Determinação de perfil inflamatório em linhagem de macrófagos murinos RAW 264.7 expostos ao domínio de ligação ao receptor da proteína spike S1 do SARS-CoV-2

Abstract

One of the main aggravating factors of the disease caused by the new coronavirus (COVID-19) is acute lung injury and respiratory failure, caused by an increase in the expression of proinflammatory cytokines, known as cytokine storm. In addition to the respiratory condition, patients with the SARS-CoV-2 virus have neurological complications, including encephalopathy, encephalitis and cerebrovascular pathologies, which can remain for a long term, the so-called "Long-COVID". For a better understanding and possible prevention of the damage induced by the virus, it is necessary to understand the inflammatory changes caused by its antigens. Macrophages play a key role in an effective immune response by bridging the gap between innate and adaptive immunity and the maintenance of inflammation. Therefore, this study aimed to evaluate the immune activation induced by the receptor binding domain of the Spike S1 protein of SARS-CoV-2 (RBD-S1) in a murine macrophage lineage RAW 264.7. For this, RAW 264.7 macrophages were treated for 2 or 24 hours with RBD-S1 (10, 50 and 100 ng/ml). Cell viability tests were performed by MTT reduction (3-4,5-dimethyl-thiazol-2-yl-2,5- diphenyltetrazolium bromide), arginase and myeloperoxidase enzyme activity were measured, as well as levels of IL-6, IL- 10, TNFα, IFNγ and nitrite. RBD-S1 induced a differential profile of inflammatory response that was time and concentration dependent. At its highest concentration, it promoted a classic pro-inflammatory activation in macrophages, with increased levels of IFN-γ, IL-6 and nitrite. However, at the lowest concentration, it induced a state with characteristics of an anti-inflammatory response, with increased arginase activity and IL-10 levels. In addition, a dose-dependent effect of RBD in decreasing cell viability was also observed. Therefore, it can be inferred that the inflammatory pathway in murine macrophages is activated by the receptor binding domain of the Spike S1 protein of the SARS-CoV-2 virus (RBD-S1) and a better understanding of this pathway may establish therapeutic tools to reduce the inflammatory responses and complications induced by this virus.