Pharmacological phosphodiesterase 4D (PDE4D) inhibition shows therapeutic potential to restore memory function in Alzheimer's disease (AD), but will likely evoke adverse side effects. As PDE4D encodes multiple isoforms, targeting specific isoforms may improve treatment efficacy and safety. Here, we investigated whether PDE4D isoform expression and PDE4D DNA methylation is affected in AD and whether expression changes are associated with severity of pathology and cognitive impairment. In post-mortem temporal lobe brain material from AD patients (n = 42) and age-matched controls (n = 40), we measured PDE4D isoform expression and PDE4D DNA (hydroxy)methylation using quantitative polymerase chain reaction and Illumina 450k Beadarrays, respectively. Linear regression revealed increased PDE4D1, -D3, -D5, and -D8 expression in AD with concurrent (hydroxy)methylation changes in associated promoter regions. Moreover, increased PDE4D1 and -D3 expression was associated with higherplaque and tau pathology levels, higher Braak stages, and progressed cognitive impairment. Future studies should indicate functional roles of specific PDE4D isoforms and the efficacy and safety of their selective inhibition to restore memory function in AD.This article is freely available via Open Access. Click on the Publisher URL to access it via the publisher's site.This work was financially supported by grants from ISAO/Alz-heimer Nederland WE.03-2016-07, Young European Research Universities Network (YERUN), and the Baeter Laeve foundation. Additional funds have been provided by the Internationale StichtingAlzheimer Onderzoek (ISAO)/Alzheimer Netherlands (Award#11532; Funded by the Dorpmans-Wigmans Foundation) (DvdH),and by the Joint Programme Neurodegenerative Disease Research(JPND) for the EPI-AD consortium (http://www.neurodegenerationresearch.eu/wp-content/uploads/2015/10/Factsheet_EPI-AD.pdf).The project is supported through the following funding organizations under the aegis of JPND; The Netherlands, The Netherlands Organisation for Health Research and Development (ZonMw);United Kingdom, Medical Research Council; Germany, German Federal Ministry of Education and Research (BMBF); Luxembourg, National Research Fund (FNR). This project has received funding from the European Union’s Horizon 2020 research and innovation program under Grant Agreement No. 643417.We thank Dr. Ir. Jochen De Vry for primer and qPCR experiment designpublished version, accepted version (12 month embargo
