Abstract
INTRODUCTION: Hyperphosphorylation and aggregation of the microtubule-associated tau protein, which plays a critical role in many neurodegenerative diseases (ie, tauopathies) including Alzheimer's disease (AD), are known to be regulated by a variety of environmental factors including temperature. In this study we evaluated the effects of FDA-approved poly (D,L-lactide-co-glycolic) acid (PLGA) nanoparticles, which can inhibit amyloid-β aggregation/toxicity in cellular/animal models of AD, on temperature-dependent aggregation of 0N4R tau isoforms in vitro. METHODS: We have used a variety of biophysical (Thioflavin T kinetics, dynamic light scattering and asymmetric-flow field-flow fractionation), structural (fluorescence imaging and transmission electron microscopy) and biochemical (Filter-trap assay and detection of soluble protein) approaches, to evaluate the effects of native PLGA nanoparticles on the temperature-dependent tau aggregation. RESULTS: Our results show that the aggregation propensity of 0N4R tau increases significantly in a dose-dependent manner with a rise in temperature from 27°C to 40°C, as measured by lag time and aggregation rate. Additionally, the aggregation of 2N4R tau increases in a dose-dependent manner. Native PLGA significantly inhibits tau aggregation at all temperatures in a concentration-dependent manner, possibly by interacting with the aggregation-prone hydrophobic hexapeptide motifs of tau. Additionally, native PLGA is able to trigger disassembly of preformed 0N4R tau aggregates as a function of temperature from 27°C to 40°C. CONCLUSION: These results, taken together, suggest that native PLGA nanoparticles can not only attenuate temperature-dependent tau aggregation but also promote disassembly of preformed aggregates, which increased with a rise of temperature. Given the evidence that temperature can influence tau pathology, we believe that native PLGA may have a unique potential to regulate tau abnormalities associated with AD-related pathology.