Arginase 1 Regulation of Nitric Oxide Production Is Key to Survival of Trophic Factor-Deprived Motor Neurons

Abstract

When deprived of trophic factors, the majority of cultured motor neurons undergo nitric oxide-dependent apoptosis. However, for reasons that have remained unclear, 30 -50% of the motor neurons survive for several days without trophic factors. Here we hypothesize that the resistance of this motor neuron subpopulation to trophic factor deprivation can be attributed to diminished nitric oxide production resulting from the activity of the arginine-degrading enzyme arginase. When incubated with nor-N G -hydroxy-nor-L-arginine (NOHA), the normally resistant trophic factor-deprived motor neurons showed a drop in survival rates, whereas trophic factor-treated neurons did not. NOHA-induced motor neuron death was inhibited by blocking nitric oxide synthesis and the scavenging of superoxide and peroxynitrite, suggesting that peroxynitrite mediates NOHA toxicity. When we transfected arginase 1 into motor neurons to see whether it alone could abrogate trophic factor deprivation-induced death, we found that its forced expression did indeed do so. The protection afforded by arginase 1 expression is reversed when cells are incubated with NOHA or with low concentrations of nitric oxide. These results reveal that arginase acts as a central regulator of trophic factor-deprived motor neuron survival by suppressing nitric oxide production and the consequent peroxynitrite toxicity. They also suggest that the resistance of motor neuron subpopulations to trophic factor deprivation may result from increased arginase activity.

MiRNA-124 induces neuroprotection and functional improvement after focal cerebral ischemia

“…As miR-124 was unable to increase the number of Arg-1 expressing neurons, the previously described neuroprotective effects of Arg-1 [19,23], cannot be the main factor responsible for the miR-124 induced neuroprotection observed in our study. Rather, other mechanisms induced by the exogenous miR-124 application must have led to neuroprotection observed in the present study.…”

“…The enzyme is considered to have protective and regenerative properties [18,19,23], beneficial for disease outcome [24]. Up to now, stroke induced changes in the Arg-1 expression level of different cells within the CNS had so far only been studied in rats [18].…”

“…Arg-1 is generally considered a protective and regeneration promoting enzyme as it counteracts the excessive production of cytotoxic NO and is responsible for the generation of polyamines and collagen [17]. Apart from microglia and macrophages, Arg-1 is expressed in a variety of cell types including neurons and astrocytes [18,19]; and thus is considered a suitable marker to observe the miR-124 effects on the different cell types.…”

Identification and Characterization of Cholest-4-en-3-one, Oxime (TRO19622), a Novel Drug Candidate for Amyotrophic Lateral Sclerosis

“…This fluorescence-based image analyzer was designed to count calcein-stained live neurons or other cells by rapidly capturing fluorescent images encompassing the entire well of 96-well or 384-well culture dishes. Subsequently, dedicated image analysis software distinguished cell bodies from debris or aggregates, and it automatically evaluated the number of live neurons in each well (Valenza et al, 2005;Estévez et al, 2006;Jacquier et al, 2006). This technological breakthrough allowed for screening of approximately 1500 compounds per week, the throughput being limited only by the number of motor neuron cultures that could be prepared.…”

Neuronal growth and survival mediated by eIF5A, a polyamine-modified translation initiation factor

“…Arginine is also the direct precursor of nitric oxide (NO), as NO synthase (NOS) abstracts NO from the guanidino group of arginine giving rise to citrulline as a by-product (23). Both NO and polyamines have been implicated in neuronal growth and survival (24,25), and differential movement of arginine into the polyamine and NO pathways influences neuronal survival (26). In the present study, we provide evidence that hypusinated eIF5A physiologically regulates nerve process extension and neuronal survival both in PC12 cells and brain neurons.…”