The nucleoprotein (NP) of influenza A virus (IAV) required for IAV replication is a promising target for new antivirals. We previously identified by in silico screening naproxen being a dual inhibitor of NP and cyclooxygenase COX2, thus combining antiviral and anti-inflammatory effects. However, the recently shown strong COX2 antiviral potential makes COX2 inhibition undesirable. Here we designed and synthesized two new series of naproxen analogues called derivatives 2, 3, and 4 targeting highly conserved residues of the RNA binding groove, stabilizing NP monomer without inhibiting COX2. Derivative 2 presented improved antiviral effects in infected cells compared to that of naproxen and afforded a total protection of mice against a lethal viral challenge. Derivative 4 also protected infected cells challenged with circulating 2009-pandemic and oseltamivir-resistant H1N1 virus. This improved antiviral effect likely results from derivatives 2 and 4 inhibiting NP-RNA and NP-polymerase acidic subunit PA N-terminal interactions.

Ascorbic acid (AA) is the active component of vitamin C and antioxidant activity was long considered to be the primary molecular mechanism underlying the physiological actions of AA. We recently demonstrated that AA is a competitive inhibitor of adenylate cyclase, acting as a global regulator of intracellular cyclic adenosine monophosphate (cAMP) levels. Our study, therefore, aimed to determine new targets of AA that would account for its potential effect on signal transduction, particularly during cell differentiation. We demonstrated that AA is an inhibitor of pre-adipocyte cell line differentiation, with a dose-dependent effect. Additionally, we describe the impact of AA on the expression of genes involved in adipogenesis and/or the adipocyte phenotype. Moreover, our data suggest that treatment with AA partially reverses lipid accumulation in mature adipocytes. These properties likely reflect the function of AA as a global regulator of the cAMP pool, since an analog of AA without any antioxidant properties elicited the same effect. Additionally, we demonstrated that AA inhibits adipogenesis in OP9 mesenchymal cell line and drives the differentiation of this line toward osteogenesis. Finally, our data suggest that the intracellular transporter SVCT2 is involved in these processes and may act as a receptor for AA.