title: 4-(N,N-dipropylamino)benzaldehyde inhibits the oxidation of all-trans retinal to all-trans retinoic acid by ALDH1A1, but not the differentiation of HL-60 promyelocytic leukemia cells exposed to all-trans retinal.
abstract: BACKGROUND
  The signal transduction pathways mediated by retinoic acid play a critical role in the regulation of cell growth and differentiation during embryogenesis and hematopoiesis as well as in a variety of tumor cell lines in culture. Following the reports that two members of the superfamily of aldehyde dehydrogenase (ALDH) enzymes, ALDH1A1 and ALDH1A2, were capable of catalyzing the oxidation of all-trans retinal to all-trans retinoic acid with submicromolar Km values, we initiated an investigation of the ability of 4-(N,N-dipropylamino)benzaldehyde (DPAB) to inhibit the oxidation of retinal by purified mouse and human ALDH1A1.
  
  
  RESULTS
  Our results show that DPAB potently inhibits retinal oxidation, with IC50 values of 0.11 and 0.13 microM for purified mouse and human ALDH1A1, respectively. Since the HL-60 human myeloid leukemic cell line has been used extensively to study the retinoic acid induced differentiation of HL-60 cells to granulocytes, and ALDH1A1 activity had previously been reported in HL-60 cells, we investigated the ability of DPAB to block differentiation of HL-60 promyelocytic leukemia cells exposed to retinal in culture. In HL-60 cells coincubated with 1 microM retinal and 50 microM DPAB for 144 hours, cell differentiation was inhibited only 30%. Furthermore, the NAD-dependent oxidation of propanal or retinal was less than 0.05 nmoles NADH formed/min-10(7) cells in spectrophotometric assays using HL-60 cell extracts.
  
  
  CONCLUSIONS
  Although ALDH1A1 may be the major catalytic activity for retinal oxidation in some retinoid-dependent mouse and Xenopus embryonic tissues and in adult human and mouse hematopoietic stem cells, another catalytic activity appears to synthesize the retinoic acid ligand necessary to stimulate the differentiation of HL-60 cells to end stage granulocytes.
authors.affiliation: Department of Chemistry, Whitman College, Walla Walla, WA 99362, USA. russo@whitman.edu
authors.forename: James
authors.initials: J
authors.lastname: Russo
authors.forename: Annette
authors.initials: A
authors.lastname: Barnes
authors.forename: Katie
authors.initials: K
authors.lastname: Berger
authors.forename: Jay
authors.initials: J
authors.lastname: Desgrosellier
authors.forename: Jennifer
authors.initials: J
authors.lastname: Henderson
authors.forename: Ana
authors.initials: A
authors.lastname: Kanters
authors.forename: Lubo
authors.initials: L
authors.lastname: Merkov
mesh_terms: D000444:Aldehyde Dehydrogenase / Q000378:metabolism; D000080924:Aldehyde Dehydrogenase 1 Family; D000818:Animals; D001547:Benzaldehydes / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects*; D018922:HL-60 Cells; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D051379:Mice; D010084:Oxidation-Reduction / Q000187:drug effects; D050697:Retinal Dehydrogenase; D012172:Retinaldehyde / Q000378:metabolism*; D014212:Tretinoin / Q000378:metabolism*
chemical_list: D001547:Benzaldehydes; D007527:Isoenzymes; D014212:Tretinoin; C095172:4-(N,N-dipropylamino)benzaldehyde; D000080924:Aldehyde Dehydrogenase 1 Family; D000444:Aldehyde Dehydrogenase; C510223:ALDH1A1 protein, human; C515028:ALDH1A1 protein, mouse; D050697:Retinal Dehydrogenase; D012172:Retinaldehyde