Haemodialysis induces mitochondrial dysfunction and apoptosis.
BACKGROUND
Mitochondria play a crucial role in the regulation of the endogenous pathways of apoptosis activated by oxidant stress. Nuclear factor-kappaB (NF-kappaB) is a central integration site for pro-inflammatory signals and oxidative stress.


METHODS
Peripheral blood mononuclear cells (PBMC) were isolated from eight end-stage renal disease (ESRD) patients before haemodialysis (Pre-HD) and during the last 10 min of HD (End-HD). A new polysulfone membrane (F70, Fresenius) was used for dialysis. Intracellular generation of reactive oxygen species (ROS), mitochondrial redox potential (Deltapsim) and PBMC apoptosis were determined by flow-cytometry.


RESULTS
Plasma levels of interleukin-6 (IL-6) (24.9+/-7.0 vs. 17.4+/-5.5 pg dL(-1), P<0.05), IL-6 soluble receptor (52.2+/-4.9 vs. 37.6+/-3.2 ng dL(-1), P<0.02) and IL-6 gp130 (405.7+/-41.0 vs. 235.1+/-38.4 ng dL(-1), P<0.02) were higher end-HD compared to pre-HD. IL-6 secretion by the isolated PBMC (24.0+/-2.3 vs. 19.3+/-3.5 pg dL(-1), P<0.02) increased end-HD. Percentage of lymphocytes exhibiting collapse of mitochondrial membrane potential (43.4+/-4.6% vs. 32.6+/-2.9%, P<0.01), apoptosis (33.4+/-7.1% vs. 23.7+/-7.7%, P<0.01), and generation of superoxide (20.7+/-5.2% vs. 12.5+/-2.9%, P<0.02) and hydrogen peroxide (51.1+/-7.8% vs.38.2+/-5.9%, P<0.04) were higher at end-HD than pre-HD. NF-kappaB activation (3144.1+/-208.1 vs. 2033.4+/-454.6 pg well(-1), P<0.02), expression of B-cell lymphoma protein-2 (6494.6+/-1461 vs. 3501.5+/-796.5 ng mL(-1), P<0.03) and heat shock protein-70 (9.81+/-1.47 vs. 6.38+/-1.0 ng mL(-1), P<0.05) increased during HD.


CONCLUSIONS
Intra-dialytic activation of cytokines, together with impaired mitochondrial function, promotes generation of ROS culminating in augmented PBMC apoptosis. There is concomitant activation of pathways aimed at attenuation of cell stress and apoptosis during HD.
University of New Mexico Health Sciences Center, Division of Nephrology and Epidemiology, Department of Medicine, Albuquerque, New Mexico 87131-5271, USA. draj@salud.unm.edu
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Raj
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Boivin
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Dominic
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Boyd
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Roy
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Rihani
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Tzamaloukas
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Shah
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Moseley
D017209:Apoptosis; D005434:Flow Cytometry; D006360:Heat-Shock Proteins / Q000096:biosynthesis; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D015850:Interleukin-6 / Q000096:biosynthesis; D007668:Kidney / Q000378:metabolism*; D007676:Kidney Failure, Chronic / Q000378:metabolism / Q000628:therapy; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D008875:Middle Aged; D008928:Mitochondria / Q000378:metabolism*; D016328:NF-kappa B / Q000096:biosynthesis; D018384:Oxidative Stress; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D017382:Reactive Oxygen Species / Q000378:metabolism*; D006435:Renal Dialysis / Q000009:adverse effects; D013481:Superoxides / Q000378:metabolism
D006360:Heat-Shock Proteins; D015850:Interleukin-6; D016328:NF-kappa B; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D013481:Superoxides; D006861:Hydrogen Peroxide