Ammonium accumulation and chemokine decrease in culture media of Gcdh -/- 3D reaggregated brain cell cultures.

Glutaric Aciduria type I (GA-I) is caused by mutations in the GCDH gene. Its deficiency results in accumulation of the key metabolites glutaric acid (GA) and 3-hydroxyglutaric acid (3-OHGA) in body tissues and fluids. Present knowledge on the neuropathogenesis of GA-I suggests that GA and 3-OHGA have toxic properties on the developing brain. We analyzed morphological and biochemical features of 3D brain cell aggregates issued from Gcdh ^-/- mice at two different developmental stages, day-in-vitro (DIV) 8 and 14, corresponding to the neonatal period and early childhood. We also induced a metabolic stress by exposing the aggregates to 10 mM l-lysine (Lys). Significant amounts of GA and 3-OHGA were detected in Gcdh ^-/- aggregates and their culture media. Ammonium was significantly increased in culture media of Gcdh ^-/- aggregates at the early developmental stage. Concentrations of GA, 3-OHGA and ammonium increased significantly after exposure to Lys. Gcdh ^-/- aggregates manifested morphological alterations of all brain cell types at DIV 8 while at DIV 14 they were only visible after exposure to Lys. Several chemokine levels were significantly decreased in culture media of Gcdh ^-/- aggregates at DIV 14 and after exposure to Lys at DIV 8. This new in vitro model for brain damage in GA-I mimics well in vivo conditions. As seen previously in WT aggregates exposed to 3-OHGA, we confirmed a significant ammonium production by immature Gcdh ^-/- brain cells. We described for the first time a decrease of chemokines in Gcdh ^-/- culture media which might contribute to brain cell injury in GA-I.
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