Toxicity of serum albumin on microglia upon seeding effect of amyloid peptide

Abstract

We demonstrate in vitro cross-seeding of bovine serum albumin (BSA) in the presence of Aβ and their cytotoxic effects on microglial cells. To investigate the cross-seeding of BSA in the presence of Aβ fibrils, we examined how Aβ fibrils can function as seeds to trigger and accelerate BSA fibrillogenesis using ThT, intrinsic fluorescence, ANS fluorescence and transmission electron microscopy (TEM). Moreover, the effects of these fibrils on microglial viability were measured using MTT and Annexin V/propidium iodide (PI) staining. Although Aβ is toxic against microglia, it acted as seed and affected the aggregation pathway and accelerated the fibrillogenesis of BSA in vitro, resulted in an enhanced cytotoxic effect in comparison with Aβ or BSA alone. These observations thought to be helpful to understand the molecular mechanism of enhanced toxicity due to the coexistence of the aggregation prone proteins/peptides,. then cross-seeding effect on microglial cells that may involve in neurodegenerative diseases such as Alzheimer's disease (AD).

The role of microglia in processing and spreading of bioactive tau seeds in Alzheimer’s disease

“…The resulting cell pellets were incubated with anti-CD11b magnetic microbeads (Miltenyi Biotec) in a 0.5% bovine serum albumin (BSA) solution and separated via positive selection using magnetic columns (Miltenyi Biotec) per the manufacturer’s instructions. It is notable that BSA at comparable concentrations can act as a seed for Aβ and enhance toxicity to microglia [ 13 ], but we did not observe notable microglia toxicity in our cultures or observe cross-seeding of tau in Tg21221 microglia. CD11b + microglia were then either immediately frozen at − 80 °C for protein analysis after lysis with PBS containing protein inhibitor cocktail (Roche) or plated at a density of 1 × 10 5 cells per well in 24-well plates previously coated for at least 3 h with poly-D-lysine (PDL; 50 μg/ml, Sigma) for at least 3 h. Cultures were maintained at 37 °C with 5% CO 2 in DMEM/F12 medium supplemented with 10 ng/ml recombinant species-specific macrophage colony stimulating factor (MCSF), 2 mM Glutamax, 100 U/ml penicillin, and 100 g/ml streptomycin (microglia medium).…”

Seeding of proteins into amyloid structures by metabolite assemblies may clarify certain unexplained epidemiological associations

“…HGA was suggested to be an important amyloid co-component in alkaptonuria amyloidosis [24]. Self-and cross-seeding of proteins by amyloid assemblies is well established in the literature [28,38], and we propose to extend this concept to include metabolite assemblies as possible seeds that may be formed upstream to protein aggregation and may facilitate this process. This ability of simple metabolites to form ordered structures, and the seeding effect demonstrated by phenylalanine and HGA, provides new paradigm for numerous diseases that could be tested experimentally.…”

“…HGA was suggested to be an important amyloid co-component in alkaptonuria amyloidosis [ 24 ]. Self- and cross-seeding of proteins by amyloid assemblies is well established in the literature [ 28 , 38 ], and we propose to extend this concept to include metabolite assemblies as possible seeds that may be formed upstream to protein aggregation and may facilitate this process.…”

Conditions Governing Food Protein Amyloid Fibril Formation. Part II: Milk and Legume Proteins

“…Whether different protein types participated in the formation of a single fibril remains unknown. Also, Aβ 25‐35 , a fragment of the amyloid β‐peptide, which is present in the form of senile plaques in the brain of patients suffering from Alzheimer's disease, can act as seed and accelerate BSA fibril formation at 37 °C (Ferdousi et al., ).…”