title: Mononuclear leukocyte apoptosis in haemodialysis patients: the role of cell thiols and vitamin E.
abstract: BACKGROUND
  An increased apoptotic rate of peripheral blood mononuclear leukocytes (PBMLs) in haemodialysis (HD) patients has been reported in several studies, but its underlying mechanisms remain poorly understood. Oxidant stress is a well known cause of cell damage, and several lines of evidence suggest that it might influence the induction and signalling steps of mononuclear cell apoptosis through different mechanisms so as to provoke disturbances of the intracellular pool of thiols (SHi). In this study, we investigated the in vitro apoptotic rate and SHi of PBMLs in end-stage renal disease (ESRD) patients on HD or peritoneal dialysis (PD).
  
  
  METHODS
  Apoptosis and SHi were evaluated in vitro in PBMLs obtained from 40 ESRD patients (HD, n = 30 and PD, n = 10) and 10 healthy controls. A subgroup of HD patients was also studied before and after 1 month of treatment with a vitamin E-coated dialyser (CL-E). Cell thiols and viability were also assessed in the monocyte-like cell line U937 and PBMLs after incubation in the presence of uraemic plasma with or without supplementation of the antioxidants vitamin E (70 micro M) or N-acetyl-cysteine (NAC) (0.5 mM).
  
  
  RESULTS
  After 24 h in culture, the PBMLs of HD patients, but not those of CAPD patients, showed an apoptotic rate twice that of healthy controls and a 40% decrease of SHi levels (P < 0.01 in both). A negative correlation between the apoptotic rate and SHi was observed in both patients and controls (r = 0.648, P < 0.001). Plasma and ultrafiltrate samples from HD patients contained solutes (mainly in the low-middle molecular weight range) able to trigger apoptosis and oxidative stress in U937 cells. The treatment of HD patients with CL-E, as well as the in vitro supplementation of U937 cells with vitamin E or NAC during the exposure to uraemic plasma, decreased the rate of apoptosis and partially restored SHi.
  
  
  CONCLUSIONS
  This study showed an association between an increased apoptotic rate and decreased SHi in PBML of HD patients, but not of CAPD patients. These changes are partially due to different pro-apoptogens that accumulate in the plasma and are at least partially prevented by exogenous antioxidants able to restore SHi, such as vitamin E or thiol suppliers.
authors.affiliation: Department of Internal Medicine, Section of Applied and Clinical Biochemistry, University of Perugia, Perugia, Italy. f.galli@unipg.it
authors.forename: Francesco
authors.initials: F
authors.lastname: Galli
authors.forename: Lina
authors.initials: L
authors.lastname: Ghibelli
authors.forename: Umberto
authors.initials: U
authors.lastname: Buoncristiani
authors.forename: Valeria
authors.initials: V
authors.lastname: Bordoni
authors.forename: Vincenzo
authors.initials: V
authors.lastname: D'Intini
authors.forename: Serena
authors.initials: S
authors.lastname: Benedetti
authors.forename: Franco
authors.initials: F
authors.lastname: Canestrari
authors.forename: Claudio
authors.initials: C
authors.lastname: Ronco
authors.forename: Ardesio
authors.initials: A
authors.lastname: Floridi
mesh_terms: D000368:Aged; D017209:Apoptosis / Q000502:physiology; D001205:Ascorbic Acid / Q000502:physiology*; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000503:physiopathology* / Q000628:therapy; D007963:Leukocytes, Mononuclear / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D018384:Oxidative Stress / Q000502:physiology; D010530:Peritoneal Dialysis; D006435:Renal Dialysis; D013438:Sulfhydryl Compounds / Q000502:physiology*; D014462:Ultrafiltration
chemical_list: D013438:Sulfhydryl Compounds; D001205:Ascorbic Acid