The Pseudomonas aeruginosa protease LasB directly activates IL-1β

Quercetin: a promising virulence inhibitor of Pseudomonas aeruginosa LasB in vitro

With the inappropriate use of antibiotics, antibiotic resistance has emerged as a major dilemma for patients infected with Pseudomonas aeruginosa. Elastase B (LasB), a crucial extracellular virulence factor secreted by P. aeruginosa, has been identified as a key target for antivirulence therapy. Quercetin, a natural flavonoid, exhibits promising potential as an antivirulence agent. We aim to evaluate the impact of quercetin on P. aeruginosa LasB and elucidate the underlying mechanism. Molecular docking and molecular dynamics simulation revealed a rather favorable intermolecular interaction between quercetin and LasB. At the sub-MICs of ≤256 μg/ml, quercetin was found to effectively inhibit the production and activity of LasB elastase, as well as downregulate the transcription level of the lasB gene in both PAO1 and clinical strains of P. aeruginosa. Through correlation analysis, significant positive correlations were shown between the virulence gene lasB and the QS system regulatory genes lasI, lasR, rhlI, and rhlR in clinical strains of P. aeruginosa. Then, we found the lasB gene expression and LasB activity were significantly deficient in PAO1 ΔlasI and ΔlasIΔrhlI mutants. In addition, quercetin significantly downregulated the expression levels of regulated genes lasI, lasR, rhlI, rhlR, pqsA, and pqsR as well as effectively attenuated the synthesis of signaling molecules 3-oxo-C12-HSL and C4-HSL in the QS system of PAO1. Quercetin was also able to compete with the natural ligands OdDHL, BHL, and PQS for binding to the receptor proteins LasR, RhlR, and PqsR, respectively, resulting in the formation of more stabilized complexes. Taken together, quercetin exhibits enormous potential in combating LasB production and activity by disrupting the QS system of P. aeruginosa in vitro, thereby offering an alternative approach for the antivirulence therapy of P. aeruginosa infections. KEY POINTS: • Quercetin diminished the content and activity of LasB elastase of P. aeruginosa. • Quercetin inhibited the QS system activity of P. aeruginosa. • Quercetin acted on LasB based on the QS system.

Revealing quorum-sensing networks in Pseudomonas aeruginosa infections through internal and external signals to prevent new resistance trends

In the context of growing antibiotic resistance in bacteria, the quorum-sensing (QS) system of Pseudomonas aeruginosa (P. aeruginosa) has become a target for new therapeutic strategies. QS is a crucial communication process and an essential pathogenic mechanism. This comprehensive review explores the critical role of QS in the pathogenesis of P. aeruginosa infections, including lung, burn, bloodstream, gastrointestinal, corneal, and urinary tract infections. In addition, this review delves into the complexity of the bacterial QS communication network and highlights the intricate mechanisms underlying these pathological processes. Notably, in addition to the four main QS systems, bacterial QS can interact with various external and internal signaling networks, such as host environments and nutrients in the external microbiome, as well as internal virulence regulation systems within bacteria. These elements can significantly influence the behavior and virulence of microbial communities. Therefore, this review reveals that inhibitors targeting singular QS pathways may inadvertently promote virulence in other pathways, leading to new trends in drug resistance. In response to evolving resistance challenges, this study proposes more cautious treatment strategies, including multitarget interventions and combination therapies, aimed at combating the escalating issue of resistance.

Dual inhibitors of Pseudomonas aeruginosa virulence factors LecA and LasB

Dual inhibitors of two key virulence factors of Pseudomonas aeruginosa, the lectin LecA and the protease LasB, open up an opportunity in the current antimicrobial-resistance crisis. A molecular hybridization approach enabled the discovery of potent, selective, and non-toxic thiol-based inhibitors, which simultaneously inhibit these two major extracellular virulence factors and therefore synergistically interfere with virulence. We further demonstrated that the dimerization of these monovalent dual inhibitors under physiological conditions affords divalent inhibitors of LecA with a 200-fold increase in binding affinity. The bifunctional LecA/LasB-blocker 12 showed superiority for the inhibition of virulence mediated by both targets over the individual inhibitors or combinations thereof in vitro. Our study sets the stage for a systematic exploration of dual inhibitors as pathoblockers for a more effective treatment of P. aeruginosa infections and the concept can certainly be extended to other targets and pathogens.

Airway IL-1β is related to disease severity and mucociliary function in bronchiectasis

RATIONALE

The inflammasome is a key regulatory complex of the inflammatory response leading to interleukin-1β (IL-1β) release and activation. IL-1β amplifies inflammatory responses and induces mucus secretion and hyperconcentration in other diseases. The role of IL-1β in bronchiectasis has not been investigated.

OBJECTIVES

To characterise the role of airway IL-1β in bronchiectasis, including the association with mucus properties, ciliary function, airway inflammation, microbiome and disease severity.

METHODS

Stable bronchiectasis patients were enrolled in an international cohort study (n=269). IL-1β was measured in sputum supernatant. A validation cohort also had sputum rheology and hydration measured (n=53). For analysis, patients were stratified according to the median value of IL-1β in the population (high versus low) to compare disease severity, airway infection, microbiome (16S rRNA sequencing), inflammation and caspase-1 activity. Primary human nasal epithelial cells grown in air-liquid interface culture were used to study the effect of IL-1β on cilia function.

RESULTS

Patients with high sputum IL-1β had more severe disease, increased caspase-1 activity and an increased T-helper type 1, T-helper type 2 and neutrophil inflammatory response compared with patients with low IL-1β. The active-dominant form of IL-1β was associated with increased disease severity. High IL-1β was related to higher relative abundance of Proteobacteria in the microbiome and increased mucus solid content and viscoelastic properties. Chronic IL-1β treatment reduced the functionality of cilia and tight junctions of epithelial cells in vitro.

CONCLUSIONS

A subset of stable bronchiectasis patients show increased airway IL-1β, suggesting pulmonary inflammasome activation is linked with more severe disease, airway infection, mucus dehydration and epithelial dysfunction.

Exploring roles of the chitinase ChiC in modulating Pseudomonas aeruginosa virulence phenotypes

Chitinases are ubiquitous enzymes involved in biomass degradation and chitin turnover in nature. Pseudomonas aeruginosa (PA), an opportunistic human pathogen, expresses ChiC, a secreted glycoside hydrolase 18 family chitinase. Despite speculation about ChiC's role in PA disease pathogenesis, there is scant evidence supporting this hypothesis. Since PA cannot catabolize chitin, we investigated the potential function(s) of ChiC in PA pathophysiology. Our findings show that ChiC exhibits activity against both insoluble (α- and β-chitin) and soluble chitooligosaccharides. Enzyme kinetics toward (GlcNAc)4 revealed a kcat of 6.50 s-1 and a KM of 1.38 mM, the latter remarkably high for a canonical chitinase. In our label-free proteomics investigation, ChiC was among the most abundant proteins in the Pel biofilm, suggesting a potential contribution to PA biofilm formation. Using an intratracheal challenge model of PA pneumonia, the chiC::ISphoA/hah transposon insertion mutant paradoxically showed slightly increased virulence compared to the wild-type parent strain. Our results indicate that ChiC is a genuine chitinase that contributes to a PA pathoadaptive pathway.IMPORTANCEIn addition to performing chitin degradation, chitinases from the glycoside hydrolase 18 family have been found to play important roles during pathogenic bacterial infection. Pseudomonas aeruginosa is an opportunistic pathogen capable of causing pneumonia in immunocompromised individuals. Despite not being able to grow on chitin, the bacterium produces a chitinase (ChiC) with hitherto unknown function. This study describes an in-depth characterization of ChiC, focusing on its potential contribution to the bacterium's disease-causing ability. We demonstrate that ChiC can degrade both polymeric chitin and chitooligosaccharides, and proteomic analysis of Pseudomonas aeruginosa biofilm revealed an abundance of ChiC, hinting at a potential role in biofilm formation. Surprisingly, a mutant strain incapable of ChiC production showed higher virulence than the wild-type strain. While ChiC appears to be a genuine chitinase, further investigation is required to fully elucidate its contribution to Pseudomonas aeruginosa virulence, an important task given the evident health risk posed by this bacterium.

Exacerbations of bronchiectasis

Bronchiectasis presents a significant challenge due to its rising prevalence, associated economic burden and clinical heterogeneity. This review synthesises contemporary understanding and literature of bronchiectasis exacerbations, addressing the transition from stable state to exacerbations, underlining the importance of early and precise recognition, rigorous severity assessment, prompt treatment, and prevention measures, as well as emphasising the need for strategies to assess and improve early and long-term patient outcomes. The review highlights the interplay between stable state phases and exacerbations in bronchiectasis, introducing the concept of "exogenous and endogenous changes in airways homeostasis" and the "adapted island model" with a particular focus on "frequent exacerbators", a group of patients associated with specific clinical characteristics and worse outcomes. The pathophysiology of exacerbations is explored through the lens of microbial and nonmicrobial triggers and the presence and the activity of comorbidities, elaborating on the impact of both exogenous insults, such as infections and pollution, and endogenous factors such as inflammatory endotypes. Finally, the review proposes a multidisciplinary approach to care, integrating advancements in precision medicine and biomarker research, paving the way for tailored treatments that challenge the traditional antibiotic paradigm.

Species-specific IL-1β is an inflammatory sensor of Seneca Valley Virus 3C Protease

Inflammasomes play pivotal roles in inflammation by processing and promoting the secretion of IL-1β. Caspase-1 is involved in the maturation of IL-1β and IL-18, while human caspase-4 specifically processes IL-18. Recent structural studies of caspase-4 bound to Pro-IL-18 reveal the molecular basis of Pro-IL-18 activation by caspase-4. However, the mechanism of caspase-1 processing of pro-IL-1β and other IL-1β-converting enzymes remains elusive. Here, we observed that swine Pro-IL-1β (sPro-IL-1β) exists as an oligomeric precursor unlike monomeric human Pro-IL-1β (hPro-IL-1β). Interestingly, Seneca Valley Virus (SVV) 3C protease cleaves sPro-IL-1β to produce mature IL-1β, while it cleaves hPro-IL-1β but does not produce mature IL-1β in a specific manner. When the inflammasome is blocked, SVV 3C continues to activate IL-1β through direct cleavage in porcine alveolar macrophages (PAMs). Through molecular modeling and mutagenesis studies, we discovered that the pro-domain of sPro-IL-1β serves as an 'exosite' with its hydrophobic residues docking into a positively charged 3C protease pocket, thereby directing the substrate to the active site. The cleavage of sPro-IL-1β generates a monomeric and active form of IL-1β, initiating the downstream signaling. Thus, these studies provide IL-1β is an inflammatory sensor that directly detects viral protease through an independent pathway operating in parallel with host inflammasomes.

Abnormal functional lymphoid tolerance and enhanced myeloid exocytosis are characteristics of resting and stimulated PBMCs in cystic fibrosis patients

Introduction

Cystic Fibrosis (CF) is the commonest genetically inherited disease (1 in 4,500 newborns) and 70% of people with CF (pwCF) harbour the F508Del mutation, resulting in misfolding and incorrect addressing of the channel CFTR to the epithelial membrane and subsequent dysregulation of fluid homeostasis. Although studies have underscored the importance and over-activation of myeloid cells, and in particular neutrophils in the lungs of people with CF (pwCF), relatively less emphasis has been put on the potential immunological bias in CF blood cells, at homeostasis or following stimulation/infection.

Methods

Here, we revisited, in an exhaustive fashion, in pwCF with mild disease (median age of 15, median % FEV1 predicted = 87), whether their PBMCs, unprimed or primed with a 'non specific' stimulus (PMA+ionomycin mix) and a 'specific' one (live P.a =PAO1 strain), were differentially activated, compared to healthy controls (HC) PBMCs.

Results

1) we analysed the lymphocytic and myeloid populations present in CF and Control PBMCs (T cells, NKT, Tgd, ILCs) and their production of the signature cytokines IFN-g, IL-13, IL-17, IL-22. 2) By q-PCR, ELISA and Luminex analysis we showed that CF PBMCs have increased background cytokines and mediators production and a partial functional tolerance phenotype, when restimulated. 3) we showed that CF PBMCs low-density neutrophils release higher levels of granule components (S100A8/A9, lactoferrin, MMP-3, MMP-7, MMP-8, MMP-9, NE), demonstrating enhanced exocytosis of potentially harmful mediators.

Discussion

In conclusion, we demonstrated that functional lymphoid tolerance and enhanced myeloid protease activity are key features of cystic fibrosis PBMCs.

Higher levels of Pseudomonas aeruginosa LasB elastase expression are associated with early-stage infection in cystic fibrosis patients

Pseudomonas aeruginosa is a common pathogen in cystic fibrosis (CF) patients and a major contributor to progressive lung damage. P. aeruginosa elastase (LasB), a key virulence factor, has been identified as a potential target for anti-virulence therapy. Here, we sought to differentiate the P. aeruginosa isolates from early versus established stages of infection in CF patients and to determine if LasB was associated with either stage. The lasB gene was amplified from 255 P. aeruginosa clinical isolates from 70 CF patients from the Toulouse region (France). Nine LasB variants were identified and 69% of the isolates produced detectable levels of LasB activity. Hierarchical clustering using experimental and clinical data distinguished two classes of isolates, designated as 'Early' and 'Established' infection. Multivariate analysis revealed that the isolates from the Early infection class show higher LasB activity, fast growth, tobramycin susceptibility, non-mucoid, pigmented colonies and wild-type lasR genotype. These traits were associated with younger patients with polymicrobial infections and high pFEV1. Our findings show a correlation between elevated LasB activity in P. aeruginosa isolates and early-stage infection in CF patients. Hence, it is this patient group, prior to the onset of chronic disease, that may benefit most from novel therapies targeting LasB.

Subversion of the Complement System by Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic pathogen heavily implicated in chronic diseases. Immunocompromised patients that become infected with P. aeruginosa usually are afflicted with a lifelong chronic infection, leading to worsened patient outcomes. The complement system is an integral piece of the first line of defense against invading microorganisms. Gram-negative bacteria are thought to be generally susceptible to attack from complement; however, P. aeruginosa can be an exception, with certain strains being serum resistant. Various molecular mechanisms have been described that confer P. aeruginosa unique resistance to numerous aspects of the complement response. In this review, we summarize the current published literature regarding the interactions of P. aeruginosa and complement, as well as the mechanisms used by P. aeruginosa to exploit various complement deficiencies and the strategies used to disrupt or hijack normal complement activities.

Suppurative Meningoencephalitis by Pseudomonas aeruginosa from Direct Extension of Chronic Otitis in a Gir Cow

This paper aims to report clinical, laboratory and pathological features in a case of suppurative meningoencephalitis by P. aeruginosa from the direct extension of chronic otitis in a Gir cow. The cow was recumbent during physical examination, and neurological examination revealed depression, absence of left eyelid and auricular motor reflex, and hypotonic tongue. Hematology revealed hemoconcentration, leukocytosis by neutrophilia, and hyperfibrinogenemia. Cerebrospinal fluid was slightly turbid, and presented polymorphonuclear pleocytosis, and hyperproteinorrachia. Grossly, the skull floor showed a purulent green-yellow exudate that drained from the left inner ear to the cisterna magna. There was diffuse congestion of the telencephalon, and meninges showed severe hyperemia, moderate thickening, and opacity with the deposition of fibrinosuppurative material ventrally, extending to the cerebellum and brainstem. The left cerebellar hemisphere showed an approximately 1.5 cm in diameter liquefaction area surrounded by a hemorrhagic halo. Histologically, cerebellar, mesencephalic, thalamic, and brain base meninges were intensely thickened and showed severe suppurative inflammation and fibrin deposition. Small multifocal suppurative areas were observed in the cerebellum and brainstem, characterized by a necrotic core, a number of neutrophils, and Gram-negative intralesional bacillary myriads. Pure cultures of P. aeruginosa were obtained and identified in the suppurative CNS lesions, meninges, and inner ear samples. This report highlights an uncommon clinical evolution of secondary P. aeruginosa suppurative meningoencephalitis, probably triggered by recurrent parasitic otitis in an adult Gir cow. Veterinarians, practitioners, and farmers must be aware of the risk of CNS infections after unresolved media and inner otitis, especially in cattle breeds more prone to developing parasitic otitis, such as the Gir and Indubrasil breeds.

Improved understanding of biorisk for research involving microbial modification using annotated sequences of concern

Regulation of research on microbes that cause disease in humans has historically been focused on taxonomic lists of 'bad bugs'. However, given our increased knowledge of these pathogens through inexpensive genome sequencing, 5 decades of research in microbial pathogenesis, and the burgeoning capacity of synthetic biologists, the limitations of this approach are apparent. With heightened scientific and public attention focused on biosafety and biosecurity, and an ongoing review by US authorities of dual-use research oversight, this article proposes the incorporation of sequences of concern (SoCs) into the biorisk management regime governing genetic engineering of pathogens. SoCs enable pathogenesis in all microbes infecting hosts that are 'of concern' to human civilization. Here we review the functions of SoCs (FunSoCs) and discuss how they might bring clarity to potentially problematic research outcomes involving infectious agents. We believe that annotation of SoCs with FunSoCs has the potential to improve the likelihood that dual use research of concern is recognized by both scientists and regulators before it occurs.

How Staphylococcus aureus and Pseudomonas aeruginosa Hijack the Host Immune Response in the Context of Cystic Fibrosis

Cystic fibrosis (CF) is a serious genetic disease that leads to premature death, mainly due to impaired lung function. CF lungs are characterized by ongoing inflammation, impaired immune response, and chronic bacterial colonization. Staphylococcus aureus (SA) and Pseudomonas aeruginosa (PA) are the two most predominant bacterial agents of these chronic infections. Both can colonize the lungs for years by developing host adaptation strategies. In this review, we examined the mechanisms by which SA and PA adapt to the host immune response. They are able to bypass the physical integrity of airway epithelia, evade recognition, and then modulate host immune cell proliferation. They also modulate the immune response by regulating cytokine production and by counteracting the activity of neutrophils and other immune cells. Inhibition of the immune response benefits not only the species that implements them but also other species present, and we therefore discuss how these mechanisms can promote the establishment of coinfections in CF lungs.

Spiramycin Disarms Pseudomonas aeruginosa without Inhibiting Growth

Spiramycin is a 16-membered macrolide antibiotic currently used in therapy to treat infections caused by Gram-positive bacteria responsible for respiratory tract infections, and it is also effective against some Gram-negative bacteria and against Toxoplasma spp. In contrast, Pseudomonas aeruginosa, which is one of the pathogens of most concern globally, is intrinsically resistant to spiramycin. In this study we show that spiramycin inhibits the expression of virulence determinants in P. aeruginosa in the absence of any significant effect on bacterial multiplication. In vitro experiments demonstrated that production of pyoverdine and pyocyanin by an environmental strain of P. aeruginosa was markedly reduced in the presence of spiramycin, as were biofilm formation, swarming motility, and rhamnolipid production. Moreover, treatment of P. aeruginosa with spiramycin sensitized the bacterium to H2O2 exposure. The ability of spiramycin to dampen the virulence of the P. aeruginosa strain was confirmed in a Galleria mellonella animal model. The results demonstrated that when G. mellonella larvae were infected with P. aeruginosa, the mortality after 24 h was >90%. In contrast, when the spiramycin was injected together with the bacterium, the mortality dropped to about 50%. Furthermore, marked reduction in transcript levels of the antimicrobial peptides gallerimycin, gloverin and moricin, and lysozyme was found in G. mellonella larvae infected with P. aeruginosa and treated with spiramycin, compared to the larvae infected without spiramycin treatment suggesting an immunomodulatory activity of spiramycin. These results lay the foundation for clinical studies to investigate the possibility of using the spiramycin as an anti-virulence and anti-inflammatory drug for a more effective treatment of P. aeruginosa infections, in combination with other antibiotics.

A Staphylococcal Glucosaminidase Drives Inflammatory Responses by Processing Peptidoglycan Chains to Physiological Lengths

The peptidoglycan of Staphylococcus aureus is a critical cell envelope constituent and virulence factor that subverts host immune defenses and provides protection against environmental stressors. Peptidoglycan chains of the S. aureus cell wall are processed to characteristically short lengths by the glucosaminidase SagB. It is well established that peptidoglycan is an important pathogen-associated molecular pattern (PAMP) that is recognized by the host innate immune system and promotes production of proinflammatory cytokines, including interleukin-1β (IL-1β). However, how bacterial processing of peptidoglycan drives IL-1β production is comparatively unexplored. Here, we tested the involvement of staphylococcal glucosaminidases in shaping innate immune responses and identified SagB as a mediator of IL-1β production. A ΔsagB mutant fails to promote IL-1β production by macrophages and dendritic cells, and processing of peptidoglycan by SagB is essential for this response. SagB-dependent IL-1β production by macrophages is independent of canonical pattern recognition receptor engagement and NLRP3 inflammasome-mediated caspase activity. Instead, treatment of macrophages with heat-killed cells from a ΔsagB mutant leads to reduced caspase-independent cleavage of pro-IL-1β, resulting in accumulation of the pro form in the macrophage cytosol. Furthermore, SagB is required for virulence in systemic infection and promotes IL-1β production in a skin and soft tissue infection model. Taken together, our results suggest that the length of S. aureus cell wall glycan chains can drive IL-1β production by innate immune cells through a previously undescribed mechanism related to IL-1β maturation.

Chemical Optimization of Selective Pseudomonas aeruginosa LasB Elastase Inhibitors and Their Impact on LasB-Mediated Activation of IL-1β in Cellular and Animal Infection Models

LasB elastase is a broad-spectrum exoprotease and a key virulence factor of Pseudomonas aeruginosa, a major pathogen causing lung damage and inflammation in acute and chronic respiratory infections. Here, we describe the chemical optimization of specific LasB inhibitors with druglike properties and investigate their impact in cellular and animal models of P. aeruginosa infection. Competitive inhibition of LasB was demonstrated through structural and kinetic studies. In vitro LasB inhibition was confirmed with respect to several host target proteins, namely, elastin, IgG, and pro-IL-1β. Furthermore, inhibition of LasB-mediated IL-1β activation was demonstrated in macrophage and mouse lung infection models. In mice, intravenous administration of inhibitors also resulted in reduced bacterial numbers at 24 h. These highly potent, selective, and soluble LasB inhibitors constitute valuable tools to study the proinflammatory impact of LasB in P. aeruginosa infections and, most importantly, show clear potential for the clinical development of a novel therapy for life-threatening respiratory infections caused by this opportunistic pathogen.

Host cell responses against the pseudomonal biofilm: A continued tale of host-pathogen interactions

In biofilm formation, pathogens within the bacterial community coordinate a cell-cell communication system called quorum sensing (QS). This is achieved through various signalling pathways that regulate bacterial virulence and host immune response. Here, we reviewed the host responses, key clinical implications, and novel therapeutic approaches against the biofilms of P. aeruginosa. Given the high degree of intrinsic antibiotic resistance and biofilm formation by the pathogen, the ensuing treatment complications could result in high morbidity and mortality rates worldwide. Notwithstanding the availability of intervention strategies, there remains a paucity of effective therapeutic options to control biofilmogenesis. This review discusses the basic understanding of QS-associated virulence factors and several key therapeutic interventions to foil the biofilm menace of P. aeruginosa.

Assessing Interleukin-1β Activation During Pyroptosis

The cytokine interleukin-1β (IL-1β) is a major mediator of inflammation in autoinflammatory disease and the host response to infection. IL-1β is stored within cells in an inert form, which requires proteolytic removal of an amino-terminal fragment in order to bind the IL-1 receptor complex and have pro-inflammatory activity. This cleavage event is canonically carried out by inflammasome-activated caspase proteases, but microbe and host proteases can also generate unique active forms. Post-translational regulation of IL-1β and the diversity in resulting products can present challenges to the evaluation of IL-1β activation. This chapter details methods and important controls for the accurate and sensitive measurement of IL-1β activation within biological samples.

Multiplex substrate profiling by mass spectrometry for proteases

Proteolysis is a central regulator of many biological pathways and the study of proteases has had a significant impact on our understanding of both native biology and disease. Proteases are key regulators of infectious disease and misregulated proteolysis in humans contributes to a variety of maladies, including cardiovascular disease, neurodegeneration, inflammatory diseases, and cancer. Central to understanding a protease's biological role, is characterizing its substrate specificity. This chapter will facilitate the characterization of individual proteases and complex, heterogeneous proteolytic mixtures and provide examples of the breadth of applications that leverage the characterization of misregulated proteolysis. Here we present the protocol of Multiplex Substrate Profiling by Mass Spectrometry (MSP-MS), a functional assay that quantitatively characterizes proteolysis using a synthetic library of physiochemically diverse, model peptide substrates, and mass spectrometry. We present a detailed protocol as well as examples of the use of MSP-MS for the study of disease states, for the development of diagnostic and prognostic tests, for the generation of tool compounds, and for the development of protease-targeted drugs.

PEG2-Induced Pyroptosis Regulates the Expression of HMGB1 and Promotes hEM15A Migration in Endometriosis

Endometriosis (EMS) is a common gynecological disease. Prostaglandin E2 (PGE2), which induces chronic pelvic inflammation and cell pyroptosis, a form of programmed cell death based on inflammasome activation, are involved in EMS, but the extent of their involvement and roles remain unclear. The present study aimed to evaluate PGE2-induced pyroptosis in EMS and the influence of PGE2 in EMS progression. Using western blotting, it was found that the expressions of PGE2 and pyroptosis-related proteins (NLRP3, cleaved caspase-1, interleukin (IL)-1β and IL-18) were higher in EMS tissues than in normal endometrial tissues. The levels of PGE2, IL-1β, and IL-18 in the serum of patients with EMS and cell culture fluids were also detected. Using the transwell assay, we verified that PGE2 promoted hEM15A migration via the NLRP3/caspase-1 pyroptotic pathway, and PGE2-induced pyroptosis upregulated the expressions of high mobility group box 1 (HMGB1), E-cadherin, and vimentin. Immunohistochemistry analysis confirmed that PGE2-induced pyroptosis contributed to EMS invasion. These results suggest that PGE2-induced pyroptosis affects the progression of EMS by changing the migration ability of pyroptotic cells and upregulating the expression of HMGB1, E-cadherin, and vimentin. Our findings provide crucial evidence for new treatment pathways and use of anti-inflammatory drugs in EMS.

The matricellular protein thrombospondin-1 in lung inflammation and injury

Matricellular proteins comprise a diverse group of molecular entities secreted into the extracellular space. They interact with the extracellular matrix (ECM), integrins, and other cell-surface receptors, and can alter matrix strength, cell attachment to the matrix, and cell-cell adhesion. A founding member of this group is thrombospondin-1 (TSP-1), a high molecular-mass homotrimeric glycoprotein. Given the importance of the matrix and ECM remodeling in the lung following injury, TSP-1 has been implicated in a number of lung pathologies. This review examines the role of TSP-1 as a damage controller in the context of lung inflammation, injury resolution, and repair in noninfectious and infectious models. This review also discusses the potential role of TSP-1 in human diseases as it relates to lung inflammation and injury.

Pseudomonas Aeruginosa Lung Infection Subverts Lymphocytic Responses through IL-23 and IL-22 Post-Transcriptional Regulation

Pseudomonas aeruginosa (P.a) is a pathogen causing significant morbidity and mortality, particularly in hospital patients undergoing ventilation and in individuals with cystic fibrosis. Although we and others have investigated mechanisms used by P.a to subvert innate immunity, relatively less is known about the potential strategies used by this bacterium to fight the adaptive immune system and, in particular, T cells. Here, using RAG KO (devoid of ‘classical’ αβ and γδ TCR T lymphocytes) and double RAG γC KO mice (devoid of T, NK and ILC cells), we demonstrate that the lymphocytic compartment is important to combat P.a (PAO1 strain). Indeed, we show that PAO1 load was increased in double RAG γC KO mice. In addition, we show that PAO1 down-regulates IL-23 and IL-22 protein accumulation in the lungs of infected mice while up-regulating their RNA production, thereby pointing towards a specific post-transcriptional regulatory mechanism not affecting other inflammatory mediators. Finally, we demonstrate that an adenovirus-mediated over-expression of IL-1, IL-23 and IL-7 induced lung neutrophil and lymphocytic influx and rescued mice against P.a-induced lethality in all WT, RAG γC KO and RAG γC KO RAG-deficient mice, suggesting that this regimen might be of value in ‘locally immunosuppressed’ individuals such as cystic fibrosis patients.

Pseudomonas aeruginosa: pathogenesis, virulence factors, antibiotic resistance, interaction with host, technology advances and emerging therapeutics

Pseudomonas aeruginosa (P. aeruginosa) is a Gram-negative opportunistic pathogen that infects patients with cystic fibrosis, burn wounds, immunodeficiency, chronic obstructive pulmonary disorder (COPD), cancer, and severe infection requiring ventilation, such as COVID-19. P. aeruginosa is also a widely-used model bacterium for all biological areas. In addition to continued, intense efforts in understanding bacterial pathogenesis of P. aeruginosa including virulence factors (LPS, quorum sensing, two-component systems, 6 type secretion systems, outer membrane vesicles (OMVs), CRISPR-Cas and their regulation), rapid progress has been made in further studying host-pathogen interaction, particularly host immune networks involving autophagy, inflammasome, non-coding RNAs, cGAS, etc. Furthermore, numerous technologic advances, such as bioinformatics, metabolomics, scRNA-seq, nanoparticles, drug screening, and phage therapy, have been used to improve our understanding of P. aeruginosa pathogenesis and host defense. Nevertheless, much remains to be uncovered about interactions between P. aeruginosa and host immune responses, including mechanisms of drug resistance by known or unannotated bacterial virulence factors as well as mammalian cell signaling pathways. The widespread use of antibiotics and the slow development of effective antimicrobials present daunting challenges and necessitate new theoretical and practical platforms to screen and develop mechanism-tested novel drugs to treat intractable infections, especially those caused by multi-drug resistance strains. Benefited from has advancing in research tools and technology, dissecting this pathogen's feature has entered into molecular and mechanistic details as well as dynamic and holistic views. Herein, we comprehensively review the progress and discuss the current status of P. aeruginosa biophysical traits, behaviors, virulence factors, invasive regulators, and host defense patterns against its infection, which point out new directions for future investigation and add to the design of novel and/or alternative therapeutics to combat this clinically significant pathogen.

IL-1 family cytokines serve as 'activity recognition receptors' for aberrant protease activity indicative of danger

Members of the extended IL-1 cytokine family play key roles as instigators of inflammation in numerous infectious and sterile injury contexts and are highly enriched at barrier surfaces such as the skin, lungs and intestinal mucosa. Because IL-1 family cytokines do not possess conventional ER-golgi trafficking and secretory signals, these cytokines are typically released into the extracellular space due to tissue damage resulting in necrosis, or pathogen detection resulting in pyroptosis. The latter feature, in combination with other factors, suggests that IL-1 family cytokines serve as canonical damage-associated molecular patterns (DAMPs), which instigate inflammation in response to tissue damage. However, IL-1 family cytokines also require a proteolytic activation step and diverse intracellular, extracellular and non-self proteases have been identified that are capable of processing and activating members of this family. This suggests that IL-1 family members function as sentinels for aberrant protease activity, which is frequently associated with infection or tissue damage. Here, we overview the diversity of proteases implicated in the activation of IL-1 family cytokines and suggest that this ancient cytokine family may have evolved to complement 'pattern recognition receptors', by serving as 'activity recognition receptors' enabling the detection of aberrant enzyme activity indicative of 'danger'.

Inhibition of the Quorum Sensing System, Elastase Production and Biofilm Formation in Pseudomonas aeruginosa by Psammaplin A and Bisaprasin

Natural products derived from marine sponges have exhibited bioactivity and, in some cases, serve as potent quorum sensing inhibitory agents that prevent biofilm formation and attenuate virulence factor expression by pathogenic microorganisms. In this study, the inhibitory activity of the psammaplin-type compounds, psammaplin A (1) and bisaprasin (2), isolated from the marine sponge, Aplysinellarhax, are evaluated in quorum sensing inhibitory assays based on the Pseudomonas aeruginosa PAO1 lasB-gfp(ASV) and rhlA-gfp(ASV) biosensor strains. The results indicate that psammaplin A (1) showed moderate inhibition on lasB-gfp expression, but significantly inhibited the QS-gene promoter, rhlA-gfp, with IC50 values at 14.02 μM and 4.99 μM, respectively. In contrast, bisaprasin (2) displayed significant florescence inhibition in both biosensors, PAO1 lasB-gfp and rhlA-gfp, with IC50 values at 3.53 μM and 2.41 μM, respectively. Preliminary analysis suggested the importance of the bromotyrosine and oxime functionalities for QSI activity in these molecules. In addition, psammaplin A and bisaprasin downregulated elastase expression as determined by the standard enzymatic elastase assay, although greater reduction in elastase production was observed with 1 at 50 μM and 100 μM. Furthermore, the study revealed that bisaprasin (2) reduced biofilm formation in P. aeruginosa.

Playing With Fire: Proinflammatory Virulence Mechanisms of Group A Streptococcus

Group A Streptococcus is an obligate human pathogen that is a major cause of infectious morbidity and mortality. It has a natural tropism for the oropharynx and skin, where it causes infections with excessive inflammation due to its expression of proinflammatory toxins and other virulence factors. Inflammation directly contributes to the severity of invasive infections, toxic shock syndrome, and the induction of severe post-infection autoimmune disease caused by autoreactive antibodies. This review discusses what is known about how the virulence factors of Group A Streptococcus induce inflammation and how this inflammation can promote disease. Understanding of streptococcal pathogenesis and the role of hyper-immune activation during infection may provide new therapeutic targets to treat the often-fatal outcome of severe disease.

Pseudomonas aeruginosa in bronchiectasis: infection, inflammation, and therapies

Introduction: Bronchiectasis is a chronic endobronchial suppurative disease characterized by irreversibly dilated bronchi damaged by repeated polymicrobial infections and predominantly, neutrophilic airway inflammation. Some consider bronchiectasis a syndromic consequence of several different causes whilst others view it as an individual disease entity. In most patients, identifying an underlying cause remains challenging. The acquisition and colonization of affected airways by Pseudomonas aeruginosa represent a critical and adverse clinical consequence for its progression and management.Areas covered: In this review, we outline clinical and pre-clinical peer-reviewed research published in the last 5 years, focusing on the pathogenesis of bronchiectasis and the role of P. aeruginosa and its virulence in shaping host inflammatory and immune responses in the airway. We further detail its role in airway infection, the lung microbiome, and address therapeutic options in bronchiectasis.Expert opinion: P. aeruginosa represents a key pulmonary pathogen in bronchiectasis that causes acute and/or chronic airway infection. Eradication can prevent adverse clinical consequence and/or disease progression. Novel therapeutic strategies are emerging and include combination-based approaches. Addressing airway infection caused by P. aeruginosa in bronchiectasis is necessary to prevent airway damage, loss of lung function and exacerbations, all of which contribute to adverse clinical outcome.

Pseudomonas aeruginosa elastase (LasB) as a therapeutic target

Why is P. aeruginosa LasB elastase an attractive target for antivirulence therapy and what is the state-of-the art in LasB inhibitor design and development?