Vol. 276, Issue 4, F521-F527, April 1999
Partial characterization of apoptotic factor in Alzheimer
plasma
John K.
Maesaka1,
Thomas
Palaia1,
Soheli A.
Chowdhury1,
Tetsuo
Shimamura2,
Steven
Fishbane1,
William
Reichman3,
Andrew
Coyne3,
Julian J.
O'Rear1, and
Marwan E.
El-Sabban1,4
1 Department of Medicine,
Winthrop-University Hospital, Mineola, New York 11501; Departments
of 2 Pathology and
3 Geriatric Services, Robert Wood
Johnson Medical School, Piscataway, New Jersey 08854; and
4 Department of Human
Morphology, American University of Beirut, Beirut,
Lebanon
We have previously demonstrated that a plasma natriuretic factor
is present in Alzheimer's disease (AD), but not in multi-infarct dementia (MID) or normal controls (C). We postulated that the natriuretic factor might induce the increased cytosolic calcium reported in AD by inhibiting the sodium-calcium antiporter, thereby activating the apoptotic pathway. To test for a factor in AD plasma that induces apoptosis, we exposed nonconfluent cultured
LLC-PK1 cells to plasma from AD,
MID, and C for 2 h and performed a terminal transferase-dUTP-nick-end
labeling (TUNEL) assay. The plasma from AD increased apoptosis nearly
fourfold compared with MID and C. The effect was dose dependent and the
peak effect was attained after a 2-h exposure. Additionally, apoptotic
morphology was detected by electron microscopy, and internucleosomal
DNA cleavage was found. We inhibited apoptosis by removing
calcium from the medium, inhibiting protein synthesis with
cycloheximide, alternately boiling or freezing and thawing the plasma,
and digesting a partially purified fraction with trypsin. Heating AD
plasma to 56°C did not deactivate the apoptotic factor. These
results demonstrate the presence of an apoptotic factor in the plasma
of patients with AD.
LLC-PK1 cells; apoptosis; terminal transferase-dUTP-nick-end labeling; natriuretic factor
