Interaction of some polyoxotunstates with acetylcholinesterase

Polyoxometalates (POMs) are polyanionic oligomeric aggregates of transition metal ions, such as tungsten, molybdenum, vanadium, etc. held together by oxygen bridges, with a high density of negative charge. They are relatively stable, some even highly stable in aqueous solutions at biological pH values. In addition to applications in catalysis, separations, analysis, and as electrondense imaging agents, some of these complexes have been shown to exhibit biological activity in vitro as well as in vivo ranging from anti-cancer, antibiotic, and antiviral to antidiabetic effects. Recent investigations reported some polyoxotungstates as reversible inhibitors of acetylcholinesterase (AChE), making them potential anti-Alzheimer’s drugs. AChE is a serine hydrolase mainly found at neuromuscular junctions and cholinergic brain synapses. Its principal biological role is the termination of impulse transmission at cholinergic synapses. Reversible inhibitors of AChE mostly have therapeutic applications, while toxic effects are associated with irreversible AChE activity modulators. Reversible inhibitors play an important role in the pharmacological manipulation of the enzyme activity, and have been applied in the diagnostic and/or treatment of various diseases such as: myasthenia gravis, AD, postoperative ileus, bladder distention, glaucoma, as well as antidote to anticholinergic overdose. The effect of four new synthesized polyoxotungstates soluble in water on AChE activity was studied. AChE is purified from electric eel and commercially available. The enzyme was treated in vitro with polyoxotungstates in the concentration range from 1 × 10-7 to 1 × 10-3 mol/L at 37ºC for 15 minutes, and the incubation time was 12 min. The obtained dependence remaining enzyme activity vs. the inhibitor concentration fitted the sigmoidal function. IC50values, indicating the enzyme sensitivity toward the inhibitor and the inhibitory capacity of the analyzed compounds, were determined from the inhibition sigmoidal curves. Na10[H2W12O42] × 27H2O did not markedly reduce AChE activity at the highest investigated concentration (1 mmol/L). K7[SiV3W9O40] × 10H2O exhibited a weak inhibitory potential, causing 50% decrease in the enzyme activity at 5 × 10-4 mol/L. However, AChE sensitivity in the presence of K7[Ti2PW10O40] was several hundred times higher, reaching IC50 at 1.15 × 10-6 mol/L. Furthermore, (NH4)14[NaP5W30O110] × 31H2O demonstrated the strongest capacity to inhibit AChE. In the presence of its low concentration of 2 × 10-8 mol/L, the enzyme activity was noticeably reduced related to the control value (obtained without inhibitor), while 50% decrease in AChE activity was achieved at 3.8 × 10-7 mol/L.Fourth International Conferenceon Radiation and Applications in Various Fields of Research, RAD 2016, May 23-27, 2016, Niš, Serbi

The influence of synthesized polyoxotungstates on Na+/K+-ATPase activity

The in vitro influence of seven polyoxotungstates containing various central atoms on Na+/K+-ATPase activity was investigated. Na+/K+-ATPase is commercially available and purified from porcine cerebral cortex. The enzyme was exposed to the polyxotungstates in the concentration range from 1 × 10-10 to 2 × 10-3 mol/L, during 15 min at 37 °C and pH 7.4. All investigated compounds: K6[PV3W9O40] × 3H2O, K6H2[TiW11CoO40] × 13H2O, Na6[TeW6O24] × 22H2O, (NH4)14[NaP5W30O110] × 31H2O, Na10[H2W12O42] × 27H2O, K7[SiV3W9O40] × 10H2O, and K7[Ti2PW10O40] induced the enzyme inhibition in a concentration-dependent manner, but with various potencies. The dependence of the remaining Na+/K+-ATPase activity, expressed as a percentage of the control enzyme value (obtained without inhibitor), on the inhibitor concentrations fitted a sigmoidal function for all inhibiting polyoxotungstates. Inhibitory power of the investigated compounds was evaluated using IC50 values (polyoxotungstate concentration inducing 50% Na+/K+-ATPase inhibition), which were determined by Hill analysis. Na6[TeW6O24] × 22H2O and Na10[H2W12O42] × 27H2O affected enzyme activity with lowest potency, inducing half-maximum inhibition at millimolar concentrations, while the same effect was achieved in the presence of about hundred times lower concentrations of (NH4)14[NaP5W30O110] × 31H2O, K7[SiV3W9O40] × 10H2O, and K7[Ti2PW10O40]. Finally, K6[PV3W9O40] × 3H2O and K6H2[TiW11CoO40] × 13H2O were found as the most potent inhibitors of Na+/K+ATPase activity (IC50 = 3.3 × 10-7 mol/L and 1.1 × 10-6 mol/L, respectively). These results suggest potential biological applications of polyoxotungstates as inhibitors of Na+/K+-ATPase, the enzyme which has key role in normal functioning of most eukaryotic cells, as well as in development and progression of different cancers.Frontiers in Metal-Oxide Cluster Science IV and Final Meeting of COST Action CM12033 "Polyoxometalate Chemistry for Molecular Nanoscience 2016" : July 10-14, 2016, Newcastle Unicersity. Newcastle, UK

Polyoxopalladates as potential antitumor drugs: in vitro toxicity assessment

Polyoxopalladates (POPs) are a subclass of polyoxometalates (POMs) comprising discrete, anionic palladium(II)-oxo complexes. Although numerous studies have been conducted on the biological activity of POMs, their toxicity (e.g. nonselectivity) is frequently a limitation for real-world biomedical applications. Thus, the aim of this study was to evaluate the in vitro safety of the three POPs Pd13 As8 , SrPd12 As6 , and Pd13 (PhAs)8 , which exhibited strong antitumour activity against human neuroblastoma cell line SH-SY5Y, by performing a cyto/genotoxicity study on human healthy blood. Blood samples obtained from a healthy female donor were treated with three different concentrations (12.5, 25, and 50 µmol/L) of the POPs, and incubated at 37 oC for 4 and 24 h. A cytotoxicity (cell viability) assay was performed on isolated human peripheral blood lymphocytes stained with acridine orange and ethidium bromide. A genotoxicity test was carried out on whole blood by alkaline comet assay (microgel electrophoresis), and the percentage of tail DNA was used to assess the level of DNA damage. Pd13 As8 did not affect neither cell viability nor DNA damage, related to the control, at either of the investigated concentrations (after both 4 and 24 h). On the contrary, higher concentrations (25 and 50 µmol/L) of both SrPd12 As6 and Pd13 (PhAs)8 induced a statistically significant decrease in cell viability after 24 h (up to 42 %), and a relative increase of tail DNA (up to 3×) was observed at 50 µmol/L, after 24 h. Therefore, Pd13 As8 could be regarded as non-toxic to human healthy cells, whereas SrPd12 As6 and Pd13 (PhAs)8 require additional toxicity analysis.6th Croatian Congress of Toxicology with International Participation : CROTOX 2021 : Book of abstracts : October 3-6, 2021, Rabac, Croatia

Cyto/genotoxicity evaluation of promising antileukaemic palladium-based drugs

Polyoxometalates (POMs) are discrete, negatively charged metal-oxo clusters of early transition metal ions in high oxidation states. Their biological significance has greatly increased in recent years because of their approved anticancer, antibiotic, and antidiabetic properties. However, toxicity studies have reported adverse effects after in vivo POM studies, which limits their potential application in biomedicine. The aim of this study is to evaluate the in vitro cyto- and genotoxic properties of two polyoxopalladates(II) containing tetravalent metal ion guests, SnPd12 and PbPd12, that were found to possess potent antitumor activities against the human acute promyelocytic cell line HL-60. For this purpose, blood samples obtained from a healthy female donor were treated with three different concentrations (12.5, 25, and 50 µmol/L) of the tested POPs, and incubated at 37 o C for 4 and 24 h, respectively. Cytotoxicity studies were performed on isolated human peripheral blood lymphocytes which were stained with acridine orange and ethidium bromide, and then viewed under a fluorescence microscope. The genotoxicity was tested in whole blood by alkaline comet assay (microgel electrophoresis). The percentage of tail DNA was used to determine the level of DNA damage. The obtained cytotoxicity results indicated that neither SnPd12 nor PbPd12 induced statistically significant alterations of cell viability related to the control, at all of the investigated concentrations. Moreover, the results of the comet assay showed that none of the tested POPs resulted in a statistically significant relative increase of tail DNA. Accordingly, both SnPd12 and PbPd12 could be considered as safe promising antileukaemic drugs from a cyto/genotoxicity point of view.6th Croatian Congress of Toxicology with International Participation : CROTOX 2021 : Book of abstracts : October 3-6, 2021, Rabac, Croatia

Influence of polyoxopalladates(II) on ecto-nucleoside triphosphate diphosphohydrolases

Polyoxopalladates (POPs) are discrete, anionic palladium(II)- oxo nanoclusters combining properties of polyoxometalates and palladium(II), and thus are highly promising for the development of novel antitumor metallodrugs. The aim of this study was to investigate in vitro the influence of three POP salts with approved anti-neuroblastoma action, Na8[Pd13As8O34(OH)6]·42H2O (Pd13), Na4[SrPd12O6(OH)3(PhAsO3)6(OAc)3]·2NaOAc·32H2O (SrPd12), and Na6[Pd13O8(PhAsO3)8]·23H2O (Pd13L), on E-NTPDase activity using rat synaptic plasma membranes (SPMs) isolated from Wistar brain as a model system. Dose-dependent inhibition of ENTPDases was obtained within concentration range 2 × 10-6 - 1 × 10-3 mol/L for all investigated POPs. Inhibition parameters, IC50 value and Hill's coefficient, nH, were determined by sigmoidal fitting the experimental results. The calculated IC50 values were (1.08 ± 0.25) × 10-4 , (1.19 ± 0.13) × 10-4 , and (2.06 ± 0.88) × 10-4 mol/L for Pd13, SrPd12, and Pd13L, respectively, indicating their similar inhibitory strengths. The nH values were determined to be < 1, indicating negatively cooperative binding for all POPs studied. The observed inhibitory effect of these anti-neuroblastoma POPs on ENTPDase activity suggest that the inhibition of E-NTPDases, the enzymes representing the major part of purinergic signaling, could be considered as a putative mechanism of antitumor action and a new strategy in the development of novel antitumor therapeutics.The book of abstracts available at: [http://www.socphyschemserb.org/media/physical-chemistry-2021/abstracts.pdf

Inhibition of ecto-nucleoside triphosphate diphosphohydrolases by polyoxopalladates with promising antileukemic properties

Polyoxopalladates(II) (POPs) are the largest subset of polyoxo-noble-metalates (PONMs), representing a class of discrete, anionic noble metal-oxo nanoclusters. In this study, the in vitro effects of two isostructural, fully inorganic POP salts containing tetravalent metal ions (SnIV and PbIV) incorporated inside the cubic Pd12-oxo host-shell, Na12[SnIVO8Pd12(PO4)8]·43H2O (SnPd12) and Na12[PbIVO8Pd12(PO4)8]·38H2O (PbPd12), which were found to exhibit considerable antileukemic effects, on E-NTPDase activity were investigated using rat synaptic plasma membranes (SPMs) as a model system. Concentration-dependent inhibition of E-NTPDases was observed within the concentration range 5 × 10-6 - 2 × 10-4 mol/L for both POPs. Inhibition parameters, half-maximum inhibitory concentrations (IC50 values) and Hill's coefficients, nH, were determined by sigmoidal fitting the experimental results and Hill's analysis. The calculated IC50 values were (6.59 ± 1.09) × 10-5 and (9.88 ± 3.83) × 10-5 mol/L for SnPd12 and PbPd12, respectively. The calculated nH values were < 1, indicating negatively cooperative enzyme-inhibitor binding for both POPs. Accordingly, the confirmed antileukemic activities of SnPd12 and PbPd12 could be associated with the observed inhibition of E-NTPDases as a potential target of the antileukemic action of these promising drug candidates.The book of abstracts available at: [http://www.socphyschemserb.org/media/physical-chemistry-2021/abstracts.pdf

Razvoj novih antidijabetičkih lekova na bazi polioksometalatnih nanoklastera

Zahvaljujući brojnim istraživanjima koja su ispitivala biološka svojstva strukturno različitih polioksometalata, došlo se do zapažanja da ova kompleksna neorganska jedinjenja, pored antimikrobnog i antitumorskog delovanja, mogu biti delotvorna u snižavanju hiperglikemije kod pacova sa eksperimentalno izazvanim dijabetesom. Stoga, cilj ove studije je bio da se ispitaju antidijabetički potencijal i mogući toksični efekti dva polioksovolframata:(NH4 )14[NaP5 W30O110]·31H2 O, {NaP5 W30} i K14[AgP5 W30O110]·22H2 O·6KCl, {AgP5 W30}. U cilju realizacije postavljenog cilja, korišćena su tri eksperimentalna modela: (1) antihiperglikemijska screening studija u kojoj je ispitivan uticaj jednokratne intraperitonealne primene {NaP5 W30} i {AgP5 W30} (5, 10 i 20 mg/kg) na snižavanje hiperglikemije kod dijabetičkih pacova, (2) akutna peroralna toksikološka studija koja je istraživala hepato- i nefrotoksične efekte odabranih heteropolivolframata kod zdravih pacova i (3) studija posvećena rasvetljavanju mogućih mehanizama antidijabetičkog delovanja heteropolivolframata. Rezultati screening studije su pokazali da su oba ispitivana heteropolivolframata efikasna u snižavanju hiperglikemije, s tim što se {NaP5 W30}, u odnosu na {AgP5 W30}, pokazao kao moćniji antihiperglikemijski agens. Rezultati biohemijskih parametara funkcije i patohistološka analiza jetre i bubrege korišćenjem konvencionalne svetlosne i transmisione elektronske mikroskopije pokazuju da dvonedeljna primena {NaP5 W30} i {AgP5 W30} (20 mg/kg) izaziva blagi do umereni stepen hepato- i nefrotoksičnosti kod zdravih životinja. U poslednjem eksperimentalnom protokolu, pokazano je da tronedeljna peroralna primena {NaP5 W30} (20 mg/kg) povećava koncentraciju insulina u serumu dijabetičkih pacova, što može biti jedan od mehanizama njegovog antidijabetičkog delovanja. Takođe, pokazano je da {NaP5 W30} ispoljava hepato-, nefro-, kardio- i neuroprotektivno dejstvo kod dijabetičkih pacova, što je procenjeno na osnovu analize: (1) relativne mase organa, (2) biohemijskih parametara funkcije, (3) parametara oksidativnog stresa u homogenatu tkiva, (4) aktivnosti acetilholinesteraze, Na+ /K+-ATPaze i ecto-ATPaza u sinaptozomima i (5) patohistoloških promena u tkivima korišćenjem konvencionalne svetlosne i transmisione elektronske mikroskopije. Stoga, {NaP5 W30} i {AgP5 W30} mogu se smatrati mogućim neinsulinskim lekovima-kandidatima u terapiji dijabetesa tipa 2, koji bi se podvrgli daljim pretkliničkim istraživanjima.Simpozijum „Stremljenja i novine u medicini“ Medicinskog fakulteta u Beogradu, Beograd, 04-08. decembra, 2023