Epinecidin-1 antimicrobial activity: In vitro membrane lysis and In vivo efficacy against Helicobacter pylori infection in a mouse model. Biomaterials. 2015;61:41-51. [PMID: 25996410 DOI: 10.1016/j.biomaterials.2015.05.014]

A novel antimicrobial peptide S24 combats serious wound infections caused by Pseudomonas aeruginosa and Acinetobacter baumannii

OBJECTIVES

Pseudomonas aeruginosa and Acinetobacter baumannii are ranked as top-priority organisms by WHO. Antimicrobial peptides (AMPs) are promising antimicrobial agents that are highly effective against serious bacterial infections.

METHODS

In our previous study, a series of α-helical AMPs were screened using a novel multiple-descriptor strategy. The current research suggested that S24 exhibited strong antimicrobial activity against major pathogenic bacteria, and displayed minimal haemolysis, good serum stability and maintained salt resistance.

RESULTS

We found that S24 exerted an antimicrobial effect by destroying outer membrane permeability and producing a strong binding effect on bacterial genomic DNA that inhibits genomic DNA migration. Furthermore, S24 exerted a strong ability to promote healing in wound infected by P. aeruginosa, A. baumannii and mixed strains in a mouse model.

CONCLUSIONS

Overall, S24 showed good stability under physiological conditions and excellent antimicrobial activity, suggesting it may be a potential candidate for the development of serious bacterial infection treatment.

Effective Treatment of Helicobacter pylori Infection Using Supramolecular Antimicrobial Peptide Hydrogels

Helicobacter pylori can cause various gastric conditions including stomach cancer in an acidic environment. Although early H. pylori infections can be treated by antibiotics, prolonged antibiotic administrations may lead to the development of antimicrobial resistance, compromising the effectiveness of the treatments. Antimicrobial peptides (AMPs) have been reported to possess unique advantages against antimicrobial-resistant bacteria due to their rapid physical membrane disruptions and anti-inflammation/immunoregulation properties. Herein, we have developed an AMP hydrogel, which can be orally administered for the treatment of H. pylori infection. The hydrogel has potent antimicrobial activity against H. pylori, achieving bacterial eradication within minutes of action. Compared with the AMP solution, the hydrogel formulation significantly reduced the cytotoxicity and enhanced proteolytic stability. In vivo experiments suggested that the hydrogel formed at pH 4 had superior therapeutic effects to those at pH 7 and 10 hydrogels, attributed to its rapid release and bactericidal action within the acidic stomach environment. Compared to conventional antibiotic treatments, the AMP hydrogel had the advantages of fast bacterial killing in the gastric juice and obviated proton pump inhibitors during the treatment. Although both the AMP hydrogel and antibiotics suppressed the expression of pro-inflammatory cytokines, the former uniquely promoted inflammation resolution. These results indicate that the AMP hydrogels with effectiveness and biosafety may be potential candidates for the clinical treatment of H. pylori infections.

8-octyl berberine combats Staphylococcus aureus by preventing peptidoglycan synthesis

Staphylococcus aureus is an important pathogenic bacterium responsible for various organ infections. The serious side effects and the development of antibiotic resistance have rendered the antibiotic therapy against S. aureus increasingly challenging, emphasizing the pressing need for the exploration of novel therapeutic agents. Our research has uncovered the promising antimicrobial properties of 8-octyl berberine (OBBR), a novel compound derived from berberine (BBR), against S. aureus. OBBR exhibited a minimum inhibitory concentration (MIC) of 1.0 μg/mL, which closely approximated that of levofloxacin. Intriguingly, a multipassage resistance assay demonstrated that the MIC of OBBR against S. aureus remained relatively stable, while levofloxacin exhibited a 4-fold increase over 20 days, suggesting that OBBR was less prone to inducing resistance. Mechanistically, our investigation, employing Zeta potential measurements, flow cytometry, scanning electron microscopy, and transmission electron microscopy, unveiled that OBBR induced morphological alterations in the bacteria. Furthermore, it disrupted the bacterial cell wall and membrane by altering membrane potential and compromising membrane integrity. These actions culminated in bacterial disintegration and apoptosis. Transcriptomic analysis shed light on significant downregulation of gene ontology terms, predominantly associated with membranes. The Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis implicated OBBR in disturbing peptidoglycan biosynthesis, with the membrane protein MraY emerging as a potential target for OBBR's action against S. aureus. Notably, experiments involving the overexpression of MraY confirmed OBBR's inhibitory effect on peptidoglycan synthesis. Furthermore, molecular docking and cellular thermal shift assay revealed OBBR's direct interaction with MraY, potentially leading to the inhibition of the enzymatic activity of MraY and, consequently, impeding peptidoglycan synthesis. In summary, OBBR, by targeting MraY and inhibiting peptidoglycan synthesis, emerges as a promising alternative antibiotic against S. aureus, offering potential advantages in terms of limited drug resistance development.

Rational Design of Stapled Antimicrobial Peptides to Enhance Stability and In Vivo Potency against Polymicrobial Sepsis

In this work, we sought to develop a TP4-based stapled peptide that can be used to counter polymicrobial sepsis. First, we segregated the TP4 sequence into hydrophobic and cationic/hydrophilic zones and substituted the preferred residue, lysine, as the sole cationic amino acid. These modifications minimized the intensity of cationic or hydrophobic characteristics within small segments. Then, we incorporated single or multiple staples into the peptide chain, bracketing the cationic/hydrophilic segments to improve pharmacological suitability. Using this approach, we were able to develop an AMP with low toxicity and notable in vivo efficacy. IMPORTANCE In our in vitro studies, one dual stapled peptide out of the series of candidates (TP4-3: FIIXKKSXGLFKKKAGAXKKKXIKK) showed significant activity, low toxicity, and high stability (in 50% human serum). When tested in cecal ligation and puncture (CLP) mouse models of polymicrobial sepsis, TP4-3 improved survival (87.5% on day 7). Furthermore, TP4-3 enhanced the activity of meropenem against polymicrobial sepsis (100% survival on day 7) compared to meropenem alone (37.5% survival on day 7). Molecules such as TP4-3 may be well suited for a wide variety of clinical applications.

Strategic modification of low-activity natural antimicrobial peptides confers antibacterial potential in vitro and in vivo

Antimicrobial peptides (AMPs) show great promise for clinical applications, but the utility of naturally occurring AMPs is often limited by their stability. Here, we used a rational design approach to improve the characteristics of a pair of inactive peptides, tilapia piscidin 1 and 2 (TP1 and TP2). From each starting peptide, we generated a series of novel derivatives by substituting residues to adjust cationic charge density, percent hydrophobicity and hydrophilicity/hydrophobicity coefficients. This approach yielded a novel peptide, TP2-5 (KKCIAKAILKKAKKLLKKLVNP), that exhibits significant bactericidal potency, low cytotoxicity and high stability. The designed peptide further showed antibiofilm activity, rapid antibacterial action and a low capacity to induce bacterial resistance. Importantly, we also demonstrated that TP2-5 can protect mice in a Vibrio vulnificus-infected wound model. Therefore, our peptide modification strategy successfully generated a novel AMP with high potential for future clinical application.

An active domain SA-2 derived from cystatin-SA, and its antifungal activity

Infections induced by fungi, especially the drug-resistant fungi, are difficult clinical problems. Conventional antifungal treatment is effective but due to resistance, treatment failure, and treatment-related toxicity, there is a need for new antifungal drugs. In this study, SA-2 (YYRRLLRVLRRRW) was derived from Cystatin-SA, a saliva protein with a molecular weight of 14 kDa. Meanwhile, the structure-activity of SA-2 and its mutants was also studied. We detected the antimicrobial activity and cytotoxicity of SA-2 and found that SA-2 had a low cytotoxicity toward mammalian cells but a good inhibitory effect on Candida albicans (C. albicans) and Cryptococcus neoformans (C. neoformans), with MIC values of 16-64 μg/mL and 8-32 μg/mL, respectively. Interestingly, SA-2 effectively killed fluconazole-resistant C. neoformans and C. albicans within 12 h. This antifungal activity against fluconazole-resistant fungi was comparable to that of amphotericin B. In addition, the C. neoformans-infected mice model was established to evaluate the anti-infective activity of SA-2 in vivo. Results showed that SA-2 significantly reduced the counts of fungi in lung and brain tissues to protect fluconazole-resistant C. neoformans-infected mice from death without changing mice body weights. Moreover, the dramatically increased pro-inflammatory cytokines TNF-α, IL-6 and IL-1β induced by intranasal infection of C. neoformans could be obviously declined due to the treatment of SA-2, which may be attributed to the elimination of C. neoformans in time in the infected tissue. For the mode of actions underlying SA-2 against C. neoformans, we found that the cationic peptide SA-2 could adhere to the negatively charged fungal cell membrane to increase the surface potential of C. neoformans in a dose-dependent manner, and finally disrupted the integrity of fungal cell membrane, reflecting as a 60% positive rate of propidium iodide uptake of C. neoformans cells after SA-2 (4 × MIC) treatment. Our study indicated that SA-2 has the potential to develop as a new therapeutic agent against infection induced by drug-resistant fungi.

A Novel Antimicrobial Peptide Spampcin56-86 from Scylla paramamosain Exerting Rapid Bactericidal and Anti-Biofilm Activity In Vitro and Anti-Infection In Vivo

The abuse of antibiotics leads to the increase of bacterial resistance, which seriously threatens human health. Therefore, there is an urgent need to find effective alternatives to antibiotics, and antimicrobial peptides (AMPs) are the most promising antibacterial agents and have received extensive attention. In this study, a novel potential AMP was identified from the marine invertebrate Scylla paramamosain and named Spampcin. After bioinformatics analysis and AMP database prediction, four truncated peptides (Spa31, Spa22, Spa20 and Spa14) derived from Spampcin were screened, all of which showed potent antimicrobial activity with different antibacterial spectrum. Among them, Spampcin_56-86 (Spa31 for short) exhibited strong bactericidal activity against a variety of clinical pathogens and could rapidly kill the tested bacteria within minutes. Further analysis of the antibacterial mechanism revealed that Spa31 disrupted the integrity of the bacterial membrane (as confirmed by scanning electron microscopy observation, NPN, and PI staining assays), leading to bacterial rupture, leakage of cellular contents (such as elevated extracellular ATP), increased ROS production, and ultimately cell death. Furthermore, Spa31 was found to interact with LPS and effectively inhibit bacterial biofilms. The antibacterial activity of Spa31 had good thermal stability, certain ion tolerance, and no obvious cytotoxicity. It is worth noting that Spa31 could significantly improve the survival rate of zebrafish Danio rerio infected with Pseudomonas aeruginosa, indicating that Spa31 played an important role in anti-infection in vivo. This study will enrich the database of marine animal AMPs and provide theoretical reference and scientific basis for the application of marine AMPs in medical fields.

The Potential Use of Antibiotics Against Helicobacter pylori Infection: Biopharmaceutical Implications

Helicobacter pylori (H. pylori) is a notorious, recalcitrant and silent germ, which can cause a variety of debilitating stomach diseases, including gastric and duodenal ulcers and gastric cancer. This microbe predominantly colonizes the mucosal layer of the human stomach and survives in the inhospitable gastric microenvironment, by adapting to this hostile milieu. In this review, we first discuss H. pylori colonization and invasion. Thereafter, we provide a survey of current curative options based on polypharmacy, looking at pharmacokinetics, pharmacodynamics and pharmaceutical microbiology concepts, in the battle against H. pylori infection.

Expression of the Antimicrobial Peptide Piscidin 1 and Neuropeptides in Fish Gill and Skin: A Potential Participation in Neuro-Immune Interaction

Antimicrobial peptides (AMPs) are found widespread in nature and possess antimicrobial and immunomodulatory activities. Due to their multifunctional properties, these peptides are a focus of growing body of interest and have been characterized in several fish species. Due to their similarities in amino-acid composition and amphipathic design, it has been suggested that neuropeptides may be directly involved in the innate immune response against pathogen intruders. In this review, we report the molecular characterization of the fish-specific AMP piscidin1, the production of an antibody raised against this peptide and the immunohistochemical identification of this peptide and enkephalins in the neuroepithelial cells (NECs) in the gill of several teleost fish species living in different habitats. In spite of the abundant literature on Piscidin1, the biological role of this peptide in fish visceral organs remains poorly explored, as well as the role of the neuropeptides in neuroimmune interaction in fish. The NECs, by their role as sensors of hypoxia changes in the external environments, in combination with their endocrine nature and secretion of immunomodulatory substances would influence various types of immune cells that contain piscidin, such as mast cells and eosinophils, both showing interaction with the nervous system. The discovery of piscidins in the gill and skin, their diversity and their role in the regulation of immune response will lead to better selection of these immunomodulatory molecules as drug targets to retain antimicrobial barrier function and for aquaculture therapy in the future.

Pardaxin Activates Excessive Mitophagy and Mitochondria-Mediated Apoptosis in Human Ovarian Cancer by Inducing Reactive Oxygen Species

Most ovarian cancer (OC) patients are diagnosed with stage III or higher disease, resulting in a poor prognosis. Currently, paclitaxel combined with carboplatin shows the best treatment outcome for OC. However, no effective drug is available for patients that do not respond to treatment; thus, new drugs for OC are needed. We evaluated the antimicrobial peptide, pardaxin, in PA-1 and SKOV3 cells. Pardaxin induced apoptosis as determined by MTT and TUNEL assays, as well as activation of caspases-9/3, Bid, t-Bid, and Bax, whereas Bcl-2 was downregulated. The IC₅₀ values for pardaxin were 4.6-3.0 μM at 24 and 48 h. Mitochondrial and intracellular reactive oxygen species (ROS) were overproduced and associated with disrupted mitochondrial membrane potential and respiratory capacity. Additionally, the mitochondrial network was fragmented with downregulated fusogenic proteins, MFN1/2 and L-/S-OPA1, and upregulated fission-related proteins, DRP1 and FIS1. Autophagy was also activated as evidenced by increased expression of autophagosome formation-related proteins, Beclin, p62, and LC3. Enhanced mitochondrial fragmentation and autophagy indicate that mitophagy was activated. ROS-induced cytotoxicity was reversed by the addition of N-acetylcysteine, confirming ROS overproduction as a contributor. Taken together, pardaxin demonstrated promising anticancer activity in OC cells, which warrants further preclinical development of this compound.

The Emergence of Multidrug-Resistant Helicobacter pylori in Southeast Asia: A Systematic Review on the Trends and Intervention Strategies Using Antimicrobial Peptides

The emergence of multidrug-resistant H. pylori poses a public healthcare threat, particularly in low- and middle-income countries. Recently, the World Health Organization has classified clarithromycin-resistant H. pylori as high priority in the research and discovery of novel antibiotics. This study was aimed to systematically review the prevalence of primary antibiotic resistance in H. pylori in Southeast Asian countries (SEAC) and to review current studies of antimicrobial peptides against H. pylori. We systematically searched through electronic databases of studies conducted on antimicrobial resistance of H. pylori in SEA countries. Furthermore, we searched articles that conducted studies on antimicrobial peptides, naturally occurring host’s defense molecules, against H. pylori. After a series of screening processes, 15 studies were included in our systematic review. Our analysis revealed that primary resistance of H. pylori to metronidazole, clarithromycin, and levofloxacin were high in SEAC, although the primary resistance to amoxicillin and tetracycline remains low. Multidrug-resistant H. pylori are emerging in SE Asian countries. The antimicrobial peptides show promising antibacterial and antibiofilm activity against drug-resistant H. pylori. The research and discovery of antimicrobial peptides against H. pylori in SEAC will help in limiting the spread of antimicrobial resistance of H. pylori.

Three-Decade Failure to the Eradication of Refractory Helicobacter pylori Infection and Recent Efforts to Eradicate the Infection

BACKGROUND

Helicobacter pylori causes dangerous and deadly diseases such as gastric cancer and duodenal ulcers. Eradication and treatment of this bacterium are very important due to the deadly diseases caused by H. pylori and the high cost of treatment for countries.

METHODS

Thus, we present a complete list of the most important causes of failure in the treatment and eradication of H. pylori, and address new therapeutic methods that may be effective in controlling this bacterium in the future.

RESULTS

Many efforts have been made to control and eradicate this bacterium over the years, but no success has been achieved since its eradication is a complex process affected by the bacterial properties and host factors. Previous studies have shown that various factors are involved in the failure to eradicate H. pylori, such as new genotypes of the bacterium with higher pathogenicity, inappropriate patient cooperation, mutations, biofilm formation and dormant forms that cause antibiotic resistance, acidic stomach pH, high bacterial load, smoking, immunosuppressive features and intracellular occurrence of H. pylori. On the other hand, recent studies reported that the use of probiotics, nanoparticles, antimicrobial peptides, natural product and vaccines can be helpful in the treatment and eradication of H. pylori infections.

CONCLUSION

Eradication of H. pylori is crucial for the treatment of important diseases such as gastric cancer. Therefore, it seems that identifying the failure causes of treating this bacterium can be helpful in controlling the infections. Besides, further studies on new therapeutic strategies may help eradicate H. pylori in the future.

A Noncytotoxic Temporin L Analogue with In Vivo Antibacterial and Antiendotoxin Activities and a Nonmembrane-Lytic Mode of Action

Cytotoxic frog antimicrobial peptide Temporin L (TempL) is an attractive molecule for the design of lead antimicrobial agents due to its short size and versatile biological activities. However, noncytotoxic TempL variants with desirable biological activities have rarely been reported. TempL analogue Q3K,TempL is water-soluble and possesses a significant antiendotoxin property along with comparable cytotoxicity to TempL. A phenylalanine residue, located at the hydrophobic face of Q3K,TempL and the "d" position of its phenylalanine zipper sequence, was replaced with a cationic lysine residue. This analogue, Q3K,F8K,TempL, showed reduced hydrophobic moment and was noncytotoxic with lower antimicrobial activity. Interestingly, swapping between tryptophan at the fourth and serine at the sixth positions turned Q3K,F8K,TempL totally amphipathic as reflected by its helical wheel projection with clusters of hydrophobic and hydrophilic residues and the highest hydrophobic moment among these peptides. Surprisingly, this analogue, SW,Q3K,F8K,TempL, was as noncytotoxic as Q3K,F8K,TempL but showed augmented antimicrobial and antiendotoxin properties, comparable to that of TempL and Q3K,TempL. SW,Q3K,F8K,TempL exhibited appreciable survival of mice against P. aeruginosa infection and a lipopolysaccharide (LPS) challenge. Unlike TempL and Q3K,TempL, SW,Q3K,F8K,TempL adopted an unordered secondary structure in bacterial membrane mimetic lipid vesicles and did not permeabilize them or depolarize the bacterial membrane. Overall, the results demonstrate the design of a nontoxic TempL analogue that possesses clusters of hydrophobic and hydrophilic residues with impaired secondary structure and shows a nonmembrane-lytic mechanism and in vivo antiendotoxin and antimicrobial activities. This paradigm of design of antimicrobial peptide with clusters of hydrophobic and hydrophilic residues and high hydrophobic moment but low secondary structure could be attempted further.

Antifungal activity of peptide MSI-1 against Cryptococcus neoformans infection in vitro and in murine cryptococcal meningoencephalitis

The development of novel antifungal agents with high efficacy, low drug tolerance and few side effects is urgent. MSI-1 (GIWKFLKKAKKFWK-NH₂), a cationic antimicrobial peptide, may be an attractive antifungal agent because of its structural characteristics, perfect stability against pH and high-temperature/salt, low toxicity towards mammalian cells and low potential for emergence of drug tolerance. In this study, the antifungal activity of MSI-1 in vitro and in a murine model of cryptococcal meningoencephalitis was evaluated. Zeta potential assay, flow cytometry, fluorescence microscope, transmission electron microscopy and microscale thermophoresis were performed to clarify the mechanisms underlying MSI-1 against C. neoformans. The results showed that MSI-1 exerted effective anti-cryptococcal activity in vitro, with MICs of 8-16 μg/mL and MFCs of 8-32 μg/mL, and in a C neoformans-infected mouse model, with significantly improved animal survival, decreased production of pro-inflammatory cytokines and alleviated lung injury, because the potent and rapid fungicidal activity of MSI-1 could effectively eliminate fungal counts in mouse organs. We confirmed that the positively charged peptide bound to C. neoformans by electrostatic attraction after interacting with glucuronoxylomannan (the primary component of C. neoformans capsule). Subsequently, MSI-1 increased the membrane fluidity of fungal cells and the cell membrane permeability, causing destabilized membrane integrity and leading to the final death of fungi. Collectively, MSI-1 possessed potent anti-cryptococcal activity via its notable membrane disruption effect and may be a potential candidate for use in antifungal infection induced by C. neoformans, especially azole-resistant cryptococcus.

The antimicrobial peptide tilapia piscidin 3 induces mitochondria-modulated intrinsic apoptosis of osteosarcoma cells

Osteosarcoma (OS) is the most common solid tumor of the bone that most often affects adolescents. The introduction of chemotherapy for the treatment of OS has largely improved the survival rates of patients with localized tumors. However, the 5-year survival rate of OS patients with relapsed or metastatic disease is only 10 to 20%. In this study, the antimicrobial peptide tilapia piscidin 3 (TP3), isolated from Nile tilapia (Oreochromis niloticus), was treated to OS MG63 cells. Our findings showed that TP3 concentration as low as 1 μM induced significant inhibition of cell viability and increased DNA fragmentation, as determined by the MTT and TUNEL assays, respectively. The protein expression levels of cleaved caspases 3/9 were increased. An in situ live-cell time-lapse video and cell tomographic microscopy images showed cellular blebbing, shrinkage, nuclear fragmentation, and chromatin condensation, with the formation of beaded apoptopodia. Moreover, there were significant increase in the production of TP3-induced mitochondrial and cellular reactive oxygen species (ROS), as well as down-regulated mitochondrial oxygen consumption and extracellular acidification rates. Additionally, TP3 enhanced mitochondrial fission, whereas fusion was attenuated. Furthermore, after administration of the mitochondria targeted antioxidant mitoTempo, TP3-induced ROS oxidant levels and alterations in cleaved caspases 3/9 expression were rescued. TP3 promoted mitochondria-modulated intrinsic apoptosis through the induction of ROS production, activation of caspases 3/9, and the down-regulation of mitochondrial oxygen consumption and extracellular acidification rates, suggesting that TP3 has potential as an innovative alternative for OS treatment.

TP3, an antimicrobial peptide, inhibits infiltration and motility of glioblastoma cells via modulating the tumor microenvironment

Glioblastoma multiforme (GBM) is a cancer of the central nervous system with limited therapeutic outcomes. Infiltrating cancer cells are the contributing factor to high GBM malignancy. The intracranial brain cancer cell infiltration is a complex cascade involving adhesion, migration, and invasion. An arsenal of natural products has been under exploration to overcome GBM malignancy. This study applied the antimicrobial peptide tilapia piscidin 3 (TP3) to GBM8401, U87MG, and T98G cells. The cellular assays and microscopic observations showed that TP3 significantly attenuated cell adhesion, migration, and invasion. A live‐cell video clip showed the inhibition of filopodia protrusions and cell attachment. Probing at the molecular levels showed that the proteolytic activities (from secretion), the mRNA and protein expression levels of matrix metalloproteinases‐2 and ‐9 were attenuated. This result strongly evidenced that both invasion and metastasis were inhibited, although metastatic GBM is rare. Furthermore, the protein expression levels of cell‐mobilization regulators focal adhesion kinase and paxillin were decreased. Similar effects were observed in small GTPase (RAS), phosphorylated protein kinase B (AKT) and MAP kinases such as extracellular signal‐regulated kinases (ERK), JNK, and p38. Overall, TP3 showed promising activities to prevent cell infiltration and metastasis through modulating the tumor microenvironment balance, suggesting that TP3 merits further development for use in GBM treatments.

Epinecidin-1: An orange-spotted grouper antimicrobial peptide that modulates Staphylococcus aureus lipoteichoic acid-induced inflammation in macrophage cells

Orange-spotted grouper (Epinephelus coioides) is among the most economically important of all fish species farmed in Asia. This species expresses an antimicrobial peptide called epinecidin-1 (EPI), which is considered to be a host defense factor due to its strong bacterial killing activity. Antimicrobial peptides usually possess both bacterial killing and immunomodulatory activity, however, the modulatory activity of EPI on Gram-positive bacterial lipoteichoic acids (LTA)-induced inflammation has not been previously reported. In this study, we found that EPI effectively suppressed LTA-induced production of proinflammatory factors in macrophages. Mechanistically, EPI attenuated LTA-induced inflammation by inhibiting Toll-like receptor (TLR) 2 internalization and subsequent downstream signaling (reactive oxygen species, Akt, p38 and Nuclear factor κB). However, protein abundance of TLR2 was not altered by EPI or LTA. Taken together, our findings reveal for the first time that EPI possesses inhibitory activity toward LTA-induced inflammation in macrophages.

Transformation of Helicobacter pylori into Coccoid Forms as a Challenge for Research Determining Activity of Antimicrobial Substances

Morphological variability is one of the phenotypic features related to adaptation of microorganisms to stressful environmental conditions and increased tolerance to antimicrobial substances. Helicobacter pylori, a gastric mucosal pathogen, is characterized by a high heterogeneity and an ability to transform from a spiral to a coccoid form. The presence of the coccoid form is associated with the capacity to avoid immune system detection and to promote therapeutic failures. For this reason, it seems that the investigation for new, alternative methods combating H. pylori should include research of coccoid forms of this pathogen. The current review aimed at collecting information about the activity of antibacterial substances against H. pylori in the context of the morphological variability of this bacterium. The collected data was discussed in terms of the type of substances used, applied research techniques, and interpretation of results. The review was extended by a polemic on the limitations in determining the viability of coccoid H. pylori forms. Finally, recommendations which can help in future research aiming to find new compounds with a potential to eradicate H. pylori have been formulated.

Alternative extraction techniques to obtain, isolate and purify proteins and bioactive from aquaculture and by-products

Oceans cover more than 70% of the earth's surface and provide a great ecosystem for habitat of a large divers of marine species. The marine species are rich sources of bioactive compound that can be applied in medicine, pharmacology and food industry. Besides the marine species, fish processing industry also produces substantial volumes of by-products that can be used for a variety of purposes. Thus, it is important to find approaches to access to these valuable compounds. Nowadays, more factors have been considered in selecting an appropriate method for extraction of bioactive compounds such as consume less time and solvent, to be fast and ecofriendly. Concerns regarding entering the pollutions to the environment resulted to invest on the methods practicable with less chemical solvents and even green ones, however, implementation of stricter regulations and policies is required to encourage researchers to set up the procedures with reduced toxic agents to guarantee the environmental safety. In the current chapter the most common marine derived compounds and innovative methods for their extraction will be discussed.

Epinecidin-1 Protects against Methicillin Resistant Staphylococcus aureus Infection and Sepsis in Pyemia Pigs

Methicillin resistant Staphylococcus aureus (MRSA) may be found on the skin, nose, and throats of long-term hospitalized patients. While MRSA infections are usually minor, serious infections and death may occur in immunocompromised or diabetic patients, or after exposure of MRSA to blood. This report demonstrates that the antimicrobial peptide (AMP) epinecidin-1 (Epi-1) efficiently protects against MRSA infection in a pyemia pig model. We first found that Epi-1 exhibits bactericidal activity against MRSA. Next, pharmacokinetic analysis revealed that Epi-1 was stable in serum for 4 h after injection, followed by a gradual decrease. This pharmacokinetic profile suggested Epi-1 may bind serum albumin, which was confirmed in vitro. Harmful effects were not observed for doses up to 100 mg/kg body weight in pigs. When Epi-1 was supplied as a curative agent 30 min post-infection, MRSA-induced abnormalities in blood uric acid (UA), blood urea nitrogen (BUN), creatine (CRE), GOT, and GPT levels were restored to normal levels. We further showed that the bactericidal activity of Epi-1 was higher than that of the antibiotic drug vancomycin. Epi-1 significantly decreased MRSA counts in the blood, liver, kidney, heart, and lungs of infected pigs. Elevated levels of serum C reactive protein (CRP), proinflammatory cytokine IL6, IL1β, and TNFα were also attenuated by Epi-1 treatment. Moreover, the MRSA genes, enterotoxin (et)-A, et-B, intrinsic methicillin resistance A (mecA), and methicillin resistance factor A (femA), were significantly reduced or abolished in MRSA-infected pigs after treatment with Epi-1. Hematoxylin and eosin staining of heart, liver, lung, and kidney sections indicated that Epi-1 attenuated MRSA toxicity in infected pigs. A survival study showed that the pyemia pigs infected with MRSA alone died within a week, whereas the pigs post-treated with 2.5 mg/kg Epi-1 were completely protected against death. The present investigation, thus, demonstrates that Epi-1 effectively protects pyemia pigs against pathogenic MRSA without major toxic side effects.

An active domain HF-18 derived from hagfish intestinal peptide effectively inhibited drug-resistant bacteria in vitro/vivo

Antibiotic resistance is spreading faster than the development of new antibiotics into clinical practice. Currently, the design of antimicrobial peptides (AMPs), potential new antibacterial agents with rare antimicrobial resistance, is the available strategy to enhance the antimicrobial activity and lower the toxicity of AMPs. In this study, a peptide derived from hagfish intestinal peptide was designed and termed as HF-18 (GFFKKAWRKVKKAFRRVL). After antimicrobial/bactericidal test in vitro, we found that HF-18 exhibited a potent antimicrobial activity with MIC of only 4 μg/ml against drug-resistant Staphylococcus aureus (S. aureus). Meanwhile, it eliminated the test bacteria within 1 h, suggesting its rapid bactericidal effect. Importantly, this peptide had no obvious hemolytic activity and cytotoxicity to mammalian cells. Furthermore, its notable antimicrobial effects in vivo was confirmed again in S. aureus induced mouse bacteremia and skin wound infection, reflecting as the decrease in bacterial counts in mouse lung or skin (up to 1.9 or 3.5 log CFU respectively), and including the inhibitory activity on inflammatory cytokines secretion. The possible mechanisms underlying HF-18 against drug-resistant S. aureus may attribute that HF-18 neutralized the negative charge in S. aureus surface and then disrupted the integrity of cell membranes to enhance the permeation of bacterial membrane, showing as the increased uptake of NPN and PI and the obvious morphology changes of S. aureus. In addition, this peptide bound to bacterial genomic DNA to suppress the expression of Panton-Valentine leukocidin (pvl) and nuclease (nuc) genes, which play major roles in S. aureus virulence. The properties of HF-18 suggest a path towards developing antibacterial agents that has stronger antibacterial activity and greater security for clinical treatment of infection induced by S. aureus, especially drug-resistant S. aureus.

Epinecidin-1, an Antimicrobial Peptide Derived From Grouper (Epinephelus coioides): Pharmacological Activities and Applications

Epinecidin-1 is an antimicrobial peptide derived from the orange-spotted grouper (Epinephelus coioides). The mature epinecidin-1 peptide is predicted to have an amphipathic α-helical structure and a non-helical hydrophilic domain at the C-terminal RRRH. The majority of work studying the potential pharmacological activities of epinecidin-1, utilize synthesized epinecidin-1 (Epi-1), which is made up of 21 amino acids, from the amino acid sequence of 22-42 residues of Epi-1-GFIFHIIKGLFHAGKMIHGLV. The synthetized Epi-1 peptide has been demonstrated to possess diverse pharmacological activities, including antimicrobial, immunomodulatory, anticancer, and wound healing properties. It has also been utilized in different clinical and agricultural fields, including topical applications in wound healing therapy as well as the enhancement of fish immunity in aquaculture. Hence, the present work aims to consolidate the current knowledge and findings on the characteristics and pharmacological properties of epinecidin-1 and its potential applications.

Antimicrobial activities of peptide Cbf-K16 against drug-resistant Helicobacter pylori infection in vitro and in vivo

Helicobacter pylori (H. pylori) infection is highly prevalent, and has developed antimicrobial resistance to virtually all existing antibiotics. Currently, treatment of H. pylori infection (involving proton pump inhibitors and broad-spectrum antibiotics) is suboptimal, with high failure rates. Thus, there is a pressing need to develop new anti-H. pylori therapies. Cbf-K₁₆, a cathelicidin-like antimicrobial peptide, presented broad antimicrobial activity during our previous research. This study further evaluated the therapeutic potential and the mode of action underlying Cbf-K₁₆ against clarithromycin- and amoxicillin-resistant H. pylori SS1. The MIC and MBC of Cbf-K₁₆ against the tested H. pylori were 16 and 32 μg/ml, respectively, and its killing kinetics was time-dependent, reflecting the thorough elimination of drug-resistant bacteria within 24 h. This peptide also protected H. pylori-infected gastric epithelial cells (GES-1) from death by reducing the cell supernatant and intracellular bacterial counts by 1.9 and 2.9-log₁₀ units, respectively. These data indicated the powerful antimicrobial effects of Cbf-K₁₆in vitro. Meanwhile, notable antimicrobial activity in the mouse gastritis model was observed, with decreasing bacterial counts by 3.9-log₁₀ units in stomach tissues and Cbf-K₁₆ could effectively suppress the secretion of inflammatory cytokine IL-8. For its mode of action, Cbf-K₁₆ not only neutralized the negative potential and increased the membrane uptake of NPN and PI by 78.5% and 85.1%, respectively, but also bound to genomic DNA, which in turn downregulated the expression of adhesion genes (alpA and alpB) and virulence gene (cagA), indicating its effective activities on membrane disruption, DNA-binding and gene expression. The data above demonstrated that Cbf-K₁₆ possessed effective antimicrobial and anti-inflammatory activities and downregulated the expression of adhesion- and cytotoxin-associated genes of drug-resistant H. pylori SS1, making it a potential candidate for anti-infective therapy.

Hepatoma-derived growth factor participates in Helicobacter Pylori-induced neutrophils recruitment, gastritis and gastric carcinogenesis

Helicobacter pylori (Hp) infection and overexpression of hepatoma-derived growth factor (HDGF) are involved in gastric carcinogenesis. However, the relationship between Hp-induced gastric diseases and HDGF upregulation is not yet completely clear. This study aimed to elucidate the role of HDGF in Hp-induced gastric inflammation and carcinogenesis. HDGF expression in gastric biopsy and serum from patients was analyzed by immunohistochemical and ELISA analysis, respectively. Hp and gastric cells coculture system was employed to delineate the mechanism underlying HDGF overexpression during Hp infection. The gastric pathologies of wild type and HDGF knockout mice after Hp infection were investigated by immunohistochemical, immunoblot, and immunofluorescence analyses. HDGF level was significantly elevated in patients with Hp infection or intestinal metaplasia (IM, a precancerous lesion), and HDGF overexpression was positively correlated with Hp load, IM, and neutrophil infiltration in gastric biopsy. Consistently, patients with Hp infection or IM had significantly higher serum HDGF level. By using coculture assay, Hp infection led to HDGF upregulation and secretion in gastric cells. In mice model, HDGF ablation significantly suppressed the Hp-induced neutrophil infiltration and inflammatory TNF-α/COX-2 signaling, thereby relieving the tissue damage in stomach. This was further supported by that recombinant HDGF (rHDGF) stimulated the differentiation/chemotaxis of cultured neutrophils and oncogenic behaviors of gastric cells. Time series studies showed that Hp infection elicited an inflammatory TNF-α/HDGF/COX-2 cascade in stomach. HDGF secretion by Hp infection promotes the neutrophils infiltration and relays Hp-induced inflammatory signaling. Thus, HDGF may constitute a novel diagnostic marker and therapeutic target for Hp-induced gastritis and carcinogenesis.

Nobiletin and Derivatives: Functional Compounds from Citrus Fruit Peel for Colon Cancer Chemoprevention

The search for effective methods of cancer treatment and prevention has been a continuous effort since the disease was discovered. Recently, there has been increasing interest in exploring plants and fruits for molecules that may have potential as either adjuvants or as chemopreventive agents against cancer. One of the promising compounds under extensive research is nobiletin (NOB), a polymethoxyflavone (PMF) extracted exclusively from citrus peel. Not only does nobiletin itself exhibit anti-cancer properties, but its derivatives are also promising chemopreventive agents; examples of derivatives with anti-cancer activity include 3′-demethylnobiletin (3′-DMN), 4′-demethylnobiletin (4′-DMN), 3′,4′-didemethylnobiletin (3′,4′-DMN) and 5-demethylnobiletin (5-DMN). In vitro studies have demonstrated differential efficacies and mechanisms of NOB and its derivatives in inhibiting and killing of colon cancer cells. The chemopreventive potential of NOB has also been well demonstrated in several in vivo colon carcinogenesis animal models. NOB and its derivatives target multiple pathways in cancer progression and inhibit several of the hallmark features of colorectal cancer (CRC) pathophysiology, including arresting the cell cycle, inhibiting cell proliferation, inducing apoptosis, preventing tumour formation, reducing inflammatory effects and limiting angiogenesis. However, these substances have low oral bioavailability that limits their clinical utility, hence there have been numerous efforts exploring better drug delivery strategies for NOB and these are part of this review. We also reviewed data related to patents involving NOB to illustrate the extensiveness of each research area and its direction of commercialisation. Furthermore, this review also provides suggested directions for future research to advance NOB as the next promising candidate in CRC chemoprevention.

Epinecidin-1, a highly potent marine antimicrobial peptide with anticancer and immunomodulatory activities

BACKGROUND

Antibiotic-resistant pathogens are an emerging threat in this century. Epinecidin-1 is a multi-functional Antimicrobial Peptide (AMP) produced by Orange-spotted grouper (Epinephelus coioides) has been shown to have extensive potentials as an alternative for current antibiotics. Due to the huge costs for the study and the production of a new drug, if an antimicrobial peptide has other beneficial functions in addition to antimicrobial activities, it would be preferred.

METHODS

In this study, properties and applications of Epinecidin-1 were investigated and addressed comprehensively. To achieve this, the Google Scholar search engine and three databases of PubMed, Scopus, and Web of Science were used.

RESULTS

Epinecidin-1 is a cationic AMP with an alpha-helical structure. Seven functional usages of this peptide have been reported in the literature including antibacterial, antifungal, antiviral, antiprotozoal, anticancer, immunomodulatory, and wound healing properties. Moreover, this peptide has high potential to be used as an active ingredient in cleaning solutions as well as application in vaccine production.

CONCLUSION

Due to significant antimicrobial activities tested on bacteria such as Staphylococcus aureus and Helicobacter pylori and also wound healing properties, Epi-1 has high potential to be considered as an important candidate for the production of new drugs and treatment of various infections including diabetic foot ulcer and peptic ulcer. Moreover, adjuvant-like properties of Epi-1 make it a suitable candidate for the studies related to an adjuvant. Other attractive properties such as anticancer effects have also been reported for this peptide which encourages further studies on this peptide.

Review of antimicrobial peptides with anti-Helicobacter pylori activity

BACKGROUND

The emergence of antibiotic-resistant Helicobacter pylori strains in recent years has increased the need for finding an alternative in the post-antibiotic era. One of the fields being considered for this purpose is antimicrobial peptides. The aim of this review was to provide an obvious scheme from the studied anti-H. pylori peptides and to investigate their common features.

METHOD

First, all of the antimicrobial peptides with their anti-H. pylori effects have been proved up to September 2018 were selected and their information including structure, mechanism of action, and function was reviewed. To achieve this, three databases of PubMed, Scopus, and Web of science were used.

RESULTS

A total of 9 groups containing 22 antimicrobial peptides were found with demonstrated anti-H. pylori effects. The nine groups included pexiganan, tilapia piscidins, epinecidin-1, cathelicidins, defensins, bicarinalin, odorranain-HP, PGLa-AM1, and bacteriocins. Most of the antimicrobial peptides, not all, had common features such as the ability to kill antibiotic-resistant strains, having α-helical structure, being cationic, with high positive charge and isoelectric point.

CONCLUSION

Antimicrobial peptides with anti-H. pylori effects have the potential to replace the antibiotics, especially in the post-antibiotic era, if a rapid and low-cost production method would be found.

Epinecidin-1: A marine fish antimicrobial peptide with therapeutic potential against Trichomonas vaginalis infection in mice

Trichomoniasis is caused by infection with the protozoan parasite Trichomonas vaginalis, and prolonged persistence may lead to serious ill effects in patients. Thus, the development of new therapeutic strategies to combat drug-resistant T. vaginalis would be clinically beneficial. Antimicrobial peptides (AMPs) comprise an emerging class of molecules that may serve as effective alternatives to antibiotics. In this report, we demonstrate that the synthetic fish AMP, Epinecidin-1 (Epi-1), acts against T. vaginalis both in vitro and in vivo. Under in vitro conditions, Epi-1 disrupted the membrane of metronidazole-resistant T. vaginalis and completely killed the pathogen. To mimic human infection in vivo, estradiol-stimulated mice with vaginal Lactobacillus acidophilus colonization were infected with T. vaginalis, followed by treatment with Epi-1, Vigill, metronidazole or furazolidone. After seven days, the T. vaginalis content was effectively decreased in Epi-1 treated mice, as measured by acridine orange staining of wet smears and tissue biopsies, as well as qPCR of vaginal discharge DNA. Taken together, our results demonstrate that Epi-1 is a strong candidate for development as an alternative therapeutic for T. vaginalis infection.

Grouper (Epinephelus coioides) antimicrobial peptide epinecidin-1 exhibits antiviral activity against foot-and-mouth disease virus in vitro

Picornavirus is a highly contagious virus that usually infects cloven hoofed animals and causes foot-and-mouth disease. This disease is a major threat to livestock breeding worldwide and may lead to huge economic losses. Because effective vaccines or antiviral drugs remain unavailable, the search for new agents to combat FMDV infections is ongoing. Antimicrobial peptides are known to possess a broad range of biological activities, including antibacterial, antiviral, antitumor and immunomodulatory effects. In this work, we used a cell culture FMDV replication assay to evaluate several antimicrobial peptides for their ability to act as antiviral agents. We found that a synthesized form of the Epinephelus coioides antimicrobial peptide, epinecidin-1 (Epi-1), was effective at combatting FMDV. Epi-1 is known to have broad spectrum antimicrobial activity and low toxicity to normal eukaryotic cells, making it a good candidate for use as a therapeutic agent.The 50% cytotoxic concentration (CC₅₀) for BHK-21 cells was 19.5 μg/ml for synthesized Epi-1, and the 50% effective concentration (EC₅₀) for viral inhibition was 0.6 μg/ml. The selectivity index was 31.4, as calculated by the CC₅₀/EC₅₀ ratio. Furthermore, Epi-1 showed virucidal activity against FMDV at high concentrations. Interestingly, our data also showed that FMDV infection was most impaired when Epi-1 was treated at the time of viral adsorption. Taken together, our data show that Epi-1 may be a promising candidate for development as an anti-FMDV agent.

Anti-Helicobacterpylori effectiveness and targeted delivery performance of amoxicillin-UCCs-2/TPP nanoparticles based on ureido-modified chitosan derivative

The amoxicillin-UCCs-2/TPP nanoparticles constructed with ureido-modified chitosan derivative UCCs-2 and sodium tripolyphosphate (TPP) played an important role to deliver drug to achieve more efficacious and specific eradication of Helicobacterpylori (H. pylori) in vitro. In this study, the anti-H. pylori effectiveness in vivo and uptake mechanism was investigated in details, including the effect of temperature, pH values and the addition of competitive substrate urea on uptake. Compared with unmodified nanoparticles, a more efficacious and specific anti-H. pylori activities were obtained in vivo by using this biological chitosan derivative UCCs-2. Histological staining and immunological analysis verified that the amoxicillin-UCCs-2/TPP nanoparticles could diminish the proinflammatory cytokines levels and alleviate the inflammatory damages caused by H. pylori infection. The uredio-modified nanoparticles also have favorable gastric retention property, which is beneficial for the oral drug delivery to targeted eradicate H. pylori infection in stomach. These findings suggest that this targeted drug delivery system may serve for specific treatment of H. pylori infection both in vitro and in vivo, which can also be used as promising nanocarriers for other therapeutic reagents to target H. pylori.

Resistance mechanisms of Helicobacter pylori and its dual target precise therapy

Helicobacter pylori drug resistance presents a significant challenge to the successful eradication of this pathogen. To find strategies to improve the eradication efficacy of H. pylori, it is necessary to clarify the resistance mechanisms involved. The mechanisms of H. pylori drug resistance can be investigated from two angles: the pathogen and the host. A comprehensive understanding of the molecular mechanisms of H. pylori resistance based on both pathogen and host would aid the implementation of precise therapy, or ideally "dual target precise therapy" (bacteria and host-specific target therapy). In recent years, with increased understanding of the mechanisms of H. pylori resistance, the focus of eradication has shifted from disease-specific to patient-specific treatment. The implementation of "precision medicine" has also provided a new perspective on the treatment of infectious diseases. In this article, we systematically review current research on H. pylori drug resistance from the perspective of both the pathogen and the host. We also review therapeutic strategies targeted to pathogen and host factors that are aimed at achieving precise treatment of H. pylori.

Anti-Helicobacter pylori Properties of the Ant-Venom Peptide Bicarinalin

The venom peptide bicarinalin, previously isolated from the ant Tetramorium bicarinatum, is an antimicrobial agent with a broad spectrum of activity. In this study, we investigate the potential of bicarinalin as a novel agent against Helicobacter pylori, which causes several gastric diseases. First, the effects of synthetic bicarinalin have been tested against Helicobacter pylori: one ATCC strain, and forty-four isolated from stomach ulcer biopsies of Peruvian patients. Then the cytoxicity of bicarinalin on human gastric cells and murine peritoneal macrophages was measured using XTT and MTT assays, respectively. Finally, the preventive effect of bicarinalin was evaluated by scanning electron microscopy using an adherence assay of H. pylori on human gastric cells treated with bicarinalin. This peptide has a potent antibacterial activity at the same magnitude as four antibiotics currently used in therapies against H. pylori. Bicarinalin also inhibited adherence of H. pylori to gastric cells with an IC50 of 0.12 μg·mL-1 and had low toxicity for human cells. Scanning electron microscopy confirmed that bicarinalin can significantly decrease the density of H. pylori on gastric cells. We conclude that Bicarinalin is a promising compound for the development of a novel and effective anti-H. pylori agent for both curative and preventive use.

Effective Antimicrobial Activity of Plectasin-Derived Antimicrobial Peptides against Staphylococcus aureus Infection in Mammary Glands

Staphylococcus aureus (S. aureus) is the causative agent for a wide variety of illnesses ranging from minor skin infections to life-threatening diseases. Development of antibiotic resistance by the bacteria has rendered many antibiotics ineffective. It has been known that plectasin-derived antimicrobial peptides (AMPs; NZ2114 and MP1102) are promising alternatives to antibiotics. However, their activities against S. aureus in mammary glands were unknown. Our objective was to assess the antimicrobial activities of NZ2114 and MP1102 against S. aureus in milk, in cultured mammary epithelial cells, and in a mouse model in order to evaluate their potentials as anti-mastitis agents. NZ2114 and MP1102 showed in vitro bactericidal effects against S. aureus in both the culture medium and the milk. NZ2114 and MP1102 at the concentration of 100 μg/mL reduced the number of S. aureus by almost 100% within 4 h in processed bovine milk. Similarly, both NZ2114 and MP1102 were efficient to reduce the number of internalized S. aureus in cultured mammary epithelial cells. Finally, both AMPs significantly reduced the S. aureus load and concentrations of TNF-α and IL-6 in mammary glands, compared to a buffer control in the mouse model. Our results suggest that NZ2114 and MP1102 may be used to treat S. aureus-induced mastitis.

Epinecidin-1 protects mice from LPS-induced endotoxemia and cecal ligation and puncture-induced polymicrobial sepsis

The antimicrobial peptide, epinecidin-1 (Epi), was identified from Epinephelus coioides and may have clinical application for treating sepsis. Epi has been shown to ameliorate antibiotic-resistant bacteria-induced sepsis in mice, but further evaluation in mixed-flora models and a description of the protective mechanisms are essential to establish this peptide as a potential therapeutic. Therefore, we first tested the protective effects of Epi against polymicrobial sepsis-induced bactericidal infection, inflammation and lung injury that result from cecal ligation and puncture in mice. Furthermore, since lipopolysaccharide (LPS) is a key inducer of inflammation during bacterial infection and sepsis, we also tested the LPS-antagonizing activity and related mechanisms of Epi-mediated protection in mice with LPS-induced endotoxemia and LPS-treated Raw264.7 mouse macrophage cells. Epi rescued mice from both polymicrobial sepsis and endotoxemia after delayed administration and suppressed both lung and systemic inflammatory responses, while attenuating lung injury and diminishing bacterial load. In vitro studies revealed that Epi suppressed LPS-induced inflammatory cytokine production. Mechanistically, Epi disrupted the interaction between LPS and LPS binding protein, competed with LPS for binding on the cell surface, and inhibited Toll-like receptor 4 endocytosis, resulting in inhibition of LPS-induced reactive oxygen species/p38/Akt/NF-κB signaling and subsequent cytokine production. Overall, our results demonstrate that Epi is a promising therapeutic agent for endotoxemia and polymicrobial sepsis.

Bacterial factors associated with Helicobacter pylori antibiotic resistance

Helicobacter pylori (H. pylori) infection is the most widespread chronic bacterial infection and is closely associated with many diseases. In recent years, however, H. pylori is becoming increasingly difficult to eradicate due to the growing antibiotic resistance. Among the reasons for the failed eradication, some factors of H. pylori itself play a main role. H. pylori can resist antibiotics by producing inactivating enzymes, changing the drug targets, preventing oxidation-reduction electron transfer, decreasing membrane permeability and activating efflux pump, changing bacterial metabolic state and so on. Elucidating the mechanism of antibiotic resistance will be helpful in developing new targeted drugs to effectively eradicate H. pylori. Here, we review the bacteria factors associated with H. pylori antibiotic resistance.

A strategy for enhanced antibacterial activity against Staphylococcus aureus by the assembly of alamethicin with a thermo-sensitive polymeric carrier

We demonstrate here a strategy for enhanced antibacterial activity against microbial strains by the assembly of antimicrobial peptides with a temperature-responsive polymeric carrier. The assembly complex was less toxic to human cells and more stable to enzymatic cleavage. This work may provide a promising drug delivery system for antimicrobial peptides.

Isolation of hydroquinone (benzene-1,4-diol) metabolite from halotolerant Bacillus methylotrophicus MHC10 and its inhibitory activity towards bacterial pathogens

A halotolerant bacterial isolate-MHC10 with broad spectrum antibacterial activity against clinical pathogens was isolated from saltpans located in Tuticorin and Chennai (India). 16S rRNA gene analysis of MHC10 revealed close similarity to that of Bacillus methylotrophicus. The culture conditions of B. methylotrophicus MHC10 strain were optimized for antibacterial production using different carbon and nitrogen sources, as well as varying temperature, pH, sodium chloride (NaCl) concentrations and incubation periods. The maximum antibacterial activity of B. methylotrophicus MHC10 was attained when ZMB was optimized with 1 % (w/v) glucose, 0.1 % (w/v) soybean meal which corresponded to a C/N ratio of 38.83, temperature at 37 °C, pH 7.0 and 8 % NaCl. The activity remained stable between 72 and 96 h and then drastically decreased after 96 h. Solvent extraction followed by chromatographic purification steps led to the isolation of hydroquinone (benzene-1,4-diol). The structure of the purified compound was elucidated based on FTIR, (1)H NMR, and (13)C NMR spectroscopy. The compound exhibited efficient antibacterial activity against both Gram-positive and Gram-negative bacterial pathogens. The minimum inhibitory concentration (MIC) for Gram-positive pathogens ranged from 15.625 to 62.5 µg/mL(-1), while it was between 7.81 and 250 µg/mL(-1) for Gram-negative bacterial pathogens. This is the first report of hydroquinone produced by halotolerant B. methylotrophicus exhibiting promising antibacterial activity.

Marine Peptides: Bioactivities and Applications

Peptides are important bioactive natural products which are present in many marine species. These marine peptides have high potential nutraceutical and medicinal values because of their broad spectra of bioactivities. Their antimicrobial, antiviral, antitumor, antioxidative, cardioprotective (antihypertensive, antiatherosclerotic and anticoagulant), immunomodulatory, analgesic, anxiolytic anti-diabetic, appetite suppressing and neuroprotective activities have attracted the attention of the pharmaceutical industry, which attempts to design them for use in the treatment or prevention of various diseases. Some marine peptides or their derivatives have high commercial values and had reached the pharmaceutical and nutraceutical markets. A large number of them are already in different phases of the clinical and preclinical pipeline. This review highlights the recent research in marine peptides and the trends and prospects for the future, with special emphasis on nutraceutical and pharmaceutical development into marketed products.