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Background: Kaurane-type diterpenoids, obtained from various natural sources, have shown many biological activities, including anti-inflammatory and antitumor effects. Caracasine, an ent -kaurane diterpenoid isolated from the flowers of Croton micans , was shown to induce apoptosis in leukaemia cell lines., Objective: The present study aimed to ascertain the compound's mechanism of cell death induction using two leukaemia cell lines, Jurkat E6.1 (T cell) and HL-60 (promyeloblast cells)., Methods: Cell death in Jurkat and HL60 cells were evaluated by flow cytometry for apoptosis with annexin-V/PI, mitochondrial membrane potential disturbance, changes in cell cycle, CD95 expression, caspase activation, Nuclear Factor kappa B inhibition, and differentiation into a neutrophil-like cell (dHL60)., Results: Caracasine (10 μM) increased the G0/G1 phase in Jurkat and arrested the cell cycle in the S phase in HL60. Caracasine increased CD95 expression ( p <0.01 in Jurkat and p <0.05 in HL60) and caspase-8 activation ( p <0.001 in Jurkat and p<0.05 in HL60). Caspase-9 was activated in both cell lines ( p <0.001) along with the decline in mitochondrial Δψm ( p <0.05 in Jurkat and p<0.001 in HL60). In HL60 cells, the kaurane induced neutrophil differentiation was assessed by CD40 expression and reactive oxygen species production. In Jurkat cells, caracasine inhibited the NF-κB pathway in cells pretreated with PHA to activate the NF-κB pathway, suggesting a possible role in inflammatory diseases., Conclusion: Caracasine induced apoptosis through the intrinsic and extrinsic pathways in both cell lines were evaluated which could be the leading structure for new anti-leukemic and anti-inflammatory drugs., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Caracasine acid (CA) is an ent-3,4-seco-kaurene isolated from the plant Croton micans. Decreased cancer cell lines viability was reported upon CA treatment. The present study aimed to investigate the mechanism of CA induced cytotoxicity using two human cell lines, Jurkat E6.1 (human cell T lymphoma) and HL-60 (human acute promyelocytic leukemia). Significant increases of apoptotic cell death markers upon CA treatment were observed: annexin-V positiveness, potential mitochondrial disturbances, cell cycle changes, caspase activation, and CD95 expression. These effects were not detected in normal lymphocytes. CA induced the appearance of Bax, cleaved caspase 3, and cytochrome c release in Jurkat cells, and cleaved caspase 3 and phosphorylated p53 in HL60 cells. Likewise, downregulation of anti-apoptotic proteins such as Bcl-x (Jurkat), Bcl-2, and XIAP (HL60) was observed with CA treatment. Both pathways, intrinsic and extrinsic were activated when cell lines were treated with CA. NF-κB p65 inhibition was observed in Jurkat cells and cell differentiation in HL-60 cells. CA could be a potential leader compound for the development of new drugs for leukemia treatment in humans., (Copyright © 2019 Elsevier B.V. All rights reserved.)

From the stems of Croton micans Sw., five new 3,4-seco-ent-kaurene dimers: micansinoic acid (1), isomicansinoic acid (2), and the dimethyl (3), monomethyl (4) and monoethyl ester (5) of micansinoic acid were isolated. The structures of the new compounds were elucidated by spectroscopic data interpretation, mainly 1D and 2D NMR experiments and MS. These compounds are the first 3,4-seco-ent-kaurene dimers from a Croton species.

ent-Kauranes are diterpene-type compounds commonly found in most plant species, especially from the Euphorbiaceae family. These compounds have been studied due to their anti-inflammatory and anti-tumor properties. Regulation of apoptosis, or programmed cell death, is commonly bypassed by tumoral cells, giving rise to uncontrolled proliferating cells, which eventually become carcinogenic. In a previous work, we showed that both mRNA and protein expression levels of the antiapoptotic gene Bcl-2 are reduced in MCF-7 cancer cells by the effect of the natural diterpene ent-16β-17α-dihydroxykaurane (DHK). This effect was not directly associated with the inactivation of NF-κB, as has been shown with other diterpenes compounds. Herein, we report that DHK is dissociating the Ap2α-Rb activating complex, affecting its binding ability for the Bcl-2 gene promoter. These events down-regulate Bcl-2 and is temporally accompanied by the induction of E2F1 and its target pro-apoptotic gene Puma. Disruption of the Rb-Ap2α activation complex was corroborated by chromatin immunoprecipitation and protein immunolocalization, which also revealed that Ap2α sorts out from the nucleus and relocalizes in the cell periphery. Taken together, our study confirms the regulation of Bcl-2 gene transcription by the Ap2α-Rb complex and describes a singular protein relocalization for Ap2α induced by DHK, implicating a new potential therapeutic target to differentially onset apoptosis in tumor cells.