This type of transmembrane pore is induced by LL-37. The toroidal pore model combines the action of the two previous models and begins with aggregation on the membrane surface. The peptides insert into the membrane perpendicularly and induce continuous bending of the lipid monolayers through the pore lead to the water core to be lined by both the inserted peptides and the lipid head groups. During this action, the MG132 polar faces of the peptides associate with the polar head groups of the lipids, resulting in a continuous bend that connects the two leaflets of the membrane. Thus, toroidal pore formations in the membrane result
in the lipids forming micelles and subsequent membrane disruption. This model explains the activity KU-57788 research buy of antimicrobial
peptides such as magainins and protegrins [60]. Its antimicrobial properties led to the initial identification of hCAP18/LL-37 [39]. It exhibits antimicrobial activity against both gram-positive and gram-negative bacterial strains. The minimal inhibitory concentration (MIC) for LL-37 against these pathogens can range to less than 10 μg/ml [34]. This peptide is active against clinically important strains of gram-negative bacteria and periodontal pathogens such as A. actinomycetemcomitans and Capnocytophaga [61]. Similarly, we showed that the LL-37-derived 27-mer synthetic peptide (hCAP18109–135) and its analogues (LL/CAP18 and FF/CAP18) killed Porphyromonas and Prevotella species within a short time and with a low peptide concentration [62] ( Fig. 3). Additionally, LL-37 peptide is capable of killing gram-negative oral streptococci, including Streptococcus mutans, S. sanguinis, S. salivarius, and S. mitis. The LL-37 is particularly effective in killing these streptococci, especially S. mutans, when they act as cariogenic pathogens [63]. Our study demonstrated that the LL-37-derived synthetic peptides pheromone exerted potent antimicrobial activity against Streptococcus sanguis isolated from patients with Behçet’s disease (BD), thereby producing a stronger killing activity [64] ( Fig. 4). Hence, LL-37 is related
to oral mucosal defense, and the regulated expression and production of this peptide can be important for the suppression of BD. Furthermore, this antimicrobial activity is augmented by α- or β-defensins in vitro [65]. These data suggest that the LL-37 peptide acts synergistically under in vivo conditions to form an efficient barrier against microbial invasion. In the oral cavity, microbes are exposed to saliva and serum, which contain salt and reduce the antimirobial activity of β-defensins by 50% of the activity observed under control (salt-free) conditions [63]. In contrast, cathelicidin LL-37 are active against several bacteria in high salt media [34], [65] and [66], supporting its capacity to function under a variety of physiological conditions.