Background: Despite the high cost and widespread prevalence of alcohol use disorders, treatment options are limited, underscoring the need for new, effective medications. Previous results using protein kinase C epsilon (PKCε) knockout mice, RNA interference against PKCε and peptide inhibitors of PKCε predict that small-molecule inhibitors of PKCε should reduce alcohol consumption in humans. Methods: We designed a new class of PKCε inhibitors based on the Rho-associated protein kinase (ROCK) inhibitor Y-27632. In vitro kinase and binding assays were used to identify the most potent compounds. Their effects on ethanol-stimulated synaptic transmission; ethanol, sucrose, and quinine consumption; ethanol-induced loss of righting; and ethanol clearance were studied in mice. Results: We identified two compounds that inhibited PKCε with Ki <20 nM, showed selectivity for PKCε over other kinases, crossed the blood-brain barrier, achieved effective concentrations in mouse brain, prevented ethanol-stimulated gamma-aminobutyric acid release in the central amygdala, and reduced ethanol consumption when administered intraperitoneally at 40 mg/kg in wild-type but not in Prkce−/− mice. One compound also reduced sucrose and saccharin consumption, while the other was selective for ethanol. Both transiently impaired locomotion through an off-target effect that did not interfere with their ability to reduce ethanol intake. One compound prolonged recovery from ethanol-induced loss of righting but this was also due to an off-target effect since it was present in Prkce−/− mice. Neither altered ethanol clearance. Conclusions: These results identify lead compounds for development of PKCε inhibitors that reduce alcohol consumption.
Bibliographical noteFunding Information:
We thank Michael Cameron, Ph.D., and the Drug Metabolism and Pharmacokinetics Core at Scripps Florida, and Yong Huang, Ph.D., and the Drug Studies Unit, Analytical Division, UCSF College of Pharmacy for their work on the pharmacokinetics and tissue measurement of compounds 1.0 and 1.3. Data for receptor binding studies were generously provided by the National Institute of Mental Health's Psychoactive Drug Screening Program, Contract # HHSN-271-2013-00017-C(NIMH PDSP). The NIMH PDSP is Directed by Bryan L. Roth, M.D., Ph.D., at the University of North Carolina at Chapel Hill and Project Officer Jamie Driscol at NIMH, Bethesda, Maryland.
This work was supported by National Institutes of Health Grant Nos. AA13588 (to ROM), AA017072 (to ROM), AA015566 (to MR), and AA013498 (to MR); funds provided by the State of California for medical research for alcohol and substance abuse through the University of California, San Francisco (to ROM); and Graduate Research Fellowship Grant No. DGE-1110007 (to MP) from the National Science Foundation.
© 2017 Society of Biological Psychiatry
- Kinase inhibitor
- Protein kinase C epsilon