The immunotoxic effects of dual exposure to PCP and TCDD

Nanomaterials significance; contaminants degradation for environmental applications

Nanotechnology provides an innovative platform that is inexpensive, reasonable, having least chances of secondary contamination, economical, and an effective method to concurrently eradicate numerous impurities from contaminated wastewater. Presently, different researches have been conducted exhibiting versatile multifunctional nanoparticles (NPs) that concurrently confiscate several impurities existing in the water. Nanotechnology helps in eliminating impurities from water through the rapid, low-cost method. Pollutants such as 2,4-dichlorophenol (death-causing contaminant as it quickly gets absorbed via the skin), or industrial dyes including methyl violet (MV) or methyl orange (MO) causing water contamination were also concisely explained. In this mini-review, nanomaterials were critically investigated, and the practicability and effectiveness of the elimination of contaminations were debated. The analysis shows that a few of these processes can be commercialized in treating diverse toxins via multifunctional nanotechnology innovations. Hence, nanotechnology shows a promising and environmental friendly method to resolve the restrictions of current and conventional contaminated water treatment. We can progress the technology, without influencing and affecting the natural earth environment conditions.

Tetrachlorobenzoquinone exhibits immunotoxicity by inducing neutrophil extracellular traps through a mechanism involving ROS-JNK-NOX2 positive feedback loop

Tetrachlorobenzoquinone (TCBQ) is a common metabolite of persistent organic pollutants pentachlorophenol (PCP) and hexachlorobenzene (HCB). Current reports on the toxicity of TCBQmainly focused on its reproductive toxicity, neurotoxicity, carcinogenicity and cardiovascular toxicity. However, the possible immunotoxicity of TCBQ remains unclear. The release of neutrophil extracellular traps (NETs) is a recently discovered immune response mechanism, however, excess NETs play a pathogenic role in various immune diseases. In an attempt to address concerns regarding the immunotoxicity of TCBQ, we adopted primary mouse neutrophils as the research object, explored the influence of TCBQ on the formation of NETs. The results showed that TCBQ could induce NETs rapidly in a reactive oxygen species (ROS)-dependent manner. Moreover, TCBQ promoted the phosphorylation of c-Jun N-terminal kinase (JNK) mitogen activated protein kinase (MAPK), but not p38 or extracellular signal related kinase (ERK) in neutrophils. Mechanistically, JNK activation enhanced the expression of NADPH oxidase enzyme 2 (NOX2), which further accelerated the generation of ROS and thus amplified the formation of NETs. The pharmacologic blockage of JNK or NOX2 effectively ameliorated TCBQ-induced ROS and NETs, implying that ROS-JNK-NOX2 positive feedback loop was involved in TCBQ-induced NETs. In conclusion, we speculated that targeting NETs formation would be a promising therapeutic strategy in modulating the immunotoxicity of TCBQ.

Chloroanisoles and Chlorophenols Explain Mold Odor but Their Impact on the Swedish Population Is Attributed to Dampness and Mold

We recently reported that mold odor may be explained by chloroanisoles (CAs) formed by microbial biotransformation of chlorophenols (CPs) in legacy wood preservatives. Here we examine psychophysical aspects of CAs and trace their historic origins in buildings. Our exposure of healthy volunteers shows that 2,4,6-triCA is often perceived as unpleasant, characterized as musty or moldy and is detected at 13 ng/m³ or lower. Similar concentrations are reported in buildings with odor complaints. Scrutiny of written records reveal that new building construction methods were introduced in the 1950s, namely crawlspaces and concrete slabs on the ground. These constructions were prone to dampness and attack from wood decay fungi, prompting chemical companies and authorities to advocate preservatives against rot. Simultaneously, CPs became household chemicals used for example in indoor paints. When large-scale odor problems evolved, the authorities that once approved the preservatives attributed the odor to hidden mold, with no evidence that substantial microbial biomass was necessary for odor formation. Thereby the public remained unaware of problematic exposure to CPs and CAs. We conclude that the introduction of inappropriate designs of house foundations and CP-based preservatives once ignited and still provide impetus for indoor air research on "dampness and mold".

Sperm Quality in Mouse After Exposure to Low Doses of TCDD

Background:

In the last decade, the harmful use of dioxin has been demonstrated in human health and in the whole environment. It is well known among scientists that 2, 3, 7, 8-tetrachloro dibenzo-p-dioxin (TCDD) is an environmental pollutant that causes endocrine disruption, which causes male reproductive toxicity.

Objective:

The objective of the present study was to evaluate the toxicity effect of low doses of TCDD in male CD1 mice.

Materials and Methods:

Three concentrations of TCDD (0.375, 0.75, 1.5 mg / kg) were analyzed and the effects on spermatozoa were evaluated 10 days after oral administration of the product. As bioindicators of TCDD toxicity, an exhaustive analysis of several spermatic parameters including motility, vitality, count, morphology and viability, flow cytometry was used to determine the affected sperm population by cytotoxicity and apoptosis. In addition, a morphometric analysis of testicles was performed.

Results:

The results show that the body weight of the treated animals was reduced in medium and high doses (0.75, 1.5 mg / kg) with respect to the control groups. In the groups treated with TCDD, the abnormal head of the sperm increased by 52.5% more than the control group. Significant differences in apoptosis were observed between the negative control and vehicle control, including the median dose (0.75 mg / kg).

Conclusion:

It is concluded that at these low doses there was an impact on the quality of the mouse sperm, adding an effect on apoptosis and cytotoxicity of sperm exposed to these doses of TCDD.

Combined effects of pentachlorophenol and its byproduct hexachlorobenzene on endocrine and reproduction in zebrafish

Pentachlorophenol (PCP) and its byproduct hexachlorobenze (HCB) are two co-existing persistent environmental chemicals, but their combined toxicity remains unclear. In this study, adult zebrafish were exposed to 5 (low dose) and 25 μg·L^-1 (high dose) of PCP, HCB or their combination for 21 days, and the impact on endocrine and reproduction was investigated. Results showed that combined exposure to 25 μg·L^-1 PCP and 25 μg· L^-1 HCB significantly increased the plasma estradiol (E2) and testosterone (T) levels, altered the expressions of genes along the hypothalamic-pituitary-gonadal-liver (HPGL) axis, inhibited gonadal development, and eventually lead to decreased egg production of F0 zebrafish as well as inhibited development of F1 eggs/larvae. Compared to the combined exposure of high doses, significantly lower levels of plasma E2 and T were observed for either the high PCP or high HCB alone exposure, indicating a synergistic effect of the two chemicals on endocrine disruption after combination. Furthermore, the high PCP alone exposure inhibited the gonadal development in both the males and females, while the HCB alone exposure did not. Comparison of exposure effects indicated a greater decrease of mature gametes levels and egg production in the high combined group when compared to the high HCB alone group, but no significant difference was observed between the high combined group and the high PCP alone group. Taken together, the results suggested that combined exposure to PCP and HCB may synergistically affect endocrine of zebrafish, and result in reproduction impairments, with PCP being the primary contributor.

Identification of candidate biomarkers of the exposure to PCBs in contaminated cattle: A gene expression- and proteomic-based approach

Dioxins and polychlorinated biphenyls (PCBs) are widespread and persistent contaminants. Through a combined gene expression/proteomic-based approach, candidate biomarkers of the exposure to such environmental pollutants in cattle subjected to a real eco-contamination event were identified. Animals were removed from the polluted area and fed a standard ration for 6 months. The decontamination was monitored by evaluating dioxin and PCB levels in pericaudal fat two weeks after the removal from the contaminated area (day 0) and then bimonthly for six months (days 59, 125 and 188). Gene expression measurements demonstrated that CYP1B1 expression was significantly higher in blood lymphocytes collected in contaminated animals (day 0), and decreased over time during decontamination. mRNA levels of interleukin 2 showed an opposite quantitative trend. MALDI-TOF-MS polypeptide profiling of serum samples ascertained a progressive decrease (from day 0 to 188) of serum levels of fibrinogen β-chain and serpin A3-7-like fragments, apolipoprotein (APO) C-II and serum amyloid A-4 protein, along with an augmented representation of transthyretin isoforms, as well as APOC-III and APOA-II proteins during decontamination. When differentially represented species were combined with serum antioxidant, acute phase and proinflammatory protein levels already ascertained in the same animals (Cigliano et al., 2016), bioinformatics unveiled an interaction network linking together almost all components. This suggests the occurrence of a complex PCB-responsive mechanism associated with animal contamination/decontamination, including a cohort of protein/polypeptide species involved in blood redox homeostasis, inflammation and lipid transport. All together, these results suggest the use in combination of such biomarkers for identifying PCB-contaminated animals, and for monitoring the restoring of their healthy condition following a decontamination process.

Evaluating the Effects of Tetrachloro-1,4-benzoquinone, an Active Metabolite of Pentachlorophenol, on the Growth of Human Breast Cancer Cells

Tetrachloro-1,4-benzoquinone (TCBQ), an active metabolite of pentachlorophenol (PCP), is genotoxic and potentially carcinogenic. As an electrophilic and oxidative molecule, TCBQ can conjugate with deoxyguanosine in DNA molecules and/or impose oxidative stress in cells. In the current study, we investigated the effects of TCBQ on intracellular ROS production, apoptosis, and cytotoxicity against three different subtypes of human breast cancer cells. Luminal A subtype MCF7 (ER⁺, PR⁺, HER2⁻) cells maintained the highest intracellular ROS level and were subjected to TCBQ-induced ROS reduction, apoptosis, and cytotoxicity. HER2 subtype Sk-Br-3 (ER⁻, PR⁻, HER2⁺) cells possessed the lowest intracellular ROS level. TCBQ promoted ROS production, inhibited apoptosis, and elevated cytotoxicity (due to necrosis) against Sk-Br-3 cells. Triple-negative/basal-like subtype MDA-MB-231 cells were less sensitive towards TCBQ treatment. Therefore, the effect of prolonged exposure to PCP and its active metabolites on cancer growth is highly cancer-cell-type specific.

ROS-triggered signaling pathways involved in the cytotoxicity and tumor promotion effects of pentachlorophenol and tetrachlorohydroquinone

Free radical-triggered tissue damage is believed to play an essential role in a variety of human diseases. Pentachlorophenol (PCP) is applied as a pesticide worldwide in both industries and homes. It is used extensively as a biocide and wood preservative. Tetrachlorohydroquinone (TCHQ) was proved as a major toxic metabolite of PCP, contributing the release of free radicals during PCP metabolism. PCP has been proposed as a tumor promoter; however, only limited knowledge is available regarding the mechanisms of tumor promotion induced by PCP and its metabolite, TCHQ. A growing amount of literature suggests that a link between reactive oxygen species (ROS) and tumor promotion could exist. Herein, we summarize the findings regarding the ROS-triggered signaling pathways involved in the cytotoxicity and tumor promotion effects of PCP and TCHQ. Some of the notable findings demonstrated that TCHQ can induce DNA lesions and glutathione depletion in mammalian cells; meanwhile, oxidative stress and apoptosis/necrosis can be found both in vivo and in vitro. Interestingly, PCP and TCHQ were proved as mild tumor promoters in two-stage tumorigenesis models, in which the possible mechanism could be through ROS generation and changed Bcl-2 gene expression. We also found significant effects of antioxidants in attenuating the oxidative stress, cyto- and genotoxicity, and apoptosis/necrosis induced by PCP and/or TCHQ. In addition, mitogen-activated protein kinase (MAPK) activation is involved in PCP/TCHQ-triggered cytotoxicity, as evidenced by the finding that higher doses of TCHQ could lead to necrosis of freshly isolated splenocytes through the production of a large amount of ROS and sustained ERK activation. These results could explain partly the underlying molecular mechanisms contributing to the tumorigenesis induced by PCP. However, the detailed mechanisms of free radicals in triggering PCP/TCHQ-mediated tumor promotion and toxicity are still not completely resolved and need to be investigated further.

The pentachlorophenol metabolite tetrachlorohydroquinone induces massive ROS and prolonged p-ERK expression in splenocytes, leading to inhibition of apoptosis and necrotic cell death

Pentachlorophenol (PCP) has been used extensively as a biocide and a wood preservative and has been reported to be immunosuppressive in rodents and humans. Tetrachlorohydroquinone (TCHQ) is a major metabolite of PCP. TCHQ has been identified as the main cause of PCP-induced genotoxicity due to reactive oxidant stress (ROS). However, the precise mechanisms associated with the immunotoxic effects of PCP and TCHQ remain unclear. The aim of this study was to examine the effects of PCP and TCHQ on the induction of ROS and injury to primary mouse splenocytes. Our results shown that TCHQ was more toxic than PCP and that a high dose of TCHQ led to necrotic cell death of the splenocytes through induction of massive and sudden ROS and prolonged ROS-triggered ERK activation. Inhibition of ROS production by N-acetyl-cysteine (NAC) partially restored the mitochondrial membrane potential, inhibited ERK activity, elevated caspase-3 activity and PARP cleavage, and, eventually, switched the TCHQ-induced necrosis to apoptosis. We suggest that prolonged ERK activation is essential for TCHQ-induced necrosis, and that ROS play a pivotal role in the different TCHQ-induced cell death mechanisms.