Sampling, composition, and biological effects of Mexico City airborne particulate matter from multiple periods.

Air pollution is a worldwide environmental problem with an impact on human health. Particulate matter of ten micrometers or less aerodynamic diameter (PM10) as well as its fine fraction (PM2.5) is related to multiple pulmonary diseases. The impact of air pollution in Mexico City, and importantly, particulate matter has been studied and considered as a risk factor for two decades ago. Previous studies have reported the composition of Mexico City particulate matter, as well as the biological effects induced by this material. However, material collected and used in previous studies is a limited resource, and sampling and particle recovery techniques have been improved. In this study, we describe the methods used in our laboratory for Mexico City airborne particulate matter PM10 and PM2.5 sampling, considering the years 2017, 2018 and 2019. We also analyzed the PM10 and PM2.5 samples obtained to determine their composition. Finally, we exposed lung cell line cultures to PM10 and PM2.5 to evaluate the biological effect of the material in terms of cell viability, cell death, inflammatory response, and cytogenetic alterations. Our results showed that PM10 composition includes inorganic, organic and biological compounds, while PM2.5 is a mixture of more enriched organic compounds. PM10 and PM2.5 treatment in lung cells does not significantly impact cell viability/cell death. However, PM10 and PM2.5 increase the secretion levels of IL-6. Moreover, PM10 as well as PM2.5 induce cytogenetic alterations, such as micronuclei, anaphase bridges, trinucleated cells and apoptotic cells in lung cells. Our results update the evidence of the composition and biological effects of Mexico City particulate matter and provide us a reliable basis for future approaches.

The Road to Malignant Cell Transformation after Particulate Matter Exposure: From Oxidative Stress to Genotoxicity.

In cells, oxidative stress is an imbalance between the production/accumulation of oxidants and the ability of the antioxidant system to detoxify these reactive products. Reactive oxygen species (ROS), cause multiple cellular damages through their interaction with biomolecules such as lipids, proteins, and DNA. Genotoxic damage caused by oxidative stress has become relevant since it can lead to mutation and play a central role in malignant transformation. The evidence describes chronic oxidative stress as an important factor implicated in all stages of the multistep carcinogenic process: initiation, promotion, and progression. In recent years, ambient air pollution by particulate matter (PM) has been cataloged as a cancer risk factor, increasing the incidence of different types of tumors. Epidemiological and toxicological evidence shows how PM-induced oxidative stress could mediate multiple events oriented to carcinogenesis, such as proliferative signaling, evasion of growth suppressors, resistance to cell death, induction of angiogenesis, and activation of invasion/metastasis pathways. In this review, we summarize the findings regarding the involvement of oxidative and genotoxic mechanisms generated by PM in malignant cell transformation. We also discuss the importance of new approaches oriented to studying the development of tumors associated with PM with more accuracy, pursuing the goal of weighing the impact of oxidative stress and genotoxicity as one of the main mechanisms associated with its carcinogenic potential.

Airborne particulate matter (PM10) induces cell invasion through Aryl Hydrocarbon Receptor and Activator Protein 1 (AP-1) pathway deregulation in A549 lung epithelial cells.

BACKGROUND: Particulate matter with an aerodynamic size ≤ 10 µm (PM10) is a risk factor for lung cancer development, mainly because some components are highly toxic. Polycyclic aromatic hydrocarbons (PAHs) are present in PM10, such as benzo[a]pyrene (BaP), which is a well-known genotoxic and carcinogenic compound to humans, capable of activating AP-1 transcription factor family genes through the Aryl Hydrocarbon Receptor (AhR). Because effects of BaP include metalloprotease 9 (MMP-9) activation, cell invasion, and other pathways related to carcinogenesis, we aimed to demonstrate that PM10 (10 µg/cm2) exposure induces the activation of AP-1 family members as well as cell invasion in lung epithelial cells, through AhR pathway. METHODS AND RESULTS: The role of the AhR gene in cells exposed to PM10 (10 µg/cm2) and BaP (1µM) for 48 h was evaluated using AhR-targeted interference siRNA. Then, the AP-1 family members (c-Jun, Jun B, Jun D, Fos B, C-Fos, and Fra-1), the levels/activity of MMP-9, and cell invasion were analyzed. We found that PM10 increased AhR levels and promoted its nuclear localization in A549 treated cells. Also, PM10 and BaP deregulated the activity of AP-1 family members. Moreover, PM10 upregulated the secretion and activity of MMP-9 through AhR, while BaP had no effect. Finally, we found that cell invasion in A549 cells exposed to PM10 and BaP is modulated by AhR. CONCLUSION: Our results demonstrated that PM10 exposure induces upregulation of the c-Jun, Jun B, and Fra-1 activity, the expression/activity of MMP-9, and the cell invasion in lung epithelial cells, effects mediated through the AhR. Also, the Fos B and C-Fos activity were downregulated. In addition, the effects induced by PM10 exposure were like those induced by BaP, which highlights the potentially toxic effects of the PM10 mixture in lung epithelial cells.

Mutational landscape of gastric adenocarcinoma in Latin America: A genetic approach for precision medicine.

Latin-America (LATAM) is the second region in gastric cancer incidence; gastric adenocarcinoma (GA) represents 95% of all cases. We provide a mutational landscape of GA highlighting a) germline pathogenic variants associated with hereditary GA, b) germline risk variants associated with sporadic GA, and c) somatic variants present in sporadic GA in LATAM, and analyze how this landscape can be applied for precision medicine. We found that Brazil, Chile, Colombia, Mexico, Peru, and Venezuela are the countries with more published studies from LATAM explicitly related to GA. Our analysis displayed that different germline pathogenic variants for the CDH1 gene have been identified for hereditary GA in Brazilian, Chilean, Colombian, and Mexican populations. An increased risk of developing somatic GA is associated with the following germline risk variants: IL-4, IL-8, TNF-α, PTGS2, NFKB1, RAF1, KRAS and MAPK1 in Brazilian; IL-10 in Chilean; IL-10 in Colombian; EGFR and ERRB2 in Mexican, TCF7L2 and Chr8q24 in Venezuelan population. The path from mutational landscape to precision medicine requires four development levels: 1) Data compilation, 2) Data analysis and integration, 3) Development and approval of clinical approaches, and 4) Population benefits. Generating local genomic information is the initial padlock to overcome to generate and apply precision medicine.

Particulate matter (PM10) destabilizes mitotic spindle through downregulation of SETD2 in A549 lung cancer cells.

Air pollution represents an environmental problem, impacting negatively in human health. Particulate matter of 10 µm or less in diameter (PM10) is related to pulmonary diseases, including lung cancer. Mitotic spindle is made up by chromosome-microtubule (MT) interactions, where SETD2 plays an important role in MT stability. SETD2 binds and activates α-TUBULIN sub-unit and promotes MT polymerization. Alongside this mechanism, the spindle assembly checkpoint (SAC) senses the adequate mitotic progression through proteins such as BUBR1, AURORA B and SURVIVIN. Alterations in MT dynamics as well as in SAC cause aneuploidy and chromosomal instability, a common phenotype in cancer cells. In this study, we evaluated the effect of PM10 in the expression and protein levels of SETD2, as well as the effect in the expression and protein levels of SAC and mitotic components involved in chromosomal segregation/mitosis, using the A549 lung cancer cell line. A549 cell cultures were exposed to PM10 (10 µg/cm2) for 24 h to evaluate the expression and protein levels of SETD2 (SETD2), TUBA1A (α-TUBULIN), CCNB1 (CYCLIN B1), BUB1B (BUBR1), AURKB (AURORA B) and BIRC5 (SURVIVIN). We observed that PM10 decreases the expression and protein levels of SETD2, α-TUBULIN and BUBR1 and increases the levels of AURORA B and SURVIVIN in A549 cells, compared with non-treated cells. PM10 also caused a decrease in mitotic index and in the percentage of cells in G2/M when compared with control group. Co-localization of SETD2/α -TUB was lower in PM10-treated cells in comparison with non-treated cells. Finally, micronuclei (MN) frequency was higher in PM10-treated cells in contrast with non-treated cells, being whole chromosomes more common in PM10-treated MN than in non-treated MN. Our results suggest that PM10 causes missegregation and aneuploidy through downregulation of SETD2 and SAC components, inducing aneuploidy and predisposing to the generation of chromosomal instability in transformed cells.

Particulate Matter (PM10) Promotes Cell Invasion through Epithelial-Mesenchymal Transition (EMT) by TGF-ß Activation in A549 Lung Cells.

Air pollution presents a major environmental problem, inducing harmful effects on human health. Particulate matter of 10 µm or less in diameter (PM10) is considered an important risk factor in lung carcinogenesis. Epithelial-mesenchymal transition (EMT) is a regulatory program capable of inducing invasion and metastasis in cancer. In this study, we demonstrated that PM10 treatment induced phosphorylation of SMAD2/3 and upregulation of SMAD4. We also reported that PM10 increased the expression and protein levels of TGFB1 (TGF-ß), as well as EMT markers SNAI1 (Snail), SNAI2 (Slug), ZEB1 (ZEB1), CDH2 (N-cadherin), ACTA2 (α-SMA), and VIM (vimentin) in the lung A549 cell line. Cell exposed to PM10 also showed a decrease in the expression of CDH1 (E-cadherin). We also demonstrated that expression levels of these EMT markers were reduced when cells are transfected with small interfering RNAs (siRNAs) against TGFB1. Interestingly, phosphorylation of SMAD2/3 and upregulation of SMAD induced by PM10 were not affected by transfection of TGFB1 siRNAs. Finally, cells treated with PM10 exhibited an increase in the capacity of invasiveness because of EMT induction. Our results provide new evidence regarding the effect of PM10 in EMT and the acquisition of an invasive phenotype, a hallmark necessary for lung cancer progression.

Long non-coding RNA NORAD upregulation induced by airborne particulate matter (PM10) exposure leads to aneuploidy in A549 lung cells.

Air pollution is a worldwide problem that affects human health predominantly in the largest cities. Particulate matter of 10 µm or less in diameter (PM10) is considered a risk factor for multiple diseases, including lung cancer. The long non-coding RNA NORAD and the components of the spindle assembly checkpoint (SAC) ensure proper chromosomal segregation. Alterations in the SAC cause aneuploidy, a feature associated with carcinogenesis. In this study, we demonstrated that PM10 treatment increased the expression levels of NORAD as well as those of SAC components mitotic arrest deficient 1 (MAD1L1), mitotic arrest deficient 2 (MAD2L1), BubR1 (BUB1B), aurora B (AURKB), and survivin (BIRC5) in the lung A549 cell line. We also demonstrated that MAD1L1, MAD2L1, and BUB1B expression levels were reduced when cells were transfected with small interfering RNAs (siRNAs) against NORAD. Interestingly, the expression levels of AURKB and BIRC5 (survivin) were not affected by transfection with NORAD siRNAs. Cells treated with PM10 exhibited a decrease in mitotic arrest and an increase in micronuclei frequency in synchronized A549 cells. PM10 exposure induced aneuploidy events as a result of SAC deregulation. We also observed a reduction in the protein levels of Pumilio 1 after PM10 treatment. Our results provide novel clues regarding the effect of PM10 in the generation of chromosomal instability, a phenotype observed in lung cancer cells.

Airborne Particulate Matter (PM10) Inhibits Apoptosis through PI3K/AKT/FoxO3a Pathway in Lung Epithelial Cells: The Role of a Second Oxidant Stimulus.

Outdoor particulate matter (PM10) exposure is carcinogenic to humans. The cellular mechanism by which PM10 is associated specifically with lung cancer includes oxidative stress and damage to proteins, lipids, and DNA in the absence of apoptosis, suggesting that PM10 induces cellular survival. We aimed to evaluate the PI3K/AKT/FoxO3a pathway as a mechanism of cell survival in lung epithelial A549 cells exposed to PM10 that were subsequently challenged with hydrogen peroxide (H2O2). Our results showed that pre-exposure to PM10 followed by H2O2, as a second oxidant stimulus increased the phosphorylation rate of pAKTSer473, pAKTThr308, and pFoxO3aSer253 2.5-fold, 1.8-fold, and 1.2-fold, respectively. Levels of catalase and p27kip1, which are targets of the PIK3/AKT/FoxO3a pathway, decreased 38.1% and 62.7%, respectively. None of these changes had an influence on apoptosis; however, the inhibition of PI3K using the LY294002 compound revealed that the PI3K/AKT/FoxO3a pathway was involved in apoptosis evasion. We conclude that nontoxic PM10 exposure predisposes lung epithelial cell cultures to evade apoptosis through the PI3K/AKT/FoxO3a pathway when cells are treated with a second oxidant stimulus.

Deciphering the Code between Air Pollution and Disease: The Effect of Particulate Matter on Cancer Hallmarks.

Air pollution has been recognized as a global health problem, causing around 7 million deaths worldwide and representing one of the highest environmental crises that we are now facing. Close to 30% of new lung cancer cases are associated with air pollution, and the impact is more evident in major cities. In this review, we summarize and discuss the evidence regarding the effect of particulate matter (PM) and its impact in carcinogenesis, considering the "hallmarks of cancer" described by Hanahan and Weinberg in 2000 and 2011 as a guide to describing the findings that support the impact of particulate matter during the cancer continuum.

Airborne particulate matter induces mitotic slippage and chromosomal missegregation through disruption of the spindle assembly checkpoint (SAC).

Particulate matter (PM) is a risk factor for lung cancer development and chromosomal missegregation and cell cycle disruptions are key cellular events that trigger tumorigenesis. We aimed to study the effect of PM10 (PM with an aerodynamic diameter ≤10 µm) on mitotic arrest and chromosomal segregation, evaluating the spindle assembly checkpoint (SAC) protein dynamics in the human lung A549 adenocarcinoma cell line. For this purpose, synchronized cells were exposed to PM10 for 24 h to obtain the frequency of micronucleated (MN) and trinucleated (TN) cells. Then, the efficiency of the mitotic arrest after PM10 exposure was analyzed. To elucidate the effect of PM10 in chromosomal segregation, the levels and subcellular localization of essential SAC proteins were evaluated. Results indicated that A549 cells exposed to PM10 exhibited an increase in MN and TN cells and a decrease in mitotic indexes and G2/M phase. A549 cells treated with PM10 showed reduced protein levels of MDC1 and NEK2 (38% and 35% respectively), which is required for MAD2 recruitment to kinetochores, MAD2 and BUBR1, effectors of the SAC (25% and 18% respectively), and CYCLIN B1, required during G2/M phase (35%). Besides, PM10 exposure increase the levels of AURORA B and SURVIVIN, required for SAC activation through chromosome-microtubule attachment errors (85% and 74% respectively). We suggest that PM10 causes mitotic slippage due to alterations in MAD2 localization. Thus, PM10 causes inadequate chromosomal segregation and deficient mitotic arrest by altering SAC protein levels, predisposing A549 cells to chromosomal instability, a common feature observed in cancer.

Air pollution and genomic instability: The role of particulate matter in lung carcinogenesis.

In this review, we summarize and discuss the evidence regarding the interaction between air pollution, especially particulate matter (PM), and genomic instability. PM has been widely studied in the context of several diseases, and its role in lung carcinogenesis gained relevance due to an increase in cancer cases for which smoking does not seem to represent the main risk factor. According to epidemiological and toxicological evidence, PM acts as a carcinogenic factor in humans, inducing high rates of genomic alterations. Here, we discuss not only how PM is capable of inducing genomic instability during the carcinogenic process but also how our genetic background influences the response to the sources of damage.