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United States Biological

Isoprostane as a Biomarker of Oxidative Stress:
Free RadicalsFree radicals are so reactive and short-lived that direct measurement is usually not possible. However, hundreds of biomarkers are known to be derived from the interaction of free radicals with biomolecules. Isoprostanes are widely recognized as the "Gold Standard" biomarker for oxidative stress and can be quickly quantified using our ELISA kits.  


Isoprostane (8-iso-PGF2a) Serum, Tissue ELISA Kit
This kit is a competitive ELISA for determining levels of 15-isoprostane F2t in biological samples. Briefly, 15-isoprostane F2t in the samples or standards competes with 15-isoprostane F2t conjugated to HRP (HRP) for binding to a polyclonal antibody specific for 15-isoprostane F2t coated on the microplate. The HRP activity results in color development when substrate is added, with the intensity of the color proportional to the amount of 15-isoprostane F2t bound and inversely proportional to the amount of unconjugated 15-isoprostane F2t the samples or standards.The sensitivity of the assay is 0.1ng/ml, and the dynamic range is 0.1-1.0ng/ml.

This month's Special:
Isoprostane (8-iso-PGF2a) Urine ELISA Kit, BioAssay™

I9055 Isoprostanes are prostaglandin-like compounds that areproduced by free radical mediated peroxidation of lipoproteins. This kit is for the quantification of 15-isoprostane F2t (also known as 8-epi-PGF2a or 8-iso-PGF2a) in urine samples. Levels of 15-isoprostane F2t in urine are useful for the non-invasive assessment of oxidant stress in vivo. 15-isoprostane F2t has also been shown to be a potent vasoconstrictor in rat kidneys and rabbit lungs, and plays a causative role in atherogenesis. Elevated isoprostane levels are associated with hepatorenal syndrome, rheumatoid arthritis, atherosclerosis, and carcinogenesis. This kit can be used for the quantification of free 15-isoprostane F2t in urine serum samples without the need for prior purification or extraction.



Oxidative Stress

Oxidative stress is caused by an imbalance between the production of reactive oxygen species (ROS) and a biological system's ability to readily detoxify reactive intermediates or easily repair the resulting damage. Disturbances in the normal redox state of cells can cause toxic effects through the production of peroxides and free radicals that damage all components of the cell, including proteins, lipids and DNA.

In humans, oxidative stress is involved in many diseases, such as, atherosclerosis, Parkinson’s disease, Myocardial Infarction, Alzheimer’s disease and Chronic Fatigue syndrome. Oxidative stress is thought to be linked to certain cardiovascular diseases because oxidation of LDL in the vascular endothelium is a precursor to plaque formation.

Short-term oxidative stress may be beneficial in that ROS can trigger apoptosis and remove damaged cells from an organism. Reactive oxygen species can also be beneficial in the prevention of aging, they are used by the immune system as a way to attack and kill pathogens and ROS are also used in cell signaling processes (redox signaling).

One source of reactive oxygen under normal conditions in humans is the leakage of activated oxygen from mitochondria during oxidative phosphorylation. Other enzymes capable of producing superoxide are xanthine oxidase, NADPH oxidases and Cytochromes P450. Hydrogen peroxide is produced by a wide variety of enzymes including several oxidases. Disturbances in the normal redox state of cells can cause toxic effects through the production of peroxides and free radicals that damage all components of the cell, including DNA, lipids and proteins.

Selected Oxidative Damage Biomarkers

1. DNA damage
In nuclear and mitochondrial DNA, 8-hydroxydeoxyguanosine (8-OHdG), an oxidized nucleoside of DNA, is the most frequently detected and studied DNA breakdown product (1). Upon DNA repair, 8-OHdG is excreted in the urine. Several studies have indicated that urinary 8-OHdG is not only a biomarker of generalized, cellular oxidative stress but might also be a risk factor for cancer, atherosclerosis and diabetes (2-4).

8-OHdG is typically measured in both urine and serum/plasma samples. 8-OHdG is a hydroxyl radical-damaged guanine nucleotide that has been excised from DNA by endonuclease repair enzymes. Since repair is known to normally occur quickly and efficiently, the amount of excised DNA adducts in urine directly reflects the amount of damage within the entire body.

2. Lipid Damage
8-epi-PGF2a (F2-Isoprostane):
Lipid peroxidation refers to the oxidative degradation of lipids. It is the process whereby free radicals take up electrons from the lipids in cell membranes, resulting in cell damage. It most often affects polyunsaturated fatty acids, because they contain multiple double bonds that contain methylene-CH2- groups that possess especially reactive hydrogen groups.

8-epi-PGF2a (F2-Isoprostane) is the free Radical catalyzed non-enzymatic oxidation product of arachidonic acid (5). 
Peroxidation of arachidonic acid occurs in cellular membranes and lipoproteins (i.e. LDL). The damaged lipid peroxide is excised from the cell wall into the serum and then excreted in urine. Unlike the reactive aldehydes, once isoprostanes are formed they are chemically stable and can be accurately measured in urine.

3. Protein Damage
Nitrotyrosine is formed in tissue or blood proteins after exposure to nitrosating and/or nitrating agents. Reactive nitrogen species such as peroxynitrite can nitrate specific amino acids, whether free or protein bound, and nitrotyrosine is believed to be one marker of this reaction (6,7). Nitrotyrosine has been widely studied and has been associated as a biomarker for several inflammatory disorders, such as Alzheimer’s disease, ALS, asthma, atherosclerosis, cardiovascular disease, COPD, coronary artery disease, Crohn’s, cystic fibrosis, diabetes, hypercholesterolemia, lung cancer, lung injury, MS, myocardial inflammation, osteoarthritis and rheumatoid arthritis.

1. Kim H.W., Murakami A., Williams M.V., and Ohigashi H. (2003) Carcinogenesis 24: 235-241.
2. Kowluru R.A., Atasi L., and Ho Y.S. (2006) Invest. Ophthalmol. Vis. Sci. 47: 1594-1599.
3. Bowers R. et al. (2004) Am. J. Respir. Crit. Care Med. 169: 764-769.
4. Cui J., Holmes E.H., Greene T.G., and Liu P.K. (2000) Faseb J. 14: 955-967.
5. Morrow, J.D. et al., (1990) PNAS 87; 9383-9387.
6. Beckman, et al (1993) Nature 364, 584.
7. Ayata, et al (1997) J. Neurosci. 17, 6908-6917.