(Meth)acrylate monomer-induced cytotoxicity and intracellular Ca2+ mobilization in human salivary gland carcinoma cells and human gingival fibroblast cells related to monomer hydrophobicity

To elucidate a possible link between the cytotoxicity and Ca2+ mobilization by (meth)acrylates, we investigated the cell survival of and change in [Ca2+]i in human salivary gland (HSG) cells (salivary gland carcinoma cell line) and human gingival fibroblasts (HGF) cells treated separately with 9 (meth)acrylate monomers used in dentistry. The cell survival was determined by the MTT method, and the [Ca2+]i changes after the stimulation with the (meth)acrylate monomers were measured in floating indo-1/AM-loaded cells in Ca2+-free medium. For both HSG and HGF cells, the cytotoxicity of the monomers was approximately proportional to their hydrophobicity (log P). No increase in [Ca2+]i was found with hydrophilic monomers, even with 10 mm stimulation. [Ca2+]i elevation by hydrophobic monomers occurred in a dose- and hydrophobic-dependent manner. The [Ca2+]i change in HSG cells appeared as twin peaks, i.e., an initial sharp peak followed by a delayed broad one; whereas with the HGF cells only a single broad peak was seen, possibly dependent on their membrane quality. Pretreatment with n-butanol or methylmethacrylate enhanced the butylmethacrylate-induced [Ca2+]i elevation, suggesting the [Ca2+]i elevation by (meth)acrylate may be related to monomer hydrophobicity and cell type. The causal link between the cytotoxicity and [Ca2+]i mobilization of monomers is discussed.