Gut Microbiota Dysbiosis Aggravates Mycoplasma gallisepticum Colonization in the Chicken Lung

Mycoplasma gallisepticum (MG) is the pathogen that causes chronic respiratory diseases in chickens. Gut microbiota plays an important role in maintaining body health and resisting respiratory infection, but the correlation between gut microbiota and MG infection is poorly defined. Therefore, in this study, the correlation between gut microbiota and MG infection was explored by disturbing gut microbiota in chickens with antibiotic cocktail. The results showed that the gut microbiota dysbiosis impairs pulmonary immune response against MG infection. It has been noted that MG colonization in the lung was significantly increased following gut microbiota dysbiosis, and this could be reversed by intranasally administrated toll-like receptor 2 (TLR2) ligand, recombinant chicken IL-17 protein or recombinant chicken granulocyte-macrophage colony-stimulating factor (GM-CSF) protein. In addition, the levels of short-chain fatty acids (SCFAs) and vitamin A were significantly reduced in gut microbiota dysbiosis group, however, butyric acid or vitamin A as feed additives promoted MG clearance in the lung of gut microbiota dysbiosis group via increasing TLR2/IL17/GM-CSF and host defense peptides genes expression. The present study revealed an important role of gut microbiota in the defense against MG colonization in the lung of chicken.

Antibiotic-induced depletion of gut microbiota increases systemic exposure of clopidogrel active metabolite in type 2 diabetic rats

Background and Purpose: The current study investigated whether the manipulation of gut microbiome through treatment with an antibiotic cocktail can alter the bioavailability of clopidogrel active metabolite (Clop-AM) in T2DM rats. Experimental Approach: Control and T2DM rats were orally administered with either vehicle or an antibiotic cocktail containing ampicillin, neomycin, metronidazole, and vancomycin for 5 consecutive days. The levels of clopidogrel (Clop) and its metabolites were measured by LC-MS/MS. Biochemical parameters, liver microsome metabolism, mRNA, protein or activity of Clop- metabolizing enzymes and transporter, and 16S rRNA sequence of fecal samples were analyzed to explain any altered pharmacokinetic profile of Clop-AM. Key Results: Antibiotic administration markedly alleviated T2DM rats’ phenotypes including hyperglycemia, hyperlipidemia, insulin resistance, liver dysfunction and inflammation. Meanwhile, the reduced systemic exposure of Clop-AM in T2DM rats as compared to control rats was significantly reversed after antibiotic treatment, accompanied with the decreased expression of P-glycoprotein (P-gp) in small intestine, suggesting P-gp-based Clop absorption might be promoted, consequently making more Clop available for Clop-AM formation. Interestingly, fecal microbiome analysis exhibited the reduced microbial amount and the altered microbial composition in antibiotic-treated T2DM rats. Especially, there was an inconsistent change of P-gp levels between T2DM rats and SW480 cells after antibiotic treatment, suggesting antibiotic-induced microbiome depletion, not the direct role of antibiotics is associated with the enhanced Clop-AM plasma exposure in T2DM rats. Conclusion and Implication: The findings show that gut microbiota modulation is an effective therapeutic strategy to enhance Clop-AM generation under T2DM conditions.

Gut microbiota depletion from early adolescence alters anxiety and depression-related behaviours in male mice with Alzheimer-like disease

The gut-microbiota–brain axis plays an important role in stress-related disorders, and dysfunction of this complex bidirectional system is associated with Alzheimer’s disease. This study aimed to assess the idea that whether gut microbiota depletion from early adolescence can alter anxiety- and depression-related behaviours in adult mice with or without Alzheimer-like disease. Male C57BL/6 mice were treated with an antibiotic cocktail from weaning to adulthood. Adult mice received an intracerebroventricular injection of amyloid-beta (Aβ)1–42, and were subjected to anxiety and depression tests. We measured, brain malondialdehyde and glutathione following anxiety tests, and assessed brain oxytocin and the hypothalamic–pituitary–adrenal (HPA) axis function by measuring adrenocorticotrophic hormone (ACTH) and corticosterone following depression tests. Healthy antibiotic-treated mice displayed significant decreases in anxiety-like behaviours, whereas they did not show any alterations in depression-like behaviours and HPA axis function. Antibiotic treatment from early adolescence prevented the development of anxiety- and depression-related behaviours, oxidative stress and HPA axis dysregulation in Alzheimer-induced mice. Antibiotic treatment increased oxytocin in the brain of healthy but not Alzheimer-induced mice. Taken together, these findings suggest that gut microbiota depletion following antibiotic treatment from early adolescence might profoundly affect anxiety- and depression-related behaviours, and HPA axis function in adult mice with Alzheimer-like disease.

Broad-Spectrum and Gram-Negative-Targeting Antibiotics Differentially Regulate Antibody Isotype Responses to Injected Vaccines

Antibiotics are extensively used worldwide for the treatment of common infections by agents such as E. coli and Salmonella. They also represent the most common cause of alteration of the microbiota in people. We addressed whether broad-spectrum and Gram-negative-targeting antibiotics differentially regulate systemic and mucosal immune responses to vaccines. Antibiotics treatment enhances serum IgG1 responses in mice immunized systemically with a model polyvalent vaccine. This increase was not seen for other IgG subclasses and was dependent on the immunogenicity of vaccine antigens. The broad-spectrum antibiotic cocktail also enhanced serum IgA responses. Interestingly, both the broad spectrum and the antibiotic targeting Gram-negative bacteria enhanced the number of IgA antibody secreting cells in the intestinal lamina propria. This effect was unlikely to be due to an increase in cells expressing gut-homing receptors (i.e., CCR9 and α4β7) in peripheral tissues. On the other hand, the microbiome in mice treated with antibiotics was characterized by an overall reduction of the number of firmicutes. Furthermore, Bacteroidetes were increased by either treatment, and Proteobacteria were increased by the broad-spectrum antibiotics cocktail. Thus, immunoglobulin isotype and subclass responses are differentially regulated by oral antibiotics treatment and the gut microbiota shapes mucosal antibody responses after systemic immunization.

Inflammasome Signaling Regulates the Microbial–Neuroimmune Axis and Visceral Pain in Mice

Interactions between the intestinal microbiota, immune system and nervous system are essential for homeostasis in the gut. Inflammasomes contribute to innate immunity and brain–gut interactions, but their role in microbiota–neuro–immune interactions is not clear. Therefore, we investigated the effect of the inflammasome on visceral pain and local and systemic neuroimmune responses after antibiotic-induced changes to the microbiota. Wild-type (WT) and caspase-1/11 deficient (Casp1 KO) mice were orally treated for 2 weeks with an antibiotic cocktail (Abx, Bacitracin A and Neomycin), followed by quantification of representative fecal commensals (by qPCR), cecal short chain fatty acids (by HPLC), pathways implicated in the gut–neuro-immune axis (by RT-qPCR, immunofluorescence staining, and flow cytometry) in addition to capsaicin-induced visceral pain responses. Abx-treatment in WT-mice resulted in an increase in colonic macrophages, central neuro-immune interactions, colonic inflammasome and nociceptive receptor gene expression and a reduction in capsaicin-induced visceral pain. In contrast, these responses were attenuated in Abx-treated Casp1 KO mice. Collectively, the data indicate an important role for the inflammasome pathway in functional and inflammatory gastrointestinal conditions where pain and alterations in microbiota composition are prominent.

The Tick Microbiota Dysbiosis Promote Tick-Borne Pathogen Transstadial Transmission in a Babesia microti–Infected Mouse Model

Ticks are obligate hematophagous ectoparasites. They are important vectors for many pathogens, of both medical and veterinary importance. Antibiotic residues in animal food are known, but very little is known about the effects of antibiotic residues in animals on the microbiome diversity of ticks and tick-borne pathogen transmission. We used a Haemaphysalis longicornis–infested mouse model to evaluate the effect of antibiotic usage on tick microbiome. Nymphal ticks were fed on an antibiotic cocktail-treated or water control mice. Adult ticks molted from nymphs fed on the antibiotic cocktail-treated mouse had a dysbiosed microbiota. Nymphal ticks were also fed on a B. microti–infected mice that had been treated with antibiotic cocktail or water. We found that the B. microti infection in adult ticks with a dysbiosed microbiota (44.7%) was increased compared with the control adult ticks (24.2%) by using qPCR targeting 18S rRNA gene. This may increase the risk of tick-borne pathogens (TBPs) transmission from adult ticks to a vertebrate host. These results show that an antibiotic-treated mouse can induce tick microbiota dysbiosis. Antibiotic treatment of B. microti-infected mouse poses the possibility of increasing transstadial transmission of B. microti from the nymph to the adult H. longicornis. These findings suggest that B. microti transmission may be exacerbated in high antibiotic usage areas.

The gut microbiota of environmentally enriched mice regulates visual cortical plasticity

Exposing animals to an enriched environment (EE) has dramatic effects on brain structure, function and plasticity. The poorly known "EE derived signals" mediating the EE effects are thought to be generated within the central nervous system. Here, we shift the focus to the body periphery, revealing that gut microbiota signals are crucial for EE-driven plasticity. Developmental analysis of intestinal bacteria composition in EE mice revealed striking differences from standard condition (ST) animals and enhanced levels of short-chain fatty acids (SCFA). Depleting the EE mice gut microbiota with an antibiotic cocktail decreased SCFA and prevented EE induction of adult ocular dominance (OD) plasticity, spine dynamics and microglia rearrangement. SCFA treatment in ST mice mimicked the EE induction of adult OD plasticity and morphological microglial rearrangement. Remarkably, transferring the microbiota of EE mice to ST recipients activated adult OD plasticity. Thus, taken together our data suggest that experience-dependent changes in gut microbiota regulate brain plasticity.

Melatonin alleviates titanium nanoparticles induced osteolysis via activation of butyrate/GPR109A signaling pathway

Background Inflammatory osteolysis after total joint replacement (TJR) may cause implant failure, periprosthetic fractures, and be a severe threat to global public health. Our previous studies demonstrated that melatonin had a therapeutic effect on wear-particles induced osteolysis. Gut microbiota is closely related to bone homeostasis, and has been proven to be affected by melatonin. However, whether melatonin could play its anti-osteolysis effects through reprogramming gut microbiota remains elusive. Results Here, we demonstrated that melatonin could alleviate Ti-particles induced osteolysis, while this therapeutic effect was blocked by antibiotic cocktail treatment. Interestingly, transplantation of fecal microbiota from mice treated with melatonin reappeared the same beneficial effect. Analysis of the 16S rRNA revealed that melatonin could reverse dysbacteriosis triggered by osteolysis, and elevate the relative abundance of some short chain fatty acid (SCFA) producing bacteria. Moreover, butyrate was enriched by exogenous melatonin administration, while acetate and propionate did not show an evident difference. This was consistent with the results of the metagenomic approach (PICRUSt2) analysis, which revealed a general increase in the synthetic enzymes of butyrate. More importantly, direct supplementation of butyrate could also recapitulate the anti-osteolysis effect of melatonin. Further analysis identified that butyrate alleviated osteolysis via activating its receptor GPR109A, and thus to suppress the activation of NLRP3 inflammasome triggered by Ti-particles. Conclusions Taken together, our results suggested that the benefits of melatonin mainly depend on the ability of modulating gut microbiota and regulating butyrate production. Graphic Abstract

Depletion of Gut Microbiota Suppresses the Metabolite Formation of Vitamin E Forms Including Delta-tocotrienol and Its Long-chain Metabolite 13’-carboxychromanol in Mice

Objectives We recently show that supplementation of delta-tocotrienol (δTE), a vitamin E form and its metabolite δTE-13’-carboxychromanol (δTE-13’) modulated gut microbiota and meanwhile increased metabolites in feces. Since gut microbiota has been shown to metabolize phenolic compounds, we hypothesize that gut bacteria may play a role in metabolizing δTE and δTE-13’. This hypothesis was addressed in the comparison of metabolites formation between antibiotic cocktail (ABX)-treated mice and non-ABX treated mice. Methods Male Balb/c mice were given ABX or water daily for 7 days to remove the gut microbiota. Subsequently ABX or water-treated mice were given a single gavage of δTE/gamma-tocotrienol (δTE/γTE at 8:1) or δTE-13’ at 42mg/kg bw. 24-hr later, mice were sacrificed. We collected 24-hr accumulative fecal samples, adipose, plasma, colon and liver tissues and quantified the concentrations of vitamin E forms and metabolites in these samples. Results Compared with non-ABX controls, ABX-treated mice had decreased weights of liver, spleen and colon, while had doubled the amount of 24-hr fecal output. In δTE-gavaged animals, ABX treatment decreased fecal amounts of δTE and its metabolites by 61% and 98% respectively, while increased δTE level in the adipose tissue. Similarly, in animals gavaged with δTE-13’, ABX treatment led to a 98% reduction in its downstream metabolites. Additionally, ABX treatment decreased fecal excretion of metabolites from other vitamin E forms including α, γ, δ-tocopherols and γTE. Conclusions These results demonstrate that without the gut microbiota, fecal concentrations of vitamin E metabolites declined dramatically, suggesting potential role of the gut microbiota in metabolizing vitamin E forms. Funding Sources Purdue Center for Cancer Research.