Beta Adrenergic Signaling as a Therapeutic Target for Autoimmunity

Abstract

Background: We recently identified a molecular mechanism involving beta-adrenergic 1 and 2 receptors (β1/2) in the development of T_H17 lymphocytes. Pharmacological and genetic inhibition of these receptors in combination, but not separately, impaired the ability of T-lymphocytes to produce proinflammatory interleukin 17A (IL-17A) and instead promoted the production of protective T_reg cells that secrete anti-inflammatory interleukin-10 (IL-10). However, it remained unclear whether this regulatory mechanism could serve as a novel therapeutic approach for autoimmune disorders mediated by IL-17A-producing T-lymphocytes.

Methods: Multiple sclerosis (MS) is an inflammatory demyelinating disorder of the central nervous system (CNS) characterized by an autoimmune response where both T-lymphocytes and IL-17A are implicated in the pathogenesis of the disease. Using an animal model of MS, termed experimental autoimmune encephalomyelitis (EAE), we addressed the impact of beta adrenergic receptor blockade (genetically and pharmacologically) on EAE disease progression, severity, and T_H17/T_reg balance.

Results: The genetic deletion β1/2 receptors, either systemically or specifically in T-lymphocytes, significantly attenuated EAE disease severity and animal weight loss. Pharmacological blockade of β1/2 receptors with either propranolol (lipophilic) or nadolol (aqueous) limited disease severity and weight loss similar to the genetic models. All models showed degrees of shifted T_H17/T_reg balance (suppressing T_H17 and promoting T_reg) and decreased T-lymphocyte IL-17A production. Importantly, pharmacological blockade was initiated at the time of symptom development, which mimics the typical time where diagnosis of disease would occur.

Conclusions: Our data depict a novel role for β1/2 adrenergic signaling in the control of T_H17/T_reg cells in EAE. These findings provide new insight into the disease progression as well as provide a potential new pharmacological therapy for IL-17A-related autoimmune diseases.

Keywords: EAE; IL-17A; T-Lymphocyte; autonomic; propranolol.

Figure 1.. β1/2 adrenergic blockade attenuates clinical EAE score and EAE-induced weight loss.

EAE was induced in WT, β1/2^−/−, or adoptively transferred Rag2^−/− mice and were clinical scored and weighed daily. (A-B) Whole body β1/2^−/− animals versus WT (n=31). (C-D) Adoptive transfer of β1/2^−/− T-lymphocytes vs WT T-lymphocytes into immunodeficient Rag2^−/− mice (n=13). (E-F) Pharmacological adrenergic blockade using propranolol (lipophilic β1/2 antagonist) (n=41) or (G-H) nadolol (aqueous β1/2 antagonist) (n=34). Statistics by 2-way ANOVA with Bonferroni post-hoc.

Figure 2.. β1/2 signaling alters the T_H17/T_reg balance in EAE.

EAE was induced in WT, β1/2^−/−, or adoptively transferred Rag2^−/− mice. Mice were sacrificed at maximal disease severity (day 14–21 depending on model), and spleens and inguinal lymph nodes harvested for T-lymphocyte immunophenotyping. Whole body β1/2^−/− animals versus WT splenic T_H17 (A), splenic T_regs (B), lymph node T_H17 (C), and lymph node T_regs (D). Adoptive transfer of β1/2^−/− T-lymphocytes vs WT T-lymphocytes into immunodeficient Rag2^−/− mice splenic T_H17 (E), splenic T_regs (F), lymph node T_H17 (G), and lymph node T_regs (H). Pharmacological adrenergic blockade using propranolol (lipophilic β1/2 antagonist) or nadolol (aqueous β1/2 antagonist) splenic T_H17 (I), splenic T_regs (J), lymph node T_H17 (K), and lymph node T_regs (L). Statistics by Student’s t-test (A-H) and 1-way ANOVA with Dunnett’s post-hoc (I-L).

Figure 3.. β1/2 adrenergic blockade inhibits T-lymphocyte IL-17A.

EAE was induced in WT, β1/2^−/−, or adoptively transferred Rag2^−/− mice. Mice were sacrificed at maximal disease severity (day 14–21 depending on model). Plasma was harvested for circulating cytokine analysis. Spleens and inguinal lymph nodes harvested for T-lymphocyte recall with 10 μg/mL of MOG peptide for 72 hours. Whole body β1/2^−/− animals versus WT plasma IL-17A (A), splenocyte recall (B), lymph node recall (C). Adoptive transfer of β1/2^−/− T-lymphocytes vs WT T-lymphocytes into immunodeficient Rag2^−/− mice plasma IL-17A (D), splenocyte recall (E), lymph node recall (F). Pharmacological adrenergic blockade using propranolol (lipophilic β1/2 antagonist) or nadolol (aqueous β1/2 antagonist) plasma IL-17A (G), splenocyte recall (H), lymph node recall (I). Statistics by Student’s t-test (A-F) and 1-way ANOVA with Dunnett’s post-hoc (G-I).