Increased renal renin content in mice lacking the Na+/H+ exchanger NHE2

Macula densa (MD) cells express the Na(+)/H(+) exchanger (NHE) isoform NHE2 at the apical membrane, which may play an important role in tubular salt sensing through the regulation of cell volume and intracellular pH. These studies aimed to determine whether NHE2 participates in the MD control of renin synthesis. Renal renin content and activity and elements of the MD signaling pathway were analyzed using wild-type (NHE2(+/+)) and NHE2 knockout (NHE2(-/-)) mice. Immunofluorescence studies indicated that NHE2(-/-) mice lack NHE3 at the MD apical membrane, so the other apical NHE isoform has not compensated for the lack of NHE2. Importantly, the number of renin-expressing cells in the afferent arteriole in NHE2(-/-) mice was increased approximately 2.5-fold using renin immunohistochemistry. Western blotting confirmed approximately 20% higher renal cortical renin content in NHE2(-/-) mice compared with wild type. No-salt diet for 1 wk significantly increased renin content and activity in NHE2(+/+) mice, but the response was blunted in NHE2(-/-) mice. Renal tissue renin activity and plasma renin concentration were elevated three- and twofold, respectively, in NHE2(-/-) mice compared with wild type. NHE2(-/-) mice also exhibited a significantly increased renal cortical cyclooxygenase-2 (COX-2) and microsomal prostaglandin E synthase (mPGES) expression, indicating MD-specific mechanisms responsible for the increased renin content. Significant and chronic activation of ERK1/2 was observed in MD cells of NHE2(-/-) kidneys. Removal of salt or addition of NHE inhibitors to cultured mouse MD-derived (MMDD1) cells caused a time-dependent activation of ERK1/2. In conclusion, the NHE2 isoform appears to be important in the MD feedback control of renin secretion, and the signaling pathway likely involves MD cell shrinkage and activation of ERK1/2, COX-2, and mPGES, all well-established elements of the MD-PGE(2)-renin release pathway.

Skin disease is prevented but nephritis is accelerated by multiple pregnancies in autoimmune MRL/LPR mice

The role of pregnancy in the progression of systemic lupus erythematosus (SLE) is still poorly understood. We analysed the effect of repeated pregnancies in MRL/lpr mice, a murine model of SLE. Seven-week old female mice were used: multiparous mice underwent three consecutive pregnancies (M); age-matched virgin mice served as controls (V). Animals were harvested at 20 weeks of age. Skin lesions were characterized by hair loss and scabs in the dorsum of the neck. Virgin skins showed thickened dermis, fibrosis and mononuclear cell infiltrates, which were practically absent in M. This was accompanied by higher IFN-gamma and lower IL-10 mRNA expression levels in V compared to M skin. Plasma IFN-gamma protein levels were also upregulated in V versus M. However, survival and kidney function were dramatically reduced and accompanied by hypertension after multiple pregnancies. Kidney histology also showed markedly increased renal lesions in M. In contrast to plasma and skin levels, both IL-10 and IFN-gamma mRNA were lower in the kidneys of V versus M mice. Concluding our findings, the pathomechanisms of lupus kidney and skin disease may be regulated differently at the organ level during pregnancy. Both IFN-gamma and IL-10 may be important regulatory cytokines at the local level.

[The Danubian Biobank Initiative: synchronizing the biobanking activities of the Danube universities]

Aging disorders pose an increasing challenge for the public health care systems in Europe. An important approach to cope with this task is the identification of relevant novel disease genes and the control of risk factors using new technological capabilities. A key element in this process is the availability of well classified, large enough patient cohorts and the establishment of quality-controlled central banks for DNA, serum, plasma, and cells/tissues/RNA/proteins together with the development of an IT based infrastructure to provide samples and data required for biomedical studies. The Danubian Biobank initiative connects universities, associated teaching hospitals and endpoint-related rehabilitation clinics along the Danube river and in neighbouring regions. The scientific network focuses on diabetes-related endpoints, vascular disease (e.g. myocardial infarction, stroke, arterial thrombosis, kidney failure), metabolic disease (e.g. obesity, diabetes, metabolic syndrome), and neurodegenerative disorders (e.g. dementia syndromes, Parkinsonism). Task forces are set up for the relevant topics of the biobank project including patient recruitment, sample and data management, public health, epidemiology and genetics, enabling technologies, and research strategies. The project aims to select the most relevant and promising scientific targets utilizing the core competences developed in the individual partner institutions. For this purpose a series of dedicated workshops and conferences are organized as well as joint research grant proposals are submitted.

Animal models of complement-mediated hypersensitivity reactions to liposomes and other lipid-based nanoparticles

Intravenous injection of some liposomal drugs, diagnostic agents, micelles and other lipid-based nanoparticles can cause acute hypersensitivity reactions (HSRs) in a high percentage (up to 45%) of patients, with hemodynamic, respiratory and cutaneous manifestations. The phenomenon can be explained with activation of the complement (C) system on the surface of lipid particles, leading to anaphylatoxin (C5a and C3a) liberation and subsequent release reactions of mast cells, basophils and possibly other inflammatory cells in blood. These reactions can be reproduced and studied in pigs, dogs and rats, animal models which differ from each other in sensitivity and spectrum of symptoms. In the most sensitive pig model, a few miligrams of liposome (phospholipid) can cause anaphylactoid shock, characterized by pulmonary hypertension, systemic hypotension, decreased cardiac output and major cardiac arrhythmias. Pigs also display cutaneous symptoms, such as flushing and rash. The sensitivity of dogs to hemodynamic changes is close to that of pigs, but unlike pigs, dogs also react to micellar lipids (such as Cremophor EL) and their response includes pronounced blood cell and vegetative neural changes (e.g., leukopenia followed by leukocytosis, thrombocytopenia, fluid excretions). Rats are relatively insensitive inasmuch as hypotension, their most prominent response to liposomes, is induced only by one or two orders of magnitude higher phospholipid doses (based on body weight) compared to the reactogenic dose in pigs and dogs. It is suggested that the porcine and dog models are applicable for measuring and predicting the (pseudo)allergic activity of particulate "nanodrugs".

Advances in renal (patho)physiology using multiphoton microscopy

Multiphoton excitation fluorescence microscopy is a state-of-the-art confocal imaging technique ideal for deep optical sectioning of living tissues. It is capable of performing ultrasensitive, quantitative imaging of organ functions in health and disease with high spatial and temporal resolution which other imaging modalities cannot achieve. For more than a decade, multiphoton microscopy has been successfully used with various in vitro and in vivo experimental approaches to study many functions of different organs, including the kidney. This study focuses on recent advances in our knowledge of renal (patho)physiological processes made possible by the use of this imaging technology. Visualization of cellular variables like cytosolic calcium, pH, cell-to-cell communication and signal propagation, interstitial fluid flow in the juxtaglomerular apparatus (JGA), real-time imaging of tubuloglomerular feedback (TGF), and renin release mechanisms are reviewed. A brief summary is provided of kidney functions that can be measured by in vivo quantitative multiphoton imaging including glomerular filtration and permeability, concentration, dilution, and activity of the intrarenal renin-angiotensin system using this minimally invasive approach. New visual data challenge a number of existing paradigms in renal (patho)physiology. Also, quantitative imaging of kidney function with multiphoton microscopy has tremendous potential to eventually provide novel non-invasive diagnostic and therapeutic tools for future applications in clinical nephrology.

Anemia is associated with mortality in kidney-transplanted patients--a prospective cohort study

Although anemia is a known risk factor of mortality in several patient populations, no prospective study to date has demonstrated association between anemia and mortality in kidney-transplanted patients. In our prospective cohort study (TransQol-HU Study), we tested the hypothesis that anemia is associated with mortality and graft failure (return to dialysis) in transplanted patients. Data from 938 transplanted patients, followed at a single outpatient transplant center, were analyzed. Sociodemographic parameters, laboratory data, medical history and information on comorbidity were collected at baseline. Data on 4-year outcome (graft failure, mortality or combination of both) were collected prospectively from the patients' charts. Both mortality and graft failure rate during the 4-year follow-up was significantly higher in patients who were anemic at baseline (for anemic vs nonanemic patients, respectively: mortality 18% vs. 10%; p < 0.001; graft failure 17% vs 6%; p < 0.001). In multivariate Cox proportional hazard models the presence of anemia significantly predicted mortality (HR = 1.690; 95% CI: 1.115-2.560) and also graft failure (HR = 2.465; 95% CI: 1.485-4.090) after adjustment for several covariables. Anemia, which is a treatable complication, is significantly and independently associated with mortality and graft failure in kidney-transplanted patients.

[Correlation of FABP2-A54T polymorphism and the metabolic syndrome in Maros County of Romania]

OBJECTIVE

The FABP2 (intestinal fatty acid-binding protein) gene is expressed in the intestinal epithelial cells and codes for a protein involved in the fatty acid metabolism. We investigated the association of the A54T polymorphism of the FABP2 gene with the metabolic syndrome defined according to the diagnostic criteria recommended by the IDF in 2005, in our region (Marosvásárhely - Tg. Mures, Romania).

RESEARCH DESIGN AND METHODS

A case-control study was carried out on 144 metabolic syndrome patients and 73 healthy persons with similar age and lifestyle. Insulin resistance was measured by the HOMA and QUICKI indices, and gene polymorphism was analyzed with PCR followed by restriction enzyme digestion with Hha I.

RESULTS

The T54 allele was more frequent in the metabolic syndrome group than in controls (35.71% vs. 28.08%, p < 0.05). In the presence of the T54 allele we have noticed a slight but statistically significant risk, more marked in the case of TT homozygotes (TT vs. AT + AA: OR = 4.31, CI 95% 1.21-5.29, p = 0.015 and TT vs. AA: OR = 4.61, CI95%: 1.24-7.03, p = 0.0195). No significant differences of the followed metabolic parameters were observed between persons having different genotypes in the two study groups.

CONCLUSIONS

These results suggest that the FABP2 T54 allele may have a minor contribution to the metabolic syndrome in our region.

Angiotensin II activates plasminogen activator inhibitor-I promoter in renal tubular epithelial cells via the AT1receptor

BACKGROUND

Plasminogen activator inhibitor-1 (PAI-1) regulates normal extracellular matrix (ECM) metabolism and it is a key regulator of the fibrotic process. Both angiotensin II (Ang II) and angiotensin IV (Ang IV) have been reported to stimulate PAI-1 expression. It is not known how PAI-1 expression is regulated by the renin-angiotensin system (RAS) in renal tubular cells.

METHODS

To dissect signaling mechanisms contributing to the up-regulation of the PAI-1 promoter, porcine proximal tubular cells stably expressing the rabbit AT1 receptor (LLC-PK/AT1) were transiently transfected with a luciferase reporter construct containing the PAI-1 promoter. Promoter activation was assessed by measuring luciferase activity from cell lysates.

RESULTS

Ang II dose-dependently stimulated the transcriptional activity of the PAI-1 promoter in renal proximal tubular cells whereas Ang IV had no consistent effect on the promoter activity. Neither inhibition of the Extracellular Signal Regulated Kinase (ERK) cascade nor inhibition of the c-Jun-N-terminal Kinase (JNK) pathway did reduce the stimulation of the PAI-1 promoter by Ang II. However, genistein, a tyrosine kinase inhibitor blocked the effect of Ang II.

CONCLUSION

Ang II but not Ang IV activates the PAI-1 promoter in renal proximal tubular cells and this effect is mediated by tyrosine kinases.

Epithelial-mesenchymal transition in renal tubular cells in the pathogenesis of progressive tubulo-interstitial fibrosis

Epithelial-mesenchymal transition (EMT) plays an important role in embryogenesis and organ formation. Over the last 10-15 years it has been established that EMT is a significant mechanism of tumor progression and metastasis formation and also of progressive tissue fibrosis in the kidney, liver and lung. EMT seen in these diverse physiological and pathophysiological contexts shares a number of stages and modules, but also carries distinct, context specific characteristics. EMT in tissue fibrosis is a form of reverse embryogenesis, when highly specialized epithelial cells in the specific organs will respond to injury with loosing their epithelial characteristics and functions and regaining characteristics of the cells from which they originated. EMT in the context of tissue fibrosis can be induced by different forms of injury or a set of humoral factors. The process is regulated by a complex balance of humoral and microenvironmental stimuli, in which cell-cell contacts and interaction of the transitioning cell with the extracellular matrix components is very important. Intense research in this exciting field yielded good understanding of many of the details of this fascinating process, although numerous questions still await proper answers. There is indication that understanding of the molecular mechanisms underlying "fibrotic" EMT may lead to the design of specific and effective therapeutic measures for progressive tissue fibrosis.

Renin-angiotensin system affects endothelial morphology and permeability of renal afferent arteriole

The afferent arteriole (AA) is an important regulatory site of renal function and blood pressure. We have demonstrated endothelial fenestration and high permeability in the vicinity of renin granulated epithelioid cells in the juxtaglomerular portion of the afferent arteriole in different mammals. The permeability of fenestrated endothelium of afferent arteriole may be important in connection to various physiologic and pathophysiologic processes. We have assumed that the permeable fenestration may serve as a communication channel between the intravascular circulation and a pathway for renin secretion. Utilising the multiphoton image technique we were able to visualise the endothelial fenestration and renin granules of the in vitro microperfused AA and in vivo AA. We demonstrated that ferritin-positive, i.e., permeable portion of the afferent arteriole, under control conditions is on average 45 microm, which is about one-third to half of the total length of the afferent arteriole. The length of this portion is not constant and can change by physiologic and pharmacologic manipulation of renin formation. The permeability of the afferent arteriole is not changing only parallel with the pharmacologically stimulated renin secretion as already demonstrated in adult rats, but also with the change of renin appearance in afferent arteriole within the very first few days of life after birth. Independently from the age there is a significant correlation between the renin-positive and permeable portion of the AA. Further studies are necessary to clarify the physiological significance of afferent arteriolar permeability and its changes in the postnatal development of the kidney, as well as in correlation with activity of renin- angiotensin system.

Fluid flow in the juxtaglomerular interstitium visualized in vivo

Earlier electron microscopy studies demonstrated morphological signs of fluid flow in the juxtaglomerular apparatus (JGA), including fenestrations of the afferent arteriole (AA) endothelium facing renin granular cells. We aimed to directly visualize fluid flow in the JGA, the putative function of the fenestrated endothelium, using intravital multiphoton microscopy of Munich-Wistar rats and C57BL6 mice. Renin content of the AA correlated strongly with the length of the fenestrated, filtering AA segment. Fluorescence of the extracellular fluid marker lucifer yellow (LY) injected into the cannulated femoral vein in bolus was followed in the renal cortex by real-time imaging. LY was detected in the interstitium around the JG AA before the plasma LY filtered into Bowman's capsule and early proximal tubule. The fluorescence intensity of LY in the JGA interstitium was 17.9 ± 3.5% of that in the AA plasma ( n = 6). The JGA fluid flow was oscillatory, consisting of two components: a fast (one every 5–10 s) and a slow (one every 45–50 s) oscillation, most likely due to the rapid transmission of both the myogenic and tubuloglomerular feedback (TGF)-mediated hemodynamic changes. LY was also detected in the distal tubular lumen about 2–5 s later than in the AA, indicating the flow of JGA interstitial fluid through the macula densa. In the isolated microperfused JGA, blocking the early proximal tubule with a micropipette caused significant increases in MD cell volume by 62 ± 4% ( n = 4) and induced dilation of the intercellular lateral spaces. In summary, significant and dynamic fluid flow exists in the JGA which may help filter the released renin into the renal interstitium (endocrine function). It may also modulate TGF and renin signals in the JGA (hemodynamic function).

The effect of local nitric oxide synthase inhibition on the diameter of pulpal arteriole in dental bond material-induced vasodilation in rat

Local application of dental bond materials can cause pulpal vasodilation and hyperemia. Such local hemodynamic changes may be mediated by alterations in the levels of locally generated nitric oxide (NO). In different species systemic administration of NO synthase inhibitors leads to a decrease in pulpal blood flow. In contrast, the local administration of these inhibitors has not been tested yet. Therefore, the effect of locally blocked NO synthase on the internal diameter of rat pulpal arterioles under basal conditions and immediately after dental bond material application was studied by using vitalmicroscopic technique. The NO synthase blocker (L-NAME) was locally administered on a thinned dentine layer of the left lower incisor. L-NAME reduced the diameter of the pulpal arteriole both in basal and after bond material-induced hyperaemic conditions. These data suggest that the local formation of NO may have a significant role in the acute vasodilation induced by bond material application and also in maintenance of basal pulpal arteriolar tone.

Integrity of cell-cell contacts is a critical regulator of TGF-beta 1-induced epithelial-to-myofibroblast transition: role for beta-catenin

Injury of the tubular epithelium and TGF-beta1-induced conversion of epithelial cells to alpha-smooth muscle actin (SMA)-expressing myofibroblasts are key features of kidney fibrosis. Since injury damages intercellular junctions and promotes fibrosis, we hypothesized that cell contacts are critical regulators of TGF-beta 1-triggered epithelial-to-mesenchymal transition (EMT). Here we show that TGF-beta 1 was unable to induce EMT in intact confluent monolayers, but three different models of injury-induced loss of epithelial integrity (subconfluence, wounding, and contact disassembly by Ca(2+)-removal) restored its EMT-inducing effect. This manifested in loss of E-cadherin, increased fibronectin production and SMA expression. TGF-beta 1 or contact disassembly alone only modestly stimulated the SMA promoter in confluent layers, but together exhibited strong synergy. Since beta-catenin is a component of intact adherens junctions, but when liberated from destabilized contacts may act as a transcriptional co-activator, we investigated its role in TGF-beta 1-provoked EMT. Contact disassembly alone induced degradation of E-cadherin and beta-catenin, but TGF-beta1 selectively rescued beta-catenin and stimulated the beta-catenin-driven reporter TopFLASH. Moreover, chelation of free beta-catenin with the N-cadherin cytoplasmic tail suppressed the TGF-beta1 plus contact disassembly-induced SMA promoter activation and protein expression. These results suggest a beta-catenin-dependent two-hit mechanism in which both an initial epithelial injury and TGF-beta 1 are required for EMT.

[The effect of the surface morphology of Ti-implants on the proliferation activity of fibroblasts and osteoblasts]

It is known that surface morphology greatly influences the osseointegration of dental implants. The goal of the experiments conducted by the authors was to study in vitro the effect of various surface modifications on the activity of bone and connective tissue cells. In the experiments they introduced NIH3T3 fibroblast and MCH3T3 osteoblast cells were cultured the surface of ten titanium disks with various morphology in 24-multiwell plates. The cells were let grow on the surface of the disks for two days in a culture medium. One group of the disks underwent scanning electronmicroscopy and the changes in the number and form of cells on the surfaces were studied under various magnifications. From the surface of the second group the cells were lysed and were counted in a Bürker's chamber. After counting the cells they were lysed in a lysis buffer and their protein concentrations were measured with the help of a spectrophotometer. The authors found that only a morphological study of the cells is possible under SEM, they could not detect a quantitative difference in the number or activity of the cells. Upon counting the cells and determining their protein concentration the best result were yielded by the surface roughened by aluminium oxide. In growing fibroblasts the titanium oxide treated surfaces provided good results, while in the case of the osteoblasts the laser treated disks were more successful.

Angiotensin II activates the human renin promoter in an in vitro model: the role of c-Jun-N-terminal kinase

BACKGROUND

Angiotensin II (Ang II) down-regulates renin expression in juxtaglomerular cells, however, recent experimental evidence obtained in transgenic mice suggested that Ang II may "paradoxically" increase transcriptional activity of the proximal renin promoter.

METHODS

To dissect signalling mechanisms contributing to the up-regulation of the proximal renin promoter by Ang II, porcine proximal tubular cells stably expressing the rabbit AT(1) receptor (LLC-PK/AT(1)) were transiently transfected with a luciferase reporter construct containing the 582 bp long piece of the human renin promoter. Activation of mitogen-activated protein kinases (MAPK) was detected by western blotting using phospho-MAPK-specific antibodies.

RESULTS

Ang II dose-dependently stimulated the transcriptional activity of the human renin promoter (10(-7) M Ang II: 3.50+/-1.25-fold stimulation). In these cells Ang II activated both extracellular signal-regulated kinase (ERK) and the c-Jun-N-terminal kinase (JNK). Inhibition of the ERK cascade did not reduce the stimulation of the renin promoter by Ang II, however, two expression vectors designed to inhibit the JNK pathway, the dominant negative JNK and the Jun-kinase interacting peptide inhibited the fold stimulation induced by Ang II (2.75+/-0.69 vs 1.6+/-0.23 and 1.8+/-0.34, respectively; P<0.01). Furthermore, genistein, a tyrosine kinase inhibitor, blocked the effect of Ang II both on the JNK and the promoter activation.

CONCLUSION

Ang II may have a stimulatory effect on the proximal renin promoter in proximal tubular cells and this effect is mediated by tyrosine kinases and the JNK cascade.

Urinary albumin excretion is correlated to fibrinogen levels and protein S activity in patients with type 1 diabetes mellitus without overt diabetic nephropathy

The aim of the study was to test the hypothesis that in diabetic patients without overt nephropathy there may be a correlation between the activity of natural anticoagulant proteins and glomerular dysfunction. Assays for functional activity of proteins S and C, measurements of urinary albumin excretion, lipid parameters and haemoglobin A1c were performed in 91 patients with type 1 diabetes mellitus and 85 patients with type 2. Patients with type 1 diabetes and microalbuminuria had significantly higher mean age (44.1 +/- 10.9 vs. 37.9 +/- 12.7 years; p<0.05), fibrinogen level (3.75 +/- 1.0 vs. 3.21 +/- 0.8 g/l; p<0.01), protein S activity (92.3 +/- 17.6 vs. 84.5 +/- 15.5%; p<0.05) and higher prevalence of retinopathy (p<0.01) and macrovascular disease (p<0.01) than those with normoalbuminuria. Albumin excretion was significantly correlated to age (r=0.25, p<0.05), fibrinogen level (r=0.39, p<0.01), protein S activity (r=0.27; p<0.05), total cholesterol (r=0.23; p<0.05), apoprotein B (r=0.22; p<0.05), retinopathy (r=0.33; p<0.01) and macrovascular disease (r=0.33; p<0.01). Patients with type 2 diabetes mellitus and microalbuminuria had significantly higher apoprotein B levels (1.17 +/- 0.3 vs. 1.06 +/- 1.2 mg/dl; p<0.05) than those with normoalbuminuria, and apoprotein B was significantly correlated to albumin excretion (r=0.22; p<0.05). In a multivariate model of type 1 diabetes mellitus with fibrinogen, protein S and C activity, cholesterol, triglycerides, haemoglobin A1c, retinopathy, and macrovascular disease as independent parameters (r=0.53; p<0.003), there was significant independent correlation of fibrinogen (beta=0.28; p<0.01), protein S activity (beta=0.27; p<0.05) and retinopathy (beta=0.21; p<0.01) with albumin excretion. We conclude that in type 1 diabetes, relative elevation of fibrinogen level and protein S activity appear in the early stages of development of diabetic nephropathy, and may be related to the pathogenesis of diabetic kidney disease.

Effect of an "all-in-one" adhesive on pulp blood vessels: a vitalmicroscopic study of rat's teeth

The newly developed self-etching, self-priming all-in-one adhesives are appealing to clinicians because they are simple and efficient to use. These single-application bonding systems contain chemically active compounds that can alter pulpal blood circulation when applied to deep dentin surfaces. Since adequate microcirculation and oxygenation are the basic requirements for tissue survival, the aim of this study was to investigate the immediate vascular effect of a new self-etching adhesive, Prompt L-Pop/composite and compomer version/(test group). The technique of vitalmicroscopy was used to record the changes in vessel diameter of the first lower incisor of 20 (10-10 in each group) male Sprague-Dawley rats (weighing 315 +/- 74/SE/g) prior to, and at 5, 15, 30 and 60 minutes after the investigated materials were applied to dentin. The application of saline served as the untreated control. The systemic arterial pressure remained unchanged throughout the experiments both in the control (110 +/- 8 mmHg) and in test animals (114 +/- 4 mmHg). In control rats, the diameter of the vessels was stable during the experiment. In the presence of Prompt L-Pop, the diameters decreased significantly during the experimental period (5 minutes: -11.15 +/- 5.03%; 15 minutes: -14.66 +/- 7.71%; 30 minutes: -13.35 +/- 5.79%; 60 minutes: -11.82 +/- 5.63% p < 0.05 in each cases). In this group, stasis developed in pulpal circulation was 1 out of 10 rats. The results from the rat model used in this study suggest that Prompt L-Pop may result in compromised pulpal microcirculation.

Diurnal blood pressure pattern may predict the increase of urinary albumin excretion in normotensive normoalbuminuric type 1 diabetes mellitus patients

To characterise the relationship between diurnal blood pressure and the subsequent increase of urinary albumin excretion (UAE) in normotensive normoalbuminuric type 1 diabetic patients, ambulatory blood pressure monitoring (ABPM) was performed in 53 patients, who were then followed for 5 years. Albumin excretion rate changed from 12.4 (8.9-17.2) to 29.3 (15.2-47.0) mg/day. Macroalbuminuria developed in 2 (3.8%), microalbuminuria in 22 (41.5%) patients, 29 (54.7%) remained normoalbuminuric. Night-time diastolic blood pressure was significantly higher (64.3+/-6.5 vs. 60.9+/-5.5 mmHg, P<0.05), diastolic diurnal index significantly lower (15.5+/-9.7 vs. 22.3+/-6.2%, P<0.01) in patients who later progressed to micro- or macroalbuminuria. Diastolic diurnal index (r=-0.40; P<0.01) and nocturnal diastolic pressure (r=0.35; P<0.01) were correlated to the change in albumin excretion. In a multivariate analysis model with the change of albumin excretion as dependent, and means and diurnal indices of systolic and diastolic blood pressure, baseline UAE, cholesterol, triglycerides, HbA1c and retinopathy as independent parameters (r=0.68; P=0.001), diurnal index for diastolic blood pressure (beta=-0.30; r=0.013), baseline HbA1c (beta=0.32; P=0.010) and retinopathy (beta=0.44; P=0.001) were significant independent correlates. We conclude that the relative increase of nocturnal blood pressure is associated with the subsequent increase of albuminuria, which in turn is predictive of overt diabetic nephropathy.

Neuronal Nitric Oxide Synthase: Its Role and Regulation in Macula Densa Cells

ABSTRACT. Macula densa (MD) cells detect changes in distal tubular sodium chloride concentration ([NaCl]L), at least in part, through an apical Na:2Cl:K co-transporter. This co-transporter may be a site for regulation of tubuloglomerular feedback (TGF), and recently angiotensin II (Ang II) was shown to regulate the MD Na:2Cl:K co-transporter. In addition, nitric oxide (NO) produced via neuronal NO synthase (nNOS) in MD cells attenuates MD-TGF signaling. This study investigated [NaCl]L-dependent MD-NO production, the regulation of co-transporter activity by NO, and the possible interaction of NO with Ang II. MD cell Na+ concentration ([Na+]i) and NO production were measured using sodium-binding benzofuran isophthalate and 4-amino-5-methylamino-2′,7′-difluorescein diacetate, respectively, using fluorescence microscopy. Na:2Cl:K co-transport activity was assessed as the initial rate of increase in [Na+]i when [NaCl]L was elevated from 25 to 150 mM. 10−4 M 7-nitroindazole, a specific nNOS blocker, significantly increased by twofold the initial rate of rise in [Na+]i when [NaCl]L was increased from 25 to 150 mM, indicating co-transporter stimulation. There was no evidence for an interaction between the stimulatory effect of Ang II and the inhibitory effect of NO on co-transport activity, and, furthermore, Ang II failed to alter MD-NO production. NO production was sensitive to [NaCl]L but increased only when [NaCl]L was elevated from 60 to 150 mM. These studies indicate that MD-NO directly inhibits Na:2Cl:K co-transport and that NO and Ang II independently alter co-transporter activity. In addition, generation of MD-NO seems to occur only at markedly elevated [NaCl]L, suggesting that NO may serve as a buffer against high rates of MD cell transport and excessive TGF-mediated vasoconstriction. E-mail: pdbell@uab.edu

[Role of mitogen-activated protein kinase cascade in the intracellular signaling of angiotensin II]

It has been recently recognized that angiotensin II (Ang II), in addition to its role in the regulation of the salt-fluid homeostasis is also a growth factor and contributes to the regulation of cellular hypertrophy or proliferation and extracellular matrix (ECM) formation. This article gives an overview on the role of mitogen activated protein kinase (MAPK) cascades in transducing the growth factor-like effects of Ang II.