A monoamine oxidase B inhibitor altered gene expression of catalytically active dual-specificity phosphatases in human oral gingival keratinocytes.

Objective: Monoamine oxidase (MAO) inhibitors reduce inflammation in a number of in vitro and in vivo models. This finding led to the development of a novel MAO-B selective inhibitor (RG0216) designed to reduce blood-brain barrier penetration. To elucidate RG0216's regulatory role in inflammation-relevant signaling pathways, we employed a transcriptome analytic approach to identify genes that are differentially regulated by RG0216 and then globally identified which inflammation-relevant biological signaling pathways were altered by this drug.

Material and methods: Primary human gingival keratinocyte (HGK) cells were treated with RG0216, and RNA was extracted (4 h). RNAseq transcriptome analysis was utilized to identify differentially expressed genes (DEGs), while Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were used to identify significantly enriched biological pathways. Relevant genes associated with these pathways and RG0216 regulation of Porphyromonnas gingivalis lipopolysaccharide (PgLPS)-induced cytokine/chemokine expression were evaluated using the real-time quantitative reverse-transcription polymerase chain reaction (RT-qPCR) approach.

Results: RG0216 significantly altered the expression of 50 DEGs in HGK cells. Using GO and KEGG analytic approaches, these genes were associated with the biological pathways relevant to mitogen-activated protein kinase (MAPK) and MAPK phosphatases. These phosphatases are part of the 10-member catalytically active dual-specificity phosphatase (DUSP) family. RG0216 induced the expression of DUSP10, reduced the expression of DUSP4 and DUSP6, and decreased IL-6 and IL-8 expression in control and PgLPS-stimulated cultures.

Conclusions: In HGK cells, a novel MAO-B inhibitor (RG0216) significantly altered DUSP4, DUSP6, and DUSP10 expression. DUSPs play a regulatory role in MAPK activity and, therefore, can alter cellular inflammatory responses. We found that RG0216 inhibited IL-6 and IL-8 expression. Further studies are planned to examine RG0216's regulatory role in DUSP expression and its impact on the regulation of cytokine/chemokine expression.