Vagus nerve stimulation leads to contraction of the spleen and dampened IFNγ production in response to TLR stimulation

Abstract

Abstract Vagus nerve stimulation (VNS) generates an anti-inflammatory state and limits the pathology of inflammatory diseases, such as sepsis and acute kidney injury. Interestingly, splenectomy prior to stimulation results in a loss of this protection. Thus, the spleen is a central organ for converting VNS signals into protective anti-inflammation. To better understand the interplay between VNS and the spleen and gain insight into the mechanisms of anti-inflammation, we performed a broad query of the spleen post-VNS. Mice received either electrical stimulation of the left-cervical vagus nerve or sham surgery. Spleens were harvested and assessed for mass, immune cell populations, and splenocyte in vitro cytokine production in response to TLR4, 3, and 9 agonists (LPS, poly I:C, and CpG, respectively). We discovered that by 48 hours post-VNS, spleen mass was reduced and the number of CD45+ cells was significantly decreased compared to sham mice. Analysis of CD45+ cells revealed that many individual immune cell populations were diminished. B cells, T cells, NK cells, dendritic cells, and basophils were all significantly reduced and eosinophils and monocytes showed strong trends towards reduction, nearing significance. In response to TLR agonists, our Luminex analysis revealed a strong impact on TLR4 stimulation, with 12 of the 32 measured cytokines showing a significant reduction in supernatants from VNS samples. TLR3 and TLR9 stimulation also exhibited significant reductions in a subset of the measured cytokines, but only IFNγ exhibited strong signs of reduced production in all TLR stimulation conditions. Thus, VNS has profound impacts in the spleen and some of the observed protection could be due to tighter control of immune cell IFNγ secretion. Supported by grants from the NIH (R01 DK123248)