Activation of oral keratinocytes by mercuric chloride: relevance to dentalamalgam-induced oral lichenoid reactions

Background Despite the benefits of mercury-containing amalgam dental fillin gs there are growing concerns regarding the potential adverse health effect s arising from exposure to mercury released from fillings. In some individu als this process may result in a local lichenoid reaction of the oral mucos a. Objectives The aim of this study was to investigate the possibility that me rcury salts released from amalgam fillings might act directly on oral kerat inocytes to induce changes that could promote the development of such lesio ns. Methods In vitro experiments were performed in which normal oral and cutane ous keratinocytes were cultured in the presence of mercuric chloride (HgCl2 ). ICAM-1 expression and the release of cytokines was determined by enzyme- linked immunosorbent assay techniques. T-cell binding to HgCl2-pretreated k eratinocytes was assessed using a colorimetric method. Results Subcytotoxic concentrations of HgCl2 induced a concentration-relate d increase in ICAM-1 expression and consequent T-cell binding on oral, but not cutaneous, keratinocytes. HgCl2 also stimulated the release of low leve ls of tumour necrosis factor-alpha and interleukin-8 (but not RANTES), and inhibited the release of interleukin-1 alpha by oral keratinocytes. Conclusions This study provides evidence that oral keratinocytes may play a n integral part in initiating the pathogenesis of amalgam-induced lichenoid reactions.