{beta}2-Microglobulin Kinetics During Haemodialysis and Haemofiltration

Since the identification of ß₂-microglobulin as amajor component of ‘dialysis amyloid’, concern aboutits removal by different dialysis methods has been raised. Haemodialysiswith regenerated cellulose membranes increases serum ß₂-microglobulinby 10–15%. Serial measurements show a very early increaseduring cuprophan haemodialysis, the mechanism of which is asyet unknown. After cuprophan haemodialysis, serum values returnto the initial pretreatment concentrations by the time of thenext haemodialysis. In contrast to regenerated cellulose, dialysiswith polycarbonate lowers serum ß₂-microglobulin by8%, and dialysis with polysulphone by 53%. As opposed to cuprophan,after polysulphone haemodialysis the serum concentrations havenot returned to the initial pretreatment levels within 48 h.Comparison of ß₂-microglobulin removal using the samepolysulphone membrane for haemodialysis and haemofiltrationshows that ß₂-microglobulin is more effectively removedby convection than by diffusion when both treatment modes arematched for blood flow and urea clearance. Therefore, in contrast to haemodialysis with regenerated cellulosemembranes, where a transient, intradialytic release of ß₂-microglobulinis induced, significant removal is observed using, higher permeablemembranes. These findings may have implications for the generationof ‘dialysis amyloid’.     

{beta}2-Microglobulin Kinetics During Haemofiltration

To study the kinetics of ß₂-microglobulin during haemofiltration,seven patients with end-stage renal failure were treated withthe AN 69 (acrylonitrile), Duo-Flux (cellulose acetate) andF 60 (polysulphone) haemofilter. Low ß₂-microglobulinsieving coefficients and a highly negative filter mass balanceerror were observed during the initial phase of treatment withAN 69 but not with Duo-Flux or F 60, indicating a high degreeof ß₂-microglobulin adsorption by AN 69. Total removalof ß₂-microglobulin was calculated by addition ofthe total amount adsorbed by the membrane and the total amountrecovered in the collected ultrafiltrate. With AN 69 and F 60,total removal of ß₂-microglobulin amounted to 393±135(SD) and 316±35mg per treatment, while total removalwith Duo-Flux was 242±79 mg per treatment. Thus, highlypermeable membranes such as AN 69 or F 60 used in a haemofiltrationmode may nearly balance the presumed generation of ß₂-microglobulinin uraemic patients. During treatment, an increase of the calculatedß₂-microglobulin distribution volume occurred withall three membranes, probably representing extra-to-intracellularwater shifts. The water shifts occurring during haemofiltrationreduce the value of precision of ß₂-microglobulinkinetics and limit the value of the plasma level decrease asan index of ß₂-microglobulin removal.     

Tissue Uptake of 125I-{beta}2-Microglobulin({beta}2-M) in Anephric Animals in the Presence or Absence of Aluminium Intoxication

In long-term haemodialysis patients a new type of amyloidosiscomposed of ß₂-microglobulin (ß₂-M) hasrecently been described. The amyloid deposition has a particularpredilection for articular structures. In the pathogenesis ofthis complication markedly elevated plasma ß₂-M concentrations,such as those observed in anuric patients, have a role. However,other as yet ill-defined factors must also be implicated, possiblecandidates being aluminium intoxication and the widely usedregenerated cellulose (cuprophan) membrane. In the present experimentalstudy, we examined tissue distribution of exogenous ß₂-Mafter i.v. injection of ¹²⁵I-ß₂-M to bilaterally nephrectomisedrats. One hundred and twenty minutes after injection, most radioactivityremained in the vascular compartment. The accumulation in tissueswas weak, and no predilection for a particular tissue becameapparent. Interestingly, chronically aluminium-overloaded, acutelyanephric rats accumulated a significantly greater amount of¹²⁵I-ß₂-M in their spleens than anephric rats withoutprior aluminium intoxication. We then attempted to induce ß₂-M amyloid depositionin rats and mice, some of whom had undergone chronic aluminiumintoxication and subcutaneous implantation of regenerated cellulosefragments for various periods of time. They were subsequentlymade anephric to obtain high plasma ß₂-M concentrations.None of the animals developed ß₂-M amyloidosis inspleen, liver, skin and mechanically altered joint synovium. In conclusion, chronic aluminium intoxication enhances splenicaccumulation of exogenous ¹²⁵I-ß₂-M in anephric rats.The factors required to form ß₂-M-amyloidosis in vivohave still to be defined.     

High-Flux Synthetic Versus Cellulosic Membranes for {beta}2-Microglobulin Removal During Hemodialysis, Hemodiafiltration and Hemoflitration

Efficient removal of ß₂ microglobulin (ß₂-M)in end-stage renal failure patients is a continuing preoccupation,as the incidence and severity of dialysis-associated amyloidosisare increasing. To evaluate comparative ß₂-M removalwe studied six stable end-stage renal failure patients duringhigh-flux 3-h haemodialysis, haemodiafiltration, and haemofiltration,using acrylonitrile, cellulose triacetate, polyamide and polysulphonecapillary devices. The reduction of plasma ß₂-M, totalremoval in ultrafiltrate/dialysate, and ß₂-M sievingcoefficients were measured by RIA. The results suggest thatconvection plays the major role in ß₂-M removal whenhigh-flux synthetic membranes are used in combination with highblood flow rates. In contrast, using the cellulose triacetatemembrane under investigation, ß₂-M removal is diminishedwhen ultrafiltration rates are increased. Accordingly, in anyfuture prospective study on the role of ß₂-M retentionin the amyloidogenesis, it is recommended that high-flux syntheticmembranes be employed rather than the type of high-flux cellulosicmembranes used in this study. The modality with which thesesynthetic membranes are used is probably less important, aslong as maximum convective transport rates are obtained. Underpresent conditions, this will imply haemofiltration or haemodiafiltrationrather than haemodialysis.     

Determinants of Plasma {beta}2 Microglobulin Concentration: Possible Relation to Membrane Biocompatibility

Beta₂ microglobulin (ß₂m) concentrations were measuredby radioimmunoassay in the serum of haemodialysed patients.ß₂m was higher in males (n=48) than in females (n=26),i.e. 40.3±10.1 mg/l (SD) vs 31.2±8.0, P<0.01).ß₂m was not significantly higher in patients withbone cysts (37.7±11.4 mg/l vs 37.0±10.0), butmedian duration of dialysis was significantly (P<0.01) longerin patients with bone cysts (90 vs 57 months). ß₂mwas lower in patients maintained on dialysis for less than 1year and whose residual urine volume was greater than 0.1 litreper day. During one single session of dialysis, using cuprophanemembranes, ß₂m increased acutely at 15 min and hadrisen by 32.4% at the end of the dialysis session, more thancould be explained by haemoconcentration. In contrast, ß₂macutely decreased by 38.7% during a single session using polysulphonemembranes and the steady state predialysis values were lowerby 37.1% after two weeks intermittent haemodialysis with polysulphonemembranes. After re-exposure to cuprophane serum ß₂mincreased to the original value. It is concluded that ß₂m concentrations on dialysisare a function of residual urinary volume, sex, and type ofmembrane used. Data are consistent with effective removal ofß₂m by membranes with high cut-off.     

Highly sulphated glycosaminoglycans in articular cartilage and other tissues containing {beta}2 microglobulin dialysis amyloid deposits

BACKGROUND: Highly sulphated glycosaminoglycans (GAGs) are a common constituentof amyloid deposits and an integral component of articular connectivetissues where ß₂-microglobulin (ß₂M) amyloidis most often found. METHODS: Using alcian blue, magnesium chloride, critical electrolyteconcentration, mucin histochemistry, and immunohistochemistry,the GAGs composition of ß₂M amyloid deposits in jointcapsule and cartilage, carpal, and heart tissues of 22 uraemicpatients was determined. RESULTS: Highly sulphated GAGs were found in ß₂M amyloid depositsnot only within cartilage, where such GAGs are normally foundin high concentration, but also in other articular and extra-articularconnective tissues. Keratan sulphate was often specificallylocalized to ß₂M amyloid deposits in articular cartilageand to a lesser extent in periarticular tissues, with one caseshowing colocalization with systemic vascular amyloid deposition.Other sulphated GAGs, chondroitin 4 and 6 sulphate, dermatansulphate, and heparan sulphate were also identified in tissuescontaining ß₂M amyloid deposits, but with the exceptionof heparan sulphate (identified by mucin histochemistry) werenot specifically localized to the deposits themselves. CONCLUSION: These findings suggest that qualitative or quantitative changesin the composition of highly sulphated GAGs may play a rolein localization of ß₂M amyloid deposits in articularand extra-articular tissues.     

Serum {beta}2 Microglobulin and Extracellular Fluid Volume During Haemodialysis

Conflicting results have been published concerning serum ß₂microglobulin (ß₂-M) kinetics during dialysis witha cuprophane membrane which is not permeable for the protein.We have investigated the hypothesis that the apparent increaseof free serum ß₂-M could result from extracellularfluid volume (ECV) contraction. Using inulin, ECV was measuredbefore and 1 h after a dialysis session with a sodium dialysateconcentration of 145 mmol/l. Dialysis was performed either witha cuprophane or a high-flux membrane. Transcellular water shiftand changes in ß₂-M concentration were calculatedfrom total body water changes (ultrafiltration) and ECV. ECV decreased from a predialysis value of 16.6±3.51 (mean±SD)(24.9% bodyweight) to a postdialysis value of 11.9±2.11(19.8% bodyweight). Ultrafiltration was only 3.1±1.01,indicating concomitant water shift from ECV to intracellularfluid space. A significant decrease in corrected ß₂-Mconcentration was found for high-flux membranes. However, postdialysisß₂-M did not change significantly after dialysis withcellulosic membranes. In conclusion, the apparent increase of serum ß₂-Mconcentration measured during dialysis with cellulosic membranesmay be explained by ECV contraction. These results have to betaken into account for any pathogenic mechanism of the ß₂-M-associatedamyloidosis occurring in long-term haemodialysed patients.     

beta(2)-microglobulin kinetics in nocturnal haemodialysis.

BACKGROUND: beta(2)-Microglobulin (beta(2)m) is a major component of dialysis-related amyloidosis. The available therapeutic options do not permit normalization of the serum beta(2)m level. In a cross-over trial, we studied the kinetics of beta(2)m during two different dialytic techniques. METHODS: Ten stable, anuric end-stage renal disease patients were studied during two consecutive weeks of three conventional (CHD) and six nocturnal haemodialysis (NHD) sessions. CHD was performed for 4 h three times weekly using a polysulfone dialyser (F80, surface area of 1.8 m(2)) with a mean blood and dialysate flow rate of 401+/-91.6 and 514+/-10.9 ml/min, respectively. The NHD was done with a smaller dialyser (F40, surface area of 0.7 m(2)) and lower blood (281+/-17 ml/min) and dialysate flow rates (99+/-1.2 ml/min) for 8 h, six nights a week. RESULTS: Weekly removal of urea (51.6+/-24.6 vs 43.1+/-20.5 g) and creatinine (8501+/-5204 vs 6319+/-4134 mg) were comparable with the two modalities of dialysis but the mass of beta(2)m removed was significantly higher with NHD (127+/-48 vs 585+/-309 mg, P<0.001), with a percentage reduction in serum level of 20.5+/-5.8 vs 38.8+/-7. 1% (P<0.0001) and a Kt/V(beta2m) of 0.21+/-0.09 vs 0.56+/-0.17 (P<0. 0006). The mean post-dialysis beta(2)m (20.8+/-6.3 vs 14.0+/-3.8 mg/dl, P=0.02), Tac(beta2m) (26.2+/-5.2 vs 19.8+/-3.8 mg/dl, P=0.02) and pre-dialysis beta(2)m (beta(2)m(pre)) at the end of 1 week of therapy (24.4+/-7.6 vs 19.0+/-3.4 mg/dl, P=0.02) were lower with NHD. Long-term follow-up data were available in 13 and seven patients at the end of 1 and 2 years, respectively. Serum beta(2)m(pre) levels progressively declined from 27.2+/-11.7 mg/dl at initiation of NHD to 13.7+/-4.4 mg/dl by 9 months, and they remained stable thereafter. CONCLUSIONS: NHD provides a much higher clearance of beta(2)m than CHD, leading to a long-term decrease in the pre-dialysis concentration of beta(2)m.     

Biochemical characterization of serum and urinary beta 2 microglobulin in end-stage renal disease patients.

Since the identification of beta 2 microglobulin (beta 2-M) in haemodialysis-associated amyloidosis, the biochemical characterization of the different forms of beta 2-M has been sought by several groups. New beta 2-M isoforms (pI 5.1 and lower) have been identified in amyloid deposits, and it has been suggested that they are of pathogenetic importance. The finding of N-terminal proteolysed beta 2-M in amyloid deposits prompted the hypothesis that proteolysis would render beta 2-M more amyloidogenic. Finally, a 'novel beta 2-M' (pI 5.2) with a single amino acid replacement (Asn by Asp at position 17) has been reported as possibly specific for patients with dialysis associated amyloidosis, and consequently proposed as 'the amyloidogenic' form. We purified beta 2-M from serum of a newly haemodialysed patient and from urine of a transplanted patient in the early recovery period. Both patients were clinically amyloid free. Three pure isoforms were obtained from serum (pI 5.7, 5.3, and 5.1) and only two from urine (5.7 and 5.3). Further purification of each isoform was obtained by HPLC in a C4 column. Sequence analysis showed that all isoforms had an intact N-terminus. Tryptic digestion of the serum isoforms was performed after alkylation with iodoacetic acid and the peptides were isolated by HPLC in a C18 column. The 5.3 and 5.1 isoforms had identical peptide patterns with the appearance of an early peak missing in the 5.7 form. The sequence of this peptide showed a replacement of the D 42 (Asp 42) by N (Asn) after K41 (Lys 41).(ABSTRACT TRUNCATED AT 250 WORDS)     

Vascular involvement and cell damage in experimental AA and clinical beta(2)-microglobulin amyloidosis.

BACKGROUND: Amyloidosis is a highly prevalent disease characterized by the deposition of amyloid fibrils. Although several types of amyloidosis can be identified according to their protein constituents and suggest putative aetiological factors, the causes of amyloidosis remain unknown. Furthermore, the cellular participation and the ultrastructural particularities of amyloidosis have received little attention. The aim of our study was to evaluate the vascular participation in amyloidosis and the cellular consequences of this disease. METHODS: Two forms of amyloidosis were studied: experimental amyloid A (AA) and clinical beta(2)-microglobulin amyloidosis. We studied kidney, liver, and spleen in a mouse model, and examined surgically obtained carpal deposits from dialysis patients. We used light and electron microscopy with immunogold labelling for anti-beta(2)-microglobulin and anti-AA protein antibodies. RESULTS: AA amyloid fibril accumulation was associated with membrane lesions in basal, cytoplasmic organelle (endoplasmic reticulum, mitochondria), and nuclear membranes. Amyloid fibrils from beta(2)-microglobulin amyloidosis were also closely associated with elastic fibres and endothelial basement membrane. We observed proliferation of endothelial cells as well as basement membrane enlargement and disruption. CONCLUSIONS: Vascular abnormalities, including endothelial enlargement, basement membrane modifications, and vascular proliferation were associated with amyloidosis. Amyloid fibrils have a high avidity for elastic fibres and are able to contact and damage the basement membrane, the cell and intracellular organelle membranes, as well as the nuclear envelope, suggesting a toxic effect of amyloid fibrils on cells.     

Failure of a daily haemofiltration programme using a highly permeable membrane to return beta 2-microglobulin concentrations to normal in haemodialysis patients.

In an attempt to return to normal serum beta 2-microglobulin levels in a group of seven ESRD patients, a programme of daily HF with highly permeable AN69 membranes was undertaken. Pre-HF beta 2-M serum levels stabilized after 4 days at 20 mg/l, only 40% lower than the initial concentration. A total of 985 +/- 20 mg beta 2-M was removed over the week. The beta 2-M release rate averaged 97 micrograms/min with a broad range of values (63-128 micrograms/min). beta 2-M release peaked at 602 micrograms/min 1 h after the end of the HF session before returning to baseline by 12 h post-HF. We conclude that a return to normal blood beta 2-M concentrations in ESRD patients seems quite unrealistic despite a highly intensive extracorporeal therapy. Therefore other therapeutic alternatives have to be designed to prevent or cure beta 2-M amyloidosis.     

Serum {alpha}2-macroglobulin in haemodialysis patients: baseline and kinetic studies

The pathogenesis of dialysis related amyloidosis remains unresolveddespite the identification of ß₂-microglobulin (ß₂M)as the major protein constituent, as well as other proteinsbeing present in the deposits. Among the latter we have assessedthe serum concentrations of ₂-macroglobulin (₂M) both in thebaseline stage and during the haemodialysis (HD) procedure.We have also assessed the influence of the membrane on ₂M kinetics. Fifteen HD patients with histologically proven dialysis-relatedamyloidosis (DRA group) and 15 HD patients clinically and radiologicallyconsidered dialysis-related amyloidosis free (control group)were included in the baseline study. Blood was sampled the daybefore the second dialysis of the week and ₂M, ß₂Mand ₁, antitrypsin were determined along with the routine biologicalanalysis of these patients. Serum ₂M was greater in dialysis-relatedamyloidosis than in control patients (t = 2.35; P<0.026).Serum ß₂M was similar in both groups. The serum ₂Mand ß₂M correlated in patients with dialysis-relatedamyloidosis (r = 0.64; P<0.01), while no correlation wasfound in controls (r = 0.17; NS). Stepwise analysis taking thepresence of dialysis-related amyloidosis as the dependent variableretained the serum ₂M concentration as the first variable inthe model (F = 4.4; partial r = 0.38; P<0.046). The sameproteins were determined in another group of seven patients,before and hourly during HD as well as 2 and 8 h after the endof HD during nine consecutive dialyses (3 cycles of 3 HD eachusing AN69 and cuprophane membranes in a crossover design).Serum ₂M significantly increased from hour 3 and continued toincrease 2 hours post-HD (+11% and +9% with AN69 and cuprophanerespectively; P<0.001). Total proteins peaked at hour 4 (+4% and +3% P<0.01) and decreased after HD. Serum ß₂Msignificantly decreased with AN69 HD ( – 29% P<0.001)and remained unchanged during cuprophane HD. In conclusion, significant increases in serum ₂M are observedimmediately after and during the early post-dialysis periods,regardless of the membrane used. Further, serum ₂M correlateswith ß₂M only in patients with dialysis-related amyloidosis,and this variable was retained in the multivariate regressionanalysis to predict dialysis-related amyloidosis. Although thebaseline results require confirmation with larger studies, wepostulate that the present results are of relevance for dialysis-relatedamyloidosis pathogenesis since ₂M, previously identified indialysis related amyloid deposits, is closely related to acute-phasereactant proteins, and interacts with the main infiltratingcells of the deposits (macrophages). ₂M modifications couldrepresent a new manifestation of the inflammatory response tothe haemodialysis procedure.     

Regulation of beta2-microglobulin expression in different human cell lines by proinflammatory cytokines.

BACKGROUND: Proinflammatory monocytic cytokines such as interleukin-1 (IL-1), tumour necrosis factor-alpha (TNF-alpha) and IL-6 have been incriminated in the pathogenesis of elevated beta2-microglobulin (beta2M) serum concentrations in patients undergoing haemodialysis with so-called bioincompatible dialyser membranes. However, neither the source of the elevated serum beta2M nor the precise role of monocytic cytokines in the expression of the beta2M gene have been elucidated conclusively. The aim of the current study was to evaluate whether monocytic cytokines, and in particular IL-6, are regulators of beta2M gene expression in human hepatoma cells, T-lymphocytes and monocytes. METHODS: HepG2 and HuH7 human hepatoma cells, Jurkat T-cells, monocytic MonoMac6 cells, primary human monocytes and synoviocytes were stimulated with IL-1beta, IL-6, interferon-alpha (IFN-alpha), IFN-gamma or conditioned media from lipopolysaccharide (LPS)-treated monocytes. Expression of beta2M mRNA was analysed by Northern blotting, beta2M protein synthesis was determined by metabolic labelling and immunoprecipitation, and beta2M secretion was measured by an enzyme-linked immunosorbent assay (ELISA). RESULTS: In all cell types tested, IFN-gamma and, to a lesser extent, IFN-alpha stimulated gene expression of beta2M resulting in an increased synthesis and secretion of beta2M protein. Neither IL-1beta and IL-6 nor supernatants from LPS-treated monocytes were capable of inducing beta2M gene expression, with the exception of a small increase in HuH7 hepatoma cells upon IL-1beta treatment. CONCLUSIONS: The present study provides evidence that interferons are important regulators of beta2M expression. It also shows that proinflammatory monocytic cytokines do not modulate directly the expression of beta2M in cells of hepatic, monocytic and T-lymphocytic origin. Whether they influence beta2M synthesis and secretion indirectly by modulating interferon synthesis needs to be elucidated.     

Effect of high-flux dialysis on the anaemia of haemodialysis patients.

BACKGROUND: Anaemia is one of the major clinical characteristics of patients with chronic renal failure, and has a considerable effect on morbidity and mortality. Adequate dialysis is of paramount importance in correcting anaemia by removing small and medium-sized molecules, which may inhibit erythropoiesis. However, high-molecular-weight inhibitors cleared only by means of highly porous membranes have also been found in uraemic serum and it has been claimed from uncontrolled studies that high-flux dialysis could improve anaemia in haemodialysis patients. METHODS: We therefore planned this multicentre randomized controlled trial with the aim of testing whether the use of a large-pore biocompatible membrane for a fixed 12-week follow-up improves anaemia in haemodialysis patients in comparison with the use of a conventional cellulose membrane. Eighty-four (5.3%) of a total of 1576 adult haemodialysed patients attending 13 Dialysis Units fulfilled the entry criteria and were randomly assigned to the experimental treatment (42 patients) or conventional treatment (42 patients). RESULTS: Haemoglobin levels increased non-significantly from 9.5+/-0.8 to 9.8+/-1.3 g/dl (dP=0. 069) in the population as a whole, with no significant difference between the two groups (P:=0.485). Erythropoietin therapy was given to 32/39 patients (82%) in the conventional group, and 26/35 (74%) in the experimental group (P:=0.783) with subcutaneous administration to 26/32 patients in conventional and to 23/26 patients in experimental group, P:=0.495. Dialysis dose (Kt/V) remained constant in both groups (from 1.30+/-0.17 to 1.33+/-0.20 in the conventional group and from 1.28+/-0.26 to 1.26+/-0.21 in the experimental group, P:=0.242). Median pre- and post-dialysis beta(2)-microglobulin levels remained constant in the conventional group (31.9 and 34.1 mg/dl at baseline) and decreased in the experimental group (pre-dialysis values from 31.1 to 24.7 mg/dl, P:=0.004 and post-dialysis values from 24.8 to 20.8 mg/dl, P:=0.002). Median erythropoietin doses were not different at baseline (70 IU/kg/week in conventional treatment and 90 IU/kg/week in experimental treatment, P:=0.628) and remained constant during follow-up (from 70 to 69 IU/kg/week in the conventional group and from 90 to 91 IU/kg/week in the experimental group, P:=0.410). Median erythropoietin plasma levels were in the normal range and remained constant (from 12.1 to 12.9 mU/ml in the conventional group and from 13.2 to 14.0 mU/ml in the experimental group, P:=0.550). CONCLUSIONS: This study showed no difference in haemoglobin level increase between patients treated for 3 months with a high-flux biocompatible membrane in comparison with those treated with a standard membrane. When patients are highly selected, adequately dialysed, and have no iron or vitamin depletion, the effect of a high-flux membrane is much less than might be expected from the results of uncontrolled studies.     

Elimination of beta 2-microglobulin by a new polyacrylonitrile membrane dialyser: mechanism and physiokinetics

The performance and mechanism of beta 2-microglobulin (beta 2 M) removal by a new polyacrylonitrile membrane dialyser (CX2), and the physiokinetics of beta 2 M during treatment were studied. In vitro experiments showed that mean pore size of the CX2 membrane was 120 A, and the molecular cut-off point was less than 66,000 daltons. The diffusive capacity of the PAN 12CX2 dialyser (1.2 m2) for beta 2 M was calculated to be 27.3 ml/min at a blood flow of 200 ml/min, and it was considered that, compared to the elimination by local filtration induced by back-filtration and adsorption, diffusion was the major eliminating mechanism for beta 2 M. Although the elimination of beta 2 M increased linearly by augumentation of the ultrafiltration volume, diffusion was a major contributing factor for beta 2 M removal even in haemodiafiltration. Serum beta 2 M decreased to 51% and 44% of initial values after correction of haemoconcentration by a clinical haemodialysis or haemodiafiltration even under relatively low blood and filtrate flow conditions, and sieving coefficient and clearance of CX2 for beta 2 M compared well with in vitro results. The one-pool model simulation demonstrated that from 50 to 60 mg of beta 2 M was transferred from the intra- to the extracellular space during treatment. These results indicate that CX2 effectively eliminates beta 2 M mainly by diffusion, and that beta 2 M transfer to the plasma space during haemodialysis and haemodiafiltration may be accelerated.     

Comparison of the new polyethersulfone high-flux membrane DIAPES HF800 with conventional high-flux membranes during on-line haemodiafiltration.

BACKGROUND: Current modalities of renal replacement therapy allow only a limited removal of larger, possibly toxic molecules, which accumulate in uraemia. Recently, a haemodiafilter has been made available with the new, high-flux, polyethersulfone-based membrane DIAPES HF800. We performed a study to compare DIAPES HF800 with two conventional high-flux membranes in on-line haemodiafiltration (HDF), with respect to the removal properties for the two marker proteins, beta(2)-microglobulin (beta(2)m, 11.8 kDa) and albumin (66.5 kDa). METHODS: In a prospective, controlled study 10 stable end-stage renal disease patients were randomly allocated to 30 sessions of post-dilutional on-line HDF with three types of steam-sterilized membranes: DIAPES HF800, polysulfone and polyamide. Blood flow rate was 250 ml/min and treatment time was 240 min. Pre-treatment beta(2)m and albumin plasma concentrations did not differ between the three groups. The concentration of the two proteins was determined before and after treatment in plasma as well as in the continuously collected haemodiafiltrate. RESULTS: Tolerance of all treatments was very good, without any side-effects for all filters. The mean plasma reduction rate of beta(2)m was 77 +/- 1% for DIAPES HF800 and polysulfone whereas it was 71 +/- 1% for polyamide (P < 0.05). The mean beta(2)m amount removed and found in the haemodiafiltrate per session was 230 +/- 14 mg for DIAPES HF800, 186 +/- 13 mg for polysulfone and 147 +/- 13 mg for polyamide (P < 0.05 between each pair of membranes). The same ranking was obtained for albumin removed and found in haemodiafiltrate per session for the three membranes: 5.7 +/- 0.4, 3.5 +/- 0.4 and 1.0 +/- 0.4 g, respectively. Although DIAPES HF800 showed the highest value for albumin in haemodiafiltrate the mean post-treatment plasma albumin was higher after the treatment with DIAPES HF800 compared with the other membranes (P < 0.05). CONCLUSIONS: On-line HDF has shown to achieve plasma reduction rates for beta(2)m of up to 77% for the DIAPES HF800 membrane and for polysulfone. The amounts of beta(2)m and albumin in haemodiafiltrate were much higher for DIAPES HF800 than for the other two membranes indicating a greater permeability for molecules up to a molecular weight of 66.5 kDa. This could, at least theoretically, offer the advantage also to remove uraemic toxins in the molecular weight range of albumin or of albumin-bound toxins. The future must show whether this will counterbalance the loss of albumin.     

Intrarenal localization of interleukin-1{beta} mRNA in crescentic glomerulonephritis

II-1ß is a potent proinflammatory peptide, and inducesexpression of other cytokines which are involved in the immuneresponse. Kidney biopsies from nine patients with crescenticGN were studied by in-situ hybridization to determine the siteof expression of II-1ß mRNA. Biopsies from nine patientswith non-proliferative renal disease were studied as negativecontrols, and tonsillar tissue was studied as a positive control.An II-1ß cDNA probe was ³²P-labelled by random primersand hybridized to paraffin-embedded tissue sections after de-waxing.II-1ß mRNA was expressed in tonsil, but not in negativecontrols. Positive mRNA expression was seen in four of the ninecrescentic biopsies. This was observed in interstitial cellswith morphological characteristics of macrophages adjacent totubular cells, in cells within the glomerular tuft, and in tubularepithelial cells. II-1ß mRNA is expressed in renaltissue in crescentic GN. Tubular and interstitial expressionof II-1ß mRNA appears of equal prominence to glomerularexpression. Intrarenal cytokine synthesis may be involved inthe pathogenesis of crescentic glomerulonephritis.     

Use of ultrafiltered dialysate is associated with improvements in haemodialysis-associated morbidity in patients treated with reused dialysers.

BACKGROUND: Morbidity in haemodialysis patients is associated with chronic inflammation. Microbiological contaminants derived from dialysate are thought to be one inflammatory stimulus and previous studies found that highly purified dialysate reduces inflammation and morbidity. These studies were performed in the absence of practices, such as dialyser reuse, that are potentially inflammatory. We tested the hypothesis that highly purified dialysate reduces inflammation and morbidity even in the presence of other inflammatory stimuli. METHODS: This was a prospective observational study. After obtaining baseline data on inflammation, oxidant stress, nutrition and anaemia correction with standard dialysate, 105 patients were switched to dialysate that was ultrafiltered at the point of use and follow-up data were collected at 3-month intervals for 12 months. RESULTS: Introduction of ultrafiltered dialysate did not significantly reduce inflammation, as assessed by plasma concentrations of C-reactive protein and interleukin-6 or oxidant stress, as assessed by plasma concentrations of protein carbonyls and protein-free sulphydryls. Neither did it improve anaemia correction, as assessed by plasma haemoglobin and erythropoietin dose. However, introduction of ultrafiltered dialysate was associated with a significant reduction in plasma beta(2)-microglobulin concentration and a significant improvement in nutritional status, assessed by plasma albumin concentration and creatinine generation rate as a marker of muscle mass. CONCLUSION: Use of ultrafiltered dialysate was associated with improvements in some measures of morbidity, such as plasma beta(2)-microglubulin and nutrition. These changes occurred in spite of the presence of inflammatory stimuli, such as dialyser reuse, and with no measurable reduction in inflammation and oxidant stress.