Cdc42 Inhibition Compromises the Junctional Epithelial Barrier via Decreased Adhesion Molecule Levels and the Induction of Pro-inflammatory Responses

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 Purpose: The junctional epithelium (JE) serves as the primary line of host defense at the dentogingival interface. The role of Cdc42 in regulating the barrier function of the JE remains largely unknown. This study aimed to investigate the role of the small GTPase Cdc42 in regulating JE barrier function, inflammatory responses, and adhesion molecule expression using the murine JE cell line JE-1 and the selective Cdc42 inhibitor ML141.

 Methods: JE-1 cells were treated with ML141, and cell viability was assessed using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay to determine the non-cytotoxic concentration. Epithelial barrier function was evaluated via a fluorescein isothiocyanate (FITC)-dextran permeability assay. Additionally, quantitative real-time polymerase chain reaction was performed to analyze the gene expression levels of inflammatory mediators (Il1b, Il6, Mmp12) and various cell adhesion molecules (Cldn1, Gja1, Itgb4, Dst, Col17a1, Dsp, Dsg3).

 Results: Treatment with 10μM ML141 did not significantly affect JE-1 cell viability, but resulted in a significant increase in epithelial permeability. Cdc42 inhibition led to significant upregulation of the pro-inflammatory genes Il1b, Il6, and Mmp12. Furthermore, the expression levels of key intercellular and hemidesmosomal adhesion molecules (Cldn1, Gja1, Itgb4, Dst, Col17a1, Dsp, Dsg3) were markedly decreased following ML141 treatment.

 Conclusion: These findings demonstrate that Cdc42 plays a critical role in maintaining the structural integrity and homeostasis of the JE. Pharmacological inhibition of Cdc42 compromises epithelial barrier function, induces a pro-inflammatory phenotype, and significantly reduces the expression of adhesion molecules. Consequently, Cdc42 dysfunction may contribute to the breakdown of the periodontal epithelial barrier.