Search

L. reuteri dietary enrichment protects the F1 progeny of NWD-fed mothers from transgenerational cancer. Pulmonary adenocarcinoma, hepatocellular carcinoma and mesenteric lymph node lymphoma in the children of mothers consuming NWD are shown in the left column. Compare with normal lung, liver and mesenteric lymph node histology from mice of similar descend that were also treated with L. reuteri.

Nutritional profile of special diets fed to mice.

Control and NWD-treated mice cluster separately by microbiota. NWD-treated mice carry fewer Bacteroidetes in general than their control diet-fed counterparts. Overall, there is a shift towards higher abundance of OTUs from the Firmicutes phyla and decrease in OTUs from the Bacteroidetes phyla in mice treated with NWD. These data are consistent with previous findings of elevation of Firmicutes to Bacteroidetes phyla in obese mice.

(A) Selected immunohistochemical features of transgenerational neoplasms including TTF1 immunoreactivity of pulmonary carcinoma, Von Willebrand factor expression of hepatic hemagiosarcoma and high numbers of proliferating ki-67-positive cells of theca cell tumor of the ovary. Foci of neoplastic cells with nuclear p53 accumulation in hepatocellular carcinoma (left), pulmonary carcinoma (middle) and ovarian thecoma (right panel). (B) Histology of underrepresented transgenerational cancers. Typical histomorphology of islet cell adenoma of pancreas, ovarian granulosa cell tumor and skin lymphoma. (C) Tabular display of lung and liver tumor types according to treatment. IHC; Di-aminobenzidine chromogen, Hematoxylin counterstain. (A). Hematoxylin and Eosin (B).

Environmental factors are suspected in the increase of obesity and cancer in industrialized countries but are poorly understood. Here, we used animal models to test how future generations may be affected by Westernized diets. We discover long-term consequences of grandmothers' in utero dietary exposures, leading to high rates of obesity and frequent cancers of lung and liver in two subsequent generations of mice. Transgenerational effects were transplantable using diet-associated bacteria communities alone. Consequently, feeding of beneficial microbes was sufficient to lower transgenerational risk for cancer and obesity regardless of diet history. Targeting microbes may be a highly effective population-based approach to lower risk for cancer. Cancer Res; 75(7); 1197–204. ©2015 AACR.

The equilibrium between host animals and their microbiota has been convincingly linked with overall host health. Numerous reports describe beneficial effects of probiotic microbiota on the health of humans and other species extending to improved immune functions, wound repair capacity, metabolism, and psychiatry. Among candidate unifying host effector molecules is oxytocin, a neuropeptide hormone related to sociability and a sense of physical and mental well-being. It has been shown in mouse models that endogenous oxytocin levels are upregulated after consuming the probiotic Lactobacillus reuteri derived from human breast milk, with interesting evolutionary implications. Using heirloom microbiota such as L. reuteri to naturally upregulate host endogenous oxytocin levels potentially overcomes the known therapeutic challenges of oxytocin's short half-life and obscure brain targets.

Environmental factors such as diet, gut microbiota, and infections have proven to have a significant role in epigenetic modifications. It is known that epigenetic modifications may cause behavioral and neuronal changes observed in neurodevelopmental disabilities, including fragile X syndrome (FXS) and autism (ASD). Probiotics are live microorganisms that provide health benefits when consumed, and in some cases are shown to decrease the chance of developing neurological disorders. Here, we examined the epigenetic outcomes in offspring mice after feeding of a probiotic organism, Lactobacillus reuteri (L. reuteri), to pregnant mother animals. In this study, we tested a cohort of Western diet-fed descendant mice exhibiting a high frequency of behavioral features and lower FMRP protein expression similar to what is observed in FXS in humans (described in a companion manuscript in this same GENES special topic issue). By investigating 17,735 CpG sites spanning the whole mouse genome, we characterized the epigenetic profile in two cohorts of mice descended from mothers treated and non-treated with L. reuteri to determine the effect of prenatal probiotic exposure on the prevention of FXS-like symptoms. We found several genes involved in different neurological pathways being differentially methylated (p ≤ 0.05) between the cohorts. Among the key functions, synaptogenesis, neurogenesis, synaptic modulation, synaptic transmission, reelin signaling pathway, promotion of specification and maturation of neurons, and long-term potentiation were observed. The results of this study are relevant as they could lead to a better understanding of the pathways involved in these disorders, to novel therapeutics approaches, and to the identification of potential biomarkers for early detection of these conditions.

Inflammation is a major risk factor for many types of cancer, including colorectal (CRC). There are two fundamentally different mechanisms by which inflammation can contribute to carcinogenesis. First, reactive oxygen and nitrogen species (RONS) can damage DNA to cause mutations that initiate cancer. Second, inflammatory cytokines and chemokines promote proliferation, migration, and invasion. Although it is known that inflammation-associated RONS can be mutagenic, the extent to which they induce mutations in intestinal stem cells (ISCs) has been little explored. Furthermore, it is now widely accepted that cancer is caused by successive rounds of clonal expansion with associated de novo mutations that further promote tumor development. As such, we aimed to understand the extent to which inflammation promotes clonal expansion in normal and tumor tissue. Using an engineered mouse model that is prone to cancer and within which mutant cells fluoresce, here we have explored the impact of inflammation on de novo mutagenesis and clonal expansion in normal and tumor tissue. While inflammation is strongly associated with susceptibility to cancer and a concomitant increase in the overall proportion of mutant cells in the tissue, we did not observe an increase in mutations in normal adjacent tissue. These results are consistent with opportunities for de novo mutations and clonal expansion during tumor growth, and they suggest protective mechanisms that suppress the risk of inflammation-induced accumulation of mutant cells in normal tissue.

Although Clostridium difficile is widely considered an antibiotic- and hospital-associated pathogen, recent evidence indicates that this is an insufficient depiction of the risks and reservoirs. A common thread that links all major risk factors of infection is their association with gastrointestinal disturbances, but this relationship to C. difficile colonization has never been tested directly. Here, we show that disturbances caused by diarrhoeal events trigger susceptibility to C. difficile colonization. Using survey data of the human gut microbiome, we detected C. difficile colonization and blooms in people recovering from food poisoning and Vibrio cholerae infections. Carriers remained colonized for year-long time scales and experienced highly variable patterns of C. difficile abundance, where increased shedding over short periods of 1–2 d interrupted week-long periods in which C. difficile was undetectable. Given that short shedding events were often linked to gastrointestinal disturbances, our results help explain why C. difficile is frequently detected as a co-infecting pathogen in patients with diarrhoea. To directly test the impact of diarrhoea on susceptibility to colonization, we developed a mouse model of variable disturbance intensity, which allowed us to monitor colonization in the absence of disease. As mice exposed to avirulent C. difficile spores ingested increasing quantities of laxatives, more individuals experienced C. difficile blooms. Our results indicate that the likelihood of colonization is highest in the days immediately following acute disturbances, suggesting that this could be an important window during which transmission could be interrupted and the incidence of infection lowered. Gastrointestinal disturbances, such as non-antibiotic-induced diarrhoea, promote susceptibility to colonization by Clostridium difficile, providing additional insights into antibiotic-independent triggers for this infection.

The “Earthrise” photograph, taken on the 1968 Apollo 8 mission, became one of the most significant images of the 20th Century. It triggered a profound shift in environmental awareness and the potential for human unity—inspiring the first Earth Day in 1970. Taking inspiration from these events 50 years later, we initiated Project Earthrise at our 2020 annual conference of inVIVO Planetary Health. This builds on the emergent concept of planetary health, which provides a shared narrative to integrate rich and diverse approaches from all aspects of society towards shared solutions to global challenges. The acute catastrophe of the COVID-19 pandemic has drawn greater attention to many other interconnected global health, environmental, social, spiritual, and economic problems that have been underappreciated or neglected for decades. This is accelerating opportunities for greater collaborative action, as many groups now focus on the necessity of a “Great Transition”. While ambitious integrative efforts have never been more important, it is imperative to apply these with mutualistic value systems as a compass, as we seek to make wiser choices. Project Earthrise is our contribution to this important process. This underscores the imperative for creative ecological solutions to challenges in all systems, on all scales with advancing global urbanization in the digital age—for personal, environmental, economic and societal health alike. At the same time, our agenda seeks to equally consider our social and spiritual ecology as it does natural ecology. Revisiting the inspiration of “Earthrise”, we welcome diverse perspectives from across all dimensions of the arts and the sciences, to explore novel solutions and new normative values. Building on academic rigor, we seek to place greater value on imagination, kindness and mutualism as we address our greatest challenges, for the health of people, places and planet.

Coronavirus disease 2019 (COVID-19) continues to exact a devastating global toll. Ascertaining the factors underlying differential susceptibility and prognosis following viral exposure is critical to improving public health responses. We propose that gut microbes may contribute to variation in COVID-19 outcomes. We synthesise evidence for gut microbial contributions to immunity and inflammation, and associations with demographic factors affecting disease severity. We suggest mechanisms potentially underlying microbially mediated differential susceptibility to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). These include gut microbiome-mediated priming of host inflammatory responses and regulation of endocrine signalling, with consequences for the cellular features exploited by SARS-CoV-2 virions. We argue that considering gut microbiome-mediated mechanisms may offer a lens for appreciating differential susceptibility to SARS-CoV-2, potentially contributing to clinical and epidemiological approaches to understanding and managing COVID-19.

Maternal microbial dysbiosis has been implicated in adverse postnatal health conditions in offspring, such as obesity, cancer, and neurological disorders. We observed that the progeny of mice fed a Westernized diet (WD) with low fiber and extra fat exhibited higher frequencies of stereotypy, hyperactivity, cranial features and lower FMRP protein expression, similar to what is typically observed in Fragile X Syndrome (FXS) in humans. We hypothesized that gut dysbiosis and inflammation during pregnancy influenced the prenatal uterine environment, leading to abnormal phenotypes in offspring. We found that oral in utero supplementation with a beneficial anti-inflammatory probiotic microbe, Lactobacillus reuteri, was sufficient to inhibit FXS-like phenotypes in offspring mice. Cytokine profiles in the pregnant WD females showed that their circulating levels of pro-inflammatory cytokine interleukin (Il)-17 were increased relative to matched gravid mice and to those given supplementary L. reuteri probiotic. To test our hypothesis of prenatal contributions to this neurodevelopmental phenotype, we performed Caesarian (C-section) births using dissimilar foster mothers to eliminate effects of maternal microbiota transferred during vaginal delivery or nursing after birth. We found that foster-reared offspring still displayed a high frequency of these FXS-like features, indicating significant in utero contributions. In contrast, matched foster-reared progeny of L. reuteri-treated mothers did not exhibit the FXS-like typical features, supporting a key role for microbiota during pregnancy. Our findings suggest that diet-induced dysbiosis in the prenatal uterine environment is strongly associated with the incidence of this neurological phenotype in progeny but can be alleviated by addressing gut dysbiosis through probiotic supplementation.

Broad spectrum antibiotics cause both transient and lasting damage to the ecology of the gut microbiome. Antibiotic-induced loss of gut bacterial diversity has been linked to susceptibility to enteric infections. Prior work on subtherapeutic antibiotic treatment in humans and non-human animals has suggested that entire gut communities may exhibit tolerance phenotypes. In this study, we validate the existence of these community tolerance phenotypes in the murine gut and explore how antibiotic treatment duration or a diet enriched in antimicrobial phytochemicals might influence the frequency of this phenotype. Almost a third of mice exhibited whole-community tolerance to a high dose of the β-lactam antibiotic cefoperazone, independent of antibiotic treatment duration or dietary phytochemical amendment. We observed few compositional differences between non-responder microbiota during antibiotic treatment and the untreated control microbiota. However, gene expression was vastly different between non-responder microbiota and controls during treatment, with non-responder communities showing an upregulation of antimicrobial tolerance genes, like efflux transporters, and a down-regulation of central metabolism. Future work should focus on what specific host- or microbiome-associated factors are responsible for tipping communities between responder and non-responder phenotypes so that we might learn to harness this phenomenon to protect our microbiota from routine antibiotic treatment., Diener, Hoge et al. show that a third of mice exhibit tolerance to a high dose of the β-lactam antibiotic cefoperazone, independent of antibiotic treatment duration or dietary phytochemical amendment. They find that non-responder microbiota upregulates antimicrobial tolerance genes and downregulates central metabolism without altering community composition or diversity, providing insights into the mechanisms of community-wide antibiotic tolerance.

Emerging evidence shows that microbe interactions with the host immune system impact diverse aspects of cancer development and treatment. As a result, exciting new opportunities exist for engineering diets and microbe cocktails to lower cancer risks with fewer adverse clinical effects than traditional strategies. Microbe-based therapies may ultimately be used to reinforce host immune balance and extinguish cancer for generations to come.

During the past forty years there has been an inexplicable increase in chronic inflammatory disorders, including obesity. One theory, the 'hygiene hypothesis', involves dysregulated immunity arising after too few beneficial early life microbe exposures. Indeed, earlier studies have shown that gut microbe-immune interactions contribute to smoldering inflammation, adiposity, and weight gain. Here we tested a safe and well-established microbe-based immune adjuvant to restore immune homeostasis and counteract inflammation-associated obesity in animal models. We found that consuming Vibrio cholerae exotoxin subunit B (ctB) was sufficient to inhibit age-associated obesogenic outcomes in wild type mice, including reduced crown-like structures (CLS) and granulomatous necrosis histopathology in fat depots. Administration of cholera toxin reduced weight gain irrespective of age during administration; however, exposure during youth imparted greater slenderizing effects when compared with animals receiving ctB for the first time during adulthood. Beneficial effects were transplantable to other obesity-prone animals using immune cells alone, demonstrating an immune-mediated mechanism. Taken together, we concluded that oral vaccination with cholera toxin B helps stimulate health-protective immune responses that counteract age-associated obesity.

Microbes colonise all multicellular life, and the gut microbiome has been shown to influence a range of host physiological and behavioural phenotypes. One of the most intriguing and least understood of these influences lies in the domain of the microbiome's interactions with host social behaviour, with new evidence revealing that the gut microbiome makes important contributions to animal sociality. However, little is known about the biological processes through which the microbiome might influence host social behaviour. Here, we synthesise evidence of the gut microbiome's interactions with various aspects of host sociality, including sociability, social cognition, social stress, and autism. We discuss evidence of microbial associations with the most likely physiological mediators of animal social interaction. These include the structure and function of regions of the 'social' brain (the amygdala, the prefrontal cortex, and the hippocampus) and the regulation of 'social' signalling molecules (glucocorticoids including corticosterone and cortisol, sex hormones including testosterone, oestrogens, and progestogens, neuropeptide hormones such as oxytocin and arginine vasopressin, and monoamine neurotransmitters such as serotonin and dopamine). We also discuss microbiome-associated host genetic and epigenetic processes relevant to social behaviour. We then review research on microbial interactions with olfaction in insects and mammals, which contribute to social signalling and communication. Following these discussions, we examine evidence of microbial associations with emotion and social behaviour in humans, focussing on psychobiotic studies, microbe-depression correlations, early human development, autism, and issues of statistical power, replication, and causality. We analyse how the putative physiological mediators of the microbiome-sociality connection may be investigated, and discuss issues relating to the interpretation of results. We also suggest that other candidate molecules should be studied, insofar as they exert effects on social behaviour and are known to interact with the microbiome. Finally, we consider different models of the sequence of microbial effects on host physiological development, and how these may contribute to host social behaviour.

Broad spectrum antibiotics can cause both transient and lasting damage to the ecology of the gut microbiome. Loss of gut bacterial diversity has been linked to immune dysregulation and disease susceptibility. Antibiotic-resistant populations of cells are known to arise spontaneously in single-strain systems. Furthermore, prior work on subtherapeutic antibiotic treatment in humans and therapeutic treatments in non-human animals have suggested that entire gut communities may exhibit spontaneous resistance phenotypes. In this study, we validate the existence of these community resistance phenotypes in the murine gut and explore how antibiotic duration or diet influence the frequency of this phenotype. We find that almost a third of mice exhibit whole-community resistance to a therapeutic concentration of theβ-lactam antibiotic cefoperazone, independent of antibiotic treatment duration or xenobiotic dietary amendment. These non-responder (i.e. resistant) microbiota were protected from biomass depletion, transient ecological community collapse, and lasting diversity loss seen in the susceptible microbiota. There were no major differences between non-responder microbiota and untreated control microbiota at the community structure level. However, gene expression was vastly different between non-responder microbiota and controls during antibiotic treatment, with non-responder communities showing an upregulation of antimicrobial resistance genes and a down-regulation of central metabolism. Thus, non-responder phenotypes appear to combat antibiotic assault through a combination of efflux transporter upregulation and a reduced growth rate across the entire gut community. Future work should focus on what factors are responsible for tipping entire communities from susceptible to resistant phenotypes so that we might harness this phenomenon to protect our microbiota from exposure to therapeutic antibiotic treatment regimes.

Anatomical studies of cephalic bones and muscles combined with cine and high-speed videographic analyses of feeding demonstrate that Amphiuma tridactylum uses two distinct types of suction feeding. Small or relatively immobile prey generally elicit a stationary capture mode in which mouth opening precedes buccal expansion and there is no forward movement of the head of the salamander. Actively moving prey are captured by a rapid strike during which mouth opening and buccal expansion are synchronous and the extent of buccal expansion is greater than in stationary feeding. Differences between these feeding modes may be due to differences in the timing of contraction of the rectus cervicis muscle. Synchronous hyoid and mandibular excursions during the strike are probably generated by simultaneous contractions of the depressor mandibulae and rectus cervicis, whereas delay of hyoid excursions during stationary capture suggests sequential contraction of the depressor and rectus cervicis.

Muscle wasting, known as cachexia, is a debilitating condition associated with chronic inflammation such as during cancer. Beneficial microbes have been shown to optimize systemic inflammatory tone during good health; however, interactions between microbes and host immunity in the context of cachexia are incompletely understood. Here we use mouse models to test roles for bacteria in muscle wasting syndromes. We find that feeding of a human commensal microbe, Lactobacillus reuteri, to mice is sufficient to lower systemic indices of inflammation and inhibit cachexia. Further, the microbial muscle-building phenomenon extends to normal aging as wild type animals exhibited increased growth hormone levels and up-regulation of transcription factor Forkhead Box N1 [FoxN1] associated with thymus gland retention and longevity. Interestingly, mice with a defective FoxN1 gene (athymic nude) fail to inhibit sarcopenia after L. reuteri therapy, indicating a FoxN1-mediated mechanism. In conclusion, symbiotic bacteria may serve to stimulate FoxN1 and thymic functions that regulate inflammation, offering possible alternatives for cachexia prevention and novel insights into roles for microbiota in mammalian ontogeny and phylogeny.

Environmental factors are suspected in the increase of obesity and cancer in industrialized countries but are poorly understood. Here, we used animal models to test how future generations may be affected by Westernized diets. We discover long-term consequences of grandmothers' in utero dietary exposures, leading to high rates of obesity and frequent cancers of lung and liver in two subsequent generations of mice. Transgenerational effects were transplantable using diet-associated bacteria communities alone. Consequently, feeding of beneficial microbes was sufficient to lower transgenerational risk for cancer and obesity regardless of diet history. Targeting microbes may be a highly effective population-based approach to lower risk for cancer., National Institutes of Health (U.S.) (RO1CA108854), National Institutes of Health (U.S.) (U01 CA164337), National Institutes of Health (U.S.) (P30-ES002109)

Recent studies suggest that gastrointestinal tract microbiota modulate cancer development in distant non-intestinal tissues. Here we tested mechanistic hypotheses using a targeted pathogenic gut microbial infection animal model with a predilection to breast cancer. FVB-Tg(C3-1-TAg)cJeg/JegJ female mice were infected by gastric gavage with Helicobacter hepaticus at three-months-of-age putting them at increased risk for mammary tumor development. Tumorigenesis was multifocal and characterized by extensive infiltrates of myeloperoxidase-positive neutrophils otherwise implicated in cancer progression in humans and animal models. To test whether neutrophils were important in etiopathogenesis in this bacteria-triggered model system, we next systemically depleted mice of neutrophils using thrice weekly intraperitoneal injections with anti-Ly-6G antibody. We found that antibody depletion entirely inhibited tumor development in this H. hepaticus-infected model. These data demonstrate that host neutrophil-associated immune responses to intestinal tract microbes significantly impact cancer progression in distal tissues such as mammary glands, and identify gut microbes as novel targets for extra-intestinal cancer therapy.

It has been recently shown that gut microbes modulate whole host immune and hormonal factors impacting the fate of distant preneoplastic lesions toward malignancy or regression. This raises the possibility that the tumor microenvironment interacts with broader systemic microbial-immune networks. These accumulated findings suggest novel therapeutic opportunities for holobiont engineering in emerging tumor microenvironments.

Maternal obesity during pregnancy has been associated with increased risk of neurodevelopmental disorders, including autism spectrum disorder (ASD), in offspring. Here, we report that maternal high-fat diet (MHFD) induces a shift in microbial ecology that negatively impacts offspring social behavior. Social deficits and gut microbiota dysbiosis in MHFD offspring are prevented by co-housing with offspring of mothers on a regular diet (MRD) and transferable to germ-free mice. In addition, social interaction induces synaptic potentiation (LTP) in the ventral tegmental area (VTA) of MRD, but not MHFD offspring. Moreover, MHFD offspring had fewer oxytocin immunoreactive neurons in the hypothalamus. Using metagenomics and precision microbiota reconstitution, we identified a single commensal strain that corrects oxytocin levels, LTP, and social deficits in MHFD offspring. Our findings causally link maternal diet, gut microbial imbalance, VTA plasticity, and behavior and suggest that probiotic treatment may relieve specific behavioral abnormalities associated with neurodevelopmental disorders. VIDEO ABSTRACT.

Neuropeptide hormone oxytocin has roles in social bonding, energy metabolism, and wound healing contributing to good physical, mental and social health. It was previously shown that feeding of a human commensal microbe Lactobacillus reuteri (L. reuteri) is sufficient to up-regulate endogenous oxytocin levels and improve wound healing capacity in mice. Here we show that oral L. reuteri-induced skin wound repair benefits extend to human subjects. Further, dietary supplementation with a sterile lysate of this microbe alone is sufficient to boost systemic oxytocin levels and improve wound repair capacity. Oxytocin-producing cells were found to be increased in the caudal paraventricular nucleus [PVN] of the hypothalamus after feeding of a sterile lysed preparation of L. reuteri, coincident with lowered blood levels of stress hormone corticosterone and more rapid epidermal closure, in mouse models. We conclude that microbe viability is not essential for regulating host oxytocin levels. The results suggest that a peptide or metabolite produced by bacteria may modulate host oxytocin secretion for potential public or personalized health goals. Keywords: Bacteria; Postbiotic; Stress; Corticosterone; Thymus; Wound healing

Disturbance to human microbiota may underlie several pathologies. Yet, we lack a comprehensive understanding of how lifestyle affects the dynamics of human-associated microbial communities.Here, we link over 10,000 longitudinal measurements of human wellness and action to the daily gut and salivary microbiota dynamics of two individuals over the course of one year. These time series show overall microbial communities to be stable for months. However, rare events in each subjects’ life rapidly and broadly impacted microbiota dynamics. Travel from the developed to the developing world in one subject led to a nearly two-fold increase in the Bacteroidetes to Firmicutes ratio, which reversed upon return. Enteric infection in the other subject resulted in the permanent decline of most gut bacterial taxa, which were replaced by genetically similar species. Still, even during periods of overall community stability, the dynamics of select microbial taxa could be associated with specific host behaviors. Most prominently, changes in host fiber intake positively correlated with next-day abundance changes among 15% of gut microbiota members.Our findings suggest that although human-associated microbial communities are generally stable, they can be quickly and profoundly altered by common human actions and experiences.

The popularity of hand sanitizer and antibiotics shows how we feel about bacteria: an enemy that's bad for our health. Emerging data, however, suggest just the opposite - that exposures to certain kinds of bacteria are beneficial for a long and healthy life, at least in part by inhibiting a wasting syndrome termed cachexia [1]. Cachexia, a condition defined as muscle wasting associated with chronic disease, arises during cancer and chronic obstructive pulmonary disease (COPD) with debilitating consequences resulting in premature death and creating a major public health burden. A growing body of research involving the host immune system reveals great potential for commensal bacteria to treat diseases and improve quality of life in animal hosts [2]. It's an intriguing possibility that microbes may be harnessed for a long, healthy, and meaningful life. Varian et al. (2016) tested this concept involving cancer-associated cachexia using a probiotic microbe Lactobacillus reuteri [1] isolated from human breast milk and previously shown to prevent diarrhea in humans [3]. The authors used a targeted infection in mouse models for proof-of-concept and mechanistic insight, rather than to focus on one type of bacteria per se. Specifically, mice consuming probiotic L. reuteri were shown to have larger skeletal muscles than untreated age-matched controls (Figure ​(Figure1).1). A surprising additional finding was increased thymus gland size only in mice consuming bacteria in their drinking water. The thymus was not only larger, but also had increased expression of Forkhead Box N1 [FoxN1], a feature involved in systemic programming of immune system lymphocytes. FoxN1 is most widely recognized as the factor missing in athymic nude mice [4]. Nude mice lack a functional thymus gland creating an immune deficit, with fewer cancer-fighting immune cells thus making them exquisitely susceptible to neoplasia. Thus, their thymic deficiency has been widely exploited in biomedical research to study cancer progression. It follows logically that mice with a larger thymus and with higher levels of FoxN1 would have increased resistance against tumors, as seen in Varian et al. 2016 [1]. Although cachexia was reduced, perhaps the most powerful finding in this study was that edible microbes globally increased FoxN1 expression even in mice without cancer, leading to a more balanced immune system during normal aging. Figure 1 Oral supplementation with microbes in drinking water inhibits cancer-associated muscle wasting [cachexia] in mouse models. Bacteria therapy up-regulates FoxN1 and oxytocin leading to a more balanced immune system and longer lifespan. Bacterial stimulation of FoxN1 and increased thymus gland size has enormous implications for host good health beyond cancer and associated cachexia. Indeed, FoxN1 protein has been touted as a “Fountain of Youth” [5]. During childhood, a proficient thymus gland supplies adaptive immune cells that help fight pathogenic infections and discern self versus non-self, to lower risk of autoimmune diseases. With increasing age, the thymus gland naturally shrinks leading to immune dysregulation with higher risk for infections and cancer in elderly subjects. Other studies have shown that mouse models treated exogenously with FoxN1 had features of sustained youth [5]. Interestingly, animals lacking FoxN1 failed to develop larger muscles after microbial therapy [1], implicating the immune system in muscle-boosting effects. The precise mechanism by which bacteria stimulate FoxN1 expression in thymus gland remains unknown but likely involves the wnt signaling pathway [1, 4]. Microbes have been shown by our own lab and by others [6] to prime the immune system for sustained good health. At the same time, the thymus gland and muscle growth may also be stimulated (delete indirectly) through bacteria-triggered upregulation of central nervous system (CNS) hormones, for example growth hormone and oxytocin [1]. The hormone oxytocin, best known for roles in childbirth and maternal nurturing [3], may be a key link between probiotic bacteria and increased muscle mass. Earlier studies showed that eating L. reuteri led to higher systemic levels of oxytocin with an improved wound healing capacity [3]. Oxytocin was shown separately in mice to be indispensable for healthy muscle maintenance and repair that normally declines with age [7]. One noteworthy feature of oxytocin is the ability to boost tissue regeneration without increasing risk for cancer. Not only is oxytocin proposed as an ‘Elixir of Youth’, but also as a remedy for mental health ailments including autism spectrum disorder [ASD]. Data from Poutahidis et al. (2013) links microbe-induced oxytocin with immune system function [3] in a synergistic perinatal partnership between mammalian hosts and their microbial passengers. Perhaps exposures to bacteria can be good for us, after all. Can we formulate a bacteria cocktail that prevents cachexia and imparts a long, healthy, and meaningful life? There are certainly reasons for optimism. Human societies around the world have been consuming probiotic bacteria in fermented foods for thousands of years with few adverse health effects. Further, animal models demonstrate reproducible beneficial health outcomes throughout life using simple microbial strategies [1, 3]. Finally, tractable microbes are readily partnered with prebiotics for palatable public health benefit. Additional research is needed to explore the vast and far-reaching potential of microbes for a long and healthy life.

available in PMC 2012 February 15., Although NF-κB1 p50/p105 has critical roles in immunity, the mechanism by which NF-κB1 regulates inflammatory responses is unclear. In this study, we analyzed the gene expression profile of LPS-stimulated Nfkb1−/− macrophages that lack both p50 and p105. Deficiency of p50/p105 selectively increased the expression of IFN-responsive genes, which correlated with increased IFN-β expression and STAT1 phosphorylation. IFN Ab-blocking experiments indicated that increased STAT1 phosphorylation and expression of IFN-responsive genes observed in the absence of p50/p105 depended upon autocrine IFN-β production. Markedly higher serum levels of IFN-β were observed in Nfkb1−/− mice than in wild-type mice following LPS injection, demonstrating that Nfkb1 inhibits IFN-β production under physiological conditions. TPL-2, a mitogen-activated protein kinase kinase kinase stabilized by association with the C-terminal ankyrin repeat domain of p105, negatively regulates LPS-induced IFN-β production by macrophages via activation of ERK MAPK. Retroviral expression of TPL-2 in Nfkb1−/− macrophages, which are deficient in endogenous TPL-2, reduced LPS-induced IFN-β secretion. Expression of the C-terminal ankyrin repeat domain of p105 in Nfkb1−/− macrophages, which rescued LPS activation of ERK, also inhibited IFN-β expression. These data indicate that p50/p105 negatively regulates LPS-induced IFN signaling in macrophages by stabilizing TPL-2, thereby facilitating activation of ERK., National Institutes of Health (U.S.) (NIH AI52267), National Institutes of Health (U.S.) (NIH CA108854), National Institutes of Health (U.S.) (NIH CA67529), Medical Research Council (Great Britain)

Pioneering work in the 1990s first linked a novel microaerobic bacterium, Helicobacter hepaticus, with chronic active hepatitis and inflammatory bowel disease in several murine models. Targeted H. hepaticus infection experiments subsequently demonstrated its ability to induce colitis, colorectal cancer, and extraintestinal diseases in a number of mouse strains with defects in immune function and/or regulation. H. hepaticus is now widely utilized as a model system to dissect how intestinal microbiota interact with the host to produce both inflammatory and tolerogenic responses. This model has been used to make important advances in understanding factors that regulate both acquired and innate immune response within the intestine. Further, it has been an effective tool to help define the function of regulatory T cells, including their ability to directly inhibit the innate inflammatory response to gut microbiota. The complete genomic sequence of H. hepaticus has advanced the identification of several virulence factors and aided in the elucidation of H. hepaticus pathogenesis. Delineating targets of H. hepaticus virulence factors could facilitate novel approaches to treating microbially induced lower bowel inflammatory diseases., National Institutes of Health (U.S.) (grant R01-DK052413), National Institutes of Health (U.S.) (grant P01-CA026731), National Institutes of Health (U.S.) (grant R01-CA067529), National Institutes of Health (U.S.) (grant P30-ES02109), National Institutes of Health (U.S.) (grant R01-A1052267), National Institutes of Health (U.S.) (grantR01-CA108854)

Neoplastic epithelia may remain dormant and clinically unapparent in human patients for decades. Multiple risk factors including mutations in tumor cells or the stromal cells may affect the switch from dormancy to malignancy. Gene mutations, including p53 mutations, within the stroma of tumors are associated with a worse clinical prognosis; however, it is not known if these stromal mutations can promote tumors in genetically at-risk tissue. To address this question, Apc(Min/+) and Apc(Min/+) Rag2(-/-) mice, which have a predilection to mammary carcinoma (as well as wild-type (wt) mice), received mesenchymal stem cells (MSC) with mutant p53 (p53MSC) transferred via tail vein injection. In the wt mouse, p53MSC circulated in the periphery and homed to the marrow cavity where they could be recovered up to a year later without apparent effect on the health of the mouse. No mammary tumors were found. However, in mice carrying the Apc(Min/+) mutation, p53MSC homed to mammary tissue and significantly increased the incidence of mammary carcinoma. Tumor necrosis factor (TNF)-alpha-dependent factors elaborated from mesenchymal cells converted quiescent epithelia into clinically apparent disease. The increased cancer phenotype was completely preventable with neutralization of TNF-alpha or by transfer of CD4(+) regulatory T cells from immune competent donors, demonstrating that immune competency to regulate inflammation was sufficient to maintain neoplastic dormancy even in the presence of oncogenic epithelial and stromal mutations. The significant synergy between host immunity and mesenchymal cells identified here may restructure treatments to restore an anticancer microenvironment.

Risk for developing cancer rises substantially as a result of poorly regulated inflammatory responses to pathogenic bacterial infections. Anti-inflammatory CD4(+) regulatory cells (T(REG)) function to restore immune homeostasis during chronic inflammatory disorders. It seems logical that T(REG) cells would function to reduce risk of inflammation-associated cancer in the bowel by down-regulating inflammation. It is widely believed, however, that T(REG) function in cancer mainly to suppress protective anticancer inflammatory responses. Thus roles for inflammation, T(REG) cells, and gut bacteria in cancer are paradoxical and are the subject of controversy. Our accumulated data build upon the "hygiene hypothesis" model in which gastrointestinal (GI) infections lead to changes in T(REG) that reduce inflammation-associated diseases. Ability of T(REG) to inhibit or suppress cancer depends upon gut bacteria and IL-10, which serve to maintain immune balance and a protective anti-inflammatory T(REG) phenotype. However, under poorly regulated pro-inflammatory conditions, T(REG) fail to inhibit and may instead contribute to a T helper (Th)-17-driven procarcinogenic process, a cancer state that is reversible by down-regulation of inflammation and interleukin (IL)-6. Consequently, hygienic individuals with a weakened IL-10- and T(REG)-mediated inhibitory loop are highly susceptible to the carcinogenic consequences of elevated inflammation and show more frequent inflammation-associated cancers. Taken together, these data help explain the paradox of inflammation and T(REG) in cancer and indicate that targeted stimulation of T(REG) may promote health and significantly reduce risk of cancer.

Inflammatory bowel disease is a chronic inflammatory response of the gastrointestinal tract mediated in part by an aberrant response to intestinal microflora. Expression of IL-23 subunits p40 and p19 within cells of the innate immune system plays a central role in the development of lower bowel inflammation in response inflammatory challenge. The NF-κB subunit c-Rel can regulate expression of IL-12/23 subunits suggesting that it could have a critical role in mediating the development of chronic inflammation within the lower bowel. In this study, we have analyzed the role of c-Rel within the innate immune system in the development of lower bowel inflammation, in two well-studied models of murine colitis. We have found that the absence of c-Rel significantly impaired the ability of Helicobacter hepaticus to induce colitis upon infection of RAG-2-deficient mice, and ameliorated the ability of CD4+CD45RBhigh T cells to induce disease upon adoptive transfer into RAG-deficient mice. The absence of c-Rel interfered with the expression of IL-12/23 subunits both in cultured primary macrophages and within the colon. Thus, c-Rel plays a critical role in regulating the innate inflammatory response to microflora within the lower bowel, likely through its ability to modulate expression of IL-12/23 family members.

Anti-inflammatory drugs and antibiotics alter the risk of breast cancer in women, but roles for bacteria and inflammation in breast malignancies are poorly understood. A recent study in mice suggests that intestinal bacteria can trigger mammary carcinoma. The mechanisms involved in this effect suggest that dysregulated host immune responses to enteric bacteria can influence the development of extraintestinal cancers, highlighting the opportunities for prevention and treatment aimed at promoting intestinal homeostasis. [Cancer Res 2007;67(3):847–50]

Microbiota on the mucosal surfaces of the gastrointestinal (GI) tract greatly outnumbers the cells in the human body. Effects of antibiotics indicate that GI tract bacteria may be determining the fate of distal cancers. Recent data implicate dysregulated host responses to enteric bacteria leading to cancers in extra-intestinal sites. Together these findings point to novel anti-cancer strategies aimed at promoting GI tract homeostasis.

Human studies and clues from animal models have provided important links between gastrointestinal (GI) tract bacteria and colon cancer. Gut microbiota antigenic stimuli play an important role in shaping the intestinal immune responses. Therefore, especially in the case of inflammation-associated colon cancer, gut bacteria antigens may affect tumorigenesis. The present study aimed to investigate the effects of the oral administration of a bacterial product with known immunomodulatory properties on inflammation-driven colorectal neoplasmatogenesis. For that, we used cholera-toxin and a well-established mouse model of colon cancer in which neoplasia is initiated by a single dose of the genotoxic agent azoxymethane (AOM) and subsequently promoted by inflammation caused by the colitogenic substance dextran sodium sulfate (DSS). We found that a single, low, non-pathogenic dose of CT, given orally at the beginning of each DSS treatment cycle downregulated neutrophils and upregulated regulatory T-cells and IL-10 in the colonic mucosa. The CT-induced disruption of the tumor-promoting character of DSS-induced inflammation led to the reduction of the AOM-initiated colonic polypoidogenesis. This result adds value to the emerging notion that certain GI tract bacteria or their products affect the immune system and render the microenvironment of preneoplastic lesions less favorable for promoting their evolution to cancer.

Defects within the innate immune system sensitize NF-κB-deficient (p50−/−; p65+/−) mice to Helicobacter hepaticus (Hh)-induced colitis. Because IL-10 plays a central role in the inhibition of Hh-induced colitis, we hypothesized that the ability of IL-10 to inhibit the innate inflammatory response to Hh may be compromised in NF-κB-deficient mice. To test this hypothesis, we evaluated the ability of an IL-10-Ig fusion protein with IL-10-like properties to inhibit Hh-induced colitis in RAG-2−/− (RAG) and p50−/−; p65+/−; RAG-2−/− (3X/RAG) mice. As expected, IL-10-Ig efficiently inhibited the development of colitis in RAG mice. In contrast, the ability of IL-10-Ig to inhibit colitis was compromised in 3X/RAG mice. The defect in response to IL-10-Ig appeared to be primarily the result of the absence of the p50/p105 subunit, because the ability of IL-10-Ig to inhibit colitis was also compromised in p50−/−; RAG-2−/− (p50/RAG) mice. Radiation chimeras demonstrated that the presence of p50/p105 within hemopoietic cells of the innate immune system was necessary for efficient inhibition of colitis by IL-10-Ig. Consistent with a defect in the suppressive effects of IL-10 in the absence of p50/p105, we found that the ability of IL-10 to control LPS-induced expression of IL-12 p40 was significantly compromised in macrophages lacking p50/p105. These results suggest that the absence of the p50/p105 subunit of NF-κB within hemopoietic cells of the innate immune system interferes with the ability of IL-10 to suppress inflammatory gene expression and Hh-induced colitis.

Helicobacter hepaticus is an enterohepatic Helicobacter species that induces lower bowel inflammation in susceptible mouse strains, including those lacking the p50/p105 subunit of NF-κB. H. hepaticus-induced colitis is associated with elevated levels of IL-12 p40 expression, and p50/p105-deficient macrophages express higher levels of IL-12 p40 than wild-type macrophages after challenge with H. hepaticus. However, the molecular mechanisms by which the p50/p105 subunit of NF-κB suppresses IL-12 p40 expression have not yet been elucidated. In this study we have demonstrated that H. hepaticus challenge of macrophages induces ERK activation, and this event plays a critical role in inhibiting the ability of H. hepaticus to induce IL-12 p40. Activation of ERK requires both p50/p105 and the MAPK kinase kinase, Tpl-2. Inhibition of the induction of IL-12 p40 by ERK was independent of c-Rel, a known positive regulator of IL-12 p40. Instead, it was linked to the induction of c-Fos, a known inhibitor of IL-12 p40 expression. These results suggest that H. hepaticus induces ERK activation by a pathway dependent upon Tpl-2 and p105, and that activation of ERK inhibits the expression of IL-12 p40 by inducing c-Fos. Thus, a defect in ERK activation could play a pivotal role in the superinduction of IL-12 p40 observed after challenge of macrophages lacking the p50/p105 subunit of NF-κB with H. hepaticus.

Cancers of breast and bowel are increasingly frequent in humans. Chronic inflammation is known to be a risk factor for these malignancies, yet cellular and molecular mechanisms linking inflammation and carcinogenesis remain poorly understood. Here, we apply a widely used T-cell transfer paradigm, involving adoptive transfer of proinflammatory CD4+CD45RBhi (TE) cells to induce inflammatory bowel disease (IBD) in mice, to investigate roles of inflammation on carcinogenesis in the ApcMin/+ mouse model of intestinal polyposis. We find that transfer of TE cells significantly increases adenoma multiplicity and features of malignancy in recipient ApcMin/+ mice. Surprisingly, we find that female ApcMin/+ recipients of TE cells also rapidly develop mammary tumors. Both intestinal polyposis and mammary adenocarcinoma are abolished by cotransfer of anti-inflammatory CD4+CD45RBlo regulatory lymphocytes or by neutralization of key proinflammatory cytokine tumor necrosis factor-α. Lastly, down-regulation of cyclooxygenase-2 and c-Myc expression is observed coincident with tumor regression. These findings define a novel mouse model of inflammation-driven mammary carcinoma and suggest that epithelial carcinogenesis can be mitigated by anti-inflammatory cells and cytokines known to regulate IBD in humans and mice. (Cancer Res 2006; 66(1): 57-61)

Campylobacter jejunicontinues to be a leading cause of bacterial enteritis in humans. However, because there are no readily available animal models to study the pathogenesis ofC. jejuni-related diseases, the significance of potential virulence factors, such as cytolethal distending toxin (CDT), in vivo are poorly understood. Mice deficient in NF-κB subunits (p50−/−p65+/−) in a C57BL/129 background are particularly susceptible to colitis induced by another enterohepatic microaerobe,Helicobacter hepaticus, which, likeC. jejuni, produces CDT. Wild-typeC. jejuni81-176 and an isogenic mutant lacking CDT activity (cdtBmutant) were inoculated into NF-κB-deficient (3X) and C57BL/129 mice. Wild-typeC. jejunicolonized 29 and 50% of the C57BL/129 mice at 2 and 4 months postinfection (p.i.), respectively, whereas theC. jejuni cdtBmutant colonized 50% of the C57BL/129 mice at 2 p.i. but none of the mice at 4 months p.i. Although the C57BL/129 mice developed mild gastritis and typhlocolitis, they had robust immunoglobulin G (IgG) and Th1-promoted IgG2a humoral responses to both the wild-type strain and theC. jejuni cdtBmutant. In contrast, 75 to 100% of the 3X mice were colonized with both the wild type and theC. jejuni cdtBmutant at similar levels at all times examined. Wild-typeC. jejunicaused moderately severe gastritis and proximal duodenitis in 3X mice that were more severe than the gastrointestinal lesions caused by theC. jejuni cdtBmutant. Persistent colonization of NF-κB-deficient mice with the wild type and theC. jejuni cdtBmutant was associated with significantly impaired IgG and IgG2a humoral responses (P< 0.001), which is consistent with an innate or adaptive immune system defect(s). These results suggest that the mechanism of clearance ofC. jejuniis NF-κB dependent and that CDT may have proinflammatory activity in vivo, as well as a potential role in the ability ofC. jejunito escape immune surveillance. NF-κB-deficient mice should be a useful model to further study the role of CDT and other aspects ofC. jejunipathogenesis.

This commentary outlines our expanding opportunities to harness the gut microbiota for cancer prevention and remission. Ultimately, simple microbial strategies might impart immune balance throughout the body leading to sustained good health.

We have previously presented evidence demonstrating that mice deficient in NF-κB subunits are susceptible to colitis induced by the pathogenic enterohepatic Helicobacter species, H. hepaticus. However, it has not been determined whether NF-κB is required within inhibitory lymphocyte populations, within cells of the innate immune system, or both, to suppress inflammation. To examine these issues, we have performed a series of adoptive transfer experiments using recombination-activating gene (Rag)-2−/− or p50−/−p65+/−Rag-2−/− mice as hosts for wild-type (WT) and p50−/−p65+/− lymphocyte populations. We have shown that although the ability of H. hepaticus to induce colitis in Rag-2−/− mice is inhibited by the presence of either WT or p50−/−p65+/− splenocytes, these splenocyte populations are unable to suppress H. hepaticus-induced colitis in p50−/−p65+/−Rag-2−/− mice. Colitis in these animals is characterized by increased expression of inflammatory cytokines including IL-12 p40, and depletion of IL-12 p40 from p50−/−p65+/− mice ameliorates H. hepaticus-induced disease. Consistent with a primary defect in the regulation of IL-12 expression, H. hepaticus induced markedly higher levels of IL-12 p40 in p50−/−p65+/− macrophages than in WT macrophages. These results suggest that inhibition of H. hepaticus-induced IL-12 p40 expression by NF-κB subunits is critical to preventing colonic inflammation in response to inflammatory microflora.

Inflammatory bowel diseases, including ulcerative colitis and Crohn’s disease, increase the risk of colorectal cancer in humans. It has been recently shown in humans and animal models that intestinal microbiota and host immunity are integral in the progression of large bowel diseases. Lymphocytes are widely believed to prevent bacterially induced inflammation in the bowel, and lymphocytes are also critical in protecting against primary tumors of intestinal epithelia in mice. Taken together, this raises the possibility that lymphocytes may inhibit colon carcinogenesis by reducing bacterially driven inflammation. To examine the role of bacteria, lymphocytes, and inflammatory bowel disease in the development of colon cancer, 129/SvEv Rag-2-deficient and congenic wild-type mice were orally inoculated with a widespread enteric mouse bacterial pathogen, Helicobacter hepaticus, or sham-dosed with media only. H. hepaticus-infected Rag2−/−, but not sham-dosed Rag2−/− mice, rapidly developed colitis and large bowel carcinoma. This demonstrated a link between microbially driven inflammation and cancer in the lower bowel and suggested that innate immune dysregulation may have an important role in inflammatory bowel disease and progression to cancer. H. hepaticus-infected wild-type mice did not develop inflammation or carcinoma showing that lymphocytes were required to prevent bacterially induced cancer at this site. Adoptive transfer with CD4+ CD45RBlo CD25+ regulatory T cells into Rag-deficient hosts significantly inhibited H. hepaticus-induced inflammation and development of cancer. These results suggested that the ability of CD4+ T cells to protect against intestinal cancer was correlated with their ability to reduce bacterially induced inflammatory bowel disease. Further, regulatory T cells may act directly on the innate immune system to reduce or prevent disease. These roles for T cells in protection against colon carcinoma may have implications for new modes of prevention and treatment of cancer in humans.

Risk of developing inflammation-associated cancers has increased in industrialized countries during the past 30 years. One possible explanation is societal hygiene practices with use of antibiotics and Caesarian births that provide too few early life exposures of beneficial microbes. Building upon a ‘hygiene hypothesis’ model whereby prior microbial exposures lead to beneficial changes in CD4+ lymphocytes, here we use an adoptive cell transfer model and find that too few prior microbe exposures alternatively result in increased inflammation-associated cancer growth in susceptible recipient mice. Specifically, purified CD4+ lymphocytes collected from ‘restricted flora’ donors increases multiplicity and features of malignancy in intestinal polyps of recipient Apc[superscript Min/+] mice, coincident with increased inflammatory cell infiltrates and instability of the intestinal microbiota. We conclude that while a competent immune system serves to maintain intestinal homeostasis and good health, under hygienic rearing conditions CD4+ lymphocytes instead exacerbate inflammation-associated tumorigenesis, subsequently contributing to more frequent cancers in industrialized societies., National Institutes of Health (U.S.) (Grant P30-ES002109), National Institutes of Health (U.S.) (Grant U01 CA164337), National Institutes of Health (U.S.) (Grant RO1CA108854)

A conference entitled ‘Human microbiome science: Vision for the future’ was organized in Bethesda, MD from July 24 to 26, 2013. The event brought together experts in the field of human microbiome research and aimed at providing a comprehensive overview of the state of microbiome research, but more importantly to identify and discuss gaps, challenges and opportunities in this nascent field. This report summarizes the presentations but also describes what is needed for human microbiome research to move forward and deliver medical translational applications.