[Use of oral hypoglycemic agents in patients with chronic kidney failure]. / Farmaci ipoglicemizzanti orali nei pazienti con insufficienza renale cronica.

Type 2 diabetes mellitus is one of the most common disease worldwide. Diabetes mellitus is expected to affect over 380 million people by 2025 and one third of these patients will develop chronic kidney disease (CKD). There are many categories of hypoglycemic agents available for treatment of type 2 diabetes mellitus: sulphounilureas, glinides, biguanides, thiazolidinediones, alpha-glucosidase inhibitors, and the new brand incretines. In nephropatic patients with CKD stage I-II, any hypoglycemic agent can be used: the choice must be linked to a careful evaluation of potential risk and benefit. In CKD stage III to V, conversely, some drugs are not recommended while other agents can be used with dose reduction due to risk of hypoglycemia. In these patients the early use of insulin may be indicated. The target of this review is to evaluate evidences about the possible use of hypoglycemic agents in patients affected by diabetes and CKD stage III-V.

[Reduced nitric oxide bioavailability in chronic renal failure: a new factor of progression?]. / Ridotta biodisponibilità di ossido nitrico nell'insufficienza renale cronica: un nuovo fattore di progressione?

Nitric oxide (NO) is a gaseous free radical and an important molecular mediator of many physiologic processes in virtually every organ. NO is produced from L-arginine by nitric oxide synthase (NOS). This enzyme is expressed as 3 isoforms, all of which have been isolated from the kidney: endothelial NOS (eNOS), neuronal NOS (nNOS), and inducible NOS (iNOS). At present it is very difficult to measure authentic nitric oxide in vivo; a way to circumvent the difficulties is to study the effects of NOS stimulation and subsequent nitric oxide release directly by measurement of the resulting changes in vascular tone. In the kidney and vasculature, NO plays fundamental roles in the control of systemic and intrarenal hemodynamics, the tubuloglomerular feedback response, pressure natriuresis, release of sympathetic neurotransmitters and renin, and tubular solute and water transport. Chronic renal failure (CRF) is a state of NO deficiency secondary to decreased NO production and/or increased bioinactivation of NO by reactive oxygen species. The purpose of this review is to examine the functions of NO in the kidney, and to discuss the effects of NO deficiency in the progression of chronic kidney disease.

Platelet-leukocyte interactions in hemodialysis patients: culprit or bystander?

The formation of circulating platelet-leukocyte complexes has been observed in a variety of conditions and may be pathophysiologically significant. Platelet-leukocyte interactions in fact facilitate metabolic cooperation and mutual activation, which may be of relevance in many biological processes including inflammation, atherogenesis and hemostasis. During hemodialysis procedure, the series of reactions that can occur upon blood contact with the foreign membrane surface may involve a variety of changes affecting almost every cellular and plasmatic component of the blood. This article reviews the evidence for abnormal interactions between circulating platelets and leukocytes in uremic patients undergoing maintenance hemodialysis and the pathophysiologic implications which may stem from such interactions.

Wireless capsule endoscopy in the diagnostic of small intestine angiodysplasia in chronic uremic patient.

Gastroenteric bleeding due to angiodysplasia (AD) is a relatively common occurrence in patients with end-stage renal failure. Gastric and colon angiodysplasic lesions can be easily revealed by endoscopic procedures, whereas lesions of the small intestine are more difficult to detect. Imaging modalities used in the diagnostic imaging algorithm for the detection of small-bowel AD, include non-invasive methods like enema-helical computer tomography,(99m)Tc-labelled red blood cell scintigraphy, and angiography, and invasive methods such as intraoperative enteroscopy. We report the cases of 3 hemodialysis patients with recurrent episodes of gastrointestinal bleeding, caused by small-bowel AD diagnosed by means of wireless-capsule endoscopy. In all cases, previous gastroscopy and colonoscopy were unrevealing. Wireless-capsule endoscopy consists in swallowing a capsule endoscope (11 mmx27 mm) which contains a miniature video camera, a light source, batteries, and a radio transmitter. Video images are transmitted by means of radio telemetry to aerials taped to the body that allow images to be captured. Moving images from a period as long as 6 h are stored on a portable recorder. Wireless-capsule endoscopy may prove valuable in the assessment of gastrointestinal bleeding in uremic patients with unrevealing results at gastroscopy and colonoscopy.

[Angiodysplasia of the small bowel: a possible cause of anemia even in mild chronic renal failure]. / Angiodisplasia dell'intestino tenue: una possibile causa di anemizzazione nell'IRC anche di grado lieve.

BACKGROUND: Gastroenteric angiodysplasia (AD) is a vascular lesion characterized by vascular ectasias to the submucous sheath of the gastrointestinal tract. Lesions can be flat or raised, isolated or grouped and can break or ulcerate causing acute hemorrhage or, more commonly, chronic bleeding. CASE-REPORT: We describe a 65-year-old patient with a 3-yr history of chronic renal failure (CRF), who gradually developed anemia (hemoglobin (Hb) 10 g/dl) without any episodes of clinically relevant bleeding or any exposure to bleeding risk factors. Blood pressure (BP) was normal and renal function was stable (serum creatinine (Cr) 1.9 mg/dl). Routine laboratory tests showed a slight reduction in serum iron and transferrin saturation and a slightly elevated absolute reticulocyte count. These findings were associated with a positive occult gastrointestinal blood test and raised the clinical suspicion of chronic gastrointestinal blood loss. Oesophagogastro-duodenoscopy and colonoscopy demonstrated an absence of significant lesions, suggesting the need to investigate for a lesion localized in the small intestine. Capsular endoscopy, a recently developed endoscopic technique, particularly suited for small bowel pathology, was performed, and demonstrated the presence of an angiodysplasic lesion, located in the jejunum. CONCLUSIONS: Our case report supports the necessity for a complete clinical and laboratory evaluation of the possible causes of anemia superimposed on relative erythropoietin deficiency in CRF patients. When gastrointestinal blood loss is suspected, the entire gastroenteric tract should be examined to search for the bleeding sites. Our report also demonstrates that AD could be responsible for gastrointestinal bleeding even in mild CRF and not only, as usually reported, in end-stage renal disease (ESRD). Capsular endoscopy offers the unique possibility to determine the bleeding site in the small intestine and appears as an effective diagnostic procedure in CRF patients.

Increased platelet phosphatidylserine exposure and caspase activation in chronic uremia.

Platelet activation is associated with exposure of the aminophospholipid phosphatidylserine (PS) to the outer hemi-leaflet of the plasma membrane bilayer, which seems to be involved in the coagulation process. Because platelet activation may occur in patients suffering from chronic uremia, which is frequently associated with a thrombophilic tendency, we studied whether uremic platelets show an increased propensity to expose PS on the outer membrane leaflet and whether this process is linked with important functional and molecular changes. Flow cytometric percentage of annexin V-positive platelets, a measure of PS externalization, was significantly elevated (P < 0.001) in uremic patients when compared to normal controls under both unstimulated and agonist-stimulated conditions. Uremic platelet procoagulant activity, as measured by thrombin generation, was more than twice as high (4.13 +/- 0.3 micro mL(-1)) as that found in normal controls (1.86 +/- 0.2 micro mL(-1)). Two independent assays showed that the enzymatic activity of caspase-3, a protease involved in the loss of membrane PS asymmetry, was significantly greater in the platelets of uremic subjects than in those of healthy controls. PS exposure in agonist-stimulated platelets was markedly reduced by inhibition of caspase-3 activity but was not affected by inhibition of calpain activity. These results support the view that the thrombophilic susceptibility of uremic patients may be partly ascribed to increased PS exposure to the outer membrane leaflet of platelets. This process seems to be causally linked to an increase in caspase-3 activity, particularly during platelet activation.

Platelet activation and platelet-erythrocyte aggregates in end-stage renal disease patients on hemodialysis.

Activated platelets may engage in dynamic interplay with other blood cells. We examined the evidence for platelet activation and the formation of platelet-erythrocyte aggregates in chronic hemodialysis patients. Circulating activated platelets (P-selectin/CD63-positive platelets) were higher than normal controls (p < 0.001) and further increased during hemodialysis sessions, the increase being higher when patients were dialyzed with cellulosic than with synthetic membranes. We found direct evidence of uremic platelet-erythrocyte adherence in vitro and increased levels of circulating platelet-erythrocyte aggregates in dialysis patients, which represents a new observation in uremia. Platelet-erythrocyte aggregates were subject to further increase during hemodialysis, and again higher levels were found with cellulosic than synthetic membranes. This phenomenon was reproduced in vitro by both ADP and PAF, but not by either complement factor C3a or by heparin concentrations corresponding to those used for clinical hemodialysis. We conclude that platelet-erythrocyte aggregates occur in hemodialysis patients probably owing to a primary platelet activation mechanism.

Involvement of phosphatidylserine exposure in the recognition and phagocytosis of uremic erythrocytes.

Cell surface-exposed phosphatidylserine (PS) represents a signal for macrophage recognition and cell phagocytosis. This study examines PS exposure and susceptibility to erythrocyte phagocytosis in patients with chronic uremia in an attempt to assess the possible pathogenic mechanism behind cell removal in a condition associated with shortened erythrocyte life. Both PS-expressing erythrocytes and erythrophagocytosis (human monocyte-derived macrophages ingesting one or more erythrocytes) were significantly increased in uremic patients compared with healthy controls. Phagocytosed uremic erythrocytes appeared intact, suggesting they were identified before lysis through some surface change recognized by the macrophages. The degree of phagocytosis was markedly greater for PS-positive than PS-negative fluorescence-activated cell sorter (FACS)-sorted uremic erythrocytes. A significant correlation (r = 0.655) was found between the percentage of PS-expressing red blood cells (RBCs) and the percentage of phagocytosing macrophages in uremic patients. Reconstitution experiments showed the ability of uremic plasma to promote both PS exposure and erythrophagocytosis, the latter without direct interaction with the macrophage population. Phagocytosis of uremic erythrocytes was strongly inhibited when the macrophages were preincubated with glycerophosphorylserine (GPS), a structural derivative of PS, but this was not the case with the equivalent derivative of phosphatidylethanolamine, glycerophosphorylethanolamine. This inhibition appeared to be specific because GPS failed to inhibit the phagocytosis of opsonized uremic erythrocytes that occurs through an Fc receptor-mediated pathway. These findings suggest that a PS-recognition mechanism may promote the susceptibility of uremic RBCs to phagocytosis and thus be involved in the shortened erythrocyte life span of uremia.

Cell activation and cellular-cellular interactions during hemodialysis: effect of dialyzer membrane.

During hemodialysis (HD), circulating blood cells can be activated and also engage in dynamic interplay. These phenomena may be important factors behind dialysis membrane bio(in)compatibility. In the present prospective cross-over study, we have used flow cytometry to evaluate the influence of different dialysis membranes on the activation of circulating blood cells (leukocytes, platelets) and their dynamic interactions (formation of circulating platelet-leukocyte and platelet-erythrocyte aggregates) during in vivo HD. Each patient (n = 10) was treated with dialyzers containing membranes of cellulose diacetate, polysulfone and ethylenevinylalcohol (EVAL) in a randomized order. Upregulation of adhesion receptor expression (CD15s, CD11b/CD18) occurred mainly with the cellulosic membrane, though an increase in CD11b/CD18 circulating on neutrophils was also found with both synthetic membranes. Circulating activated platelets (P-selectin/CD63-positive platelets) increased during HD sessions with cellulose diacetate and polysulfone. An increased formation of platelet-neutrophil aggregates was found at 15 and 30 min during dialysis with cellulose diacetate and polysulfone but not with EVAL. Platelet-erythrocyte aggregates also increased with cellulose diacetate and at 15 min with polysulfone as well. Generally in concomitance with the increase in platelet-neutrophil coaggregates, there was an increased hydrogen peroxide production by neutrophils. The results of this study indicate that cellular mechanisms can be activated during HD largely depending on the membrane material, EVAL causing less reactivity than the other two membranes. It appears that each dialysis membrane has multiple and different characteristics that may contribute to interactions with blood components. Our results also indicate that derivatizing cellulose (cellulose diacetate) may be a useful way to improve the biocompatibility of the cellulose polymer and that there may be great variability in the biocompatibility profile of synthetic membranes, dialysis with polysulfone being in general associated with a higher degree of cell activation than EVAL membrane.

Endoscopy as a tool for diagnosing and treating gastrointestinal angiodysplasia in haemodialysis patients.

Gastroenteric angiodysplasia is an important cause of haemorrhage in chronic renal failure patients. This paper reports on 2 patients on maintenance haemodialysis with upper gastrointestinal bleeding due to different manifestations of angiodysplasic lesions (sudden appearance of haematemesis and melaena in one case, progressive anaemia with apparent resistance to erythropoietin in the other case). Exploratory endoscope examination of the first digestive tract showed in both cases the presence of bleeding angiodysplasic lesions. Both patients were there and then submitted to surgical endoscopy, during which the bleeding angiodysplasic lesion was sclerosed with physiological salt solution plus adrenaline 1/10000 and 1% polydocanol. In one patient, bleeding occurred again ten days later, making renewed surgical endoscopy necessary. In the course of this an elastic ligature was made to the superangular angiodysplasia. A year later in both cases there were no direct or indirect signs of further bleeding; an endoscopic check-up showed the treated lesions to be sclerosed. Endoscopy offers the unique possibility of being used for both diagnostic and therapeutic purposes in a single session. In expert hands, endoscope therapy is effective and markedly reduces the risk of side effects.

Biocompatibility and functional performance of a polyethylene glycol acid-grafted cellulosic membrane for hemodialysis.

In order to improve the biochemical reactivity of the cellulose polymer, which is mainly attributed to the presence of surface hydroxyl groups, derivatized cellulosic membranes have been engineered replacing or masking some or all of the hydroxyl groups in the manufacturing process of the membrane. The present study was set up to analyze both biocompatibility and functional performance of two different derivatized cellulosic membranes (cellulose diacetate; polyethylene glycol, PEG, acid-grafted cellulose) as compared to a synthetic membrane (polymethylmethacrylate, PMMA). Cellulose diacetate is prepared by substituting hydroxyl groups with acetyl groups; PEG cellulose is obtained by grafting PEG chains onto the cellulosic polymer with a smaller amount of substitution than cellulose diacetate. While the three dialyzers provided similar urea and creatinine removal, the dialyzer containing cellulose diacetate showed a reduced ability to remove 32-microglobulin compared to that containing PEG cellulose or PMMA. A transient reduction in leukocyte count was observed for both derivatized cellulosic membranes. The neutrophil and monocyte counts throughout the entire dialysis session showed a closer parallelism with the cellular expression of the adhesive receptor CD 15s (sialyl-Lewis x molecule) than with CD11b/CD18 expression. Platelet activation, as indicated by the percentage of cells expressing the activation markers CD62P (P-selectin) and CD63 (gp53), occurred with all membranes at 15 min of dialysis and also with PMMA at 30 min. An increased formation of platelet-neutrophil and platelet-monocyte coaggregates was found at 15 and 30 min during dialysis with cellulose diacetate and PMMA but not with PEG cellulose. Generally in concomitance with the increase in platelet-neutrophil coaggregates, an increased hydrogen peroxide production by neutrophils occurred. Our results indicate that derivatizing cellulose may represent a useful approach to improve the biocompatibility of the cellulose polymer, though some homeostatic reactions remain activated. Our results also indicate that there may be a great variability in the biocompatibility profile of derivatize cellulosic membranes which most likely stem from the different type of structural modification rather than from the degree of hydroxyl group replacement.

Leukocyte adhesion molecules and leukocyte-platelet interactions during hemodialysis: effects of different synthetic membranes.

Membranes made from synthetic polymers, in general, are considered as being biocompatible membranes and tend to be treated as a homogeneous group. However, all of these membranes have multiple and different characteristics that may contribute to interactions with blood components. As a consequence, the biocompatibility profile of synthetic membranes may vary. In the present cross-over study, we examined by flow cytometry the effects (expressed as % change from predialysis values) of three different synthetic polymers (polysulfone, PSF; polyacrylonitrile-co-sodium methallyl sulfonate, AN69; ethylenevinylalcohol, EVAL) on the expression of leukocyte adhesion molecules (CD11b/CD18, CD15s) and the interactions between leukocytes and platelets under conditions of routine clinical use. For neutrophils, a statistically significant difference was found in CD15s expression for EVAL as compared to AN69 (p<0.05) and in CD11b/CD18 expression for PSF as compared to both EVAL (p<0.01) and AN69 (p<0.05). No difference between membranes was found on the expression of such adhesive molecules on monocytes. Significant differences in platelet-neutrophil (but not in platelet-monocyte) coaggregate formation were observed between PSF and both EVAL (p<0.001) and AN69 (p<0.01). Reactive oxygen species production by neutrophil population during hemodialysis was significantly different between each pair of synthetic polymers (PSF vs EVAL, p<0.001; PSF vs AN69, p<0.001; AN69 vs EVAL, p<0.05). Our data demonstrate that in terms of leukocyte adhesion receptors and platelet-leukocyte interactions, the biocompatibility profile of the synthetic membranes polysulphone, AN69 and EVAL shows many similarities but also several significant differences. Our results support the concept that biocompatibility evaluation of each membrane should be based exclusively on data generated by that membrane in order to avoid errors based on assumptions about group characteristics.

[On-line HFR and removal of uremic toxins inducing the loss of phospholipidic asymmetry of the erythrocyte membrane]. / HFR on-line e rimozione di tossine uremiche inducenti la perdita dell'asimmetria fosfolipidica della membrana eritrocitaria.

The phospholipids of the erythrocyte membrane are normally distributed asymmetrically in the double layer with the aminophospholipid phosphatidylserine (PS) present only on the inside of the membrane, since its exposure on the outside has numerous physiopathological consequences. In previous studies we have observed that solutes retained in uremia cause increased exposure of PS on the outer surfaces of the erythrocyte membrane and that this phenomenon may be involved in the uremic physiopathology, reducing erythrocyte survival and encouraging abnormal erythrocyte-endothelium interactions. The capability of the extracorporeal blood clearance treatment in removing the circulating uremic factors, responsible for the increased exposure of PS in red blood cells (RBC), was evaluated in 6 chronic uremic patients treated with haemodialysis (HD) or with on-line HFR in a random cross-over perspective study. The PS removal was evaluated indirectly by measuring the expression of PS in normal RBC incubated with uremic plasma obtained at various moments of the clearance session. The capability of the uremic plasma to expose PS on the RBC of healthy subjects (n-times increase compared to incubation of normal RBC with autologous plasma) was essentially unmodified during HD (3.3 +/- 0.2 pre HD; 3.3 +/- 0.1 after 2 hours; 3.1 +/- 0.2 at the end of the session) but was reduced during HFR (3.1 +/- 0.2 pre HD; 2.3 +/- 0.1 after 2 hours; 1.6 +/- 0.1 at the end of dialysis; p<0.001 at the end of dialysis vs pre and after 2 hours and p<0.001 vs HD at 2 hours and at the end of the session). The reduced capability of the uremic plasma obtained during the HFR session to expose PS in normal RBC, proves removal of the plasmatic uremic factors able to externalize the PS. To assess whether this removal effect is linked to the cartridge containing styrene resin used in the treatment with HFR, samples of ultrafiltrate were taken before and after the cartridge and its capability to express PS on normal RBC was measured. The absolute RBC values expressing PS (%) were (pre-cartridge vs post-cartridge) 8.6 +/- 0.3 vs 3.8 +/- 0.2 after 5 minutes from the start of the session; 3.9 +0.1 vs 1.6 +0.2 halfway through the session; 3.1 +/- 0.1 vs 1.3 +/- 0.66 at the end of the session (p<0.005 pre vs post at all times). Our results show that uremic compounds able to cause increased exposure of PS in RBC can be removed during on-line HFR, mainly thanks to the adsorption properties of the cartridge containing resin. This removal might be of benefit to uremic patients, improving the anaemic condition and reducing abnormal RBC-endothelium interactions which may contribute to endothelial disorder during uremia.

Interactions between platelets and leukocytes during hemodialysis.

The formation of platelet-leukocyte microaggregates has been observed in a variety of conditions. When platelets and leukocytes coaggregate, in general, a reciprocal activation occurs when both cells are activated, and the interactions between activated platelets and leukocytes may be relevant in both hemostasis and inflammatory processes. The study of platelet-leukocyte interactions in hemodialysis offers the novel aspect of cellular-cellular interaction as a new parameter for evaluating the biocompatibility of dialyzer membranes. This article reviews the investigations of the interactions between platelets and leukocytes during hemodialysis and the pathophysiologic implications which may stem from such interactions.

Increased erythrocyte phosphatidylserine exposure in chronic renal failure.

The appearance of phosphatidylserine, an aminophospholipid normally confined to the inner monolayer, at the outer leaflet of red cell membrane may have several pathophysiologic implications. This study examines erythrocyte phosphatidylserine exposure in chronic renal failure (CRF) patients on conservative treatment or on dialysis, to assess possible alterations to phospholipid asymmetry in a condition associated with a state of deranged red cell function. A significant increase in phosphatidylserine-expressing erythrocytes was found in undialyzed patients with CRF (2.32%) and patients on hemodialysis (3.06%) and on peritoneal dialysis (2.14%) compared with control subjects (0.68%). In undialyzed CRF patients, a strong correlation (r = 0.903) was found between the percentage of phosphatidylserine-expressing red cells and the serum creatinine concentration. The increased exposure of phosphatidylserine in uremic erythrocytes may be due to inhibition of phosphatidylserine transport from the outer to the inner leaflet of plasma membrane and may promote an increased erythrophagocytosis. In reconstitution experiments, normal erythrocytes showed an increase in phosphatidylserine-expressing cells when incubated in uremic plasma (3.2% after 2 h versus 1.1% at beginning of incubation), whereas phosphatidylserine-positive uremic erythrocytes decreased when resuspended in normal plasma (2.03% after 2 h and 1.65% after 8 h versus 2.9% at beginning of incubation). Preliminary characterization of the putative uremic compound(s) indicates a molecular weight between 10,000 and 20,000, as well as heat instability. These findings show an impairment of erythrocyte membrane phospholipid asymmetry in CRF patients, regardless of the dialysis treatment. Such abnormality seems related to the uremic state and could contribute to the red cell pathology present in CRF.

Surface antigen expression and platelet neutrophil interactions in haemodialysis.

BACKGROUND: There is increasing evidence to show the clinical implications of membrane biocompatibility in haemodialysis therapy. METHODS: We conducted a cross-over clinical study examining the clinical biocompatibility profile of three derivatised cellulosic membranes obtained by means of different modifications to the cellulose polymer (haemophan, cellulose diacetate, benzyl cellulose) in comparison to the parent polymer (cuprophan) and a reference synthetic membrane (polysulfone). RESULTS: In terms of leukopenia production, derivatised cellulosic membranes were generally intermediate between cuprophan and polysulfone, haemophan being more marked than the other two membranes. Upregulation of CD11b/CD18 molecule on neutrophils was found with all membranes, to a greater extent with the dialyser containing cuprophan. The expression of CD11b/CD18 on monocytes was slightly affected with cuprophan only. The neutrophil and monocyte counts throughout the entire dialysis session showed a much better correlation with the cellular expression of sialyl-Lewis x (CD15s) molecule than with CD11b/CD18 expression. An increased formation of platelet-neutrophil coaggregates occurred at 15 and 30 min during dialysis with all membranes but benzyl cellulose, the increase with cuprophan being higher than with the other membranes. In concomitance with the increase in platelet-neutrophil coaggregation, an increased hydrogen peroxide production by neutrophils occurred, which proved to be significantly higher compared to the unchanged neutrophil hydrogen peroxide production during HD with benzyl cellulose. CONCLUSIONS: Our results demonstrate that derivatised cellulose is associated with a considerable improvement in the clinical biocompatibility profile. Derivatised cellulosic membranes show many similarities but also several significant differences which very likely stem from the different type of structural modification to the cellulose polymer rather than from the degree of hydroxyl group replacement.