Reactive Oxygen - Neuropedia

Reactive Oxygen

Reactive oxygen species (ROS) are unstable molecules that contain oxygen and react easily with other molecules in a cell. A type of free radical, they’re also referred to as oxygen radicals, reactive oxygen intermediates, and reactive oxygen metabolites. Reactive oxygen species are produced during cellular metabolic respiration, and are perpetuated in response to pollution, heavy metals, inflammation, and bacterial infection.[1]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3155788/#:~:text=As%20a%20matter%20of%20fact,reactive%20oxygen%20species%20(ROS)[2]https://pubmed.ncbi.nlm.nih.gov/11895129/ A buildup of ROS can damage DNA, RNA, proteins, and cause cell death. 

Some examples of receive oxygen species include: 

  • Ozone (O3)
  • Hydrogen peroxide (H2O2)
  • Singlet oxygen (1O2)
  • Lipid hydroperoxide (LOOH)
  • Hypochlorous acid (HOCl)
  • Hydroxyl radical (OH▪)
  • Peroxyl radical (LOO▪)
  • Alkoxyl radical (LO▪)
  • Superoxide (O2▪−)
  • Peroxynitrite (ONOO−)[3]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5921829/

Functions of Reactive Oxygen Species

Reactive oxygen species perform important functions in the body. They signal cells to mount an inflammatory response to pathogens. They also influence autophagy, the process of clearing out damaged or dysfunctional cells.[4]https://www.ahajournals.org/doi/10.1161/CIRCRESAHA.117.311401 

However, higher levels of ROS in relation to free-radical fighting antioxidants can trigger oxidative stress and cell damage.[5]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3454471/ This cell damage is believed to play a role in the development of diseases, including:

  • Cancer[6]https://pubmed.ncbi.nlm.nih.gov/19478820/
  • High blood pressure[7]https://pubmed.ncbi.nlm.nih.gov/16765337/
  • Neurodegenerative diseases like Parkinson’s and Alzheimer’s[8]https://pubmed.ncbi.nlm.nih.gov/21941533/ 
  • Asthma[9]https://www.nature.com/articles/pr2009174
  • Retinopathy[10]https://www.nature.com/articles/pr2009174

According to studies in rodents, reactive oxygen species also appear to play a role in the proliferation of tumors.[11]https://pubmed.ncbi.nlm.nih.gov/18388260/ They have also been studied for their negative impact on male fertility.[12]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3911811/   

Reactive Oxygen Species vs. Free Radicals

Reactive oxygen species and free radicals are often referred to as the same thing, but a few differentiating factors exist.[13]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4310837/ 

  • Reactive oxygen species are a type of free radical.
  • Reactive oxygen species are formed during cellular metabolic respiration and always involve oxygen, while not all free radicals involve oxygen.
  • Free radicals are characterized by an uneven number of electrons, while not all reactive oxygen species have unpaired electrons.

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