Novel activation of non-selective cationic channels by dinitrosyl iron-thiosulfate in PC12 cells

1. Low molecular mass dinitrosyl iron complexes (DNICs) are nitrosating agents and it is known that the dinitrosyl iron moiety can be transferred to proteins. The aim of the present study was to determine if the formation of protein-bound dinitrosyl iron can modulate ionic channel activity 2. In PC12 cells, dinitrosyl iron-thiosulfate (50 muM) caused irreversible activation of a depolarizing inward current (I-DNIC) I-DNIC was partially inhibited by the metal chelator diethyldithiocarbamate (DETC, 1 mM), but not by the reducing/denitrosylating agent dithiothreitol (DTT, 5 mM). 3. The activation of I-DNIC was not reproduced by application of nitric oxide (NO, 100 muM), S-nitrocysteine (200 muM) or ferrous iron-thiosulfate (50 muM), and was not prevented by the irreversible guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ, 1 muM). Similarly intracellular perfusion of dinitrosyl iron-thiosulfate (100 muM) did not result in activation of I-DNIC. 4. Ion replacement experiments show that the DETC-sensitive component of I-DNIC is a nonselective cationic current. In accordance, I-DNIC was blocked by antagonists of receptor-operated calcium entry gadolinium (25 muM) and SK&F 96365 (25 muM). 5. Single-channel measurements from outside-out patches reveal that the DETC-sensitive component of I-DNIC is an inward current carried bg a cationic channel having a conductance of 50 pS. 6. The present observations suggest that the formation of ion channel-bound dinitrosyl iron represents another mechanism of regulation of ion channel activity by NO.-related species, which may be particularly important in pathophysiological processes where NO is overproduced.