Resumen de Tempol decreases the levels of reactive oxygen species in human neutrophils and impairs their response to Mycobacterium tuberculosis
Cláudio Daniel Cerdeira, Jorge Kleber Chavasco, Maísa Ribeiro Pereira Lima Brigagão
Background and aims: Mycobacterium tuberculosis (Mtb), the main causative agent of human tuberculosis (TB), remains as a serious public health problem. The innate immune responsefollowing Mtb infection plays a crucial role in preventing the onset of active TB and limiting its spread. Since phagocytes-derived reactive oxygen/nitrogen species (ROS/RNS) during the oxidative burst can fight Mtb, we hypothesized that the use of antioxidants could increase the host’s susceptibility to Mtb/TB. In that way, we investigated the effects of the nitroxide Tempol, an antioxidant with superoxide dismutase-like activity, on the response of neutrophils against Mtb. Methods: Human blood-derived neutrophils were isolated from healthy volunteers and incubated with Mtb (H37Ra) at different multiplicities of infection (MOIs), in the absence or presence of Tempol. The levels of ROS in neutrophils were evaluated using the cytochrome C reduction assay (extracellular O2 •-) and luminol-(total intracellular and extracellular ROS) and isoluminol-(extracellular ROS) amplified chemiluminescence assay. The killing assay (two-step protocol) checked the mycobactericidal capacity of neutro-phils, as calculated the phagocytosis (Kp) and intracellular killing (Kk) rates. Results: The levels of ROS and killing capacity in Mtb-stimulated neutrophils were significantly decreased by 450 µM Tempol (p < 0.05). Interestingly, Tempol decreased the kk of neutrophils, but did not affect their kp, demonstrating that a putative diminution in ROS levels, ultimately, affected the intracellular killing of Mtb. Conclusion: This study provides insights regarding the role of antioxidants on the neutrophil response toward Mtb, so that our findings deserve to be considered regarding further studies and clinical implications.
