6.6. SENILE PLAQUES, TANGLES AND CURLY FIBERS CONTAIN DNA
If spirochetes play a role in the formation of senile plaques, neurofibrillary tangles and neuropil threads, we anticipated that they may contain DNA. The 4’6-diamidine-2’-phenylindole dihydrochloride (DAPI) binds selectively to DNA and forms strongly fluorescent DNA-DAPI complexes (Russel et al., 1975). DNA staining is the most popular method for the detection of cell culture Mycoplasma by its DNA content. Using this sensitive DNA stain, not only reference spirochetes may be visualized but senile plaques, neurofibrillary tangles and neuropil threads as well. DNase pretreatment abolishes the DAPI staining of these structures but not their Thioflavin S affinity indicating that they indeed contain DNA (Miklossy et al., 1995).
Miklossy J, Gern L, Darekar P, Janzer RC, Van der Loos H. Senile plaques, neurofibrillary tangles and neuropil threads contain DNA? Journal of Spirochetal and Tick-borne Diseases (JSTD), 1995;2:1-5.
It has been recently reported that microorganisms - spirochetes - may play a role in the etiology of Alzheimer's disease (AD). Further ulktrastructural sanalysis revealed that the helically shaped microorganisms isolated or cultured from the Alzheimer's brain possess axial filament that taxonomically distinguishes spirochetes from other Bacteria. The 4',6-diamidine-2'-phenylindole dihydrochloride (DAPI) binds selectively to DNA and forms strongly fluorescent DNA-DAPI complexes. DNA staining that employs DAPI is the most popular method for the detection of cell culture mycoplasmas. We expected that DAPI would also bind to the DNA of other Bacteria, namely, to the DNA of spirochetes. If senile plaques, neurofibrillary tangles, and neuropil threads are indeed formed by spirochetes , they would consequently also contain DNA and would, therefore, visualized with DAPI. Histological brain sections of AD cases, control cases, ans smears of reference spirochetes were stained with DAPI wihtout and with DNase pretreatment and were examined with fluorescent microscope. When using the sensitive fluorescent DNA stain, not only reference spirochetes may be visualized, but also senile plaques, neurofibrillary tangles as well as neuropil threads. DNase pretreatment abolishes the DAPI staining of these structures, indicating that they contain DNA. Based on observations reported here we suggest that the DNA found in the Alzheimer's type changes may be of bacterial origin and therefore would be in agreement with our earlier observations that spirochetes may well contribute to the pathogenesis of AD.