Table 2.

Role of non-immune soluble mediators in COVID-19 infection

Soluble mediator	Biological role in COVID-19 infection	Output effect	References
sFlt-1	Excess level of sFlt-1 induce endothelial dysfunction and is associated with bacterial sepsis Increase in SARS-CoV-2 infection and is correlated with disease severity, endothelial dysfunction and respiratory failure	Adverse effect	[64–69]
sACE2	Increase in viral infections like SARS-CoV-2 Interact with spike of SARS-CoV-2 and facilitate viral intery to the host Increased sACE2 has correlation with inflammatory response and endothelial dysfunction	Controversial	[70, 72, 73]
sRAGE	Is associated with inflammatory diseases, bacterial infection, and lung damage Diagnosis factor for ARDS	Adverse effect	[76–78]
suPAR	Is involved in plasminogen activation pathway, regulation of cell adhesion, and proliferation and migration by interacting with extracellular matrix proteins Increased in infection and inflammatory conditions like arthritis, HIV infection Cause immune response activation Level of suPAR has positive correlation with severity and mortality of HIV and SARS-CoV-2	Adverse effect	[86–89]

sFlt-1, soluble fms-like tyrosine kinase-1; sACE2, soluble angiotensin-converting enzyme 2; sRAGE, soluble receptor for advanced glycation end products; suPAR, soluble urokinase-type plasminogen activator receptor; HIV, human immune-deficiency virus; ARDS, acute respiratory distress syndrome