The pathogenic potential of Pseudomonas fluorescens MFN1032 on enterocytes can be modulated by serotonin, substance P and epinephrine

Stress in the microbiome-immune crosstalk

The gut microbiota exerts a mutualistic interaction with the host in a fragile ecosystem and the host intestinal, neural, and immune cells. Perturbations of the gastrointestinal track composition after stress have profound consequences on the central nervous system and the immune system. Reciprocally, brain signals after stress affect the gut microbiota highlighting the bidirectional communication between the brain and the gut. Here, we focus on the potential role of inflammation in mediating stress-induced gut-brain changes and discuss the impact of several immune cells and inflammatory molecules of the gut-brain dialogue after stress. Understanding the impact of microbial changes on the immune system after stress might provide new avenues for therapy.

Probiotics in Postoperative Pain Management

Postoperative pain is the unpleasant sensory and emotional experience after surgery, its origin being both the inflammatory reaction induced by the surgical trauma on the abdominal wall and the splanchnic pain induced by the activation of nociceptors of the viscera, which are highly sensitive to distension, ischemia, and inflammation. Nowadays, it is well recognized that there is a close relationship between the gut microbiome and pain perception, and that microbiome is highly affected by both anesthesia and surgical manipulation. Thus, efforts to restore the disturbed microbiome via supplementation with beneficial bacteria, namely probiotics, seem to be effective. In this article, the knowledge gained mainly from experimental research on this topic is analyzed, the concluding message being that each probiotic strain works in its own way towards pain relief.

The orchestra of human bacteriome by hormones

Human microbiome interact reciprocally with the host. Recent findings showed the capability of microorganisms to response towards host signaling molecules, such as hormones. Studies confirmed the complex response of bacteria in response to hormones exposure. These hormones impact many aspects on bacteria, such as the growth, metabolism, and virulence. The effects of each hormone seem to be species-specific. The most studied hormones are cathecolamines also known as stress hormones that consists of epinephrine, norepinephrine and dopamine. These hormones affect the growth of bacteria either inhibit or enhance by acting like a siderophore. Epinephrine and norepinephrine have also been reported to activate QseBC, a quorum sensing in Gram-negative bacteria and eventually enhances the virulence of pathogens. Other hormones were also reported to play a role in shaping human microbiome composition and affect their behavior. Considering the complex response of bacteria on hormones, it highlights the necessity to take the impact of hormones on bacteria into account in studying human health in relation to human microbiome.

Toward manipulating serotonin signaling via the microbiota-gut-brain axis

It is now well established in humans that there is a bidirectional pathway of communication between the central and enteric nervous systems in which members of the microbiome participate. This microbiota-gut-brain axis (MGBA) is crucial for normal development and physiology, and its dysregulation has been implicated in a range of neurological and intestinal disorders. Investigations into the mechanistic underpinnings of the MGBA have identified serotonin as a molecule of particular interest. In this review, we highlight recent advances toward understanding the role of endogenous serotonin in microbial communities, how microbial communities bidirectionally interact with host serotonin, and potential future engineering opportunities to leverage these novel mechanisms for biomedical applications.

General anesthesia bullies the gut: a toxic relationship with dysbiosis and cognitive dysfunction

Perioperative neurocognitive disorder (PND) is a common surgery outcome affecting up to a third of the elderly patients, and it is associated with high morbidity and increased risk for Alzheimer's disease development. PND is characterized by cognitive impairment that can manifest acutely in the form of postoperative delirium (POD) or after hospital discharge as postoperative cognitive dysfunction (POCD). Although POD and POCD are clinically distinct, their development seems to be mediated by a systemic inflammatory reaction triggered by surgical trauma that leads to dysfunction of the blood-brain barrier and facilitates the occurrence of neuroinflammation. Recent studies have suggested that the gut microbiota composition may play a pivotal role in the PND development by modulating the risk of neuroinflammation establishment. In fact, modulation of gut microbiome composition with pre- and probiotics seems to be effective for the prevention and treatment of PND in animals. Interestingly, general anesthetics seem to have major responsibility on the gut microbiota composition changes following surgery and, consequently, can be an important element in the process of PND initiation. This concept represents an important milestone for the understanding of PND pathogenesis and may unveil new opportunities for the development of preventive or mitigatory strategies against the development of these conditions. The aim of this review is to discuss how anesthetics used in general anesthesia can interact and alter the gut microbiome composition and contribute to PND development by favoring the emergence of neuroinflammation.

Norepinephrine and Serotonin Can Modulate the Behavior of the Probiotic Enterococcus faecium NCIMB10415 towards the Host: Is a Putative Surface Sensor Involved?

The human gut microbiota has co-evolved with humans by exchanging bidirectional signals. This study aims at deepening the knowledge of this crucial relationship by analyzing phenotypic and interactive responses of the probiotic Enterococcus faecium NCIMB10415 (E. faecium SF68) to the top-down signals norepinephrine (NE) and serotonin (5HT), two neuroactive molecules abundant in the gut. We treated E. faecium NCIMB10415 with 100 µM NE and 50 µM 5HT and tested its ability to form static biofilm (Confocal Laser Scanning Microscopy), adhere to the Caco-2/TC7 monolayer, affect the epithelial barrier function (Transepithelial Electrical Resistance) and human dendritic cells (DC) maturation, differentiation, and cytokines production. Finally, we evaluated the presence of a putative hormone sensor through in silico (whole genome sequence and protein modelling) and in vitro (Micro-Scale Thermophoresis) analyses. The hormone treatments increase biofilm formation and adhesion on Caco-2/TC7, as well as the epithelial barrier function. No differences concerning DC differentiation and maturation between stimulated and control bacteria were detected, while an enhanced TNF-α production was observed in NE-treated bacteria. Investigations on the sensor support the hypothesis that a two-component system on the bacterial surface can sense 5HT and NE. Overall, the data demonstrate that E. faecium NCIMB10415 can sense both NE and 5HT and respond accordingly.

Differential effect of polysaccharide and nonpolysaccharide components in Sijunzi decoction on spleen deficiency syndrome and their mechanisms

BACKGROUND

Sijunzi decoction (SJZD), reported in "Tai Ping Hui Min He Ji Ju Fang" of the Song dynasty, is the basic prescription for the treatment of spleen deficiency syndrome (SDS) in traditional Chinese medicine (TCM). It is composed of Ginseng Radix et Rhizoma, Atractylodisa Macricephalae Rhizoma, Poria and Glycyrrhizae Radix et Rhizoma Praeparata Cum Melle.

PURPOSE

This study sought to explore the effects of different components in SJZD (including nonpolysaccharide NPS and active polysaccharide S-3) on SDS rats and their underlying mechanisms.

STUDY DESIGN AND METHODS

First, SDS model rats were established by reserpine injection and then treated with SJZD, NPS and S-3. To clarify their effect on GI motility and immune function, the gastrointestinal (GI) hormone levels in rat serum and their related receptor expressions in rat intestine were detected by enzyme-linked immunosorbent assay (ELISA) and western blot, and the intestinal T lymphocyte expression were quantified by flow cytometry. The levels of SCFAs in feces and serum were measured by gas chromatography-mass spectrometry (GC-MS), and the gut microbiota composition was determined by 16S RNA sequencing. Furthermore, pseudo-germ-free (pGF) and gut microbiota dysbiosis (GMD) model rats were established to verify the key role of the gut microbiota in the treatment of SDS with SJZD, NPS and S-3.

RESULTS

SJZD has a stronger therapeutic effect on intestinal immune and GI hormone secretion in SDS rats, while the efficacy of NPS and S-3 showed slight differences. NPS mainly regulated the secretion of GI hormones in SDS rats and directly improved intestinal immunity by increasing the expression of T lymphocyte cells, while S-3 mainly enhanced intestinal immune function by increasing the expression of T lymphocyte cells and repairing the intestinal barrier in both direct and indirect ways. Additionally, experiments in pGF and GMD rats have proven that the immune-enhancing effects of SJZD, NPS, and S-3 on SDS rats and the regulation of GI hormones of S-3 are related to modulation of the gut microbiota composition, while the regulation of GI hormones by SJZD and NPS is not completely dependent on this modulation. In particular, Lactobacillus, SMB53, Blautia, Dorea, Collinsella and Adlercreutzia were significantly modulated by SJZD, and 3 genera (including Lactobacillus, Dorea and SMB53) were also remarkably regulated by NPS. S-3 significantly increased the abundance of Butyricimonas and Collinsella, which were different from altered genera in the SJZD group.

CONCLUSION

This study uncovered that NPS and S-3 are inseparable effective substances for SJZD in the treatment of SDS rats, in which NPS mainly improves intestinal motility dysfunction and S-3 mainly enhances intestinal immunity. The mediation effect of the gut microbiota is extremely important, but the regulating effect of NPS on gastrointestinal hormones has nothing to do with the gut microbiota.

Inter-Kingdom Signaling of Stress Hormones: Sensing, Transport and Modulation of Bacterial Physiology

Prokaryotes and eukaryotes have coexisted for millions of years. The hormonal communication between microorganisms and their hosts, dubbed inter-kingdom signaling, is a recent field of research. Eukaryotic signals such as hormones, neurotransmitters or immune system molecules have been shown to modulate bacterial physiology. Among them, catecholamines hormones epinephrine/norepinephrine, released during stress and physical effort, or used therapeutically as inotropes have been described to affect bacterial behaviors (i.e., motility, biofilm formation, virulence) of various Gram-negative bacteria (e.g., Escherichia coli, Salmonella enterica serovar Typhimurium, Pseudomonas aeruginosa, Vibrio sp.). More recently, these molecules were also shown to influence the physiology of some Gram-positive bacteria like Enterococcus faecalis. In E. coli and S. enterica, the stress-associated mammalian hormones epinephrine and norepinephrine trigger a signaling cascade by interacting with the QseC histidine sensor kinase protein. No catecholamine sensors have been well described yet in other bacteria. This review aims to provide an up to date report on catecholamine sensors in eukaryotes and prokaryotes, their transport, and known effects on bacteria.

Serotonin Exposure Improves Stress Resistance, Aggregation, and Biofilm Formation in the Probiotic Enterococcus faecium NCIMB10415

The role of the microbiota–gut–brain axis in maintaining a healthy status is well recognized. In this bidirectional flux, the influence of host hormones on gut bacteria is crucial. However, data on commensal/probiotics are scarce since most reports analyzed the effects of human bioactive compounds on opportunistic strains, highlighting the risk of increased pathogenicity under stimulation. The present investigation examined the modifications induced by 5HT, a tryptophan-derived molecule abundant in the intestine, on the probiotic Enterococcus faecium NCIMB10415. Specific phenotypic modifications concerning the probiotic potential and possible effects of treated bacteria on dendritic cells were explored together with the comparative soluble proteome evaluation. Increased resistance to bile salts and ampicillin in 5HT-stimulated conditions relate with overexpression of specific proteins (among which Zn-beta-lactamases, a Zn-transport protein and a protein involved in fatty acid incorporation into the membrane). Better auto-aggregating properties and biofilm-forming aptitude are consistent with enhanced QS peptide transport. Concerning interaction with the host, E. faecium NCIMB10415 enhanced dendritic cell maturation, but no significant differences were observed between 5HT-treated and untreated bacteria; meanwhile, after 5HT exposure, some moonlight proteins possibly involved in tissue adhesion were found in higher abundance. Finally, the finding in stimulated conditions of a higher abundance of VicR, a protein involved in two-component signal transduction system (VicK/R), suggests the existence of a possible surface receptor (VicK) for 5HT sensing in the strain studied. These overall data indicate that E. faecium NCIMB10415 modifies its physiology in response to 5HT by improving bacterial interactions and resistance to stressors.

The Ambivalent Role of Skin Microbiota and Adrenaline in Wound Healing and the Interplay between Them

After skin injury, wound healing sets into motion a dynamic process to repair and replace devitalized tissues. The healing process can be divided into four overlapping phases: hemostasis, inflammation, proliferation, and maturation. Skin microbiota has been reported to participate in orchestrating the wound healing both in negative and positive ways. Many studies reported that skin microbiota can impose negative and positive effects on the wound. Recent findings have shown that many bacterial species on human skin are able to convert aromatic amino acids into so-called trace amines (TAs) and convert corresponding precursors into dopamine and serotonin, which are all released into the environment. As a stress reaction, wounded epithelial cells release the hormone adrenaline (epinephrine), which activates the β2-adrenergic receptor (β2-AR), impairing the migration ability of keratinocytes and thus re-epithelization. This is where TAs come into play, as they act as antagonists of β2-AR and thus attenuate the effects of adrenaline. The result is that not only TAs but also TA-producing skin bacteria accelerate wound healing. Adrenergic receptors (ARs) play a key role in many physiological and disease-related processes and are expressed in numerous cell types. In this review, we describe the role of ARs in relation to wound healing in keratinocytes, immune cells, fibroblasts, and blood vessels and the possible role of the skin microbiota in wound healing.

GABAergic but not Antidepressant Medications Increase Risk for Clostridioides difficile Infection in a National Cohort of Veterans

Background

Clostridioides difficile infection (CDI) is primarily mediated by alterations in the host gut ecosystem. While antibiotic use is the primary risk factor for CDI, other medications that modulate the gut ecosystem, particularly those targeting the gut-brain axis, could impact CDI risk. This study aimed to investigate the association between recent antidepressant and gamma-aminobutyric acid (GABA)-ergic medication use with CDI risk in a national cohort of United States veterans.

Methods

This was a retrospective case-control study of patients seen in Veterans Health Administration facilities from October 2002 to September 2014. CDI and non-CDI control patients were propensity score matched 1:1 using a maximum caliper of 0.0001. Antidepressant and GABAergic medication use 90 days before cohort inclusion were analyzed for CDI association using bivariable and multivariable logistic regression models.

Results

A total of 85 831 patients were included, and 9287 CDI and 9287 control patients were propensity score matched. Antidepressant use overall was not significantly associated with CDI risk (odds ratio [OR], 1.05; 95% CI, 0.98-1.12), although GABAergic medication use was associated with increased risk (OR, 1.81; 95% CI, 1.70-1.92). In multivariable models of individual medications/classes, benzodiazepines had the strongest CDI association (OR, 1.91; 95% CI, 1.77-2.07). SSRIs (OR, 0.88; 95% CI, 0.81-0.95) and bupropion (OR, 0.67; 95% CI, 0.57-0.78) were negatively associated with CDI.

Conclusions

In this national study of veterans, GABAergic medication use was a positive predictor of CDI risk, though antidepressant use was not. Further research is needed to understand biological mechanisms, and confirmatory studies are needed to validate these findings.

Re-identification of strains deposited as Pseudomonas aeruginosa, Pseudomonas fluorescens and Pseudomonas putida in GenBank based on whole genome sequences

The taxonomic classification of Pseudomonas species has been revised and updated several times. This study utilized average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) cutoff values of 95 and 70 %, respectively, to re-identify the species of strains deposited in GenBank as P. aeruginosa, P. fluorescens and P. putida. Of the 264 deposited P. aeruginosa strains, 259 were correctly identified as P. aeruginosa, but the remaining five were not. All 28 deposited P. fluorescens strains had been incorrectly identified as P. fluorescens. Four of these strains were re-identified, including two as P. kilonensis and one each as P. aeruginosa and P. brassicacearum, but the remaining 24 could not be re-identified. Similarly, all 35 deposited P. putida strains had been incorrectly identified as P. putida. Nineteen of these strains were re-identified, including 12 as P. alloputida, four as P. asiatica and one each as P. juntendi, P. monteilii and P. mosselii. These results strongly suggest that Pseudomonas bacteria should be identified using ANI and dDDH analyses based on whole genome sequencing when Pseudomonas species are initially deposited in GenBank/DDBJ/EMBL databases.

Dialog between skin and its microbiota: Emergence of "Cutaneous Bacterial Endocrinology"

Microbial endocrinology is studying the response of microorganisms to hormones and neurohormones and the microbiota production of hormones-like molecules. Until now, it was mainly applied to the gut and revealed that the intestinal microbiota should be considered as a real organ in constant and bilateral interactions with the whole human body. The skin harbours the second most abundant microbiome and contains an abundance of nerve terminals and capillaries, which in addition to keratinocytes, fibroblasts, melanocytes, dendritic cells and endothelial cells, release a huge diversity of hormones and neurohormones. In the present review, we will examine recent experimental data showing that, in skin, molecules such as substance P, calcitonin gene-related peptide, natriuretic peptides and catecholamines can directly affect the physiology and virulence of common skin-associated bacteria. Conversely, bacteria are able to synthesize and release compounds including histamine, glutamate and γ-aminobutyric acid or peptides showing partial homology with neurohormones such as α-melanocyte-stimulating hormone (αMSH). The more surprising is that some viruses can also encode neurohormones mimicking proteins. Taken together, these elements demonstrate that there is also a cutaneous microbial endocrinology and this emerging concept will certainly have important consequences in dermatology.

Modifications of Hydroxyapatite by Gallium and Silver Ions-Physicochemical Characterization, Cytotoxicity and Antibacterial Evaluation

Hydroxyapatite (HA) powders enriched with silver or gallium ions or both were synthesized by two different routes: standard precipitation and the solid-state method. The powders were characterized by using several methods: inductively coupled plasma optical emission spectrometry (ICP-OES), powder X-ray diffractometry (PXRD), transmission electron microscopy (TEM), infrared spectroscopy (FT-IR) and solid-state nuclear magnetic resonance spectroscopy (ssNMR). The effects of enrichment of the HAs in Ag⁺ or Ga³⁺ or both on in vitro cytotoxicity and microbiological activity were discussed. PXRD experiments showed that the samples obtained by the wet method consisted of single-phase nanocrystalline HA, while the samples prepared via the solid-state method are microcrystalline with a small amount of calcium oxide. The introduction of higher amounts of silver ions was found to be more effective than enriching HA with small amounts of Ag⁺. Gallium and silver ions were found not to affect the lattice parameters. Ga³⁺ affected the crystallinity of the samples as well as the content of structural hydroxyl groups. Among samples synthesized by the wet method, only one (5Ag-HAw) was cytotoxic, whereas all Ga-containing samples obtained by the dry method showed cytotoxicity. In the preliminary antimicrobial test all the materials containing "foreign" ions showed high antibacterial activity.

Tryptophan Metabolites Along the Microbiota-Gut-Brain Axis: An Interkingdom Communication System Influencing the Gut in Health and Disease

The ‘microbiota-gut-brain axis’ plays a fundamental role in maintaining host homeostasis, and different immune, hormonal, and neuronal signals participate to this interkingdom communication system between eukaryota and prokaryota. The essential aminoacid tryptophan, as a precursor of several molecules acting at the interface between the host and the microbiota, is fundamental in the modulation of this bidirectional communication axis. In the gut, tryptophan undergoes 3 major metabolic pathways, the 5-HT, kynurenine, and AhR ligand pathways, which may be directly or indirectly controlled by the saprophytic flora. The importance of tryptophan metabolites in the modulation of the gastrointestinal tract is suggested by several preclinical and clinical studies; however, a thorough revision of the available literature has not been accomplished yet. Thus, this review attempts to cover the major aspects on the role of tryptophan metabolites in host-microbiota cross-talk underlaying regulation of gut functions in health conditions and during disease states, with particular attention to 2 major gastrointestinal diseases, such as irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD), both characterized by psychiatric disorders. Research in this area opens the possibility to target tryptophan metabolism to ameliorate the knowledge on the pathogenesis of both diseases, as well as to discover new therapeutic strategies based either on conventional pharmacological approaches or on the use of pre- and probiotics to manipulate the microbial flora.

Biofilm and Pathogenesis-Related Proteins in the Foodborne P. fluorescens ITEM 17298 With Distinctive Phenotypes During Cold Storage

In food chain, Pseudomonas spp. cause spoilage by reducing shelf life of fresh products, especially during cold storage, with a high economic burden for industries. However, recent studies have shed new light on health risks occurring when they colonize immunocompromised patient tissues. Likewise to P. aeruginosa, they exhibit antibiotic resistance and biofilm formation, responsible for their spread and persistence in the environment. Biofilm formation might be induced by environmental stresses, such as temperature fluctuations causing physiological and metabolic changes exacerbating food spoilage (by protease and pigment synthesis), and the production of adhesion molecules, chemotactic or underestimated virulence factors. In order to provide a new insight into phenotypic biodiversity of Pseudomonas spoilers isolated from cold stored cheese, in this work 19 Pseudomonas spp. were investigated for biofilm, pigments, exopolysaccharide production and motility at low temperature. Only nine strains showed these phenotypic traits and the blue pigmenting cheese strain P. fluorescens ITEM 17298 was the most distinctive. In addition, this strain decreased the survival probability of infected Galleria mellonella larvae, showing, for the first time, a pathogenic potential. Genomic and proteomic analyses performed on the ITEM 17298 planktonic cells treated or not with lactoferrin derived antibiofilm peptides allowed to reveal specific biofilm related-pathways as well as proteins involved in pathogenesis. Indeed, several genes were found related to signaling system by cGMP-dependent protein kinases, cellulose, rhamnolipid and alginate synthesis, antibiotic resistance, adhesion and virulence factors. The proteome of the untreated ITEM 17298, growing at low temperature, showed that most of the proteins associated with biofilm regulation, pigmentation motility, antibiotic resistance and pathogenecity were repressed, or decreased their levels in comparison to that of the untreated cultures. Thus, the results of this work shed light on the complex pathways network allowing psychrotrophic pseudomonads to adapt themselves to food-refrigerated conditions and enhance their spoilage. In addition, the discovery of virulence factors and antibiotic resistance determinants raises some questions about the need to deeper investigate these underestimated bacteria in order to increase awareness and provide input to update legislation on their detection limits in foods.

Successful treatment of a unique chronic multi-bacterial scalp infection with N-chlorotaurine, N-bromotaurine and bromamine T

Microbial species can act in synergy to circumvent environmental stress conditions and survive. In addition, biofilms are a serious public-health issue globally and constitute a clinical emergency. Infection persistence, increased morbidity and mortality, and antibiotic resistance are consequences of poly-microbial synergy. Due to inherited complexity and synergy between numerous species, newer antimicrobial agents of increased efficacy and tolerability are needed. In this unique medical case, a chronic (9 year) multi-bacterial scalp infection was differentially diagnosed from other inflammatory skin disorders by prolonged microbiological culture. The bacterial species found seem to have caused lesions of visible biofilm not documented previously in the medical literature. This complicated infection was treated successfully and rapidly with the combined topical application of the active halogen compounds N-chlorotaurine, N-bromotaurine and bromamine T, which is in contrast to the previous failed systemic and topical therapeutic approaches. This study strengthens the case for the use of active halogen compounds against multi-bacterial infections of the skin in the future, without the occurrence of resistance.

Epinephrine affects motility, and increases adhesion, biofilm and virulence of Pseudomonas aeruginosa H103

Microbial endocrinology has demonstrated for more than two decades, that eukaryotic substances (hormones, neurotransmitters, molecules of the immune system) can modulate the physiological behavior of bacteria. Among them, the hormones/neurotransmitters, epinephrine (Epi) and norepinephrine (NE), released in case of stress, physical effort or used in medical treatment, were shown to be able to modify biofilm formation in various bacterial species. In the present study, we have evaluated the effect of Epi on motility, adhesion, biofilm formation and virulence of Pseudomonas aeruginosa, a bacterium linked to many hospital-acquired infections, and responsible for chronic infection in immunocompromised patients including persons suffering from cystic fibrosis. The results showed that Epi increased adhesion and biofilm formation of P. aeruginosa, as well as its virulence towards the Galleria mellonella larvae in vivo model. Deciphering the sensor of this molecule in P. aeruginosa and the molecular mechanisms involved may help to find new strategies of treatment to fight against this bacterium.

Tryptophan Metabolism by Gut Microbiome and Gut-Brain-Axis: An in silico Analysis

The link between gut microbiome and brain is being slowly acknowledged due to the speculated role of resident gut microbial community in altering the functions of gut-brain axis (GBA). Recently, a number of microbial metabolites (referred to as neuro-active metabolites) produced through tryptophan metabolism have been suggested to influence the GBA. In view of this, the current study focuses on microbial tryptophan metabolism pathways which produce neuro-active metabolites. An in silico analysis was performed on bacterial genomes as well as publicly available gut microbiome data. The results provide a comprehensive catalog of the analyzed pathways across bacteria. The analysis indicates an enrichment of tryptophan metabolism pathways in five gut-associated phyla, namely, Actinobacteria, Firmicutes, Bacteroidetes, Proteobacteria, and Fusobacteria. Further, five genera, namely, Clostridium, Burkholderia, Streptomyces, Pseudomonas, and Bacillus have been predicted to be enriched in terms of number of the analyzed tryptophan metabolism pathways, suggesting a higher potential of these bacterial groups to metabolize tryptophan in gut. Analysis of available microbiome data corresponding to gut samples from patients of neurological diseases and healthy individuals suggests probable association of different sets of tryptophan metabolizing bacterial pathways with the etiology of different diseases. The insights obtained from the present study are expected to provide directions toward designing of microbiome based diagnostic and therapeutic approaches for neurological diseases/disorders.

Changes in Microbiota and Bacterial Protein Caseinolytic Peptidase B During Food Restriction in Mice: Relevance for the Onset and Perpetuation of Anorexia Nervosa

Microbiota contributes to the regulation of eating behavior and might be implicated in the pathophysiology of anorexia nervosa. ClpB (Caseinolytic peptidase B) protein produced mainly by the Enterobacteriaceae family has been identified as a conformational mimetic of α-MSH, which could result in similar anorexigenic effects. The aim of this study was to highlight the role of the microbiome and the ClpB protein in deregulation and self-maintenance of anorexia pathology. Male C57Bl/6 mice were undergone to the ABA (Activity-Based Anorexia) protocol: after 5 days of acclimatization, both ABA and LFA (Limited Food Access) mice had progressively limited access to food until D17. At the end of protocol, the plasma ClpB concentration and Enterobacteriaceae DNA in colonic content were measured. As expected, dietary restriction induced lost weight in LFA and ABA mice. At D10, colonic permeability and plasma concentration of the ClpB protein were significantly increased in LFA and ABA mice vs. controls. At D17, plasma concentration of ClpB was increased in LFA and ABA mice and, it was correlated with proportion of Enterobacteriaceae in the faeces. These abnormally high ClpB concentrations and all associated factors, and therefore might contribute to the initiation and/or perpetuation of anorexia nervosa by interfering with satiety signaling.

The Microbiota-Gut-Brain Axis

The importance of the gut-brain axis in maintaining homeostasis has long been appreciated. However, the past 15 yr have seen the emergence of the microbiota (the trillions of microorganisms within and on our bodies) as one of the key regulators of gut-brain function and has led to the appreciation of the importance of a distinct microbiota-gut-brain axis. This axis is gaining ever more traction in fields investigating the biological and physiological basis of psychiatric, neurodevelopmental, age-related, and neurodegenerative disorders. The microbiota and the brain communicate with each other via various routes including the immune system, tryptophan metabolism, the vagus nerve and the enteric nervous system, involving microbial metabolites such as short-chain fatty acids, branched chain amino acids, and peptidoglycans. Many factors can influence microbiota composition in early life, including infection, mode of birth delivery, use of antibiotic medications, the nature of nutritional provision, environmental stressors, and host genetics. At the other extreme of life, microbial diversity diminishes with aging. Stress, in particular, can significantly impact the microbiota-gut-brain axis at all stages of life. Much recent work has implicated the gut microbiota in many conditions including autism, anxiety, obesity, schizophrenia, Parkinson’s disease, and Alzheimer’s disease. Animal models have been paramount in linking the regulation of fundamental neural processes, such as neurogenesis and myelination, to microbiome activation of microglia. Moreover, translational human studies are ongoing and will greatly enhance the field. Future studies will focus on understanding the mechanisms underlying the microbiota-gut-brain axis and attempt to elucidate microbial-based intervention and therapeutic strategies for neuropsychiatric disorders.

Acne and Stress: Impact of Catecholamines on Cutibacterium acnes

Cutibacterium acnes (former Propionibacterium acnes), is a bacterium characterized by high genomic variability, consisting of four subtypes and six major ribotypes. Skin is the largest neuroendocrine organ of the human body and many cutaneous hormones and neurohormones can modulate bacterial physiology. Here, we investigated the effect of catecholamines, i.e., epinephrine and norepinephrine, on two representative strains of C. acnes, of which the genome has been fully sequenced, identified as RT4 acneic and RT6 non-acneic strains. Epinephrine and norepinephrine (10^-6 M) had no impact on the growth of C. acnes but epinephrine increased RT4 and RT6 biofilm formation, as measured by crystal violet staining, whereas norepinephrine was only active on the RT4 strain. We obtained the same results by confocal microscopy with the RT4 strain, whereas there was no effect of either catecholamine on the RT6 strain. However, this strain was also sensitive to catecholamines, as shown by MATs tests, as epinephrine and norepinephrine affected its surface polarity. Flow cytometry studies revealed that epinephrine and norepinephrine are unable to induce major changes of bacterial surface properties and membrane integrity. Exposure of sebocytes to control or catecholamine-treated bacteria showed epinephrine and norepinephrine to have no effect on the cytotoxic or inflammatory potential of either C. acnes strains but to stimulate their effect on sebocyte lipid synthesis. Uriage thermal spring water was previously shown to inhibit biofilm production by C. acnes. We thus tested its effect after exposure of the bacteria to epinephrine and norepinephrine. The effect of the thermal water on the response of C. acnes to catecholamines depended on the surface on which the biofilm was grown. Finally, an in-silico study revealed the presence of a protein in the genome of C. acnes that shows homology with the catecholamine receptor of Escherichia coli and eukaryotes. This study suggests that C. acnes may play a role as a relay between stress mediators (catecholamines) and acne.

Substance P enhances lactic acid and tyramine production in Enterococcus faecalis V583 and promotes its cytotoxic effect on intestinal Caco-2/TC7 cells

Background

Enterococcus faecalis, generally considered as a saprophytic bowel commensal, has recently emerged as an important nosocomial pathogen causing severe urinary tract infections, surgical wound infections, bacteremia, and bacterial endocarditis. This bacterium is capable of forming biofilms on various surfaces and its high level of antibiotic resistance contributes to its pathogenicity. The aim of this study was to evaluate the effect on E. faecalis, of Substance P (SP), an antimicrobial peptide that is produced in the gut and skin.

Results

We found that SP did not have antibacterial activity against E. faecalis V583 (MIC >1000 µg/ml). Conversely, SP stimulated aggregation, hydrophobicity, lactic acid and tyramine production in this bacterium. The cytotoxicity and bacterial translocation were also accelerated when E. faecalis V583 were pretreated with SP before infection of intestinal Caco-2/TC7 cells.

Conclusion

SP can modulate the physiology of E. faecalis. Extensive studies are now needed to screen within the human microbiota which bacteria are responsive to host molecules, and to identify their sensors.

The Neuro-endocrinological Role of Microbial Glutamate and GABA Signaling

Gut microbiota provides the host with multiple functions (e.g., by contributing to food digestion, vitamin supplementation, and defense against pathogenic strains) and interacts with the host organism through both direct contact (e.g., through surface antigens) and soluble molecules, which are produced by the microbial metabolism. The existence of the so-called gut–brain axis of bi-directional communication between the gastrointestinal tract and the central nervous system (CNS) also supports a communication pathway between the gut microbiota and neural circuits of the host, including the CNS. An increasing body of evidence has shown that gut microbiota is able to modulate gut and brain functions, including the mood, cognitive functions, and behavior of humans. Nonetheless, given the extreme complexity of this communication network, its comprehension is still at its early stage. The present contribution will attempt to provide a state-of-the art description of the mechanisms by which gut microbiota can affect the gut–brain axis and the multiple cellular and molecular communication circuits (i.e., neural, immune, and humoral). In this context, special attention will be paid to the microbial strains that produce bioactive compounds and display ascertained or potential probiotic activity. Several neuroactive molecules (e.g., catecholamines, histamine, serotonin, and trace amines) will be considered, with special focus on Glu and GABA circuits, receptors, and signaling. From the basic science viewpoint, “microbial endocrinology” deals with those theories in which neurochemicals, produced by both multicellular organisms and prokaryotes (e.g., serotonin, GABA, glutamate), are considered as a common shared language that enables interkingdom communication. With regards to its application, research in this area opens the way toward the possibility of the future use of neuroactive molecule-producing probiotics as therapeutic agents for the treatment of neurogastroenteric and/or psychiatric disorders.

Listeria monocytogenes Inhibits Serotonin Transporter in Human Intestinal Caco-2 Cells

Listeria monocytogenes is a Gram-positive bacterium that can cause a serious infection. Intestinal microorganisms have been demonstrated to contribute to intestinal physiology not only through immunological responses but also by modulating the intestinal serotonergic system. Serotonin (5-HT) is a neuromodulator that is synthesized in the intestinal epithelium and regulates the whole intestinal physiology. The serotonin transporter (SERT), located in enterocytes, controls intestinal 5-HT availability and therefore serotonin's effects. Infections caused by L. monocytogenes are well described as being due to the invasion of intestinal epithelial cells; however, the effect of L. monocytogenes on the intestinal epithelium remains unknown. The main aim of this work, therefore, was to study the effect of L. monocytogenes on SERT. Caco2/TC7 cell line was used as an enterocyte-like in vitro model, and SERT functional and molecular expression assays were performed. Our results demonstrate that living L. monocytogenes inhibits serotonin uptake by reducing SERT expression at the brush border membrane. However, neither inactivated L. monocytogenes nor soluble metabolites were able to affect SERT. The results also demonstrate that L. monocytogenes yields TLR2 and TLR10 transcriptional changes in intestinal epithelial cells and suggest that TLR10 is potentially involved in the inhibitory effect observed on SERT. Therefore, L. monocytogenes, through TLR10-mediated SERT inhibition, may induce increased intestinal serotonin availability and potentially contributing to intestinal physiological changes and the initiation of the inflammatory response.

Neuropeptides, Microbiota, and Behavior

The gut microbiota and the brain interact with each other through multiple bidirectional signaling pathways in which neuropeptides and neuroactive peptide messengers play potentially important mediator roles. Currently, six particular modes of a neuropeptide link are emerging. (i) Neuropeptides and neurotransmitters contribute to the mutual microbiota-host interaction. (ii) The synthesis of neuroactive peptides is influenced by microbial control of the availability of amino acids. (iii) The activity of neuropeptides is tempered by microbiota-dependent autoantibodies. (iv) Peptide signaling between periphery and brain is modified by a regulatory action of the gut microbiota on the blood-brain barrier. (v) Within the brain, gut hormones released under the influence of the gut microbiota turn into neuropeptides that regulate multiple aspects of brain activity. (vi) Cerebral neuropeptides participate in the molecular, behavioral, and autonomic alterations which the brain undergoes in response to signals from the gut microbiota.

GENETIC TRIGGERS AND NEUROHUMORAL MESSENGERS OF POSTOPERATIVE INTESTINAL PARESIS, ITS VALUE IN PREDICTION, PREVENTION AND TREATMENT

The aim of research: to study the causes and mechanisms of postoperative intestinal paresis on the base of assessment of genetic determinism of neurohormonal processes which regulate the contractile ability of the intestines, to determine their role for the choice of treatment tactics. The study presents data about connection between variants of SERT gene, which regulates the reuptake of serotonin, and its concentration in blood plasma and the probability of occurrence of postoperative intestinal paresis. This made it possible not only to predict the occurrence of postoperative disorders of motor-evacuation function of the intestines, but also to improve the algorithms of prevention and pathogenetic based treatment.