In mice, proteinuria and renal inflammatory responses to albumin overload are strain-dependent

BACKGROUND

The availability of genetically modified mice has increased the need for relevant mouse models of renal disease, but widely used C57BL/6 mice often show resistance to proteinuria. 129/Sv mice are considered more sensitive to certain renal models. Albumin overload, an important model of proteinuric disease, induces marked proteinuria in rats but barely in C57BL/6 mice. We hypothesized that albumin overload would induce more proteinuria in 129S2/Sv than C57BL/6J mice.

METHODS

Male and female C57BL/6J and 129S2/Sv mice received bovine serum albumin (BSA) for 11 days. Control groups received saline injections. Injected BSA was immunohistochemically localized to study intrarenal handling of overloaded protein. Renal macrophage infiltration (F4/80 immuno-staining) and glomerular ultrastructure (electron microscopy) were assessed.

RESULTS

The BSA-treated groups were similarly hyperproteinemic at Day 11 (D11). Proteinuria differed widely. In C57BL/6J mice, it remained unchanged in females but significantly, though mildly, increased in males (from 3+/-1 to 8+/-2 mg/day, P < 0.05). In 129S2/Sv, proteinuria was marked in both males and females (4+/-1 to 59+/-14, and 0.6+/-0.2 to 29+/-9 mg/day, respectively, both P < 0.01). Proteinuria was accompanied by tubulo-interstitial macrophage infiltration in 129S2/Sv mice. Injected BSA was visualized within glomeruli in both strains and in the urinary space and tubules of 129S2/Sv but not C57BL/6J mice, indicating much greater glomerular leakage in the former. No glomerular macrophages or ultra-structural differences were detected.

CONCLUSION

There are major strain differences in the proteinuria and renal inflammatory response of mice to albumin overload, which are not due to structural variation in the filtration barrier but possibly to functional differences in glomerular protein permeability.

Gene expression of energy and protein metabolism in hearts of hypertensive nitric oxide- or GSH-depleted mice

Hypertension demands cardiac synthetic and metabolic adaptations to increased afterload. We studied gene expression in two models of mild hypertension without overt left ventricular hypertrophy using the NO synthase inhibitor nitro-L-arginine (L-NNA) and the glutathione depletor buthionine-S,R-sulfoximine (BSO). Mice were administered L-NNA, BSO, or water for 8 weeks. RNA of left ventricles was pooled per group, reverse transcribed, Cy3 and Cy5 labeled, and hybridized to cDNA microarrays. Normalized log(2) Cy3/Cy5 ratios of > or =0.7 or < or =-0.7 were considered significant. L-NNA and BSO both caused hypertension. Gene expression was regulated in cytoskeletal components in both models, protein synthesis in L-NNA-treated mice, and energy metabolism in BSO-treated mice. Energy metabolism genes shared several common transcription factor-binding sites such as Coup-Tf2, of which gene expression was increased in BSO-treated mice, and COMP-1. Characterization of the left ventricular adaptations as assessed with gene expression profiles reveals differential expression in energy and protein metabolism related to the pathogenetic background of the hypertension.

Programming blood pressure in adult SHR by shifting perinatal balance of NO and reactive oxygen species toward NO: the inverted Barker phenomenon

The “programming hypothesis” proposes that an adverse perinatal milieu leads to adaptation that translates into cardiovascular disease in adulthood. The balance between nitric oxide (NO) and reactive oxygen species (ROS) is disturbed in cardiovascular diseases, including hypertension. Conceivably, this balance is also disturbed in pregnancy, altering the fetal environment; however, effects of perinatal manipulation of NO and ROS on adult blood pressure (BP) are unknown. In spontaneously hypertensive rats (SHR), NO availability is decreased and ROS are increased compared with normotensive Wistar-Kyoto rats, and, despite the genetic predisposition, the perinatal environment can modulate adult BP. Our hypothesis is that a disturbed NO-ROS balance in the SHR dam persistently affects BP in her offspring. Dietary supplements, which support NO formation and scavenge ROS, administered during pregnancy and lactation resulted in persistently lower BP for up to 48 wk in SHR offspring. The NO donor molsidomine and the superoxide dismutase mimic tempol-induced comparable effects. Specific inhibition of inducible nitric oxide synthase (NOS) reduces BP in adult SHR, suggesting that inducible NOS is predominantly a source of ROS in SHR. Indeed, inducible NOS inhibition in SHR dams persistently reduced BP in adult offspring. Persistent reductions in BP were accompanied by prevention of proteinuria in aged SHR. We propose that in SHR the known increase in ANG II type 1 receptor density during development leads to superoxide production, which enhances inducible NOS activity. The relative shortage of substrate and cofactors leads to uncoupling of inducible NOS, resulting in superoxide production, activating transcription factors that subsequently again increase inducible NOS expression. This vicious circle probably is perpetuated into adult life.

Arterial stiffness and fetal growth in normotensive pregnancy

BACKGROUND

Normal pregnancy is characterized by a decrease in peripheral resistance and generalized vasodilation resulting in plasma volume expansion, which is associated with intrauterine growth. Stiffness of the arterial system may be a measure of the degree of plasma volume expansion. Pulse wave velocity (PWV), measured by applanation tonometry, is a validated approach to determine arterial stiffness. Pulse pressure (PP) is considered a surrogate measure for arterial stiffness. The aim of this study was to evaluate the association between arterial stiffness and fetal growth.

METHODS

In 50 normotensive pregnancies, carotid-femoral PWV was measured in the third trimester in 30 degrees lateral position. Blood pressure measurements were performed with conventional auscultatory sphygmomanometry. Birth weight centiles and weight centiles at the age of 6 months were recorded. Linear regression models were used for statistical analyses.

RESULTS

There was a significant relationship in PWV with both birth weight centiles and catch-up growth after birth, independent of mean arterial pressure (MAP). An increase of 1 m/sec in PWV was associated with a decrease in birth weight centiles by 17.6% and a catch-up of 22.3% in weight centiles after birth. A stronger association was found for pulse pressure and birth weight centiles. An increase of 1 mm Hg was associated with a decrease in birth weight centiles by 1.8%. There was no association between MAP and birth weight centiles.

CONCLUSIONS

In normotensive pregnancy arterial stiffness is associated with birth weight centile and catch-up growth after birth, independently from MAP. This suggests that arterial stiffness reflects maternal vascular adaptation to pregnancy better than blood pressure.

Resistance to oxidative stress by chronic infusion of angiotensin II in mouse kidney is not mediated by the AT2 receptor

Wild-type mice are resistant to ANG II-induced renal injury and hence form an attractive model to study renal defense against ANG II. The present study tested whether ANG II induces expression of antioxidative genes via the AT2 receptor in renal cortex and thereby counteracts prooxidative forces. ANG II was infused in female C57BL/6J mice for 28 days and a subgroup received AT2 receptor antagonist (PD-123,319) for the last 3 days. ANG II induced hypertension and aortic hypertrophy; proteinuria and renal injury were absent. Urinary nitric oxide metabolites (NOx) were decreased, and lipid peroxide (TBARS) excretion remained unchanged. Expression of NADPH oxidase components was decreased in renal cortex but induced in aorta. Heme oxygenase-1 (HO-1) was induced in both renal cortex and aorta. In contrast, ANG II suggestively increased AT2 receptor expression in kidney but not in aorta. AT2 receptor blockade enhanced hypertension in ANG II-infused mice, reversed ANG II effects on NOx excretion, but did not affect TBARS. Despite its prohypertensive effect, expression of prooxidative genes in the renal cortex decreased rather than increased after short-term AT2 receptor blockade and renal HO-1 induction after ANG II was normalized. Thus chronic ANG II infusion in mice induces hypertension but not oxidative stress. In contrast to the response in aorta, gene expression of components of NADPH-oxidase was not enhanced in renal cortex. Although ANG II administration induced renal cortical AT2 receptor expression, blockade of that receptor did not unveil the AT2 receptor as intrarenal dampening factor of prooxidative forces.

Endothelial function in pediatric patients on peritoneal dialysis: the need for data

Cardiovascular complications are emerging as the primary cause of death for patients with childhood end-stage renal disease. Children with end-stage renal failure are subjected to many of the risk factors for cardiovascular disease identified in adult patients. Dysfunction of the endothelium is presently regarded as a first but reversible step in the development of atherosclerosis. Noninvasive techniques to assess endothelial function have been recently developed and have been proven to predict future mortality in adult patients. These techniques are readily applicable to pediatric patients. Endothelial dysfunction has been demonstrated in children in all stages of renal failure. Data on pediatric patients treated with peritoneal dialysis are currently lacking, however. Considering the abundance of cardiovascular risk factors specific to treatment with peritoneal dialysis, such studies should be initiated.

Hemodialysis acutely impairs endothelial function in children

Cardiovascular disease is the main cause of death for patients with end-stage renal disease (ESRD), including young adults. The appearance of endothelial dysfunction is an early stage in the development of atherosclerosis. There are conflicting data on the effect of hemodialysis on endothelial function in adults, but there are no studies in children. This study compares endothelial function of children on hemodialysis with healthy controls and describes the effect of a regular dialysis session on endothelial function. We studied 10 healthy children and 10 children on dialysis, before and after a regular midweek hemodialysis session. Endothelial function was studied non-invasively with ultrasound equipment as the percentage of post-ischemic flow-mediated dilation (FMD) of the brachial artery. In children on dialysis, FMD was 6.0+/-4.1%, while it was 14.2+/-5.8% in healthy controls (P=0.002). Hemodialysis induced a further decrease of FMD to 1.8+/-2.7% (P=0.003). Baseline diameter or distensibility of the brachial artery did not change. Systolic blood pressure, mean arterial pressure, and pulse pressure decreased, while diastolic blood pressure and heart rate did not change. This study demonstrates that children on hemodialysis have endothelial dysfunction. A hemodialysis procedure induces further endothelial dysfunction in children with ESRD. This repeated insult on the endothelium with maintenance hemodialysis may contribute to the cardiovascular risk of these children.

Sympathetic hyperactivity in chronic kidney disease: pathogenesis, clinical relevance, and treatment

Cardiovascular morbidity and mortality importantly influence live expectancy of patients with chronic renal disease (CKD). Traditional risk factors are usually present, but several other factors have recently been identified. There is now evidence that CKD is often characterized by an activated sympathetic nervous system. This may contribute to the pathogenesis of renal hypertension, but it may also adversely affect prognosis independently of its effect on blood pressure. The purpose of this review is to summarize available knowledge on the role of the sympathetic nervous system in the pathogenesis of renal hypertension, its clinical relevance, and the consequences of this knowledge for the choice of treatment.

Moxonidine Normalizes Sympathetic Hyperactivity in Patients with Eprosartan-Treated Chronic Renal Failure

Enalapril and losartan reduce but not normalize sympathetic hyperactivity in patients with hypertensive chronic renal failure (CRF). This study assessed the effect of chronic eprosartan on BP and sympathetic activity, and assessed the effect of moxonidine during chronic eprosartan treatment. In 11 stable patients with CRF (creatinine clearance 47 +/- 10 ml/min), muscle sympathetic nerve activity (MSNA; peroneal nerve), BP, and baroreceptor sensitivity were measured in the absence of antihypertensive drugs (except diuretics) during chronic eprosartan therapy (600 mg for 6 wk) and in 9 patients after moxonidine (0.2 mg for 6 wk) was added. Normovolemia was controlled by diuretics and confirmed by extracellular fluid volume measurements. BP, heart rate, and MSNA were higher in patients than in 22 controls. During eprosartan therapy, mean arterial pressure (111 +/- 9 to 98 +/- 7 mmHg, P < 0.001), heart rate (71 +/- 10 to 65 +/- 8 bpm, P < 0.001), and MSNA (35 +/- 10 to 27 +/- 8 bursts/min, P < 0.001) decreased. After the addition of moxonidine (n = 9), a further reduction of mean arterial pressure to 89 +/- 7 mmHg (P < 0.05) and of MSNA to 20 +/- 10 bursts/min (P < 0.05) occurred. Sympathetic activity in patients with CRF can be normalized, and angiotensin II-independent sympathetic hyperactivity contributes to the pathogenesis of renal hypertension. Sympathetic hyperactivity is associated with poor cardiovascular outcomes, implying that reduction might be beneficial to the patients. The addition of moxonidine to angiotensin II antagonist treatment might be appropriate.

Nitric oxide donor induces temporal and dose-dependent reduction of gene expression in human endothelial cells

The present study tested the hypothesis that acute increases in nitric oxide (NO) exert substantial influences on gene transcription in endothelial cells (ECs) via guanylyl cyclase (GC). Human umbilical veins ECs (HUVECs) were exposed to 0.1, 1, and 10 mM of sodium nitroprusside (SNP) for 4 h and to 1 mM SNP or 250 μM of ( Z)-1[ N-(2-aminoethyl)- N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate (DETA-NONOate) for 2, 4, 8, and 24 h. Also, cells were exposed to DETA-NONOate in the presence and absence of the GC inhibitor 1 H-[1,2,4]oxadiazolo-[4,3- a]quinoxalin-1-one (ODQ; 10 μM) for 4 h. RNA was isolated, reverse transcribed, Cy3 and Cy5 labeled, and analyzed using cDNA microarrays. Increasing doses of SNP predominantly depressed gene expression in HUVECs. Gene function was related to growth, adhesion, and cell structure. DETA-NONOate evoked a wave of expression changes (maximum at 4 h), with a remarkable downregulation of the transcription factors MSX1, RELB, and Egr-1. Both SNP- and DETA-NONOate-induced gene expression had faded after 24 h, despite continued elevation of cGMP in the medium. Coadministration of ODQ decreased many, but not all, of the transcriptional responses to DETA-NONOate. NO pronouncedly depressed EC gene expression, in particular of transcription factors. The observation that many, but not all, transcriptional changes induced by NO could be inhibited by inhibition of GC indicates the presence of GC-independent NO actions on gene expression. Thus EC gene expression responds to NO; however, the transcriptional response fades during prolonged exposure. This could allow the EC to respond to increased shear, without vigorous changes in gene expression.

Central hemodynamics of hypertensive disorders in pregnancy

BACKGROUND

Preeclampsia is characterized by an increase in peripheral vasoconstriction. Studies of central hemodynamics are limited. Noninvasive evaluation of aortic stiffness and pressure waveform is possible by applanation tonometry. We determined pulse wave velocity (PWV), augmentation index (AI), subendocardial viability ratio (SEVR), and the central to brachial pressure amplification in normotensive, hypertensive, and preeclamptic pregnancies.

METHODS

In 51 normotensive, 38 hypertensive, and 33 preeclamptic pregnancies we measured carotid-femoral PWV. The AI, SEVR, and central pressures were determined by analysis of the aortic pressure waveform derived from the radial artery. Measurements were performed in lateral position after 10 min of rest. Linear regression models and ANOVA multiple comparisons were used for statistical analyses.

RESULTS

There were no differences in age or other baseline characteristics. The mean PWV for the normotensive, hypertensive, and preeclamptic groups was 5.1 m/sec (SD 0.6), 6.2 m/sec (SD 1.0), and 7.0 m/sec (SD 1.3), respectively. The AI was 6.7% (SD 14.0), 17.7% (SD 15.9), and 31.1% (SD 12.4), respectively. The SEVR was 1.38 (SD 0.2), 1.50 (0.2), and 1.48 (0.3), respectively. Central to brachial pressure amplification was 1.6 (SD 0.2), 1.4 (SD 0.2), and 1.3 (SD 0.2), respectively. After adjustment for blood pressure, no significant differences remained between the groups.

CONCLUSIONS

In hypertensive and preeclamptic pregnancies, aortic stiffness and augmentation are significantly higher as compared to normotensive pregnancy. Amplification of central pulse pressure is significantly lower in hypertensive and preeclamptic pregnancies, resulting in relatively higher central pressure. Nevertheless, the supply and demand ratio of the heart is not impaired in hypertensive and preeclamptic pregnancies.

Effects of endothelin-1 and endothelin-1-receptor blockade on renal function in humans

BACKGROUND

In patients with renal or cardiac failure, renal function may be endangered by elevated plasma concentrations of the vasoconstrictor endothelin-1 (ET-1). To mimic effects of pathologically increased plasma ET-1, we gave intravenous ET-1 in healthy subjects and examined whether simultaneous infusion of the ETA-receptor antagonist VML 588 would prevent the effects of ET-1 on the kidney.

METHODS

Nine healthy men received on four separate days intravenous infusion of ET-1 (2.5 ng/kg/min) superimposed on vehicle (saline) or on VML 588 infusion (0.05, 0.20 and 0.40 mg/kg/h) in randomized order to assess the effects on renal function and renal haemodynamics.

RESULTS

At resting plasma ET-1, infusion of VML 588 alone had no significant effects on renal function. Infusion of ET-1 alone decreased glomerular filtration rate by 11% and this reduction was not reversed by co-infusion of VML 588. ET-1 reduced renal blood flow by 35% and VML 588 reduced this decrease by one-third, in a dose-independent fashion. ET-1 increased the filtration fraction by 34% and VML 588 reduced this increase dose-independently by one-half. ET-1 increased renal vascular resistance by 59% and VML 588 reduced this increase dose-independently by one-half. Finally, ET-1 decreased sodium excretion by 58% and VML 588 reduced this decrease dose-independently by two-thirds.

CONCLUSIONS

ET-1-induced reductions in renal function were partially but not completely prevented in a dose-independent manner by the ETA-receptor antagonist VML 588.

Temporary losartan or captopril in young SHR induces malignant hypertension despite initial normotension

BACKGROUND

Exposure of normotensive rats to angiotensin-converting enzyme (ACE) inhibitors in early life causes hypertrophy of intrarenal arteries. Similar defects have been found in knockout mice lacking angiotensinogen, ACE, or angiotensin II type 1 (AT1) receptors. On the other hand, transient inhibition of the renin-angiotensin system from 2 weeks of age in spontaneously hypertensive rats (SHR), either with ACE inhibitors or with AT1 receptor antagonists partially prevents the increase in blood pressure. However, permanent treatment of SHR from conception onwards with ACE inhibitors completely prevents hypertension. Although these studies demonstrated protection from hypertension-induced changes in the heart and large arteries, renal arteries were not studied and follow-up did not extend beyond 6 months of age. We postulated that while brief exposure to ACE inhibitors or AT1 receptor antagonists in young SHR would temporarily decrease blood pressure, it would also be associated with development of intrarenal arterial malformation, and ultimately have deleterious effects.

METHODS

Direct effects on intrarenal arterial morphology of an ACE inhibitor (captopril, 100 mg/kg/day) and an AT1 receptor antagonist (losartan, 50 mg/kg/day), administered from the last week of gestation until 8 weeks of age were examined in SHR. After stopping treatment at 8 weeks, we continued to monitor blood pressure until spontaneous death.

RESULTS

Systolic blood pressure at 8 weeks was normalized by captopril and losartan (SHR control 187 +/- 8 mm Hg; captopril 118 +/- 5 mm Hg; and losartan 120 +/- 9 mm Hg). However, by 30 weeks, blood pressure had increased to control SHR levels. At 4 weeks, the media of renal arteries and arterioles was hypertrophied. Marked smooth muscle cell hyperplasia of cortical arteries resulted in significantly increased wall thickness by 8 weeks, despite similar external diameter. Arterial wall structure was disrupted, with fragmentation of elastic fibers and irregular distribution of collagen type I fibers. After stopping treatment, the rats gradually began to show poor health and all had died by 1 year of age, while all 1-year-old control SHR females were in good health. The cause of morbidity and mortality in the rats treated in early life was clearly malignant hypertension. Severe hypertrophy of renal arterioles was found, as well as cerebral hemorrhage.

CONCLUSION

Despite initial normalization of blood pressure interference with the renin-angiotensin system during a crucial stage of development in SHR can initiate marked smooth muscle cell hyperplasia and disruption of the wall structure of the intrarenal arteries. Subsequent progression of this intrarenal process after cessation of treatment suggests an independent process that eventually results in malignant hypertension and early death.

Sympathetic nerve activity is inappropriately increased in chronic renal disease

The hypothesis that in hypertensive patients with renal parenchymal disease sympathetic activity is "inappropriately" elevated and that this overactivity is a feature of renal disease and not of a reduced number of nephrons per se is addressed. Fifty seven patients with renal disease (various causes, no diabetes, all on antihypertensive medication) were studied, age range 18 to 62, creatinine clearance 10 to 114 ml/min per 1.73 m(2). Antihypertensives were stopped, but diuretics were allowed, to prevent overhydration. Matched control subjects were also studied. The effect of changes in fluid status was examined in seven patients while on and after stopping diuretics and in eight control subjects while on low- and high-sodium diet. Seven kidney donors were studied before and after unilateral nephrectomy. Sympathetic activity was quantified as muscle sympathetic nerve activity (MSNA) in the peroneal nerve. Mean arterial pressure, MSNA, and plasma renin activity were higher in patients than in control subjects, respectively (115 +/- 12 and 88 +/- 11 mmHg, 31 +/- 15 and 18 +/- 10 bursts/min, and 500 [20 to 6940] and 220 [40 to 980] fmol/L per s; P < 0.01 for all items). Extracellular fluid volume (bromide distribution) did not differ. Seven patients were studied again after stopping diuretics. MSNA decreased from 34 +/- 18 to 19 +/- 18 bursts/min (P < 0.01). Eight healthy subjects were studied during low- and high-sodium diet. MSNA was 26 +/- 12 and 13 +/- 7 bursts/min (P < 0.01). The curves relating extracellular fluid volume to MSNA were parallel in the two groups but shifted to a higher level of MSNA in the patients. In the kidney donors, creatinine clearance reduced by 25%, but MSNA was identical before and after donation. It is concluded that in hypertensive patients with renal parenchymal disease, sympathetic activity is inappropriately high for the volume status and that reduction of nephron number in itself does not influence sympathetic activity.

Growth hormone therapy influences endothelial function in children with renal failure

Endothelial dysfunction, an early step in atherogenesis, is prevalent in children with renal insufficiency. Endothelial dysfunction in growth hormone deficiency is reversed by growth hormone (rhGH) therapy. Renal failure induces growth hormone resistance at the receptor and post-receptor level, which can be overcome by rhGH therapy. This study investigates the influence of rhGH therapy in children with renal failure on flow-mediated dilation (FMD) of the brachial artery, a marker of endothelial function. We studied 8 patients, who were on rhGH for at least 6 months, and 8 healthy children for comparison. FMD of the brachial artery was measured non-invasively as the percentage increase in diameter during post-ischemic hyperemia. Patients were studied at baseline, after 4 weeks interruption of rhGH therapy, and 4 weeks after resumption of therapy. FMD was significantly lower in patients (4.7%) than healthy controls (13.8%) ( P=0.01). During the administration of rhGH, FMD was significantly higher (3.9%) than during interruption of the treatment (1.4%) ( P=0.04). Our data support the theory that a disturbance in the GH-IGF axis contributes to the endothelial dysfunction of renal failure. Treatment with rhGH not only improves growth but may also favorably influence the risk for atherogenesis.

Perinatal L-arginine and antioxidant supplements reduce adult blood pressure in spontaneously hypertensive rats

Embryo cross-transplantation and cross-fostering between spontaneously hypertensive rats (SHR) and normotensive rats (WKY) suggest that perinatal environment modulates the genetically determined phenotype. In SHR the balance between NO and reactive oxygen species (ROS) is disturbed. We hypothesized that increasing NO and diminishing ROS in perinatal life would ameliorate hypertension in adult SHR. Pregnant SHR and WKY and their offspring received l-arginine plus antioxidants (vitamin C, vitamin E, and taurine) during the last 2 weeks of pregnancy and then until either 4 or 8 weeks after birth. Systolic blood pressure (SBP) and urinary excretion of protein, nitrates (NO(x)), and thiobarbituric acid reactive substances (TBARS) were measured. At 48 weeks of age rats were euthanized for glomerular counts. Perinatal supplements reduced SBP persistently in SHR and prevented the SBP increase observed in aging WKY. Initially NO(x) excretion was lower and TBARS excretion higher in SHR than WKY. There was a direct effect on NO(x) excretion in supplemented pregnant SHR and their offspring, but no increase was observed after stopping the supplements. TBARS excretion was only depressed up to 14 weeks by the supplements despite persistent differences in SBP. Consistent effects on nephron number were absent. Mild proteinuria, present in control SHR at 48 weeks, was prevented in all supplemented rats. Perinatal supplementation of NO substrate and antioxidants results in persistent reduction of SBP and renal protection in SHR, although effects on NO(x) and TBARS were only transient. This suggests a critical role for perinatal pro- and antioxidant balance in programming BP later in life.

Broadly Altered Gene Expression in Blood Leukocytes in Essential Hypertension Is Absent During Treatment

We assessed whether large-scale expression profiling of leukocytes of patients with essential hypertension reflects characteristics of systemic disease and whether such changes are responsive to antihypertensive therapy. Total RNA from leukocytes were obtained from untreated (n=6) and treated (n=6) hypertensive patients without apparent end-organ damage and from normotensive controls (n=9). RNA was reverse-transcribed and labeled and gene expression analyzed using a 19-K oligonucleotide microarray using dye swaps. Samples of untreated and of treated patients were pooled for each sex and compared with age- and sex-matched controls. In untreated patients, 680 genes were differentially regulated (314 up and 366 down). In the treated patients, these changes were virtually absent (4 genes up, 3 genes down). A myriad of changes was observed in pathways involved in inflammation. Inflammation-dampening interleukin receptors were decreased in expression. Intriguingly, inhibitors of cytokine signaling (the PIAS family of proteins) were differentially expressed. The expression of several genes that are involved in regulation of blood pressure were also differentially expressed: angiotensin II type 1 receptor, ANP-A receptor, endothelin-2, and 3 of the serotonin receptors were increased, whereas endothelin-converting enzyme-1 was decreased. Strikingly, virtually no changes in gene expression could be detected in hypertensive patients who had become normotensive with treatment. This observation substantiates the long-standing idea that hypertension is associated with a complex systemic response involving inflammation-related genes. Furthermore, leukocytes display differential gene expression that is of importance in blood pressure control. Importantly, treatment of blood pressure to normal values can virtually correct such disturbances.

Hypercholesterolemia in Rats Induces Podocyte Stress and Decreases Renal Cortical Nitric Oxide Synthesis via an Angiotensin II Type 1 Receptor-Sensitive Mechanism

Podocyte stress precedes proteinuria in hypercholesterolemic rats. Molsidomine, a nitric oxide (NO) donor, prevented podocyte stress and proteinuria in long-term hypercholesterolemia, suggesting that podocyte stress was due to NO deficiency. Podocytes express the angiotensin II type 1 receptor, which influences their function. Because NO counteracts angiotensin II, it was hypothesized that in a setting of impaired renal NO availability, angiotensin II receptor inhibition could prevent podocyte stress. For determining the effect of NO deficiency on podocyte stress, one group of female rats were fed 2% cholesterol and another group the arginine analogue N-omega-nitro-L-arginine (L-NNA; 40 mg/kg food) for 2 wk. Another group of rats that were fed 2% cholesterol also received the NO donor molsidomine (120 mg/L water) for 2 wk before and during cholesterol feeding. For determining the influence of angiotensin II in the setting of decreased renal NO availability, rats that were treated with cholesterol or L-NNA received the angiotensin II type 1 antagonist losartan (200 mg/L water) for 2 wk before and during cholesterol or L-NNA administration. Desmin staining and electron microscopy were used to monitor podocyte activation. Glomerular caveolin was quantified by immunohistochemistry. Renal cortical NO synthesis, NO synthase isoforms, and caveolin-1 protein mass were also measured. Both short-term cholesterol and L-NNA induced podocyte stress as evidenced by enhanced desmin staining and electron-dense fused foot processes. Podocyte stress was prevented by molsidomine in short-term hypercholesterolemia. Furthermore, losartan prevented podocyte stress in rats that were treated with cholesterol or with L-NNA. Finally, hypercholesterolemia decreased renal cortical NO synthase activity and increased caveolin-1 protein mass and glomerular caveolin staining, and these changes were also prevented by losartan. It is suggested that podocyte stress in these models of early injury results from angiotensin II, unopposed by the action of endogenous NO. This underscores the strategic role of angiotensin II blockers in early kidney disease.

Sympathetic Hyperactivity in Chronic Renal Failure: A Wake-up Call

Sympathetic hyperactivity plays an important and distinct role in hypertension associated with chronic renal failure (CRF). Renal ischemia, elevated angiotensin II, and suppressed brain nitric oxide (NO) all stimulate sympathetic activity. Evidence is accumulating for a role of sympathetic hyperactivity in renal and cardiac damage in patients with CRF. Decreased NO availability and increased oxidative stress, characteristic in CRF patients, seem to sensitize target organs for damaging actions of sympathetic hyperactivity. Fortunately, sympatholytic agents can slow down progression of renal and cardiac dysfunction. Angiotensin-converting enzyme inhibitors or angiotensin II receptor antagonists suppress sympathetic activity, but complete elimination of the effect of sympathetic hyperactivity can be obtained only with specific adrenergic blockers. However, this important therapeutic option is grossly neglected, painfully illustrated by the unwillingness to treat CRF patients with beta-blockers, even if they have had a myocardial infarction. After discussion of mechanisms and effects of the sympathetic hyperactivity, a case is made for increased application of specific adrenergic blockers in patients with CRF.

Causes and consequences of increased sympathetic activity in renal disease

Much evidence indicates increased sympathetic nervous activity (SNA) in renal disease. Renal ischemia is probably a primary event leading to increased SNA. Increased SNA often occurs in association with hypertension. However, the deleterious effect of increased SNA on the diseased kidney is not only caused by hypertension. Another characteristic of renal disease is unbalanced nitric oxide (NO) and angiotensin (Ang) activity. Increased SNA in renal disease may be sustained because a state of NO-Ang II unbalance is also present in the hypothalamus. Very few studies have directly compared the efficacy of adrenergic blockade with other renoprotective measures. Third-generation beta-blockers seem to have more protective effects than traditional beta-blockers, possibly via stimulation of NO release. Although it has been extensively documented that muscle SNA is increased in chronic renal failure, data on renal SNA and cardiac SNA are not available for these patients before end-stage renal disease. It is also unknown whether additional treatment with third-generation beta-blockers can delay the progression of renal injury and prevent cardiac injury in chronic renal failure more efficiently than conventional treatment with angiotensin-converting enzyme inhibitors only.

The benefit of STent placement and blood pressure and lipid-lowering for the prevention of progression of renal dysfunction caused by Atherosclerotic ostial stenosis of the Renal artery. The STAR-study: rationale and study design

BACKGROUND

Atherosclerotic renal artery stenosis (ARAS) is associated with progressive loss of renal function and is one of the most important causes of renal failure in the elderly. Current treatment includes restoration of the renal arterial lumen by endovascular stent placement. However, this treatment only affects damage caused by ARAS due to the stenosis and ensuing post-stenotic ischemia. ARAS patients have severe general vascular disease. Atherosclerosis and hypertension can also damage the kidney parenchyma causing renal failure. Medical treatment focuses on the latter. Lipid-lowering drugs (statins) could reduce renal failure progression and could reduce the overall high cardiovascular risk. The additional effect on preserving renal function of stent placement as compared to medical therapy alone is unknown. Therefore, the STAR-study aims to compare the effects of renal artery stent placement together with medication vs. medication alone on renal function in ARAS patients.

METHOD

Patients with an ARAS of > or = 50% and renal failure (creatinine (Cr) clearance < 80 mL/min/1.73 m2) are randomly assigned to stent placement with medication or to medication alone. Medication consists of statins, anti-hypertensive drugs and antiplatelet therapy. Patients are followed for 2 yrs with extended follow-up to 5 yrs. The primary outcome of this study is a reduction in Cr clearance > 20% compared to baseline. This trial will include 140 patients.

Validation and use of the FinometerTM for blood pressure measurement in normal, hypertensive and pre-eclamptic pregnancy

OBJECTIVE

Although a large variety of automated blood pressure devices are available, only some have been validated for use in clinical practice. The British Hypertension Society (BHS) recommends separate validation of automated devices in special subgroups, e.g. the elderly and pregnant women. The aim of this study was to compare the Finometer (FM) and the earlier validated SpaceLabs 90207 (SL) with standard auscultatory blood pressure measurements in normal, pre-eclamptic and hypertensive pregnancy, following the guidelines of the BHS and the Association for the Advancement of Medical Instrumentation (AAMI).

METHODS

The total study group consisted of 123 pregnant women, of whom were 54 normotensive, 31 pre-eclamptic and 38 hypertensive. Automated readings with the FM and SL were compared with auscultatory blood pressure measurements. Bland-Altman plots, BHS grades, mean pressure differences and 95% limits of agreement were used for analysis.

RESULTS

Bland-Altman plots showed a wide scatter of the pressure differences between auscultatory and automated measurements. FM achieved BHS grades C/D, C/B, D/D and D/D in the total, normotensive, pre-eclamptic and hypertensive group, respectively. The AAMI criteria were only met for diastolic blood pressure in the normotensive group. For SL almost identical BHS grades and 95% limits of agreement as compared to our earlier study were found.

CONCLUSIONS

The accuracy and precision of the Finometer are not sufficient for determination of absolute blood pressure levels in individual pregnant women. Our present findings on the SpaceLabs 90207 reconfirm our earlier results.

Pathophysiology of oedema in idiopathic nephrotic syndrome

The decrease in plasma protein and colloid osmotic pressure (COP) in the nephrotic syndrome is accompanied by a decrease in tissue-fluid protein and COP. The latter protects against a fall in blood volume. However, the range and speed of this protective mechanism are limited, and a decrease in blood volume can be expected if plasma COP is below approximately 10 mmHg, or (temporarily) if the protein loss starts very fast. In addition, due to this protective mechanism volume retained by the kidneys cannot effectively expand blood volume, explaining that hypertension is rarely grave and pulmonary congestion unusual, whereas peripheral oedema can be gross. The renal derangement leading to volume retention involves a decreased filtration per nephron, increased tubular reabsorption, and decreased sensitivity to ANP but the relation between these changes is incompletely resolved.

Hypoalbuminaemia enhances the renal vasoconstrictor effect of lysophosphatidylcholine

BACKGROUND

Lysophosphatidylcholine (LPC) causes vascular dysfunction in vitro. Lipoprotein LPC is increased in hypoalbuminaemia. Albumin binds LPC and restores LPC-induced abnormalities. We hypothesized that in vivo LPC impairs blood flow more in hypoalbuminaemia than in normoalbuminaemia.

METHODS

Increasing concentrations of LPC were infused intra-renally in Nagase analbuminaemic rats (NAR) and Sprague-Dawley rats (controls).

RESULTS

Intra-renal LPC (0.1 micromol/min, 20 min) reduced renal blood flow (RBF) more (P < 0.01) in NAR (from 8.3 +/- 0.3 to 4.0 +/- 1.1) than in controls (from 7.7 +/- 0.7 to 5.8 +/- 0.5 ml/min/g kidney). Lysophosphatidylethanolamine had no effect. After stopping LPC, RBF recovery was delayed in NAR [median 90 (range: 70-90) vs 45 min (40-60), P < 0.01]. Intravenous bovine serum albumin (BSA) prevented LPC-induced vasoconstriction in both strains. Prolonging LPC for 60 min delayed recovery of RBF. In this setting, intra-renal BSA completely restored RBF in 75 min (30-90), while intra-renal saline over 75 min only resulted in 33 +/- 13% recovery (P < 0.01). Baseline renal LPC content was unchanged in NAR. However, intra-renal LPC infusion doubled renal LPC content in NAR, but had no effect in controls.

CONCLUSIONS

In NAR, baseline RBF and renal LPC content are normal. However, exposure of NAR to LPC results in much more vasoconstriction and accumulation of LPC than in normoalbuminaemia. Addition of albumin prevents and restores LPC-induced vasoconstriction.

NO dependency of RBF and autoregulation in the spontaneously hypertensive rat

In the spontaneously hypertensive rat (SHR), renal blood flow (RBF) has been reported to be very dependent on nitric oxide (NO); however, autoregulation is normal, albeit shifted to higher perfusion pressures. To test the hypothesis that in the SHR NO dependency of RBF autoregulation is diminished, we investigated RBF autoregulation in anesthetized young male SHR and normotensive Wistar-Kyoto (WKY) rats before and during acute intravenous NO synthase (NOS) inhibition with N(omega)-nitro-L-arginine (L-NNA) and urinary excretion of nitrate plus nitrite (U(NOx)V) at different renal perfusion pressures (RPP). Under baseline conditions, SHR had higher mean arterial pressure (147 +/- 4 mmHg) and renal vascular resistance (16 +/- 1 U) than WKY (105 +/- 4 mmHg and 10 +/- 0.5 U, respectively, P < 0.05). RBF was similar (9.4 +/- 0.5 vs. 10.3 +/- 0.1 ml x min(-1)x g kidney wt(-1)). Acute NOS blockade increased mean arterial pressure similarly, but there was significantly more reduction in RBF and hence an enhanced increase in renal vascular resistance in SHR (to 36 +/- 3 vs. 17 +/- 1 U in WKY, P < 0.001). The renal vasculature of SHR is thus strongly dependent on NO in maintaining basal RBF. The lower limit of autoregulation was higher in SHR than WKY in the baseline situation (85 +/- 3 vs. 71 +/- 2 mmHg, P < 0.05). Acute L-NNA administration did not decrease the lower limit in the SHR (to 81 +/- 3 mmHg, not significant) and decreased the lower limit to 63 +/- 2 mmHg (P < 0.05) in the WKY. The degree of compensation as a measure of autoregulatory efficiency attained at spontaneous perfusion pressures was comparable in SHR vs. WKY but with a shift of the curve toward higher perfusion pressures in SHR. Acute NOS blockade only increased the degree of compensation in WKY. Remarkably, U(NOx)V was significantly lower at spontaneous RPP in SHR. After reduction of RPP, the observed decrease in U(NOx)V was significantly more pronounced in WKY than in SHR. In conclusion, the renal circulation in SHR is dependent on high levels of NO; however, the capacity to modulate NO in response to RPP-induced changes in shear stress seems to be limited.