We previously showed in a 3D rat brain cell in vitro model for glutaric
aciduria type-I that repeated application of 1mM 3-hydroxy-glutarate
(3-OHGA) caused ammonium accumulation, morphologic alterations
and induction of non-apoptotic cell death in developing brain cells.
Here, we performed a dose-response study with lower concentrations of 3-
OHGA.We exposed our cultures to 0.1, 0.33 and 1mM 3-OHGA every 12h
over three days at two developmental stages (DIV5-8 and DIV11-14).
Ammonium accumulation was observed at both stages starting from
0.1mM 3-OHGA, in parallel with a glutamine decrease. Morphological
changes started at 0.33mM with loss of MBP expression and loss of
astrocytic processes. Neurons were not substantially affected. At DIV8,
release of LDH in the medium and cellular TUNEL staining increased
from 0.1mM and 0.33mM 3-OHGA exposure, respectively. No increase
in activated caspase-3 was observed.
We confirmed ammonium accumulation and non-apoptotic cell
death of brain cells in our in vitro model at lower 3-OHGA
concentrations thus strongly suggesting that the observed effects
are likely to take place in the brain of affected patients. The
concomitant glutamine decrease suggests a defect in the astrocyte
ammonium buffering system. Ammonium accumulation might be
the cause of non-apoptotic cell death.