A new study clarifies the microbiology underlying the well-established link between gum disease and heart disease by identifying the effect of a bacterium common to both conditions.
The study, from Orebro University in Sweden, is published in the journal Infection and Immunity.
It surrounds the activity of a bacterium called Porphyromonas gingivalis, a well-known culprit in the development of periodontitis - a serious gum infection that damages the soft tissue that surrounds the teeth and attacks the bone that supports them.
The team found that P. gingivalis alters the expression of genes that code for proteins that boost inflammation and atherosclerosis in the coronary arteries - the vessels that supply blood to the heart.
Atherosclerosis, or hardening of the arteries, is caused by artery walls becoming clogged up with fats, cholesterol and other substances. The build-up forms plaques that can burst and trigger a blood clot.
Previous studies have already shown that P. gingivalis is present in coronary artery plaques of heart attack patients, and animal studies have also shown that it triggers and hastens atherosclerosis in the aorta - the main artery from the heart to the rest of the body - and coronary arteries.
The new study, led by Torbjörn Bengtsson, a professor in the department of clinical medicine, reveals the underlying molecular mechanisms behind such findings.
P. gingivalis enzymes boost inflammation in aortic smooth muscle cells
Prof. Bengtsson and colleagues began by culturing human aortic smooth muscle cells and infecting them with P. gingivalis.
Human aortic smooth muscle cells offer an ideal model for studying cardiovascular function and diseases like atherosclerosis at the cell level. When the heart pumps, it stretches the aorta, and the smooth muscle cells in the wall of this main artery contract it again. Changes in the wall of the aorta - such as those caused by atherosclerosis and high blood pressure - strongly influence this process.
When they injected P. gingivalis into the smooth muscle cells, the researchers found it secretes enzymes called gingipains that alter the ratio between two angiopoietins - proteins involved in inflammation - in a direction that boosts inflammation, which is thought to play an important role in atherosclerosis.
Specifically, the team found that the gingipains boosted the expression of the pro-inflammatory protein angiopoietin 2 (Angpt2) and dampened the expression of the anti-inflammatory protein angiopoietin 1 (Angpt1).
The cell-signaling protein tumor necrosis factor (TNF) - which is produced in the human body - is also a cardiovascular risk factor that promotes atherosclerosis via Angpt1 and Angpt2. However, Prof. Bengtsson points out that their study shows the ginginpains from P. gingivalis influence the two proteins independently from TNF.
First author Boxi Zhang, a PhD student in Prof. Bengtsson's lab, concludes:
"Our research clarifies the mechanism behind the association of periodontitis and cardiovascular disease. Our aim is to find biomarkers that can help us diagnose and treat both diseases."
In severe cases of periodontitis, dentists may prescribe antibiotics to fight the infection. However, Medical News Today recently learned of a study that suggests wild blueberry extract may prevent the dental plaque that leads to gum disease. The researchers say the dual antibacterial and anti-inflammatory action of lowbush blueberry polyphenols make them strong candidates for such a treatment.