ORIGINAL RESEARCH PAPER Effect of nitric oxide on microRNA-155 expression in human hepatic epithelial cells Yael Yuhas • Eva Berent • Shai Ashkenazi Received: 6 October 2013 / Revised: 4 February 2014 / Accepted: 13 March 2014 / Published online: 1 April 2014 Ó Springer Basel 2014 Abstract Objective Nitric oxide (NO) is a signaling molecule and regulator of immunity and inflammation. MicroRNAs (miRNAs) regulate gene transcription and are involved in inflammatory processes and cancer. This study sought to determine if NO activity affects miRNA expression. Methods Human liver epithelial (HepG2) cells were treated with the NO-releasing S-nitroso-N-acetylpenicilla- mine (SNAP) 100 lM for 4 h and subjected to microarray analysis. To examine the underlying mechanisms, cells were exposed to cGMP analog 8-bromo-cGMP, protein kinase inhibitor Rp-*-Br-PET-cGMPS (Rp-PET), or nitric synthase inhibitor L-NAME and evaluated with RT-PCR. Results MiR-155 was the only miRNA of the 887 arrayed that showed a change in expression after SNAP treatment. Incubation of the cells with 8-bromo-cGMP increased miR- 155 expression 4.0 ± 0.7-fold (p \ 0.05); Rp-PET before SNAP had a dual, concentration-dependent effect. SNAP treatment induced a 3.1 ± 0.7-fold change in miRNA-155 expression, Rp-PET 25 lM, a 7.3 ± 2.2-fold change, and Rp-PET 100 lM, a 0.79 ± 0.09-fold change (SNAP vs SNAP ? Rp-PET, p \ 0.05). In unstimulated cells, Rp- PET or L-NAME treatment increased miR-155 expression by 3.5 ± 0.7-fold and 5.6 ± 2.2-fold, respectively (p \ 0.05). Conclusion In HepG2 cells, exogenous NO increases miR-155 expression, but endogenous basal NO inhibits it. Both effects are mediated via cGMP/PKG signaling. The upregulation of miR-155 by NO provides a new link between NO, inflammation, and cancer. Keywords Nitric oxide Á MicroRNAs Á MiR-155 Á Inflammation Abbreviations NO Nitric oxide miRNA MicroRNA NOS Nitric oxide synthase eNOS Endothelial NOS iNOS Inducible NOS HepG2 Hepatic epithelial (cells) IL-8 Interleukin-8 SNAP S-nitroso-N-acetylpenicillamine SNP Sodium nitroprusside sGC Soluble guanylyl cyclase cGMP Cyclic guanosine monophosphate PKG Protein kinase G Rp-PET Rp-8-Bromo-beta-phenyl-1,N 2 -ethenoguanosine 3 0 5 0 -cyclic monophosphorothioate sodium salt (Rp-*-Br-PET-cGMPS) L-NAME N G -nitro-L-arginine methyl ester Responsible Editor: Graham R. Wallace. Y. Yuhas (&) Á E. Berent Á S. Ashkenazi Infectious Diseases Research Laboratory, Felsenstein Medical Research Center, Beilinson Campus, 49100 Petach Tikva, Israel e-mail: yuhas@post.tau.ac.il E. Berent e-mail: evabr@clalit.org.il S. Ashkenazi e-mail: ashai@post.tau.ac.il S. Ashkenazi Department of Pediatrics A, Schneider Children’s Medical Center, Petach Tikva, Israel Y. Yuhas Á S. Ashkenazi Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel Inflamm. Res. (2014) 63:591–596 DOI 10.1007/s00011-014-0730-8 Inflammation Research 123