Alzheimer’s disease is a chronic neurodegenerative disease and the main cause of dementia. Main common symptoms of dementia are related with memory but other cognitive processes are affected during the development of the disease. cannabinoids have great potential in the prevention and treatment of the pathogenesis and symptomatology of Alzheimer’s disease.
One therapeutic indication for CB2 is the stimulation of Amyloid β plaque removal by macrophages. Similar effects were seen for 2AG and MAGL inhibitors (Chen et al., 2012). CB1 is not involved in plaque clearance.
GPR3 has been linked to Alzheimer's disease through the modulation of amyloid β plaques (Laun & Song, 2017).
DAGL decreased its activity under the presence of Aβ1-40 oligomers, leading to lower levels of 2-AG, which could be associated to AD progression (Pascual, Gaveglio, Giusto, & Pasquaré, 2017).
In cell culture, CBD prevented hyper-phosphorylation of Tau/the formation of neurofibrillary tangles.
CBD may also have anti-inflammatory properties through activation of PPARγ. In addition, CBD stimulates neurogenesis and may therefore counteract neurodegeneration at multiple levels (Esposito et al., 2011).
Amyloid beta plaques, a hallmark of Alzheimer’s, induce neuroinflammation and astrogliosis. Endogenous PEA levels rise with astrogliosis. PEA, in turn, blocks pro-inflammatory cytokines through PPARα (Scuderi et al., 2011). This suggests that the PEA-PPARα interaction functions to curtail neuroinflammation and inhibit the progression of Alzheimer’s.
In cultured astrocytes, Aβ1-42 reduced cell viability and PPARγ expression and increased cellular inflammation and anti-oxidant capacity. Specific CB1 stimulation (with WIN55,212-2, a synthetic analog of THC) prevented all these effects and increased cellular viability (Aguirre-Rueda et al., 2015).
CBD, THC and AEA also have anti-oxidant properties, which may be neuroprotective in AD.
Exercise has been shown to be beneficial in neurological disorders like Alzheimer’s disease and depression. Exercise increases the production of new neurons in the hippocampus in rats. In addition, Anandamide levels (and to a lesser degree 2AG levels) and CB1 receptor availability are increased in the hippocampus (but not in the prefrontal cortex). Blocking the endocannabinoid system prevents the production of new neurons suggesting a role for cannabinoids in this process (Hill et al., 2010).
Alzheimer’s patients have higher serum levels of 2AG and PEA. In these patients, 2AG is positively correlated with cognitive performance suggesting therapeutic potential. PEA was inversely correlated with cognitive performance, underlining the differential characteristics of cannabinoids (Altamura et al., 2015).
Aguirre-Rueda, D., Guerra-Ojeda, S., Aldasoro, M., Iradi, A., Obrador, E., Mauricio, M.D., Vila, J.M., Marchio, P., and Valles, S.L. (2015). WIN 55,212-2, Agonist of cannabinoid Receptors, Prevents Amyloid β1-42 Effects on Astrocytes in Primary Culture. PloS One 10, e0122843.
Altamura, C., Ventriglia, M., Martini, M.G., Montesano, D., Errante, Y., Piscitelli, F., Scrascia, F., Quattrocchi, C., Palazzo, P., Seccia, S., et al. (2015). Elevation of Plasma 2-Arachidonoylglycerol Levels in Alzheimer’s Disease Patients as a Potential Protective Mechanism against Neurodegenerative Decline. J. Alzheimers Dis. JAD.
Esposito, G., Scuderi, C., Valenza, M., Togna, G.I., Latina, V., De Filippis, D., Cipriano, M., Carratù, M.R., Iuvone, T., and Steardo, L. (2011). Cannabidiol reduces Aβ-induced neuroinflammation and promotes hippocampal neurogenesis through PPARγ involvement. PloS One 6, e28668.
Chen, R., Zhang, J., Wu, Y., Wang, D., Feng, G., Tang, Y.-P., … Chen, C. (2012). Monoacylglycerol lipase is a therapeutic target for Alzheimer’s disease. Cell Reports, 2(5), 1329-1339. https://doi.org/10.1016/j.celrep.2012.09.030
Hill, M.N., Titterness, A.K., Morrish, A.C., Carrier, E.J., Lee, T.T.-Y., Gil-Mohapel, J., Gorzalka, B.B., Hillard, C.J., and Christie, B.R. (2010). Endogenous cannabinoid signaling is required for voluntary exercise-induced enhancement of progenitor cell proliferation in the hippocampus. Hippocampus 20, 513–523.
Laun, A. S., & Song, Z.-H. (2017). GPR3 and GPR6, novel molecular targets for cannabidiol. Biochemical and Biophysical Research Communications, 490(1), 17-21. https://doi.org/10.1016/j.bbrc.2017.05.165
Pascual, A. C., Gaveglio, V. L., Giusto, N. M., & Pasquaré, S. J. (2017). 2-arachidonoylglycerol metabolism is differently modulated by oligomeric and fibrillar conformations of amyloid beta in synaptic terminals. Neuroscience. https://doi.org/10.1016/j.neuroscience.2017.08.042
Scuderi, C., Esposito, G., Blasio, A., Valenza, M., Arietti, P., Steardo, L., Carnuccio, R., De Filippis, D., Petrosino, S., Iuvone, T., et al. (2011). Palmitoylethanolamide counteracts reactive astrogliosis induced by β-amyloid peptide. J. Cell. Mol. Med. 15, 2664–2674.
cannabinoids also have the potential to interfere in the pathophysiological processes underlying Alzheimer's as described in the "Literature Discussion" section. Clinical trials will have to validate these potential therapeutic properties.