Inactivation of the CB2 receptor accelerated the neuropathological deterioration in TDP-43 transgenic mice, a model of amyotrophic lateral sclerosis

Cannabinoids: Potential for Modulation and Enhancement When Combined with Vitamin B12 in Case of Neurodegenerative Disorders

The enduring relationship between humanity and the cannabis plant has witnessed significant transformations, particularly with the widespread legalization of medical cannabis. This has led to the recognition of diverse pharmacological formulations of medical cannabis, containing 545 identified natural compounds, including 144 phytocannabinoids like Δ9-THC and CBD. Cannabinoids exert distinct regulatory effects on physiological processes, prompting their investigation in neurodegenerative diseases. Recent research highlights their potential in modulating protein aggregation and mitochondrial dysfunction, crucial factors in conditions such as Alzheimer's Disease, multiple sclerosis, or Parkinson's disease. The discussion emphasizes the importance of maintaining homeodynamics in neurodegenerative disorders and explores innovative therapeutic approaches such as nanoparticles and RNA aptamers. Moreover, cannabinoids, particularly CBD, demonstrate anti-inflammatory effects through the modulation of microglial activity, offering multifaceted neuroprotection including mitigating aggregation. Additionally, the potential integration of cannabinoids with vitamin B12 presents a holistic framework for addressing neurodegeneration, considering their roles in homeodynamics and nervous system functioning including the hippocampal neurogenesis. The potential synergistic therapeutic benefits of combining CBD with vitamin B12 underscore a promising avenue for advancing treatment strategies in neurodegenerative diseases. However, further research is imperative to fully elucidate their effects and potential applications, emphasizing the dynamic nature of this field and its potential to reshape neurodegenerative disease treatment paradigms.

Cannabinoids, Endocannabinoids, and Synthetic Cannabimimetic Molecules in Neuromuscular Disorders

Neuromuscular disorders (NMDs) encompass a large heterogeneous group of hereditary and acquired diseases primarily affecting motor neurons, peripheral nerves, and the skeletal muscle system. The symptoms of NMDs may vary depending on the specific condition, but some of the most common ones include muscle weakness, pain, paresthesias, and hyporeflexia, as well as difficulties with swallowing and breathing. NMDs are currently untreatable. Therapeutic options include symptomatic and experimental medications aimed at delaying and alleviating symptoms, in some cases supplemented by surgical and physical interventions. To address this unmet medical need, ongoing research is being conducted on new treatments, including studies on medical cannabis, endocannabinoids, and related molecules with cannabimimetic properties. In this context, a significant amount of knowledge about the safety and effectiveness of cannabinoids in NMDs has been obtained from studies involving patients with multiple sclerosis experiencing pain and spasticity. In recent decades, numerous other preclinical and clinical studies have been conducted to determine the potential benefits of cannabinoids in NMDs. This review article aims to summarize and provide an unbiased point of view on the current knowledge about the use of cannabinoids, endocannabinoids, and synthetic analogs in NMDs, drawing from an array of compelling studies.

Exploring the 1,3-benzoxazine chemotype for cannabinoid receptor 2 as a promising anti-cancer therapeutic

The discovery of selective agonists of cannabinoid receptor 2 (CB2) is strongly pursued to successfully tuning endocannabinoid signaling for therapeutic purposes. However, the design of selective CB2 agonists is still challenging because of the high homology with the cannabinoid receptor 1 (CB1) and for the yet unclear molecular basis of the agonist/antagonist switch. Here, the 1,3-benzoxazine scaffold is presented as a versatile chemotype for the design of CB2 agonists from which 25 derivatives were synthesized. Among these, compound 7b5 (CB2 EC50 = 110 nM, CB1 EC50 > 10 μM) demonstrated to impair proliferation of triple negative breast cancer BT549 cells and to attenuate the release of pro-inflammatory cytokines in a CB2-dependent manner. Furthermore, 7b5 abrogated the activation of extracellular signal-regulated kinase (ERK) 1/2, a key pro-inflammatory and oncogenic enzyme. Finally, molecular dynamics studies suggested a new rationale for the in vitro measured selectivity and for the observed agonist behavior.

CB2 receptor in the CNS: from immune and neuronal modulation to behavior

Despite low levels of cannabinoid receptor type 2 (CB2R) expression in the central nervous system in human and rodents, a growing body of evidence shows CB2R involvement in many processes at the behavioral level, through both immune and neuronal modulations. Recent in vitro and in vivo evidence have highlighted the complex role of CB2R under physiological and inflammatory conditions. Under neuroinflammatory states, its activation seems to protect the brain and its functions, making it a promising target in a wide range of neurological disorders. Here, we provide a complete and updated overview of CB2R function in the central nervous system of rodents, spanning from modulation of immune function in microglia but also in other cell types, to behavior and neuronal activity, in both physiological and neuroinflammatory contexts.

Endocannabinoid signaling in brain diseases: Emerging relevance of glial cells

The discovery of cannabinoid receptors as the primary molecular targets of psychotropic cannabinoid Δ⁹ -tetrahydrocannabinol (Δ⁹ -THC) in late 1980s paved the way for investigations on the effects of cannabis-based therapeutics in brain pathology. Ever since, a wealth of results obtained from studies on human tissue samples and animal models have highlighted a promising therapeutic potential of cannabinoids and endocannabinoids in a variety of neurological disorders. However, clinical success has been limited and major questions concerning endocannabinoid signaling need to be satisfactorily addressed, particularly with regard to their role as modulators of glial cells in neurodegenerative diseases. Indeed, recent studies have brought into the limelight diverse, often unexpected functions of astrocytes, oligodendrocytes, and microglia in brain injury and disease, thus providing scientific basis for targeting glial cells to treat brain disorders. This Review summarizes the current knowledge on the molecular and cellular hallmarks of endocannabinoid signaling in glial cells and its clinical relevance in neurodegenerative and chronic inflammatory disorders.

New Statement about NRF2 in Amyotrophic Lateral Sclerosis and Frontotemporal Dementia

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are related neurodegenerative disorders displaying substantial overlay, although there are substantial differences at the molecular level. Currently, there is no effective treatment for these diseases. The transcription factor NRF2 has been postulated as a promising therapeutic target as it is capable of modulating key pathogenic events affecting cellular homeostasis. However, there is little experimental evidence on the status of this pathway in both ALS and FTD. Therefore, in this work, we wanted to carry out an exhaustive analysis of this signaling pathway in both transgenic mouse models (ALS and FTD) and human samples from patients with sporadic ALS (sALS) versus controls. In samples from patients with sALS and in the transgenic model with overexpression of TDP-43A315T, we observed a significant increase in the NRF2/ARE pathway in the motor cortex and the spinal cord, indicating that NRF2 antioxidant signaling was being induced, but it was not enough to reach cellular homeostasis. On the other hand, in the transgenic FTD model with overexpression of the TDP-43WT protein in forebrain neurons, a significantly decreased expression of NQO1 in the prefrontal cortex was seen, which cannot be attributed to alterations in the NRF2 pathway. Our results show that NRF2 signature is differently affected for ALS and FTD.

Cannabinoid CB2 Receptors Modulate Microglia Function and Amyloid Dynamics in a Mouse Model of Alzheimer's Disease

The distribution and roles of the cannabinoid CB₂ receptor in the CNS are still a matter of debate. Recent data suggest that, in addition to its presence in microglial cells, the CB₂ receptor may be also expressed at low levels, yet biologically relevant, in other cell types such as neurons. It is accepted that the expression of CB₂ receptors in the CNS is low under physiological conditions and is significantly elevated in chronic neuroinflammatory states associated with neurodegenerative diseases such as Alzheimer's disease. By using a novel mouse model (CB₂ ^EGFP/f/f), we studied the distribution of cannabinoid CB₂ receptors in the 5xFAD mouse model of Alzheimer's disease (by generating 5xFAD/CB₂ ^EGFP/f/f mice) and explored the roles of CB₂ receptors in microglial function. We used a novel selective and brain penetrant CB₂ receptor agonist (RO6866945) as well as mice lacking the CB₂ receptor (5xFAD/CB₂ ^-/-) for these studies. We found that CB₂ receptors are expressed in dystrophic neurite-associated microglia and that their modulation modifies the number and activity of microglial cells as well as the metabolism of the insoluble form of the amyloid peptide. These results support microglial CB₂ receptors as potential targets for the development of amyloid-modulating therapies.

Mitochondrial dysregulation occurs early in ALS motor cortex with TDP-43 pathology and suggests maintaining NAD+ balance as a therapeutic strategy

Mitochondrial defects result in dysregulation of metabolomics and energy homeostasis that are detected in upper motor neurons (UMNs) with TDP-43 pathology, a pathology that is predominantly present in both familial and sporadic cases of amyotrophic lateral sclerosis (ALS). While same mitochondrial problems are present in the UMNs of ALS patients with TDP-43 pathology and UMNs of TDP-43 mouse models, and since pathologies are shared at a cellular level, regardless of species, we first analyzed the metabolite profile of both healthy and diseased motor cortex to investigate whether metabolomic changes occur with respect to TDP-43 pathology. High-performance liquid chromatography, high-resolution mass spectrometry and tandem mass spectrometry (HPLC-MS/MS) for metabolite profiling began to suggest that reduced levels of NAD+ is one of the underlying causes of metabolomic problems. Since nicotinamide mononucleotide (NMN) was reported to restore NAD⁺ levels, we next investigated whether NMN treatment would improve the health of diseased corticospinal motor neurons (CSMN, a.k.a. UMN in mice). prpTDP-43^A315T-UeGFP mice, the CSMN reporter line with TDP-43 pathology, allowed cell-type specific responses of CSMN to NMN treatment to be assessed in vitro. Our results show that metabolomic defects occur early in ALS motor cortex and establishing NAD⁺ balance could offer therapeutic benefit to UMNs with TDP-43 pathology.

Peripheral nerve fibroblasts secrete neurotrophic factors to promote axon growth of motoneurons

Peripheral nerve fibroblasts play a critical role in nerve development and regeneration. Our previous study found that peripheral nerve fibroblasts have different sensory and motor phenotypes. Fibroblasts of different phenotypes can guide the migration of Schwann cells to the same sensory or motor phenotype. In this study, we analyzed the different effects of peripheral nerve-derived fibroblasts and cardiac fibroblasts on motoneurons. Compared with cardiac fibroblasts, peripheral nerve fibroblasts greatly promoted motoneuron neurite outgrowth. Transcriptome analysis results identified 491 genes that were differentially expressed in peripheral nerve fibroblasts and cardiac fibroblasts. Among these, 130 were significantly upregulated in peripheral nerve fibroblasts compared with cardiac fibroblasts. These genes may be involved in axon guidance and neuron projection. Three days after sciatic nerve transection in rats, peripheral nerve fibroblasts accumulated in the proximal and distal nerve stumps, and most expressed brain-derived neurotrophic factor. In vitro, brain-derived neurotrophic factor secreted from peripheral nerve fibroblasts increased the expression of β-actin and F-actin through the extracellular regulated protein kinase and serine/threonine kinase pathways, and enhanced motoneuron neurite outgrowth. These findings suggest that peripheral nerve fibroblasts and cardiac fibroblasts exhibit different patterns of gene expression. Peripheral nerve fibroblasts can promote motoneuron neurite outgrowth.

Preclinical Investigation in Neuroprotective Effects of the GPR55 Ligand VCE-006.1 in Experimental Models of Parkinson's Disease and Amyotrophic Lateral Sclerosis

Cannabinoids act as pleiotropic compounds exerting, among others, a broad-spectrum of neuroprotective effects. These effects have been investigated in the last years in different preclinical models of neurodegeneration, with the cannabinoid type-1 (CB₁) and type-2 (CB₂) receptors concentrating an important part of this research. However, the issue has also been extended to additional targets that are also active for cannabinoids, such as the orphan G-protein receptor 55 (GPR55). In the present study, we investigated the neuroprotective potential of VCE-006.1, a chromenopyrazole derivative with biased orthosteric and positive allosteric modulator activity at GPR55, in murine models of two neurodegenerative diseases. First, we proved that VCE-006.1 alone could induce ERK1/2 activation and calcium mobilization, as well as increase cAMP response but only in the presence of lysophosphatidyl inositol. Next, we investigated this compound administered chronically in two neurotoxin-based models of Parkinson's disease (PD), as well as in some cell-based models. VCE-006.1 was active in reversing the motor defects caused by 6-hydroxydopamine (6-OHDA) in the pole and the cylinder rearing tests, as well as the losses in tyrosine hydroxylase-containing neurons and the elevated glial reactivity detected in the substantia nigra. Similar cytoprotective effects were found in vitro in SH-SY5Y cells exposed to 6-OHDA. We also investigated VCE-006.1 in LPS-lesioned mice with similar beneficial effects, except against glial reactivity and associated inflammatory events, which remained unaltered, a fact confirmed in BV2 cells treated with LPS and VCE-006.1. We also analyzed GPR55 in these in vivo models with no changes in its gene expression, although GPR55 was down-regulated in BV2 cells treated with LPS, which may explain the lack of efficacy of VCE-006.1 in such an assay. Furthermore, we investigated VCE-006.1 in two genetic models of amyotrophic lateral sclerosis (ALS), mutant SOD1, or TDP-43 transgenic mice. Neither the neurological decline nor the deteriorated rotarod performance were prevented with this compound, and the same happened with the elevated microglial and astroglial reactivities, albeit modest spinal motor neuron preservation was achieved in both models. We also analyzed GPR55 in these in vivo models and found no changes in both TDP-43 transgenic and mSOD1 mice. Therefore, our findings support the view that targeting the GPR55 may afford neuroprotection in experimental PD, but not in ALS, thus stressing the specificities for the development of cannabinoid-based therapies in the different neurodegenerative disorders.

Oxidative Stress as a Therapeutic Target in Amyotrophic Lateral Sclerosis: Opportunities and Limitations

Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease (MND) and Lou Gehrig’s disease, is characterized by a loss of the lower motor neurons in the spinal cord and the upper motor neurons in the cerebral cortex. Due to the complex and multifactorial nature of the various risk factors and mechanisms that are related to motor neuronal degeneration, the pathological mechanisms of ALS are not fully understood. Oxidative stress is one of the known causes of ALS pathogenesis. This has been observed in patients as well as in cellular and animal models, and is known to induce mitochondrial dysfunction and the loss of motor neurons. Numerous therapeutic agents have been developed to inhibit oxidative stress and neuroinflammation. In this review, we describe the role of oxidative stress in ALS pathogenesis, and discuss several anti-inflammatory and anti-oxidative agents as potential therapeutics for ALS. Although oxidative stress and antioxidant fields are meaningful approaches to delay disease progression and prolong the survival in ALS, it is necessary to investigate various animal models or humans with different subtypes of sporadic and familial ALS.