LPS inmobilization on porous and non-porous supports as an approach for the isolation of anti-LPS host-defense peptides

Biosynthetic Microcin J25 Exerts Strong Antibacterial, Anti-Inflammatory Activities, Low Cytotoxicity Without Increasing Drug-Resistance to Bacteria Target

Multidrug resistant (MDR) bacterial infection has emerged, raising concerns about untreatable infections, and posing the highest health risks. Antimicrobial peptides (AMPs) are thought to be the best remedy for this problem. Here, we showed biosynthetic microcin J25 (MccJ25) exhibited excellent bactericidal activity against standard and clinically relevant veterinary MDR strains with high stability, no cytotoxicity, and no increase in drug resistance. Analysis of antimicrobial mechanism possessed by sensitive enterotoxigenic Escherichia coli (ETEC) based on electron microscopy and Sytox Green methods was carried out. Results showed excellent activity against ETEC was due to permeabilizing bacterial membranes and strong affinity. MccJ25 exhibited high endotoxin-neutralizing activity in both in vivo and in vitro environments, and mice exposed to lipopolysaccharide (LPS) showed decreased plasma LPS levels and improved survival after administration of MccJ25. In an LPS-treated mouse septicemia model, MccJ25 treatment significantly alleviated inflammatory responses by inhibiting proinflammatory factor secretion and expression. In a mouse E. coli infection model, administration of MccJ25 effectively improved host defense against clinically source cocktail of multidrug-resistant E. coli strains induced intestinal inflammation and bacteria dissemination. Results of studies on anti-inflammatory mechanisms showed that MccJ25 downregulated nuclear factor kappa B kinase and mitogen-activated protein kinase, thereby reducing the production of toll-like receptor 4, myeloid differentiation factor 88 and decreasing the key proinflammatory cytokines. These findings clarify MccJ25 may be an ideal antibacterial/antiendotoxic drug candidate that has the potential to further guide the development of anti-inflammatory and/or antimicrobial agents in the war against MDR bacterial infection.

A Novel Polymeric Nanohybrid Antimicrobial Engineered by Antimicrobial Peptide MccJ25 and Chitosan Nanoparticles Exerts Strong Antibacterial and Anti-Inflammatory Activities

Infection caused by antibiotic-resistant microorganisms (ARMs) has been declared a global threat to public health. Polymeric nanoparticles (PNPs) formed by antimicrobial peptides (AMPs) and synthetic PNPs against ARM infections are emerging. PNPs are also considered to be a promising natural biological preservative that prevents microbial spoilage through food processing and preservation. We engineered CNMs, a novel nanocomposite antibacterial agent based on chitosan nanoparticles and AMP microcin J25. In this study, we aimed to evaluate the comprehensive antimicrobial activity, potential antimicrobial mechanism, and anti-inflammatory activity of CNMs. We demonstrated that CNMs harbor excellent bactericidal activity against clinical foodborne pathogens and ARMs. CNMs caused fast mortality against different growth phases of tetracycline (Tet)-resistant enterotoxigenic E. coli (ETEC) and significantly killed Tet-resistant ETEC in food biological environments. Mechanistically, CNMs have the ability to bind lipopolysaccharides (LPS), neutralize endotoxin, and promote diaphragm permeability by damaging the cell membrane. CNMs did not cause mouse RAW264.7 cell cytotoxicity. Notably, CNMs significantly reduced the cytotoxicity of RAW264.7 macrophages induced by LPS. The LPS-induced inflammatory response was significantly ameliorated by CNMs by reducing the levels of nitric oxide and proinflammatory cytokines, including tumor necrosis factor α, interleukin (IL)-6, IL-8, IL-1β, Toll-like receptor 4, and nuclear factor κB (NF-κB), in LPS-challenged RAW264.7 macrophages. CNMs downregulated the NF-κB and mitogen-activated protein kinase signaling pathways, thereby inhibiting inflammatory responses upon LPS stimulation. Taken together, CNMs could be applied as effective antimicrobial/anti-inflammatory agents with lower cytotoxicity in food, medicine, and agriculture to prevent bacterial contamination and infection, respectively.

Anti-inflammatory and antioxidant effects of peptides released from germinated amaranth during in vitro simulated gastrointestinal digestion

Amaranth (Amaranthus hypochondriacus) is an ancestral nutritional grain and good source of bioactive compounds as peptides. In this study, the effect of in vitro simulated gastrointestinal digestion (SGD) of germinated amaranth on the release of antioxidant and anti-inflammatory peptides was evaluated. The germinated amaranth peptides generated during SGD were released after 90 min of incubation with pancreatin and fractioned to F1 (>10 kDa), F2 (3-10 kDa), and F3 (<3 kDa). Among germinated amaranth peptides fractions tested, F2 had the highest antioxidant activity, while F1 and F2 exhibited a high anti-inflammatory response caused by lipopolysaccharide-induced in RAW 264.7 macrophages. A total of 11 peptides sequences were identified in the fractions evaluated, and they exhibit potential biological activity against non-communicable diseases. The findings from this study showed first time report on bioactive peptides, especially anti-inflammatory, from germinated amaranth released by in vitro gastrointestinal digestion.

Antibacterial activities and molecular mechanism of amino-terminal fragments from pig nematode antimicrobial peptide CP-1

High manufacturing costs and weak cell selectivity have limited the clinical application of naturally occurring peptides when faced with an outbreak of drug resistance. To overcome these limitations, a set of antimicrobial peptides was synthesized with the general sequence of (WL)n, where n = 1, 2, 3, and WL was truncated from the N-terminus of Cecropin P1 without initial serine residues. The antimicrobial peptide WL3 exhibited stronger antimicrobial activity against both Gram-negative and Gram-positive microbes than the parental peptide CP-1. WL3 showed no hemolysis even at the highest test concentrations compared to the parental peptide CP-1. The condition sensitivity assays (salts, serum, and trypsin) demonstrated that WL3 had high stability in vitro. Fluorescence spectroscopy and electron microscopy indicated that WL3 killed microbes by means of penetrating the membrane and causing cell lysis. In a mouse model, WL3 was able to significantly reduce the bacteria load in major organs and cytokines (TNF-α, IL-6, and IL-1β) levels in serum. In summary, these findings suggest that WL3, which was modified from a natural antimicrobial peptide, has enormous potential for application as a novel antibacterial agent.

Immunomodulating peptides for food allergy prevention and treatment

Among the most promising strategies currently assayed against IgE-mediated allergic diseases stands the possibility of using immunomodulating peptides to induce oral tolerance toward offending food allergens or even to prevent allergic sensitization. This review focuses on the beneficial effects of food derived immunomodulating peptides on food allergy, which can be directly exerted in the intestinal tract or once being absorbed through the intestinal epithelial barrier to interact with immune cells. Food peptides influence intestinal homeostasis by maintaining and reinforcing barrier function or affecting intestinal cell-signalling to nearby immune cells and mucus secretion. In addition, they can stimulate cells of the innate and adaptive immune system while supressing inflammatory responses. Peptides represent an attractive alternative to whole allergens to enhance the safety and efficacy of immunotherapy treatments. The conclusions drawn from curative and preventive experiments in murine models are promising, although there is a need for more pre-clinical studies to further explore the immunomodulating strategy and its mechanisms and for a deeper knowledge of the peptide sequence and structural requirements that determine the immunoregulatory function.

Impacts of experimentally induced and clinically acquired quinolone resistance on the membrane and intracellular subproteomes of Salmonella Typhimurium DT104B

Antimicrobial resistance is a growing public health threat worldwide that is still far from a complete understanding. Salmonella Typhimurium DT104 multiresistant strains with additional quinolone resistance are highly adaptive and have been responsible for global outbreaks and high mortality. In order to give new insights about the resistance mechanisms involved, the developed work aimed to point out subproteome changes between a DT104B clinical strain (Se20) that acquired quinolone resistance after patient treatment and an in vitro induced clonally related highly-resistant mutant (Se6-M). The intracellular subproteomes were compared by a 2-DE/LC-MS/MS approach and a total of 50 unique proteins were identified (32 more abundant in Se20 and 18 more abundant in Se6-M). The membrane subproteomes were analysed by a shotgun LC-MS/MS approach, where 7 differentially abundant proteins were identified (5 more abundant in Se6-M and 2 more abundant in Se20). Several proteins known to be directly related to quinolone resistance mechanisms (AAC(6')-Ib-cr4, OmpC, OmpD, OmpX, etc.) and MipA, recently reported as novel antibiotic resistance-related protein, were identified. Other proteins (Fur, SodA, SucB, AtpD/AtpG, OmpC, GltI, CheM/CheB, etc.) reflecting the metabolic re-adjustments occurred in each strain in order to acquire quinolone resistance were also identified. Moreover, proteins involved in lipopolysaccharide biosynthesis (RfbF, RfbG, GmhA) and export (LptA) were detected, supporting the importance of exploring these proteins as targets for the development of new antimicrobial agents. In conclusion, this study provides new insights into the mechanisms involved in the acquisition of antibiotic resistance, which can be highly valuable for the development of improved therapeutic strategies.

BIOLOGICAL SIGNIFICANCE

This comparative proteomic study revealed a large number of differentially regulated proteins involved in antibiotic resistance which can be of great value to drug discovery, research and development programmes.

Lipopolysaccharide of Klebsiella pneumoniae attenuates immunity of Caenorhabditis elegans and evades by altering its supramolecular structure

Given the prominence of lipopolysaccharide (LPS) in the pathogenesis of Gram-negative bacteria, investigations at the molecular level in in vivo conditions are in dire need to understand its role in provoking infection.

Antimicrobial Peptide CMA3 Derived from the CA-MA Hybrid Peptide: Antibacterial and Anti-inflammatory Activities with Low Cytotoxicity and Mechanism of Action in Escherichia coli

CA-MA is a hybrid antimicrobial peptide (AMP) derived from two naturally occurring AMPs, cecropin A and magainin 2. CA-MA shows strong antimicrobial activity against Gram-negative and Gram-positive bacteria but also exhibits cytotoxicity toward mammalian cells. Our objective was to identify CA-MA analogues with reduced cytotoxicity by systematic replacement of amino acids with positively charged R groups (His and Lys), aliphatic R groups (Leu), or polar R groups (Glu). Among the CA-MA analogues studied (CMA1 to -6), CMA3 showed the strongest antimicrobial activity, including against drug-resistant Escherichia coli and Pseudomonas aeruginosa strains isolated from hospital patients. CMA3 appeared to act by inducing pore formation (toroidal model) in the bacterial membrane. In cytotoxicity assays, CMA3 showed little cytotoxicity toward human red blood cells (hRBCs) or HaCaT cells. Additionally, no fluorescence was released from small or giant unilamellar vesicles exposed to 60 μM CMA3 for 80 s, whereas fluorescence was released within 35 s upon exposure to CA-MA. CMA3 also exerted strong lipopolysaccharide (LPS)-neutralizing activity in RAW 264.7 cells, and BALB/c mice exposed to LPS after infection by Escherichia coli showed improved survival after administration of one 0.5-mg/kg of body weight or 1-mg/kg dose of CMA3. Finally, in a mouse model of septic shock, CMA3 reduced the levels of proinflammatory factors, including both nitric oxide and white blood cells, and correspondingly reduced lung tissue damage. This study suggests that CMA3 is an antimicrobial/antiendotoxin peptide that could serve as the basis for the development of anti-inflammatory and/or antimicrobial agents with low cytotoxicity.

Screening for anti-inflammatory components from Corydalis bungeana Turcz. based on macrophage binding combined with HPLC

Background

Corydalis bungeana Turcz. (CB; family: Corydalis DC.) is an anti-inflammatory medicinal herb used widely in traditional Chinese medicine (TCM) for upper respiratory tract infection, etc., but its anti-inflammatory active molecules are unknown. This study was designed to screen for the anti-inflammatory components from CB based on macrophage binding combined with HPLC.

Methods

Xylene-induced ear edema in mouse and carrageenan-induced hind-paw edema in rats were used to evaluate the anti-inflammatory activity of CB. The macrophage binding with high-performance liquid chromatography (HPLC) analysis and HPLC-MS were established to screen the potential active compounds. ELISA kits were performed to measure the levels of IL-6, IL-10, TNF-α and NO in RAW 264.7 macrophages culture media.

Results

The alkaloid extract of CB could inhibit significantly xylene-induced ear edema in mouse and carrageenan-induced hind-paw edema in rats. Two components binded to RAW 264.7 cell were identified as 12-hydroxycorynoline and corynoline. Bioassays demonstrated that these two compounds significantly inhibited LPS-induced IL-6, IL-10, TNF-α and NO levels.

Conclusions

The results suggest that corynoline and 12-hydroxycorynoline contribute to the anti-inflammatory effects of the alkaloid extract of CB. Our findings suggest that these two compounds can be used as candidate for anti-inflammatory drugs.

Inhibition of the Rho/Rho kinase pathway prevents lipopolysaccharide-induced hyperalgesia and the release of TNF-α and IL-1β in the mouse spinal cord

Administration of lipopolysaccharide (LPS) by various routes produces profound inflammatory pain hypersensitivity. However, the molecular events that induce this response remain largely uncharacterized. In the present study, we sought to elucidate the role of the Rho/Rho kinase (ROCK) pathway in the release of tumor necrosis factor-α (TNF-α) and interleukin 1β (IL-1β) following injection of LPS into the mouse paw, which is associated with nociceptive behavior. The spinal cord of LPS-treated mice showed increased active GTP-bound RhoA and upregulation of ROCK2 and c-fos compared to the normal saline group. Furthermore, the inflammation-related cytokines TNF-α and IL-1β were markedly increased in the spinal dorsal horn after intraplantar injection of LPS. However, the latter effects were prevented by prophylactic intrathecal administration of the Rho inhibitor (C3 exoenzyme) or the ROCK inhibitor (Y27632). Collectively, our results suggest that the Rho/ROCK signaling pathway plays a critical role in LPS-induced inflammatory pain and that this pathway is coincident with the release of the pro-nociceptive cytokines TNF-α and IL-1β, which produces hyperalgesia.

Recombinant probiotics with antimicrobial peptides: a dual strategy to improve immune response in immunocompromised patients

Bacterial infectious diseases are currently a serious health problem, especially in patients compromised by illness or those receiving immune-suppressant drugs. In this context, it is not only essential to improve the understanding of infectious mechanisms and host response but also to discover novel therapies with extreme urgency. Probiotics and antimicrobial peptides are also favorably viewed as novel strategies in the control of resistant bacteria. The present review will shed some light on the use of probiotic microorganisms expressing antimicrobial peptides as a dual therapy to control bacterial infectious diseases.