Inhibition of lipopolysaccharide induced acute inflammation in lung by chlorination

Inhalation of ferrate-disinfected Escherichia coli caused lung injury via endotoxin-induced oxidative stress and inflammation response

Ferrate (Fe(VI)) is an environmentally friendly disinfectant that is widely used to eradicate microbes in reclaimed water. However, the potential health risks associated with inhalation of Fe(VI)-treated bacteria-laden reclaimed water remains uncertain. We aimed to explore the inhalation hazards and potential mechanisms of K2FeO4-treated Escherichia coli (E. coli, ATCC 25922). Our findings indicated that Fe(VI) disinfection induced a dose- and time-dependent E. coli inactivation, accompanied by a rapid release of the bacterial endotoxin, lipopolysaccharide (LPS). Scanning electron microscopy (SEM) observations indicate that Fe(VI)-induced endotoxin production consists of at least two stages: initial binding of endotoxin to bacteria and subsequent dissociation to release free endotoxin. Furthermore, Fe(VI) disinfection was not able to effectively eliminate pure or E. coli-derived endotoxins. The E. coli strain used in this study lacks lung infection capability, thus the inhalation of bacteria alone failed to induce severe lung injury. However, mice inhaled exposure to Fe(VI)-treated E. coli showed severe impairment of lung structure and function. Moreover, we observed an accumulation of neutrophil/macrophage recruitment, cell apoptosis, and ROS generation in the lung tissue of mice subjected to Fe(VI)-treated E. coli. RNA sequencing (RNA-seq) and PCR results revealed that genes involved with endotoxin stimuli, cell apoptosis, antioxidant defence, inflammation response, chemokines and their receptors were upregulated in response to Fe(VI)-treated E. coli. In conclusion, Fe(VI) is ineffective in eliminating endotoxins and can trigger secondary hazards owing to endotoxin release from inactivated bacteria. Aerosol exposure to Fe(VI)-treated E. coli causes considerable damage to lung tissue by inducing oxidative stress and inflammatory responses.

TLR4-MyD88 signaling pathway is responsible for acute lung inflammation induced by reclaimed water

Previous research found that inhalation exposure of reclaimed water could cause severe pulmonary inflammation, and the endotoxin was proposed to be the key risk factor. To further support this view, the toxic effects of different reclaimed water induced by acute inhalation exposure were compared between wildtype C57BL/6J and TLR4 signaling pathway defect mice. It was found that reclaimed water with high levels of endotoxin could induce strong inflammation in wildtype mice, but not in Tlr4^-/- and MyD88^-/- mutants. The mixed bacterial culture from the reclaimed water showed very weak response in wildtype mice and no response in TLR4-signaling pathway deficient mice, which further suggested that the cell-bound endotoxins contribute little in the inflammation induced by reclaimed water. In addition, conditional knockout of the Tlr4 gene in myeloid cells resulted in a significant reduction of sensitivity to the reclaimed water in mutants, which indicates that myeloid cells play the most important role in the defensive immune system against the pollutants in the water. In general, this study demonstrated that the TLR4-MyD88 signaling pathway is responsible for the acute lung inflammation induced by reclaimed water, which excludes the possibility of other signaling pathway dependent inflammation inducers in reclaimed water.

Size distribution, biological characteristics and emerging contaminants of aerosols emitted from an urban wastewater treatment plant

Air-liquid exchange process could spread pathogens and pharmaceutical emerging pollutants into the air as aerosol particles in an Urban wastewater treatment plants (UWTPs). These particles can later be transported to places where such pollution is unforeseen. In this study, measurements were conducted in the aeration area of a UWTP in northern Taiwan. According to this investigation, nanoparticles are major contributors to both the number and volume concentration of particles. Most fluorescent particles may be bacterial aggregates or fungal species. Moreover, nine common emerging contaminants were analyzed and found in both air and water samples. Among these contaminants, the most abundant chemicals in the air were erythromycin-H₂O (191.45 pg/m³) and methamphetamine (39.02 pg/m³). These results imply that UWTPs could be an emission source of emerging contaminants and bioaerosols, and the potential risk of inhalation exposure should be carefully evaluated.

Bioassay: A useful tool for evaluating reclaimed water safety

Wastewater reclamation and reuse has been proved to be an effective way to relieve the fresh water crisis. However, toxic contaminants remaining in reclaimed water could lead to potential risk for reuse, and the conventional water quality standards have difficulty guaranteeing the safety of reclaimed water. Bioassays can vividly reflect the integrated biological effects of multiple toxic substances in water as a whole, and could be a powerful tool for evaluating the safety of reclaimed water. Therefore, in this study, the advantages and disadvantages of using bioassays for evaluating the safety of reclaimed water were compared with those of conventional water quality standards. Although bioassays have been widely used to describe the toxic effects of reclaimed water and treatment efficiency of reclamation techniques, a single bioassay cannot reflect the complex toxicity of reclaimed water, and a battery of bioassays involving multiple biological effects or in vitro tests with specific toxicity mechanisms would be recommended. Furthermore, in order to evaluate the safety of reclaimed water based on bioassay results, various methods including potential toxicology, the toxicity unit classification system, and a potential eco-toxic effects probe are summarized as well. Especially, some integrated ranking methods based on a bioassay battery involving multiple toxicity effects are recommended as useful tools for evaluating the safety of reclaimed water, which will benefit the promotion and guarantee the rapid development of the reclamation and reuse of wastewater.

Effects of chlorination and combined UV/Cl2 treatment on endotoxin activity and inhalation toxicity of lipopolysaccharide, gram-negative bacteria and reclaimed water

Disinfection processes were applied in reclaimed water plant to eliminate pathogens and control the related health risk during water reuse. However, extra problems might emerge such as the released free endotoxins from the ruptured cell wall of gram-negative bacteria. Endotoxins can induce lung inflammatory responses after inhalation, which has been neglected in the water quality regulation, and the removal of endotoxin was not under consideration in the process of reclamation. In the present study, two well-known disinfection processes, chlorination and combined UV/chlorine (UV/Cl₂), were performed to test the removal efficiency of endotoxin activity, as well as the inflammation inducing ability. In the pure LPS solution, UV/Cl₂ treatment significantly reduced both endotoxin activity and lung inflammation responses with better oxidizability of the generated hydroxyl radical. However, its performance on bacteria liquid and real secondary effluent was more complicated. The cell wall-bound LPS have lower endotoxin activities and inflammation inducing ability. Immediately after the cell wall was destroyed, the bound LPS were released to the solution to be free LPS, which dramatically increased both the endotoxin activity and inflammation inducing ability of the water. When these free endotoxins were continuously oxidized, the endotoxin activity and inflammatory response decreased again but not to the background level. Therefore, the inflammation inducing ability of reclaimed water could not be removed efficiently. These results suggest that in spite of its high oxidability, UV/Cl₂ treatment is not capable of removing the endotoxin-based toxicity, and other technologies are necessary to control endotoxin levels in reclaimed water.

Effects of ozonation on the activity of endotoxin and its inhalation toxicity in reclaimed water

Aerosolized reclaimed water can cause inflammatory responses in lung after inhalation, and endotoxin has been identified as the main inducer. Since the effects of disinfection treatments on endotoxins had conflicting results, this study explored the changes of endotoxin activity and inflammation inducing ability of reference endotoxin, gram-negative bacteria solutions and reclaimed water after ozonation respectively, and found that LAL assay based endotoxin activity and mouse inhalation exposure based inflammation examination had inconsistent results. The excessive ozone could not remove the endotoxin activity, but was able to reduce the inflammation inducing ability of free endotoxin. When treating on gram-negative strains, ozone first released the cell-bound endotoxin and caused the dramatic increase of endotoxin activity. But for the inflammatory response, despite the rapid increase at the very beginning, it immediately dropped back with further ozonation. The endotoxin aggregate size was proposed as a key regulator of the toxicity of endotoxin, which was modified by ozone oxidation. In real reclaimed water, insufficient ozone significantly enhanced the inflammatory response, but when the ozone dosages were large enough, the inflammation could be drawn back to the original level, which was consistent with the observations from pure endotoxin and bacteria. This work demonstrates that the endotoxin activity cannot predict the endotoxin-induced toxicity of ozone treated water, and low dosage of ozone treatment may even increase the health risk of reclaimed water.

YiQiFuMai lyophilized injection attenuates particulate matter-induced acute lung injury in mice via TLR4-mTOR-autophagy pathway

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are the serious diseases that are characterized by a severe inflammatory response of lung injuries and damage to the microvascular permeability, frequently resulting in death. YiQiFuMai (YQFM) lyophilized injection powder is a redeveloped preparation based on the well-known traditional Chinese medicine formula Sheng-Mai-San which is widely used in clinical practice in China, mainly for the treatment of microcirculatory disturbance-related diseases. However, there is little information about its role in ALI/ARDS. The aim of this study was to determine the protective effect of YQFM on particulate matter (PM)-induced ALI. The mice were intratracheally instilled with 50 mg/kg body weight of Standard Reference Material1648a (SRM1648a) in the PM-induced group. The mice in the YQFM group were given YQFM (three doses: 0.33, 0.67, and 1.34 g/kg) by tail vein injection 30 min after the intratracheal instillation of PM. The results showed that YQFM markedly reduced lung pathological injury and the lung wet/dry weight ratios induced by PM. Furthermore, we also found that YQFM significantly inhibited the PM-induced myeloperoxidase (MPO) activity in lung tissues, decreased the PM-induced inflammatory cytokines including interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α), reduced nitric oxide (NO) and total protein in bronchoalveolar lavage fluids (BALF), and effectively attenuated PM-induced increases lymphocytes in BALF. In addition, YQFM increased mammalian target of rapamycin (mTOR) phosphorylation and dramatically suppressed the PM-stimulated expression of toll-like receptor 4 (TLR4), MyD88, autophagy-related protein LC3Ⅱand Beclin 1 as well as autophagy. In conclusion, these findings indicate that YQFM had a critical anti-inflammatory effect due to its ability to regulate both TLR4-MyD88 and mTOR-autophagy pathways, and might be a possible therapeutic agent for PM-induced ALI.

Sub-chronic inhalation of reclaimed water-induced fibrotic lesion in a mouse model

When reclaimed water is used as municipal miscellaneous water, acute exposure of the generated aerosol with high levels of endotoxins can cause severe inflammation in the lungs. However, the potential risks of long-term inhalation of reclaimed water remains unclear. To identify the adverse effects of sub-chronic reclaimed water inhalation and explain the underlying mechanisms, a mouse model of 12-week sub-chronic exposure was established, and wastewater before a membrane bioreactor (MBR, positive control) and the MBR effluent (reclaimed water, which met the quality standard of urban use and was currently used for landscape irrigation) were tested in this study. The exposure dose was set to approach the real working scenarios. Lung lavage and histology were analyzed. Obvious epithelial cell apoptosis in the bronchi was observed, along with the accumulation of myofibroblasts and the collagen deposition both in main bronchi and terminal bronchioles. All these symptoms were persistent after 4 weeks of recovery. Inflammation and induced bronchus-associated lymphoid tissues (iBALT) were also observed but diminished after recovery indicating inflammation may not be the direct cause of the symptom. Furthermore, two fibrogenic cytokines (TNF-α and TGF-β) were constantly high in the lung during the study. They might be the biomarkers of lung damage after the inhalation of reclaimed water. Adaptive immune responses were also detected as elevated levels of IgG and IgA, but not for IgE. Inhalation of reclaimed water causes sustained fibrotic lesions in the lungs, which suggests potential health risks during urban application where aerosols generated.

Solar light irradiation significantly reduced cytotoxicity and disinfection byproducts in chlorinated reclaimed water

Chlorinated reclaimed water is widely used for landscaping and recreational purposes, resulting in human exposure to toxic disinfection byproducts. Although the quality of chlorinated reclaimed water might be affected by sunlight during storage, the effects of solar light irradiation on the toxicity remain unknown. This study investigated the changes in cytotoxicity and total organic halogen (TOX) of chlorinated reclaimed water exposed to solar light. Irradiation with solar light for 12 h was found to significantly reduce the cytotoxicity of chlorinated reclaimed water by about 75%, with ultraviolet light being responsible for the majority of this reduction. Chlorine residual in reclaimed water tended to increase the cytotoxicity, and the synergy between solar light and free chlorine could not enhance the reduction of cytotoxicity. Adding hydroxyl radical scavengers revealed that the contribution of hydroxyl radical to cytotoxicity reduction was limited. Solar light irradiation concurrently reduced TOX. The low molecular weight (<1 kDa) fraction was the major contributor of cytotoxicity and TOX in chlorinated reclaimed water. Detoxification of the low molecular weight fraction by light irradiation was mainly a result of TOX dehalogenation, while detoxification of the high molecular weight (>1 kDa) fraction was probably caused by photoconversion from high toxic TOX to low toxic TOX.

Mitochondria-mediated oxidative stress induced by desert dust in rat alveolar macrophages

Exposure to ambient particulate matter (PM), including PM from resuspension of soils and dusts, increases the risk for respiratory diseases. However, the exact mechanism of PM-mediated damage to the lungs remains unclear. Due to recent increases in the frequency of dust storms in many areas, we examined the cytotoxic effects of soil-dust samples collected in an arid zone in Israel on rat lung macrophages. The desert soil contains soil crusts and low levels of toxic metal content. Exposure of cells to water extracts from the dust samples caused significant reduction in the concentration of live cells and overall cell viability. The dust samples induced cell death through apoptosis, mitochondrial dysfunction, and increased mitochondrial lipid peroxidation. The dust samples generated more reactive oxygen species (ROS) compared to control-treated samples and National Institute of Standards and Technology San Joaquin Valley standard reference material. To assess whether the oxidative imbalance induced by dust extract also interferes with the antioxidant defense, we evaluated phase II detoxifying and antioxidant enzymes, which are Nrf2 classical targets. The Nrf2 transcription factor is a master regulator of cellular adaptation to stress. The dust extracts produced a significant increase in phase II detoxifying genes. This work suggests that the health-related injury observed in rat lung cells exposed to dust extracts is associated with ROS generation, mitochondrial dysfunction, mitochondrial lipid peroxidation, and cellular antioxidant imbalance. Damage to lung mitochondria may be an important mechanism by which dust-containing bacterial material induces lung injury upon inhalation.

Effects of lipopolysaccharide, multiwalled carbon nantoubes, and the combination on lung alveolar epithelial cells

Multiwalled carbon nanotubes (MWCNT) have been shown to induce lung fibrosis in animal models, however the underlying molecular factors/mechanisms are still unclear. In this study, we investigated the effects of lipopolysaccharide (LPS), MWCNT, and the combination of LPS and MWCNT on the expression of matrix metalloproteinase-9 and metalloproteinase-12 (MMP-9, MMP-12), collagen 3A1 (Col3A1), and transforming growth factor beta (TGFβ) in alveolar epithelial A549 cells. MMPs are proteinases that degrade extracellular matrix and play a role in lung fibrosis. A549 cells were exposed to LPS (1 ng/mL), MWCNT (20 μg/mL), and the combination and analyzed for paracellular permeability, TGFβ, Col3A1, MMP-9, MMP-12, NF-κB activation, and cell migration by real-time PCR and immunofluorescence. LPS, the combination of LPS and MWCNT, and MWCNT only at the highest tested dose induced blue dextran extravasation. LPS and MWCNT increased the expression of TGFβ and its downstream target gene Col3A, and MMP-9 and MMP-12 mRNA. MWCNT potently induced cell migration toward wound healing, whereas LPS slightly induced cell migration. Both, LPS and MWCNT, induced NF-κB nuclear translocation. Our results indicate that MWCNT activated alveolar epithelial cells to promote fibrogenesis, and that LPS differentially primes molecular factors involved in lung remodeling. These findings suggest a role of alveolar epithelial cells in fibrogenesis and also may aid in the design and development of tests for screening of fibrogenic agents. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 445-455, 2017.

Endotoxins: The Critical Risk Factor in Reclaimed Water via Inhalation Exposure

The use of reclaimed water for nonpotable uses requires consideration of potential adverse health effects. Considering that inhalation can be a significant route of transmission of microorganisms and inflammatory agents, this study used a mouse model to test the possible adverse effects of reclaimed water use during car washing where aerosols are generated. Intensive innate immune responses were found in the lungs after acute exposure, and the lavage polymorphonuclear cell proportion was the most sensitive end point. Four types of evidence are presented to demonstrate that the main risk factor that initiates innate inflammation is the free endotoxin. (1) Small molecules (<10 kDa) cannot induce inflammation. (2) The endotoxin levels of 11 water samples from five different plants showed positive correlations with inflammatory responses. (3) Actual water samples showed similar activities with free endotoxins other than bacterially bound endotoxins. (4) Specific removal of endotoxins with polymyxin B affinity chromatography further confirmed the role of free endotoxins. It is noteworthy that 62.9% of the investigated tertiary-treated water had endotoxin levels higher than the allowable acute threshold (120 endotoxin units/mL) under the hypothesized car wash condition, which strongly suggests the need to carefully consider the water treatment steps required to produce safe water for various reclaimed water end uses.

Lonicera caerulea berry extract suppresses lipopolysaccharide-induced inflammation via Toll-like receptor and oxidative stress-associated mitogen-activated protein kinase signaling

The protective effects of Lonicera caerulea berry extract (LCBE) against hepatic inflammation and the underlying mechanisms were investigated in a rat model of lipopolysaccharide (LPS)-induced chronic liver inflammation.