Activity of histone H1.2 in infected burn wounds

Histone H1 kills MRSA

The antimicrobial activity of histones was discovered in the 1940s, but their mechanism of action is not fully known. Here we show that methicillin-resistant Staphylococcus aureus (MRSA) is susceptible to histone H1 (H1), even in the presence of divalent cations and serum. Through selective evolution and a genome-wide screen of a transposon library, as well as physiological and pharmacological experiments, we elucidated how H1 kills MRSA. We show that H1 first binds to wall teichoic acids with high affinity. Once bound, H1 requires a potentiated membrane and a metabolically active bacterium to permeabilize the membrane and enter the cell. Upon entry, H1 accumulates intracellularly, in close association with the bacterial DNA. Of note, anti-H1 antibodies inhibit neutrophil extracellular trap killing of MRSA. Moreover, H1 colocalizes with bacterial DNA in abscess samples of MRSA-infected patients, suggesting a role for H1 in combating MRSA in vivo.

Antimicrobial and antibiofilm activity of human recombinant H1 histones against bacterial infections

Histones possess significant antimicrobial potential, yet their activity against biofilms remains underexplored. Moreover, concerns regarding adverse effects limit their clinical implementation. We investigated the antibacterial efficacy of human recombinant histone H1 subtypes against Pseudomonas aeruginosa PAO1, both planktonic and in biofilms. After the in vitro tests, toxicity and efficacy were assessed in a P. aeruginosa PAO1 infection model using Galleria mellonella larvae. Histones were also evaluated in combination with ciprofloxacin (Cpx) and gentamicin (Gm). Our results demonstrate antimicrobial activity of all three histones against P. aeruginosa PAO1, with H1.0 and H1.4 showing efficacy at lower concentrations. The bactericidal effect was associated with a mechanism of membrane disruption. In vitro studies using static and dynamic models showed that H1.4 had antibiofilm potential by reducing cell biomass. Neither H1.0 nor H1.4 showed toxicity in G. mellonella larvae, and both increased larvae survival when infected with P. aeruginosa PAO1. Although in vitro synergism was observed between ciprofloxacin and H1.0, no improvement over the antibiotic alone was noted in vivo. Differences in antibacterial and antibiofilm activity were attributed to sequence and structural variations among histone subtypes. Moreover, the efficacy of H1.0 and H1.4 was influenced by the presence and strength of the extracellular matrix. These findings suggest histones hold promise for combating acute and chronic infections caused by pathogens such as P. aeruginosa.IMPORTANCEThe constant increase of multidrug-resistant bacteria is a critical global concern. The inefficacy of current therapies to treat bacterial infections is attributed to multiple mechanisms of resistance, including the capacity to form biofilms. Therefore, the identification of novel and safe therapeutic strategies is imperative. This study confirms the antimicrobial potential of three histone H1 subtypes against both Gram-negative and Gram-positive bacteria. Furthermore, histones H1.0 and H1.4 demonstrated in vivo efficacy without associated toxicity in an acute infection model of Pseudomonas aeruginosa PAO1 in Galleria mellonella larvae. The bactericidal effect of these proteins also resulted in biomass reduction of P. aeruginosa PAO1 biofilms. Given the clinical significance of this opportunistic pathogen, our research provides a comprehensive initial evaluation of the efficacy, toxicity, and mechanism of action of a potential new therapeutic approach against acute and chronic bacterial infections.

Efficacy of LL-37 cream in enhancing healing of diabetic foot ulcer: a randomized double-blind controlled trial

Wound healing in DFU (diabetic foot ulcer) has prolonged inflammation phase and defective granulation tissue formation. LL-37 has antimicrobial property, induces angiogenesis, and keratinocyte migration and proliferation. This study analyzes the efficacy of LL-37 cream in enhancing wound healing rate and decreasing the levels of IL-1α, TNF-α, and the number of aerobic bacteria colonization in DFU with mild infection. This study was conducted from January 2020 to June 2021 in Jakarta. Subjects were instructed to apply either LL-37 cream or placebo cream twice a week for 4 weeks. Wounds were measured on days 7, 14, 21, and 28 and processed with ImageJ. The levels of LL-37, IL-1α, and TNF-α from wound fluid were measured using ELISA. The number of aerobic bacteria colonization was counted from the isolate grown in culture. The levels of LL-37 in DFU at baseline were equally low in both groups which were 1.07 (0.37-4.96) ng/mg protein in the LL-37 group and 1.11 (0.24-2.09) ng/mg protein in the placebo group. The increase in granulation index was consistently greater in the LL-37 group on days 7, 14, 21, and 28 (p = 0.031, 0.009, 0.006, and 0.037, respectively). The levels of IL-1α and TNF-α increased in both groups on days 14 and 21 (p > 0.05). The decrease in the number of aerobic bacteria colonization was greater in the LL-37 group on days 7, 14 and 21, but greater in the placebo group on day 28 (p > 0.05). In conclusion, LL-37 cream enhanced the healing rate of DFU with mild infection, but did not decrease the levels of IL-1α and TNF-α and the number of aerobic bacteria colonization. This trial is registered at ClinicalTrials.gov, number NCT04098562.

In Vitro Pharmacokinetics of LL-37 and Oncorhyncin II Combination Against Acinetobacter baumannii

Background: Multidrug-resistant (MDR) Acinetobacter baumannii is one of the most common nosocomial pathogens. Antimicrobial peptides (AMPs) have been introduced as a viable alternative to antibiotics in the treatment of MDR pathogens. Objectives: This study was designed to assess the in vitro pharmacokinetics of the combination of two potent AMPs, LL-37 and oncorhyncin II, against A. baumannii (ATCC19606). Methods: The synthesized genes of oncorhyncin II and LL-37 were introduced into Escherichia coli BL21 as the expression host. The minimum inhibitory concentration (MIC), time-kills, and growth kinetics of these peptides were used to evaluate their antimicrobial efficiencies against A. baumannii (ATCC19606). Results: LL-37 and oncorhyncin II recombinant peptides showed MIC of 30.6 and 95.87 µg/mL against A. baumannii, respectively. Additive action was confirmed by combining the generated AMPs at the checkerboard approach. The combination of LL-37 and oncorhyncin II at 2 × MIC resulted in a rapid drop in log10 CFU/mL of A. baumannii in the time-kill and growth kinetic findings studies. Conclusions: The combination of the produced LL-37 and oncorhyncin II synergizes the bioactivity of the individual peptides. Therefore, these peptides or their combinations might function as novel antibiotics and be used to develop and produce new antimicrobial drugs for the treatment of infections caused by A. baumannii.

Histones: The critical players in innate immunity

The highly conserved histones in different species seem to represent a very ancient and universal innate host defense system against microorganisms in the biological world. Histones are the essential part of nuclear matter and act as a control switch for DNA transcription. However, histones are also found in the cytoplasm, cell membranes, and extracellular fluid, where they function as host defenses and promote inflammatory responses. In some cases, extracellular histones can act as damage-associated molecular patterns (DAMPs) and bind to pattern recognition receptors (PRRs), thereby triggering innate immune responses and causing initial organ damage. Histones and their fragments serve as antimicrobial peptides (AMPs) to directly eliminate bacteria, viruses, fungi, and parasites in vitro and in vivo. Histones are also involved in phagocytes-related innate immune response as components of neutrophil extracellular traps (NETs), neutrophil activators, and plasminogen receptors. In addition, as a considerable part of epigenetic regulation, histone modifications play a vital role in regulating the innate immune response and expression of corresponding defense genes. Here, we review the regulatory role of histones in innate immune response, which provides a new strategy for the development of antibiotics and the use of histones as therapeutic targets for inflammatory diseases, sepsis, autoimmune diseases, and COVID-19.

Mechanism study on a new antimicrobial peptide Sphistin derived from the N-terminus of crab histone H2A identified in haemolymphs of Scylla paramamosain

Histone H2A is known to participate in host immune defense through generating special antimicrobial peptides (AMPs), for which it has been an interesting research focus to characterize this kind of peptides in vertebrates and invertebrates. Although thousands of AMPs have been reported in variety of life species, only several AMPs are known in crabs and in particular no H2A-derived AMP has yet been reported. In the present study, a 38-amino acid peptide with antimicrobial activity was determined based on the sequence analysis of a histone H2A identified from the mud crab Scylla paramamosain. The histone H2A derived peptide was an AMP-like molecule and designated as Sphistin. Sphistin showed typical features of AMPs such as amphiphilic α-helical second structrue and positive charge net. The synthetic Sphistin exerted high antimicrobial activity against Gram-positive, Gram-negative bacteria and yeast, among which Aeromonas hydrophila, Pseudomonas fluorescens and Pseudomonas stutzeri are important aquatic pathogens. Leakage of the cell content and disruption of the cell surface were observed in bacterial cells treated with Sphistin using scanning electron microscopy. It was proved that the increasing cytoplasmic membrane permeability of Escherichia coli was caused by Sphistin. Further observation under confocal microscopy showed that Sphistin could combine onto the membrane of Staphylococcus aureus, E. coli MC1061 and Pichia pastoris but not translocate into the cytoplasm. Moreover, the affinity of Sphistin with either LPS or LTA was also testified that there was an interaction between Sphistin and cell membrane. Thus, the antimicrobial mechanism of this peptide likely exerted via adsorption and subsequently permeabilization of the bacterial cell membranes other than penetrating cell membrane. In addition, synthetic Sphistin exhibited no cytotoxicity to primary cultured crab haemolymphs and mammalian cells even at a high concentration of 100 μg/mL for 24 h. This is the first report of a histone-derived Sphistin identified from S. paramamosain with a specific antimicrobial activity and mechanism, which could be a new candidate for future application in aquaculture and veterinary medicine.

Inter-α inhibitor protein and its associated glycosaminoglycans protect against histone-induced injury

Extracellular histones are mediators of tissue injury and organ dysfunction; therefore they constitute potential therapeutic targets in sepsis, inflammation, and thrombosis. Histone cytotoxicity in vitro decreases in the presence of plasma. Here, we demonstrate that plasma inter-α inhibitor protein (IAIP) neutralizes the cytotoxic effects of histones and decreases histone-induced platelet aggregation. These effects are mediated through the negatively charged glycosaminoglycans (GAGs) chondroitin sulfate and high-molecular-weight hyaluronan (HMW-HA) associated with IAIP. Cell surface anionic glycosaminoglycans heparan sulfate and HA protect the cells against histone-mediated damage in vitro. Surface plasmon resonance showed that both IAIP and HMW-HA directly bind to recombinant histone H4. In vivo neutralization of histones with IAIP and HMW-HA prevented histone-induced thrombocytopenia, bleeding, and lung microvascular thrombosis, decreased neutrophil activation, and averted histone-induced production of inflammatory cytokines and chemokines. IAIP and HMW-HA colocalized with histones in necrotic tissues and areas that displayed neutrophil extracellular traps. Increasing amounts of IAIP-histone complexes detected in the plasma of septic baboons correlated with increase in histones and/or nucleosomes and consumption of plasma IAIP. Our data suggest that IAIP, chondroitin sulfate, and HMW-HA are potential therapeutic agents to protect against histone-induced cytotoxicity, coagulopathy, systemic inflammation, and organ damage during inflammatory conditions such as sepsis and trauma.

Effects of cyclotides against cutaneous infections caused by Staphylococcus aureus

The main bacterium associated with skin infection is Staphylococcus aureus, occurring especially in infections acquired via surgical wounds, commonly leading to lethal hospital-acquired infections, emphasizing the importance of identifying new antimicrobial compounds. Among them, cyclotides have gained interest due to their high stability and multifunctional properties. Here, cycloviolacin 2 (CyO2) and kalata B2 (KB2) were evaluated to determinate their anti-staphylococcal activities using a subcutaneous infection model. Anti-staphylococcal activities of 50mM for KB2 and 25mM for CyO2 were detected with no cytotoxic activities against RAW 264.7 monocytes. In the in vivo assays, both cyclotides reduced bacterial load and CyO2 demonstrated an increase in the phagocytosis index, suggesting that the CyO2 in vivo anti-staphylococcal activity may be associated with phagocytic activity, additionally to direct anti-pathogenic activity.

Clavanin A improves outcome of complications from different bacterial infections

The rapid increase in the incidence of multidrug-resistant infections today has led to enormous interest in antimicrobial peptides (AMPs) as suitable compounds for developing unusual antibiotics. In this study, clavanin A, an antimicrobial peptide previously isolated from the marine tunicate Styela clava, was selected as a purposeful molecule that could be used in controlling infection and further synthesized. Clavanin A was in vitro evaluated against Staphylococcus aureus and Escherichia coli as well as toward L929 mouse fibroblasts and skin primary cells (SPCs). Moreover, this peptide was challenged here in an in vivo wound and sepsis model, and the immune response was also analyzed. Despite displaying clear in vitro antimicrobial activity toward Gram-positive and -negative bacteria, clavanin A showed no cytotoxic activities against mammalian cells, and in acute toxicity tests, no adverse reaction was observed at any of the concentrations. Moreover, clavanin A significantly reduced the S. aureus CFU in an experimental wound model. This peptide also reduced the mortality of mice infected with E. coli and S. aureus by 80% compared with that of control animals (treated with phosphate-buffered saline [PBS]): these data suggest that clavanin A prevents the start of sepsis and thereby reduces mortality. These data suggest that clavanin A is an AMP that could improve the development of novel peptide-based strategies for the treatment of wound and sepsis infections.

Controlling resistant bacteria with a novel class of β-lactamase inhibitor peptides: from rational design to in vivo analyses

Peptide rational design was used here to guide the creation of two novel short β-lactamase inhibitors, here named dBLIP-1 and -2, with length of five amino acid residues. Molecular modeling associated with peptide synthesis improved bactericidal efficacy in addition to amoxicillin, ampicillin and cefotaxime. Docked structures were consistent with calorimetric analyses against bacterial β-lactamases. These two compounds were further tested in mice. Whereas commercial antibiotics alone failed to cure mice infected with Staphylococcus aureus and Escherichia coli expressing β-lactamases, infection was cleared when treated with antibiotics in combination with dBLIPs, clearly suggesting that peptides were able to neutralize bacterial resistance. Moreover, immunological assays were also performed showing that dBLIPs were unable to modify mammalian immune response in both models, reducing the risks of collateral effects. In summary, the unusual peptides here described provide leads to overcome β-lactamase-based resistance, a remarkable clinical challenge.

A synthetic sandalwood odorant induces wound-healing processes in human keratinocytes via the olfactory receptor OR2AT4

As the outermost barrier of the body, the skin is exposed to multiple environmental factors, including temperature, humidity, mechanical stress, and chemical stimuli such as odorants that are often used in cosmetic articles. Keratinocytes, the major cell type of the epidermal layer, express a variety of different sensory receptors that enable them to react to various environmental stimuli and process information in the skin. Here we report the identification of a novel type of chemoreceptors in human keratinocytes, the olfactory receptors (ORs). We cloned and functionally expressed the cutaneous OR, OR2AT4, and identified Sandalore, a synthetic sandalwood odorant, as an agonist of this receptor. Sandalore induces strong Ca(2+) signals in cultured human keratinocytes, which are mediated by OR2AT4, as demonstrated by receptor knockdown experiments using RNA interference. The activation of OR2AT4 induces a cAMP-dependent pathway and phosphorylation of extracellular signal-regulated kinases (Erk1/2) and p38 mitogen-activated protein kinases (p38 MAPK). Moreover, the long-term stimulation of keratinocytes with Sandalore positively affected cell proliferation and migration, and regeneration of keratinocyte monolayers in an in vitro wound scratch assay. These findings combined with our studies on human skin organ cultures strongly indicate that the OR 2AT4 is involved in human keratinocyte re-epithelialization during wound-healing processes.

Analysis of the Staphylococcus aureus abscess proteome identifies antimicrobial host proteins and bacterial stress responses at the host-pathogen interface

Abscesses are a hallmark of invasive staphylococcal infections and the site of a dynamic struggle between pathogen and host. However, the precise host and bacterial factors that contribute to abscess formation and maintenance have not been completely described. In this work, we define the Staphylococcus aureus abscess proteome from both wild-type and neutropenic mice to elucidate the host response to staphylococcal infection and uncover novel S. aureus virulence factors. Among the proteins identified, the mouse protein histone H4 was enriched in the abscesses of wild-type compared with neutropenic animals. Histone H4 inhibits staphylococcal growth in vitro demonstrating a role for this protein in the innate immune response to staphylococcal infection. These analyses also identified staphylococcal proteins within the abscess, including known virulence factors and proteins with previously unrecognized roles in pathogenesis. Within the latter group was the universal stress protein Usp2, which was enriched in kidney lesions from neutropenic mice and required for the S. aureus response to stringent stress. Taken together, these data describe the S. aureus abscess proteome and lay the foundation for the identification of contributors to innate immunity and bacterial pathogenesis.

IQ-motif peptides as novel anti-microbial agents

The IQ-motif is an amphipathic, often positively charged, α-helical, calmodulin binding sequence found in a number of eukaryote signalling, transport and cytoskeletal proteins. They share common biophysical characteristics with established, cationic α-helical antimicrobial peptides, such as the human cathelicidin LL-37. Therefore, we tested eight peptides encoding the sequences of IQ-motifs derived from the human cytoskeletal scaffolding proteins IQGAP2 and IQGAP3. Some of these peptides were able to inhibit the growth of Escherichia coli and Staphylococcus aureus with minimal inhibitory concentrations (MIC) comparable to LL-37. In addition some IQ-motifs had activity against the fungus Candida albicans. This antimicrobial activity is combined with low haemolytic activity (comparable to, or lower than, that of LL-37). Those IQ-motifs with anti-microbial activity tended to be able to bind to lipopolysaccharide. Some of these were also able to permeabilise the cell membranes of both Gram positive and Gram negative bacteria. These results demonstrate that IQ-motifs are viable lead sequences for the identification and optimisation of novel anti-microbial peptides. Thus, further investigation of the anti-microbial properties of this diverse group of sequences is merited.

Nonviral human beta defensin-3 expression in a bioengineered human skin tissue: a therapeutic alternative for infected wounds

The innate immune system differentially regulates the expression of host defense peptides to combat infection during wound healing. We enhanced the expression of a host defense peptide, human beta defensin-3 (hBD-3), in keratinocytes to generate a three-dimensional biologic dressing to improve healing of infected wounds. The NIKS human keratinocyte cell line was stably transfected ex vivo with a construct containing an epidermis-specific promoter driving hBD-3 (NIKS(hBD) (-3) ) using nonviral methods. Levels of hBD-3 mRNA and protein in three-dimensional skin tissue produced from NIKS(hBD) (-3) were determined using quantitative polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. Tissue architecture was characterized by hematoxylin and eosin staining and by indirect immunofluorescence using proliferation and keratinocyte differentiation markers. Antimicrobial activity was assessed using an in vitro bacterial growth assay and in vivo using a murine burn infection model. Three-dimensional full thickness skin tissues containing epidermal NIKS(hBD) (-3) or control NIKS possessed histologic features of interfollicular epidermis and exhibited normal tissue growth and differentiation. NIKS(hBD) (-3) tissue contained approximately fivefold more hBD-3 protein than tissue containing unmodified control NIKS. In vitro studies showed that NIKS(hBD) (-3) tissue produced a significant reduction in the growth of Staphylococcus aureus multiple peptide resistance factor (mprF) compared with control tissue. In an in vivo infected murine burn model, NIKS(hBD) (-3) tissue resulted in a 90% reduction in bacterial growth. These results demonstrate that sustained delivery of hBD-3 by a bioengineered skin tissue results in a therapeutically relevant reduction in growth of a S. aureus strain in an animal model of infected third-degree burn wounds.

Innate defense regulator peptide 1018 in wound healing and wound infection

Innate defense regulators (IDRs) are synthetic immunomodulatory versions of natural host defense peptides (HDP). IDRs mediate protection against bacterial challenge in the absence of direct antimicrobial activity, representing a novel approach to anti-infective and anti-inflammatory therapy. Previously, we reported that IDR-1018 selectively induced chemokine responses and suppressed pro-inflammatory responses. As there has been an increasing appreciation for the ability of HDPs to modulate complex immune processes, including wound healing, we characterized the wound healing activities of IDR-1018 in vitro. Further, we investigated the efficacy of IDR-1018 in diabetic and non-diabetic wound healing models. In all experiments, IDR-1018 was compared to the human HDP LL-37 and HDP-derived wound healing peptide HB-107. IDR-1018 was significantly less cytotoxic in vitro as compared to either LL-37 or HB-107. Furthermore, administration of IDR-1018 resulted in a dose-dependent increase in fibroblast cellular respiration. In vivo, IDR-1018 demonstrated significantly accelerated wound healing in S. aureus infected porcine and non-diabetic but not in diabetic murine wounds. However, no significant differences in bacterial colonization were observed. Our investigation demonstrates that in addition to previously reported immunomodulatory activities IDR-1018 promotes wound healing independent of direct antibacterial activity. Interestingly, these effects were not observed in diabetic wounds. It is anticipated that the wound healing activities of IDR-1018 can be attributed to modulation of host immune pathways that are suppressed in diabetic wounds and provide further evidence of the multiple immunomodulatory activities of IDR-1018.

Impact of acute stress on antimicrobial polypeptides mRNA copy number in several tissues of marine sea bass (Dicentrarchus labrax)

Background

In comparison to higher vertebrates, fish are thought to rely heavily on innate immune system for initial protection against pathogen invasion because their acquired immune system displays a considerably poor immunological memory, and short-lived secondary response. The endogenous antimicrobial polypeptides (AMPPs) directly and rapidly killing pathogens such as bacteria, fungi, parasites, and viruses are included within the realm of innate defenses. In addition to piscidins, AMPPs that in recent years have been shown to be commonly linked to innate defense, are histones and their polypeptide fragments, and peptides derived from the respiratory protein hemoglobin. There is evidence that a number of stresses lead to significant regulation of AMPPs and thus their monitoring could be a highly sensitive measure of health status and risk of an infectious disease outbreak, which is a major impediment to the continued success of virtually all aquaculture enterprises and is often the most significant cause of economic losses.

Results

We firstly isolated and deposited in Genbank database the cDNA sequences encoding for hemoglobin-β-like protein (Hb-LP) [GeneBank: JN410659], H2B histone-like protein 1 (HLP1) GenBank: JN410660], and HLP2 [GenBank: JN410661]. The "de novo" prediction of the three-dimensional structures for each protein is presented. Phylogenetic trees were constructed on Hb-LP, HLP1, and HLP2 sequences of sea bass and those of other teleost, avian, reptiles, amphibian and mammalian species. We then used real time RT-PCR technology to monitor for the first time in sea bass, dynamic changes in mRNA copy number of Hb-LP, HLP1, HLP2, and dicentracin in gills, skin, eyes, stomach and proximal intestine in response to acute crowding/confinement stress. We showed that acute crowding stress induces an increase in the expression levels of the aforementioned genes, in gills and skin of sea bass, but not in other tissues, and that this expression patterns are not always rapidly reversed upon re-exposure to normal conditions.

Conclusion

The higher expression of the four target genes in gills and skin of sea bass suggests that this AMPP represents a first and immediate line of defense in combating pathogens and stressors since these tissues constitute the first physiological barriers of the animal.

Innate immunity in the human female reproductive tract: endocrine regulation of endogenous antimicrobial protection against HIV and other sexually transmitted infections

Mucosal surfaces of the female reproductive tract (FRT) contain a spectrum of antimicrobials that provide the first line of defense against viruses, bacteria, and fungi that enter the lower FRT. Once thought to be a sterile compartment, the upper FRT is periodically exposed to pathogens throughout the menstrual cycle. More recently, secretions from the upper FRT have been shown to contribute to downstream protection in the lower FRT. In this review, we examine the antimicrobials in FRT secretions made by immune cells and epithelial cells in the upper and lower FRT that contribute to innate protection. Because each site is hormonally regulated to maintain fertility, this review focuses on the contributions of hormone balance during the menstrual cycle to innate immune protection. As presented in this review, studies from our laboratory and others demonstrate that sex hormones regulate antimicrobials produced by innate immune cells throughout the FRT. The goal of this review is to examine the spectrum of antimicrobials in the FRT and the ways in which they are regulated to provide protection against pathogens that compromise reproductive health and threaten the lives of women.

Mapping of interactions between human macrophages and Staphylococcus aureus reveals an involvement of MAP kinase signaling in the host defense

Staphylococcus aureus is a dangerous opportunistic human pathogen that causes serious invasive diseases when it reaches the bloodstream. Recent studies have shown that S. aureus is highly resistant to killing by professional phagocytes and that such cells even provide a favorable environment for intracellular survival of S. aureus. Importantly, the reciprocal interactions between phagocytes and S. aureus have remained largely elusive. Here we have employed kinase profiling to define the nature and time resolution of the human THP-1 macrophage response toward S. aureus and proteomics to identify the response of S. aureus toward macrophages. The results of these studies reveal major macrophage signaling pathways triggered by S. aureus and proteomic signatures of the responses of S. aureus to macrophages. We also identify human proteins bound to S. aureus that have potential roles in bacterial killing and internalization. Most noticeably, our observations challenge the classical concept that macrophage responses are mainly mediated through Toll-like receptor 2 and NF-κB signaling and highlight the important role of the stress-activated MAP kinase signaling in orchestrating the host defense.

Colistin-loaded silk membranes against wound infection with Pseudomonas aeruginosa

BACKGROUND

Wound infections caused by multidrug-resistant bacteria are a major issue in wound care. An occlusive dressing delivering an antimicrobial agent to the wound may be advantageous. The objective of this study was to evaluate an occlusive silk membrane loaded with colistin to establish an effective antimicrobial wound dressing against Gram-negative bacteria in vitro and in vivo.

METHODS

ST-silk protein membranes (thickness, 100 μm; pore size, <100 nm) were loaded with log-scale colistin dilutions (0.027 to 270 mg/ml) and tested in a modified microbroth dilution assay against Pseudomonas aeruginosa (American Type Culture Collection 27853). A rat burn infection model was used to demonstrate the antimicrobial activity of ST-silk membranes loaded with 270 mg/ml colistin. Finally, a porcine wound infection model was used to study dose response (2.7, 27, and 270 mg/ml colistin loading concentration) in a time-dependent manner (0, 2, 4, and 6 days).

RESULTS

The in vitro study demonstrated a concentration-dependent antimicrobial effect against P. aeruginosa, with complete elimination at the highest loading concentrations (2.7, 27, and 270 mg/ml). All colistin membranes demonstrated lower colony-forming unit counts compared with the corresponding phosphate-buffered saline or carrier controls. The rat burn infection model demonstrated a colony-forming unit reduction of greater than 3 log-scales for the colistin-loaded ST-silk membranes after 3 days. On average, the wounds' colony-forming unit quantity remained at greater than 1000 during the entire follow-up of 6 days, apart from three wounds where complete bacterial clearance was observed.

CONCLUSION

This study demonstrates that occlusive ST-silk membranes loaded with an antimicrobial agent may be an effective dressing for infected wounds.

Efficacy of topically delivered moxifloxacin against wound infection by Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus

Wound infection is a common risk for patients with chronic nonhealing wounds, causing high morbidity and mortality. Currently, systemic antibiotic treatment is the therapy of choice, despite often leading to several side effects and the risk of an insufficient tissue penetration due to impaired blood supply. If systemically delivered, moxifloxacin penetrates well into inflammatory blister fluid, muscle, and subcutaneous adipose tissues and might therefore be a possible option for the topical treatment of skin and infected skin wounds. In this study, topical application of moxifloxacin was investigated in comparison to mupirocin, linezolid, and gentamicin using a porcine wound infection and a rat burn infection model. Both animal models were performed either by an inoculation with methicillin-resistant Staphylococcus aureus (MRSA) or Pseudomonas aeruginosa. Wound fluid, tissue, and blood samples were taken, and bacterial counts as well as the moxifloxacin concentration were determined for a 14-day follow-up. A histological comparison of the rat burn wound tissues was performed. Both strains were susceptible to moxifloxacin and gentamicin, whereas mupirocin and linezolid were effective only against MRSA. All antibiotics showed efficient reduction of bacterial counts, and except with MRSA, infected burn wounds reached bacterial counts below 10(5) CFU/g tissue. Additionally, moxifloxacin was observed to promote wound healing as determined by histologic analysis, while no induction of bacterial resistance was observed during the treatment period. The use of topical antibiotics for the treatment of infected wounds confers many benefits. Moxifloxacin is therefore an ideal candidate, due to its broad antibacterial spectrum, its high efficiency, and its potential to promote wound healing.

Molecular cloning of cecropin B responsive endonucleases in Yersinia ruckeri

We have previously demonstrated that Yersinia ruckeri resists cecropin B in an inducible manner. In this study, we sought to identify the molecular changes responsible for the inducible cecropin B resistance of Y. ruckeri. Differences in gene expression associated with the inducible resistance were investigated. Cultures of Y. ruckeri were exposed to a sublethal concentration of cecropin B and resultant changes in the messenger RNA population of the bacteria were assayed using the differential display reverse transcription polymerase chain reaction (DD-RT-PCR). A single band was consistently increased in intensity in all repeats of the experiment. The band was excised, cloned, sequenced, and used to screen a Y. ruckeri genomic DNA library. The DD-RT-PCR fragment shared 100% identity to the cDNA sequence of an ATP-dependent endonuclease of the overcome lysogenization defect (OLD) family of Y. ruckeri 29473. The genomic clone that was recovered was not identical to the DD-RT-PCR clone, but harbored a gene for a secreted endonuclease 1 (nucM) homologue. It was determined that transcription of the gene was upregulated following exposure to cecropin B via RT-PCR. Furthermore, an increase in the nuclease activity of culture supernatants of Y. ruckeri following exposure to cecropin B was demonstrated. These findings demonstrate that cecropin B exposure increases the expression of at least two endonucleases in Y. ruckeri. The production and secretion of an endonuclease by Y. ruckeri in response to an antimicrobial peptide indicates the involvement of both intracellular and extracellular DNA in the toxic effects of cecropin B.

Proteomic identification of interactions between histones and plasma proteins: implications for cytoprotection

Extracellular histones released from cells during acute inflammation contribute to organ failure and death in a mouse model of sepsis, and histones are known to exert in vitro cytotoxicity in the absence of serum. Since addition of histones to serum and plasma is known to induce protein aggregation, we reasoned that plasma proteins may afford protection from cytotoxicity. We found that MODE-K mouse small intestinal epithelial cells were protected from histone-induced toxicity in the presence of 10% FCS. Therefore, the main aim of this study was to identify histone-interacting plasma proteins that might be involved in cytoprotection. The precipitate formed following addition of calf thymus histones to human EDTA plasma was characterised by shotgun proteomics, identifying a total of 36 protein subunits, including complement components, coagulation factors, protease inhibitors and apolipoproteins. The highly sulphated glycosaminoglycan heparin inhibited histone-induced plasma protein aggregation. Moreover, histones bound to heparin agarose were capable of pulling down plasma proteins from solution, indicating their effective cross-linking properties. It was particularly notable that inter-alpha-trypsin inhibitor was prominent among the histone-precipitated proteins, since it contains a chondroitin sulphate glycan chain, and suggests a potential role for this protein in histone sequestration during acute inflammation in vivo.

A novel human skin chamber model to study wound infection ex vivo

Wound infections with multi-drug resistant bacteria increase morbidity and mortality and have considerable socioeconomic impact. They can lead to impaired wound healing, resulting in rising treatment costs. The aim of this study was to investigate an ex vivo human wound infection model. Human full-thickness skin from the operating room (OR) was placed into the Bo-Drum^® and cultivated for 7 days in an air–liquid interphase. On day 8, the skin was inoculated with either (1) Pseudomonas aeruginosa, (2) Staphylococcus aureus (10⁵ CFU, n = 3) or (3) carrier control. 1, 3 and 7 days after inoculation colony forming units in the tissue/media were determined and cytokine expression was quantified. A reliable and reproducible wound infection could be established for 7 days. At this timepoint, 1.8 × 10⁸ CFU/g tissue of P. aeruginosa and 2 × 10⁷ CFU/g tissue of S. aureus were detected. Immunohistochemical analysis demonstrated bacterial infection and epidermolysis in infected skin. RT-PCR analysis exhibited a significant induction of proinflammatory cytokines after infection. The BO-drum^® is a robust, easy-to-use, sterilizable and reusable ex vivo full-skin culture system. For investigation of wound infection, treatment and healing, the BO-drum^® presents a convenient model and may help to standardize wound research.

Host defense peptides in wound healing

Host defense peptides are effector molecules of the innate immune system. They show broad antimicrobial action against gram-positive and -negative bacteria, and they likely play a key role in activating and mediating the innate as well as adaptive immune response in infection and inflammation. These features make them of high interest for wound healing research. Non-healing and infected wounds are a major problem in patient care and health care spending. Increasing infection rates, growing bacterial resistance to common antibiotics, and the lack of effective therapeutic options for the treatment of problematic wounds emphasize the need for new approaches in therapy and pathophysiologic understanding. This review focuses on the current knowledge of host defense peptides affecting wound healing and infection. We discuss the current data and highlight the potential future developments in this field of research.

Role of host defense peptides of the innate immune response in sepsis

Innate immune response and its effector molecules have received growing attention in research. Host defense peptides are known to be antimicrobially active. Recently, the peptides have been recognized as potent signaling molecules for cellular effectors of both innate and adaptive immunity. Mammalian peptides in particular revealed immunomodulatory functions, including endotoxin-binding and -neutralizing capacity, chemotactic activities, induction of cytokines and chemokines, promotion of wound healing, and angiogenesis. In sepsis, they present a family of natural substances that can be used in combination with antibiotics to complete a broad-spectrum antimicrobial regimen with endotoxin-neutralizing properties. Although there are side effects, host defense peptides have the potential to be significant reinforcements to the currently available therapeutic options in the future. In this review, we analyze the role of host defense peptides in infection and immune response, and discuss recent efforts to establish host defense peptides as potent novel therapeutic agents for the treatment of sepsis.

Animal models of chronic lung infection with Pseudomonas aeruginosa: useful tools for cystic fibrosis studies

Cystic fibrosis (CF) is caused by a defect in the transmembrane conductance regulator (CFTR) protein that functions as a chloride channel. Dysfunction of the CFTR protein results in salty sweat, pancreatic insufficiency, intestinal obstruction, male infertility and severe pulmonary disease. In most patients with CF life expectancy is limited due to a progressive loss of functional lung tissue. Early in life a persistent neutrophylic inflammation can be demonstrated in the airways. The cause of this inflammation, the role of CFTR and the cause of lung morbidity by different CF-specific bacteria, mostly Pseudomonas aeruginosa, are not well understood. The lack of an appropriate animal model with multi-organ pathology having the characteristics of the human form of CF has hampered our understanding of the pathobiology and chronic lung infections of the disease for many years. This review summarizes the main characteristics of CF and focuses on several available animal models that have been frequently used in CF research. A better understanding of the chronic lung infection caused particularly by P. aeruginosa, the pathophysiology of lung inflammation and the pathogenesis of lung disease necessitates animal models to understand CF, and to develop and improve treatment.

Antimicrobial action of histone H2B in Escherichia coli: evidence for membrane translocation and DNA-binding of a histone H2B fragment after proteolytic cleavage by outer membrane proteinase T

Previous studies have led to the isolation of histone H2B with antibacterial properties from an extract of the skin of the Schlegel's green tree frog Rhacophorus schlegelii and it is now demonstrated that the intact peptide is released into norepinephrine-stimulated skin secretions. In order to investigate the mechanism of action of this peptide, a maltose-binding protein (MBP)-fused histone H2B (MBP-H2B) conjugate was prepared and subjected to antimicrobial assay. The fusion protein showed bacteriostatic activity against Escherichia coli strain JCM5491 with a minimum inhibitory concentration of 11 microM. The lysate prepared from JCM5491 cells was capable of fragmenting MBP-H2B within the histone H2B region, but the lysate from the outer membrane proteinase T (OmpT) gene-deleted BL21(DE3) cells was not. FITC-labeled MBP-H2B (FITC-MBP-H2B) penetrated into the bacterial cell membrane of JCM5491 and ompT-transformed BL21(DE3) cells, but not into ompT-deleted BL21(DE3) cells. Gel retardation assay using MBP-H2B-deletion mutants indicated that MBP-H2B bound to DNA at a site within the N-terminal region of histone H2B. Consequently, it is proposed that the antimicrobial action of histone H2B involves, at least in part, penetration of an OmpT-produced N-terminal histone H2B fragment into the bacterial cell membrane with subsequent inhibition of cell functions.

Histone tail modifications and noncanonical functions of histones: perspectives in cancer epigenetics

Over the past few years, the histone deacetylase (HDAC) inhibitors have occupied an important place in the effort to develop novel, but less toxic, anticancer therapy. HDAC inhibitors block HDACs, which are the enzymes responsible for histone deacetylation, and therefore they modulate gene expression. The cellular effects of HDAC inhibitors include growth arrest and the induction of differentiation. Early successes in cancer therapeutics obtained using these drugs alone or in combination with other anticancer drugs emphasize the important place of posttranslational modifications of histones in cancer therapy. Histone tail modifications along with DNA methylation are the most studied epigenetic events related to cancer progression. Moreover, extranuclear functions of histones have also been described. Because HDAC inhibitors block HDACs and thereby increase histone acetylation, we propose a model wherein exogenous acetylated histones or other related acetylated proteins that are introduced into the nucleus become HDAC substrates and thereby compete with endogenous histones for HDACs. This competition may lead to the increased acetylation of the endogenous histones, as in the case of HDAC inhibitor therapy. Moreover, other mechanisms of action, such as binding to chromatin and modulating gene expression, are also possible for exogenously introduced histones.

Host defence peptides in human burns

The goal of this study was to analyse expression profiles of human epithelial host defence peptides in burned and unburned skin tissue, samples of which were obtained during debridements and snap-frozen in liquid nitrogen. Total RNA was isolated, and cDNA of epithelial host defence peptides and proteins (hCAP-18/LL-37, hBD1-hBD4, dermcidin, S100A7/psoriasin and RNAse7) was quantified by qRT-PCR. In situ hybridisation and immunohistochemical staining localised gene expression of hCAP-18/LL-37, hBD2 and hBD3 in histological sections. Most of the analysed host defence peptides and proteins showed higher mRNA levels in partial-thickness burns than in unburned tissue. In situ hybridisation revealed expression of hCAP-18/LL-37, hBD2 and hBD3 at the surface of burns that was independent of burn depth. However, the finding of higher host defence peptide gene expression rates does not correlate with the incidence of wound infection in burns. We hypothesise that the epithelial innate immune response in burns is complex.

Isolation and characterization of antimicrobial proteins and peptide from chicken liver

Endogenous antimicrobial peptides and proteins are crucial components of the innate immune system and play an essential role in the defense against infection. Antimicrobial activity was detected in the acid extract of livers harvested from healthy adult White Leghorn hens, Gallus gallus. Two antimicrobial proteins and one antimicrobial polypeptide were isolated from the liver extract by cation-exchange and gel filtration chromatography, followed by two-step reverse-phase high-performance liquid chromatography (RP-HPLC). These antimicrobial components were identified as histones H2A and H2B.V, and histone H2B C-terminal fragment using peptide mass fingerprinting and partial sequencing by tandem nanoelectrospray mass spectrometry. The proteins and the peptide identified in the present study, which exhibited antimicrobial activity against both Gram-positive and Gram-negative bacteria, were thermostable and showed salt-resistant activity. The antimicrobial properties of histones and histone fragment in chicken provide further evidence that histones, in addition to their role in nucleosome formation, may play an important role in innate host defense against intracellular or extracellular microbe invasion in a wide range of animal species.

Adenoviral gene delivery to primary human cutaneous cells and burn wounds

The adenoviral transfer of therapeutic genes into epidermal and dermal cells is an interesting approach to treat skin diseases and to promote wound healing. The aim of this study was to assess the in vitro and in vivo transfection efficacy in skin and burn wounds after adenoviral gene delivery. Primary keratinocytes (HKC), fibroblasts (HFB), and HaCaT cells were transfected using different concentrations of an adenoviral construct (eGFP). Transfection efficiency and cytotoxicity was determined up to 30 days. Expression was quantified by FACS analysis and fluorimeter. Cytotoxicity was measured using the trypan blue exclusion method. 45 male Sprague Dawley rats received 2x10(8) pfu of Ad5-CMV-LacZ or carrier control intradermally into either superficial partial thickness scald burn or unburned skin. Animals were euthanized after 48 h, 7 or 14 days posttreatment. Transgene expression was assessed using immunohistochemistry and bioluminescent assays. The highest transfection rate was observed 48 h posttransfection: 79% for HKC, 70% for HFB, and 48% for HaCaT. The eGFP expression was detectable in all groups over 30 days (P>0.05). Cytotoxic effects of the adenoviral vector were observed for HFB after 10 days and HaCaT after 30 days. Reporter gene expression in vivo was significantly higher in burned skin compared with unburned skin (P=0,004). Gene expression decreases from 2 to 7 days with no significant expression after 14 days. This study demonstrates that effective adenoviral-mediated gene transfer of epidermal primary cells and cell-lines is feasible. Ex vivo gene transfer in epithelial cells might have promise for the use in severely burned patients who receive autologous keratinocyte sheets. Transient cutaneous gene delivery in burn wounds using adenoviral vectors causes significant concentrations in the wound tissue for at least 1 week. Based on these findings, we hypothesize that transient cutaneous adenoviral gene delivery of wound healing promoting factors has potential for clinical application.

Comprehensive Proteomic Analysis of Human Cervical−Vaginal Fluid

Cervical-vaginal fluid (CVF) is a potential rich source of biomarkers for enhancing our understanding of human parturition and pathologic conditions affecting pregnancy. In this study, we performed a comprehensive survey of the CVF proteome in pregnancy utilizing multidimensional liquid chromatography (2D-LC) coupled with mass spectrometry and gel-electrophoresis-based protein separation and identification. In total, 150 unique proteins were identified using multiple protein identification algorithms. Metabolism (32%) and immune response-related (22%) proteins are the major functional categories represented in the CVF proteome. A comparison of the CVF, serum, and amniotic fluid proteomes showed that 77 proteins are unique to CVF, while 56 and 17 CVF proteins also occur in serum and amniotic fluid, respectively. This data set provides a foundation for evaluation of these proteins as potential CVF biomarkers for noninvasive diagnosis of pregnancy-related disorders.

Antimicrobial activity of the recombinant designer host defence peptide P-novispirin G10 in infected full-thickness wounds of porcine skin

OBJECTIVES

The growing number of patients with impaired wound healing and the development of multidrug-resistant bacteria demand the investigation of alternatives in wound care. The antimicrobial activity of naturally occurring host defence peptides and their derivatives could be one alternative to the existing therapy options for topical treatment of wound infection. Therefore, the aim of this study was to investigate the antimicrobial activity of proline-novispirin G10 (P-novispirin G10) in vitro and in the infected porcine titanium wound chamber model.

METHODS

The new derived designer host defence peptide P-novispirin G10 was tested in vitro against Gram-positive and Gram-negative bacterial strains. Additionally, cytotoxicity and haemolytic activities of P-novispirin G10 and protegrin-1 were measured. For in vivo studies, six wound chambers were implanted on each flank of Göttinger minipigs (n = 2, female, 6 months old, 15-20 kg). Eleven wound chambers were inoculated 8 days post-operatively with 5 x 10(8) of Staphylococcus aureus; one wound chamber remained uninfected as a system control. After wound infection had been established (4 days after inoculation), each wound chamber was topically treated with P-novispirin G10, protegrin-1 or carrier control. Wound fluid was harvested every hour for a total follow up of 3 h.

RESULTS

P-novispirin G10 demonstrated broad-spectrum antimicrobial activity with moderate haemolytic and cytotoxic activities compared with protegrin-1. In the infected wound chamber model P-novispirin G10 demonstrated a 4 log(10) reduction in bacterial counts.

CONCLUSIONS

This implicates the potential of P-novispirin G10 as an alternative in future antimicrobial wound care. However, more studies are necessary to further define clinical applications and potential side effects in greater detail.

Antimicrobial proteins in chicken reproductive system

Antimicrobial activity was detected in the ovary and oviduct tissues of healthy mature White Leghorn hens, Gallus gallus. Two antimicrobial proteins were purified to homogeneity using acid extraction followed by multiple steps of chromatography and the pure proteins were further characterized biochemically. Peptide mixtures obtained after enzymatic digestion of the chicken antimicrobial proteins were analyzed using peptide mass fingerprinting and partial sequencing by tandem nanoelectrospray mass spectrometry and the proteins were identified as histones H1 and H2B. Chicken histone antimicrobial proteins were active against both Gram-positive and Gram-negative bacteria. The abundance of these proteins in the reproductive tissues and their broad-spectrum antimicrobial nature may indicate their defensive role against pathogens during the follicle development in the ovary and egg formation in the oviduct. The discovery of antimicrobial histones in chicken reproductive system provides further evidence that histones may play a role in innate immunity against microorganisms in a wide range of animal species.

Burn wounds infected with Pseudomonas aeruginosa triggers weight loss in rats

Background

Despite dramatic improvements in the management of burns, infection still remains a serious risk for the burn patient. The aim of this study was to shed light on the impact of acute burn injury with or without infection on cytokine profiles.

Methods

Sprague-Dawley rats (n = 21) were randomized into three groups: 1) burn only 2) burn and infection or 3) sham burn. Weight was monitored and blood was collected for cytokine ELISA, LPS quantification, and peripheral blood analysis. Animals were sacrificed either after 6 or 12 days.

Results

Infected animals showed substantial weight loss until day 6 post-burn as compared to burn alone. Endotoxin and TNF-α levels were elevated early in the infected burn group within 48 hours post-burn. In contrast, significant up-regulation of the anti-inflammatory cytokine IL-10 occurred later in the clinical course and was associated with the recovery from weight loss.

Conclusion

Our results suggest that in the presence of infection, you get a SIRS response possibly due to transient endotoxemia that is only seen in the infection group. In contrast, both burn and infection get a late IL-10 (CARS) response, which is then associated with a return to normal weight in the infection group.