OBJECTIVE: This study sought to explore endothelial nitric oxide synthase (eNOS) expression in acute pulmonary thromboembolism (APE). MATERIALS AND METHODS: eNOS expression in lung tissue and bone marrow-derived endothelial progenitor cells (BM-EPCs) from APE mouse models was assessed by immunohistochemistry and real-time PCR. A gene expression profile meta-analysis was performed on human venous thromboembolism (VTE) whole blood samples recorded in the Gene Expression Omnibus (GEO) repository. Significantly expressed genes were determined from the microarray data by unsupervised clustering and supervised classification. Selected sample data with significantly expressed genes were further analyzed by principal component analysis (PCA), followed by Bayesian probit regression. Key discriminate genes were further grouped and annotated using functional annotations and gene enrichments using the online Database for Annotation, Visualization and Integrated Discovery (DAVID) software (v. 6.7). RESULTS: While eNOS expression was significantly higher, serum nitric oxide levels were significantly lower in APE mice (20.42 +/- 2.15 mu M) compared to controls (53.50 +/- 5.69 mu M, p<0.001). eNOS mRNA and protein levels were significantly upregulated in BM-EPCs from APE mice. GEO repository data reported 3,397 upregulated and 4,173 downregulated genes (including eNOS) in VTE patients. In this regression analysis, the significant principal component PC1 and PC2 (p<0.05) were useful in distinguishing the VTE classification. The coefficient value of eNOS was -0.47707 in PC1 and -0.08429 in PC2, which did have some proportions on these significantly discriminated components but did not contribute significantly to the VTE classification. Functional enrichment in terms of acetylation and phosphoproteins were high. CONCLUSIONS: Our findings, therefore, suggest that expression of eNOS is significantly altered in APE and may be a potential peripheral blood biomarker. Modulation of eNOS expression may be used for APE treatment.