Clozapine causes oxidation of proteins involved in energy metabolism: a possible mechanism for antipsychotic-induced metabolic alterations.
Although atypical antipsychotics are widely known to induce alterations in lipid and glucose metabolism, the mechanisms by which these alterations occur remain unknown. Several recent studies have shown that atypical antipsychotics induce oxidative stress and oxidative cell injury by increasing levels of lipid and protein oxidation. In this study, a novel proteomic approach was used to identify specific proteins oxidized after clozapine treatment. Differentiated neuroblastoma SKNSH cells were treated with 0, 5 or 20 mum clozapine for 24 h and protein extracts were labelled with 6-iodoacetamide fluorescein (6-IAF). The lack of incorporation of 6-IAF to cysteine residues is an indicator of protein oxidation. Labelled proteins were exposed to 2D electrophoresis, and differential protein labelling was assessed. Increased oxidation after clozapine treatment was observed in 10 protein spots (p<0.05), although only four of them remained significant after correcting for analysis with two drug concentrations. Five proteins, corresponding to nine of the spots, were identified by HPLC-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) as mitochondrial ribosomal protein S22, mitochondrial malate dehydrogenase, calumenin, pyruvate kinase and 3-oxoacid CoA transferase. The latter four proteins play important roles in energy metabolism. These results suggest that oxidative stress may be a mechanism by which antipsychotics increase the risk for metabolic syndrome and diabetes.
Walss-Bass
Consuelo
C
Department of Psychiatry, The University of Texas Health Science Center at San Antonio, TX, USA. walss@uthscsa.edu
Weintraub
Susan T
ST
Hatch
John
J
Mintz
Jim
J
Chaudhuri
Asish R
AR
D014150:Antipsychotic Agents / Q000009:adverse effects / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D003024:Clozapine / Q000009:adverse effects / Q000494:pharmacology*; D004396:Coloring Agents; D015180:Electrophoresis, Gel, Two-Dimensional; D004734:Energy Metabolism / Q000187:drug effects*; D005452:Fluoresceins; D006801:Humans; D013058:Mass Spectrometry; D008660:Metabolism / Q000187:drug effects*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D021241:Spectrometry, Mass, Electrospray Ionization
D014150:Antipsychotic Agents; D004396:Coloring Agents; D005452:Fluoresceins; D009419:Nerve Tissue Proteins; D017382:Reactive Oxygen Species; C050046:6-iodoacetamidofluorescein; D003024:Clozapine