Role and Mitigation of Inflammasomes and Inflammation During COVID-19

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Project Abstract The COVID-19 pandemic caused by SARS-CoV-2 has resulted in swift and catastrophic losses of human lives globally. Acute respiratory distress syndrome (ARDS) is one of the most detrimental outcomes of COVID-19 infection that can lead to the rapid deterioration and death of patients. ARDS is primarily caused by the cytokine storm which unleashes a plethora of inflammatory cytokines during the late stages of COVID-19. The master cytokines that are thought to be responsible for much of the damage are interleukin 1 (IL-1), interleukin 6 (IL-6) and tumor necrosis factor (TNF). Currently two clinical trials have shown the efficacy of IL-1 inhibitor in COVID- 19 patients. However, in many cases, the mechanism and impact of these cytokines during SARS-CoV-2 infection are poorly understood. An in-depth mechanistic understanding of cytokine induction is important because this understanding will significantly impact the design and success of ARDS treatment. This application focuses on the role and mitigation of the inflammasome complex which leads to the proinflammatory cytokine, IL-1β, in ARDS. The inflammasome is a protein supramolecular structure that leads to caspase 1 activation, which then cleaves pro-IL-1β and pro-IL-18 to mature IL-1β and IL-18. In addition to the release of IL-1β and IL- 18, caspase 1 cleaves gasdermin D to cause inflammatory pyroptotic cell death, thus leading to a cascade of cell death and inflammation. The inflammasome is comprised of a receptor or sensor, with the most prominent ones represented by NLRP1, NLRP3, NLRP6, NLRC4 and AIM2. It also includes an adaptor molecule ASC (apoptosis-associated speck-like protein containing a CARD), and the effector caspase-1. Each receptor or sensor can be activated by specific pathogen products called PAMPs or cell damage associated molecules called DAMPs. Single cell RNAseq data from COVID-19 patients show dramatic increases of inflammasome sensors in the bronchial alveolar lavage of severe COVID-19 patients. In addition, we find a bidirectional feed- forward loop of inflammasome activation and inflammatory cytokine induction involving myeloid cells and airway stromal cells. This proposal will test the hypothesis that this two way amplification loop is important in COVID- 19.