Use of the micronucleus test to monitor the effect of vitamin A, beta‐carotene and canthaxanthin on the buccal mucosa of betel nut/tobacco chewers

AbstractThe frequency of exfoliated cells with micronuclei in buccal swabs was used to estimate the protective effect of vitamin A, beta‐carotene and canthaxanthin (4,4′‐diketo‐beta‐carotene) on the buccal mucosa of betel (areca) nut/tobacco chewers. Micronuclei were scored on exfoliated cells taken by swabbing and stained with the Feulgen reaction and fast green. The betel (areca) nut/tobacco chewers served as their own controls. Prior to the administration of vitamin A and beta‐carotene, the examined betel quid chewers had elevated frequencies of micronucleated buccal mucosa cells, averaging 4.03% ± 1.24 sd (n = 26) and 3.43% ± 1.22 sd (n = 25), respectively. The frequency of micronucleated buccal mucosa cells in non‐chewers and non‐smokers was 0.51% (n = 52). Following a 9‐week ingestion of vitamin A (150,000 IU/week) and beta‐carotene (180 mg/week in 6 capsules), the frequency of micronucleated cells decreased significantly (p<0.001) to 1.70% and 1.16%, respectively. No significant shift in the frequencies of micronucleated cells was observed following the intake of canthaxanthin (180 mg/week in 6 capsules) for 9 weeks or that of a placebo. The lack of protective activity of canthaxanthin, which is a good trapper of oxygen singlets but cannot be converted into vitamin A, suggests that vitamin A and beta‐carotene exert their inhibitory effect on the formation of micronuclei by a mechanism not involving the scavenging of free radicals. The efficacy of beta‐carotene as an inhibitor of micronucleated cell formation, the lack of toxicity, and its availability from a multitude of dietary sources should focus attention on this carotenoid as a promising chemopreventive agent.