CALCITONIN-GENE-RELATED PEPTIDE POTENTIATES LPS-INDUCED IL-6 RELEASE FROM MOUSE PERITONEAL-MACROPHAGES

The secretion of IL-6 after stimulation of macrophages has been found to play a central role in the regulation of defense mechanism, haemato poiesis, and acute phase reaction. It was reported that cAMP is involv ed in the regulation of IL-6 production. Since calcitonin gene-related peptide (CGRP) is known to increase cAMP accumulation in mouse macrop hages, we examined whether CGRP would induce IL-6 release in macrophag es. Macrophages were obtained from the peritoneal exudate of male Balb /c mouse. The cells were plated on culture dishes at a density of 2.5 x 10(5) cells per well and allowed to adhere for 2 h. After incubation for 48 h with two changes of PRMI-1640, the macrophages were cultured with CGRP and LPS 1 mu g/ml for 12 h. The IL-6 level in medium was me asured by ELISA kits. The results showed that CGRP had no direct effec ts on IL-6 production, but it potentiated LPS-induced IL-6 production in a concentration-dependent manner. When CGRP was at a concentration of 10(-10) M, the LPS-induced IL-6 production was increased from 5.16 +/- 0.48 to 8.88 +/- 0.48 ng/ml. The effect of CGRP 10(-10) M was reve rsed by hCGRP(8-37) 10(-8) Id, an antagonist of CGRP, receptor. The LP S-induced IL-6 production from macrophages was also potentiated by for skolin 5 mu M, an activator of adenylate cyclase. Furthermore, pretrea tment with H-89 1 mu M or Rp-cAMPS 100 mu M, the inhibitors of cAMP-de pendent protein kinase, inhibited the effect of CGRP by 31% and 98%, r espectively. These results demonstrate that the LPS-induced IL-6 relea se is potentiated by CGRP via the activation of cAMP pathway in mouse resident peritoneal macrophages. (C) 1998 Elsevier Science B.V.