Effects of Fluoride on the Expression of p38MAPK Signaling Pathway-Related Genes and Proteins in Spleen Lymphocytes of Mice

Fluoride induces immunotoxicity by regulating riboflavin transport and metabolism partly through IL-17A in the spleen

The impairment of the immune system by fluoride is a public health concern worldwide, yet the underlying mechanism is unclear. Both riboflavin and IL-17A are closely related to immune function and regulate the testicular toxicity of fluoride. However, whether riboflavin or IL-17A is involved in fluoride-induced immunotoxicity is unknown. Here, we first established a male ICR mouse model by treating mice with sodium fluoride (NaF) (100 mg/L) via the drinking water for 91 days. The results showed that fluoride increased the expression of the proinflammatory factors IL-1β and IL-17A, which led to splenic inflammation and morphological injury. Moreover, the expression levels of the riboflavin transporters SLC52A2 and SLC52A3; the transformation-related enzymes RFK and FLAD1; and the key mitochondrial functional determinants SDH, COX, and ATP in the spleen were measured via real-time PCR, Western blotting, and ELISA. The results revealed that fluoride disrupted riboflavin transport, transformation, metabolism, and mitochondrial function. Furthermore, wild-type (WT) and IL-17A knockout (IL-17A-/-) C57BL/6 J male mice of the same age were treated with NaF (24 mg/kg·bw, equivalent to 100 mg/L) and/or riboflavin sodium phosphate (5 mg/kg·bw) via gavage for 91 days. Similar parameters were evaluated as above. The results confirmed that fluoride increased riboflavin metabolism through RFK but not through FLAD1. Fluoride also affected mitochondrial function and activated neutrophils (marked with Ly6g) and macrophages (marked with CD68) in the spleen. Interestingly, IL-17A partly mediated fluoride-induced riboflavin metabolism disorder and immunotoxicity in the spleen. This work not only reveals a novel toxic mechanism for fluoride but also provides new clues for exploring the physiological function of riboflavin and for diagnosing and treating the toxic effects of fluoride in the environment.

Study on the active components and mechanism of Atractylodis Macrocephalae Rhizoma for invigorating the spleen and tonifying qi based on spectrum-effect relationship and network pharmacology

Spleen deficiency can lead to various abnormal physiological functions of the spleen. Atractylodis Macrocephalae Rhizoma (AMR) is a traditional Chinese medicine used to invigorate the spleen and tonify qi. The study aimed to identify the primary active components influencing the efficacy of AMR in strengthening the spleen and replenishing qi through spectrum-effect relationship and chemometrics. Network pharmacology was used to investigate the mechanism by which AMR strengthens the spleen and replenishes qi, with molecular docking utilized for validation purposes. The findings indicated that bran-fried AMR exhibited superior efficacy, with atractylenolides and atractylone identified as the primary active constituents. Atractylenolide II emerged as the most influential component impacting the effectiveness of AMR, while the key target was androgen receptor. Furthermore, crucial pathways implicated included the mitogen-activated protein cascade (MAPK) cascade, RNA polymerase II transcription factor activity, ligand-activated sequence-specific DNA binding, and RNA polymerase II sequence-specific DNA-binding transcription factor binding. In summary, our study has identified the primary active components associated with the efficacy of AMR and has provided an initial exploration of its mechanism of action. This offers a theoretical foundation for future investigations into the material basis and molecular mechanisms underlying the pharmacodynamics of AMR.

Progress in research on the role of fluoride in immune damage

Excessive fluoride intake from residential environments may affect multiple tissues and organs; however, the specific pathogenic mechanisms are unclear. Researchers have recently focused on the damaging effects of fluoride on the immune system. Damage to immune function seriously affects the quality of life of fluoride-exposed populations and increases the incidence of infections and malignant tumors. Probing the mechanism of damage to immune function caused by fluoride helps identify effective drugs and methods to prevent and treat fluorosis and improve people's living standards in fluorosis-affected areas. Here, the recent literature on the effects of fluoride on the immune system is reviewed, and research on fluoride damage to the immune system is summarized in terms of three perspectives: immune organs, immune cells, and immune-active substances. We reviewed that excessive fluoride can damage immune organs, lead to immune cells dysfunction and interfere with the expression of immune-active substances. This review aimed to provide a potential direction for future fluorosis research from the perspective of fluoride-induced immune function impairment. In order to seek the key regulatory indicators of fluoride on immune homeostasis in the future.

Integrative transcriptome and metabolome analysis of fluoride exposure induced developmental neurotoxicity in mouse brain

Fluoride could cause developmental neurotoxicity and significantly affect the intelligence quotient (IQ) of children. However, the systematic mechanism of neuronal damage caused by excessive fluoride administration in offspring is largely unknown. Here, we present a comprehensive integrative transcriptome and metabolome analysis to study the mechanism of developmental neurotoxicity caused by chronic fluoride exposure. Comparing the different doses of fluoride treatments in two generations revealed the exclusive signature of metabolism pathways and gene expression profiles. In particular, neuronal development and synaptic ion transport are significantly altered at the gene expression and metabolite accumulation levels for both generations, which could act as messengers and enhancers of fluoride-induced systemic neuronal injury. Choline and arachidonic acid metabolism, which highlighted in the integrative analysis, exhibited different regulatory patterns between the two generations, particularly for synaptic vesicle formation and inflammatory factor transport. It may suggest that choline and arachidonic acid metabolism play important roles in developmental neurotoxic responses for offspring mice. Our study provides comprehensive insights into the metabolomic and transcriptomic regulation of fluoride stress responses in the mechanistic explanation of fluoride-induced developmental neurotoxicity.

Associations of gestational and early-life exposure to toxic metals and fluoride with a diagnosis of food allergy or atopic eczema at 1 year of age

Studies have indicated that early-life exposure to toxic metals and fluoride affects the immune system, but evidence regarding their role in allergic disease development is scarce. We aimed to evaluate the relations of exposure to such compounds in 482 pregnant women and their infants (4 months of age) with food allergy and atopic eczema diagnosed by a paediatric allergologist at 1 year of age within the Swedish birth-cohort NICE (Nutritional impact on Immunological maturation during Childhood in relation to the Environment). Urinary cadmium and erythrocyte cadmium, lead, and mercury concentrations were measured by inductively coupled plasma mass spectrometry (ICP-MS), urinary inorganic arsenic metabolites by ICP-MS after separation by ion exchange chromatography, and urinary fluoride by an ion-selective electrode. The prevalence of food allergy and atopic eczema was 8 and 7%, respectively. Gestational urinary cadmium, reflecting chronic exposure, was associated with increased odds of infant food allergy (OR [95% CI]: 1.34 [1.09, 1.66] per IQR [0.08 μg/L]). Both gestational and infant urinary fluoride were associated, albeit at a statistically non-significant level, with increased atopic eczema odds (1.48 [0.98, 2.25], 1.36 [0.95, 1.95], per doubling, respectively). By contrast, gestational and infant erythrocyte lead was associated with decreased odds of atopic eczema (0.48 [0.26, 0.87] per IQR [6.6 μg/kg] and 0.38 [0.16, 0.91] per IQR [5.94 μg/kg], respectively), and infant lead with decreased odds of food allergy (0.39 [0.16, 0.93] per IQR [5.94 μg/kg]). Multivariable adjustment had marginal impact on the estimates above. After additional adjustment for fish intake biomarkers, the methylmercury associated atopic-eczema odds were considerably increased (1.29 [0.80, 2.06] per IQR [1.36 μg/kg]). In conclusion, our results indicate that gestational cadmium exposure might be associated with food allergy at 1 year of age and, possibly, early-life exposure to fluoride with atopic eczema. Further prospective and mechanistic studies are needed to establish causality.

Comparative Transcriptome Profiling of mRNA and lncRNA of Mouse Spleens Inoculated with the Group ACYW135 Meningococcal Polysaccharide Vaccine

The Group ACYW135 meningococcal polysaccharide vaccine (MPV-ACYW135) is a classical common vaccine used to prevent Neisseria meningitidis serogroups A, C, Y, and W135, but studies on the vaccine at the transcriptional level are still limited. In the present study, mRNAs and lncRNAs related to immunity were screened from the spleens of mice inoculated with MPV-ACYW135 and compared with the control group to identify differentially expressed mRNAs and lncRNAs in the immune response. The result revealed 34375 lncRNAs and 41321 mRNAs, including 405 differentially expressed (DE) lncRNAs and 52 DE mRNAs between the MPV group and the control group. Results of GO and KEGG enrichment analysis turned out that the main pathways related to the immunity of target genes of those DE mRNAs and DE lncRNAs were largely associated with positive regulation of T cell activation, CD8-positive immunoglobulin production in mucosal tissue, alpha-beta T cell proliferation, negative regulation of CD4-positive, and negative regulation of interleukin-17 production, suggesting that the antigens of MPV-ACYW135 capsular polysaccharide might activate T cell related immune reaction in the vaccine inoculation. In addition, it was noted that Bach2 (BTB and CNC homolog 2), the target gene of lncRNA MSTRG.17645, was involved in the regulation of immune response in MPV-ACYW135 vaccination. This study provided a preliminary catalog of both mRNAs and lncRNAs associated with the proliferation and differentiation of body immune cells, which was worthy of further research to enhance the understanding of the biological immune process regulated by MPV-ACYW135.

Fluoride Can Damage the Spleen of Mice by Perturbing Th1/Th2 Cell Balance

To investigate the mechanism of fluoride-induced splenic toxicity, 0, 25, 50, and 100 mg/L sodium fluoride (NaF) were administered in male mice via drinking water for 90 days. After NaF treatment, the histological structure of the spleen, the proportion of helper T 1 cell (Th1) and helper T 2 cell (Th2), and the relative expression levels of cytokines and T-bet and GATA3 were analyzed. The results showed that 50 and 100 mg/L NaF consumption can change the normal structure of mouse spleen and the proportion of Th1/Th2 cells. It also decreased the mRNA expression levels of IL-2, INF-γ, and TGF-β, but increased the levels of IL-4, IL-6, and IL-10. Importantly, fluoride increased the protein expression of GATA3 but decreased the expression of T-bet. Our findings indicate that superfluous fluoride intake damages the balance of Th1/Th2 cells by changing the levels of T-bet and GATA3 in the spleen, and further changes the expression of Th1/Th2 cell-related cytokines in the spleen microenvironment, eventually leading to spleen injury.

Calcium relieves fluoride-induced bone damage through the PI3K/AKT pathway

Bone is the main target of fluorosis, and it has been perfectly elaborated that a moderate dosage of calcium (Ca) can alleviate bone fluorosis. However, whether Ca can alleviate fluorosis through the phosphatidylinositol 3 kinase (PI3K)/protein kinase B (AKT) signaling pathway has not yet been reported. Hence, we evaluated the histopathological structure, the imbalance of the biochemical index of bone metabolism, and the expression levels of PI3K/AKT apoptosis signaling pathway-related genes in rats treated with sodium fluoride (NaF, F) and/or calcium carbonate (CaCO3) for 120 days. Our results suggest that 100 mg L-1 NaF induced histopathological injury as alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase (StrACP) activity increased, with a decrease in the serum Ca levels (p < 0.05). Moreover, the results of qRT-PCR and western blotting showed that F increased the expression levels of transglutaminase 2 (TGM2), focal adhesion kinase (FAK), PI3K, AKT, forkhead box O1 (Foxo1), Bcl-2 interacting mediator of cell death (BIM), Bcl2-associated x protein (Bax) and Caspase 3 (p < 0.05, p < 0.01). It also decreased the expression of AnnexinA5 (Anxa5), 3'-phosphoinositide-dependent kinase 1 (PDK1) and B-cell lymphoma-2 (Bcl-2) (p < 0.05, p < 0.01), which finally activated the PI3K/AKT pathway. On the other hand, CaCO3 supplementation reversed the histopathological injury along with the levels of ALP, StrACP and serum Ca, alleviating the gene expression levels of PI3K/AKT pathway-related markers. Altogether, we can conclude that CaCO3 supplementation mitigated F-induced bone damage via the PI3K/AKT signaling pathway.

Sodium Fluoride (NaF) Induces Inflammatory Responses Via Activating MAPKs/NF-κB Signaling Pathway and Reducing Anti-inflammatory Cytokine Expression in the Mouse Liver

At present, no reports are focused on fluoride-induced hepatic inflammatory responses in human beings and animals. This study aimed to investigate the mRNA and protein levels of inflammatory cytokines and signaling molecules for evaluating the effect of different doses (0, 12, 24, and 48 mg/kg) of sodium fluoride (NaF) on inflammatory reaction in the mouse liver by using methods of experimental pathology, quantitative real-time polymerase chain reaction (qRT-PCR), and western blot analysis. We found that NaF in excess of 12 mg/kg caused the hepatic inflammatory responses, and the results showed that NaF activated the mitogen-activated protein kinases (MAPKs) signaling pathway by markedly increasing (p < 0.01 or p < 0.05) mRNA and protein levels of apoptosis signal-regulating kinase 1 (ASK1), mitogen-activated protein kinase kinases 1/2 (MEK1/2), extracellular signal-regulated protein kinases 1/2 (Erk1/2), mitogen-activated protein kinase kinases 4/7 (MEK4/7), c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (p38) and mitogen-activated protein kinase kinases 3/6 (MEK3/6), and the nuclear factor-kappa B (NF-κB) signaling pathway by increasing (p < 0.01 or p < 0.05) the production of NF-κB and inhibitor of nuclear factor kappa-B kinase subunit beta (IKK-β) and reducing (p < 0.01 or p < 0.05) the production of the inhibitory kappa B (IκB). Thus, NaF that caused the hepatic inflammatory responses was characterized by increasing (p < 0.01 or p < 0.05) the production of pro-inflammatory mediators such as interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8), monocyte chemotactic protein 1 (MCP-1), and cyclooxygenase-2 (COX-2) via the activation of MAPKs and NF-κB pathways, and by significantly inhibiting (p < 0.01 or p < 0.05) the production of anti-inflammatory mediators including interleukin-4 (IL-4) and transforming growth factor beta (TGF-β).

Downregulation of microRNA-143-5p is required for the promotion of odontoblasts differentiation of human dental pulp stem cells through the activation of the mitogen-activated protein kinases 14-dependent p38 mitogen-activated protein kinases signaling pathway

MicroRNAs (miRNAs) play critical roles in various biological processes including cell differentiation. Some researchers suggested that the p38 mitogen-activated protein kinases (MAPK) signaling pathway had an effect on regulating the odontoblastic differentiation of human dental pulp stem cells (hDPSCs). This study focuses on the effects of miR-143-5p on hDPSCs by regulating the p38 MAPK signaling pathway. The targeting relationship of MAPK14 and miR-143-5p targets were verified by TargetScan and dual-luciferase reporter gene assay. Through overexpression of miR-143-5p or silencing of miR-143-5p, expressions of miR-143-5p, MAPK14, Ras, MAPK kinase (MKK) 3/6, dentin sialophosphoprotein (DSPP), alkaline phosphatase (ALP), and osteocalcin (OCN) were detected by reverse transcription quantitative polymerase chain reaction. Protein expressions of MAPK14, Ras, and MKK3/6 were determined by western blot analysis. ALP and alizarin red S staining were used to detect mineralization. Initially, MAPK14 was found to be negatively regulated by miR-143-5p. Meanwhile, the upregulated miR-143-5p decreased the p38 MAPK signaling pathway related genes (MAPK14, Ras, and MKK3/6) and odontoblastic differentiation markers (ALP, DSPP, and OCN) expression. On the contrary, the downregulated miR-143-5p increased the p38 MAPK signaling pathway related genes (MAPK14, Ras, and MKK3/6) and odontoblastic differentiation markers (ALP, DSPP, and OCN) expression. Furthermore, ALP activity and mineralized nodules increased after downregulation of miR-143-5p, and after its upregulation, ALP activity and mineralized nodules decreased. Our data suggest that poor expression of miR-143-5p promotes hDPSCs odontoblastic differentiation through the activation of the p38 MAPK signaling pathway by upregulating MAPK14.

Fluoride: A review of pre-clinical and clinical studies

Fluoride is ubiquitous in environment and profound in bones, teeth and calcified tissues of human body. Fluoride has been the topic of regular discussion and investigations. Besides its toxicity, fluoride has also been examined for its beneficial effects like prevention and treatment of tooth decay, microbial infection, inflammation, cancer, occurrence of renal stone and many more. Since last many decades, several efforts have been made at pre-clinical and clinical level to understand role of fluoride in biological system. The present review gives a brief account of prevalence, sources of fluoride toxicity and pre-clinical and clinical studies carried out on effects of fluoride in last six decades.

Developmental fluoride exposure influenced rat's splenic development and cell cycle via disruption of the ERK signal pathway

Excessive fluoride exposure has been reported to cause damage to spleen. Neonatal period is characterized by rapid proliferation and differentiation of lymphocyte in the spleen. Children may be more sensitive to the toxicity of fluoride compared to the adults. The aim of this study was to investigate the effects of postnatal exposure (from neonatal period to early adulthood) to fluoride on the development of spleen on a regular basis and the underlying signal pathway. Results showed a marked decrease in spleen weight index and altered morphology in the spleen of fluoride-treated group on PND-84, which reflected fluoride inhibition of the development of spleen. Fluoride exposure induced cell cycle arrest of splenocytes and decreased the mRNA expression of IL-2, which indicated compromised baseline lymphocyte proliferation in the spleen. Time course research from 3-wk-of-age until 12-wk-of-age showed an adverse and cumulative impact of fluoride on the development of spleen. In view of the key role of MAPK/ERK pathway in lymphocyte development, Raf-1/MEK-1/ERK-2/c-fos mRNA expression and ERK/p-ERK protein expression were detected. Results showed despite a transitory increase in mRNA expression from PND-42 to PND-63 in fluoride-treated group, the expression of these genes on PND-84 decreased significantly compared with PND-42 or PND-63. NaF significantly inhibited the phosphorylation of ERK protein on PND-84. Taken together, these results emphasized the vital role of ERK pathway in the interfered development of spleen induced by a high dose of fluoride exposure in rats.

Effects of combined exposure to formaldehyde and benzene on immune cells in the blood and spleen in Balb/c mice

Formaldehyde and benzene are the two major indoor air pollutants due to their prevalence and toxicity. This study aimed to explore the toxic effect on the spleen and relevant immune responses of Balb/c mice caused by exposure to a combination of formaldehyde and benzene. Balb/c mice were divided randomly into five groups (n=9/group): blank control group (Ctrl); solvent ([corn] Oil) control; formaldehyde only (FA, 3mg/m(3)); benzene only (BZ, 150mg/kg BW); and, formaldehyde+benzene group (FA+BZ). Exposures were performed for 8h/day, 5 day/week, for 2 weeks. Tail blood was collected after the final exposure; 24-h later, the mice were euthanized to permit assessment of a variety of immune endpoints. The endpoints' three areas were: (1) in living mice, body weight and delayed-type hypersensitivity (DTH) responses; (2) in blood, immune cell counts and serum antibody levels (serum hemagglutination); and, (3) in spleen samples, reactive oxygen species (ROS), malondialdehyde (MDA), glutathione (GSH), caspase-3 (cell apoptosis) levels and lymphocyte proliferation. In this study we fund (1) BZ and FA+BZ exposure can lead to the reduction in the number of some immune cells in peripheral blood; (2) Formaldehyde has certain synergistic effects on benzene-induced cytotoxicity in peripheral blood, (3) FA, BZ and FA+BZ exposure can lead to ROS and GSH depletion in spleen cells, and spleen cell apoptosis (caspase-3 increased) may be one of the downstream events, decreased splenic lymphocyte proliferation; and (4) the FA+BZ combined exposure can lead to the decreased body weight, serum antibody level (by serum hemagglutination assay).