Increased FasL expression correlates with apoptotic changes in granulocytes cultured with oxidized clozapine

Toxicol Appl Pharmacol. 2006 Aug 1;214(3):326-34. doi: 10.1016/j.taap.2006.01.008. Epub 2006 Feb 28.


Clozapine has been associated with a 1% incidence of agranulocytosis. The formation of an oxidized intermediate clozapine metabolite has been implicated in direct polymorphonuclear (PMN) toxicity. We utilized two separate systems to analyze the role of oxidized clozapine in inducing apoptosis in treated cells. Human PMN cells incubated with clozapine (0-10 microM) in the presence of 0.1 mM H2O2 demonstrated a progressive decrease of surface CD16 expression along with increased apoptosis. RT-PCR analysis showed decreased CD16 but increased FasL gene expression in clozapine-treated PMN cells. No change in constitutive Fas expression was observed in treated cells. In HL-60 cells induced to differentiate with retinoic acid (RA), a similar increase in FasL expression, but no associated changes in CD16 gene expression, was observed following clozapine treatments. Our results demonstrate increased FasL gene expression in oxidized clozapine-induced apoptotic neutrophils suggesting that apoptosis in granulocytes treated with clozapine involves Fas/FasL interaction that initiates a cascade of events leading to clozapine-induced agranulocytosis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigens, CD / genetics
  • Antipsychotic Agents / adverse effects*
  • Antipsychotic Agents / chemistry
  • Apoptosis / drug effects*
  • Cell Differentiation / drug effects
  • Cell Survival / drug effects
  • Clozapine / adverse effects*
  • Clozapine / chemistry
  • Fas Ligand Protein
  • Flow Cytometry
  • GPI-Linked Proteins
  • Gene Expression / drug effects*
  • Granulocytes / drug effects*
  • Granulocytes / metabolism
  • HL-60 Cells
  • Humans
  • Hydrogen Peroxide / pharmacology
  • Membrane Glycoproteins / genetics*
  • Neutrophils / drug effects
  • Neutrophils / metabolism
  • Oxidation-Reduction
  • Receptors, IgG / genetics
  • Reverse Transcriptase Polymerase Chain Reaction
  • Tretinoin / pharmacology
  • Tumor Necrosis Factors / genetics*


  • Antigens, CD
  • Antipsychotic Agents
  • FASLG protein, human
  • FCGR3B protein, human
  • Fas Ligand Protein
  • GPI-Linked Proteins
  • Membrane Glycoproteins
  • Receptors, IgG
  • Tumor Necrosis Factors
  • Tretinoin
  • Hydrogen Peroxide
  • Clozapine