Acetylcholine Regulates Pulmonary Pathology During Viral Infection and Recovery

Alexander P Horkowitz; Ashley V Schwartz; Carlos A Alvarez; Edgar B Herrera; Marilyn L Thoman; Dale A Chatfield; Kent G Osborn; Ralph Feuer; Uduak Z George; Joy A Phillips

doi:10.2147/ITT.S279228

Acetylcholine Regulates Pulmonary Pathology During Viral Infection and Recovery

Immunotargets Ther. 2020 Dec 17:9:333-350. doi: 10.2147/ITT.S279228. eCollection 2020.

Authors

Affiliations

¹ Donald P. Shiley Biosciences Center, San Diego State University, San Diego, California, USA.
² Department of Biology, San Diego State University, San Diego, California, USA.
³ Department of Mathematics and Statistics, San Diego State University, San Diego, California, USA.
⁴ Department of Chemistry, San Diego State University, San Diego, California, USA.
⁵ Office of Animal Research, University of California San Diego, San Diego, California, USA.

Abstract

Introduction: This study was designed to explore the role of acetylcholine (ACh) in pulmonary viral infection and recovery. Inflammatory control is critical to recovery from respiratory viral infection. ACh secreted from non-neuronal sources, including lymphocytes, plays an important, albeit underappreciated, role in regulating immune-mediated inflammation.

Methods: ACh and lymphocyte cholinergic status in the lungs were measured over the course of influenza infection and recovery. The role of ACh was examined by inhibiting ACh synthesis in vivo. Pulmonary inflammation was monitored by Iba1 immunofluorescence, using a novel automated algorithm. Tissue repair was monitored histologically.

Results: Pulmonary ACh remained constant through the early stage of infection and increased during the peak of the acquired immune response. As the concentration of ACh increased, cholinergic lymphocytes appeared in the BAL and lungs. Cholinergic capacity was found primarily in CD4 T cells, but also in B cells and CD8 T cells. The cholinergic CD4⁺ T cells bound to influenza-specific tetramers and were retained in the resident memory regions of the lung up to 2 months after infection. Histologically, cholinergic lymphocytes were found in direct physical contact with activated macrophages throughout the lung. Inflammation was monitored by ionized calcium-binding adapter molecule 1 (Iba1) immunofluorescence, using a novel automated algorithm. When ACh production was inhibited, mice exhibited increased tissue inflammation and delayed recovery. Histologic examination revealed abnormal tissue repair when ACh was limited.

Conclusion: These findings point to a previously unrecognized role for ACh in the transition from active immunity to recovery and pulmonary repair following respiratory viral infection.

Keywords: Aif-1; CD4 resident memory; ChAT; Iba1; MATLAB; acetylcholine; acetylcholinesterase; automated algorithm; cholinergic anti-inflammatory pathway; cholinergic lymphocytes; inflammaging; inflammation; influenza; pulmonary repair.