Deciphering the mechanisms of reciprocal regulation or interdependence at the cannabinoid CB1 receptors and cyclooxygenase-2 level: Effects on mood, cognitive implications, and synaptic signaling

Conditional Deletion of CB1 Receptor in Parvalbumin-Expressing GABAergic Neurons Results in Hearing Loss and Abnormal Auditory Brainstem Response in Mice

Cannabinoid receptors 1 (CB1Rs) are widely expressed throughout the central auditory system and play important roles in synaptic plasticity, auditory function, and development. However, the specific functions of CB1Rs in distinct neuronal subtypes in the central auditory system remain largely unclear. In the current study, we investigated whether CB1R deficiency in the parvalbumin (PV)-expressing interneurons, a major class of GABAergic interneurons, affects hearing function. We first systematically examined the neuronal localization and distribution of CB1Rs in the mouse central auditory system using double-label immunofluorescence and confocal laser scanning microscopy. Our findings revealed that CB1Rs are widely distributed across various auditory nuclei, with especially high expression levels observed in the cochlear nucleus (CN), superior olivary complex (SOC), and lateral lemniscus (LL). Furthermore, we established a genetic mouse model for conditional CB1R knockout specifically in PV interneurons, and performed auditory brainstem response (ABR) tests to measure the effects of this deletion on hearing. Surprisingly, the analysis of the ABR revealed that conditional deletion of CB1Rs specifically from PV interneurons elevated hearing threshold at 32 kHz, prolongated the latency of Wave 1, and decreased the amplitudes of Waves 1-4. Our findings provide a solid anatomical foundation for further investigations into the functional roles of CB1Rs in the central auditory system and highlight the critical role of CB1Rs expressed in inhibitory PV interneurons in maintaining normal auditory function.

Targeting the cholinergic anti-inflammatory pathway: an innovative strategy for treating diseases

The cholinergic anti-inflammatory pathway (CAP) is comprised of the vagus nerve, acetylcholine, nicotinic acetylcholine receptors, the spleen, and the splenic nerve. It represents a sophisticated neuroimmune axis that critically regulates the crosstalk between the nervous system and the immune response via the vagus nerve. Here, we provided a nuanced exploration of the CAP's role in curbing inflammatory processes and its broad therapeutic potential across a spectrum of diseases. We meticulously dissect the intricate mechanisms by which the CAP modulates key signaling cascades, including the NF-κB, JAK2/STAT3, MAPK/ERK, PI3K/AKT, COX2/PGE2, and NRF2/HO-1 pathways, which are quintessential in the pathogenesis of various conditions. Additionally, we also summarized the CAP's profound implications in the management of inflammatory diseases, neurodegenerative disorders, metabolic syndromes, and oncological malignancies, elucidating its capacity to mitigate disease severity and progression through sophisticated immune modulation. The modulation of the CAP is suggested as a novel strategy that could potentially transform treatment approaches for a variety of conditions. However, the precise cellular and molecular underpinnings of the CAP's effects, as well as its translatability to clinical settings, remain subjects of ongoing investigation. The review calls for further research to demystify the mechanisms of the CAP and to harness its therapeutic potential fully, with the aim of developing innovative and efficacious treatment modalities that exploit the pathway's unique attributes.

Interactions between metabotropic glutamate and CB1 receptors: implications for mood, cognition, and synaptic signaling based on data from mGluR and CB1R-targeting drugs

Metabotropic glutamate receptors (mGluRs) are part of the G protein-coupled receptors (GPCRs) family. They are coupled to Gαq (group I) or Gi/o (groups II and III) proteins, which result in the generation of diacylglycerol (DAG) and inositol 1,4,5-triphosphate (IP3) or the inhibition of adenylyl cyclase, respectively. mGluRs have been implicated in anxiety, depression, learning, and synaptic plasticity. Similarly, CB1 cannabinoid receptors (CB1Rs), also GPCRs, play roles in cognitive function and mood regulation through Gαi/o-mediated inhibition of adenylyl cyclase. Both mGluRs and CB1Rs exhibit surface labeling and undergo endocytosis. Given the similar cellular distribution and mechanisms of action, this review complies with fundamental data on the potential interactions and mutual regulation of mGluRs and CB1Rs in the context of depression, anxiety, and cognition, providing pioneering insights into their interplay.

Maternal Immune Activation and the Endocannabinoid System: Focus on Two-Hit Models of Schizophrenia

The devastating effects of the COVID-19 pandemic have underscored the significant threat that infectious diseases pose to our society. Pregnancy represents a period of heightened vulnerability to infections, which can compromise maternal health and increase the risk of neurodevelopmental disorders in offspring. Preclinical and clinical investigations suggest a potential association between maternal immune activation (MIA), which is triggered by viral or bacterial infections, and increased risk for neurodevelopmental disorders such as autism and schizophrenia. Genetic and environmental factors may contribute to the overall risk. Therefore, the two-hit hypothesis of schizophrenia suggests that MIA could act as a first trigger, with subsequent factors, such as stress or drug abuse, exacerbating latent abnormalities. A growing body of research is focused on the interaction between MIA and cannabis use during adolescence, considering the role of the endocannabinoid (eCB) system in neurodevelopment and in neurodevelopmental disorders. The eCB system, crucial for fetal brain development, may be disrupted by MIA, leading to adverse outcomes in adulthood. Recent research indicates the eCB system's significant role in the pathophysiology of neurodevelopmental disorders in preclinical models. However, findings on adolescent cannabinoid exposure in MIA-exposed animals have revealed unexpected complexities, with several studies failing to support the exacerbation of MIA-related abnormalities. In this review, we delve into the functional implications of the eCB system in MIA models, emphasizing the role of 2-AG (2-arachidonoylglycerol) signaling in synaptic plasticity and neuroinflammation and its relevance to the two-hit model of schizophrenia.

Sex-Specific Differences and the Role of Environmental Enrichment in the Expression of Hippocampal CB1 Receptors following Chronic Unpredictable Stress

Stress-related mental disorders have become increasingly prevalent, thus endangering mental health worldwide. Exploring stress-associated brain alterations is vital for understanding the possible neurobiological mechanisms underlying these changes. Based on existing evidence, the brain endogenous cannabinoid system (ECS) plays a significant role in the stress response, and disruptions in its function are associated with the neurobiology of various stress-related disorders. This study primarily focuses on investigating the impact of chronic unpredictable stress (CUS) on the expression of hippocampal cannabinoid type 1 (CB1) receptors, part of the ECS, in adult male and female Wistar rats. Additionally, it explores whether environmental enrichment (EE) initiated during adolescence could mitigate the CUS-associated alterations in CB1 expression. Wistar rats, shortly after weaning, were placed in either standard housing (SH) or EE conditions for a duration of 10 weeks. On postnatal day 66, specific subgroups of SH or EE animals underwent a 4-week CUS protocol. Western blot (WB) analysis was conducted in the whole hippocampus of the left brain hemisphere to assess total CB1 protein expression, while immunohistochemistry (IHC) was performed on the right hemisphere to estimate the expression of CB1 receptors in certain hippocampal areas (i.e., CA1, CA3 and dentate gyrus-DG). The WB analysis revealed no statistically significant differences in total CB1 protein levels among the groups; however, reduced CB1 expression was found in specific hippocampal sub-regions using IHC. Specifically, CUS significantly decreased CB1 receptor expression in the CA1 and DG of both sexes, whereas in CA3 the CUS-associated decrease was limited to SH males. Interestingly, EE housing proved protective against these reductions. These findings suggest a region and sex-specific endocannabinoid response to chronic stress, emphasizing the role of positive early experiences in the protection of the adolescent brain against adverse conditions later in life.

Attenuation of cannabis withdrawal symptoms by Prosopis farcta extract, its luteolin and melatonin in mice: Involvement of brain-derived neurotrophic factor and dopamine

The aim of this study was the identification of luteolin in Prosopis farcta extract (PFE) and melatonin to evaluate its effect on THC withdrawal syndrome in mice. Luteolin was identified by high-performance liquid chromatography (HPCL). Signs of toxicity of mice in PFE and luteolin were monitored for LD50 calculation. The behavioral symptoms of THC withdrawal (stereotypies, ambulation, and inactivity time) induced by the rimonabant challenge were illustrated in THC-dependent mice receiving PFE, luteolin, and melatonin. The expression of mature BDNF (mBDNF) was evaluated by Western blot analysis. The dopamine concentrations were measured using HPLC. PFE and luteolin LD50 were 650 and 220 mg/kg, respectively. PFE (300 mg/kg), all doses of luteolin, and melatonin increased significantly the mBDNF expression and decreased the dopamine concentration. The findings suggest that PFE, luteolin, and melatonin are mighty in reducing the signs of THC withdrawal. It seems these effects were due to a decrease in dopamine concentration level and an increase in mBDNF protein expression in mice brains.