NAD+ metabolism is a key modulator of bacterial respiratory epithelial infections.

Lower respiratory tract infections caused by Streptococcus pneumoniae (Spn) are a leading cause of death globally. Here we investigate the bronchial epithelial cellular response to Spn infection on a transcriptomic, proteomic and metabolic level. We found the NAD+ salvage pathway to be dysregulated upon infection in a cell line model, primary human lung tissue and in vivo in rodents, leading to a reduced production of NAD+. Knockdown of NAD+ salvage enzymes (NAMPT, NMNAT1) increased bacterial replication. NAD+ treatment of Spn inhibited its growth while growth of other respiratory pathogens improved. Boosting NAD+ production increased NAD+ levels in immortalized and primary cells and decreased bacterial replication upon infection. NAD+ treatment of Spn dysregulated the bacterial metabolism and reduced intrabacterial ATP. Enhancing the bacterial ATP metabolism abolished the antibacterial effect of NAD+. Thus, we identified the NAD+ salvage pathway as an antibacterial pathway in Spn infections, predicting an antibacterial mechanism of NAD+.

Fragment-based Design of Zwitterionic, Strong Cation- and Weak Anion-Exchange Type Mixed-mode Liquid Chromatography Ligands and their Chromatographic Exploration.

The role of individual functional groups has been assessed with regard to surface charge and chromatographic retention. Coatings were prepared from various fragments of the chiral zwitterionic materials Chiralpak ZWIX(+) and ZWIX(-). The different chromatographic ligands allowed fine tuning of the surface charge. Chiralpak ZWIX phases showed strongly negative ζ-potentials over the entire pH-range. Zwitterionic congeners with quinuclidine and sulfonic acid moieties but lacking the quinolone ring in the ligand structure exhibited shifted ζ-potentials of around + 5 to 20 mV depending on the surrounding residues. Capillary electrophoretic mobilitiy measurements with the chromatographic ligands and molecular dynamics simulations were carried out to offer some explanation of these surface charge differences of the distinct zwitterionic stationary phases. The new mixed-mode phases were also chromatographically characterized by simple RP and HILIC tests. The results allowed their positioning within a large variety of different commercially available RP, HILIC and mixed-mode phases, which were evaluated as well, by multivariate data processing using principal component analysis. The new mixed-mode phases overall exhibit reasonable hydrophilicity-lipophilicity balance and enable retention of ionic compounds by additional ionic interactions through weak anion-exchange (WAX-type), strong cation-exchange (SCX-type) or both (RP/ZWIX-type). Hence, the new RP/ZWIX phases can be flexible tools for selectivity tuning in RP and HILIC separations.