[Acute kidney injury and drug-induced nephropathies]. / Insuffisance (atteinte) rénale aiguë et néphrotoxicité médicamenteuse.

All types of acute kidney injury (AKI) (functional /pre-renal, parenchymal/intra-renal, obstructive/post-renal) result in a sharp drop of the glomerular filtration rate, with variable reversibility according to the initial cause. In one case out of five, drug intake can be related to the onset of AKI. Antibiotics, analgesics and nonsteroidal anti-inflammatory drugs, angiotensin converting enzyme inhibitors and angiotensin II receptor antagonists are the agents mostly involved, as well as iodinated radio-contrast agents. Mechanisms are often complex: toxic cellular effect directed on a nephron segment (tubular necrosis) associated or not with intraglomerular hemodynamic changes, or immune process leading to acute tubule-interstitial nephritis. Each underlying risk factor (age > 60 year, cardiac or hepatic failure, hypertension, diabetes, intra-vascular volume depletion, preexisting or unknown chronic kidney disease) must be taken into consideration by the prescribing physician because it reduces the chance of functional recovery and worsens the renal and the overall prognosis. A pre-renal additional component is often present and avoidable thanks to a strict hemodynamic monitoring. The present article summarizes some recent physiopathological aspects of AKI and makes the link between clinical situations and currently prescribed drugs. Lessons from the radio-contrast induced nephropathy are examined by taking into account prevention aspects and risk factors screening. An effective collaboration between the general practitioner and the nephrologist would benefit in optimizing the treatment of difficult cases.

[Experimental nephrology unit: overview and research projects]. / Unité de néphrologie expérimentale facultaire: etat des lieux et projets d'avenir.

After a short historical background of the Laboratory, the main research topics--renal toxicology, physiopathology of renal interstitial fibrosis and hormonology--are described in the perspective of a partnership between research clinicians and full time scientists. National as well as international scientific collaborations underline the need of combining expertises, stimulating also the training of youngest colleagues to the experimental approach of their future discipline.

Role of complement and platelet-activating factor in the stimulation of phagocytosis and reactive oxygen species production during haemodialysis.

BACKGROUND: Neutrophil phagocytic functions have been studied extensively in haemodialysis (HD) patients; however, results are contradictory and the mechanisms that modulate phagocytosis and oxidative burst during dialysis are not completely understood. METHODS: The present study investigated neutrophil functions in a selected population of patients before and during clinical dialysis with cuprophane, and polyacrylonitrile (AN69) membranes. We measured phagocytosis of Escherichia coli and intracellular hydrogen peroxide (H2O2) production by flow cytometry in whole blood. RESULTS: Before dialysis, neutrophils from HD patients showed normal phagocytic capability and H2O2 formation. Phagocytosis of FITC-E. coli was significantly stimulated in cuprophane but not AN69-treated patients. Spontaneous and stimulated H2O2 production was enhanced with both cuprophane and AN69 membranes. We then investigated in vitro the role of complement and platelet-activating factor (PAF) in the activation of neutrophils. Incubation of whole blood with C5a increased phagocytosis but not H2O2 production. On the contrary, the addition of synthetic PAF showed a markedly stimulated H2O2 production without increase in phagocytosis. Moreover, during dialysis with formaldehyde-reused cuprophane, complement activation was abolished and phagocytosis was no longer enhanced, while the stimulation of H2O2 production persisted. In addition, we also excluded a particular role of the membrane itself in the activation of neutrophils. CONCLUSION: We demonstrated that in a selected population of HD patients, neutrophils exhibit normal phagocytic capability and normal intracellular H2O2 production. During dialysis, the stimulation of phagocytosis observed with cuprophane is complement dependent, whereas the enhanced H2O2 production observed with both cuprophane and AN69 membranes might be related to PAF production.

Comparison of cellulose diacetate and polysulfone membranes in the outcome of acute renal failure. A prospective randomized study.

BACKGROUND: Whether the nature of haemodialysis (HD) membranes can influence the outcome of acute renal failure (ARF) remains debatable. Recent studies have suggested that dialysis with bioincompatible unsubstituted cellulosic membranes is associated with a less favourable patient outcome than dialysis with biocompatible synthetic membranes. Since we generally use a modified cellulosic membrane with substantially lower complement- and leukocyte-activating potential than cuprophane, for dialysis of patients with ARF, and because there are no data in the literature regarding the influence of modified cellulosic membranes on the outcome of patients with ARF, we compared the outcome of ARF patients dialysed either with cellulose diacetate or with a synthetic polysulfone membrane. We also investigated the potential role of permeability by comparing membranes with high-flux versus low-flux characteristics. METHODS: This prospective, randomized, single centre study included 159 patients with ARF requiring HD. Patients were stratified according to age, gender, and APACHE II score and then randomized in chronological order to one of three dialysis membranes: low-flux polysulfone, high-flux polysulfone and meltspun cellulose diacetate. RESULTS: Aetiologies of ARF and the prevalence of oliguria were similarly distributed among the three groups. There was no significant difference between the three groups for survival (multivariate Cox's proportional hazards model, P=0.57), time necessary to recover renal function (P=0.82), and number of dialysis sessions required before recovery (P=0.86). Multivariate analysis showed that survival was significantly influenced only by the severity of the disease state (APACHE III score, P<0.0001), but not by the nature of the dialysis membrane (P=0.57) or the presence of oliguria (P=0.24). CONCLUSIONS: Among patients with ARF requiring HD survival and recovery time are not significantly influenced by the use of either meltspun cellulose diacetate or the more biocompatible high-flux or low-flux polysulfone. Dialysis using modified cellulose membranes is just as effective as dialysis using synthetic polysulfone membranes, but at a lower cost. In addition, the flux of the membrane did not influence patient outcome.

Efficacy of oral immunotherapy on respiratory infections in hemodialysis patients: a double-blind, placebo-controlled study.

BACKGROUND: Hemodialysis (HD) patients suffer from several immune defects that make them prone to develop bacterial infections, in particular respiratory tract infections (RTIs). PATIENTS AND METHODS: As previous studies have shown that oral immunotherapy with an immunomodulating bacterial extract (IBE) is effective against RTIs, we decided to test its efficacy and safety in HD patients during a double-blind placebo-controlled prospective study. 40 HD patients with a documented history of RTIs in the previous year were treated for 24 weeks of the endemic season with one capsule daily of IBE (n = 21) or placebo (PL, n = 19). Clinical examinations, measurements of Mac-1 and gp150.95 on circulating phagocytes and routine laboratory evaluations were performed at week 0, 4, 12 and 24. Patients were also examined at each dialysis session allowing an accurate recording of any infectious episode, its treatment and of any untoward effect. RESULTS: During the last period of the study (weeks 13-24), IBE significantly reduced the number of patients with RTIs and consequently of antibiotic treatment courses as compared to PL (p = 0.018), whereas no difference was detected between IBE and PL during periods I (weeks 0-4) and II (weeks 5-12). There was no difference between IBE and PL for other, non respiratory infections. IBE was associated at several time points with an increased expression on phagocytes of adhesion molecules involved in phagocytosis (Mac-1 and gp150.95). However, the expression of these molecules was not predictive for the occurrence of RTI. IBE was on the whole as well tolerated as PL, 7 patients presented side effects (5 IBE, 2 PL, NS) which led to drop-out in 4 cases (3 IBE, 1 PL). No serious side effect was recorded, gastrointestinal upset being the most prevalent type. CONCLUSION: The results of this study indicate that immunomodulation with selected bacterial extracts constitutes a promising approach for the prevention of bacterial airway infections in groups at risk, such as HD patients.

[Does the biocompatibility of the hemodialysis membrane influence the prognosis of acute renal insufficiency?]. / La biocompatibilité de la membrane d'hémodialyse influence-t-elle le pronostic de l'insuffisance rénale aiguë?

Several recent publications have suggested that the use of cuprophane in the setting of acute renal failure is associated with a higher mortality (especially from sepsis) and a slower recovery of renal function in the survivors in comparison with more biocompatible membranes. We present here a critical review of these publications and point to several methodological bias that might invalidate their conclusions. However, while waiting further information, we would advocate to abandon the use of cuprophane to dialyze patients with acute renal failure.

Cuprophane haemodialysis induces upregulation of LPS receptor (CD14) on monocytes: role of complement activation.

BACKGROUND: The CD14 molecule is a high-affinity receptor for the complex formed by lipopolysaccharide (LPS) and LPS-binding protein. METHODS: We examined by flow cytometry the effect of in vitro and in vivo haemodialysis on cuprophane membrane and recombinant C5a on the expression of CD14 molecules at the surface on monocytes. Monocyte CD14 expression was also studied during in vitro and in vivo haemodialysis on polyacrylonitrile AN69 membrane. RESULTS: In vitro haemodialysis of whole blood from healthy volunteers on cuprophane membrane resulted within 30 min in upregulation of monocyte CD14 expression. The reuse of the cuprophane membrane abolished both complement activation and CD14 upregulation. Moreover, incubation of whole blood with recombinant C5a led to an increased monocyte CD14 expression supporting a role for complement activation in the rapid cuprophane-induced CD14 upregulation. During AN69 dialysis which is not associated with complement activation in the blood phase, monocyte CD14 expression did not change during the first 60 min but was significantly increased after 3 h of in vitro haemodialysis. This late increase might be related to the presence of complement activation products adsorbed on the membrane. In vivo dialysis on cuprophane membrane also resulted in early monocyte CD14 upregulation as indicated by higher CD14 expression found after 60 min on monocytes obtained from the efferent as compared to the afferent line of the dialyser, a phenomenon that was not observed during haemodialysis on AN69 membrane. CONCLUSION: Haemodialysis on the complement-activating cuprophane membrane induces the rapid upregulation of the CD14 LPS-receptor on monocytes.

Effects of ultrapure and non-sterile dialysate on the inflammatory response during in vitro hemodialysis.

Several studies support the hypothesis that bacterial contamination of the dialysate stimulates the inflammatory response to hemodialysis (HD) and increases the long-term morbidity of HD patients; this phenomenon could also be modulated by the nature of the HD membrane. Therefore, this study was designed to compare the effects of non-sterile (NSBD, mean endotoxin content +/- SEM 97 +/- 22 EU/ml) and ultrapure bicarbonate dialysate (UPBD, sterile and pyrogen-free, obtained by ultrafiltration through polyamide) on several aspects of the inflammatory reaction during in vitro HD. The HD sessions (7 in each experimental group) were performed using miniaturized new cuprophane (CU) and polyacrylonitrile (PAN) hollow fiber dialyzers, and closed dialysate and blood circuits (the latter filled with heparinized blood from healthy donors). Plasma C3aDesarg levels were significantly increased after 15 minutes (t1) and increased further after three hours (t2) of CU HD, while during PAN dialysis they decreased from t0 to t1 and t2; however, no difference appeared between experiments with NSBD and UPBD. Granulocyte (PMN) and monocyte (MNC) expression of LFA-1, Mac-1, and CD45 at the start (t0), t1 and t2 was quantitated by flow cytometry analysis, after staining of the cells with specific fluorescinated monoclonal antibodies. In contrast with published data of in vivo HD, LFA-1 was overexpressed at t1 and peaked at t2, which suggests that the leukocytes expressing more LFA-1 leave the systemic circulation during in vivo HD. During CU HD, Mac-1 and CD45 on PMN and MNC were significantly increased at t1, and still more at t2. During PAN HD, Mac-1 and CD45 remained unchanged at t1, but increased significantly at t2 on PMN as on MNC. Again, no significant difference was found between NSBD and UPBD in LFA-1, Mac-1 and CD45 expression on PMN and MNC, during both CU and PAN HD. AFter three hours of dialysis, plasma levels of TNF-alpha, but not of IL-6, were significantly increased with CU and PAN. Again, no difference appeared when NSBD and UPBD were compared. Moreover, the lack of influence of bacterial contamination of the dialysate on TNF-alpha production was confirmed when MNC were cultured up to 24 hours after the end of the HD session. We conclude that complement activation products, either in plasma (CU) of those adsorbed on the HD membrane (CU and PAN) play the major role in the overexpression of beta 2-integrins and CD45 by PMN and MNC during HD. Also, bacterial products (at the levels that can be found in clinical conditions) do not influence either beta 2-integrin overexpression or TNF-alpha production induced by the dialysis membrane.

Resistance to erythropoietin in iron-overloaded haemodialysis patients can be overcome by ascorbic acid administration.

Haemodialysis patients with iron overload sometimes develop resistance to erythropoietin therapy due to 'functional iron deficiency'. It is known that this resistance may be overcome by iron supplementation; however, the latter could worsen haemosiderosis. Therefore, we treated four iron-overloaded haemodialysis patients who had developed relative resistance to erythropoietin (among whom three had features of 'functional iron deficiency') with ascorbic acid (500 mg intravenously after haemodialysis, 1-3 times a week). The erythropoietin doses were voluntarily kept unchanged during the study. After a latency of 2-4 weeks, haematocrit and haemoglobin had increased respectively from 26.5 +/- 0.7 to 32.7 +/- 0.4 vol% and from 8.8 +/- 0.3 to 10.8 +/- 0.2 g/dl (means +/- SEM, P < 0.001). While serum ferritin remained unchanged, transferrin saturation increased from 27 +/- 7 to 54 +/- 12% (P < 0.05), suggesting that ascorbic acid supplementation had allowed mobilization of iron from tissue burdens. In one patient, haematocrit declined after withdrawal of vitamin C and increased again after rechallenge. Also, ascorbate supplementation was continued after the study in two patients and allowed the erythropoietin doses to be decreased, 8 and 11 weeks, respectively, after the start of the trial. When a control group of seven patients with normal iron status and without resistance to erythropoietin were challenged in the same manner with ascorbate, no elevation of haematocrit or transferrin saturation was noted. We conclude that ascorbate supplementation may circumvent resistance to erythropoietin that sometimes occurs in iron-overloaded patients, in particular, in the setting of 'functional iron deficiency'.

High haematocrit in haemodialysis patients can be controlled by theophylline administration.

Three patients on chronic maintenance haemodialysis have progressively increased their haematocrit to reach values between 40 and 45%, a situation associated with an increased risk of thrombosis of their arteriovenous fistulae. Two of them had been submitted to repeated phlebotomies, which remained unsuccessful despite the induction of a profound iron deficiency in one of them. Hence, a trial with oral theophylline was performed in the three patients, resulting in a sustained decrease of the haematocrit (from 43.6 to 33%) and endogenous erythropoietin (from 46 to 15 mU/ml) levels. In two patients, theophylline therapy was stopped transiently due to gastrointestinal side-effects, which resulted in a rapid return to previous haematocrit levels; rechallenge with a better tolerated preparation, however, was efficient again. We conclude that oral theophylline appears to be an efficient treatment to control too high haematocrit levels in dialysis patients.

Evidence that pentoxifylline reduces anti-CD3 monoclonal antibody-induced cytokine release syndrome.

Pretreatment with pentoxifylline (PTX), a methylxanthine known for its beneficial effects on tissue lesions induced by the injection of endotoxin or recombinant cytokines, was shown to decrease the systemic release of tumor necrosis factor and interleukin 2 occurring after the administration of the anti-CD3 monoclonal antibody 145-2C11 in mice. In parallel, PTX attenuated the hypothermia and the rise in blood urea nitrogen observed in this model. The protective effect of PTX on the toxicity of 145-2C11 was confirmed by the reduction of the mortality among D-galactosamine-sensitized animals. The mitigation by PTX of the release of cytokines did not affect the immunosuppression entailed by 145-2C11 as assessed by the unmodified cytotoxic T lymphocytes (CTL) unresponsiveness against alloantigens measured 48 hr after the injection of the mAb. In vitro experiments on human peripheral blood leukocytes indicated that PTX alone or in synergy with methylprednisolone (m-PDS) also inhibited the release of TNF and IL-2 induced by OKT3. Finally, in a preliminary pilot trial conducted in kidney transplant recipients, we observed that pretreatment with PTX (20 mg/kg i.v.) in addition to m-PDS (2 g i.v.) reduced by half the amount of TNF released in the blood stream after the first injection of OKT3, while no further reduction of the low levels of IL-2 was found.