Mechanisms And Effects Of Perfluorodecanoic Acid-induced Intestinal Microbiota Disorder

Background and PurposePerfluorodecanoic acid(PFDA)is a widely used perfluorinated compound that is of great concern because of its dioxin-like toxicity characteristics.However,the organismal toxic effects of PFDA exposure leading to dysbiosis are not clear,nor is its relevance to the development of disease.The intestinal tract is the "ermenter" of the human body.and the intestinal microbiota maintains a delicate dynamic balance,and the imbalance of the microbiota and its metabolites can be associated through neurotransmission,metabolites and inflammatory factors.i.e.,the Gut-Brain axis(GBA),causing mood,cognitive and behavioral changes.The function of the GBA in the toxic effects of environmental pollutants remains to be elucidated.In this thesis,the possible mechanisms and effects of intestinal microbiota disorders under PFDA treatment were investigated by studying intestinal microbiota disorders.abnormal bile acid metabolism,immunosuppression and behavioral abnormalities induced by PFDA exposure,providing a new reference for the damage and pathogenesis of environmental pollutant PFDA in humans.Perfluorodecanoic acid(PFDA)is a widely used perfluorinated compound that is of great concern because of its dioxin-like toxicity characteristics.However,the organismal toxic effects of PFDA exposure leading to dysbiosis are not clear,nor is its relevance to the development of disease.Research methodsThe transcriptome results were analyzed by DAVID(The Database for Annotation,Visualization and Integrated Discovery)to identify the most likely KEGG pathways affected by PFDA exposure and the major The results were validated by Western Blot,qRT-PCR and metabolomics.Feces were isolated and cultured,and K.pneumoniae isolates were obtained by BLAST(Basic Local Alignment Search Tool)comparison.C57BL/6J mice were treated with the isolates by enema,and immune cells in the spleens of PFDA and isolate-treated mice were monitored by flow cytometry.NOD-like receptor thermoprotein structural domain-associated protein 3(NLR family pyrin domain containing 3.NLRP3)knockout mice were assayed for alterations in intestinal microbiota before and after PFDA exposure.Animal behavioral characteristics of PFDA-exposed mice were assessed by forced swimming and tail suspension experiments.Pathological and immunological assays were performed to detect relevant brain regions.Results1.PFDA exposure induces impaired intestinal function and intestinal microbiota disorders in miceThe results of H&E staining of mouse intestinal tissues showed that the intestinal wall cells were damaged.Fecal 16S rRNA sequencing results showed that the intestinal microbiota was disturbed,with Klebsiella pneumoniae being the genus with the most significant increase in abundance.2.PFDA exposure triggers abnormal metabolism of bile acids in mice may be a factor in intestinal microbiota disordersIt has been reported that microbiota disorders are often associated with alterations in the immune status of intestinal tissues and the bile acid secretion signaling pathway.mRNA and protein level validation of the genes involved in this pathway,ATP binding cassette subfamily C member 4(ABCC4),Solute Carrier Organic Anion Transporter Family Member 1A2(SLCO1A2)and Solute Carrier Organic Anion Transporter Family Member 1A2(SLCO1A2).cassette subfamily C member 4(ABCC4).Solute Carrier Organic Anion Transporter Family Member 1A2(SLCO1A2)and Solute Carrier Organic Anion Transporter Family Member 1A2(SLCO1A2).(SLCO1A2)and Solute Carrier Organic Anion Transporter Family Member 1A2(SULT2A1).Non-targeted metabolomics results also showed an increase in the levels of secondary bile acid metabolites and related products in mice such as deoxycholic acid and a decrease in the levels of primary bile acids and related products such asβ-rhodopsin.further demonstrating the altered bile acid secretion signaling pathway.3.PFDA inhibition of NLRP3 expression is an important factor in intestinal microbiota dysbiosisKlebsiella pneumoniae abundance showed a significant increase in the intestinal microbiota disorder triggered by PFDA in mice.Our previous study showed that PFDA triggers altered expression of the inflammatory vesicle gene NLRP3.Intestinal transcriptome results also indicated a downregulation of NLRP3 expression.Fecal 16S rRNA sequencing results showed no significant difference in the abundance of Klebsiella pneumoniae in PFDA-treated NLRP3 knockout mice(KOT mice)compared to control mice(KOC mice)and compared to wild-type(NC mice),suggesting that PFDA-induced immunosuppression in mice is associated with altered abundance of Klebsiella pneumoniae.4.Klebsiella pneumoniae isolates cause immunosuppression in miceFlow cytometry results showed a significant decrease in the proportion of macrophage and Th1 cell subsets in the spleen of mice after PFDA exposure.Because the number of K.pneumoniae increased in mice after PFDA exposure.mice treated with K.pneumoniae isolates by enema showed changes in macrophages and Th1 cells in the spleen consistent with PFDA treatment.suggesting that the PFDA-induced increase in the abundance of K.pneumoniae contributed to the immunosuppression induced by it.5.Manic-like behavior and ventral hippocampal damage in mice after PFDA exposureImbalance of intestinal microbiota acts on the gut-brain axis and may affect mood and behavior.transcriptomic results from the intestine of PFDA-exposed mice showed that the neural ligand-receptor interaction signaling pathway was the enriched signaling pathway,and fecal metabolomic results showed that dopaminergic synapses were the pathway with the smallest p-value and most statistically significant among the cations.These high-throughput results suggested that PFDA may affect the gut-brain axis,so behavioral characteristics of mice were examined,and the results showed that PFDA-treated mice exhibited significant abnormalities in forced swimming and tail suspension experiments,mania-like behavior.ventral hippocampal damage.glial fibrillary acidic protein(GFAP)protein The mice showed abnormalities in the PFDA-treated mice in the forced swimming and tail suspension experiments.ConclusionThe intestinal microbiota was disturbed after PFDA exposure.with Klebsiella pneumoniae being the most abundant genus.and the important mediating mechanism of the microbiota disturbance might be immune impairment in mice triggered by abnormal bile acid metabolism and altered NLRP3 expression.Klebsiella pneumoniae inhibited macrophages and Thl cells,suggesting that the PFDA-induced increase in the abundance of Klebsiella pneumoniae contributed to the immunosuppression induced by it.Analysis of the intestinal transcriptome and fecal metabolome of mice suggested that PFDA may affect the gut-brain axis,and our results showed that it could cause mice exhibiting manic-like behavior and ventral hippocampal damage.