Mitodepressive effect of (-)-cathinone, from Catha edulis (khat), on the meristematic region of Allium cepa root tips

Overview of Cell Synchronization

The widespread interest in cell synchronization is maintained by the studies of control mechanism involved in cell cycle regulation. During the synchronization distinct subpopulations of cells are obtained representing different stages of the cell cycle. These subpopulations are then used to study regulatory mechanisms of the cycle at the level of macromolecular biosynthesis (DNA synthesis, gene expression, protein synthesis), protein phosphorylation, development of new drugs, etc. Although several synchronization methods have been described, it is of general interest that scientists get a compilation and an updated view of these synchronization techniques. This introductory chapter summarizes: (1) the basic concepts and principal criteria of cell cycle synchronizations, (2) the most frequently used synchronization methods, such as physical fractionation (flow cytometry, dielectrophoresis, cytofluorometric purification), chemical blockade, (3) synchronization of embryonic cells, (4) synchronization at low temperature, (5) comparison of cell synchrony techniques, (6) synchronization of unicellular organisms, and (7) the effect of synchronization on transfection.

Catha edulis (khat) Induces Apoptosis in Madin-Darby Bovine Kidney Cell Line

Background:

Khat (Catha edulis) is a controversial plant having a euphoretic effect, at the same time part of culture in many countries such as Africa and Arabian Peninsula. The presence of amphetamine-like substance, cathinone and cathine make this plant banned in many countries. Many neurological and other system related studies have been carried out in this plant, but the lack of toxicity studies are there especially the mechanism.

Objective:

In this study, Madin-Darby Bovine Kidney cell line was used as an in vitro model to study the cell death mechanism. Crude extract of fresh Khat plant leaves were prepared and exposed to cells.

Materials and Methods:

Trypan blue assay, phase-contrast microscopy, fluorescent microscopy, clonogenic assay, annexin-V assay, and hematoxylin and eosin (H and E) staining were employed to check the objectives.

Results:

Reductions in cellular viability were observed at concentrations above 1.25 mg/ml while using Trypan blue assay. The results of the clonogenic assay had shown that the untreated control with the highest number of colonies (100% survival) and the 0.1562 concentration could not prevent the colony formation significantly. The high concentrations reduced the colony formation at concentration dependent manner 27.4% and 24.9%, for 0.625 mg/ml and 1.25 mg/ml concentrations, respectively. The acridine orange/ethidium bromide experiment had observed the cells were intact with round nucleus while the apoptosis features such as blebbing and nuclear chromatin condensation were clearly observed in treatment. The shrinkage of cells was clearly observed in H and E staining.

Conclusion:

In addition, annexin-V binding confirmed the presence of apoptosis significantly on Khat treatment.

SUMMARY

Khat (Catha edulis) is a controversial plant having euphoretic effect

Reductions in cellular viability were observed at concentrations above 1.25 mg/ml while using Trypan blue assay

The high concentrations of khat extract had reduced the colony formation at concentration dependent manner

The acridine orange/ethidium bromide experiment had observed the apoptosis features such as blebbing and nuclear chromatin in treatment

Annexin-V binding confirmed the presence of apoptosis significantly on Khat treatment.

Abbreviation used: PS: Phosphatidylserine (PS); MDBK: Madin-Darby Bovine Kidney; DMEM: Dulbecco's modified Eagle's medium; PI: propidium iodide; EB: ethidium bromide; PBS: Phosphate Buffer saline; FITC: fluorescein isothiocyante; TUNEL: Terminal deoxynucleotidyl transferase dUTP nick end labeling.

Overview of cell synchronization

Widespread interest in cell synchronization is maintained by the studies of control mechanisms involved in cell cycle regulation. During the synchronization distinct subpopulations of cells are obtained representing different stages of the cell cycle. These subpopulations are then used to study regulatory mechanisms of the cycle at the level of macromolecular biosynthesis (DNA synthesis, gene expression, protein synthesis), protein phosphorylation, development of new drugs, etc. Although several synchronization methods have been described, it is of general interest that scientists get a compilation and an updated view of these synchronization techniques. This introductory chapter summarizes: (1) the basic concepts and principal criteria of cell cycle synchronizations, (2) the most frequently used synchronization methods, such as physical fractionation (flow cytometry, dielectrophoresis, cytofluorometric purification), chemical blockade, (3) synchronization of embryonic cells, (4) synchronization at low temperature, (5) comparison of cell synchrony techniques, (6) synchronization of unicellular organisms, and (7) the effect of synchronization on transfection.

Khat induces G1-phase arrest and increased expression of stress-sensitive p53 and p16 proteins in normal human oral keratinocytes and fibroblasts

Khat is a psychostimulant plant used by over 10 million people daily, mainly in eastern Africa and the Middle East. Previous studies have suggested an association between khat use and oral lesions such as hyperkeratosis and oral cancer. This study investigated the effects of an extract of khat on primary normal human oral keratinocytes (NOK) and normal human oral fibroblasts (NOF). Low (sublethal) concentrations of khat inhibited the proliferation of both cell types in a dose-dependent and time-dependent manner. Both NOK and NOF treated with khat accumulated in the G1-phase of the cell cycle and showed increased expression of the stress-sensitive p53 protein after 24 h. Normal human oral keratinocytes showed a profound increase in p16(INK4A) (p16) after 24 h and showed morphological changes suggesting cell differentiation. Normal human oral fibroblasts showed growth inhibition and increased expression of p21(WAF1/CIP1) (p21) within 24 h. The concentrations of khat tested in this study were within the range of those found in the oral cavity of khat chewers. The results show that stress induced by khat modulates the cell cycle in oral keratinocytes and fibroblasts. It is further speculated whether khat could have similar effects in vivo, especially in keratinocytes.

Khat (Catha edulis) lowers plasma luteinizing hormone (LH) and testosterone secretion, but increases cortisol levels in male rabbits

AIM

This study investigated the effects of fresh khat extract on specific circulating hormones in male rabbits.

MATERIALS AND METHODS

A total of 25 male New Zealand White rabbits were divided into five groups each comprising five animals. The first four groups were fed four doses (1.5 g/kg, 4.5 g/kg, 13.5 g/kg and 40.5 g/kg body weight) of khat extract twice a week for 5 weeks while the last group, serving as control, was fed only normal saline via intragastric tube. Blood samples were collected at 15 min interval for up to 3 h after khat extract administration and plasma assayed for luteinizing hormone (LH), testosterone and cortisol levels using radioimmunoassay technique.

RESULTS

Khat extract at all doses significantly lowered (P<0.05) LH pulse frequency, area under LH curve, mean plasma LH and mean plasma testosterone levels. Plasma cortisol levels were significantly elevated (P<0.05) in khat-treated rabbits in a dose-dependent manner.

CONCLUSION

This study demonstrates that khat may impair reproductive function in male rabbits by interfering with sex hormone profiles.

The toxicity of Catha edulis (khat) in mice

A large number of people in East Africa and Southern Arabia chew khat leaves because of its pleasurable and stimulating effects. Due to its habit forming property, the khat has been classified as a "Substance of Abuse" by the World Health Organization. In view of the large number of medical problems reported in khat chewers, the present study was undertaken to investigate the chronic toxicity of khat in mice. Three groups of mice were treated with aqueous solution of khat extract in the dose of 50, 100, and 200 mg/kg. body weight daily by oral intubation route for 6 weeks. The results indicated a dose-dependent decrease in body weight, an increase in the incidence of mortality and induction of site specific body and eye lesions. The histopathological examination of the lesions revealed reactive hyperplasia and necrosis in the lymphoid tissues. The necrotic areas in the subcutaneous tissues showed the presence of numerous polymorphs.

An evaluation of the male reproductive toxicity of cathinone

(-)-Cathinone is the major psychoactive component of khat plant (Catha edulis Forssk.). Khat has been shown to produce reproductive toxicity in human beings and experimental animals. However, the chemical constituents of khat leaves responsible for sexual dysfunction are not known. In the present study cathinone enantiomers have been investigated for their reproductive toxicity in rats. Cathinone produced a dose-dependent decrease in food consumption and suppressed the gain in body weight. There was a significant decrease in sperm count and motility and increase in the number of abnormal sperms in cathinone treated animals. Histopathological examination of testes revealed degeneration of interstitial tissue, cellular infiltration and atrophy of Sertoli and Leydig's cells in cathinone treated animals. Cathinone also produced a significant decrease in plasma testosterone levels of the rats. Although both enantiomers of cathinone produced deleterious effects on male reproductive system, (-)-cathinone was found to be more toxic. From this study it may be concluded that the cathinone content in khat may be partially or totally responsible for the reproductive toxicity in khat chewers.

The induction of dominant lethal mutations upon chronic administration of khat (Catha edulis) in albino mice

The mutagenicity of a methanolic extract of khat has been evaluated on male germ cells using the dominant lethal test in albino mice. An aqueous solution of khat extract was administered orally in doses of 50, 100 and 200 mg/kg body wt., respectively, to 3 different groups of male mice for a period of 6 weeks. At the end of treatment each male mouse was allowed to mate with 2 different groups of 3 females each, on 2 consecutive weeks. These females were necropsied on the 13th day of their presumptive mating, and the number of implants in each female and the ratio of live and dead embryos were determined. The results of this study showed that the treatment of male mice over a period of 6 weeks produced a dose-dependent reduction in the rate of fertility in the first week after mating, which was irreversible in the second week at the highest dose (200 mg/kg). Khat extract also induced post-implantation loss during the first week following treatment. However, a comparison of the results of the first and second weeks showed a reversible pattern of dominant lethality.

Pharmacological properties of the stimulant khat

The chewing of the stimulant leaf khat is a habit that is widespread in certain countries of East Africa and the Arabian peninsula. During the last decade, important progress has been made in understanding the pharmacological basis for the effects of khat. It is now known that the CNS action of this drug is due to the presence of the alkaloid cathinone, and the results of various in vitro and in vivo experiments indicate that this substance must be considered a natural amphetamine. It is the purpose of the present review to describe briefly the khat habit and to summarize the pharmacology of khat and of its active constituents.

Cytological effects of khat (Catha edulis) in somatic and male germ cells of mice

Cytological effects of khat (Catha edulis), a popular drug of abuse from Southern Arabia and Eastern Africa, have been studied in Swiss albino mice. The studies on the somatic system involved the use of micronucleus test and the cytological analysis of the mitotic index in the femoral cells of mice. In the micronucleus test, the mice were treated with different doses of khat extract (125, 250 and 500 mg/kg, p.o.) 30 and 6 hours before sacrificing the animals. The polychromatic erythrocytes were screened for the induction of micronuclei. For the analysis of bone marrow cytotoxicity, the mice were treated with the dose of 125, 250 and 500 mg/kg, body weight, p.o. daily for 5 consecutive days. The animals were sacrificed and the femoral cells were microscopically examined for the mitoses. Following the same schedule of treatment, studies on the cytogenetic analysis of meiotic chromosomal aberrations and the sperm head abnormality were undertaken. Khat extract significantly increased the frequency of micronucleated polychromatic erythrocytes, induced bone marrow depression and reduced the mitotic index of the somatic cells. It induced significant chromosomal aberrations viz., aneuploids, autosomal univalents, univalents of the sex chromosomes and polyploids. The frequency of abnormal sperms was also increased.