Simultaneous induction of apoptosis and necroptosis by Tanshinone IIA in human hepatocellular carcinoma HepG2 cells.

Tanshinone IIA (Tan IIA), a constituent of the traditional medicinal plant Salvia miltiorrhiza BUNGE, has been reported to possess anticancer activity through induction of apoptosis in many cancer cells. Surprisingly, the present study finds that Tan IIA simultaneously causes apoptosis and necroptosis in human hepatocellular carcinoma HepG2 cells. We further find that apoptosis can be converted to necroptosis by pan-caspase inhibitor Z-VAD-fmk, and the two death modes can be blocked by necroptotic inhibitor necrostatin-1. The underlying mechanisms are revealed by analysis of the signaling molecules using western blotting. In control cells, FLICE inhibitory protein in short form (FLIPS) is expressed in relatively high levels and binds to caspase 8 in ripoptosome, which supposedly sustains cell survival. However, in Tan IIA-treated cells, FLIPS is down-regulated and may thus cause homodimer formation of cleaved caspase 8, cleavage of receptor-interacting serine/threonine-protein kinases 1, 3 (RIP1, RIP3), and mixed-lineage kinase domain-like (MLKL), in turn leads to cell apoptosis. In parallel, Tan IIA causes necroptosis by forming a suggested necrosomal complex composed of RIP1/RIP3. Regarding the inhibitors, z-VAD-fmk diminishes the cleaved caspase 8, RIP1, RIP3, and MLKL induced by Tan IIA, and reconstructs the ripoptosome complex, which marks cells moving from apoptosis to necroptosis. Nec-1 recovers the Tan IIA down-regulated FLIPS, consequently causes FLIPS to form heterodimer with caspase 8 and thus block apoptosis. Meanwhile, cleaved forms of RIP1 and RIP3 were observed preventing necroptosis. Intriguingly, the cytotoxicity of tumor necrosis factor-related apoptosis-inducing ligand to HepG2 cells is enhanced by Tan IIA in a pilot study, which may be attributed to low FLIPS levels induced by Tan IIA. In short, Tan IIA simultaneously induces both Nec-1 inhibition and FLIPS regulation-mediated apoptosis/necroptosis, which has not been previously documented. Moreover, the involvement of the cleavage type of MLKL in executing necroptosis warrants further investigation.

Learning behaviour and cerebral protein kinase C, antioxidant status, lipid composition in senescence-accelerated mouse: influence of a phosphatidylcholine-vitamin B12 diet.

Our objective was to determine whether dietary supplementation with phosphatidylcholine (PC) plus vitamin B12 could afford beneficial effects on biochemical and biophysical events in the brain of senescence-accelerated mouse (SAM) substrain SAMP8. We measured learning behaviour, hippocampal protein kinase C (PKC) activity, cerebral antioxidant status, phospholipid composition and fatty acid composition in 6-month-old SAMP8 and in age-matched controls (SAM substrain SAMR1). In comparison with SAMR1, SAMP8 showed a significant elevation in total grading score of senescence and a significant decline in acquisition SAMP8 had a lower hippocampal PKC activity and cerebral PKC-beta mRNA abundance than SAMR1. SAMP8 had increased cerebral lipid peroxide levels and proportion of sphingomyelin, and a lower proportion of 20 : 4n-6 and 22 : 6n-3 in cerebral phosphtidylethanolamine than SAMR1. SAMP8 fed the PC combined with vitamin B12 diet had an increased PKC activity and a higher proportion of 22 : 6n-3 than SAMP8 fed the control diet. These results indicate the potential benefit of PC combined with vitamin B12 as a dietary supplement.

Effectiveness of water soluble poly(L-glutamic acid)-camptothecin conjugate against resistant human lung cancer xenografted in nude mice.

A camptothecin (CPT) formulation that can be easily administered, is less toxic, and has greater antitumor effect is needed. In this study, a water-soluble CPT derivative was obtained by direct coupling of CPT to poly(L-glutamic acid) (PG) through the C20(S)-hydroxyl group. CPT was released from the resulting conjugate, PG-CPT, in phosphate-buffered saline with a zero-order kinetics in the initial 50 days. The release rates were 0.623% per day, 1.081% per day, and 1.396% per day at pH 5.3, 7.4, and 9.0, respectively. In vitro, PG-CPT was less potent in inhibiting cell growth than was free CPT in all human tumor cell lines tested. However, PG-CPT showed better antitumor activity and tolerability than did CPT in vivo. When H322 human lung tumor cells were inoculated subcutaneously in nude mice, PG-CPT delayed the growth of these well-established tumors with an absolute growth delay of 32 days when given as 4 doses with 4-day intervals between injections at an equivalent CPT dose of 40 mg/kg. When H322 cells were inoculated intratracheally in nude mice, 5 doses of intravenous injection of PG-CPT at an equivalent CPT dose of 10 mg/kg on days 4, 8, 12, 16, and 20 after inoculation significantly prolonged the median survival of treated mice, averaging 1.8-fold that of untreated mice (p=0.01). Increasing the dose of PG-CPT to an equivalent CPT dose of 40 mg/kg per injection administered in 4 doses on days 4, 8, 12, and 16 prolonged the median survival of treated mice by 4-fold (p=0.0008). Significantly, mice with intratracheally inoculated H322 tumors were resistant to both CPT and cisplatin treatments. These studies demonstrated that PG may be used as an effective solubilizing carrier for CPT and that PG-CPT may have potential application in the treatment of lung cancer.

Taxane diterpenoids from seeds of Taxus mairei.

A new 2(3-->20) abeotaxane, taxumairone A (1), and a new cis-p-coumaroyl myo-inositol have been isolated from the seeds of Taxus mairei in addition to taxin B (2), taxinine A, taxuspine X, decinnamoyltaxinine E, 5alpha-cinnamoyloxy-9alpha,10beta,13alpha- triacetoxy-taxa-4(20)11-diene and 5alpha-cinnamoyloxy-2alpha,9alpha,10beta,+ ++13alpha-tetraacetoxy-taxa-4(20)11-diene. The structure of 1 was determined by 2D-NMR spectral analysis and chemical correlation with taxin B (2). Compound 1 exhibited potent cytotoxicity against human colon carcinoma cells with an ED50 of 0.1 microg/ml.

New taxanes with an opened oxetane ring from the roots of Taxus mairei.

Two novel taxoids, taxumairols N (1) and O (2), have been isolated from extracts of the roots of Taxus mairei. The structures of 1 and 2 were identified as 7beta,9alpha,10beta,13alpha-tetraacetoxy-2alp ha, 4alpha,5alpha,20-tetrahydroxytax-11-ene and 7beta,9alpha,10beta, 13alpha-tetraacetoxy-1beta,2alpha,4alpha,5alp ha, 20-pentahydroxytax-11-ene on the basis of 1D and 2D NMR techniques including COSY, HMQC, HMBC, and NOESY experiments.

Ibotenic acid-induced lesions of the medial septum increase hippocampal membrane associated protein kinase c activity and reduce acetylcholine synthesis: prevention by a phosphatidylcholine/vitamin B12 diet.

Ibotenic acid infusion into the medial septum (MS) results in biochemical alterations in the hippocampus. The biochemical events involved in this neuronal lesion are poorly understood. We investigated the effect of a purified diet supplemented with egg phosphatidylcholine (PC) and vitamin B(12) on ibotenic acid-medicated biochemical changes in the rat hippocampus and crude synaptosomal membranes. Male Wistar rats with this MS lesion were fed a purified diet (control diet) or a purified diet supplemented with 5.7 g PC and 125 microg vitamin B(12) per 100 g (experimental diet) for 18 days. Sham-operated rats were fed the control diet. Compared with the sham-operated rats, MS-lesioned rats fed the control diet showed increased activity of membrane-bound protein kinase C (PKC), decreased activity of choline acetyltransferase, and decreased concentrations of acetylcholine in the hippocampus. The ratio of cholesterol to phospholipid in the crude synaptic membrane was lower in the lesioned rats than in the sham-operated rats, but this was not accompanied by any alteration in membrane lipid fluidity. MS-lesioned rats fed the experimental diet showed lowered PKC activity and elevated acetylcholine concentrations than did rats fed the control diet, but there were no significant effects on choline acetyltransferase activity and the lipid ratio. The ibotenic acid-mediated elevation of PKC activity was observed as early as 2 days postinjury in the control diet-fed rats but not in the experimental diet-fed rats. We propose that ibotenic acid mediates pathophysiologic actions through the activation of PKC and that PC combined with vitamin B(12) ameliorates the second messenger-mediated injury.

Hyperthermia enhances the cytotoxicity of National Institutes of Health 3T3 cells transfected with a noncleavable transmembrane pro-tumor necrosis factor deletion mutant.

Hyperthermia has been shown to potentiate the cytotoxicity of exogenously added tumor necrosis factor (TNF) against tumor cell targets. The mechanism for that interaction is not known, but among the possibilities are that heat enhances internalization of ligand-bound TNF or enhances processing of internalized TNF. In this study, we found that NIH 3T3 cells transfected with an expression vector containing the full-length human pro-TNF secreted TNF and that hyperthermic treatment of chromium-labeled L929 target cells at 43 degrees C for 1 h potentiated the cytotoxicity of these transfectants against the L929 cells in clonogenic survival and chromium-release assays. On the other hand, transfectants expressing a transmembrane, nonsecretable pro-TNF mutant that kills L929 cells by cell-to-cell contact without internalization also exhibited enhanced cytotoxicity against heated L929 cell targets. Thus, potentiation of the cytotoxicity of TNF by hyperthermia is not strictly dependent on enhanced internalization of ligand-bound TNF or enhanced processing of internalized TNF.