Investigating neutrophil AMPK activity in COVID-19 and pneumonia

Introduction: COVID19 can cause neutrophilic inflammation and reaction oxygen species (ROS) production, leading to acute lung injury and mortality. AMPK is a key regulator of cellular energy with profound effects on neutrophil function. This study aims to investigate the role of AMPK activity in neutrophils during COVID-19 and pneumonia caused by pathogens other than SARS-CoV-2. Methods: Patients hospitalised due to pneumonia or COVID-19 were recruited from Ninewells Hospital (Dundee, UK). Blood was sampled at day 1, 8, and 15. ROS production, phospho-AMPK (pAMPK), and NQO1 were stained in neutrophils, and then analysed by flow cytometry. The endogenous AMPK inhibitor, resistin, was quantified by ELISA, in serum (day 1, 8, 15). WHO clinical scale and CURB65 score were utilised to define severity. Results: 133 patients were enrolled (mean age 63.6 years). Resistin was not different between pneumonia and COVID-19 on day1. However, day 1 resistin was higher in severe disease defined by CURB65 Score (p=0.0220) and WHO score (p=0.0184). Resistin reduced over time at day 1 (mean 63.1pg/mL;n=121) to day 15 (mean 59.5pg/mL;n=66)(p=0.0002). Zymosan stimulation significantly increases neutrophil ROS production (p<0.0001), and significantly decreases NQO1 (p<0.0001), but caused no changes with pAMPK. There were no changes in these markers over time. pAMPK significantly correlated with NQO1 in unstimulated neutrophils (p=0.0388), but not when stimulated with zymosan. There were no associations between resistin and pAMPK, and no difference in these markers between pneumonia and COVID-19 groups. Conclusion: Our study suggests resistin as a marker of severity and disease course in COVID-19, independent of neutrophil AMPK signalling.