Limits...
Soluble aggregates of the amyloid-beta peptide are trapped by serum albumin to enhance amyloid-beta activation of endothelial cells.

Reyes Barcelo AA, Gonzalez-Velasquez FJ, Moss MA - J Biol Eng (2009)

Bottom Line: Inhibition of Abeta1-40 monomer aggregation is observed down to stoichiometric ratios with partial inhibition leading to an increase in the population of small soluble aggregates.These results demonstrate that inhibitors of Abeta self-assembly have the potential to trap small soluble aggregates resulting in an elevation rather than a reduction of cellular responses.These findings provide further support that small soluble aggregates possess high levels of physiological activity and underscore the importance of resolving the effect of Abeta aggregation inhibitors on aggregate size.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Chemical Engineering, University of South Carolina, 2C02 Swearingen Engineering Center, Columbia, South Carolina 29208, USA. Adriana.ReyesBarcelo@kraft.com

ABSTRACT

Background: Self-assembly of the amyloid-beta peptide (Abeta) has been implicated in the pathogenesis of Alzheimer's disease (AD). As a result, synthetic molecules capable of inhibiting Abeta self-assembly could serve as therapeutic agents and endogenous molecules that modulate Abeta self-assembly may influence disease progression. However, increasing evidence implicating a principal pathogenic role for small soluble Abeta aggregates warns that inhibition at intermediate stages of Abeta self-assembly may prove detrimental. Here, we explore the inhibition of Abeta1-40 self-assembly by serum albumin, the most abundant plasma protein, and the influence of this inhibition on Abeta1-40 activation of endothelial cells for monocyte adhesion.

Results: It is demonstrated that serum albumin is capable of inhibiting in a dose-dependent manner both the formation of Abeta1-40 aggregates from monomeric peptide and the ongoing growth of Abeta1-40 fibrils. Inhibition of fibrillar Abeta1-40 aggregate growth is observed at substoichiometric concentrations, suggesting that serum albumin recognizes aggregated forms of the peptide to prevent monomer addition. Inhibition of Abeta1-40 monomer aggregation is observed down to stoichiometric ratios with partial inhibition leading to an increase in the population of small soluble aggregates. Such partial inhibition of Abeta1-40 aggregation leads to an increase in the ability of resulting aggregates to activate endothelial cells for adhesion of monocytes. In contrast, Abeta1-40 activation of endothelial cells for monocyte adhesion is reduced when more complete inhibition is observed.

Conclusion: These results demonstrate that inhibitors of Abeta self-assembly have the potential to trap small soluble aggregates resulting in an elevation rather than a reduction of cellular responses. These findings provide further support that small soluble aggregates possess high levels of physiological activity and underscore the importance of resolving the effect of Abeta aggregation inhibitors on aggregate size.

No MeSH data available.


Related in: MedlinePlus

Effect of BSA on Aβ1–40 fibril growth via monomer addition. Aβ1–40 fibril in 40 mM Tris-HCl (pH 8.0) containing 10 μM thioflavin T was pre-incubated for 15 min alone or in the presence of BSA. Solutions were then diluted for final concentrations of 2 μM Aβ1–40 fibril (concentration expressed in monomer units) with 0 μM (control, [white circle]), 0.5 μM [black square], 2 μM [black triangle], or 10 μM [black diamond] BSA, and 40 μM Aβ1–40 monomer was added to induce fibril growth. Incorporation of Aβ1–40 monomer into fibrillar structures was monitored using thioflavin T fluorescence. Linear regression (solid lines) was performed to determine growth rates. Results are representative of three independent experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2683804&req=5

Figure 2: Effect of BSA on Aβ1–40 fibril growth via monomer addition. Aβ1–40 fibril in 40 mM Tris-HCl (pH 8.0) containing 10 μM thioflavin T was pre-incubated for 15 min alone or in the presence of BSA. Solutions were then diluted for final concentrations of 2 μM Aβ1–40 fibril (concentration expressed in monomer units) with 0 μM (control, [white circle]), 0.5 μM [black square], 2 μM [black triangle], or 10 μM [black diamond] BSA, and 40 μM Aβ1–40 monomer was added to induce fibril growth. Incorporation of Aβ1–40 monomer into fibrillar structures was monitored using thioflavin T fluorescence. Linear regression (solid lines) was performed to determine growth rates. Results are representative of three independent experiments.

Mentions: As shown in Figure 2, steady growth was observed when 2 μM Aβ1–40 fibril was incubated with 40 μM Aβ1–40 monomer (Figure 2). This uninhibited rate of fibril growth was compared to the rate of growth observed in the presence of BSA to determine the extent of inhibition. Aβ1–40 fibrils pre-incubated in the presence of BSA at a level 5-fold in excess of monomeric units within Aβ1–40 fibrils exhibited a much slower rate of growth (Figure 2) and therefore significant inhibition (Table 1), confirming that BSA is able to prevent the addition of Aβ1–40 monomer to pre-formed Aβ1–40 fibrils. Pronounced inhibition was also evident when BSA was present at concentrations equimolar to monomeric units within Aβ1–40 fibrils. Further reduction in the concentration of BSA to a substoichiometric ratio of 1:4 BSA:Aβ1–40 fibril continued to inhibit fibril growth at lower but still significant levels. These results illustrate the ability of BSA to modulate the growth of pre-formed Aβ1–40 aggregates in a dose-dependent manner and, in contrast to BSA inhibition of monomer aggregation, demonstrate the strength of this inhibition at substoichiometic BSA concentrations.


Soluble aggregates of the amyloid-beta peptide are trapped by serum albumin to enhance amyloid-beta activation of endothelial cells.

Reyes Barcelo AA, Gonzalez-Velasquez FJ, Moss MA - J Biol Eng (2009)

Effect of BSA on Aβ1–40 fibril growth via monomer addition. Aβ1–40 fibril in 40 mM Tris-HCl (pH 8.0) containing 10 μM thioflavin T was pre-incubated for 15 min alone or in the presence of BSA. Solutions were then diluted for final concentrations of 2 μM Aβ1–40 fibril (concentration expressed in monomer units) with 0 μM (control, [white circle]), 0.5 μM [black square], 2 μM [black triangle], or 10 μM [black diamond] BSA, and 40 μM Aβ1–40 monomer was added to induce fibril growth. Incorporation of Aβ1–40 monomer into fibrillar structures was monitored using thioflavin T fluorescence. Linear regression (solid lines) was performed to determine growth rates. Results are representative of three independent experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2683804&req=5

Figure 2: Effect of BSA on Aβ1–40 fibril growth via monomer addition. Aβ1–40 fibril in 40 mM Tris-HCl (pH 8.0) containing 10 μM thioflavin T was pre-incubated for 15 min alone or in the presence of BSA. Solutions were then diluted for final concentrations of 2 μM Aβ1–40 fibril (concentration expressed in monomer units) with 0 μM (control, [white circle]), 0.5 μM [black square], 2 μM [black triangle], or 10 μM [black diamond] BSA, and 40 μM Aβ1–40 monomer was added to induce fibril growth. Incorporation of Aβ1–40 monomer into fibrillar structures was monitored using thioflavin T fluorescence. Linear regression (solid lines) was performed to determine growth rates. Results are representative of three independent experiments.
Mentions: As shown in Figure 2, steady growth was observed when 2 μM Aβ1–40 fibril was incubated with 40 μM Aβ1–40 monomer (Figure 2). This uninhibited rate of fibril growth was compared to the rate of growth observed in the presence of BSA to determine the extent of inhibition. Aβ1–40 fibrils pre-incubated in the presence of BSA at a level 5-fold in excess of monomeric units within Aβ1–40 fibrils exhibited a much slower rate of growth (Figure 2) and therefore significant inhibition (Table 1), confirming that BSA is able to prevent the addition of Aβ1–40 monomer to pre-formed Aβ1–40 fibrils. Pronounced inhibition was also evident when BSA was present at concentrations equimolar to monomeric units within Aβ1–40 fibrils. Further reduction in the concentration of BSA to a substoichiometric ratio of 1:4 BSA:Aβ1–40 fibril continued to inhibit fibril growth at lower but still significant levels. These results illustrate the ability of BSA to modulate the growth of pre-formed Aβ1–40 aggregates in a dose-dependent manner and, in contrast to BSA inhibition of monomer aggregation, demonstrate the strength of this inhibition at substoichiometic BSA concentrations.

Bottom Line: Inhibition of Abeta1-40 monomer aggregation is observed down to stoichiometric ratios with partial inhibition leading to an increase in the population of small soluble aggregates.These results demonstrate that inhibitors of Abeta self-assembly have the potential to trap small soluble aggregates resulting in an elevation rather than a reduction of cellular responses.These findings provide further support that small soluble aggregates possess high levels of physiological activity and underscore the importance of resolving the effect of Abeta aggregation inhibitors on aggregate size.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Chemical Engineering, University of South Carolina, 2C02 Swearingen Engineering Center, Columbia, South Carolina 29208, USA. Adriana.ReyesBarcelo@kraft.com

ABSTRACT

Background: Self-assembly of the amyloid-beta peptide (Abeta) has been implicated in the pathogenesis of Alzheimer's disease (AD). As a result, synthetic molecules capable of inhibiting Abeta self-assembly could serve as therapeutic agents and endogenous molecules that modulate Abeta self-assembly may influence disease progression. However, increasing evidence implicating a principal pathogenic role for small soluble Abeta aggregates warns that inhibition at intermediate stages of Abeta self-assembly may prove detrimental. Here, we explore the inhibition of Abeta1-40 self-assembly by serum albumin, the most abundant plasma protein, and the influence of this inhibition on Abeta1-40 activation of endothelial cells for monocyte adhesion.

Results: It is demonstrated that serum albumin is capable of inhibiting in a dose-dependent manner both the formation of Abeta1-40 aggregates from monomeric peptide and the ongoing growth of Abeta1-40 fibrils. Inhibition of fibrillar Abeta1-40 aggregate growth is observed at substoichiometric concentrations, suggesting that serum albumin recognizes aggregated forms of the peptide to prevent monomer addition. Inhibition of Abeta1-40 monomer aggregation is observed down to stoichiometric ratios with partial inhibition leading to an increase in the population of small soluble aggregates. Such partial inhibition of Abeta1-40 aggregation leads to an increase in the ability of resulting aggregates to activate endothelial cells for adhesion of monocytes. In contrast, Abeta1-40 activation of endothelial cells for monocyte adhesion is reduced when more complete inhibition is observed.

Conclusion: These results demonstrate that inhibitors of Abeta self-assembly have the potential to trap small soluble aggregates resulting in an elevation rather than a reduction of cellular responses. These findings provide further support that small soluble aggregates possess high levels of physiological activity and underscore the importance of resolving the effect of Abeta aggregation inhibitors on aggregate size.

No MeSH data available.


Related in: MedlinePlus