Benzodiazepine-induced superoxide signals B cell apoptosis: mechanistic insight and potential therapeutic utility.
The properties of a proapoptotic 1,4-benzodiazepine, Bz-423, identified through combinatorial chemistry and phenotype screening are described. Bz-423 rapidly generated superoxide (O(2)(-)) in transformed Ramos B cells. This O(2)(-) response originated from mitochondria prior to mitochondrial transmembrane gradient collapse and opening of the permeability transition pore. Bz-423-induced O(2)(-) functioned as an upstream signal that initiated an apoptotic program characterized by cytochrome c release, mitochondrial depolarization, and caspase activation. Pretreatment of cells with agents that either block the formation of Bz-423-induced O(2)(-) or scavenge free radicals attenuated the death cascade, which demonstrated that cell killing by Bz-423 depends on O(2)(-). Parallels between Ramos cells and germinal center B cells prompted experiments to determine whether Bz-423 had therapeutic activity in vivo. This possibility was tested using the (NZB x NZW)F(1) murine model of lupus, in which the pathologically enhanced survival and expansion of germinal center B cells mediate disease. Administration of Bz-423 for 12 weeks specifically controlled germinal center hyperplasia and reduced the histological evidence of glomerulonephritis. Collectively, these studies define a new structure-function relationship for benzodiazepines and point to a new target and mechanism that could be of value for developing improved drugs to manage systemic lupus erythematosus and related disorders.
Blatt
Neal B
NB
Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, USA.
Bednarski
Jeffrey J
JJ
Warner
Roscoe E
RE
Leonetti
Francesco
F
Johnson
Kathryn M
KM
Boitano
Anthony
A
Yung
Raymond
R
Richardson
Bruce C
BC
Johnson
Kent J
KJ
Ellman
Jonathan A
JA
Opipari
Anthony W
AW
Glick
Gary D
GD
D000818:Animals; D000974:Antibodies, Antinuclear / Q000097:blood; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001402:B-Lymphocytes / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D001569:Benzodiazepines / Q000737:chemistry / Q000494:pharmacology*; D002461:Cell Line, Transformed; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008180:Lupus Erythematosus, Systemic / Q000188:drug therapy / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008814:Mice, Inbred NZB; D008954:Models, Biological; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013481:Superoxides / Q000378:metabolism*
D000974:Antibodies, Antinuclear; D017382:Reactive Oxygen Species; D013481:Superoxides; D001569:Benzodiazepines; C468549:Bz-423