Antimicrobial mechanism of action of transferrins: selective inhibition of H+-ATPase

The Antimicrobial Activity of Human Defensins at Physiological Non-Permeabilizing Concentrations Is Caused by the Inhibition of the Plasma Membrane H+-ATPases

Human defensins are cysteine-rich peptides (Cys-rich peptides) of the innate immune system. Defensins contain an ancestral structural motif (i.e., γ-core motif) associated with the antimicrobial activity of natural Cys-rich peptides. In this study, low concentrations of human α- and β-defensins showed microbicidal activity that was not associated with cell membrane permeabilization. The cell death pathway was similar to that previously described for human lactoferrin, also an immunoprotein containing a γ-core motif. The common features were (1) cell death not related to plasma membrane (PM) disruption, (2) the inhibition of microbicidal activity via extracellular potassium, (3) the influence of cellular respiration on microbicidal activity, and (4) the influence of intracellular pH on bactericidal activity. In addition, in yeast, we also observed (1) partial K+-efflux mediated via Tok1p K+-channels, (2) the essential role of mitochondrial ATP synthase in cell death, (3) the increment of intracellular ATP, (4) plasma membrane depolarization, and (5) the inhibition of external acidification mediated via PM Pma1p H+-ATPase. Similar features were also observed with BM2, an antifungal peptide that inhibits Pma1p H+-ATPase, showing that the above coincident characteristics were a consequence of PM H+-ATPase inhibition. These findings suggest, for the first time, that human defensins inhibit PM H+-ATPases at physiological concentrations, and that the subsequent cytosolic acidification is responsible for the in vitro microbicidal activity. This mechanism of action is shared with human lactoferrin and probably other antimicrobial peptides containing γ-core motifs.

Essential-Oils-Loaded Biopolymeric Nanoparticles as Strategies for Microbial and Biofilm Control: A Current Status

The emergence of bacterial strains displaying resistance to the currently available antibiotics is a critical global concern. These resilient bacteria can form biofilms that play a pivotal role in the failure of bacterial infection treatments as antibiotics struggle to penetrate all biofilm regions. Consequently, eradicating bacteria residing within biofilms becomes considerably more challenging than their planktonic counterparts, leading to persistent and chronic infections. Among various approaches explored, essential oils loaded in nanoparticles based on biopolymers have emerged, promising strategies that enhance bioavailability and biological activities, minimize side effects, and control release through regulated pharmacokinetics. Different available reviews analyze nanosystems and essential oils; however, usually, their main goal is the analysis of their antimicrobial properties, and progress in biofilm combat is rarely discussed, or it is not the primary objective. This review aims to provide a global vision of biofilm conformation and describes mechanisms of action attributed to each EO. Furthermore, we present a comprehensive overview of the latest developments in biopolymeric nanoparticles research, especially in chitosan- and zein-based nanosystems, targeting multidrug-resistant bacteria in both their sessile and biofilm forms, which will help to design precise strategies for combating biofilms.

Bacterial acid stress response: from cellular changes to antibiotic tolerance and phenotypic heterogeneity

Most bacteria are neutralophiles but can survive fluctuations in pH in their environment. Herein, we provide an overview of the adaptation of several human, soil, and food bacteria to acid stress, mainly based on next-generation sequencing studies, highlighting common and specific strategies. We also discuss the interplay between acid stress response and antibiotic tolerance, as well as the response of individual cells.

Bovine Lactoferrin-Loaded Plasmonic Magnetoliposomes for Antifungal Therapeutic Applications

Bovine lactoferrin (bLf) is a milk-derived protein that exhibits potent broad-spectrum antifungal activity against multiple fungi. bLf is susceptible to degradation, while some of its properties depend on the tertiary structure. So, the encapsulation of bLf in stimuli-responsive therapeutic formulations provides an added value to enhance its biological activities. Plasmonic magnetoliposomes (PMLs) arise as promising nanocarriers for dual hyperthermia (magneto-photothermia) and local chemotherapy, since the combination of magnetic and gold nanoparticles (NPs) in a single nanosystem (multifunctional liposomes) enables the targeting and controlled release of loaded drugs. In this work, plasmonic magnetoliposomes (PMLs) containing manganese ferrite nanoparticles (28 nm size) and gold nanoparticles (5-7.5 nm size), functionalized with 11-mercaptoundecanoic acid or octadecanethiol, were prepared and loaded with bLf. The NPs' optical, magnetic and structural properties were measured via UV/vis/NIR absorption spectroscopy, SQUID and TEM, respectively. The Specific Absorption Rate (SAR) was calculated to assess the capabilities for magnetic and photothermal hyperthermia. Finally, the antifungal potential of bLf-loaded PMLs and their mechanism of internalization were assessed in Saccharomyces cerevisiae by counting the colony forming units and using fluorescence microscopy. The results demonstrate that PMLs are mainly internalized through an energy- and temperature-dependent endocytic process, though the contribution of a diffusion component cannot be discarded. Most notably, only bLf-loaded plasmonic magnetoliposomes display cytotoxicity with an efficiency similar to free bLf, attesting their promising potential for bLf delivery in the context of antifungal therapeutic interventions.

Colostrum and Lactoferrin Protect against Side Effects of Therapy with Antibiotics, Anti-inflammatory Drugs and Steroids, and Psychophysical Stress: A Comprehensive Review

In this article, we review the benefits of applying bovine colostrum (BC) and lactoferrin (LF) in animal models and clinical trials that include corticosteroid application and psychic stress, treatment with non-steroid anti-inflammatory drugs (NSAIDs) and antibiotics. A majority of the reported investigations were performed with native bovine or recombinant human LF, applied alone or in combination with probiotics, as nutraceutics and diet supplements. Apart from reducing adverse side effects of the applied therapeutics, BC and LF augmented their efficacy and improved the wellness of patients. In conclusion, LF and complete native colostrum, preferably administered with probiotic bacteria, are highly recommended for inclusion in therapeutic protocols in NSAIDs and corticosteroid anti-inflammatory, as well as antibiotic, therapies. These colostrum-based products can also be of value for individuals subjected to prolonged psychophysical stress (mediated by endogenous corticosteroids), especially at high ambient temperatures (soldiers and emergency services), as well as physically active people and training athletes. They are also recommended for patients during recovery from trauma and surgery, which are always associated with severe psychophysical stress.

Bacterial Stress Responses as Potential Targets in Overcoming Antibiotic Resistance

Bacteria can be adapted to adverse and detrimental conditions that induce general and specific responses to DNA damage as well as acid, heat, cold, starvation, oxidative, envelope, and osmotic stresses. The stress-triggered regulatory systems are involved in bacterial survival processes, such as adaptation, physiological changes, virulence potential, and antibiotic resistance. Antibiotic susceptibility to several antibiotics is reduced due to the activation of stress responses in cellular physiology by the stimulation of resistance mechanisms, the promotion of a resistant lifestyle (biofilm or persistence), and/or the induction of resistance mutations. Hence, the activation of bacterial stress responses poses a serious threat to the efficacy and clinical success of antibiotic therapy. Bacterial stress responses can be potential targets for therapeutic alternatives to antibiotics. An understanding of the regulation of stress response in association with antibiotic resistance provides useful information for the discovery of novel antimicrobial adjuvants and the development of effective therapeutic strategies to control antibiotic resistance in bacteria. Therefore, this review discusses bacterial stress responses linked to antibiotic resistance in Gram-negative bacteria and also provides information on novel therapies targeting bacterial stress responses that have been identified as potential candidates for the effective control of Gram-negative antibiotic-resistant bacteria.

Lactoferrin as a Human Genome “Guardian”—An Overall Point of View

Structural abnormalities causing DNA modifications of the ethene and propanoadducts can lead to mutations and permanent damage to human genetic material. Such changes may cause premature aging and cell degeneration and death as well as severe impairment of tissue and organ function. This may lead to the development of various diseases, including cancer. In response to a damage, cells have developed defense mechanisms aimed at preventing disease and repairing damaged genetic material or diverting it into apoptosis. All of the mechanisms described above are part of the repertoire of action of Lactoferrin—an endogenous protein that contains iron in its structure, which gives it numerous antibacterial, antiviral, antifungal and anticancer properties. The aim of the article is to synthetically present the new and innovative role of lactoferrin in the protection of human genetic material against internal and external damage, described by the modulation mechanisms of the cell cycle at all its levels and the mechanisms of its repair.

A review on lactoferrin as a proton pump inhibitor

Lactoferrin (Lf) is a versatile natural milk-derived protein that exhibits multiple interesting biological activities. Since it is safe for human administration and currently manufactured using low cost and well-established large-scale processes, the Lf scientific community has been devoted at dissecting its mechanisms of action towards its more rational and efficient use for various applications. Emerging literature has identified proton pumping ATPases as molecular targets of Lf in different cellular models linked to distinct activities of this natural protein. Information on this subject has not been systematically analysed before, hence herein we review the current state of art on the effect of Lf on proton pumping ATPases. Though structurally different, we propose that Lf holds a proton pump inhibitor (PPI)-like activity based on the functional resemblance with the classical inhibitors of the stomach H⁺/K⁺-ATPase. The downstream events and outcomes of the PPI-like activity of Lf, as well as its impact for the development of improved Lf applications are also discussed.

Anticandidal Potential of Two Cyanobacteria-Synthesized Silver Nanoparticles: Effects on Growth, Cell Morphology, and Key Virulence Attributes of Candida albicans

Candida albicans is an opportunistic human fungal pathogen responsible for 90-100% of mucosal and nosocomial infections worldwide. The emergence of drug-resistant strains has resulted in adverse consequences for human health, including numerous deaths. Consequently, there is an urgent need to identify and develop new antimicrobial drugs to counter these effects. Antimicrobial nanoagents have shown potent inhibitory activity against a number of pathogens through targeting their defense systems, such as biofilm formation. Here, we investigated the anticandidal activity of silver nanoparticles biosynthesized by the cyanobacterial strains Desertifilum sp. IPPAS B-1220 and Nostoc Bahar_M (D-SNPs and N-SNPs, respectively), along with that of silver nitrate (AgNO3), and examined the mechanisms underlying their lethal effects. For this, we performed agar well diffusion and enzyme activity assays (lactate dehydrogenase, adenosine triphosphatase, glutathione peroxidase, and catalase) and undertook morphological examinations using transmission electron microscopy. The effects of the three treatments on Hwp1 and CDR1 gene expression and protein patterns were assessed using qRT-PCR and SDS-PAGE assays, respectively. All of the three treatments inhibited C. albicans growth; disrupted membrane integrity, metabolic function, and antioxidant activity; induced ultrastructural changes in the cell envelope; and disrupted cytoplasmic and nuclear contents. Of the three agents, D-SNPs showed the greatest biocidal activity against C. albicans. Additionally, the D-SNP treatment significantly reduced the gene expression of Hwp1 and CDR1, suggestive of negative effects on biofilm formation ability and resistance potential of C. albicans, and promoted protein degradation. The mechanism involved in the biocidal effects of both D-SNPs and N-SNPs against C. albicans could be attributed to their ability to interfere with fungal cell structures and/or stimulate oxidative stress, enabling them to be used as a robust antimycotic agent.

Antioxidant thymoquinone and eugenol alleviate TiO2 nanoparticle-induced toxicity in human blood cells in vitro

Titanium dioxide (TiO₂) nanoparticles (NPs) are used extensively in a variety of commercial, industrial, and medical products, due to which human exposure is inevitable. This study aimed to explore the potential of eugenol and thymoquinone (TQ), two well-known antioxidants, in counteracting the NP-induced toxicity in human blood cells in vitro. Fresh lymphocytes and erythrocytes were isolated from volunteer human blood donors and incubated with 50 μg/mL of TiO₂ NPs in the presence and absence of 50 μM of TQ and 20 μg/mL of eugenol for 3 h. Results showed that NP-treatment-induced hemolysis, oxidative stress, lactate dehydrogenase (LDH) leakage, and reduced ATPase activity in the erythrocytes. In the lymphocytes treated with NPs alone (50 μg/mL), cytotoxicity in MTT assay and DNA damage in comet assay were observed; in addition, mitochondrial membrane potential collapsed and ADP/ATP ratio increased indicating mitochondrial function impairment. However, in the presence of antioxidants, all these NP-induced changes were mitigated significantly. The results were more significant when both antioxidants eugenol and TQ were given together. Thus, it seems that antioxidants eugenol and TQ can be used as a protective agent against TiO₂ NP-induced toxicity.

The milk-derived lactoferrin inhibits V-ATPase activity by targeting its V1 domain

Lactoferrin (Lf), a bioactive milk protein, exhibits strong anticancer and antifungal activities. The search for Lf targets and mechanisms of action is of utmost importance to enhance its effective applications. A common feature among Lf-treated cancer and fungal cells is the inhibition of a proton pump called V-ATPase. Lf-driven V-ATPase inhibition leads to cytosolic acidification, ultimately causing cell death of cancer and fungal cells. Given that a detailed elucidation of how Lf and V-ATPase interact is still missing, herein we aimed to fill this gap by employing a five-stage computational approach. Molecular dynamics simulations of both proteins were performed to obtain a robust sampling of their conformational landscape, followed by clustering, which allowed retrieving representative structures, to then perform protein-protein docking. Subsequently, molecular dynamics simulations of the docked complexes and free binding energy calculations were carried out to evaluate the dynamic binding process and build a final ranking based on the binding affinities. Detailed atomist analysis of the top ranked complexes clearly indicates that Lf binds to the V₁ cytosolic domain of V-ATPase. Particularly, our data suggest that Lf binds to the interfaces between A/B subunits, where the ATP hydrolysis occurs, thus inhibiting this process. The free energy decomposition analysis further identified key binding residues that will certainly aid in the rational design of follow-up experimental studies, hence bridging computational and experimental biochemistry.

A prospective observational study of urinary cytokines and inflammatory response in patients with Overactive Bladder Syndrome

BACKGROUND

Contemporary studies have discredited the methods used to exclude urinary tract infection (UTI) when treating overactive bladder (OAB). Thus we must revisit the OAB phenotype to check that UTI has not been overlooked.

AIMS

To examine the differences in urinary cytokines IL6 and lactoferrin in OAB patients compared to controls, with references to microscopy of urine and enhanced quantitative urine culture.

METHODS

A blinded, prospective cohort study with normal controls using six repeated measures, achieved two-monthly, over 12 months.

RESULTS

The differences between patients and controls in urine IL6 (F = 49.0, p < .001) and lactoferrin (F = 228.5, p < .001) were significant and of a magnitude to have clinical implications. These differences were for lactoferrin correlated to symptoms (9.3, p = .003); for both to pyuria (IL6 F = 66.2, p < .001, Lactoferrin F = 73.9, p < .001); and for IL6 microbial abundance (F = 5.1, p = .024). The pathological markers had been missed by urinary dipsticks and routine MSU culture.

CONCLUSION

The OAB phenotype may encompass patients with UTI that is being overlooked because of the failure of standard screening methods.

Lethal Mechanisms of Nostoc-Synthesized Silver Nanoparticles Against Different Pathogenic Bacteria

BACKGROUND

Increasing antibiotic resistance and the emergence of multidrug-resistant (MDR) pathogens have led to the need to develop new therapeutic agents to tackle microbial infections. Nano-antibiotics are a novel generation of nanomaterials with significant antimicrobial activities that target bacterial defense systems including biofilm formation, membrane permeability, and virulence activity.

PURPOSE

In addition to AgNO3, the current study aimed to explore for first time the antibacterial potential of silver nanoparticles synthesized by Nostoc sp. Bahar_M (N-SNPs) and their killing mechanisms against Streptococcus mutans, methicillin-resistant Staphylococcus aureus, Escherichia coli, and Salmonella typhimurium.

METHODS

Potential mechanisms of action of both silver species against bacteria were systematically explored using agar well diffusion, enzyme (lactate dehydrogenase (LDH) and ATPase) and antioxidant (glutathione peroxidase and catalase)   assays, and morphological examinations. qRT-PCR and SDS-PAGE were employed to investigate the effect of both treatments on mfD, flu, and hly gene expression and protein patterns, respectively.

RESULTS

N-SNPs exhibited greater biocidal activity than AgNO3 against the four tested bacteria. E. coli treated with N-SNPs showed significant surges in LDH levels, imbalances in other antioxidant and enzyme activities, and marked morphological changes, including cell membrane disruption and cytoplasmic dissolution. N-SNPs caused more significant upregulation of mfD expression and downregulation of both flu and hly expression and increased protein denaturation compared with AgNO3.

CONCLUSION

N-SNPs exhibited significant inhibitory potential against E. coli by direct interfering with bacterial cellular structures and/or enhancing oxidative stress, indicating their potential for use as an alternative antimicrobial agent. However, the potential of N-SNPs to be usable and biocompatible antibacterial drug will evaluate by their toxicity against normal cells.

Canine Bone Marrow Mesenchymal Stem Cell Conditioned Media Affect Bacterial Growth, Biofilm-Associated Staphylococcus aureus and AHL-Dependent Quorum Sensing

The present study investigated the in vitro antibacterial, antibiofilm and anti-Quorum Sensing (anti-QS) activities of canine bone marrow mesenchymal stem cell-conditioned media (cBM MSC CM) containing all secreted factors <30 K, using a disc diffusion test (DDT), spectrophotometric Crystal Violet Assay (SCVA) and Bioluminescence Assay (BA) with QS-reporter Escherichia coli JM109 pSB1142. The results show a sample-specific bacterial growth inhibition (zones varied between 7–30 mm), statistically significant modulation of biofilm-associated Staphylococcus aureus and Escherichia coli bioluminescence (0.391 ± 0.062 in the positive control to the lowest 0.150 ± 0.096 in the experimental group, cf. 11,714 ± 1362 to 7753 ± 700, given as average values of absorbance A₅₅₀ ± SD versus average values of relative light units to growth RLU/A₅₅₀ ± SD). The proteomic analysis performed in our previous experiment revealed the presence of several substances with documented antibacterial, antibiofilm and immunomodulatory properties (namely, apolipoprotein B and D; amyloid-β peptide; cathepsin B; protein S100-A4, galectin 3, CLEC3A, granulin, transferrin). This study highlights that cBM MSC CM may represent an important new approach to managing biofilm-associated and QS signal molecule-dependent bacterial infections. To the best of our knowledge, there is no previous documentation of canine BM MSC CM associated with in vitro antibiofilm and anti-QS activity.

Oxidative Stress and Apoptotic Responses Elicited by Nostoc-Synthesized Silver Nanoparticles against Different Cancer Cell Lines

Green nanoparticles represent a revolution in bionanotechnology, providing opportunities to fight life-threatening diseases, such as cancer, with less risk to the environment and to human health. Here, for the first time, we systematically investigated the anticancer activity and possible mechanism of novel silver nanoparticles (N-SNPs) synthesized by Nostoc Bahar M against the MCF-7 breast cancer cells, HCT-116 colorectal adenocarcinoma cells, and HepG2 liver cancer cells, using cell viability assays, morphological characterization with inverted light and transmission electron microscopy, antioxidants and enzymes (glutathione peroxidase (GPx), glutathione (GSH), adenosine triphosphatase (ATPase), and lactate dehydrogenase (LDH)), and western blotting (protein kinase B (Akt), phosphorylated-Akt (p-Akt), mammalian target of rapamycin (mTOR), B-cell lymphoma 2 (Bcl-2), tumor suppressor (p53), and caspase 3). N-SNPs decreased the viability of MCF-7, HCT-116, and HepG2 cells, with half-maximal inhibitory concentrations of 54, 56, and 80 µg/mL, respectively. They also significantly increased LDH leakage, enhanced oxidative stress via effects on antioxidative markers, and caused metabolic stress by significantly decreasing ATPase levels. N-SNPs caused extensive ultrastructural alterations in cell and nuclear structures, as well as in various organelles. Furthermore, N-SNPs triggered apoptosis via the activation of caspase 3 and p53, and suppressed the mTOR signaling pathway via downregulating apoptosis-evading proteins in MCF-7, HCT-116, and HepG2 cells. Ultrastructural analysis, together with biochemical and molecular analyses, revealed that N-SNPs enhanced apoptosis via the induction of oxidative stress and/or through direct interactions with cellular structures in all tested cells. The cytotoxicity of Nostoc-mediated SNPs represents a new strategy for cancer treatment via targeting various cell death pathways. However, the potential of N-SNPs to be usable and biocompatible anticancer drug will depend on their toxicity against normal cells.

Multitarget Approaches against Multiresistant Superbugs

Despite efforts to develop new antibiotics, antibacterial resistance still develops too fast for drug discovery to keep pace. Often, resistance against a new drug develops even before it reaches the market. This continued resistance crisis has demonstrated that resistance to antibiotics with single protein targets develops too rapidly to be sustainable. Most successful long-established antibiotics target more than one molecule or possess targets, which are encoded by multiple genes. This realization has motivated a change in antibiotic development toward drug candidates with multiple targets. Some mechanisms of action presuppose multiple targets or at least multiple effects, such as targeting the cytoplasmic membrane or the carrier molecule bactoprenol phosphate and are therefore particularly promising. Moreover, combination therapy approaches are being developed to break antibiotic resistance or to sensitize bacteria to antibiotic action. In this Review, we provide an overview of antibacterial multitarget approaches and the mechanisms behind them.

Cytotoxic effect of green silver nanoparticles against ampicillin-resistant Klebsiella pneumoniae

Considering the harmful effects and high spread of drug-resistant Klebsiella pneumoniae, many researchers have been trying to produce new antibacterial agents to combat the emergence of multidrug-resistant (MDR) strains of this bacterium. Recent progress in the nanomedicine field has provided opportunities for synthesizing unique nanoagents to battle MDR bacteria by targeting virulence and resistance signalling. The biocidal effects of 14.9 nm silver nanoparticles fabricated using Nostoc sp. Bahar M (N-SNPs) and AgNO3 were examined against drug-resistant K. pneumoniae using the agar well diffusion method. Transmission electron microscopy (TEM) was used to detect the ultrastructural changes caused by N-SNPs and AgNO3. To address the mode of action of N-SNPs and AgNO3, CAT, GPx, LDH and ATPase levels were assessed. The toxicity of N-SNPs and AgNO3 was evaluated against the mfD, flu, hly, 23S, hns, hcp-1, VgrG-1 and VgrG-3 genes as well as cellular proteins. N-SNPs showed the greatest inhibitory activity against K. pneumoniae, with MIC and MBC values of 0.9 and 1.2 mg mL-1, respectively. Furthermore, N-SNPs and AgNO3 induced apoptotic features, including cell shrinkage and cell atrophy. N-SNPs were more potent bactericidal compounds than AgNO3, causing increased leakage of LDH and GPx activities and depletion of ATPase and CAT activities, resulting in induced oxidative stress and metabolic toxicity. Compared to AgNO3, N-SNPs exhibited the highest toxicity towards the selected genes and the greatest damage to bacterial proteins. N-SNPs were the most potent agents that induced bacterial membrane damage, oxidative stress and disruption of biomolecules such as DNA and proteins. N-SNPs may be used as effective nanodrugs against MDR bacteria.

Novel Biogenic Silver Nanoparticle-Induced Reactive Oxygen Species Inhibit the Biofilm Formation and Virulence Activities of Methicillin-Resistant Staphylococcus aureus (MRSA) Strain

Emerging antibiotic-resistant bacteria result in increased mortality and have negative economic impacts. It is necessary to discover new strategies to create alternative antibacterial agents that suppress the bacterial resistance mechanism and limit the spread of serious infectious bacterial diseases. Silver nanoparticles may represent a new medicinal agents as alternative antibiotics affect different bacterial mechanisms such as virulence and resistance. In addition to that of silver nitrate (AgNO₃) and ampicillin, for the first time, the inhibitory effect of silver nanoparticles synthesized using Desertifilum sp. (D-SNPs) was evaluated against five pathogenic bacteria using the agar well diffusion method. Also, the influence of D-SNPs and AgNO₃ on bacterial antioxidant and metabolic activities was studied. The antibacterial activity of D-SNPs and AgNO₃ against methicillin-resistant Staphylococcus aureus (MRSA) strains was studied at the morphological and molecular level. D-SNPs and AgNO₃ have the ability to inhibit the growth of the five bacterial strains and resulted in an imbalance in the CAT, GSH, GPx and ATPase levels. MRSA treated with D-SNPs and AgNO₃ showed different morphological changes such as apoptotic bodies formation and cell wall damage. Moreover, both caused genotoxicity and denaturation of MRSA cellular proteins. Additionally, TEM micrographs showed the distribution of SNPs synthesized by MRSA. This result shows the ability of MRSA to reduce silver nitrate into silver nanoparticles. These data indicate that D-SNPs may be a significant alternative antibacterial agent against different bacteria, especially MDR bacteria, by targeting the virulence mechanism and biofilm formation, leading to bacterial death.

Antibacterial mode of action of trans-cinnamaldehyde derived from cinnamon bark (Cinnamomum verum) essential oil against Agrobacterium tumefaciens

The fumigant antibacterial activities of 50 plant essential oils belonging to 10 families were investigated against Agrobacterium tumefaciens. Among the test plant essential oils, Cinnamomum verum (cinnamon bark) essential oil showed the most potent fumigant antibacterial activity. When we investigated the antibacterial activities of compounds identified from cinnamon bark essential oil and 9 congeners of trans-cinnamaldehyde, lengths of inhibition zone of trans-cinnamaldehyde, salicylaldehyde and hydrocinnamaldehyde were 1.28, 1.73, and 1.24 cm at 0.625 mg/paper disc concentration, respectively. To determine the mode of action of trans-cinnamaldehyde and salicylaldehyde, intercellular reactive oxygen species (ROS) generation and cell membrane integrity were determined using a confocal laser scanning microscopy. Furthermore, we compared the up- and down-regulated gene expression of A. tumefaciens treated with trans-cinnamaldehyde and salicylaldehyde with that of untreated A. tumefaciens. With cutoffs of |log2FC| > 1 and FDR < 0.05, 29 and 43 down-regulated genes and 27 and 117 up-regulated genes were found in the treatment of trans-cinnamaldehyde and salicylaldehyde, respectively. Based on the ROS generation results, cell membrane integrity assay, and gene expression, we conclude that the antibacterial mode of action of trans-cinnamaldehyde and salicylaldehyde is ROS generation by the Fenton reaction caused by the down-regulation of an ATP synthesis-related gene cluster, corrupted iron ion homeostasis, and a corrupted ROS defense mechanism. The high concentration of ROS damaged the A. tumefaciens cell membrane, which caused cell death.

Inactivation of Bacteria by γ-Irradiation to Investigate the Interaction with Antimicrobial Peptides

The activity of antimicrobial peptides (AMPs) has been investigated extensively using model membranes composed of phospholipids or lipopolysaccharides in aqueous environments. However, from a biophysical perspective, there is a large scientific interest regarding the direct interaction of membrane-active peptides with whole bacteria. Working with living bacteria limits the usability of experimental setups and the interpretation of the resulting data because of safety risks and the overlap of active and passive effects induced by AMPs. We killed or inactivated metabolic-active bacteria using γ-irradiation or sodium azide, respectively. Microscopy, flow cytometry, and SYTOX green assays showed that the cell envelope remained intact to a high degree at the minimal bactericidal dose. Furthermore, the tumor-necrosis-factor-α-inducing activity of the lipopolysaccharides and the chemical lipid composition was unchanged. Determining the binding capacity of AMPs to the bacterial cell envelope by calorimetry is difficult because of an overlapping of the binding heat and metabolic activities of the bacteria-induced by the AMPs. The inactivation of all active processes helps to decipher the complex thermodynamic information. From the isothermal titration calorimetry (ITC) results, we propose that the bacterial membrane potential (Δψ) is possibly an underestimated modulator of the AMP activity. The negative surface charge of the outer leaflet of the outer membrane of Gram-negative bacteria is already neutralized by peptide concentrations below the minimal inhibitory concentration. This proves that peptide aggregation on the bacterial membrane surface plays a decisive role in the degree of antimicrobial activity. This will not only enable many biophysical approaches for the investigation between bacteria and membrane-active peptides in the future but will also make it possible to compare biophysical parameters of active and inactive bacteria. This opens up new possibilities to better understand the active and passive interaction processes between AMPs and bacteria.

Differential proteomics analysis of bile between gangrenous cholecystitis and chronic cholecystitis

To establish human biliary protein expression profiles of gangrenous cholecystitis, chronic cholecystitis, and to discover differently expressed proteins for gangrenous cholecystitis by comparative proteomics, we gathered human gallbladder bile samples from gangrenous cholecystitis and chronic cholecystitis patients, respectively After removing the bile salts and lipid peptide fragments were identified by the iTRAQ-coupled LC-MS/MS technology,then identified in SwissProt with Mascot software. A total of 2251 proteins from chronic cholecystitis patients and 2180 proteins from gangrenous cholecystitis patients were identified. A total of 575 differential proteins were found between gangrenous cholecystitis and chronic cholecystitis, 159 proteins were over-expressed and 416 proteins were under-expressed in gangrenous cholecystitis. By bio-informatics analysis, in gangrenous cholecystitis, cell death, necrosis,immune response of neutrophils, apoptosis and degranulation of cells were activated; while cell survival, fatty acid metabolism, transport of molecular and proliferation of cells were inhibited, which might reflect the de-compensatory phase. Pathway analysis showed acute phase proteins were changed, indicating the role of the inflammatory response in the pathogenesis of gangrenous cholecystitis. Six acute phase proteins were found up-regulated,implying a close linkage to gangrenous gallbladder. Our study could be applicable in the biomarker discovery of gangrenous cholecystitis.

Serological proteomic biomarkers to identify Paracoccidioides species and risk of relapse

The sensitivity of the double agar gel immunodiffusion test is about 90% in patients with untreated paracoccidioidomycosis (PCM), but it is much lower in cases of relapse. In addition, serum from patients with PCM caused by Paracoccidioides lutzii, frequent in the Midwest region of Brazil, do not react with the classical antigen obtained from Pb B-339. These findings showed the need for alternative diagnostic methods, such as biological markers through proteomics. The aim of this study was to identify biomarkers for the safe identification of PCM relapse and specific proteins that could distinguish infections caused by Paracoccidioides brasiliensis from those produced by Paracoccidioides lutzii. Proteomic analysis was performed in serum from 9 patients with PCM caused by P. brasiliensis, with and without relapse, from 4 patients with PCM produced by P. lutzii, and from 3 healthy controls. The comparative evaluation of the 29 identified plasma proteins suggested that the presence of the immunoglobulin (Ig) alpha-2 chain C region and the absence of Ig heavy chain V-III TIL indicate infection by P. lutzii. In addition, the absence of complement factor B protein might be a predictor of relapse. The evaluation of these proteins in a higher number of patients should be carried out in order to validate these findings.

Antimicrobial peptides (AMPs): The quintessential 'offense and defense' molecules are more than antimicrobials

Antimicrobial peptides (AMPs) are cationic amphiphilic molecules with α-helix or β-sheet linear motifs and linear or cyclic configurations. For their role in 'defense and offense', they are present in all living organisms. AMPs are named so, as they inhibit a wide array of microbes by membrane pore formation and subsequent perturbation of mitochondrial membrane ionic balance. However, their functional repertoire is expanding with validated roles in cytotoxicity, wound healing, angiogenesis, apoptosis, and chemotaxis [1]. A number of endogenous AMPs have been characterized in human body such as defensins, cathelicidins, histatins etc. They mediate critical functions, but when homeostasis is broken, they turn hostile and initiate inflammatory diseases. This review discusses the sources of therapeutic AMPs; auto-immunity risks of endogenous AMPs, and their dermatological applications; normally overlooked risks of the peptides; and scopes ahead. This holistic work is expected to be a valuable reference for further research in this field.

Molecular, structural, and functional comparison of N lobe and C lobe of the transferrin from rock bream, Oplegnathus fasciatus, with respect to its immune response

The iron-withholding strategy of innate immunity is an effective antimicrobial defense mechanism that combats microbial infection by depriving microorganisms of Fe³⁺, which is important for their growth and propagation. Transferrins (Tfs) are a group of iron-binding proteins that exert their antimicrobial function through Fe³⁺ sequestration. The current study describes both structural and functional characteristics of a transferrin ortholog from rock bream Oplegnathus fasciatus (RbTf). The RbTf cDNA possesses an open reading frame (ORF) of 2079 bp encoding 693 amino acids. It has a molecular mass of approximately 74 kDa and an isoelectric point of 5.4. In silico analysis revealed that RbTf has two conserved domains: N-terminal domain and C-terminal domain. Pairwise homology analysis and phylogenetic analysis revealed that RbTf shared the highest identity (82.6%) with Dicentrarchus labrax Tf. According to the genomic analysis, RbTf possesses 17 exons and 16 introns, similar to the other orthologs. Here, we cloned the N terminal and C terminal domains of RbTf to evaluate their distinct functional features. Results obtained through the CAS (chrome azurol S) assay confirmed the iron-binding ability of the RbTf, and it was further determined that the iron-binding ability of rRbTfN was higher than that of rRbTfC. The antimicrobial functions of the rRbTfN and the rRbTfC were confirmed via the iron-dependent bacterial growth inhibition assay. Tissue distribution profiling revealed a ubiquitous expression with intense expression in the liver. Temporal assessment revealed that RbTf increased after stimulation of LPS, Edwardsiella tarda, and Streptococcus iniae post injection (p.i.). These findings demonstrated that RbTf is an important antimicrobial protein that can combat bacterial pathogens.

Protonation and electronic structure of 2,6-dichlorophenolindophenolate during reduction. A theoretical study including explicit solvent

Protonation in the two-electron/two-proton reduction processes of 2,6-dichlorophenolindophenolate (DCIP) is investigated combining density functional theory (DFT) and molecular dynamics (MD) methods. DCIP (anion), DCIP^•- (radical anion), and DCIP^2- (dianion) are considered, including the electronic structure analysis from the prospective of quantum theory of atoms and molecules (QTAIM). It is shown that oxygen on the indophenolate moiety and nitrogen are the first and/or the second proton acceptor sites and their energetic order depends on the total charge of the system. MD simulations of differently charged species interacting with the solvent molecules have been performed for methanol, water, and oxonium cation (H₃O⁺). Methanol and water molecules are found to form only hydrogen bonds with the solute irrespective of its charge. The calculated pK_a values show that the imino group of DCIPH^- is a weaker acid than water. While in the case of DCIP (and DCIP^•-) plus oxonium cation, proton transfer from the solvent to the solute was evidenced for both aforementioned acceptor sites. In addition, MD simulations of bulks containing 15 and 43 molecules of water around the DCIP molecule have been performed, revealing the formation of 2-4 hydrogen bonds. Graphical Abstract 2,6-Dichlorophenolindophenolate interacts with solvent molecules (water, oxonium cation and methanol). Hydrogen transfer and electronic structure are studied by DFT and molecular dynamics methods.

Antifungal Mechanism of Action of Lactoferrin: Identification of H+-ATPase (P3A-Type) as a New Apoptotic-Cell Membrane Receptor

Human lactoferrin (hLf) is a protein of the innate immune system which induces an apoptotic-like process in yeast. Determination of the susceptibility to lactoferrin of several yeast species under different metabolic conditions, respiratory activity, cytoplasmic ATP levels, and external medium acidification mediated by glucose assays suggested plasma membrane Pma1p (P3A-type ATPase) as the hLf molecular target. The inhibition of plasma membrane ATPase activity by hLf and the identification of Pma1p as the hLf-binding membrane protein confirmed the previous physiological evidence. Consistent with this, cytoplasmic ATP levels progressively increased in hLf-treated Candida albicans cells. However, oligomycin, a specific inhibitor of the mitochondrial F-type ATPase proton pump (mtATPase), abrogated the antifungal activity of hLf, indicating a crucial role for mtATPase in the apoptotic process. We suggest that lactoferrin targeted plasma membrane Pma1p H(+)-ATPase, perturbing the cytoplasmic ion homeostasis (i.e., cytoplasmic H(+) accumulation and subsequent K(+) efflux) and inducing a lethal mitochondrial dysfunction. This initial event involved a normal mitochondrial ATP synthase activity responsible for both the ATP increment and subsequent hypothetical mitochondrial proton flooding process. We conclude that human lactoferrin inhibited Pma1p H(+)-ATPase, inducing an apoptotic-like process in metabolically active yeast. Involvement of mitochondrial H(+)-ATPase (nonreverted) was essential for the progress of this programmed cell death in which the ionic homeostasis perturbation seems to precede classical nonionic apoptotic events.

Enhancing the antitumor effect of methotrexate in intro and in vivo by a novel targeted single-walled carbon nanohorn-based drug delivery system

The present research reports a smart multifunctional oxidized single-wall carbon nanohorns (oxSWNHs) drug delivery system (DDS) which could enhance the anti-tumor effect of methotrexate (MTX).

Hepatocytes: a key cell type for innate immunity

Hepatocytes, the major parenchymal cells in the liver, play pivotal roles in metabolism, detoxification, and protein synthesis. Hepatocytes also activate innate immunity against invading microorganisms by secreting innate immunity proteins. These proteins include bactericidal proteins that directly kill bacteria, opsonins that assist in the phagocytosis of foreign bacteria, iron-sequestering proteins that block iron uptake by bacteria, several soluble factors that regulate lipopolysaccharide signaling, and the coagulation factor fibrinogen that activates innate immunity. In this review, we summarize the wide variety of innate immunity proteins produced by hepatocytes and discuss liver-enriched transcription factors (e.g. hepatocyte nuclear factors and CCAAT/enhancer-binding proteins), pro-inflammatory mediators (e.g. interleukin (IL)-6, IL-22, IL-1β and tumor necrosis factor-α), and downstream signaling pathways (e.g. signal transducer and activator of transcription factor 3 and nuclear factor-κB) that regulate the expression of these innate immunity proteins. We also briefly discuss the dysregulation of these innate immunity proteins in chronic liver disease, which may contribute to an increased susceptibility to bacterial infection in patients with cirrhosis.

Transferrin-bound proteins as potential biomarkers for advanced breast cancer patients

Background

Serum profiling using mass spectrometry-based proteomic techniques has great potential to detect biomarkers that might improve the management for advanced breast cancer patients. The albuminome has previously been investigated as a tool in biomarker discovery, however other high abundant blood proteins are also likely to sequester potentially interesting molecules.

Methods

Affinity resin purified and isolated Transferrin and associated bound proteins from normal control and breast cancer patient serum samples were analysed by label-free mass spectrometry during the discovery phase.

Results

21 significant proteins were identified with Fibrinogen and Fibronectin selected for further analysis in an independent sample set, with significant difference found when comparing the controls groups (normal healthy control, inflammatory bowel disease and benign breast disease) to stage IV breast cancer.

Conclusions

The area under the curve value for Fibrinogen compared favourably with cancer antigen 15-3, an established breast cancer tumour marker. A combination of all three biomarkers improved accuracy when comparing control/benign to stage IV breast cancer patient groups.

General significance

Mass spectrometry profiling of Transferrin-bound proteins has revealed serum proteins that can distinguish between serum from advanced breast cancer patients and healthy control subjects with high confidence.

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Transferrin was found to interact with many candidate biomarkers.

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21 significant proteins were identified bound to Transferrin.

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Many of these proteins are associated with the complement and coagulations systems.

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Fibrinogen and Fibronectin were found to have significant AUC values.

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High abundant proteins harbour potential diagnostic molecules.

Small cationic antimicrobial peptides delocalize peripheral membrane proteins

Short antimicrobial peptides rich in arginine (R) and tryptophan (W) interact with membranes. To learn how this interaction leads to bacterial death, we characterized the effects of the minimal pharmacophore RWRWRW-NH2. A ruthenium-substituted derivative of this peptide localized to the membrane in vivo, and the peptide also integrated readily into mixed phospholipid bilayers that resemble Gram-positive membranes. Proteome and Western blot analyses showed that integration of the peptide caused delocalization of peripheral membrane proteins essential for respiration and cell-wall biosynthesis, limiting cellular energy and undermining cell-wall integrity. This delocalization phenomenon also was observed with the cyclic peptide gramicidin S, indicating the generality of the mechanism. Exogenous glutamate increases tolerance to the peptide, indicating that osmotic destabilization also contributes to antibacterial efficacy. Bacillus subtilis responds to peptide stress by releasing osmoprotective amino acids, in part via mechanosensitive channels. This response is triggered by membrane-targeting bacteriolytic peptides of different structural classes as well as by hypoosmotic conditions.

EndoE from Enterococcus faecalis hydrolyzes the glycans of the biofilm inhibiting protein lactoferrin and mediates growth

Glycosidases are widespread among bacteria. The opportunistic human pathogen Enterococcus faecalis encodes several putative glycosidases but little is known about their functions. The identified endo-β-N-acetylglucosaminidase EndoE has activity on the N-linked glycans of the human immunoglobulin G (IgG). In this report we identified the human glycoprotein lactoferrin (hLF) as a new substrate for EndoE. Hydrolysis of the N-glycans from hLF was investigated using lectin blot, UHPLC and mass spectrometry, showing that EndoE releases major glycoforms from this protein. hLF was shown to inhibit biofilm formation of E. faecalis in vitro. Glycans of hLF influence the binding to E. faecalis, and EndoE-hydrolyzed hLF inhibits biofilm formation to lesser extent than intact hLF indicating that EndoE prevents the inhibition of biofilm. In addition, hLF binds to a surface-associated enolase of E. faecalis. Culture experiments showed that the activity of EndoE enables E. faecalis to use the glycans derived from lactoferrin as a carbon source indicating that they could be used as nutrients in vivo when no other preferred carbon source is available. This report adds important information about the enzymatic activity of EndoE from the commensal and opportunist E. faecalis. The activity on the human glycoprotein hLF, and the functional consequences with reduced inhibition of biofilm formation highlights both innate immunity functions of hLF and a bacterial mechanism to evade this innate immunity function. Taken together, our results underline the importance of glycans in the interplay between bacteria and the human host, with possible implications for both commensalism and opportunism.

Lactoferrin-derived resistance against plant pathogens in transgenic plants

Lactoferrin (LF) is a ubiquitous cationic iron-binding milk glycoprotein that contributes to nutrition and exerts a broad-spectrum primary defense against bacteria, fungi, protozoa, and viruses in mammals. These qualities make lactoferrin protein and its antimicrobial motifs highly desirable candidates to be incorporated in plants to impart broad-based resistance against plant pathogens or to economically produce them in bulk quantities for pharmaceutical and nutritional purposes. This study introduced bovine LF (BLF) gene into tobacco ( Nicotiana tabacum var. Xanthi), Arabidopsis ( A. thaliana ) and wheat ( Triticum aestivum ) via Agrobacterium -mediated plant transformation. Transgenic plants or detached leaves exhibited high levels of resistance against the damping-off causing fungal pathogen Rhizoctonia solani and the head blight causing fungal pathogen Fusarium graminearum . LF also imparted resistance to tomato plants against a bacterial pathogen, Ralstonia solanacearum . Similarly, other researchers demonstrated expression of LF and LF-mediated high-quality resistance to several other aggressive fungal and bacterial plant pathogens in transgenic plants and against viral pathogens by foliar applications of LF or its derivatives. Taken together, these studies demonstrated the effectiveness of LF for improving crop quality and its biopharming potentials for pharmaceautical and nutritional applications.

Identification of altered plasma proteins by proteomic study in valvular heart diseases and the potential clinical significance

BACKGROUND

Little is known about genetic basis and proteomics in valvular heart disease (VHD) including rheumatic (RVD) and degenerative (DVD) valvular disease. The present proteomic study examined the hypothesis that certain proteins may be associated with the pathological changes in the plasma of VHD patients.

METHODS AND RESULTS

Differential protein analysis in the plasma identified 18 differentially expressed protein spots and 14 corresponding proteins or polypeptides by two-dimensional electrophoresis and mass spectrometry in 120 subjects. Two up-regulated (complement C4A and carbonic anhydrase 1) and three down-regulated proteins (serotransferrin, alpha-1-antichymotrypsin, and vitronectin) were validated by ELISA in enlarging samples. The plasma levels (n = 40 for each) of complement C4A in RVD (715.8±35.6 vs. 594.7±28.2 ng/ml, P = 0.009) and carbonic anhydrase 1 (237.70±15.7 vs. 184.7±10.8 U/L, P = 0.007) in DVD patients were significantly higher and that of serotransferrin (2.36±0.20 vs. 2.93±0.16 mg/ml, P = 0.025) and alpha-1-antichymotrypsin (370.0±13.7 vs. 413.0±11.6 µg/ml, P = 0.019) in RVD patients were significantly lower than those in controls. The plasma vitronectin level in both RVD (281.3±11.0 vs. 323.2±10.0 µg/ml, P = 0.006) and DVD (283.6±11.4 vs. 323.2±10.0 µg/ml, P = 0.011) was significantly lower than those in normal controls.

CONCLUSIONS

We have for the first time identified alterations of 14 differential proteins or polypeptides in the plasma of patients with various VHD. The elevation of plasma complement C4A in RVD and carbonic anhydrase 1 in DVD and the decrease of serotransferrin and alpha-1-antichymotrypsin in RVD patients may be useful biomarkers for these valvular diseases. The decreased plasma level of vitronectin - a protein related to the formation of valvular structure - in both RVD and DVD patients might indicate the possible genetic deficiency in these patients.

Holo and apo-transferrins interfere with adherence to abiotic surfaces and with adhesion/invasion to HeLa cells in Staphylococcus spp

Staphylococcus aureus and Staphylococcus epidermidis are the major cause of infections associated with implanted medical devices. Colonization on abiotic and biotic surfaces is often sustained by biofilm forming strains. Human natural defenses can interfere with this virulence factor. We investigated the effect of human apo-transferrin (apo-Tf, the iron-free form of transferrin, Tf) and holo-transferrin (holo-Tf, the iron-saturated form) on biofilm formation by CA-MRSA S. aureus USA300 type (ST8-IV) and S. epidermidis (a clinical isolate and ATCC 35984 strain). Furthermore S. aureus adhesion and invasion assays were performed in a eukaryotic cell line. A strong reduction in biofilm formation with both Tfs was obtained albeit at very different concentrations. In particular, the reduction in biofilm formation was higher with apo-Tf rather than obtained with holo-Tf. Furthermore, while S. aureus adhesion to eukaryotic cells was not appreciably affected, their invasion was highly inhibited in the presence of holo-Tf, and partially inhibited by the apo form. Our results suggest that Tfs could be used as antibacterial adjuvant therapy in infection sustained by staphylococci to strongly reduce their virulence related to adhesion and cellular invasion.