Intestinal barrier damage involved in intestinal microflora changes in fluoride-induced mice

Fluoride exposure-induced gut microbiota alteration mediates colonic ferroptosis through N6-methyladenosine (m6A) mediated silencing of SLC7A11

Fluoride exposure is widespread worldwide and poses a significant threat to organisms, particularly to their gastrointestinal tracts. However, due to limited knowledge of the mechanism of fluoride induced intestinal injury, it has been challenging to develop an effective treatment. To address this issue, we used a series of molecular biology in vitro and in vivo experiments. NaF triggered m6A mediated ferroptosis to cause intestinal damage. Mechanistically, NaF exposure increased the m6A level of SLC7A11 mRNA, promoted YTHDF2 binding to m6A-modified SLC7A11 mRNA, drove the degradation of SLC7A11 mRNA, and led to a decrease in its protein expression, which eventually triggers ferroptosis. Moreover, NaF aggravated ferroptosis of the colon after antibiotics destroyed the composition of gut microbiota. 16 S rRNA sequencing and SPEC-OCCU plots, Zi-Pi relationships, and Spearman correlation coefficients verified that Lactobacillus murinus (ASV54, ASV58, and ASV82) plays a key role in the response to NaF-induced ferroptosis. Collectively, NaF-induced gut microbiota alteration mediates severe intestinal cell injury by inducing m6A modification-mediated ferroptosis. Our results highlight a key mechanism of the gut in response to NaF exposure and suggest a valuable theoretical basis for its prevention and treatment.

Alleviation of fluoride-induced colitis by tea polysaccharides: Insights into the role of Limosilactobacillus vaginalis and butyric acid

Endemic fluorosis has gained increasing attention as a public health concern, and the escalating risk of colitis resulting from excessive fluoride intake calls for effective mitigation strategies. This study aimed to investigate the potential mechanisms underlying the alleviation of fluoride-induced colitis by Tea polysaccharides (TPS). Under conditions of excessive fluoride intake, significant changes were observed in the gut microbiota of rats, leading to aggravated colitis. However, the intervention of TPS exerted a notable alleviating effect on colitis symptoms. Antibiotic intervention and fecal microbiota transplantation (FMT) experiments provided evidence that TPS-mediated relief of fluoride-induced colitis is mediated through its effects on the gut microbiota. Furthermore, TPS supplementation was found to modulate the structure of gut microbiota, enhance the relative abundance of Limosilactobacillus vaginalis in the gut microbiota, and promote the expression of short-chain fatty acid (SCFAs) receptors in colonic tissue. Notably, L. vaginalis played a significant role in alleviating fluoride-induced colitis and facilitating the absorption of butyric acid in the rat colon. Subsequent butyric acid intervention experiments confirmed its remarkable alleviating effect on fluoride-induced colitis. Overall, these findings provide a potential preventive strategy for fluoride-induced colitis by TPS intervention, which is mediated by L. vaginalis and butyric acid.

Microbiome and metabolome analyses indicate variations in the gut microbiota that disrupt regulation of appetite

The mechanism connecting gut microbiota to appetite regulation is not yet fully understood. This study identifies specific microbial community and metabolites that may influence appetite regulation. In the initial phase of the study, mice were administered a broad-spectrum antibiotic cocktail (ABX) for 10 days. The treatment significantly reduced gut microbes and disrupted the metabolism of arginine and tryptophan. Consequently, ABX-treated mice demonstrated a notable reduction in feed consumption. The hypothalamic expression levels of CART and POMC, two key anorexigenic factors, were significantly increased, while orexigenic factors, such as NPY and AGRP, were decreased. Notably, the levels of appetite-suppressing hormone cholecystokinin in the blood were significantly elevated. In the second phase, control mice were maintained, while the ABX-treated mice received saline, probiotics, and short-chain fatty acids (SCFAs) for an additional 10 days to restore their gut microbiota. The microbiota reconstructed by probiotic and SCFA treatments were quite similar, while microbiota of the naturally recovering mice demonstrated greater resemblance to that of the control mice. Notably, the abundance of Akkermansia and Bacteroides genera significantly increased in the reconstructed microbiota. Moreover, microbiota reconstruction corrected the disrupted arginine and tryptophan metabolism and the abnormal peripheral hormone levels caused by ABX treatment. Among the groups, SCFA-treated mice had the highest feed intake and NPY expression. Our findings indicate that gut microbes, especially Akkermansia, regulate arginine and tryptophan metabolism, thereby influencing appetite through the microbe-gut-brain axis.

Carboxypeptidase inhibitor Latexin (LXN) regulates intestinal organogenesis and intestinal remodeling involved in intestinal injury repair in mice

The self-renewal and regeneration of intestinal epithelium are mainly driven by intestinal stem cells resided in crypts, which are crucial for rapid recovery intestinal tissue following injury. Latexin (LXN) is a highly expressed stem cell proliferation and differentiation related gene in intestinal tissue. However, it is still ambiguous whether LXN participates in intestine regeneration by regulating intestinal stem cells (ISCs). Here, we report that LXN colocalizes with Leucine-rich repeat-containing G-protein coupled receptor 5 (Lgr5) in intestinal crypts, and deletion of LXN upregulates the expression of Lgr5 in intestinal crypts. LXN deficiency promotes the proliferation of ISCs, thereby enhances the development of intestinal organoids. Mechanically, we show that LXN deficiency enhances the expression of Lgr5 in ISCs by activating the Yes-associated protein (YAP) and wingless (Wnt) signal pathways, thus accelerating intestinal normal growth and regeneration post-injury. In summary, these findings uncover a novel function of LXN in intestinal regeneration post-injury and intestinal organogenesis, suggesting the potential role of LXN in the treatment of inflammatory bowel diseases.

Gut dysbiosis contributes to the development of Budd-Chiari syndrome through immune imbalance

Budd-Chiari syndrome (B-CS) is a rare and lethal condition characterized by hepatic venous outflow tract blockage. Gut microbiota has been linked to numerous hepatic disorders, but its significance in B-CS pathogenesis is uncertain. First, we performed a case-control study (Ncase = 140, Ncontrol = 63) to compare the fecal microbiota of B-CS and healthy individuals by metagenomics sequencing. B-CS patients' gut microbial composition and activity changed significantly, with a different metagenomic makeup, increased potentially pathogenic bacteria, including Prevotella, and disease-linked microbial function. Imbalanced cytokines in patients were demonstrated to be associated with gut dysbiosis, which led us to suspect that B-CS is associated with gut microbiota and immune dysregulation. Next, 16S ribosomal DNA sequencing on fecal microbiota transplantation (FMT) mice models examined the link between gut dysbiosis and B-CS. FMT models showed damaged liver tissues, posterior inferior vena cava, and increased Prevotella in the disturbed gut microbiota of FMT mice. Notably, B-CS-FMT impaired the morphological structure of colonic tissues and increased intestinal permeability. Furthermore, a significant increase of the same cytokines (IL-5, IL-6, IL-9, IL-10, IL-17A, IL-17F, and IL-13) and endotoxin levels in B-CS-FMT mice were observed. Our study suggested that gut microbial dysbiosis may cause B-CS through immunological dysregulation.

IMPORTANCE

This study revealed that gut microbial dysbiosis may cause Budd-Chiari syndrome (B-CS). Gut dysbiosis enhanced intestinal permeability, and toxic metabolites and imbalanced cytokines activated the immune system. Consequently, the escalation of causative factors led to their concentration in the portal vein, thereby compromising both the liver parenchyma and outflow tract. Therefore, we proposed that gut microbial dysbiosis induced immune imbalance by chronic systemic inflammation, which contributed to the B-CS development. Furthermore, Prevotella may mediate inflammation development and immune imbalance, showing potential in B-CS pathogenesis.

Underlying Mechanism of Fluoride Inhibits Colonic Gland Cells Proliferation by Inducing an Inflammation Response

The integrity of colonic gland cells is a prerequisite for normal colonic function and maintenance. To evaluate the underlying injury mechanisms in colonic gland cells induced by excessive fluoride (F), forty-eight female Kunming mice were randomly allocated into four groups and treated with different concentrations of NaF (0, 25, 50, and 100 mg F-/L) for 70 days. As a result, the integrity of the colonic mucosa and the cell layer was seriously damaged after F treatment, as manifested by atrophy of the colonic glands, colonic cell surface collapse, breakage of microvilli, and mitochondrial vacuolization. Alcian blue and periodic acid Schiff staining revealed that F decreased the number of goblet cells and glycoprotein secretion. Furthermore, F increased the protein expression of TLR4, NF-κB, and ERK1/2 and decreased IL-6, interfered with NF-κB signaling, following induced colonic gland cells inflammation. The accumulation of F inhibited proliferation via the JAK/STAT signaling pathway, as characterized by decreased mRNA and protein expression of JAK, STAT3, STAT5, PCNA, and Ki67 in colon tissue. Additionally, the expression of CDK4 was up-regulated by increased F concentration. In conclusion, excessive F triggered colonic inflammation and inhibited colonic gland cell proliferation via regulation of the NF-κB and JAK/STAT signaling pathways, leading to histopathology and barrier damage in the colon. The results explain the damaging effect of the F-induced inflammatory response on the colon from the perspective of cell proliferation and provide a new idea for explaining the potential mechanism of F-induced intestinal damage.

Aflatoxin B1 exposure causes splenic pyroptosis by disturbing the gut microbiota-immune axis

Aflatoxin B1 (AFB1) causes serious immunotoxicity and has attracted considerable attention owing to its high sensitivity and common chemical-viral interactions in living organisms. However, the sensitivity of different species to AFB1 widely varies, which cannot be explained by the different metabolism in species. The gut microbiota plays a crucial role in the immune system, but the interaction of the microbiota with AFB1-induced immunotoxicity still needs to be determined. Our results indicated that AFB1 exposure disrupted the structure of the gut microbiota and damaged the gut barrier, which caused translocation of microbiota metabolites, lipopolysaccharides, to the spleen. Subsequently, pyroptosis of the spleen was activated. Interestingly, AFB1 exposure had little effect on the splenic pyroptosis of pseudo-germfree mice (antibiotic mixtures eliminated their gut microbiota, ABX). Then, fecal microbiota transplant (FMT) and sterile fecal filtrate (SFF) were employed to validate the function of the gut microbiota and its metabolites in AFB1-induced splenic pyroptosis. The AFB1-disrupted microbiota and its metabolites significantly promoted splenic pyroptosis, which was worse than that in control mice. Overall, AFB1-induced splenic pyroptosis is associated with the gut microbiota and its metabolites, which was further demonstrated by FMT and SFF. The mechanism of AFB1-induced splenic pyroptosis was explored for the first time, which paves a new way for preventing and treating the immunotoxicity from mycotoxins by regulating the gut microbiota.

Bifidobacterium Relieved Fluoride-Induced Hepatic and Ileal Toxicity via Inflammatory Response and Bile Acid Transporters in Mice

Fluoride is a pervasive environmental contaminant. Prolonged excessive fluoride intake can inflict severe damage on the liver and intestines. Previous 16S rDNA sequencing revealed a decrease in ileal Bifidobacterium abundance during fluoride-induced hepatointestinal injury. Hence, this work aimed to investigate the possible mitigating function of Bifidobacterium on hepatointestinal injury caused by fluoride. Thirty-six 6-week-old C57BL/6J mice (equally divided between males and females) were allotted randomly to three groups: Ctrl group (distilled water), NaF group, and NaF + Ba group (100 mg/L NaF distilled water). After 10 weeks, the mice were given 1 × 109 CFU/mL Bifidobacterium solution (0.2 mL/day) intragastrically in the NaF + Ba group for 8 weeks, and the mice in other groups were given the same amount of distilled water. Dental damage, bone fluoride content, blood routine, liver and intestinal microstructure and function, inflammatory factors, and regulatory cholic acid transporters were examined. Our results showed that fluoride increased glutamic-oxalacetic transaminase (GOT), glutamic-pyruvic transaminase (GPT) activities, and the levels of lipopolysaccharide (LPS), IL-1β, IL-6, TNF-α, and IL-10 levels in serum, liver, and ileum. However, Bifidobacterium intervention alleviated fluoride-induced changes in the above indicators. In addition, Bifidobacterium reduced the mRNA expression levels of bile acid transporters ASBT, IBABP, OST-α, and OST-β in the ileum. In summary, Bifidobacterium supplementation relieved fluoride-induced hepatic and ileal toxicity via an inflammatory response and bile acid transporters in the liver and ileum of mice.

The triangular relationship between traditional Chinese medicines, intestinal flora, and colorectal cancer

Over the past decade, colorectal cancer has reported a higher incidence in younger adults and a lower mortality rate. Recently, the influence of the intestinal flora in the initiation, progression, and treatment of colorectal cancer has been extensively studied, as well as their positive therapeutic impact on inflammation and the cancer microenvironment. Historically, traditional Chinese medicine (TCM) has been widely used in the treatment of colorectal cancer via promoted cancer cell apoptosis, inhibited cancer metastasis, and reduced drug resistance and side effects. The present research is more on the effect of either herbal medicine or intestinal flora on colorectal cancer. The interactions between TCM and intestinal flora are bidirectional and the combined impacts of TCM and gut microbiota in the treatment of colon cancer should not be neglected. Therefore, this review discusses the role of intestinal bacteria in the progression and treatment of colorectal cancer by inhibiting carcinogenesis, participating in therapy, and assisting in healing. Then the complex anticolon cancer effects of different kinds of TCM monomers, TCM drug pairs, and traditional Chinese prescriptions embodied in apoptosis, metastasis, immune suppression, and drug resistance are summarized separately. In addition, the interaction between TCM and intestinal flora and the combined effect on cancer treatment were analyzed. This review provides a mechanistic reference for the application of TCM and intestinal flora in the clinical treatment of colorectal cancer and paves the way for the combined development and application of microbiome and TCM.

Inactivation of Mst/Nrf2/Keap1 signaling flexibly mitigates MAPK/NQO-HO1 activation in the reproductive axis of experimental fluorosis

Fluoride induced reprotoxicity through oxidative stress-mediated reproductive cell death. Hence, the current study evaluated the importance of the MST/Nrf2/MAPK/NQO-HO1 signaling pathway in fluorosis-induced reproductive toxicity. For this purpose, the reproductive toxicity of sodium fluoride (NaF) at physiological, biochemical, and intracellular levels was evaluated. In-vivo, NaF at 100 mg/L instigated physiological dysfunction, morphological, stereological, and structural injuries in the gut-gonadal axis of fluorosis mice through weakening the antioxidant signaling, Nrf2/HO-1/NQO1signaling pathway, causing the gut-gonadal barrier disintegrated via oxidative stress-induced inflammation, mitochondrial damage, apoptosis, and autophagy. Similar trends were also observed in-vitro in the isolated Leydig cells (LCs) challenging with 20 mg/L NaF. Henceforth, activating the cellular antioxidant signaling pathway, Nrf2/HO-1/NQO1, inactivating autophagy and apoptosis, or attenuating lipopolysaccharide (LPS) can be the theoretical basis and valuable therapeutic targets for coping with NaF-induced reproductive toxicity.

Huanglian Ganjiang decoction alleviates ulcerative colitis by restoring gut barrier via APOC1-JNK/P38 MAPK signal pathway based on proteomic analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Ulcerative colitis (UC) is a kind of chronic intestinal inflammation accompanied with abdominal pain, diarrhea and hematochezia. Huanglian Ganjiang decoction (HGD) derived from "Beiji Qianjin Yao Fang" was used for UC patients clinically. However, the specific mechanism of HGD in treating UC remain unclear.

AIM OF STUDY

Our study devoted to demonstrating the therapeutic effect of HGD for colitis and clarifying the underlying mechanism.

MATERIALS AND METHODS

UPLC-MS was carried out to identify the ingredients of HGD. UC mice were induced by giving 3% dextran sulfate sodium (DSS) solution for one week and treated by HGD for another week. Body weight fluctuation, disease activity index (DAI), colon length and pathological change of colon tissues were observed to evaluate therapeutical effect of HGD. ELISA and qPCR were carried out to estimate the inflammatory state. Western blot, qPCR and immunofluorescence were used to access the expression of tight junction proteins. Tandem mass tag (TMT)-Based proteomics and network pharmacology was launched to screen and predict the potential targets and pathway regulated by HGD.

RESULTS

Based on the UPLC-MS/MS analysis, 100 components were identified in HGD. After 7-day treatment, HGD significantly alleviated colitis-associated symptoms including body weight loss, shorted colon, increase of DAI score, histopathologic lesions. HGD also reduced inflammatory cytokines IL-6 and IL-1β levels, increased the number of goblet cells and restored tight junction proteins Occludin, Claudin-1 in colon. Network pharmacology study predicted that tight junction and MAPK pathway might be affected by HGD in colitis mice. APOC1 was screened out as key target in HGD-treated mice using TMT-based proteomics study. Further Western blot results showed that HGD reduced expressions of APOC1, p-P38 and p-JNK.

CONCLUSION

HGD improves general symptoms of colitis mice at medium and high doses, which may be associated with restoring tight junction and intestinal barrier integrity and function through suppression of APOC1-JNK/P38 MAPK signal pathway.

Tert-butylhydroquinone attenuates LPS-induced pyroptosis of IPEC-J2 cells via downregulating HMGB1/TLR4/NF-κB axis

Inflammatory response induced by biological stress usually occurs in weaning piglets, it reduces the production performance of piglets and even causes death. Tert-butylhydroquinone (TBHQ) is a food additive that has the effect of anti-inflammation and anti-oxidation. However, there are few reports related to the protective mechanisms of TBHQ on lipopolysaccharide (LPS) induced injury in intestinal porcine epithelial (IPEC-J2) cells. Quantitative real-time polymerase chain reaction and western blot analysis, respectively, detected the mRNA levels and protein expressions related to pyroptosis, tight junction (TJ) protein and high-mobility group box 1/toll-like receptor 4/nuclear factor kappa-B (HMGB1/TLR4/NF-κB) axis. Localisation and expression of NOD-like receptor pyrin domain containing 3 (NLRP3), HMGB1 and P-NF-κB proteins detected by immunofluorescence. The results showed that TBHQ (12.5 and 25 μM) can increase cell activity and reduce intracellular lactate dehydrogenase (LDH) levels in a dose-dependent manner. LPS significantly decreases cell viability and increases the LDH level. However, pretreatment with TBHQ evidently increases cell viability and decreases the LDH level of IPEC-J2 cells. In addition, treatment with LPS decreased the mRNA level and protein expression of zonula occludens-1, occludin and claudin-1, and increased the mRNA level and protein expression of pyroptosis and HMGB1/TLR4/NF-κB axis. Interestingly, pretreatment with TBHQ increased the TJ protein expressions as well as decreased the mRNA level and protein expressions of pyroptosis and HMGB1/TLR4/NF-κB axis. Moreover, the results of immunofluorescence showed that TBHQ significantly reduced the expression of NLRP3, HMGB1 and P-NF-κB in LPS-induced injury of IPEC-J2 cells. Therefore, we come to the conclusion that TBHQ attenuates LPS-induced pyroptosis in IPEC-J2 cells through downregulation of the HMGB1/TLR4/NF-κB axis, TBHQ may become a potential feed additive for preventing inflammatory diarrhoea in piglets.

Antibiotics attenuate diet-induced nonalcoholic fatty liver disease without altering intestinal barrier dysfunction

To date the role of the alterations of intestinal microbiota in the development of intestinal barrier dysfunction in settings of nonalcoholic fatty liver disease (NAFLD) has not been fully understood. Here, we assessed the effect of antibiotics on development of NAFLD and their impact on intestinal barrier dysfunction. Male C57BL/6J mice were either pair-fed a liquid control diet (C) or fat- and fructose-rich diet (FFr) +/- antibiotics (AB, ampicillin/vancomycin/metronidazole/gentamycin) for 7 weeks. Fasting blood glucose was determined and markers of liver damage, inflammation, intestinal barrier function, and microbiota composition were assessed. The development of hepatic steatosis with early signs of inflammation found in FFr-fed mice was significantly abolished in FFr+AB-fed mice. Also, while prevalence of bacteria in feces was not detectable and TLR4 ligand levels in portal plasma were at the level of controls in FFr+AB-fed mice, impairments of intestinal barrier function like an increased permeation of xylose and iNOS protein levels persisted to a similar extent in both FFr-fed groups irrespective of AB use. Exposure of everted small intestinal tissue sacs of naïve mice to fructose resulted in a significant increase in tissue permeability and loss of tight junction proteins, being not affected by the presence of AB, whereas the concomitant treatment of tissue sacs with the NOS inhibitor aminoguanidine attenuated these alterations. Taken together, our data suggest that intestinal barrier dysfunction in diet-induced NAFLD in mice may not be predominantly dependent on changes in intestinal microbiota but rather that fructose-induced alterations of intestinal NO-homeostasis might be critically involved.

Arsenic induced neurotoxicity in the brain of ducks: The potential involvement of the gut-brain axis

BACKGROUND

Arsenic is a widely distributed ecotoxic pollutant that has been found to cause neurotoxicity in a variety of species. Gut-brain axis is a two-way information network between the gut microbiome and the brain, which is closely related to organismal health. However, the role of the gut-brain axis in arsenic-induced neurotoxicity remains largely unknown.

METHODS

In order to explore whether there is a relationship between brain and gut microbiota of meat ducks, we performed molecular biological detection including RT-qPCR and Western blot, as well as morphological detection including, HE staining and immunohistochemistry. Meanwhile, intestinal contents were analyzed using 16 S ribosomal RNA gene sequencing and analysis RESULTS: In this study, we investigated whether arsenic trioxide (ATO) can activate the gut microbiome-brain axis to induce intestinal and brain injury. The results showed that ATO-exposure disrupted the diversity balance of intestinal microbiota and integrity and injured the intestinal structure. ATO-exposure also reduced the number of glycogen and goblet cells in the duodenum. In addition, exposure to ATO caused intestinal inflammatory injury by activating NF-κB signaling pathway and promoting the expression of its target genes. Meanwhile, the tight junction-related proteins (ZO-1, occludin) of gut and brain were reduced by ATO exposure. Furthermore, results also revealed that ATO-exposure induced brain injury, including neuronal cell vacuolization and reduced numbers of neuronal cells in the cortex and hippocampus. Remarkably, ATO-exposure also disrupted neurotransmitter levels. Additionally, our further molecular mechanism study revealed that ATO-exposure increased the expression of autophagy and apoptosis related mRNA and proteins levels in the brain tissues.

CONCLUSION

Altogether, these findings provide a new insight into that ATO-exposure induced intestinal injury and aggravated neurotoxicity via the gut-brain axis.

The Dose-Response Effect of Fluoride Exposure on the Gut Microbiome and Its Functional Pathways in Rats

Metabolic activities within the gut microbiome are intimately linked to human health and disease, especially within the context of environmental exposure and its potential ramifications. Perturbations within this microbiome, termed "gut microbiome perturbations", have emerged as plausible intermediaries in the onset or exacerbation of diseases following environmental chemical exposures, with fluoride being a compound of particular concern. Despite the well-documented adverse impacts of excessive fluoride on various human physiological systems-ranging from skeletal to neurological-the nuanced dynamics between fluoride exposure, the gut microbiome, and the resulting dose-response relationship remains a scientific enigma. Leveraging the precision of 16S rRNA high-throughput sequencing, this study meticulously examines the ramifications of diverse fluoride concentrations on the gut microbiome's composition and functional capabilities within Wistar rats. Our findings indicate a profound shift in the intestinal microbial composition following fluoride exposure, marked by a dose-dependent modulation in the abundance of key genera, including Pelagibacterium, Bilophila, Turicibacter, and Roseburia. Moreover, discernible alterations were observed in critical functional and metabolic pathways of the microbiome, such as D-lyxose ketol-isomerase and DNA polymerase III subunit gamma/tau, underscoring the broad-reaching implications of fluoride exposure. Intriguingly, correlation analyses elucidated strong associations between specific bacterial co-abundance groups (CAGs) and these shifted metabolic pathways. In essence, fluoride exposure not only perturbs the compositional equilibrium of the gut microbiota but also instigates profound shifts in its metabolic landscape. These intricate alterations may provide a mechanistic foundation for understanding fluoride's potential toxicological effects mediated via gut microbiome modulation.

Environmental cadmium exposure facilitates mammary tumorigenesis via reprogramming gut microbiota-mediated glutamine metabolism in MMTV-Erbb2 mice

Cadmium (Cd) is a heavy metal that has been widely reported to be linked to the onset and progression of breast cancer (BC). However, the mechanism of Cd-induced mammary tumorigenesis remains elusive. In our study, a transgenic mouse model that spontaneously develops tumors through overexpression of wild-type Erbb2 (MMTV-Erbb2) was constructed to investigate the effects of Cd exposure on BC tumorigenesis. The results showed that oral exposure to 3.6 mg/L Cd for 23 weeks dramatically accelerated tumor appearance and growth, increased Ki67 density and enhanced focal necrosis and neovascularization in the tumor tissue of MMTV-Erbb2 mice. Notably, Cd exposure enhanced glutamine (Gln) metabolism in tumor tissue, and 6-diazo-5-oxo-l-norleucine (DON), a Gln metabolism antagonist, inhibited Cd-induced breast carcinogenesis. Then our metagenomic sequencing and mass spectrometry-based metabolomics confirmed that Cd exposure disturbed gut microbiota homeostasis, especially Helicobacter and Campylobacter abundance remodeling, which altered the gut metabolic homeostasis of Gln. Moreover, intratumoral Gln metabolism profoundly increased under Cd-elevated gut permeability. Importantly, depletion of microbiota with an antibiotic cocktail (AbX) treatment led to a significant delay in the appearance of palpable tumors, inhibition of tumor growth, decrease in tumor weight, reduction in Ki67 expression and low-grade pathology in Cd-exposed MMTV-Erbb2 mice. Also, transplantation of Cd-modulated microbiota decreased tumor latency, accelerated tumor growth, increased tumor weight, upregulated Ki67 expression and exacerbated neovascularization as well as focal necrosis in MMTV-Erbb2 mice. In summary, Cd exposure induced gut microbiota dysbiosis, elevated gut permeability and increased intratumoral Gln metabolism, leading to the promotion of mammary tumorigenesis. This study provides novel insights into environmental Cd exposure-mediated carcinogenesis.

Oxygen enrichment protects against intestinal damage and gut microbiota disturbance in rats exposed to acute high-altitude hypoxia

Acute high-altitude hypoxia can lead to intestinal damage and changes in gut microbiota. Sustained and reliable oxygen enrichment can resist hypoxic damage at high altitude to a certain extent. However, it remains unclear whether oxygen enrichment can protect against gut damage and changes in intestinal flora caused by acute altitude hypoxia. For this study, eighteen male Sprague-Dawley rats were divided into three groups, control (NN), hypobaric hypoxic (HH), and oxygen-enriched (HO). The NN group was raised under normobaric normoxia, whereas the HH group was placed in a hypobaric hypoxic chamber simulating 7,000 m for 3 days. The HO group was exposed to oxygen-enriched air in the same hypobaric hypoxic chamber as the HH group for 12 h daily. Our findings indicate that an acute HH environment caused a fracture of the crypt structure, loss of epithelial cells, and reduction in goblet cells. Additionally, the structure and diversity of bacteria decreased in richness and evenness. The species composition at Phylum and Genus level was characterized by a higher ratio of Firmicutes and Bacteroides and an increased abundance of Lactobacillus with the abundance of Prevotellaceae_NK3B31_group decreased in the HH group. Interestingly, after oxygen enrichment intervention, the intestinal injury was significantly restrained. This was confirmed by an increase in the crypt depth, intact epithelial cell morphology, increased relative density of goblet cells, and higher evenness and richness of the gut microbiota, Bacteroidetes and Prevotellaceae as the main microbiota in the HO group. Finally, functional analysis showed significant differences between the different groups with respect to different metabolic pathways, including Amino acid metabolism, energy metabolism, and metabolism. In conclusion, this study verifies, for the first time, the positive effects of oxygen enrichment on gut structure and microbiota in animals experiencing acute hypobaric hypoxia.

Identifying Serum Metabolites and Gut Bacterial Species Associated with Nephrotoxicity Caused by Arsenic and Fluoride Exposure

Co-contamination of arsenic (As) and fluoride (F) is widely distributed in groundwater, which are known risk factors for the nephrotoxicity. Emerging evidence has linked environmentally associated nephrotoxicity with the disturbance of gut microbiota and blood metabolites. In this study, we generated gut microbiota and blood metabolomic profile and identified multiple serum metabolites and gut bacteria species, which were associated with kidney injury on rat model exposed to As and F alone or combined. Combined As and F exposure significantly increased creatinine level. Abnormal autophagosomes and lysosome were observed, and the autophagic genes were enhanced in kidney tissue after single and combined As and F exposure. The metabolome data showed that single and combined As and F exposure remarkably altered the serum metabolites associated with the proximal tubule reabsorption function pathway, with glutamine and alpha-ketoglutarate level decreased in all exposed group. Furthermore, phosphatidylethanolamine (PE), the key contributor of autophagosomes, was decreased significantly in As and F + As exposed groups during the screen of autophagy-animal pathway. Multiple altered gut bacterial microbiota at phylum and species levels post As and F exposure were associated with targeted kidney injury, including p_Bacteroidetes, s_Chromohalobacter_unclassified, s_Halomonas_unclassified, s_Ignatzschineria_unclassified, s_Bacillus_subtilis, and s_Brevundimonas_sp._NA6. Meanwhile, our analysis indicated that As and F co-exposure possessed an interactive influence on gut microbiota. In conclusion, single or combined As and F exposure leads to the disruption of serum metabolic and gut microbiota profiles. Multiple metabolites and bacterial species are identified and associated with nephrotoxicity, which have potential to be developed as biomarkers of As and/or F-induced kidney damage.

Lactiplantibacillus plantarum L47 and inulin alleviate enterotoxigenic Escherichia coli induced ileal inflammation in piglets by upregulating the levels of α-linolenic acid and 12,13-epoxyoctadecenoic acid

Alternatives to antibiotics for preventing bacteria-induced inflammation in early-weaned farm animals are sorely needed. Our previous study showed that Lactiplantibacillus plantarum L47 and inulin could alleviate dextran sulfate sodium (DSS)-induced colitis in mice. To explore the protective effects of L. plantarum L47 and inulin on the ileal inflammatory response in weaned piglets challenged with enterotoxigenic Escherichia coli (ETEC), 28 weaned piglets were assigned into four groups, namely, CON group-orally given 10 mL/d phosphate buffer saline (PBS), LI47 group-orally given a mixture of 10 mL/d L. plantarum L47 and inulin, ECON group-orally given 10 mL/d PBS and challenged by ETEC, and ELI47 group-orally given 10 mL/d L. plantarum L47 and inulin mixture and challenged by ETEC. The results demonstrated that the combination of L. plantarum L47 and inulin reduced inflammatory responses and relieved the inflammatory damage caused by ETEC, including ileal morphological damage, reduced protein expression of ileal tight junction, decreased antioxidant capacity, and decreased anti-inflammatory factors. Transcriptome analysis revealed that L. plantarum L47 and inulin up-regulated the gene expression of phospholipase A2 group IIA (PLA2G2A) (P < 0.05) as well as affected alpha-linolenic acid (ALA) metabolism and linoleic acid metabolism. Moreover, L. plantarum L47 and inulin increased the levels of ALA (P < 0.05), lipoteichoic acid (LTA) (P < 0.05), and 12,13-epoxyoctadecenoic acid (12,13-EpOME) (P < 0.05) and the protein expression of Toll-like receptor 2 (TLR2) (P = 0.05) in the ileal mucosa. In conclusion, L. plantarum L47 and inulin together alleviated ETEC-induced ileal inflammation in piglets by up-regulating the levels of ALA and 12,13-EpOME via the LTA/TLR2/PLA2G2A pathway.

Difenoconazole disrupts carp intestinal physical barrier and causes inflammatory response via triggering oxidative stress and apoptosis

As a common fungicide, difenoconazole (DFZ) is widespread in the natural environment and poses many potential threats. Carp makes up a significant proportion of China's freshwater aquaculture population and are vulnerable to the DFZ. Therefore, this study investigated the effects of DFZ (0.488 mg/L and 1.953 mg/L) exposure for 4 d on the intestinal tissues of carp and explored the mechanisms. Specifically, DFZ exposure caused pathological damage to the intestinal tissues of carp, reducing the expression levels of intestinal tight junction proteins, and leading to damage to the intestinal barrier. In addition, DFZ exposure activated the NF-κB signaling pathway, increasing the levels of pro-inflammatory factors (TNF-α, IL-1β, IL-6) and decreasing the levels of anti-inflammatory factors (IL-10, TGF-β1). As disruption of the intestinal barrier is closely linked to oxidative stress and apoptosis, we have conducted research in both areas for this reason. The results showed that DFZ exposure elevated reactive oxygen species in carp intestines, decreased antioxidant enzyme activity, and suppressed the expression of oxidative stress-related genes. TUNEL results showed that DFZ induced the onset of apoptosis. In addition, the expression levels of apoptosis-related genes and proteins were examined. Western blotting results showed that DFZ could upregulate the protein expression levels of Bax, Cytochrome C and downregulate the protein levels of Bcl-2. qPCR results showed that DFZ could upregulate the transcript levels of Bax, Caspase-3, Caspase-8 and Caspase-9 and downregulate the transcript levels of Bcl-2 transcript levels. This suggests that DFZ can induce apoptosis of mitochondrial pathway in carp intestine. In conclusion, DFZ can induce oxidative stress and apoptosis in carp intestine, leading to the destruction of intestinal physical barrier and the occurrence of inflammation. Our data support the idea that oxidative stress and apoptosis are important triggers of pesticide-induced inflammatory bowel illness.

Aberrant gut microbiota and fecal metabolites in patients with coal-burning endemic fluorosis in Guizhou, China

Chronic exposure to excessive environmental fluoride has caused fluorosis to become a major public health problem worldwide. Although studies on stress pathways, signaling pathways, and apoptosis induced by fluoride have provided an in-depth understanding of the mechanism of this disease, its exact pathogenesis remains unclear. We hypothesized that the human gut microbiota and metabolome are associated with the pathogenesis of this disease. To get further insight into the profiles of intestinal microbiota and metabolome in coal-burning-induced endemic fluorosis patients, we conducted 16S rRNA sequencing of the intestinal microbial DNA and carried out non-targeted metabolomics of fecal samples from 32 patients with skeletal fluorosis and 33 matched healthy controls in Guizhou, China. We found that the gut microbiota of coal-burning endemic fluorosis patients displayed significant differences in composition, diversity, and abundance compared with healthy controls. This was characterized by an increase in the relative abundance of Verrucomicrobiota, Desulfobacterota, Nitrospirota, Crenarchaeota, Chloroflexi, Myxococcota, Acidobacteriota, Proteobacteria, and unidentified_Bacteria, and a significant decrease in the relative abundance of Firmicutes and Bacteroidetes at the phylum level. Additionally, at the genus level, the relative abundance of some beneficial bacteria, such as Bacteroides, Megamonas, Bifidobacterium, and Faecalibacterium, was significantly reduced. We also demonstrated that, at the genus level, some gut microbial markers, including Anaeromyxobacter, MND1, oc32, Haliangium, and Adurb.Bin063_1, showed potential for identifying coal-burning endemic fluorosis. Moreover, non-targeted metabolomics and correlation analysis revealed the changes in the metabolome, particularly the gut microbiota-derived tryptophan metabolites such as tryptamine, 5-hydroxyindoleacetic acid, and indoleacetaldehyde. Our results indicated that excessive fluoride might cause xenobiotic-mediated dysbiosis of human gut microbiota and metabolic disorders. These findings suggest that the alterations in gut microbiota and metabolome play vital roles in regulating disease susceptibility and multi-organ damage after excessive fluoride exposure.

Low dosage fluorine ameliorates the bioaccumulation, hepatorenal dysfunction and oxidative stress, and gut microbiota perturbation of cadmium in rats

Many "hot spot" geographic areas around the world with soils and crops co-polluted with cadmium (Cd) and fluorine (F), two of the most representative pollutants in the environment. However, it still exists argumentative on the dose-effect relationship between F and Cd so far. To explore this, a rat model was established to evaluate the effects of F on Cd-mediated bioaccumulation, hepatorenal dysfunction and oxidative stress, and the disorder of intestinal microbiota as well. 30 healthy rats were randomly assigned to Control group (C group), Cd 1 mg/kg (Cd group), Cd 1 mg/kg and F 15 mg/kg (L group), Cd 1 mg/kg and F 45 mg/kg (M group), and Cd 1 mg/kg and F 75 mg/kg (H group) for 12 weeks by gavage. Our results showed that Cd exposure could accumulate in organs, cause hepatorenal function damage and oxidative stress, and disorder of gut microflora. However, different dosages of F showed various effects on Cd-induced damages in liver, kidney, and intestine, and only the low supplement of F showed a consistent trend. After low supplement of F, Cd levels were declined by 31.29% for liver, 18.31% for kidney, and 2.89% for colon, respectively. The serum aspartate aminotransferase (AST), blood urea nitrogen (BUN), creatinine (Cr), and N-acetyl-β-glucosaminidase (NAG) were significantly reduced (p < 0.01); The activity of superoxide dismutase (SOD) was elevated and mRNA expression level of NAD(P)H quinone oxidoreductase 1 (NQO1) was decreased in the liver and kidney (p < 0.05). Moreover, low F dosage up-regulated the abundance of Lactobacillus from 15.56% to 28.73% and the 6.23% of F/B ratio was declined to 3.70%. Collectively, this highlights that low dosage of F might be a potential strategy to ameliorate the hazardous effects by Cd-exposed in the environment.

Changes in intestinal morphology, number of mucus-producing cells and expression of coronavirus receptors APN, DPP4, ACE2 and TMPRSS2 in pigs with aging

Porcine enteric viral infections cause high morbidity and mortality in young piglets (<3 weeks). Later, these rates decrease with age. This age-dependent infectivity remains largely unexplored. This study investigated the changes in intestinal morphology, number of mucus-producing cells and expression level of coronavirus receptors in three age groups of pigs. Villus height and crypt depth increased with age from 3 days to 3 months in duodenum and ileum but not in mid-jejunum, where the villus height decreased from 580 µm at 3 days to 430 µm at 3 months. Enterocyte length-to-width ratio increased from 3 days to 3 months in all intestinal regions. The number of mucus-producing cells increased with age in the intestinal villi and crypts. The Brunner's glands of the duodenum contained the highest concentration of mucus-producing cells. The expression of coronavirus receptor APN was highest in the small intestinal villi at all ages. DPP4 expression slightly decreased over time in jejunum and ileum; it was highest in the ileal villi of 3-day-old piglets (70.2% of cells). ACE2 and TMPRSS2 positive cells increased with age in jejunal and ileal crypts and were particularly dominant in the ileal crypts (> 45% of cells). Except for the expression of DPP4 in the jejunum and ileum of young pigs, the expression pattern of the selected coronavirus receptors was very different and not correlated with the age-dependent susceptibility to viral infections. In contrast, the number of mucus-producing cells increased over time and may play an essential role in protecting enteric mucosae against intestinal viruses.

Does fluoride exposure impact on the human microbiome?

Fluoride is added to drinking water in some countries to prevent tooth decay (caries). There is no conclusive evidence that community water fluoridation (CWF) at WHO recommended concentrations for caries prevention has any harmful effects. However, research is ongoing regarding potential effects of ingested fluoride on human neurodevelopment and endocrine dysfunction. Simultaneously, research has emerged highlighting the significance of the human microbiome in gastrointestinal and immune health. In this review we evaluate the literature examining the effect of fluoride exposure on the human microbiome. Unfortunately, none of the studies retrieved examined the effects of ingested fluoridated water on the human microbiome. Animal studies generally examined acute fluoride toxicity following ingestion of fluoridated food and water and conclude that fluoride exposure can detrimentally perturb the normal microbiome. These data are difficult to extrapolate to physiologically relevant human exposure dose ranges and the significance to humans living in areas with CWF requires further investigation. Conversely, evidence suggests that the use of fluoride containing oral hygiene products may have beneficial effects on the oral microbiome regarding caries prevention. Overall, while fluoride exposure does appear to impact the human and animal microbiome, the long-term consequences of this requires further study.

Tea (Camellia sinensis) ameliorates DSS-induced colitis and liver injury by inhibiting TLR4/NF-κB/NLRP3 inflammasome in mice

The gut-liver axis is a bidirectional relationship between the gut with its microbiota and the hepatic. Ulcerative colitis (UC) disrupts the intestinal barrier and influx of intestinal microorganisms and their products into the liver, which trigger liver injury. Tea consumption is associated with a low incidence of UC in Asian countries. In this study, we revealed the mechanisms of six types of tea water extracts (TWEs) obtained from the leaves of Camellia sinensis on the dextran sodium sulfate (DSS)-induced colitis and liver injury in mice. The TWEs significantly restored mucin production and increased the expression levels of tight junction (TJ) proteins such as zonula occludens-1 (ZO-1), occluding, and claudin-1. In addition, TWEs also reduced the levels of pro-inflammatory cytokines in the colon and liver tissue by inactivating the NF-κB/NLRP3. Moreover, TEWs treatment promoted the integrity of the intestinal barrier to reduce serum lipopolysaccharide (LPS) levels, thereby reducing liver injury caused by intestinal microbial translocation and LPS induction. Analysis of 16 S rRNA microbial sequencing revealed that tea water extracts (TWEs) restored the DSS-induced gut dysbiosis. Interestingly, our results showed that the degree of fermentation of tea leaves was negatively associated with the alleviation of DSS-induced colitis effects, and there was also an overall negative trend with colitis-induced liver injury, except for black tea. Taken together, tea consumption mitigated DSS-induced colitis and liver injury in mice via inhibiting the TLR4/NF-κB/NLRP3 inflammasome pathway.

Dynamic distribution of gut microbiota in cattle at different breeds and health states

Weining cattle is a precious species with high tolerance to cold, disease, and stress, and accounts for a large proportion of agricultural economic output in Guizhou, China. However, there are gaps in information about the intestinal flora of Weining cattle. In this study, high-throughput sequencing were employed to analyze the intestinal flora of Weining cattle (WN), Angus cattle (An), and diarrheal Angus cattle (DA), and explore the potential bacteria associated with diarrhea. We collected 18 fecal samples from Weining, Guizhou, including Weining cattle, Healthy Angus, and Diarrheal Angus. The results of intestinal microbiota analysis showed there were no significant differences in intestinal flora diversity and richness among groups (p > 0.05). The abundance of beneficial bacteria (Lachnospiraceae, Rikenellaceae, Coprostanoligenes, and Cyanobacteria) in Weining cattle were significantly higher than in Angus cattle (p < 0.05). The potential pathogens including Anaerosporobacter and Campylobacteria were enriched in the DA group. Furthermore, the abundance of Lachnospiraceae was very high in the WN group (p < 0.05), which might explain why Weining cattle are less prone to diarrhea. This is the first report on the intestinal flora of Weining cattle, furthering understanding of the relationship between intestinal flora and health.

Effects of topical fluoride application on oral microbiota in young children with severe dental caries

While the effect of fluoride on severe early childhood caries (S-ECC) is clear, knowledge of how it influences the oral microbiota and the consequential effects on oral health is limited. In this cohort study, we investigated the changes introduced in the oral ecosystem before and after using fluoride varnish in 54- to 66-month-old individuals (n=90: 18 children were sampled at 5 different time points). 16S rDNA was amplified from bacterial samples using polymerase chain reaction, and high-throughput sequencing was performed using Illumina MiSeq platforms. Many pronounced microbial changes were related to the effects of fluoride varnishing. The health-associated Bacteroides and Uncultured_bacterium_f_Enterobacteriaceae were enriched in the saliva microbiome following treatment with fluoride varnishing. Co-occurrence network analysis of the dominant genera showed that different groups clearly showed different bacterial correlations. The PICRUSt algorithm was used to predict the function of the microbial communities from saliva samples. The results showed that starch and sucrose metabolism was greater after fluoride use. BugBase was used to determine phenotypes present in microbial community samples. The results showed that Haemophilus and Neisseria (phylum Proteobacteria) was greater before fluoride use. We conclude that the changes in oral microbiology play a role in fluoride prevention of S-ECC.

Intestinal toxicity and resistance gene threat assessment of multidrug-resistant Shigella: A novel biotype pollutant

Multidrug-resistant bacteria, especially pathogens, pose a serious threat to disease treatment and recovery, but their potential toxicity to animal development is not entirely clear. As the most important site for nutrient absorption, we studied the intestinal microbiome of Xenopus tropicalis by analyzing the effect of multidrug-resistant Shigella on its intestinal health. Unlike in the control, Shigella intake promoted the secretion of neutral mucus and inhibited intestinal development and weight gain. Following 60 days of exposure, intestinal crypt atrophy, intestinal villus shortening, internal cavity enlargement, and external mucosal muscle disintegration were observed. The circular and longitudinal intestinal muscles became thinner with increasing pathogen exposure. In addition, the presence of Shigella altered the expression of multiple cytokines and classic antioxidant enzyme activities in the gut, which may have caused the intestinal lesions that we observed. 16 S rDNA sequencing analysis of intestinal samples showed that exposure to Shigella destroyed the normal gut microbial abundance and diversity and increased the functional bacterial ratio. Notably, the increased abundance of intestinal antibiotic resistance genes (ARGs) may imply that the resistance genes carried by Shigella easily migrate and transmit within the intestine. Our results expand existing knowledge concerning multidrug-resistant Shigella-induced intestinal toxicity in X. tropicalis and provide new insights for the threat assessment of resistance genes carried by drug-resistant pathogens.

Effects of maternal T-2 toxin exposure on microorganisms and intestinal barrier function in young mice

T-2 toxin belongs to the trichothecenes group A compound, mainly produced by Fusarium fungi. It has been shown that T-2 toxin could cross the placental barrier and breast milk, thus endangering the health of offspring. The present study aimed to explore the effects of maternal T-2 toxin exposure on the integrity of the intestinal barrier and the intestinal microflora of young mice. From late pregnancy (GD 14) to lactation (LD 21), pregnant mice were given T-2 toxin daily at 0, 0.005, or 0.05 mg T-2 toxin/kg BW. Postnatal day 21 (PND21), PND28, and PND56 young mice were chosen as objects to detect the influences of maternal T-2 toxin exposure to mice on the offspring. The results showed that maternal exposure to T-2 toxin disturbed the balance of the intestinal microbial flora of the young mice. Villous adhesions and fusion of ileum were observed in T-2-treated groups. In addition, supplementation of T-2 toxin significantly decreased the gene expressions of Claudin 1, Occludin, Tjp1, Il10, Il6, and Tnf in PND 21. However, in PND 28, the expressions of Tnf were significantly increased. The expressions of Claudin 1, Occludin, Tjp1, Il10, Il6 and Tnf were significantly increased after T-2 toxin treatment in PND 56. These results suggested that maternal exposure to T-2 toxin has negative influences on the intestine of young mice, which may be due to the alterations of microbial composition.

Impairments of intestinal arginine and NO metabolisms trigger aging-associated intestinal barrier dysfunction and 'inflammaging'

Aging is considered a state of low grade inflammation, occurring in the absence of any overt infection often referred to as 'inflammaging'. Maintaining intestinal homeostasis may be a target to extend a healthier status in older adults. Here, we report that even in healthy older men low grade bacterial endotoxemia is prevalent. In addition, employing multiple mouse models, we also show that while intestinal microbiota composition changes significantly during aging, fecal microbiota transplantation to old mice does not protect against aging-associated intestinal barrier dysfunction in small intestine. Rather, intestinal NO homeostasis and arginine metabolism mediated through arginase and NO synthesis is altered in small intestine of aging mice. Treatment with the arginase inhibitor norNOHA prevented aging-associated intestinal barrier dysfunction, low grade endotoxemia and delayed the onset of senescence in peripheral tissue e.g., liver. Intestinal arginine and NO metabolisms could be a target in the prevention of aging-associated intestinal barrier dysfunction and subsequently decline and 'inflammaging'.

Estrogen deficiency aggravates fluoride-induced small intestinal mucosa damage and junctional complexes proteins expression disorder in rats

To investigate the effect of estrogen deficiency on the small intestinal mucosal barrier induced by fluoride (F), F exposure models of ovariectomy (OVX) rats (surgically removed ovaries) and non-OVX rats (normal condition) were established by adding sodium fluoride (NaF) (0, 25, 50, and 100 mg/L, calculated by F ion) in drinking water for 90 days. The intestinal mucosal histomorphology, mucosal barrier function, and protein expression levels of tight junctions (TJs), adhesion junctions (AJs), and desmosomes were evaluated in the duodenum, jejunum, and ileum. Hematoxylin-eosin (HE) staining and 5-Bromo-2-deoxyUridine (BrdU) measurement showed that excessive F-induced damage to intestinal epithelial cells and inhibited the proliferation of intestinal epithelial cells, eventually decreasing the number of goblet cells and decreasing glycoprotein secretion, as indicated by Alcian blue and periodic acid-Schiff (AB-PAS) and periodic acid-Schiff (PAS) staining. Further immunofluorescence analysis demonstrated that excessive F decreased the protein expression levels of occludin, zonula occludens-1 (ZO-1), E-cadherin, and desmoplakin (P < 0.05, P < 0.01) and enhanced the expression of claudin-2 (P < 0.01), suggesting that cell-to-cell junctions were disrupted. Collectively, F exposure impaired the small intestinal mucosal barrier by inducing damage to intestinal epithelial cells and inhibiting intestinal epithelial cell proliferation. Disorders in the junctional complex protein expression blocked the synergy between intercellular communication and aggravated mucosal injury. In particular, estrogen deficiency exacerbated F-induced enterotoxicity, which provides new explanations for the development and severity of intestinal disease in postmenopausal women with high-F areas.

Dynamic changes of gut fungal community in horse at different health states

Accumulating studies indicated that gut microbial changes played key roles in the progression of multiple diseases, which seriously threaten the host health. Gut microbial dysbiosis is closely associated with the development of diarrhea, but gut microbial composition and variability in diarrheic horses have not been well characterized. Here, we investigated gut fungal compositions and changes in healthy and diarrheic horses using amplicon sequencing. Results indicated that the alpha and beta diversities of gut fungal community in diarrheal horses changed significantly, accompanied by distinct changes in taxonomic compositions. The types of main fungal phyla (Neocallimastigomycota, Ascomycota, and Basidiomycota) in healthy and diarrheal horses were same but different in relative abundances. However, the species and abundances of dominant fungal genera in diarrheal horses changed significantly compared with healthy horses. Results of Metastats analysis indicated that all differential fungal phyla (Blastocladiomycota, Kickxellomycota, Rozellomycota, Ascomycota, Basidiomycota, Chytridiomycota, Mortierellomycota, Neocallimastigomycota, Glomeromycota, and Olpidiomycota) showed a decreasing trend during diarrhea. Moreover, a total of 175 differential fungal genera were identified for the gut fungal community between healthy and diarrheal horses, where 4 fungal genera increased significantly, 171 bacterial genera decreased dramatically during diarrhea. Among these decreased bacteria, 74 fungal genera even completely disappeared from the intestine. Moreover, this is the first comparative analysis of equine gut fungal community in different health states, which is beneficial to understand the important role of gut fungal community in equine health.

In-depth insights into the disruption of the microbiota-gut-blood barrier of model organism (Bombyx mori) by fluoride

Fluoride is a serious health risk to animals and humans. The microbiota-gut-blood barrier (MGBB) plays an indispensable role in maintaining the systematic homeostasis of host organisms. However, the toxic effects of fluoride on MGBB of organisms have not been extensively investigated. Here, we used the silkworm interspecies model to explore the adverse effects of fluoride on the gut microbiota and intestinal tissue and circulating metabolites of organisms. Results showed that fluoride exposure significantly declined the body weight gain and survival rate of organisms and evidently damaged intestinal epithelial cells. In addition, fluoride altered the composition and abundance of intestinal microbiota, which was accompanied by changing gene expression levels of antimicrobial peptides in intestinal tissue. Shifts in the relative abundance of Enterococcus, Aquabacterium, Aureimonas and Methylobacterium in the gut had significant correlations with the concentrations of certain differential metabolites (e.g., amino acids, nucleotides, and nucleotide derivatives) in the bloodstream. Moreover, most circulating metabolites in related nucleotide metabolism pathways were upregulated, whereas those in the pathways of amino acid metabolism were downregulated. This study deepens our understanding of the disruptive effect of fluoride on the MGBB of host organisms and may provide a new insight into the preventive therapy of fluoride-induced diseases.

Pesticide thiram exposure alters the gut microbial diversity of chickens

Thiram is a major dithiocarbamate pesticide commonly found in polluted field crops, feed, and rivers. Environmental thiram exposure has been demonstrated to cause angiogenesis and osteogenesis disorders in chickens, but information regarding thiram influences on gut microbiota, apoptosis, and autophagy in chickens has been insufficient. Here, we explored the effect of thiram exposure on gut microbiota, apoptosis, and autophagy of chickens. Results demonstrated that thiram exposure impaired the morphology and structure of intestinal and liver tissues. Moreover, thiram exposure also triggered liver apoptosis and autophagy. The gut microbiota in chickens exposed to thiram exhibited a significant decline in alpha diversity, accompanied by significant shifts in taxonomic compositions. Bacterial taxonomic analysis indicated that thiram exposure causes a significant reduction in the levels of eight genera, as well as a significant increase in the levels of two phyla and 10 genera. Among decreased bacterial genera, seven genera even cannot be observed in the thiram-induced chickens. In summary, this study demonstrated that thiram exposure not only dramatically altered the gut microbial diversity and composition but also induced liver apoptosis and autophagy in chickens. Importantly, this study also conveyed a key message that the dysbiosis of gut microbiota may be one of the major pathways for thiram to exert its toxic effects.

New insights into the interaction between duodenal toxicity and microbiota disorder under copper exposure in chicken: Involving in endoplasmic reticulum stress and mitochondrial toxicity

Copper (Cu) has been widely used in industrial agricultural production, but excess use can lead to toxic effect on host physiology, which poses a threaten to public hygiene. However, the relationship between gut microbiota and Cu-induced intestinal toxicity is unclear. Here, we identified that intestinal flora disturbance was related to duodenal toxicity under Cu exposure. We found that excess Cu disturbed gut microbiota homeostasis, resulting in Cu accumulation and intestinal damage. In addition, Cu considerably increased intestinal permeability by reducing expression of tight junction proteins (Claudlin-1, Occludin, and ZO-1). Meanwhile, Cu could induce endoplasmic reticulum stress, mitophagy, and mitochondria-mediated apoptosis in the duodenum, with the evidence by the elevated levels of GRP78, GRP94, LC3Ⅱ/LC3Ⅰ and Caspase-3 protein expression. Correlation analysis showed that Melainabacteria was closely related to tight junction proteins and endoplasmic reticulum stress of duodenum, indicating that disturbance of intestinal flora may aggravate the toxic effect of Cu. Therefore, our results suggest that the destruction of intestinal flora induced by excessive Cu may further lead to intestinal barrier damage, ultimately leading to endoplasmic reticulum stress, mitophagy and apoptosis. This research provides a new insight into interpretation of the interrelationship between microbiota disorder and duodenal toxicity under Cu exposure.

Challenges of fluoride pollution in environment: Mechanisms and pathological significance of toxicity - A review

Fluoride is an important trace element in the living body. A suitable amount of fluoride has a beneficial effect on the body, but disproportionate fluoride entering the body will affect various organs and systems, especially the liver, kidneys, nervous system, endocrine system, reproductive system, bone, and intestinal system. In recent years, with the rapid development of agriculture and industry, fluoride pollution has become one of the important factors of environmental pollution, and fluoride pollution in any form is becoming a serious problem. Although countries around the world have made great breakthroughs in controlling fluoride pollution, however fluorosis still exists. A large amount of fluoride accumulated in animals will not only produce the toxic effects, but it also causes cell damage and affect the normal physiological activities of the body. There is no systematic description of the damage mechanism of fluoride. Therefore, the study on the toxicity mechanism of fluoride is still in progress. This review summarizes the existing information of several molecular mechanisms of the fluoride toxicity comprehensively, aiming to clarify the toxic mechanism of fluoride on various body systems. We have also summerized the pathological changes of those organ systems after fluoride poisoning in order to provide some ideas and solutions to the reader for the prevention and control of modern fluoride pollution.

Comparative analysis of gut microbiota in healthy and diarrheic yaks

BACKGROUND

Yak (Bos grunniens) mainly inhabiting Tibet Plateau, displayed a high incidence of diarrhea due to harsh living environment and nutritional deficit. Gut microbial community has been reported to be closely related to many diseases including diabetes, obesity and inflammatory bowel disease, but information regarding diarrheic influence on gut microbiota in yaks remains scarce. Here, this study was performed to investigate the gut bacterial and fungal alternations of diarrheic yaks.

RESULTS

Results revealed that the gut bacterial and fungal communities of diarrheic yaks showed a distinct decline in alpha diversity, accompanied by significant shifts in taxonomic compositions. Specifically, diarrhea caused a distinct increase in the relative abundance of 1 phylum and 8 genera as well as a distinct decrease in 3 phyla and 30 genera. Fungal taxonomic analysis indicated that the relative richness of 1 phylum and 2 genera dramatically increased, whereas the relative richness of 2 phylum and 43 genera significantly decreased during diarrhea. Surprisingly, 2 bacterial genera and 5 fungal genera even cannot be detected in the gut microbiota of diarrheic yaks.

CONCLUSIONS

In summary, this study indicated that the gut bacterial and fungal compositions and diversities of yaks altered significantly during diarrhea. Moreover, these findings also contribute to understanding the gut microbial composition and diversity of yaks and developing strategies to alleviate and prevent diarrhea from gut microbial perspective.

Long-term hexavalent chromium exposure disturbs the gut microbial homeostasis of chickens

Industrial production, ore smelting and sewage disposal plant can discharge large amounts of heavy metals every year, which may contaminate soil, water and air, posing a great threat to ecological environment and animal production. Hexavalent chromium [Cr (VI)], a recognized metallic contaminant, has been shown to impair kidney, liver and gastrointestinal tract of many species, but little is known about the gut microbial characteristics of chickens exposed to Cr (VI). Herein, this study characterized the gut microbial alternations of chickens exposed to Cr (VI). Results indicated that the gut microbial alpha-diversity in chickens exposed to Cr (VI) decreased significantly, accompanied by a distinct shifts in taxonomic composition. Microbial taxonomic analysis demonstrated that the preponderant phyla (Firmicutes, Bacteroidetes, Proteobacteria and Epsilonbacteraeota) were the same in both groups, but different in types and relative abundances of dominant genera. Moreover, some bacterial taxa including 2 phyla and 47 genera significantly decreased, whereas 3 phyla and 17 genera significantly increased during Cr (VI) exposure. Among decreased taxa, 9 genera (Coprobacter, Ruminococcus_1, Faecalicoccus, Eubacterium_nodatum_group, Parasutterella, Slackia, Barnesiella, Family_XIII_UCG-001 and Collinsella) even cannot be detected. In conclusion, this study revealed that Cr (VI) exposure dramatically decrased the gut microbial diversity and altered microbial composition of chickens. Additionally, this study also provided a theoretical basis for relieving Cr (VI) poisoning from the perspective of gut microbiota.

Intestinal toxicity of micro- and nano-particles of foodborne titanium dioxide in juvenile mice: Disorders of gut microbiota-host co-metabolites and intestinal barrier damage

The wide use of TiO₂ particles in food and the high exposure risk to children have prompted research into the health risks of TiO₂. We used the microbiome and targeted metabolomics to explore the potential mechanism of intestinal toxicity of foodborne TiO₂ micro-/nanoparticles after oral exposure for 28 days in juvenile mice. Results showed that the gut microbiota-including the abundance of Bacteroides, Bifidobacterium, Lactobacillus, and Prevotella-changed dynamically during exposure. The organic inflammatory response was activated, and lipopolysaccharide levels increased. Intestinal toxicity manifested as increased mucosal permeability, impaired intestinal barrier, immune damage, and pathological changes. The expression of antimicrobial peptides, occludin, and ZO-1 significantly reduced, while that of JNK2 and Src/pSrc increased. Compared with micro-TiO₂ particles, the nano-TiO₂ particles had strong toxicity. Fecal microbiota transplant confirmed the key role of gut microbiota in intestinal toxicity. The levels of gut microbiota-host co-metabolites, including pyroglutamic acid, L-glutamic acid, phenylacetic acid, and 3-hydroxyphenylacetic acid, changed significantly. Significant changes were observed in the glutathione and propanoate metabolic pathways. There was a significant correlation between the changes in gut microbiota, metabolites, and intestinal cytokine levels. These, together with the intestinal barrier damage signaling pathway, constitute the network mechanism of the intestinal toxicity of TiO₂ particles.

Comparative Analysis of Gut Microbiota Between Healthy and Diarrheic Horses

Increasing evidence reveals the importance of gut microbiota in animals for regulating intestinal homeostasis, metabolism, and host health. The gut microbial community has been reported to be closely related to many diseases, but information regarding diarrheic influence on gut microbiota in horses remains scarce. This study investigated and compared gut microbial changes in horses during diarrhea. The results showed that the alpha diversity of gut microbiota in diarrheic horses decreased observably, accompanied by obvious shifts in taxonomic compositions. The dominant bacterial phyla (Firmicutes, Bacteroidetes, Spirochaetes, and Kiritimatiellaeota) and genera (uncultured_bacterium_f_Lachnospiraceae, uncultured_bacterium_f_p-251-o5, Lachnospiraceae_AC2044_group, and Treponema_2) in the healthy and diarrheic horses were same regardless of health status but different in abundances. Compared with the healthy horses, the relative abundances of Planctomycetes, Tenericutes, Firmicutes, Patescibacteria, and Proteobacteria in the diarrheic horses were observably decreased, whereas Bacteroidetes, Verrucomicrobia, and Fibrobacteres were dramatically increased. Moreover, diarrhea also resulted in a significant reduction in the proportions of 31 genera and a significant increase in the proportions of 14 genera. Taken together, this study demonstrated that the gut bacterial diversity and abundance of horses changed significantly during diarrhea. Additionally, these findings also demonstrated that the dysbiosis of gut microbiota may be an important driving factor of diarrhea in horses.

Study of Chitosan Ingestion Remitting the Bone Damage on Fluorosis Mice with Micro-CT

Chronic excessive fluoride exposure may lead to fluorosis, which causes health problems like a decrease in bone mechanical strength. It was speculated that chitosan may combine with fluorine to form in vivo organic fluorine, and may reduce the damage caused by fluorine. Hence, it is necessary to conduct a study to investigate the influence of chitosan on fluorosis mice. To investigate this problem, forty-four 4-week-old male Kunming mice were randomly divided into four groups, the control group, the fluoride group, the fluoride plus chitosan group, and the chitosan group. After 100 days of feeding, the femurs were collected to scan the Micro-CT image. The ultimate load of the femur in the fluoride group was significantly lower than control group. The trabecular separation was increased in the fluoride group compared with the fluoride plus chitosan group and the chitosan group. The level of trabecular thickness was increased in the fluoride plus chitosan group compared with the fluoride group. Our findings suggest that chitosan ingestion can improve the condition of cancellous bone and cortical bone affected by fluorine.

Effect of Different Pig Fecal Microbiota Transplantation on Mice Intestinal Function and Microbiota Changes During Cold Exposure

Cold stress influences intestinal processes, causing physiological and immunological responses in animals. Intestinal microbiota participates in maintaining the stability of the intestinal environment. However, phenotypic characteristics and the effects of porcine microbiota changes under cold conditions remain poorly understood. Here, the fecal microbiota of cold tolerant breed (Mashen) and cold sensitive breed (Duroc-Landrace-Yorkshire) was transferred to germ-free mice, respectively. After a cold exposure (4°C) for 21 days, intestinal function and microbe changes of mice were explored. The results showed that Mashen pigs microbiota transplantation made the body temperature of the mice stable, in which the fat weight and expression of uncoupling protein 1 (UCP1), carnitine palmitoyltransferase 1B (Cpt1b), and Peroxisome proliferator-activated receptor-gamma coactivator (PGC-1α) were significantly higher (P &lt; 0.05) than those of the control group. The results of intestinal structure and expression of serum inflammatory factors showed that fecal microbiota transplantation (FMT) mice have more intact intestinal structure and high expression of proinflammatory factor such as interleukin-4 (IL-4). The study of mice fecal microbiome characterized via 16S rRNA sequencing found that pig microbiota transplantation changed the abundance of Firmicutes. In addition, it identified discriminative features of Firmicutes in the microbiota between two breeds of pig, in which Clostridiaceae were enriched in the microbiota community of Mashen pig and Coriobacteriales were significantly (P &lt; 0.05) enriched in the Duroc-Landrace-Yorkshire pig microbiota transplantation group based on linear discriminant analysis effect size (LEfSe) analysis. Finally, we found that the content of propionic acid and butyric acid in rectal contents significantly changed and the abundances of Clostridium and Lachnospira showed significant correlations with changes in short-chain fatty acids. The results suggest that pig fecal microbiota transplantation can alleviate the changes in physiological and biochemical indicators in mice caused by cold exposure. Mice have gut microbes altered and improved gut barrier function via fecal microbiota transplantation in pigs.

Dissecting the Effect of Berberine on the Intestinal Microbiome in the Weaned Piglets by Metagenomic Sequencing

This study aimed to investigate the microbial structure and function in the rectum of weaned piglets with berberine supplementation. Twelve healthy 21-day-old Duorc × (Landrace × Large White) weaned piglets (similar body weight) were evenly divided into control and berberine groups and were fed a basal diet supplemented with 0 and 0.1% berberine, respectively. After 21 days, metagenomic sequencing analysis was performed to detect microbial composition and function in the rectum of weaned piglets. Results showed that there were 10,597,721,931-14,059,392,900 base pairs (bp) and 10,186,558,171-15,859,563,342 bp of clean data in the control and berberine groups, respectively. The Q20s of the control and berberine groups were 97.15 to 97.7% and 96.26 to 97.68%, respectively. The microorganisms in the berberine group had lower (p < 0.05) Chao1, alternating conditional expectation, Shannon, and Simpson indices at the species levels than those in the control group. Analysis of similarity showed that there were significant differences (p < 0.01) between the control and berberine groups at the genus and species levels of the gut microorganisms. Dietary berberine significantly increased (p < 0.05) the abundance of Subdoligranulum variabile, but decreased (p < 0.05) the abundance of Prevotella copri compared with the control group. Carbohydrate-active enzymes analysis revealed that the levels of polysaccharide lyases and carbohydrate esterases were lower (p < 0.05) in the berberine group than that in the control group. Linear discriminant analysis effect size analysis showed that berberine supplementation could induce various significant Kyoto Encyclopedia of Genes and Genomes pathways, including carbohydrate metabolism, environmental information processing, and microbial metabolism in diverse environments. In conclusion, our findings suggest that berberine could improve the composition, abundance, structure, and function of gut microbiome in the weaned piglets, potentially providing a suitable approach for the application of berberine in human and animal health.

The inducing of caspase and Bcl-2 pathway with royal jelly decreases the muscle tissue damage exposed with fluoride in rats

In this study, 42 Wistar albino male rats (n = 42, 8 weeks old) were used. Rats were divided into 6 groups and 7 rats included each group. Groups: (i) Control group: Standard diet; (ii) RJ (royal jelly) group: Standard diet + royal jelly; (iii) F50 group: Standard diet + 50 mg/kg fluoride; (iv): F100 group: Standard diet + 100 mg/kg fluoride; (v) F50+RJ group: Standard diet + 50 mg/kg fluoride + royal jelly; (vi): F100+RJ group: Standard diet + 100 mg/kg fluoride + royal jelly. After 8 weeks, the rats were decapitated, and their muscle tissues were removed. Expression levels of Caspase-3, Caspase-6, Bax, tumor necrosis factor-α (TNF-α), interleukin 1 alpha (IL1-α) and Bcl-2 proteins in muscle tissue were determined by western blotting method. Histopathological analyses were also performed on the muscle tissue. Malondialdehyde (MDA), glutathione (GSH) and catalase (CAT) analyses were determined by a spectrophotometer. According to the obtained results, Bcl-2, TNF-α and IL1-α protein expression was increased in damage groups compared to the control and royal jelly groups, while Caspase-3, Caspase-6 and Bax protein expression levels decreased in damage groups. MDA level increased in damage groups compared to the control and royal jelly groups, while CAT and GSH levels increased with royal jelly application in royal jelly-given group in comparison to the flouride-exposed group. According to histopathological analysis results, edema and inflammatory cell formations were found in the injury groups, a tendency to decrease in these injuries was observed in the treatment groups. Based on these results, we can say that royal jelly has protective effects on muscle tissue against fluoride damage.

Exercise alleviated intestinal damage and microbial disturbances in mice exposed to fluoride

Gastrointestinal reaction is an important symptom of fluorosis and is associated with intestinal morphological and functional impairment. Regular moderate exercise may reduce the incidence of infection and contribute to the maintenance of intestinal mucosal function and immune homeostasis. In this study, the mice were randomly divided to four groups: control group (C, distilled water), exercise group (E, distilled water and treadmill exercise), fluoride group (F, 100 mg/L NaF), and exercise plus fluoride group (EF, 100 mg/L NaF and treadmill exercise). The treadmill exercise was performed as 5 m/min, 5 min; 10 or 12 m/min, 20 min; 5 m/min, 5 min, with 5 consecutive days per week. After 6 months, exercise alleviated the intestinal morphological structure damage and restored the villus height (VH) and VH/crypt depth (VH/CD) in the duodenum of fluoride-exposed mice. Exercise decreased the mRNA expressions of IL-1β, IL-6, TNF-α, TLR2 and NF-κB (p65) in fluoride-exposed mice, and restored the gene levels of Occludin and ZO-1 in the duodenum, as well as Occludin, ZO-1, and Claudin-1 in the colon. Although there were no significant differences in the Occludin and ZO-1 protein expressions between F and EF, two proteins in EF presented statistical homogeneousness when compared with the C. The 16S rDNA high-throughput sequencing found that exercise restored the variations in intestinal microbiota composition and the abundances of specific bacteria in fluoride-exposed mice, including increasing the abundances of Epsilonbacteraenta and Firmicutes, reducing the Bacteroidetes abundance at the phylum level, and restoring the abundances of 13 bacterial genera. In conclusion, exercise improved intestinal morphological structure damage in fluoride-exposed mice, inhibited the secretion of duodenal inflammatory factors, increased the expression of tight junctions, and alleviated the microbial disorder in mice caused by fluoride exposure for 6 months through actively regulating the composition of intestinal microorganisms and the abundance of specific bacteria.

Exercise Ameliorates Fluoride-induced Anxiety- and Depression-like Behavior in Mice: Role of GABA

Fluoride exposure caused anxiety- and depression-like behavior in mice. Meanwhile, exercise contributes to relieve anxiety and depression. However, the effects of exercise on anxiety- and depression-like behavior in fluorosis mice remain unclear. In the current study, thirty-six Institute of Cancer Research (ICR) female mice were randomly assigned to four groups: control group (C, gavage with distilled water); exercise group (E, gavage with distilled water and treadmill exercise (speed, 10 m/min; time, 30 min/day)); fluoride group (F, gavage with 24 mg/kg sodium fluoride (NaF)); and exercise plus fluoride group (EF, gavage with 24 mg/kg NaF and treadmill exercise). All treatments lasted for 8 weeks. A number of entries into and time spent in the open zone in the elevated zero maze (EZM), resting time in the tail suspension test (TST) and levels of serotonin (5-HT) and gamma-aminobutyric acid (GABA), were significantly altered in F when compared to C. Meanwhile, the anxiety-like behavior in the EZM and the depression-like behavior in the TST were significantly improved in EF when compared to group F. Exercise significantly enhanced fluoride-induced low GABA level, with less effect on the concentration of 5-HT. Moreover, the mRNA and protein expressions of GABA synthesis and transport-related proteins of glutamic acid decarboxylase (GAD) 65 and GAD67 and vesicular GABA transporter (VGAT) were all strikingly decreased in F, while those in EF were increased. In conclusion, exercise ameliorates anxiety- and depression-like behavior in fluorosis mice through increasing the expressions of GABA synthesis and transport-related proteins, rather than 5-HT system.

Alterations in the Gut Microbial Composition and Diversity of Tibetan Sheep Infected With Echinococcus granulosus

Hydatidosis/cystic echinococcosis (CE) caused by Echinococcus granulosus is a parasitic zoonotic disease worldwide, threatening animal health and production and public health safety. However, it is still unclear that whether E. granulosus infection can result in the alteration of gut microbiota in Tibetan sheep. Therefore, a study was designed to investigate the influences of E. granulosus infection on gut microbiota of Tibetan sheep. A total of 10 ovine small intestinal contents (five from healthy and five from infected) were obtained and subjected to high-throughput sequencing by MiSeq platform. A total of 2,395,641 sequences and 585 operational taxonomic units (OTUs) were identified. Firmicutes and Proteobacteria were the most dominant phyla in all samples. Moreover, the proportions of Armatimonadetes and Firmicutes in the infected Tibetan sheep were significantly decreased, whereas Actinobacteria, Chloroflexi, and Acidobacteria had significantly increased. At the genus level, the Christensenellaceae_R-7_group and Ruminococcaceae_NK4A214_group were the predominant bacterial genera in all the samples. Furthermore, the healthy Tibetan sheep exhibited higher abundances of Intestinimonas, Butyrivibrio, Pseudobutyrivibrio, Ruminococcaceae, Eubacterium_coprostanoligenes_group, Oxobacter, Prevotella_1, Ruminiclostridium_6, Coprococcus_1, Ruminococcus, Lachnospiraceae_UCG-002, Olsenella, and Acetitomaculum, whereas Kocuria, Clostridium_sensu_stricto_1, Slackia, Achromobacter, and Stenotrophomonas levels were lower. In conclusion, our results conveyed an information that E. granulosus infection may cause an increase in pathogenic bacteria and a decrease in beneficial bacteria. Additionally, a significant dynamical change in gut microbiota could be associated with E. granulosus infection.