In silico identification of small molecules engaging the TNFR2-TNF-α interaction: a novel approach for targeting demyelinating diseases

Tumor necrosis factor alpha (TNF-α) is a cytokine secreted by macrophages, involved in immune and proinflammatory responses, cellular proliferation and differentiation. TNF-α exists in two isoforms: a soluble one, that participates to pathological mechanisms of demyelinating and neurodegenerative diseases preferably via TNF receptor 1 (TNFR1), and a transmembrane form, which can mediate neurorepair and remyelination via TNFR2. Due to the protective role of TNFR2 in central nervous system (CNS), our aim was to identify ligands able to selectively enhance TNFR2::TNF-α engagement for promoting its reparative effects. First, we characterized in silico the differences between TNFR1 and TNFR2 structures. We found that the interaction surfaces of both receptors show opposite electrostatic potential surfaces, suggesting that the selective engagement of the two TNF-α isoforms to TNFR1 or TNFR2 may depend on these electrostatic differences. Then, we tested a large library of commercially available drug-like compounds against the TNFR2::TNF-α complex, through virtual high-throughput screening. We identified 20 compounds with high affinity for the complex. Moreover, each TNFR2::TNF-α complex in association with the investigated ligands showed a G binding free energy gain with respect to the complex alone, suggesting that all the 20 compounds may enhance the affinity of TNF-α for TNFR2. Finally, to assess if these compounds could be efficiently delivered to the brain, their ability to target CNS was predicted in silico by computing significant pharmacokinetic descriptors. Five out of the 20 selected compounds were characterized by a potential CNS activity. To date, all the available approaches targeting the TNFR1/2: TNF-α axis for promoting TNFR2 neuroprotection are based on biotechnological drugs. On this basis, our data pave the way for the development of a new therapeutic strategy for demyelinating diseases based on TNFR2 engagement by small molecules with drug-like properties.