Toxicity of Formaldehyde to Human Oral Fibroblasts and Epithelial Cells: Influences of Culture Conditions and Role of Thiol Status

Abstract

The toxicity of formaldehyde, a monomer released from certain polymeric dental materials, was studied in cultured human oral fibroblasts and epithelial cells. The influences of growth conditions were evaluated for both cell types, as well as the role of the internal and external thiol states. A one-hour exposure to formaldehyde decreased the colony-forming efficiency (CFE) of both cell types in a concentration-dependent manner, although the toxicity varied up to 100-fold with the conditions. Clearly, the presence of serum and the thiol cysteine counteracted the toxicity in fibroblasts. Similarly, pituitary extract and cysteine, or a mixture of amino acids and ethanolamines, counteracted the formaldehyde toxicity in serum-free cultures of epithelial cells. In contrast, a growth-promoting surface matrix of fibronectin and collagen did not influence the formaldehyde toxicity, as shown by both the CFE assay and a dye reduction assay. Further, a short-term change to the various growth media per se with or without the supplements serum or cysteine did not significantly alter the CFE. Analysis of the thiol state demonstrated significant differences between epithelial cells and fibroblasts, i.e., comparatively lower cellular levels of the free low-molecular-weight thiols glutathione and cysteine in fibroblasts. This result correlated to significantly higher formaldehyde toxicity in the fibroblasts than in the epithelial cells. Taken together, the results indicated the cytoprotective function of both intracellular and extracellular thiols toward formaldehyde, as well as the usefulness of thiol-free and chemically defined conditions for toxicity assessments in oral epithelial cells and fibroblasts. We conclude that the combined use of a controlled external milieu and the presumed target cell type may be advantageous in evaluations of oral toxicity mechanisms or the toxic potency of dental materials, particularly those which, like formaldehyde, may react with thiols or amines.

Investigations of the Diurnal Variation of Vertical HCHO Profiles Based on MAX-DOAS Measurements in Beijing: Comparisons with OMI Vertical Column Data

“…Figure 9 shows the temporal variations in HCHO VCDs retrieved from the MAX-DOAS measurements, and those obtained from the OMI measurements in Beijing. In Figure 9, the error bars of the MAX-DOAS VCDs were calculated using Equation (1). The MAX-DOAS HCHO VCDs, which were temporally collocated within ±45 min of the OMI overpass time at 13:45 LT, are plotted in Figures 9 and 10.…”

“…Formaldehyde (HCHO) is known to have adverse health effects such as damage to oral fibroblasts and epithelial cells [1]. Most HCHO is produced by the photo-oxidation of volatile organic compounds (VOCs) released from biogenic, anthropogenic, and pyrogenic sources [2].…”

“…However, the MAX-DOAS technique has recently been employed to retrieve information regarding the vertical distribution of HCHO. Previous studies [1,[21][22][23] retrieved vertical profiles of trace gases combining MAX-DOAS measurements with the output from radiative transfer models (RTMs). These studies derived both the vertical column amount of HCHO and its vertical distribution.…”

Toxic effects of formaldehyde on the urinary system

“…In addition, there are available data in the literature regarding the symptoms and side effects of FA on several systems (Table 2). [29][30][31][32][33][34] Effects of formaldehyde on the urinary system The toxic effects of formaldehyde occur in several systems of the body, and both experimental and clinical investigations have attempted to elucidate the toxic effects of formaldehyde on the urinary system. In a study conducted in workers with occupational FA exposure, it was found that there was a significant increase in the incidence of renal cancers among these employees.…”

Transcript profiling of enzymes involved in detoxification of xenobiotics and reactive oxygen in human normal and simian virus 40 T antigen‐immortalized oral keratinocytes

“…The preparation procedure and compositions of the various growth media were recently summarized. 18,23 For the RT-PCR and cDNA chip analysis the cells were seeded at 2.5 ϫ 10 3 /cm 2 and incubated in 60 mm dishes in EMHA for 3 to 4 days, assuring that proliferative sub-confluent cultures were studied.…”