Mutagenicity Induced by Hyperthermia, Hot Mate Infusion, and Hot Caffeine in Saccharomyces cerevisiae

Mate, an infusion containing caffeine (3 g/liter), is drunk hot by most Uruguayan, North Argentinian, and South Brazilian people. This beverage has been recently associated with esophageal cancer in Brazil and Uruguay. To test the mutagenic and lethal effects of mate infusion, caffeine, hyperthermia, and their combinations, we used Saccharomyces cer. evisiae as an eucaryotic model system measuring lys to Lu reversions. We showed that mate infusion was not mutagenic, whereas caffeine at the same concentration contained in mate, produced a 5-fold increase in the spontaneous mutation rate. The highest observed mutagenic rate corresponded to hyperthermia (54~ at 60 min). Hot caffeine also produced a time-dependent mutagenic effect, whereas hot mate infusion determined a significantly lower mutagenic effect than hot caffeine. The differential lethality produced by the tested agents plays an important role in the expression of the induced mutagenic damage. Caffeine and mate infusion could decrease the mutagenic effect of hyperthermia through the chano neling of par t of the induced DNA lesions into an error-free repair pathway. I N T R O D U C T I O N The intake of beverages conta in ing caffeine such as coffee and tea is associated or correlated with cancer as sugges ted by ep idemiolog i cal s tudies (see Ref. 1 for review). Recently, hot mate infus ion drinking has been associated with esophagea l cancer in Brazil and Uruguay (Refs. 2--4; see Ref. 5 for a review). In addit ion, in South Amer ica the highest rate of this type of neoplasia is reported in Uruguay (4). Mate is an infusion of the herb Ilex paraguayensis which conta ins caffeine (6). Interestingly, its concentra t ion is the highest one found among other tested dr inks conta in ing caffeine (7). It is d runk habitual ly hot and in large quanti t ies (approximate ly 1 li ter/day in 2 separate intakes) by mos t Uruguayan , Nor th Argent inian, and South Brazilian people . Studies on the mutagenic , carcinogenic , and teratogenic effects of caffeine have g iven contradic tory results (8-10). On the other hand, invest igat ions in vitro us ing different cell lines have been pe r fo rmed in relation to the lethal and mutagen ic effects o f hyper thermia (11-13) and several ep idemiologica l studies found dr inking tempera tures important for esophageal cancer both for mate and tea (5). We invest igated the putat ive mutagen ic effect of either hot mate or hot caffeine as a first step to elucidate their role in esophageal carcinogenesis . To characterize mutagen ic effects, an auxot rophic haplo id strain of Saccharomyces cerevisiae was used as a mode l sys tem (14, 15). We showed that mate infus ion was not mutagen ic whereas caffeine at the same concent ra t ion conta ined in the mate infus ion disp layed a modera te mutagen ic effect. Both hot mate infusion and hot caffeine solut ion were highly mutagenic . This effect depended on exposure t imes. Moreover , hyper thermia as a s ingle agent induced the highest observed mutagen ic rate as well as a dramatic lethality. These f indings are in favor of the hypothes is that carc inogenic i ty o f the hot mate beverage is not due to caffeine or other mate c o m p o n e n t s itself, but to hyper the rmia alone. M A T E R I A L S A N D M E T H O D S