Nitro-oxidative stress induced by Environmental Contaminants in human cells

Nitrosative stress (NS) is a condition determined by increased concentration of radical nitrogen species (RNS), among which nitric oxide (NO), a second messenger with physiological regulatory role and modulator of mitochondrial function. In cells, nitrosative stress is often part of a wider alteration of redox homeostasis that includes oxidative stress (OS), featured by a rise in reactive oxygen species (ROS) and low antioxidant defense. Under nitro-oxidative stress, accumulation of macro-molecule damages lead to impairment of cell processes and favors, on a wider scale, inflammation induction. Environmental contaminants (EC) are responsible for detrimental effects due to their high diffusion and bioaccumulation in animal cells and tissues. Imidacloprid (IMI) is a neonicotinoid insecticide widely utilized in the treatments of crops. As for other ECs, IMI was proposed to exert endocrine disruption (ED) activity and damage mitochondria through dysregulation of ROS/RNS. Our research is aimed at investigating the nitro-oxidative stress induced by ECs, particularly IMI, in cell models for xenobiotics response. We treated Hepatocytes 24 h with different concentration of IMI and evaluated the alterations of the NO-signalling axis by following the expression of the NO-synthases enzymes by real time PCR and immunoblot. The nitration of tyrosine residues(3-NT) was also quantified by ELISA assay as a specific marker of NS. To assess the OS level, the signal of ROS-targeting fluorophores was monitored and the mRNA/protein expression of SOD2 was evaluated; furthermore, the mitochondrial membrane potential was measured to assess the detrimental effect of the ECs on mitochondrial function. Our results indicate IMI to play a role in the induction of nitro-oxidative stress in hepatocytes; effect strengthened by the association with other ECs. These findings may suggest the exposure to ECs as a favoring factor for pathological states, such as neuro-inflammatory, autoimmune or cancerous, whose incidence is steadily growing