Mechanisms of induction of apoptosis by anthraquinone anticancer drugs aclarubicin and mitoxantrone in comparison with doxorubicin: relation to drug cytotoxicity and caspase-3 activation

We examined molecular events and morphological features associated with apoptosis induced by anthraquinone anticancer drugs aclarubicin, mitoxantrone and doxorubicin in two spontaneously immortalized cell lines (NIH 3T3 and B14) in relation to cytotoxicity of these drugs. The investigated cells showed similar sensitivity to aclarubicin but different sensitivity to doxorubicin and mitoxantrone: mitoxantrone was the most cytotoxic drug in both cell lines. All three drugs triggered both apoptosis and necrosis but none of these processes was positively correlated with their cytotoxicity. Apoptosis was the prevalent form of cell kill by aclarubicin, while doxorubicin and mitoxantrone induced mainly the necrotic mode of cell death. The extent and the timing of apoptosis were strongly dependent on the cell line, the type of the drug and its dose, and were mediated by caspase-3 activation. A significant increase in caspase-3 activity and the percentage of apoptotic cells, oligonucleosomal DNA fragmentation, chromatin condensation and formation of apoptotic bodies was observed predominantly in B14 cells. NIH 3T3 cells showed lesser changes and a lack of DNA fragmentation. Aclarubicin was the fastest acting drug, inducing DNA fragmentation 12 h earlier than doxorubicin, and 24 h earlier than mitoxantrone. Caspase-3 inhibitor Ac-DEVD-CHO did not show any significant effect on drug cytotoxicity and DNA nucleosomal fragmentation.

Different effectiveness of piperidine nitroxides against oxidative stress induced by doxorubicin and hydrogen peroxide

The piperidine nitroxides Tempamine and Tempace have been studied for their effect on doxorubicin (DOX) and hydrogen peroxide (H(2)O(2)) cytotoxicity in immortalized B14 cells, a model for neoplastic phenotype. The significance for nitroxide performance of the substituent in position 4 of the piperidine ring was evaluated. The cells were exposed to DOX/H(2)O(2) alone or in combination with the nitroxides Tempamine or Tempace. Two other piperidine nitroxides, Tempo and Tempol, were used for comparison. All the nitroxides except Tempamine modestly reduced DOX cytotoxicity. Tempamine evoked a biphasic response: at concentrations lower than 200 micromol/L the nitroxide decreased DOX cytotoxicity, while at concentrations higher than 200 micromol/L, it enhanced DOX cytotoxicity. In contrast to Tempo and Tempol, Tempamine and Tempace ameliorated hydrogen peroxide cytotoxicity, but none of the nitroxides influenced TBARS stimulated by hydrogen peroxide. The cytoprotective effect of Tempace, Tempo and Tempol in DOX-treated cells correlated with the inhibition of DOX-induced lipid peroxidation. The bioreduction rates of the investigated nitroxides differed significantly and were variously affected by DOX depending on the nitroxide substituent. In combination with DOX, Tempo and Tempol were reduced significantly more slowly, while no influence of DOX on Tempamine and Tempace bioreduction was observed. Our results suggest that the structure of the 4-position substituent is an important factor for biological activity of piperidine nitroxides. Among the investigated nitroxides, Tempace displayed the best protective properties in vitro but Tempamine was the only nitroxide that potentiated cytotoxicity of DOX and did not influence DOX-induced lipid peroxidation. However, this nitroxide showed different performance depending on its concentration and conditions of oxidative stress.

Tempicol-3, a novel piperidine-N-oxide stable radical and antioxidant, with low toxicity acts as apoptosis inducer and cell proliferation modifier of Yoshida Sarcoma cells in vivo

The novel nitroxyl, Tempicol-3 (nitroxide-N-oxide) was synthesized and its capacity to act as a scavenger of hydroxyl radicals was tested. The concentration-dependent reducibility of this novel compound was also examined and compared with those of previously characterized nitroxides, Tempo and Tempace. The cytotoxicity of Tempicol-3 in vitro was measured by the modified tetrazolium assay (MTT), using, model cells for neoplastic phenotype (mouse NIH 3T3 fibroblast line). The ability of Tempicol-3 to act as an antitumor agent in vivo was also investigated in a pharmacological test, using rats bearing 3-day old Yoshida Sarcoma (promotion phase of the disease). Our results clearly indicated that Tempicol-3 acts as an effective and promising hydroxyl radical scavenger-antioxidant. Structure- and concentration-dependent bioreduction of Tempicol-3 by ascorbic acid may account for some of its biological effects, causing modulation of the antioxidant status of cells. The presence of one nitrone moiety per molecule of Tempicol-3 caused a significant decrease in nitroxide cytotoxicity as compared with Tempo, in vitro. The results clearly confirmed that the toxic effect could result either from the presence or structure of substituent(s) at position 4 of the free radical piperidine moiety. It can be stated that Tempicol-3 is a lowtoxicity nitroxide, which could be effective in providing antioxidative activity. We have also observed that lowtoxic Tempicol-3, at m.e.d. (minimal effective dose) suppressed tumorigenesis, acting as a cell proliferation modifier and apoptosis inducer in vivo. This work provides the base for further investigations on nitroxide-N-oxide derivatives since the serious question remains to be solved as to what is the molecular mechanism of action of the nitroxide-N-oxides.

Changes in plasma membrane fluidity of immortal rodent cells induced by anticancer drugs doxorubicin, aclarubicin and mitoxantrone

The aim of this study was to examine the effect of three structurally different anticancer drugs-the pro-oxidative anthracyclines doxorubicin (DOX) and aclarubicin (ACL), and antioxidative anthraquinone mitoxantrone (MTX) on the fluidity of plasma membrane of immortalized rodent fibroblasts using fluorescence spectroscopy and electron spin resonance (ESR) techniques. Two kinds of fluorescent probes (TMA-DPH and 12-AS) and spin labels (5-DS and methyl-12-DS) were used to monitor fluidity in the hydrophobic core and in the polar headgroup region of the lipid bilayer. Immortalized hamster B14 and NIH 3T3 mouse fibroblasts were exposed to DOX, ACL and MTX. We demonstrate that these drugs influence predominantly the hydrophobic core of the lipid bilayer, inducing significant decrease in its fluidity at low concentrations (2-5 microM). A decreased membrane fluidity at the surface of the lipid bilayer was observed only at a higher concentration (20 microM) of the drugs, which indicates that DOX, ACL and MTX intercalate mainly into the hydrophobic core of the membrane, thereby perturbing its structure.

TTT, a novel free radical spin trap, induces apoptosis in sarcoma Yoshida cells in vivo: comparative investigations of its cytotoxicity in vitro

In light of our previous SAR studies on nitroxides acting as less toxic anticancer agents, antioxidants and radioprotectors, we designed and tested, in vivo an in vitro, a new triradical spin trap -N,N',N"-tris-(l-oxyl-2,2,6,6-tetramethylpiperidine-4-yl)-1,3, 5-tnazine-2,4,6-triamine (TTT). The ability of TTT to act as an antitumor agent in vivo was investigated in pharmacological tests. The administration of TTT to rats bearing 3 day-old Sarcoma Yoshida (promotion phase of the disease) led to induction of apoptotic cell(s) death. Our results clearly indicated the suggested involvement of the free radical moiety of piperidine ring(s), thus indicating that the anticancer activity of nitroxide(s) may involve its intracellular redox reactions. To assess the relationship between the apoptotic effects of TTT in vivo and its possible cytotoxicity, we determined the relative antiproliferative and cytostatic potential of TTT in vitro as compared with this of the anticancer drugs: doxorubicin, aclarubicin and mitoxantrone, currently used in clinical practice in Poland. We found that TTT inhibits the growth and proliferation of two immortalized cell types-hamster B14 cell line and mouse NIH 3T3 fibroblasts which we used as a model for neoplastic phenotype, in a dose-dependent manner.

Antiproliferative and cytotoxic effects of N,N-diethylaminoethyl ethers of flavanone oximes: a comparison with anthracycline(s), anthraquinone and nitroxides action

Since flavanone oximes derivatives (ethers) have been shown to modulate the growth of Yoshida Sarcoma cells in vivo and to induce apoptosis, the effects of these substances on immortalized cell lines growth were examined. Cell viability and sensitivity to investigated substances was measured by the modified tetrazolium salt (MTT) assay. The antiproliferative effects were expressed as IC50 and IC90, respectively. There were very substantial differences in the dose-dependency of the observed antiproliferative and cytotoxic effects. The structure-activity relationship was evident and revealed that the substitution at B-ring of molecule seems to be an important factor in flavanone oxime (ether) potency. Compared to anticancer drugs (doxorubicin, aclarubicin and mitoxantrone) flavanone oximes displayed cytotoxicity at considerably higher concentrations. The antiproliferative action of the investigated model nitroxides depended on the free radical part of the molecule. N-hydroxy derivative (reduced cation form) did not influence cells proliferation and nor display any cytotoxicity at the applied range about 60 times higher than those of flavanone derivatives. Taken together it seems reasonable to suggest that flavanone oxime(s) (ethers) as compared with antracycline(s), anthraquinone and nitroxides might be especially good candidates for in the future development of new therapeutic techniques.

Anticancer potential of N,N-diethylaminoethyl ethers of flavanone oximes: a comparison with mitoxantrone action on rat Yoshida sarcoma cells in vivo

This study was performed to evaluate the anticancer abilities of four biologically active N,N-diethylaminoethyl ethers of flavanone oximes against rat Yoshida Sarcoma cells in vivo, and to investigate the mechanism(s) involved. The effects were compared with those of anthraquinone drug (mitoxantrone) action. The presented results provide the first evidence that all the investigated substances induce programmed cell death (apoptosis) of Yoshida Sarcoma cells in vivo. On interpretative grounds, the administration of investigated flavanone derivatives in the promotion phase of the disease led to both growth inhibition (cell cycle perturbation) and apoptosis. A correlation was found between structure of the substituent(s) at B-ring of substances and the revealed anticancer activity. The data suggest that flavanone derivatives (oxime ethers) besides their antiradical, antioxidant and radioprotector properties observed before, may act as promising anticancer agents acting in the promotion phase of disease. This finding prompted us to consider the development of a new strategy: modulation of effects using combination therapy involving mitoxantrone and flavanone oximes.

Changes in DNA supercoiling in fibroblasts cultured in the presence of hydralazine

We have analyzed changes in the supercoiling of nucleoid DNA of murine fibroblasts cultured in the presence of hydralazine. The entire DNA attached to the nuclear matrix was extracted from the cells and sedimented in neutral sucrose density gradients containing ethidium bromide. Nucleoids from cells treated with hydralazine responded to increasing ethidium bromide concentrations in a different way than those from control cultures. That is, supercoiled loops of DNA unwound with lower concentrations of ethidium bromide sedimented less rapidly than those of control cells, indicating that hydralazine reduced the degree of DNA supercoiling. Also, nucleoids from the drug-treated cells resisted the transition from relaxed to positive supercoiling at higher concentrations of ethidium bromide. Changes in nucleoid DNA supercoiling correlated directly with the dose of hydralazine in the fibroblast culture.

Single-strand breaks and repair in nuclear DNA in the presence of hydralazine assayed by the nucleoid technique

The nucleoid sedimentation assay was used to study hydralazine-induced DNA structural changes and repair in the fibroblasts cultured in vitro. The drug induced a dose dependent loss in negative DNA supercoiling due to the physical breakage of the DNA. Relaxation of supercoiled DNA resulted in the nucleoids sedimenting with lower velocities than those of undamaged control cultures. Repair incubation of the cells did not cause the restoration of DNA supercoiling to control level. Unsuccessful repair of DNA damaged by hydralazine may result in maintaining the damaged DNA in the cell which could have immunologic consequences.