Neuronal loss in specific brain regions and neurons with intracellular 
inclusions termed Lewy bodies are the pathologic hallmark in both Parkinson's 
disease (PD) and dementia with Lewy bodies (DLB). Lewy bodies comprise of 
aggregated intracellular vesicles and proteins and α-synuclein is reported to be 
a major protein component. Using human brain tissue from control, PD and DLB and 
light and confocal immunohistochemistry with antibodies to superoxide dismutase 
2 as a marker for mitochondria, α-synuclein for Lewy bodies and βIII Tubulin for 
microtubules we have examined the relationship between Lewy bodies and 
mitochondrial loss. We have shown microtubule regression and mitochondrial and 
nuclear degradation in neurons with developing Lewy bodies. In PD, multiple Lewy 
bodies were often observed with α-synuclein interacting with DNA to cause marked 
nuclear degradation. In DLB, the mitochondria are drawn into the Lewy body and 
the mitochondrial integrity is lost. This work suggests that Lewy bodies are 
cytotoxic. In DLB, we suggest that microtubule regression and mitochondrial loss 
results in decreased cellular energy and axonal transport that leads to cell 
death. In PD, α-synuclein aggregations are associated with intact mitochondria 
but interacts with and causes nuclear degradation which may be the major cause 
of cell death.