title: Mitochondrial toxicity of nucleoside analogues in primary human lymphocytes.
abstract: OBJECTIVE
  To evaluate if nucleoside analogue reverse transcriptase inhibitors (NRTIs) and polymerase-gamma inhibitors deplete mitochondrial DNA (mtDNA) in cultured primary lymphocytes and if such depletion might be associated with functional defects.
  
  
  METHODS
  Primary peripheral blood CD4 and CD8 lymphocytes were purified from six healthy humans (three male and three female), stimulated mitotically (CD3/CD28) and cultured for 10 days in the presence or absence of NRTIs. Lymphocyte proliferation, mtDNA content, the expression of mtDNA-encoded cytochrome c-oxidase II (COXII) and lactate production were assessed.
  
  
  RESULTS
  In CD4 lymphocytes, 10-day exposure to zalcitabine (1.77 microM), didanosine (118 microM) and stavudine (361 microM) induced a time-dependent decline of mtDNA. Compared with controls, residual mtDNA levels were 25%, 21% and 40%, respectively. COXII was reduced to 55%, 35% and 70% of control values. Lactic acid production was increased (by 214%, 294% and 175%, respectively). At day 10, lymphocyte counts were reduced (to 60%, 51%, and 41%, respectively). Zidovudine (71 microM) also reduced lymphocyte counts to 34% and increased lactic acid production by 170%, but did not induce mtDNA and COXII depletion. All these changes were highly significant. Lower NRTI concentrations (0.177 microM of zalcitabine, 11.8 microM of didanosine, 3.6 microM of stavudine and 7.1 microM of zidovudine) had effects at the border of significance. Similar observations were made in CD8 lymphocytes.
  
  
  CONCLUSIONS
  In human lymphocytes, zalcitabine, didanosine and stavudine induce dose- and time-dependent mtDNA depletion, which is associated with decreased cell proliferation and increased lactate production. Zidovudine impairs lymphocyte division without inducing mtDNA depletion.
authors.affiliation: Department of Rheumatology and Clinical Immunology, Medizinische Universitätsklinik, Freiburg, Germany.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Setzer
authors.forename: Michael
authors.initials: M
authors.lastname: Schlesier
authors.forename: Anna K
authors.initials: AK
authors.lastname: Thomas
authors.forename: Ulrich A
authors.initials: UA
authors.lastname: Walker
mesh_terms: D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D002478:Cells, Cultured; D004272:DNA, Mitochondrial / Q000187:drug effects* / Q000378:metabolism; D016049:Didanosine / Q000633:toxicity*; D005260:Female; D006801:Humans; D019344:Lactic Acid / Q000096:biosynthesis / Q000378:metabolism; D008213:Lymphocyte Activation; D008297:Male; D028361:Mitochondrial Diseases / Q000139:chemically induced; D018894:Reverse Transcriptase Inhibitors / Q000633:toxicity*; D018119:Stavudine / Q000633:toxicity*; D016047:Zalcitabine / Q000633:toxicity*
chemical_list: D004272:DNA, Mitochondrial; D018894:Reverse Transcriptase Inhibitors; D019344:Lactic Acid; D016047:Zalcitabine; D018119:Stavudine; D016049:Didanosine