Anti-inflammatory potential of pyocyanin in LPS-stimulated murine macrophages

Unravelling host-pathogen interactions by biofilm infected human wound models

Approximately 80 % of persistent wound infections are affected by the presence of bacterial biofilms, resulting in a severe clinical challenge associated with prolonged healing periods, increased morbidity, and high healthcare costs. Unfortunately, in vitro models for wound infection research almost exclusively focus on early infection stages with planktonic bacteria. In this study, we present a new approach to emulate biofilm-infected human wounds by three-dimensional human in vitro systems. For this purpose, a matured biofilm consisting of the clinical key wound pathogen Pseudomonas aeruginosa was pre-cultivated on electrospun scaffolds allowing for non-destructive transfer of the matured biofilm to human in vitro wound models. We infected tissue-engineered human in vitro skin models as well as ex vivo human skin explants with the biofilm and analyzed structural tissue characteristics, biofilm growth behavior, and biofilm-tissue interactions. The structural development of biofilms in close proximity to the tissue, resulting in high bacterial burden and in vivo-like morphology, confirmed a manifest wound infection on all tested wound models, validating their applicability for general investigations of biofilm growth and structure. The extent of bacterial colonization of the wound bed, as well as the subsequent changes in molecular composition of skin tissue, were inherently linked to the characteristics of the underlying wound models including their viability and origin. Notably, the immune response observed in viable ex vivo and in vitro models was consistent with previous in vivo reports. While ex vivo models offered greater complexity and closer similarity to the in vivo conditions, in vitro models consistently demonstrated higher reproducibility. As a consequence, when focusing on direct biofilm-skin interactions, the viability of the wound models as well as their advantages and limitations should be aligned to the particular research question of future studies. Altogether, the novel model allows for a systematic investigation of host-pathogen interactions of bacterial biofilms and human wound tissue, also paving the way for development and predictive testing of novel therapeutics to combat biofilm-infected wounds.

Changes in Intracellular and Extracellular Metabolites of Mixed Lactobacillus Strains Enhance Inhibition of Pathogenic Bacterial Growth and Lipopolysaccharide-Induced Alleviation of RAW264.7 Cellular Inflammation

It is important to explore whether there are antagonistic and synergistic effects between different strains of Lactobacillus when developing mixed Lactobacillus strain products. In this study, we investigated the antagonistic and symbiotic effects of co-cultured Lactobacillus strains, as well as their amelioratory effects on lipopolysaccharide (LPS)-induced inflammation and oxidative stress in RAW264.7 cells. The Lactobacillus strains tested in this paper showed no antagonism. Co-culture of Lactiplantibacillus plantarum Y44 and L. plantarum AKS-WS9 was found to show inhibiting effects on the growth of Escherichia coli and Staphylococcus aureus. Additionally, the co-cultured Lactiplantibacillus plantarum Y44 and L. plantarum AKS-WS9 relieved inflammation in RAW264.7 cells induced by LPS by inhibiting the activation of NF-κB and P38 signaling pathways and down-regulating the expression of pro-inflammatory cytokines NO, ROS, iNOs and TNF-α. And the co-cultured Lactobacillus strains activated the Nrf2 signaling pathway in the LPS-induced RAW264.7 cells to promote the expression of antioxidant enzymes in response to oxidative stress. There was a difference in intracellular and extracellular metabolites between single or co-cultured Lactobacillus strains, and the co-cultured Lactobacillus strains significantly increased extracellular metabolites 4-chlorobenzaldehyde, psoromic acid, and 2-dodecylbenzenesulfonic acid and intracellular metabolites 9(S)-HODE, pyocyanin, and LysoPA. We inferred that the better antibacterial and anti-inflammatory ability of the co-cultured Lactobacillus strains were related to the changes in the metabolites of the co-cultured Lactobacillus strains. The co-cultured L. plantarum Y44 and L. plantarum AKS-WS9 strains exhibited better anti-inflammatory abilities and had the potential to alleviate the symptoms of inflammatory diseases as mixed probiotics.

Targeting Pseudomonas aeruginosa quorum sensing with sodium salicylate modulates immune responses in vitro and in vivo

Introduction

Chronic infections are a major clinical challenge in hard-to-heal wounds and implanted devices. Pseudomonas aeruginosa is a common causative pathogen that produces numerous virulence factors. Due to the increasing problem of antibiotic resistance, new alternative treatment strategies are needed. Quorum sensing (QS) is a bacterial communication system that regulates virulence and dampens inflammation, promoting bacterial survival. QS inhibition is a potent strategy to reduce bacterial virulence and alleviate the negative impact on host immune response.

Aim

This study investigates how secreted factors from P. aeruginosa PAO1, cultured in the presence or absence of the QS inhibitor sodium salicylate (NaSa), influence host immune response.

Material and methods

In vitro, THP-1 macrophages and neutrophil-like HL-60 cells were used. In vivo, discs of titanium were implanted in a subcutaneous rat model with local administration of P. aeruginosa culture supernatants. The host immune response to virulence factors contained in culture supernatants (+/-NaSa) was characterized through cell viability, migration, phagocytosis, gene expression, cytokine secretion, and histology.

Results

In vitro, P. aeruginosa supernatants from NaSa-containing cultures significantly increased THP-1 phagocytosis and HL-60 cell migration compared with untreated supernatants (-NaSa). Stimulation with NaSa-treated supernatants in vivo resulted in: (i) significantly increased immune cell infiltration and cell attachment to titanium discs; (ii) increased gene expression of IL-8, IL-10, ARG1, and iNOS, and (iii) increased GRO-α protein secretion and decreased IL-1β, IL-6, and IL-1α secretion, as compared with untreated supernatants.

Conclusion

In conclusion, treating P. aeruginosa with NaSa reduces the production of virulence factors and modulates major immune events, such as promoting phagocytosis and cell migration, and decreasing the secretion of several pro-inflammatory cytokines.

Pseudomonas aeruginosa's greenish-blue pigment pyocyanin: its production and biological activities

A subject of great interest is the bioprospecting of microorganisms and their bioactive byproducts, such as pigments. Microbial pigments have various benefits, including being safe to use due to their natural makeup, having therapeutic effects, and being produced all year round, regardless of the weather or location. Pseudomonas aeruginosa produces phenazine pigments that are crucial for interactions between Pseudomonas species and other living things. Pyocyanin pigment, which is synthesized by 90-95% of P. aeruginosa, has potent antibacterial, antioxidant, and anticancer properties. Herein, we will concentrate on the production and extraction of pyocyanin pigment and its biological use in different areas of biotechnology, engineering, and biology.

Antibacterial, antibiofilm, and anti-quorum sensing activities of pyocyanin against methicillin-resistant Staphylococcus aureus: in vitro and in vivo study

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) infections are considered a major public health problem, as the treatment options are restricted. Biofilm formation and the quorum sensing (QS) system play a pivotal role in S. aureus pathogenicity. Hence, this study was performed to explore the antibacterial effect of pyocyanin (PCN) on MRSA as well as its effect on MRSA biofilm and QS.

RESULTS

Data revealed that PCN exhibited strong antibacterial activity against all test MRSA isolates (n = 30) with a MIC value equal to 8 µg/ml. About 88% of MRSA biofilms were eradicated by PCN treatment using the crystal violet assay. The disruption of MRSA biofilm was confirmed using confocal laser scanning microscopy, which showed a reduction in bacterial viability (approximately equal to 82%) and biofilm thickness (approximately equal to 60%). Additionally, the disruption of the formation of microcolonies and the disturbance of the connection between bacterial cells in the MRSA biofilm after PCN treatment were examined by scanning electron microscopy. The 1/2 and 1/4 MICs of PCN exerted promising anti-QS activity without affecting bacterial viability; Agr QS-dependent virulence factors (hemolysin, protease, and motility), and the expression of agrA gene, decreased after PCN treatment. The in silico analysis confirmed the binding of PCN to the AgrA protein active site, which blocked its action. The in vivo study using the rat wound infection model confirmed the ability of PCN to modulate the biofilm and QS of MRSA isolates.

CONCLUSION

The extracted PCN seems to be a good candidate for treating MRSA infection through biofilm eradication and Agr QS inhibition.

Two Pairs of 7,7'-Cyclolignan Enantiomers with Anti-Inflammatory Activities from Perilla frutescens

Perilla frutescens (L.) Britt. (Labiatae), a medicinal plant, has been widely used for the therapy of multiple diseases since about 1800 years ago. It has been demonstrated that the extracts of P. frutescens exert significant anti-inflammatory effects. In this research, two pairs of 7,7′-cyclolignan enantiomers, possessing a cyclobutane moiety, (+)/(−)-perfrancin [(+)/(−)-1] and (+)/(−)-magnosalin [(+)/(−)-2], were separated from P. frutescens leaves. The present study achieved the chiral separation and determined the absolute configuration of (±)-1 and (±)-2. Compounds (+)-1 and (−)-1 have notable anti-inflammatory effects by reducing the secretion of pro-inflammatory factors (NO, TNF-α and IL-6) and the expression of pro-inflammatory mediators (iNOS and COX-2). These findings indicate that cyclolignans are effective substances of P. frutescens with anti-inflammatory activity. The present study partially elucidates the mechanisms underlying the effects of P. frutescens.

Colour Me Blue: The History and the Biotechnological Potential of Pyocyanin

Pyocyanin was the first natural phenazine described. The molecule is synthesized by about 95% of the strains of Pseudomonas aeruginosa. From discovery up to now, pyocyanin has been characterised by a very rich and avant-garde history, which includes its use in antimicrobial therapy, even before the discovery of penicillin opened the era of antibiotic therapy, as well as its use in electric current generation. Exhibiting an exuberant blue colour and being easy to obtain, this pigment is the subject of the present review, aiming to narrate its history as well as to unveil its mechanisms and suggest new horizons for applications in different areas of engineering, biology and biotechnology.

PA2146 Gene Knockout Is Associated With Pseudomonas aeruginosa Pathogenicity in Macrophage and Host Immune Response

Pseudomonas aeruginosa is a common gram-negative bacterium that usually causes nosocomial infection. The main pathogenicity of P. aeruginosa is caused by its virulence factors. PA2146 is reported to be a potential virulence-regulating gene and is highly expressed in the biofilms of P. aeruginosa. However, the effect of PA2146 mutant (PAO1ΔPA2146) on the macrophage immune response and murine models has not been reported. In the present study, PA2146 knockout was performed by homologous recombination. We found that PAO1ΔPA2146 stimulation significantly increased pyocyanin production but inhibited interleukin-6 secretion by neutrophils compared to PAO1 stimulation. In addition, PAO1ΔPA2146 treatment significantly inhibited cytokine production in macrophages independent of cell killing. In an acute pneumonia murine infection model, treatment with P. aeruginosa infected with PAO1ΔPA2146 inhibited cytokine secretion in the lungs but increased the infiltration of inflammatory cells compared to the wild-type group. The paradoxical results indicate that PA2146 deletion may also increase the production of virulence factors other than pyocyanin, which may not only increase inflammatory cell infiltration in the lungs but also lead to immune cells “shock.” Overall, our findings suggest that PA2146 could serve as a P. aeruginosa virulence-regulating gene that regulates its macrophage and host immune response.

Brd4 inhibition ameliorates Pyocyanin-mediated macrophage dysfunction via transcriptional repression of reactive oxygen and nitrogen free radical pathways

Macrophages play critical roles in the first-line immune defense against airway infections caused by Pseudomonas aeruginosa (PA). The redox-active phenazine-pyocyanin (PCN), as one of the most essential virulence factors, facilities PA-related infection via a wide spectrum of cellular oxidative damages. However, little is known for PCN cytotoxicity in macrophages. In this study, besides showing PCN-mediated reactive oxygen species (ROS) indeed involved in macrophage viability and function impairment, we at the first time demonstrated a novel role of reactive nitrogen species (RNS) pathway causing cellular damage in PCN-challenged macrophages. Using small molecule inhibitor JQ1 targeting Bromodomain and extra-terminal family proteins, we showed restrained iNOS-dependent nitric oxide (NO) production correlated with abolished Brd4 recruitment to the NOS2 (encoding inducible nitric oxide synthase-iNOS) promoter. Application of JQ1 diminished PCN-mediated peroxynitrite (ONOO-) that followed ROS and NO induction, restored macrophage survival and bacteria clearance as well as repressed local inflammation in PA/PCN-challenged mice lungs. Our results uncover a novel link between PCN-mediated macrophage dysfunction and reactive free radicals that rely on Brd4-dependent transcription modulation of multiple stress-response genes, suggesting Brd4 could be a promising therapeutic target in treating PA-related lung infection.