Cathelicidin rCRAMP stimulates rat mast cells to generate cysteinyl leukotrienes, synthesize TNF and migrate: involvement of PLC/A2, PI3K and MAPK signaling pathways.

Cathelicidins represent a family of cationic peptides involved in host defense systems. Apart from exerting direct anti-microbial effects, cathelicidins can regulate immune responses by affecting the activity of cells playing a role in antibacterial defense. Taking into account that mast cells are critical components of host defense, the aim of this study was to determine whether rat cathelicidin-related anti-microbial peptide (rCRAMP) can influence mast cell activity. We have demonstrated that activation of fully mature rat mast cells with rCRAMP resulted in generation and release of cysteinyl leukotrienes (cysLTs). However, rCRAMP failed to induce mast cell degranulation and histamine release. We also found that rCRAMP stimulated rat mast cells to synthesize TNF, but not CXCL8. What is more, this peptide induced GM-CSF, IL-1β, CCL2 and CCL3 but not IL-33 mRNA expression in mast cells. Finally, we showed that this cathelicidin serves as potent chemoattractant for rat mast cells. rCRAMP-mediated cysLT synthesis and mast cell migration were strongly inhibited by IL-10 pre-treatment. With the use of specific inhibitors, we established that activation of PLC/A2 and ERK1/2, but not p38, was required for rCRAMP-induced mast cell stimulation, while PI3K-dependent pathway is involved in both TNF synthesis and mast cell migration. Our results suggest that cathelicidins can amplify inflammatory responses by causing mast cells accumulation and by stimulating these cells to release potent pro-inflammatory mediators.