Epithelial cell‐derived human β‐defensin‐2 acts as a chemotaxin for mast cells through a pertussis toxin‐sensitive and phospholipase C‐dependent pathway

Abstract

Mast cells are known to accumulate at the sites of inflammation in response to chemoattractants generated in the local milieu. Since human beta-defensin-2 (hBD-2) is generated in several epithelial tissues where mast cells are present and because we have recently reported that this human antibacterial peptide induces mast cell degranulation, we thus hypothesized that hBD-2 could be a mast cell chemotaxin. Here we report that hBD-2 directly and specifically induces mast cell migration with an optimal concentration of 3 microg/ml. Checkerboard analysis showed that the migration was more chemotactic rather than chemokinetic. Moreover, Scatchard analysis using 125I-labeled hBD-2 revealed that mast cells have at least two classes of receptors, high- and low-affinity receptors, for this peptide. Moreover, the competitive binding assay suggested that hBD-2 is unlikely to utilize CCR6, a functional receptor for hBD-2-mediated dendritic and T cell migration, on mast cells. In addition, treatment of mast cells with G protein inhibitor, pertussis toxin, and phospholipase C inhibitor, U-73122, abolished the cell chemotaxis in response to hBD-2, indicating that the G protein-phospholipase C signaling pathway is involved in hBD-2-induced mast cell activation. Thus, we suggest that hBD-2, which was originally believed to be involved in innate host defense, may participate in the recruitment of mast cells to inflammation foci.

β‐Defensins chemoattract macrophages and mast cells but not lymphocytes and dendritic cells: CCR6 is not involved

“…Rat peritoneal mast cells have been reported to be chemoattracted by HBD-2 to -4 but not HBD-1 [21,22]. This result contrasted with our finding that HBD-1 was a Figure 7.…”

“…To find further support for this hypothesis, we investigated receptor desensitization, which is a regulatory mechanism to prevent the damaging effects of prolonged or excessive activation of G protein-coupled receptors [26]. We found b-dein receptors to be coupled to Ga i proteins due to their sensitivity to pertussis toxin, which confirms previously published observations [16,21]. Heterologous desensitization involving different G protein-coupled receptors is mediated by second messenger-regulated kinases such as PKC and does not require agonist occupancy [25].…”

“…HBD-2 to -4 have been shown to induce in vitro chemoattraction of rat peritoneal mast cells whereas HBD-1 completely lacked this activity [21,22]. Investigating chemotaxis of murine mast cells generated from bone marrow precursors in the presence of SCF and IL-3, we observed that HBD-1 as well as HBD-2 to -4 are effective chemotaxins in vitro (Fig.…”

“…In keeping with these findings, human b-defensin (HBD)-1 to -3 as well as murine b-defensin (mBD)-2, -3 and -29 were shown to selectively chemoattract memory T lymphocytes and/or immature DC via CCR6 [12, [16][17][18]. As some b-defensins additionally induced migration of monocytes and mast cells [19][20][21][22] that do not express CCR6, further receptors for b-defensins were postulated [23]. To this end, studies of the immunomodulatory properties of defensins are still in their infancy despite the well-appreciated importance of these peptides for the host defense [24].…”

Differential Regulation of β-Defensin Expression in Human Skin by Microbial Stimuli

“…It is important to note that hBD-2 and also hBD-3 are not only antimicrobial peptides but display proinflammatory properties by stimulating the chemotaxis of immature dendritic cells, T cells, and neutrophils (33)(34)(35)(36). The same has not been found for hBD-1 (34).…”