Surgical site infections (SSI) are a clinical and economic burden. Suture-associated SSI may develop when bacteria colonize the suture surface and form biofilms that are resistant to antibiotics. Thrombin-derived C-terminal peptide (TCP)-25 is a host defense peptide with a unique dual mode of action that can target both bacteria and the excessive inflammation induced by bacterial products. The peptide demonstrates therapeutic potential in preclinical in vivo wound infection models. In this study, the authors set out to explore whether TCP-25 can provide a new bioactive innate immune feature to hydrophilic polyglactin sutures (Vicryl). Using a combination of biochemical, biophysical, antibacterial, biofilm, and anti-inflammatory assays in vitro, in silico molecular modeling studies, along with experimental infection and inflammation models in mice, a proof-of-concept that TCP-25 can provide Vicryl sutures with a previously undisclosed host defense capacity, that enables targeting of bacteria, biofilms, and the accompanying inflammatory response, is shown.
Abstract The classical tachykinin substance P (SP) has numerous potent neuroimmunomodulatory effects on all kinds of airway functions. Belonging to a class of neuromediators targeting not only residential cells but also inflammatory cells, studying SP provides important information on the bidirectional linkage between how neural function affects inflammatory events and, in turn, how inflammatory responses alter neural activity. Therefore, this study aimed to investigate the effect of local burn injury on inducing distant organ pulmonary SP release and its relevance to lung injury. Our results show that burn injury in male BALB/c mice subjected to 30% total body surface area full thickness burn augments significant production of SP, preprotachykinin-A gene expression, which encodes for SP, and biological activity of SP-neurokinin-1 receptor (NK1R) signaling. Furthermore, the enhanced SP-NK1R response correlates with exacerbated lung damage after burn as evidenced by increased microvascular permeability, edema, and neutrophil accumulation. The development of heightened inflammation and lung damage was observed along with increased proinflammatory IL-1β, TNF-α, and IL-6 mRNA and protein production after injury in lung. Chemokines MIP-2 and MIP-1α were markedly increased, suggesting the active role of SP-induced chemoattractants production in trafficking inflammatory cells. More importantly, administration of L703606, a specific NK1R antagonist, 1 h before burn injury significantly disrupted the SP-NK1R signaling and reversed pulmonary inflammation and injury. The present findings show for the first time the role of SP in contributing to exaggerated pulmonary inflammatory damage after burn injury via activation of NK1R signaling.
Asthma exacerbations are commonly triggered by rhinovirus infections. Viruses can activate the NFκB pathway resulting in airway inflammation and increased Th2 cytokine expression. NFκB signaling is also involved in early activation of IFNβ, which is a central mediator of antiviral responses to rhinovirus infection. Using a mouse model, this study tests our hypothesis that NFκB signaling is involved in impaired IFNβ production at viral-induced asthma exacerbations. C57BL/6 wild-type and NFκB1−/− mice were challenged with house dust mite for 3 weeks and were subsequently stimulated with the rhinoviral mimic poly(I:C). General lung inflammatory parameters and levels of the Th2 upstream cytokine IL-33 were measured after allergen challenge. At exacerbation, production of IFNβ and antiviral proteins as well as gene expression of pattern recognition receptors and IRF3/IRF7 was assessed. In the asthma exacerbation mouse model, lack of NFκB1 resulted in lower levels of IL-33 after allergen challenge alone and was associated with reduced eosinophilia. At exacerbation, mice deficient in NFκB1 exhibited enhanced expression of IFNβ and antiviral proteins. This was accompanied by increased IRF3/IRF7 expression and induction of pattern recognition receptor expression. In a human asthma dataset, a negative correlation between IRF3 and NFκB1 expression was observed. NFκB may impair antiviral responses at exacerbation, possibly by reducing expression of the transcription factors IRF3/IRF7. These findings suggest a therapeutic potential for targeting NFκB pathways at viral infection-induced exacerbations.
ABSTRACT Skin barrier damage and subsequent development of harmful microbiota contribute to conditions such as wound infections, atopic dermatitis and chronic wounds, which impact millions of people globally and pose a significant economic burden on healthcare systems. Established microbial sampling methods, such as swabs and tissue biopsies, provide limited information on the spatial distribution of bacteria. We here describe a new method that produces a visual map of the distribution of cultivable bacteria, denoted ‘Bactogram’, across the whole wound and surrounding skin, suitable for image‐based quantification. As part of an exploratory endpoint in a clinical trial we applied the Bactogram method to 48 suction blister wounds in 24 healthy volunteers. Bacteria developed in all wounds, predominantly on the skin under the dressing and near wound edges. Two quantification methods, based on visual scoring and image analysis, demonstrated high inter‐, and intra‐rater agreement and were used to characterise bacterial re‐colonisation during epidermal wound healing. We also demonstrated proof of concept that the method can be used with chromogenic agar to enable spatial identification of pathogenic bacterial species, such as Staphylococcus aureus . In conclusion, this study introduces a simple method for sampling bacteria over large areas and generating a bacterial map that can identify spatial variations in bacterial composition and abundance in skin and wound conditions. Trial Registration: ClinicalTrials.gov identifier: NCT05378997
Abstract Pulmonary tuberculosis (TB) causes progressive and irreversible damage to lung tissue, a damage that may not fully resolve after treatment. Mycobacterial vesicles (MVs), which are poorly understood, may contribute to TB pathology. This study investigated the effects of stress, such as treatment with conventional TB antibiotics rifampicin, isoniazid, ethambutol, or treatment with an antimycobacterial peptide (NZX), on mycobacterial vesiculation. Stress from minimal inhibitory concentrations of antibiotics, or peptide all increased MV formation. Electron microscopy and lipid profiling revealed that these vesicles, about 40 nm in size, were released from the bacterial inner membrane and consisted of apolar lipids. Using mass spectrometry, the study identified key differences in MVs protein cargo dependent on the antibiotic used, especially with ethambutol-induced MVs that contained proteins from several mycobacterial pathways. Additionally, toxicology analysis using different concentrations of MVs on primary human macrophages and the monocytic cells indicated that MVs from the different treatments were not toxic to human cells, however induced specific inflammatory profiles. In conclusion, this study identified mycobacterial vesicles to be a potential contributor to tuberculosis pathology.
The mechanisms involved in the maintenance of memory IgE responses are poorly understood, and the role played by germinal center (GC) IgE+ cells in memory responses is particularly unclear. IgE+ B cell differentiation is characterized by a transient GC phase, a bias toward the plasma cell (PC) fate, and dependence on sequential switching for the production of high-affinity IgE. We show here that IgE+ GC B cells are unfit to undergo the conventional GC differentiation program due to impaired B cell receptor function and increased apoptosis. IgE+ GC cells fail to populate the GC light zone and are unable to contribute to the memory and long-lived PC compartments. Furthermore, we demonstrate that direct and sequential switching are linked to distinct B cell differentiation fates: direct switching generates IgE+ GC cells, whereas sequential switching gives rise to IgE+ PCs. We propose a comprehensive model for the generation and memory of IgE responses.
Neutrophils recruited to the postischemic kidney contribute to the pathogenesis of ischemia-reperfusion injury (IRI), which is the most common cause of renal failure among hospitalized patients. The Slit family of secreted proteins inhibits chemotaxis of leukocytes by preventing activation of Rho-family GTPases, suggesting that members of this family might modulate the recruitment of neutrophils and the resulting IRI. Here, in static and microfluidic shear assays, Slit2 inhibited multiple steps required for the infiltration of neutrophils into tissue. Specifically, Slit2 blocked the capture and firm adhesion of human neutrophils to inflamed vascular endothelial barriers as well as their subsequent transmigration. To examine whether these observations were relevant to renal IRI, we administered Slit2 to mice before bilateral clamping of the renal pedicles. Assessed at 18 hours after reperfusion, Slit2 significantly inhibited renal tubular necrosis, neutrophil and macrophage infiltration, and rise in plasma creatinine. In vitro, Slit2 did not impair the protective functions of neutrophils, including phagocytosis and superoxide production, and did not inhibit neutrophils from killing the extracellular pathogen Staphylococcus aureus. In vivo, administration of Slit2 did not attenuate neutrophil recruitment or bacterial clearance in mice with ascending Escherichia coli urinary tract infections and did not increase the bacterial load in the livers of mice infected with the intracellular pathogen Listeria monocytogenes. Collectively, these results suggest that Slit2 may hold promise as a strategy to combat renal IRI without compromising the protective innate immune response.
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