Biomedical subjects

R Supino

Publications and source records attributed to R Supino.

100 records · Page 6Linked to original sources

PubMedDate not supplied

Influence of daunorubicin on membrane permeability properties: detection by means of intracellular accumulation and efflux of fluorescein.

The influence of daunorubicin (DNR) on membrane permeability properties was assessed by studying the ability of living HeLa cells to exhibit fluorochromasia; that is, to take up a fluorogenic substrate and retain the fluorescent compound obtained by enzymatic reaction. The intracellular accumulation of the fluorescent product as well as its release by the cells may be considered indicators of the permeability properties, since both processes are mediated by the cell membrane. The influence of the drug on the accumulation and on the efflux of fluorescein, obtained intracellularly from the hydrolysis of fluorescein diacetate (FDA), was evaluated, after DNR treatment, by measuring the fluorescence intensity of the product in single living cells by flow cytometry. The results showed that DNR, up to a concentration of 5 X 10(-6) M, did not significantly affect the accumulation of fluorescein. On the contrary, the efflux was strongly inhibited. A comparative study of the influence of drugs with known action mechanism was performed with the membrane-active compound hydrocortisone (HC) and with the metabolic inhibitor KCN. The results obtained indicate that DNR significantly affects membrane permeability properties and that its influence is similar to that exerted by metabolic inhibitors.

Cell Membrane Permeability↗

PubMedDate not supplied

Role of apoptotic response in cellular resistance to cytotoxic agents.

The development of drug resistance is a major obstacle to effectiveness of chemotherapeutic treatment of human tumors with cytotoxic agents. Drug resistance is described as a multifactorial phenomenon, involving the expression of defense factors and/or detoxification mechanisms, alterations in drug-target interactions, and cellular response to specific cytotoxic lesions (in particular, DNA damage). Although the proposed mechanisms may contribute to the development of a variable degree of cellular resistance, it is possible that the cell response (i.e., DNA repair or apoptosis) following DNA damage plays a critical role in determining cellular chemosensitivity. The preclinical observations that tumor response to effective drug treatments is associated with induction of apoptosis support the possibility that a decreased susceptibility to apoptosis (apoptosis resistance) is relevant to clinical resistance. A number of molecular alterations associated with transformation and/or tumor progression may also be implicated in regulation of cell death pathways and in the development of drug resistance. There is evidence that the wild-type p53 is involved in cellular response to DNA damage, including cell cycle regulation, DNA repair, and activation of the pathway leading to apoptosis. Loss of wild-type p53 function could cause resistance to DNA-damaging agents, as a consequence of abrogation of p53-dependent apoptosis. The identification of new agents able to trigger p53-independent apoptosis and the search for biochemical modulators downstream of p53 may be of clinical relevance because many tumors are deficient in p53 function due to mutation or deletion. An overview of the resistance mechanisms is presented, with particular reference to the role of p53 mutations in clinical resistance and of apoptosis-related genes in cellular chemosensitivity.

Animals↗

PubMedDate not supplied

New developments in antitumor anthracyclines.

Doxorubicin is a major anticancer agent introduced to extended clinical use in the early 1970s. The fulfillment of a wide program of analogue synthesis led to the development of the better tolerated epirubicin and of a highly potent antileukemic drug, idarubicin. In recent years, on the basis of the available information on the molecular requirements for action, a new synthetic program, coupled with target-oriented pharmacological experiments, was carried out. Various interesting derivatives, namely, the 8- and 10-fluoro compounds and the disaccharides, were obtained. The latter compounds exhibited a strong dependence of biological activity on the orientation (axial vs. equatorial) of the second sugar moiety, daunosamine. A member of this group, namely, 7-O-(4'-O-alpha-L-daunosaminyl-2'-deoxy-alpha-L-fucosyl)-4-demetho xy-adriamycinone, is presently undergoing clinical trials as a third generation antitumor anthracycline.

Animals↗

PubMedDate not supplied

On the combination of photodynamic therapy with ionizing radiation.

Ehrlich ascites carcinoma growth and cell damage have been examined after photodynamic therapy (PDT), radiotherapy (RT) and combined treatment. Haematoporphyrin dimethyl ether (HPde) is used as a photosensitizer for PDT and tested as a radiosensitizer for RT. For PDT a non-coherent light source (370 < lambda < 680 nm) equipped with filters is used. gamma-Irradiation consists of 60Co irradiation at a dose of 2 Gy. Both PDT and RT induce a significant delay and inhibition in tumour growth (33 and 38%, respectively). Nevertheless cell damage after these treatments is different: after PDT the cell membrane integrity is damaged and no serious chromosomal aberrations are observed; whereas after gamma-irradiation there is no cell membrane integrity damage, but more significant DNA injuries are observed. It seems evident that HPde is able to act as a photosensitizer as well as a radiosensitizer. Combining PDT and RT produces an additive effect, not dependent on the sequence in which the two treatments are given, when a 1 h time window is used.

Animals↗

PubMedDate not supplied

Effect of daunorubicin and adriamycin on nucleic acid synthesis of serum stimulated mouse embryo fibroblasts.

This paper reports the effects of daunorubicin and adriamycin on DNA and RNA synthesis of in vitro cultured mouse embryo fibroblasts (MEF) stimulated by fetal calf serum (FCS). The addition of FCS to quiescent MEF cultures brings about a wave of RNA synthesis, followed by DNA synthesis which starts between 8 and 12 h after change of medium and proceed for up to 24 h. These cells are therefore partially synchronized. The level of DNA synthesis depends on the amount of FCS added. Daunorubicin and adriamycin are almost equally effective in inhibiting DNA synthesis, as well as cell proliferation, which takes place later. Adriamycin is more active than daunorubicin on RNA synthesis. In cultures treated for an 8 h period starting at different times after FCS addition, the highest DNA synthesis inhibition is achieved by treatment during the first 8 h, when DNA synthesis has not yet started. The cellular uptake of daunorubicin is constantly higher than that of adriamycin, in any experimental condition tested. The results show that FCS-stimulated MEFcan provide a simple method for studying the effects of anthracycline antibiotics on partially synchronized cells.

Animals↗

PubMedDate not supplied

Topoisomerase II alpha and beta in human tumor cells grown in vitro and in vivo.

The cellular content and the cell-cycle distribution of the 170 kD- and 180 kD-isoforms of DNA topoisomerase II were investigated in human tumor cells with specific monoclonal antibodies and by immunofluorescent detection with flow cytometry. Levels of topo II alpha were almost three-fold higher than the beta-isozyme in exponentially growing cells in vitro. In contrast, topo II alpha but not beta, was markedly reduced in plateau-phase cells. Tumor cells from surgical biopsies, mainly in G0/G1 phase, exhibited a 95% beta- versus 5% alpha-isoform expression. These results support the hypothesis that topo II alpha is mainly related to DNA synthesis, and topo II beta to DNA transcription.

Antibodies, Monoclonal↗

PubMedDate not supplied

Metabolic energy availability and proliferative activity in adriamycin-treated cells.

Metabolic energy availability and proliferative activity were studied in HeLa cells treated with Adriamycin (Adr). Conditions (ID50) that induced growth delay, without significant cell lethality, did not appreciably alter ATP content, over 72 hours after treatment. Energy-dependent membrane permeability properties, assessed with the vital dye fluorescein, were similarly unaffected. The cytostatic effect was confirmed by the incorporation rate of 3H-thymidine and 14C-leucine, and by flow cytometric analysis of cell cycle progression. Early depletion in cellular ATP occurred when Adr induced an evident cytocidal effect.

Adenosine Triphosphate↗

PubMedDate not supplied

Doxorubicin resistance circumvention by verapamil in B16 melanoma cells.

We present data on the cellular drug pharmacokinetic alterations correlated with the circumvention of doxorubicin resistance by verapamil in a B16 melanoma cell line. An increased drug uptake, a decreased drug efflux and a different intracellular drug distribution appear to be responsible for the enhancement of doxorubicin cytotoxicity induced by treatment with verapamil in drug-resistant cells. However, doxorubicin pharmacokinetics and cytotoxicity were not affected by verapamil in doxorubicin-sensitive melanoma cells.

Animals↗

PubMedDate not supplied

Free radical-dependent DNA lesions are involved in the delayed cardiotoxicity induced by adriamycin in the rat.

The role of free radicals in the genesis of adriamycin (ADR)-induced delayed cardiotoxicity and the cardioprotective effects of the spin trap N-tert-butyl-alpha-phenylnitrone (PBN) were investigated in an in vivo rat model. As ADR and free radicals are no longer present in the myocardium by the time the delayed effects of the drug become apparent, ADR has been proposed to act by causing early radical-dependent DNA lesions, resulting in impaired synthesis of critical target proteins. DNA lesions were detected 10 days after ADR treatment (3X3 mg/kg i.v.) and were still present at the time of onset of the delayed cardiomyopathy. PBN, administered by a slow-release osmotic pump to maintain constant plasma levels throughout the time of persistence of ADR in the myocardium (approximately 2 weeks), prevented the development of DNA lesions, as well as the late contractile and electrical impairment induced by the anthracycline, thus supporting the hypothesis that free radicals play a causal role in both phenomena.

Animals↗

PubMedDate not supplied

The spin trap alpha-phenyl-tert-butyl nitrone protects against myelotoxicity and cardiotoxicity of adriamycin while preserving the cytotoxic activity.

The possibility of preventing the myelo- and cardiotoxicity of adriamycin (ADR), was explored in in vivo experiments in the rat. Assuming that free radicals play a key role in the ADR organotoxicity, a new anti-radical approach was set up by administering a spin trapping compound (PBN) which is taken up by the cells and specifically interacts with radicals. ADR was given i.v., 3 mg/kg every 3rd day for 3 times. PBN was continuously administered throughout the persistence time of ADR in myocardium (15 days). Serial ECG and leukocyte counting were performed during 10 weeks, then hearts were isolated and Langendorff-perfused; functional parameters (heart rate, contractility, coronary flow) were evaluated. PBN improved ECG and prevented the myelotoxicity, while functional parameters were not significantly different from those of control. Cytotoxicity was evaluated in vitro in 3 different human tumour cell lines; PBN did not modify the cytotoxicity of ADR, thus excluding a free radical involvement in this activity. The present results suggest that a proper administration schedule of spin traps might be a promising approach for improving the therapeutic index of ADR.

Animals↗