Effect of 6-Hydroxydopamine on Host Resistance againstListeria monocytogenesInfection

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Abstract
Recent studies have shown that immunocompetent cells bear receptors of neuropeptides and neurotransmitters and that these ligands play roles in the immune response. In this study, the role of the sympathetic nervous system in host resistance againstListeria monocytogenesinfection was investigated in mice pretreated with 6-hydroxydopamine (6-OHDA), which destroys sympathetic nerve termini. The norepinephrine contents of the plasma and spleens were significantly lower in 6-OHDA-treated mice than in vehicle-treated mice. The 50% lethal dose ofL. monocytogeneswas about 20 times higher for 6-OHDA-treated mice than for vehicle-treated mice. Chemical sympathectomy by 6-OHDA upregulated interleukin-12 (IL-12) and tumor necrosis factor-alpha (TNF-α) production in enriched dendritic cell cultures and gamma interferon (IFN-γ) and TNF-α production in spleen cell cultures, whereas chemical sympathectomy had no apparent effect on phagocytic activities, listericidal activities, and nitric oxide production in peritoneal exudate cells and splenic macrophages. Augmentation of host resistance againstL. monocytogenesinfection by 6-OHDA was abrogated in IFN-γ−/−or TNF-α−/−mice, suggesting that upregulation of IFN-γ, IL-12, and TNF-α production may be involved in 6-OHDA-mediated augmentation of antilisterial resistance. Furthermore, adoptive transfer of spleen cells immune toL. monocytogenesfrom 6-OHDA-treated mice resulted in untreated naive recipients that had a high level of resistance againstL. monocytogenesinfection. These results suggest that the sympathetic nervous system may modulate host resistance againstL. monocytogenesinfection through regulation of production of IFN-γ, IL-12, and TNF-α, which are critical in antilisterial resistance.