Alcohol and the alveolar epithelial barrier

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Project Summary The COVID-19 pandemic represents the most significant public health crisis to occur in generations. A major cause of death due to COVID-19 is acute respiratory distress syndrome (ARDS). Whether chronic alcohol use disorder exacerbates the severity of COVID-19 is not known, but is highly likely given the known impact of alcohol on several organ systems including priming the lung epithelial barrier for increased paracellular leak. In addition, it is well established that chronic alcohol consumption exacerbates the severity of lung injury when combined with an additional insult, a so-called “second hit”. Of note, alcoholic lung syndrome increases the incidence of ARDS by 3-4 fold when compared with non-alcoholic ICU patients. We have identified properties of SARS-CoV-2 that predispose it towards a milder phase of infection, related to the virus E protein. The original SARS coronavirus, SARS-CoV-1, has an E protein that specifically targets tight junction protein PDZ binding motifs and thus readily disrupts the epithelial barrier of infected epithelia. By contrast, the COVID-19 virus SARS-CoV-2 has E protein mutations that inhibit its ability to bind to PDZ binding motifs which can help preserve infected epithelial cell barrier function. However, SARS-CoV-2 in the context of alcoholic lung syndrome is more likely to result in a more severe outcome, since the epithelial barrier is already impaired as a result of chronic alcohol abuse. Primary human bronchiolar epithelial cells derived from alcoholic and non- alcoholic subjects will be infected with SARS-CoV-2 in vitro and we will measure several outcome variables related to severity of infection. We also have preliminary data showing that cells from alcoholics retain signature differences in gene expression and function relative to non-alcoholic cells, leading to decreased barrier function and altered cell morphology. This supports a hypothesis that chronic alcohol exposure induces persistent, epigenetic changes to the airway epithelial cell genome. In this supplement proposal, we will determine the impact of SARS-CoV-2 on the epigenome of host cells from alcoholics and non-alcoholics, focusing on DNA methylation. Of particular interest will be to examine the impact of DNA methylation induced by alcohol and/or SARS-CoV-2 infection on the expression and downstream targets of the transcription factors Nrf2 and PU.1, known to be impaired by chronic alcohol exposure and that play key roles in regulating epithelial antiviral responses. We will also identify novel host genome loci showing patterns of differential methylation that correlate with disease severity. We anticipate that identifying differentially methylated loci impacted by chronic alcohol exposure and SARS-CoV-2 infection will lead to drug targets with the potential to reduce the severity of COVID-19 in alcoholic patients.