Immortalized Human Gingival Keratinocytes (Gie-No3B11)

Metabolic Activity of Gingival Epithelial Cells in Response to Core-Multishell Nanocarriers

Drug delivery systems target the oral mucosa because it provides easy access and avoids hepatic first-pass metabolism. The bioavailability of drugs used in local therapy for oral diseases decreases because of the mucosal barrier and the diluting effects of saliva and crevicular fluid. To address this, Jager et al. characterized core-multishell (CMS) nanocarriers for their potential use in oral mucosal drug delivery.

To evaluate potential cytotoxic effects of the CMS nanocarrier, we performed MTT assays to monitor the metabolic activity (cell survival) of cells after CNS nanocarrier application (Fig. 1). They used the immortalized gingiva keratinocytes Gie-No3B11 due to an intended topical use of the particles at the oral mucosa. The application of the unloaded CMS nanocarrier did not affect viability of the cells at concentrations ranging from 1 to 50 μg/mL after 24 hours. The higher concentrations 100 and 500 μg/mL slightly decreased the metabolic activity when compared to control epithelial cells (Fig. 1A). After 48 hours, CMS nanocarriers did not influence epithelial cell survival at any concentration tested (Fig. 1B). After 72 hours, the metabolic activity was unaffected at CMS concentrations between 1 and 100 μg/mL, and a reduced metabolic activity was found for the highest concentration (500 μg/mL) applied compared to control cells (Fig. 1C).

Fig. 1. Metabolic activity in gingival epithelial cells was monitored when exposed to different concentrations the CMS nanocarrier for 24 (A), 48 (B) or 72 hours (C) using the MTT assay (Jager J, Obst K, et al., 2018).

Glycation of Host Proteins Increases Pathogenic Potential of Porphyromonas gingivalis

The connection between periodontitis and diabetes exists because diabetes raises periodontitis risk through increased inflammatory responses and protein glycation. The non-enzymatic process of glucose binding to proteins known as glycation occurs frequently in diabetic individuals and can modify protein functions. Śmiga et al. aim to determine if glycated proteins enhance the growth and pathogenic potential of Porphyromonas gingivalis, a key periodontal pathogen.

They found that glycation increases the ability of P. gingivalis to acquire heme from hemoglobin, mostly due to heme sequestration by the HmuY hemophore-like protein. Based on their results, they hypothesize that differences in hemoglobin degradation and heme release between glycated and un-glycated hemoglobin may not significantly enhance P. gingivalis growth in laboratory liquid culture media. P. gingivalis-mediated diseases involve the bacterium's ability to infect host cells and evade immune defenses. We examined how P. gingivalis infected keratinocytes cultured with hemoglobin as the sole heme source. Glycated hemoglobin slightly increased P. gingivalis infection ability, mainly through enhanced bacterial attachment rather than invasion (Fig. 2). The evidence indicates that glycation could permit P. gingivalis survival and deeper penetration into the epithelium through intercellular pathways. Statistical analysis revealed no significant differences between cultures containing glycated hemoglobin and those containing un-glycated hemoglobin. The simple keratinocyte culture model used for this test likely fails to completely simulate real-life in vivo conditions. Research with a three-dimensional gingival model featuring collagen microfibers revealed comparable results.

Fig. 2. Comparison of HmuY-Fe(III)heme complex formation from hemoglobin (Śmiga M, Smalley JW, et al., 2021).