ACE2-modulating compounds for the treatment of respiratory viral infections

Introduction: ACE2, the SARS-CoV2 receptor, is a member of the renin-angiotensin system (RAS) that hydrolyzes Ang-II to form Ang (1-7) eliciting anti-inflammatory pathways and modulating intracellular redox state. Despite its role in viral entry, the protective role of ACE2 in the pathogenesis of respiratory lung infections, including SARS-CoV and influenza virus, was demonstrated in many in vitro and in vivo studies. Indeed, during respiratory viral infection the down-regulation of ACE2 has been related to the induction of Acute Respiratory Distress Syndrome (ARDS). This evidence suggests that the use of compounds that modulate ACE2 expression could decrease the severity of infection and ameliorate its outcomes. RAS interfering compounds such as Stilbenes has been also reported to impair the replication of several viruses, suggesting that ACE2 modulation could affect viral life-cycle. The aim of this study was to evaluate the effect of Resveratrol (RV) analogue compounds, such as Polydatin (RV glicoside form) and A5+ (Stilbene compounds and Sirtuin-1 activator), on ACE2 modulation and their efficacy against respiratory viral infections. Materials and Methods: ACE2 expressing cell lines were treated with different concentrations of Polydatin and A5+ compounds (ranging from 5 to 30 ?g/ml) for 24hrs, then the cytotoxicity of compounds was evaluated by MTT assay. No cytotoxic concentrations of Polydatin and A5+ were selected to treat cells infected with influenza A PR8/H1N1 virus. After 24hrs ACE2 protein expression was analyzed by Western blot, and viral titer was evaluated by Hemagglutination assay (HAU) and In Cell Western (ICW), through quantification of viral protein expression, nucleoprotein (NP) and hemagglutinin (HA), on infected cell monolayers. Results: We found that both Polydatin and A5+ compounds (used at 20-30 ?g/ml) increased by 30% the expression of ACE2 in mock-infected cells (controls) with respect to untreated controls. In addition, A5+, used at higher concentration (30 ?g/ml) counteracted the PR8-induced decrease of ACE2, up-regulating the protein expression at the levels of mock-infected cells. Moreover, both compounds were able to significantly decrease hemagglutinating activity. A5+, at concentration ranging between 20-30 ?g/ml inhibited by 50% viral infectivity measured in terms of NP and HA expression in infected cells. Discussion and Conclusions: Overall data indicate that stilbene derivatives up-regulate ACE2 expression and inhibit influenza virus replication in host cells. Further studies are needed to clarify the mechanisms underlying the antiviral effect of ACE2 modulators and to explore their potential efficacy against respiratory viruses including SARS-CoV2.