Manipulating Stress Receptor Signaling to Enhance Immunosuppression and Prolong Survival of Vascularized Composite Tissue

Vascularized composite tissue allotransplantation (VCA) can replace severely damaged body parts but the unavoidable toxicity of high doses of immunosuppressive drugs, such as tacrolimus, required results in significant morbidity. Here we tested whether we could suppress immune activity in a mouse model of VCA by mimicking the natural immune suppression generated by nervous system-induced signaling of adrenergic receptors (AR) by using a safe and well-studied β-AR agonist (terbutaline). Using wild-type and β2-AR-knockout (KO) mice, we found that increased β2-AR signaling results in delayed rejection in VCA recipients, even with subtherapeutic doses of tacrolimus, and this was associated with changes in immune contexture, expression of pro-inflammatory cytokines and chemokines, and function of endothelial adhesion molecules. We propose that β-AR agonists can be used safely to mimic the natural suppression of immune responses generated by adrenergic stress signaling and thereby reduce the dose needed of other more toxic immunosuppressive drugs.