The interference of alpha- and beta-naphthoflavone with triclosan effects on viability, apoptosis and reactive oxygen species production in mouse neocortical neurons

Multigenerational immunotoxicity assessment: A three-generation study in Drosophila melanogaster upon developmental exposure to triclosan

Triclosan (TCS) is widely used as an antibacterial agent, nevertheless, its presence in different environmental matrices and its persistent environmental nature pose a significant threat to the organism, including humans. Numerous studies showed that TCS exposure could lead to multiple toxicities, including immune dysfunction. However, whether parental TCS exposure could impair the offspring's immune response remains limited. Maintaining the immune homeostasis is imperative to neutralize the pathogen and crucial for tissue repair and the organism's survival. Thus, this study aimed to assess the multigenerational immune response of TCS using Drosophila melanogaster. TCS was administered to organisms (1.0, 10, and 100.0 μg/mL) over three generations during their developing phases, and its effect on the immunological response of the unexposed progeny was evaluated. Total circulatory hemocyte (immune cells) count, crystal cell count, phagocytic activity, clotting time, gene expression related to immune response and epigenetics, ROS generation, and cell death were assessed in the offspring. A concentration-dependent decline in total hemocytes, crystal cells, phagocytic activity, and increased clotting time in the subsequent generations was observed. Furthermore, parental TCS exposure enhanced the ROS levels, induced cell death, and altered the expression of antimicrobial peptides drosomycin, diptericin, and inflammatory genes upd1, upd2, and upd3, in the offspring's hemocytes across successive generations. The upregulation of reaper hid, and grim suggests that TCS promotes apoptotic death in the offspring's hemocytes. Notably, the increased mRNA expression of epigenetic regulators dnmt2 and g9a in the hemocytes of the offspring indicates epigenetic modifications. Further, we also observed that the antioxidant N-acetylcysteine (NAC) supplementation to the parents alleviated TCS toxicity and improved immunological functions in the progeny, indicating the role of ROS in the TCS-induced multigenerational immune toxicity. This finding provides valuable insights into the potential immune risk of prenatal TCS exposure to their offspring in the higher organism.

Current state of knowledge of triclosan (TCS)-dependent reactive oxygen species (ROS) production

Triclosan (TCS) is widely used in a number of industrial and personal care products. This molecule can induce reactive oxygen species (ROS) production in various cell types, which results in diverse types of cell responses. Therefore, the aim of the present study was to summarize the current state of knowledge of TCS-dependent ROS production and the influence of TCS on antioxidant enzymes and pathways. To date, the TCS mechanism of action has been widely investigated in non-mammalian organisms that may be exposed to contaminated water and soil, but there are also in vivo and in vitro studies on plants, algae, mammalians, and humans. This literature review has revealed that mammalian organisms are more resistant to TCS than non-mammalian organisms and, to obtain a toxic effect, the effective TCS dose must be significantly higher. The TCS-dependent increase in the ROS level causes damage to DNA, protein, and lipids, which together with general oxidative stress leads to cell apoptosis or necrosis and, in the case of cancer cells, faster oncogenesis and even initiation of oncogenic transformation in normal human cells. The review presents the direct and indirect TCS action through different receptor pathways.

Neurotoxic mechanisms of triclosan: The antimicrobial agent emerging as a toxicant

Several scientific studies have suggested a link between increased exposure to pollutants and a rise in the number of neurodegenerative disorders of unknown origin. Notably, triclosan (an antimicrobial agent) is used in concentrations ranging from 0.3% to 1% in various consumer products. Recent studies have also highlighted triclosan as an emerging toxic pollutant due to its increasing global use. However, a definitive link is missing to associate the rising use of triclosan and the growing number of neurodegenerative disorders or neurotoxicity. In this article, we present systematic scientific evidence which are otherwise scattered to suggest that triclosan can indeed induce neurotoxic effects, especially in vertebrate organisms including humans. Mechanistically, triclosan affected important developmental and differentiation genes, structural genes, genes for signaling receptors and genes for neurotransmitter controlling enzymes. Triclosan-induced oxidative stress impacting cellular proteins and homeostasis which triggers apoptosis. Though the scientific evidence collated in this article unequivocally indicates that triclosan can cause neurotoxicity, further epidemiological studies may be needed to confirm the effects on humans.

Involvement of sirtuins (Sirt1 and Sirt3) and aryl hydrocarbon receptor (AhR) in the effects of triclosan (TCS) on production of neurosteroids in primary mouse cortical neurons cultures

Epidemiological studies have shown the presence of triclosan (TCS) in the brain due to its widespread use as an antibacterial ingredient. One of the confirmed mechanisms of its action is the interaction with the aryl hydrocarbon receptor (AhR). In nerve cells, sirtuins (Sirt1 and Sirt3) act as cellular sensors detecting energy availability and modulate metabolic processes. Moreover, it has been found that Sirt1 inhibits the activation of estrogen receptors, regulates the androgen receptor, and may interact with the AhR receptor. It is also known that Sirt3 stimulates the production of estradiol (E₂) via the estradiol receptor β (Erβ). Therefore, the aim of the present study was to evaluate the effect of TCS alone or in combination with synthetic flavonoids on the production of neurosteroids such as progesterone (P₄), testosterone (T), and E₂ in primary neural cortical neurons in vitro. The contribution of Sirt1 and Sirt3 as well as AhR to these TCS-induced effects was investigated as well. The results of the experiments showed that both short and long exposure of neurons to TCS increased the expression of the Sirt1 and Sirt3 proteins in response to AhR stimulation. After an initial increase in the production of all tested neurosteroids, TCS acting for a longer time lowered their levels in the cells. This suggests that TCS activating AhR as well as Sirt1 and Sirt3 in short time intervals stimulates the levels of P₄, T, and E₂ in neurons, and then the amount of neurosteroids decreases despite the activation of AhR and the increase in the expression of the Sirt1 and Sirt3 proteins. The use of both the AhR agonist and antagonist prevented changes in the expression of Sirt1, Sirt3, and AhR and the production of P₄, T, and E₂, which confirmed that this receptor is a key in the mechanism of the TCS action.

Triclosan-induced neuroinflammation develops caspase-independent and TNF-α signaling pathway associated necroptosis in Neuro-2a cells

Triclosan (TCS) is widely used in cosmetics and healthcare industry as a broad-spectrum antibacterial agent. The lipophilic property and persistent nature of TCS has led to severe health issues. In the present study, we have evaluated the neuroinflammatory effect of TCS on mouse Neuro-2a cells. Initial investigation confirmed a dose-dependent loss in viability and morphology of cells in presence of TCS. The transcription and translation studies confirmed a downregulation in the expression of autophagy markers in Neuro-2a cells. The confocal microscopy study revealed that the abrogated autophagy in TCS-treated cells occurred due to loss in the autophagy flux and prevention in the lipidation of autophagosome bilayer. The fluorescence microscopy also confirmed a loss in the formation of autophagolysosomes in neuronal cells with increasing TCS concentrations. TCS treatment resulted in loss of mitochondrial integrity in cells as evidenced by a decrease in mitochondrial membrane potential in JC-1 staining. Further, the transcriptional and translational studies confirmed the activation of TNF-α signaling pathway in TCS-treated cells thus enhancing the expression of RIPK1, RIPK3 and MLKL proteins and their phosphorylated forms. TCS was also found to increase the tau protein pathogenesis in Neuro-2a cells, which alludes to the development of tau-associated neurodegeneration. Altogether, this study confirms the neuroinflammatory actions of TCS in Neuro-2a cells involving a TNF-α-induced MLKL-mediated signaling.

Triclosan (TCS) affects the level of DNA methylation in the human oral squamous cell carcinoma (SCC-15) cell line in a nontoxic concentration

The oral cancer is presumably caused by genetic factors and exposure to substances derived from cosmetics and disinfectants. Triclosan (TCS) is widely spread in many consumer products and oral care products. Since TCS can affect DNA methylation, which is one of the key mechanisms of gene expression that may lead to cancerogenesis, it is necessary to study this mechanism in oral cell carcinoma. The aim of the present study was to evaluate the impact of TCS on metabolic parameters, oxidative stress, gene expression, and DNA methylation and hydroxymethylation in the SCC-15 cell line. The experiments have shown TCS toxicity to SCC-15 cells only in the highest concentrations of 50 and 100 µM. TCS in a wide range of concentrations increases ROS production and caspase-3 activity. Our experiments have shown that TCS in the nontoxic concentrations of 10 µM exerts an impact on SOD2 mRNA expression and SOD activity in the SCC-15 cell line. Finally, our experiments have demonstrated that 6-h treatment with TCS decreases the mRNA expression of DNMT3A and DNMT3B. After 72-h exposure to TCS, an increased level of 5-methylcytosine and 5-hydroxymethylcytosine was observed in the SCC-15 cell line, but it was abolished by the NAC treatment. However, it is very likely that these results can be an effect of TET enzyme activity, especially in the case of the decrease in 5mC and the increase in 5hmC after the 48-h exposure to TCS, which was accompanied with a decrease in the mRNA expression of DNMT3A and DNMT3B.

Triclosan affects the expression of nitric oxide synthases (NOSs), peroxisome proliferator-activated receptor gamma (PPARγ), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) in mouse neocortical neurons in vitro

Triclosan (TCS) is a well-known compound that can be found in disinfectants, personal care products. There is one publication concerning the involvement of PPARγ in the mechanism of action of TCS. It is known that activation of PPARγ regulates the expression of the NF-κB mediated inflammation by acting on nitric oxide synthase (NOS) genes. However, there are no studies demonstrating a relationship between the effects of TCS on the PPARγ signaling pathway, changes in NF-κB expression, and NOS isoform synthesis. Therefore, the aim of this study was to evaluate the effect of TCS on the expression of PPARγ, NF-κB, nNOS, iNOS, and eNOS in mouse neocortical neurons. In addition, the effects of co-administration of synthetic alpha-naphthoflavone (αNF) or beta-naphthoflavone (βNF) flavonoids and triclosan were investigated. Our results show that TCS alters PPARγ, NF-κB, iNOS, and eNOS expression in mouse neurons in vitro. After 48 h of exposure, TCS increased PPARγ expression and decreased NF-κB expression. Moreover, under the influence of TCS, the expression of iNOS was increased and at the same time the expression of nNOS was decreased, which was probably caused by high levels of ROS. The experiments have shown that both αNF and βNF are able to modulate the effects of TCS in primary cultures of mouse cortical neurons.