Increased toll-like receptor 9 expression is associated with the severity of paraquat-induced lung injury in mice

Reproductive toxicity and cross-generational effect of polyethylene microplastics in Paramisgurnus dabryanus

Pollution of microplastics (MPs) has become a global environmental issue due to the difficulty in its degradation and may cause unexpected ecological effects. Nevertheless, little is known about the potential effects of MPs on reproduction toxicity in aquatic species. In this study, adult loach (Paramisgurnus dabryanus, F0 generation) were exposed to two concentrations (1 and 10 mg/L) of polyethylene MPs (PE-MPs) for 15 or 30 days, and the toxic effects in parental loach and the offspring (F1 generation) were examined. Our results showed that PE-MPs exposure could change the indicators content of antioxidant system in the brain, liver, and gonad. PE-MPs can accumulate in the gonads, disrupt the transcription of HPG-axis related genes, alter sex hormone levels, increase cell apoptosis and gonadal pathological lesions, lead to the damage of biological characteristics of semen, and affect the reproduction in F0 generation. PE-MPs remaining in the parental gonads can be transferred to the F1 generation embryos and accumulated on the embryonic chorionic membrane, increasing mortality and malformation rates, accelerating hatching time, and decreasing hatching rate and body length. These results suggest that PE-MPs leads to a potential adverse influence on reproduction and serious impacts on population sustainability. This work provides a new perspective into the effects of MPs on reproductive damage and cross-generational effects in teleost fish, which have implications in fields of freshwater ecology and environmental toxicology.

Immunosuppressive therapies attenuate paraquat-induced renal dysfunction by suppressing inflammatory responses and lipid peroxidation

Although paraquat (PQ) induces oxidative damage and inflammatory responses in the lungs, the mechanism underlying PQ-induced acute kidney injury in patients is unclear. Immunosuppressive therapy with glucocorticoids and the immunosuppressant cyclophosphamide (CP) has been employed to treat patients with PQ poisoning. This study examined whether PQ could concurrently cause renal injury, inflammatory responses, and oxidative damage in the kidneys, and whether CP and dexamethasone (DEX) could suppress PQ-induced alterations. Mice were assigned to eight groups: Control, PQ, DEX, PQ plus DEX, CP, PQ plus CP, DEX plus CP, and PQ plus DEX with CP. DEX, CP, and DEX plus CP reversed PQ-induced renal injury, as indicated by urinary albumin-to-creatinine ratios and urea nitrogen levels in serum. The treatments also attenuated PQ-induced renal infiltration of leukocytes and macrophages and induction of the Il6, Tnf, Icam, Cxcl2, Tlr4, and Tlr9 genes encoding the inflammatory mediators in the kidneys. However, DEX only partially suppressed the macrophage infiltration, whereas DEX plus CP provided stronger protection than DEX or CP alone for the induction of Il6 and Cxcl2. Moreover, through the detection of F₂-isoprostanes (F₂-IsoPs) and isofurans in the kidneys and lungs and F₂-IsoPs in the plasma and urine, the therapies were found to suppress PQ-induced lipid peroxidation, although DEX was less effective. Finally, PQ decreased ubiquinol-9:ubiquinone-9 ratios in the kidneys. This effect of PQ was not found under CP treatment, but the ratio was lower than that of the control group. Our findings suggest that the suppression of PQ-induced inflammatory responses by DEX and CP in the kidneys can mitigate oxidative damage and acute kidney injury.

Impairment of apoptosis pathway via Apaf1 downregulation during chlorpyrifos and/or cypermethrin induced lung damage

Chlorpyrifos is an organophosphate and the cypermethrin is type 2 pyrethroid insecticide that are used for indoor and outdoor pest control. The present study aimed to investigate differential transcriptional profiling to identify the candidate gene associated with lung injury following exposure to chlorpyrifos and/or cypermethrin in a mouse model system. Swiss male albino mice (n = 24) were divided into three treatment groups (n = 6 each) that were given chlorpyrifos (2.76 mg kg^-1 body weight), cypermethrin (2 mg kg^-1 body weight) and the combination of both pesticides orally dissolved in corn oil and one control group (n = 6) that received corn oil for 90 days. The pulmonary expression of the Apaf1 was observed using RT2 Profiler PCR Array. The results showed that chronic exposure to chlorpyrifos, cypermethrin and their combination downregulated (67, 63 and 66 genes) and upregulated (4, 2 and 2 genes), respectively. The pulmonary expression of Apaf1 that plays important role in apoptosis was found to be downregulated. The immunohistochemistry depicted reduced expression of Apaf1 in both airway epithelium and alveolar septa following exposure to chlorpyrifos and/or cypermethrin. In conclusion, results demonstrated that exposure to chlorpyrifos, cypermethrin and their combination cause lung damage by the dysregulation of Apaf1 gene expression.

The STING-IRF3 pathway contributes to paraquat-induced acute lung injury

Immune and inflammatory responses play significant roles in paraquat (PQ)-induced acute lung injury (ALI), but the specific mechanisms remain unclear. Our study aimed to investigate the action of STING-IRF3 signaling on PQ-induced ALI in mice. Following PQ administration, samples were collected at 2, 12, 24, and 48 h for in vivo studies, and 24 h for in vitro studies. Following PQ administration (30 mg/kg, i.p.), injury to mouse lungs was evaluated by H&E staining and wet/dry ratios, and lung oxidative damage was evaluated by MDA and SOD assays. The mRNA levels of Sting, Irf3, and Ifnβ were detected by RT-PCR, the expression of STING and IRF3 were assessed by western blotting and IHC/IF, and the secretion of IFNβ was detected by ELISA. In vivo, PQ administration induced pathological changes and increased wet/dry ratios in lungs after 48 h. Sting, Irf3, and Ifnβ mRNA levels in lung tissues, STING and pIRF3 protein levels in lung tissues, and IFNβ secretion in serum, were upregulated by PQ in a time-dependent manner. PQ administration promoted IRF3 nuclear translocation in lung tissues after 48 h. The above changes were all attenuated by dexamethasone treatment (5 mg/kg, i.p., qd). In vitro, PQ induced STING and IRF3 translocation. Irf3 or Sting silencing decreased the mRNA levels and supernatant secretion of IFNβ in PQ-treated RAW264.7 mouse macrophages. Sting silencing also inhibited the protein and mRNA levels of IRF3 in vitro. Our study suggests that STING-IRF3 signaling contributes to PQ-induced ALI, providing new information for future treatment strategies.

Characterizing the protracted neurobiological and neuroanatomical effects of paraquat in a murine model of Parkinson's disease

The primary motor symptoms of Parkinson's disease (PD) result from the degeneration of dopamine-producing neurons of the substantia nigra pars compacta (SNc), and often, the loss is asymmetrical, resulting in unilateral tremor presentation. Notably, age is the primary risk factor for PD, and it is likely that the disease ultimately stems from the impact of environmental factors, which interact with the aging process. Recent research has focused on the role of microglia and pro-oxidative responses in dopaminergic neuronal death. In this study, we sought to examine the neurodegenerative, inflammatory, and stress effects of exposure to the etiologically relevant pesticide, paraquat, over time (up to 6 months after injections). We also were interested in whether a high-resolution, 7-Tesla animal magnetic resonance imaging would be sensitive enough to detect the degenerative impact of paraquat. We found that paraquat induced a loss of dopaminergic SNc neurons and activation of microglia that surprisingly did not change over 6 months after the last injection. A long-lasting reduction was evident for body weight, and alterations in organ (lung and heart) weight were evident, which reflect the peripheral impact of the toxicant. The microglial proinflammatory actin-remodeling factor, WAVE2, along with the inflammatory transcription factor, nuclear factor kappa B were also elevated within the brain. Remarkably, the stress hormone, corticosterone, was still significantly elevated 1 month after paraquat, whereas the inflammasome factor, caspase-1, and antigen presentation factor, MFG-E8, both displayed delayed rises after the 6-month time. Using high-resolution magnetic resonance imaging, we detected no striatal changes but modest hemispheric differences in the SNc and time-dependent volumetric enlargement of the ventricles in paraquat-treated mice. These data suggest that paraquat induces long-term nigrostriatal pathology (possibly asymmetric) and inflammatory changes and stress and trophic/apoptotic effects that appear to either increase with the passage of time or are evident for at least 1 month. In brief, paraquat may be a useful nonspecific means to model widespread stress and inflammatory changes related to PD or age-related disease in general, but not the progressive nature of such diseases.

The herbicide paraquat-induced molecular mechanisms in the development of acute lung injury and lung fibrosis

The herbicide paraquat (PQ; 1,1'-dimethyl-4,4'-bipyridylium dichloride) is a highly toxic organic heterocyclic herbicide that has been widely used in agricultural settings. Since its commercial introduction in the early 1960s, numerous cases of fatal PQ poisonings attributed to accidental and/or intentional ingestion of PQ concentrated formulations have been reported. The clinical manifestations of the respiratory system during the acute phase of PQ poisoning mainly include acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), followed by pulmonary fibrosis in a later phase. The focus of this review is to summarize the most recent publications related to PQ-induced lung toxicity as well as the underlying molecular mechanisms for PQ-mediated pathologic processes. Growing sets of data from in vitro and in vivo models have demonstrated the involvement of the PQ in regulating lung oxidative stress, inflammatory response, epigenetics, apoptosis, autophagy, and the progression of lung fibrosis. The article also summarizes novel therapeutic avenues based on a literature review, which can be explored as potential means to combat PQ-induced lung toxicity. Finally, we also presented clinical studies on the association of PQ exposure with the incidence of lung injury and pulmonary fibrosis.

Converging TLR9 and PI3Kgamma signaling induces sterile inflammation and organ damage

Toll-like receptor 9 (TLR9) and Phosphatidylinositol-3-kinase gamma (PI3Kγ) are very important effectors of the immune response, however, the importance of such crosstalk for disease development is still a matter of discussion. Here we show that PI3Kγ is required for immune responses in which TLR9 is a relevant trigger. We demonstrate the requirement of PI3Kγ for TLR9-induced inflammation in a model of CpG-induced pleurisy. Such requirement was further observed in inflammatory models where DNA sensing via TLR9 contributes to disease, such as silicosis and drug-induced liver injury. Using adoptive transfer, we demonstrate that PI3Kγ is important not only in leukocytes but also in parenchymal cells for the progression of inflammation. We demonstrate this crosstalk between TLR9 and PI3Kγ in vitro using human PBMCs. The inhibition of PI3Kγ in CpG-stimulated PBMCs resulted in reduction of both cytokine production and phosphorylated Akt. Therefore, drugs that target PI3Kγ have the potential to treat diseases mediated by excessive TLR9 signalling.

Paraquat Preferentially Induces Apoptosis of Late Stage Effector Lymphocyte and Impairs Memory Immune Response in Mice

Paraquat (PQ) is a toxic non-selective herbicide. To date, the effect of PQ on memory immune response is still unknown. We investigated the impact of PQ on memory immune response. Adult C57BL/6 mice were subcutaneously injected with 2 mg/kg PQ, 20 mg/kg PQ or vehicle control every three days for two weeks. A single injection of keyhole limpet hemocyanin (KLH) at day four after the initial PQ treatment was used to induce a primary immune response; a second KLH challenge was performed at three months post the first KLH immunization to induce a secondary immune response. In steady state, treatment with 20 mg/kg PQ reduced the level of serum total IgG, but not that of IgM; treatment with 20 mg/kg PQ decreased the number of effector and memory lymphocytes, but not naïve or inactivated lymphocytes. During the primary immune response to KLH, treatment with 20 mg/kg PQ did not influence the proliferation of lymphocytes or expression of co-stimulatory molecules. Instead, treatment with 20 mg/kg PQ increased the apoptosis of lymphocytes at late stage, but not early stage of the primary immune response. During the secondary immune response to KLH, treatment with 20 mg/kg PQ reduced the serum anti-KLH IgG and KLH-responsive CD4 T cells and B cells. Moreover, effector or activated lymphocytes were more sensitive to PQ-induced apoptosis in vitro. Treatment with 2 mg/kg PQ did not impact memory immune response to KLH. Thus, treatment with 20 mg/kg PQ increased apoptosis of late stage effector cells to yield less memory cells and thereafter impair memory immune response, providing a novel understanding of the immunotoxicity of PQ.

Leucine-rich repeat kinase-2 (LRRK2) modulates paraquat-induced inflammatory sickness and stress phenotype

Background

Leucine-rich repeat kinase 2 (LRRK2) is a common gene implicated in Parkinson’s disease (PD) and is also thought to be fundamentally involved in numerous immune functions. Thus, we assessed the role of LRRK2 in the context of the effects of the environmental toxicant, paraquat, that has been implicated in PD and is known to affect inflammatory processes.

Methods

Male LRRK2 knockout (KO) and transgenic mice bearing the G2019S LRRK2 mutation (aged 6–8 months) or their littermate controls were exposed to paraquat (two times per week for 3 weeks), and sickness measures, motivational scores, and total home-cage activity levels were assessed. Following sacrifice, western blot and ELISA assays were performed to see whether or not LRRK2 expression would alter processes related to plasticity, immune response processes, or the stress response.

Results

Paraquat-induced signs of sickness, inflammation (elevated IL-6), and peripheral toxicity (e.g., organ weight) were completely prevented by LRRK2 knockout. In fact, LRRK2 knockout dramatically reduced not only signs of illness, but also the motivational (nest building) and home-cage activity deficits induced by paraquat. Although LRRK2 deficiency did not affect the striatal BDNF reduction that was provoked by paraquat, it did blunt the corticosterone elevation induced by paraquat, raising the possibility that LRRK2 may modulate aspects of the HPA stress axis. Accordingly, we found that transgenic mice bearing the G2019S LRRK2 mutation had elevated basal corticosterone, along with diminished hippocampal 5-HT1A levels.

Conclusion

We are the first to show the importance of LRRK2 in the peripheral neurotoxic and stressor-like effects of paraquat. These data are consistent with LRRK2 playing a role in the general inflammatory tone and stressor effects induced by environmental toxicant exposure.

Paraquat Induces Peripheral Myelin Disruption and Locomotor Defects: Crosstalk with LXR and Wnt Pathways

AIMS

Paraquat (PQT), a redox-active herbicide, is a free radical-producing molecule, causing damage particularly to the nervous system; thus, it is employed as an animal model for Parkinson's disease. However, its impact on peripheral nerve demyelination is still unknown. Our aim is to decipher the influence of PQT-induced reactive oxygen species (ROS) production on peripheral myelin.

RESULTS

We report that PQT provokes severe locomotor and sensory defects in mice. PQT elicited an oxidative stress in the nerve, resulting in an increase of lipid peroxidation and protein carbonylation, despite the induction of nuclear factor erythroid 2-related factor 2 (Nrf2)-dependent antioxidant defenses. We observed a dramatic disorganization of myelin sheaths in the sciatic nerves, dysregulation of myelin gene expression, and aggregation of myelin proteins, a hallmark of demyelination. PQT altered myelin gene expression via liver X receptor (LXR) signaling, a negative regulator of peripheral myelin gene expression through its dialog with the Wnt/β-catenin pathway. PQT prevented β-catenin binding on myelin gene promoters, resulting in the inhibition of Wnt/β-catenin-dependent myelin gene expression. Wnt pathway activation by LiCl dampened the deleterious effects of PQT. LiCl blocked PQT-induced oxidative stress and reduced Schwann cell death. LiCl+PQT-treated mice had normal sensorimotor behaviors and a usual nerve structure.

INNOVATION

We reveal that PQT damages the sciatic nerve by generating an oxidative stress, dysregulating LXR and Wnt/β-catenin pathways. The activation of Wnt signaling by LiCl reduced the deleterious effects of PQT on the nerve.

CONCLUSION

We demonstrate that PQT instigates peripheral nerve demyelinating neuropathies by enhancing ROS production and deregulating LXR and Wnt pathways. Stimulating Wnt pathway could be a therapeutic strategy for neuropathy treatment. Antioxid. Redox Signal. 27, 168-183.

Toll-like receptor 9 mediates paraquat-induced acute lung injury: an in vitro and in vivo study

AIMS

This study aimed to investigate the role of Toll-like receptor 9 in paraquat-induced acute lung injury (ALI).

MAIN METHODS

For in vivo study,C57BL mice were randomly assigned into the vehicle control group, paraquat group, paraquat + TLR9 antagonist (ODN2088) group, and TLR9 antagonist (ODN2088) group (n=36 per group). After paraquat 30mg/kg ip for 2, 24 and 48h, serum samples and lung tissues were collected to evaluate ALI and TLR9 signaling by lung injury score, protein levels of TLR9, MyD88, p-IRAK4, p-p65, and serum TNF-α and IL-1β levels. As for in vitro research A549 cells were randomly divided into the control group, paraquat group, paraquat + TLR9 siRNA group, and TLR9 siRNA group. After paraquat treatment for 24h, the cells and supernatant were collected to measureTLR9, TNF-α, IL-1 mRNA expression, and detect activation of NF-κB, caspase-3.

KEY FINDINGS

In vivo, the lung injury score, the TLR9, MyD88, p-IRAK4 and p-p65 protein levels, and cytokines TNF-α and IL-1β levels in paraquat group were significantly higher than that in the control group;TLR9 blocker ODN2088 pretreatment attenuated lung injury, inhibited MyD88 and NF-κB activation, and reduced TNF-α and IL-1β in serum. In vitro result shows that the gene silencing of TLR9 reduced the mRNA expression of TLR9, TNF-α and IL-1, inhibited NF-κB and caspase-3 activation, attenuated cell apoptosis.

SIGNIFICANCE

TLR9 mediates paraquat-induced ALI, antagonizing TLR9 or silencing TLR9gene may attenuate paraquat-induced ALI.

Pulmonary innate inflammatory responses to agricultural occupational contaminants

Agricultural workers are exposed to many contaminants and suffer from respiratory and other symptoms. Dusts, gases, microbial products and pesticide residues from farms have been linked to effects on the health of agricultural workers. Growing sets of data from in vitro and in vivo models demonstrate the role of the innate immune system, especially Toll-like receptor 4 (TLR4) and TLR9, in lung inflammation induced following exposure to contaminants in agricultural environments. Interestingly, inflammation and lung function changes appear to be discordant indicating the complexity of inflammatory responses to exposures. Whereas the recent development of rodent models and exposure systems have yielded valuable data, we need new systems to examine the combined effects of multiple contaminants in order to increase our understanding of farm-exposure-induced negative health effects.

Toll-like receptor 4 ablation rescues against paraquat-triggered myocardial dysfunction: Role of ER stress and apoptosis

Paraquat is a nitrogen herbicide imposing severe organ toxicity in human leading to acute lung injury and heart failure. The present study was designed to examine the impact of ablation of the innate proinflammatory mediator toll-like receptor 4 (TLR4) in paraquat-induced cardiac contractile dysfunction and the underlying mechanisms involved with a focus on endoplasmic reticulum (ER) stress and apoptosis. Adult male wild-type (WT) and TLR4 knockout (TLR4^-/- ) mice were challenged with paraquat (45 mg/kg, i.p.) for 48 h prior to the assessment of myocardial and cardiomyocyte sarcomere function, ER stress, apoptosis and inflammation. Acute paraquat challenge exerted myocardial functional and geometric alterations including enlarged left ventricular end systolic diameter (LVESD), reduced fractional shortening, decreased sarcomere shortening, maximal velocities of sarcomere shortening and relengthening associated with unchanged LV posterior wall thickness, septal thickness, LV end diastolic diameter (LVEDD), heart rate, sarcomere length, time-to-peak shortening and time-to-90% relengthening. Although TLR4 ablation did not affect mechanical properties in the heart, it significantly attenuated or ablated paraquat-induced cardiac contractile anomalies. Moreover, paraquat imposed overt ER stress, apoptosis and inflammation as evidenced by upregulation of Bip, CHOP, Caspase-3, -9, Bax, Bad, and IL-1β, phosphorylation of PERK, eIF2α and IΚB, as well as activation of the stress molecules ERK and p38, with unchanged Caspase-8, Bcl2, TNF-α, p53, HMGB1, MyD88 and phosphorylation of Akt, GSK3β and JNK, the effects of which were attenuated or negated by TLR4 knockout. Taken together, our results suggested that TLR4 ablation alleviated paraquat-induced myocardial contractile dysfunction possibly through attenuation of ER stress, apoptosis and inflammation. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 656-668, 2017.