title: Lipophilicity of analogs of pyridoxal isonicotinoyl hydrazone (PIH) determines the efflux of iron complexes and toxicity in K562 cells.
abstract: Iron overload secondary to beta-thalassemia and other iron-loading anemias is the most serious obstacle to be overcome in the treatment of these diseases, since there is no physiological mechanism for excretion of the excess iron acquired by chronic blood transfusion. Due to the inconvenience and cost of the current iron chelation therapy, the search for an orally available iron chelator is ongoing. Pyridoxal isonicotinoyl hydrazone (PIH) and many of its analogs are effective at mobilizing iron in vivo and in vitro at doses that are not toxic. PIH analogs were approximately equally effective at binding 59Fe within K562 cells; their efficacy depended upon the kinetics of release of the iron-chelator complex from the cell, which was correlated inversely with the lipophilicity of the chelators. Addition of BSA, which has a well-characterized affinity for lipophilic species, to the extracellular medium enhanced iron-chelator efflux, such that all analogs caused 59Fe release from the cells as quickly as it was chelated; this suggests that BSA acts as an extracellular sink for the iron-chelator complexes, many of which are highly lipophilic. The toxicity of the free chelators varied over two orders of magnitude, and was correlated with the amount of intracellular 59Fe-chelator complexes, implicating the complexes in the mechanism of toxicity of the chelators. Understanding the structural features that determine the efficacy and toxicity of iron chelators in biological systems is of value in the selection of PIH analogs for in vivo examination.
authors.affiliation: Department of Physiology, McGill University, and Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital, 3755 Chemin de la Cote-Ste-Catherine, Montreal, Que., Canada H3T 1E2.
authors.forename: Joan L
authors.initials: JL
authors.lastname: Buss
authors.forename: Emmanuele
authors.initials: E
authors.lastname: Arduini
authors.forename: Kyle C
authors.initials: KC
authors.lastname: Shephard
authors.forename: Prem
authors.initials: P
authors.lastname: Ponka
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D006801:Humans; D007501:Iron / Q000378:metabolism*; D007502:Iron Chelating Agents / Q000494:pharmacology*; D007538:Isoniazid / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology*; D020014:K562 Cells; D011730:Pyridoxal / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; D007502:Iron Chelating Agents; D011730:Pyridoxal; C021079:pyridoxal isonicotinoyl hydrazone; D007501:Iron; D007538:Isoniazid