Human aortic endothelial cells respond to shear flow in well-plate microfluidic devices.

Although chronic progressive cardiovascular diseases such as atherosclerosis are often challenging to fully model in vitro, it has been shown that certain in vitro methods can effectively evaluate some aspects of disease progression. This has been demonstrated in in vitro and in vivo studies of endothelial cells that have illustrated the effects of nitric oxide (NO) production, filamentous actin (F-actin) formation, and cell and actin angle alignment on vascular function and homeostasis. Systems utilising shear flow have been established, in order to create a physiologically relevant environment for cells that require shear flow for homeostasis. Here, we investigated the use of a well-plate microfluidic system and associated devices (0-20dyn/cm²) to demonstrate applied shear effects on primary Human Aortic Endothelial Cells (HAECs). Changes in cell and actin alignment in the direction of flow, real-time production of NO and gross cell membrane shape changes in response to physiological shear flow were observed. These commercial systems have a range of potential applications, including within the consumer and pharmaceutical industries, thereby reducing the dependency on animal testing for regulatory safety assessments.

Mechanisms of whole smoke conditioned media induced cytotoxicity to human aortic endothelial cells.

Chronic exposure to cigarette smoke can lead to endothelial dysfunction and potentially endothelial cell death. Here, we exposed Human Aortic Endothelial Cells (HAECs) to whole smoke conditioned media (WSCM) over a range of nicotine equivalence (n.e.) concentrations (0-8000 ng/mL n.e.). After 24 h, Neutral Red Uptake (NRU) and reduction of 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) to formazan was determined for each exposure concentration and compared to control. IC50 values in the NRU assay were: 4582 ng/mL n.e. ± 1074, 4587 ng/mL n.e. ± 951, 4993 ng/mL n.e. ± 1239 and 4691 ng/mL n.e. ± 402 for four HAEC donors. IC50 values in the MTT assay were: 4885 ng/mL n.e. ± 1341, 4584 ng/mL n.e. ± 806, 5749 ng/mL n.e. ± 783 and 5228 ng/mL n.e. ± 593 for the four donors. To examine the mechanism responsible for WSCM-induced cytotoxicity in HAECs, flow cytometry using necrosis (Propidium Iodide) and apoptosis (Annexin V) markers were used. Annexin V-positive cell populations increased in a dose dependent manner while increases in PI-positive cell populations occurred at the highest doses of WSCM (5000-8000 ng/mL n.e.). Western blotting for cleaved caspase-3 confirmed that apoptosis occurs at >5000 ng/mL n.e. WSCM, coinciding with reduced HAEC survival.

Investigation of multiple whole smoke dosimetry techniques using a VITROCELL®VC10® smoke exposure system.

The Vitrocell® VC10® smoke exposure system offers multiple platforms for air liquid interface (ALI) and air agar interface (AAI) exposure that mimic in vivo conditions for assessing toxicological impact of whole smoke using in vitro assays. The aim of this study was to investigate and compare multiple dosimetry techniques that may be employed during combustible cigarette whole smoke exposure using the Vitrocell® VC10® smoking robot. The following techniques were assessed: (1) quartz crystal microbalances (QCMs), (2) aerosol photometers (using area under curve, AUC), and (3) fluorescence of anhydrous dimethyl sulfoxide (DMSO)-captured smoke constituents. Results showed that each of the dosimetry techniques was able to distinguish different levels of whole smoke airflow in a concentration-related manner. When compared to each other, the three techniques showed a high level of consistency and all were considered efficient tools in quantifying dose during an exposure, although higher variation was observed at the higher airflows tested. Overall, the dosimetry tools investigated here provide effective measures of the whole smoke concentrations tested during the exposure.

Development of a quantitative method for assessment of dose in in vitro evaluations using a VITROCELL® VC10® smoke exposure system.

The assessment of potential cytotoxicity or genotoxicity of combustible tobacco products has historically been performed using partitioned exposures (i.e. total particulate matter [TPM], gas vapor phase [GVP]) rather than whole smoke. The VITROCELL® VC10® smoke exposure system offers multiple platforms for air liquid interface (ALI) or air agar interface (AAI) exposure to mimic in vivo-like conditions for assessing the toxicological impact of whole smoke using in vitro assays (e.g. cytotoxicity, mutagenicity and DNA modifications). The aims of this study were to investigate dosimetry during whole smoke exposure in the VITROCELL® VC10® smoking robot using quartz crystal microbalances (QCMs) and to support the use of photometers for concurrent assessment of 'dose' during whole smoke exposures. QCM results showed consistent deposition across different exposure chambers, between dilution bars, experiments and modules. Higher levels of variation were noted at higher airflows (i.e., >8 L/min). Dosimetry assessed using photometers also showed a high level of consistency between experiments, with no notable impact on deposition on the QCM when the photometers were placed 'in-line' between the dilution bar and the exposure module. However, the use of photometers alone may be not be sufficient to estimate deposition; the predictability of the data-generated equation was poor. Further development of dosimetry methodology and information for use in validated in vitro biological test methods is needed to facilitate on-going aerosol-based research and relative assessment.

The time course of expression of genes involved in specific pathways in normal human bronchial epithelial cells following exposure to cigarette smoke.

This study was conducted to determine the time course of gene expression associated with specific signaling pathways in normal human bronchial epithelial (NHBE) cells after exposure to 2 concentrations of 2R4F tobacco mainstream smoke (MSS). Expression of 84 genes representing 18 signal transduction pathways was quantitated in MSS- and air-exposed cultures using real-time polymerase chain reaction (PCR) arrays at 1, 4, and 24 hours following exposure. A confidence score, calculated based on statistical analysis of the degree and reproducibility of expression changes, was used to identify potential biologically significant changes in gene expression. Stimulation of NIAP, an apoptosis inhibitor, suppression of NFKB1 and MYC, representing pro-apoptotic activity, and down-regulation of TCF7 and up-regulation of KLK2, representing anti-/pro-inflammatory responses, were altered 1 hour after exposure to the high concentration of MSS. At the 4-hour time point, the pattern had changed such that 10 different genes were now up-regulated and an additional gene was now down-regulated. Significant changes included genes involved in inflammatory response (LTA, SELPLG, and IL8), repair and wound-healing activity (MMP10), and growth activity (GREB1, EGR1), suggesting repair in this period. By 24 hours, the only up-regulated genes in common with the 4-hour profile were SELPLG and IL8, suggesting continued inflammatory signaling. These results suggest that identification of specific gene expression-based biomarkers of MSS toxicity is promising for investigating specific mechanisms of cellular damage. As expected, the expressed signals were dependent on the concentration of MSS and the postexposure times.

Development, qualification, validation and application of the Ames test using a VITROCELL® VC10® smoke exposure system.

The Ames test has established use in the assessment of potential mutagenicity of tobacco products but has generally been performed using partitioned exposures (e.g. total particulate matter [TPM], gas vapor phase [GVP]) rather than whole smoke (WS). The VITROCELL®VC10® smoke exposure system offers multiple platforms for air liquid interface (ALI), or air agar interface (AAI) in the case of the Ames test exposure to mimic in vivo-like conditions for assessing the toxicological impact of fresh WS in in vitro assays. The goals of this study were to 1) qualify the VITROCELL®VC10® to demonstrate functionality of the system, 2) develop and validate the Ames test following WS exposure with the VITROCELL®VC10® and 3) assess the ability of the Ames test to differentiate between a reference combustible product (3R4F Kentucky reference cigarette) and a primarily tobacco heating product (Eclipse). Based on critical function assessments, the VITROCELL®VC10® was demonstrated to be fit for the purpose of consistent generation of WS. Assay validation was conducted for 5 bacterial strains (TA97, TA98, TA100, TA1535 and TA102) and reproducible exposure-related changes in revertants were observed for TA98 and TA100 in the presence of rat liver S-9 following exposure to 3R4F WS. In the comparative studies, exposure-related changes in in vitro mutagenicity following exposure of TA98 and TA100 in the presence of S9 to both 3R4F and Eclipse WS were observed, with the response for Eclipse being significantly less than that for 3R4F (p < 0.001) which is consistent with the fewer chemical constituents liberated by primarily-heating the product.

Development, qualification, validation and application of the neutral red uptake assay in Chinese Hamster Ovary (CHO) cells using a VITROCELL® VC10® smoke exposure system.

Cytotoxicity assessment of combustible tobacco products by neutral red uptake (NRU) has historically used total particulate matter (TPM) or solvent captured gas vapor phase (GVP), rather than fresh whole smoke. Here, the development, validation and application of the NRU assay in Chinese Hamster Ovary (CHO) cells, following exposure to fresh whole smoke generated with the VITROCELL® VC10® system is described. Whole smoke exposure is particularly important as both particulate and vapor phases of tobacco smoke show cytotoxicity in vitro. The VITROCELL® VC10® system provides exposure at the air liquid interface (ALI) to mimic in vivo conditions for assessing the toxicological impact of smoke in vitro. Instrument and assay validations are crucial for comparative analyses. GOALS OF THIS STUDY: 1) demonstrate functionality of the VITROCELL® VC10® system by installation, operational and performance qualification, 2) develop and validate a cellular system for assessing cytotoxicity following whole smoke exposure and 3) assess the whole smoke NRU assay sensitivity for statistical differentiation between a reference combustible cigarette (3R4F) and a primarily "heat-not-burn" cigarette (Eclipse). RESULTS: The VITROCELL® VC10® provided consistent generation and delivery of whole smoke; exposure-related changes in in vitro cytotoxicity were observed with reproducible IC50 values; comparative analysis showed that the heat-not-burn cigarette was significantly (P<0.001) less cytotoxic than the 3R4F combustible cigarette, consistent with the lower levels of chemical constituents liberated by primarily-heating the cigarette versus burning.

Gene expression in normal human bronchial epithelial (NHBE) cells following in vitro exposure to cigarette smoke condensate.

Cigarettes that burn tobacco produce a complex mixture of chemicals, including mutagens and carcinogens. Cigarettes that primarily heat tobacco produce smoke with marked reductions in the amount of mutagens and carcinogens and demonstrate reduced mutagenicity and carcinogenicity in a battery of toxicological assays. Chemically induced oxidative stress, DNA damage, and inflammation may alter cell cycle regulation and are important biological events in the carcinogenic process. The objective of this study was to characterize and compare the effects of smoke condensates from cigarettes that burn tobacco and those that primarily heat tobacco on gene expression in NHBE cells. For this comparison, we used quantitative RT/PCR and further evaluated the effects on cell cycling using flow cytometry. Cigarette smoke condensates (CSCs) were prepared from Kentucky 1R4F cigarettes (a tobacco-burning product designed to represent the average full-flavor, low "tar" cigarette in the US market) and Eclipse (a cigarette that primarily heats tobacco) using FTC machine smoking conditions. The CSC from 1R4F cigarettes induced statistically significant increases in the mRNA levels of genes responsive to DNA damage (GADD45) and involved in cell cycle regulation (p21;WAF1/CIP1), compared to the CSC from Eclipse cigarettes. In addition, genes coding for cyclooxygenase-2 (COX-2) and interleukin 8 (IL-8), which are associated with oxidative stress and inflammation, respectively, were increased statistically significantly more by CSC from 1R4F than by that from Eclipse. Furthermore, a dose-dependent increase in IL-8 protein secretion into cell culture media was stimulated by 1R4F exposure, whereas minimal IL-8 protein was secreted after Eclipse treatment. The biological relevance of the differential effect on gene expression was reflected in differential cell cycle regulation, as cells exposed to 1R4F CSC exhibited more significant S phase and G2 phase accumulation than cells exposed to Eclipse CSC. These data indicate that the simplified smoke chemistry of the tobacco-heating Eclipse cigarette yields statistically significant reductions in the expression of key genes involved in DNA damage, oxidative stress, inflammatory response, and cell cycle regulation in normal human bronchial epithelial cells compared to a representative tobacco-burning cigarette.

Kinetic analysis of cytokine response to cigarette smoke condensate by human endothelial and monocytic cells.

Atherosclerosis is generally considered an inflammatory disease characterized by the accumulation of lipid in large and medium elastic arteries. Individuals who smoke are at increased risk for developing atherosclerosis and the clinical events associated with this disease. Underlying the mechanisms involved in atherosclerotic lesion development exists a complex pattern of signaling, involving molecules (cytokines and chemokines) that mediate the progression of arterial lesions. The unique nature of exposure to tobacco-related toxicants during the process of smoking prompted our investigation of the time-dependent responses of two critical cell types to cigarette smoke condensate exposure. In this study, we examined the kinetic responses, using suspension array technology and RT-PCR of 17 cytokines (IL-1beta, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12, IL-13, IL-17 GM-CSF, G-CSF, INF-gamma, TNF-alpha, MCP-1 and MIP-1beta) in human aortic endothelial cells (HAECs) and THP-1 monocyte macrophages following exposure to cigarette smoke condensate (CSC) for 24h. In HAECs, IL-8 and IL-4 were rapidly stimulated by CSC exposure while, surprisingly, MCP-1 expression was downregulated. In THP-1 macrophages, IL-6, MIP-1beta, MCP-1 and IL-1beta protein expression were suppressed upon CSC exposure. All other measurable cytokines in THP-1 cells exposed to CSC had levels of protein and mRNA similar to controls. Depending on cell type, CSC uniquely influences the expression of cytokines. The complex interplay of these signaling molecules within the framework of atherosclerosis points to the ability of cigarette smoke components to alter such signaling following acute exposure, and by this mechanism may alter the course of both atherogenesis initiation and progression.

Matrix-degrading and pro-inflammatory changes in human vascular endothelial cells exposed to cigarette smoke condensate.

Cigarette smoking has been associated with an increase in the severity and prevalence of atherosclerosis in the abdominal aorta. To begin our investigation of this finding, we used an integrated approach combining gene expression profiling, protein analysis, cytokine measurements, and cytotoxicity determinations to examine molecular responses of cultured human aortic and coronary endothelial cells exposed to cigarette smoke condensate (CSC) and nicotine. Exposure of endothelial cells to CSC (30 and 60 microg/mL TPM) for 24 h resulted in minimal cytotoxicity, and the upregulation of genes involved in matrix degradation (MMP-1, MMP-8, and MMP-9), xenobiotic metabolism (HO-1 and CYP1A2), and downregulation of genes involved in cell cycle regulation (including TOP2A, CCNB1, CCNA, CDKN3). Exposure of cells to a high physiological concentration of nicotine resulted in few differentially expressed genes. Immunoblot analysis of proteins selected from genes shown to be differentially regulated by microarray analysis revealed similar responses. Finally, a number of inflammatory cytokines measured in culture media were elevated in response to CSC. Together, these results describe a complex proinflammatory response, possibly mediating the recruitment of leukocytes through cytokine signaling. Additionally, fibrous cap destabilization may be facilitated by matrix metalloproteinase upregulation.

Distinct regulatory profiles of interleukins and chemokines in response to cigarette smoke condensate in normal human bronchial epithelial (NHBE) cells.

Bronchial epithelium is frequently exposed to air pollutants, and it is hypothesized that these cells elicit inflammatory responses as early elements in pulmonary defense. Our purpose was to evaluate changes in messenger RNA levels of 84 genes representing cytokines and receptors over a repetitive-exposure time course to further define the inflammatory responses associated with mainstream cigarette smoke (MSS) exposure in an in vitro lung model. Normal human bronchial epithelial cells were treated with mainstream cigarette smoke condensate (CSC) prepared from Kentucky 2R4F cigarettes (60 microg total particulate matter/mL media, 0.2% dimethylsulfoxide), and examined by quantitative real-time polymerase chain reaction. Applications of CSC were designed in seven groups to test immediate, early, intermediate, and late responses evaluated at the end of alternating exposure/recovery periods. Three predominant gene expression responses were observed: adaptive (return to baseline), sustained (maintained expression during treatment), and chronic (maintained expression posttreatment). Overall, 25 genes exhibited statistically significant changes: 14 genes exclusively elevated, 10 genes exclusively depressed, and 1, interleukin-8 (IL8), exhibiting both up- and downregulation in the seven groups. The most responsive genes were osteopontin (34-fold upregulation) and CXCL14 (23-fold downregulation). Our observations suggest that specific genes involved in inflammatory pathways respond to CSC in chronic, sustained, or adaptive patterns with the chronic pattern as the predominant behavior.

Differential c-myc expression profiles in normal human bronchial epithelial cells following treatment with benzo[a]pyrene, benzo[a]pyrene-4,5 epoxide, and benzo[a]pyrene-7,8-9,10 diol epoxide.

Bronchial epithelial cells are often exposed to airborne mutagens that have the potential to induce genetic changes involved in the development of lung cancer. Although lung tumors often display alterations in the expression of oncogenes and/or tumor suppressor genes, the role of specific chemicals and/or metabolites in causing these alterations is not well defined. The polycyclic aromatic hydrocarbon (PAH) benzo[a]pyrene (B[a]P), a by-product of combustion, is a prevalent airborne environmental mutagen and a constituent of cigarette smoke. The primary objective of this study was to compare the effect of B[a]P and two of its reactive metabolites, benzo[a]pyrene diol epoxide (BPDE or bay region epoxide) and benzo[a]pyrene-4,5-dihydroepoxide (BPE or K-region epoxide), on expression of the proto-oncogene c-myc in normal human bronchial epithelial (NHBE) cells using a quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) method. Changes in c-myc gene expression were compared with DNA adduct formation, growth inhibition, and cell-cycle progression as determined by (32)P-postlabelling, neutral red (NR), and flow cytometric analyses, respectively. None of the three test compounds altered the levels of 18S ribosomal RNA or beta-actin at the concentrations evaluated for c-myc expression, indicating that nonspecific changes in gene expression induced by cytotoxicity, for example, were not present at the concentrations evaluated. Cells exposed to B[a]P exhibited a dose-dependent increase in c-myc expression; conversely, a dose-dependent decrease in c-myc expression was observed following BPDE exposure. A marginal but concentration-dependent increase in c-myc mRNA levels was observed following exposure to the K-region epoxide. Our results demonstrated that, although B[a]P and its metabolites alter c-myc expression, the parent compound and its metabolites produce unequal and contrasting effects on the expression of this gene.