Special gum cells that trigger the immune system to control the amount and type of bacteria in the mouth could one day lead to personalized dental treatments against gum disease. Researchers with the Monell Chemical Senses Center and Sichuan University have learned that chemical-sensing cells in the gums protect the mouth by standing guard against infections that damage soft tissue and destroy the bone that supports the teeth.
They say in Nature Communications that the newly identified sensory cells are present in the gums of mice, where they express several types of taste receptors along with a downstream coupling protein called gustducin. These solitary chemosensory cells – known as SCCs - are taste-like chemical detectors that sense irritants and bacteria. The biologists have found them throughout the gut, urinary tract, nasal cavities, and now in the gums. “These sensory cells may provide a new approach for personalized treatment of periodontitis by harnessing a person’s own innate immune system to regulate their oral microbiome,” says Monell Director and President Robert Margolskee, MD, Ph.D. “Our study adds to a growing list of tissues we now know contain SCCs and indicates that the common molecular pathways in gum SCCs are involved in the regulation of oral microbiota,” added cell biologist Marco Tizzano, Ph.D. “In the absence of taste signaling in the gums, the oral microbiome changed in mice without gustducin.”
Knocking out taste-signaling molecules or genetically removing gum SCCs in mice leads to overgrowth of pathogenic oral bacteria and periodontitis. Stimulating bitter taste receptors in mouse SCCs promotes the production of anti-microbial molecules. Mice without gustducin in their SSCs have a more damaging set of microbes living in their mouths compared to normal mice, implying that the lack of gustducin disconnects the sentinel cells’ molecular signal. Differences in the oral bacterial composition of the gustducin-less mice compared to normal mice occurred before any loss of bone in the gums, implying that differences in the oral microbiome could be used as a harbinger of disease.
To examine the effects of repeated stimulation of gum SCCs on periodontitis - and the release of gum AMPs - the researchers applied a mouthwash containing the ultra-bitter substance denatonium to the gums of the mice twice a day. This activated gum SCCs as well as their antimicrobial molecules, which reduced periodontitis in normal mice, but not in the periodontitis-susceptible animals without gustducin. After receiving the denatonium, normal mice showed an enhanced release of an AMP called β-defensin, which was produced at more than twice the levels seen in control mice only treated with saline mouthwash. On the other hand, when the gustducin-less mice were given denatonium mouthwash, there was no effect on the level of β-defensin.
From this study, the team expects that gum SCCs in humans play a similar role in regulating the make-up of the oral microbiome. They surmise that since genetic differences in taste receptors are commonly detected in people, particularly loss-of-function of the bitter taste receptor TAS2R38, the dysfunction of taste-receptor-mediated innate immune responses could be used for dental chair-side screening for individuals who may be most susceptible to oral infectious diseases.
Link Between Severe Gum Disease And Cancer Risk
Advanced gum disease, also called periodontitis, is caused by bacterial infection that damages the soft tissue and bone that support the teeth. Previous research has shown a link between periodontitis and increased cancer risk, although the mechanism connecting the two diseases is still uncertain. Data collected during a long-term health study provides additional evidence for a link between increased risk of cancer in individuals with advanced gum disease, says a study led by epidemiologists Dominique Michaud at Tufts University School of Medicine and Elizabeth Platz of the Johns Hopkins Bloomberg School of Public Health and Kimmel Cancer Center. “This is the largest study addressing the association of gum disease and cancer risk using dental examinations to measure gum disease prior to cancer diagnosis,” says first and corresponding author Dominique Michaud, Sc.D., professor of public health and community medicine at Tufts University School of Medicine. “Additional research is needed to evaluate if periodontal disease prevention and treatment could help alleviate the incidence of cancer and reduce the number of deaths due to certain types of cancer.”
The study - published in the Journal of the National Cancer Institute - used data from comprehensive dental exams performed on 7,466 participants from Maryland, Minnesota, Mississippi, and North Carolina, as part of their participation in the Atherosclerosis Risk in Communities (ARIC) study who were then followed from the late 1990s until 2012. During the follow-up period, 1,648 new cancer cases were diagnosed. What they found was a 24 percent increase in the risk of developing cancer among participants with severe periodontitis, compared to those with mild to no periodontitis at baseline. Among patients who had no teeth - which can be a sign of severe periodontitis - the increase in risk was 28 percent. The highest risk was observed in cases of lung cancer, followed by colorectal cancer. When the researchers did sub-group analyses, they found that participants with severe periodontal disease had more than double the risk of developing lung cancer, compared with no/mild periodontitis.
An 80 percent increase in risk of colon cancer was observed for participants who were edentulous at baseline, which is consistent with prior findings, and among never smokers. A two-fold higher risk was noted for participants with severe periodontitis, compared to those who had no/mild periodontitis. The findings were particularly interesting in light of research, including a recent study in Science that determined that colorectal cancer tissues contain bacteria that are present in the mouth, including bacteria that have been associated with periodontal disease. The researchers also uncovered a small increase in the risk of pancreatic cancer in patients with severe periodontitis. Although not significant statistically, the association has been seen in other similar studies, including a number of studies led by Michaud of Tufts.
Dental Insurance Support
The impact of smoking among the participants was took into account, since people who smoke are more likely to get periodontal disease, and smoking raises the risk of lung and colon cancers. “When we looked at data for the people who had never smoked, we also found evidence that having severe periodontal disease was related to an increased risk of lung cancer and colorectal cancer,” added Elizabeth Platz, Sc.D., deputy chair of the department of epidemiology at the Johns Hopkins Bloomberg School of Public Health and co-leader of the Cancer Prevention and Control Program at the Johns Hopkins Kimmel Cancer Center.
Additional research is needed to understand cancer-site specific and racial differences in findings. The researchers caution that the study was limited in size for subgroup analyses, and less common cancers. The findings, however, suggest the need for further study. The study also points to the importance of expanding dental insurance to more individuals. “Knowing more about the risks that come about with periodontal disease might give more support to having dental insurance in the way that we should be offering health insurance to everyone,” Platz continued.
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With over 30 years of writing and editing experience for newspapers, magazines and corporate communications, Kevin Kerfoot writes about natural health, nutrition, skincare and oral hygiene for Trusted Health Products’ natural health blog and newsletters.
Founder Ray Spotts has a passion for all things natural and has made a life study of nature as it relates to health and well-being. Ray became a forerunner bringing products to market that are extraordinarily effective and free from potentially harmful chemicals and additives. For this reason Ray formed Trusted Health Products, a company you can trust for clean, effective, and healthy products. Ray is an organic gardener, likes fishing, hiking, and teaching and mentoring people to start new businesses. You can get his book for free, “How To Succeed In Business Based On God’s Word,” at www.rayspotts.com.