Immunohistochemical Study of Human Mitochondrial Ferritin in the Substantia Nigra Following Subarachnoid Hemorrhage

Mitochondrial ferritin (FtMt) is a novel ferritin that sequesters iron and plays a protective role against oxidative stress. FtMt shares a high homology with H-ferritin but is expressed only in the brain, heart, and testis. In the midbrain, FtMt expression is observed in the substantia nigra. FtMt plays a neuroprotective role in the pathology of neurodegenerative diseases such as Parkinson's disease, where excessive iron induces oxidative stress, causing cell death. Herein, we investigated FtMt immunoreactivity in the brains of patients with subarachnoid hemorrhage (SAH). Double immunofluorescence labeling of tyrosine hydroxylase (TH) and FtMt showed high colocalization in the substantia nigra pars compacta (SNc) in control and SAH cases. However, in SAH cases, FtMt immunoreactivity was observed in some THnegative neurons. Double immunofluorescence labeling of glial cell markers and FtMt showed no apparent colocalization. The number and ratio of FtMt-positive but TH-negative neurons significantly differed between the control and SAH groups. Prussian blue staining in SAH cases showed positive iron staining over a wide surface range and the substantia nigra. Thus, FtMt may be related to iron dynamics in the substantia nigra following subarachnoid hemorrhage.