Regulation by CRAMP of the responses of murine peritoneal macrophages to extracellular ATP

Abstract

Peritoneal macrophages were isolated from wild type (WT) mice and from mice invalidated for the P2X(7) receptor (KO) which had been pretreated with thioglycolate. In cells from WT mice, 1 mM ATP increased the intracellular concentration of calcium ([Ca(2+)](i)), the uptake of ethidium bromide, the production of reactive oxygen species (ROS), the secretion of IL-1beta, the release of oleic acid and of lactate dehydrogenase; it decreased the intracellular concentration of potassium ([K(+)](i)). In KO mice, ATP transiently increased the [Ca(2+)](i) confirming that the P2X(7) receptor is a major receptor of peritoneal macrophages. WKYMVm, an agonist of receptors for formylated peptides (FPR) also increased the [Ca(2+)](i) in murine macrophages. The slight increase of the [Ca(2+)](i) was strongly potentiated by ivermectin confirming the expression of functional P2X(4) receptors by murine peritoneal macrophages. CRAMP, the unique antimicrobial peptide derived from cathelin in mouse inhibited all the responses coupled to P2X(7) receptors in macrophages from WT mice. Agonists for FPR had no effect on the increase of the [Ca(2+)](i) in response to ATP. CRAMP had no effect on the increase of the [Ca(2+)](i) evoked by a combination of ATP and ivermectin in macrophages from P2X(7)-KO mice. In summary CRAMP inhibits the responses secondary to the activation of the murine P2X(7) receptors expressed by peritoneal macrophages. This inhibition is not mediated by FPR receptors and is specific since CRAMP has no effect on the response coupled to P2X(4) receptors. It can thus be concluded that the interaction between P2X(7) receptors and cathelin-derived antimicrobial peptides is species-specific, in some cases (man) positive in others (mouse) negative.

Identification of Peptides Derived from the Human Antimicrobial Peptide LL-37 Active against Biofilms Formed by Pseudomonas aeruginosa Using a Library of Truncated Fragments

“…These authors also reported that the score for LL17-37, the C-terminal fragment of LL-37, was close to 3. In line with this result, the C-terminal fragment of LL-37 formed an ␣-helix (36).…”

A parasitic helminth-derived peptide that targets the macrophage lysosome is a novel therapeutic option for autoimmune disease

“…Both the human LL-37 and the murine CRAMP (cathelicidin-related antimicrobial peptide, an orthologue of human LL-37) have been shown in vitro to reduce the activation of IL-1␤ by the Nlrp3 inflammasome in macrophages (Pochet et al, 2006;Seil et al, 2010;Hu et al, 2014). In all of these cases, ATP activated the inflammasome protein complex and inhibition was achieved via interaction of the cathelicidin peptide with the receptor for ATP, P2X7.…”

The P2X7 Receptor Channel: Recent Developments and the Use of P2X7 Antagonists in Models of Disease

“…The human antimicrobial peptide LL-37 can potentiate both human and mouse P2X7 activation (Elssner et al, 2004). In contrast, the murine antimicrobial peptide CRAMP can enhance human but impair murine P2X7 activation (Seil et al, 2010). The antibiotic polymyxin B can potentiate human P2X7 activation (Ferrari et al, 2004), whereas the antiparasitic ivermectin can potentiate human but not murine P2X7 (Norenberg et al, 2012).…”