Cannabis is the most commonly abused illicit drug in the United States. Daily marijuana use is now at a 30-year peak level among high school seniors. Heavy adolescent cannabis use (ACU) has deleterious effects that include cognitive impairments and serious psychiatric sequelae, with a large body of literature showing an association between ACU and adult onset schizophrenia. ?9 tetrahydrocannabinol (?9-THC), the main psychotropic constituent of cannabis, mediates its effects via cannabinoid 1 (CB1) receptors, which are among the most highly expressed receptors in the brain. In recent years, the K2 synthetic cannabinoids, compounds with high affinity for CB1 receptors, have been linked to inducing psychosis, implicating CB1 receptors in generating psychotic symptoms. The reason/s that a subset of adolescent cannabis users develop these adverse outcomes is not known. Our overarching hypothesis is that heavy ACU leads to a persistent disruption in endocannabinoid (eCB) signaling that alters the developmental trajectory of specific neural circuits. The eCBs are a key activity- dependent signaling system influencing synaptic plasticity in the brain. In this New Investigator application, we propose to use clinically well-characterized high quality human post mortem brain tissue to identify the persistent impact of heavy ACU on genes involved in eCB-induced synaptic plasticity. We hypothesize that we will find a distinct expression profile of eCB signaling genes in the human dorsolateral prefrontal cortex (DLPFC) and hippocampus (HC), brain regions rich in CB1 receptors and repeatedly implicated in schizophrenia pathophysiology. Using a cohort of human post mortem brain tissue from control and schizophrenia cases, divided into groups with and without heavy ACU, we will conduct a series of assays at the mRNA, protein and cellular level to characterize expression profile of our target genes in the DLPFC and HC.
Our aims i nclude hypothesis testing and hypothesis generating aims.
In Aim 1, we will characterize expression profiles of genes involved in endocannabinoid signaling including CB1, mGluR5 and their associated proteins.
In Aim 2, we will use ChIP- PCR to determine the histone methylation profile of CB1 and mGluR5 promoters with the goal of identifying a mechanism by which ACU can lead to persistent gene expression changes. Since we do not expect our target genes to be the only ones involved in the long term effects of ACU, we will broaden and build on our hypothesis by generating whole transcriptome sequences with RNA-Seq in Aim 3. These studies are designed to provide evidence of the persistent effects of ACU on synaptic plasticity markers in the human brain and will (i) identify gene targets associated with ACU-induced cognitive deficits and ACU-induced psychosis, (ii) identify cellular substrates for the gene changes and (iii) determine potential mechanisms for the persistent changes in gene expression.
Heavy cannabis use during adolescence is a significant public health problem. Some individuals develop long-term problems in learning and memory and even serious mental illnesses like schizophrenia. Using a cohort of clinically well-characterized human post mortem brain tissue from control and schizophrenia cases, we will use hypotheses testing and hypothesis generating aims to identify molecular targets and pathways involved in the long term effects of adolescent cannabis use.