Interleukin‐8 induces DNA synthesis, migration and down‐regulation of cleaved caspase‐3 in cultured human gingival epithelial cells

Abstract

Migration of the junctional epithelium occurs in association with the formation of a periodontal pocket. Although the migration of junctional epithelium is known to be related to the proliferation and migration of gingival junctional epithelial cells, the mechanism has not been clarified. In patients with periodontitis, the levels of interleukin-8 (IL-8) in both gingival tissue and gingival crevicular fluid are dramatically increased. IL-8 has broad bioactive functions. In this study, we examined the role of IL-8 in DNA synthesis, migration and protection against apoptosis in cultured human gingival epithelial cells (HGEC). DNA synthesis was estimated by measuring the incorporation of bromodeoxyuridine. The migration of gingival epithelial cells was assessed in a wound-healing assay. The expression of integrin beta-1 was analyzed using immunofluorescence confocal microscopy and western blotting. Cleaved caspase-3 was detected using western blotting and a Caspase-Glo assay kit. IL-8 increased the synthesis of DNA in HGEC, and the maximal effect was seen at 25 or 50 ng/mL of IL-8. In addition, 50 ng/mL of IL-8 induced cell migration, and a neutralizing antibody of integrin beta-1 inhibited the migration. IL-8 also activated expression of integrin beta-1. Furthermore, IL-8 reduced the Aggregatibacter actinomycetemcomitans-induced increase in caspase-3 expression in HGEC. IL-8 may facilitate the migration of gingival junctional epithelium by enhancing DNA synthesis, migration and preventing apoptosis of gingival epithelial cells.