Serum or target deprivation‐induced neuronal death causes oxidative neuronal accumulation of Zn²⁺ and loss of NAD⁺

Abstract

Trophic deprivation mediated neuronal death is important during development, acute brain or nerve trauma, and neurodegeneration. Serum deprivation (SD) approximates trophic deprivation in vitro, and an in vivo model is neuronal death in the mouse dorsal lateral geniculate nucleus (LGNd) after ablation of the visual cortex (VCA). Oxidant-induced intracellular Zn 2+ release, ([Zn 2+ ] i ), from metallothionein-3 (MT-III), mitochondria, or "protein Zn 2+ " was implicated in trophic deprivation neurotoxicity. We previously showed that neurotoxicity of extracellular Zn 2+ required entry, elevation in [Zn 2+ ] i , reduction of NAD + and ATP levels causing inhibition of glycolysis and cellular metabolism. Exogenous NAD + and sirtuin inhibition attenuated Zn 2+ neurotoxicity. Here we show that: 1) Zn 2+ is released intracellularly after oxidant and SD injuries, and sensitivity to these injuries is proportional to neuronal Zn 2+ content; 2) NAD + loss is involved; restoration of NAD + using exogenous NAD + , pyruvate, or nicotinamide attenuated these injuries, and potentiation of NAD + loss potentiated injury; 3) Neurons from genetically modified mouse strains which reduce intracellular Zn 2+ content (MT-III knockout), reduce NAD + catabolism (PARP-1 knockout), or increase expression of an NAD + synthetic enzyme (Wld s ) each had attenuated SD and oxidant neurotoxicities; 4) Sirtuin inhibitors attenuated, and sirtuin activators potentiated these neurotoxicities; 5) VCA induces Zn 2+ staining and death only in ipsilateral LGNd neurons, and a 1ppm Zn 2+ diet attenuated injury; 6) Finally, NAD + synthesis and levels are involved because LGNd neuronal death after VCA was dramatically reduced in Wld s animals, and by intraperitoneal pyruvate or nicotinamide. Zn 2+ toxicity is involved in serum and trophic deprivation induced neuronal death. Keywordsvisual cortex ablation; mouse; pyruvate; sirtuin; dorsal lateral geniculate nucleus Target deprivation mediated neuronal death plays a large role during development, trauma, and neurodegeneration. In the developing nervous system, 20-80% of all neurons produced during embryogenesis die before reaching adulthood as a result of competition between neurons for innervation of their targets. This results in matching of the size of the target cell population with the number of innervating neurons (Oppenheim, 1991;Purves et al., 1988). Target deprivation mediated neuronal death is apoptotic and occurs by programmed cell death (PCD) (Deshmukh & Johnson, 1997;Martin et al., 1998). PCD is required for the * corresponding author, FAX: (504) 568-5801, telephone: (504) 599-0880, csheli@lsuhsc.edu. NIH Public Access Author ManuscriptEur J Neurosci. Author manuscript; available in PMC 2011 September 1. Serum Deprivation Models Target Deprivation, and Both Induce an Oxidative InjuryWe and others have shown that serum deprivation (SD) induces substantial oxidative stress leading to partial ATP depletion, K + loss involving inhibition of the Na + /K + ATPase, and the apoptotic cascade . We...

Mitochondrial Inhibitor Models of Huntington’s Disease and Parkinson’s Disease Induce Zinc Accumulation and Are Attenuated by Inhibition of Zinc Neurotoxicity in vitro or in vivo

“…The toxins studied here (MPP + , 6-OHDA and 3-NPA) have been reported to induce ROS, and ROS have been shown to induce [Zn 2+ ] i release [17]. We show that 3 or 8 h after exposure of striatal/midbrain or cortical neuronal cultures to toxic levels of these compounds (fig.…”

“…Thiamine, a pyruvate dehydrogenase and α-ketoglutarate dehydrogenase cofactor, was ineffective for all toxins. Pyruvate, nicotinamide, lactate, thiamine and NAD + do not chelate Zn 2+ [17,25]. Other than lactate, the beneficial compounds increase the intracellular concentration of NAD + (table 1 and [17]).…”

“…Pyruvate, nicotinamide, lactate, thiamine and NAD + do not chelate Zn 2+ [17,25]. Other than lactate, the beneficial compounds increase the intracellular concentration of NAD + (table 1 and [17]). The number of TH + neurons was reduced by lower toxin exposures and restored by pyruvate, NAD + and TPEN in striatal/midbrain cultures, confirming that similar mechanisms are involved in TH + neurons (fig.…”

“…1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is the precursor to MPP + , and both have been shown to induce Zn 2+ release and an increase in intracellular zinc ([Zn 2+ ] i ) in degenerating striatal neurons in vivo and in situ [15,16]. We recently showed that ROS induces an increase in [Zn 2+ ] i and a loss of nicotinamide adenine dinucleotide (NAD + ), causing inhibition of glycolysis and neuronal death; accordingly, preventing this increase or loss prevents this outcome [17]. …”

Real-Time Impedance-based Cell Analyzer as a Tool to Delineate Molecular Pathways Involved in Neurotoxicity and Neuroprotection in a Neuronal Cell Line

“…In the current protocol serum deprivation neurotoxicity paradigm is presented due to its robustness, ease of use and utility to approximate trophic deprivation mediated neuronal death, which is important during development, acute brain or nerve trauma, and neurodegeneration 11 . However, a wide range of neurotoxicity paradigms can be used with the real-time cell analyzer system.…”