HNO and mycobacteria: A new ally to fight tuberculosis

MARIANA PIURI; JORDANA GALIZIA; MARIANO PRADO ACOSTA; MARCELO A. MARTÍ

Buenos Aires

Congreso; 2018 International Congress on Infectious Diseases (ICID); 2018

International Society for Infectious Diseases

Nitroxyl (HNO) is a highly elusive and reactive molecule whose biological effects and pharmacological potential are becoming increasingly relevant. Due to its intrinsic instability, to study nitroxyl we must rely on the use of donors that spontaneously release HNO. M. tuberculosis (TB) infection is one of the world?s largest health problems. TB treatment involves a long regime with several drugs and is increasingly hampered by the emergence of MDR and XDR strains. That?s why there is an urgent need for new and more efficient antitubercular drugs. Reactive Nitrogen and Oxygen Species (RNOS) are key compounds used by the immune system to fight intracellular infections, particularly M. tuberculosis. In this context, we sought to analyze nitroxyl potential to kill mycobacteria.We evaluated the viability and biological response of mycobacteria towards HNO releasing compounds. For this, we followed M. smegmatis growth curves with increasing concentrations of HNO donors in order to determine their minimum inhibitory concentrations (MICs). Later we analyzed if HNO interacts with commonly frontline drugs used in TB treatment so we repeated the growth curves in the presence of combined addition of HNO and anti-TB antibiotics. To evaluate HNO?s effect in M. tuberculosis, we used a fluoromycobacteriophage based WCS (whole cell screening) assay developed by our group. Our results show that HNO donors exhibit a mycobactericidal effect, for both M. smegmatis and M. tuberculosis. The effect can be observed using a single dose or with successive additions of lower concentrations of the donor, mimicking continuous HNO exposure. When analyzing the effect of the simultaneous addition of sub-inhibitory concentrations of nitroxyl with antibiotics commonly used for M. tuberculosis infection treatment we observed two types of effects: a positive interaction for Rifampicin, Kanamycin and Delamanid; and a negative interaction for Isoniazid and Ethambutol. Regarding a possible mechanism of action, based on the recently developed fluoromycobacteriophage assay, we propose that HNO acts by interfering with general mycobacterial physiological state. Taken all together, the results of this work positions HNO donors as potential candidates as new drugs for a new tuberculosis treatment.