Effects of dioxins on stress-responsive systems and their relevance to toxicity

Background: Dioxins and related compounds, exemplified by 2,3,7,8-tetrachlorodibenzo-p-dioxin, are recognized as widespread, persistent and highly toxic environmental pollutants. Although numerous studies have been performed to clarify the mechanisms governing dioxin toxicity, these are not yet fully understood because of their complexity. In 1968, subacute poisoning by polychlorinated biphenyls, called 'Yusho', occurred in the southwest part of Japan. Although many of the Yusho patients appear to be free from any of the symptoms produced by the pollutant at present, they remain at high risk of dioxin toxicity because of the high concentrations present in the body. To date, no effective method for combating this toxicity has been developed. Objective: In this review, we summarize dioxin toxicity by focusing on the quenching systems of reactive oxygen species and chaperone proteins. In addition, the possibility of the development of protective and therapeutic treatments for dioxin toxicity is discussed.