Neuroprotective Effect of Uncaria rhynchophylla in Kainic Acid-Induced Epileptic Seizures by Modulating Hippocampal Mossy Fiber Sprouting, Neuron Survival, Astrocyte Proliferation, and S100B Expression

Abstract

Uncaria rhynchophylla (UR), which is a traditional Chinese medicine, has anticonvulsive effect in our previous studies, and the cellular mechanisms behind this are still little known. Because of this, we wanted to determine the importance of the role of UR on kainic acid- (KA-) induced epilepsy. Oral UR for 6 weeks can successfully attenuate the onset of epileptic seizure in animal tests. Hippocampal mossy fiber sprouting dramatically decreased, while neuronal survival increased with UR treatment in hippocampal CA1 and CA3 areas. Furthermore, oral UR for 6 weeks significantly attenuated the overexpression of astrocyte proliferation and S100B proteins but not γ-aminobutyric acid A (GABA(A)) receptors. These results indicate that oral UR for 6 weeks can successfully attenuate mossy fiber sprouting, astrocyte proliferation, and S100B protein overexpression and increase neuronal survival in KA-induced epileptic rat hippocampus.

Figure 1

The alteration of electroencephalographic (EEG) signals in KA-injected animals. Basal EEG activity from the sensorimotor cortex was characterized by 6–8 Hz activity in rats when awake (a). KA-induced temporal lobe seizures, including wet dog shakes (WDS) with intermittent polyspike-like activity (b), facial myoclonia with continuous sharp waves (c) and paw tremor (PT) with continuous spike activity (d). Lt Cx = EEG recording from the left sensorimotor cortex; Rt Cx = EEG recording from the right sensorimotor cortex; EMG = EMG recording from the neck muscle.

Figure 2

Timm's stain in hippocampal slices from PBS, KA, and UR pretreated groups. (a) whole hippocampus in PBS group (b) DG molecular layer in PBS group (c) whole hippocampus in KA-induced group. (d) DG molecular layer in KA-induced group (e) whole hippocampus in UR-treated group (f) DG molecular layer in UR-treated group. Timm's staining indicated with arrows (brown). The left panel was captured at 40x magnification while the right panel was at 400x magnification.

Figure 3

Immunohistochemistry staining of Hematoxylin and Eosin (HE) and NeuN in hippocampal slices from PBS, KA-induced, and UR-pretreated groups. HE (blue) and NeuN (brown) positive staining in whole hippocampus (a), CA1 (b), CA3 (c), and Hilus regions in PBS group. HE (blue) and NeuN (brown) positive staining in whole hippocampus (e), CA1 (f), CA3 (g), and Hilus (h) regions in KA-induced group. HE (blue) and NeuN (brown) immunostaining in whole hippocampus (i), CA1 (j), CA3 (k), and Hilus (l) regions in UR-treated group. The left panel was captured at 40x magnification, while the others were at 400x magnification.

Figure 4

Immunohistochemistry staining of HE and GFAP in hippocampal slices from PBS, KA-induced, and UR-treated groups. HE (blue) and GFAP (brown) positive staining in whole hippocampus (a), CA1 (b), CA3 (c), and Hilus (d) regions in PBS group. HE (blue) and GFAP (brown) positive staining in whole hippocampus (e), CA1 (f), CA3 (g), and Hilus (h) regions in KA-Induced group. HE (blue) and GFAP (brown) positive staining in whole hippocampus (i), CA1 (j), CA3 (k), and Hilus (l) regions in UR-treated group. The left panel was captured at 40x magnification, while the others were at 400x magnification.

Figure 5

Immunohistochemistry staining of HE and S100B in hippocampal slices from PBS, KA-induced, and UR-treated groups. HE (blue) and S100B (brown) positive staining in whole hippocampus (a), CA1 (b), CA3 (c), and Hilus (d) regions in PBS group. HE (blue) and S100B (brown) positive staining in whole hippocampus (e), CA1 (f), CA3 (g), and Hilus (h) regions in KA-Induced group. HE (blue) and S100B (brown) positive staining in whole hippocampus (i), CA1 (j), CA3 (k), and Hilus (l) regions in UR-treated group. The left panel was captured at 40x magnification, while the others were at 400x magnification.

Figure 6

Immunohistochemistry staining of HE and GABA_A in hippocampal slices from PBS, KA-induced, and UR-treated groups. HE (blue) and S100B (brown) positive staining in whole hippocampus (a), CA1 (b), CA3 (c), and Hilus (d) regions in PBS group. HE (blue) and GABA_A (brown) positive staining in whole hippocampus (e), CA1 (f), CA3 (g), and Hilus (h) regions in KA-Induced group. HE (blue) and GABA_A (brown) positive staining in whole hippocampus (i), CA1 (j), CA3 (k), and Hilus (l) regions in UR-treated group. The left panel was captured at 40x magnification, while the others were at 400x magnification.