Evaluation of the Effects of Tetrahydrocannabinol (THC) and Cannabidiol (CBD) on Gingival and Skin Keratinocyte Growth, Migration, Metabolic Activity, and Pro-Inflammatory Cytokine Secretion

<b>Background</b>: Cannabinoids, such as tetrahydrocannabinol (∆-9-THC) and cannabidiol (CBD) have been proposed for topical medicinal use as a treatment for tissue inflammation. In this context, keratinocytes are the first cells that encounter cannabinoids. The present study evaluated the dose-response relationship between different concentrations of THC and CBD and their effects on human skin and gingival keratinocyte growth and migration, to identify suitable non-toxic concentrations of cannabinoids. <b>Methods:</b> Human gingival and skin keratinocytes were exposed to CBD or THC at different concentrations for 24 h, and then cell adhesion, morphology, and growth/viability were assessed. The effects of cannabinoids on keratinocyte migration were evaluated at 6, 12, and 24 h. Cytotoxicity of CBD and THC against keratinocyte cells was assessed using an LHD cytotoxicity test. Cell metabolic profiles were evaluated using Mito and Glyco Stress Assays. The anti-inflammatory effects of cannabis derivatives were assessed against LPS-stimulated keratinocytes. Data analysis was performed by one-way ANOVA. <b>Results:</b> Only high concentrations (10 and 20 μg/mL) of CBD and THC were cytotoxic to gingival and skin keratinocytes, reduced cell adhesion and growth, and were associated with a delay in cell migration after wounding. Cells exposed to high concentrations (20 μg/mL) of cannabinoids displayed high levels of lactate dehydrogenase (LDH) activity and changes in mitochondrial activities. CBD induced a metabolic shift in skin keratinocyte cells toward glycolysis, while reducing mitochondrial oxidative phosphorylation. In contrast, THC did not alter the metabolic profile of skin keratinocytes. Interestingly, both CBD and THC significantly reduced the LPS-induced inflammatory response by decreasing secretion of IL-6 and IL-8 by gingival and skin keratinocytes. <b>Conclusions:</b> Gingival and skin keratinocytes interact differently with cannabinoids. Only high concentrations of cannabinoids were cytotoxic, suggesting that the use of low concentrations of CBD and THC for topical medicinal applications may help control tissue inflammation.