Metformin Suppresses Monocyte Immunometabolic Activation by SARS-CoV-2 and Spike Protein Subunit 1

Abstract

A hallmark of COVID-19 is a hyperinflammatory state that is associated with severity. Various anti-inflammatory therapeutics have shown mixed efficacy in treating COVID-19, and the mechanisms by which hyperinflammation occurs are not well understood. Previous research indicated that monocytes, a key innate immune cell, undergo metabolic reprogramming and produce inflammatory cytokines when stimulated with SARS-CoV-2. We hypothesized that binding by the viral spike protein mediates this effect, and that drugs which regulate immunometabolism could inhibit the inflammatory response in monocytes. Monocytes stimulated with recombinant SARS-CoV-2 spike protein subunit 1 showed a dose-dependent increase in glycolytic metabolism that was associated with production of pro-inflammatory cytokines including interleukin-6 and tumor necrosis factor-α. This response was dependent on hypoxia-inducible factor-1α, as chetomin inhibited glycolysis and cytokine production. Inhibition of glycolytic metabolism by 2-deoxyglucose (2-DG) or glucose deprivation also inhibited the glycolytic response, and 2-DG strongly suppressed cytokine production. Glucose-deprived monocytes rescued cytokine production by upregulating oxidative phosphorylation, an effect which was not present in 2-DG-treated monocytes due to the known effect of 2-DG on suppressing mitochondrial metabolism. Finally, pre-treatment of monocytes with metformin strongly suppressed spike protein-mediated cytokine production in monocytes, and abrogated glycolytic and mitochondrial metabolism. Likewise, metformin pre-treatment blocked cytokine induction by SARS-CoV-2 strain WA1/2020 in direct infection experiments in monocytes. In summary, the SARS-CoV-2 spike protein induces a pro-inflammatory immunometabolic response in monocytes that can be suppressed by metformin, and metformin likewise suppresses inflammatory responses to live SARS-CoV-2. This has potential implications for the treatment of hyperinflammation during COVID-19.

COVID‐19 immunopathology: From acute diseases to chronic sequelae

“…Metformin injection in SARS‐CoV‐2 infected hACE2 transgenic mice improved the morbidity and rescued the mice from ARDS 258 . In an in vitro setting, it was also demonstrated that metformin results in the rescue of monocytes from inflammation 255 …”

“…258 In an in vitro setting, it was also demonstrated that metformin results in the rescue of monocytes from inflammation. 255 However, in clinical trials, metformin showed uncertainty. In a retrospective cohort analysis, the use of metformin was not associated with a reduced risk of mortality in total samples of both men and women from COVID-19.…”

“…SARS‐CoV‐2 infection is also known to alter the metabolic profile of infected monocytes, 119 which is mediated by its spike protein, 255 leading to HIF‐1α‐dependent enhanced inflammation 119,255 . Metformin is an antidiabetic drug that has been suggested as a repurposed drug for COVID‐19 due to its anti‐inflammatory property 256 .…”

“…SARS-CoV-2 infection is also known to alter the metabolic profile of infected monocytes, 119 which is mediated by its spike protein, 255 leading to HIF-1α-dependent enhanced inflammation. 119,255 Metformin is an antidiabetic drug that has been suggested as a repurposed drug for COVID-19 due to its anti-inflammatory property. 256 In addition to its anti-inflammatory property, metformin is known to phosphorylate the entry receptor for SARS-CoV-2, the ACE2, suggesting its possible role in blocking the entry of SARS-CoV-2.…”

Metformin Suppresses Monocyte Immunometabolic Activation by SARS-CoV-2 Spike Protein Subunit 1

“…All raw data and analytical scripts (as R markdown files) are available in a dedicated FigShare repository ( 49 ). This manuscript was posted to the preprint server bioRxiv prior to submission for publication ( 52 ).…”