Inhibition of tubulin guanosine-5′-triphosphatase by lipid peroxides: Protective effects of vitamin A derivatives |
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Authors: | Misako Kawakami Larry Ward Hiroshi Doi |
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Affiliation: | (1) Department of Food Science and Nutrition, School of Human Environmental Sciences, Mukogawa Women’s University, Nishinomiya, 663-8558 Hyogo, Japan;(2) AMRAD Operations, 3121 Richmond, Victoria, Australia |
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Abstract: | Lipid peroxidation of cellular proteins has been postulated to be involved in cellular aging. Given the importance of the
cytoskeleton in cellular function, it is a prime candidate as a potential target for the deleterious effects of lipid peroxides.
In this study, the effects of lipid peroxides on microtubule assembly have been studied in an in vitro assay system, as have the protective effects of the vitamin A group (β-carotene, retinal, and retinol). The assay was based
on tubulin guanosine-5′-triphosphatase (GTPase) activity, which is associated with all steps of microtubule assembly. Soybean
lecithin was utilized as the starting point to generate lipid peroxides. Its selection was based on the high proportion of
phospholipids in the cellular membrane. Lipid peroxides were generated by photooxidation of lecithin, dissolved in methanol,
in the presence of 0.004% methylene blue at 4°C for 8 h. Lipid peroxides (1.0 mg/mL) inhibited tubulin GTPase by 49%, relative
to the control. Vitamin A derivatives (retinol, retinal, and β-carotene) all had the ability to protect against the inhibitory
effects of lipid peroxides, presumably owing to their antioxidant activities. This protective effect was more pronounced when
utilizing a 30-min, as opposed to a 15-min, reaction time. This suggests a relatively slow rate of reaction between the peroxide
and vitamin A group. These studies present a mechanism for the ability of vitamin A to inhibit aging of the cell. |
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Keywords: | β -carotene GTPase activity phospholipid peroxides retinal retinol tubulin |
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