Pharmacological Enhancement of Adult Hippocampal Neurogenesis Improves Behavioral Pattern Separation in Young and Aged Mice

BACKGROUNDImpairments in behavioral pattern separation (BPS)--the ability to distinguish between similar contexts or experiences--contribute to memory interference and overgeneralization seen in many neuropsychiatric conditions, including depression, anxiety, PTSD, dementia, and age-related cognitive decline. While BPS relies on the dentate gyrus and is sensitive to changes in adult hippocampal neurogenesis (AHN), its significance as a pharmacological target has not been tested. METHODSIn this study, we applied a human neural stem cell high-throughput screening cascade to identify compounds that increase human neurogenesis. One compound with a favorable profile, RO6871135, was then tested in BPS in mice. RESULTSChronic treatment with RO6871135, 7.5 mg/kg increased AHN and improved BPS in a fear discrimination task in both young and aged mice. RO6871135 treatment also lowered innate anxiety-like behavior, which was more apparent in mice exposed to chronic corticosterone. Ablation of AHN by hippocampal irradiation supported a neurogenesis-dependent mechanism for RO6871135-induced improvements in BPS. To identify possible mechanisms of action, in vitro and in vivo kinase inhibition and chemical proteomics assays were performed. These tests indicated that RO6871135 inhibited CDK8, CDK11, CaMK2a, CaMK2b, MAP2K6, and GSK3b. An analog compound also demonstrated high affinity for CDK8, CaMK2a, and GSK3b. CONCLUSIONSThese studies demonstrate a method for empirical identification and preclinical testing of novel neurogenic compounds that can improve BPS, and points to possible novel mechanisms that can be interrogated for the development of new therapies to improve specific endophenotypes such as impaired BPS.