Peritoneal Dialysis Retardation of Progression of Advanced Renal Failure

♦ Objectives

The rate of decline of residual renal function is slower in peritoneal dialysis (PD) than in hemodialysis. However, it is unclear which and whether either of the two techniques modifies the natural course of renal failure. We tested whether PD influences the natural course of the progression of chronic renal failure in humans.

♦ Design

Retrospective review of clinical charts.

♦ Setting

Tertiary-care center.

♦ Patients

Fourteen patients were selected from the 36 patients that were treated with PD in our center from January 1997 to June 2000, applying the following criteria: predialysis follow-up longer than 12 months, renal creatinine clearance 20 mL/minute or more at the start of predialysis follow-up, follow-up while on PD longer than 6 months, and renal creatinine clearance above 0 mL/minute at the start of PD.

♦ Main Outcome Measure

Residual renal function calculated as renal creatinine clearance obtained from 24-hour urine samples.

♦ Results

A lower mean rate of decline of residual renal function was observed during PD than during the predialysis period (–0.06 ± 0.16 vs –0.94 ± 0.74 mL/min/month, p < 0.0005). The rate of decline in renal creatinine clearance was faster in every patient during the predialysis period than during his or her time on PD.

♦ Conclusions

These preliminary data support the hypothesis that PD may contribute to the slowing of the natural progression of renal disease in humans, as it does in rodents. Prospective studies involving a larger number of patients are needed to settle the question.

An integrative approach to the anatomy of Syllis gracilis Grube, 1840 (Annelida) using micro-computed X-ray tomography

BACKGROUND

The overall anatomy of the genus Syllis (Annelida: Syllidae) has been largely studied; however, an integrative approach considering different anatomical techniques has never been considered. Here, we use micro-computed X-ray tomography (micro-CT) to examine the internal anatomy of Syllis gracilis Grube, 1840, along with other widely available techniques.

METHODS

We studied the anatomy of the marine annelid S. gracilis through an integrative approach, including micro-CT along with stereo and light compound microscopy (STM, LCM), scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and histological sectioning (HIS). In this manner, we evaluated the applicability of micro-CT for the examination of annelid anatomy by testing whether the images obtained make it possible to visualize the main body structures, in comparison with other current techniques, of the various elements of its internal anatomy.

RESULTS

Overall external and internal body elements are clearly shown by the integrative use of all techniques, thus overcoming the limitations of each when studied separately.Any given method shows disparate results, depending on the body part considered. For instance, micro-CT provided good images of the external anatomy, including relevant characters such as the shape, length and number of articles of dorsal parapodial cirri. However, it is especially useful for the examination of internal anatomy, thus allowing for 3D visualization of the natural spatial arrangement of the different organs. The features best visualized are those of higher tissue density (i.e., body musculature, anterior parts of the digestive tract), particularly in 3D images of unstained specimens, whereas less electrodense tissues (i.e., the peritoneal lining of septa and nervous system) are less clearly visualized. The use of iodine stain with micro-CT has shown advantages against non-staining for the adequate observation of delicate elements of low density, such as the segmental organs, the connective between the ganglia, the ventral nerve cord and segmental nerves.

DISCUSSION

Main external anatomical elements of S. gracilis are well shown with micro-CT, but images show lesser optical resolution and contrast when compared to micrographs provided by SEM and CLSM, especially for fine structural features of chaetae. Comparison of micro-CT and HIS images revealed the utility and reliability of the former to show the presence, shape and spatial disposition of most internal body organs; the resolution of micro-CT images at a cellular level is, however, much lower than that of HIS, which makes both techniques complementary.

Pegylated interferon (alone or with ribavirin) for chronic hepatitis C in haemodialysis population

BACKGROUND/AIMS

Hepatitis C virus infection remains prevalent among patients undergoing long-term haemodialysis and has a detrimental impact on survival in this population. Antiviral therapy for chronic hepatitis C in haemodialysis patients is still a challenge to clinicians. The aim of the current study is to evaluate the efficacy and safety of therapy with pegylated interferon, alone or combined with ribavirin, for chronic hepatitis C among patients undergoing long-term hemodialysis.

METHODS

We conducted a retrospective, multicenter cohort trial with monotherapy (pegylated interferon) (n=21) or combined antiviral therapy (pegylated interferon plus ribavirin) (n=5) for chronic hepatitis C in patients undergoing long-term haemodialysis.

RESULTS

Sustained virological response was obtained in eleven (42%) patients. Seven (26.9%) patients interrupted prematurely the antiviral treatment due to serious side-effects, the most frequent cause of treatment withdrawal being hematological (n=3). HCV RNA load was lower in responder than non-responder patients, 5.44 (3.45; 6.36) vs. 5.86 (4.61; 6.46) log10 copies/mL, even if the difference was not significant (P=0.099). Blood transfusion requirement was greater in patients on combined antiviral therapy than those on pegylated interferon alone, 100% (5/5) vs. 0% (0/21), P=0.0001. No difference in sustained viral response occurred between patients on combined antiviral therapy and those on pegylated interferon monotherapy [40% (2/5) vs. 42.8% (9/21), P=0.90].

CONCLUSIONS

Results from this study showed that pegylated interferon alone or with ribavirin is unsatisfactory in terms of efficacy and safety. Prospective trials based on interferon-free regimens (i.e., sofosbuvir plus ribavirin or sofosbuvir plus daclatasvir) are under way in patients with hepatitis C receiving long-term hemodialysis.

AG490 promotes HIF-1α accumulation by inhibiting its hydroxylation

AG490 is a tyrphostin originally described as a Janus Activated Kinase (JAK) 2 inhibitor. AG490 also inhibits epidermal growth factor receptor (EGFR) and guanylyl cyclases (GC). More recently, AG490 was associated with oxidative stress protection in experimental acute kidney injury models. We now show that AG490 is also a strong activator of the Hypoxia Inducible Factor (HIF)-1. Under normoxic conditions HIF-1α is degraded through hydroxylation, von Hippel Lindau protein (VHL)-mediated ubiquitin tagging and proteasomal degradation. AG490 increased HIF-1α protein, but not HIF-1α mRNA levels, dose- and time-dependently in cultured endothelial, vascular smooth muscle and kidney proximal tubular epithelial cells. AG490 increased HIF-1α protein half-life, suggesting that HIF-1α protein accumulation resulted from a decreased degradation. In this regard, AG490 prevented HIF-1α hydroxylation and increased HIF-1α protein levels in human renal carcinoma cells expressing VHL, but did not further increase HIF-1α in VHL negative cells. AG490 did not prevent the proteasomal degradation of other proteins. HIF-1α was not upregulated by dominant negative JAK2constructs, tyrphostin AG9, the EGFR inhibitors erbstatin and genistein, the GC inhibitor Ly83583 or cGMP analogues. Finally, AG490 also increased HIF-1α transcriptional activity evidenced by the increased HIF-1α-dependent VEGF expression. In conclusion, AG490 is a novel HIF-1α activator that increases HIF-1α half-life and protein levels through interference with HIF-1α hydroxylation and VHL-mediated degradation. This action may contribute to the cell and tissue protective effects of AG490.

External sense receptors in microdrile oligochaetes (Annelida, Clitellata) as revealed by scanning electron microscopy: Typology and patterns of distribution in the main taxonomic groups

This work summarizes the observations on 30 species of microdriles belonging to the families Naididae (Rhyacodrilinae, Pristininae, Naidinae, Phallodrilinae, and Tubificinae), Phreodrilidae, Lumbriculidae, and Enchytraeidae using scanning electron microscopy. The lumbricid Eiseniella tetraedra, a megadrile species common in typical microdrile habitats, was used for comparison. Microdriles display external ciliate sense structures along the entire body; even at the clitellum and in budding and regeneration zones. According to the shape of the cilia, these sense structures can be divided into receptors of blunt cilia, receptors of sharp cilia, and composed receptors. Sense receptors can be morphologically unconspicuous or clearly defined on sensory buds or papillae. All microdriles studied have receptors of blunt cilia. Enchytraeids have characteristic receptors of short cilia. Pristina (Pristininae), Chaetogaster, Ophidonais, and Stylaria (Naidinae) have receptors of long blunt cilia. Composed receptors were found only in some microdriles and E. tetraedra. Receptors of sharp cilia have been found in most microdriles. Enchytraeids might be the only exception, but sharp cilia are probably present in the amphibiotic Cognettia sphagnetorum. Sensory cells with long sharp cilia might play a rheoreceptor role, and their presence in E. tetraedra and C. sphagnetorum would imply the reappearing of an ancient character that was probably lost with the transit from aquatic to terrestrial habitats. Some lumbriculids have ciliated fields. Anatomically, these structures appear as intermediate between the typical isolate sensory structures of microdriles and the sensillae of the hirudineans. The general pattern in microdriles is that uniciliate receptors and multiciliate receptors are separated, which supports the presumed aquatic origin of the clitellates.

Alkalinization potentiates vascular calcium deposition in an uremic milieu

BACKGROUND

Vascular calcification is a serious complication of chronic kidney disease. Acid-base balance is a relevant, albeit somewhat forgotten factor in the regulation of calcium deposition. Hemodialysis patients undergo repeated episodes of alkaline loading from the dialysate, resulting in prolonged alkalinization. We have hypothesized that extracellular alkalinization may promote vascular calcification.

METHODS

Primary cultures of vascular smooth muscle cells were induced to calcify by the phosphate donor beta-glycerophosphate, in the presence of normal or uremic sera from hemodialysis patients and at different pH conditions. The influence of sodium bicarbonate supplementation for 2 months on aorta calcification was studied in 5/6 nephrectomized uremic rats.

RESULTS

Uremic serum increased vascular smooth muscle cell calcification (twofold over nonuremic human serum at day 12, p<0.001). Alkalinization of the extracellular medium also increased vascular smooth muscle cell calcification. Increasing the extracellular pH from 7.42 to 7.53 resulted in a 2.5-fold increase in calcium accumulation at day 12 (p<0.05). In vivo, arterial calcification was significantly higher in alkalinized uremic animals (aorta calcification index, uremic + sodium bicarbonate, 164 +/- 57 units, vs. uremic + vehicle, 56 +/- 14 units; p<0.01).

CONCLUSIONS

Alkalinization increases vascular calcification in cultured cells and uremic rats. These data may be used to optimize dialysate composition and the degree of alkalinization in calcification-prone individuals with advanced renal disease.

Endovascular repair of mycotic aneurysms of the aorta: An alternative to conventional bypass surgery in patients with acute sepsis

Treatment of mycotic aneurysms of the aorta includes excision of infected tissue followed by anatomic or extra-anatomic bypass. However, operative mortality remains high particularly in elderly patients with comorbidities. We describe here 2 patients with mycotic aneurysms of the descending aorta in whom endovascular repair was successfully performed. In 1 of these patients, stent grafting was attained during the acute, bacteraemic phase of infection. After 12 and 20 months, respectively, of diagnosis, both patients are doing well.

TRPC6 mutational analysis in a large cohort of patients with focal segmental glomerulosclerosis

BACKGROUND

Mutations in the TRPC6 gene have been reported in six families with adult-onset (17-57 years) autosomal dominant focal segmental glomerulosclerosis (FSGS). Electrophysiology studies confirmed augmented calcium influx only in three of these six TRPC6 mutations. To date, the role of TRPC6 in childhood and adulthood non-familial forms is unknown.

METHODS

TRPC6 mutation analysis was performed by direct sequencing in 130 Spanish patients from 115 unrelated families with FSGS. An in silico scoring matrix was developed to evaluate the pathogenicity of amino acid substitutions, by using the bio-physical and bio-chemical differences between wild-type and mutant amino acid, the evolutionary conservation of the amino acid residue in orthologues, homologues and defined domains, with the addition of contextual information.

RESULTS

Three new missense substitutions were identified in two clinically non-familial cases and in one familial case. The analysis by means of this scoring system allowed us to classify these variants as likely pathogenic mutations. One of them was detected in a female patient with unusual clinical features: mesangial proliferative FSGS in childhood (7 years) and partial response to immunosupressive therapy (CsA + MMF). Asymptomatic carriers of this likely mutation were found within her family.

CONCLUSIONS

We describe for the first time TRPC6 mutations in children and adults with non-familial FSGS. It seems that TRPC6 is a gene with a very variable penetrance that may contribute to glomerular diseases in a multi-hit setting.

Hyperphosphatemia and hyperparathyroidism in incident chronic kidney disease patients

Disturbances in bone and mineral metabolism are common in chronic kidney disease (CKD) patients. Most studies have been performed in hemodialysis and there is less information on non-dialysis patients, on the coexistence of other risk factors and on the achievement of more recent and stringent guidelines. Cross sectional study of analytical mineral and bone parameters in 125 incident patients (creatinine clearance <60 ml/min) in a monographic CKD clinic. Evaluation after one year of follow-up in 69 patients. Progression of CKD was associated with significant increased levels of phosphate, calcium x phosphate and iPTH and decreased calcium and 1,25 dihydroxyvitamin D. Levels of 25-hydroxyvitamin D were unchanged, but lower than recommended. Phosphate correlated negatively with 1,25-dihydroxivitamin D and creatinine clearance, and positively with iPTH. At every stage of CKD, most patients had PTH values outside recommended limits. More than 69% CKD 3 and CKD 4 patients had higher than recommended PTH levels. Above recommended phosphate levels were present in 25% of CKD 4 and 47% of CKD 5 patients. Most of these had associated high LDL-cholesterol. Higher than recommended calcium levels were more prevalent than low calcium and there was a high prevalence (31%) of vascular calcification. One year of intervention improved the percentage of patients with controlled calcium or iPTH, but not phosphate.

CONCLUSIONS

In incident CKD patients there is a high prevalence of out-of-target mineral and bone analytical parameters. The currently authorized therapeutic arsenal for these patients may not be adequate to deal with the problem.

Induction of hypoxia-inducible factor 1alpha gene expression by vascular endothelial growth factor

Transcriptional regulation of vascular endothelial growth factor (VEGF) is critically dependent on hypoxia-inducible factor 1 (HIF-1). However, not only hypoxia, but selected growth factors can induce HIF-1. High levels of both VEGF and HIF-1 coexist in certain conditions, e.g. tumors. Nonetheless, the possibility that the stimulatory relationship between HIF-1 and VEGF may be bi-directional has not been addressed up to date. The present study in endothelial cells analyzed whether HIF-1 is regulated by a product of its own transcriptionally activated genes, namely, VEGF. As a main finding, VEGF-A(165) induced the increase of HIF-1alpha mRNA and HIF-1alpha protein and nuclear translocation. Autologous endothelial cell VEGF mRNA and protein were also increased upon exposure to exogenous VEGF. The signaling implication of reactive oxygen species was examined by comparison with H(2)O(2) and hypoxanthine/xanthine oxidase and by the superoxide dismutase mimetic, MnTMPyP, the Rac1-NAD(P)H oxidase complex inhibitor, apocynin, transfection of a dominant negative Rac1 mutant, and transfection of a p67phox antisense oligonucleotide. Superoxide anion, largely dependent on Rac1-NAD(P)H oxidase complex activity, was the critical signaling element. The transductional functionality of the pathway was confirmed by means of a reporter gene flanked by a transcription site-related VEGF sequence and by quantitative PCR. In summary, the present results reveal a previously undescribed action of VEGF on the expression of its own transcription factor, HIF-1, and on VEGF itself. This effect is principally mediated by superoxide anion, therefore identifying a new, potentially relevant role of reactive oxygen species in VEGF signaling.

[Systemic and renal effects of preventing contrast nephrotoxicity with isotonic (0.9%) and hypotonic (0.45%) saline]

INTRODUCTION AND OBJECTIVES

Physiological and hypotonic saline solutions have been used interchangeably for preventing contrast media nephrotoxicity. No analysis of the possible differential effects of the two solutions on the milieu interieur or intercompartmental fluid volumes has been performed. Our aim was to study the systemic and renal effects of two types of saline solution regularly used to prevent contrast media nephrotoxicity in patients undergoing coronary angiography.

METHODS

Changes in electrolyte levels and volume distribution were studied in 71 individuals who were randomized to receive either 0.9% isotonic saline (n=36) or 0.45% hypotonic saline (n=35) during the 12 hours before and after contrast injection (2000 mL in each period).

RESULTS

The creatinine level was elevated equally often in the isotonic and hypotonic saline groups. Isotonic saline administration led to reductions in hemoglobin level, hematocrit and plasma albumin level, and to increases in plasma volume, by 12.3% and 10.4% at 24 and 48 hours, respectively. These changes were significant compared with baseline measurements and compared with the group that received hypotonic saline. Neither of the two saline solutions resulted in a change in plasma atrial natriuretic peptide level. Plasma and urine osmolality decreased only with hypotonic saline. The increase in plasma creatinine level was similar with both isotonic and hypotonic saline.

CONCLUSIONS

During standard therapy for preventing contrast media nephrotoxicity, (1) isotonic saline, but not hypotonic saline, increased plasma volume; (2) this increase did not raise the atrial natriuretic peptide level; and (3) no difference in the increase in serum creatinine level was observed between the two saline solutions. These findings provide evidence that 0.45% saline, at a dose suitable for preventing contrast media nephrotoxicity, is associated with a lower risk of volume expansion. This result is important for patients with severely impaired ventricular function.

[Fluid therapy in surgical patients: composition and influences on the internal milieu]

Intravenous fluids administration is the usual practice in the postoperative period. Nonetheless, consensus about the more appropriate fluid reposition recipe is still insufficient.

OBJECTIVE

To study the type of intravenous reposition used in Surgical Units and its impact on the internal milieu.

DESIGN

prospective study of 112 patients with scheduled surgery, receiving only intravenous fluids.

METHODS

biochemical study on postoperative fluids management in uncomplicated surgery. Principal variables: 1. Water and electrolytes administrated. 2. Differences in sodium/water balances before surgery vs first day after surgery. 3. Symptoms related to hyponatremia.

RESULTS

Median P[Na] before and after surgery was 139.9+/-2.9 and 137.7+/-3.7, respectively (p<0.01). Fourteen patients (12.5%) had P[Na]<135, and 12 of them had a reduction of more than 6 mmol/L; accordingly, twenty-six patients (23.2%) had an increased free-water retention (p<0.05). Relevantly, they did not receive a higher amount of free-water and the proportion of isotonic saline/free water varied from <1 to >3. As possible mechanism of free-water accumulation: the postoperative P[Na] was lower in the patients who had a negative free-water clearance >or= -1 L (136.7+/-4.1 vs 138.5+/-3.2 mmol/L, p 0.015).

CONCLUSION

The present study provides new information about the intravenous fluids prescribed in postoperative patients, ie, different proportions saline/water are basically equivalent with respect to inducing symptomatic hyponatremia. The mean value of the relation saline/water is 2:1. Hypotonic fluids input is not clearly related to more intense hyponatremia; the latter appears to depend more on a reduced capacity of the kidney to generate sufficient free water output.

[Anemia in heart failure: pathophysiology, pathogenesis, treatment, and incognitae]

Although anemia now occupies an important place in our present understanding of the pathogenesis of heart failure, the condition is surrounded in mystery. Anemia is highly prevalent in patients with heart failure and is of great clinical significance. However, the treatment targets for anemia in patients with heart failure have still not been accurately defined. The present article reviews of the clinical and pathophysiological characteristics of anemia in this context. Particular emphasis has been placed on cellular and molecular regulatory mechanisms, and their implications for treatment.

Plasma amyloid-beta, Abeta1-42, load is reduced by haemodialysis

Patients with chronic renal failure treated with haemodialysis have vascular risk factors that, in the general population, are associated with increased prevalence of Alzheimer's disease (AD). Patients in haemodialysis, however, present different kinds of dementia but they do not have an increased risk of AD. We have hypothesized that amyloid-beta (Abeta)1-42 is washed out from plasma during the dialysis and that this procedure enhances Abeta elimination and reduces the risk of AD. We have measured plasma Abeta1-42 levels in 11 patients with renal failure, before and after haemodialysis. A single procedure reduced the plasma Abeta levels in all subjects with a mean decrement of 30% of baseline. Since Abeta deposition could be altered by certain metals like Cu and Zn, we have also measured the effects of dialysis on the levels of these ions in plasma. We found no changes in levels of Cu and Zn after dialysis. Haemodialysis, therefore, reduces very effectively plasma Abeta without modifying Cu and Zn levels. The potential use of this strategy in patients with AD requires further investigation.

Cilastatin protection against cyclosporin A-induced nephrotoxicity: clinical evidence

BACKGROUND

Several studies have documented the nephroprotective effect of cilastatin co-administered with imipenem in subjects treated with cyclosporin A. However, no large clinical studies are available to confirm this observation. Here the quality of the evidence on cilastatin nephroprotection against cyclosporin-induced nephrotoxicity is evaluated.

METHODS

The results of all studies where cyclosporin was used alone or combined with imipenem/cilastatin (Tienam) on the same clinical setting were systematically reviewed. Primary outcome was the reduction in serum creatinine concentration. Secondary outcome included development of acute renal failure. Medline was searched using three different retrieval systems (Pubmed, Silver Platter, Knowledge Finder) from January 1966 to February 2006. Attempts were made to contact authors of relevant studies to obtain additional data. Five clinical studies were found, including 125 patients under cyclosporin plus imipenem/cilastatin and 104 under cyclosporin alone.

RESULTS

Cyclosporin increased serum creatinine in all the studies. Average reduction of serum creatinine in cilastatin-treated versus untreated patients was Delta = -0.53 mg/dL (95%CI: -0.90 to -0.17) (Z = 2.84, p = 0.004). Variability between studies was large (from Delta = -0.21 to Delta= -1.59 mg/dL) and heterogeneity pronounced (chi(2) = 8.760, df = 4; p = 0.067). Meta-regression of serum creatinine reduction versus baseline serum creatinine explained 84% of this variability, by the variation in basal serum creatinine. When randomized and observational clinical studies were analyzed separately, conclusions were the same: serum creatinine in cilastatin treated patients was reduced by Delta = -0.98 mg/dL (95%CI: -1.57 to -0.38) in randomized studies (Z = 3.213, p = 0.001) and Delta= -0.32 mg/dL (95%CI: -0.63 to -0.01) in observational studies (Z = 2.013, p = 0.044). Odds Ratio for developing acute renal failure was 0.24 (95% CI: 0.11-0.53, p < 0.0001) on patients simultaneously treated with cyclosporin plus imipenem/cilastatin compared to patients treated with cyclosporin alone.

CONCLUSIONS

Administration of cilastatin may reduce acute cyclosporin nephrotoxicity.

[Renal infarction and kidney rupture: complication of a massive cocaine intoxication in an intestinal carrier]

Major complications derived from the use of cocaine have been described, alter nasal or intravenous administration of the drug. These complications are related to vascular spasm and secondary organ damage. We present the case of an intestinal cocaine packer--in slang, "mule"--, who suffered massive absorption of the drug, resulting n bowel, liver and renal ischemia. This situation, previously undescribe in the literature, ended in kidney rupture. An attempt of embolization, was unsatisfactory, and nephrectomy was finally required. The patient recovered uneventfully, with progressive renal functional improvement. This case, albeit quite exceptional, is illustrative of several of the renal actions of cocaine, and reveals the effects of absorption of cocaine at the intestinal level.

Mechanisms of endothelial cell protection by blockade of the JAK2 pathway

Inhibition of the JAK2/STAT pathway has been implicated recently in cytoprotective mechanisms in both vascular smooth muscle cells and astrocytes. The advent of JAK2-specific inhibitors provides a practical tool for the study of this pathway in different cellular types. An interest in finding methods to improve endothelial cell (EC) resistance to injury led us to examine the effect of JAK2/STAT inhibition on EC protection. Furthermore, the signaling pathways involved in JAK2/STAT inhibition-related actions were examined. Our results reveal, for the first time, that blockade of JAK2 with the tyrosine kinase inhibitor AG490 strongly protects cultured EC against cell detachment-dependent death and serum deprivation and increases reseeding efficiency. Confirmation of the specificity of the effects of JAK2 inhibition was attained by finding protective effects on transfection with a dominant negative JAK2. Furthermore, AG490 blocked serum deprivation-induced phosphorylation of JAK2. In terms of mechanism, treatment with AG490 induces several relevant responses, both in monolayer and detached cells. These mechanisms include the following: 1) Increase and nuclear translocation of the active, dephosphorylated form of beta-catenin. In functional terms, this translocation is transcriptionally active, and its protective effect is further supported by the stimulation of EC cytoprotection by transfectionally induced excess of beta-catenin. 2) Increase of platelet endothelial cell adhesion molecule (PECAM)/CD31 levels. 3) Increase in total and phosphorylated AKT. 4) Increase in phosphorylated glycogen synthase kinase (GSK)3alpha/beta. The present findings imply potential practical applications of JAK2 inhibition on EC. These applications affect not only EC in the monolayer but also circulating detached cells and involve mechanistic interactions not previously described.

Mechanisms of endothelial response to oxidative aggression: protective role of autologous VEGF and induction of VEGFR2 by H2O2

The defense mechanisms of endothelial cells (EC) against reactive oxygen species (ROS) are insufficiently characterized. We have addressed the hypothesis that vascular endothelial growth factor (VEGF) and its receptors are relevant elements in this response. Cell viability, VEGF and VEGF receptor (VEGFR1 and VEGFR2) expression, and transcription factor activation were studied on transient exposure of monolayer EC to H2O2. Wild-type and mutant inhibitors of κBα (IκBα) constructions were used to further assess the role of NF-κB in the induction of VEGFR2 expression. A concentration of H2O2 ≥60 μM elicited clear-cut damaging effects on EC, whereas lower concentrations (2–4 μM) were cytoprotective. The cytoprotective effect was shifted to an EC-damaging pattern by means of specific VEGF blockade, therefore revealing a major role of autologous VEGF. Exposure to H2O2 increased VEGF and VEGFR2 mRNA and protein in EC, without affecting VEGFR1 expression. Also, H2O2 challenge was accompanied by increased NF-κB, activator protein-1, and specific protein-1 nuclear binding. A role of NF-κB as the mediator of the H2O2 induction of VEGFR2 mRNA expression was supported by inhibition by the ROS scavenger pyrrolidine dithiocarbamate and by the blocking effect of transfected IκBα. Exposure to exogenous VEGF also increased VEGFR2 and induced NF-κB in EC. In summary, autologous VEGF is instrumental for EC protection induced by low concentrations of ROS. ROS induce expression not only of VEGF but also of VEGFR2. VEGFR2 increase by ROS is mainly driven through a NF-κB-dependent pathway.

Recurrent acute postinfectious glomerulonephritis

Recurrent acute postinfectious glomerulonephritis is infrequent in childhood and exceptional in adults. The factors that determine recurrence are poorly understood. Selective IgA deficiency is characterized by an increased incidence of gastrointestinal and respiratory infections. The case of a 33-year-old man with a history of repetitive sinopulmonary infections and diagnosed with selective IgA deficiency is described. He suffered 2 episodes of postinfectious glomerulonephritis within a 15-year period. Selective IgA deficiency may have predisposed to the development of recurrent postinfectious glomerulonephritis

Association between phosphate removal and markers of bone turnover in haemodialysis patients

BACKGROUND

As the main mineral reservoir, bone acts as a calcium (Ca) and phosphate buffering system. Accordingly, phosphate removal by haemodialysis (HD) might be theoretically influenced by bone turnover, as well as by the interaction of regulatory molecules, such as PTH and osteoprotegerin (OPG). The present study investigated the relationship between these variables and phosphate removal by HD.

METHODS

Blood samples for serum Ca, phosphate, bicarbonate, intact PTH, PTH (1-84), bone alkaline phosphatase, tartrate-resistant acid phosphatase 5b, OPG and receptor activator of nuclear factor-kappaB ligand (RANKL) were obtained in 28 HD patients. Phosphate removal was measured by a continuous collection of the dialysate.

RESULTS

Pre-dialysis serum phosphate concentration is the critical factor in determining dialytic phosphate removal. However, multiple regression analysis reveals that phosphate removal is better explained by a combination of factors than by phosphate concentration alone. In this model, the PTH/OPG ratio is an additional positive factor, whereas age and vitamin D treatment are negative factors. Patients with pre-HD bicarbonate higher than 20 mEq/l had higher serum phosphate and, accordingly, higher phosphate removal; of interest, these individuals also have significant differences in RANKL/OPG. Mean (SD) OPG levels were significantly higher than that in the healthy population (16.2 (12.5) pmol/l; these values correlated with age (r = 0.4, P<0.04). Mean serum RANKL (1.03 (1.02) pmol/l) was within the range of normal individuals.

CONCLUSIONS

Dialytic phosphate removal has a crucial, direct relationship with pre-HD plasma phosphate levels. However, the phenomenon of phosphate removal is more precisely explained using a more complex relationship, defined by the interaction between serum phosphate, PTH/OPG, age and vitamin D administration. Serum RANKL levels are first reported in HD patients, and are not different from the normal population.

[Response to hypoxia. A systemic mechanism based on the control of gene expression]

New, critically important data have been recently generated about the response to hypoxia. This response can be schematized in three main systems or functions, ie, detectional or oxygen sensing, regulatory, which controls gene expression and effector. The principal organizer of the regulatory branch is a specific transcription factor, the hypoxia-inducible factor 1 (HIF-1). In the presence of oxygen, the alpha subunit of HIF-1 (HIF-1alpha) is modified by hydroxylases, that represent the central point of the oxygen sensing mechanism. This type of hydroxylation induces HIF-1alpha catabolism by the proteosome. On the contrary, in hypoxia, or in the presence of certain growth factors that increase HIF-1alpha synthesis, HIF-1alpha translocates to the nucleus, where it binds HIF-1beta, and thence acts on transcription of genes carrying hypoxia responsive elements (HRE) on their promoters. These genes regulate the synthesis of an ample series of proteins, which span from respiratory enzymes and transporters to hormones regulating circulation and erythropoiesis. The role of HIF-1alpha is not restricted to the mere induction of adaptation to decreased oxygen: instead, it significantly participates in cell repairing mechanisms. A simple list of some of the stimulatory or inhibitory alterations of pathophysiological importance involving the HIF-1 system, would include: chronic lung disease, smoking adaptation, anemia/hemorrhage, ischemia/reperfusion, growth, vascularization and cell resistance of tumors, preeclampsia and intrauterine growth retardation, retinal hyper o hypovascularization, drug intoxications, bowel inflammatory disease and wound repair. This list illustrates by itself the importance of the mechanism herein reviewed.

Cardio-renal insufficiency: the search for management strategies

PURPOSE OF REVIEW

This review focuses on the pathophysiology and treatment of an increasingly common entity, cardio-renal insufficiency. Cardio-renal insufficiency is more than a simultaneous cardiac and renal disease. Patients with this condition live within a fragile equilibrium challenged by the interaction of profibrogenic, atherosclerotic, neurohumoral, and other less known factors. Regarding therapy, the avoidance of oscillations between overfilled-decompensated and emptied-overtreated states becomes of critical importance. Particular focus should be paid to personalized treatment, adjusted according to heart and kidney reserve, the predictable complications of therapy, prevention of decompensations, simple measures-based follow-up and alternative procedures.

RECENT FINDINGS

Recent studies have established the important repercussions of unbalanced renal function on cardiovascular prognosis. In the heart failure setting, trials involving extensive cohorts of ageing or comorbidity-affected patients are presently under way. Special attention should be paid to recognize the presence of renal failure coexisting with heart failure, especially in patients with deceivingly near-normal plasma creatinine. Formulae to predict creatinine clearance are being increasingly incorporated into daily clinical practice. Disturbed renal function is an underappreciated prognostic factor in heart failure, and renal failure is frequently viewed as a relative contraindication to some proven efficacious therapies.

SUMMARY

Cardio-renal insufficiency is an emerging entity, with affected individuals surviving with extreme degrees of simultaneous heart failure and renal failure. Management of the condition is an intellectually demanding process. Crucial to this management is extensive medical expertise and an in-depth understanding of the particular renal, haemodynamic and internal milieu equilibrium of the patients.

Modulation of the effect of vascular endothelial growth factor on endothelial cells by heparin: critical role of nitric oxide-mediated mechanisms

BACKGROUND

In spite of intensive research, the actual role of heparin in endothelial cell (EC) biology remains incompletely understood. In particular, further insight is needed into the interaction of heparin with the potent heparin-binding angiogenic factor, vascular endothelial growth factor (VEGF). This study aimed to examine the effect of heparin on VEGF-mediated EC responses.

METHODS

Confluent bovine aorta EC were treated with high (HMWH) and low molecular weight heparin (LMWH). 3H-Thymidine (3H-Thy) uptake, flow cytometry, 51Cr-release, nitrites accumulation, and cytosolic free Ca2+ ([Ca2+]i), endothelial nitric oxide synthase (eNOS) mRNA expression and tissue factor (TF) concentration were measured.

RESULTS

HMWH and LMWH blocked VEGF proliferative actions and blunted VEGF-induced [Ca2+]i transients. However, the heparins did not block the VEGF protective effects on EC. These changes occurred in parallel with a potentiation of the VEGF-related NO production by both heparins. The Akt/PI3K inhibitor, LY 294002, blocked this potentiation, related to increased eNOS activity rather than eNOS expression. Connecting both effects, the NO antagonist, L-NAME, shifted the protective effects of VEGF to a cytotoxic mode.

CONCLUSION

HMWH and LMWH block the proliferative and [Ca2+]i-mobilizing effects of VEGF on EC, by a NO-dependent mechanism. On the contrary, VEGF-induced NO production is stimulated. The Akt/PI3K pathway at least in part mediates this effect. By changing the way the VEGF intracellular signaling is driven, heparin could act as a stabilizing factor for the endothelium, without stimulating vessel proliferation.

Tubular cell apoptosis and cidofovir-induced acute renal failure

Cidofovir is an antiviral drug with activity against a wide array of DNA viruses including poxvirus. The therapeutic use of cidofovir is marred by a dose-limiting side effect, nephrotoxicity, leading to proximal tubular cell injury and acute renal failure. Treatment with cidofovir requires the routine use of prophylactic measures. A correct knowledge of the cellular and molecular mechanisms of cidofovir toxicity may lead to the development of alternative prophylactic strategies. We recently cared for a patient with irreversible acute renal failure due to cidofovir. Renal biopsy showed tubular cell apoptosis. Cidofovir induced apoptosis in primary cultures of human proximal tubular cells in a temporal (peak apoptosis at 7 days) and concentration (10-40 microg/ml) pattern consistent with that of clinical toxicity. Apoptosis was identified by the presence of hypodiploid cells, by the exposure of annexin V binding sites and by morphological features and was associated with the appearance of active caspase-3 fragments. Cell death was specific as it was also present in a human proximal tubular epithelial cell line (HK-2), but not in a human kidney fibroblast cell line, and was prevented by probenecid. An inhibitor of caspase-3 (DEVD) prevented cidofovir apoptosis. The survival factors present in serum, insulin-like growth factor-1 and hepatocyte growth factor, were also protective. The present data suggest that apoptosis induction is a mechanism contributing to cidofovir nephrotoxicity. The prophylactic administration of factors with survival activity for tubular epithelium should be further explored in cidofovir renal injury.

Tubular Cell Apoptosis and Cidofovir-Induced Acute Renal Failure

Cidofovir is an antiviral drug with activity against a wide array of DNA viruses including poxvirus. The therapeutic use of cidofovir is marred by a dose-limiting side effect, nephrotoxicity, leading to proximal tubular cell injury and acute renal failure. Treatment with cidofovir requires the routine use of prophylactic measures. A correct knowledge of the cellular and molecular mechanisms of cidofovir toxicity may lead to the development of alternative prophylactic strategies.

We recently cared for a patient with irreversible acute renal failure due to cidofovir. Renal biopsy showed tubular cell apoptosis. Cidofovir induced apoptosis in primary cultures of human proximal tubular cells in a temporal (peak apoptosis at 7 days) and concentration (10–40 μg/ml) pattern consistent with that of clinical toxicity. Apoptosis was identified by the presence of hypodiploid cells, by the exposure of annexin V binding sites and by morphological features and was associated with the appearance of active caspase-3 fragments. Cell death was specific as it was also present in a human proximal tubular epithelial cell line (HK-2), but not in a human kidney fibroblast cell line, and was prevented by probenecid. An inhibitor of caspase-3 (DEVD) prevented cidofovir apoptosis. The survival factors present in serum, insulin-like growth factor-1 and hepatocyte growth factor, were also protective.

The present data suggest that apoptosis induction is a mechanism contributing to cidofovir nephrotoxicity. The prophylactic administration of factors with survival activity for tubular epithelium should be further explored in cidofovir renal injury.

Tumor-induced endothelial cell activation: role of vascular endothelial growth factor

Proangiogenic, proliferative effects of tumors have been extensively characterized in subconfluent endothelial cells (EC), but results in confluent, contact-inhibited EC are critically lacking. The present study examined the effect of tumor-conditioned medium (CM) of the malignant osteoblastic cell line MG63 on monolayer, quiescent bovine aorta EC. MG63-CM and MG63-CM + CoCl(2) significantly increased EC survival in serum-starved conditions, without inducing EC proliferation. Furthermore, MG63-CM and MG63-CM + CoCl(2), both containing high amounts of vascular endothelial growth factor (VEGF), induced relevant phenotypic changes in EC (all P < 0.01) involving increase of nucleoli/chromatin condensations, nucleus-to-cytosol ratio, capillary-like vacuolated structures, vessel-like acellular areas, migration through Matrigel, growth advantage in reseeding, and factor VIII content. All these actions were significantly inhibited by VEGF and VEGF receptor (VEGFR2) blockade. Of particular importance, a set of similar effects were detected in a human microvascular endothelial cell line (HMEC). With regard to gene expression, incubation with MG63-CM abolished endogenous VEGF mRNA and protein but induced a clear-cut increase in VEGFR2 mRNA expression in EC. In terms of mechanism, MG63-CM activates protein kinase B (PKB)/Akt, p44/p42-mitogen-activated protein kinase (MAPK)-mediated pathways, as suggested by both inhibition and phosphorylation experiments. In conclusion, tumor cells activate confluent, quiescent EC, promoting survival, phenotypic, and gene expression changes. Of importance, VEGF antagonism converts MG63-CM from protective to EC-damaging effects.

[Reticulocyte response after immediate withdrawal of recombinant human erythropoietin in chronic hemodialysis patients]

The sudden interruption of recombinant human erythropoietin (rHuEPO) in end-stage renal disease (ESRD) patients leads to rapid anemization. The mechanisms of this phenomenon are, however, insufficiently understood. The present study examined the response to immediate rHuEPO withdrawal in dialysis patients.

METHODS

10 chronic hemodialysis (HD) patients regularly receiving rHuEPO were studied. rHuEPO was stopped and reinitiated after 7 days. Reticulocyte profile, haemoglobin and haematocrit were measured at 0, 7 and 15 days. As a complementary study, and with the purpose of analyzying whether uremia was a relevant factor, 10 non-uremic male Wistar rats were treated with rHuEPO. After two weeks, rHuEPO was withdrawn in 5 animals, and continued for 7 additional days in the remainder. The same variables than in the human study were determined.

RESULTS

Changes in reticulocyte subtypes from baseline to day 7 were: total 18.2 +/- 0.9 vs 14.3 +/- 1.8% (p < 0.06); high-fluorescence (HFR): 2.6 +/- 0.4 vs 0.75 +/- 0.2 (p < 0.001); medium-fluorescence (MFR): 13.0 +/- 1.1 vs 6.6 +/- 0.9% (p < 0.02); and low-fluorescence (LFR): 84.2 +/- 1.4 vs 92.7 +/- 1% (p NS). The baseline pattern was recovered upon 7 days of rHuEPO reinitiation (p NS). Mean hemoglobin and hematocrit decreased by day 14 (p < 0.02) in spite of rHuEPO reinitiation at day 7. In non-uremic rats, changes were similar to that in the ESRD patients.

CONCLUSION

rHuEPO induces changes in the reticulocyte pattern, consisting in a reduction of immature reticulocytes. These changes appear to be independent of the presence of uremia. Accordingly, complete rHuEPO withdrawal in HD patients will cause a rapidly-developing anaemia due to an alteration in the reticulocyte maturation series; therefore, sudden rHuEPO interruption should be avoided whenever is possible. As a collateral application, the specific changes described herein have potential use for detecting illegal administration of rHuEPO.

[Guidelines on hemodialysis-associated viral infections]

The viric infections influence morbi-mortality in Chronic kidney Disease patients in hemodialysis therapy and can affect to the Staff of the Units. The guides considered the most relevant virus at the present moment: C Virus, B Virus and HIV. To prevent horizontal nosocomial transmission is necessary the observance always the universal precautions in the HD units, although sometimes can appeared seroconversions and epidemic bud when exist a break of these. Is analyzed different situations with special focus in units for acute patients. The following steps under the suspicious of the epidemic bud appeared in one of the annexes together with legislation according to this case. Respect to the staff in every one of the virus is shown prevention patterns, serologic markers to perform when an accident with infected blood occur, also is considered when treatment is indicated. The guides considered too the conditions necessary for include these patients on waiting list for kidney transplantation.

[Progressive deterioration in an elderly patient]

Vasculitis is diagnosed with increasing frequency in the elderly. We hereby present the case of an 84-year-old male, who had weight loss, low-degree fever, anemia and epigastric pain. After 14 days of study with the tentative diagnosis of digestive neoplasia, a progressive renal insufficiency was detected. This clinical picture was secondary to ANCA-positive vasculitis. The case poses the differential diagnosis of non-oliguric acute renal failure (FRA) in elder people and the systematics of the study of renal insufficiency in individuals with previously unknown renal function. Also, this patient's history emphasizes the importance of acute deterioration of renal function as a guiding symptom for orienting the interpretation of clinical data. In the present case, a diagnostic hypothesis based only in the pursue of an occult digestive tumor misguided the attention from the main cause of the disease.

Fluorescent complex of pyoverdin with aluminum

When a pyoverdin (PV), (a siderophore) from Pseudomonas fluorescens, binds aluminum 1:1, its natural fluorescence almost doubles, whereas PV-Fe is non-fluorescent. Complex formation allows [Al] determination down to 1 mug/l. Fe(III) in the sample interferes with [Al] determination, but added after PV, improves the assay's performance. Ascorbic acid does not eliminate Fe(III) interference. PV-Al fluorescence could have analytical and toxicological applications.

[Can we increase phosphate removal with conventional hemodialysis?]

BACKGROUND

The aim of the present study was to investigate the effect of different dialysate buffer and glucose concentrations, membrane surface (S) bigger than 2 m2 and increased dialysate flow (Qd) in phosphate (P) removal.

METHODS

A. First phase (5 patients): the following variations in dialysate composition were introduced. A: glucose 1.60 g/L, bicarbonate: 39 mEq/L, acetate 4 mEq/L, B: glucose 1.5 g/L bicarbonate 17 mEq/L, acetate 10 mEq/L; C: glucose 0, bicarbonate: 39 mEq/L, acetate 4 mEq/L; and D: glucose 0, bicarbonate 17 mEq/L, acetate 10 mEq/L. B. Second phase (14 patients): variations in S and Qd were: 1. Qd: 500 mL/min + Hemophan 2 m2, 2. Qd: 500 mL/min + Hemophan 2.6 m2, 3. Qd: 750 mL/min + Hemophan 2 m2, 4. Qd: 750 mL/min + Hemophan 2.6 m2.

RESULTS

Comparing HDs performed with low bicarbonate (B and D) respect to current buffer formulations (A and C), total P removal was 997.3 (+/- 237.3) vs 882 (+/- 216.1) mg (p NS). No differences were found by grouping the sessions according to glucose concentration. There were no significant differences in total phosphate removal between the two different S or Qd. The most important predictive factor of total P removal was the initial P and 2 hours serum P concentration, and PTH concentration.

CONCLUSIONS

i) Removal of P is better predicted by pre-dialysis P serum concentration; ii) P removal was not affected by the changes in bicarbonate and glucose concentration in the dialysate; iii) the increase of the dialyzer area between 2 and 2.6 m2 augments Kt/V, but without influencing P elimination; iv) a higher Qd does not determine significant differences in P removal and v) higher PTH is associated with a higher P elimination.