ImmunoTargets and Therapy (Dec 2020)
Acetylcholine Regulates Pulmonary Pathology During Viral Infection and Recovery
Abstract
Alexander P Horkowitz,1,2 Ashley V Schwartz,3 Carlos A Alvarez,1,2 Edgar B Herrera,1 Marilyn L Thoman,1 Dale A Chatfield,4 Kent G Osborn,5 Ralph Feuer,2 Uduak Z George,3 Joy A Phillips1 1Donald P. Shiley Biosciences Center, San Diego State University, San Diego, California, USA; 2Department of Biology, San Diego State University, San Diego, California, USA; 3Department of Mathematics and Statistics, San Diego State University, San Diego, California, USA; 4Department of Chemistry, San Diego State University, San Diego, California, USA; 5Office of Animal Research, University of California San Diego, San Diego, California, USACorrespondence: Joy A PhillipsDonald P Shiley BioSciences Center, San Diego State University, 5500 Campanile Dr MC4650, San Diego, CA 92182-4650, USATel +1 619 488 2169Fax +1 619 0594 8184Email [email protected]: 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: influenza, acetylcholine, acetylcholinesterase, inflammation, pulmonary repair, ChAT, cholinergic lymphocytes, CD4 resident memory, Iba1, Aif-1, automated algorithm, MATLAB, inflammaging, cholinergic anti-inflammatory pathway
