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Cannabis Smoke Damages Cells in the Mouth, Study Finds

By Alexander Beadle

Published: Jul 12, 2022   
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It is well known that smoking tobacco can negatively impact a person’s oral health. But what about smoking cannabis?

Cannabis smoke contains many of the same chemicals present in tobacco smoke, but it also contains cannabinoids and other compounds that present unknown risks to health when inhaled. For example, recent studies on lung health have found that cannabis smoke is still damaging to the lungs, but in a different way to tobacco smoke.

Now, new research published in the Archives of Oral Biology has found that cannabis smoke can damage the gingival epithelial cells in the mouth and suppress their proliferation. This may cause problems for gingival epithelial cell innate immune function, the researchers say, which could lead to future gingivitis and periodontitis. The researchers caution that oral health professionals should be careful to document any changes in oral health in their patients who use cannabis and be aware of these possible complications.

Cannabis smoke disrupts cell shape and viability

This new study, led by researchers from Québec’s Université Laval, studied the effects of cannabis smoke condensate (CSC) on human gingival epithelial cells. This included an evaluation of the cell shape and adhesion, and cell viability when exposed to different concentrations of CSC for times ranging between 30 minutes and 24 hours. These domains were studied using microscope measurements, cell metabolic activity measurements, and lactate dehydrogenase (LDH) activity assays.

The researchers found stark differences in cell shape and adherence after exposure to CSC, with unexposed cells being elongated, adherent, and packed together rather densely. In contrast, this elongated shape was rarely seen in the samples exposed to 10% CSC for 60 minutes or more. Cell adhesion was also affected in these 60-minute samples; no more adherent cells were seen in the samples exposed to 10% or 20% CSC.

A trypan blue assay was used to analyze cell viability, which found high levels of toxic effects after exposure to 5% or greater CSC, regardless of the exposure time.

“All tested CSC concentrations led to a significant decrease in cell viability,” the researchers wrote. “Even with 1 percent CSC at a low contact period (15 min), a decrease was evidenced in the number of live cells.”

The researchers theorized that this cell damage may be related to altered levels of lactate dehydrogenase (LDH) in these cells; LDH is an enzyme that is key to the process of turning sugar into energy for cells to use. An LDH activity assay confirmed that the release of LDH increased significantly following exposure to CSC, and so this is a likely cause of the gingival epithelial cell damage.

Exposure may lead to cell death and gum disease

Increased LDH cytotoxicity can lead to cell apoptosis (the programmed death of a damaged cell) and autophagy (the self-degradation and renewal of a cell). As a result, the researchers employed flow cytometry to examine the effects of CSC on cell apoptosis, necrosis, autophagy, and oxidative stress. Further measurements of apoptotic and autophagic gene expression were made using real-time polymerase chain reaction (RT2-PCR) arrays.

The researchers found that exposure to CSC led to dose-dependent increases in cell apoptosis and necrosis, as well as the displaying of greater autophagy than a comparable batch of control cells. As a result, the researchers concluded that CSC can induce cell damage through any of these three pathways.

Gene analysis also showed that exposure to 20% CSC resulted in the modulation of seven apoptotic genes and six autophagic genes. Included in this was an observed decrease in CD40 ligand gene expression. CD40L is a proinflammatory mediator that has previously been noted as being an important biomarker in periodontal disease, and so a decrease in its expression may have important consequences for oral health.

“The decreased CD40L gene expression demonstrated in our investigation could disrupt epithelial cell communication, thereby contributing to cell apoptosis,” the researchers wrote. “Indeed, an epithelial cell’s interaction with its neighbors is important for the preservation of epithelial cell integrity and innate immune function.”

Disruption of this innate immune function can also lead to problematic inflammatory conditions, such as gingivitis or periodontitis. Gingivitis is a mild gum disease that involves the inflammation of the gingiva gum tissue; periodontitis is a severe inflammation of the gums that can lead to tooth loss and bone destruction.

Finally, the researchers noted that exposure to CSC also tended to result in higher levels of reactive oxygen species in the cells, indicating increased amounts of oxidative stress. From other studies, it is known that oxidative stress triggered by tobacco smoke can lead to DNA and lung damage, so this would suggest that cannabis smoke might carry a similar risk.

As a result of these findings, the Université Laval researchers recommend that oral health professionals document any notable changes in their patients who smoke cannabis, and that these risks should be considered when providing care.

Cannabis smoke and oral health

This study is not the first to suggest that cannabis might be detrimental to oral hygiene. Last year, a study published in EBioMedicine found that smoking cannabis could change the kind of bacteria present in a person’s mouth.

The research, led by scientists at the Medical University of South Carolina, found that smokers had more species of Streptococcus and Actinomyces bacteria in their mouths than non-smokers. The cannabis smokers also tended to have fewer species of Neisseria bacteria than their non-smoking counterparts.

These findings are a concern, as the presence of some Actinomyces species has been associated with Alzheimer’s disease. Indeed, in the EBioMedicine study, the researchers reported that mice infected with oral Actinomyces meyeri bacteria also tended to move more slowly and move less on average than mice treated with other bacterial strains. Further research by this group into cannabis use, bacteria, and how these factors may affect the brain is still ongoing.


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