Tokyo, Jun 26 (IANS) Scientists have found that the presence of the female hormone oestrogen gives women an advantage over men against severe psoriasis -- a skin disease marked by red, itchy, scaly patches.

However, the underlying reason for the sex differences had been unclear so far.

Now, a team from Hamamatsu University found that the female hormone oestradiol -- oestrogen steroid hormone -- suppresses psoriasis, and the protective role of the hormone has provided a basis for its therapeutic potential.

"Our results have not only revealed the molecular mechanisms of sex differences in psoriasis but also shed new light on our understanding of the physiological role of estradiol," said Tetsuya Honda, from the University's School of Medicine.

The team tested conditional knockout mice, or cko mice, with ovaries removed but supplemented with oestradiol pellets or a placebo. In contrast to wild-type mice, the cko mice without the natural ovarian hormones estradiol showed symptoms of severe skin inflammation.

Once these mice were given oestradiol, the production of IL-17A and IL-1beta cytokines in neutrophil and macrophage immune cells was reversed, reducing the inflammation. This effect was also observed in human neutrophils in vitro.

What intrigued the researchers was how the lack of oestrogen receptors in immune cells made estradiol ineffective against the cytokines.

"These results indicate that estradiol suppresses psoriatic inflammation by regulating neutrophil and macrophage cells," the team wrote in the paper published in the Journal of Allergy and Clinical Immunology.