CLASS SEMINAR

DEPARTMENT OF BIOTECHNOLOGY

RADIATION BIOLOGY

TOPIC : RADIOPROTECTOR & RADATION HORMESIS

PRESENTATION BYGOPI KRISHNA GIRI

RADIOPROTECTORRadio protector is the compound that are

designed to reduce damage in the normal tissue cause by radiation.

Radiotherapy is used in cancer treatment.

Ionizing radiation produces free radicals in the cell that induce damage to the DNA and lead to side effects and or secondary tumors.

What Comes Under Radio protectorChemical Radio protector: Agents delivered

prior or at the time of irradiation with the intent of preventing or reducing damage to normal tissues.

Mitigators : Agents delivered at the time or after irradiation is complete but prior to the manifestation of normal tissue toxicity.

Treatments : Agents delivered to ameliorate established normal tissue toxicity.

RADIOPROTECTOR COMPOUNDS Radio protective compounds are aminothiols,

aminodisulphides, tiourei derivatives, thiosulphur and thiophosphoric acid, dithiocarbamates, thiazole, some biogen amines and their derivatives .

Among the large number of tested compounds, the most examined were cisteamine derivatives, i.e. compounds known as aminothiol radioprotectors .

These radioprotectors synthesize in a form of ester with phosphor acid for achieving better stability, lower toxicity and for better penetration and distribution into the tissue.

How do Radio Protectors work ?Radio protective activity is accomplished

through different mechanisms on three special levels of cell organization.

1. Molecular level: cleansing of free radicals donation of H-atom bounding to critical biological targets forming mixed disulphide formations

How do Radio Protectors work ?2. Physiological-biochemical level: hypoxsy loosening unproteined disulphidebiochemical stroke Hypothermia.3.Organic level:stimulating reparation of cells

RADIATION HORMESIS Radiation hormesis ( radiation

homeostasis) is the hypothesis that low doses of ionizing radiation are beneficial, stimulating the activation of repair mechanisms that protect against disease, that are not activated in absence of ionizing radiation.

MECHANISM OF RADIATION HOMESIS

DNA repair (Molecular level): 

According to this theory, low doses of ionizing radiation induce the production of special proteins, that are involved in DNA repair processes .

MECHANISM OF RADIATION HOMESIS

Free radical detoxification (Molecular level)  Low doses of ionizing radiation cause a

temporary inhibition in DNA synthesis. This temporary inhibition of DNA synthesis

would provide a longer time for irradiated cells to recover.

This inhibition also may induce the production of free radical scavengers, so irradiated cells would be more resistant to any further exposures.

MECHANISM OF RADIATION HOMESIS

Stimulation of immune system (Cellular level) High doses of ionizing radiation are

immunosuppressive, many studies have indicated that low doses radiation may stimulate the function of the immune system.

In 1909 Russ first showed that mice treated with low-level radiation were more resistant against bacterial diseases.