Bacteria and Stress May Trigger Heart Attacks and Strokes

Heart attacks and strokes have been thought to be prompted by stress. But why is this — why does stress trigger these dangerous medical events? Based on a study published earlier this month, a key player may actually be some specific species of bacteria.

Researchers examined plaques in the arteries of 15 patients with advanced atherosclerosis and found that at least 10 species of bacteria lived closely with the plaques. (Plaques are created by the buildup of a variety of biological substances on arterial walls, including fat, cholesterol, calcium, other debris, and clearly bacteria too.) What are the bacteria doing there? It turns out that some are making biofilms, which are clumps of bacteria that harmoniously grow together to cover a surface. And when the harmony is disrupted, researchers found that bits of the plaque may break off, which could cause blood clots that result in heart attacks and/or strokes.

How did they find this out? One of the bacteria species identified was Pseudomonas aeruginosa, which is known to form biofilms. When the researchers grew biofilms in silicone tubing using P. aeruginosa, they simulated an elevation in stress levels and watched as this caused the biofilm to dissolve. Stress was imitated in the tubing by flooding it with norepinephrine (also called noradrenaline), which is a stress hormone. The researchers theorize that an increase of iron in the bloodstream due to the body’s response to norepinephrine is what causes the bacteria to disperse.

This finding is important for helping us better understand underlying causes of heart attacks and strokes, as well as develop more effective treatments — ones that better target the causes instead of the effects.

This study is also yet another example of how much we have to learn about the microbiomes in our very own bodies, and the therapeutic strategies they may offer.

For more Biology Bytes exploring the microbiome, check out the Further Reading section below.

For further reading:

• Bernard B. Lanter, Karin Sauer, and David G. Davies’s article “Bacteria Present in Carotid Arterial Plaques Are Found as Biofilm Deposits Which May Contribute to Enhanced Risk of Plaque Rupture”
• Sara Reardon’s article “Bacteria implicated in stress-related heart attacks” in Nature News
• Jef Akst’s article “Stress, Bacteria Trigger Heart Attack?”
• Teisha J. Rowland’s Biology Bytes articles “What is a ‘Healthy’ Gut Microbiome?,” “Fecal Transplants and C. difficile,” “Chocolate: It Does a Microbe Good,” “The Necrobiome: How Our Bacteria Change After Death”
• Teisha J. Rowland’s book Biology Bytes: Digestible Essays on Stem Cells and Modern Medicine