Mechanisms by which smoking worsens periodontitis discovered

 

Smoking tobacco is known to worsen symptoms of periodontitis and reduce responsiveness to treatment. Using high-resolution spatial transcriptomics, researchers identified differences between smokers and non-smokers in the expression of genes that weaken gum epithelial integrity and cause bone damage through inflammation. They also identified CXCL12 secreted by endothelial cells in gums as a crucial mediator of immune-cell recruitment that drives excessive inflammation. CXCL12 is a possible target for new therapies against periodontitis aggravated by smoking.

Healthy gums, or periodontal tissue, are a key to good oral health. Gums provide crucial nutritional, immunological and mechanical support to the teeth and jaws. Unfortunately, millions of people suffer from severe chronic inflammation of the gums, a condition called periodontitis. Periodontitis occurs when the immune system responds abnormally to microbes entering the gum tissue. Over time, periodontitis causes gums to recede, bones surrounding the mouth to weaken, and may even lead to the loss of teeth.

Previous research has shown that tobacco smokers are not only more likely to develop periodontitis, but the disease also progresses faster, shows more severe symptoms, and responds poorly to treatment compared with non-smokers. These differences have been linked to smoking-related alterations in:

• the gum’s epithelial barrier,
• fibroblast function and epithelial–fibroblast communication, and
• immune and inflammatory responses within periodontal tissue.

Yet, the precise cellular mechanisms have remained unclear due to limitations in available research technologies.

A team of researchers from Sun Yat-sen University, China, led by Professor Chuanjiang Zhao, have used high resolution Visium HD single-cell spatial transcriptomics to analyze the different molecular pathways activated in smokers and non-smokers with periodontitis. Their findings have been published in Volume 17 of the International Journal of Oral Science on August 01, 2025.

“Understanding the complex cellular interactions that contribute to disease progression in smoking-associated periodontitis is important,” remarked Prof. Zhao regarding the importance of this study. He added, “By employing the Visium HD platform, we aimed to map the spatial distribution of different cell types within healthy and diseased periodontal tissues and identify smoking-induced changes in gene expression patterns across various cell populations.”

To explore how smoking affects epithelial cells, the team first examined cells exposed to bacterial lipopolysaccharide (LPS) alone versus LPS plus nicotine. The combination triggered larger changes in genes related to epithelial structure, barrier integrity, communication, and inflammation—suggesting that smoking weakens the epithelial barrier and heightens inflammatory susceptibility.

The researchers then compared gene expression across multiple cell types in tissue samples from healthy gums (HG), non-smokers with periodontitis (P), and smokers with periodontitis (SP).

Describing differences in fibroblasts, cells that maintain gum structure and integrity, Prof. Zhao says, “Our results revealed that individuals in the smoking group, as opposed to healthy controls, presented upregulated expression of genes linked to ageing, intrinsic apoptotic signalling, and mitotic processes.” SP fibroblasts also showed elevated expression of genes associated with inflammation and immune cell recruitment, helping explain the more pronounced tissue damage in smokers.

Spatial transcriptomic analysis further revealed that endothelial cells and macrophages were positioned in close proximity only in smoking-associated periodontitis, enabling stronger inflammatory interactions. SP tissues also contained a higher proportion of pro-inflammatory macrophages, which played a central role in driving periodontal destruction.

Interestingly, this recruitment and activation of macrophages seemed to depend on one molecule –C-X-C motif chemokine 12 or CXCL12. In the presence of CXCL12 secreted by endothelial cells, macrophages turned pro-inflammatory. Suppressing CXCL12 secretion made the macrophages anti-inflammatory. As further confirmation of these findings, the team found that CXCL12 suppression reduced inflammation and bone damage in mice with periodontitis aggravated by nicotine.

“Targeting CXCL12 shows promise in mitigating inflammation and bone resorption in individuals with smoking-induced periodontitis,” says Prof. Zhao, describing a potential new therapeutic approach.  He concludes, “Future research should investigate local delivery systems, like nanoparticles or liposomes, to reduce systemic side effects and improve treatment precision.”

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Reference

A new ally against tooth decay: Arginine offers sweet relief

Fermentation of sugars in our food by the numerous bacteria in our mouth produces acids that destroy our teeth to form caries cavities. These bacteria reside in plaque-like communities called “dental biofilms”. Arginine, an amino acid naturally found in our saliva, has been shown to be helpful in preventing tooth decay. A few beneficial bacteria have an arginine deiminase system (ADS) that helps break down arginine to form alkali that can neutralize the acids. Increased availability of arginine helps in the multiplication of these beneficial bacteria, while at the same time inhibiting the growth of acid-producing bacteria. Recently, studies conducted outside the human body also showed that arginine availability changes the composition of dental biofilms.

To further prove these findings in the human mouth, a team of dentists and researchers led by Post.doc. Yumi C. Del Rey and Professor Sebastian Schlafer from Aarhus University in Denmark have conducted a clinical trial and published their findings in the International Journal of Oral Science.

They recruited 12 participants with active caries and prepared specialized dentures that allow for the collection of intact biofilms, spanning both sides of the jaw. The participants were instructed to dip the dentures in a sugar solution for 5 minutes, immediately followed by distilled water (as placebo) or arginine for 30 minutes, one on each side. This was to be repeated three times a day, with arginine treatment done on the same side each time. “The aim was to investigate the impact of arginine treatment on the acidity, type of bacteria, and the carbohydrate matrix of biofilms from patients with active caries,” explains Sebastian Schlafer, professor at the Department of Dentistry and Oral Health. After 4 days, when the biofilm was developed, the dentures were removed for detailed analysis.

A special pH-sensitive dye called “C-SNARF-4” was used to analyze the acidity of the collected biofilms in different locations. Biofilms treated with arginine showed a significantly higher pH (lower acidity) at 10 and 35 minutes after a sugar challenge. “Our results revealed differences in acidity of the biofilms, with the ones treated with arginine being significantly more protected against acidification caused by sugar metabolism” says the first author, Yumi C. Del Rey.

Then, carbohydrate-binding proteins called lectins, tagged with a fluorescent dye, were used to stain two common carbohydrate components of the biofilms: fucose and galactose. These components make up a large portion of dental biofilms and may contribute to the creation of “acidic pockets” inside them. With arginine treatment, an overall reduction was seen in the amount of fucose-based carbohydrates, possibly making the biofilm less harmful. In addition, there was a change in the structure of the biofilm, with galactose-containing carbohydrates decreasing at the bottom and increasing at the top.

Further, to determine which bacteria were present in the biofilm, they sequenced all bacterial genomes using a technique called “16S rRNA gene sequencing”. Though biofilms treated with arginine and placebo were predominantly dominated by Streptococcus and Veillonella species, arginine significantly reduced the mitis/oralis group of streptococci, which produce acid but are not strong producers of alkali, and slightly increased streptococci with considerable arginine metabolism, thereby improving the pH. Overall, arginine made the biofilms less harmful by reducing their acidity, altering their carbohydrate structure, and reshaping the microbiome within them.

Dental caries, being prevalent across all ages and regions, could be combated using strategies such as supplementation of arginine in toothpastes or oral rinses for people who are more susceptible to them. Arginine, being an amino acid naturally produced in our body and present in dietary proteins, is harmless and could find application even in children. 

Study links low lycopene intake to higher risk of severe gum disease in older adults

 

 — A new study has found that insufficient dietary lycopene intake is associated with a significantly higher risk of severe periodontitis among U.S. adults ages 65 to 79, with differences in risk patterns observed across race and sex. The research was published in The Journal of Nutrition, Health and Aging.

The research team included lead author Katherine Kwong of the Department of Human Development at Connecticut College in New London, Connecticut, along with collaborators from Tulane University, the University of California San Diego, Yunnan University, Southern Illinois University and Louisiana State University Health Sciences Center.

The study analyzed data from 1,227 participants in the National Health and Nutrition Examination Survey (2009–2014). Nearly half (48.7%) of older adults in the study had some level of periodontitis, and 77.9% consumed insufficient dietary lycopene — a carotenoid commonly found in tomatoes and other red fruits.

After adjusting for age, sex, race, smoking status and education, the study found that older adults with sufficient lycopene intake had about one-third the odds of severe periodontitis compared with those with insufficient intake.

The study also found disparities in disease risk. Severe periodontitis was more common among men and non-Hispanic Black adults.

Key findings include:

• Adequate lycopene intake was associated with a reduced likelihood of severe periodontitis (odds ratio 0.33; 95% CI 0.17–0.65).
• Non-Hispanic Black adults had higher odds of severe periodontitis than non-Hispanic White adults (odds ratio 2.82; 95% CI 1.46–5.45).
• Women were less likely than men to experience severe periodontitis (odds ratio 0.27; 95% CI 0.14–0.55).
• Among non-Hispanic White adults, both female sex and sufficient lycopene intake were associated with lower risk.
• Among non-Hispanic Black adults, the same lycopene association was not observed, suggesting differences in risk patterns.

The authors write that the findings suggest dietary lycopene may be an important modifiable factor for preventing severe gum disease among older adults. However, because the study was cross-sectional, causality cannot be determined.

The study also highlights racial and sex disparities in periodontal disease, with non-Hispanic Black adults and men experiencing a higher prevalence of severe disease. The authors recommend that future prevention strategies consider race- and sex-specific dietary interventions, and call for longitudinal or randomized controlled trials to examine whether increasing lycopene intake reduces disease risk or progression.

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Artificial saliva containing sugarcane protein helps protect the teeth of patients with head and neck cancer

 

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An artificial saliva in the form of a mouthwash, produced with the CANECPI-5 protein extracted from sugarcane and modified in a laboratory, can aid in treating teeth in patients with head and neck cancer. In these cases, radiotherapy very close to the mouth can destroy salivary glands and compromise saliva production, which is essential for controlling bacteria and disease.

According to research conducted at the Bauru School of Dentistry at the University of São Paulo (FOB-USP) in Brazil, CANECPI-5 forms a protective “shield” for the teeth, guarding the enamel against weakening acids found in juices, alcoholic beverages, and even stomach acids. The results were published in the Journal of Dentistry. 

The study was conducted during Natara Dias Gomes da Silva’s doctoral studies at FOB-USP. She collaborated with researchers from the Federal University of São Carlos (UFSCar), also in Brazil; the University of California in San Francisco, in the United States; and Yonsei University College of Dentistry, in South Korea.
    
The work is part of the Thematic Project “Modulation of acquired pellicle to control dental mineral loss: unveiling mechanisms to make therapies possible”, which is coordinated by Professor Marília Afonso Rabelo Buzalaf from FOB-USP. 

“We tested the mouthwash developed with CANECPI-5 by applying this solution to small pieces of animal teeth once a day for one minute. Based on these results, we’ll conduct further research so that we can think about applications of this product,” adds Silva, the first author of the article.

“This is the first product that uses the concept of acquired pellicle [a thin protective layer that quickly forms on the tooth surface] to treat xerostomia, which is the sensation of a dry mouth caused by a lack of saliva. We use substances that will reformulate the composition of the proteins that bind to the teeth,” explains Buzalaf.

“We’ve developed a process in which CANECPI-5 binds directly to tooth enamel, helping to make teeth more resistant to the action of acids produced by bacteria,” Silva points out.

The data published in the article showed that the CANECPI-5 protein is most effective when combined with fluoride and xylitol. In these tests, the artificial saliva spray significantly reduced bacterial activity and tooth demineralization – the process by which teeth lose calcium and phosphate, making them more susceptible to cavities. 

This discovery is significant because patients undergoing treatment for head and neck cancer do not yet have access to a specific product on the market that can help combat and treat the most aggressive cavities that develop after radiation therapy.

“Artificial saliva improves the sensation of dry mouth and sores. This helps with discomfort and also combats bacteria. In some cases, the use of this type of product is only for a short time. In others, it’s permanent, because many individuals lose the ability to produce saliva,” adds Buzalaf.

The patent for the CANECPI-5 protein was filed a few years ago. According to the researchers, the challenge now is to scale up in partnership with companies interested in the technology so that the artificial saliva can be produced.

“We’ve already tested the solution as a mouthwash, gel, and orodispersible film, which is a type of plastic that’s placed on the tongue and dissolves, releasing the protein. We’ve tested it in several vehicles and found that CANECPI-5 works very well in all of them. We’ll continue testing other technologies within the Thematic Project to use not only this protein, but others as well,” says Buzalaf.

Regarding the discovery of CANECPI-5

According to Flávio Henrique Silva, a professor in the Department of Genetics and Evolution at UFSCar, who worked on developing the CANECPI-5 protein, the work with cystatins (a family of proteins involved in various biological processes) is linked to research carried out under the Sugarcane Genome Project (SUCEST, FAPESP). His laboratory is part of that project.

“At that time, our group identified and produced, in a recombinant form in bacteria, the first cystatin from sugarcane. We named it CANECPI-1. We then identified and produced five other cane cystatins, including CANECPI-5, which had potent inhibitory activities against cysteine peptidases, which are its target enzymes. Throughout our work, we noticed that this protein bound strongly to smooth surfaces, such as the quartz cuvettes used in activity measurements. This led us to conduct tests in partnership with Professor Marília Buzalaf on the binding of the protein to tooth enamel.”

According to the researchers, the discovery that CANECPI-5 protects tooth enamel while also regulating the oral microbiota makes it a highly promising molecule for dentistry research.

“CANECPI-5 has also been used in the work of other colleagues in the field of dentistry, particularly involving periodontitis. We also have a collaborative project with a colleague from the Federal University of Uberlândia, using subcutaneous sponge implants in mice, which has shown that it’s capable of reducing inflammation and promoting angiogenesis [the formation of new blood vessels] and fibrinogenesis [the formation of fibrin, a protein essential for blood clotting], important processes in tissue repair, making it a candidate molecule for use in wound healing,” Silva points out.

Next steps 

Within the Thematic Project, the researchers will continue trying to understand how CANECPI-5 interacts with other substances. 

According to Buzalaf, one possible avenue is to study CANECPI-5 fused with a peptide derived from statherin, a protein found in saliva, to see if the new hybrid protein is more effective against the acids that weaken teeth when they come from the stomach. Another possible avenue is to try to understand how to combat periodontal disease.

“Another aspect of the Thematic Project is to associate CANECPI-5 with vitamin E because this vitamin acts as a carrier, bringing the protein into contact with the tooth. We imagine that this could facilitate the application of the product directly by the patient at home,” says the researcher.

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Journal

Journal of Dentistry

DOI

10.1016/j.jdent.2025.106176