Laily B. Din

Loss of mitochondrial transmembrane potential and caspase-9 activation during apoptosis induced by the novel styryl-lactone goniothalamin in HL-60 leukemia cells

Styryl-lactones such as goniothalamin represent a new class of compounds with potential anti-cancer properties. In this study, we investigated the mechanisms of goniothalamin (GTN), a plant styryl-lactone induced apoptosis in human promyelocytic leukemia HL-60 cells. This plant extract resulted in apoptosis in HL-60 cells as assessed by the externalisation of phosphatidylserine. Using the mitochondrial membrane dye (DIOC(6)) in conjunction with flow cytometry, we found that GTN treated HL-60 cells demonstrated a loss of mitochondrial transmembrane potential (Deltapsi(m)). Further immunoblotting on these cells showed activation of initiator caspase-9 and the executioner caspases-3 and -7. Pretreatment with the pharmacological caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp fluoromethyl ketone (Z-VAD.FMK) abrogated apoptosis as assessed by all of the apoptotic features in this study. In summary, our results demonstrate that goniothalamin-induced apoptosis occurs via the mitochondrial pathway in a caspase dependent manner.

Caspases-3 and -7 are activated in goniothalamin-induced apoptosis in human Jurkat T-cells

Goniothalamin, a plant styrylpyrone derivative isolated from Goniothalamus andersonii, induced apoptosis in Jurkat T‐cells as assessed by the externalisation of phosphatidylserine. Immunoblotting showed processing of caspases‐3 and ‐7 with the appearance of their catalytically active large subunits of 17 and 19 kDa, respectively. Activation of these caspases was further evidenced by detection of poly(ADP‐ribose) polymerase cleavage (PARP). Pre‐treatment with the caspase inhibitor benzyloxycarbonyl‐Val‐Ala‐Asp fluoromethyl ketone (Z‐VAD.FMK) blocked apoptosis and the resultant cleavage of these caspases and PARP. Our results demonstrate that activation of at least two effector caspases is a key feature of goniothalamin‐induced apoptosis in Jurkat T‐cells.

Goniothalamin-induced oxidative stress, DNA damage and apoptosis via caspase-2 independent and Bcl-2 independent pathways in Jurkat T-cells.

Goniothalamin (GTN) isolated from Goniothalamus sp. has been demonstrated to induce apoptosis in a variety of cancer cell lines including Jurkat T leukemia cells. However, the mechanism of GTN-induced apoptosis upstream of mitochondria is still poorly defined. In this study, GTN caused a decrease in GSH with an elevation of reactive oxygen species as early as 30 min and DNA damage as assessed by Comet assay. Analysis using topoisomerase II processing of supercoiled pBR 322 DNA showed that GTN caused DNA damage via a topoisomerase II-independent pathway suggesting that cellular oxidative stress may contribute to genotoxicity. A 12-fold increase of caspase-2 activity was observed in GTN-treated Jurkat cells after 4 h treatment and this was confirmed using Western blotting. Although the caspase-2 inhibitor Z-VDVAD-FMK inhibited the proteolytic activity of caspase-2, apoptosis ensued confirming that caspase-2 activity was not crucial for GTN-induced apoptosis. However, GTN-induced apoptosis was completely abrogated by N-acetylcysteine further confirming the role of oxidative stress. Since cytochrome c release was observed as early as 1 h without any appreciable change in Bcl-2 protein expression, we further investigated whether overexpression of Bcl-2 confers resistance in GTN-induced cytotoxicity. Using a panel of Jurkat Bcl-2 transfectants, GTN cytotoxicity was not abrogated in these cells. In conclusion, GTN induces DNA damage and oxidative stress resulting in apoptosis which is independent of both caspase-2 and Bcl-2.

(+)-Isoaltholactone: A furanopyrone isolated from Goniothalamus species

(+)-Isoaltholactone, (2S,3S,3aR,7aS)-3-hydroxy-2-phenyl-(2H,3aH)-furano[3,2-b]pyran-5-one was isolated from stembark of Goniothalamus malayanus, stembark and leaves of G. montanus and roots of G. tapis.

Synthesis of silver nanoparticles with antibacterial activity using the lichen Parmotrema praesorediosum

Development of a green chemistry process for the synthesis of silver nanoparticles has become a focus of interest. This would offer numerous benefits, including ecofriendliness and compatibility for biomedical applications. Here we report the synthesis of silver nanoparticles from the reduction of silver nitrate and an aqueous extract of the lichen Parmotrema praesorediosum as a reductant as well as a stabilizer. The physical appearance of these silver nanoparticles was characterized using ultraviolet-visible spectroscopy, electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction techniques. The results show that silver nanoparticles synthesized using P. praesorediosum have an average particle size of 19 nm with a cubic structure. The antibacterial activity of the synthesized silver nanoparticles was tested against eight micro-organisms using the disk diffusion method. The results reveal that silver nanoparticles synthesized using P. praesorediosum have potential antibacterial activity against Gram-negative bacteria.

Goniothalamin induces coronary artery smooth muscle cells apoptosis: the p53-dependent caspase-2 activation pathway.

Goniothalamin (GN), a styryl-lactone isolated from Goniothalamus andersonii, has been demonstrated to possess antirestenostic properties by inducing apoptosis on coronary artery smooth muscle cells (CASMCs). In this study, the molecular mechanisms of GN-induced CASMCs apoptosis were further elucidated. Apoptosis assessment based on the externalization of phosphatidylserine demonstrated that GN induces CASMCs apoptosis in a concentration-dependent manner. The GN-induced DNA damage occurred with concomitant elevation of p53 as early as 2 h, demonstrating an upstream signal for apoptosis. However, the p53 elevation in GN-treated CASMCs was independent of NAD(P)H: quinone oxidoreductase 1 and Mdm-2 expression. An increase in hydrogen peroxide and reduction in free thiols confirmed the role for oxidative stress in GN treatment. Pretreatment with the pan-caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (z-VAD-FMK) that significantly abrogated GN-induced CASMCs apoptosis suggested the involvement of caspase(s). The role of apical caspase-2, -8, and -9 was then investigated, and sequential activation of caspase-2 and -9 but not caspase-8 leading to downstream caspase-3 cleavage was observed in GN-treated CASMCs. Reduction of ATP level and decrease in oxygen consumption further confirmed the role of mitochondria in GN-induced apoptosis in CASMCs. The mitochondrial release of cytochrome c was seen without mitochondrial membrane potential loss and was independent of cardiolipin. These data provide insight into the mechanisms of GN-induced apoptosis, which may have important implications in the development of drug-eluting stents.

Scorazanone, a 1-aza-anthraquinone from Goniothalamus scortechinii.

The air dried roots of Goniothalamus scortechinii, collected in Malaysia, yielded a new 1 -aza-anthraquinone, scorazanone, which was identified using spectroscopic techniques.

Cytotoxic Properties of Oligostilbenoids from the Tree Barks of Hopea dryobalanoides

Abstract A new modified stilbene dimer, diptoindonesin D (1), was isolated from the acetone extract of the tree bark of Hopea dryobalanoides, together with seven known compounds, parviflorol (2), (D)-balanocarpol (3), heimiol A (4), hopeafuran (5), (+)-α-viniferin (6), vaticanol B (7) and (D)-hopeaphenol (8). Cytotoxic properties of compounds 1-8 were evaluated against murine leukemia P-388 cells. Compound 8 was found to be the most active with IC50 of 5.7 μm

RACK-1 overexpression protects against goniothalamin-induced cell death

Goniothalamin, a styryllactone, has been shown to induce cytotoxicity via apoptosis in several tumor cell lines. In this study, we have examined the potential role of several genes, which were stably transfected into T-cell lines and which regulate apoptosis in different ways, on goniothalamin-induced cell death. Overexpression of full-length receptor for activated protein C-kinase 1 (RACK-1) and pc3n3, which up-regulates endogenous RACK-1, in both Jurkat and W7.2 T cells resulted in inhibition of goniothalamin-induced cell death as assessed by MTT and clonogenic assays. However, overexpression of rFau (antisense sequence to Finkel–Biskis–Reilly murine sarcoma virus-associated ubiquitously expressed gene) in W7.2 cells did not confer resistance to goniothalamin-induced cell death. Etoposide, a clinically used cytotoxic agent, was equipotent in causing cytotoxicity in all the stable transfectants. Assessment of DNA damage by Comet assay revealed goniothalamin-induced DNA strand breaks as early as 1 h in vector control but this effect was inhibited in RACK-1 and pc3n3 stably transfected W7.2 cells. This data demonstrate that RACK-1 plays a crucial role in regulating cell death signalling pathways induced by goniothalamin.

Tepanone, a retrochalcone from Ellipeia cuneifolia

Tepanone, (2E)-1-phenyl-3-(2-hydroxy-3,4,6-trimethoxyphenyl)prop-2-enone was isolated from roots and stembark of Ellipeia cuneifolia. The structure was deduced from spectroscopic data and confirmed by synthesis of the methylated derivative, methyltepanone. Methyltepanone exists as the two readily interconvertible trans and cis isomers.