Efeito da pré-exposição ao etanol na reatividade microglial induzida pela proteína spike de SARS-CoV2

Abstract

COVID-19, caused by the coronavirus, SARS-CoV-2, has caused more than 700 million confirmed cases according to the World Health Organization (WHO). Along with life threatening symptoms, WHO also recognized, during the peak of the pandemic, an increase in alcoholic beverages consumption by population in different countries, reported as way to deal with depression and anxiety resulting from social isolation. In the Central Nervous System (CNS), microglial cells control the immune response by mediating neuroinflammation. It is known that alcohol consumption leads to neuroinflammation and neurodegeneration in CNS. In the context of COVID19, neuroinflammation and glial reactivity are events mediated by the infection of human glial cells by SARS-CoV2, which recognizes, through its Spike-1 surface protein, the angiotensin-converting enzyme-2 (ACE-2) and other proteins such as TMPRSS2 and TLR4. Although different risk factors for COVID-19 have been described, it is not known whether alcohol consumption could represent a risk factor for SARS-CoV2-induced microglial reactivity. In this study, murine microglial cultures (BV-2) were treated with ethanol (170mM or 340mM) acute for 24h or chronically (1 treatment per day/72hs), and then exposed to the Spike1 protein (1μg/ml) for 24h. We observed by immunofluorescence that the ethanol treatment increases the levels of ACE2 by 1.2x, compared to the control. When analyzing markers of microglial reactivity, only spike-1 treated cells showed an increase in C3 expression levels, an event that was prevented by previous chronic treatment with ethanol. The chronic treatment alone or exposure to spike-1 alone appears to increase the levels of IL-1β and CD-86, an event that was lost by the spike-1 treatment in cells previously exposed to ethanol. Ethanol treatment alone did not induce phagocytic activity, an event that is only observed by Spike treatment in cells previously exposed to ethanol. In vivo, ethanol appeared to induce microglial reactivity by increasing IBA1 levels in the cerebral cortex and altered the expression of ACE-2, TMPRSS2 and TLR4 in the CNS in a region-specific manner. Human cortical microglia showed levels of expression of ACE-2, TLR4, CD-11b and IBA-1 induced by ethanol in a dosedependent manner. These data suggest that exposure to ethanol appears to reduce the microglial response to Spike-1, which could contribute to the loss of microglial function in controlling the immune response and neuroinflammation in the CNS.