TABLE 2.

Comparison of different types of abnormal oxygen metabolism.

Type of abnormal oxygen metabolism	Explanation	Mediators
Hypoxia	Any state of insufficient physiological oxygen or insufficient tissue oxygen demand	Hypoxia-inducible factor (HIF)
Oxidative stress	The imbalance between oxidation and antioxidation and a tendency for increased oxidation	Reactive oxygen species (ROS)
Nitrosative stress	The joint biochemical reaction of nitric oxide (NO) and the free radical superoxide (O2–)	Reactive nitrogen species (RNS)
Carbonyl stress	The joint biochemical reaction of oxidation and glycosylation, increasing the accumulation of reactive carbonyl compounds from unsaturated aldehyde ketone	Advanced glycation end product (AGEs)
Endoplasmic reticulum stress	In order to cope with the accumulation of misfolded and unfolded proteins in the endoplasmic reticulum lumen and the calcium ion imbalance, cells activate signal pathways such as unfolded protein response (UPR) and endoplasmic reticulum overload response	Inositol requiring (IRE) 1α, PKR-like ER kinase (PERK), and activating transcription factor (ATF) 6α
Mitochondrial dysfunction	Mitochondria are the primary source and direct target of ROS. Abnormal respiratory chain function and ATP synthesis disorders are the main characteristics of mitochondrial dysfunction.	Adenosine-triphosphate (ATP)