ABSTRACT
To date, the severe acute respiratory syndrome coronavirus 2 that causes the disease Coronavirus 2019, has infected 601 million people, claiming the lives of 6.4 million people worldwide. Of the patients who survive, 60% suffer from inflammatory problems leading to post-acute sequelae of COVID-19 (PASC). Inflammation in these patients is marked by an increase in pro-inflammatory cytokines which ultimately damage the body's organs, contributing to PASC. Understanding the main mechanism by which this cytokine storm occurs is of utmost importance in order to develop therapeutic strategies for counteracting inflammation in people suffering from COVID-19 and PASC. This project seeks to find out if an innate anti-inflammatory mechanism, the cholinergic anti-inflammatory response (CAR), works properly in patients suffering from COVID-19 and PASC by interrogating its functioning in its cellular substrate, macrophages.We hypothesized that disruption of the CAR in primary human monocytederived macrophages (MDMs) exposed to the SARS-CoV-2 spike protein trimer contributes to the chronic inflammation/ cytokine storm exhibited in these patients. To this end, we exposed MDMs to the SARS-CoV-2 spike protein in order to assess levels of the anti-inflammatory alpha-7 nicotinic acetylcholine receptor (alpha7-nAChR) by means of confocal imaging. Our results demonstrate a statistically significant reduction (P <= 0.01) of alpha7-nAChR expression in MDMs, in a time-dependent manner, after the addition of SARS-CoV-2 spike protein concentrations (30 nM and 100 nM), at different time points. Interestingly, when the receptor employed by the virus to infect, Angiotensin-converting enzyme 2 (ACE-2), was blocked, we detected a significant reduction in the levels of alpha7- nAChRs (P <= 0.001). Collectively, our results support the hypothesis of this work given that the SARS-CoV-2 spike protein is capable of compromising the functioning of the CAR by reducing the levels of alpha7-nAChRs available in macrophages to suppress inflammation. These results could position the alpha7- nAChR as a key target for the development of novel anti-inflammatory therapeutic strategies to counteract the inflammatory problem found in patients suffering from COVID-19 and PASC. We would like to acknowledge Dr. Negin Martin & Dr. Jerrel Yakel, for providing the Purified Spike Protein expressed by SARS-CoV-2 and Pseudotyped Virions in this collaborative study. Also, these experiments are being supported by the University of Puerto Rico - Rio Piedras NIH-RISE program. RISE Grant Number: 5R25GM061151-20.Copyright © 2023 The American Society for Biochemistry and Molecular Biology, Inc.