Cannabidiol as an add-on therapy to overcome the slow-onset and, possibly, resistance to antidepressant treatment : involvement of NAPE-PLD in the medial prefrontal cortex.
Franciele F. Scarante, Vinícius D. Lopes, Eduardo J. Fusse, Maria A. Vicente, Melissa R. Araújo, Davi S. Scomparin, Rafael P. Aguiar, Francisco S. Guimarães, Viviani Nardinid, Carlos Arterio Sorgid, Lucia H. Faccioli, RhD, PhDd, Jaime E. C. Hallak, MD, PhDe,f; Samia Joca, Kenneth Mackie, Antonio Waldo Zuardi, José Alexandre S. Crippa, Alline C. Campos.
bioRxiv preprint, April 26, 2021.
doi : 10.1101/2021.04.23.441143
- ● In mice, cannabidiol (CBD), but not escitalopram, induced a fast-onset anti-stress action.
- ● Combinations of sub-effective doses of CBD and escitalopram produce anti-stress effects after only 7 days.
- ● The Escitalopram + CBD treatment modulated synaptic protein markers in the medial prefrontal cortex.
- ● CRISPR-Cas9-mediated knockdown of NAPE-PLD in the medial PFC prevents the anti-stress effect of the Escitalopram + CBD.
- ● Adding CBD to an antidepressants regimen successfully treated three patients with treatment resistant depression.
Antidepressants such as serotonin uptake inhibitors are the first-line pharmacological treatment for chronic stress-related psychiatric disorders. However, their late-onset therapeutic action and frequent side effects, however, are important challenges for clinicians and patients. Besides, around 30% of major depression patients are considered treatment-resistant. Cannabidiol (CBD) is a non-psychotomimetic phytocannabinoid with a wide range of psychopharmacological effects, but its mechanism of action remains unclear. Here, we found that in male mice submitted to two different repeated stress protocols (chronic unpredictable and social defeat stress), low doses of CBD (7.5mg/Kg) caused an early-onset behavioral effect when combined to the antidepressant escitalopram (ESC-10mg/Kg). The behavioral effects of the ESC+CBD combination depended on the expression/activity of the N-acyl phosphatidylethanolamine phospholipase D (NAPE-PLD, responsible for synthesizing the endocannabinoid anandamide), but not the DAGLα, enzyme in the ventromedial prefrontal cortex. In addition, we described a case series with three treatment-resistant depression that were successfully treated with CBD as adjuvant therapy, as evaluated by standardized clinical rating scales. After 12 weeks of treatment, two patients were considered depression remitted (MADRS score lower than 10) while one patient successfully responded to CBD as add-on treatment (more than 50% decrease from the baseline MADRS). Our results suggest that CBD might be useful as an add-on therapy for optimizing the action of antidepressants. They also suggest that CBD’s beneficial actions depends on the facilitation of N-acylethanolamines actions in the medial prefrontal cortex.
Keywords : cannabidiol; antidepressant; chronic stress; NAPE-PLD; late-onset; treatment- resistant
Antidepressants, especially the selective serotonin reuptake inhibitors (SSRIs), are widely prescribed to treat psychiatric disorders such as major depression and anxiety. However, their late-onset action and associated side-effects are vexing clinical problems, contributing to low adherence to the therapy. Moreover, about 30% of patients are considered treatment- resistant (Caraci et al., 2018). Of great current concern in the clinical practice, treatment- resistant depression (TRD) is an unsatisfactory response to at least two adequate antidepressant medication trials, and is usually linked to significant cognitive function impairment, low quality of life, and higher suicide rates (Mrazek et al., 2014; Thase, 2011).
In clinical practice, combined therapy is a strategy commonly adopted for patients who do not respond appropriately to monotherapy. One advantages of combining agents include decreasing the dose and, as a consequence, diminishing the incidence or the severity of side effects. However, whether the combination with other promising antidepressant drugs might decrease the latency for the onset of action of antidepressants has not yet to be investigated.
The phytocannabinoid cannabidiol (CBD) is a major non-psychotomimetic component of the Cannabis sativa plant. Antidepressant, anxiolytic, sleep regulator, anti-inflammatory, antioxidant, and neuroprotective are among the described properties of this cannabinoid (Crippa et al., 2018). Like clinically used antidepressants, CBD counteracts the behavioral and neuroplastic outcomes of stress exposure in rodents (Campos et al., 2013; Fogaça et al., 2018). Even though the exact mechanisms of this effect remain unclear, the endocannabinoid system has been associated with CBD and SSRI actions (Hill et al., 2008b).
Using the chronic unpredictable stress (CUS) model, we showed attenuation of the stress-induced behavioral and neuroplastic changes by repeated CBD administration depends on CB1 and CB2 receptors (Campos et al., 2013; Fogaça et al., 2018). Chronic treatment with CBD increased hippocampal levels of anandamide (AEA), but not other endocannabinoids (Campos et al., 2013).
The N-acyl phosphatidylethanolamine phospholipase D (NAPE-PLD) is considered major biochemical pathway responsible for synthesizing AEA and other N-acylethanolamines (NAESs). Like AEA, NAEs can also modulate neuronal and glial cell function by different mechanisms (interference with inflammation, metabolism, energy homeostasis, etc.). Recently, Leishman et al. (2018) demonstrated that CBD (3mg/Kg) enhanced NAPE-PLD activity and increase NAEs production in the brain (Leishman et al., 2018). Regarding the effects of SSRI on this enzyme, Smaga and colleagues (2014) showed that chronic treatment with escitalopram (10 mg/Kg) increases NAPE-PLD expression in the hippocampus and dorsal striatum (Smaga et al., 2014).
Among the brain regions associated with depression, neuroplastic mechanisms within the prefrontal cortex (PFC) are likely to be involved in the effects of antidepressants, particularly those of fast-acting “antidepressants” such as ketamine and, possibly, CBD (Pothula et al., 2020; Sales et al., 2019; Zhang et al., 2020). Moreover, direct administration of CBD into the PFC eleicits antidepressant-like effect dependent on CB1 receptor activation (Sartim et al., 2016).
Based on these pieces of evidence, the current study aimed at addressing to the following questions :
1. Can the combination of sub-effective doses of CBD and the SSRI escitalopram prevent behavioral effects of chronic stress ?;
2. Will these effects be associated with plastic changes in the PFC ?;
3. Are endocannabinoids or NAEs involved in CBD’sactions ?;
4. Would CBD be useful in treatment-resistant depressive patients as an add-on therapy ?