Overexpression of brain-derived neurotrophic factor in the hippocampus protects against post-stroke depression

Abstract

Post-stroke depression is associated with reduced expression of brain-derived neurotrophic factor (BDNF). In this study, we evaluated whether BDNF overexpression affects depression-like behavior in a rat model of post-stroke depression. The middle cerebral artery was occluded to produce a model of focal cerebral ischemia. These rats were then subjected to isolation-housing combined with chronic unpredictable mild stress to generate a model of post-stroke depression. A BDNF gene lentiviral vector was injected into the hippocampus. At 7 days after injection, western blot assay and real-time quantitative PCR revealed that BDNF expression in the hippocampus was increased in depressive rats injected with BDNF lentivirus compared with depressive rats injected with control vector. Furthermore, sucrose solution consumption was higher, and horizontal and vertical movement scores were increased in the open field test in these rats as well. These findings suggest that BDNF overexpression in the hippocampus of post-stroke depressive rats alleviates depression-like behaviors.

Keywords: brain injury; brain-derived neurotrophic factor; cerebral ischemia; chronic unpredictable mild stress; depression-like behavior; hippocampus; lentivirus; nerve regeneration; neural regeneration; open field test; post-stroke depression; sucrose solution consumption; western blot assay.

Figure 1

The timeline of experimental procedures. MCAO: Middle cerebral artery occlusion; CUMS: chronic unpredictable mild stress.

Figure 2

Images of representative slices from the hippocampus of rats injected with lentivirus. (A) The cell nuclei were stained with DAPI (blue, arrow). (B) The distribution of lentivirus, as revealed by GFP expression (green, arrow). (C) Merged image of A and B. (D) GFP fluorescence (arrow) showing that the hippocampus was accurately targeted by the lentivirus injection. Scale bars: 50 μm. DAPI: 4′,6-Diamidino-2-phenylindole; GFP: green fluorescent protein.

Figure 3

BDNF mRNA expression in the hippocampus of PSD rats at 7 days after lentiviral injection (real-time quantitative PCR). *P < 0.05, vs. control group; #P < 0.05, vs. PSD + LV-BDNF group. Data are presented as the mean ± SEM with five rats in each group. Statistical analysis was done using one-way analysis of variance and Tukey's post hoc test. PSD: Post-stroke depression; LV: lentivirus; GFP: green fluorescent protein; BDNF: brain-derived neurotrophic factor.

Figure 4

BDNF protein expression in rat hippocampus at 7 days post injection of lentivirus by western blot assay. (A) Molecular weight of BDNF is 27 kDa, and β-actin protein is 42 kDa. Bands for the four groups are shown (control, PSD, PSD + LV-GFP and PSD + LV-BDNF). (B) The gray value ratio of the BDNF band to the β-actin band was calculated, and the relative expression was compared with the control group. *P < 0.05, vs. control group; #P < 0.05, vs. PSD + LV-GFP group. The data are presented as the mean ± SEM with five rats in each group. Statistical analysis was performed using one-way analysis of variance and Tukey's post hoc test. PSD: Post-stroke depression; LV: lentivirus; GFP: green fluorescent protein; BDNF: brain-derived neurotrophic factor.

Figure 5

Effects of BDNF on depression-like behaviors in rats with PSD. (A) The horizontal movement scores for the four groups (control, PSD, PSD + LV-GFP and PSD + LV-BDNF) at three time points (before surgery, after CUMS and on day 7 post injection). (B) Vertical movement scores. *P < 0.05, vs. control group at 7 days post injection; &P < 0.05, vs. PSD + LV-GFP group at 7 days post injection; *P < 0.05, vs. control group after CUMS. The data are presented as the mean ± SEM. Statistical analysis was performed using one-way analysis of variance and Tukey's post hoc test. CUMS: Chronic unpredictable mild stress; PSD: post-stroke depression; LV: lentivirus; GFP: green fluorescent protein; BDNF: brain-derived neurotrophic factor.