Participação dos receptores purinérgicos na ação estimulatória da crotoxina sobre a produção de espécies reativas do oxigênio por linhagem de monócito humano (THP-1)

Abstract

Crotoxin (CTX), the major toxin of Crotalus durissus terrificus snake venom, induces immunomodulatory action, particularly on the macrophages function, crucial cells to innate defense mechanisms. In these cells, dual action of this toxin is observed, since both inhibition of some functional parameters such as spreading and phagocytosis, as well as respiratory burst (hydrogen peroxide-H2O2 generation and nitric oxide-NO generation), Lipoxin A4 (LXA4) and its stable analog (15-Epi-LXA4) secretion and glucose and glutamine metabolism increased. Recent studies have demonstrated the importance of these CTX stimulatory actions on the metabolism of macrophages for the control of infectious inflammatory response and for tumor progression. Furthermore, FPRs are crucial for the different effects of CTX on macrophage function and metabolism. In spite of these evidences, the mechanisms involved with the CTX stimulatory actions on the metabolism of these cells are not known in their entirety. Among the mechanisms involved in the regulation of energetic metabolism of macrophages, purinergic signaling is essential in the stimulation of cytokine secretion and the reactive oxygen species and reactive nitrogen species generation by macrophages, besides being receptors responsive to stimuli via FPRs. Therefore, the objective of the present project was to investigate the possible participation of purinergic receptors on the H2O2 production by CTX treated THP-1 monocytic cells and whether FPRs participate in this signaling. For this purpose, THP-1 cells were used, such as monocytes or macrophage-differentiated or LPS-stimulated cells. The results show that THP-1 monocytes, such as macrophages differentiated from THP-1, by previous incubation with PMA, showed a significant increase of H2O2 production in the presence of different concentrations of CTX. CTX-induced H2O2 production increased was also observed after 24 hours by differentiated and LPS-stimulated macrophages. Different CTX concentrations lead to a significant increase in the ATP releasing by THP-1, in the absence or presence of LPS. Furthermore, different concentrations of CTX enhanced visualization of P2Y11 purinergic receptors and FPRs in LPS-stimulated THP-1. Blocking of P2X and P2Y purinergic receptors by non-selective antagonists abolished CTX-induced H2O2 production. Blocking of the FPRs by the selective antagonist partially interfered with the production of this toxin-induced reaction. The results together demonstrate, in an unprecedented way, that human monocytes are responsive to the action stimulatory CTX on ROS production and release of ATP and demonstrate for the first time that purinergic receptors are involved in this CTX-stimulatory action, with the FPRs participation.