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

Sorbicillinoid HSL-2 inhibits the infection of influenza A virus via interaction with the PPAR-γ/NF-κB pathway

BACKGROUND

Drug resistance is an important factor in the fight against influenza A virus (IAV). Natural products offer a rich source of lead compounds for the discovery of novel antiviral drugs. In a previous study, we isolated the sorbicillinoid polyketide HSL-2 from the mycelium of fungus Trichoderma sp. T-4-1. Here, we show that this compound exerts strong antiviral activity against a panel of IAVs.

METHODS

The immunofluorescence and qRT-PCR assays were used to detect the inhibitory effect of HSL-2 toward the replication of influenza virus and IAV-induced expression of the pro-inflammatory cytokines such as TNF-α, IL-6, and IL-1β.

RESULTS

The results indicated that HSL-2 inhibited influenza virus replication, and it significantly inhibited IAV-induced overexpression of the pro-inflammatory cytokines TNF-α, IL-6, and IL-1β through modulating the PPAR-γ/NF-κB pathway. Notably, this effect was decreased when cells were transfected with PPAR-γ siRNA or treated with the PPAR-γ inhibitor T0070907. In addition, HSL-2 was able to attenuate lung inflammatory responses and to improve lung lesions in a mouse model of IAV infection.

CONCLUSIONS

In this paper, we identified a microbial secondary metabolite, HSL-2, with anti-influenza virus activity. This report is the first to describe the antiviral activity and mechanism of action of HSL-2, and it provides a new strategy for the development of novel anti-influenza virus drugs from natural sources.

Immunomodulatory activities and biomedical applications of melittin and its recent advances

Melittin (MLT), a peptide containing 26 amino acids, is a key constituent of bee venom. It comprises ∼40%-60% of the venom's dry weight and is the main pricing index for bee venom, being the causative factor of pain. The unique properties of MLT extracted from bee venom have made it a very valuable active ingredient in the pharmaceutical industry as this cationic and amphipathic peptide has propitious effects on human health in diverse biological processes. It has the ability to strongly impact the membranes of cells and display hemolytic activity with anticancer characteristics. However, the clinical application of MLT has been limited by its severe hemolytic activity, which poses a challenge for therapeutic use. By employing more efficient mechanisms, such as modifying the MLT sequence, genetic engineering, and nano-delivery systems, it is anticipated that the limitations posed by MLT can be overcome, thereby enabling its wider application in therapeutic contexts. This review has outlined recent advancements in MLT's nano-delivery systems and genetically engineered cells expressing MLT and provided an overview of where the MLTMLT's platforms are and where they will go in the future with the challenges ahead. The focus is on exploring how these approaches can overcome the limitations associated with MLT's hemolytic activity and improve its selectivity and efficacy in targeting cancer cells. These advancements hold promise for the creation of innovative and enhanced therapeutic approaches based on MLT for the treatment of cancer.

A Hybrid Antimicrobial Peptide Targeting Staphylococcus aureus with a Dual Function of Inhibiting Quorum Sensing Signaling and an Antibacterial Effect

Community-associated methicillin-resistant Staphylococcus aureus (MRSA) is now a major cause of bacterial infection. Antivirulence therapy does not stimulate evolution of a pathogen toward a resistant phenotype, providing a novel method to treat infectious diseases. Here, we used a cyclic peptide of CP7, an AIP-III variant that specifically inhibited the virulence and biofilm formation of Staphylococcus aureus (S. aureus) in a nonbiocidal manner, to conjugate with a broad-spectrum antimicrobial peptide (AMP) via two N-termini to obtain a hybrid AMP called CP7-FP13-2. This peptide not only specifically inhibited the production of virulence of S. aureus at low micromolar concentrations but also killed S. aureus, including MRSA, by disrupting the integrity of the bacterial cell membrane. In addition, CP7-FP13-2 inhibited the formation of the S. aureus biofilm and showed good antimicrobial efficacy against the S. aureus-infected Kunming mice model. Therefore, this study provides a promising strategy against the resistance and virulence of S. aureus.

Characterization of a Cutibacterium acnes Camp Factor 1-Related Peptide as a New TLR-2 Modulator in In Vitro and Ex Vivo Models of Inflammation

Cutibacterium acnes (C. acnes) has been implicated in inflammatory acne where highly mutated Christie-Atkins-Munch-Petersen factor (CAMP)1 displays strong toll like receptor (TLR)-2 binding activity. Using specific antibodies, we showed that CAMP1 production was independent of C. acnes phylotype and involved in the induction of inflammation. We confirmed that TLR-2 bound both mutated and non-mutated recombinant CAMP1, and peptide array analysis showed that seven peptides (A14, A15, B1, B2, B3, C1 and C3) were involved in TLR-2 binding, located on the same side of the three-dimensional structure of CAMP1. Both mutated and non-mutated recombinant CAMP1 proteins induced the production of C-X-C motif chemokine ligand interleukin (CXCL)8/(IL)-8 in vitro in keratinocytes and that of granulocyte macrophage-colony stimulating factor (GM-CSF), tumor necrosis factor (TNF)-α, IL-1β and IL-10 in ex vivo human skin explants. Only A14, B1 and B2 inhibited the production of CXCL8/IL-8 by keratinocytes and that of (GM-CSF), TNF-α, IL-1β and IL-10 in human skin explants stimulated with rCAMP1 and C. acnes. Following pretreatment with B2, RNA sequencing on skin explants identified the 10 genes displaying the strongest differential expression as IL6, TNF, CXCL1, CXCL2, CXCL3, CXCL8, IL-1β, chemokine ligand (CCL)2, CCL4 and colony stimulating factor (CSF)2. We, thus, identified a new CAMP1-derived peptide as a TLR-2 modulator likely to be a good candidate for clinical evaluation.

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.

Surfactin-oleogel with therapeutic potential for inflammatory acne vulgaris induced by Propionibacterium acnes

Accumulating evidence suggested that suppression of Propionibacterium acnes-induced inflammation was a promising strategy to alleviate acne vulgaris. This study evaluated the alleviating effect of surfactin-oleogel on P. acnes-induced inflammatory acne vulgaris in mice. Epidermis morphology and histopathological examination showed that surfactin-oleogel effectively ameliorated the P. acnes-induced epidermis swelling and erythema. Surfactin-oleogel reduced the epidermis thickness to 48.52% compared to the model control group. The colony of P. acnes in the epidermis was decreased by 1 log CFU/mL after receiving surfactin-oleogel treatment. Furthermore, surfactin-oleogel attenuated oxidative stress in the epidermis by increasing the activities of superoxide dismutase, catalase, and glutathione peroxidase. In addition, the expression of inducible nitric oxide synthase, nitric oxide, cyclooxygenase-2, pro-inflammatory cytokines (e.g. tumour necrosis factor-α and interleukin-1β), and nuclear factor kappa-B in the epidermis were reduced after treating with surfactin-oleogel. Moreover, total cholesterol and free fatty acids were decreased, whereas the treatment of surfactin-oleogel increased triglycerides and linoleic acid content. Besides, immunohistochemical assay and real-time PCR analysis indicated that surfactin-oleogel blocked the TLR2-mediated NF-κB signalling pathways in the epidermis. Consequently, our results demonstrated that surfactin-oleogel had antibacterial and anti-inflammation activities to treat P. acnes-induced inflammatory acne vulgaris.Key points• Surfactin-oleogel effectively relieves inflammation and oxidative stress caused by P. acnes.• Surfactin-oleogel effectively reduced the P. acnes colony.• Surfactin-oleogel relieves P. acnes-induced inflammation by inactivated the TLR-mediated NF-κB.

Surfactin inhibits the growth of Propionibacterium acnes by destroying the cell wall and membrane

Propionibacterium acnes plays a major role in acne vulgaris. In the pre-experiment, the growth of P. acnes was inhibited effectively using surfactin; however, the antibacterial mechanism has not been described. Therefore, the aim of this study was to evaluate antibacterial activity and analyse the mechanism of surfactin against P. acnes. Minimum inhibitory concentration, time-killing kinetics and scanning electron microscopy were used to evaluate the activity of surfactin against P. acnes, which showed that 128 μg ml^-1 effectively inhibited growth. Cell wall permeability was evaluated by detecting the extracellular alkaline phosphatase activity, which increased to 1·83- and 2·32-fold after incubating with 128 and 256 μg ml^-1 of surfactin for 10 h, respectively. Propidium iodide fluorescence, leakage of nucleic acid, protein, K⁺ , and Ca²⁺ , membrane potential and the leakage of calcein from small unilamellar vesicles all increased after incubation with surfactin, indicating that its strong biological activities act mainly by altering membrane integrity. In a mouse model of acne, surfactin significantly reduced P. acnes-induced epidermal swelling and erythema. These results indicate that surfactin effectively inhibited the growth of P. acnes by destroying the cell wall and membrane, and is a potential candidate for acne treatment.

Silicate bioceramics elicit proliferation and odonto-genic differentiation of human dental pulp cells

This study aimed to investigate the effects of silicates on the proliferation and odontogenic differentiation of human dental pulp cells (hDPCs) in vitro. HDPCs were cultured in the presence of calcium silicate (CS) extracts, while calcium hydroxide (CH) extracts and culture medium without CH or CS were used as the control groups. The calcium and phosphorus ion concentrations in the CS were similar to those in the control groups, but the concentration of silicon ions in the CS extracts was higher than that in the control groups. HDPCs cultured with CS and CH extracts at dilution of 1/128 proliferated significantly more than those cultured with the control treatments. CS extracts promoted cell migration, enhanced the expression of odontogenic marker genes and conspicuously increased odontogenesis-related protein production and the release of cytokines, suggesting that CS bioactive ceramics possess excellent biocompatibility and bioactivity and have the potential for application as pulp-capping agents.

The seafood Musculus senhousei shows anti-influenza A virus activity by targeting virion envelope lipids

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Pyropheophorbide a (PPa) was isolated from the seafood of M. senhousei.

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PPa shows a potent activity against a broad panel of influenza A viral strains.

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The mechanism of PPa is to block the entry of virus in the early stage of infection.

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The target of PPa may be that of lipid bilayer of the enveloped viruses.

Marine environments are known to be a new source of structurally diverse bioactive molecules. In this paper, we identified a porphyrin derivative of Pyropheophorbide a (PPa) from the mussel Musculus senhousei (M. senhousei) that showed broad anti-influenza A virus activity in vitro against a panel of influenza A viral strains. The analysis of the mechanism of action indicated that PPa functions in the early stage of virus infection by interacting with the lipid bilayer of the virion, resulting in an alteration of membrane-associated functions, thereby blocking the entry of enveloped viruses into host cells. In addition, the anti-influenza A virus activity of PPa was further assessed in mice infected with the influenza A virus. The survival rate and mean survival time of mice were apparently prolonged compared with the control group which was not treated with the drug. Therefore, PPa and its derivatives may represent lead compounds for controlling influenza A virus infection.

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

BACKGROUND AND PURPOSE

Propionibacterium acnes is a Gram-positive bacterium associated with the skin disorder acne. In this study, as fatty acids are considered to be important 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

The antimicrobial activity of various lipopeptides was determined by measuring their minimal inhibitory concentration (MIC). Lipids from P. acnes were used to explore their mode of action. RAW264.7 cells stimulated with LPS and P. acnes respectively were used to measure their 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 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 the bacterial membrane, thereby impairing membrane permeability and causing leakage of inner contents of bacterial cells. Furthermore, 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 verified in the in vivo animal studies.

CONCLUSIONS AND IMPLICATIONS

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