Nitróxidos como reguladores da produção de oxidantes por macrófagos

Abstract

Thiols are required to maintain cellular functions. For instance, glutathione (GSH) is an important reductant to repair oxidized biomolecules, to cycle proteins involved in cell signaling and to scavenge bioradicals, although the relatively reactive glutathionyl radical (GS•) is produced in the latter case. To investigate GS• participation in macrophage respiratory burst, we employed the nitroxide 4-9((-acridinecarbonil)-amino)- 2,2,6,6-tetramethylpiperidine-1-oxil (Ac-Tempo) whose interaction with GS• and carbon centered radicals switches off Ac-Tempo EPR signal while switching on acridine moiety fluorescence (ëexc 361 nm, ëemi 440 nm) (Borisenko et al JACS 126, 9221,2004). Inflammatory macrophages unstimulated displayed low fluorescence accompanied by maintenance of Ac-Tempo EPR signal. Cells stimulated with PMA in the presence of Ac- Tempo elicited a dose-dependent fluorescence in synchrony with EPR signal decay and O2 consumption. Changes in fluorescence and EPR signal intensity were dependent on GSH levels as demonstrated by pre-treatment of cells with buthionine sulfoximine and N-ethylmaleimide. The macrophage protein S-glutathionylation process due to NADPH oxidase activation was significantly decreased under Ac-Tempo cellular treatment. These results suggest a role of thiyl radicals in the maintenance of the macrophages respiratory burst and may provide a therapeutic target for inflammation management.