Generation and role of free radicals 11

Free radicals are unstable, highly reactive molecules which are generated both in the body and outside the body. They are described as electron hungry molecules produced when oxygen is metabolized or burned by the body
Role of Free Radical in diseases

1. GENERATION OF FREE RADICAL AND ITS ROLE IN DISEASES

2. INTRODUCTION Free radicals are unstable, highly reactive molecules which are generated both in the body and outside the body. They are described as electron hungry molecules produced when oxygen is metabolized or burned by the body. They travel via cells disrupting the structure of molecules causing cellular damage. They do serve useful purposes in the human body and under certain situations have several deleterious effects in the body. The changes induced by free radicals are believed to be a major cause of aging, disease development and death.

3. GENERATION OF FREE RADICALS By either of mechanisms: First, from the normal metabolism of oxygen requiring nutrients: Mitochondria-the intracellular powerhouse which produces the universal energy molecules Adenosine triphosphate (ATP) normally consume oxygen in the process and convert it to water. However unwanted by-products such as hydrogen peroxide and hydroxyl radical are inevitably produced due to incomplete reduction of the oxygen molecule. It has been estimated that more than 20 billion molecules of oxidants are produced per day by each cell during normal metabolism.

4. Secondly, white blood cells destroy parasites, bacteria and viruses by using oxidants (free radicals) such as nitric oxide, super oxide and hydrogen peroxide. This is done by the release of free radicals to destroy invading pathogenic microbes as part of the body’s defense mechanism against diseases but with electrons unhinged, free radicals roam the body wrecking havoc. The free radical in an effort to achieve stability attacks nearby molecules in order to obtain another electron, and once this is done the attacked molecules become damaged. When the attacked molecule losses its electron, it becomes a free radical itself, beginning a chain reaction. Once the process is started it can cascade finally resulting in the disruption of living cells, which in turn rip through the tissues and ultimately results in tissue damage.

5. Thirdly other cellular components called peroxisomes produce hydrogen peroxide as a by-product of the degradation of fatty acids and other molecules. In contrast to the mitochondria which oxidizes fatty acids to produce ATP and water, peroxisomes oxidizes fatty acids to produce heat and hydrogen peroxide. The peroxide is then degraded by an enzymatic antioxidant called catalase . Under certain conditions some of the hydrogen peroxide escapes to wreak havoc in other compartments in the cell. Polyunsaturated fats contribute immensely to the over production of free radicals because they have multiple double bonds which become oxidized and cause an increased production of free radicals in the form of lipid peroxide radicals.

6. Finally an enzyme in the cells called cytochrome P450 is one of the body’s primary defenses against toxic chemicals ingested with food. The induction of these enzymes to prevent damage by toxic foreign chemicals like drugs and pesticides also result in the production of oxidant by-products. Virtually all organs and tissues in the body are under constant attack by these free radicals behaving like biological terrorists ripping through our bodies and they need to be stopped quickly. To prevent free radical damage, the body has a defense system called antioxidants. Antioxidants are molecules which can safely interact with free radicals and terminate the chain reactions before vital molecules are damaged.

7. Role of Free Radical in diseases Free radical reactions are expected to produce progressive adverse changes that accumulate with age throughout the body. Fortunately the body is naturally equipped with antioxidants defense system to detoxify these dangerous agents but unfortunately the body’s defense system becomes less effective as we get older leading to accumulation of oxidative damage and the development of chronic degenerative diseases. Irrespective of how and why free radicals are produced, they are harmful and can impair vital molecules within the body such as lipids, protein and DNA. These result to oxidative stress. It also affect cellular calcium metabolism if uncontrolled, and this can result in cell injury or death.

8. Oxidative stress causes damage to three major structures: DNA, Lipids and Proteins. The damage to DNA strands can occur directly by free radical in close proximity to the DNA or indirectly, by impairing production of protein needed to repair DNA. Alteration in DNA is a major factor in the development of cancer. The oxidative damage to DNA overtime could cause changes to both the structure and functions of chromosomes, which can lead to cancer and chronic diseases. Free radical could attack fatty acid side chains of intracellular membranes and lipoproteins. A chain reaction known as lipid peroxidation . The product of lipid peroxidation can further damage membrane proteins making the cell membrane ‘leaky’ and eventually leading to loss of membrane integrity. Lipid peroxidation is implicated in the development of arteriosclerosis.

9. The last structures damaged by oxidative stress are cellular proteins. This plays a role in the causation of cataracts. Free radicals can interfere with protein function leading to irregular, abnormal metabolism and rapid aging . Oxidative stress (free radical reactions) occurs in most human diseases. This is not to say that oxidative stress is the cause of most diseases. The increase in free radicals may be secondary to the disease process. Clinical conditions associated with free radical damage include the following diseases stated below: Alzheimer, Diabetes, Amyotropic lateral sclerosis, Coronary artery diseases, Arthritis, Heart failure, Arteriosclerosis, Hypertension and many other diseases. In fact free radicals are believed to play a role in more than 60 different health conditions.

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