Transcriptome analysis of lung tissue reveals rapid activation of innate immune system in response to inhaled rCNT. a: heatmap of differentially expressed genes (linear FC > |1.5|, post hoc adjusted P-value = 0.01) in lungs of mice exposed to rCNT or tCNT for 4 h and sacrificed either immediately after exposure or on the following day. Genes are arranged by hierarchical clustering analysis. Untreated (UT) and tCNT-exposed lung samples share similar expression patterns shortly after 4-h exposure. Red color indicates higher expression while green denotes lower expression. b: Venn diagram of the microarray results summarizing the numbers of differentially expressed genes (linear FC > |1.5|, post hoc adjusted P-value = 0.01) in lung tissue after 4 h exposure to CNT. The diagram shows that rCNT cause a markable expression of multiple distinct genes already after 4-h exposure (776 genes) while the number of genes specific to tCNT is notably lower (109 genes). c: pathway bubble-plot shows that inhalation of rCNT activates several innate immunity-associated pathways after the 4 h exposure. The diameter of each circle represents the number of genes annotated in each pathway (legend “count”). Red color indicates up-regulated pathways and green color down-regulated pathways compared to untreated controls.