Epigenetic Regulation of Cytosolic Phospholipase A2 in SH-SY5Y Human Neuroblastoma Cells

Group IVA cytosolic phospholipase A(2) (cPLA(2) or PLA2G4A) is a key enzyme that contributes to inflammation via the generation of arachidonic acid and eicosanoids. While much is known about regulation of cPLA2 by posttranslational modification such as phosphorylation, little is known about its epigenetic regulation. In this study, treatment with histone deacetylase (HDAC) inhibitors, trichostatin A (TSA), valproic acid, tubacin and the class I HDAC inhibitor, MS-275, were found to increase cPLA(2)alpha messenger RNA (mRNA) expression in SH-SY5Y human neuroblastoma cells. Co-treatment of the histone acetyltransferase (HAT) inhibitor, anacardic acid, modulated upregulation of cPLA(2)alpha induced by TSA. Specific involvement of class I HDACs and HAT in cPLA(2)alpha regulation was further shown, and a Tip60-specific HAT inhibitor, NU9056, modulated the upregulation of cPLA(2)alpha induced by MS-275. In addition, co-treatment of with histone methyltransferase (HMT) inhibitor, 5'-deoxy-5'-methylthioadenosine (MTA) suppressed TSA-induced cPLA(2)alpha upregulation. The above changes in cPLA(2) mRNA expression were reflected at the protein level by Western blots and immunocytochemistry. Chromatin immunoprecipitation (ChIP) showed TSA increased binding of trimethylated H3K4 to the proximal promoter region of the cPLA(2)alpha gene. Cell injury after TSA treatment as indicated by lactate dehydrogenase (LDH) release was modulated by anacardic acid, and a role of cPLA(2) in mediating TSA-induced injury shown, after co-incubation with the cPLA(2) selective inhibitor, arachidonoyl trifluoromethyl ketone (AACOCF(3)). Together, results indicate epigenetic regulation of cPLA(2) and the potential of such regulation for treatment of chronic inflammation.