Resveratrol counteracts lipopolysaccharide-induced depressive-like behaviors via enhanced hippocampal neurogenesis

Abstract

Radial glial-like cells (RGLs) in the adult dentate gyrus (DG) function as progenitor cells for adult hippocampal neurogenesis, a process involved in the stress-related pathophysiology and treatment efficiency of depression. Resveratrol (RSV) has been demonstrated to be a potent activator of neurogenesis. The present study investigated whether chronic RSV treatment has antidepressant potential in relation to hippocampal neurogenesis. Mice received two weeks of RSV (20 mg/kg) or dimethylsulfoxide (DMSO) treatment, followed by lipopolysaccharide (LPS; 1 mg/kg) or saline injections for 5 days. We found that RSV treatment abrogated the increased immobility in the forced swimming test and tail suspension test induced by LPS. Immunohistochemical staining revealed that RSV treatment reversed the increase in microglial activation and the inhibition in DG neurogenesis. RSV treatment also attenuated LPS-induced defects in the expanding of RGLs through promoting symmetric division. In addition, RSV ameliorated LPS-induced NF-κB activation in the hippocampus coincides with the up-regulation levels of Sirt1 and Hes1. Taken together, these data indicated that RSV-induced Sirt1 activation counteracts LPS-induced depression-like behaviors via a neurogenic mechanism. A new model to understand the role of RSV in treating depression may result from these findings.

Keywords: LPS; Pathology Section; depression; neurogenesis; radial glial cells; resveratrol.

Figure 1. Effects of RSV on the duration of immobility on the forced swimming test (FST) and tail suspension test (TST) in LPS injected mice

A. and B. LPS induced depression-like behaviors on the FST and TST. A. LPS treated mice displayed more immobility time on the FST, and pretreatment with RSV reversed this effect (n = 8). B. LPS treated mice displayed an increased duration of immobility on the TST, and pretreatment with RSV reversed this effect (n = 8). Data are presented as mean ± SEM.*p < 0.05; **p < 0.01.

Figure 2. The effect of RSV on LPS injected mice in the elevated plus-maze test and the open field test

A. and B. Behavior of the 4 groups of mice in the elevated plus-maze test. There were no difference in the percentage of time spent in the open arms (A) or the percentage of open arm entries (B) between the 4 groups (n = 8). C.-E. Behavior of the 4 groups of mice in the open field test. LPS treatment decreased the overall distance traveled (C) and distance in center (E), but there were no significant differences in the duration of time spent in the center of the field (D). Data are presented as mean ± SEM.*p < 0.05; **p < 0.01.

Figure 3. Pretreatment with RSV inhibited LPS-induced over-activation of microglia in the SGZ

A.-D. Microglia in the SGZ of the 4 groups, as shown by immunostaining with the microglia-specific marker Iba1. E.-H. Higher-power views of the boxed areas in (A-D). Arrowheads indicate Iba1⁺ cells in the SGZ. I. The number of Iba1⁺ cells in the SGZ. Data are presented as mean ± SEM (n = 5). **p < 0.01. Scale bar in D = 200 μm and applies to (A-D), in H = 20 μm and applies to (E-H).

Figure 4. Pretreatment with RSV prevented the LPS-induced decrease of BrdU-positive cells and DCX-positive cells in the SGZ

A.-D. BrdU-positive cells in the SGZ for each of the 4 groups. Mice were sacrificed 24 h after the last BrdU injection. E.-H. Doublecortin positive (DCX⁺) cells in the SGZ. I.-L. Higher-power views of the boxed areas in E-H. RSV treatment reversed the LPS-induced decrease of BrdU-positive cells M. and DCX-positive cells N. Data are presented as mean ± SEM (n = 5). **p < 0.01. Scale bar in (D) = 100 μm and applies to (A-D), in (H) = 200 μm applies to (E-H) and in (L) =20μm applies to (I-L).

Figure 5. Pretreatment with RSV prevented the decrease of BrdU-positive cells, as well as the number of cells positive for both BrdU and DCX in the DG at 14 d following BrdU injection

A.-D. BrdU-positive cells and DCX-positive cells in the DG. Mice were sacrificed 14 d after the last BrdU injection. RSV treatment reversed the decrease of BrdU-positive cells E., as well as BrdU and DCX double-positive cells F. induced 14 d following LPS injection. Data are presented as mean ± SEM (n = 5).*p < 0.05. Scale bar in (D) = 20 μm and applies to (A-D).

Figure 6. Pretreatment with RSV inhibited the LPS-induced decrease in neuronal stem cells in the SGZ

A.-D. SOX2 and GFAP double immunostaining in the DG-SGZ for each of the 4 groups. E.-H. Higher-power views of the boxed areas in (A-D). Arrowheads indicate SOX2⁺GFAP⁺ cells in the SGZ. White triangle decorators indicate SOX2⁺GFAP^- cells in the SGZ. LPS treatment decreased the number of SOX2-positive and GFAP-positive (SOX2⁺GFAP⁺) cells I., as well as SOX2-positive and GFAP-negative (SOX2⁺GFAP^-) cells J. in the SGZ, but pretreatment with RSV only inhibited the LPS-induced (SOX2⁺GFAP⁺) cell decrease. Data are presented as mean ± SEM (n = 5).*p < 0.05. Scale bar in D = 100 μm and applies to (A-D), in H = 25 μm and applies to (E-H).

Figure 7. Pretreatment with RSV modulated the division mode of RGL progenitor cells in the GCL that was altered by LPS

A.-D. BrdU and GFAP double immunostaining in the GCL for each of the 4 groups. There were differently aligned patterns of BrdU-labeled RGL progenitor cells, including horizontally and vertically aligned patterns. Single arrowhead indicates horizontally aligned patterns. Two arrowheads arranged along the up-down direction indicate vertically aligned patterns. E. Quantitative analysis of the cell alignment modes between the 4 groups. LPS treatment decreased the horizontally aligned pattern compared to the other groups (Saline+DMSO, 77.5%; LPS+DMSO, 39.5%. p < 0.01), and pretreatment with RSV reversed this effect (LPS+DMSO, 39.5%; LPS+RSV, 76%. p < 0.01). Data are presented as mean ± SEM (n = 5). Scale bar in D = 20 μm and applies to (A-D).

Figure 8. Expression of NF-κB, Sirt1, and Hes1 in the mouse hippocampus

A. and B. Western blots assessing NF-κB and Sirt1 expression in the hippocampus of the 4 groups. LPS treatment significantly increased NF-κB expression in the hippocampus, whereas pretreatment with RSV inhibited this effect D. Conversely, compared to the saline treated group, LPS treatment decreased Sirt1 expression in the hippocampus, whereas pretreatment with RSV reversed this effect E. C. Western blots assessing Hes1 expression in the hippocampus of the 4 groups. Hes1 was significantly decreased in the hippocampus of LPS treated mice, whereas pretreatment with RSV prevented this effect F. Data are presented as mean ± SEM (n = 3).*p < 0.05; **p < 0.01.