Neonatal Astrocyte Damage Is Sufficient to Trigger Progressive Striatal Degeneration in a Rat Model of Glutaric Acidemia-I

Abstract

BackgroundWe have investigated whether an acute metabolic damage to astrocytes during the neonatal period may critically disrupt subsequent brain development, leading to neurodevelopmental disorders. Astrocytes are vulnerable to glutaric acid (GA), a dicarboxylic acid that accumulates in millimolar concentrations in Glutaric Acidemia I (GA-I), an inherited neurometabolic childhood disease characterized by degeneration of striatal neurons. While GA induces astrocyte mitochondrial dysfunction, oxidative stress and subsequent increased proliferation, it is presently unknown whether such astrocytic dysfunction is sufficient to trigger striatal neuronal loss.Methodology/Principal FindingsA single intracerebroventricular dose of GA was administered to rat pups at postnatal day 0 (P0) to induce an acute, transient rise of GA levels in the central nervous system (CNS). GA administration potently elicited proliferation of astrocytes expressing S100β followed by GFAP astrocytosis and nitrotyrosine staining lasting until P45. Remarkably, GA did not induce acute neuronal loss assessed by FluoroJade C and NeuN cell count. Instead, neuronal death appeared several days after GA treatment and progressively increased until P45, suggesting a delayed onset of striatal degeneration. The axonal bundles perforating the striatum were disorganized following GA administration. In cell cultures, GA did not affect survival of either striatal astrocytes or neurons, even at high concentrations. However, astrocytes activated by a short exposure to GA caused neuronal death through the production of soluble factors. Iron porphyrin antioxidants prevented GA-induced astrocyte proliferation and striatal degeneration in vivo, as well as astrocyte-mediated neuronal loss in vitro.Conclusions/SignificanceTaken together, these results indicate that a transient metabolic insult with GA induces long lasting phenotypic changes in astrocytes that cause them to promote striatal neuronal death. Pharmacological protection of astrocytes with antioxidants during encephalopatic crisis may prevent astrocyte dysfunction and the ineluctable progression of disease in children with GA-I.

Experimental evidence that bioenergetics disruption is not mainly involved in the brain injury of glutaryl-CoA dehydrogenase deficient mice submitted to lysine overload

“…In contrast, vacuolation in the cerebral cortex seems to be progressive as age advances and independent of Lys supplementation. These data, allied to a recent study showing delayed onset of striatum degeneration caused by early GA treatment in rat pups (Olivera-Bravo et al, 2011), suggest that striatum can also be progressively damaged by the persistent increase of the accumulating metabolites of GA I, in particular GA. This is in accordance with recent publications demonstrating that, apart from the progressive cortical injury and acute striatum degeneration, chronic striatum injury also takes place in GA I patients (Garbade et al, 2014;Harting et al, 2009;NeumaierProbst et al, 2004).…”

Disruption of brain redox homeostasis in glutaryl-CoA dehydrogenase deficient mice treated with high dietary lysine supplementation

“…Sections were then washed, mounted in glycerol and imaged in a FV300 Olympus confocal microscope provided with 405, 488, 546 and 633 nm lasers. Primary or secondary antibodies were omitted in negative controls [29].…”

Marked reduction of Na+, K+-ATPase and creatine kinase activities induced by acute lysine administration in glutaryl-CoA dehydrogenase deficient mice

“…However, progressive neurological symptoms with mental developmental delay and hypotonia without apparent acute episodes may also occur in a considerable number of patients [5][6][7][8][9]. Neuroradiological imaging shows, besides basal ganglia degeneration, widened Sylvian fissures, cortical atrophy with frontotemporal volume loss, delayed myelination, ventriculomegaly and subdural hemorrhages [1,5,6,8,10,11] Although the pathogenesis of the brain damage in GA I is not fully established, accumulating evidence from in vitro and in vivo experiments performed in brain tissue and cultivated neural cells from rodents and chick suggest that excitotoxicity [6,[12][13][14][15][16][17][18][19][20][21], oxidative stress [22][23][24][25][26][27][28][29][30][31] and cellular bioenergetic dysfunction [2,[32][33][34][35][36][37][38][39] are involved in the brain damage of GA I patients. It is emphasized that these studies were carried out in animal tissues with normal GCDH activity.…”