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I
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Excess O2 (oxygen therapy)
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II
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Absorption of radiant energy (ultraviolet light) or ionizing radiation (radiotherapy)
|
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III
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Exposure to toxins: carbon tetrachloride, dioxin, alloxan and streptozotocin to name just a few
|
|
IV
|
Reduction-oxidation (redox) reactions during normal physiologic processes (cellular respiration)
|
| |
A. Respiratory chain enzymes and oxygen
|
| |
B. Xanthine oxidase
|
| |
C. Cytochrome P450 monooxygenase activity
|
| |
D. NAD(P)H / NADH oxidase
|
| |
E. Fenton reaction: Fe++ + H2O2 → Fe+++ + OH + OH-
|
| |
F. Haber-Weiss Reaction H2O2 + O2- → -OH- + O2 +OH-
|
|
V
|
Ischemia – Ischemia reperfusion injury
|
|
VI
|
Inflammatory processes. Acute and chronic
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VII
|
Once free ROS radicals form, they can react with membrane lipids, proteins and nucleic acid to initiate auto-catalytic reactions (ROS beget ROS) [9]
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