SARS-CoV-2 N Protein Triggers Acute Lung Injury via Modulating Macrophage Activation and Infiltration in in vitro and in vivo

Abstract

Background SARS-CoV-2-induced acute lung injury but its nucleocapsid (N) and/or Spike (S) protein involvements in the disease pathology remain elusive. Methods In vitro, the cultured THP-1 macrophages were stimulated with alive SARS-CoV-2 virus at different loading dose, N protein or S protein with/without TICAM2-siRNA, TIRAP-siRNA or MyD88-siRNA. The TICAM2, TIRAP and MyD88 expression in the THP-1 cells after N protein stimulation were determined. In vivo, naïve mice or mice with depletion macrophages were injected with N protein or dead SARS-CoV-2. The macrophages in the lung were analyzed with flow cytometry, and lung sections were stained with H&E or immunohistochemistry. Culture supernatants and serum were harvested for cytokines measurements with cytometric bead array. Results Alive SARS-CoV-2 virus or N protein but not S protein induced high cytokine releases from macrophages in a time or virus loading dependent manner. MyD88 and TIRAP but not TICAM2 were highly involved in macrophage activation triggered by N protein whilst both inhibited with siRNA decreased inflammatory responses. Moreover, N protein and dead SARS-CoV-2 caused systemic inflammation, macrophage accumulation and acute lung injury in mice. Macrophage depletion in mice decreased cytokines in response to N protein. Conclusion SARS-CoV-2 and its N protein but not S protein induced acute lung injury and systemic inflammation, which was closely related to macrophage activation, infiltration and release cytokines.

Successful salvage of a severe COVID-19 patient previously with lung cancer and radiation pneumonitis by mesenchymal stem cells: a case report and literature review

“…Induction of inflammatory cytokines from macrophages by the nucleocapsid (N) protein of SARS-CoV-2 has been proven. N-protein could promote tumor necrosis factor (TNF), interleukin-1 β (IL-1 β ), interleukin-6 (IL-6), and monocyte chemoattractant protein-1 (MCP-1) secretion of macrophages, which was associated with the occurrence of severe COVID-19 ( 45 ). MSCs affect macrophages through contact-dependent interaction, paracrine-mediated mechanisms, autophagy, mitophagy, and oxidative stress ( 46 ).…”

Macrophage Polarizations in the Placenta and Lung are Associated with Bronchopulmonary Dysplasia

“…The connection between macrophage polarization and its influence on developing organ systems, particularly the lungs, is a subject of growing interest. [7][8][9] However, there are no studies linking placental macrophage polarization and lung development. In the context of neonatal outcomes, bronchopulmonary dysplasia (BPD), a common developmental chronic lung disorder affecting premature infants, has been associated with aberrant immune responses, including lung macrophage activation and polarization.…”