Treadmill Running Improves Spatial Learning Memory Through Inactivation of Nuclear Factor Kappa B/Mitogen-Activated Protein Kinase Signaling Pathway in Amyloid-β-Induced Alzheimer Disease Rats

Abstract

Purpose: Exercise is known to reduce proinflammatory cytokines production and apoptosis. We investigated the effect of treadmill running on spatial learning memory in terms of activation of nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathway in Alzheimer disease (AD) rats. We also evaluated the effect of treadmill running on proinflammatory cytokine production and apoptosis.

Methods: Using the stereotaxic frame, amyloid-β (Aβ) was injected into the lateral ventricle of the brain. The rats belong to treadmill running groups were forced to run on a motorized treadmill for 30 minutes per a day during 4 weeks, starting 3 days after Aβ injection. Morris water maze task was done for the determination of spatial learning memory. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, immunohistochemistry for cleaved caspase-3, and western blot for NF-κB, inhibitory protein of NF-κB (IκB), MAPK signaling pathway, tumor necrosis factor (TNF)-α, interleukin (IL)-1β were done.

Results: Induction of AD increased proinflammatory cytokine secretion by activating the NF-κB/MAPK signaling pathway. These changes induced apoptosis in the hippocampus and reduced spatial learning memory. In contrast, treadmill running inactivated the NF-κB/MAPK signaling pathway and suppressed proinflammatory cytokine production. These changes inhibited apoptosis and improved spatial learning memory.

Conclusion: Current results showed that treadmill running promoted spatial learning memory through suppressing proinflammatory cytokine production and apoptosis via inactivation of NF-κB/MAPK signaling pathway. Treadmill exercise can be considered an effective intervention for symptom relieve of AD.

Keywords: Alzheimer disease; Amyloid-β; Apoptosis; Inflammation; Treadmill exercise.

Fig. 1.

Experimental schedule. AD, Alzheimer disease.

Fig. 2.

Spatial learning memory. Upper panel: representative swimming path. Lower left panel: latency for finding target. Lower right panel: distance for finding target. A, control group; B, running group; C, Alzheimer disease (AD)-evoked group; D, AD-evoked and running group. ^*P<0.05 compared to the control group. ^#P<0.05 compared to the AD-evoked group. NS, nonsignificant.

Fig. 3.

Tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) expression in the hippocampus. Left upper panel: representative expression of TNF-α. Left lower panel: relative expression of TNF-α. Right upper panel: representative expression of IL-1β. Right lower panel: relative expression of IL-1β. A, control group; B, running group; C, Alzheimer disease (AD)-evoked group; D, ADevoked and running group. *P<0.05 compared to the control group. ^#P<0.05 compared to the AD-evoked group. NS, nonsignificant.

Fig. 4.

Nuclear factor kappa B (NF-κB) and inhibitory protein of NF-κB (IκB) expression in the hippocampus. Left upper panel: representative expression of NF-κB. Left lower panel: relative expression of NF-κB. Right upper panel: representative expression of IκBα. Right lower panel: relative expression of IκBα. A, control group; B, running group; C, Alzheimer disease (AD)-evoked group; D, ADevoked and running group. ^*P<0.05 compared to the control group. ^#P<0.05 compared to the AD-evoked group. NS, nonsignificant.

Fig. 5.

Mitogen-activated protein kinase (MAPK) expression in the hippocampus. Left upper panel: representative expression of expression of extracellular signal-regulated kinase (ERK). Left lower panel: relative expression of ERK. Middle upper panel: representative expression of c-Jun N-terminal kinase (JNK). Middle lower panel: relative expression of JNK. Right upper panel: representative expression of p-38. Right lower panel: relative expression of p-38. A, control group; B, running group; C, Alzheimer disease (AD)-evoked group; D, AD-evoked and running group. ^*P<0.05 compared to the control group. ^#P<0.05 compared to the AD-evoked group. NS, nonsignificant.

Fig. 6.

Apoptosis in the hippocampus. Left upper panel: photomicrographs of terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells (red arrows) and cleaved caspase-3-positive cells (black arrows) in the dentate gyrus of hippocampus. The scale bar represents 100 μm. Left lower panel: number of TUNEL-positive cells and cleaved caspase-3-positive cells. Right upper panel: representative expression of Bcl-2-associated X protein (Bax) and B-cell lymphoma-2 (Bcl-2) in the hippocampus. Right lower panel: expression of Bax, Bcl-2, and ratio of Bax to Bcl-2. A, control group; B, treadmill running group; C, Alzheimer disease (AD)-evoked group; D, AD-evoked and running group. ^*P<0.05 compared to the control group. ^#P<0.05 compared to the AD-evoked group. NS, nonsignificant.