Expression and Purification of Hybrid LL-37Tα1 Peptide in Pichia pastoris and Evaluation of Its Immunomodulatory and Anti-inflammatory Activities by LPS Neutralization

Antibacterial efficacy and mechanism of Cyprinus carpio chemokine-derived L-10 against multidrug-resistant Escherichia coli infections

OBJECTIVES

Antimicrobial resistance has raised concerns regarding untreatable infections and poses a growing threat to public health. Rational design of new AMPs is an ideal solution to this threat.

METHODS

In this study, we designed, modified, and synthesised an excellent AMP, L-10, based on the original sequence of the Cyprinus carpio chemokine. All experimental data were presented as the mean ± standard deviation (SD), and the two-tailed unpaired T-test method was used to analyze all data.

RESULTS

L-10 exhibited excellent antibacterial activity with negligible toxicity and improved the efficacy of a broad class of antibiotics against MDR Gram-negative pathogens, including tetracycline, meropenem, levofloxacin, and rifampin. Mechanistic studies have suggested that L-10 targets the bacterial membrane components, LPS and PG, to disrupt bacterial membrane integrity, thereby exerting antibacterial effects and enhancing the efficacy of antibiotics. Moreover, in animal infection models, L-10 significantly increased the survival rate of infected animals and effectively reduced the tissue bacterial load and inflammatory factor levels. In addition to its direct antibacterial activity, L-10 dramatically reduced pulmonary pathological alterations in a mouse model of endotoxemia and suppressed LPS-induced proinflammatory cytokines in vitro and in vivo. Lastly, L-10 was successfully expressed in Pichia pastoris and maintained antimicrobial activity against MDR Gram-negative pathogens in vivo and in vitro.

CONCLUSION

Collectively, these results reveal the potential of L-10 as an ideal candidate against MDR bacterial infections and provide new insights into the design, development, and clinical application of AMPs.

Purification and characterization of a novel immunoregulatory peptide from Sipunculus nudus L. protein

This study aimed to purify and characterize immunoregulatory peptides from Sipunculus nudus L. and to explore the underlying mechanisms. Ultrafiltration, gel filtration chromatography, and reverse phase high-performance liquid chromatography (RP-HPLC) were used to purify the peptide following enzymatic hydrolysis. Rates of lymphocyte proliferation and phagocytosis as well as nitric oxide (NO) production levels were used as indicators of immunoregulatory activity to screen the fractions. The amino acid sequence of the peptide, designated as SNLP, was identified as Arg-Val-Lys-Gly-Lys-Ile-Leu-Ala-Lys-Arg-Leu-Asn (RVKGKILAKRLN) by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Treatment with the synthetic SNLP increased the proliferation and phagocytosis of RAW 264.7 macrophages and promoted the secretion of tumor necrosis factor-ɑ (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β), and NO levels. The mRNA levels of these cytokines and iNOS were also increased by SNLP. Our results provide preliminary evidence suggesting that SNLP acts as a dual immunomodulatory peptide with immunostimulatory and anti-inflammatory activities. In summary, SNLP derived from Sipunculus nudus L. is a potent immunoregulatory peptide and represents a potential functional food or immunoregulatory drug.

Toxicity study of pro-angiogenic casein manganese oxide nanoparticles: an in vitro and in vivo approach

Recently, we have demonstrated casein manganese oxide nanoparticles (CMnNP) that exhibit pro-angiogenic property established through different in vitro and in vivo experiments. The CMnNP was explored for therapeutic angiogenesis for treatment of wounds and recovery of hindlimb ischemia in pre-clinical mouse prototypical. It is well known that to translate any therapeutic nanoparticle for future clinical applications, their biosafety evaluation in small and large animals is essential. Herein, in the current study, the biosafety and bioavailability of the CMnNP have been explored by a systematic toxicity profiling study in C57BL/6J mice model. Initially, the in vitro cytotoxic effects of CMnNP were validated in RAW 264.7 cells. Later, the CMnNP was administered intraperitoneally with different doses (50, 300, and 2000 mg/kg b.wt./day) at different time points of exposure (acute: 2 weeks, sub-chronic: 4 weeks as well as chronic exposure: 8 and 20 weeks) with reference to the maximum tolerable dose (MTD) of CMnNP as per the OECD guidelines. The blood hematological and serum biochemical parameters of CMnNP treatment groups indicate negligible changes similar to untreated group. The histopathological examination of CMnNP-treated vital organs (lung, spleen, liver, brain, kidney, and heart) illustrates no major changes even at higher doses. Further, the biodistribution and excretion study depicts normal clearance of CMnNP. Additionally, the serum cytokine levels were normal in the therapeutic dose of CMnNP. The results altogether indicate that the non-toxic nature of CMnNP makes them useful as future therapeutic angiogenic agent for the treatment of various diseases where angiogenesis plays an important role.

Yeast Expressed Hybrid Peptide CLP Abridged Pro-Inflammatory Cytokine Levels by Endotoxin Neutralization

The aim of this study was to apply a strategy to express a recombinant CLP peptide and explore its application as a product derived from natural compounds. The amphiphilic CLP peptide was hybridized from three parent peptides (CM4, LL37, and TP5) and was considered to have potent endotoxin-neutralizing activity with minimal cytotoxic and hemolytic activity. To achieve high secretion expression, an expression vector of pPICZαA-HSA-CLP was constructed by the golden gate cloning strategy before being transformed into Pichia pastoris and integrated into the genome. The recombinant CLP was purified through the Ni-NTA affinity chromatography and analyzed by SDS-PAGE and mass spectrometry. The Limulus amebocyte lysate (LAL) test exhibited that the hybrid peptide CLP inhibited lipopolysaccharides (LPS) in a dose-dependent manner and was significantly (p < 0.05) more efficient compared to the parent peptides. In addition, it essentially diminished (p < 0.05) the levels of nitric oxide and pro-inflammatory cytokines (including TNF-α, IL6, and IL-1β) in LPS-induced mouse RAW264.7 macrophages. As an attendant to the control and the parental peptide LL37, the number of LPS-induced apoptotic cells was diminished compared to the control parental peptide LL37 (p < 0.05) with the treatment of CLP. Consequently, we concluded that the hybrid peptide CLP might be used as a therapeutic agent.

Peptide Conjugates Derived from flg15, Pep13, and PIP1 That Are Active against Plant-Pathogenic Bacteria and Trigger Plant Defense Responses

Thirty peptide conjugates were designed by combining an antimicrobial peptide (BP16, BP100, BP143, KSL-W, BP387, or BP475) at the N- or C-terminus of a plant defense elicitor peptide (flg15, BP13, Pep13, or PIP1). These conjugates were highly active in vitro against six plant-pathogenic bacteria, especially against Xanthomonas arboricola pv. pruni, Xanthomonas fragariae and Xanthomonas axonopodis pv. vesicatoria. The most active peptides were those incorporating Pep13. The order of the conjugation influenced the antibacterial activity and the hemolysis. Regarding the former, peptide conjugates incorporating the elicitor peptide flg15 or Pep13 at the C-terminus were, in general, more active against Pseudomonas syringae pv. actinidiae and P. syringae pv. syringae, whereas those bearing these elicitor peptides at the N-terminus displayed higher activity against Erwinia. amylovora and the Xanthomonas species. The best peptide conjugates displayed MIC values between 0.8 and 12.5 μM against all the bacteria tested and also had low levels of hemolysis and low phytotoxicity. Analysis of the structural and physicochemical parameters revealed that a positive charge ranging from +5 to +7 and a moderate hydrophobic moment/amphipathic character is required for an optimal biological profile. Interestingly, flg15-BP475 exhibited a dual activity, causing the upregulation of the same genes as flg15 and reducing the severity of bacterial spot in tomato plants with a similar or even higher efficacy than copper oxychloride. Characterization by nuclear magnetic resonance (NMR) of the secondary structure of flg15-BP475 showed that residues 10 to 25 fold into an α-helix. This study establishes trends to design new bifunctional peptides useful against plant diseases caused by plant-pathogenic bacteria.

IMPORTANCE The consequences of plant pathogens on crop production together with the lack of effective and environmentally friendly pesticides evidence the need of new agents to control plant diseases. Antimicrobial and plant defense elicitor peptides have emerged as good candidates to tackle this problem. This study focused on combining these two types of peptides into a single conjugate with the aim to potentiate the activity of the individual fragments. Differences in the biological activity of the resulting peptide conjugates were obtained depending on their charge, amphipathicity, and hydrophobicity, as well as on the order of the conjugation of the monomers. This work provided bifunctional peptide conjugates able to inhibit several plant-pathogenic bacteria, to stimulate plant defense responses, and to reduce the severity of bacterial spot in tomato plants. Thus, this study could serve as the basis for the development of new antibacterial/plant defense elicitor peptides to control bacterial plant pathogens.

Recombinant human β-defensin130 inhibited the growth of foodborne bacteria through membrane disruption and exerted anti-inflammatory activity

Foodborne pathogens causing food poisoning and infections are detrimental to human health, and the abuse of antibiotics induced severe antibiotic resistance in past decades. Thus, it is urgent to develop new antimicrobial agents. In the current study, human β-defensin 130 (hBD130), which is an antimicrobial peptide identified in human macrophages in 2017, was initially produced in Pichia pastoris. The purified hBD130 demonstrated broad bactericidal spectrum against foodborne pathogens through a membrane disruption, with concentrations ranging from 10 to 45 μg/mL. Moreover, hBD130 showed a low hemolytic effect and nearly no cytotoxicity to mammalian cells with a dosage of 400 μg/mL. In addition, the secretion amounts and mRNA levels of NO, IL-6, IL-1β, and TNF-α in LPS-induced mouse macrophage were significantly decreased with 1 mg/mL of hBD130. Taken together, these results showed that hBD130 is a promising antimicrobial agent to treat foodborne bacterial infections and inflammation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-022-01087-y.

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.

An update on endotoxin neutralization strategies in Gram-negative bacterial infections

INTRODUCTION

Gram-negative bacterial infections represent still a severe problem of human health care, regarding the increase in multi-resistance against classical antibiotics and the lack of newly developed antimicrobials. For the fight against these germs, anti-infective agents must overcome and/or bind to the Gram-negative outer membrane consisting of a lipopolysaccharide (LPS, endotoxin) outer leaflet and an inner leaflet from phospholipids, with additional peripheral or integral membrane proteins (OMP's).

AREAS COVERED

The current article reviews data of existing therapeutic options and summarizes newer approaches for targeting and neutralizing endotoxins, ranging from in vitro over in vivo animal data to clinical applications by using databases such as Medline.

EXPERT OPINION

Conventional antibiotic treatment of the bacteria leads to their killing, but not necessary LPS neutralization, which may be a severe problem in particular for the systemic pathway. This is the reason why there is an increasing number of therapeutic approaches, which - besides combating whole bacteria - at the same time try to neutralize endotoxin within or outside the bacterial cells mainly responsible for the high inflammation induction in Gram-negative species.

Mucosal IgG in inflammatory bowel disease - a question of (sub)class?

Immunoglobulins (Igs) form a cornerstone of mucosal immunity. In the gastrointestinal tract, secretory IgA and IgM bind to commensal microorganisms within the intestinal lumen to prevent them from breaching the intestinal epithelium - a process known as immune exclusion. In recent years, there has been renewed interest in the role of IgG in intestinal immunity, driven in part by a genetic association of an affinity-lowering variant of an IgG receptor, FcγRIIA, with protection from ulcerative colitis (UC), a subclass of inflammatory bowel disease (IBD). We recently demonstrated a role for IgG and Fcγ receptor signalling in driving pathogenic IL-1β production by colonic mononuclear phagocytes and the subsequent induction of a local type 17 response in UC. Here, we discuss the potential relevance of our observations to the other major subclass of IBD - Crohn's disease (CD) - where the genetic association with FCGR variants is less robust and consider how this may impact therapeutic interventions in these disease subsets.

Anti-Inflammatory Activity of Antimicrobial Peptide Periplanetasin-5 Derived from the Cockroach Periplaneta americana

Previously, we performed an in silico analysis of the Periplaneta americana transcriptome. Antimicrobial peptide candidates were selected using an in silico antimicrobial peptide prediction method. It was found that periplanetasin-5 had antimicrobial activity against yeast and grampositive and gram-negative bacteria. In the present study, we demonstrated the anti-inflammatory activities of periplanetasin-5 in mouse macrophage Raw264.7 cells. No cytotoxicity was observed at 60 μg/ml periplanetasin-5, and treatment decreased nitric oxide production in Raw264.7 cells exposed to lipopolysaccharide (LPS). In addition, quantitative RT-PCR and enzyme-linked immunosorbent assay revealed that periplanetasin-5 reduced cytokine (tumor necrosis factor-α, interleukin-6) expression levels in the Raw264.7 cells. Periplanetasin-5 controlled inflammation by inhibiting phosphorylation of MAPKs, an inflammatory signaling element, and reducing the degradation of IκB. Through LAL assay, LPS toxicity was found to decrease in a periplanetasin-5 dose-dependent manner. Collectively, these data showed that periplanetasin-5 had antiinflammatory activities, exemplified in LPS-exposed Raw264.7 cells. Thus, we have provided a potentially useful antibacterial peptide candidate with anti-inflammatory activities.

Strategies for Optimizing the Production of Proteins and Peptides with Multiple Disulfide Bonds

Bacteria can produce recombinant proteins quickly and cost effectively. However, their physiological properties limit their use for the production of proteins in their native form, especially polypeptides that are subjected to major post-translational modifications. Proteins that rely on disulfide bridges for their stability are difficult to produce in Escherichia coli. The bacterium offers the least costly, simplest, and fastest method for protein production. However, it is difficult to produce proteins with a very large size. Saccharomyces cerevisiae and Pichia pastoris are the most commonly used yeast species for protein production. At a low expense, yeasts can offer high protein yields, generate proteins with a molecular weight greater than 50 kDa, extract signal sequences, and glycosylate proteins. Both eukaryotic and prokaryotic species maintain reducing conditions in the cytoplasm. Hence, the formation of disulfide bonds is inhibited. These bonds are formed in eukaryotic cells during the export cycle, under the oxidizing conditions of the endoplasmic reticulum. Bacteria do not have an advanced subcellular space, but in the oxidizing periplasm, they exhibit both export systems and enzymatic activities directed at the formation and quality of disulfide bonds. Here, we discuss current techniques used to target eukaryotic and prokaryotic species for the generation of correctly folded proteins with disulfide bonds.

A Novel Cecropin-LL37 Hybrid Peptide Protects Mice Against EHEC Infection-Mediated Changes in Gut Microbiota, Intestinal Inflammation, and Impairment of Mucosal Barrier Functions

Intestinal inflammation can cause impaired epithelial barrier function and disrupt immune homeostasis, which increases the risks of developing many highly fatal diseases. Enterohemorrhagic Escherichia coli (EHEC) O157:H7 causes intestinal infections worldwide and is a major pathogen that induces intestinal inflammation. Various antibacterial peptides have been described as having the potential to suppress and treat pathogen-induced intestinal inflammation. Cecropin A (1–8)-LL37 (17–30) (C-L), a novel hybrid peptide designed in our laboratory that combines the active center of C with the core functional region of L, shows superior antibacterial properties and minimized cytotoxicity compared to its parental peptides. Herein, to examine whether C-L could inhibit pathogen-induced intestinal inflammation, we investigated the anti-inflammatory effects of C-L in EHEC O157:H7-infected mice. C-L treatment improved the microbiota composition and microbial community balance in mouse intestines. The hybrid peptide exhibited improved anti-inflammatory effects than did the antibiotic, enrofloxacin. Hybrid peptide treated infected mice demonstrated reduced clinical signs of inflammation, reduced weight loss, reduced expression of pro-inflammatory cytokines [tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interferon-gamma (IFN-γ)], reduced apoptosis, and reduced markers of jejunal epithelial barrier function. The peptide also affected the MyD88–nuclear factor κB signaling pathway, thereby modulating inflammatory responses upon EHEC stimulation. Collectively, these findings suggest that the novel hybrid peptide C-L could be developed into a new anti-inflammatory agent for use in animals or humans.

In vitro Impact of Yeast Expressed Hybrid Peptide CATH-2TP5 as a Prophylactic Measure Toward Sepsis and Inflammation

CATH-2TP5 is a linear cationic hybrid peptide, consequent from naturally occurring antimicrobial peptide (AMPs) Cathelicidin-2 (CATH-2) and Immunomodulatory peptide Thymopentin (TP5) having dynamic and potent anti-inflammatory activities without hemolytic effect. The biocompatible mechanism of CATH-2TP5 is favored to explore new methodologies in the direction of biomedical applications. In this retrospectively study, an antiendotoxin and anti-inflammatory hybrid peptide CATH-2TP5 was emulated into pPICZα-A and successfully expressed in Pichia pastoris (P. pastoris). The recombinant CATH-2TP5 was purified through the Ni-affinity column and reversed-phase HPLC. The purified CATH-2TP5 peptide exhibited robust anti-endotoxin activity and significantly (p < 0.05) neutralized the effect of lipopolysaccharide (LPS). Furthermore, the down-regulated effect of CATH-2TP was more pronounced (p < 0.05) on LPS-induced cytotoxic effects, nitric oxide secretion and pro-inflammatory cytokines (TNF-α, IL-6, and IL-1β) in murine RAW264.7 macrophages. As associated to control and parental peptide the number of apoptotic cells was also contracted with the treatment of CATH-2TP5. Thus, we concluded that CATH-2TP5 peptide may be used in various biomedical applications as a therapeutic drug.

A Hybrid Peptide DEFB-TP5 Expressed in Methylotrophic Yeast Neutralizes LPS With Potent Anti-inflammatory Activities

DEFB-TP5 is a novel auspicious health-beneficial peptide derivative from two naturally occurring peptides, β-Defensin (DEFB) and thymopentin (TP5), and shows strong anti-inflammatory activity and binds to LPS without cytotoxicity and hemolytic effect. Furthermore, the application of DEFB-TP5 peptide is inadequate by its high cost. In the current study, we developed a biocompatible mechanism for expression of the DEFB-TP5 peptide in Pichia pastoris. The transgenic strain of hybrid DEFB-TP5 peptide with a molecular weight of 6.7kDa as predictable was obtained. The recombinant DEFB-TP5 peptide was purified by Ni-NTA chromatography, estimated 30.41 mg/L was obtained from the cell culture medium with 98.2% purity. Additionally, The purified DEFB-TP5 peptide significantly (p< 0.05) diminished the release of nitric oxide (NO), TNF-α, IL-6, IL-1β in LPS-stimulated RAW264.7 macrophages in a dose-dependent manner. This study will not only help to understand the molecular mechanism of expression that can potentially be used to develop an anti-endotoxin peptide but also to serve as the basis for the development of antimicrobial and anti-inflammatory agents as well, which also provides a potential source for the production of recombinant bioactive DEFB-TP5 at the industrial level.

Octominin Inhibits LPS-Induced Chemokine and Pro-inflammatory Cytokine Secretion from RAW 264.7 Macrophages via Blocking TLRs/NF-κB Signal Transduction

Inflammation is a well-organized innate immune response that plays an important role during the pathogen attacks and mechanical injuries. The Toll-like receptors (TLR)/nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) is a major signal transduction pathway observed in RAW 264.7 macrophages during the inflammatory responses. Here, we investigated the anti-inflammatory effects of Octominin; a bio-active peptide developed from Octopus minor in RAW 264.7 macrophages in vitro. Octominin was found to inhibit lipopolysaccharides (LPS)-stimulated transcriptional activation of NF-κB in RAW 264.7 cells and dose-dependently decreased the mRNA expression levels of TLR4. Specifically, in silico docking results demonstrated that Octominin has a potential to inhibit TLR4 mediated inflammatory responses via blocking formation of TLR4/MD-2/LPS complex. We also demonstrated that Octominin could significantly inhibit LPS-induced secretion of pro-inflammatory cytokine (interleukin-β; IL-1β, IL-6, and tumor necrosis factor-α) and chemokines (CCL3, CCL4, CCL5, and CXCL10) from RAW 264.7 cells. Additionally, Octominin repressed the LPS-induced pro-inflammatory mediators including nitric oxide (NO), prostaglandin E2, inducible NO synthase, and cyclooxygenase 2 in macrophages. These results suggest that Octominin is a potential inhibitor of TLRs/NF-κB signal transduction pathway and is a potential candidate for the treatment of inflammatory diseases.

Immunomodulatory significance of natural peptides in mammalians: Promising agents for medical application

Modulation of immune responses by immunoregulatory agents, such as the natural or synthetic immunomodulatory peptides, has been suggested as a potential strategy to modulate immune system against infection and other immune-related diseases. These compositionally simple peptides have attracted much attention for many drug developers, due to their high activity, low toxicity and clear target specificity. Host defence peptides and milk-derived peptides are two kinds of natural immunomodulatory peptides which have been widely studied in mammalians. They could participate at the interface of innate and adaptive immunity by regulating immune effector cells. This review summarizes the recent advances in host defence peptides and milk-derived peptides as well as their general characteristics, immunomodulatory functions and possible applications.