Biocompatibility of haemodialysis membranes: haemodialysis-related leukotriene B4 and C4 generation. France

High-flux versus low-flux membranes for end-stage kidney disease

BACKGROUND

Clinical practice guidelines regarding the use of high-flux haemodialysis membranes vary widely.

OBJECTIVES

We aimed to analyse the current evidence reported for the benefits and harms of high-flux and low-flux haemodialysis.

SEARCH METHODS

We searched Cochrane Renal Group's specialised register (July 2012), the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (1948 to March 2011), and EMBASE (1947 to March 2011) without language restriction.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that compared high-flux haemodialysis with low-flux haemodialysis in people with end-stage kidney disease (ESKD) who required long-term haemodialysis.

DATA COLLECTION AND ANALYSIS

Data were extracted independently by two authors for study characteristics (participants and interventions), risks of bias, and outcomes (all-cause mortality and cause-specific mortality, hospitalisation, health-related quality of life, carpal tunnel syndrome, dialysis-related arthropathy, kidney function, and symptoms) among people on haemodialysis. Treatment effects were expressed as a risk ratio (RR) or mean difference (MD), with 95% confidence intervals (CI) using the random-effects model.

MAIN RESULTS

We included 33 studies that involved 3820 participants with ESKD. High-flux membranes reduced cardiovascular mortality (5 studies, 2612 participants: RR 0.83, 95% CI 0.70 to 0.99) but not all-cause mortality (10 studies, 2915 participants: RR 0.95, 95% CI 0.87 to 1.04) or infection-related mortality (3 studies, 2547 participants: RR 0.91, 95% CI 0.71 to 1.14). In absolute terms, high-flux membranes may prevent three cardiovascular deaths in 100 people treated with haemodialysis for two years. While high-flux membranes reduced predialysis beta-2 microglobulin levels (MD -12.17 mg/L, 95% CI -15.83 to -8.51 mg/L), insufficient data were available to reliably estimate the effects of membrane flux on hospitalisation, carpal tunnel syndrome, or amyloid-related arthropathy. Evidence for effects of high-flux membranes was limited by selective reporting in a few studies. Insufficient numbers of studies limited our ability to conduct subgroup analyses for membrane type, biocompatibility, or reuse. In general, the risk of bias was either high or unclear in the majority of studies.

AUTHORS' CONCLUSIONS

High-flux haemodialysis may reduce cardiovascular mortality in people requiring haemodialysis by about 15%. A large well-designed RCT is now required to confirm this finding.

Emerging roles for eicosanoids in renal diseases

PURPOSE OF REVIEW

Eicosanoids are products of arachidonic acid metabolism which have important roles in renal homeostasis and disease. In recent years the development of genetically modified animals and new drugs targeting eicosanoids producing enzymes and receptors has unveiled new roles for eicosanoids in kidney function. This review provides an overview of eicosanoid biosynthesis and receptors and discusses recent findings on their role in acute and chronic renal diseases and in renal transplantation.

RECENT FINDINGS

Products of the cyclooxygenases, 5-lipoxygenase, and cytochrome P450 pathways of arachidonic acid metabolism act through distinct receptors presented at different segment of the nephron. Apart from its role in renal physiology and hemodynamic, eicosanoids actively participate in the pathogenesis of acute and chronic renal diseases and have immunoregulatory role in kidney transplantation.

SUMMARY

The new discoveries on the role of eicosanoids in kidney functions and the development of drugs targeting eicosanoids synthesis or action should help to envisage novel therapeutic approaches for patients suffering from renal diseases.

Red blood cell fatty acid profile of chronic renal failure patients receiving maintenance haemodialysis treatment

The fatty acid profile of chronic renal failure (CRF) patients on maintenance haemodialysis treatment (MHT) is abnormal and results point towards an essential fatty acid (EFA) deficiency. However, controversies still exist as to which of the essential fatty acids (EFAs) or EFA-products are decreased. In this study, the results of a comprehensive analysis of the fatty acids, performed on the red blood cells of 14 CRF patients on MHT, are presented. The red blood cell membrane fatty acids determined in this study include a range of saturated fatty acids (SFAs), mono-unsaturated fatty acids (MUFAs) and poly-unsaturated fatty acids (PUFAs). Results confirmed the suggested presence of an essential fatty acid deficiency in CRF patients on MHT. It showed the total content of the n-6 fatty acids (31.66 +/- 3.21 vs 34.67 +/- 2.05), as well as the total content of the PUFAs (37.22 +/- 4.08 vs 40.93 +/- 2.35), to be significantly decreased. The total MUFA content was, in contrast, significantly increased (16.87 +/- 0.91 vs 15.49 +/- 1.18). The EFA deficiency profile seen in this study points towards that of a chronic inflammatory condition. This is borne out by the fact that all three precursors of the eicosanoids--the mediators of various inflammatory and immune responses--were reduced in the presence of an increase in MUFAs as well as SFAs. The possibility of the fatty acid profile of CRF patients on MHT being that of a chronic inflammatory condition is supported by the fact that continuous complement-dependent and complement-independent immune activation, due to bio-incompatibility between blood cells and the dialysis membranes, is known to occur during the dialysis process.

Continuous interleukin-6 application in vivo via macroencapsulation of interleukin-6-expressing COS-7 cells induces massive gliosis

The inflammatory cytokine interleukin-6 (IL-6) was found in senile plaques of Alzheimer's patients and might be involved in the pathology of Parkinson's disease and multiple sclerosis. Interestingly, an astocytosis is also found in these neurodegenerative disorders. To evaluate the direct effects of IL-6 in vivo on glial cells, we created a new in vivo model. IL-6 and mock-transfected (control group) COS-7 cells were encapsulated in a poly-acryl-nitril membrane for implantation into the rat striatum. Afterward, the host immune reaction to the membrane without encapsulated cells and the biological action of IL-6-producing capsules was evaluated. Animals with an implanted membrane without cells showed a moderate astrocytosis 5 days after the operation. Furthermore, microglia and T-cells could be detected and after 30 days the astrocytosis decreased to a small layer around the membrane. In comparison to the control group, which received a sham operation, our results demonstrate that the response of glial cells is caused by the mechanical damage of the surgical procedure itself rather than due to the introduced membrane material. In contrast, we found a massive proliferation and activation of astrocytes and microglia after 10 days by IL-6-secreting capsules, indicating that IL-6 is involved in the induction of gliosis. Control animals that received encapsulated mock-transfected COS-7 cells showed only a weak response. These data point to an involvement of IL-6 in the proliferation and activation of glial cells as seen in neurodegenerative disorders.