Arsenic stress proteins, effect

The majority of literature on metal-induced stress proteins results from studies employing the arsenic oxides, sodium arsenate and sodium arsenite (Table 2). Although these compounds are very effective inducers of stress proteins, arsenite has been shown to be the more potent inducer (Bournias-Vardiabasis et al. 1990 Bauman et al. 1993). Sodium arsenite has been shown to elicit thermotolerance, self-tolerance, and cross-tolerance in response to a variety of physiologic stresses (see Sect. D). The thermotolerance induced by arsenite treatment has been correlated with the increase in newly synthesized stress proteins (Lee and Dewey 1987). Arsenite has been shown to induce the same proteins as heat in several experimental systems (De Jong et al. 1986 Bournias-Vardiabasis et al. 1990 Cohen et al. 1991 Honda et al. 1992). In contrast, there are reported differences in the stress protein responses produced by these two stressors. 

On the other hand, several ROS are highly cytotoxic. Consequently, eukaryotic cells have developed an elaborate arsenal of antioxidant mechanisms to neutrahze their deleterious effects (enzymes such as superoxide dismutases, catalases, glutathione peroxidases, thioredoxin inhibitors of free-radical chain reaction such as tocopherol, carotenoids, ascorbic acid chelating proteins such as lactoferrin and transferrin). It can be postulated that ROS may induce an oxidative stress leading to cell death when the level of intracellular ROS exceeds an undefined threshold. Indeed, numerous observations have shown that ROS are mediators of cell death, particularly apoptosis (Maziere et al., 2000 Girotti, 1998 Kinscherf et al., 1998 Suzuki et al., 1997 Buttke and Sanstrom, 1994 Albina et al., 1993). 

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