ABSTRACT
The present study describes the immunotoxic effect of chronic fluoride exposure on adult zebrafish (Danio rerio). Zebrafish were exposed to fluoride (71.12 mg/L; 1/10 LC50) for 30 d and the expression of selected genes studied. We observed significant elevation in the detoxification pathway gene cyp1a suggesting chronic exposure to non-lethal concentration of fluoride is indeed toxic to fish. Fluoride mediated pro-oxidative stress is implicated with the downregulation in superoxide dismutase 1 and 2 (sod1/2) genes. Fluoride affected DNA repair machinery by abrogating the expression of the DNA repair gene rad51 and growth arrest and DNA damage inducible beta a gene gadd45ba. The upregulated expression of casp3a coupled with altered Bcl-2 associated X protein/B-cell lymphoma 2 ratio (baxa/bcl2a) clearly suggested chronic fluoride exposure induced the apoptotic cascade in zebrafish. Fluoride-exposed zebrafish when challenged with non-lethal dose of fish pathogen A. hydrophila revealed gross histopathology in spleen, bacterial persistence and significant mortality. We report that fluoride interferes with system-level output of pro-inflammatory cytokines tumour necrosis factor-α, interleukin-1ß and interferon-γ, as a consequence, bacteria replicate efficiently causing significant fish mortality. We conclude, chronic fluoride exposure impairs the redox balance, affects DNA repair machinery with pro-apoptotic implications and suppresses pro-inflammatory cytokines expression abrogating host immunity to bacterial infections.
Subject(s)
Antioxidants/metabolism , Cytokines/genetics , DNA Repair/drug effects , Fluorides/toxicity , Gene Expression/drug effects , Water Pollutants, Chemical/toxicity , Zebrafish/immunology , Animals , Cytokines/metabolism , Fish Proteins/genetics , Fish Proteins/metabolism , Fluorides/immunology , Interferon-gamma/genetics , Interferon-gamma/metabolism , Interleukin-1beta/genetics , Interleukin-1beta/metabolism , Tumor Necrosis Factor-alpha/genetics , Tumor Necrosis Factor-alpha/metabolism , Water Pollutants, Chemical/immunologyABSTRACT
Although dental composites are in extensive use today, little is known about the biological effects of the filler particles. As composite materials are gradually broken down in the aggressive environment of the oral cavity, the filler particles may leak and induce toxic effects on the surrounding tissue and cells. The aim of this study was to elucidate possible adverse biological effects of commonly used dental filler particles; bariumaluminiumsilica (BaAlSi) and bariumaluminiumfluorosilica (BaAlFSi) with mean size of 1 microm. BEAS-2B cells were used as a model system. Particle morphology, mean particle size in solution, and particle surface charge were determined by scanning electron microscopy and Malvern zetasizer technology, respectively. Enzyme-linked immunosorbent assay was used to detect secretion of cytokine and chemokine (IL-8 and IL-6) and quantitative PCR for detection of gene activity. Both types of particle increased the release of IL-6 and IL-8 in a dose-dependent manner. BaAlFSi particles induced a more marked IL-8 response compared to BaAlSi particles, whereas no significant difference was observed for the IL-6 response. Mechanistic studies using specific inhibitors and activators indicated that cyclic AMP-dependent protein kinase A is partly involved in the observed IL-8 response. In conclusion, we consider dental filler particles to have potential to induce adverse biological response in cell cultures.
Subject(s)
Biocompatible Materials/metabolism , Dental Materials/metabolism , Inflammation Mediators/immunology , Aluminum Silicates/chemistry , Aluminum Silicates/immunology , Barium Compounds/chemistry , Barium Compounds/immunology , Biocompatible Materials/chemistry , Cell Line , Cyclic AMP-Dependent Protein Kinases/metabolism , Dental Materials/chemistry , Fluorides/chemistry , Fluorides/immunology , Humans , Inflammation Mediators/chemistry , Interleukin-6/genetics , Interleukin-6/immunology , Interleukin-8/genetics , Interleukin-8/immunology , Materials Testing , Particle Size , RNA, Messenger/metabolismABSTRACT
Using a sensitive flow cytometric assay, which measures the intracellular oxidation of 2'7' dichlorofluorescein (DCFH) by H2O2, we have assessed, at a single-cell level, the effects of a variety of physiological priming agonists and cytochalasin B (CB) on purified populations of neutrophils stimulated at different points along the signal response transduction pathway. Pretreatment of purified neutrophils with the physiological priming agonists monocyte interleukin-8 (IL-8), granulocyte-monocyte colony-stimulating factor (GM-CSF), platelet-activating factor (PAF), IL-1 beta, tumour necrosis factor-alpha (TNF-alpha), IL-6, and non-stimulatory doses of formyl-methionyl-leucyl-phenylalanine (FMLP), resulted in an increased percentage of cells generating an oxidative burst in response to subsequent receptor stimulation with FMLP. CB had a similar but much more pronounced effect on cellular recruitment to a receptor-mediated responsive state. Activation of protein kinase C (PKC) using the phorbol ester phorbol myristate acetate (PMA) resulted in a heterogeneous response, with all cells generating H2O2, but with two populations differing in their magnitude of response. Physiological priming agonists had no effect on the heterogeneity of the PMA response. However, pretreatment with CB dramatically altered the PMA response, producing a homogeneous population highly responsive to stimulation with PKC. In contrast, direct stimulation of G proteins with fluoride (A1F-4) was primed both by physiological priming agonists and by CB. These results demonstrate that priming of neutrophils by physiological agonists involves changes at the level of signal transduction which enable a previously non-responsive cell to respond to a secondary stimulus.(ABSTRACT TRUNCATED AT 250 WORDS)
