PRKAA2 and susceptibility to pneumonia measurement: We have two intentions by means of this review: to summarize the contributions of oxidative stress, either pulmonary lesions related ROS accumulation and metabolic/endocrine disorders-related ROS accumulation, to pneumonia susceptibility, and to discuss how AMPK-Nrf2 signaling contributes to maintain the metabolic and endocrine homeostasis that is the fundamental status of the body to resist pulmonary infection, to alleviate pulmonary lesions, and to prevent pneumonia.