Antibiotic-induced dysbiosis alters host-bacterial interactions and leads to colonic sensory and motor changes in mice

Morphological elucidation of short-chain fatty acid receptor GPR41-positive enteric sensory neurons in the colon of mice with dextran sulfate sodium-induced colitis

Although the etiology of inflammatory bowel disease (IBD) remains unclear, it has generally been accepted that abnormalities in the intestinal immune system and dysbiosis of the gut microbiota are involved in the pathology of IBD. Recently, short-chain fatty acids (SCFAs) produced by gut microbiota were reported to maintain intestinal homeostasis through their receptors, such as GPR41. However, there are contradictory reports about the role of GPR41 in intestinal inflammation. Consequently, the roles of GPR41 in dysbiosis induced by intestinal inflammation remain unclear. Thus, we investigated the distribution of GPR41 in the colonic mucosa of mice with dextran sulfate sodium (DSS)-induced colitis. GPR41-immunoreactive fibrous structures were observed in the colonic lamina propria and muscularis layer of normal mice. In addition, GPR41-immunoreactive fibrous structures partly colocalized with calcitonin gene-related peptide (CGRP; a neurotransmitter of cholinergic enteric sensory neurons)-immunoreactive nerve fibers in the colonic lamina propria, indicating that GPR41 is expressed in cholinergic intrinsic sensory neurons. Furthermore, both GPR41-immunoreactivities and CGRP-immunoreactivities were significantly increased in the lamina propria of the colon in mice with DSS-induced colitis. Interestingly, GPR41-immunoreactivities were often found in close proximity to F4/80⁺ macrophages in the colonic mucosa of normal mice, and their frequency was elevated in the colonic mucosa of mice with DSS-induced colitis. Therefore, the crosstalk between SCFA-sensing intrinsic sensory neurons and macrophages might be involved in the pathology of acute colitis.

Peripherally acting opioid analgesics and peripherally-induced analgesia

The management of pain, particularly chronic pain, is still an area of medical need. In this context, opioids remain a gold standard for the treatment of pain. However, significant side effects, mainly of central origin, limit their clinical use. Here, we review recent progress to improve the therapeutic and safety profiles of opioids for pain management. Characterization of peripheral opioid-mediated pain mechanisms have been a key component of this process. Several studies identified peripheral µ, δ, and κ opioid receptors (MOR, DOR, and KOR, respectively) and nociceptin/orphanin FQ (NOP) receptors as significant players of opioid-mediated antinociception, able to achieve clinically significant effects independently of any central action. Following this, particularly from a medicinal chemistry point of view, main efforts have been directed towards the peripheralization of opioid receptor agonists with the objective of optimizing receptor activity and minimizing central exposure and the associated undesired effects. These activities have allowed the characterization of a great variety of compounds and investigational drugs that show low central nervous system (CNS) penetration (and therefore a reduced side effect profile) yet maintaining the desired opioid-related peripheral antinociceptive activity. These include highly hydrophilic/amphiphilic and massive molecules unable to easily cross lipid membranes, substrates of glycoprotein P (a extrusion pump that avoids CNS penetration), nanocarriers that release the analgesic agent at the site of inflammation and pain, and pH-sensitive opioid agonists that selectively activate at those sites (and represent a new pharmacodynamic paradigm). Hopefully, patients with pain will benefit soon from the incorporation of these new entities.

Perspectives on how mucosal immune responses, infections and gut microbiome shape IgA nephropathy and future therapies

Infections have been considered to play a critical role in the pathogenesis of IgA nephropathy (IgAN) because synpharyngitic hematuria is a common feature in IgAN. However, how infections participate in this process is still debated. More recent studies have also revealed that the alteration of the gut microbiome exerts a profound effect on host immune responses, contributing to the etiology or progression of autoimmunity. Considering IgA as the first line of defense against bacterial and viral antigens, this review evaluates the relationships among intestinal infections, gut microbiome, and IgA for a better understanding of the pathogenesis of IgAN. Moreover, as a prototype of IgA immunity, we provide detailed clarification of IgAN pathogenesis to shed light on other diseases in which IgA plays a role. Finally, we discuss potential therapies focusing on microbes and mucosal immune responses in IgAN.

Norepinephrine depleting toxin DSP-4 and LPS alter gut microbiota and induce neurotoxicity in α-synuclein mutant mice

This study examined the genetic mutation and toxicant exposure in producing gut microbiota alteration and neurotoxicity. Homozygous α-synuclein mutant (SNCA) mice that overexpress human A53T protein and littermate wild-type mice received a single injection of LPS (2 mg/kg) or a selective norepinephrine depleting toxin DSP-4 (50 mg/kg), then the motor activity, dopaminergic neuron loss, colon gene expression and gut microbiome were examined 13 months later. LPS and DSP-4 decreased rotarod and wirehang activity, reduced dopaminergic neurons in substantia nigra pars compacta (SNpc), and SNCA mice were more vulnerable. SNCA mice had 1,000-fold higher human SNCA mRNA expression in the gut, and twofold higher gut expression of NADPH oxidase (NOX2) and translocator protein (TSPO). LPS further increased expression of TSPO and IL-6 in SNCA mice. Both LPS and DSP-4 caused microbiome alterations, and SNCA mice were more susceptible. The altered colon microbiome approximated clinical findings in PD patients, characterized by increased abundance of Verrucomicrobiaceae, and decreased abundance of Prevotellaceae, as evidenced by qPCR with 16S rRNA primers. The Firmicutes/Bacteroidetes ratio was increased by LPS in SNCA mice. This study demonstrated a critical role of α-synuclein and toxins interactions in producing gut microbiota disruption, aberrant gut pro-inflammatory gene expression, and dopaminergic neuron loss.

Opposing effects of antibiotics and germ-free status on neuropeptide systems involved in social behaviour and pain regulation

Background

Recent research has revealed that the community of microorganisms inhabiting the gut affects brain development, function and behaviour. In particular, disruption of the gut microbiome during critical developmental windows can have lasting effects on host physiology. Both antibiotic exposure and germ-free conditions impact the central nervous system and can alter multiple aspects of behaviour. Social impairments are typically displayed by antibiotic-treated and germ-free animals, yet there is a lack of understanding of the underlying neurobiological changes. Since the μ-opioid, oxytocin and vasopressin systems are key modulators of mammalian social behaviour, here we investigate the effect of experimentally manipulating the gut microbiome on the expression of these pathways.

Results

We show that social neuropeptide signalling is disrupted in germ-free and antibiotic-treated mice, which may contribute to the behavioural deficits observed in these animal models. The most notable finding is the reduction in neuroreceptor gene expression in the frontal cortex of mice administered an antibiotic cocktail post-weaning. Additionally, the changes observed in germ-free mice were generally in the opposite direction to the antibiotic-treated mice.

Conclusions

Antibiotic treatment when young can impact brain signalling pathways underpinning social behaviour and pain regulation. Since antibiotic administration is common in childhood and adolescence, our findings highlight the potential adverse effects that antibiotic exposure during these key neurodevelopmental periods may have on the human brain, including the possible increased risk of neuropsychiatric conditions later in life. In addition, since antibiotics are often considered a more amenable alternative to germ-free conditions, our contrasting results for these two treatments suggest that they should be viewed as distinct models.

Fucoidan isolated from Ascophyllum nodosum alleviates gut microbiota dysbiosis and colonic inflammation in antibiotic-treated mice

Antibiotic treatment, as an important therapeutic intervention, can cause damage to the host microbiome and the intestinal mucosal barrier. In order to find a way to alleviate the side effects of antibiotics, the present study investigated the effects of fucoidan (ANP) isolated from Ascophyllum nodosum on gut microbiota dysbiosis and colonic inflammation induced by ciprofloxacin-metronidazole (CiMe) in C57BL/6J mice. Our results showed that dietary ANP prevented colon shortening, alleviated the colonic tissue damages, and partially reversed the alteration of gut microbiota by increasing the abundance of potentially beneficial bacteria, e.g., Ruminococcaceae_UCG_014 and Akkermansia and decreasing the abundance of harmful bacteria, e.g., Proteus and Enterococcus. ANP also suppressed the overproduction of TNF-α, IL-1β, and IL-6 and promoted the expression of IL-10. In addition, ANP reversed the decreased production of short-chain fatty acids in CiMe-treated mice. Furthermore, correlation analysis indicated the presence of critical gut microbiota, which played important roles in reducing the inflammation-related indices. Thus, the present study suggests that fucoidan isolated from Ascophyllum nodosum is effective in providing protection against the negative effects of antibiotics on gut microbiota and colonic health.

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.

Early and Short-Term Interventions in the Gut Microbiota Affects Lupus Severity, Progression, and Treatment in MRL/lpr Mice

There have been attempts to reveal the possible associations between systemic lupus erythematosus (SLE) and gut microbiota. Using MRL/lpr mice, this study was performed to reveal whether early and short-term interventions in gut microbiota affect lupus. MRL/lpr mice were treated with antibiotics or fecal microbiota transplantation (FMT) before onset. Then, prednisone was used to treat the lupus mice with initially different gut microbiota compositions. The compositions of gut microbiota were assessed by the V3-V4 region of 16S rRNA gene sequence. Early and short-term antibiotics exposure aggravated lupus severity by depleting beneficial gut microbiota for lupus, such as Lactobacillus and Bifidobacterium, and enriching harmful gut microbiota for lupus, such as Klebsiella and Proteus. FMT alleviated lupus severity by renovating the antibiotic-induced dysbiosis of gut microbiota in the following 1 week after antibiotics exposure. Besides, short-term antibiotics exposure before onset imposed no significant effects on lupus progression, but the following one week of FMT suppressed lupus progression. Moreover, the short-term antibiotics or FMT before onset inhibited the therapeutic efficiency of prednisone on lupus from 9 to 13 weeks old of MRL/lpr mice. These data demonstrate that the gut microbiota before onset is important for lupus severity, progression and treatment.

Intestinal dysbiosis promotes epithelial-mesenchymal transition by activating tumor-associated macrophages in ovarian cancer

We aimed to investigate the relationship of intestinal dysbiosis (IDB) and ovarian cancer progression, and understand its underlying signaling mechanisms. IDB was induced with high dose antibiotics. The xenograft mouse model was used to assess the tumor progression. Real-time polymerase chain reaction and immunoblotting are commonly used quantitative methods, and they were used to quantify epithelial-mesenchymal transition (EMT) markers in this paper. Meanwhile, cellular proliferation was also measured. First, IDB could promote the growth of xenograft tumors and induce the EMT. Serum levels of tumor necrosis factor (TNF)-α and interleukin (IL)-6 also increased remarkably. In addition, the production and secretion of TNF-α and IL-6 in macrophages isolated from IDB model mice were observably higher. In vitro, conditioned medium could significantly stimulate the development of EMT in ovarian cancer cells. Loss of macrophages completely offset the pro-tumor effects of IDB. IDB can stimulate the activation of tumor-associated macrophages in ovarian cancer, which is achieved by secreting pro-inflammatory cytokines IL-6 and TNF-α, and ultimately induces the development of EMT.

The progress of gut microbiome research related to brain disorders

There is increasing evidence showing that the dynamic changes in the gut microbiota can alter brain physiology and behavior. Cognition was originally thought to be regulated only by the central nervous system. However, it is now becoming clear that many non-nervous system factors, including the gut-resident bacteria of the gastrointestinal tract, regulate and influence cognitive dysfunction as well as the process of neurodegeneration and cerebrovascular diseases. Extrinsic and intrinsic factors including dietary habits can regulate the composition of the microbiota. Microbes release metabolites and microbiota-derived molecules to further trigger host-derived cytokines and inflammation in the central nervous system, which contribute greatly to the pathogenesis of host brain disorders such as pain, depression, anxiety, autism, Alzheimer’s diseases, Parkinson’s disease, and stroke. Change of blood–brain barrier permeability, brain vascular physiology, and brain structure are among the most critical causes of the development of downstream neurological dysfunction. In this review, we will discuss the following parts:

Overview of technical approaches used in gut microbiome studies

Microbiota and immunity

Gut microbiota and metabolites

Microbiota-induced blood–brain barrier dysfunction

Neuropsychiatric diseases

■ Stress and depression

■ Pain and migraine

■ Autism spectrum disorders

Neurodegenerative diseases

■ Parkinson’s disease

■ Alzheimer’s disease

■ Amyotrophic lateral sclerosis

■ Multiple sclerosis

Cerebrovascular disease

■ Atherosclerosis

■ Stroke

■ Arteriovenous malformation

Conclusions and perspectives

Adherent-invasive Escherichia coli (AIEC): Cause or consequence of inflammation, dysbiosis, and rupture of cellular joints in patients with IBD?

There are many factors contributing to the development of gastrointestinal diseases, grouped into genetic, environmental, and lifestyle factors. In recent years attention has fallen on pathogens; in particular, Bacteroides fragilis, Fusobacterium nucleatum, Escherichia coli (E. coli) and Helicobacter pylori have been studied. Several points remain to be clarified, and above all, as regards the adherent-invasive E. coli strains of E. coli, one wonders if they are a cause or a consequence of the disease. In this review, we have tried to clarify some points by examining a series of recent publications regarding the involvement of the bacterium in the pathology, even if other studies are necessary.

Vancomycin-induced gut dysbiosis during Pseudomonas aeruginosa pulmonary infection in a mice model

Pseudomonas aeruginosa is one of the most common opportunistic pathogens causing respiratory infections in hospitals. Vancomycin, the antimicrobial agent usually used to treat bacterial nosocomial infections, is associated with gut dysbiosis. As a lung-gut immunologic axis has been described, this study aimed to evaluate both the immunologic and histopathologic effects on the lungs and the large intestine resulting from vancomycin-induced gut dysbiosis in the P. aeruginosa pneumonia murine model. Metagenomic analysis demonstrated that vancomycin-induced gut dysbiosis resulted in higher Proteobacteria and lower Bacteroidetes populations in feces. Given that gut dysbiosis could augment the proinflammatory status of the intestines leading to a variety of acute inflammatory diseases, bone marrow-derived macrophages were stimulated with cecal content from dysbiotic mice showing a higher expression of proinflammatory cytokines and lower expression of IL-10. Dysbiotic mice showed higher levels of viable bacteria in the lungs and spleen when acutely infected with P. aeruginosa, with more lung and cecal damage and increased IL-10 expression in bronchoalveolar lavage. The susceptible and tissue damage phenotype was reversed when dysbiotic mice received fecal microbiota transplantation. In spite of higher recruitment of CD11b+ cells in the lungs, there was no higher CD80+ expression, DC+ cell amounts or proinflammatory cytokine expression. Taken together, our results indicate that the bacterial community found in vancomycin-induced dysbiosis dysregulates the gut inflammatory status, influencing the lung-gut immunologic axis to favor increased opportunistic infections, for example, by P. aeruginosa.

µ-opioid receptor, β-endorphin, and cannabinoid receptor-2 are increased in the colonic mucosa of irritable bowel syndrome patients

BACKGROUND AND AIMS

The gut immune, cannabinoid, and opioid systems constitute an integrated network contributing to visceral sensation and pain modulation. We aimed to assess the expression of the µ-opioid receptor (MOR), its ligand β-endorphin (β-END), and cannabinoid receptor-2 (CB2 ) in patients with irritable bowel syndrome (IBS) and asymptomatic controls (AC) and their correlation with sex and symptom perception.

METHODS

Mucosal biopsies were obtained from the left colon of 31 IBS patients (45% women) with predominant constipation (IBS-C, 9) or diarrhea (IBS-D, 10) or with mixed bowel habits (IBS-M, 12) and 32 AC (44% women) and processed for qRT-PCR, Western blotting, and immunohistochemistry.

KEY RESULTS

µ-opioid receptor and CB2 mRNA and protein expression and β-END protein levels were increased in patients with IBS compared to AC (all Ps=0.021). A significant sex by IBS interaction was found in relation to CB2 mRNA expression (P = .003) with women showing a markedly higher expression to men (P = .035). In contrast, in AC, men had higher expression than women (P = .033). β-END, MOR, and CB2 immunoreactivities (IR) were localized to CD4+T cells including EMR-1+ eosinophils and CD31+ T cells but not to mast cells.

CONCLUSIONS

The increased expression of MOR, β-END, and CB2 in the mucosa of IBS patients, where they are localized to immune cells, suggests that opioid and cannabinoid systems play an immune-related compensatory role in visceral pain in IBS patients. Further work is necessary to support this hypothesis.

The Role of Gut-Derived Microbial Antigens on Liver Fibrosis Initiation and Progression

Intestinal dysbiosis has recently become known as an important driver of gastrointestinal and liver disease. It remains poorly understood, however, how gastrointestinal microbes bypass the intestinal mucosa and enter systemic circulation to enact an inflammatory immune response. In the context of chronic liver disease (CLD), insults that drive hepatic inflammation and fibrogenesis (alcohol, fat) can drastically increase intestinal permeability, hence flooding the liver with gut-derived microbiota. Consequently, this may result in exacerbated liver inflammation and fibrosis through activation of liver-resident Kupffer and stellate cells by bacterial, viral, and fungal antigens transported to the liver via the portal vein. This review summarizes the current understanding of microbial translocation in CLD, the cell-specific hepatic response to intestinal antigens, and how this drives the development and progression of hepatic inflammation and fibrosis. Further, we reviewed current and future therapies targeting intestinal permeability and the associated, potentially harmful anti-microbial immune response with respect to their potential in terms of limiting the development and progression of liver fibrosis and end-stage cirrhosis.

Painful interactions: Microbial compounds and visceral pain

Visceral pain, characterized by abdominal discomfort, originates from organs in the abdominal cavity and is a characteristic symptom in patients suffering from irritable bowel syndrome, vulvodynia or interstitial cystitis. Most organs in which visceral pain originates are in contact with the external milieu and continuously exposed to microbes. In order to maintain homeostasis and prevent infections, the immune- and nervous system in these organs cooperate to sense and eliminate (harmful) microbes. Recognition of microbial components or products by receptors expressed on cells from the immune and nervous system can activate immune responses but may also cause pain. We review the microbial compounds and their receptors that could be involved in visceral pain development.

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.

Microbiota: a novel regulator of pain

Among the various regulators of the nervous system, the gut microbiota has been recently described to have the potential to modulate neuronal cells activation. While bacteria-derived products can induce aversive responses and influence pain perception, recent work suggests that "abnormal" microbiota is associated with neurological diseases such as Alzheimer's, Parkinson's disease or autism spectrum disorder (ASD). Here we review how the gut microbiota modulates afferent sensory neurons function and pain, highlighting the role of the microbiota/gut/brain axis in the control of behaviors and neurological diseases. We outline the changes in gut microbiota, known as dysbiosis, and their influence on painful gastrointestinal disorders. Furthermore, both direct host/microbiota interaction that implicates activation of "pain-sensing" neurons by metabolites, or indirect communication via immune activation is discussed. Finally, treatment options targeting the gut microbiota, including pre- or probiotics, will be proposed. Further studies on microbiota/nervous system interaction should lead to the identification of novel microbial ligands and host receptor-targeted drugs, which could ultimately improve chronic pain management and well-being.

Pain regulation by gut microbiota: molecular mechanisms and therapeutic potential

The relationship between gut microbiota and neurological diseases, including chronic pain, has received increasing attention. The gut microbiome is a crucial modulator of visceral pain, whereas recent evidence suggests that gut microbiota may also play a critical role in many other types of chronic pain, including inflammatory pain, headache, neuropathic pain, and opioid tolerance. We present a narrative review of the current understanding on the role of gut microbiota in pain regulation and discuss the possibility of targeting gut microbiota for the management of chronic pain. Numerous signalling molecules derived from gut microbiota, such as by-products of microbiota, metabolites, neurotransmitters, and neuromodulators, act on their receptors and remarkably regulate the peripheral and central sensitisation, which in turn mediate the development of chronic pain. Gut microbiota-derived mediators serve as critical modulators for the induction of peripheral sensitisation, directly or indirectly regulating the excitability of primary nociceptive neurones. In the central nervous system, gut microbiota-derived mediators may regulate neuroinflammation, which involves the activation of cells in the blood-brain barrier, microglia, and infiltrating immune cells, to modulate induction and maintenance of central sensitisation. Thus, we propose that gut microbiota regulates pain in the peripheral and central nervous system, and targeting gut microbiota by diet and pharmabiotic intervention may represent a new therapeutic strategy for the management of chronic pain.

Preparation and characterization of selenium enriched-Bifidobacterium longum DD98, and its repairing effects on antibiotic-induced intestinal dysbacteriosis in mice

The aim of this study was to investigate the characteristics of a novel selenium-enriched Bifidobacterium longum DD98 (Se-B. longum DD98) supplement food and its repairing effects on the intestinal ecology of mammals. We assessed the growth, Se accumulation, and Se biotransformation of B. longum DD98 and its effects on antibiotic-induced intestinal dysbacteriosis in mice. The viable bacterial count at the end of fermentation was not significantly affected by the presence of Se. Bifidobacterium longum DD98 took up inorganic Se from the medium and biotransformed it into Se-containing proteins and selenoamino acids. The dominant Se species was selenomethionine (SeMet), which comprised 87% of the total Se in Se-B. longum DD98. Furthermore, Se-B. longum DD98 showed better regulation of the disrupted intestinal microbiota back to normal levels and repaired damaged colon tissues compared to the natural recovery and B. longum DD98 treatments. These findings suggest that B. longum DD98 efficiently biotransformed inorganic Se into more bioactive organic Se forms and may have therapeutic potential for the restoration of antibiotic-induced intestinal dysbacteriosis.

Preexisting Commensal Dysbiosis Is a Host-Intrinsic Regulator of Tissue Inflammation and Tumor Cell Dissemination in Hormone Receptor-Positive Breast Cancer

It is unknown why some patients with hormone receptor-positive (HR+) breast cancer present with more aggressive and invasive disease. Metastatic dissemination occurs early in disease and is facilitated by cross-talk between the tumor and tissue environment, suggesting that undefined host-intrinsic factors enhance early dissemination and the probability of developing metastatic disease. Here, we have identified commensal dysbiosis as a host-intrinsic factor associated with metastatic dissemination. Using a mouse model of HR+ mammary cancer, we demonstrate that a preestablished disruption of commensal homeostasis results in enhanced circulating tumor cells and subsequent dissemination to the tumor-draining lymph nodes and lungs. Commensal dysbiosis promoted early inflammation within the mammary gland that was sustained during HR+ mammary tumor progression. Furthermore, dysbiosis enhanced fibrosis and collagen deposition both systemically and locally within the tumor microenvironment and induced significant myeloid infiltration into the mammary gland and breast tumor. These effects were recapitulated both by directly targeting gut microbes using nonabsorbable antibiotics and by fecal microbiota transplantation of dysbiotic cecal contents, demonstrating the direct impact of gut dysbiosis on mammary tumor dissemination. This study identifies dysbiosis as a preexisting, host-intrinsic regulator of tissue inflammation, myeloid recruitment, fibrosis, and dissemination of tumor cells in HR+ breast cancer. SIGNIFICANCE: Identification of commensal dysbiosis as a host-intrinsic factor mediating evolution of metastatic breast cancer allows for development of interventions or diagnostic tools for patients at highest risk for developing metastatic disease.See related commentary by Ingman, p. 3539.

Methodology and application of Escherichia coli F4 and F18 encoding infection models in post-weaning pigs

The enterotoxigenic Escherichia coli (ETEC) expressing F4 and F18 fimbriae are the two main pathogens associated with post-weaning diarrhea (PWD) in piglets. The growing global concern regarding antimicrobial resistance (AMR) has encouraged research into the development of nutritional and feeding strategies as well as vaccination protocols in order to counteract the PWD due to ETEC. A valid approach to researching effective strategies is to implement piglet in vivo challenge models with ETEC infection. Thus, the proper application and standardization of ETEC F4 and F18 challenge models represent an urgent priority. The current review provides an overview regarding the current piglet ETEC F4 and F18 challenge models; it highlights the key points for setting the challenge protocols and the most important indicators which should be included in research studies to verify the effectiveness of the ETEC challenge.

Based on the current review, it is recommended that the setting of the model correctly assesses the choice and preconditioning of pigs, and the timing and dosage of the ETEC inoculation. Furthermore, the evaluation of the ETEC challenge response should include both clinical parameters (such as the occurrence of diarrhea, rectal temperature and bacterial fecal shedding) and biomarkers for the specific expression of ETEC F4/F18 (such as antibody production, specific F4/F18 immunoglobulins (Igs), ETEC F4/F18 fecal enumeration and analysis of the F4/F18 receptors expression in the intestinal brush borders). On the basis of the review, the piglets’ response upon F4 or F18 inoculation differed in terms of the timing and intensity of the diarrhea development, on ETEC fecal shedding and in the piglets’ immunological antibody response. This information was considered to be relevant to correctly define the experimental protocol, the data recording and the sample collections. Appropriate challenge settings and evaluation of the response parameters will allow future research studies to comply with the replacement, reduction and refinement (3R) approach, and to be able to evaluate the efficiency of a given feeding, nutritional or vaccination intervention in order to combat ETEC infection.

Bifidobacterium breve MCC1274 with glycosidic activity enhances in vivo isoflavone bioavailability

Polyphenols are plant derived compounds that exert many beneficial health effects to the human host. However, associated health benefits of dietary polyphenol are highly dependent on their intestinal metabolism, bioavailability, and absorption. Bifidobacteria, which represent the key members of gut microbiota, have been suggested to promote gut microbial homeostasis and may be involved in the metabolism of polyphenols. In this study, the capabilities of thirteen Bifidobacterium strains in hydrolysing polyphenol glycosides were evaluated. Among the tested strains, Bifidobacterium breve MCC1274 was found to possess the highest β-glucosidase activity and strong capability to convert daidzin and trans-polydatin to their aglycones; while kinetic analysis revealed that B. breve MCC1274 hydrolysed more than 50% of daidzin and trans-polydatin at less than 3 h of incubation. Further investigation using rats with an antibiotics-disturbed microbiome revealed that following the ingestion of daidzin glycoside, oral administration of B. breve MCC1274 significantly enhanced the plasma concentration of daidzein in rats pre-treated with antibiotics as compared to antibiotics-pre-treated control and non-treated control groups. The relative abundance of Actinobacteria and the total numbers of B. breve were also significantly higher in antibiotics-pre-treated rats administered with B. breve MCC1274 than that of the control groups. These findings suggest that B. breve MCC1274 is effective in enhancing the bioavailability of daidzein in the gut under dysbiosis conditions and may potentially improve intestinal absorption of isoflavones and promote human health.

Dysregulation of the gut-brain axis in schizophrenia and bipolar disorder: probiotic supplementation as a supportive treatment in psychiatric disorders

PURPOSE OF REVIEW

Schizophrenia (SCZ) and bipolar disorder are severe mental disorders, both placing a significant burden on individuals' wellbeing and global health generally. The complex interaction of multiple mechanisms, underlying these disorders, still needs further elucidation. Increased activation of components of the immune system may be involved, including alterations in intestinal permeability and gut microbiome. Probiotics, defined as living microorganisms conferring health benefits to the host when administered in adequate amounts, seem to have supportive therapeutic effect in psychiatric disorders. The authors in this review provide an overview of this emerging research field and summarize both the publicated microbiome studies in SCZ and bipolar disorder and the current clinical research using probiotic supplementation in patients diagnosed with these disorders.

RECENT FINDINGS

The current data indicate that there are differences in the microbiome in SCZ and bipolar disorder patients as compared with healthy controls. Part of these differences may be induced by medication use, others by smoking and other lifestyle factors. Correlations between microbiome quantification and symptom severity have been observed in cross-sectional studies, but unfortunately, no replicated findings so far. Probiotic supplementation was shown not only to alleviate gastrointestinal complaints but also reduce symptom severity, rehospitalization rates and cognitive improvement. Replication of improvement of cognition is needed.

SUMMARY

Differences in microbiome have been shown in both SCZ and bipolar disorder in comparison to healthy controls. Evidence that probiotics can improve psychiatric functioning is still very limited.

Irritable Bowel Syndrome in Terms of Changes in the Microbiota

Aim:to review available data confirming the pathogenetic role of the intestinal microbiota in the formation of irritable bowel syndrome (IBS).

Key findings.Changes in the intestinal biotope cause the development of visceral hypersensitivity and impaired intestinal motor activity, as well as neuroimmune transmission. This article discusses the main aspects of the biological properties of probiotic bacteria in terms of their action within the “brain — intestine — microbiota” chain. The results of experimental and clinical studies elucidating the mechanisms of action of probiotic cultures have been generalized. The understanding of these mechanisms allows practitioners to make informed decisions in prescribing probiotics to IBS patients. Key concepts concerning fecal microbiota transplantation, as well as the prospects and difficulties of implementing this approach are considered.

Conclusions.The term “microbiota — intestine — brain” clearly demonstrates the correlation between the main functional components of IBS. Meta-analyses and systematic reviews confirm the efficacy of probiotics in IBS. However, further research into probiotic therapy options is needed to identify specific bacterial strains with proven clinical efficacy. The fecal microbiota transplantation method also requires further research, since many issues associated with this approach remain unclear.

Glutamatergic Signaling Along The Microbiota-Gut-Brain Axis

A complex bidirectional communication system exists between the gastrointestinal tract and the brain. Initially termed the “gut-brain axis” it is now renamed the “microbiota-gut-brain axis” considering the pivotal role of gut microbiota in maintaining local and systemic homeostasis. Different cellular and molecular pathways act along this axis and strong attention is paid to neuroactive molecules (neurotransmitters, i.e., noradrenaline, dopamine, serotonin, gamma aminobutyric acid and glutamate and metabolites, i.e., tryptophan metabolites), sustaining a possible interkingdom communication system between eukaryota and prokaryota. This review provides a description of the most up-to-date evidence on glutamate as a neurotransmitter/neuromodulator in this bidirectional communication axis. Modulation of glutamatergic receptor activity along the microbiota-gut-brain axis may influence gut (i.e., taste, visceral sensitivity and motility) and brain functions (stress response, mood and behavior) and alterations of glutamatergic transmission may participate to the pathogenesis of local and brain disorders. In this latter context, we will focus on two major gut disorders, such as irritable bowel syndrome and inflammatory bowel disease, both characterized by psychiatric co-morbidity. Research in this area opens the possibility to target glutamatergic neurotransmission, either pharmacologically or by the use of probiotics producing neuroactive molecules, as a therapeutic approach for the treatment of gastrointestinal and related psychiatric disorders.

Antibiotics and the nervous system: More than just the microbes?

The use of antibiotics has recently risen to prominence in neuroscience due to their potential value in studying the microbiota-gut-brain axis. In this context they have been largely employed to illustrate the many influences of the gut microbiota on brain function and behaviour. Much of this research is bolstered by the abnormal behaviour seen in germ-free animals and other well-controlled experiments. However, this literature has largely failed to consider the neuroactive potential of antibiotics themselves, independent from, or in addition to, their microbicidal effects. This is problematic, as clinical as well as experimental literature, largely neglected through the past decade, has clearly demonstrated that broad classes of antibiotics are neuroactive or neurotoxic. This is true even for some antibiotics that are widely regarded as not absorbed in the intestinal tract, and is especially concerning when considering the highly-concentrated and widely-ranging doses that have been used. In this review we will critically survey the clinical and experimental evidence that antibiotics may influence a variety of nervous system functions, from the enteric nervous system through to the brain and resultant behaviour. We will discuss substantial evidence which clearly suggests neuro-activity or -toxicity by most classes of antibiotics. We will conclude that, while evidence for the microbiota-gut-brain axis remains strong, clinical and experimental studies which employ antibiotics to probe it must consider this potential confound.

Antibiotic treatment triggers gut dysbiosis and modulates metabolism in a chicken model of gastro-intestinal infection

Background

Infection of the digestive track by gastro-intestinal pathogens results in the development of symptoms ranging from mild diarrhea to more severe clinical signs such as dysentery, severe dehydration and potentially death. Although, antibiotics are efficient to tackle infections, they also trigger dysbiosis that has been suggested to result in variation in weight gain in animal production systems.

Results

Here is the first study demonstrating the metabolic impact of infection by a gastro-intestinal pathogen (Brachyspira pilosicoli) and its resolution by antibiotic treatment (tiamulin) on the host (chicken) systemic metabolism and gut microbiota composition using high-resolution ¹H nuclear magnetic resonance (NMR) spectroscopy and 16S rDNA next generation sequencing (NGS). Clear systemic metabolic markers of infections such as glycerol and betaine were identified. Weight loss in untreated animals was in part explained by the observation of a modification of systemic host energy metabolism characterized by the utilization of glycerol as a glucose precursor. However, antibiotic treatment triggered an increased VLDL/HDL ratio in plasma that may contribute to reducing weight loss observed in treated birds. All metabolic responses co-occurred with significant shift of the microbiota upon infection or antibiotic treatment.

Conclusion

This study indicates that infection and antibiotic treatment trigger dysbiosis that may impact host systemic energy metabolism and cause phenotypic and health modifications.

Electronic supplementary material

The online version of this article (10.1186/s12917-018-1761-0) contains supplementary material, which is available to authorized users.

The Gut Microbiota-Host Partnership as a Potential Driver of Kawasaki Syndrome

Kawasaki syndrome (KS) is a necrotizing vasculitis of small- and medium-sized vessels mostly affecting children under 5 years of age; a host of clinical and epidemiological data supports the notion that KS might result from an infectious disease. However, many efforts have failed to identify a potentially universal trigger of KS. The contribution of the intestinal microbial community-called the "microbiota"-to KS has been evaluated by an increasing number of studies, though limited to small cohorts of patients. Differences in the microbiota composition were found in children with KS, both its acute and non-acute phase, with abnormal colonization by Streptococcus species in the intestinal tract and a wider presence of Gram-positive cocci in jejunal biopsies. In particular, a higher number of Gram-positive cocci (of the genera Streptococcus and Staphylococcus), Eubacterium, Peptostreptococcus, and HSP60-producing Gram-negative microbes have been found in the stools of KS children, and their effects on the antigenic repertoire of specific T cells and Vβ2 T cell expansion have been assessed. Conversely, Lactobacilli were lacking in most children with KS compared with other febrile illnesses and healthy controls. All studies available to date have confirmed that an imbalance in the gut microbiota might indirectly interfere with the normal function of innate and adaptive immunity, and that variable microbiota interactions with environmental factors, mainly infectious agents, might selectively drive the development of KS in genetically susceptible children. Further investigations of the intestinal microflora in larger cohorts of KS patients will provide clues to disentangle the pathogenesis of this disease and probably indicate disease-modifying agents or more rational KS-specific therapies.

Visceral pain: gut microbiota, a new hope?

BACKGROUND

Visceral pain is a complex and heterogeneous disorder, which can range from the mild discomfort of indigestion to the agonizing pain of renal colic. Regulation of visceral pain involves the spinal cord as well as higher order brain structures. Recent findings have linked the microbiota to gastrointestinal disorders characterized by abdominal pain suggesting the ability of microbes to modulate visceral hypersensitivity and nociception to pain.

MAIN BODY

In this review we describe the neuroanatomical basis of visceral pain signaling and the existing evidence of its manipulation exerted by the gut microbiota. We included an updated overview of the potential therapeutic effects of dietary intervention, specifically probiotics and prebiotics, in alleviating hypersensitivity to visceral pain stimuli.

CONCLUSIONS

The gut microbiota dramatically impacts normal visceral pain sensation and affects the mechanisms mediating visceral nociception. Furthermore, manipulation of the gut microbiota using prebiotics and probiotics plays a potential role in the regulation of visceral pain disorders.

A Polysaccharide Isolated from Dictyophora indusiata Promotes Recovery from Antibiotic-Driven Intestinal Dysbiosis and Improves Gut Epithelial Barrier Function in a Mouse Model

Despite the tremendous biological activity of polysaccharides from the mushroom Dictyophora indusiata, its role in the restoration of gut microbiota has not yet been explored. The present study aimed to investigate whether D. indusiata polysaccharide (DIP) could modulate the recovery of gut microbiota composition and intestinal barrier function after broad-spectrum antibiotic-driven dysbiosis. Alteration and restoration in the microbial communities were elucidated by the Illumina MiSeq platform. Colon histology, expression of tight-junction associated proteins, and serum/tissue endotoxin and cytokine levels were evaluated. Two-week daily oral administration of clindamycin and metronidazole resulted in reduced bacterial diversity and richness, and perturbed the microbial flora at various taxonomic levels (altered Firmicutes/Bacteroidetes ratio and increased relative abundance of harmful flora (Proteobacteria, Enterococcus, and Bacteroides)), whereas DIP administration reversed the dysbiosis and increased beneficial flora, including Lactobacillaceae (lactic acid-producing bacteria), and Ruminococaceae (butyrate-producing bacteria). In addition, it resulted in the reduction of endotoxemia (through lipopolysaccharides (LPSs)) and pro-inflammatory cytokine (tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), and interleukin 1β (IL-1β)) levels, with the increased expression of tight-junction associated proteins (claudin-1, occludin, and zonula occludens-1). These findings not only suggested a comprehensive understanding of the protective effects of a DIP in the restoration of gut microbiota but also highlighted its role in the enhancement of gut barrier integrity, reduction of inflammation and lowering of endotoxin levels in mice.

Effects of medicines used to treat gastrointestinal diseases on the pharmacokinetics of coadministered drugs: a PEARRL Review

Objectives

Drugs used to treat gastrointestinal diseases (GI drugs) are widely used either as prescription or over-the-counter (OTC) medications and belong to both the 10 most prescribed and 10 most sold OTC medications worldwide. The objective of this review article is to discuss the most frequent interactions between GI and other drugs, including identification of the mechanisms behind these interactions, where possible.

Key findings

Current clinical practice shows that in many cases, these drugs are administered concomitantly with other drug products. Due to their metabolic properties and mechanisms of action, the drugs used to treat gastrointestinal diseases can change the pharmacokinetics of some coadministered drugs. In certain cases, these interactions can lead to failure of treatment or to the occurrence of serious adverse events. The mechanism of interaction depends highly on drug properties and differs among therapeutic categories. Understanding these interactions is essential to providing recommendations for optimal drug therapy.

Summary

Interactions with GI drugs are numerous and can be highly significant clinically in some cases. While alterations in bioavailability due to changes in solubility, dissolution rate, GI transit and metabolic interactions can be (for the most part) easily identified, interactions that are mediated through other mechanisms, such as permeability or microbiota, are less well-understood. Future work should focus on characterising these aspects.

Butyrate promotes visceral hypersensitivity in an IBS-like model via enteric glial cell-derived nerve growth factor

BACKGROUND

Altered visceral sensation is common in irritable bowel syndrome (IBS) and nerve growth factor (NGF) participates in visceral pain development. Sodium butyrate (NaB) could induce colonic hypersensitivity via peripheral up-regulation of NGF in animals. Enteric glial cells (EGCs) appear to be an important source of NGF. Whether butyrate could induce visceral hypersensitivity via increased EGC-derived NGF is still unknown.

METHODS

CRL-2690 cells were used for transcriptome analyses after butyrate treatment. Rats received butyrate enemas to induce colonic hypersensitivity. Colorectal distention test was performed to assess visceral sensitivity. Immunofluorescence studies were used to evaluate the co-expression of glial fibrillary acidic protein (GFAP) and NGF or growth associated protein 43 in animal model. NGF expression in rat colon was also investigated. In vitro, CRL-2690 cells were stimulated with NaB or trichostatin A (TSA). NGF or GFAP expression was also examined.

KEY RESULTS

Transcriptome analyses showed that butyrate induced marked changes of genes expression related to neurotrophic signaling pathways. NaB-treated rats showed increased visceral sensitivity. An improved NGF expression level was observed in NaB-treated rats. Meanwhile, a 2.1-fold increase in co-expression of GFAP and NGF was also determined in rats received NaB enemas. In cultured cells, both NaB and TSA treatment could cause obvious NGF expression. Thus, butyrate might regulate EGC function via histone deacetylase inhibition.

CONCLUSIONS & INFERENCES

Butyrate-EGC interplay may play a pivotal role in regulation of NGF expression and the development of colonic hypersensitivity in IBS-like animal model.

Antibiotic Driven Changes in Gut Motility Suggest Direct Modulation of Enteric Nervous System

Antibiotic-mediated changes to the intestinal microbiome have largely been assumed to be the basis of antibiotic-induced neurophysiological and behavioral changes. However, relatively little research has addressed whether antibiotics act directly on the host nervous system to produce these changes. We aimed to identify whether acute exposure of the gastrointestinal tract to antibiotics directly modulates neuronally dependent motility reflexes, ex vivo. Motility of colon and jejunum segments in a perfusion organ bath was recorded by video and alterations to neuronally dependent propagating contractile clusters (PCC), measured using spatiotemporal maps of diameter changes. Short latency (<10 min) changes to PCC serve as an index of putative effects on the host nervous system. Bacitracin, penicillin V, and neomycin, all produced dose-dependent alterations to the velocity, frequency, and amplitude of PCC. Most significantly, colonic PCC velocity increased by 53% [probability of superiority (PS) = 87%] with 1.42 mg/ml bacitracin, 19% (PS = 81%) with 0.91 mg/ml neomycin, and 19% (PS = 86%) with 3.88 mg/ml penicillin V. Colonic frequency increased by 16% (PS = 73%) with 1.42 mg/ml bacitracin, 21% (PS = 79%) with 0.91 mg/ml neomycin, and 34% (PS = 85%) at 3.88 mg/ml penicillin V. Conversely, colonic amplitude decreased by 41% (PS = 79%) with 1.42 mg/ml bacitracin, 30% (PS = 80%) with 0.27 mg/ml neomycin and 25% (PS = 79%) at 3.88 mg/ml penicillin V. In the jejunum, antibiotic-specific changes were identified. Taken together, our findings provide evidence that acute exposure of the gastrointestinal lumen to antibiotics modulates neuronal reflexes. Future work should acknowledge the importance of this mechanism in mediating antibiotic-driven changes on gut-brain signaling.

Mechanical allodynia corresponds to Oprm1 downregulation within the descending pain network of male and female rats exposed to neonatal immune challenge

Exposure to painful procedures and/or stressors during the early neonatal period can reprogram the underlying neurocircuitry involved in nociception and neuropathic pain perception. The reprogramming of these systems can result in an enduring elevation in sensitivity towards mechanical and thermal stimuli. Recent evidence suggests that exposure to mild inflammatory mediators during the neonatal period can induce similar pain responses in both adolescent and adult rats. Therefore, we sought to profile changes in the expression of several genes across brain areas involved in the active modulation of nociception and neuropathic pain using a well-recognized model of neonatal inflammation. In the present study male and female Sprague-Dawley rats were administered either the inflammatory endotoxin lipopolysaccharide (LPS; 0.05mg/kg, i.p.) or saline (equivolume) on postnatal days (PND) 3 and 5. During adolescence, hind paw mechanical withdrawal thresholds were evaluated using an electronic von Frey anesthesiometer. Animals challenged neonatally with LPS (nLPS) had increased pain sensitivity on this measure which was associated with decreased Oprm1 expression in the prefrontal cortex (PFC) and periaqueductal gray (PAG) of both male and female rats. Although a 'second hit' with LPS in adolescence (aLPS) did not confer protection or reveal additional vulnerabilities, aLPS given to animals treated neonatally with saline was associated with increased pain sensitivity, but only in females. Interestingly, adolescent inflammatory challenge decreased Hcrt2 mRNA in the PAG and elevated Trpv1 in the PAG and PFC of both sexes. There was no effect of inflammatory treatment on either anxiety or depressive-like behavior suggesting that affective functioning did not account for differences in mechanical pain sensitivity. Finally, a preliminary investigation demonstrated that administration of a broad spectrum antibiotic cocktail attenuated the mechanical sensitivity that followed nLPS. Together, these data extend upon evidence that inflammation imparts long term changes in quality of life and pain responses via interference within the descending pain network. Moreover, they highlight a potential window of opportunity to target the microbiota-gut-brain axis and reverse pain processing disturbances following perinatal inflammation.

New insights into the pathogenesis and treatment of irritable bowel syndrome

Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders (FGID), characterized by abdominal pain and a change in stool form that cannot be explained by structural abnormalities. Its prevalence ranges from 9 to 23% of the worldwide population. The pathophysiology of IBS is diverse and not well understood. Biopsychosocial concept assumes that the disease is a product of psychosocial factors and altered at multiple levels of gut physiology interactions. Some aetiological factors have been identified, yet. One of the most important is the disruption of brain-gut mutual communication that leads to visceral hypersensitivity. Also genetic and epigenetic factors are involved. Chronic stress may predispose to IBS as well as exacerbate its symptoms. Both quantitative and qualitative disorders of the gut microbiota are observed. There is also a relationship between the IBS symptoms and the intake of a specific type of food products. In the diarrhoea type of IBS the role of previous gastrointestinal infection is demonstrated. Recent studies have suggested that visceral hypersensitivity in patients with IBS may be secondary to the activation of the immune cells and low-grade inflammation. Clinical symptoms of IBS include abdominal pain and change in bowel habits as well as somatic and psychiatric comorbidities. IBS is diagnosed on the basis of Rome Diagnostic Criteria. Recently, their newest version (Rome IV) has been presented. The aim of this review is to summarize the past decade progress in IBS diagnosis, main pathophysiological aspects and therapeutic management strategy.

The Role of the Gastrointestinal Microbiota in Visceral Pain

A growing body of preclinical and clinical evidence supports a relationship between the complexity and diversity of the microorganisms that inhabit our gut (human gastrointestinal microbiota) and health status. Under normal homeostatic conditions this microbial population helps maintain intestinal peristalsis, mucosal integrity, pH balance, immune priming and protection against invading pathogens. Furthermore, these microbes can influence centrally regulated emotional behaviour through mechanisms including microbially derived bioactive molecules (amino acid metabolites, short-chain fatty acids, neuropeptides and neurotransmitters), mucosal immune and enteroendocrine cell activation, as well as vagal nerve stimulation.The microbiota-gut-brain axis comprises a dynamic matrix of tissues and organs including the brain, autonomic nervous system, glands, gut, immune cells and gastrointestinal microbiota that communicate in a complex multidirectional manner to maintain homeostasis and resist perturbation to the system. Changes to the microbial environment, as a consequence of illness, stress or injury, can lead to a broad spectrum of physiological and behavioural effects locally including a decrease in gut barrier integrity, altered gut motility, inflammatory mediator release as well as nociceptive and distension receptor sensitisation. Centrally mediated events including hypothalamic-pituitary-adrenal (HPA) axis, neuroinflammatory events and neurotransmitter systems are concomitantly altered. Thus, both central and peripheral pathways associated with pain manifestation and perception are altered as a consequence of the microbiota-gut-brain axis imbalance.In this chapter the involvement of the gastrointestinal microbiota in visceral pain is reviewed. We focus on the anatomical and physiological nodes whereby microbiota may be mediating pain response, and address the potential for manipulating gastrointestinal microbiota as a therapeutic target for visceral pain.

The gastrointestinal tract - a central organ of cannabinoid signaling in health and disease

BACKGROUND

In ancient medicine, extracts of the marijuana plant Cannabis sativa were used against diseases of the gastrointestinal (GI) tract. Today, our knowledge of the ingredients of the Cannabis plant has remarkably advanced enabling us to use a variety of herbal and synthetic cannabinoid (CB) compounds to study the endocannabinoid system (ECS), a physiologic entity that controls tissue homeostasis with the help of endogenously produced CBs and their receptors. After many anecdotal reports suggested beneficial effects of Cannabis in GI disorders, it was not surprising to discover that the GI tract accommodates and expresses all the components of the ECS. Cannabinoid receptors and their endogenous ligands, the endocannabinoids, participate in the regulation of GI motility, secretion, and the maintenance of the epithelial barrier integrity. In addition, other receptors, such as the transient receptor potential cation channel subfamily V member 1 (TRPV1), the peroxisome proliferator-activated receptor alpha (PPARα) and the G-protein coupled receptor 55 (GPR55), are important participants in the actions of CBs in the gut and critically determine the course of bowel inflammation and colon cancer.

PURPOSE

The following review summarizes important and recent findings on the role of CB receptors and their ligands in the GI tract with emphasis on GI disorders, such as irritable bowel syndrome, inflammatory bowel disease, and colon cancer.

May the Force Be With You: The Light and Dark Sides of the Microbiota-Gut-Brain Axis in Neuropsychiatry

The role of the gut microbiota in health and disease is becoming increasingly recognized. The microbiota-gut-brain axis is a bi-directional pathway between the brain and the gastrointestinal system. The bacterial commensals in our gut can signal to the brain through a variety of mechanisms, which are slowly being resolved. These include the vagus nerve, immune mediators and microbial metabolites, which influence central processes such as neurotransmission and behaviour. Dysregulation in the composition of the gut microbiota has been identified in several neuropsychiatric disorders, such as autism, schizophrenia and depression. Moreover, preclinical studies suggest that they may be the driving force behind the behavioural abnormalities observed in these conditions. Understanding how bacterial commensals are involved in regulating brain function may lead to novel strategies for development of microbiota-based therapies for these neuropsychiatric disorders.

Neonatal abstinence syndrome and the gastrointestinal tract

Development of a healthy gut microbiome is essential in newborns to establish immunity and protection from pathogens. Recent studies suggest that infants who develop dysbiosis may be at risk for lifelong adverse health consequences. Exposure to opioid drugs during pregnancy is a factor of potential importance for microbiome health that has not yet been investigated. Since these infants are born after an entire gestation exposed to mu opioid receptor agonists and have severe gastrointestinal and neurological symptoms, we hypothesize that these infants are at risk for dysbiosis. We speculate that opioid exposure during gestation and development of NAS at birth may lead to a dysbiotic gut microbiome, which may impair normal microbiome succession and development, and impact future health of these children.

The Intestinal Microbiota in the Irritable Bowel Syndrome

The irritable bowel syndrome (IBS) is a chronic abdominal symptom complex occurring in a bowel devoid of discernible relevant pathology. There is growing interest in the role of the intestinal microbiota as a basis for the intestinal and possibly behavioral manifestations of this condition. Molecular-based microbial profiling has revealed compositional changes in the microbiota of at least a subset of IBS patients but the data are often conflicting and no microbial signature for this condition has yet been defined. Animal studies in which a previously stable intestinal microbiota is perturbed, by antibiotics or dietary change, results in alterations in intestinal function reminiscent of that seen in IBS patients. These include visceral sensitivity to painful stimuli, altered motility and intestinal barrier function as well as immune activation, and low-grade inflammation. More recent studies have shown that perturbation of the microbial composition of the gut alters brain chemistry and behavior. In a step toward establishing a causal link between an altar microbiota and gut-brain manifestations of IBS, colonization of germ-free mice with microbiota from IBS patients results in an IBS-like phenotype, including alterations and behavior if the donor exhibited psychiatric comorbidity, such as high levels of anxiety. This model provides an opportunity for exploring the mechanisms underlying host-microbe interactions relevant to the pathogenesis of IBS and for developing novel therapeutic targets.

Giardia lamblia infection increases risk of chronic gastrointestinal disorders

BACKGROUND

Giardia lamblia is a common parasitic cause of infectious gastroenteritis in the United States and the world and may be linked to an increased risk of chronic gastrointestinal (GI) disorders. We sought to assess the risk of several chronic GI disorders following Giardia infection among active duty US military personnel.

METHODS

This study was designed as a retrospective cohort study in which active duty military personnel with documented G. lamblia infection were assessed for the subsequent risk of developing a chronic GI disorder including irritable bowel syndrome (IBS), dyspepsia and gastroesophageal reflux disease (GERD). Post-giardia chronic GI disorder risk was compared to risk in uninfected personnel matched on several demographic characteristics and medical encounter information. Data were obtained from the Defense Medical Surveillance System and exposures (1998-2009) with outcomes identified based on documented medical encounters with specific medical billing codes. Modified Poisson regression was used to evaluate the relationship between G. lamblia infection and chronic GI disorders.

RESULTS

A total of 80 Giardia cases were identified for an estimated incidence of 0.55 cases per 100,000 person-years. Cases were matched to 294 unexposed subjects. After adjusting for important covariates, there was an increased risk of IBS (relative risk: 2.1, p = 0.03) associated with antecedent Giardia infection.

CONCLUSION

These data add to a growing body of literature and demonstrate an increased risk of IBS after infection with G. lamblia.

Gastric microbiota and carcinogenesis - Current evidence and controversy

Growing research on the human microbiome, even beyond the gastrointestinal area, is not surprising mainly due to significant advances in study methods. Current reporting in this area is so intensive that clinicians are changing the unsuitable "bacterial flora" expression for more appropriate terms such as "microbiota" (the entire microbial community colonizing an ecologic niche), "microbiome" (their collective genome), or "dysbiosis" (microbial composition imbalance with respect to the normatively considered pattern). Since the diseases involved in the altered microbiota hypothesis are increasing, its implication for cancer should come as no surprise to us.

Irritable bowel syndrome, the microbiota and the gut-brain axis

Irritable bowel syndrome is a common functional gastrointestinal disorder and it is now evident that irritable bowel syndrome is a multi-factorial complex of changes in microbiota and immunology. The bidirectional neurohumoral integrated communication between the microbiota and the autonomous nervous system is called the gut-brain-axis, which integrates brain and GI functions, such as gut motility, appetite and weight. The gut-brain-axis has a central function in the perpetuation of irritable bowel syndrome and the microbiota plays a critical role. The purpose of this article is to review recent research concerning the epidemiology of irritable bowel syndrome, influence of microbiota, probiota, gut-brain-axis, and possible treatment modalities on irritable bowel syndrome.

Relationship between gastrointestinal micro-ecological imbalance and development of gastric cancer

The human body and microorganisms present in the body form a symbiotic system as the relationship between eukaryotes and prokaryotes. Therefore, it is not enough to study human diseases only in terms of human body. Recent studies have pointed out that microorganisms are involved in the occurrence of a large number of malignant tumors. According to a conservative estimate, at least 15% of cancer cases are associated with infectious agents. Gastric cancer is the second major cause of global cancer deaths. For a long period of time, researchers believe that Helicobacter pylori associated with chronic gastritis is the strongest risk factor for the occurrence of gastric cancer. However, with the progress of molecular biology research, it has been found that there is a close interaction between the large microbial flora and Helicobacter pylori in the gastrointestinal tract. The changes of microbial community composition have important effects on the formation, development and intervention of gastric cancer. This article will review the occurrence and development of gastrointestinal microorganism and gastric cancer.

Moody microbes or fecal phrenology: what do we know about the microbiota-gut-brain axis?

INTRODUCTION

The microbiota-gut-brain axis is a term that is commonly used and covers a broad set of functions and interactions between the gut microbiome, endocrine, immune and nervous systems and the brain. The field is not much more than a decade old and so large holes exist in our knowledge.

DISCUSSION

At first sight it appears gut microbes are largely responsible for the development, maturation and adult function of the enteric nervous system as well as the blood brain barrier, microglia and many aspects of the central nervous system structure and function. Given the state of the art in this exploding field and the hopes, as well as the skepticism, which have been engendered by its popular appeal, we explore recent examples of evidence in rodents and data derived from studies in humans, which offer insights as to pathways involved. Communication between gut and brain depends on both humoral and nervous connections. Since these are bi-directional and occur through complex communication pathways, it is perhaps not surprising that while striking observations have been reported, they have often either not yet been reproduced or their replication by others has not been successful.

CONCLUSIONS

We offer critical and cautionary commentary on the available evidence, and identify gaps in our knowledge that need to be filled so as to achieve translation, where possible, into beneficial application in the clinical setting.