Public Release:  Estrogen worsens allergic reactions in mice

NIH study may help explain gender disparity observed in people

NIH/National Institute of Allergy and Infectious Diseases

WHAT:

Estradiol, a type of estrogen, enhances the levels and activity in mice of an enzyme that drives life-threatening allergic reactions, according to researchers from the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH). The study results may help explain why women frequently experience more severe allergic reactions compared to men. Furthermore, the results reaffirm the importance of accounting for gender in the design of animal experiments.

Anaphylaxis is an allergic reaction triggered by food, medication or insect stings and bites. Immune cells, particularly mast cells, release enzymes that cause tissues to swell and blood vessels to widen. As a result, skin may flush or develop a rash, and in extreme cases, breathing difficulties, shock or heart attack may occur. Clinical studies have shown that women tend to experience anaphylaxis more frequently than men, but why this difference exists is unclear.

In the current study, NIAID researchers found that female mice experience more severe and longer lasting anaphylactic reactions than males. Instead of targeting immune cells, estrogen influences blood vessels, enhancing the levels and activity of endothelial nitric oxide synthase (eNOS), an enzyme that causes some of the symptoms of anaphylaxis. When the researchers blocked eNOS activity, the gender disparity disappeared. In addition, giving estrogen-blocking treatments to female mice reduced the severity of their allergic responses to a level similar to those seen in males.

While the study has identified a clear role for estrogen and eNOS in driving severe anaphylactic reactions in female mice, more work is needed to see if the effects are similar in people and may be applied toward future preventive therapies.

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ARTICLE:

Hox V et al. Estrogen increases the severity of anaphylaxis in female mice through enhanced eNOS expression and NO production. The Journal of Allergy and Clinical Immunology DOI: 10.1016/j.jaci.2014.11.003 (2014).

WHO:

Dean D. Metcalfe, M.D., chief of NIAID's Laboratory of Allergic Diseases (LAD) and Ana Olivera, Ph.D., staff scientist in LAD's Mast Cell Biology Section, are available to discuss the findings.

CONTACT:

To schedule interviews, please contact Linda Huynh, (301) 402-1663, niaidnews@niaid.nih.gov.

NIAID conducts and supports research--at NIH, throughout the United States, and worldwide--to study the causes of infectious and immune-mediated diseases, and to develop better means of preventing, diagnosing and treating these illnesses. News releases, fact sheets and other NIAID-related materials are available on the NIAID Web site at http://www.niaid.nih.gov.

About the National Institutes of Health (NIH): NIH, the nation's medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit http://www.nih.gov/.

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