Repeated exposure to JWH-018 induces adaptive changes in the mesolimbic and mesocortical dopaminergic pathways, glial cells alterations, and behavioural correlates

Evidence for enduring cardiac and multiorgan toxicity after repeated exposure to the synthetic cannabinoid JWH-018 in male rats

The use of synthetic cannabinoid receptor agonists (SCRAs) represents a public health concern. Besides abuse liability and cognitive impairments, SCRAs consumption is associated with serious medical consequences in humans, including cardiotoxicity. The precise mechanisms underlying cardiac or other toxicities induced by SCRAs are not well understood. Here, we used in silico, in vivo, and ex vivo approaches to investigate the toxicological consequences induced by exposure to the SCRA JWH-018. Along with in silico predictive toxicological screening of 36 SCRAs by MC4PC software, adult male Sprague-Dawley rats were repeatedly exposed to JWH-018 (0.25 mg/kg ip) for 14 consecutive days, with body temperature and cardiovascular parameters measured over the course of treatment. At 1 and 7 days after JWH-018 discontinuation, multiorgan tissue pathologies and heart mitochondria bioenergetics were assessed. The in silico findings predicted risk of cardiac adverse effects specifically for JWH-018 and other aminoalkylindole SCRAs (i.e., electrocardiogram abnormality and QT prolongation). The results from rats revealed that repeated, but not single, JWH-018 exposure induced hypothermia and cardiovascular stimulation (e.g., increased blood pressure and heart rate) which persisted throughout treatment. Post-mortem findings demonstrated cardiac lesions (i.e., vacuolization, waving, edema) 1 day after JWH-018 discontinuation, which may contribute to lung, kidney, and liver tissue degeneration observed 7 days later. Importantly, repeated JWH-018 exposure induced mitochondrial dysfunction in cardiomyocytes, i.e., defective lipid OXPHOS, which may represent one mechanism of JWH-018-induced toxicity. Our results demonstrate that repeated administration of even a relatively low dose of JWH-018 is sufficient to affect cardiovascular function and induce enduring toxicological consequences, pointing to risks associated with SCRA consumption.

Immune and glial cell alterations in the rat brain after repeated exposure to the synthetic cannabinoid JWH-018

The use of synthetic cannabinoid receptor agonists (SCRAs) poses major psychiatric risks. We previously showed that repeated exposure to the prototypical SCRA JWH-018 induces alterations in dopamine (DA) transmission, abnormalities in the emotional state, and glial cell activation in the mesocorticolimbic DA circuits of rats. Despite growing evidence suggesting the relationship between substance use disorders (SUD) and neuroinflammation, little is known about the impact of SCRAs on the neuroimmune system. Here, we investigated whether repeated JWH-018 exposure altered neuroimmune signaling, which could be linked with previously reported central effects. Adult male Sprague-Dawley (SD) rats were exposed to JWH-018 (0.25 mg/kg, i.p.) for fourteen consecutive days, and the expression of cytokines, chemokines, and growth factors was measured seven days after treatment discontinuation in the striatum, cortex, and hippocampus. Moreover, microglial (ionized calcium-binding adaptor molecule 1, IBA-1) and astrocyte (glial fibrillary acidic protein, GFAP) activation markers were evaluated in the caudate-putamen (CPu). Repeated JWH-018 exposure induces a perturbation of neuroimmune signaling specifically in the striatum, as shown by increased levels of cytokines [interleukins (IL) -2, -4, -12p70, -13, interferon (IFN) γ], chemokines [macrophage inflammatory protein (MIP) -1α, -3α], and growth factors [macrophage colony-stimulating factor (M-CSF), vascular endothelial growth factor (VEGF)], together with increased IBA-1 and GFAP expression in the CPu. JWH-018 exposure induces persistant brain region-specific immune alterations up to seven days after drug discontinuation, which may contribute to the behavioral and neurochemical dysregulations in striatal areas that play a role in the reward-related processes that are frequently impaired in SUD.

Cognitive dysfunction and impaired neuroplasticity following repeated exposure to the synthetic cannabinoid JWH-018 in male mice

BACKGROUND AND PURPOSE

Psychotic disorders have been reported in long-term users of synthetic cannabinoids. This study aims at investigating the long-lasting effects of repeated JWH-018 exposure.

EXPERIMENTAL APPROACH

Male CD-1 mice were injected with vehicle, JWH-018 (6 mg·kg-1 ), the CB1 -antagonist NESS-0327 (1 mg·kg-1 ) or co-administration of NESS-0327 and JWH-018, every day for 7 days. After 15 or 16 days washout, we investigated the effects of JWH-018 on motor function, memory, social dominance and prepulse inhibition (PPI). We also evaluated glutamate levels in dialysates from dorsal striatum, striatal dopamine content and striatal/hippocampal neuroplasticity focusing on the NMDA receptor complex and the neurotrophin BDNF. These measurements were accompanied by in vitro electrophysiological evaluations in hippocampal preparations. Finally, we investigated the density of CB1 receptors and levels of the endocannabinoid anandamide (AEA) and 2-arachidonoylglycerol (2-AG) and their main synthetic and degrading enzymes in the striatum and hippocampus.

KEY RESULTS

The repeated treatment with JWH-018 induced psychomotor agitation while reducing social dominance, recognition memory and PPI in mice. JWH-018 disrupted hippocampal LTP and decreased BDNF expression, reduced the synaptic levels of NMDA receptor subunits and decreased the expression of PSD95. Repeated exposure to JWH-018, reduced hippocampal CB1 receptor density and induced a long-term alteration in AEA and 2-AG levels and their degrading enzymes, FAAH and MAGL, in the striatum.

CONCLUSION AND IMPLICATIONS

Our findings suggest that repeated administration of a high dose of JWH-018 leads to the manifestation of psychotic-like symptoms accompanied by alterations in neuroplasticity and change in the endocannabinoid system.

Deletion of Cryab increases the vulnerability of mice to the addiction-like effects of the cannabinoid JWH-018 via upregulation of striatal NF-κB expression

Synthetic cannabinoids have exhibited unpredictable abuse liabilities, especially self-administration (SA) responses in normal rodent models, despite seemingly inducing addiction-like effects in humans. Thus, an efficient pre-clinical model must be developed to determine cannabinoid abuse potential in animals and describe the mechanism that may mediate cannabinoid sensitivity. The Cryab knockout (KO) mice were recently discovered to be potentially sensitive to the addictive effects of psychoactive drugs. Herein, we examined the responses of Cryab KO mice to JWH-018 using SA, conditioned place preference, and electroencephalography. Additionally, the effects of repeated JWH-018 exposure on endocannabinoid- and dopamine-related genes in various addiction-associated brain regions were examined, along with protein expressions involving neuroinflammation and synaptic plasticity. Cryab KO mice exhibited greater cannabinoid-induced SA responses and place preference, along with divergent gamma wave alterations, compared to wild-type (WT) mice, implying their higher sensitivity to cannabinoids. Endocannabinoid- or dopamine-related mRNA expressions and accumbal dopamine concentrations after repeated JWH-018 exposure were not significantly different between the WT and Cryab KO mice. Further analyses revealed that repeated JWH-018 administration led to possibly greater neuroinflammation in Cryab KO mice, which may arise from upregulated NF-κB, accompanied by higher expressions of synaptic plasticity markers, which might have contributed to the development of cannabinoid addiction-related behavior in Cryab KO mice. These findings signify that increased neuroinflammation via NF-κB may mediate the enhanced addiction-like responses of Cryab KO mice to cannabinoids. Altogether, Cryab KO mice may be a potential model for cannabinoid abuse susceptibility.

THC and CBD: Villain versus Hero? Insights into Adolescent Exposure

Cannabis is the most used drug of abuse worldwide. It is well established that the most abundant phytocannabinoids in this plant are Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD). These two compounds have remarkably similar chemical structures yet vastly different effects in the brain. By binding to the same receptors, THC is psychoactive, while CBD has anxiolytic and antipsychotic properties. Lately, a variety of hemp-based products, including CBD and THC, have become widely available in the food and health industry, and medical and recreational use of cannabis has been legalized in many states/countries. As a result, people, including youths, are consuming CBD because it is considered “safe”. An extensive literature exists evaluating the harmful effects of THC in both adults and adolescents, but little is known about the long-term effects of CBD exposure, especially in adolescence. The aim of this review is to collect preclinical and clinical evidence about the effects of cannabidiol.

Chronic adolescent exposure to cannabis in mice leads to sex-biased changes in gene expression networks across brain regions

During adolescence, frequent and heavy cannabis use can lead to serious adverse health effects and cannabis use disorder (CUD). Rodent models of adolescent exposure to the main psychoactive component of cannabis, delta-9-tetrahydrocannabinol (THC), mimic the behavioral alterations observed in adolescent users. However, the underlying molecular mechanisms remain largely unknown. Here, we treated female and male C57BL6/N mice with high doses of THC during early adolescence and assessed their memory and social behaviors in late adolescence. We then profiled the transcriptome of five brain regions involved in cognitive and addiction-related processes. We applied gene coexpression network analysis and identified gene coexpression modules, termed cognitive modules, that simultaneously correlated with THC treatment and memory traits reduced by THC. The cognitive modules were related to endocannabinoid signaling in the female dorsal medial striatum, inflammation in the female ventral tegmental area, and synaptic transmission in the male nucleus accumbens. Moreover, cross-brain region module-module interaction networks uncovered intra- and inter-region molecular circuitries influenced by THC. Lastly, we identified key driver genes of gene networks associated with THC in mice and genetic susceptibility to CUD in humans. This analysis revealed a common regulatory mechanism linked to CUD vulnerability in the nucleus accumbens of females and males, which shared four key drivers (Hapln4, Kcnc1, Elavl2, Zcchc12). These genes regulate transcriptional subnetworks implicated in addiction processes, synaptic transmission, brain development, and lipid metabolism. Our study provides novel insights into disease mechanisms regulated by adolescent exposure to THC in a sex- and brain region-specific manner.

Adolescent self-administration of the synthetic cannabinoid receptor agonist JWH-018 induces neurobiological and behavioral alterations in adult male mice

RATIONALE

The use of synthetic cannabinoid receptor agonists (SCRAs) is growing among adolescents, posing major medical and psychiatric risks. JWH-018 represents the reference compound of SCRA-containing products.

OBJECTIVES

This study was performed to evaluate the enduring consequences of adolescent voluntary consumption of JWH-018.

METHODS

The reinforcing properties of JWH-018 were characterized in male CD1 adolescent mice by intravenous self-administration (IVSA). Afterwards, behavioral, neurochemical, and molecular evaluations were performed at adulthood.

RESULTS

Adolescent mice acquired operant behavior (lever pressing, Fixed Ratio 1-3; 7.5 µg/kg/inf); this behavior was specifically directed at obtaining JWH-018 since it increased under Progressive Ratio schedule of reinforcement, and was absent in vehicle mice. JWH-018 IVSA was reduced by pretreatment of the CB1-antagonist/inverse agonist AM251. Adolescent exposure to JWH-018 by IVSA increased, at adulthood, both nestlet shredding and marble burying phenotypes, suggesting long-lasting repetitive/compulsive-like behavioral effects. JWH-018 did not affect risk proclivity in the wire-beam bridge task. In adult brains, there was an increase of ionized calcium binding adaptor molecule 1 (IBA-1) positive cells in the caudate-putamen (CPu) and nucleus accumbens (NAc), along with a decrease of glial fibrillary acidic protein (GFAP) immunoreactivity in the CPu. These glial alterations in adult brains were coupled with an increase of the chemokine RANTES and a decrease of the cytokines IL2 and IL13 in the cortex, and an increase of the chemokine MPC1 in the striatum.

CONCLUSIONS

This study suggests for the first time that male mice self-administer the prototypical SCRA JWH-018 during adolescence. The adolescent voluntary consumption of JWH-018 leads to long-lasting behavioral and neurochemical aberrations along with glia-mediated inflammatory responses in adult brains.

Epigenetic Studies for Evaluation of NPS Toxicity: Focus on Synthetic Cannabinoids and Cathinones

In the recent decade, numerous new psychoactive substances (NPSs) have been added to the illicit drug market. These are synthetized to mimic the effects of classic drugs of abuse (i.e., cannabis, cocaine, etc.), with the purpose of bypassing substance legislations and increasing the pharmacotoxicological effects. To date, research into the acute pharmacological effects of new NPSs is ongoing and necessary in order to provide an appropriate contribution to public health. In fact, multiple examples of NPS-related acute intoxication and mortality have been recorded in the literature. Accordingly, several in vitro and in vivo studies have investigated the pharmacotoxicological profiles of these compounds, revealing that they can cause adverse effects involving various organ systems (i.e., cardiovascular, respiratory effects) and highlighting their potential increased consumption risks. In this sense, NPSs should be regarded as a complex issue that requires continuous monitoring. Moreover, knowledge of long-term NPS effects is lacking. Because genetic and environmental variables may impact NPS responses, epigenetics may aid in understanding the processes behind the harmful events induced by long-term NPS usage. Taken together, “pharmacoepigenomics” may provide a new field of combined study on genetic differences and epigenetic changes in drug reactions that might be predictive in forensic implications.

Frustrative nonreward and cannabinoid receptors: Chronic (but not acute) WIN 55,212-2 treatment increased resistance to change in two reward downshift tasks

Assessing the role of cannabinoid (CB) receptors in behavior is relevant given the trend toward the legalization of medicinal and recreational marijuana. The present research aims at bridging a gap in our understanding of CB-receptor function in animal models of frustrative nonreward. These experiments were designed to (1) determine the effects of chronic administration of the nonselective CB1-receptor agonist WIN 55,212-2 (WIN) on reward downshift in rats and (2) determine whether the effects of chronic WIN were reducible to acute effects. In Experiment 1, chronic WIN (7 daily injections, 10 mg/kg, ip) accelerated the recovery of consummatory behavior after a 32-to-4% sucrose downshift relative to vehicle controls. In addition, chronic WIN eliminated the preference for an unshifted lever when the other lever was subject to a 12-to-2 pellet downshift in free-choice trials, but only in animals with previous experience with a sucrose downshift. In Experiment 2, acute WIN (1 mg/kg, ip) reduced consummatory behavior, but did not affect recovery from a 32-to-4% sucrose downshift. The antagonist SR 141716A (3 mg/kg, ip) also failed to interfere with recovery after the sucrose downshift. In Experiment 3, acute WIN administration (1 mg/kg, ip) did not affect free-choice behavior after a pellet downshift, although it reduced lever pressing and increased magazine entries relative to vehicle controls. The effects of chronic WIN on frustrative nonreward were not reducible to acute effects of the drug. Chronic WIN treatment in rats, like chronic marijuana use in humans, seems to increase resistance to the effects of frustrative nonreward.