What is Parkinson’s disease?
Parkinson’s disease is a neurodegenerative disease caused by the gradual death of nerve cells situated in the ‘Substantia Nigra’, a specific area of the brain that controls the movements of the whole body through a neurotransmitter called “dopamine”.
At the onset of Parkinson’s disease, the nerve cells that produce dopamine start to die and this reduces the ability to control body movements. In fact, the first evident symptoms are trembling of the limbs, stiffness and a slightly reduced speed of movement. At an advantaged stage, this disease severely impairs the sense of balance and walking, preventing the person from carrying out normal everyday activities.
At the most advanced stage, the patient needs continuous assistance but, with the forms of treatment now available, no longer reaches a condition of total immobility as was previously the case. The reference specialist for this disease is the neurologist.
Causes and new hypotheses
Although Parkinson’s disease was described as early as 1817 by Dr. James Parkinson, the causes of the disease are still unknown. The scientific community currently gives consideration to two types of hypothesis: environmental and genetic.
Epidemiological studies have shown a correlation between exposure to factors such as pesticides and heavy metals and the onset of Parkinson’s disease. The latest studies conducted correlate the onset of the disease with a genetic defect which has indeed been identified in 20% of patients with a family history of Parkinson’s disease and, in some of these families, alterations of at least 5 precise genes, including the alpha-synuclein gene and the DJ-1 gene, have been identified.
These genes could be functionally correlated with one another, as suggested by the recent demonstration of the fact that genetically induced modifications of the DJ-1 protein alter the functions of alpha-synuclein, making it toxic for cells.
The normal physiology of the nerve cell is based on the removal of the proteins and cell organelles but these systems must function effectively above all in order to dispose of altered proteins or the organelles (principally mitochondria) that – following specific damage or physiological aging – are no longer capable of performing their normal function.
The two most important of these “disposal” systems are the ubiquitin proteasome system (UPS), which normally disposes of membrane proteins that have a short half-life, and autophagia, which plays a decisive role in the clearance of proteins with a long half-life and is the only system capable of disposing of cell organelles.
When these systems are blocked or, in any case, do not function perfectly, which is what seems to happen in Parkinson’s disease, the toxic proteins accumulate and block the physiological functioning of the dopaminergic cells.