DNA damage and repair, oxidative stress and metabolism biomarker responses in lungs of rats exposed to ambient atmospheric 1-nitropyrene

Potential therapeutic targets for COVID-19 complicated with pulmonary hypertension: a bioinformatics and early validation study

Coronavirus disease (COVID-19) and pulmonary hypertension (PH) are closely correlated. However, the mechanism is still poorly understood. In this article, we analyzed the molecular action network driving the emergence of this event. Two datasets (GSE113439 and GSE147507) from the GEO database were used for the identification of differentially expressed genes (DEGs).Common DEGs were selected by VennDiagram and their enrichment in biological pathways was analyzed. Candidate gene biomarkers were selected using three different machine-learning algorithms (SVM-RFE, LASSO, RF).The diagnostic efficacy of these foundational genes was validated using independent datasets. Eventually, we validated molecular docking and medication prediction. We found 62 common DEGs, including several ones that could be enriched for Immune Response and Inflammation. Two DEGs (SELE and CCL20) could be identified by machine-learning algorithms. They performed well in diagnostic tests on independent datasets. In particular, we observed an upregulation of functions associated with the adaptive immune response, the leukocyte-lymphocyte-driven immunological response, and the proinflammatory response. Moreover, by ssGSEA, natural killer T cells, activated dendritic cells, activated CD4 T cells, neutrophils, and plasmacytoid dendritic cells were correlated with COVID-19 and PH, with SELE and CCL20 showing the strongest correlation with dendritic cells. Potential therapeutic compounds like FENRETI-NIDE, AFLATOXIN B1 and 1-nitropyrene were predicted. Further molecular docking and molecular dynamics simulations showed that 1-nitropyrene had the most stable binding with SELE and CCL20.The findings indicated that SELE and CCL20 were identified as novel diagnostic biomarkers for COVID-19 complicated with PH, and the target of these two key genes, FENRETI-NIDE and 1-nitropyrene, was predicted to be a potential therapeutic target, thus providing new insights into the prediction and treatment of COVID-19 complicated with PH in clinical practice.

ALKBH5 SUMOylation-mediated FBXW7 m6A modification regulates alveolar cells senescence during 1-nitropyrene-induced pulmonary fibrosis

Our previous study revealed that 1-nitropyrene (1-NP) exposure evoked pulmonary fibrosis in mice. However, the exact mechanism remained elusive. We found that 1-NP induced telomere damage and cellular senescence in mice lungs, and two alveolar epithelial cells lines. 1-NP downregulated telomere repeat binding factor 2 (TRF2), and upregulated FBXW7. Mechanistically, 1-NP-caused TRF2 ubiquitination and proteasomal degradation depended on E3 ubiquitin ligase activity of FBXW7. Moreover, 1-NP upregulated FBXW7 m6A modification via an ALKBH5-YTHDF1-dependent manner. Further analysis suggested 1-NP promoted ALKBH5 SUMOylation and subsequent proteasomal degradation. Additionally, 1-NP evoked mitochondrial reactive oxygen species (mtROS) overproduction. Mito-TEMPO, a mitochondrial-targeted antioxidant, mitigated 1-NP-caused mtROS overproduction, ALKBH5 SUMOylation, FBXW7 m6A modification, TRF2 degradation, cellular senescence, and pulmonary fibrosis. Taken together, mtROS-initiated ALKBH5 SUMOylation and subsequent FBXW7 m6A modification is indispensable for TRF2 degradation and cellular senescence in alveolar epithelial cells during 1-NP-induced pulmonary fibrosis. Our study provides target intervention measures towards 1-NP-evoked pulmonary fibrosis.

1-Nitropyrene disrupts testosterone biogenesis via AKAP1 degradation promoted mitochondrial fission in mouse Leydig cell

Previous study found 1-NP disrupted steroidogenesis in mouse testis, but the underlying mechanism remained elusive. The current work aims to explore the roles of ROS-promoted AKAP1 degradation and excessive mitochondrial fission in 1-NP-induced steroidogenesis disruption in MLTC-1 cells. Transmission electron microscope analysis found 1-NP promoted excessive mitochondrial fission. Further data showed 1-NP disrupted mitochondrial function. pDRP1 (Ser637), a negative regulator of mitochondrial fission, was reduced in 1-NP-treated MLTC-1 cells. Mechanistically, 1-NP caused degradation of AKAP1, an upstream regulator of pDRP1 (Ser637). MG132, a proteasome inhibitor, attenuated 1-NP-induced AKAP1 degradation and downstream pDRP1 (Ser637) reduction, thereby ameliorating 1-NP-downregulated steroidogenesis. Further analysis found that cellular ROS was elevated and NOX4, HO-1 and SOD2 were upregulated in 1-NP-exposed MLTC-1 cells. NAC, a well-known commercial antioxidant, alleviated 1-NP-induced excessive ROS and oxidative stress. 1-NP-induced AKAP1 degradation and subsequent downregulation of pDRP1 (Ser637) were prevented by NAC pretreatment. Moreover, NAC attenuated 1-NP-resulted T synthesis disturbance in MLTC-1 cells. The present study indicates that ROS mediated AKAP1 degradation and subsequent pDRP1 (Ser637) dependent mitochondrial fission is indispensable in 1-NP caused T synthesis disruption. This study provides a new insight into 1-NP-induced endocrine disruption, and offers theoretical basis in public health prevention.

A comparative study of persistent DNA oxidation and chromosomal instability induced in vitro by oxidizers and reference airborne particles

Adverse health effects driven by airborne particulate matter (PM) are mainly associated with reactive oxygen species formation, pro-inflammatory effects, and genome instability. Therefore, a better understanding of the underlying mechanisms is needed to evaluate health risks caused by exposure to PM. The aim of this study was to compare the genotoxic effects of two oxidizing agents (menadione and 3-chloro-1,2-propanediol) with three different reference PM (fine dust ERM-CZ100, urban dust SRM1649, and diesel PM SRM2975) on monocytic THP-1 and alveolar epithelial A549 cells. We assessed DNA oxidation by measuring the oxidized derivative 8-hydroxy-2'-deoxyguanosine (8-OHdG) following short and long exposure times to evaluate the persistency of oxidative DNA damage. Cytokinesis-block micronucleus cytome assay was performed to assess chromosomal instability, cytostasis, and cytotoxicity. Particles were characterized by inductively coupled plasma mass spectrometry in terms of selected elemental content, the release of ions in cell medium and the cellular uptake of metals. PM deposition and cellular dose were investigated by a spectrophotometric method on adherent A549 cells. The level of lipid peroxidation was evaluated via malondialdehyde concentration measurement. Despite differences in the tested concentrations, deposition efficiency, and lipid peroxidation levels, all reference PM samples caused oxidative DNA damage to a similar extent as the two oxidizers in terms of magnitude but with different oxidative DNA damage persistence. Diesel SRM2975 were more effective in inducing chromosomal instability with respect to fine and urban dust highlighting the role of polycyclic aromatic hydrocarbons derivatives on chromosomal instability. The persistence of 8-OHdG lesions strongly correlated with different types of chromosomal damage and revealed distinguishing sensitivity of cell types as well as specific features of particles versus oxidizing agent effects. In conclusion, this study revealed that an interplay between DNA oxidation persistence and chromosomal damage is driving particulate matter-induced genome instability.

Toxicity screening of air extracts representing different source sectors in the Greater Toronto and Hamilton areas: In vitro oxidative stress, pro-inflammatory response, and toxicogenomic analysis

In the present study, the suitability and sensitivity of different in vitro toxicity endpoints were determined to evaluate and distinguish the specific contributions of polycyclic aromatic carbon (PAC) mixtures from various sites in Toronto (Canada), to pulmonary toxicity. Air samples were collected for two-month periods from April 2014 to March 2015 from one location, and from August 2016 to August 2017 from multiple locations reflecting different geographical areas in Toronto, and the Greater Toronto Area, with varying source emissions including background, traffic, urban, industrial and residential sites. Relative concentrations of PACs and their derivatives in these air samples were characterised. In vitro cytotoxicity, pro-inflammatory, and oxidative stress assays were employed to assess the acute pulmonary effects of urban-air-derived air pollutants. In addition, global transcriptional profiling was utilized to understand how these chemical mixtures exert their harmful effects. Lastly, the transcriptomic data and the chemical profiles for each site and season were used to relate the biological response back to individual constituents. Site-specific responses could not be derived; however, the Spring season was identified as the most responsive through benchmark concentration analysis. A combination of correlational analysis and principal component analysis revealed that nitrated and oxygenated polycyclic aromatic hydrocarbons (PAHs) drive the response at lower concentrations while specific PAHs drive the response at the highest concentration tested. Unsubstituted PAHs are the current targets for analysis as priority pollutants. The present study highlights the importance of by-products of PAH degradation in the assessment of risk. The study also demonstrates the usefulness of in vitro toxicity assays to derive meaningful data in support of risk assessment.

Occurrence and toxicity of polycyclic aromatic hydrocarbons derivatives in environmental matrices

In the last years, there is great attention paid to the determination of polycyclic aromatic hydrocarbons (PAHs) in different environmental matrices. Extensive reviews on PAHs presence and toxicity were published recently. However, PAHs formation and transformation in the environment lead to the production of PAHs derivatives containing oxygen (O-PAHs), nitrogen (N-PAHs and aazarenes AZA) or sulfur (PASHs) in the aromatic ring. The development of new analytical methods enabled the determination of these novel contaminants. The presence of oxygen, nitrogen, or sulfur in PAHs aromatic rings increased their toxicity. The most common primary sources of PAHs derivatives are biological processes such as microbial activity (in soil, water, and wastewater treatment plants (O-PAHs)) and all processes involving combustion of fuel, coal, and biomass (O-PAHs, N-PAHs, AZA, PASHs). The secondary resources involved i) photochemical (UV light), ii) radical-mediated (OH, NO₃), and iii) reactions with oxidants (O₃, NO_x) (O-PAHs, N-PAHs, AZA). Furthermore, N-PAHs were able to transform to their corresponding O-PAHs, while other derivatives were not. It indicated that N-PAHs are more vulnerable to photooxidation in the environment. 85% of O- and N-PAHs were detected with particle matter below 2.5 μm suggesting their easier bioaccessibility. More than 90% of compounds with four and more aromatic cycles were present in the particle phase in the air. Although the concentrations of N-PAHs or O-PAHs may be similar to PAHs concentration or even 1000 times lower than parent PAHs, PAHs derivatives accounted for a significant portion of the total mutagenicity. The present review is describing the results of the studies on the determination of PAHs derivatives in different environmental matrices including airborne particles, sediments, soil, and organisms. The mechanisms of their formation and toxicity were assessed.

Hazards of Chronic Exposure to Nonylphenol: Concomitant Effect on Non-alcoholic Fatty Liver Disease in Male Albino Rats

BACKGROUND: Chronic exposure to environmental endocrine disruptors like nonylphenol (NP), has been shown in previous studies to predispose to non-alcoholic fatty liver disease. METHODS: In this work, forty adult male albino rats were divided into four groups, a high sucrose-high-fat diet (HSHFD) group, a group receiving 20 μg/kg/day of NP, an NP + HSHFD group, and a control group. The rats were sacrificed on day 60 after anesthetization. RESULTS: Biochemical tests indicated that serum transaminases (alanine aminotransferase, aspartate aminotransferase) were significantly increased in the NP + HSHFD group. Lipid metabolism was most disrupted in the NP + HSHFD with a highly significant increase (p < 0.001) of serum cholesterol, triglyceride, and low-density lipoprotein cholesterol compared to other groups. Heme oxygenase 1 showed the highest expression in the NP + HSHFD group, with a highly significant difference in comparison with the other groups (p < 0.001). Histopathological studies revealed fatty changes and dilatation in the central vein in the HSHFD group. Lymphoid cell aggregates were detected in the NP group. Massive inflammation and degeneration were revealed in the NP + HSHFD group. There was also marked expression of the apoptotic protein caspase-3 in the NP + HSHFD group. CONCLUSION: In conclusion, exposure to a 20 μg/kg/day of NP induced oxidative stress leading to non-alcoholic steatohepatitis.

Application of Text Mining in Risk Assessment of Chemical Mixtures: A Case Study of Polycyclic Aromatic Hydrocarbons (PAHs)

BACKGROUND

Cancer risk assessment of complex exposures, such as exposure to mixtures of polycyclic aromatic hydrocarbons (PAHs), is challenging due to the diverse biological activities of these compounds. With the help of text mining (TM), we have developed TM tools-the latest iteration of the Cancer Risk Assessment using Biomedical literature tool (CRAB3) and a Cancer Hallmarks Analytics Tool (CHAT)-that could be useful for automatic literature analyses in cancer risk assessment and research. Although CRAB3 analyses are based on carcinogenic modes of action (MOAs) and cover almost all the key characteristics of carcinogens, CHAT evaluates literature according to the hallmarks of cancer referring to the alterations in cellular behavior that characterize the cancer cell.

OBJECTIVES

The objective was to evaluate the usefulness of these tools to support cancer risk assessment by performing a case study of 22 European Union and U.S. Environmental Protection Agency priority PAHs and diesel exhaust and a case study of PAH interactions with silica.

METHODS

We analyzed PubMed literature, comprising 57,498 references concerning priority PAHs and complex PAH mixtures, using CRAB3 and CHAT.

RESULTS

CRAB3 analyses correctly identified similarities and differences in genotoxic and nongenotoxic MOAs of the 22 priority PAHs and grouped them according to their known carcinogenic potential. CHAT had the same capacity and complemented the CRAB output when comparing, for example, benzo[a]pyrene and dibenzo[a,l]pyrene. Both CRAB3 and CHAT analyses highlighted potentially interacting mechanisms within and across complex PAH mixtures and mechanisms of possible importance for interactions with silica.

CONCLUSION

These data suggest that our TM approach can be useful in the hazard identification of PAHs and mixtures including PAHs. The tools can assist in grouping chemicals and identifying similarities and differences in carcinogenic MOAs and their interactions. https://doi.org/10.1289/EHP6702.

Polycyclic Aromatic Hydrocarbon Levels in Wistar Rats Exposed to Ambient Air of Port Harcourt, Nigeria: An Indicator for Tissue Toxicity

This study investigated the PAH levels in Wistar rats exposed to ambient air of the Port Harcourt metropolis. Twenty Wistar rats imported from a nonpolluted city (Enugu) were exposed to both indoor and outdoor air. Following the IACUC regulation, baseline data were obtained from 4 randomly selected rats, while the remaining 16 rats (8 each for indoor and outdoor) were left till day 90. Blood samples were obtained by cardiac puncture, and the PAH levels were determined using Gas Chromatography Flame-Ionization Detector (GC-FID). GraphPad Prism (version 8.0.2) Sidak's (for multiple data set) and unpaired t-tests (for two data sets) were used to evaluate the differences in group means. Seven of the PAHs found in indoor and outdoor rats were absent in baseline rats. The mean concentrations of PAH in indoor and outdoor animals were higher than those of baseline animals, except for Benzo(a)pyrene, which was found in baseline animals but absent in other animal groups. Additionally, Dibenz(a,h)anthracene, Indeno(1,2,3-c,d)pyrene, Pyrene, 2-methyl, and other carcinogenic PAHs were all significantly higher (p < 0.05) in outdoor groups. The vulnerable groups in Port Harcourt are at the greatest risk of such pollution. Therefore, urgent environmental and public health measures are necessary to mitigate the looming danger.

Maternal 1-nitropyrene exposure during pregnancy increases susceptibility of allergic asthma in adolescent offspring

1-nitropyrene (1-NP) is widespread in the environment, as a typical nitrated polycyclic aromatic hydrocarbon. The purpose of this research was to explore the effects of gestational 1-NP exposure on susceptibility of allergic asthma in offspring. Maternal mice were exposed to 1-NP (100 μg kg^-1) by gavage throughout the whole pregnancy. Pups were sensitized by injecting with ovalbumin (OVA) on postnatal day (PND)23, 29, and 36, respectively. At 7 days following the last injection, sensitized mice were exposed to aerosol OVA. As expected, there were quite a few inflammatory cells in the lungs of OVA-sensitized pups, accompanied by bronchial wall thickening and hyperemia. Elevated goblet cells and overproduced mucus were observed in the airways of OVA-sensitized pups. Interestingly, gestational 1-NP exposure aggravated infiltration of inflammatory cells, mainly eosinophils, in OVA-sensitized offspring. Although it had little effect on airway smooth muscle layer thickening and basement membrane fibrosis, gestational 1-NP exposure aggravated goblet cell hyperplasia, Muc5ac mRNA upregulation, and mucus secretion in the airways of OVA-sensitized and challenged offspring. Mechanistically, gestational 1-NP exposure aggravated elevation of pulmonary IL-5 in OVA-sensitized pups. These findings suggest that gestational 1-NP exposure increases susceptibility of allergic asthma in offspring.

Acute 1-NP exposure induces inflammatory responses through activating various inflammatory signaling pathways in mouse lungs and human A549 cells

1-Nitropyrene (1-NP), a key component of fine particulate matter (PM2.5), is a representative of nitrated polycyclic aromatic hydrocarbons (NPAHs). The aim of this research is to investigate proinflammatory effects of acute 1-NP exposure in mouse lungs and human A549 cells. All mice except controls were intratracheally instilled with 1-NP (20 μg/mouse). A549 cell, a human lung cancer cell line, was cultured with or without 1-NP (5 μM). Acute 1-NP exposure elevated lung weight and caused infiltration of inflammatory cells, especially neutrophils in mouse lungs. Although it had little effect on serum TNF-α and KC, acute 1-NP exposure elevated the levels of TNF-α and KC in BALF. Correspondingly, acute 1-NP exposure upregulated pulmonary Il-1β, Il-6, Tnf-α and Kc. Mechanistically, acute 1-NP exposure activated nuclear factor kappa B (NF-κB) in mouse lungs and human A549 cells. Additionally, acute 1-NP exposure induced Akt phosphorylation in mouse lungs and human A549 cells. Moreover, acute 1-NP exposure induced phosphorylation of pulmonary JNK and ERK1/2, molecules of the mitogen-activated protein kinase (MAPK) pathway. This study provides evidence that acute 1-NP exposure induces inflammatory responses through activating various inflammatory signaling pathways in mouse lungs and human A549 cells.

Nickel Carcinogenesis Mechanism: DNA Damage

Nickel (Ni) is known to be a major carcinogenic heavy metal. Occupational and environmental exposure to Ni has been implicated in human lung and nasal cancers. Currently, the molecular mechanisms of Ni carcinogenicity remain unclear, but studies have shown that Ni-caused DNA damage is an important carcinogenic mechanism. Therefore, we conducted a literature search of DNA damage associated with Ni exposure and summarized known Ni-caused DNA damage effects. In vitro and vivo studies demonstrated that Ni can induce DNA damage through direct DNA binding and reactive oxygen species (ROS) stimulation. Ni can also repress the DNA damage repair systems, including direct reversal, nucleotide repair (NER), base excision repair (BER), mismatch repair (MMR), homologous-recombination repair (HR), and nonhomologous end-joining (NHEJ) repair pathways. The repression of DNA repair is through direct enzyme inhibition and the downregulation of DNA repair molecule expression. Up to now, the exact mechanisms of DNA damage caused by Ni and Ni compounds remain unclear. Revealing the mechanisms of DNA damage from Ni exposure may contribute to the development of preventive strategies in Ni carcinogenicity.

Cold stress provokes lung injury in rats co-exposed to fine particulate matter and lipopolysaccharide

Cold exposure aggravates respiratory diseases, which are also influenced by the exposures to particulate matter and endotoxin in the air. The aim of this study was to investigate the potential interactions among cold stress, fine particulate matter (PM_2.5, particles with aerodynamic diameter of 2.5 µm or less) and lipopolysaccharide (LPS, pure chemical form of endotoxin) on rat lung and to explore the related possible mechanisms of the interactions. Wistar rats were randomly grouped to be exposed to, 1) normal saline (0.9% NaCl), 2) PM_2.5, 3) LPS, and 4) PM_2.5 and LPS (PM_2.5 + LPS) through intratracheal instillation under cold stress (0 °C) and normal temperature (20 °C). Lung function, lung tissue histology, inflammatory response and oxidative stress levels were measured to examine the lung injury and to investigate the potential mechanisms. Exposure to PM_2.5 or LPS substantially changed pulmonary function [indicated by peak inspiratory flow (PIF) and peak expiratory flow (PEF)], inflammatory cytokine levels [indicated by interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α)] and lung histology, compared to the non-exposed groups. Exposure to PM_2.5 + LPS under cold stress induced the most significant changes, including the increases of IL-6, TNF-α and thiobarbituric acid-reactive substances (TBARS), the decreases of PIF and PEF and more severe lung injury, among all exposure scenarios. Glutathione peroxidase activity and, nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) were found to be suppressed under cold stress, whereas Nrf2 and HO-1 levels were observed to be upregulated by exposure to PM_2.5 or LPS under normal temperature. In conclusion, cold stress may aggravate the lung injury in rats induced by simultaneous exposure to PM_2.5 and LPS. The progress may involve the suppressing of Nrf2/HO-1 signal pathway.

A magnetic covalent organic framework as an adsorbent and a new matrix for enrichment and rapid determination of PAHs and their derivatives in PM2.5 by surface-assisted laser desorption/ionization-time of flight-mass spectrometry

Fe₃O₄@COFs served as an adsorbent and new matrix for SALDI-TOF-MS analysis of PAHs and their derivatives in PM_2.5 with clear background, good reproducibility and sensitivity.

Response of the freshwater mussel, Dreissena polymorpha to sub-lethal concentrations of samarium and yttrium after chronic exposure

Samarium (Sm) and yttrium (Y) are commonly used rare earth elements (REEs) but there is a scarcity of information concerning their biological effects in non-target aquatic organisms. The purpose of this study was to determine the bioavailability of those REEs and their toxicity on Dreissena polymorpha after exposure to increasing concentration of Sm and Y for 28 days at 15 °C. At the end of the exposure period, the gene expression of superoxide dismutase (SOD), catalase (CAT), metallothionein (MT), glutathione-S-transferase (GST), cytochrome c oxidase 1 (CO1) and cyclin D (Cyc D) were analysed. In addition, we examined lipid peroxidation (LPO), DNA strand breaks (DSB), GST and prostaglandin cyclooxygenase (COX) activities. Results showed a concentration dependent increase in the level of the REEs accumulated in the soft tissue of mussels. Both REEs decreased CAT but did not significantly modulated SOD and MT expressions. Furthermore, Sm³⁺ up-regulated GST, CO1 and Cyc D, while Y³⁺ increased and decreased GST and CO1 transcripts levels, respectively. Biomarker activities showed no oxidative damage as evidenced by LPO, while COX activity was decreased and DNA strand breaks levels were changed suggesting that Sm and Y exhibit anti-inflammatory and genotoxic effects. Factorial analysis revealed that the major impacted biomarkers by Sm were LPO, CAT, CO1 and COX, while GST gene expression, COX, Cyc D and CAT as the major biomarkers affected by Y. We conclude that these REEs display different mode of action but further investigations are required in order to define the exact mechanism involved in their toxicity.

Simultaneous determination of eighteen nitro-polyaromatic hydrocarbons in PM2.5 by atmospheric pressure gas chromatography-tandem mass spectrometry

A new atmospheric pressure gas chromatography-tandem mass spectrometry (APGC-MS/MS) was developed to simultaneously separate, identify and quantify 18 nitro-polyaromatic hydrocarbons (NPAHs) in air fine particulate matter (PM_2.5). Compared with traditional negative chemical ionization (NCI) or electron impact ionization (EI)-MS/MS methods, APGC-MS/MS equipped with an atmospheric pressure chemical ionization (APCI) source provided better sensitivity and selectivity for NPAHs analysis in PM_2.5.18 NPAHs were completely separated, and satisfactory linear response (R² > 0.99), low instrumental detection limits (0.20-2.18 pg mL^-1) and method detection limits (0.001-0.015 pg m^-3) were achieved. Due to the reliable performance of the instrument, only minimal sample pretreatment is needed. It ensured the satisfactory method recovery (70%-120%) and qualified repeatability (RSD: 1.1%-17.2%), which met the requirement of trace analysis of NAPHs in the real environmental PM_2.5. Using the developed method, the actual PM_2.5 samples collected from Taiyuan, China in both summer and winter were analyzed, and 17 NPAHs but 2-nitrofluorene were detected and quantified. According to the obtained NAPH concentration results, the generation mechanism of NPAHs in PM_2.5 and the effects on NPAHs formation caused by some ambient air pollutants were preliminarily discussed: secondary photochemical reaction might be the dominant source of NPAHs in PM_2.5 collected from Taiyuan in both summer and winter; ambient air pollutants (NO₂, SO₂, CO) had more contribution on the NPAHs secondary formation of PM_2.5 in winter.