Inhibition of LPS-induced TNF-alpha production by calcitonin gene-related peptide (CGRP) in cultured mouse peritoneal macrophages

The purpose of this study was to examine whether rCGRP has effects on TNF-alpha produced by mouse resident peritoneal macrophages. Macrophages were obtained from the peritoneal exudate of male Balb/c mouse. The cells were plated on culture dishes at a density of 2.5x10(5) cells per well and allowed to adhere for 2 hr. Pretreatment with rCGRP (10 nM-1 mu M) for 24 hr, the macrophages were cultured with LPS 1 mu g/ml for another 24 h. The medium was harvested for measuring TNF-alpha by ELISA kits. The results showed that rCGRP had no direct effects on TNF-alpha production, but it inhibited LPS-induced TNF-alpha production in a concentration-dependent manner. When rCGRP was at a concentration of 1 mu M, the LPS-induced TNF-alpha production was inhibited by 39%. The effect of rCGRP was reversed by hCGRP(8-37) (10 mu M), an antagonist of CGRP(I) receptor. The LPS-induced TNF-alpha production from macrophages was also inhibited by forskolin 3 mu M, an activator of adenylate cyclase. Furthermore, pretreatment with H-89 1 mu M or Rp-cAMPS 100 mu M, the inhibitors of cAMP-dependent protein kinase, the effect of rCGRP was abolished. These data suggest that the LPS-induced TNF-alpha production is inhibited by rCGRP via activation of cAMP responses in mouse resident peritoneal macrophages. (C) 1997 Elsevier Science Inc.