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Comparative Study
. 2012 Feb;233(2):783-90.
doi: 10.1016/j.expneurol.2011.11.042. Epub 2011 Dec 8.

Valproic Acid Improves Locomotion in Vivo After SCI and Axonal Growth of Neurons in Vitro

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Free PMC article
Comparative Study

Valproic Acid Improves Locomotion in Vivo After SCI and Axonal Growth of Neurons in Vitro

Lei Lv et al. Exp Neurol. .
Free PMC article

Abstract

Previous studies have found that valproic acid (VPA), a histone deacetylases (HDAC) inhibitor, improves outcomes in a rat model of spinal cord injury (SCI). The study here aimed to further illuminate the neuroprotective effects of VPA against SCI, both in vivo and in vitro. First, spinal cord injury was performed in rats using NYU impactor. Delayed VPA injection (8 h following SCI) significantly accelerated locomotor recovery. VPA therapy also suppressed SCI-induced hypoacetylation of histone and promoted expressions of BDNF and GDNF. Next, the influence of VPA on axonal growth inhibited by a myelin protein was tested. Neurons from embryonic spinal cord or hippocampus were cultured on plates coated with Nogo-A peptide, and escalating concentrations of VPA were added into the cultures. VPA treatment, in a concentration dependent manner, allowed neurons to overcome Nogo-A inhibition of neurite outgrowth. Meanwhile, VPA exposure increased the level of histone acetylation and expression of BDNF in spinal neurons. Cumulatively, these findings indicate that VPA is possibly a promising medication and deserves translational trials for spinal cord injury.

Conflict of interest statement

Statement of interest

None.

Figures

Fig. 1
Fig. 1
Delayed administration of VPA improved functional recovery. SCI rats were treated by VPA or saline, staring 8 h after surgery. Compared to the controls, VPA significantly accelerated locomotion recovery after SCI. (A) The rats treated by VPA had higher scores in BBB test, starting from week 4 and lasting to endpoint. (B) At week 6, SCI rats injected by VPA showed better performance in footprint analysis. Reduced foot exorotation and support were found in animals with VPA-injection. Data were presented as mean±SEM (n=12), and p<0.05*, p<0.01**.
Fig. 2
Fig. 2
Delayed VPA treatment reduced apoptotic cells and lesion size. (A) Apoptotic cells were detected by TUNEL kit week 1 post operative. Delayed VPA treatment significantly decreased apoptotic cells. (B) Lesion volume was measured 6 weeks after injury. Delayed VPA treatment also significantly reduced lesion size. Data were presented as means±SEM (n=8), Bar=20 μm, and p<0.05*, as compared to controls.
Fig. 3
Fig. 3
Delayed VPA therapy unregulated H3 acetylation, and mRNA expressions of BDNF and GDNF. Rats were sacrificed to investigate acetylation of histone and expressions of neurotrophic genes. (A/B) VPA injection ameliorated SCI-induced hypoacetylation of H3. (C/D) The mRNA expressions of BDNF and GDNF were also elevated by VPA therapy. Data were presented as means±SEM (n=6), and p<0.05*, p<0.01**.
Fig. 4
Fig. 4
VPA attenuated Nogo-A inhibition on axonal growth of spinal neurons. (A) Spinal neurons were cultured on 24-well coated with or without Nogo-A peptide. Compared to control, Nogo-A inhibited axonal growth. However, VPA exposure attenuated Nogo-A inhibition and promoted neurite outgrowth. (B) Neurons were immunostained with antibodies to β-III tubulin to trace neurite (red), and nuclei were stained by DAPI (blue). VPA obviously enhanced neurite generation. Bar A=40 μm, Bar B=100 μm.
Fig. 5
Fig. 5
VPA enhances axon outgrowth in a concentration dependent manner. (A) Spinal neurons were stained with antibodies to β-III tubulin (red) and digital images were taken for morphometrical analysis. (B) The length of axon was determined and average outgrowth was calculated. VPA attenuated the inhibitory effect of Nogo-A and enhanced neurite regeneration in a concentration dependent manner. Neurite outgrowth was expressed as a ratio to control and presented as mean±SEM (n=3). Bar=100 μm, and p<0.05*, p<0.01** as compared to Nogo-A group; p<0.05# as compared to control group.
Fig. 6
Fig. 6
VPA enhances axonal growth of hippocampus neurons. (A) Immunostaining of β-III tubulin (green) was performed in hippocampus neurons. (B) The average outgrowth of neurite was analyzed. VPA in a concentration dependent manner enhanced axonal regeneration. Neurite outgrowth was expressed as a ratio to control and presented as mean± SEM (n=3). Bar=100 μm, and p<0.05*, p<0.01** as compared to Nogo-A group; p<0.05# as compared to control group.
Fig. 7
Fig. 7
VPA enhanced H3 acetylating and BDNF transcript in spinal neurons. (A) Neurons were immunostained with antibodies to β-III tubulin (red) and acetylated histone 3 (green). Compared to controls, VPA (1.2 mM) increased Ac-H3. (B) Weston blot was performed to quantify Ac-H3. VPA significantly enhanced H3 acetylating in neurons attained from spinal cord. (C) The level of BDNF mRNA in spinal cord neurons was measured by q-PCR. Compared to controls, VPA significantly upregulated BDNF transcript. Data were presented as means±SEM (n=3), Bar=100 μm, p<0.05* and p<0.01**.

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