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Biochim Biophys Acta. 2011 May;1810(5):519-25. doi: 10.1016/j.bbagen.2011.02.010. Epub 2011 Mar 5.

Agaritine from Agaricus blazei Murrill induces apoptosis in the leukemic cell line U937.

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  • 1Department of Clinical Hematology, Fujita Health University School of Health Sciences, Toyoake, Aichi 470-1192, Japan. hakiyama@fujita-hu.ac.jp

Abstract

BACKGROUND:

Agaricus blazei Murrill (ABM) has been shown to exhibit immunostimulatory and anti-cancer activities; however, its mechanism of action is poorly understood. We recently found that the diffusible fraction of hot-water extract of ABM exhibits anti-tumor activity toward leukemic cells, and identified it as agaritine, a hydrazine-containing compound. In the present study, we examined the morphological and cytochemical effects of agaritine on U937 cells to elucidate the tumoricidal mechanism of agaritine.

METHODS:

Surface expression of phosphatidylserine (evaluated by annexin V binding), Fas antigen, DNA cleavage using TUNEL staining, changes in caspase activities and cytochrome c release, before and after treatment with agaritine, were examined using U937 cells.

RESULTS:

Nuclear damage, DNA fragmentation, was observed by Wright-Giemsa, TUNEL staining and agarose gel electrophoresis when U937 cells were incubated with 10μg/mL of agaritine for 48h. Flow cytometric analysis indicated that agaritine augments the proportion of annexin V-positive U937 cells without significant change in Fas antigen expression. Activities of caspase-3, -8 and -9 were gradually increased after the addition of agaritine. In the presence of caspase-3 or granzyme B inhibitor, except for the caspase-8 inhibitor, annexin V expression was significantly decreased, suggesting that mainly caspase-3 and -9 participate in the apoptotic pathway. Furthermore, cytochrome c release was detected by western blotting analysis after agaritine treatment.

CONCLUSIONS:

These results strongly suggest that the ABM constituent agaritine moderately induces apoptosis in U937 leukemic cells via caspase activation through cytochrome c release from mitochondria.

GENERAL SIGNIFICANCE:

This is the first report suggesting that the anti-tumor effect of agaritine is mediated through apoptosis. The present results might provide helpful suggestions for the design of anti-tumor drugs toward leukemia patients.

Copyright © 2011 Elsevier B.V. All rights reserved.

PMID:
21382445
[PubMed - indexed for MEDLINE]
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