The Ca2+-ATPase Inhibition Potential of Gold(I, III) Compounds

Evaluation of Gold Complexes to Address Bacterial Resistance, Quorum Sensing, Biofilm Formation, and Their Antiviral Properties against Bacteriophages

The worldwide increase in antibiotic resistance poses a significant challenge, and researchers are diligently seeking new drugs to combat infections and prevent bacterial pathogens from developing resistance. Gold (I and III) complexes are suitable for this purpose. In this study, we tested four gold (I and III) complexes, (1) chlorotrimethylphosphine gold(I); (2) chlorotriphenylphosphine gold(I); (3) dichloro(2-pyridinecarboxylate) gold (III); and (4) 1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene gold(I) chloride, for their antibacterial, antibiofilm, antiviral, and anti-quorum sensing activities. Results reveal that 1 significantly inhibits Escherichia coli DSM 1077 and Staphylococcus aureus ATCC 6538, while 2, 3, and 4 only inhibit S. aureus ATCC 6538. The minimum inhibitory concentration (MIC) of 1 for S. aureus ATCC 6538 is 0.59 μg/mL (1.91 μM), and for methicillin-resistant S. aureus strains MRSA 12 and MRSA 15, it is 1.16 μg/mL (3.75 μM). For E. coli DSM 1077 (Gram-negative), the MIC is 4.63 μg/mL (15 μM), and for multi-resistant E. coli I731940778-1, it is 9.25 μg/mL (30 μM). Complex 1 also disrupts biofilm formation in E. coli and S. aureus after 6 h or 24 h exposure. Moreover, 1 and 2 inhibit the replication of two enterobacteria phages. Anti-quorum sensing potential still requires further clarification. These findings highlight the potential of gold complexes as effective agents to combat bacterial and viral infections.

Inhibition of SERCA and PMCA Ca(2+)-ATPase activities by polyoxotungstates

Plasma membrane calcium ATPases (PMCA) and sarco(endo) reticulum calcium ATPases (SERCA) are key proteins in the maintenance of calcium homeostasis. Herein, we compare for the first time the inhibition of SERCA and PMCA calcium pumps by several polyoxotungstates (POTs), namely by Wells-Dawson phosphotungstate anions [P₂W₁₈O₆₂]^6- (intact, {P₂W₁₈}), [P₂W₁₇O₆₁]^10- (monolacunary, {P₂W₁₇}), [P₂W₁₅O₅₆]^12- (trilacunary, {P₂W₁₅}), [H₂P₂W₁₂O₄₈]^12- (hexalacunary, {P₂W₁₂}), [H₃P₂W₁₅V₃O₆₂]^6- (trivanadium-substituted, {P₂W₁₅V₃}) and by Preyssler-type anion [NaP₅W₃₀O₁₁₀]^14- ({P₅W₃₀}). The speciation in the solutions of tested POTs was investigated by ³¹P and ⁵¹V NMR spectroscopy. The tested POTs inhibited SERCA Ca²⁺-ATPase activity, whereby the Preyssler POT showed the strongest effect, with an IC₅₀ value of 0.37 μM. For {P₂W₁₇} and {P₂W₁₅V₃} higher IC₅₀ values were determined: 0.72 and 0.95 μM, respectively. The studied POTs showed to be more potent inhibitors of PMCA Ca²⁺-ATPase activity, with lower IC₅₀ values for {P₂W₁₇}, {P₅W₃₀} and {P₂W₁₅V₃}.

Decavanadate and metformin-decavanadate effects in human melanoma cells

Decavanadate is a polyoxometalate (POMs) that has shown extensive biological activities, including antidiabetic and anticancer activity. Importantly, vanadium-based compounds as well as antidiabetic biguanide drugs, such as metformin, have shown to exert therapeutic effects in melanoma. A combination of these agents, the metformin-decavanadate complex, was also recognized for its antidiabetic effects and recently described as a better treatment than the monotherapy with metformin enabling lower dosage in rodent models of diabetes. Herein, we compare the effects of decavanadate and metformin-decavanadate on Ca²⁺-ATPase activity in sarcoplasmic reticulum vesicles from rabbit skeletal muscles and on cell signaling events and viability in human melanoma cells. We show that unlike the decavanadate-mediated non-competitive mechanism, metformin-decavanadate inhibits Ca²⁺-ATPase by a mixed-type competitive-non-competitive inhibition with an IC₅₀ value about 6 times higher (87 μM) than the previously described for decavanadate (15 μM). We also found that both decavanadate and metformin-decavanadate exert antiproliferative effects on melanoma cells at 10 times lower concentrations than monomeric vanadate. Western blot analysis revealed that both, decavanadate and metformin-decavanadate increased phosphorylation of extracellular signal-regulated kinase (ERK) and serine/threonine protein kinase AKT signaling proteins upon 24 h drug exposure, suggesting that the anti-proliferative activities of these compounds act independent of growth-factor signaling pathways.

Gold Compounds Inhibit the Ca2+-ATPase Activity of Brain PMCA and Human Neuroblastoma SH-SY5Y Cells and Decrease Cell Viability

Plasma membrane calcium ATPases (PMCA) are key proteins in the maintenance of calcium (Ca2+) homeostasis. Dysregulation of PMCA function is associated with several human pathologies, including neurodegenerative diseases, and, therefore, these proteins are potential drug targets to counteract those diseases. Gold compounds, namely of Au(I), are well-known for their therapeutic use in rheumatoid arthritis and other diseases for centuries. Herein, we report the ability of dichloro(2-pyridinecarboxylate)gold(III) (1), chlorotrimethylphosphinegold(I) (2), 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidenegold(I) chloride (3), and chlorotriphenylphosphinegold(I) (4) compounds to interfere with the Ca2+-ATPase activity of pig brain purified PMCA and with membranes from SH-SY5Y neuroblastoma cell cultures. The Au(III) compound (1) inhibits PMCA activity with the IC50 value of 4.9 µM, while Au(I) compounds (2, 3, and 4) inhibit the protein activity with IC50 values of 2.8, 21, and 0.9 µM, respectively. Regarding the native substrate MgATP, gold compounds 1 and 4 showed a non-competitive type of inhibition, whereas compounds 2 and 3 showed a mixed type of inhibition. All gold complexes showed cytotoxic effects on human neuroblastoma SH-SY5Y cells, although compounds 1 and 3 were more cytotoxic than compounds 2 and 4. In summary, this work shows that both Au (I and III) compounds are high-affinity inhibitors of the Ca2+-ATPase activity in purified PMCA fractions and in membranes from SH-SY5Y human neuroblastoma cells. Additionally, they exert strong cytotoxic effects.

Vanadium and Melanoma: A Systematic Review

The application of metals in biological systems has been a rapidly growing branch of science. Vanadium has been investigated and reported as an anticancer agent. Melanoma is the most aggressive type of skin cancer, the incidence of which has been increasing annually worldwide. It is of paramount importance to identify novel pharmacological agents for melanoma treatment. Herein, a systematic review of publications including “Melanoma and Vanadium” was performed. Nine vanadium articles in several melanoma cells lines such as human A375, human CN-mel and murine B16F10, as well as in vivo studies, are described. Vanadium-based compounds with anticancer activity against melanoma include: (1) oxidovanadium(IV); (2) XMenes; (3) vanadium pentoxide, (4) oxidovanadium(IV) pyridinonate compounds; (5) vanadate; (6) polysaccharides vanadium(IV/V) complexes; (7) mixed-metal binuclear ruthenium(II)–vanadium(IV) complexes; (8) pyridoxal-based oxidovanadium(IV) complexes and (9) functionalized nanoparticles of yttrium vanadate doped with europium. Vanadium compounds and/or vanadium materials show potential anticancer activities that may be used as a useful approach to treat melanoma.