Khat (Catha edulis)-induced apoptosis is inhibited by antagonists of caspase-1 and -8 in human leukaemia cells

Abstract

Khat chewing is a widespread habit that has a deep-rooted sociocultural tradition in Africa and the Middle East. The biological effects of khat are inadequately investigated and controversial. For the first time, we show that an organic extract of khat induces a selective type of cell death having all morphological and biochemical features of apoptotic cell death. Khat extract was shown to contain the major alkaloid compounds cathinone and cathine. The compounds alone and in combination also induced apoptosis. Khat-induced apoptosis occurred synchronously in various human cell lines (HL-60, NB4, Jurkat) within 8 h of exposure. It was partially reversed after removal of khat and the effect was dependent on de novo protein synthesis, as demonstrated by cotreatment with cycloheximide. The cell death was blocked by the pan-caspase inhibitor Z-VAD-fmk, and also by submicromolar concentrations of Z-YVAD-fmk and Z-IETD-fmk, inhibitors of caspase-1 and -8, respectively. The 50% inhibition constant (IC 50 ) for khat (200 mg ml À1 )-induced apoptosis by Z-VAD-fmk, Z-YVAD-fmk and Z-IETD-fmk was 8 Â 10 À7 M as compared to 2 Â 10 À8 M and 8 Â 10 À8 M, respectively. Western blot analysis showed a specific cleavage of procaspase-3 in apoptotic cells, which was inhibited by Z-VAD-fmk. The cell death by khat was more sensitively induced in leukaemia cell lines than in human peripheral blood leukocytes. It is concluded that khat induces a rather swift and sensitive cell death by apoptosis through mechanisms involving activation of caspase-1, -3 and -8.

Antibacterial and Anti-Acanthamoebic Properties of Catha Edulis (Khat)

“…The results are representative of at least three independent experiments performed in duplicate. leukaemia cell lines including HL-60, NB4, Jurkat cells in a caspase-1 and -8 dependent manner [4]. As the single-celled A. castellanii is not yet known to undergo programmed cell death, future studies are needed to understand the molecular mechanisms of C. edulis-mediated A. castellanii death as well as its antibacterial properties.…”

“…The use of natural products, such as medicinal plants as therapy against infectious diseases is a traditional therapeutic measure especially in developing countries as they contain a combination of potential antimicrobial compound(s) instead of a single purified molecule [3]. Khat, Catha edulis, from the family Celastraceae is a natural stimulant that is found as a flowering evergreen tree and is widely cultivated in Africa and southern parts of Arabia [4][5][6]. The chewing of young shoots and leaves of C. edulis is a traditional and social habit in some countries of East Africa and Arab Peninsula [5,6].…”

Qat and its health effects

“…46 Qat was also shown to promote apoptotic cell death through mechanisms involving the activation of a family of cysteine proteases named caspases (caspase -1, -3 and -8). 47,48 A more recent paper investigated the effects of qat on human oral keratinocytes and human oral fi broblasts in respect to changes present at the cell cycle level. 49 The results showed qat to have a strong inhibitory effect on the growth of these two cell types, with increased expression of tumour suppressor genes involving senescence related to differentiation.…”

Cation-exchange solid-phase and liquid-liquid extraction for the determination of khat alkaloids by reversed phase HPLC-DAD

“…Several analytical methods involving gas chromatography-mass spectrometry (GC-MS) [9,17,18], gas chromatography-flame ionization detection (GC-FID) [8], high performance liquid chromatography-diode array detection (HPLC-DAD) [19][20][21][22], liquid chromatography-tandem mass spectrometry (LC-MS/MS) [23] and capillary electrophoresis-diode array detection (EC-DAD) [24] have been developed for the determination of the phenylpropylamino alkaloids in khat leaf samples. These methods have been applied in pharmacological, phytochemical, forensic and law enforcement environments.…”