomyopathy (IDC; n = 7) or to coronary heart disease (CHD; n = 6), and from normal hearts (n = 6). The expression of BK-1Rs was analyzed by means of competitive RT-PCR, Western blot analysis, and immunohistochemistry. Expression of BK-1R mRNA was increased in both IDC (2.8-fold) and CHD (2.1-fold) hearts compared with normal hearts. The observed changes were verified at the protein level. Expression of BK-1Rs in failing hearts localized to the endothelium of intramyocardial coronary vessels and correlated with an increased expression of TNF-alpha in the vessel wall. Treatment of human coronary artery endothelial cells with TNF-alpha increases their BK-1R expression. These novel results show that BK-1Rs are induced in the endothelium of intramyocardial coronary vessels in failing human hearts and so may participate in the pathogenesis of heart failure.

Renin-angiotensin system blockade prevents the increase in plasma transforming growth factor beta 1, and reduces proteinuria and kidney hypertrophy in the streptozotocin-diabetic rat

INTRODUCTION

Combination therapy with angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) is used to improve renal outcome achieved by monotherapy in diabetic patients. In addition, interference with the renin-angiotensin system (RAS) reduced expression and excretion of transforming growth factor beta 1 (TGF-beta 1) in diabetic nephropathy. The aim of this study was to investigate the effects of interrupting the RAS by ACE inhibitor (ACE-I) or ARB monotherapy or by combination therapy on proteinuria, kidney hypertrophy and plasma TGF-beta 1 in diabetic rats.

MATERIALS AND METHODS

Forty-one male Wistar rats were allocated to five groups: 1 = control rats, 2 = diabetic rats (streptozotocin [STZ] 55 mg/kg), 3 = diabetic rats as above receiving enalapril (20 mg/kg/day), 4 = diabetic rats receiving losartan (80 mg/kg/day), 5 = diabetic rats receiving both losartan and enalapril. The study lasted 60 days.

RESULTS

Urinary protein excretion, kidney weight, serum ACE activity and plasma TGF-beta1 increased significantly in untreated diabetic rats compared with controls. Administration of losartan, enalapril, or both for 60 days prevented these changes. Furthermore, combined therapy for 30 days normalised urinary protein excretion, while monotherapy did not. Losartan inhibited serum ACE activity both in vivo and in vitro. Plasma TGF-beta 1 levels were positively correlated with blood glucose levels (r=0.4059) and with urinary protein excretion (r=0.3558).

CONCLUSIONS

Combination therapy with losartan and enalapril was more effective than monotherapy with either drug in achieving an early antiproteinuric response. Long-term treatment with losartan was as effective as the combined treatment, possibly due to a dual inhibitory effect on the RAS. The antiproteinuric effect may be related, in part, to reduced TGF-beta 1.