Protective Effects of Scolopendra Water Extract on Trimethyltin-Induced Hippocampal Neurodegeneration and Seizures in Mice

Abstract

Trimethyltin (TMT) is an organotin compound with potent neurotoxic action characterized by neuronal degeneration in the hippocampus. This study evaluated the protective effects of a Scolopendra water extract (SWE) against TMT intoxication in hippocampal neurons, using both in vitro and in vivo model systems. Specifically, we examined the actions of SWE on TMT- (5 mM) induced cytotoxicity in primary cultures of mouse hippocampal neurons (7 days in vitro) and the effects of SWE on hippocampal degeneration in adult TMT- (2.6 mg/kg, intraperitoneal) treated C57BL/6 mice. We found that SWE pretreatment (0-100 μg/mL) significantly reduced TMT-induced cytotoxicity in cultured hippocampal neurons in a dose-dependent manner, as determined by lactate dehydrogenase and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assays. Additionally, this study showed that perioral administration of SWE (5 mg/kg), from -6 to 0 days before TMT injection, significantly attenuated hippocampal cell degeneration and seizures in adult mice. Furthermore, quantitative analysis of Iba-1 (Allograft inflammatory factor 1)- and GFAP (Glial fibrillary acidic protein)-immunostained cells revealed a significant reduction in the levels of Iba-1- and GFAP-positive cell bodies in the dentate gyrus (DG) of mice treated with SWE prior to TMT injection. These data indicated that SWE pretreatment significantly protected the hippocampus against the massive activation of microglia and astrocytes elicited by TMT. In addition, our data showed that the SWE-induced reduction of immune cell activation was linked to a significant reduction in cell death and a significant improvement in TMT-induced seizure behavior. Thus, we conclude that SWE ameliorated the detrimental effects of TMT toxicity on hippocampal neurons, both in vivo and in vitro. Altogether, our findings hint at a promising pharmacotherapeutic use of SWE in hippocampal degeneration and dysfunction.

Keywords: Scolopendra subspinipes; hippocampus; neuronal degeneration; seizure; trimethyltin.

Figure 1

Protective effects of a Scolopendra water extract (SWE) on trimethyltin (TMT)-induced cytotoxicity. SWE treatment reduced the cytotoxic effects of TMT on hippocampal neurons. lactate dehydrogenase (LDH) assay (a) and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay (b). Values are reported as mean ± SE, * p < 0.05.

Figure 2

Protective effects of SWE on seizure symptoms in TMT-treated mice. (a) Schematic diagram of drug treatment, tissue preparation, and behavioral test. (b) SWE treatment ameliorated TMT-induced seizure behaviors (n = 6 mice per group). Values are reported as mean ± SE, * p < 0.05.

Figure 3

Protective effects of SWE on microglial cell activation in the hippocampus 4 days after TMT treatment. Representative images (X 200) showing microglial Iba-1 immunostaining in untreated control, TMT control, and SWE + TMT group (a). The graph (b) depicts the relative intensity of Iba-1 positive cells in the dentate gyrus (DG) of the hippocampus sections. Values are reported as mean ± SE, n = 3 in each group. * p < 0.05. Scale bar = 250um.

Figure 4

Protective effects of SWE on astrocyte levels in the DG, 4 days after TMT treatment. Representative images (X 200) showing GFAP immunostaining in untreated control, TMT control, and SWE + TMT group (a) The graph (b) depicts the relative number of GFAP-positive cells per dentate gyrus in the hippocampus sections. Values are reported as mean ± SE, n = 3 in each group. * p < 0.05. Scale bar = 250um.

Figure 5

Protective effects of SWE on the incidence of Fluoro-Jade (FJC)-1-positive dead cells in the DG of the hippocampus, 4 days after TMT treatment. Representative images (X 200) showing degenerating cells stained with FJC stain in untreated control, TMT control, and SWE + TMT group (a). All tissues were collected at 4 days after TMT treatment. The graph (b) depicts the intensity of FJC-1-positive cells per dentate gyrus (b) and entire hippocampus (c) in the brain sections. Values are reported as the mean ± SE, n = 3 in each group. * p < 0.05. Scale bar = 500um.