Analysis of differentially expressed genes in nitric oxide-exposed human monocytic cells

In this study we examined the gene expression pattern of *NO-dependent genes in U937 and Mono Mac 6 monocytes exposed to the synthetic NO-donor DPTA-NO using microarray technology. cDNA microarray data were validated by Northern blot analysis and quantitative real-time PCR. This approach allowed the identification of 17 *NO-sensitive genes that showed at least a twofold difference in expression, in both U937 cells and Mono Mac 6 cells exposed to 500 microM DPTA-NO for 4 h. NO-stimulated genes belong to various functional groups, including transcription factors, signaling molecules, and cytokines. Among the selected genes, 11 (ATF-4, c-maf, SGK-1, PBEF, ATPase 8, NADH dehydrogenase 4, STK6, TRAF4-associated factor 1, molybdopterin synthase, CKS1, and CIDE-B) have not been previously reported to be sensitive to *NO. Because several *NO-stimulated genes are transcription factors, we analyzed the mRNA expression profile in U937 cells exposed to DPTA-NO for 14 h. We found that long-term *NO treatment influenced transcription rates of a rather limited set of genes, including CIDE-B, BNIP3, p21/Cip1, molybdopterin synthase, and TRAF4-associated factor 1. To accelerate formation of nitrosating species, U937 cells were exposed to DPTA-NO along with suboptimal concentrations of 2-phenyl-4,4,5,5-tetramethylimidazole-1-oxyl 3-oxide (PTIO). PTIO-mediated increase in nitrosating species remarkably enhanced *NO-dependent induction of IL-8, p21/Cip1, and MKP-1 and built a specific gene expression profile.