Photoaddition of fluphenazine to nucleophiles in peptides and proteins. Possible cause of immune side effects.
By the action of UVA light, fluphenazine reacted with nucleophiles through a mechanism involving defluorination of its trifluoromethyl group, giving rise to carboxylic acid derivatives that were easily detected by electrospray mass spectrometry. This photoreaction took place with alcohols, sulphydryls, and amines. When irradiation of fluphenazine was carried out in the presence of an amino acid at pH 7.4, the alpha-amino group was covalently bound to the drug. With amino acids possessing a further nucleophilic residue on the side chain, such as lysine, tyrosine, and cysteine--but not serine--both groups reacted, resulting in a fluphenazine-amino acid-fluphenazine diadduct. The same occurred with the physiological peptide glutathione (gamma-glutamylcysteinylglycine). By means of MALDI mass spectrometry, it was shown that fluphenazine also covalently bound to peptides and proteins such as calmodulin. This binding may result in the formation of antibodies, ultimately leading to the destruction of the granulocytes and thus suggesting that photoactivation of this drug may play a role in its clinical side effects, such as agranulocytosis.
Caffieri
Sergio
S
Department of Pharmaceutical Sciences, University of Padova, Italy. sergio.caffieri@unipd.it
Miolo
Giorgia
G
Seraglia
Roberta
R
Dalzoppo
Daniele
D
Toma
Francesca M
FM
van Henegouwen
Gerard M J Beyersbergen
GM
D000380:Agranulocytosis / Q000139:chemically induced / Q000276:immunology; D000596:Amino Acids / Q000737:chemistry / Q000276:immunology / Q000528:radiation effects*; D014150:Antipsychotic Agents / Q000737:chemistry / Q000276:immunology / Q000528:radiation effects*; D002264:Carboxylic Acids / Q000032:analysis; D003545:Cysteine / Q000737:chemistry / Q000528:radiation effects; D005476:Fluphenazine / Q000737:chemistry / Q000276:immunology / Q000528:radiation effects*; D006863:Hydrogen-Ion Concentration; D008239:Lysine / Q000737:chemistry / Q000528:radiation effects; D010455:Peptides / Q000737:chemistry / Q000276:immunology / Q000528:radiation effects*; D010782:Photolysis / Q000528:radiation effects*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014443:Tyrosine / Q000737:chemistry / Q000528:radiation effects; D014466:Ultraviolet Rays
D000596:Amino Acids; D014150:Antipsychotic Agents; D002264:Carboxylic Acids; D010455:Peptides; D014443:Tyrosine; D008239:Lysine; D003545:Cysteine; D005476:Fluphenazine