Involvement of phospholipase D in regulating expression of anti-microbial peptide human β-defensin-2

• Published in: International immunology Vol. 20; no. 1; pp. 21 - 29
• Main Authors: Krisanaprakornkit, Suttichai, Chotjumlong, Pareena, Kongtawelert, Prachya, Reutrakul, Vichai
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01.01.2008
• Subjects: beta-Defensins - genetics; beta-Defensins - metabolism; Cells, Cultured; commensal bacteria; Enzyme Activation; Epithelial Cells - cytology; Epithelial Cells - immunology; Fusobacterium nucleatum; Fusobacterium nucleatum - immunology; Gene Expression Regulation; gene regulation; Gingiva - cytology; Gingiva - immunology; gingival epithelial cells; Humans; Immunity, Innate; innate immunity; Phospholipase D - metabolism; Phospholipase D - pharmacology; Signal Transduction; Up-Regulation; gingival epithelial cells; commensal bacteria; innate immunity; gene regulation; signal transduction
• ISSN: 0953-8178; 1460-2377
• DOI: 10.1093/intimm/dxm115

Human β-defensin expression correlates with differentiation in oral epithelium, and calcium ion, an important regulator of epithelial differentiation, plays a critical role in regulation of human β-defensin-2 (hBD-2) mRNA expression. Phospholipase D (PLD) also regulates epithelial differentiation. Therefore, we examined the role of PLD in hBD-2 up-regulation by cell wall extract of Fusobacterium nucleatum and phorbol 12-myristate 13-acetate (PMA), two known hBD-2 activators. We found that hBD-2 mRNA up-regulation in human gingival epithelial cells (HGECs) by these two activators was mediated by PLD activation and blocked by ethanol and 1-butanol, PLD inhibitors. PLD activity was induced by stimulation with these two activators, and phosphatidic acid (PA), a product generated from the PLD enzymatic activity, was detected in stimulated HGECs. Dioctanoyl PA commonly used for PA induced hBD-2 mRNA expression. mRNAs for PLD1α and β splice variants as well as PLD1 protein were constitutively expressed, whereas mRNA and protein for PLD2 were expressed at much lower levels than those for PLD1. Moreover, pre-treatment with (±)-propanolol, an inhibitor of phosphatidic acid phosphohydrolases that are the downstream signaling molecules in the PLD pathway, significantly blocked hBD-2 mRNA induction by PMA in a dose-dependent manner. In conclusion, these findings indicate the involvement of PLD activation in hBD-2 up-regulation in HGECs, which correlates with the state of epithelial differentiation.