Blockade of catecholamine-induced growth by adrenergic and dopaminergic receptor antagonists in Escherichia coli O157:H7, Salmonella enterica and Yersinia enterocolitica

Microbiota-immune-brain interactions: A new vision in the understanding of periodontal health and disease

This review highlights the significance of interactions between the microbiota, immune system, nervous and hormonal systems, and the brain on periodontal health and disease. Microorganisms in the microbiota, immune cells, and neurons communicate via homeostatic nervous and hormonal systems, regulating vital body functions. By modulating pro-inflammatory and anti-inflammatory adaptive immune responses, these systems control the composition and number of microorganisms in the microbiota. The strength of these brain-controlled responses is genetically determined but is sensitive to early childhood stressors, which can permanently alter their responsiveness via epigenetic mechanisms, and to adult stressors, causing temporary changes. Clinical evidence and research with humans and animal models indicate that factors linked to severe periodontitis enhance the responsiveness of these homeostatic systems, leading to persistent hyperactivation. This weakens the immune defense against invasive symbiotic microorganisms (pathobionts) while strengthening the defense against non-invasive symbionts at the gingival margin. The result is an increased gingival tissue load of pathobionts, including Gram-negative bacteria, followed by an excessive innate immune response, which prevents infection but simultaneously destroys gingival and periodontal tissues. Thus, the balance between pro-inflammatory and anti-inflammatory adaptive immunity is crucial in controlling the microbiota, and the responsiveness of brain-controlled homeostatic systems determines periodontal health.

Whole-body mass spectrometry imaging reveals the systemic metabolic disorder and catecholamines biosynthesis alteration on heart-gut axis in heart failure rat

INTRODUCTION

Heart failure (HF) is a systemic metabolic disorder disease, across multiorgan investigations advancing knowledge of progression and treatment of HF. Whole-body MSI provides spatiotemporal information of metabolites in multiorgan and is expected to be a potent tool to dig out the complex mechanism of HF.

OBJECTIVES

This study aimed at exploring the systemic metabolic disorder in multiorgan and catecholamines biosynthesis alteration on heart-gut axis after HF.

METHODS

Whole-body MSI was used to characterize metabolic disorder of the whole rat body after HF. An integrated method by MSI, LC-MS/MS and ELISA was utilized to analyze key metabolites and enzymes on heart, small intestine, cecum and colon tissues of rat. Gut microbiota dysbiosis was investigated by 16S rDNA sequencing and metagenomic sequencing. Validation experiments and in vitro experiments were performed to verify the effect of catecholamines biosynthesis alteration on heart-gut axis after HF.

RESULTS

Whole-body MSI exhibited varieties of metabolites alteration in multiple organs. Remarkably, catecholamine biosynthesis was significantly altered in the serum, heart and intestines of rats. Furthermore, catecholamines and tyrosine hydroxylase were obviously upregulated in heart and colon tissue. Turicibacter_sanguinis was relevant to catecholamines of heart and colon. Validation experiments demonstrated excessive norepinephrine induced cardio-intestinal injury, including significantly elevating the levels of BNP, pro-BNP, LPS, DAO, and increased the abundance of Turicibacter_sanguinis. These alterations could be reversed by metoprolol treatment blocking the effect of norepinephrine. Additionally, in vitro studies demonstrated that norepinephrine promoted the growth of Turicibacter_sanguinis and Turicibacter_sanguinis could import and metabolize norepinephrine. Collectively, excessive norepinephrine exerted bidirectional effects on cardio-intestinal function to participate in the progression of HF.

CONCLUSION

Our study provides a new approach to elucidate multiorgan metabolic disorder and proposes new insights into heart-gut axis in HF development.

Genomic Characterization of Piscicolin CM22 Produced by Carnobacterium maltaromaticum CM22 Strain Isolated from Salmon (Salmo salar)

Carnobacterium maltaromaticum is a species of lactic acid bacteria (LAB) that has been isolated from various natural environments. It is well-known for producing a diverse spectrum of bacteriocins with potential biotechnological applications. In the present study, a new psychrotolerant strain of C. maltaromaticum CM22 is reported, isolated from a salmon gut sample and producing a variant of the bacteriocin piscicolin 126 that has been named piscicolin CM22. After identification by 16S rRNA gene, this strain has been genomically characterized by sequencing and assembling its complete genome. Moreover, its bacteriocin was purified and characterized. In vitro tests demonstrated that both the strain and its bacteriocin possess antimicrobial activity against several Gram-positive bacteria of interest in human and animal health, such as Listeria monocytogenes, Clostridium perfringens, or Enterococcus faecalis. However, this bacteriocin did not produce any antimicrobial effect on Gram-negative species. The study of its genome showed the genetic structure of the gene cluster that encodes the bacteriocin, showing a high degree of homology to the gene cluster of piscicolin 126 described in other C. maltaromaticum. Although more studies are necessary concerning its functional properties, this new psychrotolerant strain C. maltaromaticum CM22 and its bacteriocin could be considered an interesting candidate with potential application in agri-food industry.

Dronedarone Enhances the Antibacterial Activity of Polymyxin B and Inhibits the Quorum Sensing System by Interacting with LuxS

Quorum sensing (QS) is considered an appealing target for interference with bacterial infections. β-Adrenergic blockers are promising anti-QS agents but do not have antibacterial activity. We assessed the potential ability of adrenergic receptor inhibitors to enhance the antibacterial activity of polymyxin B (PB) against Klebsiella pneumoniae and determined that dronedarone has the most potent activity both in vitro and in vivo. We found that dronedarone increases the thermal stability of LuxS, decreases the production of AI-2, and affects the biofilm formation of K. pneumoniae. We also identified the direct binding of dronedarone to LuxS. However, the mechanism by which dronedarone enhances the antibacterial activity of PB has not been elucidated and is worthy of further exploration. Our study provides a basis for the future development of drug combination regimens.

Epinephrine Stimulates Mycobacterium tuberculosis Growth and Biofilm Formation

The human stress hormones catecholamines play a critical role in communication between human microbiota and their hosts and influence the outcomes of bacterial infections. However, it is unclear how M. tuberculosis senses and responds to certain types of human stress hormones. In this study, we screened several human catecholamine stress hormones (epinephrine, norepinephrine, and dopamine) for their effects on Mycobacterium growth. Our results showed that epinephrine significantly stimulated the growth of M. tuberculosis in the serum-based medium as well as macrophages. In silico analysis and molecular docking suggested that the extra-cytoplasmic domain of the MprB might be the putative adrenergic sensor. Furthermore, we showed that epinephrine significantly enhances M. tuberculosis biofilm formation, which has distinct texture composition, antibiotic resistance, and stress tolerance. Together, our data revealed the effect and mechanism of epinephrine on the growth and biofilm formation of M. tuberculosis, which contributes to the understanding of the environmental perception and antibiotic resistance of M. tuberculosis and provides important clues for the understanding of bacterial pathogenesis and the development of novel antibacterial therapeutics.

Neuromodulators as Interdomain Signaling Molecules Capable of Occupying Effector Binding Sites in Bacterial Transcription Factors

Hormones and neurotransmitters are important components of inter-kingdom signaling systems that ensure the coexistence of eukaryotes with their microbial community. Their ability to affect bacterial physiology, metabolism, and gene expression was evidenced by various experimental approaches, but direct penetration into bacteria has only recently been reported. This opened the possibility of considering neuromodulators as potential effectors of bacterial ligand-dependent regulatory proteins. Here, we assessed the validity of this assumption for the neurotransmitters epinephrine, dopamine, and norepinephrine and two hormones (melatonin and serotonin). Using flexible molecular docking for transcription factors with ligand-dependent activity, we assessed the ability of neuromodulators to occupy their effector binding sites. For many transcription factors, including the global regulator of carbohydrate metabolism, CRP, and the key regulator of lactose assimilation, LacI, this ability was predicted based on the analysis of several 3D models. By occupying the ligand binding site, neuromodulators can sterically hinder the interaction of the target proteins with the natural effectors or even replace them. The data obtained suggest that the direct modulation of the activity of at least some bacterial transcriptional factors by neuromodulators is possible. Therefore, the natural hormonal background may be a factor that preadapts bacteria to the habitat through direct perception of host signaling molecules.

Characterisation of the E. coli and Salmonella qseC and qseE mutants reveals a metabolic rather than adrenergic receptor role

Catecholamine stress hormones (norepinephrine, epinephrine, and dopamine) are signals that have been shown to be used as environmental cues, which affect the growth and virulence of normal microbiota as well as pathogenic bacteria. It has been reported that Escherichia coli and Salmonella use the two-component system proteins QseC and QseE to recognise catecholamines and so act as bacterial adrenergic receptors. In this study, we mutated the E. coli O157:H7 and Salmonella enterica serovar Typhimurium genes encoding QseC and QseE and found that this did not block stress hormone responsiveness in either species. Motility, biofilm formation, and analysis of virulence of the mutants using two infection models were similar to the wild-type strains. The main differences in phenotypes of the qseC and qseE mutants were responses to changes in temperature and growth in different media particularly with respect to salt, carbon, and nitrogen salt sources. In this physiological respect, it was also found that the phenotypes of the qseC and qseE mutants differed between E. coli and Salmonella. These findings collectively suggest that QseC and QseE are not essential for E. coli and Salmonella to respond to stress hormones and that the proteins may be playing a role in regulating metabolism.

Effects of Guava (Psidium guajava L.) Leaf Extract on the Metabolomics of Serum and Feces in Weaned Piglets Challenged by Escherichia coli

The effects of dietary supplementation with guava leaf extracts (GE) on intestinal barrier function and serum and fecal metabolome in weaned piglets challenged by enterotoxigenic Escherichia coli (ETEC) were investigated. In total, 50 weaned piglets (Duroc × Yorkshire × Landrace) from 25 pens (two piglets per pen) were randomly divided into five groups: BC (blank control), NC (negative control), S50 (supplemented with 50 mg kg⁻¹ diet GE), S100 (100 mg kg⁻¹ diet GE), and S200 (200 mg kg⁻¹ diet GE), respectively. On day 4, all groups (except BC) were orally challenged with enterotoxigenic ETEC at a dose of 1.0 × 10⁹ colony-forming units (CFUs). After treatment for 28 days, intestinal barrier function and parallel serum and fecal metabolomics analysis were carried out. Results suggested that dietary supplementation with GE (50–200 mg kg⁻¹) increased protein expression of intestinal tight junction proteins (ZO-1, occludin, claudin-1) (p < 0.05) and Na⁺/H⁺ exchanger 3 (NHE3) (p < 0.05). Moreover, dietary supplementation with GE (50–200 mg kg⁻¹) increased the level of tetrahydrofolic acid (THF) and reversed the higher level of nicotinamide-adenine dinucleotide phosphate (NADP) induced by ETEC in serum compared with the NC group (p < 0.05), and enhanced the antioxidant capacity of piglets. In addition, dietary addition with GE (100 mg kg⁻¹) reversed the lower level of L-pipecolic acid induced by ETEC in feces compared with the NC group (p < 0.05) and decreased the oxidative stress of piglets. Collectively, dietary supplementation with GE exhibited a positive effect on improving intestinal barrier function. It can reprogram energy metabolism through similar or dissimilar metabolic pathways and finally enhance the antioxidant ability of piglets challenged by ETEC.

Norepinephrine affects the interaction of adherent-invasive Escherichia coli with intestinal epithelial cells

Norepinephrine (NE), the stress hormone, stimulates many bacterial species’ growth and virulence, including Escherichia coli. However, the hormone’s impact on the adherent-invasive E. coli (AIEC) implicated in Crohn’s disease is poorly understood. In the study, we have investigated the effect of NE on the interaction of six AIEC strains isolated from an intestinal biopsy from 6 children with Crohn’s disease with Caco-2 cells. Our study focused on type 1 fimbria and CEACAM6 molecules serving as docking sites for these adhesins. The study results demonstrated that the hormone significantly increased the adherence and invasion of AIEC to Caco-2 cells in vitro. However, the effect was not associated with the impact of NE on the increased proliferation rate of AIEC or the fimA gene expression vital for their interaction with intestinal epithelial cells. Instead, the carcinoembryonic antigen-related cell-adhesion-molecule-6 (CEACAM6) level was increased significantly in NE-treated Caco-2 cells infected with AIEC in contrast to control uninfected NE-treated cells. These results indicated that NE influenced the interaction of AIEC with intestinal epithelium by increasing the level of CEACAM6 in epithelial cells, strengthening their adherence and invasion.

Role of dietary polyphenols on gut microbiota, their metabolites and health benefits

The beneficial health roles of dietary polyphenols in preventing oxidative stress related chronic diseases have been subjected to intense investigation over the last two decades. As our understanding of the role of gut microbiota advances our knowledge of the antioxidant and anti-inflammatory functions of polyphenols accumulates, there emerges a need to examine the prebiotic role of dietary polyphenols. This review focused onthe role of different types and sources of dietary polyphenols on the modulation of the gut microbiota, their metabolites and how they impact on host health benefits. Inter-dependence between the gut microbiota and polyphenol metabolites and the vital balance between the two in maintaining the host gut homeostasis were discussed with reference to different types and sources of dietary polyphenols. Similarly, the mechanisms behind the health benefits by various polyphenolic metabolites bio-transformed by gut microbiota were also explained. However, further research should focus on the importance of human trials and profound links of polyphenols-gut microbiota-nerve-brain as they provide the key to unlock the mechanisms behind the observed benefits of dietary polyphenols found in vitro and in vivo studies.

Pyruvate is required for catecholamine-stimulated growth of different strains of Campylobacter jejuni

Humans and food-producing animals are constantly exposed to and affected by stress. As a consequence of stress, the release of stress-related catecholamines, such as norepinephrine (NE) and dopamine (DA), from nerve terminals in the gastrointestinal tract potentiates both the growth and the virulence of pathogenic bacteria. This may lead to the enhancement of gastrointestinal infections in humans or food-producing animals. Compared with foodborne bacterial pathogens such as Escherichia coli and Salmonella spp., less is known about the effect of stress catecholamines on Campylobacter jejuni subsp. jejuni. The present study focuses on the effect(s) of stress catecholamines DA and NE in iron-restricted media and how they affect the growth of different C. jejuni strains NCTC 11168, 81-176, and ML2126. Results demonstrated that DA- and NE-enhanced growth of C. jejuni in iron-restricted media may involve different mechanisms that cannot be explained by current understanding which relies on catecholamine-mediated iron delivery. Specifically, we found that DA-enhanced growth requires pyruvate, whereas NE-enhanced growth does not. We further report significant strain-specific dependence of C. jejuni growth on various catecholamines in the presence or absence of pyruvate. These data provide novel insights into the effect(s) of stress catecholamines on the in vitro growth of C. jejuni in iron-restricted environments, such as the intestinal tract. They suggest a mechanism by which stress-related catecholamines affect the growth of C. jejuni in the intestinal tract of food-producing animals, which in turn may influence colonization and transmission to humans.

Unexpected Cell Wall Alteration-Mediated Bactericidal Activity of the Antifungal Caspofungin against Vancomycin-Resistant Enterococcus faecium

Enterococcus faecium has become a major opportunistic pathogen with the emergence of vancomycin-resistant enterococci (VRE). As part of the gut microbiota, they have to cope with numerous stresses, including effects of antibiotics and other xenobiotics, especially in patients hospitalized in intensive care units (ICUs) who receive many medications. The aim of this study was to investigate the impact of the most frequently prescribed xenobiotics for ICU patients on fitness, pathogenicity, and antimicrobial resistance of the vanB-positive E. faecium Aus0004 reference strain. Several phenotypic analyses were carried out, and we observed that caspofungin, an antifungal agent belonging to the family of echinocandins, had an important effect on E. faecium growth in vitro We confirmed this effect by electron microscopy and peptidoglycan analysis and showed that, even at a subinhibitory concentration (1/4× MIC, 8 mg/liter), caspofungin had an impact on cell wall organization, especially with respect to the abundance of some muropeptide precursors. By transcriptome sequencing (RNA-seq), it was also shown that around 20% of the transcriptome was altered in the presence of caspofungin, with 321 and 259 significantly upregulated and downregulated genes, respectively. Since the fungal target of caspofungin (i.e., β-1,3-glucan synthase) was absent in bacteria, the mechanistic pathway of caspofungin activity was investigated. The repression of genes involved in the metabolism of pyruvate seemed to have a drastic impact on bacterial cell viability, while a decrease of glycerol metabolism could explain the conformational modifications of peptidoglycan. This is the first report of caspofungin antibacterial activity against E. faecium, highlighting the potential impact of nonantibiotic xenobiotics against bacterial pathogens.

[Norepinephrine and intestinal microbiome in the early stages of demyelination: clinical-immunological parallels]

Biogenic amines are key mediators of neuroimmune interaction and may influence on multiple sclerosis (MS) pathogenesis and MS course. At the same time, the role of biogenic amines in immunoregulation of early stages of demyelination, in particular clinically isolated syndrome (CIS) and radiologically isolated syndrome (RIS) is still unclear. This literature review addresses a role of norepinephrine in the regulation of neuroimmune interactions in the early stages of the demyelination. Neuropsychological disorders, immunological characteristics, gut-brain axis as well as the role of norepinephrine in these interactions in patients with CIS, RIS and early MS are discussed.

Oral Treatments With Probiotics and Live Salmonella Vaccine Induce Unique Changes in Gut Neurochemicals and Microbiome in Chickens

Cross-talk between the gut microbiota and neurochemicals affects health and well-being of animals. However, little is known about this interaction in chickens despite their importance in food production. Probiotics and live Salmonella vaccines are microbial products commonly given orally to layer pullets to improve health and ensure food safety. This study's objective was to determine how these oral treatments, individually or in combination, would impact the gut environment of chickens. White Leghorn chicks were either non-treated (CON) or orally given probiotics (PRO), a recombinant attenuated Salmonella vaccine (RASV; VAX), or both (P+V). Birds were fed with probiotics daily beginning at 1-day-old and orally immunized with RASV at 4-days-old and boosted 2 weeks post-primary vaccination. At 5 weeks, ceca content, ceca tissues, and small intestinal scrapings (SISs) were collected from ten birds/group post-euthanasia for analyses. Catecholamine, but not serotonergic, metabolism was affected by treatments. Dopamine metabolism, indicated by L-DOPA and DOPAC levels, were increased in P+V birds versus CON and PRO birds. Based on 16S sequencing, beta diversity was more similar among vaccinated birds versus birds given probiotics, suggesting live Salmonella vaccination has a major selective pressure on microbial diversity. Abundances of Akkermansia muciniphila and Enterobacteriaceae positively correlated with levels of tyrosine and norepinephrine, respectively. Both enumeration and 16S sequencing, determined that PRO exhibited the greatest levels of Enterobacteriaceae in the ceca and feces, which was associated with greater IgA production against E. coli virulence factors as tested by ELISA. In summary, we demonstrate that using probiotics alone versus in combination with a live vaccine has major implications in catecholamine production and the microbiota of layer pullets. Additionally, unique correlations between changes in some neurochemicals and specific bacteria have been shown.

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.

The roles of hormones in the modulation of growth and virulence genes' expressions in UPEC strains

BACKGROUND

Host factors such as hormones are known to modulate growth, virulence and antibiotic susceptibility of bacteria. In the present study, the effect of norepinephrine (NE) and estradiol (Est) on growth and expression levels of virulence genes (usp, sfa/foc, cnf1, aer) of uropathogenic E. coli (UPEC) strains C7 and C149 were investigated.

METHODS

E. coli C7 and C149 were grown in serum based SAPI broth with and without three different concentrations of norepinephrine and estradiol. Growths were determined via optical density measurement in a spectrophotometer. Real-time polymerase chain reaction was used to determine gene expression levels. Statistical analyses were performed by one way Anova Tukey's post hoc-test.

RESULTS

According to our results it has been shown that, growths of bacteria could be affected in the presence of hormones which are variable according to incubation period and hormones' concentrations. Up regulation of usp, sfa/foc, cnf1 were shown to be statistically significant (p < 0.05) in the presence of low, medium levels NE and all concentrations of Est. The expression of aer was down regulated significantly in the presence of low (p < 0.001) and medium level of Est; but all levels of NE was shown to be increased the expression of aer significantly (p < 0.05).

CONCLUSIONS

The results of the present study has shown once more that host factors (norepinephrine and estradiol) could influence the growth of a bacterium as well as gene expressions.

Influences of stress hormones on microbial infections

Stress hormones have been recently suggested to influence the pathogenicity of bacteria significantly. Stress has been identified as part of the factors causing an outbreak of infections in the aquaculture industry. The most studied neuroendocrine hormonal family from a microbial endocrinology perspective is the catecholamine comprising of norepinephrine, epinephrine, and dopamine. It is of importance that catecholamine affects the growth and virulence of bacteria. The influence of stress on bacterial infections is attributed to the ability of catecholamines to suppress the immune system as the mode of action for increased bacterial growth. Catecholamines have increased the growth of bacteria, virulence-associated factors, adhesions, and biofilm formation and consequently influence the outcome of infections by these bacteria in many hosts. The siderophores and the ferric iron transport system plays a vital role in the mechanism by which catecholamines stimulates growth and exposure of genes to stress hormones enhances the expression of genes involved in bacterial virulence. In recent years, it has been discovered that intestinal microflora takes part in bidirectional communication between the gut and brain. The rapidly growing field of microbiome research, understanding the communities of bacteria living within our bodies and the genes they contain is yielding new perspectives. This review reveals catecholamines effects on the growth and virulence of bacteria and the latest trends in microbial endocrinology.

[Gut human microbiota and multiple sclerosis]

Recently the relationship between gut microbiota changes and the development of immune-mediated diseases of the central nervous system (CNS) has been reported. This review presents literature data on the effect of gut microbiota on the function of the immune and nervous systems. The authors discuss possible mechanisms of the relationship between gut microbiota changes and CNS diseases on the model of multiple sclerosis (MS).

Effect of catecholamine stress hormones (dopamine and norepinephrine) on growth, swimming motility, biofilm formation and virulence factors of Yersinia ruckeri in vitro and an in vivo evaluation in rainbow trout

In this study, we evaluated the impact of the catecholamines on growth, swimming motility, biofilm formation and some virulence factors activities of pathogenic Yersinia ruckeri. Norepinephrine and dopamine (at 100 µM) significantly increased the growth of Y. ruckeri in culture media containing serum. An increase in swimming motility of the pathogen was found following the exposure to the hormones; however, no effect was seen on caseinase, phospholipase and haemolysin productions. Further, antagonists for the catecholamine receptors were observed to block some of the influences of the catecholamines. Indeed, the effects of catecholamines were inhibited by chlorpromazine (the dopaminergic receptor antagonist) for dopamine, labetalol (α-and β-adrenergic receptor antagonist) and phenoxybenzamine (the α-adrenergic receptor antagonist) for norepinephrine, but propranolol (the β-adrenergic receptor antagonist) showed no effect. Pretreatment of Y. ruckeri with the catecholamines resulted in a significant enhancement of its virulence towards rainbow trout and the antagonists could neutralize the effect of the stress hormones in vivo. In summary, our results show that the catecholamines increase the virulence of Y. ruckeri which is pathogenic to trout through increasing the motility, biofilm formation and growth.

Role of Neurochemicals in the Interaction between the Microbiota and the Immune and the Nervous System of the Host Organism

This work is concerned with the role of evolutionary conserved substances, neurotransmitters, and neurohormones, within the complex framework of the microbial consortium-immune system-nervous system axis in the human or animal organism. Although the operation of each of these systems per se is relatively well understood, their combined effects on the host organism still await further research. Drawing on recent research on host-produced and microbial low-molecular-weight neurochemicals such as biogenic amines, amino acids, and short-chain fatty acids (SCFAs), we suggest that these mediators form a part of a universal neurochemical "language." It mediates the whole gamut of harmonious and disharmonious interactions between (a) the intestinal microbial consortium, (b) local and systemic immune cells, and (c) the central and peripheral nervous system. Importantly, the ongoing microbiota-host interactivity is bidirectional. We present evidence that a large number of microbially produced low-molecular-weight compounds are identical or homologous to mediators that are synthesized by immune or nervous cells and, therefore, can bind to the corresponding host receptors. In addition, microbial cells specifically respond to host-produced neuromediators/neurohormones because they have adapted to them during the course of many millions of years of microbiota-host coevolution. We emphasize that the terms "microbiota" and "microbial consortium" are to be used in the broadest sense, so as to include, apart from bacteria, also eukaryotic microorganisms. These are exemplified by the mycobiota whose role in the microbial consortium-immune system-nervous system axis researchers are only beginning to elucidate. In light of the above, it is imperative to reform the current strategies of using probiotic microorganisms and their metabolites for treating and preventing dysbiosis-related diseases. The review demonstrates, in the example of novel probiotics (psychobiotics), that many target-oriented probiotic preparations produce important side effects on a wide variety of processes in the host organism. In particular, we should take into account probiotics' capacity to produce mediators that can considerably modify the operation of the microecological, immune, and nervous system of the human organism.

Chemotaxis of Escherichia coli to major hormones and polyamines present in human gut

The microorganisms in the gastrointestinal (GI) tract can influence the metabolism, immunity, and behavior of animal hosts. Increasing evidence suggests that communication between the host and the microbiome also occurs in the opposite direction, with hormones and other host-secreted compounds being sensed by microorganisms. Here, we addressed one key aspect of the host–microbe communication by studying chemotaxis of a model commensal bacterium, Escherichia coli, to several compounds present abundantly in the GI tract, namely catecholamines, thyroid hormones, and polyamines. Our results show that E. coli reacts to five out of ten analyzed chemicals, sensing melatonin, and spermidine as chemorepellents and showing mixed responses to dopamine, norepinephrine and 3,4-dihydroxymandelic acid. The strongest repellent response was observed for the polyamine spermidine, and we demonstrate that this response involves the low-abundance chemoreceptor Trg and the periplasmic binding protein PotD of the spermidine uptake system. The chemotactic effects of the tested compounds apparently correlate with their influence on growth and their stability in the GI tract, pointing to the specificity of the observed behavior. We hypothesize that the repellent responses observed at high concentrations of chemoeffective compounds might enable bacteria to avoid harmful levels of hormones and polyamines in the gut and, more generally, antimicrobial activities of the mucous layer.

Norepinephrine augmented in vitro growth of uropathogenic E. coli in Type 2 diabetes mellitus and its suppression by silodosin (alpha blocker)

Norepinephrine is secreted under conditions of stress in humans. The ability of bacteria to sense mammalian hormone may have a role in propagation of infection. The present study investigated the effect of norepinephrine on in vitro growth of uropathogenic E. coli (UPEC) and the effect of silodosin on norepinephrine-induced changes. The spot urine samples were collected from 56 individuals (14 diabetic patients with UTI, 14 diabetic without UTI, 14 non-diabetic UTI and 14 healthy volunteer controls) for the measurement of urinary norepinephrine concentrations. The concentration of norepinephrine, as found in urine of human subjects, was reproduced in artificial urine medium to study the growth of UPEC. The norepinephrine concentration showing maximum growth response was selected to study the effect of silodosin on the growth inhibition of UPEC. Result showed significantly elevated urinary norepinephrine in diabetic patients with and without UTI and also in nondiabetic UTI groups. The norepinephrine concentration equivalent to that in diabetic UTI patients enhanced the growth of UPEC. Furthermore, silodosin (0.32 μM) inhibited the growth of the UPEC.

The stress hormone norepinephrine increases the growth and virulence of Aeromonas hydrophila

Stress is an important contributing factor in the outbreak of infectious fish diseases. To comprehensively understand the impact of catecholamine stress hormone norepinephrine (NE) on the pathogenicity of Aeromonas hydrophila, we assessed variations in bacterial growth, virulence‐related genes expression and virulence factors activity after NE addition in serum‐SAPI medium. Further, we assessed the effects of NE on A. hydrophila virulence in vivo by challenging fish with pathogenic strain AH196 and following with or without NE injection. The NE‐associated stimulation of A. hydrophila strain growth was not linear‐dose‐dependent, and only 100 μM, or higher concentrations, could stimulate growth. Real‐time PCR analyses revealed that NE notably changed 13 out of the 16 virulence‐associated genes (e.g. ompW, ahp, aha, ela, ahyR, ompA, and fur) expression, which were all significantly upregulated in A. hydrophila AH196 (p < 0.01). NE could enhance the protease activity, but not affect the lipase activity, hemolysis, and motility. Further, the mortality of crucian carp challenged with A. hydrophila AH196 was significantly higher in the group treated with NE (p < 0.01). Collectively, our results showed that NE enhanced the growth and virulence of pathogenic bacterium A. hydrophila.

Microbial endocrinology: Why the intersection of microbiology and neurobiology matters to poultry health

The union of microbiology and neurobiology has led to a revolution in the way we view the microbiome. Now recognized as important symbionts, the microorganisms which inhabit multiple niches in mammalian and avian (chicken) hosts, such as the intestinal tract and skin, serve and influence many important physiological functions. The realization that the gut microbiome serves as a kind of "microbial organ" has important implications for many areas of biology. In this paper advances in the field of microbial endocrinology which may hold relevance for the poultry industry are examined.

Evidence for PMAT- and OCT-like biogenic amine transporters in a probiotic strain of Lactobacillus: Implications for interkingdom communication within the microbiota-gut-brain axis

The ability of prokaryotic microbes to produce and respond to neurochemicals that are more often associated with eukaryotic systems is increasingly recognized through the concept of microbial endocrinology. Most studies have described the phenomena of neurochemical production by bacteria, but there remains an incomplete understanding of the mechanisms by which microbe- or host-derived neuroactive substances can be recognized by bacteria. Based on the evolutionary origins of eukaryotic solute carrier transporters, we hypothesized that bacteria may possess an analogous uptake function for neuroactive biogenic amines. Using specific fluorescence-based assays, Lactobacillus salivarius biofilms appear to express both plasma membrane monoamine transporter (PMAT)- and organic cation transporter (OCT)-like uptake of transporter-specific fluorophores. This phenomenon is not distributed throughout the genus Lactobacillus as L. rhamnosus biofilms did not take up these fluorophores. PMAT probe uptake into L. salivarius biofilms was attenuated by the protonophore CCCP, the cation transport inhibitor decynium-22, and the natural substrates norepinephrine, serotonin and fluoxetine. These results provide the first evidence, to our knowledge, for the existence of PMAT- and OCT-like uptake systems in a bacterium. They also suggest the existence of a hitherto unrecognized mechanism by which a probiotic bacterium may interact with host signals and may provide a means to examine microbial endocrinology-based interactions in health and disease that are part of the larger microbiota-gut-brain axis.

Microbial Endocrinology in the Pathogenesis of Infectious Disease

Microbial endocrinology represents the intersection of two seemingly disparate fields, microbiology and neurobiology, and is based on the shared presence of neurochemicals that are exactly the same in host as well as in the microorganism. The ability of microorganisms to not only respond to, but also produce, many of the same neurochemicals that are produced by the host, such as during periods of stress, has led to the introduction of this evolutionary-based mechanism which has a role in the pathogenesis of infectious disease. The consideration of microbial endocrinology-based mechanisms has demonstrated, for example, that the prevalent use of catecholamine-based synthetic drugs in the clinical setting contributes to the formation of biofilms in indwelling medical devices. Production of neurochemicals by microorganisms most often employs the same biosynthetic pathways as those utilized by the host, indicating that acquisition of host neurochemical-based signaling system in the host may have been acquired due to lateral gene transfer from microorganisms. That both host and microorganism produce and respond to the very same neurochemicals means that there is bidirectionality contained with the theoretical underpinnings of microbial endocrinology. This can be seen in the role of microbial endocrinology in the microbiota-gut-brain axis and its relevance to infectious disease. Such shared pathways argue for a role of microorganism-neurochemical interactions in infectious disease.

Catecholamine-Stimulated Growth of Aeromonas hydrophila Requires the TonB2 Energy Transduction System but Is Independent of the Amonabactin Siderophore

The growth-stimulating effects of catecholamine stress hormones have been demonstrated in many pathogens. However, catecholamine-induced growth and its underlying mechanisms remain poorly understood in Aeromonas hydrophila. The present study sought to demonstrate that norepinephrine (NE), epinephrine (Epi), dopamine (Dopa), and L-dopa stimulate the growth of A. hydrophila in iron-restricted media containing serum. NE exhibited the strongest growth stimulation, which could be blocked by adrenergic antagonists. Furthermore, it was demonstrated that NE could sequester iron from transferrin, thereby providing a more accessible iron source for utilization by A. hydrophila. The deletion of the amoA gene associated with amonabactin synthesis revealed that the amonabactin siderophore is not required for NE-stimulated growth. However, the deletion of the TonB2 energy transduction system resulted in the loss of growth promotion by NE, indicating that a specific TonB-dependent outer membrane receptor might be involved in the transport of iron from transferrin. Collectively, our data show that catecholamine sensing promotes the growth of A. hydrophila in a manner that is dependent on the TonB2 energy transduction system.

Salmonella Typhimurium and Multidirectional Communication in the Gut

The mammalian digestive tract is home to trillions of microbes, including bacteria, archaea, protozoa, fungi, and viruses. In monogastric mammals the stomach and small intestine harbor diverse bacterial populations but are typically less populated than the colon. The gut bacterial community (microbiota hereafter) varies widely among different host species and individuals within a species. It is influenced by season of the year, age of the host, stress and disease. Ideally, the host and microbiota benefit each other. The host provides nutrients to the microbiota and the microbiota assists the host with digestion and nutrient metabolism. The resident microbiota competes with pathogens for space and nutrients and, through this competition, protects the host in a phenomenon called colonization resistance. The microbiota participates in development of the host immune system, particularly regulation of autoimmunity and mucosal immune response. The microbiota also shapes gut–brain communication and host responses to stress; and, indeed, the microbiota is a newly recognized endocrine organ within mammalian hosts. Salmonella enterica serovar Typhimurium (S. Typhimurium hereafter) is a food-borne pathogen which adapts to and alters the gastrointestinal (GI) environment. In the GI tract, S. Typhimurium competes with the microbiota for nutrients and overcomes colonization resistance to establish infection. To do this, S. Typhimurium uses multiple defense mechanisms to resist environmental stressors, like the acidic pH of the stomach, and virulence mechanisms which allow it to invade the intestinal epithelium and disseminate throughout the host. To coordinate gene expression and disrupt signaling within the microbiota and between host and microbiota, S. Typhimurium employs its own chemical signaling and may regulate host hormone metabolism. This review will discuss the multidirectional interaction between S. Typhimurium, host and microbiota as well as mechanisms that allow S. Typhimurium to succeed in the gut.

Role of the Intestinal Microbiota in Host Responses to Stressor Exposure

Humans have coevolved over time to not only tolerate but also rely on trillions of microbes that aid in the development of our immune system, provide nutrients, break down potentially noxious substances, and act as a barrier against potentially pathogenic organisms. These microbes, collectively known as the microbiota, live in relatively stable communities on mucosal surfaces such as the respiratory tract and gastrointestinal tract. Changes to the microbiota are often transient, due to changes in diet, antibiotic exposure, and psychological stressor exposure. This chapter will discuss how psychological stressors can shape the intestinal microbial community and how these perturbations can contribute to stressor-induced changes in immune function, neurodevelopment, and behavioral deficits.

The Role of the Microbiome in the Relationship of Asthma and Affective Disorders

The effect of stress, anxiety and other affective states on inflammatory conditions such as asthma is well documented. Although several immune pathway mechanisms have been proposed and studied, they cannot fully explain the relationship. In this chapter we present a new perspective on asthma development and exacerbation that integrates findings on the role of psychological factors in asthma with the microbiome and the hygiene hypothesis in asthma development.

New Trends and Perspectives in the Evolution of Neurotransmitters in Microbial, Plant, and Animal Cells

The evolutionary perspective on the universal roles of compounds known as neurotransmitters may help in the analysis of relations between all organisms in biocenosis-from microorganisms to plant and animals. This phenomenon, significant for chemosignaling and cellular endocrinology, has been important in human health and the ability to cause disease or immunity, because the "living environment" influences every organism in a biocenosis relationship (microorganism-microorganism, microorganism-plant, microorganism-animal, plant-animal, plant-plant and animal-animal). Non-nervous functions of neurotransmitters (rather "biomediators" on a cellular level) are considered in this review and ample consideration is given to similarities and differences that unite, as well as distinguish, taxonomical kingdoms.

Gut Microbiota Modification: Another Piece in the Puzzle of the Benefits of Physical Exercise in Health?

Regular physical exercise provides many health benefits, protecting against the development of chronic diseases, and improving quality of life. Some of the mechanisms by which exercise provides these effects are the promotion of an anti-inflammatory state, reinforcement of the neuromuscular function, and activation of the hypothalamic-pituitary-adrenal (HPA) axis. Recently, it has been proposed that physical exercise is able to modify gut microbiota, and thus this could be another factor by which exercise promotes well-being, since gut microbiota appears to be closely related to health and disease. The purpose of this paper is to review the recent findings on gut microbiota modification by exercise, proposing several mechanisms by which physical exercise might cause changes in gut microbiota.

Dietary Catechols and their Relationship to Microbial Endocrinology

This chapter examines the evidence that the ability of neuroendocrine hormones, notably norepinephrine and epinephrine, to stimulate bacterial growth in iron-restricted media is not limited to molecules with a catecholamine structure but is also possessed by a variety of other catechols, many of which are of plant origin and are common in the diet. Catechols derived from the diet, such as the tea flavanols, can be present in the plasma at submicromolar and micromolar concentrations, comparable with the concentrations of catecholamines that have been shown to be effective in promoting bacterial growth under conditions of iron restriction, although many dietary catechols, notably quercetin derivatives, are present in the plasma and tissues largely as conjugates, from which the catechol function has been lost. Finally, although bacterial growth promotion through relief of iron restriction appears to be exhibited by a wide range of catechols, the gene-activation effects of catecholamines demonstrated to occur in some bacteria may be much more specific, although the definitive experiments to establish structure-function relationships have yet to be reported.

CRH promotes S. pneumoniae growth in vitro and increases lung carriage in mice

Streptococcus pneumoniae (S. pneumoniae), a commensal across the nasal passages, is responsible for the majority of infectious pneumonia cases worldwide. Previous studies have shown that hormonal factors may be influential in regulating S. pneumoniae’s transition from a non-pathogen to a pathogenic state. The current study investigated the effects of corticotropin-releasing hormone (CRH), a peptide hormone involved in stress, on the pathogenicity of S. pneumoniae. Mice were infected with CRH-treated S. pneumoniae via intranasal route, showing an increase in pulmonary bacterial burden. We also quantified S. pneumoniae’s response to CRH through limited serial dilutions and growth curve analysis. We demonstrated that CRH promotes S. pneumoniae titer-dependent proliferation, as well as accelerates log-phase growth. Results also showed an increase in pneumococcal-associated virulence protein A virulence gene expression in response to CRH. These results demonstrate a role for CRH in S. pneumoniae pathogenicity, thus implicating CRH in mediating the transition of S. pneumoniae into a pathogenic state.

Catecholamines promote Actinobacillus pleuropneumoniae growth by regulating iron metabolism

Catecholamines are host stress hormones that can induce the growth of many bacteria by facilitating iron utilization and/or regulate the expression of virulence genes through specific hormone receptors. Whether these two responsive pathways are interconnected is unknown. In our previous study, it was found that catecholamines can regulate the expression of a great number of genes of Actinobacillus pleuropneumoniae, an important swine respiratory pathogen. However, bacterial growth was not affected by catecholamines in rich medium. In this study, it was discovered that catecholamines affected A. pleuropneumoniae growth in chemically defined medium (CDM). We found that serum inhibited A. pleuropneumoniae growth in CDM, while epinephrine, norepinephrine and dopamine promoted A. pleuropneumoniae growth in the CDM containing serum. The known bacterial hormone receptor QseC didn’t play roles in this process. Ion-supplementation and transcriptome analysis indicated that serum addition resulted in iron-restricted conditions which were alleviated by the addition of catecholamines. Transferrin, one of the components in serum, inhibited the growth of A. pleuropneumoniae in CDM, an effect reversed by addition of catecholamines in a TonB2-dependent manner. Our data demonstrate that catecholamines promote A. pleuropneumoniae growth by regulating iron-acquisition and metabolism, which is independent of the adrenergic receptor QseC.

Norepinephrine and dopamine increase motility, biofilm formation, and virulence of Vibrio harveyi

Vibrio harveyi is one of the major pathogens of aquatic organisms, affecting both vertebrates and invertebrates, and causes important losses in the aquaculture industry. In order to develop novel methods to control disease caused by this pathogen, we need to obtain a better understanding of pathogenicity mechanisms. Sensing of catecholamines increases both growth and production of virulence-related factors in pathogens of terrestrial animals and humans. However, at this moment, knowledge on the impact of catecholamines on the virulence of pathogens of aquatic organisms is lacking. In the present study, we report that in V. harveyi, norepinephrine (NE) and dopamine (Dopa) increased growth in serum-supplemented medium, siderophore production, swimming motility, and expression of genes involved in flagellar motility, biofilm formation, and exopolysaccharide production. Consistent with this, pretreatment of V. harveyi with catecholamines prior to inoculation into the rearing water resulted in significantly decreased survival of gnotobiotic brine shrimp larvae, when compared to larvae challenged with untreated V. harveyi. Further, NE-induced effects could be neutralized by α-adrenergic antagonists or by the bacterial catecholamine receptor antagonist LED209, but not by β-adrenergic or dopaminergic antagonists. Dopa-induced effects could be neutralized by dopaminergic antagonists or LED209, but not by adrenergic antagonists. Together, our results indicate that catecholamine sensing increases the success of transmission of V. harveyi and that interfering with catecholamine sensing might be an interesting strategy to control vibriosis in aquaculture. We hypothesize that upon tissue and/or hemocyte damage during infection, pathogens come into contact with elevated catecholamine levels, and that this stimulates the expression of virulence factors that are required to colonize a new host.

Host stress hormone norepinephrine stimulates pneumococcal growth, biofilm formation and virulence gene expression

Background

Host signals are being shown to have a major impact on the bacterial phenotype. One of them is the endogenously produced catecholamine stress hormones, which are also used therapeutically as inotropes. Recent work form our laboratories have found that stress hormones can markedly increase bacterial growth and virulence. This report reveals that Streptococcus pneumoniae, a commensal that can also be a major cause of community acquired and nosocomial pneumonia, is highly inotrope responsive. Therapeutic levels of the stress hormone norepinephrine increased pneumococcal growth via a mechanism involving provision of iron from serum-transferrin and inotrope uptake, as well as enhancing expression of key genes in central metabolism and virulence. Collectively, our data suggests that Streptococcus pneumoniae recognises host stress as an environmental cue to initiate growth and pathogenic processes.

Results

Effects of a clinically attainable concentration of norepinephrine on S. pneumoniae pathogenicity were explored using in vitro growth and virulence assays, and RT-PCR gene expression profiling of genes involved in metabolism and virulence.

We found that norepinephrine was a potent stimulator of growth, via a mechanism involving norepinephrine-delivery of transferrin-iron and internalisation of the inotrope. Stress hormone exposure also markedly increased biofilm formation. Importantly, gene profiling showed that norepinephrine significantly enhanced expression of genes involved in central metabolism and host colonisation. Analysis of the response of the pneumococcal pspA and pspC mutants to the stress hormone showed them to have a central involvement in the catecholamine response mechanism.

Conclusions

Collectively, our evidence suggests that the pneumococcus has mechanisms to recognise and process host stress hormones to augment its virulence properties. The ability to respond to host stress signals may be important for the pneumococcal transition from colonization to invasion mode, which is key to its capacity to cause life-threatening pneumonia, septicaemia and meningitis.

Immunological consequences of ischemic stroke

The treatment of ischemic stroke is one of the great challenges in modern neurology. The localization and the size of the infarct determine the long-term disability of stroke survivors. Recent observations have revealed that stroke also alters the function of the immune system and vice versa: At the site of the infarct, a local inflammatory response develops that enhances brain lesion development. In experimental stroke, proof-of-concept studies confirm that inhibition of this immune response reduces lesion volume and improves outcome. In the peripheral blood of stroke patients, though, lymphocytopenia and monocyte dysfunction develop. These changes reflect a clinically relevant impairment of bacterial defense mechanisms because they are associated with an enhanced risk to acquire post-stroke infections. Stress hormones have been identified as important mediators of stroke-induced immune suppression. The pharmacological inhibition of beta adrenergic receptors, but not the inhibition of steroids, is effective in reducing infection and improving clinical outcome in experimental stroke; catecholamine release therefore appears causally related to stroke-induced immune suppression. Strong evidence supports the hypothesis that these immune alterations impact the clinical course of stroke patients. Thus, the development of new therapeutic strategies targeted to alter the immunological consequences of stroke appears promising. However, to date, the beneficial effects seen in experimental stroke have not been successfully translated into a clinical trial. This brief review summarizes the current understanding of the immunological consequences of ischemic stroke. Finally, we propose a concept that links the peripheral immune suppression with the development of local inflammation.