title: Restoration of adenosine deaminase-deficient human thymocyte development in vitro by inhibition of deoxynucleoside kinases.
abstract: Mutations in the gene encoding adenosine deaminase (ADA), a purine salvage enzyme, lead to immunodeficiency in humans. Although ADA deficiency has been analyzed in cell culture and murine models, information is lacking concerning its impact on the development of human thymocytes. We have used chimeric human/mouse fetal thymic organ culture to study ADA-deficient human thymocyte development in an "in vivo-like" environment where toxic metabolites accumulate in situ. Inhibition of ADA during human thymocyte development resulted in a severe reduction in cellular expansion as well as impaired differentiation, largely affecting mature thymocyte populations. Thymocyte differentiation was not blocked at a discrete stage; rather, the paucity of mature thymocytes was due to the induction of apoptosis as evidenced by activation of caspases and was accompanied by the accumulation of intracellular dATP. Inhibition of adenosine kinase and deoxycytidine kinase prevented the accumulation of dATP and restored thymocyte differentiation and proliferation. Our work reveals that multiple deoxynucleoside kinases are involved in the phosphorylation of deoxyadenosine when ADA is absent, and suggests an alternate therapeutic strategy for treatment of ADA-deficient patients.
authors.affiliation: Immunobiology and Cancer Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA.
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Joachims
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Marble
authors.forename: Aletha B
authors.initials: AB
authors.lastname: Laurent
authors.forename: Peter
authors.initials: P
authors.lastname: Pastuszko
authors.forename: Marco
authors.initials: M
authors.lastname: Paliotta
authors.forename: Michael R
authors.initials: MR
authors.lastname: Blackburn
authors.forename: Linda F
authors.initials: LF
authors.lastname: Thompson
mesh_terms: D000243:Adenosine Deaminase / Q000172:deficiency* / Q000276:immunology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000276:immunology; D018929:Cell Culture Techniques; D002454:Cell Differentiation / Q000187:drug effects* / Q000276:immunology; D018920:Coculture Techniques; D003838:Deoxyadenine Nucleotides / Q000276:immunology / Q000378:metabolism; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D005333:Fetus / Q000201:enzymology / Q000276:immunology / Q000473:pathology; D006801:Humans; D051379:Mice; D017853:Phosphotransferases (Alcohol Group Acceptor); D016511:Severe Combined Immunodeficiency / Q000188:drug therapy / Q000201:enzymology / Q000276:immunology*; D013950:Thymus Gland / Q000201:enzymology / Q000276:immunology* / Q000473:pathology
chemical_list: D003838:Deoxyadenine Nucleotides; D004791:Enzyme Inhibitors; D017853:Phosphotransferases (Alcohol Group Acceptor); C020018:deoxyribonucleoside kinases; D000243:Adenosine Deaminase; C026600:2'-deoxyadenosine triphosphate