Chronic vagus nerve stimulation (VNS) altered IL-6, IL-1β, CXCL-1 and IL-13 levels in the hippocampus of rats with LiCl-pilocarpine-induced epilepsy

An increasing number of observations have indicated that the activation of inflammatory processes is involved in the pathogenesis of epilepsy. As an effective adjunctive therapy for medically intractable seizures, vagus nerve stimulation (VNS) is thought to interact with the inflammatory process to play an antiepileptic role. In this study, we examined the levels of multiple cytokine in focal brain tissue and peripheral blood to determine whether the antiepileptic effect of chronic VNS is related to the expression of cytokines. We observed that the frequency and duration of seizures significantly decreased in epileptic rats after two weeks of chronic VNS treatment. Pathological staining showed that the number of neural cells in the hippocampus was higher in the Epi + VNS group than in the Epi group, indicating that chronic VNS had a significant neuroprotective effect on epileptic rats. After comparing the expression of 9 cytokines, we found that the levels of the proinflammatory cytokines IL-6, IL-1β and CXCL-1 in the hippocampus were significantly increased in the Epi group, while these cytokines were significantly decreased in the Epi + VNS group. Moreover, the level of the anti-inflammatory cytokine IL-13 was found to be reduced in Epi rats, while its levels were increased after VNS treatment. However, these changes in cytokine expression were not found in the hypothalamus or peripheral blood. These results suggest that the antiepileptic mechanism of VNS may work by inhibiting the activation of inflammatory processes in the epileptogenic focus.