ABSTRACT: Methods: To better understand the role of OX40 in the regulation of monocyte activation and polarization, OX40/Fc- or control IgG-treated liver monocytes were compared in a transcriptome sequencing study. Total RNA was isolated from FACS-separated hepatic monocytes. Transcriptome sequencing libraries were generated using NEBNext® Ultra™ RNA Library Prep Kit for Illumina® (NEB, USA) following manufacturer’s recommendations and sequenced on an Illumina Hiseq platform (Illumina, San Diego, CA). Sequences were aligned to the reference genome with TopHat and processed with Cufflinks, which quantifies each transcript in each sample using reference annotations produced bythe University of California Santa Cruz UCSC. Differentially expressed genes with a fold change of >=2.0 and padj < 0.05 between OX40 treated and control monocytes were submitted to GO and KEGG enrichment analysis, which uses unbiased methods to assess pathway enrichment. Results: Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses revealed that upregulated genes from OX40-stimulated monocytes are involved in inflammatory response; cytokine production regulation; lipid, cytokine and bacteria responses; innate immune response; enhanced cellular response to cytokines and the cytokine-cytokine receptor interaction; and the phagosome and chemokine signaling pathway, among others. Compared to control monocytes, OX40/Fc-treated monocytes exhibited upregulated levels of cytokines (Tnf, Il1a, Il1b, Il6 and Il12a), cytokine receptors (Il1rl1, Il2r, Il18r and Il23r), chemokines (Ccl3, Ccl4, Ccl22, Cxcl1, Cxcl2, Cxcl10 and Cx3cl1), chemokine receptors ( Ccrl2, Cxcr5 and Cxcr6) and antigen processing and presentation molecules (Cd40, Cd80, Cd86, Tlr1, Tlr2, and Ox40l). The coordinated action of various inflammatory modulators, signaling molecules, and transcription factors, including Nlrp3, Tank, Jak2, Stat5a, Hif1a, Nos2, Socs3, Mir155hg and Pparg, was determined to be involved in the OX40 regulation of monocyte M1 polarization. MyD88, Irf3, Irf5, Stat1, Nod1 and Nod2 may not be involved in OX40-triggered monocyte M1 polarization.
