Neurotoxicity of Clostridium perfringens Epsilon-Toxin for the Rat Hippocampus via the Glutamatergic System

Abstract

The neurotoxicity of epsilon-toxin, one of the major lethal toxins produced by Clostridium perfringens type B, was studied by histological examination of the rat brain. When the toxin was injected intravenously at a lethal dose (100 ng/kg), neuronal damage was observed in many areas of the brain. Injection of the toxin at a sublethal dose (50 ng/kg) caused neuronal damage predominantly in the hippocampus: pyramidal cells in the hippocampus showed marked shrinkage and karyopyknosis, or so-called dark cells. The dark cells lost the immunoreactivity to microtubule-associated protein-2, a postsynaptic somal and dendric marker, while acetylcholinesterase-positive fibers were not affected. Timm’s zinc staining revealed that zinc ions were depleted in the mossy layers of the CA3 subfield containing glutamate as a synaptic transmitter. The cerebral blood flow in the hippocampus was not altered significantly before or after administration of the toxin, as measured by laser-Doppler flowmetry, excluding the possibility that the observed histological change was due to a secondary effect of ischemia in the hippocampus. Prior injection of either a glutamate release inhibitor or a glutamate receptor antagonist protected the hippocampus from the neuronal damage caused by epsilon-toxin. These results suggest that epsilon-toxin acts on the glutamatergic system and evokes excessive release of glutamate, leading to neuronal damage.

Epsilon toxin: a fascinating pore‐forming toxin

“…First, it was found that ETX injected at a low dose in rats rapidly (4 h) induces neuronal damage, characterized by cell shrinking, vacuolation and nucleus pyknosis, mainly in the hippocampus and cortex. These effects were not accompanied by perivascular edema or a reduction in blood flow in the hippocampus and were specifically inhibited by glutamate receptor inhibitors, indicating that ETX interferes directly with glutamatergic neurons [70]. It was then shown that ETX increases glutamate release from mouse hippocampus and not from other brain areas [71].…”

Clostridium perfringens epsilon toxin causes excessive release of glutamate in the mouse hippocampus

“…Epsilon toxin is a major virulence determinant of Clostridium perfringens types B and D, which cause fetal enterotoxemia of domestic animals [1]. Neurologic features, such as tremor and opisthotonus, which are characteristically observed during the course of the enterotoxemia [2], can be induced by epsilon intoxication in experimental models [3,4]. The toxin accumulates mainly in the brain and a high-a¤nity binding site for epsilon toxin exists in the synaptosomal membrane [5,6].…”

Molecular basis of toxicity of Clostridium perfringens epsilon toxin

“…In mice, the lethal activity of the toxin was reduced by dopamine receptor antagonists and by drugs which directly or indirectly inhibit dopamine release, indicating that the toxin specifically stimulates release of dopamine from dopaminergic nerve endings [57]. In another study, prior injection of either a presynaptic glutamate release inhibitor or a glutamate receptor antagonist protected the rat hippocampus from toxin-induced neuronal damage, indicating that the toxin specifically stimulates glutamate release [53]. Stimulated release of glutamate was also demonstrated in the mouse hippocampus after intravenous administration of the toxin, leading to seizure and neuronal damage [58].…”