Resistance to cigarette smoke is increased in periodontal ligament cells by attachment to collagen and fibronectin

In vitro comparison of zinc-based, chlorhexidine, and essential oil mouth rinses

BACKGROUND

Chlorhexidine (CHX)-based mouth rinses are frequently prescribed following periodontal surgeries. A more recently available brand of zinc-based mouth rinses advertises one of its mouth rinses as a substitute for chlorhexidine. The purpose of this study was to evaluate, in vitro, the effects of this brand of zinc-based mouth rinses on cell survival, cell motility, and gene expression of human gingival fibroblasts (HGFs).

METHODS

HGFs were exposed to essential oil (EO), CHX, and three types of one brand of zinc-based mouth rinses designed to treat breath malodor (ZnA), dry mouth (ZnB), and gingivitis (ZnC). Each mouth rinse was tested over a range of concentrations for its effects on HGF survival and motility. Gene expression of cytokines, interleukins, and growth factors were evaluated via reverse transcriptase-polymerase chain reaction (RT-PCR), as a means to assess potential influences on inflammation and wound healing.

RESULTS

Cell survival was significantly decreased for CHX and ZnC at 10% dilutions (p < 0.05). For all time points, cells exposed to ZnC displayed the greatest reduction in cell motility (p < 0.05). The various mouth rinses examined differentially altered the expression of growth factor transcripts. ZnC particularly enhanced the expression of BMP-2 and FGF-2.

CONCLUSION

ZnC was more cytotoxic and inhibited cell motility to a greater extent than any of the other mouth rinses. Therefore, using ZnC as an alternative to CHX could potentially have negative effects on wound healing after periodontal surgery. However, further investigation is required to confirm the clinical relevance of these in vitro findings.

PLAIN LANGUAGE SUMMARY

One type of zinc-based mouth rinse designed to replace chlorhexidine (often prescribed after oral surgeries) demonstrated the greatest oral cell death and reduction in cell movement when compared to other zinc-based mouth rinses. These zinc-based mouth rinses also reduced the amounts of proteins involved in regulating inflammation, potentially reducing the destruction of bone holding the teeth in place. They also changed the amounts of several molecules involved in tissue healing. It is unknown if this will speed or slow the healing of the soft tissues of the mouth.

Protective effect of catalpol on nicotine‑induced injury of alveolar bone and associated underlying mechanisms

Smoking is an important factor that causes periodontitis, which manifests as alveolar bone injury and absorption, and has a high incidence and unfavorable treatment efficacy. Nicotine causes ischemia and inflammation of the periodontium and inhibits the mineralization of alveolar bones. Previous studies have revealed the anti‑tumor biological activities of catalpol, in addition to neuroprotection and anti‑inflammation. The present study therefore investigated the underlying protective mechanism of catalpol in alveolar bone injury. A total of 24 Wistar rats were infused with nicotine (0.7 mg/kg for 30 days), followed by subcutaneous injection of catalpol (2 µg/kg for 14 days). The loss of alveolar bone was examined, and bone alkaline phosphatase (AP) and osteocalcin levels were examined by ELISA. The expression of tumor necrosis factor (TNF)‑α and cyclooxygenase‑2 (COX‑2) was quantified by reverse transcription‑quantitative polymerase chain reaction analysis and western blotting. Treatment with nicotine decreased AP and osteocalcin levels, increased TNF‑α and COX‑2 expression levels, and led to alveolar bone loss compared with the control group. Catalpol decreased bone loss, increased AP and osteocalcin, and decreased TNF‑α and COX‑2 expression compared with the nicotine treatment group. Catalpol may alleviate nicotine‑induced injury and alveolar bone loss via inhibition of inflammatory factors, and facilitate the mineralization of alveolar bones.

Greater Sensitivity of Oral Fibroblasts to Smoked Versus Smokeless Tobacco

BACKGROUND

Smokers have an increased incidence and severity of periodontal disease. Although cigarette smoke contains >4,000 chemical components that could affect periodontal tissues, less is understood about the effect of smokeless tobacco. Therefore, this study compares the effects of cigarette smoke extract (CSE) and smokeless tobacco extract (STE) on cell survival and motility of periodontal ligament (PDL) and gingival fibroblasts in vitro.

METHODS

PDL and gingival fibroblasts were exposed to various concentrations of CSE, STE, or nicotine alone. Viable cells were labeled with calcein acetoxymethyl, visualized using fluorescent microscopy, and quantified using a fluorescence multi-well plate reader. In vitro wounding and collagen gel contraction assays were used to assess cell motility.

RESULTS

Both gingival and PDL fibroblasts displayed reduced cell viability with increasing concentrations of CSE and STE. Based on relative nicotine content, CSE was significantly more cytotoxic than STE. PDL fibroblasts were also more sensitive to both CSE and STE compared with gingival fibroblasts. Finally, sublethal doses of CSE reduced cell motility and gel contraction, whereas STE had less effect. Nicotine alone ≤0.5 mM had little to no effect in any of these assays.

CONCLUSIONS

Many of the underlying effects of tobacco products on periodontal tissues may be due to direct inhibition of normal fibroblast function. CSE is found to be more deleterious to the function of both PDL and gingival fibroblasts than STE. PDL fibroblasts appear to be more sensitive to CSE and STE than gingival fibroblasts. Therefore, cigarette smoke may have more profound effects than smokeless tobacco.

The Bioavailability of Soluble Cigarette Smoke Extract Is Reduced through Interactions with Cells and Affects the Cellular Response to CSE Exposure

Cellular exposure to cigarette smoke leads to an array of complex responses including apoptosis, cellular senescence, telomere dysfunction, cellular aging, and neoplastic transformation. To study the cellular response to cigarette smoke, a common in vitro model exposes cultured cells to a nominal concentration (i.e. initial concentration) of soluble cigarette smoke extract (CSE). However, we report that use of the nominal concentration of CSE as the only measure of cellular exposure is inadequate. Instead, we demonstrate that cellular response to CSE exposure is dependent not only on the nominal concentration of CSE, but also on specific experimental variables, including the total cell number, and the volume of CSE solution used. As found in other similar xenobiotic assays, our work suggests that the effective dose of CSE is more accurately related to the amount of bioavailable chemicals per cell. In particular, interactions of CSE components both with cells and other physical factors limit CSE bioavailability, as demonstrated by a quantifiably reduced cellular response to CSE that is first modified by such interactions. This has broad implications for the nature of cellular response to CSE exposure, and for the design of in vitro assays using CSE.