Bacterial lipids: powerful modifiers of the innate immune response

Comprehensive lipidomic analysis of the genus Cutibacterium

Cutibacterium are part of the human skin microbiota and are opportunistic microorganisms that become pathogenic in immunodeficient states. These lipophilic bacteria willingly inhabit areas of the skin where sebaceous glands are abundant; hence, there is a need to thoroughly understand their metabolism. Lipids are no longer considered only structural elements but also serve as signaling molecules and may have antigenic properties. Lipidomics remains a major research challenge, mainly due to the diverse physicochemical properties of lipids. Therefore, this study aimed to perform a large comparative lipidomic analysis of eight representatives of the Cutibacterium genus, including four phylotypes of C. acnes and two strains of C. granulosum, C. avidum, and C. namnetense. Lipidomic analysis was performed by liquid chromatography‒mass spectrometry (LC-MS) in both positive and negative ion modes, allowing the detection of the widest range of metabolites. Fatty acid analysis by gas chromatography‒mass spectrometry (GC-MS) corroborated the lipidomic data. As a result, 128 lipids were identified, among which it was possible to select marker compounds, some of which were characteristic even of individual C. acnes phylotypes. These include phosphatidylcholine PC 30:0, sphingomyelins (SM 33:1, SM 35:1), and phosphatidylglycerol with an alkyl ether substituent PG O-32:0. Moreover, cardiolipins and fatty acid amides were identified in Cutibacterium spp. for the first time. This comparative characterization of the cutibacterial lipidome with the search for specific molecular markers reveals its diagnostic potential for clinical microbiology.

IMPORTANCE

Cutibacterium (previously Propionibacterium) represents an important part of the human skin microbiota, and its role in clinical microbiology is growing due to opportunistic infections. Lipidomics, apart from protein profiling, has the potential to prove to be a useful tool for defining the cellular fingerprint, allowing for precise differentiation of microorganisms. In this work, we presented a comparative analysis of lipids found in eight strains of the genus Cutibacterium, including a few C. acnes phylotypes. Our results are one of the first large-scale comprehensive studies regarding the bacterial lipidome, which also enabled the selection of C. acnes phylotype-specific lipid markers. The increased role of lipids not only as structural components but also as diagnostic markers or potential antigens has led to new lipid markers that can be used as diagnostic tools for clinical microbiology. We believe that the findings in our paper will appeal to a wide range of researchers.

Impact of a varied set of stimuli on a suite of immunological parameters within peripheral blood mononuclear cells: toward a non-animal approach for assessing immune modulation by materials intended for human use

Introduction: In toxicology, steps are being taken towards more mechanism-focused and human relevant approaches to risk assessment, requiring new approaches and methods. Additionally, there is increasing emphasis by regulators on risk assessment of immunotoxicity. Methods: Here we present data from a peripheral blood mononuclear cell (PBMC) system whereby a varied set of stimuli, including those against the TCR and Toll-like receptors, enable readouts of cytokine and prostaglandin E2 (PGE2) production with monocyte, T cell and B cell viability, proliferation, and associated activation markers. In addition to results on the impact of the stimuli used, initial profiling data for a case study chemical, curcumin, is presented, illustrating how the system can be used to generate information on the impact of exogenous materials on three major constituent immune cell subsets for use in risk assessment and to direct follow-on studies. Results: The different stimuli drove distinct responses, not only in relation to the "quantity" of the response but also the "quality". Curcumin had a limited impact on the B cell parameters measured, with the stimuli used, and it was noted that in contrast to T cells where there was either no impact or a reduction in viability and proliferation with increasing concentration, for B cells there was a small but significant increase in both measurements at curcumin concentrations below 20 µM. Similarly, whilst expression of activation markers by T cells was reduced by the highest concentration of curcumin, they were increased in B cells. Curcumin only impacted the viability of stimulated monocytes at the highest concentration and had differential impact on different activation markers. Levels of all cytokines and PGE2 were reduced at higher concentrations. Discussion: Although the platform has certain limitations, it nevertheless enables assessment of healthy baseline monocyte, T-, and B-cell responses, and scrutiny of the impact of different stimuli to detect potential immune suppression or enhancement from exogenous materials. In the case of curcumin, a pattern of responses indicative of immune suppressive / anti-inflammatory effects was detected. It is an accessible, highly modifiable system that can be used to screen materials and guide further studies, providing a holistic, integrated picture of effects.

Multiple stage linear ion-trap mass spectrometry toward characterization of native bacterial lipids-a critical review

Great strides in the field of lipidomics driven by advances in mass spectrometry techniques in the last decade have moved lipid analysis to a new level and significantly improved our understanding of lipid biochemistry. Multiple stage mass spectrometry (MSn) with high resolution mass spectrometry (HRMS) that allows sequential isolation, fragmentation, and recognition of ion structures, is a powerful tool for characterization of complex and diversified lipid in bacterial cells, in which lipids are often critical for cell aggregation and dissociation, and play important biological roles. In addition to common phospholipids, many bacteria contain unique lipids that are specific to the bacterium genus and even to the bacterium species. In this review, application of linear ion-trap (LIT) MSn in the structural characterization of native bacterial lipids including (1) novel lipids consisting of many isomeric structures, (2) lipids with unique functional groups and modification, (3) complex sphingolipids, peptidolipids, and lipocyclopeptides from various bacteria are presented. LIT MSn approach affords realization of the mechanisms underlying the fragmentation processes, resulting in identification of complex lipid structures that would be very difficult to define using other analytical methods.

Immulina as an Immunostimulatory Supplement: Formulation and Pharmacological Studies

Immulina is a commercially available extract of Arthrospira platensis enriched with bacterial lipoproteins that acts as a potent Toll-like receptor 2 agonist. However, the immunostimulatory effect of Immulina is not well understood in vivo. Here, to devise an Immulina formulation suitable for in vivo oral gavage dosing, Immulina nanosuspension was prepared and freeze-dried to yield lyophilized nano-Immulina, which had an average particle size of around 300 nm and fully retained the bioactivity as a Toll-like receptor 2 agonist. Compared to the regular Immulina powder, lyophilized nano-Immulina notably accelerated the dissolution in aqueous media. Immulina nanosuspension was found to stimulate the production of proinflammatory cytokines in murine bone marrow-derived dendritic cells and macrophages. The immune response to Immulina was investigated in healthy mice by longitudinally monitoring the phagocytic activity of circulating neutrophils as a surrogate marker. Following daily oral ingestion of Immulina nanosuspension (10 mg/mouse/day), the phagocytic activity of circulating neutrophils was significantly elevated, suggesting an important mechanism for Immulina to enhance innate immunity.

Role of Legionella pneumophila outer membrane vesicles in host-pathogen interaction

Legionella pneumophila is an opportunistic intracellular pathogen that inhabits artificial water systems and can be transmitted to human hosts by contaminated aerosols. Upon inhalation, it colonizes and grows inside the alveolar macrophages and causes Legionnaires' disease. To effectively control and manage Legionnaires' disease, a deep understanding of the host-pathogen interaction is crucial. Bacterial extracellular vesicles, particularly outer membrane vesicles (OMVs) have emerged as mediators of intercellular communication between bacteria and host cells. These OMVs carry a diverse cargo, including proteins, toxins, virulence factors, and nucleic acids. OMVs play a pivotal role in disease pathogenesis by helping bacteria in colonization, delivering virulence factors into host cells, and modulating host immune responses. This review highlights the role of OMVs in the context of host-pathogen interaction shedding light on the pathogenesis of L. pneumophila. Understanding the functions of OMVs and their cargo provides valuable insights into potential therapeutic targets and interventions for combating Legionnaires' disease.

The Role of Lipids in the Regulation of Immune Responses

Lipid metabolism plays a major role in the regulation of the immune system. Exogenous (dietary and microbial-derived) and endogenous (non-microbial-derived) lipids play a direct role in regulating immune cell activation, differentiation and expansion, and inflammatory phenotypes. Understanding the complexities of lipid-immune interactions may have important implications for human health, as certain lipids or immune pathways may be beneficial in circumstances of acute infection yet detrimental in chronic inflammatory diseases. Further, there are key differences in the lipid effects between specific immune cell types and location (e.g., gut mucosal vs. systemic immune cells), suggesting that the immunomodulatory properties of lipids may be tissue-compartment-specific, although the direct effect of dietary lipids on the mucosal immune system warrants further investigation. Importantly, there is recent evidence to suggest that lipid-immune interactions are dependent on sex, metabolic status, and the gut microbiome in preclinical models. While the lipid-immune relationship has not been adequately established in/translated to humans, research is warranted to evaluate the differences in lipid-immune interactions across individuals and whether the optimization of lipid-immune interactions requires precision nutrition approaches to mitigate or manage disease. In this review, we discuss the mechanisms by which lipids regulate immune responses and the influence of dietary lipids on these processes, highlighting compelling areas for future research.

Exploring the Molecular Dynamics of a Lipid-A Vesicle at the Atom Level: Morphology and Permeation Mechanism

Lipid-A was previously shown to spontaneously aggregate into a vesicle via the hybrid particle field approach. We assess the validity of the proposed vesiculation mechanism by simulating the resulting lipid-A vesicle at the atom level. The spatial confinement imposed by the vesicle geometry on the conformation and packing of lipid-A induces significant heterogeneity of physical properties in the inner and outer leaflets. It also induces tighter molecular packing and lower acyl chain order compared to the lamellar arrangement. Around 5% of water molecules passively permeates the vesicle membrane inward and outward. The permeation is facilitated by interactions with water molecules that are transported across the membrane by a network of electrostatic interactions with the hydrogen bond donors/acceptors in the N-acetylglucosamine ring and upper region of the acyl chains of lipid-A. The permeation process takes place at low rates but still at higher frequencies than observed for the lamellar arrangement of lipid-A. These findings not only substantiate the proposed lipid-A vesiculation mechanism but also reveal the complex structural dynamics of an important nonlamellar arrangement of lipid-A.

Probiotics and Postbiotics as an Alternative to Antibiotics: An Emphasis on Pigs

Probiotics are being used as feed/food supplements as an alternative to antibiotics. It has been demonstrated that probiotics provide several health benefits, including preventing diarrhea, irritable bowel syndrome, and immunomodulation. Alongside probiotic bacteria-fermented foods, the different structural components, such as lipoteichoic acids, teichoic acids, peptidoglycans, and surface-layer proteins, offer several advantages. Probiotics can produce different antimicrobial components, enzymes, peptides, vitamins, and exopolysaccharides. Besides live probiotics, there has been growing interest in consuming inactivated probiotics in farm animals, including pigs. Several reports have shown that live and killed probiotics can boost immunity, modulate intestinal microbiota, improve feed efficiency and growth performance, and decrease the incidence of diarrhea, positioning them as an interesting strategy as a potential feed supplement for pigs. Therefore, effective selection and approach to the use of probiotics might provide essential features of using probiotics as an important functional feed for pigs. This review aimed to systematically investigate the potential effects of lactic acid bacteria in their live and inactivated forms on pigs.

Gut microbiome lipid metabolism and its impact on host physiology

Metabolites produced by commensal gut microbes impact host health through their recognition by the immune system and their influence on numerous metabolic pathways. Notably, the gut microbiota can both transform and synthesize lipids as well as break down dietary lipids to generate secondary metabolites with host modulatory properties. Although lipids have largely been consigned to structural roles, particularly in cell membranes, recent research has led to an increased appreciation of their signaling activities, with potential impacts on host health and physiology. This review focuses on studies that highlight the functions of bioactive lipids in mammalian physiology, with a special emphasis on immunity and metabolism.

Evidence on the Preventive Effects of the Postbiotic Derived from Cow's Milk Fermentation with Lacticaseibacillus paracasei CBA L74 against Pediatric Gastrointestinal Infections

Postbiotics are commonly defined as preparations of inanimate probiotics and/or their cellular components and/or their metabolites/end products that confer health benefits on the host. They have been suggested as a promising strategy to limit infectious diseases. Emerging evidence support the efficacy of the postbiotic derived from cow's milk fermentation with the probiotic Lacticaseibacillus paracasei CBAL74 (FM-CBAL74) in preventing pediatric infectious diseases. We aimed at reviewing the evidence available.

A Sensitive GC-MS Method for Quantitation of Lipid A Backbone Components and Terminal Phosphate Modifications

Lipid A, the hydrophobic anchor of lipopolysaccharide (LPS) present in the outer membrane of Gram-negative bacteria, serves as a target for cationic antimicrobial peptides, such as polymyxins. Membrane stress from polymyxins results in activation of two-component regulatory systems that produce lipid A modifying enzymes. These enzymes add neutral moieties, such as aminoarabinose (AraN) and ethanolamine (EtN) to lipid A terminal phosphates that mask the phosphate's negative charge and inhibit electrostatic interaction with the cationic polymyxins. Currently, these modifications may be detected by MALDI-TOF MS; however, this analysis is only semiquantitative. Herein we describe a GC-MS method to quantitate lipid A backbone components, glucosamine (GlcN) and inorganic phosphate (Pi), along with terminal phosphate modifications AraN and EtN. In this assay, lipid A is isolated from Gram-negative bacterial samples, hydrolyzed into its individual moieties, and derivatized via methoximation followed by silylation prior to analysis via GC-MS. Changes in AraN and EtN quantity were characterized using a variety of regulatory mutants of Salmonella, revealing differences that were not detected using MALDI-TOF MS analysis. Additionally, an increase in the abundance of AraN and EtN modifications were observed when resistant Enterobacter and Escherichia coli strains were grown in the presence of colistin (polymyxin E). Lastly, increased levels of Pi were found in bisphosphorylated lipid A compared to monophosphorylated lipid A samples. Because lipid A modifications serve as indicators of polymyxin resistance in Gram-negative bacteria, this method provides the capacity to monitor polymyxin resistance by quantification of lipid A modification using GC-MS.

Outer Membrane Vesicles: An Emerging Vaccine Platform

Vaccine adjuvants are substances that improve the immune capacity of a recombinant vaccine to a great extent and have been in use since the early 1900s; they are primarily short-lived and initiate antigen activity, mainly an inflammatory response. With the developing technologies and innovation, early options such as alum were modified, yet the inorganic nature of major vaccine adjuvants caused several side effects. Outer membrane vesicles, which respond to the stressed environment, are small nano-sized particles secreted by gram-negative bacteria. The secretory nature of OMV gives us many benefits in terms of infection bioengineering. This article aims to provide a detailed overview of bacteria's outer membrane vesicles (OMV) and their potential usage as adjuvants in making OMV-based vaccines. The OMV adjuvant-based vaccines can be a great benefactor, and there are ongoing trials for formulating OMV adjuvant-based vaccines for SARS-CoV-2. This study emphasizes engineering the OMVs to develop better versions for safety purposes. This article will also provide a gist about the advantages and disadvantages of such vaccines, along with other aspects.

Reversing BCG-mediated autophagy inhibition and mycobacterial survival to improve vaccine efficacy

Background

Autophagy is an important mechanism for promoting Mycobacterium clearance from macrophages. Pathogenic and non-pathogenic mycobacterium can activate the mTOR pathway while simultaneously inducing autophagy. M. tuberculosis and M. bovis BCG inhibit autophagy and favor intracellular bacteria survival.

Results

We observed that pre-infection of live or heat-killed BCG could prevent autophagy induced by pharmacological activators or M. smegmatis, a strong autophagy-inducing mycobacterium. BCG-derived lipids are responsible for autophagy inhibition. However, post-infection with BCG could not stop the autophagy initiated by M. smegmatis, which increases further autophagy induction and mycobacteria clearance. Coinfection with BCG and heat killed M. smegmatis enhanced antigen specific CD4⁺ T cell responses and reduced mycobacterial survival.

Conclusion

These results suggest that autophagy-inducing M. smegmatis could be used to promote better innate and consequential adaptive immune responses, improving BCG vaccine efficacy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12865-022-00518-z.

Rhodococcus equi-Derived Extracellular Vesicles Promoting Inflammatory Response in Macrophage through TLR2-NF-κB/MAPK Pathways

Rhodococcus equi (R. equi) is a Gram-positive coccobacillus that causes pneumonia in foals of less than 3 months, which have the ability of replication in macrophages. The ability of R. equi persist in macrophages is dependent on the virulence plasmid pVAPA. Gram-positive extracellular vesicles (EVs) carry a variety of virulence factors and play an important role in pathogenic infection. There are few studies on R. equi-derived EVs (R. equi-EVs), and little knowledge regarding the mechanisms of how R. equi-EVs communicate with the host cell. In this study, we examine the properties of EVs produced by the virulence strain R. equi 103+ (103+-EVs) and avirulenct strain R. equi 103− (103−-EVs). We observed that 103+-EVs and 103−-EVs are similar to other Gram-positive extracellular vesicles, which range from 40 to 260 nm in diameter. The 103+-EVs or 103−-EVs could be taken up by mouse macrophage J774A.1 and cause macrophage cytotoxicity. Incubation of 103+-EVs or 103−-EVs with J774A.1 cells would result in increased expression levels of IL-1β, IL-6, and TNF-α. Moreover, the expression of TLR2, p-NF-κB, p-p38, and p-ERK were significantly increased in J774A.1 cells stimulated with R. equi-EVs. In addition, we presented that the level of inflammatory factors and expression of TLR2, p-NF-κB, p-p38, and p-ERK in J774A.1 cells showed a significant decreased when incubation with proteinase K pretreated-R. equi-EVs. Overall, our data indicate that R. equi-derived EVs are capable of mediating inflammatory responses in macrophages via TLR2-NF-κB/MAPK pathways, and R. equi-EVs proteins were responsible for TLR2-NF-κB/MAPK mediated inflammatory responses in macrophage. Our study is the first to reveal potential roles for R. equi-EVs in immune response in R. equi-host interactions and to compare the differences in macrophage inflammatory responses mediated by EVs derived from virulent strain R. equi and avirulent strain R. equi. The results of this study have improved our knowledge of the pathogenicity of R. equi.

Identification and Characterization of a Novel Species of Genus Akkermansia with Metabolic Health Effects in a Diet-Induced Obesity Mouse Model

Akkermansia muciniphila is a well-known bacterium with the ability to degrade mucin. This metabolic capability is believed to play an important role in the colonization of this bacterium in the gut. In this study, we report the identification and characterization of a novel Akkermansia sp. DSM 33459 isolated from human feces of a healthy donor. Phylogenetic analysis based on the genome-wide average nucleotide identity indicated that the Akkermansia sp. DSM 33459 has only 87.5% similarity with the type strain A. muciniphila ATCC BAA-835. Akkermansia sp. DSM 33459 showed significant differences in its fatty acid profile and carbon utilization as compared to the type strain. The Akkermansia sp. DSM 33459 strain was tested in a preclinical obesity model to determine its effect on metabolic markers. Akkermansia sp. DSM 33459 showed significant improvement in body weight, total fat weight, and resistin and insulin levels. Interestingly, these effects were more pronounced with the live form as compared to a pasteurized form of the strain. The strain showed production of agmatine, suggesting a potential novel mechanism for supporting metabolic and cognitive health. Based on its phenotypic features and phylogenetic position, it is proposed that this isolate represents a novel species in the genus Akkermansia and a promising therapeutic candidate for the management of metabolic diseases.

Acinetobacter baumannii Secretes a Bioactive Lipid That Triggers Inflammatory Signaling and Cell Death

Acinetobacter baumannii is a highly pathogenic Gram-negative bacterium that causes severe infections with very high fatality rates. A. baumannii infection triggers innate as well as adaptive immunity, however, our understanding of the inflammatory factors secreted by A. baumannii that alarm the immune system remains limited. In this study, we report that the lab adapted and clinical strains of A. baumannii secrete an inflammatory bioactive factor which activates TLR2, leading to canonical IRAK4-dependent NF-κB signaling and production of pro-inflammatory cytokines interleukin (IL)-6 and IL-8 and activation of the inflammasome pathway causing pyroptotic cell death. Biochemical fractionation of the A. baumannii culture filtrate revealed the hydrophobic nature of the inflammatory factor. Concordantly, lipase treatment of the culture filtrate or TLR2 inhibition in macrophages abrogated NF-κB activation and cell death induction. Culture filtrates from the LPS- and lipoprotein-deficient A. baumannii mutants retain immuno-stimulatory properties suggesting that a lipid other than these known stimulatory molecules can trigger inflammation during A. baumannii infection. Our results reveal that A. baumannii secretes a previously unappreciated inflammatory bioactive lipid that activates multiple pro-inflammatory signaling pathways and induces cell death in human and murine macrophages.

Ex vivo 1H-MRS brain metabolic profiling in a two-hit model of neurodevelopmental disorders: Prenatal immune activation and peripubertal stress

Prenatal infections are environmental risk factors for neurodevelopmental disorders. In addition, traumatic experiences during adolescence in individuals exposed to infections during gestation could increase the risk of schizophrenia. It is of the most crucial importance to discover potential markers of the disease in its early stages or before its onset, so that therapeutic strategies may be implemented. In the present study, we combined a proposed two-hit model of schizophrenia-related symptoms with proton magnetic resonance spectroscopy (¹H-MRS) to discover potential biomarkers. To this end, we i.p. injected 100 μg/kg/ml of lipopolysaccharide (LPS) or saline on gestational days 15 and 16 to pregnant rats. Their male offspring were then subjected to five episodes of stress or handling on alternate days during postnatal days (PND) 28-38. Once the animals reached adulthood (PND70), we evaluated prepulse inhibition (PPI). At PND90, we performed an ex vivo ¹H-MRS study in the cortex and striatum. While we did not detect alterations in PPI at the age tested, we found neurochemical disturbances induced by LPS, stress or (more interestingly) their interaction. LPS decreased glucose levels in the cortex and striatum and altered glutamate, glutamine and N-acetylaspartate levels. Glutamate and glutamine levels in the left (but not right) striatum were differentially affected by prenatal LPS exposure in a manner that depended on stress experiences. These results suggest that alterations in the glutamate cycle in the striatum could be used as early markers of developmental disorders.

Towards the prediction of non-peptidic epitopes

In-silico methods for the prediction of epitopes can support and improve workflows for vaccine design, antibody production, and disease therapy. So far, the scope of B cell and T cell epitope prediction has been directed exclusively towards peptidic antigens. Nevertheless, various non-peptidic molecular classes can be recognized by immune cells. These compounds have not been systematically studied yet, and prediction approaches are lacking. The ability to predict the epitope activity of non-peptidic compounds could have vast implications; for example, for immunogenic risk assessment of the vast number of drugs and other xenobiotics. Here we present the first general attempt to predict the epitope activity of non-peptidic compounds using the Immune Epitope Database (IEDB) as a source for positive samples. The molecules stored in the Chemical Entities of Biological Interest (ChEBI) database were chosen as background samples. The molecules were clustered into eight homogeneous molecular groups, and classifiers were built for each cluster with the aim of separating the epitopes from the background. Different molecular feature encoding schemes and machine learning models were compared against each other. For those models where a high performance could be achieved based on simple decision rules, the molecular features were then further investigated. Additionally, the findings were used to build a web server that allows for the immunogenic investigation of non-peptidic molecules (http://tools-staging.iedb.org/np_epitope_predictor). The prediction quality was tested with samples from independent evaluation datasets, and the implemented method received noteworthy Receiver Operating Characteristic-Area Under Curve (ROC-AUC) values, ranging from 0.69–0.96 depending on the molecule cluster.

Small molecules found in cosmetics, foodstuffs, dyes, and industrial materials, but also those produced by plants, bacteria, and animals can trigger strong reactions of the human immune system and can therefore be hazardous to health. In the present work, several thousand immune-reactive small molecules (so-called non-peptidic epitopes) were classified by molecular structure and studied with the aim of identifying specific parts of the molecules responsible for such immune responses. Using a machine-learning approach (random forests and neural networks), we identified some substructures that appear strikingly often in non-peptidic epitopes and which may be responsible for the hazardous immune response. Such knowledge may help to explain allergic reactions to chemicals and also to minimize the health risks of new chemicals in industrial production. To support this endeavor, we have implemented the method in a publicly available web application. This can be used for the prediction and identification of non-peptidic epitopes and their underlying substructures.

Interplay between Dysbiosis of Gut Microbiome, Lipid Metabolism, and Tumorigenesis: Can Gut Dysbiosis Stand as a Prognostic Marker in Cancer?

The gut bacterial community is involved in the metabolism of bile acids and short-chain fatty acids (SCFAs). Bile acids are involved in the absorption of fat and the regulation of lipid homeostasis through emulsification and are transformed into unconjugated bile acids by the gut microbiota. The gut microbiota is actively involved in the production of bile acid metabolites, such as deoxycholic acid, lithocholic acid, choline, and SCFAs such as acetate, butyrate, and propionate. Metabolites derived from the gut microbiota or modified gut microbiota metabolites contribute significantly to host pathophysiology. Gut bacterial metabolites, such as deoxycholic acid, contribute to the development of hepatocellular carcinoma and colon cancer by factors such as inflammation and oxidative DNA damage. Butyrate, which is derived from gut bacteria such as Megasphaera, Roseburia, Faecalibacterium, and Clostridium, is associated with the activation of Treg cell differentiation in the intestine through histone acetylation. Butyrate averts the action of class I histone deacetylases (HDAC), such as HDAC1 and HDAC3, which are responsible for the transcription of genes such as p21/Cip1, and cyclin D3 through hyperacetylation of histones, which orchestrates G1 cell cycle arrest. It is essential to identify the interaction between the gut microbiota and bile acid and SCFA metabolism to understand their role in gastrointestinal carcinogenesis including colon, gastric, and liver cancer. Metagenomic approaches with bioinformatic analyses are used to identify the bacterial species in the metabolism of bile acids and SCFAs. This review provides an overview of the current knowledge of gut microbiota-derived bile acid metabolism in tumor development and whether it can stand as a marker for carcinogenesis. Additionally, this review assesses the evidence of gut microbiota-derived short-chain fatty acids including butyric acid in antitumor activity. Future research is required to identify the beneficial commensal gut bacteria and their metabolites which will be considered to be therapeutic targets in inflammation-mediated gastrointestinal cancers.

A Mathematical Model of the Dynamics of Cytokine Expression and Human Immune Cell Activation in Response to the Pathogen Staphylococcus aureus

Cell-based mathematical models have previously been developed to simulate the immune system in response to pathogens. Mathematical modeling papers which study the human immune response to pathogens have predicted concentrations of a variety of cells, including activated and resting macrophages, plasma cells, and antibodies. This study aims to create a comprehensive mathematical model that can predict cytokine levels in response to a gram-positive bacterium, S. aureus by coupling previous models. To accomplish this, the cytokines Tumor Necrosis Factor Alpha (TNF-α), Interleukin 6 (IL-6), Interleukin 8 (IL-8), and Interleukin 10 (IL-10) are included to quantify the relationship between cytokine release from macrophages and the concentration of the pathogen, S. aureus, ex vivo. Partial differential equations (PDEs) are used to model cellular response and ordinary differential equations (ODEs) are used to model cytokine response, and interactions between both components produce a more robust and more complete systems-level understanding of immune activation. In the coupled cellular and cytokine model outlined in this paper, a low concentration of S. aureus is used to stimulate the measured cellular response and cytokine expression. Results show that our cellular activation and cytokine expression model characterizing septic conditions can predict ex vivo mechanisms in response to gram-negative and gram-positive bacteria. Our simulations provide new insights into how the human immune system responds to infections from different pathogens. Novel applications of these insights help in the development of more powerful tools and protocols in infection biology.

Recent advances in the mass spectrometric profiling of bacterial lipids

Exploring the lipids of bacteria presents a predicament that may not be broadly recognized in a field dominated by the biology and biochemistry of eukaryotic - and especially, mammalian - lipids. Bacteria make multifarious metabolites that contain fatty acyl chains of unusual length and unsaturation attached to assorted headgroups, including sugars and fatty alcohols. Lipid profiling approaches developed for eukaryotic lipids often fail to detect, resolve, or identify bacterial lipids due to their wide range of polarities (including very hydrophobic species) and diverse positional and stereochemical variations. Global lipid profiling, or lipidomics, of bacteria has thus developed as a separate mission with methodological and scientific considerations tailored to the biology of these organisms. In this review, we summarize findings primarily from the last three years that exemplify recent advances and continuing challenges to learning about bacterial lipids.

The role played by bacterial infections in the onset and metastasis of cancer

Understanding various responses of cells towards change in their external environment, presence of other species and is important in identifying and correlating the mechanisms leading to malignant transformations and cancer development. Although uncovering and comprehending the association between bacteria and cancer is highly challenging, it promises excellent perspectives and approaches for successful cancer therapy. This review introduces various bacterial species, their virulence factors, and their role in cell transformations leading to cancer (particularly gastric, oral, colon, and breast cancer). Bacterial dysbiosis permutates host cells, causes inflammation, and results in tumorigenesis. This review explored bacterial-mediated host cell transformation causing chronic inflammation, immune receptor hyperactivation/absconding immune recognition, and genomic instability. Bacterial infections downregulate E-cadherin, leading to loosening of epithelial tight junction polarity and triggers metastasis. In addition to understanding the role of bacterial infections in cancer development, we have also reviewed the application of bacteria for cancer therapy. The emergence of bacteriotherapy combined with conventional therapies led to new and effective ways of overcoming challenges associated with available treatments. This review discusses the application of bacterial minicells, microswimmers, and outer cell membrane vesicles (OMV) for drug delivery applications.

Allergic Diseases: A Comprehensive Review on Risk Factors, Immunological Mechanisms, Link with COVID-19, Potential Treatments, and Role of Allergen Bioinformatics

The prevalence of allergic diseases is regarded as one of the key challenges in health worldwide. Although the precise mechanisms underlying this rapid increase in prevalence are unknown, emerging evidence suggests that genetic and environmental factors play a significant role. The immune system, microbiota, viruses, and bacteria have all been linked to the onset of allergy disorders in recent years. Avoiding allergen exposure is the best treatment option; however, steroids, antihistamines, and other symptom-relieving drugs are also used. Allergen bioinformatics encompasses both computational tools/methods and allergen-related data resources for managing, archiving, and analyzing allergological data. This study highlights allergy-promoting mechanisms, algorithms, and concepts in allergen bioinformatics, as well as major areas for future research in the field of allergology.

Chemically Synthesized Alcaligenes Lipid A as an Adjuvant to Augment Immune Responses to Haemophilus Influenzae Type B Conjugate Vaccine

We previously identified Alcaligenes spp. as a commensal bacterium that resides in lymphoid tissues, including Peyer’s patches. We found that Alcaligenes-derived lipopolysaccharide acted as a weak agonist of Toll-like receptor four due to the unique structure of lipid A, which lies in the core of lipopolysaccharide. This feature allowed the use of chemically synthesized Alcaligenes lipid A as a safe synthetic vaccine adjuvant that induces Th17 polarization to enhance systemic IgG and respiratory IgA responses to T-cell–dependent antigens (e.g., ovalbumin and pneumococcal surface protein A) without excessive inflammation. Here, we examined the adjuvant activity of Alcaligenes lipid A on a Haemophilus influenzae B conjugate vaccine that contains capsular polysaccharide polyribosyl ribitol phosphate (PRP), a T-cell–independent antigen, conjugated with the T-cell–dependent tetanus toxoid (TT) antigen (i.e., PRP-TT). When mice were subcutaneously immunized with PRP alone or mixed with TT, Alcaligenes lipid A did not affect PRP-specific IgG production. In contrast, PRP-specific serum IgG responses were enhanced when mice were immunized with PRP-TT, but these responses were impaired in similarly immunized T-cell—deficient nude mice. Furthermore, TT-specific—but not PRP-specific—T-cell activation occurred in mice immunized with PRP-TT together with Alcaligenes lipid A. In addition, coculture with Alcaligenes lipid A promoted significant proliferation of and enhanced antibody production by B cells. Together, these findings suggest that Alcaligenes lipid A exerts an adjuvant activity on thymus-independent Hib polysaccharide antigen in the presence of a T-cell–dependent conjugate carrier antigen.

Bacterial Ghosts-Based Vaccine and Drug Delivery Systems

Bacterial ghosts (BGs) are empty bacterial envelopes of Gram-negative bacteria produced by controlled expressions of cloned gene E, forming a lysis tunnel structure within the envelope of the living bacteria. Globally, BGs have been used as vaccine delivery systems and vaccine adjuvants. There is an increasing interest in the development of novel delivery systems that are based on BGs for biomedical applications. Due to intact reservation of bacterial cell membranes, BGs have an inherent immunogenicity, which enables targeted drug delivery and controlled release. As carrier vehicles, BGs protect drugs from interference by external factors. In recent years, there has been an increasing interest in BG-based delivery systems against tumors, inflammation, and infection, among others. Herein, we reviewed the preparation methods for BGs, interactions between BGs and the host, and further highlighted research progress in BG development.

Extracellular vesicles derived from the periodontal pathogen Filifactor alocis induce systemic bone loss through Toll-like receptor 2

Periodontitis is an inflammatory disease induced by local infection in tooth-supporting tissue. Periodontitis is associated with systemic bone diseases, but little is known about the mechanism of the causal effect of periodontitis on systemic bone resorption. Bacteria-derived extracellular vesicles (EVs) act as natural carriers of virulence factors that are responsible for systemic inflammation. In this study, we investigated the role of EVs derived from Filifactor alocis, a Gram-positive, anaerobic periodontal pathogen, in systemic bone loss and osteoclast differentiation. F. alocis EVs accumulated in the long bones of mice after intraperitoneal administration. These EVs induced proinflammatory cytokines, osteoclastogenesis, and bone resorption via Toll-like receptor 2 (TLR2). The phase separation of F. alocis EVs showed that amphiphilic molecules were responsible for the induced bone resorption and osteoclastogenesis. The osteoclastogenic effects of F. alocis EVs were reduced by lipoprotein lipase. Proteomic analysis of the amphiphilic molecules identified seven lipoproteins. Our results indicate that lipoprotein-like molecules in F. alocis EVs may contribute to systemic bone loss via TLR2.

Baicalin relieves Mycoplasma pneumoniae infection‑induced lung injury through regulating microRNA‑221 to inhibit the TLR4/NF‑κB signaling pathway

Mycoplasma pneumoniae (MP) is a common pathogen that can cause respiratory infections. MP pneumonia (MPP) leads to numerous complications, including lung injury and even death. The present study aimed to investigate the protective effects of Baicalin treatment on MP infection‑induced lung injury and the molecular mechanism underlying these effects. Briefly, after mice were infected intranasally by MP and treated with Baicalin (80 mg/kg), serum levels of MP‑immunoglobulin M (IgM) were detected by ELISA. The expression levels of C‑reactive protein (CRP) in lung tissue were detected by immunohistochemistry and the bronchoalveolar lavage fluid (BALF) was examined by ELISA. Inflammatory factors and inflammatory cells in the BALF were assessed. The expression levels of microRNA (miR)‑221 in lung tissue were examined by reverse transcription‑quantitative PCR and pathological changes in lung tissue were detected by H&E staining. Cell apoptosis was evaluated by TUNEL assay and the protein expression levels of TLR4, MyD88 and NF‑κB were detected by western blotting. Baicalin treatment significantly reduced serum levels of MP‑IgM and CRP expression in lung tissue during MP infection. In addition, Baicalin decreased the levels of IL‑1β, IL‑6, IL‑18 and TNF‑α in the BALF, and the number of inflammatory cells. Baicalin also reduced the inflammatory infiltration in lung tissue induced by MP infection, improved the pathological changes detected in lung tissue, reduced apoptosis, and downregulated the protein expression levels of TLR4, MyD88 and NF‑κB. Furthermore, Baicalin treatment downregulated the expression of miR‑221 and the protective effects of Baicalin were attenuated by miR‑221 overexpression. In conclusion, Baicalin has a therapeutic effect on mice with MP infection‑induced lung injury, which may be related to inhibition of miR‑221 expression and regulation of the TLR4/NF‑κB signaling pathway.

Oral health and longitudinal changes in fasting glucose levels: A nationwide cohort study

We investigated the association between oral hygiene indicators of periodontitis, tooth loss, and tooth brushing on the longitudinal fasting glucose level in non-diabetic subjects. Using a nationwide health screening database in Korea, we included non-diabetic individuals who received a health screening program with oral health check in 2009–2010. We constructed a linear mixed model for the longitudinal data of fasting glucose from the baseline to 2015. During the 4.84-year of median follow-up, 91,963 individuals (mean age 56.2 at baseline) underwent 392,780 health examinations with fasting glucose level (mmol/L). The presence of periodontitis was 39.3%. In the multivariate linear mixed analysis, periodontitis was related with increased fasting glucose levels (β = 0.0084, standard error = 0.0035, p = 0.018). Similarly, tooth loss was associated with increased level of fasting glucose (β = 0.0246, standard error = 0.0038, p < 0.001). Compared with tooth brushing ≤2 times/day, tooth brushing ≥3 times/day was associated with decreased fasting glucose levels (β = -0.0207, standard error = 0.0033, p < 0.001). Our data showed that periodontitis and tooth loss were associated with increased fasting glucose levels in non-diabetic individuals. The study findings imply that frequent tooth brushing may reduce fasting glucose levels. Further research is needed to determine the effect of periodontal intervention on glycemic control.

Modulation of Bovine Endometrial Cell Receptors and Signaling Pathways as a Nanotherapeutic Exploration against Dairy Cow Postpartum Endometritis

Simple Summary

The provision of updated information on the molecular pathogenesis of bovine endometritis with host-pathogen interactions and the possibility of exploring the cellular sensors mechanism in a nanotechnology-based drug delivery system against persistent endometritis were reported in this review. The mechanism of Gram-negative bacteria and their ligands has been vividly explored, with the paucity of research detail on Gram-positive bacteria in bovine endometritis. The function of cell receptors, biomolecules proteins, and sensors were reportedly essential in transferring signals into cell signaling pathways to induce immuno-inflammatory responses by elevating pro-inflammatory cytokines. Therefore, understanding endometrial cellular components and signaling mechanisms across pathogenesis are essential for nanotherapeutic exploration against bovine endometritis. The nanotherapeutic discovery that could inhibit infectious signals at the various cell receptors and signal transduction levels, interfering with transcription factors activation and pro-inflammatory cytokines and gene expression, significantly halts endometritis.

Abstract

In order to control and prevent bovine endometritis, there is a need to understand the molecular pathogenesis of the infectious disease. Bovine endometrium is usually invaded by a massive mobilization of microorganisms, especially bacteria, during postpartum dairy cows. Several reports have implicated the Gram-negative bacteria in the pathogenesis of bovine endometritis, with information dearth on the potentials of Gram-positive bacteria and their endotoxins. The invasive bacteria and their ligands pass through cellular receptors such as TLRs, NLRs, and biomolecular proteins of cells activate the specific receptors, which spontaneously stimulates cellular signaling pathways like MAPK, NF-kB and sequentially triggers upregulation of pro-inflammatory cytokines. The cascade of inflammatory induction involves a dual signaling pathway; the transcription factor NF-κB is released from its inhibitory molecule and can bind to various inflammatory genes promoter. The MAPK pathways are concomitantly activated, leading to specific phosphorylation of the NF-κB. The provision of detailed information on the molecular pathomechanism of bovine endometritis with the interaction between host endometrial cells and invasive bacteria in this review would widen the gap of exploring the potential of receptors and signal transduction pathways in nanotechnology-based drug delivery system. The nanotherapeutic discovery of endometrial cell receptors, signal transduction pathway, and cell biomolecules inhibitors could be developed for strategic inhibition of infectious signals at the various cell receptors and signal transduction levels, interfering on transcription factors activation and pro-inflammatory cytokines and genes expression, which may significantly protect endometrium against postpartum microbial invasion.

PCT Kinetics in the First Week Postburn for Sepsis Diagnosis and Death Prognosis-An Accuracy Study

Despite continuous advances in burn care, sepsis is still the main cause of death in burn patients. Procalcitonin (PCT) has been reported as an accurate sepsis biomarker and also as a fair predictor of death. The aim of this study was to assess PCT kinetics in the first week postburn regarding sepsis diagnosis and death prognosis. Sample included 142 patients with ≥15% TBSA, admitted from January 2011 to December 2014 at Coimbra Burns Unit, Portugal. Sepsis diagnosis was done according to American Burn Association criteria. PCT range and median values in the first 7 days after burns were statistically analyzed for its potential for sepsis diagnosis and death prognosis. A subanalysis was done regarding TBSA, sex, age, and inhalation injury. First week PCT range and median were significant for sepsis diagnosis and death prognosis, but the median area under the curve was greater in the last case. TBSA influenced PCT accuracy, which was greater for TBSA less than 40% either for diagnosis or prognosis. Age was inversely related to the accuracy, being better in younger than 40 years in both cases. PCT diagnostic accuracy was not affected by sex, opposing to the prognostic one which is better in women. Inhalation injury had no effect on diagnostic accuracy, but it happens with prognostic accuracy. PCT levels' variation is related to sepsis evolution and outcome. Its median performs better than its range. Always coupled with clinical examination, monitoring PCT levels kinetics may help early sepsis detection, potentially reducing morbidity and mortality, being also useful for death prognosis.

Fusobacterium nucleatum Extracellular Vesicles Modulate Gut Epithelial Cell Innate Immunity via FomA and TLR2

Extracellular vesicles (EVs) derived from the gut microbiota are largely uncharacterized and their impacts on host intestinal physiology remain unresolved. Here, we isolated EVs from F. nucleatum for detailed characterization. Our analyses highlight the presence of the outer membrane protein porin FomA on EVs. Besides, we evaluated the impact of EVs on human intestinal epithelial cells (IECs) in a non-inflammatory context. Our results show no detrimental impact on the epithelial barrier. No internalization of EVs was observed. Moreover, we demonstrate that F. nucleatum EVs trigger innate immunity of IECs by promoting NF-κB activation via the dynamin-mediated endocytosis. The NF-κB activation was found to be TLR2-dependent yet, TLR4 was dispensable. Using competitive binding assays, we establish that FomA is involved in the NF-κB response. Taken together, our data indicate that EVs induce effects similar to those observed with whole F. nucleatum bacteria on IECs. In particular, our study highlights the role of TLR2 and FomA as major modulators of the gut epithelium immune responses to F. nucleatum.

Bacteriome Structure, Function, and Probiotics in Fish Larviculture: The Good, the Bad, and the Gaps

Aquaculture is the fastest-growing sector in food production worldwide. For decades, research on animal physiology, nutrition, and behavior established the foundations of best practices in land-based fish rearing and disease control. Current DNA sequencing, bioinformatics, and data science technologies now allow deep investigations of host-associated microbiomes in a tractable fashion. Adequate use of these technologies can illuminate microbiome dynamics and aid the engineering of microbiome-based solutions to disease prevention in an unprecedented manner. This review examines molecular studies of bacterial diversity, function, and host immunitymodulation at early stages of fish development, where microbial infections cause important economic losses. We uncover host colonization and virulence factors within a synthetic assemblage of fish pathogens using high-end comparative genomics and address the use of probiotics and paraprobiotics as applicable disease-prevention strategies in fish larval and juvenile rearing. We finally propose guidelines for future microbiome research of presumed relevance to fish larviculture.

Streptococcus gordonii: Pathogenesis and Host Response to Its Cell Wall Components

Streptococcus gordonii, a Gram-positive bacterium, is a commensal bacterium that is commonly found in the skin, oral cavity, and intestine. It is also known as an opportunistic pathogen that can cause local or systemic diseases, such as apical periodontitis and infective endocarditis. S. gordonii, an early colonizer, easily attaches to host tissues, including tooth surfaces and heart valves, forming biofilms. S. gordonii penetrates into root canals and blood streams, subsequently interacting with various host immune and non-immune cells. The cell wall components of S. gordonii, which include lipoteichoic acids, lipoproteins, serine-rich repeat adhesins, peptidoglycans, and cell wall proteins, are recognizable by individual host receptors. They are involved in virulence and immunoregulatory processes causing host inflammatory responses. Therefore, S.gordonii cell wall components act as virulence factors that often progressively develop diseases through overwhelming host responses. This review provides an overview of S. gordonii, and how its cell wall components could contribute to the pathogenesis and development of therapeutic strategies.

Bile Acids: A Communication Channel in the Gut-Brain Axis

Bile acids are signalling hormones involved in the regulation of several metabolic pathways. The ability of bile acids to bind and signal through their receptors is modulated by the gut microbiome, since the microbiome contributes to the regulation and synthesis of bile acids as well to their physiochemical properties. From the gut, bacteria have been shown to send signals to the central nervous system via their metabolites, thus affecting the behaviour and brain function of the host organism. In the last years it has become increasingly evident that bile acids affect brain function, during normal physiological and pathological conditions. Although bile acids may be synthesized locally in the brain, the majority of brain bile acids are taken up from the systemic circulation. Since the composition of the brain bile acid pool may be regulated by the action of intestinal bacteria, it is possible that bile acids function as a communication bridge between the gut microbiome and the brain. However, little is known about the molecular mechanisms and the physiological roles of bile acids in the central nervous system. The possibility that bile acids may be a direct link between the intestinal microbiome and the brain is also an understudied subject. Here we review the influence of gut bacteria on the bile acid pool composition and properties, as well as striking evidence showing the role of bile acids as neuroactive molecules.

Postbiotics against Pathogens Commonly Involved in Pediatric Infectious Diseases

The Sustainable Development goals for 2020 included reducing all causes associated with infant and perinatal mortality in their priorities. The use of compounds with bioactive properties has been proposed as a therapeutic strategy due to their stimulating effect on the host's immune system. Additionally, biotherapeutic products such as postbiotics, tentatively defined as compounds produced during a fermentation process that support health and well-being, promote intestinal barrier integrity without posing considerable risks to children's health. Although this is a concept in development, there are increasing studies in the field of nutrition, chemistry, and health that aim to understand how postbiotics can help prevent different types of infections in priority populations such as minors under the age of five. The present review aims to describe the main mechanisms of action of postbiotics. In addition, it presents the available current evidence regarding the effects of postbiotics against pathogens commonly involved in pediatric infections. Postbiotics may constitute a safe alternative capable of modulating the cellular response and stimulating the host's humoral response.

Inhibition of chikusetsusaponin IVa on inflammatory responses in RAW264.7 cell line via MAPK pathway

Chikusetsusaponin IVa (CHS-IVa), a saponin from herb Panacis japonicas, possesses extensive biological activities. However, the roles and underlying mechanisms of CHS-IVa on inflammation have not been fully clarified in the setting of murine macrophages. In this study, we found that CHS-IVa effectively reduced the expression of inflammatory mediators, including interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), interleukin-10 (IL-10), interleukin-1β (IL-1β), cyclooxygenase (COX-2), inducible nitric oxide synthase (iNOS) in lipopolysaccharide (LPS)-stimulated murine macrophage-like RAW264.7 cells. Meanwhile, CHS-IVa could also evidently bate the contents of nitric oxide (NO) and prostaglandin E2 (PGE2) in cell culture supernatants. Furthermore, the anti-inflammatory activity of CHS-IVa may be via diminishing the phosphorylation of extracellular regulated protein kinases (ERK), p38, and c-Jun N-terminal kinase (JNK). Collectively, these findings will help to understand of the anti-inflammatory effects and mechanisms of P. japonicas deeply, and suggest a validated therapeutic use as an anti-inflammatory medication.

Pairing Bacteroides vulgatus LPS Structure with Its Immunomodulatory Effects on Human Cellular Models

The gut microbiota guide the development of the host immune system by setting a systemic threshold for immune activation. Lipopolysaccharides (LPSs) from gut bacteria are able to trigger systemic and local proinflammatory and immunomodulatory responses, and this capability strongly relies on their fine structures. Up to now, only a few LPS structures from gut commensals have been elucidated; therefore, the molecular motifs that may be important for LPS-mammalian cell interactions at the gut level are still obscure. Here, we report on the full structure of the LPS isolated from one of the prominent species of the genus Bacteroides, Bacteroides vulgatus. The LPS turned out to consist of a particular chemical structure based on hypoacylated and mono-phosphorylated lipid A and with a galactofuranose-containing core oligosaccharide and an O-antigen built up of mannose and rhamnose. The evaluation of the immunological properties of this LPS on human in vitro models revealed a very interesting capability to produce anti-inflammatory cytokines and to induce a synergistic action of MD-2/TLR4- and TLR2-mediated signaling pathways.

Immune System Modulations by Products of the Gut Microbiota

The gut microbiota, which consists of all bacteria, viruses, fungus, and protozoa living in the intestine, and the immune system have co-evolved in a symbiotic relationship since the origin of the immune system. The bacterial community forming the microbiota plays an important role in the regulation of multiple aspects of the immune system. This regulation depends, among other things, on the production of a variety of metabolites by the microbiota. These metabolites range from small molecules to large macro-molecules. All types of immune cells from the host interact with these metabolites resulting in the activation of different pathways, which result in either positive or negative responses. The understanding of these pathways and their modulations will help establish the microbiota as a therapeutic target in the prevention and treatment of a variety of immune-related diseases.

Exogenous Fatty Acids Remodel Staphylococcus aureus Lipid Composition through Fatty Acid Kinase

Staphylococcus aureus can utilize exogenous fatty acids for phospholipid synthesis. The fatty acid kinase FakA is essential for this utilization by phosphorylating exogenous fatty acids for incorporation into lipids. How FakA impacts the lipid membrane composition is unknown. In this study, we used mass spectrometry to determine the membrane lipid composition and properties of S. aureus in the absence of fakA We found the fakA mutant to have increased abundance of lipids containing longer acyl chains. Since S. aureus does not synthesize unsaturated fatty acids, we utilized oleic acid (18:1) to track exogenous fatty acid incorporation into lipids. We observed a concentration-dependent incorporation of exogenous fatty acids into the membrane that required FakA. We also tested how FakA and exogenous fatty acids impact membrane-related physiology and identified changes in membrane potential, cellular respiration, and membrane fluidity. To mimic the host environment, we characterized the lipid composition of wild-type and fakA mutant bacteria grown in mouse skin homogenate. We show that wild-type S. aureus can incorporate exogenous unsaturated fatty acids from host tissue, highlighting the importance of FakA in the presence of host skin tissue. In conclusion, FakA is important for maintaining the composition and properties of the phospholipid membrane in the presence of exogenous fatty acids, impacting overall cell physiology.IMPORTANCE Environmental fatty acids can be harvested to supplement endogenous fatty acid synthesis to produce membranes and circumvent fatty acid biosynthesis inhibitors. However, how the inability to use these fatty acids impacts lipids is unclear. Our results reveal lipid composition changes in response to fatty acid addition and when S. aureus is unable to activate fatty acids through FakA. We identify concentration-dependent utilization of oleic acid that, when combined with previous work, provides evidence that fatty acids can serve as a signal to S. aureus Furthermore, using mouse skin homogenates as a surrogate for in vivo conditions, we showed that S. aureus can incorporate host fatty acids. This study highlights how exogenous fatty acids impact bacterial membrane composition and function.

Outer Membrane Lipid Secretion and the Innate Immune Response to Gram-Negative Bacteria

The outer membrane (OM) of Gram-negative bacteria is an asymmetric lipid bilayer that consists of inner leaflet phospholipids and outer leaflet lipopolysaccharides (LPS). The asymmetric character and unique biochemistry of LPS molecules contribute to the OM's ability to function as a molecular permeability barrier that protects the bacterium against hazards in the environment. Assembly and regulation of the OM have been extensively studied for understanding mechanisms of antibiotic resistance and bacterial defense against host immunity; however, there is little knowledge on how Gram-negative bacteria release their OMs into their environment to manipulate their hosts. Discoveries in bacterial lipid trafficking, OM lipid homeostasis, and host recognition of microbial patterns have shed new light on how microbes secrete OM vesicles (OMVs) to influence inflammation, cell death, and disease pathogenesis. Pathogens release OMVs that contain phospholipids, like cardiolipins, and components of LPS molecules, like lipid A endotoxins. These multiacylated lipid amphiphiles are molecular patterns that are differentially detected by host receptors like the Toll-like receptor 4/myeloid differentiation factor 2 complex (TLR4/MD-2), mouse caspase-11, and human caspases 4 and 5. We discuss how lipid ligands on OMVs engage these pattern recognition receptors on the membranes and in the cytosol of mammalian cells. We then detail how bacteria regulate OM lipid asymmetry, negative membrane curvature, and the phospholipid-to-LPS ratio to control OMV formation. The goal is to highlight intersections between OM lipid regulation and host immunity and to provide working models for how bacterial lipids influence vesicle formation.

Driver Gene Mutations and Epigenetics in Colorectal Cancer

OBJECTIVE

The majority of patients with colorectal cancer are diagnosed with locally advanced and/or disseminated disease, and treatment options include surgery in combination with cytotoxic chemotherapy regimens, biologics, and/or radiotherapy. Thus, colorectal cancer remains a heavy burden on society and health care systems.Mounting evidence show that driver gene mutations play only part of the role in carcinogenesis. Epigenetics are strongly implicated in initiation and progression of colorectal cancer along with major players such as intestinal microbiotic dysbiosis and chronic mucosal inflammation.To assess phenotypic changes in proteins and gene expression, multigene expression signatures based on sequencing techniques have been developed to hopefully improve predictors of the tumor profile, immune response, and therapeutic outcomes. Our objective was to review current advances in the field and to update surgeons and academics on driver gene mutations and epigenetics in colorectal cancer.

BACKGROUND AND METHODS

This is a narrative review studying relevant research published in the PUBMED database from 2012-2018.

RESULTS AND CONCLUSION

Increased understanding of the molecular biology will improve options to characterize colorectal cancer with regard to mutations and molecular pathways, including microsatellite instability, epigenetics, microbiota, and microenvironment. Research will inevitably improve risk group stratification and targeted treatment approaches.Epigenetic profiling and epigenetic modulating drugs will increase risk stratification, increase accessibility for DNA targeting chemotherapeutics and reduce cytotoxic drug resistance.New generation antibiotics such as biofilm inhibitors and quorum sensing inhibitors are being developed to target the carcinogenetic impact of colonic dysbiosis and inflammation.

Acute Phase Response as a Biological Mechanism-of-Action of (Nano)particle-Induced Cardiovascular Disease

Inhaled nanoparticles constitute a potential health hazard due to their size-dependent lung deposition and large surface to mass ratio. Exposure to high levels contributes to the risk of developing respiratory and cardiovascular diseases, as well as of lung cancer. Particle-induced acute phase response may be an important mechanism of action of particle-induced cardiovascular disease. Here, the authors review new important scientific evidence showing causal relationships between inhalation of particle and nanomaterials, induction of acute phase response, and risk of cardiovascular disease. Particle-induced acute phase response provides a means for risk assessment of particle-induced cardiovascular disease and underscores cardiovascular disease as an occupational disease.

Grass carp (Ctenopharyngodon idellus) TRAF6 up-regulates IFN1 expression by activating IRF5

In mammals, interferon regulatory factor 5 (IRF5) can be activated by tumor necrosis factor receptor-associated factor 6 (TRAF6). Upon activation, IRF5 translocates into the nucleus, where it binds to IFN promoter and up-regulates IFN expression. However, there are few reports on the molecular mechanism by which TRAF6 up-regulates IFN expression in fish. In this study, we explored how Grass carp (Ctenopharyngodon idellus) TRAF6 initiated innate immunity by activating IRF5. We found that CiTRAF6, CiIRF5 and CiIFN1 were all significantly up-regulated in LPS-stimulated CIK cells and the expression of CiTRAF6 was earlier than the expressions of CiIRF5 and CiIFN1. These findings suggested that CiIFN1 expression might be induced by CiTRAF6 in fish. CiIFN1 expression, CiIFN1 promoter activity and CO cells viability were all significantly up-regulated in the overexpression experiments, but they were significantly down-regulated in the gene silencing experiments. This indicated that CiTRAF6, along with CiIRF5, regulated CiIFN1 expression. The localization analysis found that both CiTRAF6 and CiIRF5 located in the cytoplasm. Following LPS stimulation, CiIRF5 was observed to translocate to the nucleus. GST-pull down and co-IP experiments revealed that CiTRAF6 interacted with CiIRF5. The colocalization analysis also showed that CiTRAF6 bound with CiIRF5 in the cytoplasm. Overexpression of CiTRAF6 increased the endogenous CiIRF5, promoted its ubiquitination and nuclear translocation. In conclusion, CiTRAF6 bound to CiIRF5 in the cytoplasm, and then activated CiIRF5, resulting in up-regulating the expression of CiIFN1.

Recent trends in cell membrane-cloaked nanoparticles for therapeutic applications

Synthetic nanoparticles are extensively utilized in various biomedical engineering fields because of their unique physicochemical properties. However, their exogenous characteristics result in synthetic nanosystem invaders that easily induce the passive immune clearance mechanism, thereby increasing the retention effect caused by reticuloendothelial system (RES), resulting in low therapeutic efficacy and toxic effects. Recently, a cell membrane cloaking has been emerging technique as a novel interfacing approach from the biological/immunological perspective. This has been considered as useful technique for improving the performance of synthetic nanocarriers in vivo. By cell membrane cloaking, nanoparticles acquire the biological functions of natural cell membranes due to the presence of membrane-anchored proteins, antigens, and immunological moieties as well as physicochemical property of natural cell membrane. Due to cell membrane cloaking, the derived biological properties and functions of nanoparticles such as their immunosuppressive capability, long circulation time, and disease targeting ability have enhanced their future potential in biomedicine. Here, we review the cell membrane-cloaked nanosystems, highlight their novelty, introduce the preparation and characterization methods with relevant biomedical applications, and describe the prospects for using this novel biomimetic system that was developed from a combination of cell membranes and synthetic nanomaterials.

Re-assessing microbiomes in the low-biomass reproductive niche

The female reproductive tract represents a continuum between the vagina and the upper genital tract. New evidence from cultivation-independent studies suggests that the female upper genital tract is not sterile; however, the significance of this for reproductive health and disease remains to be elucidated fully. Further, diagnosis and treatment of infectious reproductive tract pathologies using cultivation-independent technologies represents a largely unchartered area of modern medical science. The challenge now is to design well-controlled experiments to account for the ease of contamination known to confound molecular-based studies of low-biomass niches, including the uterus and placenta. This will support robust assessment of the potential function of microorganisms, microbial metabolites, and cell-free bacterial DNA on reproductive function in health and disease. TWEETABLE ABSTRACT: Molecular microbial studies of low-biomass niches require stringent experimental controls to reveal causal relations in reproductive health and disease.

Neutrophils in Psoriasis

Neutrophils are the most abundant innate immune cells. The pathogenic roles of neutrophils are related to chronic inflammation and autoimmune diseases. Psoriasis is a chronic systemic inflammatory disease affecting ~2–3% of the world population. The abundant presence of neutrophils in the psoriatic skin lesions serves as a typical histopathologic hallmark of psoriasis. Recent reports indicated that oxidative stress, granular components, and neutrophil extracellular traps from psoriatic neutrophils are related to the initial and maintenance phases of psoriasis. This review provides an overview on the recent (up to 2019) advances in understanding the role of neutrophils in the pathophysiology of psoriasis, including the effects of respiratory burst, degranulation, and neutrophil extracellular trap formation on psoriatic immunity and the clinical relationships.

The effects of mechanically loaded osteocytes and inflammation on bone remodeling in a bisphosphonate-induced environment

Bisphosphonate-related osteonecrosis of the jaw is a disease appearing after tooth removal in patients undergoing bisphosphonate treatment for metastasizing cancers and osteoporosis. The complexity of the condition requires a multicellular model to address the net effects of two key risk factors: mechanical trauma (pathologic overload) and inflammation. In this work, a system comprised of a polydimethylsiloxane chip and mechanical loading device is used to expose bisphosphonate-treated osteocytes to mechanical trauma. Specifically, osteocytes are treated with the potent nitrogen-containing bisphosphonate, zoledronic acid, and exposed to short-term pathologic overload via substrate stretch. During bone remodeling, osteocyte apoptosis plays a role in attracting pre-osteoclasts to sites of damage; as such, lactate dehydrogenase activity, cell death and protein expression are evaluated as functions of load. Additionally, the effects of osteocyte soluble factors on osteoclast and osteoblast functional activity are quantified. Osteoclast activity and bone resorption are quantified in the presence and absence of inflammatory components, lipopolysaccharide and interferon gamma. Results suggest that inflammation associated with bacterial infection may hinder bone resorption by osteoclasts. In addition, osteocytes may respond to overload by altering expression of soluble signals that act on osteoblasts to attenuate bone formation. These findings give insight into the multicellular interactions implicated in bisphosphonate-related osteonecrosis of the jaw.