The ca²⁺-atpase inhibition potential of gold(I, iii) compounds

The therapeutic applications of gold are well-known for many centuries. The most used gold compounds contain Au(I). Herein, we report, for the first time, the ability of four Au(I) and Au(III) complexes, namely dichloro (2-pyridinecarboxylate) Au(III) (abbreviated as 1), chlorotrimethylphosphine Au(I) (2), 1,3-bis(2,6-diisopropylphenyl) imidazole-2-ylidene Au(I) chloride (3), and chlorotriphenylphosphine Au(I) (4), to affect the sarcoplasmic reticulum (SR) Ca²⁺-ATPase activity. The tested gold compounds strongly inhibit the Ca²⁺-ATPase activity with different effects, being Au(I) compounds 2 and 4 the strongest, with half maximal inhibitory concentration (IC₅₀ ) values of 0.8 and 0.9 µM, respectively. For Au(III) compound 1 and Au(I) compound 3, higher IC₅₀ values are found (4.5 µM and 16.3 µM, respectively). The type of enzymatic inhibition is also different, with gold compounds 1 and 2 showing a non-competitive inhibition regarding the native substrate MgATP, whereas for Au compounds 3 and 4, a mixed type of inhibition is observed. Our data reveal, for the first time, Au(I) compounds with powerful inhibitory capacity towards SR Ca²⁺ ATPase function. These results also show, unprecedently, that Au (III) and Au(I) compounds can act as P-type ATPase inhibitors, unveiling a potential application of these complexes.