Drugs That Induce Gingival Overgrowth Drive the Pro-Inflammatory Polarization of Macrophages In Vitro

Abstract: Several attempts have been made to elucidate the pathogenesis of drug-induced gingi- val overgrowth (DIGO), which is triggered by the chronic use of certain drugs that fall into three main categories: anticonvulsants, immunosuppressants, and calcium channel blockers. Previous research suggests that cytokines and impaired cellular functions play a role in DIGO. Of particular interest are macrophages, immune cells that can switch between M1 (pro-inflammatory) and M2 (anti-inflammatory) phenotypes in response to exogenous signals and stimuli. An imbalance be- tween M1 and M2 macrophage populations may underlie DIGO. M1 may contribute to the initial tissue damage in DIGO, while M2 may then attempt to repair the damage with anti-inflammatory mechanisms. To test the hypothesis that drugs associated with DIGO could influence macrophage polarization, human monocytes (precursors of macrophages) were induced to differentiate into M0- naïve macrophages and then exposed to drugs: diphenylhydantoin, gabapentin, mycophenolate, and amlodipine. Quantitative real-time PCR amplification was used to measure the expression of specific genes associated with macrophage polarization. All of the drugs tested induced M0 macrophages to overexpress genes typical of the M1 phenotype, such as CCL5, CXCL10, and IDO1. This investigation provides the first evidence of a link between drugs that cause DIGO and M1 pro-inflammatory macrophage polarization. The knowledge gained from this research could be valuable for future DIGO treatment strategies.