Molecular and behavioral mechanisms mediating paclitaxel-induced changes in affect-like behavior in mice

The antineoplastic paclitaxel is associated with negative affective outcomes, such as depression, anxiety, and decreased quality of life during treatment and convalescence. With the Baby Boomer population approaching peak cancer age, it is dire that the mechanisms behind paclitaxel-induced changes in mood are uncovered. Cancer-free male and female C57BL/6J mice were treated with one set of four injections of vehicle or paclitaxel (32mg/kg cumulative), or two sets of four injections of vehicle or paclitaxel (64mg/kg cumulative), and periodically assessed for depression-like behaviors. Paclitaxel caused significant, time-dependent deficits in sucrose preference and operant responding for palatable food. Because there is growing evidence to support the role of kappa opioid receptors (KORs) in stress-mediated depression and reward dysfunction, we investigated KOR signaling as a putative mechanism of paclitaxel-induced depression-like behaviors. The selective KOR antagonist norbinaltorphimine (norBNI) reversed paclitaxel-induced attenuation of sucrose preference. At the molecular level, paclitaxel time-dependently induced an increase in the expression of Prodynorphin mRNA, the precursor for endogenous KOR agonists, in the nucleus accumbens (NAc). Using the [35S]GTPγS assay, we discovered that a history of paclitaxel time-dependently attenuated activation of dopamine D2 receptors (D2R) and KORs in the NAc but not caudate putamen. These data suggest that paclitaxel-induced changes in affect-like behavior may be due to time- and region-dependent dysregulation of KOR and D2R signaling. These observations help to establish the roles of KOR and D2R systems in paclitaxel-induced disruption of behavioral reward, thus revealing potential neurochemical targets for therapeutic intervention in cancer survivors with treatment-resistant depression.https://scholarscompass.vcu.edu/gradposters/1038/thumbnail.jp

Cannabinoid receptor interacting protein suppresses agonist-driven CB1 receptor internalization and regulates receptor replenishment in an agonist-biased manner

Cannabinoid receptor interacting protein 1a (CRIP1a) is a CB1 receptor (CB1R) distal C-terminus-associated protein that modulates CB1R signaling via G proteins, and CB1R down-regulation but not desensitization (Blume et al. [2015] Cell Signal., 27, 716-726; Smith et al. [2015] Mol. Pharmacol., 87, 747-765). In this study, we determined the involvement of CRIP1a in CB1R plasma membrane trafficking. To follow the effects of agonists and antagonists on cell surface CB(1)Rs, we utilized the genetically homogeneous cloned neuronal cell line N18TG2, which endogenously expresses both CB1R and CRIP1a, and exhibits a well-characterized endocannabinoid signaling system. We developed stable CRIP1a-over-expressing and CRIP1a-siRNA-silenced knockdown clones to investigate gene dose effects of CRIP1a on CB1R plasma membrane expression. Results indicate that CP55940 or WIN55212-2 (10 nM, 5 min) reduced cell surface CB1R by a dynamin-and clathrin-dependent process, and this was attenuated by CRIP1a over-expression. CP55940-mediated cell surface CB1R loss was followed by a cycloheximide-sensitive recovery of surface receptors (30120 min), suggesting the requirement for new protein synthesis. In contrast, WIN55212-2-mediated cell surface CB(1)Rs recovered only in CRIP1a knockdown cells. Changes in CRIP1a expression levels did not affect a transient rimonabant (10 nM)mediated increase in cell surface CB(1)Rs, which is postulated to be as a result of rimonabant effects on \u27non-agonist-driven\u27 internalization. These studies demonstrate a novel role for CRIP1a in agonist-driven CB1R cell surface regulation postulated to occur by two mechanisms: 1) attenuating internalization that is agonist-mediated, but not that in the absence of exogenous agonists, and 2) biased agonist-dependent trafficking of de novo synthesized receptor to the cell surface

Exploration of bivalent ligands targeting putative mu opioid receptor and chemokine receptor CCR5 dimerization

Modern antiretroviral therapies have provided HIV-1 infected patients longer lifespans and better quality of life. However, several neurological complications are now being seen in these patients due to HIV-1 associated injury of neurons by infected microglia and astrocytes. In addition, these effects can be further exacerbated with opiate use and abuse. One possible mechanism for such potentiation effects of opiates is the interaction of the mu opioid receptor (MOR) with the chemokine receptor CCR5 (CCR5), a known HIV-1 co-receptor, to form MOR-CCR5 heterodimer. In an attempt to understand this putative interaction and its relevance to neuroAIDS, we designed and synthesized a series of bivalent ligands targeting the putative CCR5-MOR heterodimer. To understand how these bivalent ligands may interact with the heterodimer, biological studies including calcium mobilization inhibition, binding affinity, HIV-1 invasion, and cell fusion assays were applied. In particular, HIV-1 infection assays using human peripheral blood mononuclear cells, macrophages, and astrocytes revealed a notable synergy in activity for one particular bivalent ligand. Further, a molecular model of the putative CCR5-MOR heterodimer was constructed, docked with the bivalent ligand, and molecular dynamics simulations of the complex was performed in a membrane-water system to help understand the biological observation

Antipsychotic-induced alterations in CB1 receptor-mediated G-protein signaling and in vivo pharmacology in rats

Dysregulation of the endocannabinoid and dopamine systems has been implicated in schizophrenia. The purpose of this study was to examine the effects of sub-chronic treatment with two antipsychotics on CB1 receptor-mediated in vitro and in vivo effects. Adult and adolescent male and female rats were injected twice daily with haloperidol (0.3 mg/kg), clozapine (10 mg/kg), or saline for 10 days. Subsequently, CB1 receptor number and function were assessed by [3H]SR141716 and WIN55,212-2-stimulated [35S]GTPγS binding, respectively. The effects of sub-chronic antipsychotic treatment on the in vivo actions of Δ9-tetrahydrocannabinol (Δ9-THC) were also evaluated. In adult female rats, antipsychotic treatment attenuated maximal stimulation of CB1 receptor-mediated G-protein activity in the striatum (clozapine) and prefrontal cortex (both antipsychotics), but not in the ventral midbrain. Associated changes in CB1 receptor number were not observed, suggesting that this attenuation was not due to downregulation. In vivo, sub-chronic treatment with clozapine, but not haloperidol, attenuated Δ9-THC-induced suppression of activity in adult females, whereas neither drug altered hypothermia or catalepsy. In contrast, antipsychotic treatment did not change CB1 receptor-mediated G-protein activation in any brain region in adult male rats and in adolescents of either sex. In vivo, haloperidol, but not clozapine, enhanced Δ9-THC-mediated suppression of activity and hypothermia in adult male rats whereas neither antipsychotic affected Δ9-THC-induced in vivo effects in adolescent rats. These findings suggest that modulation of the endocannabinoid system might contribute in a sex- and age-selective manner to differences in motor side effects of clozapine versus haloperidol

Prolonged recovery rate of CB1 receptor adaptation after cessation of long-term cannabinoid administration." Mol Pharmacol 70(3

ABSTRACT Long-term cannabinoid administration produces region-dependent CB 1 receptor desensitization and down-regulation. This study examined the time course for normalization of CB 1 receptors and G-protein activation using 35 S]GTP␥S binding were decreased in both regions 1 day after treatment. WIN55,212-2-stimulated G-protein activation in striatum/GP returned to control level at 3 days after cessation of treatment with either drug but did not return to control level in hippocampus until 14 days. CB 1 receptor binding did not recover to control levels until day 7 or 14 after treatment in striatum/GP and hippocampus, respectively. The mechanism of CB 1 binding site down-regulation was investigated after long-term ⌬ 9 -THC treatment. Analysis of CB 1 receptor mRNA in hippocampus and striatum/GP showed that transcriptional regulation could not explain prolonged recovery rates from CB 1 receptor down-regulation. In contrast, CB 1 receptor protein, as determined by immunoblot analysis, matched the down-regulation and recovery rates of CB 1 receptor binding sites relatively closely. These data demonstrate that cannabinoid-induced decreases in CB 1 receptor function persist for relatively long time periods after cessation of long-term drug treatment and that CB 1 receptor signaling recovers more quickly in striatum/GP than hippocampus. Moreover, down-regulation of CB 1 receptor binding sites does not seem to result mainly from transcriptional regulation, suggesting that adaptive regulation of CB 1 receptors in brain primarily occurs at the protein level