Assessing the Influence of Extracellular Mitochondria on Neuroinflammation

A prominent aspect of Alzheimer’s disease (AD) is the presence of neuroinflammation is mediated by the activation of microglial cells, which are the immune cells in the central nervous system (CNS) that express an array of cytokines that may promote an inflammatory response. The main cytokines produced are: tumor necrosis factor-alpha (TNF-), interleukin-1β (IL-1β), and interleukin-6 (IL-6). The presence of these cytokines in the CNS may lead to neuronal death, to the production of toxic chemicals (such as nitric oxide), and to the generation of amyloid beta (a major pathological feature of AD). Previous studies have shown that modulation of the inflammatory response in the nervous system can potentially prevent and/or delay the onset of neurodegenerative diseases such as AD. Therefore, it is important to identify the process that induces CNS inflammation. For example, mitochondrial lysates have been found to produce an inflammatory response due to their ability to stimulate TNF-, Aβ, and APP mRNA [10]. Interestingly, extracellular mitochondria have been detected in the brain due to neurons degrading old mitochondria extracellularly. Therefore, we set out to study the effect of whole mitochondria isolated by differential centrifugation from human neuroblastoma cells (BE(2)-M17 cells) on the neuroinflammatory response in a human microglia model (THP-1 cells). Despite our best efforts, in the end it was unclear whether the mitochondrial fraction or other cellular components induced the inflammatory response we observed. Thus, further work with an improved mitochondrial isolation method should be carried out to address this issue.