However, the most appropriate method AZD2281 research buy for evaluating and comparing the condensate responses involves quantitative analyses of the dose–response functions. Therefore, benchmark dose modelling was conducted using BMDExpress (Yang et al., 2007) to define and compare the points of departure for KEGG pathways. There were 68 pathways with significant benchmark doses (BMD) that were common to both condensates and both time points. The points of departure for 61 of these pathways were lower for

cells exposed to MSC as compared to TSC, highlighting the greater potency of MSC. Moreover, the BMDs for 30 (i.e., 44%) of the pathways were a full order of magnitude lower for MSC than for TSC exposed cells. In addition, the mean of all the BMDs for the common pathways was significantly lower (Student’s t-test, p < 0.001) for MSC exposed cells. Mean BMDs at the 6 h time point were 3.1 ± 1.5 and 24.2 ± 10.1 μg/ml for MSC and TSC, respectively. At the 6 + 4 h time point the mean BMDs were 2.6 ± 0.6 and 17.5 ± 14.7 μg/ml for MSC and

TSC, respectively. BMDs tended to be lower at the 6 + 4 h time point and contain a higher percentage of significant genes in the pathway relative to the 6 h time point. The median BMDs for selected KEGG pathways are shown in Table 4. Three RT-PCR pathway specific arrays (i.e., stress and toxicity, cell cycle and apoptosis) were used to confirm the expression changes measured by the DNA microarrays (Table 5). The fold changes Cyclopamine concentration tended to be larger for the RT-PCR generated data, however, considerable agreement exists between the DNA microarray and RT-PCR findings. In our previous genotoxicity study we showed that MSC and TSC were both cytotoxic and genotoxic (Maertens et al., 2009). However, quantitatively, MSC was more cytotoxic and mutagenic Hydroxychloroquine research buy than TSC, and TSC

appeared to induce chromosomal damage (i.e., micronuclei) in a concentration-dependent manner whereas MSC did not. Our earlier chemical analyses of MSC and TSC noted that aside from the nicotine in tobacco and the cannabinoids in marijuana, the two smoke condensates contained mixtures of chemicals that were qualitatively similar though quantitatively different (Moir et al., 2008). The similarities in the chemical profiles and some of the toxicity findings suggested that the two smoke condensates might elicit somewhat comparable gene expression profiles. Hierarchal clustering of all the MSC and TSC exposed samples in the present study supported this notion (for all but the highest dose of MSC) and samples clustered first by concentration as opposed to smoke type. In addition, analysis of the top ten greatest gene expression changes relative to control revealed that half of the genes were common to both marijuana and tobacco. A number of previous studies have examined gene expression changes in pulmonary cells following exposure to tobacco smoke (Bosio et al., 2002, Fields et al., 2005, Jorgensen et al., 2004 and Maunders et al., 2007).