Nitric oxide in the kidney: functions and regulation of synthesis

The ureteric bud epithelium: morphogenesis and roles in metanephric kidney patterning

The mammalian metanephric kidney is composed of two epithelial components, the collecting duct system and the nephron epithelium, that differentiate from two different tissues -the ureteric bud epithelium and the nephron progenitors, respectively-of intermediate mesoderm origin. The collecting duct system is generated through reiterative ureteric bud branching morphogenesis, whereas the nephron epithelium is formed in a process termed nephrogenesis, which is initiated with the mesenchymal-epithelial transition of the nephron progenitors. Ureteric bud branching morphogenesis is regulated by nephron progenitors, and in return, the ureteric bud epithelium regulates nephrogenesis. The metanephric kidney is physiologically divided along the corticomedullary axis into subcompartments that are enriched with specific segments of these two epithelial structures. Here, we provide an overview of the major molecular and cellular processes underlying the morphogenesis and patterning of the ureteric bud epithelium and its roles in the cortico-medullary patterning of the metanephric kidney.

Endogenous female sex hormones delay the development of renal dysfunction in apolipoprotein E-deficient mice

Background

Hypercholesterolemia is a well-established risk factor for the development of kidney injury. Considering that female sex hormones may play a preventative role in both cardiovascular and renal diseases, the aim of the present study was to evaluate the effects of female sex hormones on hypercholesterolemia-induced renal dysfunction.

Methods

Apolipoprotein E-deficient (ApoE) and C57 control female mice underwent an ovariectomy (OVX) or sham surgery and after 2 months, creatinine clearance, uremia and proteinuria were determined. Renal oxidative stress and lipid deposition were also quantified. Values are presented as mean ± SEM. Statistical analyses were performed using Two-way ANOVA followed by Tukey’s post hoc test.

Results

Creatinine clearance (μL/min) was similar between C57 (171 ± 17) and ApoE (140 ± 26) mice underwent sham surgery. OVX resulted in a reduced glomerular filtration rate in both C57 (112 ± 8, ~ − 35%, p < 0.05) and ApoE (61 ± 10, ~ − 56%, p < 0.05) animals. Plasma levels of urea (mg/dL) were higher in both ApoE groups (Sham: 73 ± 7; OVX: 73 ± 8, p < 0.05) when compared to C57 animals (Sham: 49 ± 3; OVX: 60 ± 4), with no changes among ovariectomized groups. Proteinuria levels (mg/24 h) were similar between C57 (Sham: 25.1 ± 5.7; OVX: 33.7 ± 4.7) and ApoE sham animals (26.4 ± 3.5), however, 24-h urine protein excretion was augmented in ApoE OVX animals (49.6 ± 5.8, p < 0.05). Histological kidney analysis demonstrated that the absence of female sex hormones resulted in increased oxidative stress, which was more severe in ApoE mice (C57 Sham: 9.2 ± 0.4; C57 OVX: 22.9 ± 1.0; ApoE Sham: 13.9 ± 0.7; ApoE OVX: 34.0 ± 1.4 au x 10³, p < 0.05). As expected, ApoE mice presented higher lipid deposition, which was not affected by OVX (C57 Sham: 0 ± 0; C57 OVX: 0 ± 0; ApoE Sham: 6.8 ± 1.6; ApoE OVX: 5.2 ± 0.8% x 10⁻², p < 0.05). Ovariectomy resulted in a similar reduction in ER-α protein expression in the renal cortex (C57: 0.78 ± 0.04; ApoE: 0.81 ± 0.04 au, p < 0.05) when compared to sham animals (C57:1.00 ± 0.04; ApoE: 1.03 ± 0.03 au).

Conclusion

Taken together these data indicate that female sex hormones may delay hypercholesterolemia-induced renal dysfunction and emphasizes the importance of plasma cholesterol control in post-menopausal women.

Female sex hormones protect against salt-sensitive hypertension but not essential hypertension

Initial studies found that female Dahl salt-sensitive (DS) rats exhibit greater blood pressure (BP) salt sensitivity than female spontaneously hypertensive rats (SHR). On the basis of the central role played by NO in sodium excretion and BP control, we further tested the hypothesis that blunted increases in BP in female SHR will be accompanied by greater increases in renal inner medullary nitric oxide synthase (NOS) activity and expression in response to a high-salt (HS) diet compared with DS rats. Gonad-intact and ovariectomized (OVX) female SHR and DS rats were placed on normal salt (NS; 0.4% salt) or HS (4% salt) diet for 2 wk. OVX did not alter BP in SHR, and HS diet produced a modest increase in BP. OVX significantly increased BP in DS rats on NS; HS further increased BP in all DS rats, although OVX had a greater increase in BP. Renal inner medullary NOS activity, total NOS3 protein, and NOS3 phosphorylated on serine residue 1177 were not altered by salt or OVX in either strain. NOS1 protein expression, however, significantly increased with HS only in SHR, and this corresponded to an increase in urinary nitrate/nitrite excretion. SHR also exhibit greater NOS1 and NOS3 protein expression than DS rats. These data indicate that female sex hormones offer protection against HS-mediated elevations in BP in DS rats but not SHR. We propose that the relative resistance to HS-mediated increases in BP in SHR is related to greater NOS expression and the ability to increase NOS1 protein expression compared with DS rats.

Nitric oxide in the normal kidney and in patients with diabetic nephropathy

Nitric oxide (NO) is a gas with biological and regulatory properties, produced from arginine by the way of nitric oxide synthases (NOS), and with a very short half-life (few seconds). A "coupled" NOS activity leads to NO generation, whereas its uncoupling produces the reactive oxygen species peroxynitrite (ONOO(-)). Uncoupling is usually due to inflammation, oxidative stress, decreased cofactor availability, or excessive NO production. Competitive inhibitors of NO production are post-translationally methylated arginine residues in proteins, which are constantly released into the circulation. NO availability is altered in many clinical conditions associated with vascular dysfunction, such as diabetes mellitus. The kidney plays an important role in body NO homeostasis. This article provides an overview of current literature, on NO production/availability, with a focus on diabetic nephropathy. In diabetes, NO availability is usually decreased (with exception of the early, hyper filtration phase of nephropathy in Type 1 diabetes), and it could constitute a factor of the generalized vasculopathy present in diabetic nephropathy. NO generation in Type 2 diabetes with nephropathy is inversely associated with the dimethyl-arginine concentrations, which are therefore important modulators of NO synthesis independently from the classic stimulatory pathways (such as the insulin effect). A disturbed NO metabolism is present in diabetes associated with nephropathy. Although modulation of NO production is not yet a common therapeutical strategy, a number of yet experimental compounds need to be tested as potential interventions to treat the vascular dysfunction and nephropathy in diabetes, as well as in other diseased states. Finally, in diabetic nephropathy NO deficiency may be associated to that of hydrogen sulfide, another interesting gaseous mediator which is increasingly investigated.

Renal response to L-arginine in diabetic rats. A possible link between nitric oxide system and aquaporin-2

The aim of this study was to evaluate whether L-Arginine (L-Arg) supplementation modifies nitric oxide (NO) system and consequently aquaporin-2 (AQP2) expression in the renal outer medulla of streptozotocin-diabetic rats at an early time point after induction of diabetes. Male Wistar rats were divided in four groups: Control, Diabetic, Diabetic treated with L-Arginine and Control treated with L-Arginine. Nitric oxide synthase (NOS) activity was estimated by [¹⁴C] L-citrulline production in homogenates of the renal outer medulla and by NADPH-diaphorase staining in renal outer medullary tubules. Western blot was used to detect the expression of AQP2 and NOS types I and III; real time PCR was used to quantify AQP2 mRNA. The expression of both NOS isoforms, NOS I and NOS III, was decreased in the renal outer medulla of diabetic rats and L-Arg failed to prevent these decreases. However, L-Arg improved NO production, NADPH-diaphorase activity in collecting ducts and other tubular structures, and NOS activity in renal homogenates from diabetic rats. AQP2 protein and mRNA were decreased in the renal outer medulla of diabetic rats and L-Arg administration prevented these decreases. These results suggest that the decreased NOS activity in collecting ducts of the renal outer medulla may cause, at least in part, the decreased expression of AQP2 in this model of diabetes and constitute additional evidence supporting a role for NO in contributing to renal water reabsorption through the modulation of AQP2 expression in this pathological condition. However, we cannot discard that another pathway different from NOS also exists that links L-Arg to AQP2 expression.

Oxidative stress induces claudin-2 nitration in experimental type 1 diabetic nephropathy

Renal complications in diabetes are severe and may lead to renal insufficiency. Early alterations in tight junction (TJ) proteins in diabetic nephropathy (DN) have not been explored and the role of oxidative stress in their disassembly has been poorly characterized. We investigated the expression and distribution of TJ proteins: claudin-5 in glomeruli (GL), occludin and claudin-2 in proximal tubules (PTs), and ZO-1 and claudin-1, -4, and -8 in distal tubules (DTs) of rats 21 days after streptozotocin injection. Redox status along the nephron segments was evaluated. Diabetes increased kidney injury molecule-1 expression. Expression of sodium glucose cotransporters (SGLT1 and SGLT2) and facilitative glucose transporter (GLUT2) was induced. Increased oxidative stress was present in GL and PTs and to a lesser extent in DTs (measured by superoxide production and PKCβ2 expression), owing to NADPH oxidase activation and uncoupling of the endothelial nitric oxide synthase-dependent pathway. Claudin-5, occludin, and claudin-2 expression was decreased, whereas claudin-4 and -8 expression increased. ZO-1 was redistributed from membrane to cytosol. Increased nitration of tyrosine residues in claudin-2 was found, which might contribute to decrement of this protein in proximal tubule. In contrast, occludin was not nitrated. We suggest that loss of claudin-2 is associated with increased natriuresis and that loss of glomerular claudin-5 might explain early presence of proteinuria. These findings suggest that oxidative stress is related to alterations in TJ proteins in the kidney that are relevant to the pathogenesis and progression of DN and for altered sodium regulation in diabetes.

Homocysteine in renovascular complications: hydrogen sulfide is a modulator and plausible anaerobic ATP generator

Homocysteine (Hcy) is a non-protein amino acid derived from dietary methionine. High levels of Hcy, known as hyperhomocysteinemia (HHcy) is known to cause vascular complications. In the mammalian tissue, Hcy is metabolized by transsulfuration enzymes to produce hydrogen sulfide (H2S). H2S, a pungent smelling gas was previously known for its toxic effects in the central nervous system, recent studies however has revealed protective effects in a variety of diseases including hypertension, diabetes, inflammation, atherosclerosis, and renal disease progression and failure. Interestingly, under stress conditions including hypoxia, H2S can reduce metabolic demand and also act as a substrate for ATP production. This review highlights some of the recent advances in H2S research as a potential therapeutic agent targeting renovascular diseases associated with HHcy.

[Variability of plasma angiotensinogen levels and risk of hypertension in a transgenic rat model]

AIM

Genetic polymorphisms of the human angiotensinogen gene are frequent and may induce up to 30% increase of plasma angiotensinogen concentrations with a blood pressure increase of up to 5mmHg. Their role for the pathogenesis of human arterial hypertension remains unclear. High plasma angiotensinogen levels could increase the sensitivity to other blood pressure stressors.

METHODS

Male transgenic rats with a 9-fold increase of plasma angiotensinogen concentrations and male non-transgenic rats aged 10 weeks were treated or not with NG-Nitro-L-arginine-methyl ester for 3 weeks in their drinking water (n=3/group). Systolic blood pressure and body weight were measured at baseline and at the end of the study when left ventricular weight and ventricular expression of angiotensin I-converting enzyme and procollagen Iα1 were determined (polymerase chain reaction).

RESULTS

At baseline, transgenic rats had +18mmHg higher bood pressure and -8% lower body weight compared to non-transgenic rats (P<0.05) without significant changes for the vehicle groups throughout the study (P>0.05). NG-Nitro-L-arginine-methyl ester increased blood pressure, left ventricular weight and left ventricular weight indexed for body weight by +41%, +17.6% and +18.6% (P<0.05) in transgenic and +25%, +5.3% and +6.7% (P>0.05) in non-transgenic rats compared to untreated animals, respectively. Cardiac gene expression showed no differences between groups (P>0.05).

CONCLUSION

Increased plasma angiotensinogen levels may sensitize to additional blood pressure stressors. Our preliminary results point towards an independent role of angiotensinogen in the pathogenesis of human hypertension and associated end-organ damage.

Exercise training upregulates nitric oxide synthases in the kidney of rats with chronic heart failure

There is an interaction between heart and kidney diseases, which is a condition termed cardiorenal syndrome. Exercise training has cardioprotective effects, involving upregulation of endothelial (e) nitric oxide synthase (NOS) in the cardiovascular system. However, the effects of exercise training on NOS in the kidney with heart disease are unknown. The aim of the present study was to investigate whether exercise training upregulates NOS in the kidney, left ventricle and aorta of rats with chronic heart failure (CHF). Male Sprague-Dawley rats underwent left coronary artery ligation (LCAL) to induce CHF and were randomly assigned to sedentary or treadmill exercise groups 4 weeks after LCAL. Three days after exercising for 4 weeks, urine samples were collected for 24 h and blood samples were collected following decapitation. Nitric oxide synthase activity and protein expression were examined. Significant interactions between CHF and exercise training were observed on parameters of cardiac and renal function. Exercise training improved cardiac function, decreased plasma B-type natriuretic peptide levels, decreased urinary albumin excretion and increased creatinine clearance in CHF rats. Nitric oxide synthase activity, eNOS expression and neuronal (n) NOS expression were significantly decreased in the left ventricle and kidney of CHF rats. Exercise training significantly increased NOS activity and eNOS and nNOS expression. Upregulation of NOS in the kidney and left ventricle may contribute, in part, to the renal and cardiac protective effects of exercise training in cardiorenal syndrome in CHF rats.

Nitric oxide system and diabetic nephropathy

About 30% of patients with type 2 diabetes mellitus develop clinically overt nephropathy. Hyperglycemia is necessary, but not sufficient, to cause the renal damage that leads to kidney failure. Diabetic nephropathy (DN) is a multifactorial disorder that results from interaction between environmental and genetic factors. In the present article we will review the role of the nitric oxide synthase (NOS) in the pathogenesis of DN.Nitric oxide (NO) is a short-lived gaseous lipophilic molecule produced in almost all tissues, and it has three distinct genes that encode three NOS isoforms: neuronal (nNOS), inducible (iNOS) and endothelial (eNOS).The correct function of the endothelium depends on NO, participating in hemostasis control, vascular tone regulation, proliferation of vascular smooth muscle cells and blood pressure homeostasis, among other features. In the kidney, NO plays many different roles, including control of renal and glomerular hemodynamics. The net effect of NO in the kidney is to promote natriuresis and diuresis, along with renal adaptation to dietary salt intake.The eNOS gene has been considered a potential candidate gene for DN susceptibility. Three polymorphisms have been extensively researched: G894T missense mutation (rs1799983), a 27-bp repeat in intron 4, and the T786C single nucleotide polymorphism (SNP) in the promoter (rs2070744). However, the potential link between eNOS gene variants and the induction and progression of DN yielded contradictory results in the literature.In conclusion, NOS seems to be involve in the development and progression of DN. Despite the discrepant results of many studies, the eNOS gene is also a good candidate gene for DN.

Endothelial nitric oxide synthase gene polymorphisms and risk of diabetic nephropathy: a systematic review and meta-analysis

Background

Nitric oxide (NO) has numerous functions in the kidney, including control of renal and glomerular hemodynamics, by interfering at multiple pathological and physiologically critical steps of nephron function. Endothelial NOS (eNOS) gene has been considered a potential candidate gene to diabetic nephropathy (DN) susceptibility. Endothelial nitric oxide synthase gene (eNOS-3) polymorphisms have been associated with DN, however some studies do not confirm this association. The analyzed polymorphisms were 4b/4a, T-786C, and G986T.

Methods

The Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement was used in this report. Case–control studies that had diabetic patients with DN as cases and diabetic patients without nephropathy as controls, as well as that evaluated at least one of the three polymorphisms of interest were considered eligible. All studies published up until December 31^st, 2012 were identified by searching electronic databases. Hardy-Weinberg equilibrium assessment was performed. Gene-disease association was measured using odds ratio estimation based on the following genetic contrast/models: (1) allele contrast; (2) additive model; (3) recessive model; (4) dominant model and (4) co-dominant model.

Results

Twenty-two studies were eligible for meta-analysis (4b/a: 15 studies, T-786C: 5 studies, and G984T: 12 studies). Considering 4b/a polymorphism, an association with DN was observed for all genetic models: allele contrast (OR = 1.14, CI: 1.04-1.25); additive (OR = 1.77, CI: 1.37-2.28); recessive (OR = 1.77, CI: 1.38-2,27); dominant (OR = 1.12, CI: 1.01-1.24), with the exception for co-dominance model. As well, T-786C polymorphism showed association with all models, with exception for co-dominance model: allele contrast (OR = 1.22, CI: 1.07-1.39), additive (OR = 1.52, CI: 1.18-1.97), recessive (OR = 1.50, CI: 1.16-1.93), and dominant (OR = 1.11, CI: 1.01-1.23). For the G894T polymorphism, an association with DN was observed in allelic contrast (OR = 1.12, CI: 1.03-1.25) and co-dominance models (OR = 1.13, CI: 1.04-1.37).

Conclusions

In the present study, there was association of DN with eNOS 4b/a and T-786C polymorphism, which held in all genetic models tested, except for co-dominance model. G894T polymorphism was associated with DN only in allele contrast and in co-dominance model. This data suggested that the eNOS gene could play a role in the development of DN.

Rho-kinase contributes to pressure-induced constriction of renal microvessels

Renal afferent arterioles (AFF) regulate glomerular capillary pressure through two main mechanisms: the myogenic response (MYO) and tubuloglomerular feedback (TGF). Because Rho-kinase and nitric oxide synthase (NOS) are established factors that modulate vascular tone, we examined the role of these factors in pressure-induced AFF tone in Wistar-Kyoto rats and in spontaneously hypertensive rats (SHR) using an intravital CCD camera. Elevated renal perfusion pressure elicited marked AFF constriction that was partially inhibited by gadolinium, furosemide and fasudil, which inhibit MYO, TGF and Rho-kinase, respectively; however, this AFF constriction was completely blocked by combined treatment with fasudil+gadolinium or fasudil+furosemide. S-methyl-L-thiocitrulline (SMTC) partially reversed the fasudil-induced inhibition of TGF-mediated, but not that of MYO-mediated, AFF constriction. In SHR, the pressure-induced AFF response was enhanced, and MYO- and TGF-induced constriction were exaggerated. In the presence of gadolinium, SMTC partially mitigated the fasudil-induced inhibition of TGF-mediated AFF constriction. Immunoblot analyses demonstrated that both Rho-kinase activity and neuronal NOS were augmented in SHR kidneys. In conclusion, Rho-kinase contributes to MYO- and TGF-mediated AFF responses, and these responses are enhanced in SHR. Furthermore, neuronal NOS-induced nitric oxide modulates the TGF mechanism. This mechanism constitutes a target for Rho-kinase in TGF-mediated AFF constriction.

Pre- or post-treatment with aminoguanidine attenuates a renal distal acidification defect induced by acute ureteral obstruction in rats

Acute unilateral ureteral obstruction (UUO) impairs distal nephron acid secretion and stimulates expression of inducible nitric oxide synthase (iNOS) in post-obstructed kidney (POK). This study investigated the influence of pre- or post-treatment with aminoguanidine as a selective iNOS inhibitor on UUO-induced renal functional disturbances. To induce acute UUO, the left ureter in rats was ligated and released after 24 h. Then, a 3 h clearance period followed by bicarbonate loading and thereafter a 30 min clearance period were allocated. Aminoguanidine was administered either prior to the UUO induction or after release of the obstruction in the different rat groups, while untreated and sham groups received normal saline. During the first clearance period, fractional bicarbonate excretion and urinary pH increased markedly in the POK of the untreated group compared with the left kidney of sham group, and a large drop in the difference between urine and blood pCO2 (U–B pCO2) was observed after bicarbonate loading; all of these parameters were ameliorated in the pre-treated and post-treated groups. However, the UUO-induced decreases in creatinine clearance, sodium reabsorption, urine osmolality, and free-water reabsorption in the POK were attenuated only in the post-treated group. Therefore, the in vivo application of a selective iNOS inhibitor partially improved the acute UUO-induced distal nephron acidification defect, while post-treatment but not pre-treatment with aminoguanidine ameliorated decrements of glomerular filtration, sodium reabsorption, and urine-concentrating ability.

Activation of transient receptor potential vanilloid 1 decreases endothelial nitric oxide synthase phosphorylation at Thr497 by protein phosphatase 2B-dependent dephosphorylation of protein kinase C

AIMS

We investigated the effects and underlying molecular mechanism of transient receptor potential vanilloid 1 (TRPV1), a calcium (Ca(2+) )-permeable non-selective cation channel, on phosphorylation of endothelial nitric oxide synthase (eNOS) at threonine 497 (Thr497) in bovine aortic endothelial cells (BAECs) and in mice.

METHODS

Western blotting and immunoprecipitation were used for the evaluation of protein phosphorylation; protein phosphatase 2B (PP2B) activity was assessed by convention kit; Griess assay was for NO production; tube formation and Matrigel plug assay were used for angiogenesis.

RESULTS

In BAECs, treatment with the TRPV1 ligand evodiamine decreased the phosphorylation of eNOS at Thr497, protein kinase Cα (PKCα) at Serine 657 (Ser657) and PKCβ2 at Ser660. Evodiamine increased protein phosphatase 2B (PP2B) activity and promoted the formation of a PP2B-PKC complex. Inhibition of TRPV1 activation by the pharmacological antagonists, removal of extracellular Ca(2+) or pharmacological inhibition of PI3K/Akt/calmodulin-dependent protein kinase II/AMP-activated protein kinase signalling pathway abolished the evodiamine-induced alterations in phosphorylation of eNOS at Thr497, PKCα at Ser657, PKCβ2 at Ser660 and PP2B activity, as well as the formation of a PP2B-PKC complex. Inhibition of PP2B activation partially reduced the evodiamine-induced NO bioavailability and tube formation in endothelial cells (ECs) and angiogenesis in mice. Moreover, evodiamine decreased the phosphorylation of eNOS at Thr497, PKCα at Ser657 and PKCβ2 at Ser660 in apolipoprotein E (ApoE)-deficient mouse aortas but not TRPV1-deficient or ApoE/TRPV1 double-knockout mice.

CONCLUSION

TRPV1 activation in ECs may elicit a Ca(2+) -dependent effect on PP2B-PKC signalling, which leads to dephosphorylation of eNOS at Thr497 in ECs and in mice.

Distinct regulation of inner medullary collecting duct nitric oxide production from mice and rats

Nitric oxide (NO) and NO synthase 1 (NOS1) maintain sodium and water homeostasis. The NOS1α and NOS1β splice variants are expressed in the rat inner medulla, but only NOS1β is expressed in the mouse. Collecting duct NOS1 is necessary for blood pressure control. We hypothesized that NOS1 splice variant expression and NO production in the inner medullary collecting duct (IMCD) are regulated differently in mice and rats by high dietary sodium. Male C57blk/J6 mice and Sprague-Dawley rats were fed a 0.4% (normal salt; NS), or 4% (high salt; HS) NaCl diet for 2 or 7 days. Mean arterial pressure was not altered by HS, whereas urinary sodium excretion in mice and rats was increased significantly. Urinary excretion of nitrate/nitrite (NO(x)) and IMCD nitrite production were significantly greater in mice compared with rats on the HS diet. Western blotting indicated that only NOS1β and NOS3 were expressed in the mouse IMCD and that expression was unaffected by the HS diet at either time point. In contrast, NOS1α was detected in the IMCD of rats, in addition to NOS1β and NOS3. Feeding of the HS diet for 2 days increased NOS1α and NOS1β expression in the rat IMCD and 7 day feeding of the HS diet further increased NOS1β expression. Expression of NOS3 was unchanged by the HS diet at either time point. In conclusion, IMCD NO production in mice and rats is distinctly regulated under both NS and HS conditions, including expression of NOS1 splice variants.

Nox4 NADPH oxidase mediates peroxynitrite-dependent uncoupling of endothelial nitric-oxide synthase and fibronectin expression in response to angiotensin II: role of mitochondrial reactive oxygen species

Activation of glomerular mesangial cells (MCs) by angiotensin II (Ang II) leads to extracellular matrix accumulation. Here, we demonstrate that, in MCs, Ang II induces endothelial nitric-oxide synthase (eNOS) uncoupling with enhanced generation of reactive oxygen species (ROS) and decreased production of NO. Ang II promotes a rapid increase in 3-nitrotyrosine formation, and uric acid attenuates Ang II-induced decrease in NO bioavailability, demonstrating that peroxynitrite mediates the effects of Ang II on eNOS dysfunction. Ang II rapidly up-regulates Nox4 protein. Inhibition of Nox4 abolishes the increase in ROS and peroxynitrite generation as well as eNOS uncoupling triggered by Ang II, indicating that Nox4 is upstream of eNOS. This pathway contributes to Ang II-mediated fibronectin accumulation in MCs. Ang II also elicits an increase in mitochondrial abundance of Nox4 protein, and the oxidase contributes to ROS production in mitochondria. Overexpression of mitochondrial manganese superoxide dismutase prevents the stimulatory effects of Ang II on mitochondrial ROS production, loss of NO availability, and MC fibronectin accumulation, whereas manganese superoxide dismutase depletion increases mitochondrial ROS, NO deficiency, and fibronectin synthesis basally and in cells exposed to Ang II. This work provides the first evidence that uncoupled eNOS is responsible for Ang II-induced MC fibronectin accumulation and identifies Nox4 and mitochondrial ROS as mediators of eNOS dysfunction. These data shed light on molecular processes underlying the oxidative signaling cascade engaged by Ang II and identify potential targets for intervention to prevent renal fibrosis.

FTY720 prevents progression of renal fibrosis by inhibiting renal microvasculature endothelial dysfunction in a rat model of chronic kidney disease

Recent studies have shown that chronic endothelial dysfunction can impair multiple aspects of renal physiology and, in turn, contribute to renal fibrosis. Sphingosine 1-phosphate (S1P) has been highlighted as an endothelial barrier-stabilizing mediator. The aim of our study was to investigate the effect of FTY720, an S1P analog, on the progression of renal fibrosis by inhibiting renal microvasculature endothelial dysfunction in a rat model of chronic kidney disease. Thirty male Sprague-Dawley rats were used in this study. Seven days after surgery, we placed the animals into three groups: sham surgery; 5/6 nephrectomized (Nx) rats; and 5/6Nx + FTY720 (1 mg/kg/day). All of the animals were sacrificed 12 weeks after surgery. We obtained and analyzed blood and kidney tissue samples from all of the groups. Glomerular capillary density and peritubular capillary (PTC) density were determined by CD31 immunostaining. The expression of transforming growth factor beta 1 (TGF-β1), collagen IV, fibronectin, endothelial nitric oxide synthase (eNOS) and vascular endothelial growth factor (VEGF) were analyzed by immunohistochemistry, reverse transcription-polymerase chain reaction and western blotting. The 5/6Nx group exhibited increased blood urea nitrogen and serum creatinine, visible renal histological changes, pro-fibrotic molecule (TGF-β1) and production of extracellular matrix proteins such as collagen IV and fibronectin and decreased glomerular and PTC density, compared to the sham controls (P < 0.01). We observed that treatment with FTY720 reduced these abnormalities. Furthermore, the level of NO, the expression levels of eNOS and VEGF were downregulated in the kidney tissue in 5/6Nx rats, FTY720 treatment significantly attenuated this decrease. FTY720 prevents the progression of renal fibrosis by inhibiting renal microvasculature endothelial dysfunction in a rat model of chronic kidney disease.

Sestrin 2 and AMPK connect hyperglycemia to Nox4-dependent endothelial nitric oxide synthase uncoupling and matrix protein expression

Mesangial matrix accumulation is an early feature of glomerular pathology in diabetes. Oxidative stress plays a critical role in hyperglycemia-induced glomerular injury. Here, we demonstrate that, in glomerular mesangial cells (MCs), endothelial nitric oxide synthase (eNOS) is uncoupled upon exposure to high glucose (HG), with enhanced generation of reactive oxygen species (ROS) and decreased production of nitric oxide. Peroxynitrite mediates the effects of HG on eNOS dysfunction. HG upregulates Nox4 protein, and inhibition of Nox4 abrogates the increase in ROS and peroxynitrite generation, as well as the eNOS uncoupling triggered by HG, demonstrating that Nox4 functions upstream from eNOS. Importantly, this pathway contributes to HG-induced MC fibronectin accumulation. Nox4-mediated eNOS dysfunction was confirmed in glomeruli of a rat model of type 1 diabetes. Sestrin 2-dependent AMP-activated protein kinase (AMPK) activation attenuates HG-induced MC fibronectin synthesis through blockade of Nox4-dependent ROS and peroxynitrite generation, with subsequent eNOS uncoupling. We also find that HG negatively regulates sestrin 2 and AMPK, thereby promoting Nox4-mediated eNOS dysfunction and increased fibronectin. These data identify a protective function for sestrin 2/AMPK and potential targets for intervention to prevent fibrotic injury in diabetes.

Role of asymmetrical dimethylarginine in the progression of renal disease

Asymmetric dimethylarginine (ADMA) is a naturally occurring amino acid found in tissues and cells that circulates in plasma and is excreted in urine. It inhibits nitric oxide synthases (NOs) and produces considerable cardiovascular biological effects. Several studies have suggested that plasma concentrations of ADMA provide a marker of risk for endothelial dysfunction and cardiovascular disease. In animal and in population studies ADMA has been associated with progression of CKD. Several mechanisms may be involved in this association, such as compromise of the integrity of the glomerular filtration barrier and development of renal fibrosis. This review summarizes the existing literature on the biology and physiology of ADMA focusing on its role in the progression of renal disease.

Chronic elevation of IL-1β induces diuresis via a cyclooxygenase 2-mediated mechanism

Chronic renal inflammation is an increasingly recognized phenomenon in multiple disease states, but the impact of specific cytokines on renal function is unclear. Previously, we found that 14-day interleukin-1β (IL-1β) infusion increased urine flow in mice. To determine the mechanism by which this occurs, the current study tested the possible involvement of three classical prodiuretic pathways. Chronic IL-1β infusion significantly increased urine flow (6.5 ± 1 ml/day at day 14 vs. 2.3 ± 0.3 ml/day in vehicle group; P < 0.05) and expression of cyclooxygenase (COX)-2, all three nitric oxide synthase (NOS) isoforms, and endothelin (ET)-1 in the kidney (P < 0.05 in all cases). Urinary prostaglandin E metabolite (PGEM) excretion was also significantly increased at day 14 of IL-1β infusion (1.21 ± 0.26 vs. 0.29 ± 0.06 ng/day in vehicle-infused mice; P = 0.001). The selective COX-2 inhibitor celecoxib markedly attenuated urinary PGEM excretion and abolished the diuretic response to chronic IL-1β infusion. In contrast, deletion of NOS3, or inhibition of NOS1 with L-VNIO, did not blunt the diuretic effect of IL-1β, nor did pharmacological blockade of endothelin ETA and ETB receptors with A-182086. Consistent with a primary effect on water transport, IL-1β infusion markedly reduced inner medullary aquaporin-2 expression (P < 0.05) and did not alter urinary Na⁺ or K⁺ excretion. These data indicate a critical role for COX-2 in mediating the effects of chronic IL-1β elevation on the kidney.

Renal inflammatory changes in acute hepatic failure-associated acute kidney injury

BACKGROUND/AIMS

Acute kidney injury (AKI) is a common complication in advanced liver dysfunction. Our aim is to clarify the mechanisms of acute hepatic failure (AHF)-associated AKI.

METHODS

We examined the mechanisms of AHF-associated AKI, which is characterized by AKI in AHF and hyperbilirubinemia, following DA-to-Lewis rat liver transplantation.

RESULTS

During the progression of AHF and hyperbilirubinemia in liver graft rejection, AHF-associated AKI gradually developed by day 11. Degeneration and apoptotic cells were apparent in tubular epithelial cells with bile pigment accumulation and mitochondrial degeneration. Injury of peritubular capillaries (PTCs) was also noted with apoptotic endothelial cells, decreased expression of endothelial nitric oxide synthase, accumulation of α-smooth muscle actin+ pericytes and/or myofibroblasts, and inflammation. Angiogenic factors including vascular endothelial growth factor, angiopoietin-1, and angiopoietin-2 in the cortex were decreased on day 11. In addition, a marked reduction in the velocity of red blood cells in PTCs was evident in vivo.

CONCLUSIONS

AHF-associated AKI seems to be mediated by renal tubular epithelial cell injury with bile pigment accumulation, impaired microcirculation caused by PTC endothelial cell injury with depletion of endothelial nitric oxide synthase and angiogenic factors, and by a decrease in RBC velocity and renal inflammation. Multiple mechanisms including tubular and PTC injuries and renal inflammation may be involved in the development of AHF-associated AKI.

Ovine uterine space restriction alters placental transferrin receptor and fetal iron status during late pregnancy

BACKGROUND

Fetal growth restriction is reported to be associated with impaired placental iron transport. Transferrin receptor (TfR) is a major placental iron transporter in humans but has not been studied in sheep. TfR is regulated by both iron and nitric oxide (NO), the molecule produced by endothelial nitric oxide synthase (eNOS). We hypothesized that limited placental development downregulates both placental TfR and eNOS expression, thereby lowering fetal tissue iron.

METHODS

An ovine surgical uterine space restriction (USR) model, combined with multifetal gestation, tested the extremes of uterine and placental adaptation. Blood, tissues, and placentomes from non-space restricted (NSR) singletons were compared with USR fetuses at gestational day (GD) 120 or 130.

RESULTS

When expressed proportionate to fetal weight, liver iron content did not differ, whereas renal iron was higher in USR vs. NSR fetuses. Renal TfR protein expression did not differ, but placental TfR expression was lower in USR fetuses at GD130. Placental levels of TfR correlated to eNOS. TfR was localized throughout the placentome, including the hemophagous zone, implicating a role for TfR in ovine placental iron transport.

CONCLUSION

Fetal iron was regulated in an organ-specific manner. In USR fetuses, NO-mediated placental adaptations may prevent the normal upregulation of placental TfR at GD130.

Influence of endothelial nitric oxide synthase gene polymorphisms (-786T/C, 4a4b, 894G/T) on Iranian kidney transplant recipients

OBJECTIVES

Nitric oxide is a major mediator in vascular biology and regulator of regional blood flow. Its production is catalyzed by the enzyme endothelial nitric oxide synthase. Protective actions of nitric oxide in ischemia and reperfusion are due to its potential as an antioxidant and anti-inflammatory agent, along with its inhibitory effects on cell signaling pathways of nuclear proteins, such as NF-kB. The endothelial nitric oxide synthase gene polymorphisms affect endothelial nitric oxide synthase activity and are associated with endothelial dysfunction. This study sought to examine the association between single nucleotide polymorphisms in endothelial nitric oxide synthase gene (rs 2070744, 27VNTR, and rs1799983) and the development of acute rejection in renal transplant patients.

MATERIALS AND METHODS

Sixty-six renal transplant recipients (33 patients with an episode of acute rejection and 33 recipients an episode of acute rejection), between June 2010 and March 2011, were included. The polymorphism was determined by simple polymerase chain reaction and polymerase chain reaction-restriction fragment-length polymorphism analysis.

RESULTS

There was only a significant association of endothelial nitric oxide synthase -786T allele and acute rejection (P = .03). Recessive model of T-786C alleles (TT vs TC+CC) and acute rejection confirmed a significant association (odds ratio: 3.12; 95% CI: 0.01-9.83; P = .025). Haplotype CbG was higher in recipients without rejection as compared to rejection group (OR: 0.42, 95% CI: 0.16-1.13; P < .05). Respecting the endothelial nitric oxide synthase gene 894G/T single nucleotide polymorphisms and 27VNTR, no significant association between the allele/genotype and acute rejection was seen.

CONCLUSION

Recipient endothelial nitric oxide synthase gene polymorphisms do not alter the risk of acute rejection after a renal transplant. Rejection is a complex immunologic event. Therefore, finding associated genetic variants demands a multicentric larger sample size.

Effects of atorvastatin on systemic and renal nitric oxide in healthy man

Statin treatment improves endothelial function but the effects of statins on renal nitric oxide have not been clarified. In this crossover study, 26 healthy subjects received atorvastatin 80 mg per day or placebo for 5 days. After 5 days of treatment, L-N(G)-monomethyl arginine caused a similar increase in blood pressure and decrease in urine output and glomerular filtration rate. The decrease in fractional excretion of sodium to L-N(G)-monomethyl arginine was more pronounced after atorvastatin treatment. Atorvastatin did not change the response to several vasoactive hormones. The results indicate that atorvastatin increase renal nitric oxide, which may explain a part of the pleiotropic effects of statins.

The genetic deletion of Mas abolishes salt induced hypertension in mice

The G protein-coupled receptor Mas is a physiological antagonist of the angiotensin II type 1 receptor and is associated with angiotensin-(1-7) signaling. We investigated the effect of Mas-deficiency on blood pressure regulation under physiological conditions and salt load using radiotelemetry. Mas-knockout mice and their wild-type controls received a telemetry implant in the carotid artery. One week after surgery, animals were monitored for 3 days receiving normal diet (0.6% NaCl) followed by one-week high-salt diet (8% NaCl). Under same high-salt diet, another set of mice was placed in individual metabolic cages for 4 days. Basal mean arterial pressure, heart rate and locomotor activity displayed normal day-night rhythm in Mas-deficient mice. Mas-knockout mice were normotensive. High dietary NaCl ingestion did not alter heart rate or locomotor activity in both groups, but significantly increased night time mean arterial pressure in control mice whereas this increase was blunted in Mas-deficient mice. Baseline food and water intake and urine osmolality were not different between both genotypes. Under high-salt diet, water consumption and food intake were equally increased in wild-type controls and Mas-knockout, but urinary electrolytes and osmolality were significantly higher in Mas-knockout. Taken together, basal hemodynamic parameters are unchanged in Mas-knockout mice. In contrast to wild-type controls, telemetric mean arterial pressure measurement revealed salt resistance in Mas-deficient animals, probably due to their higher urinary NaCl excretion. This is the first direct proof that Mas blockade might be a new option in the treatment of salt-sensitive hypertension.

[In utero fetal programming and its impact on health in adulthood]

Adverse events during intrauterine life may program organ growth and favor disease later in life. This is the usually called 'Barker's hypothesis'. Increasing evidence suggests that conditions like vascular disease, hypertension, metabolic syndrome, and type 2 diabetes mellitus are programmed during the early stages of fetal development and become manifest in late stages of life, when there is an added impact of lifestyle and other conventional acquired environmental risk factors that interact with genetic factors. The aim of this review was to provide additional, updated evidence to support the association between intrauterine fetal health and increased prevalence of chronic non-communicable diseases in adulthood. Various potential cellular and molecular mechanisms proposed to be related to the above hypothesis are discussed, including endothelial function, oxidative stress, insulin resistance, and mitochondrial function.

Melatonin and vitamin C ameliorate alcohol-induced oxidative stress and eNOS expression in rat kidney

OBJECTIVES

The aim of this study was to investigate the preventive effects of melatonin and vitamin C as antioxidants on renal injury in chronic alcohol consumption.

MATERIALS AND METHODS

A total of 24 adult male Wistar rats weighing 200-250 g were used in the study. Rats were divided into four equal groups. Group I (control): rats were not fed on alcohol; Group II: rats were fed on alcohol; Group III: rats were fed on alcohol and 40 mg/kg vitamin C; and Group IV: rats were fed on alcohol and 4 mg/kg melatonin.

RESULTS

Light microscopic examination revealed atrophic renal corpuscles, dilatation and congestion of the peritubular vessels, and renal corpuscles with obscure Bowman's space and a few foamy-appearing tubules due to alcohol consumption were observed. Expression of endothelial nitric oxide synthase (eNOS) was localized to glomerulus, distal, and collector tubules. eNOS staining decreased in alcohol treatment group and melatonin and vitamin C encore increased expression pattern of eNOS. Alcohol consumption increased malondialdehyde (MDA) level and superoxide dismutase (SOD) and catalase (CAT) activities significantly in the alcohol consumption groups compared with that in the control group, while in melatonin give group just MDA level was decreased statistically significant and SOD and CAT activities were also decreased numerically compared with the alcohol consumption groups.

CONCLUSIONS

These results indicated that chronic alcohol consumption caused renal damage by increased lipid peroxidation and melatonin and vitamin C administration produced in some degree protection against alcohol-induced damage.

Phosphodiesterase-5 inhibition prevents postcardiopulmonary bypass acute kidney injury in swine

BACKGROUND

Acute kidney injury after cardiac surgery is common, has no effective treatments, and is associated with adverse outcomes. The aim of this study was to determine whether administration of the phosphodiesterase-5 inhibitor sildenafil citrate (SDF) would prevent the development of post-cardiopulmonary bypass (CPB) acute kidney injury in swine.

METHODS

Adult pigs (n = 8 per group) were randomized to undergo sham procedure, CPB, or CPB plus administration of SDF, with recovery and reassessment at 24 hours.

RESULTS

Cardiopulmonary bypass resulted in a significant reduction in creatinine clearance relative to sham pigs (mean difference CPB versus sham, -47.9 mL/min; 95% confidence interval [CI]: -93.7 to -2.2; p = 0.039). This was prevented by the administration of SDF during CPB (mean difference CPB+SDF versus CPB, +55.6 mL/min; 95% CI: +6.5 to +104.7; p = 0.024). Cardiopulmonary bypass also resulted in a significant rise in the urinary biomarker interleukin-18 compared with sham procedures (mean difference 209.3 pg/mL; 95% CI: 120.6 to 298.1; p < 0.001) that was prevented by SDF administration. Post-CPB kidney injury was associated with vascular endothelial injury and dysfunction, reduced nitric oxide bioavailability, medullary hypoxia, cortical adenosine triphosphate depletion, inflammation, and evidence of proximal tubule epithelial cell stress manifest as phenotypic change. Administration of SDF to CPB pigs preserved nitric oxide bioavailability and prevented endothelial dysfunction, regional hypoxia, inflammation, and tubular changes.

CONCLUSIONS

In this model, phosphodiesterase-5 inhibition using SDF prevented post-CPB acute kidney injury by the preservation of nitric oxide bioavailability, and warrants evaluation as a renoprotective agent in clinical trials.

Prenatally programmed hypertension: role of maternal diabetes

Epidemiological and experimental studies have led to the hypothesis of the fetal origin of adult diseases, suggesting that some adult diseases might be determined before birth by altered fetal development. Maternal diabetes subjects the fetus to an adverse environment that has been demonstrated to result in metabolic, cardiovascular and renal impairment in the offspring. The growing amount of obesity in young females in developed and some developing countries should contribute to increasing the incidence of diabetes among pregnant women. In this review, we discuss how renal and extrarenal mechanisms participate in the genesis of hypertension induced by a diabetic status during fetal development.

Response of renal parenchyma and interstitium of Rana snk. esculenta to environmental pollution

The mesonephroi of two groups of Rana esculenta collected from two rice fields near Pavia, one relatively unpolluted and one polluted, were morphologically and histochemically investigated. Light and electron microscopy analyses were performed and certain enzyme activities studied (succinic dehydrogenase, SDH, alkaline phosphatase, AlkPase, acid phosphatase, AcPase, catalase, CAT, and NOS-related nicotinamide adenine dinucleotide phosphatase, NOS/NADPHd). The expression of the inducible NOS (iNOS) was evaluated through immunohistochemistry. In the renal parenchyma of the polluted group some structural modifications, mainly in the glomeruli and the proximal tubule epithelium, were observed. Peritubular inflammatory foci in most polluted samples were often found to be in combination with parasitic cysts. However, no necrotic processes were found in the renal parenchyma. Compared to controls, the histochemical studies on contaminated frogs evidenced an increase of the AcPase, NOS and CAT activities, and of the iNOS immunoexpression as well. All the results showed a good correspondence between the biomarkers responses and the environmental stress conditions. Overall, we can state that studying the sub-lethal effects of contamination in amphibians naturally exposed to toxicants has shown to be significant for the assessment of site-specific risk and potential hazards behind the phenomenon of progressive amphibian decline.

Podocyte dysfunction in aging--related glomerulosclerosis

We review podocyte molecular structure and function, consider the underlying mechanisms related to podocyte dysfunction and propose that podocyte dysfunction be considered in the evaluation and management of age-associated glomerulosclerosis. With aging, progressive sympathetic activation, increased intrarenal renin-angiotensin system (RAS) activity, endothelin system and oxidative stress and reduced nitric oxide (NO)-availability can damage podocytes. Apoptosis and proliferation are the principal podocyte changes following injury with the latter leading to sclerosis and loss of nephrons. Podocyte loss can be evaluated by either determining their average number in biopsed glomeruli or by estimating podocyte number or their associated molecules in urine sediment. Podocyturia may be considered a marker of active glomerular disease. Preliminary data suggest that antiadrenergic drugs, angiotensin converting enzyme (ACE) inhibitors, RAS blocking drugs, endothelin system inhibitors and reduced oxidative stress can protect podocytes. Thus podocytes appear to play an important role in the pathogenesis, evaluation and therapy of age related glomerulosclerosis.

Interaction of nitric oxide and the cytochrome P-450 system on blood pressure and renal function in the rat: dependence on sodium intake

AIM

Interaction was examined of nitric oxide (NO) and cytochrome P-450 (CYP-450)-dependent arachidonic acid derivatives, 20-HETE and EETs, in control of arterial pressure (MABP) and renal function. Modification of this interaction by changing sodium intake was also studied.

METHODS

On low, standard or high Na diet (LS, STD and HS rats respectively) effects of sequential blockade of NO synthases (NOS) and CYP-450 enzyme activity on MABP, renal blood flow (RBF, Transonic probe), renal medullary perfusion (MBF, laser-Doppler technique), medullary tissue NO (selective electrode) and renal excretion were examined in anaesthetized rats. All NOS were blocked with N(ϖ) -nitro-l-arginine methyl ester (l-NAME), the neuronal NOS with S-methyl-l-thiocitrulline (SMTC), and CYP-450 with 1-aminobenzotriazole (ABT).

RESULTS

In each diet group the baseline MABP was highest in rats pre-treated with l-NAME. CYP-450 inhibition significantly decreased MABP only in LS (-9%) and HS rats (-22%) pre-treated with l-NAME. This MABP decrease correlated directly with the dietary sodium content (r = 0.644, P < 0.001). CYP-450 inhibition decreased RBF in LS and HS rats (not in HS pre-treated with l-NAME). Acute exclusion of CYP-450 significantly increased MBF only in STD, SMTC pre-treated rats; in HS group it significantly increased medullary tissue NO by about 1.0 nA. The post-ABT changes in renal excretion occurred in LS and HS rats, irrespective of the status of NO synthesis.

CONCLUSIONS

Both NO- and CYP-450-dependent agents contribute to blood pressure and kidney function control, however, the role of 20-HETE and EETs becomes crucial only under conditions of high sodium intake or after NOS inhibition.

Heme oxygenase regulates renal arterial resistance and sodium excretion in cirrhotic rats

BACKGROUND & AIMS

Heme oxygenase (HO) catabolizes heme into biliverdin, carbon monoxide (CO), and free iron. CO generated in endothelial and smooth muscle layers of blood vessels modulates vascular tone by inducing relaxation of vascular smooth muscle cells. The aim of this study was to verify the role played by HO in regulating renal arterial resistance and Na(+) excretion in cirrhosis.

METHODS

Twenty control rats and 20 rats with CCl(4)(-) induced cirrhosis, 10 of which were chronically treated with the HO inducer cobalt-protoporphyrin (CoPP), were studied. Pressurized renal interlobar arteries were challenged with increasing doses of phenylephrine (PE) and acetylcholine (ACh). Dose-response curves were evaluated under basal conditions and after inhibition of HO with chromium-mesoporphyrin (CrMP). HO-1 (inducible form) and HO-2 (constitutive form) expression was measured in the main and interlobar renal arteries. Serum and urinary levels of Na(+) and creatinine were also evaluated.

RESULTS

In renal interlobar arteries from cirrhotic rats, the response to PE was increased, while that to ACh was blunted. After HO inhibition, the responsiveness to these vasoactive substances was comparable in the two groups. In cirrhotic rats, HO-1 expression was impaired in the main and the interlobar renal arteries. Chronic HO induction normalized the response to the vasoconstrictor, but not to the vasodilator. Cirrhotic rats treated with CoPP showed higher urinary Na(+) concentration and fractional Na(+) excretion, compared to both untreated cirrhotic and control rats.

CONCLUSIONS

In cirrhotic rats, an impaired HO-1 expression promotes vasoconstriction of renal interlobar arteries. Chronic HO induction normalizes the sensitivity to PE and promotes Na(+) excretion.

Zinc restriction during different periods of life: influence in renal and cardiovascular diseases

Micronutrient undernutrition during critical periods of growth has become an important health issue in developing and developed countries, particularly among pregnant women and children having an imbalanced diet. Zinc is a widely studied microelement in infant feeding because it is a component of several enzymes involved in intermediary metabolism ranging from growth to cell differentiation and metabolism of proteins, carbohydrates, and lipids. Human and experimental studies have reported an association between zinc deficiency and the etiopathogenesis of cardiovascular and renal diseases like hypertension, atherosclerosis, congestive heart failure, coronary heart disease, and diabetes. The main links between the development of these pathologies and zinc deficiency are multiple mechanisms involving oxidative stress damage, apoptosis, and inflammation. A substantial body of evidence suggests that a poor in utero environment elicited by maternal dietary or placental insufficiency may "programme" susceptibility in the fetus to later development of cardiovascular, renal, metabolic, and endocrine diseases. Zinc deficiency in rats during intrauterine and postnatal growth can also be considered a model of fetal programming of cardiovascular and renal diseases in adult life. Dietary zinc restriction during fetal life, lactation, and/or postweaning induces an increase in arterial blood pressure and impairs renal function in adult life. This review focuses on the contributions of experimental and clinical studies to current knowledge of the physiologic role of zinc in the cardiovascular and renal systems. Moreover, this review examines the relationship between zinc deficiency during different periods of life and the development of cardiovascular and renal diseases in adult life.

High-protein-induced glomerular hyperfiltration is independent of the tubuloglomerular feedback mechanism and nitric oxide synthases

A high protein intake is associated with increased glomerular filtration rate (GFR), which has been suggested to be mediated by reduced signaling of the tubuloglomerular feedback (TGF) mechanism. Nitric oxide (NO) has been shown to contribute to high protein-induced glomerular hyperfiltration, but the specific NO synthase (NOS) isoform responsible is not clear. In this study, a model for high-protein-induced hyperfiltration in conscious mice was developed. Using this model, we investigated the role of TGF using adenosine A1-receptor knockout mice lacking the TGF mechanism. Furthermore, the role of the different NOS isoforms was studied using neuronal-, inducible-, and endothelial-NOS knockout mice, and furthermore, wild-type mice acutely administered with the unspecific NOS inhibitor Nω-nitro-l-arginine methyl ester (100 mg/kg). GFR was measured consecutively in mice given a low-protein diet (8% casein) for 10 days, followed by a high-protein diet (50% casein) for 10 days. All mice developed high protein-induced hyperfiltration to a similar degree. These results demonstrate that high protein-induced glomerular hyperfiltration is independent of the TGF mechanism and NOS isoforms.

Autonomic control of the urogenital tract

The urogenital tract houses many of the organs that play a major role in homeostasis, in particular those that control water and salt balance, and reproductive function. This review focuses on the anatomical and functional innervation of the kidneys, urinary ducts and bladders of the urinary system, and the gonads, gonadal ducts, and intromittent organs of the reproductive tract. The literature, especially in recent years, is overwhelmingly skewed toward the situation in mammals. Nevertheless, where specific neurochemical markers have been investigated, common patterns of innervation can be found in representatives from most vertebrate classes. Not surprisingly the vasculature, epithelia and smooth muscle of all urogenital organs receives adrenergic innervation. These nerves may contain non-adrenergic non-cholinergic (NANC) neurotransmitters such as ATP and NPY. Cholinergic nerves increase motility in most urogenital organs with the exception of the kidney. The major NANC nerves found to influence urogenital organs include those containing VIP/PACAP, galanin and neuronal nitric oxide synthase. These can be found associated with both smooth muscle and epithelia. The role these nerves play, and the circumstances where they are activated are for the most part unknown.

PPARalpha: an emerging therapeutic target in diabetic microvascular damage

The global pandemic of diabetes mellitus portends an alarming rise in the prevalence of microvascular complications, despite advanced therapies for hyperglycemia, hypertension and dyslipidemia. Peroxisome proliferator-activated receptor alpha (PPARalpha) is expressed in organs affected by diabetic microvascular disease (retina, kidney and nerves), and its expression is regulated specifically in these tissues. Experimental evidence suggests that PPARalpha activation attenuates or inhibits several mediators of vascular damage, including lipotoxicity, inflammation, reactive oxygen species generation, endothelial dysfunction, angiogenesis and thrombosis, and thus might influence intracellular signaling pathways that lead to microvascular complications. PPARalpha has emerged as a novel target to prevent microvascular disease, via both its lipid-related and lipid-unrelated actions. Despite strong experimental evidence of the potential benefits of PPARalpha agonists in the prevention of vascular damage, the evidence from clinical studies in patients with diabetes mellitus remains limited. Promising findings from the Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) study on microvascular outcomes are countered by elevations in participants' homocysteine and creatinine levels that might potentially attenuate the benefits of PPARalpha activation. This Review focuses on the role of PPARalpha activation in diabetic microvascular disease and highlights the available experimental and clinical evidence from studies of PPARalpha agonists.

Endothelial nitric oxide synthase (eNOS) gene polymorphism in early term chronic allograft nephropathy

Chronic allograft nephropathy (CAN) is a complex phenomenon caused by underlying kidney disease with superimposed enviromental and genetic factors. CAN development begins with progressive renal microvascular injury. Endothelial cells play key roles in the regulation of vascular tone, permeability, and remodeling. A reduction in basal nitric oxide (NO) release as a result of genetic variation in endothelial NO synthase (eNOS) function may predispose to hypertension, thrombosis, vasospasm, and atherosclerosis, all contributing to the development of CAN. We analyzed the G894T mutation at exon 7 of the eNOS gene in relationship to CAN among 81 children with renal transplantations. The 20 patients who developed CAN underwent renal biopsies for histological confirmation. Proteinuria and hypertension were observed in CAN. We selected 173 healthy reference subjects. The G894T polymorphism of the eNOS gene was determined by PCR-restriction fragment-length polymorphism analysis. The group included 33 male and 48 female subjects who received 32 living-related grafts and 49 from deceased donors (DD) donors. Donor age (y) was 32.7 +/- 13.7 and the HLA A,B,DR mismatch number of the cadaveric cases was 3.5 +/- 0.79. The distribution of the genotypes were ENOS GG/GT/TT 48%, 33%, 19%, respectively. G-alleles frequency was 64.8%; T-allele frequency was 35.2%. ENOS G894T gene polymorphism did not seem to influence long-term renal allograft outcome. Recipient ENOS G894T gene polymorphism did not alter the risk of chronic allograft failure. Even if NO synthesis and bioactivity are influenced by this polymorphism, many vasoactive factors may have roles to suppress the advantageous effects of NO.

Exposure to zinc deficiency in fetal and postnatal life determines nitric oxide system activity and arterial blood pressure levels in adult rats

We had previously shown that prenatal exposure to Zn-deficient diets induces an increase in blood pressure and impairs renal function in adult rats. The aim of the present study was to investigate if moderate Zn restriction during early growth periods, fetal life and lactation would induce impairment in the vascular and renal NO system and alterations in plasma lipid profile. We also investigated if these effects persisted into adult life, even when a Zn-replete diet was provided after weaning. Pregnant rats were fed control (30 parts per million (ppm)) or low (8 ppm) Zn diets throughout gestation up to weaning. Afterwards, male offspring from low-Zn mothers were assigned to low- or control-Zn diets during 60 d. Male offspring from control mothers were fed a control diet. Animals exposed to Zn restriction showed low birth weight, increased systolic blood pressure and serum TAG levels, and decreased glomerular filtration rate in adulthood. Zn restriction induced a decrease in vascular and renal NO synthase activity and a reduced expression of the endothelial NO synthase isoform in aorta. A control-Zn diet during post-weaning growth returned TAG levels to normal but was unsuccessful in normalising systolic blood pressure, glomerular filtration rate or NO system activity in Zn-deficient offspring. Zn restriction during fetal life, lactation and/or post-weaning growth induced alterations in the vascular and renal NO system and in lipid metabolism that could contribute to the programming of hypertension and renal dysfunction in adulthood.