An immune mechanism eliminates the nerve fibers that warn the smells in the early stages of Alzheimer: from the tests of the smell the early diagnosis?
A worsening in the perception of smells can be an early alarm bell of Alzheimer’s disease: this has been known for some time, but now a research published on Nature Communications clarifies because it happens. The results of the study could help to develop tests of the smell that help to recognize Alzheimer when it is still in the initial phase and before it can damage the memory.
After analyzing with various techniques brains affected by Alzheimer’s in human and mice, researchers from the German center for neurodegenerative diseases and Ludwig-Maximilians-university in Monaco concluded that the malfunction of the smell insories because, in the early stages of Alzheimer, the immune cells of the brain remove the neural connections between two crucial brain regions for the perception of the smells, the olfactory bulb and the Locus Coeruleus.
A harmful change
The olfactory bulb is a brain structure that receives the smelling stimuli from the olfactory epithelium of the nose and which first analyzes and elaborates them. The locus coeruleus is a set of nerve cells that is located in the brain trunk, the area of the brain that follows the spinal cord: regulates many physiological mechanisms and is a place of sorting of the stimuli from the meaning organs, including the olfactory signals.
According to the authors of the study, in the early stages of Alzheimer they would warn changes in the nerve fibers that connect olfactory bulb and locus coeruleus. To change in particular would be the composition of the membranes of the nerve fibers: the phosphatidilserinea fatty acid that is usually located in the internal part of the membrane, is moved outwards. A signal that is read from the immune cells of the brain (the micoglia) as a clear message – “eat me”.
In non -pathological situations, in the olfactory bulb, this signal regulates the glimpse mechanism of unnecessary neural connections. It exists for this: but in the case of Alzheimer, to alter the composition of the membrane it would be the hyperactivity of the affected neurons, and the effects of this are far from useful.
Interrupted highway
The micoglia reads the fibers marked by the signal as harmful or superfluous and cut them. The connection between olfactory bulb and locus coeruleus degrades. The researchers checked all this by studying both the brain tissue of patients with alzheimer’s deceased, and by analyzing the pet exam (positron emission tomography) of patients with Alzheimer’s or mild cognitive decline, which highlights the pathological alterations of the cells. They also studied mice with a condition similar to that of dementia.
Do you recognize this smell?
The discovery could strengthen the possibility of developing the smell of the smell to identify patients with very early phase Alzheimers, and to direct them to therapies who target the beta-amyloid protein deposits in the brain, more effective if administered before the disease can cause more extensive damage.