[Treatment of uremia in frail elderly patients: the issue of prolonged conservative management]

The chronic use of renal replacement therapy in frail elderly patients sometimes provides no tangible benefits and may even have a negative fallout on their quality of life, making prolonged conservative management a reasonable option. However, this is mostly a feeling, since very few papers have addressed this issue and there is no evidence-based medicine related to it. On the other hand, ethical issues are extraordinarily relevant and in this clinical setting extend beyond topics such as end-of-life care and advance care planning. It is evident that clinical decision-making in frail elderly patients with endstage renal disease may be very difficult and needs to be supported by ad hoc clinical trials. In the meantime, the ethical issues must be discussed in society.

Medullary sponge kidney (Lenarduzzi–Cacchi–Ricci disease): A Padua Medical School discovery in the 1930s

The introduction of radiological contrast media and intravenous (i.v.) urography in clinical diagnostics in the 1930s enabled the discovery of several diseases, including the medullary sponge kidney (MSK). MSK is a renal malformation characterized by cystic anomalies of precalyceal ducts, which is frequently associated with nephrocalcinosis and renal stones. Although it was first recognized by G Lenarduzzi in 1939, its thorough description was the result of the ante litteram multidisciplinary cooperation between a radiologist (Lenarduzzi), a urologist (Cacchi), and a pathologist (Ricci), all at the Padua University Hospital. These authors 'established' the paradigm for its diagnosis that is still used today. I.v. urography is the gold standard for the diagnosis of MSK, but as the technique is used less and less, there is a concrete possibility of this renal condition being forgotten in the future. Although the pathogenesis of MSK has yet to be elucidated, its association with different malformative conditions supports the idea that it is a developmental disorder. Recent findings suggest that MSK may be the consequence of a disruption of the ureteral-bud/metanephric-blastema interface.

Family history may be misleading in the diagnosis of Dent’s disease

The rare Dent's disease manifests with medullary nephrocalcinosis, nephrolithiasis, hypercalciuria, low molecular weight proteinuria and other tubular dysfunctions, rickets or osteomalacia, and renal failure, in various combinations. It is a recessive X-linked condition. Clinicians consider family history a fundamental pointer to its diagnosis, but this is not invariably the case as clearly pointed out by the two reported cases.

Lithiasis in cystic kidney disease and malformations of the urinary tract

The prevalence of renal stones in renal cystic and malformative conditions exceeds the prevalence of renal stones in the general population, suggesting that the above-mentioned cystic and malformative disorders favor stone formation. Urinary stasis is generally assumed to play a major part in the pathogenesis of the nephrolithiasis associated with distorted renal anatomy due to a delayed washout of crystals and risk of urinary infections. However metabolic factors are also important in the pathogenesis of stones in these conditions. Indeed, metabolic abnormalities have been observed in the majority of stone-forming patients with conditions such as horseshoe kidney and ureteropelvic junction obstruction. Five different models of stone formation can be identified, depending on stone composition, risk of infection stones, and pathogenesis of renal cystic and malformative conditions. A proper metabolic evaluation should be conducted to diagnose specific, treatable metabolic disorders, thereby reducing the frequency of recurrent stone disease in these conditions as well.

[Dent's disease: hereditary nephrolithiasis related to defective tubular endocytosis processes]

Dent's disease, a X-linked hypercalciuric nephrolithiasis, is caused by mutations of the CLCN5 gene. The disease is characterised by low molecular weight proteinuria with variable presence of hypercalciuria, hyperphosphaturia, nephrocalcinosis, and kidney stones. CLCN5 encodes a chloride channel belonging to the voltage-gated chloride channel family, which is predominantly expressed in the endosomes of proximal tubular cells. By shunting the current of electrogenic H+-ATPase, ClC-5 is crucial for efficient acidification of renal endosomes. As shown in knock-out mouse models, the ClC-5 loss of function causes severe impairment of receptor-mediated endocytosis, as well as the endocytotic retrieval of plasma membrane proteins including megalin. In a minority of patients with classical Dent's disease, the analysis of CLCN5 coding sequences failed to identify causative mutations. It is conceivable that mutations in the 5' upstream regulatory regions could impair the correct processing and translation of CLCN5. The complexity of its promoter region seems to support this hypothesis. Molecular diagnosis of Dent's disease is now available; since the risk of developing renal insufficiency in adult life is elevated for this type of nephrolithiasis, the correct diagnosis could potentially modify the natural history of the disease by preventing the evolution towards uraemia.

Adverse renal effects of anti-inflammatory agents: evaluation of selective and nonselective cyclooxygenase inhibitors

Conventional nonsteroidal anti-inflammatory drugs (NSAIDs), i.e. nonselective cyclooxygenase COX inhibitors have well-documented nephrotoxicity. Adverse renal effects occur because of inhibition of the synthesis of cyclooxygenase-derived prostaglandins which act to modulate pathologic processes that would normally impair various renal functions. The introduction of the selective COX-2 inhibitors raised hope that this class of drugs would reduce injury in both the gastrointestinal tract and the kidneys. Animal and human data, however, suggest that COX-2 synthesized prostaglandins are important in the modulation of renal physiology during adverse conditions. Hence, it appears that these drugs are equal in causing nephrotoxicity as the nonselective COX inhibitors.

[In search of renal stem cells]

The therapeutic potential of stem cell research is very promising. Although arising ethical questions, especially in the field of embryonic stem cells (ES), it is astonishing how, in the last few years, the potential application of stem cells for treating proliferative as well as degenerative diseases, is becoming increasingly evident. It was recently demonstrated that somatic stem cells showed unexpected plasticity similar to ES. In fact, if somatic stem cells are exposed to proper stimuli they can differentiate into a multitude of cell types that may be different from those of the tissue they belong to. In addition, it was recently demonstrated that circulating blood stem cells, probably of bone marrow origin, were recruited at the sites of injury to regenerate or repair damaged tissues. Very little is known about renal stem cells. Although the great capacity of the kidney to regenerate injured nephrons is well established, renal somatic stem cells have yet to be identified. The question we are now faced with is whether renal stem cells exist and, if they do exist, where do they reside. In the attempt to answer this question, the present review will focus on the achievements both in the fields of somatic stem cells and renal embryogenesis and in the field of renal repair and regeneration mechanisms.

[Gout and kidney during XVII and XIX centuries]

The authors briefly describe the history of gout, mainly focusing their attention on the renal involvement. They report some works and theories on gout of great ancient physicians, such as Paracelsus, Sydenham, Boerhaave, Van Swieten and Morgagni.

Cigarette smoking is a risk factor for nephropathy and its progression in type 2 diabetes mellitus

Cigarette smoking is a risk factor for diabetic nephropathy in Type 1 diabetes (T1DM); a few reports support this possibility in Type 2 diabetes (T2DM) as well. Since heterogeneity among populations could exist, we investigated the association of cigarette smoking and nephropathy, and progression of nephropathy in Italian T2DM patients. A retrospective study was conducted in 273 long-duration T2DM subjects with a 3-year follow-up in the out-patient clinic, and at least one access per year. Albumin excretion rate, serum creatinine, and a number of other parameters implicated in the development of diabetic renal disease were evaluated. Progression of nephropathy was defined as the passage from different stages of renal involvement (no renal derangement, microalbuminuria, proteinuric disease or severe nephropathy). At baseline, 13.2% of the subjects had microalbuminuria, and 3.7% proteinuric disease. Microalbuminuria and proteinuric disease were more frequent in actual smokers than in non- and former smokers (chi2=8.35; p=0.015). Progression of nephropathy was less common in non- and former smokers than in smokers (31 of 134, 23%, and 15 of 67, 22%, and 30 of 72, 42%, respectively; chi2=9.32;p=0.009). From logistic regression analysis, smoking (p=0.0012) emerged as the most important factor associated with progression of nephropathy, followed by packyears (p=0.011), HbA1c mean value at follow-up (p=0.024), and total cholesterol (p=0.038). In conclusion, cigarette smoking is a risk factor for progression of nephropathy also in Italian T2DM patients; reducing or quitting smoking should be part of the therapy or of the preventive measures in these patients and their relatives.

Low-molecular-weight heparin prevents high glucose- and phorbol ester-induced TGF-beta 1 gene activation

BACKGROUND

Hyperglycemia-induced overexpression of prosclerotic transforming growth factor-beta 1 (TGF-beta 1) has been implicated in the pathogenesis of diabetic nephropathy. Since previous in vivo studies demonstrated a renoprotective effect of low-molecular-weight (LMW) heparin in experimental animals, and recent in vitro data showed an interaction of this drug with the overactivated TGF-beta 1 cascade in high glucose- and phorbol ester-stimulated mesangial cells, we studied the molecular mechanism of these effects on TGF-beta 1 gene expression.

METHODS

Mesangial cells were stimulated with 30 mmol/L glucose or with 0.5 micromol/L phorbol ester [phorbol myristate acetate (PMA)] in the absence or presence of LMW heparin. TGF-beta 1 promoter activity was determined in promoter-reporter luciferase assays. The effect of LMW heparin on the binding of nuclear proteins to a regulatory activator protein-1 (AP-1) site, which mediates the high glucose and PMA responsiveness of the TGF-beta 1 promoter, was studied by electrophoretic mobility shift assays.

RESULTS

The presence of LMW heparin completely prevented TGF-beta 1 gene activation in both high glucose- and PMA-stimulated cells. Preincubation of the cells with LMW heparin and subsequent stimulation of the cells with both stimuli yielded the same result. Furthermore, treatment with LMW heparin prevented the enhanced binding of nuclear proteins to the regulatory AP-1 site, while binding to a Sp1 site was unaffected. Basal promoter activity and basal AP-1 binding also was reduced by LMW heparin. The LMW heparin effect on basal promoter activity was abolished by mutation of the regulatory AP-1 box B and by deletion of this AP-1 binding site.

CONCLUSIONS

LMW heparin prevents high glucose- and PMA-mediated TGF-beta 1 expression by inhibiting the activation of the TGF-beta 1 promoter and by preventing the enhanced binding of nuclear proteins to the regulatory AP-1 site.

Renal involvement in subjects with peripheral atherosclerosis

BACKGROUND

Ischemic nephropathy is an important cause of renal failure in western countries. Subclinical renal function abnormalities may exist in patients with extrarenal atherosclerosis, and may precede the onset of overt ischemic nephropathy.

METHODS

To assess the impact of extrarenal atherosclerosis on the kidney, we evaluated renal function in 89 subjects with differing degrees of peripheral atherosclerosis, without manifest clinical or laboratory signs of ischemic nephropathy and renovascular hypertension. All laboratory testing, ultrasonography with Doppler analysis for the localization of peripheral vascular disease (carotid and lower limb arteries), and non-invasive evaluation of renal function by radionuclide studies of renal plasma flow (MAG3 clearance) and glomerular filtration (DTPA clearance), as well as total, LDL and HDL cholesterol, and triglycerides were determined; smoking habit was recorded. By combining sonographic data on arterial tree stenosis (ATS), the subjects were grouped according to the atherosclerotic vascular damage (ATS involvement).

RESULTS

Despite no change in plasma creatinine and DTPA clearance (from 91.58+/-26.53 mL/min/1.73 m2 to 93.47+/-24.82), MAG3 clearance progressively declined with the severity of vascular damage (from 244.86+/-60.60 mL/min/1.73 m2 to 173.59+/-58.74). Stepwise multiple regression analysis indicated that MAG3 clearance was best explained by ATS involvement (standardized beta coefficient -0.40; p<0.001), smoking habit (-0.34; p= 0.004), and serum LDL-cholesterol (-0.24; p<0.035).

CONCLUSIONS

The renal hemodynamic profile in atherosclerotic patients might constitute functional evidence of the silent phase of ischemic renal disease. The findings suggest that renal function should be carefully assessed in patients with extrarenal atherosclerosis, particularly in those with classic cardiovascular risk factors.

Quantitation of TGF-beta1 mRNA in porcine mesangial cells by comparative kinetic RT/PCR: comparison with ribonuclease protection assay and in situ hybridization

Gene expression can be examined with different techniques including ribonuclease protection assay (RPA), in situ hybridisation (ISH), and quantitative reverse transcription-polymerase chain reaction (RT/PCR). These methods differ considerably in their sensitivity and precision in detecting and quantifying low abundance mRNA. Although there is evidence that RT/PCR can be performed in a quantitative manner, the quantitative capacity of this method is generally underestimated. To demonstrate that the comparative kinetic RT/PCR strategy-which uses a housekeeping gene as internal standard-is a quantitative method to detect significant differences in mRNA levels between different samples, the inhibitory effect of heparin on phorbol 12-myristate 13-acetate (PMA)-induced-TGF-beta1 mRNA expression was evaluated by RT/PCR and RPA, the standard method of mRNA quantification, and the results were compared. The reproducibility of RT/PCR amplification was calculated by comparing the quantity of G3PDH and TGF-beta1 PCR products, generated during the exponential phases, estimated from two different RT/PCR (G3PDH, r = 0.968, P = 0.0000; TGF-beta1, r = 0.966, P = 0.0000). The quantitative capacity of comparative kinetic RT/PCR was demonstrated by comparing the results obtained from RPA and RT/PCR using linear regression analysis. Starting from the same RNA extraction, but using only 1% of the RNA for the RT/PCR compared to RPA, significant correlation was observed (r = 0.984, P = 0.0004). Moreover the morphometric analysis of ISH signal was applied for the semi-quantitative evaluation of the expression and localisation of TGF-beta1 mRNA in the entire cell population. Our results demonstrate the close similarity of the RT/PCR and RPA methods in giving quantitative information on mRNA expression and indicate the possibility to adopt the comparative kinetic RT/PCR as reliable quantitative method of mRNA analysis.

Monocyte/mesangial cell interactions in high-glucose co-cultures

BACKGROUND

Monocytes bind to human mesangial cells (HMC) in a co-culture model of leukocyte/ glomerular cell interactions. Since monocytic infiltration has been demonstrated in the early stages of diabetic glomerulopathy, we examined whether co-culture with myelomonocytes of the U937 cell line in media mimicking the diabetic microenvironment modulated phenotype, growth, and extracellular matrix production patterns of HMC.

METHODS

HMC monolayers grown for 5 days in 5.5 mmol/l (NG) or 30 mmol/l (HG) glucose media were examined 3, 24 and 48 h after addition of U937 cells by computer-assisted image analysis/fluorescence microscopy following fixation, staining for cell adhesion, and TUNEL/propidium iodide labelling for apoptosis. As matrix components may be relevant to both phenotype of cultured HMC and monocyte adhesion, reverse transcription-polymerase chain reaction, zymography, and ELISA were used to detect urokinase-plasminogen activator (uPa), collagen type IV (COL IV), transforming growth factor beta1 (TGF-beta1), matrix metalloproteinases (MMP), and relative inhibitors (tissue inhibitor of MMP (TIMP)) expression in co-cultures in NG/HG.

RESULTS

U937 adhesion at 1-3 h was increased in HG (from 54.9+/-6.6 to 87.1+/-5.8% U937/HMC). Control HMC proliferating in NG supplemented with 10% fetal bovine serum had an average cross-sectional area of 9993+/-505 micro(2) with 1.2+/-0.1 hillocks/high-power field, which increased to 13 651+/- 1114 micro(2) with 0.5+/-0.2 hillocks/high-power field in HG (P<0.05). TUNEL+HMC were nearly identical (4.9+/-1.7 vs 4.2+/-0.4% in HG, P=NS). Enhanced transcription and secretion of urokinase (uPA, +656%), COL IV (+137%), TGF-beta1 (+590%) were observed in co-cultures in HG. COL IV and TGF-beta1, but not uPA, were also increased in HMC alone, exposed to HG for 5 days. MMP-2/TIMP-2 ratio was decreased while MMP-1/TIMP-1 was increased in HG co-cultures. In both NG and HG, U937 adhesion reduced HMC number and hillocks at 24 h, with constant apoptosis. The effects of U937 were no longer detectable at 48 h, when apoptosis was 2.1+/-0.6 vs 4.0+/-0.4% in HG, and cell counts returned above basal, possibly due to a delayed proliferative response.

CONCLUSIONS

High glucose medium increases U937 cell adhesion to HMC. In turn, monocytes modulate number and spatial distribution of HMC, which are also markedly affected by ambient glucose levels. These interactions may be relevant to leukocyte infiltration, mesangial expansion, and glomerulosclerosis in diabetes.

Vascular endothelial growth factor (VEGF) and VEGF receptors in diabetic nephropathy: expression studies in biopsies of type 2 diabetic patients

Vascular endothelial growth factor (VEGF) is involved in the pathogenesis of diabetic retinopathy but its role in diabetic nephropathy is only speculative so far. It has been shown that in renal cortex of normal kidneys, glomerular and tubular epithelial cells express VEGF and that VEGF 165 is the predominant isoform. Two VEGF receptors, KDR (kinase domain region) and Flt-1 (fms-like tyrosine kinase) are co-expressed by glomerular and peritubular capillary endothelial cells. However, VEGF and VEGF receptors are predominantly expressed at glomerular level. We recently demonstrated that in type 2 diabetic patients glomerular qualitative and quantitative changes of VEGF mRNA expression are associated with functional and structural renal changes. In the present work we focused on the tubulo-interstitial compartment; by reverse transcription/polymerase chain reaction (RT/PCR) we evaluated the expression of VEGF, KDR, Flt-1 and the relationship between the two main type of VEGF isoforms, VEGF121 and VEGF165 in the tubulo-interstitium of type 2 diabetic patients. Patients were divided in three category on the basis of renal structure pattern: CI, with normal or near normal renal structure; CII, with glomerular and tubulo-interstitial lesions occurring in parallel (typical diabetic nephropathology); CIII, with atypical pattern of renal injury, i.e., more severe tubulo-interstitial and vascular than glomerular changes. Comparison between the two cortical compartments revealed that, both in glomeruli and in tubulo-interstitium. VEGF121 isoform exceed VEGF165 while Flt-1 was significantly lower in glomeruli. CIII patients had the lowest tubulo-interstitial level of VEGF and Flt-1 mRNAs. These results suggest that the transcriptional shifting from VEGF165 to VEGF121 isoform and the unbalanced FIt-1 expression between tubulo-interstitium and glomeruli could be involved in the pathogenesis of diabetic nephropathy. Furthermore, at least in CIII patients, down-regulation of the VEGF-Flt-1 system could be involved in the mechanisms leading to tubulointerstitial diabetic lesions.