Induction of oxidative stress and apoptosis in human neutrophils by p-phenylenediamine

Exposure to paraphenylenediamine (PPD), a derivative of paranitroaniline widely used as an oxidisable hair dye, is often associated with the development of allergic contact dermatitis. Such reactions involve activation of the subject’s immune system and it is known that neutrophils are the first cells to arrive at the site of perturbation. In view of its pivotal role in the initiation and amplification of inflammation, the fate of the neutrophil in presence of PPD requires attention. Thus, the purpose of the present study was to evaluate the vitro effects of PPD on human neutrophils viability and on reactive oxygen species production. Neutrophils from healthy volunteers were incubated with three concentrations of PPD (11.5, 23 and 46 µM). Apoptosis was evaluated by light microscopy and DNA gel electrophoresis, and oxidative stress was evaluated by spectrophotometry. Results showed that PPD induces neutrophils apoptosis in a dose and time dependent manner with a LC50 value of 23 µM at 6 h of treatment. Furthermore, at 5 h of treatment, PPD markedly increased lipid peroxidation (47%) and enhanced the activity of catalase, glutathione reductase and superoxide dismutase. These results suggest that PPD can induce neutrophils apoptosis and an oxidative stress.   Key words: Paraphenylenediamine, neutrophils, apoptosis, oxidative stress, catalase, lipid peroxidation, glutathione reductase, superoxide dismutase.