Short lipopeptides specifically inhibit the growth of Propionibacterium acnes with dual antibacterial and anti-inflammatory action

Antibacterial activity and mechanism of cell-free supernatants of Lacticaseibacillus paracasei against Propionibacterium acnes

Propionibacterium acnes (P. acnes) is an anaerobic and gram-positive bacterium involved in the pathogenesis and inflammation of acne vulgaris. This study particularly focuses on the antimicrobial effect of Lacticaseibacillus paracasei LPH01 against P. acnes, a bacterium that causes acne vulgaris. Fifty-seven Lactobacillus strains were tested for their ability to inhibit P. acnes growth employing the Oxford Cup and double dilution methods. The cell-free supernatant (CFS) of L. paracasei LPH01 demonstrated a strong inhibitory effect, with an inhibition zone diameter of 24.65 ± 0.27 mm and a minimum inhibitory concentration of 12.5 mg/mL. Among the CFS, the fraction over 10 kDa (CFS-10) revealed the best antibacterial effect. Confocal laser scanning microscopes and flow cytometry showed that CFS-10 could reduce cell metabolic activity and cell viability and destroy the integrity and permeability of the cell membrane. A scanning electron microscope revealed that bacterial cells exhibited obvious morphological and ultrastructural changes, which further confirmed the damage of CFS-10 to the cell membrane and cell wall. Findings demonstrated that CFS-10 inhibited the conversion of triglycerides, decreased the production of free fatty acids, and down-regulated the extracellular expression of the lipase gene. This study provides a theoretical basis for the metabolite of L. paracasei LPH01 as a potential antibiotic alternative in cosmeceutical skincare products.

Anti-Toxoplasma gondii Effects of Lipopeptide Derivatives of Lycosin-I

Toxoplasmosis, caused by Toxoplasma gondii (T. gondii), is a serious zoonotic parasitic disease. We previously found that Lycosin-I exhibited anti-T. gondii activity, but its serum stability was not good enough. In this study, we aimed to improve the stability and activity of Lycosin-I through fatty acid chain modification, so as to find a better anti-T. gondii drug candidate. The α/ε-amino residues of different lysine residues of Lycosin-I were covalently coupled with lauric acid to obtain eight lipopeptides, namely L-C12, L-C12-1, L-C12-2, L-C12-3, L-C12-4, L-C12-5, L-C12-6, and L-C12-7. Among these eight lipopeptides, L-C12 showed the best activity against T. gondii in vitro in a trypan blue assay. We then conjugated a shorter length fatty chain, aminocaproic acid, at the same modification site of L-C12, namely L-an. The anti-T. gondii effects of Lycosin-I, L-C12 and L-an were evaluated via an invasion assay, proliferation assay and plaque assay in vitro. A mouse model acutely infected with T. gondii tachyzoites was established to evaluate their efficacy in vivo. The serum stability of L-C12 and L-an was improved, and they showed comparable or even better activity than Lycosin-I did in inhibiting the invasion and proliferation of tachyzoites. L-an effectively prolonged the survival time of mice acutely infected with T. gondii. These results suggest that appropriate fatty acid chain modification can improve serum stability and enhance anti-T. gondii effect of Lycosin-I. The lipopeptide derivatives of Lycosin-I have potential as a novel anti-T. gondii drug candidate.

Effect of combining Zingiber officinale and Juglans regia extracts on Propionibacterium acnes, Staphylococcus aureus and Staphylococcus epidermidis: antibiofilm action and low toxicity

Objective was evaluated the therapeutic effect of Juglans regia (J) and Zingiber officinale (Z) extracts, alone or associated (Z75% + J25%, Z50% + J50% and Z25% + J75%) applied on planktonic cultures and biofilms of Propionibacterium acnes, Staphylococcus epidermidis and Staphylococcus aureus, as well as analyzing the cytotoxic effects of plant extracts on mouse macrophages (Raw 264-7). Broth microdilution assay was performed (M7-A6 - CLSI). Anti-biofilm activities and cytotoxicity on Raw 264-7 were studied using MTT assay and scanning electron microscopy. ANOVA with post-hoc Tukey HSD applied for parametric data and Kruskal-Wallis with Conover-Iman test, for non-parametric (p<0.05). On P. acnes biofilm, Z50% + J50% reduced 46.9% in 5 min and Z25% + J75% reduced 74.1% in 24hs. On S. aureus, Z75% + J25% reduced 23.1% in 5 min Z25% +J75% reduced 79.4% in 24hs. On S. epidermidis, Z75% + J25% reduced 74.6% in 5 min and 82.05% in 24 h. The treatments on macrophages for 24 h promoted a maximum reduction by 14,5% for groups of extracts associations. On multispecies biofilm, Z75%+J25% reduced 84.3% in 24 h. In conclusion association of glycolic extracts provided therapeutic effect, demonstrated antimicrobial activity and low cytotoxicity.

Suppression of Cutibacterium acnes-Mediated Inflammatory Reactions by Fibroblast Growth Factor 21 in Skin

Cutibacterium acnes (C. acnes) is a common commensal bacterium that is closely associated with the pathogenesis of acne. Fibroblast growth factor 21 (FGF21), as a favorable regulator of glucose and lipid metabolism and insulin sensitivity, was recently shown to exert anti-inflammatory effects. The role and mechanism of FGF21 in the inflammatory reactions induced by C. acnes, however, have not been determined. The present study shows that FGF21 in the dermis inhibits epidermal C. acnes-induced inflammation in a paracrine manner while it functions on the epidermal layer through a receptor complex consisting of FGF receptor 1 (FGFR1) and β-Klotho (KLB). The effects of FGF21 in heat-killed C. acnes-induced HaCaT cells and living C. acnes-injected mouse ears were examined. In the presence of C. acnes, FGF21 largely counteracted the activation of Toll-like receptor 2 (TLR2), the downstream nuclear factor-κB (NF-κB), and mitogen-activated protein kinase (MAPK) signaling pathways induced by C. acnes. FGF21 also significantly reduced the expression of proinflammatory cytokines, including interleukin (IL)-1β, IL-6, IL-8, and tumor necrosis factor (TNF)-α. Taken together, these findings indicate that FGF21 suppresses C. acnes-induced inflammation and might be used clinically in the management and treatment of acne.

Ultra-short lipopeptides against gram-positive bacteria while alleviating antimicrobial resistance

Facing the continuously urgent demands for novel antimicrobial agents since the growing emergence of bacterial resistance, a series of new ultra-short lipopeptides, composed of tryptophan and arginine and fatty acids, were de novo designed and synthesized in this study. Most of the new lipopeptides exhibited preferable antimicrobial potential against gram-positive bacteria, including MRSA clinical isolates. Among them, the new lipopeptides C14-R1 (C14-RWW-NH₂) and C12-R2 (C12-RRW-NH₂) presented higher selectivity to bacterial membranes over mammalian membranes and low cytotoxicity, which also maintained better antimicrobial activity in the presence of physiological salts or serum. Most importantly, C14-R1 and C12-R2 not only expressed low tendency of bacterial resistance, but also displayed synergistic antimicrobial activity against antibiotics-resistant bacteria when be used in combination with antibiotics. Especially, they could alleviate or reverse the ciprofloxacin resistance, implying an ideal anti-resistance function. Moreover, the new lipopeptides showed rapid killing kinetics, obvious effectiveness for persistent cells that escaped from antibiotics, and strong anti-biofilm ability, which further indicated a preferable anti-resistance ability. The typical non-receptor-mediated membrane mechanisms were characterized by LPS/LTA competitive inhibition, cytoplasmic membrane depolarization, PI uptake assay and scanning electron microscopy analyses systematically. Reactive oxygen species (ROS) generation assays supplemented their intracellular targets in the meanwhile. In addition to the remarkable antimicrobial activity in vivo, the new lipopeptides also displayed significant anti-inflammatory effect in vivo. To sum up, the new lipopeptides C14-R1 and C12-R2 viewed as novel antimicrobial alternatives for tackling the impending crisis of antimicrobial resistance.

Effect of N-methylated and fatty acid conjugation on analogs of antimicrobial peptide Anoplin

With the increment of drug-resistant bacteria and the slow development of novel antibiotics, antimicrobial peptides have gained increasing attention as a potential antibiotic alternative. They not only displayed a broad-spectrum antimicrobial activity but also were difficult to induce resistance development because of their unique membrane-lytic activity. Herein, to improve the limitations of Anoplin, the N-methyl amino acids were first used to replace the amino acids of Anoplin at sensitive enzymatic cleave sites (Leu, Ile, Lys and Arg). Afterward, the N-methylated analogs M3.6/M4.7/M5.7 with high stability were screened out and further modified by N-terminal fatty acid conjugation to develop new antimicrobial peptide analogs with both potent antimicrobial activity and high proteolytic stability, and 12 new Anoplin analogs Cn-M3.6/M4.7/M5.7 (n = 8,10,12,14) were designed and synthesized. Our results showed that compared with native Anoplin, the stability of these N-methylated lipopeptides against trypsin and chymotrypsin degradation were increased by 10⁴-10⁶ times. Besides, they still possessed potent antimicrobial activity under physiological salts and serum environment. Among them, the new designed analogs C12-M3.6/M4.7/M5.7 showed the optimal antimicrobial activity, synergy and additive effects were also observed when they were combined with traditional antibiotics polymyxin B, rifampin, and kanamycin. Moreover, they could effectively inhibit the formation of biofilms by P. aeruginosa and S. aureus. The antimicrobial mechanism studied revealed that these N-methylated lipopeptides could display a rapid bactericidal effect by destroying the bacterial cell membrane. Notably, no detectable resistance of these new designed peptides was developed after continuous cultured with E. coli for 20 passages. In summary, we have designed a new class of antimicrobial peptide analogs with potent antimicrobial activity and high proteolytic stability through N-methyl amino acids substitution and N-terminal fatty acid conjugation. This study also provides new ideas and methods for the modification of antimicrobial peptides in the future.

Novel composite unit with one pyridinium and three N-halamine structures for enhanced synergism and superior biocidability on magnetic nanoparticles

A novel composite unit of enhanced synergism that rises from the use of a cationic pyridinium structure to attract anionic bacteria to three N-halamine structures was designed for superior biocidability on recyclable magnetic nanoparticles. Briefly, 5-(4-hydroxybenzylidene)hydantoin (HBH), containing one imide and amide NH bonds, was synthesized by Knoevenagel condensation ofp-hydroxybenzaldehyde with hydantoin. 3-Triethoxysilylpropyl succinic anhydride was ammonolyzed with 4-aminopyridine to introduce a pyridine structure and form an amide NH and a carboxylic acid group that was esterified with HBH to introduce its two NH bonds. The triethoxysilyl groups of the esterification product were hydrolyzed into silanols to condense with the counterparts of different hydrolysates and on silica modified Fe₃O₄nanoparticles to provide a layer of polymeric modifier. After quaternization of the pyridine and chlorination of NH bonds from each esterification product, the resultant layer is composed of units each of which contains one pyridinium and threeN-halamine sites and exerted higher biocidability against Escherichia coli and Staphylococcus aureus than comparable systems including synergistic ones with one cationic center and one N-halamine, demonstrating an enhanced synergism. The biocidal layer had promising stability under quenching-chlorinating cycles and long-term storage. The study affords a strategy for syntheses of more powerful biocidal surfaces.

Engineering of antibacterial/recyclable difunctional nanoparticles via synergism of quaternary ammonia salt site and N-halamine sites on magnetic surface

A biocidal composite unit with improved synergism, using one cationic quaternary ammonia salt (QAS) site to attract electronegative bacteria to three highly biocidal N-halamine sites, was designed for the first time and attached onto surface of magnetic silica coated Fe₃O₄ nanoparticles (silica@Fe₃O₄NPs) for superior biocidability, large killing area, and easy recyclability. Briefly, a compound containing one imide and two amide NH bonds, 2-(2,5-dioxoimidazolidin-4-yl)-N-(4-hydroxyphenyl)acetamide (DHPA), was prepared by amidation of hydantoin acetic acid with p-aminophenol. A biocidal precursor of one QAS site and three N-halamine sites was then constructed by alcoholysis of 3-triethoxysilylpropyl succinic anhydride with 2-(dimethylamino)ethan-1-ol to introduce a tertiary amine and subsequent esterification with DHPA to introduce three NH bonds. The triethoxysilyl groups in the precursor were hydrolyzed to silanol groups to condense with their counterparts on silica@Fe₃O₄ NPs. The surface of resultant NPs carried units each contains one QAS site and three N-halamine sites after quaternization and chlorination. The biocidal surface showed superior biocidability against Escherichia coli and Staphylococcus aureus than reported systems due to the improved synergism between multiple antibacterial groups of different types and was stable towards quenching-chlorinating process and storage. The successful design opens insight in the syntheses of more powerful biocides.

Short lipopeptides specifically inhibit the growth of Propionibacterium acnes with dual antibacterial and anti-inflammatory action

BACKGROUND AND PURPOSE

Propionibacterium acnes (P. acnes) is a Gram-positive bacterium associated with the skin disorder acne. In this study, we determined the importance of fatty acids in the life habitat of P. acnes; we tested our lipopeptide library in an attempt to create potent P. acnes-specific antimicrobial agents.

EXPERIMENTAL APPROACH

Antimicrobial activity was determined by the minimal inhibitory concentration (MIC). Lipids from P. acnes were used to explore the mode of action. RAW264.7 cells respectively stimulated with LPS and P. acnes were used to measure the anti-inflammatory activity. Mice ears injected with P. acnes were used to assess the antimicrobial and anti-inflammatory effects of the peptides tested in vivo.

KEY RESULTS

The most potent candidate, C16-KWKW, was observed to be more active against P. acnes, with an MIC of 2 μg·ml^-1 , than against other non-targeted bacterial strains, such as Streptococcus mutans, Staphylococcus aureus, and Escherichia coli. The mode of action of C16-KWKW was observed to be through interference with the integrity of bacterial membrane, thereby impairing membrane permeability and causing leakage of the inner contents of bacterial cells. In addition, C16-KWKW inhibited the expression of pro-inflammatory cytokines, such as IL-1β, TNF-α, and inducible NOS, stimulated by both LPS and P. acnes, thus showing potential anti-inflammatory activity, which was further assessed in animal studies in vivo.

CONCLUSIONS AND IMPLICATIONS

C16-KWKW is a lipopeptide displaying both anti-P. acnes and anti-inflammatory effects in vitro and in vivo, and exhibits potential as a treatment for acne vulgaris induced by P. acnes.