LL-37 Opsonizes and Inhibits Biofilm Formation of Aggregatibacter actinomycetemcomitans at Subbactericidal Concentrations

Abstract

Host defense peptides are immediate responders of the innate immunity that express antimicrobial, immunoregulatory, and wound-healing activities. Neutrophils are a major source for oral host defense peptides, and phagocytosis by neutrophils is a major mechanism for bacterial clearance in the gingival tissue. Dysfunction of or reduction in the numbers of neutrophils or deficiency in the LL-37 host defense peptide was each previously linked with proliferation of oral Aggregatibacter actinomycetemcomitans which resulted in an aggressive periodontal disease. Surprisingly, A. actinomycetemcomitans shows resistance to high concentrations of LL-37. In this study, we demonstrated that submicrocidal concentrations of LL-37 inhibit biofilm formation by A. actinomycetemcomitans and act as opsonins and agglutinins that greatly enhance its clearance by neutrophils and macrophages. Improved uptake of A. actinomycetemcomitans by neutrophils was mediated by their opsonization with LL-37. Enhanced phagocytosis and killing of A. actinomycetemcomitans by murine macrophage-like RAW 264.7 cells were dependent on their preagglutination by LL-37. Although A. actinomycetemcomitans is resistant to the bactericidal effect of LL-37, our results offer a rationale for the epidemiological association between LL-37 deficiency and the expansion of oral A. actinomycetemcomitans and indicate a possible therapeutic use of cationic peptides for host defense.

Porphyromonas gingivalis gingipain is involved in the detachment and aggregation of Aggregatibacter actinomycetemcomitans biofilm

“…Other enzymes possibly processed by gingipains have the ability to degrade aggregation factors of A. actinomycetemcomitans, indicating that gingipains are indirectly involved in inhibiting autoaggregation and/or coaggregation of A. actinomycetemcomitans. tion with other species in co-cultured biofilm (Rosen et al, 2003;Periasamy & Kolenbrander, 2009;Sol et al, 2013). The present study showed the results using a non-fimbriated A. actinomycetemcomitans strain.…”

“…Some previous studies used non‐fimbriated A.actinomycetemcomitans strains to examine a part of their nature in mono‐cultured biofilm and coaggregation with other species in co‐cultured biofilm (Rosen et al ., ; Periasamy & Kolenbrander, ; Sol et al ., ). The present study showed the results using a non‐fimbriated A. actinomycetemcomitans strain.…”

Inherited diseases caused by mutations in cathepsin protease genes

“…Nonetheless, the hallmark of Papillon–Lefèvre syndrome is the aggressive periodontitis. Thus, a lack of serine proteases and neutrophil dysfunction may lead to the outgrowth of periodontal pathogenic bacteria .…”

“…Reports have shown that patient gingivae harbor Aggregatibacter actinomycetemcomitans preferentially , although some have not detected a specific pathogenic flora . Neutrophil periodontal clearance of A. actinomycetemcomitans employs antimicrobial peptides like the cathelicidin antimicrobial peptide LL‐37 . Recent reports show that proteinase 3 is needed for the generation of LL‐37 from the cathelicidin antimicrobial peptide (hCAP‐18/LL‐37) .…”

Identification of human cathelicidin peptide LL-37 as a ligand for macrophage integrin α_Mβ₂ (Mac-1, CD11b/CD18) that promotes phagocytosis by opsonizing bacteria

“…Previous studies reported that several neutrophil-derived granule proteins/peptides opsonize bacteria resulting in enhanced phagocytosis. 51,52 With regard to LL-37, it was shown that opsonization of oral Aggregatibacter actinomycetemcomitans with the peptide resulted in increased phagocytosis by murine macrophages, 53 and an uptake of LL-37-coated polystyrene beads by nondifferentiated primary human monocytes was increased compared with uncoated beads. 45 On the other hand, bacterial phagocytosis was also shown to be augmented by pretreatment of macrophages with neutrophil secretion products, 54 including LL-37.…”