Endothelins (ETs), potent vasoconstricting peptides, are produced by macrophages upon stimulation and may participate in the amplification or regulation of the inflammatory response. However, it is not clear whether ETs can act in an autocrine manner on macrophages and which role they play in relationship with other cytokines. To address these issues, we studied the effects of ETs on the production of inflammatory cytokines by mouse peritoneal macrophages or by a retrovirus-transformed microglial cell line. Here, we report that ET-2, but not ET-1 or ET-3, is able to stimulate the production of interleukin-1 (IL-1) and interleukin-6 (IL-6) by peptone- elicited mouse macrophages (pMO). In contrast, ET-3 and ET-1, but not ET-2, are active on microglial cells. No tumour necrosis factor-α (TNF-α) or nitric oxide (NO) were detected in the supernatants of ET-stimulated cultures. The activity of ET-2 on pMO was time and dose dependent and was inhibited by the addition of ET(A) and ET(B) receptor antagonists, BQ 123 and IRL1038, respectively. In addition, when pMO were stimulated by interferon- γ (IFN-γ) in the presence of ET-2, a significant inhibition of IL-6 and IL- 1 production was observed compared with the effects of the same doses of IFN- γ or ET-2 used separately. The inhibition was specifically due to the activity of ET-2, since it was reversed by the addition of BQ123 or IRL1038. Similar results were seen when the content of NO in the supernatants of pMO stimulated by IFN-γ plus ET-2 was evaluated. These results suggest that ETs may possess both a pro-inflammatory action on macrophages from different tissues and a regulatory activity on IFN-γ.
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