Induction of apoptosis and G2 /M cell cycle arrest by Scrophularia striata in a human leukaemia cell line

Abstract

Objectives: Scrophularia striata Boiss (Scrophulariaceae) is a plant that grows in northeastern Iran; it has been used traditionally to treat various inflammatory disorders. This study was designed to investigate cytotoxic effects of S. striata extract, on the Jurkat human leukaemia cell line (T-cell leukaemia).

Materials and methods: Phytochemical assay by thin layer chromatography and 2, 2 diphenyl-1-picryl-hydrazyl were used to evaluate main compounds and antioxidant capacity of the plant extract, respectively. Its inhibitory effect on Jurkat cells was evaluated by MTT assay. In addition, cell cycle distribution and apoptotic cell death were evaluated by propidium iodide and annexin V-FITC/ propidium iodide staining.

Results: These showed that the main components present in S. striata extract included flavonoids, phenolic compounds and phenyl propanoids. Treatment with extract was significantly cytotoxic to the tumour cell line. In addition, flow cytometry analysis indicated that S. striata extract induced cell cycle arrest in G2 /M phase and apoptosis of tumour cells.

Conclusions: Results of the study indicated that S. striata extract could inhibit leukaemia cell proliferation by inducing G2 /M phase arrest and apoptosis.

Figure 1

Effect of Scrophularia striata extract on viability of Jurkat human leukaemia tumour cells. Tumour cells were incubated with selected concentrations (0–400 μg/ml) of extract for 48 h. Results indicated that the extract significantly (*P < 0.05, **P < 0.001) inhibited Jurkat cell population growth in a dose‐ and time‐dependent manner compared to non‐treated (control group) cells. Results shown are representative of three independent experiments.

Figure 2

Effect of Scrophularia striata extract on induction of apoptosis in Jurkat cells. Apoptosis‐inducing effect of S. striata extract on Jurkat human leukaemia cells evaluated by the annexin V‐FITC (AV)/PI method. Dot‐plot graphs show viable cells (AV⁻/PI⁻), early phase apoptotic cells (AV⁺/PI⁻), late phase apoptotic cells (AV⁺/PI⁺) and necrotic cells (AV⁻/PI⁺).

Figure 3

Effect of Scrophularia striata extract on cell cycle of Jurkat cells. Jurkat cell line treated with selected concentrations of S. striata extract for 24 h. Distribution of cells in different phases of the cell cycle was evaluated by measuring DNA content. Results showed that S. striata extract induced G₂/M cell cycle arrest in Jurkat cells in a dose‐dependent manner. Taxol treatment was used as positive control. Results shown are representative of three independent experiments.

Figure 4

Effect of Scrophularia striata on DNA fragmentation in Jurkat cell line. Cell line after treatment with 1 = 50μg/ml, 2 = 100lg/ml, 3 = 200μg/ml, 4 = 400μg/ml, T = Taxol μg/ml, C = negative control. DNA laddering typical for apoptotic cells are visible for the cells treated with the extract.