Differential Effect of Nimodipine in Attenuating Iron-Induced Toxicity in Brain- and Blood–Brain Barrier-Associated Cell Types

Abstract

Metal homeostasis is increasingly being evaluated as a therapeutic target in stroke and neurodegenerative diseases. Metal dysregulation has been shown to lead to protein aggregation, plaque formation and neuronal death. In 2007, we first reported that voltage-gated calcium channels act as a facile conduit for the entry of free ferrous (Fe(2+)) ions into neurons. Herein, we evaluate differential iron toxicity to central nervous system cells and assess the ability of the typical L-type voltage-gated calcium channel blocker nimodipine to attenuate iron-induced toxicity. The data demonstrate that iron sulfate induces a dose-dependent decrease in cell viability in rat brain endothelial cells (RBE4; LC(50) = 150 μM), neuronal cells (Neuro-2α neuroblastoma; LC(50) = 400 μM), and in astrocytes (DI TNC1; LC(50) = 1.1 mM). Pre-treatment with nimodipine prior to iron sulfate exposure provided a significant (P < 0.05) increase in viable cell numbers for RBE4 (2.5-fold), Neuro2-α (~2-fold), and nearly abolished toxicity in primary neurons. Astrocytes were highly resistant to iron toxicity compared to the other cell types tested and nimodipine had no (P > 0.05) protective effect in these cells. The data demonstrate variable susceptibility to iron overload conditions in different cell types of the brain and suggest that typical L-type voltage-gated calcium channel blockers (here represented by nimodipine), may serve as protective agents in conditions involving iron overload, particularly in cell types highly susceptible to iron toxicity.

Inhibition of Toll-Like Receptor-4 (TLR-4) Improves Neurobehavioral Outcomes After Acute Ischemic Stroke in Diabetic Rats: Possible Role of Vascular Endothelial TLR-4

“…When cells (passage 6-8) reached 80-90% confluency, media was replaced with glucose free 1% serum containing media and then placed in a hypoxic chamber (0.2% O 2 , 5% CO 2 ) for 6 hours, followed by 12 hours of normoxia (21% O 2 , 5% CO 2 and normal glucose) to mimic ischemia and reperfusion injury. Some plates were treated with 0.1mM iron(III)sulfate hydrate (iron; cat # 518212, Sigma Aldrich) at re-oxygenation to mimic bleeding and free iron release after stroke in diabetes [23]. To inhibit TLR-4 activity, 10μg/ml TLR-4 neutralizing antibody (SC 13591, Santa Cruz Biotechnology) or 30μM TAK242 was added upon reoxygenation.…”

Effect of nimodipine on rat spinal cord injury

“…Following the initial spinal cord injury, free radical damage caused by biochemical changes associated with lipid peroxidation are thought to cause additional deterioration of the original area of damage (Hawryluk et al, 2008;Ouardouz et al, 2009;Lockman et al, 2012). Biological markers of lipid peroxidation include MDA (malondialdehyde), a major end-product of polyunsaturated fatty acid peroxidation found in cell membranes (Ouardouz et al, 2009).…”

“…Biological markers of lipid peroxidation include MDA (malondialdehyde), a major end-product of polyunsaturated fatty acid peroxidation found in cell membranes (Ouardouz et al, 2009). The early inflammatory response involves extensive accumulation of inflammatory cells and cytokines and the secretion of large amounts of toxic free radicals, thereby increasing the extent of spinal cord injury; however, secretion of protective cytokines and growth factors, which mediate neuroprotection and promote nerve regeneration, also occurs in response to spinal cord injury (Hawryluk et al, 2008;Doukas et al, 2011;Lockman et al, 2012).…”

Noxious Iron–Calcium Connections in Neurodegeneration

“…The role of voltage-gated Ca 2+ channels as mediators of iron transport into neuronal cells is well established (Gaasch et al, 2007; Lockman et al, 2012). Another link between iron and calcium during neurodegeneration was provided by the observation that the hippocampal and nigral neuron loss induced by intra-cerebroventricular FeCl 3 injection in rats is largely prevented by pre-treatment with nicardipine, a blocker of L-type VGCCs (Bostanci and Bagirici, 2013).…”