Induction of fibroblast growth factor-9 and interleukin-1alpha gene expression by motorcycle exhaust particulate extracts and benzo(a)pyrene in human lung adenocarcinoma cells

Exploring the multifaceted effects of Interleukin-1 in lung cancer: From tumor development to immune modulation

Lung cancer, acknowledged as one of the most fatal cancers globally, faces limited treatment options on an international scale. The success of clinical treatment is impeded by challenges such as late diagnosis, restricted treatment alternatives, relapse, and the emergence of drug resistance. This predicament has led to a saturation point in lung cancer treatment, prompting a rapid shift in focus towards the tumor microenvironment (TME) as a pivotal area in cancer research. Within the TME, Interleukin-1 (IL-1) is abundantly present, originating from immune cells, tissue stromal cells, and tumor cells. IL-1's induction of pro-inflammatory mediators and chemokines establishes an inflammatory milieu influencing tumor occurrence, development, and the interaction between tumors and the host immune system. Notably, IL-1 expression in the TME exhibits characteristics such as staging, tissue specificity, and functional pluripotency. This comprehensive review aims to delve into the impact of IL-1 on lung cancer, encompassing aspects of occurrence, invasion, metastasis, immunosuppression, and immune surveillance. The ultimate goal is to propose a novel treatment approach, considering the intricate dynamics of IL-1 within the TME.

Benzo[a]pyrene exposure in muscle triggers sarcopenia through aryl hydrocarbon receptor-mediated reactive oxygen species production

BACKGROUND

Benzo[a]pyrene (BaP), a toxic carcinogen, is associated with various adverse effects but is rarely discussed in muscle-related disorders. This study investigated in vitro and in vivo effects triggered by BaP exposure in muscles and hypothesized that exposure might induce conditions similar to sarcopenia due to the shared mechanism of oxidative stress. In vitro experiments used C2C12 mouse myoblasts to examine effects induced by BaP exposure in control (untreated) and BaP-treated (10 µM/ml) muscle cells. An established TNF-α-treated sarcopenia model was utilized to verify our results. In vivo experiments compared immunohistochemical staining of sarcopenia-related markers in rats exposed to clean air and polluted air.

RESULTS

In C2C12 cells, after 2-72 h of BaP exposure, elevated mRNA and protein expressions were observed in aryl hydrocarbon receptor (AhR) and cytochrome P450 1A1, subsequently in ROS (NOX2 and NOX4) production, inflammatory cytokines (IL-6, TNF-α, and NF-kB), and proteins mediating apoptotic cell death (caspase-3 and PARP). Two myokines also altered mRNA and protein expressions akin to changes in sarcopenia, namely decreased irisin levels and increased myostatin levels. In addition, N-acetylcysteine, a well-known antioxidant, led to decrease in oxidative markers induced by BaP. The validation by TNF-α-treated sarcopenia model revealed comparable biological responses in either TNF-α or BaP treated C2C12 cells. In vivo experiments with rats exposed to air pollution showed increased expression of BaP, AhR, 8-hydroxydeoxyguanosine, and myostatin and decreased irisin expression in immunohistochemical staining.

CONCLUSIONS

Our results suggest that BaP exerts deleterious effects on the muscle, leading to conditions indicative of sarcopenia. Antioxidant supplementation may be a treatment option for BaP-induced sarcopenia, but further validation studies are needed.

Baicalein Inhibits Benzo[a]pyrene-Induced Toxic Response by Downregulating Src Phosphorylation and by Upregulating NRF2-HMOX1 System

Benzo[a]pyrene (BaP), a major environmental pollutant, activates aryl hydrocarbon receptor (AHR), induces its cytoplasmic-to-nuclear translocation and upregulates the production of cytochrome P450 1A1 (CYP1A1), a xenobiotic metabolizing enzyme which metabolize BaP. The BaP-AHR-CYP1A1 axis generates reactive oxygen species (ROS) and induces proinflammatory cytokines. Although the anti-inflammatory phytochemical baicalein (BAI) is known to inhibit the BaP-AHR-mediated CYP1A1 expression, its subcellular signaling remains elusive. In this study, normal human epidermal keratinocytes and HaCaT keratinocytes were treated with BAI, BaP, or BAI + BaP, and assessed for the CYP1A1 expression, antioxidative pathways, ROS generation, and proinflammatory cytokine expressions. BAI and BAI-containing herbal medicine Wogon and Oren-gedoku-to could inhibit the BaP-induced CYP1A1 expression. In addition, BAI activated antioxidative system nuclear factor-erythroid 2-related factor-2 (NRF2) and heme oxygenase 1 (HMOX1), leading the reduction of BaP-induced ROS production. The BaP-induced IL1A and IL1B was also downregulated by BAI. BAI inhibited the phosphorylation of Src, a component of AHR cytoplasmic complex, which eventually interfered with the cytoplasmic-to-nuclear translocation of AHR. These results indicate that BAI and BAI-containing herbal drugs may be useful for inhibiting the toxic effects of BaP via dual AHR-CYP1A1-inhibiting and NRF2-HMOX1-activating activities.

Evidence for Aryl hydrocarbon Receptor-Mediated Inhibition of Osteoblast Differentiation in Human Mesenchymal Stem Cells

Multipotent mesenchymal stem cells (MSCs) maintain the ability to differentiate into adipogenic, chondrogenic, or osteogenic cell lineages. There is increasing concern that exposure to environmental agents such as aryl hydrocarbon receptor (AhR) ligands, may perturb the osteogenic pathways responsible for normal bone formation. The objective of the current study was to evaluate the potential of the prototypic AhR ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to disrupt osteogenic differentiation of human bone-derived MSCs (hBMSCs) in vitro. Primary hBMSCs from three donors were exposed to 10 nM TCDD and differentiation was interrogated using select histological, biochemical, and transcriptional markers of osteogenesis. Exposure to 10 nM TCDD resulted in an overall consistent attenuation of alkaline phosphatase (ALP) activity and matrix mineralization at terminal stages of differentiation in primary hBMSCs. At the transcriptional level, the transcriptional regulator DLX5 and additional osteogenic markers (ALP, OPN, and IBSP) displayed attenuated expression; conversely, FGF9 and FGF18 were consistently upregulated in each donor. Expression of stem cell potency markers SOX2, NANOG, and SALL4 decreased in the osteogenic controls, whereas expression in TCDD-treated cells resembled that of undifferentiated cells. Coexposure with the AhR antagonist GNF351 blocked TCDD-mediated attenuation of matrix mineralization, and either fully or partially rescued expression of genes associated with osteogenic regulation, extracellular matrix, and/or maintenance of multipotency. Thus, experimental evidence from this study suggests that AhR transactivation likely attenuates osteoblast differentiation in multipotent hBMSCs. This study also underscores the use of primary human MSCs to evaluate osteoinductive or osteotoxic potential of chemical and pharmacologic agents in vitro.

The use of a 0.20 μm particulate matter filter decreases cytotoxicity in lung epithelial cells following air-liquid interface exposure to motorcycle exhaust

This study was designed to investigate whether the use of a 0.20 μm particulate matter (PM) filter reduced the cytotoxicity induced by motorcycle exhaust (ME), a mixture of gases and particles, in lung epithelial cells cultured in air-liquid interface (ALI) inserts. The concentrations of PM, carbon monoxide, carbon dioxide, total hydrocarbons (THC), total volatile organic compounds, and nitrogen oxides in both filtered ME (fME) by a 0.20 μm filter and non-filtered ME (non-fME) were measured. Lung epithelial cells were exposed to clean air, fME, or non-fME in the ALI chamber. Cell relative viabilities (CRV) and the reactive oxygen species (ROS) generation were determined. Our results revealed that PM_2.5 was the main compound of PM in ME. After filtration, PM and THC levels were significantly reduced, as compared with non-fME. When compared with the clean air exposed group, the CRV in both fME and non-fME-exposed group was significantly reduced (p < 0.001), while their ROS generation were markedly increased (p < 0.001). When compared with non-fME-exposed group, the CRV and ROS generation were significantly improved following fME exposure (p < 0.05). As a result, of PM and THC concentrations were decreased approximately 90% and 22.71%, respectively, the CRV was improved from 40.4% (non-fME) to 55.7% (fME), and the increased ROS generation by non-fME was decreased about 51.6%. When BEAS-2B cells were exposed to fME, a time-dependent reduction in CRV was observed. In conclusion, our findings suggest that ME-exposure in the ALI system induces cytotoxicity and oxidative stress responses. The addition of a 0.20 μm PM filter significantly modifies the particulate composition in PM and the concentration of THC, and shows protective effects by improving the survival of exposed lung epithelial cells and reducing the ROS generation. Therefore, emission factors such as different size of PM and THC from motorcycles may play a role in ME-induced toxicity.

Pollution and regional variations of lung cancer mortality in the United States

INTRODUCTION

The aims of this study were to identify counties in the United States (US) with high rates of lung cancer mortality, and to characterize the associated community-level factors while focusing on particulate-matter pollution.

METHODS

We performed a descriptive analysis of lung cancer deaths in the US from 2004 through 2014. We categorized counties as "clustered" or "non-clustered" - based on whether or not they had high lung cancer mortality rates - using novel geospatial autocorrelation methods. We contrasted community characteristics between cluster categories. We performed logistic regression for the association between cluster category and particulate-matter pollution.

RESULTS

Among 362 counties (11.6%) categorized as clustered, the age-adjusted lung cancer mortality rate was 99.70 deaths per 100,000 persons (95%CI: 99.1-100.3). Compared with non-clustered counties, clustered counties were more likely in the south (72.9% versus 42.1%, P<0.01) and in non-urban communities (73.2% versus 57.4, P<0.01). Clustered counties had greater particulate-matter pollution, lower education and income, higher rates of obesity and physical inactivity, less access to healthcare, and greater unemployment rates (P<0.01). Higher levels of particulate-matter pollution (4th quartile versus 1st quartile) were associated with two-fold greater odds of being a clustered county (adjusted OR: 2.10; 95%CI: 1.23-3.59).

CONCLUSION

We observed a belt of counties with high lung mortality ranging from eastern Oklahoma through central Appalachia; these counties were characterized by higher pollution, a more rural population, lower socioeconomic status and poorer access to healthcare. To mitigate the burden of lung cancer mortality in the US, both urban and rural areas should consider minimizing air pollution.

Comparative assessment of HIF-1α and Akt responses in human lung and skin cells exposed to benzo[α]pyrene: Effect of conditioned medium from pre-exposed primary fibroblasts

Exposure to atmospheric pollutants has been accused for many adverse health effects. Benzo[α]pyrene (Β[α]Ρ) in particular, the most extensively studied member of pollutants, is implicated in both cancer initiation and promotion. In the present study, we compared the effects of noncytotoxic doses of Β[α]Ρ, between human skin and lung epithelial cells A431 and A549, respectively, focusing on Akt kinase and HIF-1α, as it is well known that these proteins are upregulated in various human cancers promoting survival, angiogenesis and metastasis of tumor cells. Also, taking into consideration that fibroblasts are involved in cancer progression, we tested the possible modulation of epithelial cell response by paracrine factors secreted by Β[α]Ρ-treated fibroblasts. Low doses of Β[α]Ρ were found to enhance epithelial cell proliferation and upregulate both Akt kinase and HIF-1α, with A549 cells exhibiting a more sustained profile of upregulation. It is to notice that, the response of HIF-1α was remarkably early, acting as a sensitive marker in response to airborne pollutants. Also, HIF-1α was induced by Β[α]Ρ in both lung and skin fibroblasts indicating that this effect may be conserved throughout different cell types and tissues. Interestingly however, the response of both proteins was differentially modified upon treatment with conditioned medium from Β[α]Ρ-exposed fibroblasts. This is particularly evident in A459 cells and confirms the critical role of intercellular and paracrine factors in the modulation of the final response to an extracellular signal. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1103-1112, 2016.

Benzo(a)pyrene induces interleukin (IL)-6 production and reduces lipid synthesis in human SZ95 sebocytes via the aryl hydrocarbon receptor signaling pathway

In this study, we determined the effects of benzo(a)pyrene (BaP) on the expression of aryl hydrocarbon receptor (AhR) and cytochrome P450 1A1 (CYP1A1), and assessed the action of BaP on inflammatory cytokine expression and lipid synthesis in SZ95 sebocytes in vitro. BaP (10(-8), 10(-7), 10(-6) and 10(-5)M) was not cytotoxic for SZ95 sebocytes after 24h exposure. Expression of AhR was promoted in mRNA lever, while was inhibited in protein lever after BaP (10(-5)M) exposure. CYP1A1 expression was up-regulated in both mRNA and protein levels. BaP (10(-5)M) exerted a stimulatory action on interleukin (IL)-6 secretion, while a dose-dependently inhibitory effect on lipid synthesis from 10(-8)M to 10(-5)M in SZ95 sebocytes. Both actions were partly antagonized in AhR-knockdowned SZ95 sebocytes. This study demonstrates that BaP can activate AhR signaling pathway, and exhibits pro-inflammatory effects and inhibitory effects on sebum production in human sebocytes.

CD4+CD25+FoxP3+ Regulatory Tregs inhibit fibrocyte recruitment and fibrosis via suppression of FGF-9 production in the TGF-β1 exposed murine lung

Pulmonary fibrosis is a difficult to treat, often fatal disease whose pathogenesis involves dysregulated TGF-β1 signaling. CD4+CD25+FoxP3+ Regulatory T cells (“Tregs”) exert important effects on host tolerance and arise from naïve CD4+ lymphocytes in response to TGF-β1. However, the precise contribution of Tregs to experimentally induced murine lung fibrosis remains unclear. We sought to better understand the role of Tregs in this context. Using a model of fibrosis caused by lung specific, doxycycline inducible overexpression of the bioactive form of the human TGF-β1 gene we find that Tregs accumulate in the lung parenchyma within 5 days of transgene activation and that this enhancement persists to at least 14 days. Anti-CD25 Antibody mediated depletion of Tregs causes increased accumulation of soluble collagen and of intrapulmonary CD45+Col Iα1 fibrocytes. These effects are accompanied by enhanced local concentrations of the classical inflammatory mediators CD40L, TNF-α, and IL-1α, along with the neuroimmune molecule fibroblast growth factor 9 (FGF-9, also known as “glial activating factor”). FGF-9 expression localizes to parenchymal cells and alveolar macrophages in this model and antibody mediated neutralization of FGF-9 results in attenuated detection of intrapulmonary collagen and fibrocytes without affecting Treg quantities. These data indicate that CD4+CD25+FoxP3+ Tregs attenuate TGF-β1 induced lung fibrosis and fibrocyte accumulation in part via suppression of FGF-9.

Rapid induction of lung adenocarcinoma by fibroblast growth factor 9 signaling through FGF receptor 3

Fibroblast growth factors (FGF) are expressed in many non-small cell lung carcinoma (NSCLC) primary tumors and derived cell lines, and mutations in FGF receptor 3 (FGFR3) have been identified in human lung adenocarcinoma. FGF9 has been implicated in the pathogenesis of NSCLC by synergizing with EGFR pathways or by providing an escape pathway mediating resistance to EGFR inhibition. To model pathogenic mechanisms mediated by FGF signals, we have established a mouse model in which FGF9 expression can be induced in adult lung epithelium. Here, we show that induced expression of FGF9 in adult lung leads to the rapid proliferation of distal airway epithelial cells that express the stem cell marker, Sca-1, and the proximal and distal epithelial markers, Sftpc and CC10, the rapid formation of Sftpc-positive adenocarcinomas, and eventual metastasis in some mice. Furthermore, we have identified FGFR3 as the obligate receptor mediating the FGF9 oncogenic signal. These results identify an FGF9-FGFR3 signal as a primary oncogenic pathway for lung adenocarcinoma and suggest that this pathway could be exploited for customized therapeutic applications for both primary tumors and those that have acquired resistance to inhibition of other signaling pathways.

Aryl hydrocarbon receptor activation and overexpression upregulated fibroblast growth factor-9 in human lung adenocarcinomas

We had previously reported that aryl hydrocarbon receptors (AhRs) are overexpressed in lung adenocarcinomas. Benzo[a]pyrene (BaP), an AhR agonist, increased FGF-9 expression in human lung adenocarcinoma cells. Similarly, several AhR agonists increased FGF-9 mRNA levels, and BaP-induced FGF-9 expression was prevented by cotreatment with AhR antagonist in human lung adenocarcinoma cells. Furthermore, AhR agonists increased transcriptional activity of FGF-9 promoter. Modulation of AhR expression via RNA interference or transient overexpression respectively reduced or increased both constitutive and BaP-induced FGF-9 expression in human lung cells. These results suggested that AhR activation and overexpression increased FGF-9 expression in lung cells. FGF-9 increased growth of lung fibroblasts but not that of lung adenocarcinoma cells. However, conditioned media collected from FGF-9-treated fibroblasts increased cell growth of lung adenocarcinoma cells. Furthermore, lung adenocarcinoma cells expressed FGF receptor 2 and cotreatment with anti-FGF receptor 2 prevented the interaction between fibroblasts and tumor cells. It is likely that FGF-9-stimulated fibroblasts secreted unknown factors, which activated FGF receptor 2 and subsequently promoted growth of lung adenocarcinoma cells. We further compared AhR and FGF-9 expression in 146 non-small cell lung cancer (NSCLC) cases by immunohistochemistry. FGF-9 expression was more common in adenocarcinomas than in squamous cell carcinomas. Furthermore, FGF-9 and AhR expression were well correlated in lung adenocarcinomas. These results suggest that AhR expression correlated positively with FGF-9 expression in lung adenocarcinomas, which might promote tumor growth by modulating communication between tumor cells and fibroblasts. Preventing AhR overexpression or disturbing FGF-9 function may reduce the development of lung adenocarcinomas. (c) 2009 UICC.

Global transcriptional characterization of a mouse pulmonary epithelial cell line for use in genetic toxicology

Prior to its application for in vitro toxicological assays, thorough characterization of a cell line is essential. The present study uses global transcriptional profiling to characterize a lung epithelial cell line (FE1) derived from MutaMouse [White, P.A., Douglas, G.R., Gingerich, J., Parfett, C., Shwed, P., Seligy, V., Soper, L., Berndt, L., Bayley, J., Wagner, S., Pound, K., Blakey, D., 2003. Development and characterization of a stable epithelial cell line from Muta Mouse lung. Environmental and Molecular Mutagenesis 42, 166-184]. Results presented here demonstrate the origin of the FE1 lung cell line as epithelial, presenting both type I and type II alveolar phenotype. An assessment of toxicologically-relevant genes, including those involved in the response to stress and stimuli, DNA repair, cellular metabolism, and programmed cell death, revealed changes in expression of 22-27% of genes in one or more culture type (proliferating and static FE1 cultures, primary epithelial cultures) compared with whole lung isolates. Gene expression analysis at 4 and 24h following benzo(a)pyrene exposure revealed the induction of cyp1a1, cyp1a2, and cyp1b1 in FE1 cells and lung isolates. The use of DNA microarrays for gene expression profiling allows an improved understanding of global, coordinated cellular events arising in cells under different physiological conditions. Taken together, these data indicate that the FE1 cell line is derived from a cell type relevant to toxic responses in vivo, and shows some similarity in response to chemical insult as the original tissue.

Motorcycle exhaust induces reproductive toxicity and testicular interleukin-6 in male rats

Motorcycle exhaust (ME) from two-stroke engines contains many toxicants and poses a potential health hazard. The major objectives of the present study were to investigate the male reproductive toxicity of ME and the underlying mechanisms of toxicity. Male Wistar rats were exposed to ME by inhalation 1 h each in the morning and afternoon, Monday through Friday. Exposures to 1:50 diluted ME for 4 weeks or to 1:10 diluted ME for 2 and 4 weeks showed concentration- and time-dependent decreases of testicular weight, spermatid number, and cauda epididymal sperm number. Subsequent studies were done using 4-week exposure to 1:10 diluted ME. ME caused histopathological changes including testicular spermatocytic necrosis and seminiferous tubule atrophy and cauda epididymal formation of clusters of pyknotic and necrotic sperm cells. ME-exposed male rats mated with untreated females showed decreases of male mating index and female fertility index and an increase of implantation site loss. ME decreased 7-ethoxycoumarin O-deethylase and superoxide dismutase activities but induced proinflammatory cytokine interleukin-6 (IL-6) messenger RNA (mRNA) in the testis. Male rats were exposed to ME with or without cotreatment with 50 mg/kg vitamin E orally for 4 weeks. ME decreased serum testosterone concentration. This effect was reversed by cotreatment with vitamin E. ME decreased testicular spermatid number and induced IL-6 mRNA and protein. These effects were also reversed by the vitamin E cotreatment. The present findings show that ME causes male reproductive effects and induces testicular IL-6 in rats by mechanisms involving induction of oxidative stress and inhibition of steroidogenesis.

Upregulation of Cyclooxygenase-2 by Motorcycle Exhaust Particulate-Induced Reactive Oxygen Species Enhances Rat Vascular Smooth Muscle Cell Proliferation

Long-term exposure to particulate air pollution has been implicated as a risk factor for cardiovascular disease and mortality. Short-term exposure has also been suggested to contribute to complications of atherosclerosis. Aberrant regulation of smooth muscle cell proliferation is thought to associate with the pathophysiology of vascular disorders such as atherosclerosis. In this study, we investigate the influence of organic extracts of motorcycle exhaust particulates (MEPE) on rat vascular smooth muscle cell (VSMC) proliferation and related regulation signaling. Exposure of VSMCs to MEPE (10-100 microg/mL) enhanced serum-induced VSMC proliferation. The expression of proliferating cell nuclear antigen (PCNA) was also enhanced in the presence of MEPE. VSMCs treated with MEPE induced the increase in the extent of cyclooxygenase (COX)-2 mRNA and protein expression and prostaglandin E 2 production, whereas the level of COX-1 protein was unchanged. Moreover, MEPE increased the production of reactive oxygen species (ROS) in VSMCs in a dose-dependent manner. MEPE could also trigger time-dependently extracellular signal-regulated kinase (ERK)1/2 phosphorylation in VSMCs, which was attenuated by antioxidants N-acetylcysteine (NAC) and pyrrolidinedithiocarbamate (PDTC). The level of translocation of nuclear factor (NF)-kappaB-p65 in the nuclei of VSMCs was also increased under MEPE exposure. The potentiating effect of MEPE on serum-induced VSMC proliferation could be abolished by COX-2 selective inhibitor NS-398, specific ERK inhibitor PD98059, and antioxidants NAC and PDTC. Taken together, these findings suggest that MEPE may contribute to the enhancement of the pathogenesis of cardiovascular diseases by augmenting proliferation of VSMCs through a ROS-regulated ERK1/2-activated COX-2 signaling pathway.

The environmental carcinogen benzo[a]pyrene induces expression of monocyte-chemoattractant protein-1 in vascular tissue: a possible role in atherogenesis

Exposure to carcinogenic polycyclic aromatic hydrocarbons (PAHs) has been implicated in the aetiology of atherosclerosis. Previously we showed that chronic exposure of ApoE-/- mice to the prototype PAH benzo[a]pyrene (B[a]P) causes enhanced progression of atherosclerosis, which was characterised by an increased inflammatory cell content in the atherosclerotic plaques. The aim of the present study was to evaluate the effect of B[a]P on vascular expression of monocyte-chemoattractant protein 1 (MCP-1), which is a crucial molecule promoting the recruitment of monocytes into atherosclerotic lesions. We hypothesised that B[a]P-induced expression of MCP-1 is mediated through aryl hydrocarbon receptor (AhR) activation. Initially we performed in vivo studies showing that acute treatment with B[a]P induces MCP-1 gene expression in aortic tissue of ApoE-/- mice. These observations could be confirmed by in vitro studies with human endothelial cells (RF24 cell line and primary HUVEC), showing a dose- and time-dependent increase in MCP-1 expression upon exposure to B[a]P. This was paralleled by an induction of cytochrome P450 1A1 and 1B1, indicating Ah receptor activation. No increased gene expression (MCP-1, CYP1A1 and 1B1) was found upon incubation with the structural isomer benzo[e]pyrene, which is a weak AhR agonist. Moreover, B[a]P-induced MCP-1 gene and protein expression was inhibited by co-treatment with the AhR antagonist alpha-naphthoflavone. In addition to its effect on basal gene expression, we showed that B[a]P significantly enhanced TNFalpha-induced expression of MCP-1. We were unable to block B[a]P-induced MCP-1 expression by antioxidant treatment. In contrast, we found that addition of N-acetylcysteine or vitamin C enhanced transcription of MCP-1 by B[a]P. In conclusion, our studies revealed potent vascular pro-inflammatory effects of B[a]P, as evidenced by AhR-mediated induction of MCP-1. These observations further contribute to the concept that induction of inflammation is a crucial process in PAH-enhanced atherogenesis.