Medical Hypotheses MedicoI Hyjmheses (1991) 34. CO-61 0 Lon@nln Group UK Ltd 1991
Nitric Oxide: A Revolution of Free Radicals Theory of Aging QU HONG BIN Hunan Medical University, Box 144, Changsha 4 10078,
P.R. China
Abstract - There are two kinds of free radicals in the aging process, ‘bad’ and ‘good’. fiitric oxide is a good free radical.
Introduction In 1981, Harman published the famous Free Radical Theory of Aging, which states that free radical reaction damage fundamentally causes the age changes (1). He thought that free radicals are all ‘bad’. Are there ‘good’ free radicals? Discussion Furchgott et al first discovered that endothelial cells are obligatory in the relaxation of vascular smooth muscle by acetylcholine, and provided evidence for the release of a labile humoral factor that causes relaxation, which was later called EDRF. Interestingly, in 1987, EDRF was identified as a free radical, nitric oxide (NO). Evidence shows that NO plays important roles not only in the mechanisms of anti-hypertension but also in that of anti-atherosclerosis (2). NO is a ‘good’ free radical. With advanced age, the production and (or) activities of EDRF may decrease (3). As is well known, antioxidants can simply increase life expectancy, not life span (4). This interDate received 10 January 1990 Date accepted 27 March 1990
vention in aging can not only decrease free radical damage but also produce side effects which diminish ‘good’ functions of free radicals, such as activities of NO. Dietary restriction is another striking intervention which delays aging, decreases free radical generation, and increases the level of antioxidants in tissue. By this mechanism, dietary restriction might also lower production and (or) activities of NO. In 1980, Herlihy and Yu discovered that dietary restriction of vascular smooth muscle (5). Isoproterenol-induced relaxation of smooth muscle is at least partially dependent on the release of EDRF from endothelial cells (3). The study of the relationship between dietary restriction and NO would present a new explanation for Herlihy et al’s finding. Conclusion In the living world, there are both bad free radicals and good free radicals. The study of NO in the cardiovascular system might be a first step in revising the classic Free Radicals Theory of Aging.
61
NITRIC OXIDE AND THE FREE RADICALS THEORY OF AGING
References 1. Harman D. The aging process. Proc 78: 7124- 28, 1987. 2. Vanhoutee PM. Endothelium and function. Hypertension 13: 658 -67, 3. Lee TJF, Shirasaki Y, Nickels GA.
Nat1 Acad Sci USA control of vascular 1989. Altered endothelial
modulation of vascular tone in aging and Blood Vessels 24: 132 - 36, 1987. 4. Hayflick L. Theories of biological aging. 20: 145 - 59, 1985. 5. Herlihy JT, Yu BP. Dietary manipulation decline in vascular smooth muscle function. 238: H652- 55, 1980.
hypertension. Exp Gerontol of age-related Am J Physiol
Nitric Oxide: A Revolution of Free Radicals Theory of Aging QU HONG BIN Hunan Medical University, Box 144, Changsha 4 10078,
P.R. China
Abstract - There are two kinds of free radicals in the aging process, ‘bad’ and ‘good’. fiitric oxide is a good free radical.
Introduction In 1981, Harman published the famous Free Radical Theory of Aging, which states that free radical reaction damage fundamentally causes the age changes (1). He thought that free radicals are all ‘bad’. Are there ‘good’ free radicals? Discussion Furchgott et al first discovered that endothelial cells are obligatory in the relaxation of vascular smooth muscle by acetylcholine, and provided evidence for the release of a labile humoral factor that causes relaxation, which was later called EDRF. Interestingly, in 1987, EDRF was identified as a free radical, nitric oxide (NO). Evidence shows that NO plays important roles not only in the mechanisms of anti-hypertension but also in that of anti-atherosclerosis (2). NO is a ‘good’ free radical. With advanced age, the production and (or) activities of EDRF may decrease (3). As is well known, antioxidants can simply increase life expectancy, not life span (4). This interDate received 10 January 1990 Date accepted 27 March 1990
vention in aging can not only decrease free radical damage but also produce side effects which diminish ‘good’ functions of free radicals, such as activities of NO. Dietary restriction is another striking intervention which delays aging, decreases free radical generation, and increases the level of antioxidants in tissue. By this mechanism, dietary restriction might also lower production and (or) activities of NO. In 1980, Herlihy and Yu discovered that dietary restriction of vascular smooth muscle (5). Isoproterenol-induced relaxation of smooth muscle is at least partially dependent on the release of EDRF from endothelial cells (3). The study of the relationship between dietary restriction and NO would present a new explanation for Herlihy et al’s finding. Conclusion In the living world, there are both bad free radicals and good free radicals. The study of NO in the cardiovascular system might be a first step in revising the classic Free Radicals Theory of Aging.
61
NITRIC OXIDE AND THE FREE RADICALS THEORY OF AGING
References 1. Harman D. The aging process. Proc 78: 7124- 28, 1987. 2. Vanhoutee PM. Endothelium and function. Hypertension 13: 658 -67, 3. Lee TJF, Shirasaki Y, Nickels GA.
Nat1 Acad Sci USA control of vascular 1989. Altered endothelial
modulation of vascular tone in aging and Blood Vessels 24: 132 - 36, 1987. 4. Hayflick L. Theories of biological aging. 20: 145 - 59, 1985. 5. Herlihy JT, Yu BP. Dietary manipulation decline in vascular smooth muscle function. 238: H652- 55, 1980.
hypertension. Exp Gerontol of age-related Am J Physiol
