A further issue in Parkinson’s disease is the possible role of both endogenous
L-dopa produced by the surviving dopaminergic neurons and exogenous
L-dopa used in therapy as neurotoxins. A number of experiments
have demonstrated the ability of L-dopa to induce apoptosis in cell culture.
119-124
L-dopa synthesis and release is increased in surviving dopaminergic
neurons to compensate for loss of neurons during the illness and may
therefore contribute in a secondary manner to further injury. In addition,
toxins affecting complex I in mitochondria, calcium stress, aging-related, or
inherited mtDNA defects have been suggested as portals into apoptotic loss
of dopaminergic neurons.
125-127
Protective therapy may be directed at mitochondrial
or apoptotic mechanisms of cell injury and death