How P. gingivalis causes chronic inflammation in blood vessels

Posted on 7/31/2014 by Gregory A. Williams
Bacteria magnified on a molarPatients of Dr. Williams know that our oral health impacts the health of our entire body. Now a recent study reveals how one oral pathogen, P. gingivalis (easily remembered because it causes gingivitis) can create chronic inflammation in blood vessels.

What is P. gingivalis?

P. gingivalis is a species of bacteria, a single-celled animal– billions and billions of which live on or in our bodies, usually harmlessly (or helpfully). P. gingivalis is also a type of bacteria: gram negative. Gram negative refers to the composition of the bacterium's cell wall. Cell walls vary from species to species but all bacteria have a coat made of a lipids, with sugars and proteins scattered around for cell-signaling and markers.

The important thing about Gram negative bacterial species– like P. gingivalis– is that their cell wall contains a special molecule called Lipid A, which is responsible for the toxicity of these bacteria to humans. To learn about P. gingivalis's role in oral and systemic inflammation, researchers focused on this particular ingredient of the gram negative bacterium: Lipid A.

The battle with bacteria

The relationship between humans and disease-causing bacteria is often referred to as an "arms race." This is because each species has evolved (and in the case of bacteria, is evolving, and quickly) various cellular mechanisms of invading and defending.

From the human standpoint, our body's immune system fights bacteria by noticing molecular markers on bacterial cell walls: sugars, lipids, proteins, and Lipid A. When immune cells recognize these "non-self" markers, an immune reaction is triggered. So why isn't this immune reaction only triggered in the mouth, where the bacteria reside?

Finding a connection

Chronic oral infection with P. gingivalis not only causes local inflammation of the gums but is also associated with an increased risk of atherosclerosis— so why is that? That's what researchers Caroline Attardo Genco, from Boston University School of Medicine, and Richard Darveau, at the University of Washington School of Dentistry, were interested in learning.

In the "arms race" between humans and bacteria, bacteria have a distinct advantage: explosive reproduction. Because they multiply so quickly, bacteria are able to evolve ways to evade the human immune system much faster than the human immune system itself can change.

That's what appears to be causing the connection between oral inflammation and atherosclerosis, Genco and Darveau found. P. gingivalis was able to alter the composition of its Lipid A so that it could go undetected by the human immune system, resulting in "progression of inflammation at a site that is distant from local infection by gaining access to the vasculature." Meaning, because the immune system was unable to stop P. gingivalis at the mouth, the bacteria was able to spread via blood, thus pointing at one possible connection between oral infection and atherosclerosis.

Information is power

Besides being a potent reminder to always take the full course of antibiotics prescribed (this stops or slows bacteria from evolving new shortcuts through our immune systems,) this study illustrates the fascinating connection between our oral health and the health of our entire body. This is why Dr. Williams is committed to his patients' healthy smiles– because a healthy smile is an integral part of a healthy body!

More questions? Please bring them with you at your next appointment with Dr. Williams!

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