Immune System Changes May Cause High Blood Pressure in Postmenopausal Women

students in lab

Doctoral students Megan Sylvester (left) and Joshua Uhlorn (right) used microscopy techniques to analyze differences in immune cell infiltration in the kidneys of pre- and postmenopausal mice.

Emma Louis, Brooks Lab

University of Arizona researcher Heddwen Brooks describes menopause as a "state of accelerated aging" that can significantly affect health in many ways.

For nearly 15 years, Brooks – a professor of physiology and biomedical engineering and member of the university's BIO5 Institute – has studied how sex differences can lead to an increase in hypertension and diabetes, resulting in increased cardiovascular and kidney disease risk in women.

Heddwen Brooks

For nearly 15 years, Heddwen Brooks has investigated the relationships between biological sex, the immune system, diabetes and high blood pressure.

Sarver Heart Center

It's known that prior to menopause, women generally have lower blood pressure than men. They also have greater protection against cardiovascular disease – the leading cause of death worldwide – as well as kidney disease and diabetic complications. The opposite is true after menopause. However, the biological mechanisms linking menopause and the associated hormonal changes to increased risk of cardiovascular disease in women are poorly understood.

A new study – conducted by the Brooks Lab in collaboration with BIO5 Institute member Dr. Janko Nikolich-Zugich, head of the UArizona Department of Immunobiology, and Merry Lindsey, chair of Cellular and Integrative Physiology at the University of Nebraska Medical College – find a potential explanation for premenopausal protection against hypertension in women. The findings are published in the American Journal of Physiology – Heart and Circulatory Physiology.

"Based on previous work, we know estrogen played an important role in preventing kidney inflammation and cardiovascular disease in women," Brooks said. "Our study shows how estrogen can directly impact the immune system to increase protective, anti-inflammatory T regulatory cells, which can guard a female from hypertension and kidney damage prior to menopause."

group photo

Lead author Dr. Dennis Pollow (second from right), found that premenopausal females had more protective immune cells than menopausal females, likely contributing to the lower blood pressures seen in premenopausal women.

Heddwen Brooks

Dennis Pollow, a former postdoctoral fellow in the Brooks Lab, found that menopausal females had less of these cells than premenopausal females. Pollow and co-authors from the UArizona Physiological Sciences Graduate Interdisciplinary Program Joshua Uhlorn and Megan Sylvester discovered that this difference correlated with an increase in pro-inflammatory markers in the kidneys of menopausal females. When T regulatory cells were depleted with a neutralizing antibody in premenopausal females, blood pressures rapidly increased.

"Our ultimate goal is to understand how high blood pressure develops in women across different ages, and how therapies and exercise could be used to control our increased risk of hypertension, the silent killer, which then leads to increased risk of stroke and heart attacks in women after menopause," Brooks said. "Based off this study, we hope to identify new pathways of treatment to help postmenopausal women better manage their blood pressure, as current medications are not as effective in women as they are in men."

Brooks said their study could also have implications for sex differences in COVID-19 susceptibility and disease severity.

Men have more pronounced immune responses to the disease than women. This hyperactive immune response, termed the cytokine storm, is an inflammatory reaction that causes immune cells to release a large amount of pro-inflammatory cytokines, or small proteins, that can lead to widespread tissue damage and failure of organs, including those fed by the circulatory system.

"Further research into the role that anti-inflammatory immune cells have in protecting against hypertension could also be relevant in protecting women against this COVID-19 cytokine storm," Brooks said.

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