led209 and Salmonella-Infections--Animal

QseC is a membrane-bound histidine sensor kinase found in Gram-negative pathogens and is involved in the regulation of bacterial virulence. LED209, a QseC-specific inhibitor, significantly inhibits the virulence of several pathogens and partially protects infected mice from death by blocking QseC. However, the mechanism of its antibacterial effects remains unclear. In this experiment, a Salmonella Typhimurium (S. Typhimurium) and macrophage co-culture system was utilized to investigate possible mechanisms underlying the antimicrobial effects of the QseC inhibitor. QseC blockade inhibited the expression of QseC-dependent virulence genes, including flhDC, sifA, and sopB, in S. Typhimurium, leading to inhibition of swimming motility, invasion capacity, and replication capacity of the pathogens. Release of lactate dehydrogenase (LDH) from S. Typhimurium-infected macrophages was significantly inhibited by blocking QseC. Activated caspase-1 and IL-1β levels were suppressed, and intracellular bacterial count was reduced in infected macrophages. QseC blockade effectively reduced the virulence of S. Typhimurium, inhibited S. Typhimurium-induced pyroptosis of macrophages, and promoted elimination of intracellular bacteria from infected macrophages. Thus, the antibacterial effects of QseC inhibitor are mediated via enhancement of intracellular killing of S. Typhimurium in macrophages.

Topics: Animals; Anti-Bacterial Agents; Bacterial Proteins; Caspase 1; Gene Expression Regulation, Bacterial; Glycoproteins; HeLa Cells; Host-Pathogen Interactions; Humans; Interleukin-1beta; L-Lactate Dehydrogenase; Macrophages; Male; Mice; Mice, Inbred BALB C; Primary Cell Culture; Pyroptosis; Quorum Sensing; Salmonella Infections, Animal; Salmonella typhimurium; Signal Transduction; Sulfonamides; Trans-Activators

Many bacterial pathogens rely on a conserved membrane histidine sensor kinase, QseC, to respond to host adrenergic signaling molecules and bacterial signals in order to promote the expression of virulence factors. Using a high-throughput screen, we identified a small molecule, LED209, that inhibits the binding of signals to QseC, preventing its autophosphorylation and consequently inhibiting QseC-mediated activation of virulence gene expression. LED209 is not toxic and does not inhibit pathogen growth; however, this compound markedly inhibits the virulence of several pathogens in vitro and in vivo in animals. Inhibition of signaling offers a strategy for the development of broad-spectrum antimicrobial drugs.

Topics: Animals; Anti-Bacterial Agents; Enterohemorrhagic Escherichia coli; Escherichia coli Infections; Escherichia coli Proteins; Francisella tularensis; Gene Expression Regulation, Bacterial; Gram-Negative Bacterial Infections; Histidine Kinase; Mice; Norepinephrine; Phosphorylation; Protein Kinases; Rabbits; Salmonella Infections, Animal; Salmonella typhimurium; Signal Transduction; Small Molecule Libraries; Sulfonamides; Tularemia; Virulence Factors