Inhibition of Na+/K+-ATPase and cytotoxicity of a few selected gold(III) complexes.

Na+/K+-ATPase is in charge of maintaining the ionic and osmotic intracellular balance by using ATP as an energy
source to drive excess Na+ions out of the cell in exchange for K+ions.Weexploredwhether three representative
cytotoxic gold(III) compounds might interferewithNa+/K+-ATPase and cause its inhibition at pharmacologically
relevant concentrations. The tested complexes were [Au(bipy)(OH)2][PF6] (bipy= 2,2′-bipyridine), [Au(pydmb-
H)(CH3COO)2] (pydmb-H = deprotonated 6-(1,1-dimethylbenzyl)-pyridine), and [Au(bipydmb-H)(OH)][PF6]
(bipydmb-H = deprotonated 6-(1,1-dimethylbenzyl)-2,2′-bipyridine). We found that all of them caused a pronounced
and similar inhibition of Na+/K+-ATPase activity. Inhibition was found to be non-competitive and reversible.
Remarkably, treatment with cysteine resulted in reversal or prevention of Na+/K+-ATPase inhibition.
It is very likely that the described effects may contribute to the overall cytotoxic profile of these gold complexes.