Figure 2.

Hierarchical oxidative stress model in response to air pollutants. Low ROS production (Step I) induces activation of cellular antioxidant systems to restore redox homeostasis. If this protection is insufficient, the increased stress (Step II) triggers an inflammatory response through MAPK and NFκB pathways. At a final stage (Step III), all the defense systems are overwhelmed and high ROS levels lead to PTP opening and cell death by apoptosis. These responses depend on the pro/antioxidant balance which varies from one living being to another (adapted from [180]).