damage caused by reactive oxygen species formation of ros functions of ros oxidation and signal transduction

1. Functions of ROS
under Drought
University ofAgriculturalSciences,Dharwad
CollegeofAgriculture, Vijayapur
Submitted to
Dr. Kiran B O
Dept. Of Crop Physiology
College of Agriculture, Vijayapur
Submitted by
Brahmesh Reddy B R
Id No. 8073 III Yr A sec
College of Agriculture, Vijayapur

2. What actually is an ROS?
 that participate in the initiation and/or
 propagation of chain reaction. ROS : is a collective term
that includes all reactive forms of oxygen, including
 both radical and non radical species

3. In Shorts...
 Reactive oxygen species are chemically reactive molecules
that contain oxygen.
 Superoxide, hydroxyl radical, hydroxyl ion
 m o s t reactive oxygen species are highly reactive due
to thepresence of unpaired valence shell electrons.
 Reactive oxygen species form as a natural byproduct of the
normal metabolism of oxygen and have important roles in
cell signaling and homeostasis.

4. ROS formation in cells
 These are formed as normal aerobic processes that occur
in the body; some as necessary intermediates of enzymatic
reactions.
 Most are produced in the ETC when oxygen is reduced to
water in the mitochondria.
o2
•Molecular
oxygen
•reduction
H2O
•Water

5.  During this conversion various reactive oxygen species are
formed!
 ē ē ē ē
 O2 O2- H202 OH- H20
Molecular super oxide hydrogen peroxide hydroxide water
oxygen

6. Site of synthesis and Affecting
sites

7. Why are ROS important?
 Reactive oxygen's serve to some capacity as signalling
molecules in cells.
 These molecules usually activate transcription factors that
produce different proteins in the body
 And many more

8. ROS and Signal Transduction
ROS are important mediators in signal transduction
 Receptor + hormone
(upstream signalling)
Receptor-ligand complex
 Intracellular ROS production
(downstream signalling)
Other pathways
 promote regions of intermediate response genes
governing cell proliferation & differentiation

9. Oxidants and signal transduction
 Oxidants modulate cell signaling events bymodifying cell
surface receptors, phosphatases and protein
phosphorylation, etc.
 These phenomena are important in transactivation of
transcription factors
 activation/inactivation of gene transcription that may
regulate steps in the development of disease.

10. ROS and Signal Transduction
 ROS are not only injurious by-products of cellular
metabolism but also essential participants in cell signaling
and regulation
 The cellular functions/toxic properties of ROS is dependent
on their concentration.
 For e.g. when produced in low concentrations by nitric
oxide synthase(NOS) NO· functions as a signaling molecule
mediating vasodilation.
 While when produced in high concentrations in
macrophages, it is a toxic oxidant for microbicidal killing

11. ROS damage
 The problem is when ROS is produced in excess and can
oxidize membranes and DNA leading to aging and other
biological damage
 Superoxide is created from the electron transfer but it is
not able to pass through the membrane of the
mitochondria.

12. Harmful activities of ROS
1.Damage to a number of macromolecules such as
lipids, proteins and DNA caused by ROS implicate
them in many disease processes, ranging from
arthritis, atherosclerosis, pulmonary fibrosis,
cancer, neurodegenerative diseases, and aging
2.Toxic effects such as damage to cell membranes
initiated by lipid peroxidation.
3.A common target for peroxidation is unsaturated
fatty acids present in membrane phospholipids

13. References
1)Robinson, K.M. et al. Selective fluorescent imaging of
superoxide in vivo using ethidium-based probes. Proc. Natl.
Acad. Sci. USA 103, 15038–15043 (2006).
2) Murphy, M.P. How mitochondria produce reactive
oxygen species. Biochem. J. 417, 1–13 (2009).
3) Ray G, Husain SA. Oxidants, antioxidants and
carcinogenesis. Indian J Exp Biol 2002;40:1213–32