Senolytic intervention improves cognition, metabolism, and adiposity in female APPNL-F/NL-F mice

Abstract

Senescent cells accumulate throughout the body and brain contributing to unhealthy aging and Alzheimer's disease (AD). The APP^NL-F/NL-F amyloidogenic AD mouse model exhibits increased markers of senescent cells and the senescence-associated secretory phenotype (SASP) in visceral white adipose tissue and the hippocampus before plaque accumulation and cognitive decline. We hypothesized that senolytic intervention would alleviate cellular senescence thereby improving spatial memory in APP^NL-F/NL-F mice. Thus, 4-month-old male and female APP^NL-F/NL-F mice were treated monthly with vehicle, 5 mg/kg dasatinib + 50 mg/kg quercetin, or 100 mg/kg fisetin. Blood glucose levels, energy metabolism, spatial memory, amyloid burden, and senescent cell markers were assayed. Dasatinib + quercetin treatment in female APP^NL-F/NL-F mice increased oxygen consumption and energy expenditure resulting in decreased body mass. White adipose tissue mass was decreased along with senescence markers, SASP, blood glucose, and plasma insulin and triglycerides. Hippocampal senescence markers and SASP were reduced along with soluble and insoluble amyloid-β (Aβ)₄₂ and senescence-associated-β-gal activity leading to improved spatial memory. Fisetin had negligible effects on these measures in female APP^NL-F/NL-F mice while neither senolytic intervention altered these parameters in the male mice. Considering women have a greater risk of dementia, identifying senotherapeutics appropriate for sex and disease stage is necessary for personalized medicine.

Keywords: Alzheimer’s disease; Amyloid plaques; Cell senescence; Cognition; Dasatinib and quercetin; Fisetin.

Fig. 1

Senolytic intervention reduced adiposity and circulating lipid levels in female APP^{NL−F/NL−F} mice. Mouse body weight (A) along with percentages of total (B), WAT depots (C–E), and BAT (F) in relation to body weight. Plasma triglyceride and cholesterol levels were determined by enzymatic determination (G–H). All tissue was collected at the time of euthanization (14 months of age). Data are represented as means ± SEM (n = 15–21). Results of a two factorial analysis are shown above each bar graph for the Sex (S) and Treatment (T) categorial variables and their interaction (S × T). *p < 0.05, **p < 0.01, ***p < 0.001 based on a two-tailed Student’s t test

Fig. 2

Blood glucose and plasma insulin are improved after senolytic treatment in female APP^{NL−F/NL−F} mice. Glucose tolerance test (GTT) and insulin tolerance test (ITT), and their respective area under the curve (AUC) after five treatments (A–F). Fasting (G) and fed (H) blood glucose levels were determined from time = 0 during the GTT and ITT, respectively. Circulating insulin and adiponectin levels were determined by ELISA from plasma collected at the time of euthanization (10 treatments). Data are represented as means ± SEM (n = 13–23). Results of a two factorial analysis are shown above each bar graph for the Sex (S) and Treatment (T) categorial variables and their interaction (S × T). *p < 0.05, **p < 0.01, ****p < 0.0001 based on a two-tailed Student’s t test

Fig. 3

D + Q treatment improves oxygen consumption and energy expenditure in female APP^{NL−F/NL−F} mice. Twenty-four-hour male and female oxygen consumption (A–C), energy expenditure (D–F), and respiratory quotient (G–I; VCO₂/VO₂) along with their corresponding AUC after 9 treatments were determined by indirect calorimetry. White and black bars along the abscissa indicates the hours of lights on or off, respectively. Data are represented as means ± SEM (n = 15–23). Results of a two factorial analysis are shown above each bar graph for the Sex (S) and Treatment (T) categorial variables and their interaction (S × T). *p < 0.05 based on a two-tailed Student’s t test

Fig. 4

D + Q treatment altered senescent cell markers and SASP profile in a sexually dimorphic manner. Gene expression profiles in vWAT (A–H) and the hippocampus (I–K). Data are represented as means ± SEM (n = 8–10). Results of a two factorial analysis are shown above each bar graph for the Sex (S) and Treatment (T) categorial variables and their interaction (S × T). *p < 0.05, **p < 0.01, ***p < 0.001 based on a two-tailed Student’s t test

Fig. 5

APP^{NL−F/NL−F} mice have reduced hippocampal senescent cell burden as well as insoluble and soluble Aβ₄₂ after D + Q treatment. Representative × 4 and × 40 hippocampal images (A) of SA-β-gal staining (blue) and plaque accumulation (red) for male (left) and female (right) after 10 treatments of vehicle (top), D + Q (middle), or fisetin (bottom). Arrows indicate magnified image area shown to the right of each whole hippocampal image. Percentage of SA-β-gal staining (B) along with insoluble (C–F) and soluble Aβ₄₂ (G) levels are shown. Data are represented as means ± SEM (n = 8–10). Results of a two factorial analysis are shown above each bar graph for the Sex (S) and Treatment (T) categorial variables and their interaction (S × T). *p < 0.05, **p < 0.01 based on a two-tailed Student’s t test

Fig. 6

Spatial learning and memory recall was improved in female APP^{NL−F/NL−F} mice receiving D + Q treatment. An eight-day MWM paradigm consisting of 5 training days followed by a single probe challenge 48 h after was used to assess spatial cognition after the ninth treatment (13 months of age). The cumulative distance (A–C), corrected integrated path length (CIPL; D–F), and path efficiency (G–I) along with their corresponding AUC are shown for each training day. The number of platform crosses into the former location of the hidden escape platform (J) and annulus 40 (K) are reported for the probe challenge. Data are represented as means ± SEM (n = 20–25). Results of a two factorial analysis are shown above each bar graph for the Sex (S) and Treatment (T) categorial variables and their interaction (S × T). *p < 0.05 based on a two-tailed Student’s t test