Sympathetic blockade prevents the decrease in cardiac VEGF expression and capillary supply in experimental renal failure.

Uremic cardiomyopathy of men and rodents is characterized by lower myocardial capillary supply that in rats could be prevented by central and peripheral blockade of the sympathetic nervous system. The underlying pathomechanisms remain largely unknown. We investigated whether alterations of cardiac vascular endothelial growth factor (VEGF) gene and protein expression were involved. In our long-term experiment, we analyzed whether VEGF gene and protein expression was altered in the heart of male Sprague-Dawley rats with either sham operation (sham, n=10) or subtotal nephrectomy (SNX, n=10). In our short-term experiment (17 sham, 24 SNX), the effect of a putative downregulation of sympathetic nervous activity by surgical renal denervation (interruption of renal afferent pathways) on cardiac gene expression of VEGF, flt-1, and flk-1 and on myocardial capillary supply was analyzed. In the long-term study, cardiac capillary supply and vascular endothelial growth factor gene and protein expression were significantly lower in SNX than in sham. In the short-term experiment, cardiac VEGF mRNA expression was significantly lower in untreated SNX (4,258±2,078 units) than in both sham groups (11,709±4,169 and 8,998±4,823 units); this decrease was significantly prevented by renal denervation (8,190±3,889, P<0.05). We conclude that cardiac VEGF gene and protein expression is reduced in experimental renal failure, and this may be considered as one potential reason for impaired myocardial adaptation under the situation of cardiac hypertrophy. The beneficial effect of sympathetic downregulation on cardiac structure and function in renal failure may be at least in part explained by increased cardiac VEGF gene expression.

Differential regulation of transforming growth factor receptors by angiotensin II and transforming growth factor-beta1 in vascular smooth muscle.

Angiotensin II (Ang II) and transforming growth factor (TGF) beta1 play a role in vascular remodeling in hypertension. In this process they may interact on various levels, including that of receptor regulation. This consideration prompted the present study on transcriptional regulation of TGF-beta receptors by Ang II and TGF-beta in vascular smooth muscle cells. Transcriptional expression of the components of the TGF-beta system was demonstrated for TGF-beta and for TGF-beta receptors I, II, and III. As measured by quantitative reverse transcriptase polymerase chain reaction, TGF-beta mRNA increased about 2.4-fold in the presence of 40 pM exogenous TGF-beta. Ang II at 10(-6) M increased TGF-beta mRNA 2.5-fold compared to control cells (P<0.05). Ang II also significantly increased TGF-beta protein concentration in the supernatant of confluent vascular smooth muscle cells. Ang II caused the induction of TGF-beta, but short-term experiments showed TGF-beta receptor II mRNA to be differentially regulated by Ang II and TGF-beta; while TGF-beta caused a 40% decrease in TGF-beta receptor II mRNA after 4 h (P<0.05), Ang II caused an increase by about 70%. In contrast, both TGF-beta and Ang II increased TGF-beta receptor I mRNA to about 260% or 180% of controls (P<0.05). TGF-beta effects were abrogated by coincubation with a TGF-beta neutralizing antibody, and Ang II effects were abrogated by losartan, an AT-1 receptor antagonist. Coincubation of Ang II with the TGF-beta neutralizing antibody did not inhibit the effect of Ang II, indicating that the short-term effects of Ang II on the expression of the TGF-beta receptors are not mediated via TGF-beta. Furthermore, Ang II stimulated DNA synthesis even in the presence of the TGF-beta neutralizing antibody. In conclusion, this study indicates (a) that in vascular smooth muscle TGF-beta receptors are regulated on the RNA level by TGF-beta and Ang II, and (b) that Ang II dependent regulation of TGF-beta receptors is at least partially independent of endogenous TGF-beta. Stimulation of the transcriptional expression of TGF-beta receptors by Ang II may increase sensitivity of vascular smooth muscle cells to TGF-beta.

Nephroprotection of an ET(A)-receptor blocker (LU 135252) in salt-loaded uninephrectomized stroke-prone spontaneously hypertensive rats.

The present study was designed to assess whether the orally active and highly specific endothelin A (ET(A)) receptor antagonist LU 135252 affects progressive renal dysfunction in a hypertensive rat model of renal damage, ie, the uninephrectomized (UNX) stroke-prone spontaneously hypertensive rat (SHRsp). The animals were examined on a normal salt (0.25%) diet and, to sensitize the kidney to hypertensive injury, also on a high salt (3%) diet. Stereological methods were used to quantify indices of glomerulosclerosis, vascular damage, and tubulointerstitial damage. Treatment with LU 135252 (100 mg/kg body wt) did not affect systolic blood pressure (BP) in animals on a normal salt diet during the whole period of the experiment (18 weeks) or in salt-loaded animals until week 10; subsequently, BP was slightly but significantly lower in salt-loaded UNX-SHRsp given LU 135252. Between weeks 6 and 12, 40% of the untreated UNX-SHRsp on a high salt diet, but none on a standard salt diet, died; such mortality was completely prevented by LU 135252. Indices of renal damage were more abnormal in salt-loaded UNX-SHRsp compared with UNX-SHRsp on a normal salt diet. Development of glomerulosclerosis and tubulointerstitial and vascular damage in UNX-SHRsp on high salt was completely prevented by LU 135252. The respective indices were no longer significantly different from those of salt-loaded sham-operated SHRsp controls. In the less severely damaged kidneys of UNX-SHRsp on normal salt, treatment with LU 135252 tended to ameliorate the indices, but the difference was not statistically significant. The results document a role of the ET system, specifically of ET(A) receptors, in the development of progressive renal injury in salt-loaded UNX-SHRsp. LU 135252 completely prevented death and renal damage resulting from salt loading.

Nephroprotective effect of ACE inhibitors.

In most cases of renal disease, progression of renal failure occurs via nonspecific mechanisms that can be dissociated from the primary cause of renal damage. Progression of disease is accompanied by glomerulosclerosis and tubulointerstitial fibrosis. Loss of autoregulation and afferent renal vasodilation renders the glomerular microcirculation particularly susceptible to systemic hypertension. Glomerular growth is an ancillary factor permitting the development of glomerulosclerosis. Experimental and clinical studies indicate that angiotensin converting enzyme (ACE) inhibitors may prevent progressive renal deterioration. Furthermore, it appears that this effect can be dissociated, at least in part, from the haemodynamic effects of ACE inhibitors. Some evidence indicates that the renal-protective effects of ACE inhibitors results from their effects on glomerular growth and glomerular permselectivity. The role of reduced generation of angiotensin II or accumulation of kinins in the renal effects of ACE inhibitors is under investigation. Prospective clinical trials have demonstrated that ACE inhibitors reduce proteinuria and interfere with progression of renal disease to a greater degree than can be explained by their blood pressure lowering effects alone.

Smoking: a factor promoting onset and progression of diabetic nephropathy.

Although smoking was identified two decades ago as a factor promoting the onset and progression of nephropathy in Type 1 and then in Type 2 diabetes, its role has been largely neglected. More recently, it has been shown that smoking adversely affects renal haemodynamics and protein excretion even in subjects without renal disease. In addition, it impairs the prognosis for renal function in patients with non-diabetic renal disease. Recent studies have suggested the involvement of sympathetic activation, increased endothelin production, and impaired endothelial cell-dependent vasodilatation in the genesis of smoking-induced renal function impairement. Cessation of smoking apparently slows progression to renal failure, but the decision to stop smoking is difficult because of the high addictive potential of the habit. The challenge remains for diabetologists and nephrologists to motivate patients to stop smoking.

Endothelin in renal diseases and cardiovascular remodeling in renal failure.

The pathogenetic mechanisms leading to progression of renal failure are only partly understood. Several studies in immune- and non-immune-mediated models of renal damage have recently implicated the endothelin (ET) system as a major player in these processes. In animal models, ET receptor antagonists have been shown to be highly effective in abrogating the progression of renal failure. Furthermore, cardiac structural alterations seen in hypertension and/or renal insufficiency, e.g. left ventricular hypertrophy, thickening of intramyocardial arterioles, and the increase in non-vascular interstitial tissue, are largely prevented by ET receptor antagonists. In this context it is of interest that these beneficial renal and cardiac effects are, at least in most studies, independent of systemic blood pressure. In addition to the specific pharmacological blockade of the renin-angiotensin system [ACE inhibitors, angiotensin II receptor (AT1) antagonists], blockade of ET receptors or ET converting enzyme (ECE) may be a new tool to interfere with progression of renal failure and cardiovascular remodeling in humans.

[Adverse renal effects of legal and illicit drugs]. / Nierenschädigung durch legale und illegale Drogen.

The most important task of clinical and experimental nephrology is to identify risk factors for progression of renal failure with the ultimate goal to counteract the dramatic increase of patients reaching end-stage renal disease. Recently, cigarette smoking has been recognized to be one of the most important remediable renal risk factors. The adverse renal effects of smoking seem to be independent of the underlying renal disease and the current evidence suggests a near doubling of the rate of progression in smokers vs. non-smokers. Cessation of smoking slows the rate of progression. Besides smoking, alcohol abuse has also been implicated as a renal risk factor. The present article reviews the current knowledge about the adverse renal effects of these legal drugs. Furthermore, the acute and chronic renal complications due to illegal recreational drugs is discussed. The impact of these drugs on the risk to reach end-stage renal failure is difficult to assess, which is mainly due to the fact that it is difficult to perform controlled prospective studies in substance abusers. According to estimates, 5-6% of new patients starting end-stage renal disease therapy may have opiate-use-related renal diseases in the USA--a figure which documents the magnitude of the problem. Thus, in any case of unexplained renal functional impairment substance abuse should be considered by the physician.

Angiotensin converting enzyme inhibitors, calcium channel blockers, and their combination in the treatment of glomerular disease.

BACKGROUND: Glomerular diseases may progress to end-stage renal failure via the development of glomerulosclerosis. Systemic hypertension and intraglomerular hypertension are important, although not the only, determinants of this process. Proteinuria (albuminuria) is a surrogate marker for glomerular damage and renal prognosis. EFFICACY OF ANGIOTENSIN CONVERTING ENZYME (ACE) INHIBITORS: In animal experiments and in controlled clinical studies, ACE inhibitors have proved to be effective in reducing proteinuria and in preventing glomerulosclerosis or progression to end-stage renal failure, possibly more than can be explained by their effects on blood pressure. EFFICACY OF CALCIUM CHANNEL BLOCKERS: In contrast to the uniform efficacy of ACE inhibitors, the effect of calcium channel blockers is less uniform. It depends on the model of renal damage used, the extent of the fall in systemic blood pressure and the type of calcium channel blocker used. Nevertheless, clinical studies have shown a reduction in proteinuria and at least an attenuation of progression with the use of long-acting calcium channel blockers. RATIONALE FOR THE COMBINATION OF ACE INHIBITORS AND CALCIUM CHANNEL BLOCKERS: If angiotensin II influences the progression of renal failure, as is universally accepted, then the combination of an ACE inhibitor (reducing the generation of angiotensin II) and a calcium channel blocker (reducing target-organ responsiveness to angiotensin II) appears a promising one. EVIDENCE FOR THE EFFECTIVENESS OF THIS COMBINATION: In animal experiments, co-administration of an ACE inhibitor and a calcium channel blocker caused a more marked reduction in glomerulosclerosis, and this was seen in the stroke-prone spontaneously hypertensive rat model even at non-antihypertensive doses. In human diabetic nephropathy at least, proteinuria (measured as a surrogate marker of the illness) was lowered more effectively by the combination of an ACE inhibitor and a calcium channel blocker than either drug used as monotherapy despite a similar fall in blood pressure.

H5N1 influenza virus and the safety of plasma products.

BACKGROUND: The ever-increasing number of human H5N1 influenza virus infections may enable these viruses to acquire the ability to spread effectively among humans and potentially to cause a pandemic. Recently, more systemic virus dissemination was reported during H5N1 virus infection of humans, resulting in significant virus concentrations also in the blood. The observation has raised concerns about the safety of labile blood products for transfusion and consequentially also for plasma derivatives. To confirm the safety margins of plasma products, dedicated virus inactivation processes used during their production were investigated for their effectiveness in inactivating this virus of recent concern. STUDY DESIGN AND METHODS: Virus inactivation by steps commonly used during the manufacture of plasma derivatives, such as pasteurization for human albumin, solvent/detergent treatment for intravenous immunoglobulin (IVIG), vapor heating for factor VIII inhibitor bypassing activity, and incubation at low pH for IVIG, were investigated with a reassortant strain of H5N1 influenza virus. RESULTS: The results show that H5N1 influenza behaves as expected for lipid-enveloped viruses; that is, the virus is effectively inactivated by all the commonly used virus inactivation procedures tested. CONCLUSION: The safety margins of plasma derivatives against the theoretical transmission of H5N1 influenza virus are very substantial.

Cigarette smoking: an important renal risk factor - far beyond carcinogenesis.

In recent years, it has become apparent that smoking has a negative impact on renal function, being one of the most important remediable renal risk factors. It has been clearly shown that the risk for high-normal urinary albumin excretion and microalbuminuria is increased in smoking compared to non-smoking subjects of the general population. Data from the Multiple Risk Factor Intervention Trial (MRFIT) indicate that at least in males, smoking increases the risk to reach end-stage renal failure. Smoking is particularly "nephrotoxic" in older subjects, subjects with essential hypertension and patients with preexisting renal disease. Of interest, the magnitude of the adverse renal effect of smoking seems to be independent of the underlying renal disease. Death-censored renal graft survival is decreased in smokers, indicating that smoking also damages the renal transplant. Cessation of smoking has been show to reduce the rate of progression of renal failure both in patients with renal disease or a renal transplant. The mechanisms of smoking-induced renal damage are only partly understood and comprise acute hemodynamic (e.g., increase in blood pressure and presumably intraglomerular pressure) and chronic effects (e.g., endothelial cell dysfunction). Renal failure per se leads to an increased cardiovascular risk. The latter is further aggravated by smoking. Particularly survival of smokers with diabetes mellitus on hemodialysis is abysmal. In the present review article the current state of knowledge about the renal risks of smoking is reviewed. It is the aim of the article to point out that smoking not only increases the risk of renal cell carcinoma or uroepithelial cell carcinoma, but also the risk of a faster decline of renal function. The latter is a relatively new negative aspect which has not been widely recognized.

Smoking--a renal risk factor.

One of the most important tasks of clinical and experimental nephrology is to identify the risk factors of progression of renal failure. A major renal risk factor which has not been sufficiently acknowledged despite increasing evidence is cigarette smoking. Diabetologists were the first to recognize the adverse effects of smoking on the kidney: both in type 1 and in type 2 diabetes smoking (i) increases the risk of development of nephropathy and (ii) nearly doubles the rate of progression to end-stage renal failure. Until recently it was not known whether smoking also increases the risk to progress to end-stage renal failure in patients with primary renal disease. A retrospective multicenter European case-control study showed that smoking is an independent risk factor for end-stage renal failure in patients with inflammatory and noninflammatory renal disease, i.e. IgA glomerulonephritis and polycystic kidney disease. The pathogenesis of the smoking-related renal damage is largely unknown. The intermittent increase in blood pressure during smoking seems to play a major role in causing renal damage, but further potential pathomechanisms are presumably also operative. Smoking as a renal risk factor is of great interest to diabetologists as well as nephrologists, but unfortunately so far this information has had little impact on patient management. The present article reviews the current knowledge about the renal risks of smoking and discusses the potential mechanisms of smoking-mediated renal injury.

[Bacterial and abacterial inflammatory kidney diseases. Diagnostic value of the sonographic determination of kidney volume]. / Bakterielle und abakterielle entzündliche Nierenerkrankungen. Diagnostische Wertigkeit der sonographischen Nierenvolumenbestimmung.

The diagnostic value of ultrasound kidney biometry in the diagnosis of parenchymatous kidney disease was evaluated in 277 children. Kidney enlargement of more than 140% of normal volume proved to be a sensitive criterion for differentiation of acute bacterial interstitial nephritis (pyelonephritis) and isolated lower urinary tract infection. Mean kidney volume in acute pyelonephritis was 175%. Normalization of kidney volume under antibiotic treatment required 4-6 days. Kidneys with non-bacterial nephritis and glomerulonephritis showed a 63% pathological size increase at biopsy; the kinetics of kidney volume in the acute phase of the disease paralleled the clinical course.

Renal sonography in the differentiation of upper from lower urinary tract infection.

Increase in renal volume and asymmetry in kidney size determined by sonography proved to be a valuable diagnostic criterion for differentiation between infections of the upper and lower urinary tract in 175 children: acute bacterial interstitial nephritis (79) and lower urinary tract infection (96). Kidney volume in acute pyelonephritis increased to an average of 175% of normal. In 71% of cases, affected kidneys showed an enlargement of at least 2 SD when compared with a group of 325 children without kidney pathology. Most impressive kidney enlargement was seen during the first year of life. In 50% of cases, acute pyelonephritis caused a bilateral increase in renal size and/or distinct volume asymmetry. Kidneys of patients with lower urinary tract infections had a mean volume of 99.68% and a physiologic volume asymmetry comparable to normal kidneys.

Adverse effects of smoking in the renal patient.

Smoking is a known risk factor for cardiovascular diseases, cancer, and several other health problems. It is the number one preventable cause of death in modern countries. The first evidence that smoking may be a renal risk factor was published in 1978. Since then, several studies documented that smoking is nephrotoxic in patients with diabetic and non-diabetic renal disease. Data from the Multiple Risk Factor Intervention Trial indicate that smoking even increases the renal risk in the general male population: an increased relative risk for end-stage renal failure (ESRF) was found for smokers as compared to non-smokers (up to 1.69 for heavy smokers). Several potential mechanisms of smoking-induced renal damage have been discussed, e.g. increase in blood pressure, alteration of intrarenal hemodynamics, as well as activation of the sympathetic nerve, the reninangiotensin and the endothelin systems. The pathomechanisms are, however, only partly understood. Once ESRF has become established, the failure to discontinue smoking adversely affects the prognosis of patients on renal replacement therapy, mainly by increasing the risk of cardiovascular complications. Discontinuation of smoking has been shown to improve both renal and cardiovascular prognosis in the renal patient and is probably the single most effective measure to retard progression of renal failure.

Sympathetic overactivity and arterial hypertension in renal failure.

In the past, it had been presumed that hypertension in chronic renal disease can be explained by the dual effects of sodium retention and inappropriate activity of the renin-angiotensin system. Recent experimental and clinical data provide strong evidence that the increase in blood pressure is to a large part due to sympathetic overactivity which is triggered by afferent signals emanating from the kidney and resetting sympathetic tone by stimulation of hypothalamic centres. The sequelae of sympathetic overactivity extend beyond their effects on blood pressure and include accelerated progression of renal failure and presumably increased cardiac arrhythmia.

Glial cell line-derived neurotrophic factor (GDNF) is expressed in the human kidney and is a growth factor for human mesangial cells.

BACKGROUND: Glial cell line-derived neurotrophic factor (GDNF), a recently cloned member of the transforming growth factor-beta (TGF-beta) superfamily, is a potent neurotrophic factor in vitro and in vivo. GDNF is essential for nephrogenesis and the highest expression of GDNF is found in the developing kidney. Increased plasma GDNF levels have recently been documented in patients with chronic renal failure; the source and role of this increase, however, remain unclear. No data are available about the expression of GDNF in human adult kidney or human adult mesangial cell (HMC) cultures. We hypothesized that GDNF, similar to other members of the TGF-beta superfamily, might play a role as a growth factor in the pathogenesis of glomerulosclerosis. METHODS: To address this hypothesis, we first investigated (by RT-PCR) the expression of GDNF mRNA and the mRNAs of the GDNF receptors Ret and GFRalpha-1 in (i) adult human renal cortex and medulla and (ii) in HMC in culture. The results were compared to the expression of these molecules in different developmental stages of the rat kidney. We found that both GDNF and its receptors were expressed in human adult kidney and HMC. Since this finding implicates a role for GDNF beyond nephrogenesis, i.e. in renal physiology/pathophysiology, we investigated the effect of GDNF on HMC growth, i.e. (i) cellular protein synthesis as an index of hypertrophy ([(3)H]methionine incorporation), (ii) DNA synthesis ([(3)H]thymidine incorporation) and cell proliferation (cell numbers) as indices of hyperplasia, and (iii) extracellular matrix synthesis, i.e. collagenous and non-collagenous extracellular proteins ([(3)H]proline incorporation into the collagenase-sensitive and -insensitive fraction). HMC cultures were used as a surrogate model for the development of glomerulosclerosis. RESULTS: GDNF induced a biphasic growth stimulatory effect in HMC with stimulation at the lowest concentration used (2 ng/ml) but had no effect at higher concentrations (20 and 50 ng/ml). In contrast, cellular protein synthesis and extracellular matrix synthesis were significantly and dose-dependently increased by GDNF. CONCLUSIONS: These results suggest that GDNF, similar to other members of the TGF-beta superfamily, might play a role as a growth factor for mesangial cells and might thus be a player in the pathogenesis of glomerulosclerosis.

Inhibitory effect of calcium channel blockers on human mesangial cell growth: evidence for actions independent of L-type Ca2+ channels.

Calcium channel blockers (CCB) are known to affect the outcome of glomerulosclerosis in vivo and to suppress mesangial cell proliferation and cytokine production in vitro. It is uncertain, however, whether (i) human adult mesangial cells (HMC) express L-type Ca2+ channels and (ii) whether the effect of CCB on HMC is mediated by inhibition of L-type Ca2+ channels. In single cell preparations of HMC, the L-type Ca2+ channel agonist Bay K 8644 and K+-depolarization of the cell membrane caused a transient increase of cytosolic free Ca2+ ([Ca2+]i) in 60 to 80% of the cells. The CCB verapamil and nifedipine partially inhibited the effect of Bay K 8644 and K+-depolarization on [Ca2+]i. Binding experiments confirmed these functional studies by showing specific binding at the phenylalkylamine binding site of L-Type Ca2+ channels. Quiescent HMC were stimulated with fetal calf serum (FCS) or growth factors (platelet derived growth factor A/B, epidermal growth factor, angiotensin II, endothelin 1) in the presence of various concentrations (10(-10) to 10(-5) M) of different CCB: either (R)-verapamil, (S)-verapamil or the raceme of verapamil, and nifedipine or diltiazem, respectively. In addition, the enantiomers of devapamil were studied, because their action on the L-type Ca2+ channel is more stereoselective than that of the enantiomers of verapamil. At high concentrations (10(-6) to 10(-5) M) (R,S)-verapamil decreased cell numbers in cultures of quiescent HMC, increased LDH in the supernatant, and caused loss of trypan blue exclusion (cytotoxicity). At lower concentrations (R,S)-verapamil showed no cytotoxicity, but had two effects: (1.) concentration dependent (down to 10(-8) M) inhibition of indices of cell proliferation, that is, (i) stimulated (FCS or growth factor) 3H-thymidine incorporation and (ii) increment in cell number; and (2.) inhibition of indices of cell or matrix protein synthesis, that is, (i) stimulated 3H-methionine incorporation and (ii) 3H-proline incorporation. At equimolar concentrations the dihydropyridine nifedipine was equipotent with verapamil, whereas the benzothiazepine diltiazem was conspicuously less effective. Even at the lowest effective concentration (10(-8) M) comparison of (R)- and (S)-verapamil showed no significant difference between the enantiomer with weak or with strong effect on L-type Ca2+ channels, and this was true even when the more stereoselective enantiomers of devapamil were tested. These observations argue against the notion that effects of CCB result from specific interaction with L-type Ca2+ channels. The data are more consistent with the idea that interactions with targets other than L-type Ca2+ channels are involved.

Inhibition of growth by calcitriol in a proximal tubular cell line (OK).

Calcitriol has been shown to inhibit (i) cell proliferation of renal carcinoma cell lines and of cultured adult human mesangial cells in vitro, and (ii) renal compensatory growth in vivo. In the present study we examined the effects of calcitriol on DNA synthesis and cell replication in an immortalized cell line showing the phenotypic characteristics of proximal tubular cells (opossum kidney, OK cells). The viability of OK cells was not affected by calcitriol (Trypan-blue exclusion, LDH and K+ release), but the cells did not convert 3H-25(OH)2D3 to 3H-1,25(OH)2D3. In the log growth phase, calcitriol (but not alternative vitamin D metabolites) caused dose-dependent (10(-12) to 10(-6) M) inhibition of radiothymidine incorporation. Inhibition was calcium dependent, i.e. it was more pronounced at the lower nominal calcium concentration in tissue culture media (0.9 versus 1.8 mmol/l) and amplified by coincubation with nifedipine (1 microM). Inhibition of DNA synthesis was paralleled by inhibition of cell replication (growth curve) under basal conditions and after stimulation with EGF (10 ng/ml). In conclusion, calcitriol inhibits proliferation of proximal tubular cells which normally express 1-alpha-hydroxylase activity.