Researchers show that these immune cells attack one of the main manifestations of Alzheimer’s disease
An article published in the journal Cell Reports by researchers from Université Laval reveals the existence of a natural mechanism to prevent one of the manifestations of Alzheimer’s in the brain. Using medical imaging techniques to view live events that occur in living mice with Alzheimer’s, researchers have discovered that a type of white blood cells – patrolling monocytes – selectively attack amyloid aggregates attached to the inner lining of blood vessels in the brain.
One of the main characteristics of Alzheimer’s disease is the production of beta – amyloid, a molecule toxic to the brain tissue. This peptide forms aggregates and accumulates on the walls of blood vessels or on nervous tissue. In the latter case, they lead to the formation of senile or amyloid plaques. “We believe that the presence of these aggregates in the blood vessels is a major cause of the disease because it interferes with the oxygenation of the brain, says study leader, Serge Rivest. It would lead to the deterioration of cognitive abilities of patients. “
His team at the Québec CHU Research Centre uses sophisticated techniques to visualize the evolution of amyloid aggregates in transgenic mice expressing the main features of Alzheimer’s. “We make a small opening in the skull of the mouse and we use intravital microscopy to visualize markers for amyloid and monocytes in the blood vessels. We can follow the evolution of the disease by examining the same mouse at regular intervals for several months. “
Striking images obtained by the researchers show that patrolling monocytes are attracted by amyloid found in the veins of the brain. They attach themselves to nearby clusters and they phagocytose them. Once the work is completed, amyloid-loaded monocytes detach themselves and return to the bloodstream.
“In young mice, the mechanism is efficient enough to prevent the formation of aggregates. However, it becomes less effective as the mice age, as if the immune system was exhausted,”says Professor Rivest. Other tests performed on a line of mice lacking patrolling monocytes indicate that the concentration of amyloid is significantly higher in the brains of these animals.
The researchers believe that the same defense mechanism and the same faults may exist in humans. “In people with Alzheimer’s, monocytes are less abundant or they do not do their job well. If the situation is corrected, we believe that the condition of the patients could improve. “The researchers are now on the trail of molecules capable of stimulating the synthesis of patrolling monocytes. The visualization technique they refined will allow them to observe the effects of these molecules on amyloid aggregates and to relate them to changes in cognitive abilities of mice.
The study published in Cell Reports is signed by Jean -Philippe Michaud, Marc- André Bellavance, Paul Préfontaine and Serge Rivest.
Source of text: Université Laval, Jean Hamann, le Fil
Translation: CAN-ACN
Original research article:
Michaud JP, Bellavance MA, Préfontaine P, Rivest S. Real-time in vivo imaging reveals the ability of monocytes to clear vascular amyloid Beta. Cell Rep. 2013 Nov 14;5(3):646-53. doi: 10.1016/j.celrep.2013.10.010. Epub 2013 Nov 7.
