Effects of Disrupting Calcium Homeostasis on Neuronal Maturation: Early Inhibition and Later Recovery

Abstract

It has become increasingly clear that agents that disrupt calcium homeostasis may also be toxic to developing neurons. Using isolated primary neurons, we sought to understand the neurotoxicity of agents such as MK801 (which blocks ligand-gated calcium entry), BAPTA (which chelates intracellular calcium), and thapsigargin (TG; which inhibits the endoplasmic reticulum Ca 2+ -ATPase pump). Thus, E18 at cotical neuons wee grown for 1 day in vitro (DIV) and then exposed to vehicle (0.1% DMSO), MK801 (0.01-20 μM), BAPTA (0.1-20 μM), or TG (0.001-1 μM) for 24 h. We found that all three agents could profoundly influence early neuronal maturation (growth cone expansion, neurite length, neurite complexity), with the order of potency being MK801 < BAPTA < TG. We next asked if cultures exposed to these agents were able to re-establish their developmental program once the agent was removed. When we examined network maturity at 4 and 7 DIV, the order of recovery was MK801 > BAPTA > TG. Thus, mechanistically distinct ways of disrupting calcium homeostasis differentially influenced both short-term and long-term neuronal maturation. These observations suggest that agents that act by altering intracellular calcium and are used in obstetrics or neonatology may be quite harmful to the still-developing human brain.

A “double hit” murine model for schizophrenia shows alterations in the structure and neurochemistry of the medial prefrontal cortex and the hippocampus

“…The effects on cell death will have an important impact on the integrity of neuronal networks, but these circuits will be also affected by the MK801-induced downregulation of the expression of different neurotrophins (Hansen et al, 2004), which are critical to regulate neuronal migration, neurite extension and synaptogenesis during this period. Not surprisingly, MK-801 receptor antagonism was found to impair growth cone activity and neurite extension/branching (Ringler et al, 2008), which may be the result of the direct effects of NMDA receptors on these processes (Contestabile, 2000) or of their indirect effects through changes in neurotrophin expression. The contribution of the social isolation during adolescence included in our "double hit" model may appear less dramatic than that of the NMDA antagonist injection, but it certainly contributes to the observed alterations.…”

In vivo and in vitro ketamine exposure exhibits a dose-dependent induction of activity-dependent neuroprotective protein in rat neurons

“…Neuron cell bodies, indicated by large, stained DAPI nuclei (Ringler et al, 2008), were counted for each well. Expanded growth cones were identified via dense rhodamine phalloidin staining and characteristic finger-like morphology (Forscher and Smith, 1988;Lewis and Bridgman, 1992).…”

“…Disruptions in calcium homeostasis are sufficient to alter growth cone cytoarchitecture, potentially leading to apoptosis (Ringler et al (2008). Ketamine disrupts calcium signaling in cortical neuron cultures (Ringler et al, 2008).…”

“…Disruptions in calcium homeostasis are sufficient to alter growth cone cytoarchitecture, potentially leading to apoptosis (Ringler et al (2008). Ketamine disrupts calcium signaling in cortical neuron cultures (Ringler et al, 2008). Because of the differential effects on neuronal cell death we saw in vivo with varying ketamine concentrations, and because ADNP has been linked to microtubule stability Gozes and Divinski, 2007;Mandel et al, 2008;Zemlyak et al, 2009a), we looked at the state of primary cortical neuron growth cones as a function of ketamine concentration.…”

“…Ketamine is a non-competitive N-methyl-D-aspartate (NMDA) antagonist that disrupts calcium homeostasis in neurons (Sinner et al, 2005;Slikker et al, 2007). Since calcium signaling has an important role in cytoskeleton stability (Lankford and Letourneau, 1989) as well as neuronal viability (Turner et al, 2007;Ringler et al, 2008), ketamineinduced calcium deregulation may lead to alterations in axonal outgrowth and induction of apoptotic cell death (Wang et al, 2005;Turner et al, 2012;Bai et al, 2013;Dong and Anand, 2013).…”