An aberrant STAT pathway is central to COVID-19

Area of Science:

• Immunology
• Virology
• Pathophysiology

Background:

• COVID-19, caused by SARS-CoV-2, presents diverse symptoms, with severe cases marked by impaired Type I interferon (IFN-I) production, acute respiratory distress syndrome (ARDS), and coagulopathy.
• The pathophysiology of severe COVID-19 involves viral proteins disrupting host cell signaling pathways, notably affecting signal transducer and activator of transcription (STAT) proteins.

Purpose of the Study:

• To elucidate the molecular mechanisms driving COVID-19 pathophysiology, focusing on the roles of SARS-CoV-2 NSP1 and ORF6 proteins.
• To identify key signaling pathways, particularly the STAT3/PAI-1 axis, involved in COVID-19 pathogenesis.
• To propose therapeutic strategies targeting these pathways for COVID-19 treatment.

Main Methods:

• Analysis of SARS-CoV-2 gene products (NSP1, ORF6) and their impact on host cell signaling.
• Investigation of the interplay between STAT1, STAT3, and plasminogen activator inhibitor-1 (PAI-1) in infected cells.
• Correlation of molecular findings with clinical observations, including autopsy findings (DAD, HA) and risk factors (hypertension, obesity, diabetes, age).

Main Results:

• SARS-CoV-2 NSP1 and ORF6 proteins induce STAT1 dysfunction and STAT3 hyperactivation.
• A positive feedback loop between STAT3 and PAI-1 is established, leading to PAI-1 upregulation, coagulopathy, and intravascular thrombi.
• PAI-1 upregulation promotes inflammation via TLR4, drives lung tissue destruction, and is exacerbated by hypoxia and EGFR activation.
• Diffuse alveolar damage (DAD) and increased hyaluronan (HA) production observed in COVID-19 patients are linked to elevated PAI-1 levels.
• COVID-19 risk factors (hypertension, obesity, diabetes, age) are associated with increased PAI-1 levels.

Conclusions:

• The STAT3/PAI-1 positive feedback loop is central to COVID-19 pathophysiology, driving coagulopathy and lung injury.
• Therapeutic strategies aimed at enhancing STAT1 activity and/or inhibiting STAT3 function hold promise for treating COVID-19.
• Targeting this viral-induced signaling cascade could mitigate the severe manifestations of COVID-19.