Early withdrawal of calcineurin inhibitor from a sirolimus-based immunosuppression stabilizes fibrosis and the transforming growth factor-ß signalling pathway in kidney transplant.

AIM: The focus in renal transplantation is to increase long-term allograft survival. One of the limiting factors is calcineurin inhibitor (CNI)-induced fibrosis. This study attempted to examine the histological aspect of interstitial fibrosis and the modulation of the transforming growth factor-ß (TGF-ß) canonical signalling pathway following early withdrawal of CNI from sirolimus-based immunosuppressive therapy. METHODS: Forty-five kidney transplant recipients with low-medium immunologic risk were randomized and underwent protocol biopsies obtained at the time of transplantation and at 3 and 12 months thereafter. The recipients were taking tacrolimus, sirolimus and prednisone. After the 3rd month, patients were randomized into two groups: sirolimus (SRL) (removed CNI and increased sirolimus) and tacrolimus (TAC) (maintained CNI). Renal biopsies were analyzed according to Banff's 2007 criteria. The sum of Banff's ct and ci constituted the chronicity index. Fibrosis was evaluated by the histomorphometrical analysis of the total collagen and myofibroblast deposition. Immunohistochemical characterization and quantification of TGF-ß, TGF-ß receptor 1 (TGF-ß-R1), receptor 2 (TGF-ß-R2) and phospho-Smad2/3 (p-Smad2/3) were performed. RESULTS: Maintenance of CNI was associated with the increase of the surface density of collagen and α-smooth muscle actin (α-SMA), (P = 0.001). Furthermore, increased TGF-ß (P = 0.02), TGF-ß-R1 (P = 0.02), p-Smad2/3 (P = 0.03) and stabilized TGF-ß-R2. On the other hand, the removal of CNI with increase in the dose of sirolimus limited the enhancement of the chronicity index at 12 m (SRL, 2.18 vs TAC, 3.12, P = 0.0007), diminished the deposition of fibrosis and promoted the stabilization of TGF-ß, TGF-ß-R2, p-Smad2/3 and myofibroblasts as well as the reduction of TGF-ß-R1 (P = 0.01). CONCLUSION: The early withdrawal of CNI limited the fibrosis progression through the stabilization of chronicity index and of the canonical TGF-ß signalling pathway.

The renal clearance of dextran sulfate decreases in puromycin aminonucleoside-induced glomerulosclerosis: a puzzle observation.

BACKGROUND: Puromycin aminonucleoside-induced nephrosis is characterized by increased renal excretion of plasma proteins. We employed this experimental model to study the urinary clearance of dextran sulfate. METHODS: The dextran sulfate eliminated by the urine was determined using a metachromatic assay. Polysaccharide fragments were analyzed by chromatographic and electrophoretic procedures. Disaccharide composition of the glomerular heparan sulfate was assessed using digestion with specific lyases. RESULTS: In normal rats dextran sulfate is partially degraded to lower molecular weight fragments and only then eliminated by the urine. Surprisingly, in puromycin aminonucleoside-induced glomerulosclerosis the molecular size of the fragments of dextran sulfate found in the urine is the same or even lower than in control animals in spite of the marked proteinuria. Furthermore, urinary excretion of dextran sulfate decreases in the experimentally induced nephrosis. This observation cannot be totally attributed to a reduced number of physiologically active nephrons since the glomerular filtration rate decreases approximately 32% after puromycin aminonucleoside administration while the urinary excretion of 8 kDa-dextran sulfate decreases 3-fold. The glomerular heparan sulfate shows reduced sulfation when compared with normal animals. Possibly puromycin aminonucleoside decreases the activity of kidney endoglycosidases, which reduce the molecular size of the sulfated polysaccharide, leading to a decrease in its renal clearance. Reduced sulfation of the glomerular heparan sulfate in the puromycin aminonucleoside-induced nephrosis does not alter the size of the dextran sulfate eliminated by the kidney, as suggested for protein. CONCLUSIONS: Each pathological process induces a particular modification in the kidney, which in turn can affect the renal selectivity to specific macromolecules in different ways.

Low-molecular-weight dextran sulfate prevents experimental urolithiasis in rats.

BACKGROUND: Low-molecular-weight dextran sulfate was tested on an experimental model of urolithiasis induced in rats. METHODS: Male Wistar rats weighing 250 g had a 15-mg calcium oxalate stone surgically placed into the bladder. A group was sham operated, another group was treated by daily intraperitoneal injection of low-molecular-weight dextran sulfate and the other by daily intraperitoneal saline injection. RESULTS: This treatment prevents the growth of exogenous calcium oxalate stone introduced into the bladder and also avoided the formation of secondary stones in the animals. In addition, low-molecular-weight dextran sulfate prevented the aggregation of other ions, such as ammonium, phosphate and magnesium to the calcium oxalate stone placed in the bladder. These effects of the low-molecular-weight dextran sulfate are associated with the presence of the sulfated polysaccharide in the urine. However, the polysaccharide did not adhere to the bladder stone. Possibly, dextran sulfate forms soluble complex with calcium ions dissolved in the urine and therefore prevented calcium salt crystallization. CONCLUSION: Dextran sulfate, 8000 Da, led to a decrease in calculi glycosaminoglycans in animals treated with dextran, and there was an inhibition in bladder-implanted stones growth.

Correction of acidosis by hemodialysis: proposal of a correlation with urea kinetics.

BACKGROUND/AIMS: We examined the effect of hemodialysis (HD) on acid-base status and its relation to urea kinetics in clinically stable renal HD patients. The purpose of this study was to design a practical approach to monitoring the correction of acidosis, as it can be assisted by routine parameters of adequacy. METHODS: Blood samples were drawn immediately before and after HD from 46 chronic renal patients to determine electrolytes, blood gases, serum albumin and blood urea nitrogen (BUN). Additional measurements of pH and serum bicarbonate were done in 35 patients in the periods before, immediately after and 4 h after HD. The normalized protein catabolic rate (nPCR) was calculated and correlated with the serum albumin and bicarbonate values before HD. Equilibrated KT/V (eKT/V) and urea reduction ratio (URR) were calculated and correlated with the degree of bicarbonate correction, defined as DeltaHCO(3)(-). RESULTS: There was no correlation between nPCR and pre-HD HCO(3)(-), while there was a significant correlation between URR and eKT/V and DeltaHCO(3)(-) (p < 0.003). CONCLUSIONS: The Deltabicarbonate was well correlated with URR and eKT/V, and the study suggests that in standard HD the correction of acidosis may be related to target URR and eKT/V levels.

Effects of mycophenolate mofetil and lisinopril on collagen deposition in unilateral ureteral obstruction in rats.

BACKGROUND/AIMS: Unilateral ureteral obstruction (UUO) in rats has been used as a model of renal interstitial fibrosis, in which therapeutic trials can be of important clinical relevance. In this study, we investigated the effects of mycophenolate mofetil (MMF), the angiotensin-converting enzyme (ACE) inhibitor lisinopril (L), and the combination of both drugs, given daily for 14 days to UUO rats, on the renal fibrogenic process triggered by UUO. METHODS: Rats underwent surgical UUO, followed by treatment with daily doses of either MMF, lisinopril, or both, and were then sacrificed after 14 days. Kidney fragments were fixed for histopathological examination (hematoxylin-eosin and periodic acid-Schiff reactive) and immunohistochemistry for myofibroblasts (alpha-smooth muscle actin; alpha-SMA) and macrophages (ED-1). Histomorphometrical analysis of collagen was performed with Sirius red staining, and collagen content was assessed by the amount of hydroxyproline. Cortex and medulla were analyzed separately. RESULTS: MMF, lisinopril and MMF+L reduced the density of alpha-SMA- and ED-1-positive cells (p < 0.05), interstitial volume (p < 0.05) and decreased Sirius-red-stained areas by 54.6, 35.6 and 58.0%, and hydroxyproline content by 60.1, 49.7 and 62.7%, respectively. No differences were observed among treated groups. CONCLUSION: MMF and the ACE inhibitor lisinopril attenuated the progression of the fibrogenic process of UUO in an equivalent manner. The combination of both drugs did not add any further improvement in the collagen content.

Idade e tempo em diálise são associações maiores com placas de carótida em pacientes não diabéticos em HD / Age and time on dialysis are major associations with carotid plaques in non-diabetic HD patients

Introdução: Aterosclerose acelerada é uma característica bem reconhecida da doença renal avançada, sendo um dos fatores predominantes associados com a alta morbidade e mortalidade nesta população de pacientes. Vários estudos correlacionaram a presença de placas ateroscleróticas com o estado nutricional e a inflamação nestes pacientes. Entretanto, fatores de risco tradicionais como hipertensão, tabagismo e dislipidemia devem sempre ser considerados no contexto de aspectos étnicos, geográficos e culturais de uma dada população de pacientes renais. Objetivo: Este estudo teve por objetivo a descrição da prevalência da aterosclerose avançada, segundo avaliação através da presença de placas carotídeas, e sua correlação com dados epidemiológicos, fatores de risco tradicionais e não-tradicionais em pacientes não diabéticos em hemodiálise (HD). Métodos: Trinta e nove pacientes em um programa regular de HD foram avaliados (idade média: 47,0 ± 12,8 anos, 20 homens, tempo médio em diálise: 5,2 ± 2,9 anos). A presença de aterosclerose foi investigada por Doppler de carótida e a inflamação pela proteína C-reativa (PCR). Dados acerca do estado nutricional, pressão arterial e parâmetros bioquímicos foram igualmente analisados. Resultados: A presença de placa em carótida foi um achado prevalente, observada em 64,1% dos pacientes. A idade (50,8 ± 10,6 anos) e o tempo em diálise (6 [1-15] anos) foram significativamente maiores no grupo de pacientes com placas, comparado ao grupo de pacientes sem placas (41,3 ± 14,5 e 4 [1-11], respectivamente, p < 0,05). Não houve diferença estatística entre os grupos no que diz respeito à PCR, estado nutricional e parâmetros bioquímicos. Placas de carótida foram associadas com a idade acima de 38 anos (O.R.: 28.29; C.I.: 2.68-712.8; p < 0,001), e tempo em diálise acima de 4 anos (O.R.: 5.5; C.I.: 1.02-33.37; p < 0.05).Além disso, 70% dos pacientes com pressão diastólica pós HD menor do que 90 mmHg apresentaram placas de carótida.

Introduction: Accelerated atherosclerosis is a well-recognized characteristic of end stage renal disease (ESRD), as one of the leading factors associated with the high cardiovascular morbidity and mortality in this patient population. Several studies have been done correlating the presence of atherosclerotic carotid plaques with nutritional status and inflammation in this setting. Nevertheless, traditional risk factors like hypertension, smoking and dyslipidemia must always be taken into account in the context of the specific ethnic, geographic and cultural aspects of a given renal population. Aim: The present study was designed to describe the prevalence of advanced atherosclerosis, as detected by the presence of carotid plaques, and its correlation with epidemiological data, traditional and non-traditional risk factors in non-diabetic hemodialysis (HD) patients. Methods: Thirty-nine patients on a regular HD program were evaluated (mean age: 47.0±12.8 years, 20 men, mean time on dialysis: 5.2±2.9 years). Atherosclerosis was assessed by carotid Doppler and inflammation by serum C reactive protein (CRP). Data on nutritional status, biochemical parameters, and arterial pressure (AP) were also analyzed. Results: Carotid plaque was a prevalent finding, observed in 64.1% of the patients. The age (50.8±10.6 years) and time on dialysis (6 [1-15] years) were significantly higher in the group of patients with plaques, compared to the group of patients without plaques (41.3±14.5 and 4 [1-11], respectively, P<0.05). There was no statistical difference between the groups regarding CRP, nutritional status, biochemistry parameters, and mean pre and post HD arterial, diastolic and systolic pressure. Carotid plaques were associated with age higher than 38 (OR.: 28.29; 95% CI.: 2.68-712.8; p<0.001), and time on dialysis higher than 4 years (OR.: 5.5; 95% CI.: 1.02-33.37; p<0.05). In addition, 70% of patients with post HD diastolic AP lower than 90 mmHg presented carotid plaques.