HDAC3 negatively regulates spatial memory in a mouse model of Alzheimer's disease

Abstract

The accumulation and deposition of beta-amyloid (Aβ) is a key neuropathological hallmark of Alzheimer's disease (AD). Histone deacetylases (HDACs) are promising therapeutic targets for the treatment of AD, while the specific HDAC isoforms associated with cognitive improvement are poorly understood. In this study, we investigate the role of HDAC3 in the pathogenesis of AD. Nuclear HDAC3 is significantly increased in the hippocampus of 6- and 9-month-old APPswe/PS1dE9 (APP/PS1) mice compared with that in age-matched wild-type C57BL/6 (B6) mice. Lentivirus -mediated inhibition or overexpression of HDAC3 was used in the hippocampus of APP/PS1 mice to investigate the role of HDAC3 in spatial memory, amyloid burden, dendritic spine density, glial activation and tau phosphorylation. Inhibition of HDAC3 in the hippocampus attenuates spatial memory deficits, as indicated in the Morris water maze test, and decreases amyloid plaque load and Aβ levels in the brains of APP/PS1 mice. Dendritic spine density is increased, while microglial activation is alleviated after HDAC3 inhibition in the hippocampus of 9-month-old APP/PS1 mice. Furthermore, HDAC3 overexpression in the hippocampus increases Aβ levels, activates microglia, and decreases dendritic spine density in 6-month-old APP/PS1 mice. In conclusion, our results indicate that HDAC3 negatively regulates spatial memory in APP/PS1 mice and HDAC3 inhibition might represent a potential therapy for the treatment of AD.

Keywords: Alzheimer's disease; beta-amyloid; histone deacetylase3; spatial memory.

Figure 1

Nuclear histone deacetylase 3 (HDAC3) is increased in the hippocampus of 6‐ and 9‐month‐old APPswe/PS1dE9 (APP/PS1) mice. (A) The levels of Class I HDACs (HDAC1, HDAC2, HDAC3, and HDAC8) in the hippocampus of 6‐month‐old APP/PS1 mice were determined by Western blot. LE: low exposure; HE: high exposure. n = 4–6 mice per group. (B) Graph represents quantification of the signal intensities normalized to GAPDH as a loading control. (C) The levels of HDAC1, HDAC2, HDAC3, and HDAC8 in the hippocampus of 9‐month‐old APP/PS1 mice were determined by Western blot. n = 4–6 mice per group. (D) Graph represents quantification of the signal intensities normalized to GAPDH as a loading control. (E) The level of nuclear HDAC3 was determined by Western blot. n = 6–8 mice per group. (F) Graph represents quantification of the signal intensities normalized to lamin B1 as a loading control. **P < 0.01.

Figure 2

Lentivirus‐mediated inhibition of histone deacetylase 3 (HDAC3) in the hippocampus attenuates spatial memory deficits in 9‐month‐old APPswe/PS1dE9 (APP/PS1) mice. Nine‐month‐old APP/PS1 mice were injected with lenti‐shHDAC3 or lenti‐shcon, and the Morris water maze (MWM) tests were performed 30 days later. (A) Representative image of lenti‐shHDAC3‐injected hippocampus of 9‐month‐old APP/PS1 mice. (scale bar = 100 μm). (B) The level of HDAC3 in the hippocampus after lenti‐shHDAC3 injection was determined by Western blot. n = 4 mice per group. (C) Graph represents quantification of the signal intensities normalized to GAPDH as a loading control. In the acquisition trial, the escape latency (D) and searching distance (E) were analyzed in lenti‐shHDAC3 (n = 14)‐ and lenti‐shcon (n = 12)‐injected mice, and the number of target platform crossings (F), time in the target quadrant (G), and swimming distance in the target quadrant (H) were recorded in the probe trials. (I) A representative image of path tracings in the probe test on day 6. *P < 0.05, **P < 0.01.

Figure 3

Inhibition of histone deacetylase 3 (HDAC3) decreases Aβ levels in the hippocampus of 9‐month‐old APPswe/PS1dE9 (APP/PS1) mice. (A) The levels of TBS‐, TBS‐X‐, and FA‐soluble Aβ_1‐40 were determined by ELISA in the hippocampus. n = 4–6 mice per group. (B) The levels of TBS‐, TBS‐X‐, and FA‐soluble Aβ_1–42 were determined by ELISA in the hippocampus. n = 4–6 mice per group. (C) Representative image of Aβ staining (6E10) in the brains of lenti‐shHDAC3‐injected APP/PS1 mice. (scale bar = 250 μm). n = 4 mice per group. (D) The area percentage of 6E10‐positive Aβ plaque load in the brains. (E) The levels of APP and secretases in the hippocampus of lenti‐shHDAC3‐injected APP/PS1 mice were examined by Western blot. n = 4–5 mice per group. (F, G) Graph represents quantification of the signal intensities normalized to GAPDH as a loading control. (H) The levels of Aβ‐metabolism‐associated enzymes were determined in the hippocampus of lenti‐shHDAC3‐injected APP/PS1 mice. n = 4–5 mice per group. (I) Graph represents quantification of the signal intensities normalized to GAPDH as a loading control. **P < 0.01.

Figure 4

Inhibition of histone deacetylase 3 (HDAC3) increases dendritic spine density in the hippocampus of APPswe/PS1dE9 (APP/PS1) mice. (A) Representative image of the Golgi‐stained apical and basal dendrites in CA1 pyramidal neurons. (scale bar = 10 μm). n = 3–4 mice per group. (B) Graph represents quantification of the apical and basal dendritic spine density. (C) The levels of synaptophysin, PSD95, PSD93, CaMKII, p‐CREB, CREB, and BDNF in the hippocampus of lenti‐shHDAC3‐injected APP/PS1 mice were determined by Western blot. n = 4–5 mice per group. (D) Graph represents quantification of the signal intensities normalized to GAPDH as a loading control. *P < 0.05, **P < 0.01.

Figure 5

Inhibition of HDAC3 attenuates microglial activation in the hippocampus of APP/PS1 mice. (A) Representative image of astrocytes and microglia stained with GFAP and Iba‐1, respectively, in the hippocampus of lenti‐shHDAC3‐injected APP/PS1 mice. (scale bar = 50 μm). n = 4–5 mice per group. (B, C) Graph represents quantification of the signal intensities. (D) The levels of GFAP and Iba‐1 in the hippocampus were determined by Western blot. n = 4–6 mice per group. (E) Graph represents quantification of the signal intensities normalized to GAPDH as a loading control. *P < 0.05, **P < 0.01.