C033 - Splenic Focused Ultrasound Attenuates Alloimmune Response via the Cholinergic Anti-Inflammatory Pathway

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Author Block: C. Kupsch¹, L. Gilles¹, T. Oliveira¹, T. Fukushima¹, Z. Song¹, M. Kayumov¹, D. Savic², S. Ning³, F. Martin¹, Y. Xiao¹, S. Fichtner-Feigl⁴, N. McDannold¹, H. Zhou¹, S. G. Tullius¹, ¹Brigham and Women's Hospital, Harvard Medical School, Boston, MA, ²INIA Biosciences Inc, University of Oxford, Oxford, United Kingdom, ³INIA Biosciences Inc, Massachusetts General Hospital, Boston, MA, ⁴University Hospital, Freiburg, Germany
*Purpose: The cholinergic anti-inflammatory pathway (CAP) is a crucial mediator of neuro-immune crosstalk and represents a potential novel way of immunosuppression. As part of the CAP, vagus nerve activity modulates immune responses by limiting inflammation via acetylcholine signaling through the α7nAChR. Focused ultrasound (FUS) represents a non-invasive approach of neuromodulation that engages the CAP to modulate inflammatory response, without inducing adverse side effects. We delineated the role of neuromodulation on alloimmunity and transplant outcomes.
*Methods: A custom FUS transducer was built to allow precise targeting and stimulation of murine spleens. LPS i.p. injections (0.25mg/kg) tested immune modulation subsequent to FUS. Fully MHC mismatched models of skin and heart transplantation were used for immune phenotyping and allograft survival studies. Studies utilizing a pharmacological agonist (GTS-21) as well as an antagonist (MLA) of the α7nAChR defined mechanistic components by confirming that immunomodulatory effects are mediated via α7nAChR-dependent pathways.
*Results: LPS-induced inflammation was significantly reduced, as evidenced by lower systemic IL-6 levels (p<0.01) and increased IL-10 levels (p<0.01). Next, we tested the effects of daily FUS in fully MHC-mismatched skin and cardiac transplant models. FUS treatment prolonged skin graft survival from 8 to 10 days (p<0.018 vs sham; n=5/group); graft survival of cardiac transplants increased from 7 to 9 days (p<0.01 vs sham; n=5-6/group). Flow cytometry of draining lymph nodes on day 5 post transplantation revealed reduced activation of CD8⁺ T cells, with lower frequencies of CD69⁺ central and effector memory subsets in FUS-treated animals compared to sham controls. In the skin model, daily administration of the α7nAChR agonist GTS-21 replicated the FUS effect, resulting in comparable graft survival (11 days; p<0.01 vs sham). Notably, pretreatment with the antagonist MLA abolished the effect (9 days; p=0.95 vs sham).
*Conclusions: This data demonstrates the therapeutic potential of neuro-immunomodulation in curbing alloimmunity. Activation of the cholinergic anti-inflammatory pathway presents a novel, non-invasive approach for immune modulation in and beyond organ transplantation.