Glutamate-mediated influx of extracellular Ca2+ is coupled with reactive oxygen species generation in cultured hippocampal neurons but not in astrocytes
✍ Scribed by Stefan Kahlert; Gregor Zündorf; Georg Reiser
- Book ID
- 102383275
- Publisher
- John Wiley and Sons
- Year
- 2004
- Tongue
- English
- Weight
- 358 KB
- Volume
- 79
- Category
- Article
- ISSN
- 0360-4012
No coin nor oath required. For personal study only.
✦ Synopsis
Abstract
Generation of reactive oxygen species (ROS) in brain tissue leads to neurodegeneration. The major source of ROS is the mitochondrial respiratory chain. We studied regulation of Ca^2+^ level, mitochondrial potential, and ROS generation in defined mixed hippocampal cell cultures exposed to glutamate (100 μM). Recordings were made from individually identified astrocytes and neurons to compare the physiologic responses in both cell types. Neurons identified by synaptotagmin immunoreactivity were characterized functionally by the fast Ca^2+^ increase with K^+^ (50 mM) stimulation, and the astrocytes identified by glial fibrillary acidic protein (GFAP) staining had the functional characteristic of a transient Ca^2+^ peak in response to ATP (10 μM) stimulation. We found that the glutamate‐mediated Ca^2+^ response in neurons is due largely to influx of extracellular Ca^2+^. This is consistent with our finding that in cultured hippocampal neurons, stores depending on the activity of the sarcoendoplasmic reticulum Ca^2+^ ATPase (SERCA) pump had a low Ca^2+^ content, regardless of whether the neurons were challenged or not with K^+^ before applying the SERCA inhibitor cyclopiazonic acid (CPA). Astrocytes displayed a large CPA‐mediated Ca^2+^ response, indicating a high level of Ca^2+^ load in the stores in astrocytes. Importantly, the rise in ROS generation due to glutamate application was cell‐type specific. In neurons, glutamate induced a marked rise in generation of ROS, but not in astrocytes. In both astrocytes and neurons, the mitochondrial potential was increased in response to glutamate challenge. We conclude that in neurons, Ca^2+^ influx accounts for the increased ROS generation in response to glutamate. This might explain the high vulnerability of neurons to glutamate challenge compared to the vulnerability of astrocytes. The high resistance of astrocytes is accompanied by an efficient downregulation of cytosolic Ca^2+^, which is not found in neurons. © 2004 Wiley‐Liss, Inc.