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Iron deposits in multiple sclerosis and Alzheimer's disease brains
1Department of Physiology and the Smith Mental Retardation Research Center, University of Kansas Medical Center, Kansas City 66160, USA. slevine@kumc.edu
Abstract:
Iron may contribute to the pathogenesis of neurological diseases by promoting oxidative damage. The localization of iron in multiple sclerosis (MS) and Alzheimer's disease (AD) brains was investigated to further the understanding of its pathogenic role in these disease states. Earlier studies, utilizing a standard Perls' stain, yielded conflicting reports regarding the distribution of iron deposits in MS brains, and a previous study on AD brains utilized a diaminobenzidine (DAB) enhanced version of this stain. In the present study, a modified version of the DAB-enhanced stain was used; it utilizes sodium borohydride, proteinase K, Triton X-100 and xylenes to increase the accessibility of tissue iron to histochemical reagents. This modified method can reveal iron deposits that are missed by the Perls' or DAB-enhanced Perls' stains. In addition to its normal deposition in oligodendrocytes and myelin, iron was detected in reactive microglia, ameboid microglia and macrophages in MS brains. In AD brains, three types of plaques were stained: dense core, clear core and amorphous plaques. Punctate staining was also observed in neurons in the corticies of AD brains. The structure accounting for punctate labeling may be damaged mitochondria, lipofuscin or amyloid deposits. Dense core plaques, clear plaques and punctate labeling were not detected in the previous AD study which utilized only the DAB-enhanced Perls' stain. The labeling of these additional structures illustrates the benefit of the modified method. In summary, the localization of iron deposition in MS and AD brains indicates potential sites where iron could promote oxidative damage in these disease states.
Insights
This study developed a new iron staining method to better visualize iron deposits in neurological disease brains. The enhanced staining revealed iron in microglia and specific plaque types in multiple sclerosis (MS) and Alzheimer
Area of Science:
- Neuroscience
- Histopathology
- Biochemistry
Background:
- Iron accumulation is implicated in neurological disease pathogenesis, potentially via oxidative damage.
- Previous iron staining methods (Perls', DAB-enhanced Perls') have limitations in sensitivity and specificity.
- Conflicting reports exist on iron distribution in multiple sclerosis (MS) and Alzheimer' s disease (AD) brains.
Purpose of the Study:
- To investigate the precise localization of iron deposits in MS and AD brains.
- To develop an improved histochemical staining method for detecting tissue iron.
- To understand the pathogenic role of iron in MS and AD by identifying novel deposition sites.
Main Methods:
- Development of a modified DAB-enhanced Perls' stain using sodium borohydride, proteinase K, Triton X-100, and xylenes.
- Application of the modified stain to MS and AD brain tissue samples.
- Comparison of iron localization patterns with standard Perls' and DAB-enhanced Perls' stains.
Main Results:
- The modified stain detected iron deposits missed by previous methods.
- In MS brains, iron was found in oligodendrocytes, myelin, reactive microglia, ameboid microglia, and macrophages.
- In AD brains, iron was localized to dense core, clear core, and amorphous plaques, as well as punctate neuronal staining (potentially damaged mitochondria, lipofuscin, or amyloid deposits).
Conclusions:
- The enhanced iron staining method provides a more comprehensive view of iron distribution in MS and AD.
- Iron deposition in specific cell types (microglia, macrophages) and pathological structures (plaques) highlights potential sites of oxidative damage in these diseases.
- This improved methodology aids in understanding iron' s role in the pathogenesis of MS and AD.