Dl-3-n-Butylphthalide Reduces Cognitive Impairment Induced by Chronic Cerebral Hypoperfusion Through GDNF/GFRα1/Ret Signaling Preventing Hippocampal Neuron Apoptosis

Abstract

Hippocampal neuron death is a key factor in vascular dementia (VD) induced by chronic cerebral hypoperfusion (CCH). Dl-3-n-butylphthalide (NBP) is a multiple-effects drug. Therefore, the potential molecular mechanisms underlying CCH and its feasible treatment should be investigated. This study had two main purposes: first, to identify a potential biomarker in a rat model of CCH induced VD using antibody microarrays; and second, to explore the neuroprotective role of NBP at targeting the potential biomarker. Glial cell line-derived neurotrophic factor (GDNF)/GDNF family receptor alpha-1 (GFRα1)/receptor tyrosine kinase (Ret) signaling is altered in the hippocampus of CCH rats; however, NBP treatment improved cognitive function, protected against hippocampal neuron apoptosis via regulation of GDNF/GFRα1/Ret, and activated the phosphorylation AKT (p-AKT) and ERK1/2 (p-ERK1/2) signaling. We also found that 1 h oxygen-glucose deprivation (OGD) followed by 48 h reperfusion (R) in cultured hippocampal neurons led to downregulation of GDNF/GFRα1/Ret. NBP upregulated the signaling and increased neuronal survival. Ret inhibitor (NVP-AST487) inhibits Ret and downstream effectors, including p-AKT and p-ERK1/2. Additionally, both GDNF and GFRα1 expression are markedly inhibited in hippocampal neurons by coincubation with NVP-AST487, particularly under conditions of OGD/R. GDNF/GFRα1/Ret signaling and neuronal viability can be maintained by NBP, which activates p-AKT and p-ERK1/2, increases expression of Bcl-2, and decreases expression of Bax and cleaved caspase-3. The current study showed that GDNF/GFRα1/Ret signaling plays an essential role in the CCH induced VD. NBP was protective against hippocampal neuron apoptosis, and this was associated with regulation of GDNF/GFRα1/Ret and AKT/ERK1/2 signaling pathways, thus reducing cognitive impairment.

Recombinant Adiponectin Peptide Ameliorates Cortical Neuron Damage Induced by Chronic Cerebral Hypoperfusion by Inhibiting NF-κB Signaling and Regulating Microglial Polarization

“…In our previous study, we reported that the CCH process can lead to activation of microglia in the brain [7]. Indeed, mounting evidence has demonstrated that the microglia with the antiinflammatory phenotype play a neurorestorative role during the recovery period after ischemic events [8].…”

“…Rats were subjected to permanent bilateral common carotid artery occlusion (BCCAO) surgery to induce CCH as described previously [2,7,12]. Briefly, both common carotid arteries were ligated with two 4-0 sutures.…”

“…Learning and spatial memory in the rats from different groups were evaluated with the Morris water maze test 4, 8, and 12 weeks after BCCAO using a previously described method [7]. The mean escape latency (EL) of four training sessions was recorded as a daily learning score from the 1 st to 5 th day.…”

“…In response to CCH, a chain of homeostatic interactions occur in the brain, including neuroinflammation, oxidative stress, mitochondrial dysfunction, disorder of neurotransmitter system and lipid metabolism, and changes in expression of growth factors, which culminate in neuronal death [4,7]. Unfortunately, the neurorestorative potential of the adult brain is very limited [8].…”

“…Unfortunately, the neurorestorative potential of the adult brain is very limited [8]. Previous studies have reported that neuronal death is the key factor for cognitive impairment in CCH [7,9,10], with CCH patients often suffering long-term neurological deficits and cognitive impairment in the process of cerebral hypoperfusion [2]. Indeed, a previous study indicated that patients with vascular cognitive impairment exhibited typical neuron loss [11].…”