الفهرس 
Free Radicals and Their Relation to Oxidative StressOnly 14 pages are availabe for public view
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Abstract
Oxidative stress occurs as a result of imbalance between free radical production and antioxidant defense mechanisms. It affects cell function and causes cell damage, and so can play a role in the pathogenesis of many diseases. One of the major consequences of cellular exposure to oxidative stress is free radical induced peroxidation of cell membrane lipids.
Isoprostane is a stable prostaglandin like compound formed by oxidation of arachidonic acid in the cell membrane via non enzymatic pathway. It is produced as one of the products of oxidative stress, so it can be used as a marker for quantification of oxidative stress in biological specimens.
The present essay aims at highlighting the importance of isoprostane as a marker of oxidative stress and focusing at its clinical significance in some pulmonary and neurological diseases.
Regarding pulmonary diseases, asthmatic patients showed increased isoprostane levels, confirming increased oxidative stress in this disease. Also, isoprostane can be used in monitoring asthmatic patients under steroid treatment.
Degree of disease severity in interstitial lung disease, in addition to effect of treatment, can be assessed by measuring isoprostane levels. As it was found a direct relation between isoprostane levels in sarcoidosis and the severity of the disease.
Concerning patients with COPD isoprostane can be used to assess disease severity and monitor patients during COPD exacerbation and while receiving oxygen treatment, where those patients showed decrease in isoprostane levels after treatment.
Besides, high isoprostane levels in patients with obstructive sleep apnea decreased markedly when treated by continuous positive air way pressure.
The role of oxidative stress in the pathogenesis of other pulmonary diseases, as broncho-pulmonary dysplasia in premature infants, has also been investigated by measuring isoprostane levels in patients with such diseases.
As for neurological diseases such as traumatic brain injury, isoprostane can be used to prove the role of oxidative stress in the pathogenesis of these diseases. Moreover, isoprostane levels can be used to monitor disease activity and response to antioxidant treatment.
Alzheimer’s disease is another neurological disease in which oxidative stress plays an important role. Measuring isoprostane levels in patients with Alzheimer’s disease allows early detection of the disease and help monitoring the effect of antioxidant therapy.
In pre- eclampsia patients show marked increase in isoprostane levels resulting from increased oxidative stress. Isoprostane has a strong vaso-constricting effect which can play a role in the development of hypertension, placental vasoconstriction and cerebral vasospasm in eclampsia.
Increased urinary excretion of isoprostane and decreased antioxidant production in pregnant women is an imbalance that is consistent with oxidative stress, and it precedes clinical recognition of pre-eclampsia.
In conclusion, isoprostane can be considered as a marker of oxidative stress that can help in diagnosis of many diseases in which oxidative stress plays an important role and can allow follow up of patients while receiving treatment.