METHODS: α-Mangostin (AM) was isolated from C. arborescens and its cell death mechanism was investigated. AM-induced cytotoxicity was observed with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Acridine orange/propidium iodide staining and annexin V were used to detect cells in early phases of apoptosis. High-content screening was used to observe the nuclear condensation, cell permeability, mitochondrial membrane potential, and cytochrome c release. The role of caspases-3/7, -8, and -9, reactive oxygen species, Bcl-2 and Bax expression, and cell cycle arrest were also investigated. To determine the role of the central apoptosis-related proteins, a protein array followed by immunoblot analysis was conducted. Moreover, the involvement of nuclear factor-kappa B (NF-κB) was also analyzed.
RESULTS: Apoptosis was confirmed by the apoptotic cells stained with annexin V and increase in chromatin condensation in nucleus. Treatment of cells with AM promoted cell death-transducing signals that reduced MMP by downregulation of Bcl-2 and upregulation of Bax, triggering cytochrome c release from the mitochondria to the cytosol. The released cytochrome c triggered the activation of caspase-9 followed by the executioner caspase-3/7 and then cleaved the PARP protein. Increase of caspase-8 showed the involvement of extrinsic pathway. AM treatment significantly arrested the cells at the S phase (P<0.05) concomitant with an increase in reactive oxygen species. The protein array and Western blotting demonstrated the expression of HSP70. Moreover, AM significantly blocked the induced translocation of NF-κB from cytoplasm to nucleus.
CONCLUSION: Together, the results demonstrate that the AM isolated from C. arborescens inhibited the proliferation of MDA-MB-231 cells, leading to cell cycle arrest and programmed cell death, which was suggested to occur through both the extrinsic and intrinsic apoptosis pathways with involvement of the NF-κB and HSP70 signaling pathways.
METHODS: Sprague Dawley rats clustered into five groups, normal control (A) and cancer controls were subcutaneously injected with normal saline and 15 mg/kg azoxymethane, respectively, and nourished on 10% tween 20 and fed on 10% tween 20; reference control (C), injected with 15 mg/kg azoxymethane and injected (intraperitoneal) with 35 mg/kg 5-fluorouracil (5-FU); D and E rat groups received a subcutaneous injection of 15 mg/kg azoxymethane and nourished on 30 and 60 mg/kg of PN, respectively.
RESULTS: The acute toxicity trial showed a lack of any abnormal signs or mortality in rats ingested with 250 and 500 mg/kg of PN. The gross morphology of colon tissues revealed significantly lower total colonic aberrant crypt foci incidence in PN-treated rats than that of cancer controls. Histological examination of colon tissues showed increased aberrant crypt foci availability with bizarrely elongated nuclei, stratified cells and higher depletion of the submucosal glands in cancer controls. PN treatment caused positive modulation of apoptotic (Bax and Bcl-2) proteins and inflammatory cytokines (TNF-α, IL-6 and IL-10). Moreover, rats fed on PN had significantly higher antioxidants (superoxide dismutase) and lower malondialdehyde concentrations in their colon tissue homogenates.
CONCLUSION: The chemoprotective efficiency of PN against azoxymethane-induced aberrant crypt foci is shown by lower aberrant crypt foci values and higher aberrant crypt foci inhibition percentage, possibly through augmentation of genes responsible for apoptotic cascade and inflammations originating from azoxymethane oxidative stress insults.