Advertisement
 

doctorslounge.com

 
Powered by
Careerbuilder

 

                    Home  |  Forums  |  Humor  |  Advertising  |  Contact
   Ask a Doctor

   News via RSS

   Newsletter

   Oncology

   News

 

 Conferences


   CME

   Forum Archives

   Diseases

   Symptoms

   Labs

   Procedures

   Drugs

   Links
   Specialties

   Cardiology

   Dermatology

   Endocrinology

   Fertility

   Gastroenterology

   Gynecology

   Hematology

   Infections

   Nephrology

   Neurology

   Oncology

   Orthopedics

   Pediatrics

   Pharmacy

   Primary Care

   Psychiatry

   Pulmonology

   Rheumatology

   Surgery

   Urology

   Other Sections

   Membership

   Research Tools

   Medical Tutorials

   Medical Software

 

 Headlines:

 
 

Back to table of contents

Sunday June 16, 2002 10:25 PM GMT

free%20radicals.gif (200x200 -- 0 bytes)

 

Active oxygen species have long been known to be mutagenic, hence playing a role in cancer formation.

 
 

tellfrnd.gif (30x26 -- 1330 bytes)send to a friend
 
prntfrnd.gif (30x26 -- 1309 bytes)printer friendly version
 
 
 
 
  Related
 
 

Free Radicals; Types & Dangers
Antioxidants, classification and chemistry

 
   
 
     

The role of reactive oxygen species in DNA damage:

DNA base oxidation is a continuous process. Chromatin may offer some protection against oxidative DNA damage and specific repair processes may prevent or correct oxidative mutations. However, oxidants from both endogenous and exogenous sources can overwhelm these defences and mutagenesis can and does occur. Severe or prolonged exposure to oxidative stress can elicit all stages of carcinogenesis (Guyton and Kensler, 1993).

ROS involved in DNA damage:

It is now widely held that the mutagenic capacity of free radicals is due to the direct interaction of hydroxyl radicals (?OH) with DNA. Hydroxyl radicals have been detected by electron paramagnetic spectroscopy under conditions of active oxygen induced DNA damage. Hydrogen peroxide and superoxide do not directly interact with DNA to produce oxidative lesions in-vitro (Breimer, 1990). However, on interaction of these free radicals with transition metals the hydroxyl radical is produced which is responsible for DNA damage. In vitro both copper and iron can produce DNA damage by reactive oxygen species. Additional evidence is provided by the fact that metal chelators that block the elaboration of hydroxyl radicals can inhibit DNA damage, mutations, and malignant transformation induced by active oxygen species in cell-free and in cellular systems, as can agents that detoxify the hydroxyl radical or its precursors (Aruoma et al. 1989).

An unstable radical like the hydroxyl radical will react indiscriminately with all components of the DNA molecule. Hence, the hydroxyl radical causes DNA damage by direct interaction in the generation of many of its genetic lesions. However, it can also cause DNA damage by other methods e.g. stimulating the rise of calcium intracellularly which in turn stimulates endonucleases to cause strand breaks and degradation products from the DNA molecule.

advertisement.gif (61x7 -- 0 bytes)
 

Are you a doctor or a nurse?

Do you want to join the Doctors Lounge online medical community?

Participate in editorial activities (publish, peer review, edit) and give a helping hand to the largest online community of patients.

Click on the link below to see the requirements:

Doctors Lounge Membership Application


Types of DNA damage produced by ROS:

The forms of DNA damage produced by ROS experimentally include the following:

  1. Modification of all bases.

  2. Production of base free sites.

  3. Deletions.

  4. Frameshifts.

  5. Strand breaks.

  6. DNA-protein cross-links.

  7. Chromosomal rearrangements.

(Halliwell et al. 1991)

 

 image005.gif (14951 bytes)


Fig. 3: The role of oxidants in multistage carcinogenesis (Harris 1989). 

Article reviewed by:

Dr. Tamer Fouad, M.D.

 

 advertisement.gif (61x7 -- 0 bytes)

 

 



We subscribe to the HONcode principles of the HON Foundation. Click to verify.
We subscribe to the HONcode principles. Verify here

Privacy Statement | Terms & Conditions | Editorial Board | About us
Copyright 2001-2012 DoctorsLounge. All rights reserved.