Background Infection of SARS-CoV-2 may cause acute respiratory syndrome. It has been reported that SARS-CoV-2 nucleocapsid protein (N-protein) presents early in body fluids during infection. The direct involvement of N-protein in lung injury is poorly understood. Methods Recombinant N-protein was pretreated with polymyxin B, a lipopolysaccharide (LPS)-neutralizing agent. C57BL/6, C3H/HeJ (resistant to LPS), and C3H/HeN (control for C3H/HeJ) mice were exposed to N-protein via intratracheal administration to examine acute lung injury. In vitro , bone marrow–derived macrophages (BMDMs) were cultured with N-protein to study phosphorylation of nuclear factor kappa B (NF-ĸB) p65, macrophage polarization, and expression of proinflammatory cytokines. Results N-protein produced acute lung injury in C57BL/6 mice, with elevated protein permeability, total cell count, neutrophil infiltration, and proinflammatory cytokines in the bronchioalveolar lavage. N-protein also induced lung injury in both C3H/HeJ and C3H/HeN mice, indicating that the effect could not be attributed to the LPS contamination. N-protein triggered phosphorylation of NF-ĸB p65 in vitro , which was abolished by both N-protein denaturation and treatment with an antibody for N-protein, demonstrating that the effect is N-protein specific. In addition, N-protein promoted M1 macrophage polarization and the expression of proinflammatory cytokines, which was also blocked by N-protein denaturation and antibody for N-protein. Furthermore, N-protein induced NF-ĸB p65 phosphorylation in the lung, while pyrrolidine dithiocarbamate, an NF-ĸB inhibitor, alleviated the effect of N-protein on acute lung injury. Conclusions SARS-CoV-2 N-protein itself is toxic and induces acute lung injury in mice. Both N-protein and NF-ĸB pathway may be therapeutic targets for treating multi-organ injuries in Coronavirus disease 2019 (COVID-19).
【저자키워드】 COVID-19, SARS-CoV-2, acute lung injury, nucleocapsid (N) protein, NF- kappa B, 【초록키워드】 Treatment, coronavirus disease, Macrophage, Coronavirus disease 2019, Cytokines, macrophages, antibody, neutrophil, Infection, lung, Lung injury, in vitro, acute lung injury, nucleocapsid protein, Bone marrow, Protein, Contamination, mice, Phosphorylation, pathway, macrophage polarization, respiratory, proinflammatory cytokines, inhibitor, expression, lipopolysaccharide, therapeutic targets, LPS, administration, Injury, recombinant, body fluids, therapeutic target, body fluid, Proinflammatory cytokine, acute respiratory syndrome, Polymyxin B, pyrrolidine dithiocarbamate, SARS-CoV-2 nucleocapsid, N-protein, cell count, denaturation, toxic, nuclear, neutrophil infiltration, C57BL/6, intratracheal administration, PYRROLIDINE, Result, produced, blocked, reported, addition, elevated, induce, triggered, promoted, p65, 【제목키워드】 SARS-CoV-2 N,