Impairments in cognitive ability and widespread pathophysiological changes caused by neurotoxicity, neuroinflammation, oxidative damage, and altered cholesterol homeostasis are associated with Alzheimer’s disease (AD). Cannabidiol (CBD) has been shown to reverse cognitive deficits of AD transgenic mice and to exert neuroprotective, anti-oxidative, and anti-inflammatory properties in vitro and in vivo. Here we evaluate the preventative properties of long-term CBD treatment in male AβPPSwe/PS1ΔE9 (AβPP × PS1) mice, a transgenic model of AD. Control and AD transgenic mice were treated orally from 2.5 months of age with CBD (20 mg/kg) daily for 8 months. Mice were then assessed in the social preference test, elevated plus maze, and fear conditioning paradigms, before cortical and hippocampal tissues were analyzed for amyloid load, oxidative damage, cholesterol, phytosterols, and inflammation. We found that AβPP × PS1 mice developed a social recognition deficit, which was prevented by CBD treatment. CBD had no impact on anxiety or associative learning. The prevention of the social recognition deficit was not associated with any changes in amyloid load or oxidative damage. However, the study revealed a subtle impact of CBD on neuroinflammation, cholesterol, and dietary phytosterol retention, which deserves further investigation. This study is the first to demonstrate CBD’s ability to prevent the development of a social recognition deficit in AD transgenic mice. Our findings provide the first evidence that CBD may have potential as a preventative treatment for AD with a particular relevance for symptoms of social withdrawal and facial recognition.
Keywords: Alzheimer’s disease; amyloid load; behavior; cannabidiol; cholesterol; neuroinflammation; oxidative stress; phytosterol; social recognition memory; transgenic $Abeta PP_
Individuals with Alzheimer’s and other forms of dementia often go through a period of significant behavioral and psychological symptoms of dementia (BPSD). It is estimated that up to 90% of persons with dementia (PWD) experience behavior problems at some point. BPSDs can be challenging for both unpaid family caregivers as well as paid caregivers. Family caregivers provide the bulk of care for PWD and number over 15 million. One of the most common types of BPSDs is agitation with a prevalence of up to 87%, based on a recent systematic review. Agitation can lead to impaired daily functioning, prolongation of hospitalization, reduced time to institutionalization, and is associated with higher mortality. Additionally, agitated behavior is associated with increased injury to both patients and caregivers. Based on the 2018 Alzheimer’s disease drug development pipeline report almost 70% of clinical trials related to BPSD are dedicated to agitation behavior. Finding ways to address agitation is necessary to improve overall quality of life for PWD and their caregivers. Currently, there are no medications available specifically for the treatment of BPSDs. The use of benzodiazepines, antipsychotics and mood stabilizing agents are common, but the risks and side effects often outweigh any benefits.
Several small studies have investigated the use of cannabinoids in the treatment of pathology and symptomology of Alzheimer’s disease (AD), as well as treatment of the agitation component of BPSD. A handful of these studies showed that the symptoms of BPSD were decreased with the use of cannabinoids. However, due to small sample sizes, study design, and short trial duration of these studies, the efficacy of these agents on BPSD cannot be confirmed. In addition, cannabinoids have demonstrated anti-oxidant and anti-inflammatory effects, and both processes have been indicated as major contributors to the neurologic effects of AD. Some evidence exists that agitation is related to this neuroinflammatory process. This study will examine the effects of cannabinoids on the behavioral and psychological symptoms of individuals with a dementia diagnosis.
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