Proceedings of The Physiological Society

Mitochondria: Form and function (London, UK) (2017) Proc Physiol Soc 38, C03

Oral Communications

Amyloid-β oligomers or hyperglycaemia each reduce mitochondrial motility in mature hippocampal cells

S. Chalmers1, R. Rooney1, S. Albazi1, C. D. Saunter2

1. SIPBS, University of Strathclyde, Glasgow, Please Select, United Kingdom. 2. Physics, Durham University, Durham, United Kingdom.

Amyloid-β plaques are indicative of Alzheimer's disease. A precursor of these plaques: oligomers consisting of a few amyloid-β peptides, may be sufficient to impair brain function, partially by impairing the trafficking of mitochondria1. Hyperglycaemia may also decrease axonal mitochondrial motility2 and contribute to the risk of developing neurodegenerative disease, thus we sought to examine how both high glucose and amyloid-β oligomers influence mitochondrial motility. Complex, overlapping mitochondrial morphologies make analysis of mitochondrial dynamics challenging. We have developed image analysis techniques that enable the discrimination of individual mitochondria within optically-crowded environments3 and can track mitochondria to sub-pixel resolution4. Primary hippocampal cell cultures from p0-2 rat pups were grown in either normo- or hyper-glycaemic media (3 or 25 mM glucose) for 3 weeks then loaded with tetramethylrhodamine ethyl-ester plus Mitotracker-Green-FM (100 nM each) prior to epifluorescence imaging for 5 min. The cells were then incubated with either 5 µM amyloid-β1-42 oligomers or the reversed peptide (42-1) or vehicle (DMSO, 0.1%) for 1 hr prior to a second period of imaging. In these mature cells amyloid-β oligomers, but not reversed peptide or vehicle, caused a decrease in mitochondrial motility of cells grown in either low or high glucose. Additionally, for cells grown for 3 weeks prior to imaging, mitochondrial motility was lower in high-glucose media (4.76±1.53%, mean±S.D., total mitochondrial area moved min-1, n=9, compared to 8.04±1.54% in normo-glycaemia, n=11 coverslips of cells from ≥4 independent preparations each; p=0.012, one-way ANOVA with Tukey's post-hoc test). There was no difference in mitochondrial motility due to media glucose concentration in youngers cells, however (1 week: 8.03±3.13% total mitochondrial area moved min-1 in normo-glycaemia, n=14, c.f. 6.45±1.89% min-1 in hyper-glycaemia, n=15; 2 weeks: 6.37±1.56% total mitochondrial area moved min-1 in normo-glycaemia, n=15, c.f. 6.78±2.4% min-1 in hyper-glycaemia, n=10). A wide range of mitochondrial morphologies were observed in all cell preparations and glucose concentrations, however there was a shift towards more small, punctuate mitochondria in hyper-glycaemia, with no difference in morphology observed due to amyloid-β oligomers. In summary, hyperglycaemia caused a decrease in mitochondrial motility and size in mature (but not immature) cultured hippocampal cells. Acute exposure of mature hippocampal cells to amyloid-β oligomers caused a decrease in mitochondrial motility, both in normo-glycaemic and hyper-glycaemic conditions. Thus both amyloid-β oligomers and hyper-glycaemia may contributing to neuronal vulnerability by altering the involvement of mitochondria in calcium buffering or interactions with structures such as the endoplasmic reticulum.

Where applicable, experiments conform with Society ethical requirements