The controversy about antibiotic lethality and reactive oxygen species

by José Freire da Silva Neto

Antibiotics are powerful compounds in our battle against bacterial diseases. Despite their miraculous efficacy over decades, nowadays we are faced with the global spreading of antibiotic resistance and the decrease of our antibiotic arsenal. For many years, we learned that antibiotics exert their effect by direct interaction with different primary bacterial targets, causing killing (bactericidal drugs) or growth inhibition (bacteriostatic drugs). In 2007, an influential paper from the Collins laboratory [1] placed reactive oxygen species (ROS) as central players in the mechanism of cell death induced by bactericidal antibiotics. Ever since


Superoxide and nitric oxide induced nitrosative processes may follow unusual and different dynamic behaviors

by José Carlos Toledo

Possibly, most pathophysiological processes involving the radicals nitric oxide (NO•) and superoxide (O₂•–) depend on their simultaneous production and their favorable co-reaction to produce peroxynitrite. Peroxynitrite is an oxidant itself but in the presence of carbon dioxide it gives origin to radical species such as carbonate anion (CO₃•–) and nitrogen dioxide (NO₂•) radicals, both capable of stimulating oxidative and nitrosative events that damage biomolecules. The interplay of NO• and O₂•– in biological environments is complex, though. Using a fluorescent probe molecule to