Combined modality of 2-formylpyridine monothiosemicarbazonato copper(II) and radiation

Selectivity of a thiosemicarbazonatocopper(ii) complex towards duplex RNA. Relevant noncovalent interactions both in solid state and solution

Thiosemicarbazones and their metal derivatives have long been screened as antitumor agents, and their interactions with DNA have been analysed. Herein, we describe the synthesis and characterization of compounds containing [CuL]⁺ entities (HL = pyridine-2-carbaldehyde thiosemicarbazone) and adenine, cytosine or 9-methylguanine, and some of their corresponding nucleotides. For the first time, crystal structures of adenine- and 9-methylguanine-containing thiosemicarbazone complexes are reported. To the best of our knowledge, the first study on the affinity thiosemicarbazone-RNA is also provided here. Experimental and computational studies have shown that [CuL(OH₂)]⁺ entities at low concentration intercalate into dsRNA poly(rA)·poly(rU) through strong hydrogen bonds involving uracil residues and π-π stacking interactions. In fact, noncovalent interactions are present both in the solid state and in solution. This behaviour diverges from that observed with DNA duplexes and creates an optimistic outlook in achieving selective binding to RNA for subsequent possible medical applications.

Nitrogen, sulfur and oxygen donor adducts with copper(II) complexes of antitumor 2-formylpyridinethiosemicarbazone analogs: physicochemical and cytotoxic studies

The preparation of N-, S- and O-donor ligand adducts with CuX+ (HX = 6-methyl-2-formylpyridinethiosemicarbazone (6HL); 2-formylpyridine-2'-methylthiosemicarbazone (2'L); 2-formylpyridine-4'-methylthiosemicarbazone (4'HL) is described. The N-donors, 2,2'-bipyridyl (bipy), 4-dimethylaminopyridine (dmap) give the complexes [Cu(6L)(bipy)]PF6, [Cu(6L)(bipy)]Cl.5H2O, [Cu(4'L)(bipy)]PF6, [Cu(6L)(dmap)2]PF6.2.5 H2O and [Cu(4'L)(dmap)2]PF6.H2O which have been characterized by physical and spectroscopic techniques. Pentafluorothiophenolate (pftp) gives S-donor complexes [CuX(pftp)] (X = 6L and 4'L) and thiolato co-ordination is proposed on the basis of spectroscopic evidence. Paratritylphenolate (ptp) and HPO4(2-) give O-donor complexes [Cu(6L)(ptp)], [Cu(4'L)(ptp)], [¿Cu(6L)¿2HPO4].4H2O, and [¿Cu(4'L)¿2HPO4].5H2O which have been characterized by physical and spectroscopic techniques, as have the precursor complexes [Cu(6L)(CH3COO)].H2O, [Cu(4'L)(CH3COO)], Cu(6HL)(CF3COO)](CF3COO).0.5H2O, [Cu(4'HL)(CF3COO)](CF3COO), [Cu(2'L)Cl2) and [Cu(2'L)(NO3)2]. Protonation constants for the ligands and some of their complexes have been determined. 2-Formylpyridinethiosemicarbazone (HL) complexes of silver, gold, zinc, mercury, cadmium and lead are also discussed. Cytotoxicity against the human tumor cell line HCT-8 and antiviral data for selected compounds are presented.

Copper radionuclides and radiopharmaceuticals in nuclear medicine

The chemistry, radiochemistry, radiobiology, and radiopharmacology of radiopharmaceuticals containing copper radionuclides are reviewed. Copper radionuclides offer application in positron emission tomography, targeted radiotherapy, and single photon imaging. The chemistry of copper is relatively simple and well-suited to radiopharmaceutical application. Current radiopharmaceuticals include biomolecules labelled via bifunctional chelators primarily based on cyclic polyaminocarboxylates and polyamines, and pyruvaldehyde-bis(N4-methylthiosemicarbazone) (PTSM) and its analogues. The chemistry of copper, of which only a fraction has yet been exploited, is likely to be applied more fully in the future.

Inhibition of iron uptake in HL60 cells by 2-formylpyridine monothiosemicarbazonato Cu(II)

The electron paramagnetic resonance (EPR) signal of the tyrosyl radical attributed to ribonucleoside diphosphate reductase decreases after treatment of promyelocytic leukemic HL60 cells with 2-formylpyridine thiosemicarbazonato copper(II) (CuL). According to EPR studies, CuL forms adducts with both histidine and cysteine-like Lewis bases associated with isolated membranes from HL60 cells. After the addition of CuL, the EPR signal for the cysteine-like adduct decreases substantially over a 15-min period. The reduction of signal is consistent with oxidation of thiols as shown by an analysis of sulfhydryl content. It is hypothesized that receptor-mediated transferrin internalization is inhibited by oxidation of critical thiols. Since the uptake of 59Fe-transferrin is greatly inhibited by the treatment of HL60 cells with CuL, the reduced uptake of iron by cells, in the presence of CuL, may lead to decreased iron availability for the activity of the M2 subunit of ribonucleotide reductase and a subsequent decrease in the tyrosyl radical signal of the enzyme. Moreover, the intact subunit M2 is no longer detected by EPR, even after the addition of excess iron.

Pharmacological perturbation of murine melanoma growth by copper chelates

Groups of BDF1 and DBA mice were treated with either the cupric chelate of nitrilotriacetic acid (NTA-Cu+2) or the cuprous chelate of neocuproine (NC-Cu+1) every other day for 7 days prior to either i.p. or s.c. inoculation with 10(6) viable B16 melanoma cells, and then every other day for 15 days post-tumor inoculation. This treatment schedule was non-toxic to host mice. NC-Cu+1 acted as a tumor growth promoting factor in mice by enhancing tumorigenicity, stimulating body weight gain, inhibiting encapsulation of i.p. tumors that permitted growth as unrestrained ascites, and increasing final tumor weight over a shortened host survival period regardless of the site of tumor inoculation. Treatment with NTA-Cu+2 inhibited pigmentation in DBA mice bearing s.c. tumors, while treatment with NC-Cu+1 enhanced tumor pigmentation regardless of the site of tumor inoculation and murine strain. These results suggest that exogenous copper in the form of chelates alters the growth characteristics of a copper-requiring tumor system in both a copper-chelate- and murine-specific manner, and further suggests that the growth promoting activity of exogenous copper in the B16 melanoma system involves both enhanced copper nutrition and concomitant alteration of host reactions to tumors.

Effects of 2-formylpyridine monothiosemicarbazonato copper II on red cell components

1-Formylpyridine monothiosemicarbazonato copper II (CuL+) is readily taken up by red cells and is initially bound to glutathione and hemoglobin. Glutathione was depleted within 5 hr of incubation, presumably by oxidation mediated by CuL+ and O2 with concomitant generation of toxic oxygen species. Cupric ion was slowly transferred from CuL+ to hemoglobin within about 7 hr and hemoglobin was oxidized until the major form prevailing after 10 hr was alpha 2 beta 2+. Little increase in hemolysis due to addition of CuL+ dissolved in the radical scavenger dimethyl sulfoxide was observed with prolonged incubation. Strong inhibition of red cell hexokinase by CuL+ was observed when the enzymes in red cell lysates and hemoglobin-free red cell lysates were examined. CuL+ was also an effective inhibitor of yeast hexokinase. However, the inhibitory effect of CuL+ within the red cells was less pronounced. It is suggested that even though intracellular accumulation of CuL+ creates an oxidizing environment and is potentially capable of inhibiting thiol enzymes such as hexokinase, protective effects are exerted in the red cell by the presence of hemoglobin, of radical scavengers, and of high levels of enzymes that detoxify toxic oxygen species.

Binding of 2-formylpyridine monothiosemicarbazonato copper II to cat and normal human hemoglobins

The antitumor agent 2-formylpyridine monothiosemicarbazonato copper(II) forms adducts with sulfur and nitrogen donor atoms from cat hemoglobin but only nitrogen donor atoms from human hemoglobin. Improved resolution of the mI = 1/2 lines in the g parallel region at S-band not only confirms the number of nitrogen donor atoms in the square planar configuration but provides evidence for strong coupling from a proton. Adduct formation results in an increase in the oxygen affinity of hemoglobin. Thus, it is suggested that allosteric enzyme inhibition may be a mechanism for the action of this agent.