Pathways of the cholinergic anti-inflammatory reflex in arthritis
Final Report Abstract
Objective. Several important aspects of the anti-inflammatory effects of electrical vagal nerve stimulation (VNS) are to date still unclear. This project aimed to find out whether 1) also chronic electrical VNS is beneficial in collagen induced arthritis (CIA) and which pathways thereby are important: activation of HPA axis, the sympathetic nervous system or α7nAChR signaling, 2) if partial induction of catecholaminergicto-cholinergic transition of sympathetic nerve fibers induces a beneficial influence when applied before immunization, and 3) if anti-inflammatory effects of VNS can be transferred in an adoptive cell transfer model with Tregs. Methods. CIA was induced in DA rats after surgical implantation of VNS devices. VNS was initiated shortly after outbreak of disease. Clinical parameters, cytokines in serum and in cell cultures of splenocytes and draining lymph node cells were assessed. In vivo transition of nerve fibers to a cholinergic phenotype was checked by application of a known transition factor, and quantification of respective nerve fiber phenotypes in the spleen, draining lymph nodes and the adrenal glands. Tregs were isolated by magnetic cell separation. Results. Chronic VNS during CIA showed high drop-out rates. Due to reasons of animal welfare, nerve stimulation was hence directed to splenic nerves which resulted in an aggravation of arthritis compared to sham. In vivo application of a transition factor resulted in a decrease of sympathetic nerve fibers in the spleen, the adrenal gland cortex and in draining lymph nodes. Tregs can be obtained by magnetic cell separation of splenocytes, however at low frequency. Conclusions. Several conclusions were drawn: 1) Due to animal welfare, chronic VNS during chronic CIA is not applicable in DA rats. 2) Electric stimulation of splenic nerves unexpectedly resulted in an aggravation of CIA relative to sham animals, which themselves showed lower susceptibility and severity than normally observed in CIA with DA rats. This result might be due to a combination of known stress related beneficial effects and influences of electric spleen nerve stimulation. However we suspect that the observed aggravation strongly depends on several variables like time points of stimulator implantation, immunization, start of stimulation, and the electric nerve stimulation parameters. This should be investigated in detail in future experiments. 3) In vivo transition of sympathetic nerve fibers was observed but weaker than anticipated, hence we did not continue with this path. 4) The role of Tregs seemed promising in CIA with electric nerve stimulation, but since levels of anti-inflammatory IL-10 did not differ between groups, and the amount of Tregs which could be isolated from spleen or lymph nodes was too low for adoptive transfer experiments, we did not continue with this path. This might be different in mice, for which ready-to-use Treg isolation kits are commercially available and established.
Publications
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Catecholaminergic-to-cholinergic transition of sympathetic nerve fibers is stimulated under healthy but not under inflammatory arthritic conditions. Brain Behav Immun. 2015 May;46:180-91
Stangl H, Springorum HR, Muschter D, Grässel S, Straub RH
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Peripheral elimination of the sympathetic nervous system stimulates immunocyte retention in lymph nodes and ameliorates collagen type II arthritis. Brain Behav Immun. 2016 May;54:201-210
Klatt S, Stangl H, Kunath J, Lowin T, Pongratz G, Straub RH
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Cervical vagal nerve stimulation impairs glucose tolerance and suppresses insulin release in conscious rats. Physiol Rep. 2018;6(24):e13953
Stauss HM, Stangl H, Clark KC, Kwitek AE, Lira VA
