title: Plumbagin-induced apoptosis in lymphocytes is mediated through increased reactive oxygen species production, upregulation of Fas, and activation of the caspase cascade.
abstract: Extracts from plants containing plumbagin (PLB) continue to be used as a treatment of a number of chronic immunologically-based diseases. However, most of these claims are supported only by anecdotal evidence with few scientific reports describing the mechanism of action or the efficacy of plumbagin in the suppression of the immune response. In the current study, we tested the hypothesis that plumbagin-induced suppression of the immune response was mediated through the induction of apoptosis. Splenocytes from C57BL/6 mice cultured in the presence of 0.5 microM or greater concentrations of PLB significantly reduced proliferative responses to mitogens, including anti-CD3 mAbs, concanavalin A (Con A), lipopolysaccharide (LPS) and staphylococcal enterotoxin B (SEB) in vitro. Exposure of naïve and activated splenocytes to PLB led to a significant increase in the levels of apoptosis. In addition, PLB treatment led to a significant increase in the levels of reactive oxygen species (ROS) in naïve and activated splenocytes. Furthermore, treatment with the ROS scavenger, N-acetylcysteine (NAC), prevented PLB-induced apoptosis, suggesting a role of ROS in PLB-induced apoptosis. PLB-induced apoptosis led to ROS-mediated activation of both the extrinsic and intrinsic apoptotic pathways. In addition, plumbagin led to increased expression of Fas. Finally, treatment of mice with PLB (5mg/kg) led to thymic and splenic atrophy as well as a significant suppression of the response to SEB and dinitrofluorobenzene (DNFB) in vivo. Together, these results suggest that plumbagin has significant immunosuppressive properties which are mediated by generation of ROS, upregulation of Fas, and the induction of apoptosis.
authors.affiliation: Division of Basic Medical Sciences, School of Medicine, Mercer University, 1550 College St, Macon, GA 31207, USA. mckallip_r@mercer.edu
authors.forename: Robert J
authors.initials: RJ
authors.lastname: McKallip
authors.forename: Catherine
authors.initials: C
authors.lastname: Lombard
authors.forename: Jingping
authors.initials: J
authors.lastname: Sun
authors.forename: Rupal
authors.initials: R
authors.lastname: Ramakrishnan
mesh_terms: D000111:Acetylcysteine / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D001284:Atrophy / Q000139:chemically induced; D020169:Caspases / Q000378:metabolism*; D004139:Dinitrofluorobenzene / Q000633:toxicity; D004768:Enterotoxins / Q000633:toxicity; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D007166:Immunosuppressive Agents / Q000633:toxicity*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008214:Lymphocytes / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D009285:Naphthoquinones / Q000633:toxicity*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013154:Spleen / Q000187:drug effects / Q000473:pathology; D013950:Thymus Gland / Q000187:drug effects / Q000473:pathology; D015854:Up-Regulation / Q000187:drug effects; D019014:fas Receptor / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D004768:Enterotoxins; D007166:Immunosuppressive Agents; D009285:Naphthoquinones; D017382:Reactive Oxygen Species; D019014:fas Receptor; C031818:enterotoxin B, staphylococcal; D004139:Dinitrofluorobenzene; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020169:Caspases; D000111:Acetylcysteine; C014758:plumbagin