Short-interval exposure to ambient fine particulate matter (PM2.5) exacerbates the susceptibility of pulmonary damage in setting of lung ischemia-reperfusion injury in rodent: Pharmacomodulation of melatonin

Oxidative stress is the pivot for PM2.5-induced lung injury

Fine particulate matter (PM2.5) is a primary air pollutant recognized worldwide as a serious threat to public health. PM2.5, which has a diameter of less than 2.5 μm, is known to cause various diseases, including cardiovascular, respiratory, metabolic, and neurological diseases. Studies have shown that the respiratory system is particularly susceptible to PM2.5 as it is the first line of defense against external pollutants. PM2.5 can cause oxidative stress, which is triggered by the catalyzation of biochemical reactions, the activation of oxidases and metabolic enzymes, and mitochondrial dysfunction, all of which can lead to lung injury and aggravate various respiratory diseases including chronic obstructive pulmonary disease (COPD), asthma, pulmonary fibrosis, and cancer. Oxidative stress plays a crucial role in the harmful effects and mechanisms of PM2.5 on the respiratory system by activating several detrimental pathways related to inflammation and cellular damage. However, experimental studies have shown that antioxidative therapy methods can effectively cure PM2.5-induced lung injury. This review aims to clarify how PM2.5 induces oxidative stress and the mechanisms by which it is involved in the aggravation of various lung diseases. Additionally, we have listed antioxidant treatments to protect against PM2.5-induced lung injury.

Protective effects of inhaled antioxidants against air pollution-induced pathological responses

As the public health burden of air pollution continues to increase, new strategies to mitigate harmful health effects are needed. Dietary antioxidants have previously been explored to protect against air pollution-induced lung injury producing inconclusive results. Inhaled (pulmonary or nasal) administration of antioxidants presents a more promising approach as it could directly increase antioxidant levels in the airway surface liquid (ASL), providing protection against oxidative damage from air pollution. Several antioxidants have been shown to exhibit antioxidant, anti-inflammatory, and anti-microbial properties in in vitro and in vivo models of air pollution exposure; however, little work has been done to translate these basic research findings into practice. This narrative review summarizes these findings and data from human studies using inhaled antioxidants in response to air pollution, which have produced positive results, indicating further investigation is warranted. In addition to human studies, cell and murine studies should be conducted using more relevant models of exposure such as air-liquid interface (ALI) cultures of primary cells and non-aqueous apical delivery of antioxidants and pollutants. Inhalation of antioxidants shows promise as a protective intervention to prevent air pollution-induced lung injury and exacerbation of existing lung disease.

Astaxanthin protected against the adverse effects induced by diesel exhaust particulate matter via improving membrane stability and anti-oxidative property

Diesel exhaust particulate matter (DPM), which has been clarified as a Group I carcinogenic agent, is still challenging in its detoxification due to the complex composition and toxic mechanisms. Astaxanthin (AST) is a pleiotropic small biological molecule widely used in medical and healthcare with surprising effects and applications. The present study aimed to investigate the protective effects of AST on DPM-induced injury and the underlying mechanism. Our results indicated that AST significantly suppressed the generation of phosphorylated histone H2AX (γ-H2AX, marker of DNA damage) and inflammation caused by DPM both in vitro and in vivo. Mechanistically, AST prevented the endocytosis and intracellular accumulation of DPM via regulating the stability and fluidity of plasma membranes. Moreover, the oxidative stress elicited by DPM in cells could also be effectively inhibited by AST, together with protecting the structure and function of mitochondria. These investigations provided clear evidence that AST notably reduced DPM invasion and intracellular accumulation by modulating the membrane-endocytotic pathway, which eventually reduced intracellular oxidative stress caused by DPM. Our data might provide a novel clue for curing and treating the harmful effects of particulate matter.

Alveolar Type II Cell Damage and Nrf2-SOD1 Pathway Downregulation Are Involved in PM2.5-Induced Lung Injury in Rats

The general toxicity of fine particulate matter (PM_2.5) has been intensively studied, but its pulmonary toxicities are still not fully understood. To investigate the changes of lung tissue after PM_2.5 exposure and identify the potential mechanisms of pulmonary toxicity, PM_2.5 samples were firstly collected and analyzed. Next, different doses of PM_2.5 samples (5 mg/kg, 10 mg/kg, 20 mg/kg) were intratracheally instilled into rats to simulate lung inhalation of polluted air. After instillation for eight weeks, morphological alterations of the lung were examined, and the levels of oxidative stress were detected. The data indicated that the major contributors to PM_2.5 mass were organic carbon, elemental carbon, sulfate, nitrate, and ammonium. Different concentrations of PM_2.5 could trigger oxidative stress through increasing reactive oxygen species (ROS) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels, and decreasing expression of antioxidant-related proteins (nuclear factor erythroid 2-related factor 2 (Nrf2), superoxide dismutase 1 (SOD1) and catalase). Histochemical staining and transmission electron microscopy displayed pulmonary inflammation, collagen deposition, mitochondrial swelling, and a decreasing number of multilamellar bodies in alveolar type II cells after PM_2.5 exposure, which was related to PM_2.5-induced oxidative stress. These results provide a basis for a better understanding of pulmonary impairment in response to PM_2.5.

Ropivacaine has the potential to relieve PM2.5‑induced acute lung injury

Ropivacaine is a commonly used local anesthetic in the clinic due to its low toxicity to the cardiovascular system or central nervous system, good tolerance and high clearance rate. The present study intended to investigate the effect of ropivacaine on PM2.5-induced acute lung injury (ALI) and reveal the underlying mechanism. After ropivacaine exposure, cell viability, oxidative stress and inflammation in PM2.5-induced BEAS-2B cells were assessed by Cell Counting Kit-8 and DCFH-DA staining, corresponding commercial kits and ELISA, respectively. The effects of ropivacaine on the expression of MMP9 and MMP12 and the proteins related to NLRP3/Caspase-1 signaling were then determined by western blot and reverse transcription-quantitative PCR analyses. In addition, NLR family pyrin domain containing 3 (NLRP3) agonist monosodium urate (MSU) was used to treat BEAS-2B cells followed by ropivacaine treatment and the effects on the above-mentioned cellular behaviors were determined again. The results indicated that the viability of BEAS-2B cells was decreased after PM2.5 induction, accompanied by aggravated oxidative stress and inflammation. However, ropivacaine alleviated oxidative stress and inflammation in PM2.5-induced BEAS-2B cells in a dose-dependent manner. Ropivacaine was also indicated to decrease the expression levels of NLRP3/Caspase-1 signaling-related proteins in PM2.5-induced BEAS-2B cells. Furthermore, cell viability was decreased, while oxidative stress and inflammatory response were aggravated, in PM2.5-induced BEAS-2B cells treated with MSU. In summary, the present results implied that ropivacaine exerted protective effects on PM2.5-induced ALI, and this effect may be related to NLRP3/Caspase-1 signaling.

Mechanism of biochanin A alleviating PM2.5-induced oxidative damage based on an XRCC1 knockout BEAS-2B cell model

PM_2.5 induces oxidative/antioxidant system imbalance and excessive release of reactive oxygen species (ROS) and produces toxic effects and irreversible damage to the genetic material including chromosomes and DNA. Biochanin A (BCA), an isoflavone with strong antioxidant activity, effectively intervenes against PM_2.5-induced oxidative damage. The X-ray repair cross-complementary protein 1 (XRCC1)/BER pathway involves DNA damage repair caused by oxidative stress. This paper aims to explore the mechanism of BCA alleviating oxidative DNA damage caused by PM_2.5 by establishing the in vitro cell model based on CRISPR/Cas9 technology and combining it with mechanism pathway research. The results showed that PM_2.5 exposure inhibited the expression of BER and NER pathway proteins and induced the overexpression of ERCC1. BCA showed an effective intervention in the toxicity of PM_2.5 in normal cells, rather than XRCC1 knock-out cells. This laid a foundation for further exploring the key role of XRCC1 in PM_2.5-caused oxidative damage and the BER/DNA damage repair pathway.

Acute exposure to PM2.5 triggers lung inflammatory response and apoptosis in rat

Severe haze events, especially with high concentration of fine particulate matter (PM_2.5), are frequent in China, which have gained increasing attention among public. The purpose of our study was explored the toxic effects and potential damage mechanisms about PM_2.5 acute exposure. Here, the diverse dosages of PM_2.5 were used to treat SD rats and human bronchial epithelial cell (BEAS-2B) for 24 h, and then the bioassays were performed at the end of exposure. The results show that acute exposure to diverse dosages of PM_2.5 could trigger the inflammatory response and apoptosis. The severely oxidative stress may contribute to the apoptosis. Also, the activation of Nrf2-ARE pathway was an important compensatory process of antioxidant damage during the early stage of acute exposure to PM_2.5. Furthermore, the HO-1 was suppression by siRNA that promoted cell apoptosis triggered by PM_2.5. In other words, enhancing the expression of HO-1 may mitigate the cell apoptosis caused by acute exposure to PM_2.5. In summary, our findings present the first time that prevent or mitigate the damage triggered by PM_2.5 through antioxidant approaches was a promising strategy.

Enhanced Cerebral Microbleeds by Long-Term Air Pollution Exposure in Spontaneously Hypertensive Rats

BACKGROUND

Cerebral microbleeds (CMBs) are associated with a high risk for stroke . The present study determined whether long-term exposure to PM2.5 results in progressive worsening of CMBs and induction of systemic inflammation and microvascular oxidative stress.

METHODS

Sixteen male Spontaneously hypertensive rats (SHR) and eight Wistar-Kyoto (WKY) rats were exposed to either filtered air or PM2.5 for 12 months. To detect CMBs, rats were imaged using a 7-T MRI. To determine systemic inflammation and oxidative stress, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), as well as reactive oxygen species (ROS), NADPH activity and its subunits p22/47/67phox & gp91phox were measured.

RESULTS

During the exposure period, the mean daily concentration of PM2.5 was 59.2 ± 1.0 μg/m³. PM2.5 exposure significantly increased the incidence of CMBs compared to the PM2.5 (-) group (37.5% vs 12.5% incidence rate, p < 0.001). Animals exposed to PM2.5 also had significantly increased systolic blood pressures (SBPs) at 3 months (173 ± 5 vs 157 ± 5 mmHg, p < 0.05), 6 months (218 ± 6 vs 193 ± 7 mmHg, p < 0.01), 9 months (222 ± 6 vs 203 ± 8 mmHg, p < 0.05), and 12 months (231 ± 4 vs 207 ± 5 mmHg, p = 0.01). Additionally, there were significant elevations in IL-6, MCP-1, and TNF-α in the exposed group. Furthermore, PM2.5 significantly increased NOX activity and protein levels of gp91phox and p22/47/67phox.

CONCLUSION

In the SHR model, long-term exposure to PM2.5 worsened CMBs, increased SBPs, induced systemic inflammation and oxidative stress. Therefore, PM2.5 is potentially a controllable risk factor that promotes CMBs in certain patients, such as those with hypertension.

Different co-culture models reveal the pivotal role of TBBPA-promoted M2 macrophage polarization in the deterioration of endometrial cancer

Tetrabromobisphenol A (TBBPA), an emerging organic pollutant widely detected in human samples, has a positive correlation with the development of endometrial cancer (EC), but its underlying mechanisms have not yet been fully elucidated. Tumor-associated macrophages (TAM), one of the most vital components in tumor microenvironment (TME), play regulatory roles in the progression of EC. Consequently, this study mainly focuses on the macrophage polarization in TME to unveil the influence of TBBPA on the progression of EC and involved mechanisms. Primarily, low doses of TBBPA treatment up-regulated M2-like phenotype biomarkers in macrophage. The data from in vitro co-culture models suggested TBBPA-driven M2 macrophage polarization was responsible for the EC deterioration. Results from in vivo study further confirmed the malignant proliferation of EC promoted by TBBPA. Mechanistically, TBBPA-mediated miR-19a bound to the 3'-UTR regions of SOCS1, resulting in down-regulation of SOCS1 followed by the phosphorylation of JAK and STAT6. The present study not only revealed for the first time the molecular mechanism of TBBPA-induced EC's deterioration based on macrophage polarization, but also established co-culture models, thus providing a further evaluation method for the exploration of environmental pollutants-induced tumor effects from the role of TME.

Particulate matter air pollutants and cardiovascular disease: Strategies for intervention

Air pollution is consistently linked with elevations in cardiovascular disease (CVD) and CVD-related mortality. Particulate matter (PM) is a critical factor in air pollution-associated CVD. PM forms in the air during the combustion of fuels as solid particles and liquid droplets and the sources of airborne PM range from dust and dirt to soot and smoke. The health impacts of PM inhalation are well documented. In the US, where CVD is already the leading cause of death, it is estimated that PM2.5 (PM < 2.5 μm in size) is responsible for nearly 200,000 premature deaths annually. Despite the public health data, definitive mechanisms underlying PM-associated CVD are elusive. However, evidence to-date implicates mechanisms involving oxidative stress, inflammation, metabolic dysfunction and dyslipidemia, contributing to vascular dysfunction and atherosclerosis, along with autonomic dysfunction and hypertension. For the benefit of susceptible individuals and individuals who live in areas where PM levels exceed the National Ambient Air Quality Standard, interventional strategies for mitigating PM-associated CVD are necessary. This review will highlight current state of knowledge with respect to mechanisms for PM-dependent CVD. Based upon these mechanisms, strategies for intervention will be outlined. Citing data from animal models and human subjects, these highlighted strategies include: 1) antioxidants, such as vitamins E and C, carnosine, sulforaphane and resveratrol, to reduce oxidative stress and systemic inflammation; 2) omega-3 fatty acids, to inhibit inflammation and autonomic dysfunction; 3) statins, to decrease cholesterol accumulation and inflammation; 4) melatonin, to regulate the immune-pineal axis and 5) metformin, to address PM-associated metabolic dysfunction. Each of these will be discussed with respect to its potential role in limiting PM-associated CVD.

Ma xing shi gan decoction eliminates PM2.5-induced lung injury by reducing pulmonary cell apoptosis through Akt/mTOR/p70S6K pathway in rats

The present study was designed to investigate the anti-apoptosis effect of Ma xing shi gan decoction (MXD) on PM2.5-induced lung injury via protein kinase B (Akt)/mTOR/p70S6K pathway. A UPLC-MS/MS system was introduced for component analysis of MXD. Rats were instilled with PM2.5 solution suspension intratracheally to induce acute lung injury. The rats were then orally administered with MXD (16, 8, and 4 g/kg) once a day for 7 consecutive days. The therapeutic effects of MXD were evaluated by Hematoxylin and Eosin (HE) staining. The apoptotic cell death was analyzed by terminal-deoxynucleotidyl transferase-mediated nick-end labeling (TUNEL) assay. The alterations in cytochrome c (Cytc) and cleaved-caspase-3 (C-caspase-3) were measured by immunohistochemistry (IHC). The expressions of Bax, B-cell lymphoma 2 (Bcl-2), p-Akt, p-mTOR and p-p70S6K were detected by Western blot. In vitro, PM2.5 exposure model was introduced in A549 cell, followed by incubation with MXD-medicated serum. Hoechst staining was used to determine apoptotic rate. The levels of Bax, Bcl-2, p-Akt, p-mTOR and p-p70S6K were detected by Western blot. Our results in vivo indicated that treatment with MXD decreased histopathological changes score, TUNEL-positive cells rate, expressions of Cytc and C-caspase-3. The in vitro results revealed that incubation with MXD-mediated serum decreased apoptotic rate. Both results in vivo and in vitro demonstrated that MXD inhibited pro-apoptotic protein Bax and promoted anti-apoptotic protein Bcl-2 expression. Likewise, MXD activated Akt/mTOR/p70S6K signal pathway, which was also confirmed by Western immunoblotting. In conclusion, MXD attenuates lung injury and the underlying mechanisms may relate to regulating the apoptosis via Akt/mTOR/p70S6K signaling pathway activation.

Melatonin ameliorates PM2.5 -induced cardiac perivascular fibrosis through regulating mitochondrial redox homeostasis

Fine particulate matter (PM2.5 ) exposure is correlated with the risk of developing cardiac fibrosis. Melatonin is a major secretory product of the pineal gland that has been reported to prevent fibrosis. However, whether melatonin affects the adverse health effects of PM2.5 exposure has not been investigated. Thus, this study was aimed to investigate the protective effect of melatonin against PM2.5 -accelerated cardiac fibrosis. The echocardiography revealed that PM2.5 had impaired both systolic and diastolic cardiac function in ApoE-/- mice. Histopathological analysis demonstrated that PM2.5 induced cardiomyocyte hypertrophy and fibrosis, particularly perivascular fibrosis, while the melatonin administration was effective in alleviating PM2.5 -induced cardiac dysfunction and fibrosis in mice. Results of electron microscopy and confocal scanning laser microscope confirmed that melatonin had restorative effects against impaired mitochondrial ultrastructure and augmented mitochondrial ROS generation in PM2.5 -treated group. Further investigation revealed melatonin administration could significantly reverse the PM2.5 -induced phenotypic modulation of cardiac fibroblasts into myofibroblasts. For the first time, our study found that melatonin effectively alleviates PM2.5 -induced cardiac dysfunction and fibrosis via inhibiting mitochondrial oxidative injury and regulating SIRT3-mediated SOD2 deacetylation. Our findings indicate that melatonin could be a therapy medicine for prevention and treatment of air pollution-associated cardiac diseases.

Hepatic 31 P-magnetic resonance spectroscopy identified the impact of melatonin-pretreated mitochondria in acute liver ischaemia-reperfusion injury

Acute liver ischaemia-reperfusion injury (IRI), commonly encountered during liver resection and transplantation surgery, is strongly associated with unfavourable clinical outcome. However, a prompt and accurate diagnosis and the treatment of this entity remain formidable challenges. This study tested the hypothesis that ³¹ P-magnetic resonance spectroscopy (³¹ P-MRS) findings could provide reliable living images to accurately identify the degree of acute liver IRI and melatonin-pretreated mitochondria was an innovative treatment for protecting the liver from IRI in rat. Adult male SD rats were categorized into group 1 (sham-operated control), group 2 (IRI only) and group 3 (IRI + melatonin [ie mitochondrial donor rat received intraperitoneal administration of melatonin] pretreated mitochondria [10 mg/per rat by portal vein]). By the end of study period at 72 hours, ³¹ P-MRS showed that, as compared with group 1, the hepatic levels of ATP and NADH were significantly lower in group 2 than in groups 1 and 3, and significantly lower in group 3 than in group 1. The liver protein expressions of mitochondrial-electron-transport-chain complexes and mitochondrial integrity exhibited an identical pattern to ³¹ P-MRS finding. The protein expressions of oxidative stress, inflammatory, cellular stress signalling and mitochondrial-damaged biomarkers displayed an opposite finding of ³¹ P-MRS, whereas the protein expressions of antioxidants were significantly progressively increased from groups 1 to 3. Microscopic findings showed that the fibrotic area/liver injury score and inflammatory and DNA-damaged biomarkers exhibited an identical pattern of cellular stress signalling. Melatonin-pretreated mitochondria effectively protected liver against IRI and ³¹ P-MRS was a reliable tool for measuring the mitochondrial/ATP consumption in living animals.

Combined Therapy With Hyperbaric Oxygen and Melatonin Effectively Reduce Brain Infarct Volume and Preserve Neurological Function After Acute Ischemic Infarct in Rat

This study tested the hypothesis that combined hyperbaric oxygen (HBO) and melatonin (Mel) was superior to either one for protecting the brain functional and parenchymal integrity from acute ischemic stroke (IS) injury. Adult-male Sprague-Dawley rats were divided into groups 1 (sham-operated control), 2 (IS), 3 (IS + HBO), 4 (IS + Mel), and 5 (IS + HBO-Mel). By day 28 after IS, the brain infarct area (BIA) was lowest in group 1, highest in group 2, significantly higher in groups 3 and 4 than in group 5, but not different between groups 3 and 4. The neurological function at day 7, 14, and 28 exhibited an opposite pattern to BIA among the 5 groups. The protein expressions of inflammatory (IL-1β/IL-6/iNOS/TNF-α/p-NF-κB), apoptotic (cleaved-caspase3/cleaved-PARP/mitochondrial Bax), mitochondrial/DNA-damaged (cytochrome-C/γ-H2AX), oxidative stress (NOX-1/NOX-2), and autophagy (i.e. ratio of CL3B-II/CL3B-I) biomarkers displayed an identical pattern of BIA among 5 groups. Cellular expressions of inflammation (F4/80+/GFAP+) and DNA-damaged biomarker (γ-H2AX+) exhibited an identical pattern, whereas the integrities of myelin sheath/neuron (MPB+/NeuN+), endothelial cell (CD31+/vWF+), and number of small vessels exhibited an opposite pattern of BIA among the 5 groups. Combined HBO-Mel therapy offered an additional benefit in protecting the brain against IS injury.

Immune-pineal axis protects rat lungs exposed to polluted air

Environmental pollution in the form of particulate matter <2.5 μm (PM_2.5 ) is a major risk factor for diseases such as lung cancer, chronic respiratory infections, and major cardiovascular diseases. Our goal was to show that PM_2.5 eliciting a proinflammatory response activates the immune-pineal axis, reducing the pineal synthesis and increasing the extrapineal synthesis of melatonin. Herein, we report that the exposure of rats to polluted air for 6 hours reduced nocturnal plasma melatonin levels and increased lung melatonin levels. Melatonin synthesis in the lung reduced lipid peroxidation and increased PM_2.5 engulfment and cell viability by activating high-affinity melatonin receptors. Diesel exhaust particles (DEPs) promoted the synthesis of melatonin in a cultured cell line (RAW 264.7 cells) and rat alveolar macrophages via the expression of the gene encoding for AANAT through a mechanism dependent on activation of the NFκB pathway. Expression of the genes encoding AANAT, MT1, and MT2 was negatively correlated with cellular necroptosis, as disclosed by analysis of Gene Expression Omnibus (GEO) microarray data from the human alveolar macrophages of nonsmoking subjects. The enrichment score for antioxidant genes obtained from lung gene expression data (GTEx) was significantly correlated with the levels of AANAT and MT1 but not the MT2 melatonin receptor. Collectively, these data provide a systemic and mechanistic rationale for coordination of the pineal and extrapineal synthesis of melatonin by a standard damage-associated stimulus, which activates the immune-pineal axis and provides a new framework for understanding the effects of air pollution on lung diseases.

NADPH Oxidase-Mediated Activation of Neutral Sphingomyelinase Is Responsible for Diesel Particulate Extract-Induced Keratinocyte Apoptosis

Human epidermis is positioned at the interface with the external environment, protecting our bodies against external challenges, including air pollutants. Emerging evidence suggests that diesel particulate extract (DPE), a major component of air pollution, leads to impairment of diverse cellular functions in keratinocytes (KC). In this study, we investigated the cellular mechanism underlying DPE-induced KC apoptosis. We first addressed cell death occurring in KC exposed to DPE, paralleled by increased activation of NADPH oxidases (NOXs) and subsequent ROS generation. Blockade of NOX activation with a specific inhibitor attenuated the expected DPE-induced KC apoptosis. In contrast, pre-treatment with a specific inhibitor of reactive oxygen species (ROS) generation did not reverse DPE/NOX-mediated increase in KC apoptosis. We next noted that NOX-mediated KC apoptosis is mainly attributable to neutral sphingomyelinase (SMase)-mediated stimulation of ceramides, which is a well-known pro-apoptotic lipid. Moreover, we found that inhibition of NOX activation significantly attenuated DPE-mediated increase in the ratio of ceramide to its key metabolite sphingosine-1-phosphate (S1P), an important determinant of cell fate. Together, these results suggest that activation of neutral SMase serves as a key downstream signal for the DPE/NOX activation-mediated alteration in ceramide and S1P productions, and subsequent KC apoptosis.

Cell metabolomics to study the cytotoxicity of carbon black nanoparticles on A549 cells using UHPLC-Q/TOF-MS and multivariate data analysis

Carbon black nanoparticles (CBNPs) are core component of fine particulate matter (PM2.5) in the atmosphere. It was reported that the particle in the atmosphere with smaller size and the larger the specific surface area are easier to reach the deep respiratory tract or even the alveoli through the respiratory barrier and cause lung injury. Therefore, it has been believed that ultrafine or nanometer particles with more toxic than those with larger particle sizes. Moreover, it was confirmed that CBNPs could induce inflammation, oxidative stress and changes in cell signaling and gene expression in mammalian cells and organs. However, the cytotoxicity mechanism of them has been uncertain so far. The aim of the present study was to explore the underlying mechanism of cytotoxicity induced by CBNPs on A549 cells. In the current research, the viabilities of A549 cells were detected by Cell Counting Kit-8 (CCK-8) assay. The further metabolomics studies were conducted to detect the cytotoxic effect of CBNPs on A549 cells with an IC50 value of 70 μg/mL for 48 h. Potential differential compounds were identified and quantified using a novel on-line acquisition method based on ultra-liquid chromatography quadrupole time-of-flight mass spectrometry(UHPLC-Q-TOF/MS). The cytotoxicity mechanism of CBNPs on A549 cells was evaluated by multivariate data analysis and statistics. As a result, a total of 32 differential compounds were identified between CBNPs exposure and control groups. In addition, pathway analysis showed the metabolic changes were involved in the tricarboxylic acid (TCA) cycle, alanine, aspartate and glutamate metabolism, histidine metabolism and so on. It is also suggested that CBNPs may induce cytotoxicity by affecting the normal process of energy metabolism and disturbing several vital signaling pathways and finally induce cell apoptosis.