Immunohistochemical localization of X-linked inhibitor of apoptosis protein in brainstem-type and cortical Lewy bodies.

X-linked inhibitor of apoptosis protein (XIAP) blocks the apoptosis by binding to and inhibiting caspases-3, 7, and 9. XIAP is negatively regulated by the mitochondrial serine protease, HtrA2/Omi. The aim of this study was to investigate the role of XIAP and the relationship between XIAP and HtrA2/Omi in patients with Parkinson's disease or dementia with Lewy bodies. We conducted immunohistochemical studies on XIAP in formalin-fixed, paraffin-embedded sections from eight normal participants, 10 patients with Parkinson's disease, five patients with dementia with Lewy bodies, and seven patients with Alzheimer's disease, and then double-labeling immunohistochemistry for XIAP and HtrA2/Omi in sections from the Parkinson's disease and dementia with Lewy bodies cases. Brainstem-type and cortical Lewy bodies were intensely immunostained for XIAP, and XIAP immunoreactivity was localized to the halos of brainstem-type Lewy bodies and to the entire bodies of cortical Lewy bodies. Double immunofluorescence analyses showed that XIAP and HtrA2/Omi immunoreactivities were colocalized to both types of Lewy bodies. Our results suggest that XIAP may be partially associated with the pathogenesis of Parkinson's disease and dementia with Lewy bodies. NeuroReport 23: 162-167 (C) 2012 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.