Cannabinoid-Based Therapies and Brain Development: Potential Harmful Effect of Early Modulation of the Endocannabinoid System.

The endocannabinoid retrograde signaling pathway is widely expressed in the central nervous system, where it plays major roles in regulating synaptic plasticity (excitatory and inhibitory) through long-term potentiation and long-term depression. The endocannabinoid system (ECS) components-cannabinoid receptors, endocannabinoids and synthesis/degradation enzymes-are expressed and are functional from early developmental stages and throughout adolescent cortical development, regulating progenitor cell fate, neural differentiation, migration and survival. This may potentially confer increased vulnerability to adverse outcomes from early cannabinoid exposure. Cannabidiol (CBD) is one of the most studied exogenous cannabinoids, and CBD-enriched Cannabis extracts have been widely (and successfully) used as adjuvants to treat children with refractory epilepsy, and there is even a Food and Drug Administration (FDA)-approved drug with purified CBD derived from Cannabis. However, there is insufficient information on possible long-term changes in the central nervous system caused by cannabinoid treatments during early childhood. Like the majority of cannabinoids, CBD is able to exert its effects directly and indirectly through the ECS, which can perturb the regulatory processes mediated by this system. In addition, CBD has a large number of non-endocannabinoid targets, which can explain CBD's effects. Here, we review the current knowledge about CBD-based therapies-pure and CBD-enriched Cannabis extracts-in studies with pediatric patients, their side effects, and their mechanisms of action regarding the central nervous system and neurodevelopment aspects. Since Cannabis extracts contain Δ9-tetrahydrocannabinol (Δ9-THC), we consider that pure CBD is possibly safer for young patients. Nevertheless, CBD, as well as other natural and/or synthetic cannabinoids, should be studied in more detail as a therapeutic alternative to CBD-enriched Cannabis extracts for young patients.

Mimicking Parkinson's Disease in a Dish: Merits and Pitfalls of the Most Commonly used Dopaminergic In Vitro Models.

Parkinson's disease (PD) is the second most common neurodegenerative disorder and has both unknown etiology and non-curative therapeutic options. Patients begin to present the classic motor symptoms of PD-tremor at rest, bradykinesia and rigidity-once 50-70% of the dopaminergic neurons of the nigrostriatal pathway have degenerated. As a consequence of this, it is difficult to investigate the early-stage events of disease pathogenesis. In vitro experimental models are used extensively in PD research because they present a controlled environment that enables the direct investigation of the early molecular mechanisms that are potentially involved with dopaminergic degeneration, as well as for the screening of potential therapeutic drugs. However, the establishment of PD in vitro models is a controversial issue for neuroscience research not only because it is challenging to mimic, in isolated cell systems, the physiological neuronal environment, but also the pathophysiological conditions experienced by human dopaminergic cells in vivo during the progression of the disease. Since no previous work has attempted to systematically review the literature regarding the establishment of an optimal in vitro model, and/or the features presented by available models used in the PD field, this review aims to summarize the merits and limitations of the most widely used dopaminergic in vitro models in PD research, which may help the PD researcher to choose the most appropriate model for studies directed at the elucidation of the early-stage molecular events underlying PD onset and progression.

Autophagy inhibition improves the efficacy of curcumin/temozolomide combination therapy in glioblastomas.

Glioblastoma is a devastating primary brain tumor resistant to conventional therapies. In this study, we tested the efficacy of combining temozolomide with curcumin, a phytochemical known to inhibit glioblastoma growth, and investigated the mechanisms involved. The data showed that synergy between curcumin and temozolomide was not achieved due to redundant mechanisms that lead to activating protective autophagy both in vitro and in vivo. Autophagy preceded apoptosis, and blocking this response with autophagy inhibitors (3-methyl-adenine, ATG7 siRNA and chloroquine) rendered cells susceptible to temozolomide and curcumin alone or combinations by increasing apoptosis. While curcumin inhibited STAT3, NFκB and PI3K/Akt to affect survival, temozolomide-induced autophagy relied on the DNA damage response and repair components ATM and MSH6, as well as p38 and JNK1/2. However, the most interesting observation was that both temozolomide and curcumin required ERK1/2 to induce autophagy. Blocking this ERK1/2-mediated temozolomide and curcumin induced autophagy with resveratrol, a blood-brain barrier permeable drug, improved temozolomide/curcumin efficacy in brain-implanted tumors. Overall, the data presented demonstrate that autophagy impairs the efficacy of temozolomide/curcumin, and inhibiting this phenomenon could provide novel opportunities to improve brain tumor treatment.