title: Catha edulis (Khat) induces cell death by apoptosis in leukemia cell lines.
abstract: Khat is the Celastraceus edulis plant, a flowering evergreen tree or large shrub, which grows in the Horn of Africa and southwestern Arabia. Khat use has been associated with development of oral cancer, but its molecular effects remain controversial. This study describes a novel cytotoxic effect of whole khat extract on three leukemia cell lines. Cells were exposed to khat extract and harvested for analysis by fluorescent and electron microscopy, trypan blue exclusion, as well as immunoblotting to characterize the mode of cell death. In a separate series, cells were pretreated with a panel of caspase inhibitors for possible inhibitory effects. Khat induced a rapid cell death effect in HL-60, Jurkat, and NB4 cells that occurred within 2 h of exposure. The treated cells retained their ability to exclude trypan blue dye, a key feature in the apoptotic process. Exposed cells consistently developed morphological features of manifest apoptosis. Z-VAD, a pan-caspase inhibitor, completely inhibited toxic activity for up to 8 h, with partial inhibition by other caspase-specific agents. Western blot analysis showed specific cleavage of caspase-3 in khat-exposed cells. This study shows that khat induces cell death by apoptosis in a process sensitive to inhibition by caspase inhibitors, suggesting that subcellular interactions could be of particular relevance for the biological effects of khat in the cell death process and possibly carcinogenesis.
authors.affiliation: Department of Odontology-Oral Pathology and Forensic Odontology, Faculty of Dentistry, University of Bergen, Bergen, Norway. elizabeth.dimba@students.uib.no
authors.forename: E
authors.initials: E
authors.lastname: Dimba
authors.forename: B T
authors.initials: BT
authors.lastname: Gjertsen
authors.forename: G W
authors.initials: GW
authors.lastname: Francis
authors.forename: A C
authors.initials: AC
authors.lastname: Johannessen
authors.forename: O K
authors.initials: OK
authors.lastname: Vintermyr
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D029754:Catha; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000187:drug effects / Q000648:ultrastructure; D002843:Chromatin / Q000187:drug effects; D018922:HL-60 Cells; D006801:Humans; D019169:Jurkat Cells; D018625:Microscopy, Atomic Force; D008517:Phytotherapy; D010936:Plant Extracts / Q000633:toxicity*
chemical_list: D002843:Chromatin; D010936:Plant Extracts