3 October 2001. Tomorrow's Nature magazine carries an article on head trauma that
could inform parts of Alzheimer's research, as well. Esther Shohami at Hebrew
University's Medical Faculty in Jerusalem, and colleagues there, report that an
endogenous cannabinoid plays a role in the complex protective response prompted
by a brain injury.
The compound, 2-Arachidonoyl glycerol (2-AG) occurs in the brain and the intestine
but its physiology remains poorly understood. It can protect cerebral rat neurons
from ischemia in vitro (Sinor
AD et al.), and synthetic cannabinoids have been shown to reduce neuronal
death in the hippocampus of rats after experimentally induced ischemia (Nagayama
T et al.).
In this study, the researchers subjected mice to head trauma and analyzed the
2-AG response following this injury. 2-AG levels rose, peaking at 10-fold after
four hours. When the researchers injected additional 2-AG, the mice developed 50 percent less edema and recovered faster. More directly relevant to Alzheimer's
research, the treated mice also suffered less neuronal cell death. The researchers
counted neurons in the CA3 area of the hippocampus, and report that control
mice (head trauma without exogenous 2-AG) had lost about 40 percent of neurons
in that brain area seven days after the trauma, whereas treated mice lost about
10 percent. (The hippocampus is among the brain areas most affected by neuronal
death in AD.)
The authors write that these results are the first to record the neuroprotective
effects of this cannabinoid. In previous work, the authors had shown that 2-AG
suppresses the formation of reactive oxygen species and the inflammatory cytokine
tumor necrosis factor-β, both of which contribute to the pathophysiology
of brain injury. To the extent that oxidative damage and inflammation spur the
loss of cells in AD, this research may well bear attention.-Gabrielle Strobel.
Reference:Panikashvili D, Simeonidou C, Ben-Shabat S, Hanus L, Breuer A, Mechoulam R, Shohami E. An endogenous cannabinoid (2-AG) is neuroprotective after brain injury.
Nature. 2001 Oct 4;413(6855):527-31. Abstract
Marijuana and AD