Stress, Heart Attacks, and Bacteria

A recent study, “Bacteria Present in Carotid Arterial Plaques Are Found as Biofilm Deposits Which May Contribute to Enhanced Risk of Plaque Rupture,” was recently published in the journal ‘mBio’. This study examined the possible link between bacteria, hormonal changes, and potential heart attack or stroke.

Atherosclerosis is the hardening and restriction of one’s arteries. This tends to restrict blood flow, creating the possibility that an individual will experience heart failure, or a heart attack. Researchers studied the effect of bacteria in terms of stress-related hormones and their potential role in heart attacks and stroke.

We have long associated stress with heart attacks, but have not been able to define the true cause. We now see that bacteria may play a large role. Plaques tends to form surfaces that bacteria can attach to. Bacteria begins to multiply, creating a biofilm across the plaques of hardened arteries. If plaque breaks up and enters the bloodstream, this may influence heart attacks and stroke due to clotting.

If the bacteria holds tightly on the plaque, broken up plaque may be collateral damage when the bacteria is dispersed. To test this, 15 patients with cardiovascular disease were examined. It was found that at least ten species of bacteria were located on the plaques. This was seen using florescent tags that could track bacterial DNA.

Researchers grew Pseudomonas aeruginosa in artificial, silicone arteries. Once the bacteria created biofilm, the arteries were exposed to the hormone noradrenaline. This neurotransmitter is associated with stressful situations. Once this hormone was introduced, the biofilm broke up. This is due to iron within the bloodstream, which is triggered by noradrenaline.

David Davies of Binghamton University was one of the authors within this study. He explained, “At least one species of bacteria - Pseudomonas aeruginosa - commonly associated with carotid arteries in our studies, was able to undergo a biofilm dispersion response when exposed to norepinephrine, a hormone responsible for the fight-or-flight response in humans,” said Davies. Because the biofilms are closely bound to arterial plaques, the dispersal of a biofilm could cause the sudden release of the surrounding arterial plaque, triggering a heart attack.

Iron causes the bacteria to create enzymes that breakdown the bonds in which hold the bacteria together in the biofilm. These polymers also attach the bacteria to the plaques. The plaques are then broken up as a direct result of the bacteria dispersion. Much more worked will need to be done regarding both animals and humans, but Davies said that this study; “introduces a completely unexpected potential culprit.”

“Our hypothesis fitted with the observation that heart attack and stroke often occur following an event where elevated levels of catecholamine hormones are released into the blood and tissues, such as occurs during sudden emotional shock or stress, sudden exertion or over-exertion,” explained Davies.

Davies and his team are planning to open up this research to mice, injecting them with biofilm bacteria. They will once again introduce noradrenaline and see whether or not it disperses biofilm. They also want to explore healthy human arteries to see if this biofilm-bacteria is present.

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