Szulim Ber Zyngier

Arachidonic acid cytotoxicity in leukocytes: implications of oxidative stress and eicosanoid synthesis

Arachidonic acid (AA)‐induced cytotoxicity was evaluated in leukocytes: the human leukemia cell lines HL‐60, Jurkat and Raji and in rat lymphocytes. Such cytotoxicity was dose‐ and time‐dependent. At concentrations below 5 μM, AA was not toxic; at 10–400 μM, AA induced apoptosis and at concentrations beyond 400 μM, necrosis. The minimum exposure time to trigger cell death was of around 1 h, but the effect was increased by longer exposure times until 6–24 h. Apoptosis was morphologically characterized by a decrease in cell and nuclear volume, chromatin condensation and DNA fragmentation and the presence of lipid bodies, without changes in organelle integrity. Biochemically, AA‐induced apoptosis was associated with internucleosomal fragmentation and caspase activation, evaluated by PARP cleavage and the use of a caspase inhibitor. Necrosis was characterized by increased cell volume, presence of loose chromatin, appearance of vacuoles, loss of membrane integrity and of the definition of organelles. The apoptotic effect of AA was studied as to oxidative—reductive imbalance and the participation of eicosanoids. Apoptotic AA treatment was accompanied by an increase in the quantity of thiobarbituric acid reactive substances (TBARS), low‐level chemiluminescence and in the glutathione disulfide/reduced glutathione ratio, indicating oxidative stress. The addition of tocopherol, ascorbate, prostaglandin E2 and lipoxygenase inhibitors delayed cell death, whereas the inhibition of cyclooxygenase promoted AA‐induced cell death. Cell treatment with AA was accompanied by increased cellular production of LTB4. AA, therefore, is cytotoxic at physiological and supraphysiological concentrations, causing apoptosis and necrosis. Cell treatment with apoptotic concentrations of AA involves oxidative stress and changes in eicosanoid biosynthesis.

Water-soluble rhodium(II) carboxylate adducts: Cytotoxicity of the new compounds

Rhodium(II) carboxylate (acetate, propionate, and butyrate) adducts with isonicotinic acid (Hisonic) were prepared for study. Elemental analyses and electronic spectroscopy show that the adducts contain two isonicotinic acid ligands coordinated in the axial position at the pyridinic nitrogen. The in vitro (K562 human leukemic cell line) assay and LD10 in mice results, in addition to tests of solubility, suggest that, in the presence of blood lipids or cellular membrane, the adducts dissociate into the parent compounds and the rhodium(II) carboxylate enters the cell to carry out its biological effects.

Rh2(CF3CONH)4: The First Biological Assays of a Rhodium (II) Amidate

The rhodium (II) complexes Rh2(tfa)4.2(tfac) and Rh2(tfacam)4 (tfacam = CF3CONH-,tfa = CF3COO-,tfac = CF3CONH2) were synthesized and characterized by microanalysis and electronic and vibrational spectroscopies. Rh2(tfacam)4 was tested both in vitro (U937 and K562 human leukemia cells and Ehrlich ascitic tumor cells) and in vivo for cytostatic activity and lethal dose determination, respectively. This is the first rhodium tetra-amidate to have its biological activity evaluated. The LD50 value for Rh2(tfacam)4 is of the same order as that of cisplatin, and it was verified that the rhodium complex usually needs lower doses than cisplatin to promote the same inhibitory effects.

Metformin reduces the stimulatory effect of obesity on in vivo Walker-256 tumor development and increases the area of tumor necrosis

AIMS The objective of this study was to analyze the influence of obesity and insulin resistance on tumor development and, in turn, the effect of insulin sensitizing agents. MAIN METHODS Male offspring of Wistar rats received monosodium glutamate (400mg/kg) (obese) or saline (control) from the second to sixth day after birth. Sixteen-week-old control and obese rats received 5×10(5) Walker-256 tumor cells, subcutaneously injected into the right flank. Some of the obese and control rats received concomitant treatment with metformin (300mg/kg) by gavage. At the 18th week, obesity was characterized. The percentage of rats that developed tumors, the tumor relative weight and the percentage of cachexia incidence were analyzed. The tumor tissue was evaluated histologically by means of hematoxylin and eosin staining. KEY FINDINGS Metformin did not correct the insulin resistance in obese rats. The tumor development was significantly higher in the obese group, whereas metformin treatment reduced it. After pathological analysis, we observed that the tumor tissues were similar in all groups except for adipocytes, which were found in greater quantity in the obese and metformin-treated obese groups. The area of tumor necrosis was higher in the group treated with metformin when compared with the untreated one. SIGNIFICANCE Metformin reduced Walker-256 tumor development but not cachexia in obese rats. The reduction occurred independently of the correction of insulin resistance. Metformin increased the area of necrosis in tumor tissues, which may have contributed to the reduced tumor development.

Effects of human serun albumin in some biological properties of rhodium(II) complexes

The affinities for human albumin (HSA) of five rhodium(II) complexes of general formula [Rh2(bridge)4] (bridge = acetate, propionate, butyrate, trifluoroacetate and trifluoroacetamidate) were determined by spectrophotometry. In the case of the alkylcarboxylates, an inverse correlation of affinity with their liposolubilities was observed. Diffusion of the free or protein-bound complexes into Ehrlich cells in vitro seems to be primarily governed by the hydrophobic character of the complex. The complex [Rh2(tfc)4] exhibited affinity towards the protein (K = 214.1) as well as cell partition both in the absence (32.1%) and presence (48.6%) of HSA. The compound HSA: [Rh2(tfc)4] has had its antitumoral action in tumor-bearing Balb-c mice investigated, showing that HSA can be a drug reservoir for the rhodium complex.

Biological activity of metal-edds (ethylenediaminedisuccinate) complexes in K562 and PBMC cells

O efeito do acido S,S-etilenodiaminodi-succinico (edds) na supressao da oxidacao do acido ascorbico catalisada por metais (Mn, Fe, Co, Ni, Cu, Zn) foi testado in vitro atraves da oxidacao da sonda fluorescente cloreto de 1,2,3-diidrorodamina. A atividade pro-oxidante do ferro nao foi totalmente suprimida, mesmo sob excesso molar de quatro vezes do ligante. O efeito do meio de cultura na toxicidade dos complexos para celulas mononucleares do sangue periferico (PBMC) e da linhagem K562 foi estudado. A citotoxicidade de Fe-edds foi abolida na presenca de Trolox ou de proteinas do soro. Os provaveis mecanismos de toxicidade celular foram investigados atraves do bloqueio de transportadores de monocarboxilatos (MCT) e estudos de ciclo celular por citometria de fluxo. Celulas tratadas com os complexos metalicos e com o acido A -ciano-4-hidroxicinâmico, um conhecido bloqueador de MCT, mostraram recuperacao de viabilidade, sugerindo que esses transportadores possam estar envolvidos na internalizacao dos complexos metal-edds. O acido livre promoveu a parada do ciclo celular na fase G0/G1 (PBMC) ou S (K562), sugerindo dano direto ao DNA ou interferencia na sua duplicacao. The effect of S,S-ethylenediaminedisuccinic acid (edds) on the quenching of metal-catalyzed (metal = Mn, Fe, Co, Ni, Cu, Zn) oxidation of ascorbic acid was tested in vitro via oxidation of the fluorescent probe 1,2,3-dihydrorhodamine dihydrochloride. The pro-oxidant activity of iron was not fully suppressed, even at a four-fold molar excess of the ligand. The effect of serum on the toxicity to peripheral blood mononuclear cells (PBMC) and K562 cells was investigated. The cytotoxic effect of Fe-edds was abrogated in the presence of Trolox or serum proteins. The probable pathways of cell toxicity were investigated through blocking of the monocarboxylate transporters (MCT) in association with cell cycle studies by flow cytometry. Cells treated with metal complexes and A -cyano-4-hydroxycinnamic acid, a known MCT inhibitor, showed recovery of viability, suggesting that MCT proteins may be involved in the internalization of metal-edds complexes. The free acid induced cell cycle arrest in G0/G1 (PBMC) and S (K562) phases, suggesting direct DNA damage or interference in DNA replication.

Survival and Histopathological Study of Animals Bearing Ehrlich Tumor Treated With a Rhodium(II) Amidate.

The survival of 90% of a tumor-bearing population treated with the complex Rh2 (CF3CONH)4 was examined and the pharmacological parameter Surv90 determined. Histopathological alterations raised for this drug in several tissues were studied in Balb-c mice. A Surv90 dose of 3.8x 10-5 mol/kg was found.

Distribution of Rhodium in Mice Submitted to Treatment With the Adduct of Rhodium Propionate and Sodium Isonicotinate

The distribution of rhodium in Balb/c mice following intraperitoneal (ip) administration of a solution of adduct of rhodium propionate and sodium isonicotinate has been investigated. The metal concentration was determined in blood and in the following organ tissues: brain, heart, lung, liver, spleen, kidney, testes, and uterus/ovary, and the rhodium concentration was obtained by Inductively Coupled Argon Atomic Emission Spectroscopy (ICP-AES). The metal was detected in all organ tissues examined, mainly in spleen, liver, uterus/ovary and heart. Nine days after the injection, traces of rhodium were found in the liver and kidneys and, twenty days after the injection, only in the liver.

Qualitative erythrocyte enzymatic disorder in Ehrlich tumor-bearing mice

SummaryErythrocyte glutathione reductase Michaelis-Menten constant was found to be significantly increased in Ehrlich tumour bearing mice, indicating a clear qualitative disturbance due to a neoplastic process. No changes were observed in glucose-6-phosphate dehydrogenase.

Apoptosis induced by metal complexes and interaction with dexamethasone.

Apoptosis induced by rhodium II amidate, rhodium II propionate, cisplatin and interactions with dexamethaxone were studied on some human leukemia cell lines Raji, Jurkat and U937. Apoptosis was studied by flow cytometry, agarose gel electrophoresis and morphological analysis. Rhodium II propionate induced apoptosis in all the three cell lines, Rhodium II amidate, in the lymphoid cell lines Jurkat and Raji, and cisplatin, only in the Jurkat, a T lymphoid cell line. It has also been observed that the addition of dexamethasone enhances the apoptosis index only in U937, a monocytic line with a glucocorticoid receptor bearing.