Dioxins can mimic the effect of steroid hormones by hijacking key proteins, according to a Letter in Nature (Vol. 423, No. 6939, pp. 545-550, dated 29 May 2003). The common environmental toxin can trigger oestrogen-like effects by binding to an alternative receptor.
Oestrogens help to regulate the growth, development and function of reproductive tissues. Normally, they bind to an oestrogen receptor, triggering a series of events inside the cell. But when the hormone is absent, dioxins bind to the AhR receptor, according to Shigeaki Kato and colleagues. This hooks up with the conventional one and goes on to activate oestrogen-related genes. Dioxins produce a similar effect in mice that lack natural oestrogens, the team also find.
"Dioxins, the by-products of many industrial and combustion processes, have been detected in the blood of virtually every person tested. They are present in the fat of breast milk, and can cross the placenta from mother to fetus," say Jan J. Brosens and Malcolm G. Parker in an accompanying News and Views article. "Toxicology studies indicate that exposure to low levels of toxins during critical developmental periods can have permanent adverse effects on health." Understanding how dioxins cause their effects may be critical to counteracting them.
Shigeaki Kato (University of Tokyo and SORST, JST, Saitama, Japan)
Tel: +81 3 5841 8478
Malcolm Parker (Imperial College, London, UK)
Tel: +44 20 7594 2177
(C) Nature press release.
Message posted by: Trevor M. D'Souza