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This article is part of the supplement: Scientific Abstracts Presented at the International Research Congress on Integrative Medicine and Health 2012

Open Access Poster presentation

P01.53. Spheroid formation and axonal severing in adult neurons during oxidative stress: role of calcium

A Barsukova-Bell1*, M Forte2 and D Bourdette3

  • * Corresponding author: A Barsukova-Bell

Author Affiliations

1 Oregon Health & Science University, Department of Neurology, Portland, USA

2 Vollum Institute, Oregon Health & Science University, Portland, USA

3 Department of Neurology, Oregon Health & Science University, Portland, USA

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BMC Complementary and Alternative Medicine 2012, 12(Suppl 1):P53  doi:10.1186/1472-6882-12-S1-P53

The electronic version of this article is the complete one and can be found online at: http://www.biomedcentral.com/1472-6882/12/S1/P53


Published:12 June 2012

© 2012 Barsukova-Bell et al; licensee BioMed Central Ltd.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Purpose

Axonal severing is critical to the irreversible disability that occurs over the course of multiple sclerosis (MS). Reactive oxygen species (ROS) are implicated in neurodegenerative aspects of MS: axonal spheroid formation, severing, and axoplasmic Ca2+ elevation. However, the exact role of Ca2+ in spheroid formation remains unclear. The mechanism of action of natural anti-oxidants such as lipoic acid, which provide neuroprotection during oxidative stress in MS model, also remains unclear.

Methods

Primary cortical neurons from adult mice were subjected to physiologically-relevant levels of H2O2. Ca2+ dynamics and its sources were examined during spheroids formation using real time imaging, ratiometric Ca2+ indicators and immunocytochemistry.

Results

Exposure to ROS led to a 3.5 fold increase in axoplasmic Ca2+ by 30 min. Onset of axonal spheroid formation began at 15 min when Ca2+ increase was 2.2 fold. Axonal severing occurred at sites of spheroids around 90-120 min. Analysis of small axonal segments revealed an uneven distribution of Ca2+ during exposure to H2O2. Micrometers apart, focal Ca2+ increases in small axonal domains ranged from 2.8 to 4.4 fold. Domains with a 3.8 to 4.4-fold increase correlated with the sites of spheroids, suggesting high focal extracellular Ca2+ influx at these sites. Several treatments significantly attenuated Ca2+ increase and completely abolished spheroid formation under ROS: removal of extracellular Ca2+; N-type Ca2+ channel blocker omega-conotoxin GVIA; L-type Ca2+ channel blocker amlodipine; and reverse Na+/ Ca2+ exchanger (NCX1) blocker KB-R7943. Aggregation of reverse NCX1 and N-type voltage-gated Ca2+ channel was detected at spheroids.

Conclusion

Our results reveal a correlation between focal axoplasmic Ca2+ and spheroid formation and suggest that focal aggregation of the reverse NCX1 and N-type Ca2+ channel plays central role in high focal Ca2+ increase during oxidative stress. These findings provide a basis for investigating the neuroprotective mechanism of the natural anti-oxidant lipoic acid during oxidative stress.