New cell signaling pathway found to shield blood vessels from hypertension damage

edited by Stephanie Baum, reviewed by Andrew Zinin

By creating artificial aging in mice, researchers at Lund University in Sweden have been able to track the formation of aneurysms in the walls of blood vessels.

One finding of the study, now published in the Journal of Biological Chemistry, surprised the researchers: The mice were simultaneously protected against hypertension by activating a different signaling pathway in the cells of the vessel wall—compensating for the strain exerted on the aging vessels. The findings create potential for future complementary blood pressure medicines.

In Sweden, around one in five people has high blood pressure. More research is needed to understand how and why high blood pressure damages blood vessels. It is well known that aging makes blood vessels less flexible and more vulnerable. There is a risk of elevated blood pressure due to vascular stiffness. The strain of high blood pressure can cause an aortic aneurysm if things go awry.

The researchers behind the current article titled “Declining activity of serum response factor in aging aorta in relation to aneurysm progression” are Senior Lecturer and Associate Professor Catarina Rippe and Professor Karl Swärd, both at Lund University.

In the current study, they mapped all the genes that change with aging in healthy human arteries. They then mimicked aging in mice by knocking out a transcription factor—a protein that controls how genes are switched on or off in a cell—called serum response factor (SRF). SRF is a nuclear protein that controls gene expression in vascular smooth muscle cells. Just as the researchers expected, when the SRF disappeared, the mice quickly developed early precursors of aneurysms.

In an earlier study from 2023, the authors, together with other Lund University researchers, found that the proteins YAP/TAZ, which are also known to decline with aging, are essential for vessels to stay healthy. When YAP/TAZ was removed, the mice formed aneurysms in just a few weeks. The smooth muscle cells instead became cartilage-forming cells that caused inflammation and scarring.

In the current study, YAP/TAZ also plays a pivotal role. When the transcription factor SRF was removed, the YAP/TAZ pathway was activated. This suggests that some kind of communication is established between SRF and YAP/TAZ. Swärd draws an analogy with classical music.

“The SRF protein is the biggest composer of all, the one that is most important for the smooth muscle cell, indeed for the function of the entire vessel wall. The aging super-composer is getting worse at writing new masterpieces. Then it’s like SRF, ‘Mozart,’ telling YAP/TAZ ,’You have to help me, Beethoven!’ In the study, we see that this communication is enabled by the enzyme LATS2. This is a surprising and internationally unprecedented finding,” says Swärd.

The chain of reaction seems to be that SRF goes down, causing LATS2 to decrease, and thus activates YAP/TAZ. One of the properties of the LATS2 enzyme is that it switches off the activity of the YAP/TAZ double protein, which is already well known. So, as LATS2 declines, YAP/TAZ gets a chance to flourish.

“We thought the susceptibility to aneurysm would increase when we removed the SRF. But YAP/TAZ seems to compensate for this and protect the vessel wall, with the help of LATS2,” says Rippe.

In addition to the excitement of gaining a better understanding of biochemical processes, the researchers see pharmaceutical potential in the new results. Rippe’s focus is now on studying how to inhibit LATS2, which—together with its sister enzyme LATS1—is needed to prevent the body from developing tumors, in a controlled and safe way.

The LATS inhibitors developed by pharmaceutical companies so far inhibit both LATS1 and LATS2. The researchers therefore want to scientifically map and describe which variant of LATS2 is present in the vessel wall in order to specifically inhibit it. Later on, a vessel-specific knockout of LATS2 awaits, predicts Rippe: “We hope to show that genetic LATS2 inhibition can protect against the vascular damage caused by hypertension.”

The discovery paves the way for new complementary blood pressure medicines, according to the researchers, but they believe this process will take at least five years.

“A strong point is that our results feel incredibly reproducible, and the impact is huge. For example, LATS2 increases almost 200-fold when we activate SRF. Our discoveries also provide new, important knowledge about how the vessel wall adapts to the mechanical forces exerted by blood pressure on the vessel wall,” says Swärd.

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