AhR Agonistic Components in Urban Particulate Matter Regulate Astrocytic Activation and Function.

Exposure to atmospheric particulate matter (PM) has been found to accelerate the onset of neurological disorders via the induction of detrimental neuroinflammatory responses. To reveal how astrocytes respond to urban atmospheric PM stimulation, a commercially available standard reference material (SRM1648a) was tested in this study on the activation of rat cortical astrocytes. The results showed that SRM1648a stimulation induced both A1 and A2 phenotypes in astrocytes, as characterized by the exposure concentration-dependent increases in Fkbp5, Sphk1, S100a10, and Il6 mRNA levels. Studying the functional alterations of astrocytes indicated that the neurotrophic factors of Gdnf and Ngf were transcriptionally upregulated due to astrocytic A2-type activation. SRM1648a also promoted autonomous motility of astrocytes and elevated the expressions of chemokines. The aryl hydrocarbon receptor (AhR) agonistic components, such as polycyclic aromatic hydrocarbons (PAHs), were recognized to greatly contribute to SRM1648a-induced effects on astrocytes, which was confirmed by the attenuation of PM-disturbed astrocytic effects via AhR blockage. This study, for the first time, uncovered the direct regulation of urban atmospheric PM on astrocytic activation and function and traced the containing bioactive components (e.g., PAHs) with AhR agonistic activity. The findings provided new knowledge on understanding the ambiguous neurological disturbance from ambient fine PM pollution.

Bis(2-ethylhexyl)-tetrabromophthalate Poses a Higher Exposure Risk and Induces Gender-Specific Metabolic Disruptions in Zebrafish Liver.

Bis(2-ethylhexyl)-tetrabromophthalate (TBPH), a typical novel brominated flame retardant, has been ubiquitously identified in various environmental and biotic media. Consequently, there is an urgent need for precise risk assessment based on a comprehensive understanding of internal exposure and the corresponding toxic effects on specific tissues. In this study, we first investigated the toxicokinetic characteristics of TBPH in different tissues using the classical pseudo-first-order toxicokinetic model. We found that TBPH was prone to accumulate in the liver rather than in the gonad, brain, and muscle of both female and male zebrafish, highlighting a higher internal exposure risk for the liver. Furthermore, long-term exposure to TBPH at environmentally relevant concentrations led to increased visceral fat accumulation, signaling potential abnormal liver function. Hepatic transcriptome analysis predominantly implicated glycolipid metabolism pathways. However, alterations in the profile of associated genes and biochemical indicators revealed gender-specific responses following TBPH exposure. Besides, histopathological observations as well as the inflammatory response in the liver confirmed the development of nonalcoholic fatty liver disease, particularly in male zebrafish. Altogether, our findings highlight a higher internal exposure risk for the liver, enhancing our understanding of the gender-specific metabolic-disrupting potential associated with TBPH exposure.

Evidence for Adverse Effects on Liver Development and Regeneration in Zebrafish by Decabromodiphenyl Ethane.

Decabromodiphenyl ethane (DBDPE), a ubiquitous emerging pollutant, could be enriched in the liver of organisms, but its effects and mechanisms on liver development and regeneration remain largely unknown. In the present study, we first investigated the adverse effects on liver development and found decreased area and intensity of fluorescence in transgenic zebrafish larvae exposed to DBDPE; further results in wild-type zebrafish larvae revealed a possible mechanism involving disturbed MAPK/Fox O signaling pathways and cell cycle arrest as indicated by decreased transcription of growth arrest and DNA-damage-inducible beta a (gadd45ba). Subsequently, an obstructed recovery process of liver tissue after partial hepatectomy was characterized by the changing profiles of ventral lobe-to-intestine ratio in transgenic female adults upon DBDPE exposure; further results confirmed the adverse effects on liver regeneration by the alterations of the hepatic somatic index and proliferating cell nuclear antigen expression in wild-type female adults and also pointed out a potential role of a disturbed signaling pathway involving cell cycles and glycerolipid metabolism. Our results not only provided novel evidence for the hepatotoxicity and underlying mechanism of DBDPE but also were indicative of subsequent ecological and health risk assessment.

Multi- and Transgenerational Developmental Impairments Are Induced by Decabromodiphenyl Ethane (DBDPE) in Zebrafish Larvae.

A novel brominated flame retardant decabromodiphenyl ethane (DBDPE) has become a ubiquitous emerging pollutant; hence, the knowledge of its long-term toxic effects and underlying mechanism would be critical for further health risk assessment. In the present study, the multi- and transgenerational toxicity of DBDPE was investigated in zebrafish upon a life cycle exposure at environmentally relevant concentrations. The significantly increased malformation rate and declined survival rate specifically occurred in unexposed F2 larvae suggested transgenerational development toxicity by DBDPE. The changing profiles revealed by transcriptome and DNA methylome confirmed an increased susceptibility in F2 larvae and figured out potential disruptions of glycolipid metabolism, mitochondrial energy metabolism, and neurodevelopment. The changes of biochemical indicators such as ATP production confirmed a disturbance in the energy metabolism, whereas the alterations of neurotransmitter contents and light-dark stimulated behavior provided further evidence for multi- and transgenerational neurotoxicity in zebrafish. Our findings also highlighted the necessity for considering the long-term impacts when evaluating the health of wild animals as well as human beings by emerging pollutants.

Evaluation and Mechanistic Study of Transgenerational Neurotoxicity in Zebrafish upon Life Cycle Exposure to Decabromodiphenyl Ethane (DBDPE).

The novel brominated flame retardant decabromodiphenyl ethane (DBDPE) has become a ubiquitous emerging pollutant in the environment, which may evoke imperceptible effects in humans or wild animals. Hence in this study, zebrafish embryos were exposed to DBDPE (0, 0.1, 1, and 10 nM) until sexual maturity (F0), and F1 and F2 generations were cultured without further exposure to study the multi- and transgenerational toxicity and underlying mechanism. The growth showed sex-different changing profiles across three generations, and the social behavior confirmed transgenerational neurotoxicity in adult zebrafish upon life cycle exposure to DBDPE. Furthermore, maternal transfer of DBDPE was not detected, whereas parental transfer of neurotransmitters to zygotes was specifically disturbed in F1 and F2 offspring. A lack of changes in the F1 generation and opposite changing trends in the F0 and F2 generations were observed in a series of indicators for DNA damage, DNA methylation, and gene transcription. Taken together, life cycle exposure to DBDPE at environmentally relevant concentrations could induce transgenerational neurotoxicity in zebrafish. Our findings also highlighted potential impacts on wild gregarious fish, which would face higher risks from predators.

Thyroid Dysfunction of Zebrafish (Danio rerio) after Early-Life Exposure and Discontinued Exposure to Tetrabromobiphenyl (BB-80) and OH-BB-80.

3,3',5,5'-Tetrabromobiphenyl (BB-80) was once used as additive flame retardants. Whether its early exposure and discontinued exposure alter thyroid function remains unknown. We investigate adverse effects after early-life exposure and discontinued exposure to BB-80 and hydroxylated BB-80 (OH-BB-80) on thyroid hormone (TH) levels, thyroid tissue, and transcriptome profiles in zebrafish larvae. BB-80 at 10 µg/L induces pathological changes of thyroid with reduced thyroid follicles in larvae (P < 0.05), whereas OH-BB-80 significantly increases T4 and T3 contents (1.8 and 2.5 times of the control, P < 0.05) at 14 days postfertilization (dpf) without morphological thyroid alterations. BB-80 and OH-BB-80 cause transcriptome aberrations with key differentially expressed genes involved in the disruption of TH synthesis and signal transduction (BB-80 at 14 dpf) or TH pathway activation (OH-BB-80 at 21 dpf). After 7 days of discontinued exposure, thyroglobulin (tg) and thyroid peroxidase (tpo) genes are downregulated (P < 0.05) by 52 and 48% for BB-80 and by 49 and 39% for OH-BB-80, respectively; however, the whole-body TH levels fail to fully recover, and the locomotor activity is impaired more by BB-80. Our results indicate significant adverse impacts of BB-80 and OH-BB-80 on TH homeostasis and thyroid function of zebrafish.

Decabromodiphenyl Ethane Mainly Affected the Muscle Contraction and Reproductive Endocrine System in Female Adult Zebrafish.

The novel brominated flame retardant decabromodiphenyl ethane (DBDPE) has become a widespread environmental pollutant. However, the target tissue and toxicity of DBDPE are still not clear. In the current study, female zebrafish were exposed to 1 and 100 nM DBDPE for 28 days. Chemical analysis revealed that DBDPE tended to accumulate in the brain other than the liver and gonad. Subsequently, tandem mass tag-based quantitative proteomics and parallel reaction monitoring verification were performed to screen the differentially expressed proteins in the brain. Bioinformatics analysis revealed that DBDPE mainly affected the biological process related to muscle contraction and estrogenic response. Therefore, the neurotoxicity and reproductive disruptions were validated via multilevel toxicological endpoints. Specifically, locomotor behavioral changes proved the potency of neurotoxicity, which may be caused by disturbance of muscular proteins and calcium homeostasis; decreases of sex hormone levels and transcriptional changes of genes related to the hypothalamic-pituitary-gonad-liver axis confirmed reproductive disruptions upon DBDPE exposure. In summary, our results suggested that DBDPE primarily accumulated in the brain and evoked neurotoxicity and reproductive disruptions in female zebrafish. These findings can provide important clues for a further mechanism study and risk assessment of DBDPE.

Niclosamide Exposure at Environmentally Relevant Concentrations Efficaciously Inhibited the Growth and Disturbed the Liver-Gut Axis of Adult Male Zebrafish.

In the current study, adult male zebrafish fed a normal diet (ND) or high-fat diet (HFD) were exposed to niclosamide (NIC) at environmentally relevant concentrations to reveal the accumulation and distribution in different tissues and evaluate the effects on liver-gut axis. Chemical analysis indicated that the liver bore a greater burden of NIC compared with the brain and gonads in adult zebrafish, and the HFD-fed fish bore greater burden in their liver and brain than those ND-fed fish. The indications from body weight, growth rate, body mass index, micro-CT images, biochemical and pathological changes confirmed that NIC can efficaciously curb weight gain and improve overloads of in plasma insulin and glucose in HFD-fed zebrafish. However, the potential effects on liver-gut axis in ND-fed zebrafish were also elucidated: NIC disturbed mitochondrial energy production, inhibited the glycemic and triacylglycerol biosynthesis but promoted triacylglycerol and free fatty acid catabolism, therefore reduced lipid accumulation in hepatocytes; NIC also impaired the physical barrier, evoked inflammatory and oxidative stress and led to microbiota dysbiosis in the intestine. There findings highlighted the necessity for evaluating its potential impacts on the health of wild animals as well as human beings upon long-term exposure.

Fingerprinting fecal DNA and mRNA as a non-invasive strategy to assess the impact of polychlorinated biphenyl 126 exposure on zebrafish.

In toxicological studies, experimental animals are generally subjected to dissection to obtain the tissues of concern, which causes great harm to the animals. In this regard, it is necessary to test and develop a non-invasive strategy to prevent the animals from anthropic injury when achieving scientific objectives. Therefore, zebrafish fecal DNA and mRNA pools were assessed by using metagenomic and transcriptomic analyses based on their potential to diagnose toxicological impairment of polychlorinated biphenyl (PCB) 126, a model persistent organic pollutant. The results showed that there was abundant zebrafish DNA and mRNA in the feces, which were, however, associated with contrasting profiles of physiological activities. As compared to DNA fragments, fecal mRNA provided a better representation of zebrafish physiological status. PCB126 exposure dramatically shifted the composition of fecal zebrafish DNA and mRNA as a function of sex. The differential mRNA caused by PCB126 clearly identified the toxicological fingerprint of PCB126. In summary, this study provides preliminary clues about the potential of fecal genes (mRNA in particular) in the development of non-invasive toxicological approaches. In the future, it is expected that more works will be conducted to screen sensitive diagnostic biomarkers from feces to increase the rate and reduce the cost of ecological risk assessment.

Chrm3 protects against acinar cell necrosis by stabilizing caspase-8 expression in severe acute pancreatitis mice model.

Acinar cells in acute pancreatitis (AP) die through apoptosis and necrosis, the impacts of which are quite different. Early clinical interference strategies on preventing the progress of AP to severe acute pancreatitis (SAP) are the elimination of inflammation response and inhibition of necrosis. Muscarinic acetylcholine receptor M3 was encoded by Chrm3 gene. It is one of the best-characterized receptors of pancreatic ß cells and regulates insulin secretion, but its function in AP remains unclear. In this study, we explored the function of Chrm3 gene in the regulation of cell death in l-arginine-induced SAP animal models. We found that Chrm3 was upregulated in pancreatitis, and we further confirmed the localization of Chrm3 resided in both pancreatic islets and acinar cell membranes. The reduction of Chrm3 decreased the pathological lesion of SAP and reduced amylase activities in serum. Consistently, Chrm3 can suppress acinar cells necrosis markedly, but has no effect on regulating apoptosis after l-arginine treatment. It was shown that Chrm3 attenuated acinar cells necrosis at least in part by stabilizing caspase-8. Thus, this study indicates that Chrm3 is critical participants in SAP, and regulation of Chrm3 expression might be a useful therapeutic strategy for preventing pathologic necrosis.

Life-time exposure to decabromodiphenyl ethane (DBDPE) caused transgenerational epigenetic alterations of thyroid endocrine system in zebrafish.

Because of its ubiquitous occurrence in the environment, decabromodiphenyl ethane (DBDPE), a novel brominated flame retardant, has been widely concerned. However, its transgenerational thyroid disrupting potential and intricate mechanism are barely explored. Therefore, zebrafish embryos were exposed to environmentally relevant concentrations of DBDPE (0, 0.1, 1 and 10 nM) until sexual maturity. The results indicated that life-time exposure to DBDPE caused anxiety-like behavior in unexposed offspring. Furthermore, the changing of thyroid hormones as well as transcriptional and DNA methylation level in the promoter region of related genes were evaluated. The thyroid disruptions observed in F1 larvae were primarily attributed to excessive transfer of thyroid hormone from F0 adults to F1 eggs. Conversely, the disruptions in F2 larvae were likely due to inherited epigenetic changes, specifically hypomethylation of crh and hypermethylation of ugt1ab, passed down from the F1 generation. Additionally, our results revealed sex-specific responses of the hypothalamic-pituitary-thyroid (HPT) axis in adult zebrafish. Furthermore, thyroid disruptions observed in unexposed offspring were more likely inherited from their mothers. The current results prompted our in-depth understanding of the multi- and transgenerational toxicity by DBDPE, and also highlighted the need to consider their adverse effects on persistent and inheritable epigenetic changes in future research on emerging pollutants.

Expression and function analysis of Rac1 homolog in Chinese shrimp Fenneropenaeus chinensis.

Rac1 is a ubiquitous GTP-binding protein that plays a crucial role in multiple cellular processes. In the present study, a Rac1 homolog (FcRac1) was cloned from the Chinese shrimp Fenneropenaeus chinensis. The open reading frame (ORF) of FcRac1 consists of 579 bp encoding 192 aa. The predicted molecular weight (MW) of the deduced amino acid sequence of FcRac1 was 21.46 kDa, and its theoretical pI was 8.62. Homology analysis showed that the amino acid sequence of Rac1 had high conservation among those from different species. Phylogenetic analysis showed that FcRac1 closely related to Rac1 proteins from other arthropods. FcRac1 showed the highest expression level in the hemocytes. In situ hybridization detection showed that it distributed in all types of hemocytes. Recombinant protein of FcRac1 showed apparent activity of GTPase. The transcription of FcRac1 in juvenile shrimp changed after bacteria or WSSV challenge. The present data suggests that FcRac1 might play important roles in the innate immunity of shrimp.

Comprehensive analysis of epigenetics mechanisms in osteoporosis.

Epigenetic modification pertains to the alteration of genetic-expression, which could be transferred to the next generations, without any alteration in the fundamental DNA sequence. Epigenetic modification could include various processes such as DNA methylation, histone alteration, non-coding RNAs (ncRNAs), and chromatin adjustment are among its primary operations. Osteoporosis is a metabolic disorder that bones become more fragile due to the decrease in mineral density, which could result in a higher risk of fracturing. Recently, as the investigation of the causal pathology of osteoporosis has been progressed, remarkable improvement has been made in epigenetic research. Recent literatures have illustrated that epigenetics is estimated to be one of the most contributing factors to the emergence and progression of osteoporosis. This dissertation primarily focuses on indicating the research progresses of epigenetic mechanisms and also the regulation of bone metabolism and the pathogenesis of osteoporosis in light of the significance of epigenetic mechanisms. In addition, it aims to provide new intelligence for the treatment of diseases related to bone metabolism.

Effects of glyphosate exposure on gut-liver axis: Metabolomic and mechanistic analysis in grass carp (Ctenopharyngodon idellus).

Glyphosate, one of the most widely used herbicide worldwide, is potentially harmful to non-target aquatic organisms. However, the environmental health risks regarding impacts on metabolism homeostasis and underlying mechanisms remain unclear. Here we investigated bioaccumulation, metabolism disorders and mechanisms in grass carp after exposure to glyphosate. Higher accumulation of glyphosate and its major metabolite, aminomethylphosphonic acid, in the gut was detected. Intestinal inflammation, barrier damage and hepatic steatosis were caused by glyphosate exposure. Lipid metabolism disorder was confirmed by the decreased triglyceride, increased total cholesterol and lipoproteins in serum and decreased visceral fat. Metabolomics analysis found that glyphosate exposure significantly inhibited bile acids biosynthesis in liver with decreased total bile acids content, which was further supported by significant downregulations of cyp27a1, cyp8b1 and fxr. Moreover, the dysbiosis of gut microbiota contributed to the inflammation in liver and gut by increasing lipopolysaccharide, as well as to the declined bile acids circulation by reducing secondary bile acids. These results indicated that exposure to environmental levels of glyphosate generated higher bioaccumulation in gut, where evoked enterohepatic injury, intestinal microbiota dysbiosis and disturbed homeostasis of bile acids metabolism; then the functional dysregulation of the gut-liver axis possibly resulted in ultimate lipid metabolism disorder. These findings highlight the metabolism health risks of glyphosate exposure to fish in aquatic environment.

Blocking the large extracellular loop (LEL) domain of FcTetraspanin-3 could inhibit the infection of white spot syndrome virus (WSSV) in Chinese shrimp, Fenneropenaeus chinensis.

Tetraspanins belong to the transmembrane 4 superfamily (TM(4)SF), which span the cell membrane 4 times and act as bridges or connectors. Increasing evidences have shown that tetraspanins play important role in virus infection. The large extracellular loop (LEL) of a tetraspanin is considered as a possible target of some virus. Tetraspanins are widely found in invertebrates, but the functional roles of most invertebrate tetraspanins have remained unknown. Recently, a tetraspanin, called FcTetraspanin-3, was cloned from the cDNA library of Chinese shrimp, Fenneropenaeus chinensis. The FcTetraspanin-3 constitutive expression in all examined tissues and the expression of the gene were highly induced in hepatopancreas, lymphoid organ and intestine by white spot syndrome virus (WSSV) challenge. In this study, we expressed and purified the recombinant peptide containing the LEL domain of FcTetraspanin-3, and produced the anti-LEL polyclone antibody. The expression of FcTetraspanin-3 was observed by real-time PCR and Western blot. Also, the localization of FcTetraspanin-3-positive cells in intestine and hepatopancreas were revealed by immunofluorescence. The results of anti-LEL antibody blocking experiments shown that the antibody can significantly reduce the mortality of shrimp challenged by WSSV. Additionally, dsRNA interference was utilized to examine the functional role of FcTetraspanin-3 in response to WSSV infection, and a sensible decrease of the viral copy number in the tetraspanin knockdown shrimp. These results suggested the blocking of LEL domain of FcTetraspanin-3 could inhibit the infection of WSSV. FcTetraspanin-3 might play an important role in response to WSSV infection, and the LEL domain of FcTetraspanin-3 might mediate the entry of WSSV.

Glyphosate and glufosinate-ammonium in aquaculture ponds and aquatic products: Occurrence and health risk assessment.

As the two most commonly used organophosphorus herbicides, glyphosate (Gly) and glufosinate-ammonium (Glu) have unique properties for weed control and algae removal in aquaculture. However, the occurrences and health risks of Gly and Glu in aquaculture ponds are rare known. This study aimed to investigate the occurrences of Gly, AMPA (primary metabolity of Gly) and Glu in surface water, sediment and aquatic products from the grass carp (ctenopharyngodon idella), crayfish (procambarus clarkii) and crab (eriocheir sinensis) ponds around Lake Honghu, the largest freshwater lake in Hubei province, China where aquaculture has become the local pillar industry. Three age groups (children, young adults, middle-aged and elderly) exposure to these compounds through edible aquatic products (muscle) consumption were also assessed by target hazard quotient (THQ) method. The results indicated that Gly, AMPA and Glu were widely occurred in surface water, sediment and organisms in the fish, crayfish and crab ponds. AMPA was more likely to accumulate in the intestine of aquatic products than Gly and Glu. According to the total THQ value (1.04＞1), muscle consumption of grass carp may pose potential risk to children.

Probiotics ameliorate growth retardation of glyphosate by regulating intestinal microbiota and metabolites in crucian carp (Carassius auratus).

Glyphosate (GLY) contamination widely occurred in aquatic environments including aquaculture systems and raised hazard to aquatic organisms such as fish. Probiotics have been reported to alleviate contaminants-induced toxicity. However, whether probiotics could reduce the health risk of GLY to fish remain unknown. Here we investigated the impacts of GLY on crucian carp (Carassius auratus) by focusing on the protective roles of two commonly used aquaculture probiotics, Bacillus coagulans (BC) and Clostridium butyricum (CB). Exposure to GLY significantly caused growth retardation and reduced visceral fat and intestinal lipase activity in crucian carp. 16S rRNA sequencing indicated that dysbiosis of Bacteroidetes at phylum level and Flavobacterium at genus level might be primarily responsible for GLY-induced negative growth performance. High throughput targeted quantification for metabolites revealed that GLY changed intestinal metabolites profiles, especially the reduced bile acids and short-chain fatty acids. However, the addition of BC or CB effectively attenuated the adverse effects above by remodeling the gut microbiota composition and improving microbial metabolism. The present study provides novel evidence for ameliorating the harmful effects of GLY on fish species by adding probiotics, which highlights the potential application of probiotics in reducing the health risks of GLY in aquatic environment.

Bis(2-ethylhexyl)-tetrabromophthalate induces zebrafish obesity by altering the brain-gut axis and intestinal microbial composition.

Multiple environmental stressors, including chemicals termed obesogens, contribute to the susceptibility of organisms to obesity. Bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate (TBPH), a novel brominated flame retardant, is an environmental contaminant that may disrupt lipid metabolism. However, the risk of TBPH leading to obesity remains unknown. Herein, adult female zebrafish fed a normal-fat diet (NFD) or high-fat diet (HFD) were exposed to 0, 0.02 and 2.0 µM TBPH for 6 weeks. The results showed that chronic TBPH exposure lead to significant weight gain, adipocyte hypertrophy, and subcutaneous fat accumulation, which could be enhanced by HFD feeding. HFD individuals also showed significant visceral fat accumulation. Transcription of the main adipokines regulating lipid metabolism associated with the brain-gut axis were significantly affected by TBPH, especially leptin (brain) and adiponectin (intestine). Additionally, peroxisome proliferator-activated nuclear receptor gamma (PPAR-γ) was significantly upregulated in intestine. TBPH increased the abundance of Firmicutes and Bacteroidetes in the gut microbiota in both NFD and HFD groups, resulting in obesity. Interestingly, population diversity analysis indicated that TBPH alone had a comparable impact on gut microbiota composition to that of HDF controls. Thus, TBPH increased the susceptibility of female zebrafish to obesity by disrupting brain-gut axis regulation and gut microbial composition, leading to enhanced fat accumulation under HFD conditions.

Inhibition of CHRM3 Alleviates Necrosis Via the MAPK-p38/miR-31-5p/RIP3 Axis in L-Arginine-Induced Severe Acute Pancreatitis.

OBJECTIVES: Pancreatic acinar necrosis is a typical feature in the early phase of severe acute pancreatitis (SAP). Muscarinic acetylcholine receptor M3 (CHRM3) has been reported to play important roles in promoting insulin secretion and tumor cell proliferation, but its effect on necrosis remains unknown. This study revealed the important role of CHRM3 in regulating L-arginine-induced SAP and the molecular mechanisms. METHODS: To verify the function of CHRM3, pancreatic tissues and primary acinar cells of CRISPR/Cas9-mediated Chrm3 knockout mice were used in CHRM3 knockdown experiments, and to ascertain the CHRM3 overexpression, PLV-EGFP-Chrm3 plasmids were transfected in acinar cells in vitro. RESULTS: In L-arginine-induced SAP, CHRM3 is activated and regulates SAP through the mitogen-activated protein kinase/p38 pathway. Moreover, the expression of miR-31-5p decreased in the SAP model both in vitro and in vivo. Mir-31-5p effects the necrosis of acinar cells in SAP by upregulating the target gene RIP3, and miR-31-5p is a downstream miRNA of CHRM3. CONCLUSIONS: Necrosis in L-arginine-induced SAP is promoted by CHRM3 through the mitogen-activated protein kinase-p38/miR-31-5p/RIP3 axis.

Activation of aryl hydrocarbon receptor by dioxin directly shifts gut microbiota in zebrafish.

Gut microbiota is of critical importance to host health. Aryl hydrocarbon receptor (AhR) is found to be closely involved in the regulation of gut microbial dynamics. However, it is still not clear how AhR signaling shapes the gut microbiota. In the present study, adult zebrafish were acutely exposed to an AhR antagonist (CH223191), an AhR agonist (polychlorinated biphenyl 126; PCB126) or their combination for 7 d. Overall intestinal health and gut microbial community were temporally monitored (1 d, 3 d and 7 d) and inter-compared among different groups. The results showed that single exposure to PCB126 significantly disrupted the overall health of intestines (i.e., neural signaling, inflammation, epithelial barrier integrity, oxidative stress). However, CH223191 failed to inhibit but enhanced the physiological toxicities of PCB126, implying the involvement of extra mechanisms rather than AhR in the regulation of intestinal physiological activities. Dysbiosis of gut microbiota was also caused by PCB126 over time as a function of sex. It is intriguing that CH223191 successfully abolished the holistic effects of dioxin on gut microbiota, which inferred that growth of gut microbes was directly controlled by AhR activation without the involvement of host feedback modulation. When coming to detailed alterations at certain taxon, both antagonistic and synergistic interactions existed between CH223191 and dioxin, depending on fish sex, exposure duration and bacterial species. Correlation analysis found that gut inflammation was positively associated with pathogenic Legionella bacteria, but was negatively associated with epithelial barrier integrity, suggesting that integral intestinal epithelial barrier can prevent the influx of pathogenic bacteria to induce inflammatory response. Overall, this study has deciphered, for the first time, the direct regulative effects of AhR activity on gut microbiota. Future research is warranted to elucidate the specific mechanisms of AhR action on certain bacterial population.