Expressions of cytokines and chemokines in the dorsal motor nucleus of the vagus nerve after right vagotomy

Abstract

The aim of this study was to investigate the expression of cytokines, tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), interleukin-6 (IL-6) and transforming growth factor-beta 1 (TGF-β1) and chemokines, fractalkine, monocyte chemoattractant protein 1 (MCP-1) and stromal cell-derived factor 1 (SDF-1) in the dorsal motor nucleus of the vagus nerve (DMV) after right vagotomy. Results showed that the immunoreactivities of IL-1β, IL-6, TGF-β1, fractalkine and MCP-1 were upregulated in the DMV at 14 days and the upregulation persisted at least until 28 days following right vagotomy. Quantification analysis revealed significant increases in the number of their immunopositive cells in the right DMV at 14 and 28 days after right vagotomy. Moreover, the upregulation of TNF-α immunoreactivity and significantly increased number of TNF-α-immunopositive cells were observed in the injured DMV at 7 and 14 days, and the increase in SDF-1-immunopositive cells at 14 days, after right vagotomy. Real time RT-PCR analysis showed the significant increase in the mRNA expression of IL-1β, fractalkine and MCP-1 at 7 days, and the upregulation of TNF-α mRNA expression at 1 day after vagotomy. However, the peak increase in TGF-β1 mRNA expression was observed at 1 day and the significant increase persisted at least until 14 days following right vagotomy. Double immunofluorescence analysis showed co-localization of lectin, a marker for microglia with CX₃CR1 but not with IL-1β at 14 days following right vagotomy. This study suggests that cytokines and chemokines involved in neuroprotection and neurodestruction could be activated in the axotomized DMV. However, it warrants further investigation to understand the neurodestructive and neuroprotective mechanisms that determine the fate of the vagal motoneurons after vagotomy.