Ibuprofen reduces Abeta, hyperphosphorylated tau and memory deficits in Alzheimer mice

Abstract

We examined the effects of ibuprofen on cognitive deficits, Abeta and tau accumulation in young triple transgenic (3xTg-AD) mice. 3xTg-AD mice were fed ibuprofen-supplemented chow between 1 and 6 months. Untreated 3xTg-AD mice showed significant impairment in the ability to learn the Morris water maze (MWM) task compared to age-matched wild-type (WT) mice. The performance of 3xTg-AD mice was significantly improved with ibuprofen treatment compared to untreated 3xTg-AD mice. Ibuprofen-treated transgenic mice showed a significant decrease in intraneuronal oligomeric Abeta and hyperphosphorylated tau (AT8) immunoreactivity in the hippocampus. Confocal microscopy demonstrated co-localization of conformationally altered (MC1) and early phosphorylated tau (CP-13) with oligomeric Abeta, and less co-localization of oligomeric Abeta and later forms of phosphorylated tau (AT8 and PHF-1) in untreated 3xTg-AD mice. Our findings show that prophylactic treatment of young 3xTg-AD mice with ibuprofen reduces intraneuronal oligomeric Abeta, reduces cognitive deficits, and prevents hyperphosphorylated tau immunoreactivity. These findings provide further support for intraneuronal Abeta as a cause of cognitive impairment, and suggest that pathological alterations of tau are associated with intraneuronal oligomeric Abeta accumulation.

Figure 1. Comparison of MWM performance among 3×Tg-AD mice, ibuprofen-treated 3×Tg-AD mice and WT mice

Asterisks denote significant differences with respect to WT mice at a p < 0.05 level. Error bars indicate SEM A. Six month old ibuprofen-treated 3×Tg-AD mice learned the MWM task at the same rate as age-matched WT mice reaching the pre-set criteria for learning (mean latency <25 s) on the same day (Day 4). On Day 6 and 7 WT mice reached the platform with decreasing escape latencies (escape latency of <10 s on Day 7) while ibuprofen-treated 3×Tg-AD mice maintain their escape latency around 25 s. Untreated six month old 3×Tg-AD mice were unable to learn the MWM task, as their escape latency did not progressively decreased during the 7 consecutive days of training. On the other hand, untreated two month old 3×Tg-AD mice perform similar to 6 month WT mice. B, C and D. Probe analysis performed on day 4 (1.5 h after training day 4) and day 5 (24 h after training day 4). Ibuprofen-treated 3×Tg-AD mice spent as much time as WT mice swimming in the quadrant where the platform was supposed to be at both 1.5 and 24 h probe. While WT mice improved their performance at the 24 h probe compared to the 1.5 h probe (increased the number of platform location crosses and decreased the latency to cross the platform location), ibuprofen-treated 3×Tg-AD mice did not. Untreated 3×Tg-AD mice performed significantly worse than WT mice based on the number of platform location crosses and the latency to cross the platform location at the 24 h probe test.

Figure 2. Sections of hippocampus CA1 and subiculum immunostained for Aβ

A. Six month wild-type mouse shows no immunoreactivity for 6E10 in CA1 near the subiculum, B. Untreated 2 month 3×Tg-AD mouse shows scant granular immunoreactivity for NU-1 in the perikarya of CA1 neurons C. D. Untreated 6 month 3×Tg-AD mouse shows intense immunoreactivity for NU-1 in the perikarya of CA1 and subicular neurons. E. F. Ibuprofen treated 6 month 3×Tg-AD mouse shows markedly reduced immunoreactivity for NU-1 in the same region. A,B,D,F : Original magnification × 300, C,E: Original magnification × 38.

Fig. 3. Sections of hippocampal CA1 neurons immunostained for MC1 and CP-13

A.B. Untreated 6 month 3×Tg-AD mouse shows intense immunoreactivity for diffuse MC1 in the perikarya extending into the apical dendrite, A. Original magnification × 150, B. Occasional neurons show intense granular staining for MC1 in the perikaryon, as well as diffuse dendritic staining, original magnification × 945. C. D. Ibuprofen treated 6 month 3×Tg-AD mouse shows nearly absent immunoreactivity for MC1, C. Original magnification × 150, D. Original magnification × 945. E. F. Untreated 6 month 3×Tg-AD mouse shows intense immunoreactivity for finely granular CP-13 in the perikarya extending into the apical dendrites and dendritic arbors. E. Original magnification × 150, F. Original magnification × 945. G. H. Ibuprofen treated 6 month 3×Tg-AD mouse shows marked reduction in immunoreactivity for CP-13, immunoreactivity is primarily dendritic G. Original magnification × 150, H. Original magnification × 945.

Fig. 4. Double immunostained sections of hippocampal CA1 neurons in untreated 6 month 3×Tg-AD mice

A. Double immunostained sections for NU-1 and MC1 show diffuse MC1 immunoreactivity (brown) extending into the apical dendrite of neurons with granular perikaryal NU-1 (red, asterisks), original magnification × 945. B. Double immunostained sections for NU-1 and CP-13 shows diffuse CP-13 immunoreactivity (brown) extending into the apical dendrite of neurons with granular perikaryal NU-1 (red, asterisks), original magnification × 945. C. Double immunostained sections for NU-1 and AT8 shows granular AT8 immunoreactivity (brown) in occasional neurons, while neighboring neurons show granular perikaryal NU-1 (red, asterisk), original magnification × 945. D. Double immunostained sections for NU-1 and PHF-1 shows dense aggregates of PHF-1 immunoreactivity (brown) in the perikaryon and dendrite of occasional neurons, while neighboring neurons show granular perikaryal NU-1 (red, asterisk), original magnification × 945. E. Double immunostained sections for NU-1 and CP-13 show diffuse CP-13 immunoreactivity (brown) extending into the apical dendrites and lush dendritic arbors of neurons with granular perikaryal NU-1 (red, asterisks), original magnification × 945.

Fig. 5. Sections of CA1 hippocampus from untreated 6 month 3×Tg-AD mouse shows neurons immunoreactive for AT8

A. Original magnification × 150, B. Original magnification × 945.

Figure 6. THE co-localization of tau and NU-1 using confocal microscopy in 6 month untreated 3×Tg-AD mice

The co-localization intensity of tau [stained with MC1 (a) (green), CP13 (f) (green), AT8 (k) (green), and PHF1 (p) (green)] and NU-1 (b, g, I, and q) (red) were determined by Disk Confocal Microscopy (Olympus, Tokyo, Japan) and the line measurement (AQI-X-COMBO-CWF, MediaCybernetics Inc. Bethesda, MD). The image analysis data shown in panel e, j, o, and t demonstrate the strong co-localization of NU1 with MC1 and CP13 and less co-localization with AT8 and PHF1. Scale bar: 10 mm.