Etiology of Parkinson's disease: A research strategy.

In this essay I present a new "global approach hypothesis" to explain the pathophysiology of Parkinson's disease: "Susceptibility to Parkinsonism is genetically determined and is reflected in all cells. I propose that idiopathic Parkinson's disease is the combined result of a generalized cell aging process accelerated, in susceptible individuals, by a variety of often repetitive trigger factors. These factors have in common the fact that they cause a transient increase in turnover within catecholamine producing neurons, centrally as well as peripherally. This results in accumulation within these neurons of free radicals. When the level of the toxic substances, in quantity or in time of exposure, exceeds the scavenging capacity of the cell, damage to organelles and to membranes results, leading to the formation of Lewy bodies through an autoimmune reaction to damaged filaments and to cell death, particularly in the pigmented neurons of the brainstem. The progressive cell depletion leads to a compensatory increase in catecholamine turnover in the remaining pigmented cells, and an ever-accelerating degenerative process. The resulting neurotransmitter imbalance in the basal ganglia explains the symptoms of Parkinson's disease". In the light of this hypothesis, our research objectives should be (1) to delineate the limits of true Parkinson's disease from all phenocopies; (2) to identify individuals susceptible to parkinsonism and the most common trigger factors; (3) to reduce the metabolic effects of unavoidable trigger factors and (4) to protect susceptible individuals by increasing the functional availability of free radical trapping agents.