Apigetrin inhibits cytotoxicity and dysregulation of ACE2, IL1α and TGFβ expression induced by recombinant spike protein of SARS-CoV-2

Abstract

SARS-CoV-2 virus is a novel coronavirus that was first identified in Wuhan, China in December 2019 and has caused an ongoing global health crisis. It has been a worldwide focus in research to understand viral pathogenesis and discover effective therapies. SARS-CoV-2 belongs to the same genus as the viruses responsible for Severe Acute Respiratory Syndrome (SARS) and the Middle East Respiratory Syndrome (MERS). Spike protein (SP) on SARS-CoV-2 plays a key role in the pathogenesis of SARS-CoV-2. The virus enters human cells via the binding of SP to the angiotensin-converting enzyme 2 (ACE2) on human cells. The binding of SP inhibits ACE2 function by reducing formation of angiotensin-(1-7), a compound that has inhibitory effects on inflammation. In addition, SARS-CoV-2 induces excessive proinflammatory cytokine production through various other signaling pathways such as the NFκB and NLRP3 inflammasome pathways. Previous evidence showed that apigenin (APG), a plant phenolic compound, can bind to SP. However, whether or not apigetrin (APT), the glucoside conjugate of APG, can protect human cells against cell injury caused by SARS-CoV-2 is still unknown. Studies have shown that SARS-CoV-2 induced dysregulation of host cell ACE2 expression is one of the major pathophysiological factors of COVID-19 infection. Our current study demonstrated that recombinant SP significantly reduced ACE2 level in human neuronal cells in a dose dependent manner using ELISA assay. Interestingly, APT reversed the SP induced ACE2 downregulation in these cells. In this study, the effect of SP on cell proliferation and immune regulation was also investigated. Using MTT and LDH assays, I discovered that SP had a cytotoxic effect on these cells and significantly inhibited cell proliferation. This cytotoxic effect was mitigated by adding APT treatment. Furthermore, APT reduced SP induced cytokine production such as IL1α and TGFβ . In sum, my study demonstrated that APT inhibited SARS-CoV-2 SP induced dysregulation of human cells and reduced its cytotoxic effects on cells. APT significantly upregulated ACE2 expression and inhibited the production of cytokines IL1α and TGFβ in the cells treated with SP. My study indicated that APT has potential to be a novel therapy for COVID-19 infection. More experiments to further elucidate molecular mechanisms of how APT modulates pathological effect of SP with different in vitro models including other human cell lines and in vivo animal models are currently being performed.